Nitrido Complexes of Transition Metals

Bridging Titanium Nitrido Complexes Containing A Linear Ti-N-Ti Core with A Two-Coordinate Nitrido Ligand

A series of titanium μ2-nitrido complexes supported by the triamidoamine ligand Xy-N3N (Xy-N3N={(3,5-Me2C6H3)NCH2CH2}3N3-) is reported. The titanium azido complex [(Xy-N3N)TiN3] (1-N3), prepared by salt metathesis of the chloride complex [(Xy-N3N)TiCl] (1-Cl) with NaN3, reacted with lithium metal or with alkali metal naphthalenides (alkali metal M=Na, K, and Rb) in THF to give the corresponding dinuclear μ2-nitrido complexes M[(Xy-N3N)Ti=N-Ti(Xy-N3N)] (2-M; M=Li, Na, K, Rb). Single crystal X-ray diffraction studies of 2-Li, 2-Na, and 2-K revealed alkali metal dependent structures in the solid state. While 2-Li and 2-K contain a μ2-nitrido ligand with a linear Ti-N-Ti core, 2-Na includes a μ3-nitrido ligand as part of a T-shape Ti2NaN fragment with the sodium cation weekly coordinated to the nitrido nitrogen atom. When the synthesis of the nitrido complexes was carried out in the presence of excess alkali metals, decomposition of the nitrido complexes was observed affording some intractable titanium species along with the trialkali metal salts [M3(Xy-N3N)] (3-M) (M=Li, Na, K, and Rb). These salts were also prepared by deprotonation of (Xy-N3N)H3 with the corresponding alkali metal hexamethyldisilazide and characterized by multinuclear NMR spectroscopy as well as single crystal X-ray diffraction.

Molybdenum(VI) Nitrido Complexes with Tripodal Silanolate Ligands. Structure and Electronic Character of an Unsymmetrical Dimolybdenum μ-Nitrido Complex Formed by Incomplete Nitrogen Atom Transfer

In contrast to a tungsten nitrido complex endowed with a tripodal silanolate ligand framework, which was reported in the literature to be a dimeric species with a metallacyclic core, the corresponding molybdenum nitrides 3 are monomeric entities comprising a regular terminal nitride unit, as proven by single-crystal X-ray diffraction (SC-XRD). Their electronic character is largely determined by the constraints imposed on the metal center by the podand ligand architecture. 95Mo nuclear magnetic resonance (NMR) and, to a lesser extent, 14N NMR spectroscopy allow these effects to be studied, which become particularly apparent upon comparison with the spectral data of related molybdenum nitrides comprising unrestrained silanolate, alkoxide, or amide ligands. Attempted nitrogen atom transfer from these novel terminal nitrides to [(tBuArN)3Mo] (Ar = 3,5-dimethylphenyl) as the potential acceptor stopped at the stage of unsymmetric dimolybdenum μ-nitrido complex 13a as the first intermediate along the reaction pathway. SC-XRD, NMR, electron paramagnetic resonance, and ultraviolet-visible spectroscopy as well as magnetometry in combination with density functional theory allowed a clear picture of the geometric and electronic structure of this mixed-valent species to be drawn. 13a is formally best described as an adduct of the type [(Mo[O])+III-(μN)-III-(Mo[N])+VI], S = 1/2 complex with (Mo[O])+III in the low-spin configuration, whereas related complexes such as [(AdS)3Mo-(μN)-Mo(NtBuAr)3] (19; Ad = 1-adamantyl) have previously been regarded in the literature as mixed-valent Mo+IV/Mo+V species. The spin population at the two Mo centers is uneven and notably larger at the more reduced Mo[O] atom, whereas the only spin present at the (μN) bridge is derived from spin polarization.

Recent advances in the chemistry of isolable carbene analogues with group 13-15 elements

Carbenes (R2C:), compounds with a divalent carbon atom containing only six valence shell electrons, have evolved into a broader class with the replacement of the carbene carbon or the RC moiety with main group elements, leading to the creation of main group carbene analogues. These analogues, mirroring the electronic structure of carbenes (a lone pair of electrons and an empty orbital), demonstrate unique reactivity. Over the last three decades, this area has seen substantial advancements, paralleling the innovations in carbene chemistry. Recent studies have revealed a spectrum of unique carbene analogues, such as monocoordinate aluminylenes, nitrenes, and bismuthinidenes, notable for their extraordinary properties and diverse reactivity, offering promising applications in small molecule activation. This review delves into the isolable main group carbene analogues that are in the forefront from 2010 and beyond, spanning elements from group 13 (B, Al, Ga, In, and Tl), group 14 (Si, Ge, Sn, and Pb) and group 15 (N, P, As, Sb, and Bi). Specifically, this review focuses on the potential amphiphilic species that possess both lone pairs of electrons and vacant orbitals. We detail their comprehensive synthesis and stabilization strategies, outlining the reactivity arising from their distinct structural characteristics.

Studies on the chemical reduction of polynuclear titanium(IV) nitrido complexes

The redox chemistry of cube-type titanium(IV) nitrido complexes [{Ti4(η5-C5Me5)3(R)}(μ3-N)4] (R = η5-C5Me5 (1), N(SiMe3)2 (2), η5-C5H4SiMe3 (3), and η5-C5H5 (4)) was investigated by electrochemical methods and chemical reactions. Cyclic voltammetry studies indicate that 1-4 undergo a reversible one-electron reduction at ca. -1.8 V vs. ferrocenium/ferrocene. Thus, complex 1 reacts with sodium sand in tetrahydrofuran to produce the highly reactive ionic compound [Na(thf)6][{Ti(η5-C5Me5)}4(μ3-N)4] (5). The treatment of complexes 1-4 in toluene with one equivalent of [K(C5Me5)] in the presence of macrocycles (L) leads to C10Me10 and the formation of more stable derivatives [K(L)][{Ti4(η5-C5Me5)3(R)}(μ3-N)4] (R = η5-C5Me5, L = 18-crown-6 (6), crypt-222 (7); R = N(SiMe3)2, L = 18-crown-6 (8), crypt-222 (9); R = η5-C5H4SiMe3, L = 18-crown-6 (10), crypt-222 (11); R = η5-C5H5, L = crypt-222 (12)). However, the analogous reaction of 4 with [K(C5Me5)] and 18-crown-6 affords [{(18-crown-6)K}2(μ-η5:η5-C5H5)][{Ti4(η5-C5Me5)3(η5-C5H5)}(μ3-N)4] (13) via abstraction of one cyclopentadienide group from a putative intermediate [(18-crown-6)K(μ-η5:η5-C5H5)Ti4(η5-C5Me5)3(μ3-N)4]. In contrast to the cube-type nitrido systems 1-4, the cyclic voltammogram of the trinuclear imido-nitrido titanium(IV) complex [{Ti(η5-C5Me5)(μ-NH)}3(μ3-N)] (14) does not reveal any reversible redox event and 14 readily reacts with [K(C5Me5)] to afford C5Me5H and the diamagnetic derivative [{K(μ4-N)(μ3-NH)2Ti3(η5-C5Me5)3(μ3-N)}2] (15). The treatment of 15 with two equiv. of 18-crown-6 polyethers produces the molecular species [(L)K{(μ3-N)(μ3-NH)2Ti3(η5-C5Me5)3(μ3-N)}] (L = 18-crown-6 (16), dibenzo-18-crown-6 (17)). Complex 17 further reacts with one equiv. of dibenzo-18-crown-6 to yield the ion-separated compound [K(dibenzo-18-crown-6)2][Ti3(η5-C5Me5)3(μ3-N)(μ-N)(μ-NH)2] (18) similar to the ion pair [K(crypt-222)][Ti3(η5-C5Me5)3(μ3-N)(μ-N)(μ-NH)2] (19) obtained in the treatment of 15 with cryptand-222.

Isonitrile μ2-carbido complexes

The μ-carbido complex [WPt(μ-C)Br(CO)2(PPh3)2(Tp*)] (Tp = hydrotris(dimethylpyrazolyl)borate) undergoes substitution of one phosphine ligand with isonitriles to afford complexes [WPt(μ-C)Br(CNR)(CO)2(PPh3)(Tp*)] (R = tBu, C6H3Me2-2,6, C6H2Me3-2,4,6). For aryl but not alkyl isocyanides disubstitution follows to afford [WPt(μ-C)Br(CNR)2(CO)2(Tp*)] (R = C6H2Me2-2,6, C6H2Me3-2,4,6). The bis(isonitrile) derivatives, including [WPt(μ-C)Br(CNtBu)2(CO)2(Tp*)], may also be prepared from the reactions of triangulo-[Pt3(CNR)6] with [W(CBr)(CO)2(Tp*)]. Bis- and tris(dimethylpyrazolyl)borate pro-ligand salts replace the bromide and one phosphine in [WPt(μ-C)Br(CNC6H2Me3)(CO)2(PPh3)(Tp*)] or the bromide and one isonitrile in [WPt(μ-C)Br(CNC6H2Me3)2(CO)2(Tp*)] to afford [WPt(μ-C)(CNC6H2Me3)(CO)2(Tp*)(L)] (L = κ2-Tp*, dihydrobis(pyrazolyl)borate). Structural, spectroscopic and computational data for the complexes are discussed to interrogate the nature of the WC-Pt carbido bridge by analogy with a range of other sp-C1 and sp-B1 ligands (CN, CCH, CP, CAs, CSb, CNO, BO, BNH and BCH2).

Prospects and challenges for nitrogen-atom transfer catalysis

Conversion of C-H bonds to C-N bonds via C-H amination promises to streamline the synthesis of nitrogen-containing compounds. Nitrogen-group transfer (NGT) from metal nitrenes ([M]-NR complexes) has been the focus of intense research and development. By contrast, potentially complementary nitrogen-atom transfer (NAT) chemistry, in which a terminal metal nitride (an [M]-N complex) engages with a C-H bond, is underdeveloped. Although the earliest examples of stoichiometric NAT chemistry were reported 25 years ago, catalytic protocols are only now beginning to emerge. Here, we summarize the current state of the art in NAT chemistry and discuss opportunities and challenges for its development. We highlight the synthetic complementarity of NGT and NAT and discuss critical aspects of nitride electronic structure that dictate the philicity of the metal-supported nitrogen atom. We also examine the characteristic reactivity of metal nitrides and present emerging strategies and remaining obstacles to harnessing NAT for selective, catalytic nitrogenation of unfunctionalized organic small molecules.

Bond dissociation energies of diatomic transition metal nitrides

Resonant two-photon ionization (R2PI) spectroscopy has been used to measure the bond dissociation energies (BDEs) of the diatomic transition metal nitrides ScN, TiN, YN, MoN, RuN, RhN, HfN, OsN, and IrN. Of these, the BDEs of only TiN and HfN had been previously measured. Due to the many ways electrons can be distributed among the d orbitals, these molecules possess an extremely high density of electronic states near the ground separated atom limit. Spin-orbit and nonadiabatic interactions couple these states quite effectively, so that the molecules readily find a path to dissociation when excited above the ground separated atom limit. The result is a sharp drop in ion signal in the R2PI spectrum when the molecule is excited above this limit, allowing the BDE to be readily measured. Using this method, the values D₀(ScN) = 3.905(29) eV, D₀(TiN) = 5.000(19) eV, D₀(YN) = 4.125(24) eV, D₀(MoN) = 5.220(4) eV, D₀(RuN) = 4.905(3) eV, D₀(RhN) = 3.659(32) eV, D₀(HfN) = 5.374(4) eV, D₀(OsN) = 5.732(3) eV, and D₀(IrN) = 5.115(4) eV are obtained. To support the experimental findings, ab initio coupled-cluster calculations extrapolated to the complete basis set limit (CBS) were performed. With a semiempirical correction for spin-orbit effects, these coupled-cluster single double triple-CBS calculations give a mean absolute deviation from the experimental BDE values of 0.20 eV. A discussion of the periodic trends, summaries of previous work, and comparisons to isoelectronic species is also provided.

A Synthetic Cycle for Heteroarene Synthesis by Nitride Insertion

Recent interest in skeletal editing necessitates the continued development of reagent classes with the ability to transfer single atoms. Terminal transition metal nitrides hold immense promise for single-atom transfer, though their use in organic synthesis has so far been limited. Here we demonstrate a synthetic cycle with associated detailed mechanistic studies that primes the development of terminal transition metal nitrides as valuable single-atom transfer reagents. Specifically, we show [cis-terpyOsNCl2 ]PF6 inserts nitrogen into indenes to afford isoquinolines. Mechanistic studies for each step (insertion, aromatization, product release, and nitride regeneration) are reported, including crystallographic characterization of diverted intermediates, kinetics, and computational studies. The mechanistic foundation set by this synthetic cycle opens the door to the further development of nitrogen insertion heteroarene syntheses promoted by late transition metal nitrides.

Facile conversion of ammonia to a nitride in a rhenium system that cleaves dinitrogen

Rhenium complexes with aliphatic PNP pincer ligands have been shown to be capable of reductive N₂ splitting to nitride complexes. However, the conversion of the resulting nitride to ammonia has not been observed. Here, the thermodynamics and mechanism of the hypothetical N–H bond forming steps are evaluated through the reverse reaction, conversion of ammonia to the nitride complex. Depending on the conditions, treatment of a rhenium(iii) precursor with ammonia gives either a bis(amine) complex [(PNP)Re(NH₂)₂Cl]⁺, or results in dehydrohalogenation to the rhenium(iii) amido complex, (PNP)Re(NH₂)Cl. The N–H hydrogen atoms in this amido complex can be abstracted by PCET reagents which implies that they are quite weak. Calorimetric measurements show that the average bond dissociation enthalpy of the two amido N–H bonds is 57 kcal mol⁻¹, while DFT computations indicate a substantially weaker N–H bond of the putative rhenium(iv)-imide intermediate (BDE = 38 kcal mol⁻¹). Our analysis demonstrates that addition of the first H atom to the nitride complex is a thermochemical bottleneck for NH₃ generation.

Rhenium–PNP complexes split N₂ to nitrides, but the nitrides do not give ammonia. Here, the thermodynamics of the hypothetical N–H bond forming steps are evaluated through the reverse reaction, showing that the first H addition is the bottleneck.

Reactivity of Multimetallic Thorium Nitrides Generated by Reduction of Thorium Azides

Thorium nitrides are likely intermediates in the reported cleavage and functionalization of dinitrogen by molecular thorium complexes and are attractive compounds for the study of multiple bond formation in f-element chemistry, but only one example of thorium nitride isolable from solution was reported. Here, we show that stable multimetallic azide/nitride thorium complexes can be generated by reduction of thorium azide precursors─a route that has failed so far to produce Th nitrides. Once isolated, the thorium azide/nitride clusters, M₃Th═N═Th (M = K or Cs), are stable in solutions probably due to the presence of alkali ions capping the nitride, but their synthesis requires a careful control of the reaction conditions (solvent, temperature, nature of precursor, and alkali ion). The nature of the cation plays an important role in generating a nitride product and results in large structural differences with a bent Th═N═Th moiety found in the K-bound nitride as a result of a strong K-nitride interaction and a linear arrangement in the Cs-bound nitride. Reactivity studies demonstrated the ability of Th nitrides to cleave CO in ambient conditions yielding CN^-.

On the crystal chemistry of inorganic nitrides: crystal-chemical parameters, bonding behavior, and opportunities in the exploration of their compositional space

The scarcity of nitrogen in Earth's crust, combined with challenging synthesis, have made inorganic nitrides a relatively unexplored class of compounds compared to their naturally abundant oxide counterparts. To facilitate exploration of their compositional space via a priori modeling, and to help a posteriori structure verification not limited to inferring the oxidation state of redox-active cations, we derive a suite of bond-valence parameters and Lewis acid strength values for 76 cations observed bonding to N3-, and further outline a baseline statistical knowledge of bond lengths for these compounds. Examination of structural and electronic effects responsible for the functional properties and anomalous bonding behavior of inorganic nitrides shows that many mechanisms of bond-length variation ubiquitous to oxide and oxysalt compounds (e.g., lone-pair stereoactivity, the Jahn-Teller and pseudo Jahn-Teller effects) are similarly pervasive in inorganic nitrides, and are occasionally observed to result in greater distortion magnitude than their oxide counterparts. We identify promising functional units for exploring uncharted chemical spaces of inorganic nitrides, e.g. multiple-bond metal centers with promise regarding the development of a post-Haber-Bosch process proceeding at milder reaction conditions, and promote an atomistic understanding of chemical bonding in nitrides relevant to such pursuits as the development of a model of ion substitution in solids, a problem of great relevance to semiconductor doping whose solution would fast-track the development of compound solar cells, battery materials, electronics, and more.

Successive Protonation and Methylation of Bridging Imido and Nitrido Ligands at Titanium Complexes

The reactions of nitrido complexes [{Ti(η⁵-C₅Me₅)(μ-NH)}₃(μ₃-N)] (1) and [{Ti(η⁵-C₅Me₅)}₄(μ₃-N)₄] (2) with electrophilic reagents ROTf (R = H, Me; OTf = OSO₂CF₃) in different molar ratios have allowed the structural characterization of a series of titanium intermediates en route to the formation of the ammonium salts [NR₄]OTf and [NR₄][Ti(η⁵-C₅Me₅)(OTf)₄]. The treatment of the trinuclear imido-nitrido complex 1 with 5.5 equiv of triflic acid in toluene at room temperature led to the dinuclear complex [Ti₂(η⁵-C₅Me₅)₂(μ-N)(NH₃)(μ-O₂SOCF₃)₂(OTf)] (3) and [NH₄]OTf. Compound 3, along with the ammonium salts [NMe₄]OTf and [NMe₄][Ti(η⁵-C₅Me₅)(OTf)₄] (5), was also obtained in the reaction of 1 with 8 equiv of methyl triflate in toluene at 100 °C. The trinuclear complex [Ti₃(η⁵-C₅Me₅)₃(μ-N)(μ-NH)₂(μ-O₂SOCF₃)(OTf)] (4), an intermediate in the formation of 3, was isolated in the treatment of 1 with 4 equiv of MeOTf, although compound 4 was prepared in better yield by treatment of 1 with Me₃SiOTf (2 equiv). Addition of a large excess of MeOTf or HOTf reagents to solutions of 3 resulted in the clean formation of ammonium salts [NR₄][Ti(η⁵-C₅Me₅)(OTf)₄] (R = Me (5), H (6)). Treatment of the tetranuclear nitrido complex [{Ti(η⁵-C₅Me₅)}₄(μ₃-N)₄] (2) with 1 equiv of ROTf in toluene afforded the precipitation of the ionic compounds [{Ti(η⁵-C₅Me₅)}₄(μ₃-N)₃(μ₃-NR)][OTf] (R = H (8), Me (9)), while a large excess of HOTf led to the formation of [{Ti(η⁵-C₅Me₅)}₄(μ₃-N)₃(μ₃-NH)][Ti(η⁵-C₅Me₅)(OTf)₄(NH₃)] (10) by rupture of a fraction of tetranuclear molecules. Complex 2 reacted with 1 equiv of [M(η⁵-C₅H₅)(CO)₃H] (M = Mo, Cr) via hydrogenation of one nitrido ligand to give the molecular derivative [{Ti(η⁵-C₅Me₅)}₄(μ₃-N)₃(μ₃-NH)] (11) and [{M(η⁵-C₅H₅)(CO)₃}₂], while a second 1 equiv of [M(η⁵-C₅H₅)(CO)₃H] produced the ionic compounds [{Ti(η⁵-C₅Me₅)}₄(μ₃-N)₂(μ₃-NH)₂][M(η⁵-C₅H₅)(CO)₃] (M = Mo (12), Cr (13)) by protonation of another nitrido group. The X-ray crystal structures of 3-5, 9, 10, and 13 were determined.

Thermal Isomerization of [Co(acac)2(N3)(py)] in Liquid Solution Studied by Time-Resolved Fourier-Transform Infrared Spectroscopy

The thermally induced stereochemical interconversion between the trans and cis isomers of [Co(acac)2(N3)(py)] in liquid solution is investigated with time-resolved Fourier-transform infrared spectroscopy. The complex is synthesized stereo-selectively in its trans-form. Upon dissolution of the trans-form, the kinetic build-up of the cis-form is evidenced by the spectro-temporal evolution of the FTIR-spectrum. The individual isomer-specific component spectra are in good agreement with calculated spectra obtained from density functional theory. The rate constants of the forward and backward reactions responsible for the trans-cis isomerization equilibrium are derived from the kinetic traces in combination with existing thermochemical data from the literature. Moreover, the temperature-dependence of the rate constants are in line with Arrhenius activation energies of (122 ± 8) kJ/mol and (109 ± 8) kJ/mol for the forward and backward reactions, respectively. DFT-calculations suggest that the stereochemical rearrangement is caused by a pyridine rebound mechanism involving penta-coordinated square-pyramidal [Co(acac)2(N3)]-intermediates.

Intra- and intermolecular interception of a photochemically generated terminal uranium nitride

The photochemically generated synthesis of a terminal uranium nitride species is here reported and an examination of its intra- and intermolecular chemistry is presented. Treatment of the U(iii) complex L^ArUI(DME) ((L^Ar)²⁻ = 2,2′′-bis(Dippanilide)-p-terphenyl; Dipp = 2,6-diisopropylphenyl) with LiNIm^Dipp ((NIm^Dipp)⁻ = 1,3-bis(Dipp)-imidazolin-2-iminato) generates the sterically congested 3N-coordinate compound L^ArU(NIm^Dipp) (1). Complex 1 reacts with 1 equiv. of Ph₃CN₃ to give the U(iv) azide L^ArU(N₃)(NIm^Dipp) (2). Structural analysis of 2 reveals inequivalent N_α–N_β > N_β–N_γ distances indicative of an activated azide moiety predisposed to N₂ loss. Room-temperature photolysis of benzene solutions of 2 affords the U(iv) amide (N-L^Ar)U(NIm^Dipp) (3) via intramolecular N-atom insertion into the benzylic C–H bond of a pendant isopropyl group of the (L^Ar)²⁻ ligand. The formation of 3 occurs as a result of the intramolecular interception of the intermediately generated, terminal uranium nitride (L^Ar)U(N)(NIm^Dipp) (3′). Evidence for the formation of 3′ is further bolstered by its intermolecular capture, accomplished by photolyzing solutions of 2 in the presence of an isocyanide or PMe₃ to give (L^Ar)U[NCN(C₆H₃Me₂)](NIm^Dipp) (5) and (N,C-L^Ar*)U(N Created by potrace 1.16, written by Peter Selinger 2001-2019 ]]> PMe₃)(NIm^Dipp) (6), respectively. These results expand upon the limited reactivity studies of terminal uranium–nitride moieties and provide new insights into their chemical properties.

Photolysis of the U(iv) azide L^ArU(NIm^Dipp) generates a reactive uranium nitride intermediate that can be intercepted by nucleophilic substrates – the first example of intermolecular chemistry of a rare photochemically generated uranium nitride.

Probing the primary processes of a triazido-cobalt(III) complex with femtosecond vibrational and electronic spectroscopies. Photochemical selectivity and multi-state reactivity

The elementary dynamics following 355 nm-excitation of the complex, mer-[Co(dien)(N3)3], were studied in liquid dimethyl sulfoxide (DMSO) solution using femtosecond-ultraviolet-pump/mid-infrared-to-near-ultraviolet probe spectroscopy in conjunction with electronic structure calculations based on density functional theory. Following the initial N3--to-Co charge transfer excitation, the parent complex undergoes an ultrafast metal-to-ligand back electron transfer (BET) within 2 ps thereby populating a metal-centered singlet excited state, 1MC, which can either repopulate the electronic ground state or cleave an azido ligand from the ligand sphere surrounding the metal center. From the asymptotic ground-state bleaching signal after 1 ns, a primary quantum yield for ligand loss of ca. 13% is estimated. The IR-spectrum of the product demonstrates that the photodissociation occurs selectively from the equatorial binding site thereby leading exclusively to the solvolysis product, mer-trans-[Co(dien)(N3)2(DMSO)]+, which features the solvent ligand in the equatorial coordination plane and the azides in the two axial positions. The remarkable photochemical selectivity is traced back to the initial BET and the nature of the intermediate state, 1MC, whose electronic structure entails occupancy of the σ-antibonding d(x2-y2)-orbital. A stereochemical scrambling at the stage of the primary penta-coordinated diazido product is kinetically inhibited on the singlet surface by an energy barrier of roughly 27 kJ mol-1. Primary penta-coordinated products that may be born on the triplet surface are funneled to their singlet ground-state preferentially from geometries with trans-oriented azido ligands thereby also preventing a stereochemical isomerization that could possibly arise from an intersystem crossing.

Development and evaluation of a 99mTc(V)-nitrido complex derived from estradiol for breast cancer imaging

Estrogen receptors are overexpressed in 70% of breast cancer and identification of their presence is important to select the appropriate treatment. This work proposes the preparation and evaluation of an estradiol derived as potential ER imaging agent. Ethinylestradiol was derivatized to introduce a dithiocarbamate function for Tc coordination. Labeling was achieved through the formation of a symmetric Tc(V)-nitrido complex with a radiochemical purity (RCP) > 95%. Physicochemical evaluation, cell uptake, biodistribution in normal animals and in nude mice bearing induced ER + breast tumors showed promising results.

High-Oxidation-State 3d Metal (Ti-Cu) Complexes with N-Heterocyclic Carbene Ligation

High-oxidation-state 3d metal species have found a wide range of applications in modern synthetic chemistry and materials science. They are also implicated as key reactive species in biological reactions. These applications have thus prompted explorations of their formation, structure, and properties. While the traditional wisdom regarding these species was gained mainly from complexes supported by nitrogen- and oxygen-donor ligands, recent studies with N-heterocyclic carbenes (NHCs), which are widely used for the preparation of low-oxidation-state transition metal complexes in organometallic chemistry, have led to the preparation of a large variety of isolable high-oxidation-state 3d metal complexes with NHC ligation. Since the first report in this area in the 1990s, isolable complexes of this type have been reported for titanium(IV), vanadium(IV,V), chromium(IV,V), manganese(IV,V), iron(III,IV,V), cobalt(III,IV,V), nickel(IV), and copper(II). With the aim of providing an overview of this intriguing field, this Review summarizes our current understanding of the synthetic methods, structure and spectroscopic features, reactivity, and catalytic applications of high-oxidation-state 3d metal NHC complexes of titanium to copper. In addition to this progress, factors affecting the stability and reactivity of high-oxidation-state 3d metal NHC species are also presented, as well as perspectives on future efforts.

A Nitrido-bridged Heterometallic Ruthenium(IV)/Iron(IV) Phthalocyanine Complex Supported by A Tripodal Oxygen Ligand, [Co(η5-C5H5){P(O)(OEt)2}3]-: Synthesis, Structure, and Its Oxidation to Give Phthalocyanine Cation Radical and Hydroxyphthalocyanine Complexes

Dinuclear iron nitrido phthalocyanine complexes are of interest owing to their applications in catalytic oxidation of hydrocarbons. While nitrido-bridged diiron phthalocyanine complexes are well documented, the oxidation chemistry of heterodinuclear iron(IV) phthalocyanine nitrides has not been well explored. In this paper we report on the synthesis of a heterometallic Fe^IV/Ru^IV phthalocyanine nitride and its oxidation to yield phthalocyanine cation radical and hydroxyphthalocyanine complexes. Treatment of [Fe^II(Pc)] (Pc^2- = phthalocyanine dianion) with [Ru^VI(L_OEt)(N)Cl₂] (L_OEt^- = [Co(η⁵-C₅H₅){P(O)(OEt)₂}₃]^-) (1) afforded the heterometallic μ-nitrido complex [Cl₂(L_OEt)Ru^IV(μ-N)Fe^IV(Pc)(H₂O)] (2) that contains an Ru^IV=N = Fe^IV linkage with the Ru-N and Fe-N distances of 1.689(6) and 1.677(6) Å, respectively, and Ru-N-Fe angle of 176.0(4)°. Substitution of 2 with 4- tert-butylpyridine (Bupy) gave [Cl₂(L_OEt)Ru^IV(μ-N)Fe^IV(Pc)(Bupy)]. The cyclic voltammogram of 2 displayed a reversible Pc-centered oxidation couple at +0.18 V versus Fc^+/0 (Fc = ferrocene). The oxidation of 2 with [N(4-BrC₆H₄)₃]SbCl₆ led to isolation of the cationic complex [Cl₂(L_OEt)Ru^IV(μ-N)Fe^IV(Pc^·+)(H₂O)][SbCl₆]_0.85[SbCl₅(OH)]_0.15 (2[SbCl₆]_0.85[SbCl₅(OH)]_0.15), whereas that with PhICl₂ yielded the chloride complex [Cl₂(L_OEt)Ru^IV(μ-N)Fe^IV(Pc^·+)Cl] (3). Complexes 2[SbCl₆]_0.85[SbCl₅(OH)]_0.15 and 3 have been characterized by X-ray crystallography. The UV/visible spectra of 2⁺ (λ_max = 515 and 747 nm) and 3 (λ_max = 506 and 748 nm) displayed absorption bands that are characteristic of Pc cation radical. The EPR spectrum of 3 showed a signal with the g value of 2.0012 (width = 5 G) that is consistent with an organic radical. The spectroscopic data support the formulation of 2⁺ and 3 as Ru^IV-Fe^IV Pc cation radical complexes. The reaction of 2 with PhI(CF₃CO₂)₂ in dried CH₂Cl₂ afforded a mixture of [Cl₂(L_OEt)Ru^IV(μ-N)Fe^IV(Pc^·+)(CF₃CO₂)] (4) and a hydroxyphthalocyanine complex, [Cl₂(L_OEt)Ru^IV(μ-N)Fe^IV(Pc-OH)(H₂O)](CF₃CO₂) (5), whereas that in wet CH₂Cl₂ (containing ca. 0.5% water) led to isolation of 5 as the sole product. Complex 4 was independently prepared by salt metathesis of 3 with AgCF₃CO₂.

Heterobimetallic Nitrido Complexes of Group 8 Metalloporphyrins

Heterobimetallic nitrido porphyrin complexes with the [(L)(por)M-N-M'(L_OEt)Cl₂] formula {por^2- = 5,10,15,20-tetraphenylporphyrin (TPP^2-) or 5,10,15,20-tetra(p-tolyl)porphyrin (TTP^2-) dianion; L_OEt^- = [Co(η⁵-C₅H₅){P(O)(OEt)₂}₃]^-; M = Fe, Ru, or Os; M' = Ru or Os; L = H₂O or pyridine} have been synthesized, and their electrochemistry has been studied. Treatment of trans-[Fe(TPP)(py)₂] (py = pyridine) with Ru(VI) nitride [Ru(L_OEt)(N)Cl₂] (1) afforded Fe/Ru μ-nitrido complex [(py)(TPP)Fe(μ-N)Ru(L_OEt)Cl₂] (2). Similarly, Fe/Os analogue [(py)(TPP)Fe(μ-N)Os(L_OEt)Cl₂] (3) was obtained from trans-[Fe(TPP)(py)₂] and [Os(L_OEt)(N)Cl₂]. However, no reaction was found between trans-[Fe(TPP)(py)₂] and [Re(L_OEt)(N)Cl(PPh₃)]. Treatment of trans-[M(TPP)(CO)(EtOH)] with 1 afforded μ-nitrido complexes [(H₂O)(TPP)M(μ-N)Ru(L_OEt)Cl₂] [M = Ru (4a) or Os (5)]. TTP analogue [(H₂O)(TTP)Ru(μ-N)Ru(L_OEt)Cl₂] (4b) was prepared similarly from trans-[Ru(TTP)(CO)(EtOH)] and 1. Reaction of [(H₂O)(por)M(μ-N)M(L_OEt)Cl₂] with pyridine gave adducts [(py)(por)M(μ-N)Ru(L_OEt)Cl₂] [por = TTP, and M = Ru (6); por = TPP, and M = Os (7)]. The diamagnetism and short (por)M-N(nitride) distances in 2 [Fe-N, 1.683(3) Å] and 4b [Ru-N, 1.743(3) Å] are indicative of the M^IV═N═M'^IV bonding description. The cyclic voltammograms of the Fe/Ru (2) and Ru/Ru (4b) complexes in CH₂Cl₂ displayed oxidation couples at approximately +0.29 and +0.35 V versus Fc^+/0 (Fc = ferrocene) that are tentatively ascribed to the oxidation of the {L_OEtRu} and {Ru(TTP)} moieties, respectively, whereas the Fe/Os (3) and Os/Ru (5) complexes exhibited Os-centered oxidation at approximately -0.06 and +0.05 V versus Fc^+/0, respectively. The crystal structures of 2 and 4b have been determined.

Terminal Uranium(V/VI) Nitride Activation of Carbon Dioxide and Carbon Disulfide: Factors Governing Diverse and Well-Defined Cleavage and Redox Reactions

The reactivity of terminal uranium(V/VI) nitrides with CE₂ (E=O, S) is presented. Well-defined C=E cleavage followed by zero-, one-, and two-electron redox events is observed. The uranium(V) nitride [U(Tren^TIPS )(N)][K(B15C5)₂ ] (1, Tren^TIPS =N(CH₂ CH₂ NSiiPr₃ )₃ ; B15C5=benzo-15-crown-5) reacts with CO₂ to give [U(Tren^TIPS )(O)(NCO)][K(B15C5)₂ ] (3), whereas the uranium(VI) nitride [U(Tren^TIPS )(N)] (2) reacts with CO₂ to give isolable [U(Tren^TIPS )(O)(NCO)] (4); complex 4 rapidly decomposes to known [U(Tren^TIPS )(O)] (5) with concomitant formation of N₂ and CO proposed, with the latter trapped as a vanadocene adduct. In contrast, 1 reacts with CS₂ to give [U(Tren^TIPS )(κ² -CS₃ )][K(B15C5)₂ ] (6), 2, and [K(B15C5)₂ ][NCS] (7), whereas 2 reacts with CS₂ to give [U(Tren^TIPS )(NCS)] (8) and "S", with the latter trapped as Ph₃ PS. Calculated reaction profiles reveal outer-sphere reactivity for uranium(V) but inner-sphere mechanisms for uranium(VI); despite the wide divergence of products the initial activation of CE₂ follows mechanistically related pathways, providing insight into the factors of uranium oxidation state, chalcogen, and NCE groups that govern the subsequent divergent redox reactions that include common one-electron reactions and a less-common two-electron redox event. Caution, we suggest, is warranted when utilising CS₂ as a reactivity surrogate for CO₂ .

Molecular and electronic structure of terminal and alkali metal-capped uranium(V) nitride complexes

Determining the electronic structure of actinide complexes is intrinsically challenging because inter-electronic repulsion, crystal field, and spin-orbit coupling effects can be of similar magnitude. Moreover, such efforts have been hampered by the lack of structurally analogous families of complexes to study. Here we report an improved method to U≡N triple bonds, and assemble a family of uranium(V) nitrides. Along with an isoelectronic oxo, we quantify the electronic structure of this 5f1 family by magnetometry, optical and electron paramagnetic resonance (EPR) spectroscopies and modelling. Thus, we define the relative importance of the spin-orbit and crystal field interactions, and explain the experimentally observed different ground states. We find optical absorption linewidths give a potential tool to identify spin-orbit coupled states, and show measurement of UV···UV super-exchange coupling in dimers by EPR. We show that observed slow magnetic relaxation occurs via two-phonon processes, with no obvious correlation to the crystal field.

Synthesis and biodistribution of novel 99mTcN complexes of glucose dithiocarbamate as potential probes for tumor imaging

^99mTcN-3b can be prepared from a kit without the need for purification and would be a promising tumor imaging agent.

Homo and heteropolymetallic Group 4 molecular nitrides

Treatment of [{Ti(η(5)-C5Me5)(μ-NH)}3(μ3-N)] (1) with zirconium or hafnium tetrachloride adducts [MCl4(thf)2] affords complexes [Cl3M{(μ3-N)(μ3-NH)2Ti3(η(5)-C5Me5)3(μ3-N)}] (M = Zr (2), Hf (3)). Titanium chloride complexes [Cl2Ti{(μ3-N)2(μ3-NH)Ti3(η(5)-C5Me5)3(μ3-N)}] (4) and [(Me2NH)ClTi{(μ3-N)3Ti3(η(5)-C5Me5)3(μ3-N)}] (5) are obtained by reaction of 1 with [TiCl4-x(NMe2)x] (x = 2, 3). The dimethylamine ligand in 5 is displaced by pyridine to give the analogue complex [(py)2ClTi{(μ3-N)3Ti3(η(5)-C5Me5)3(μ3-N)}] (6). Treatment of the titanium chloride complexes 4 and 5 with sodium cyclopentadienide or lithium bis(trimethylsilyl)amide reagents leads to the cube-type nitrido derivatives [RTi{(μ3-N)3Ti3(η(5)-C5Me5)3(μ3-N)}] (R = η(5)-C5H5 (7), N(SiMe3)2 (8)). The reaction of the zirconium trichloride complex 2 with [Tl(C5H5)] yields exclusively the dichloride-monocyclopentadienyl derivative [(η(5)-C5H5)Cl2Zr{(μ3-N)(μ3-NH)2Ti3(η(5)-C5Me5)3(μ3-N)}] (9). However, the treatment of 2 with excess [Na(C5H5)] causes further chloride replacement in 9 and subsequent cyclopentadiene elimination to give [(η(5)-C5H5)Zr{(μ3-N)3Ti3(η(5)-C5Me5)3(μ3-N)}] (10) via intermediates [(η(5)-C5H5)2ClZr{(μ3-N)Ti3(η(5)-C5Me5)3(μ-NH)2(μ3-N)}] (11) and [(η(5)-C5H5)ClZr{(μ3-N)2(μ3-NH)Ti3(η(5)-C5Me5)3(μ3-N)}] (12). Treatment of 2 or 9 with [Mg(C5H5)2] leads to the magnesium derivative [(η(5)-C5H5)Mg(μ-Cl)2(η(5)-C5H5)Zr{(μ4-N)(μ3-N)(μ3-NH)Ti3(η(5)-C5Me5)3(μ3-N)}] (13), which can be visualized as a result of the incorporation of one [Mg(η(5)-C5H5)Cl] moiety to complex 12. In contrast to the metathesis process with [M(C5H5)x] derivatives and subsequent C5H6 eliminations, the reaction of 2 with potassium pentamethylcyclopentadienide in toluene produces the paramagnetic derivative [K(μ-Cl)3Zr{(μ3-N)(μ3-NH)2Ti3(η(5)-C5Me5)3(μ3-N)}] (14) and C10Me10. Complex 14 reacts with one equivalent of 18-crown-6 or cryptand-222 to give the molecular complex [(18-crown-6)K(μ-Cl)3Zr{(μ3-N)(μ3-NH)2Ti3(η(5)-C5Me5)3(μ3-N)}] (15) or the ion pair [K(crypt-222)][Cl3Zr{(μ3-N)(μ3-NH)2Ti3(η(5)-C5Me5)3(μ3-N)}] (16). The X-ray crystal structures of 2, 8, 13 and 15 have been determined.

Carbon-nitrogen bond construction and carbon-oxygen double bond cleavage on a molecular titanium oxonitride: a combined experimental and computational study

New carbon-nitrogen bonds were formed on addition of isocyanide and ketone reagents to the oxonitride species [{Ti(η(5)-C5Me5)(μ-O)}3(μ3-N)] (1). Reaction of 1 with XylNC (Xyl = 2,6-Me2C6H3) in a 1:3 molar ratio at room temperature leads to compound [{Ti(η(5)-C5Me5)(μ-O)}3(μ-XylNCCNXyl)(NCNXyl)] (2), after the addition of the nitrido group to one coordinated isocyanide and the carbon-carbon coupling of the other two isocyanide molecules have taken place. Thermolysis of 2 gives [{Ti(η(5)-C5Me5)(μ-O)}3(XylNCNXyl)(CN)] (3) where the heterocumulene [XylNCCNXyl] moiety and the carbodiimido [NCNXyl] fragment in 2 have undergone net transformations. Similarly, tert-butyl isocyanide (tBuNC) reacts with the starting material 1 under mild conditions to give the paramagnetic derivative [{Ti3(η(5)-C5Me5)3(μ-O)3(NCNtBu)}2(μ-CN)2] (4). However, compound 1 provides the oxo ketimide derivatives [{Ti3(η(5)-C5Me5)3(μ-O)4}(NCRPh)] [R = Ph (5), p-Me(C6H4) (6), o-Me(C6H4) (7)] upon reaction with benzophenone, p-methylbenzophenone, and o-methylbenzophenone, respectively. In these reactions, the carbon-oxygen double bond is completely ruptured, leading to the formation of a carbon-nitrogen and two metal-oxygen bonds. The molecular structures of complexes 2-4, 6, and 7 were determined by single-crystal X-ray diffraction analyses. Density functional theory calculations were performed on the incorporation of isocyanides and ketones to the model complex [{Ti(η(5)-C5H5)(μ-O)}3(μ3-N)] (1H). The mechanism involves the coordination of the substrates to one of the titanium metal centers, followed by an isomerization to place those substrates cis with respect to the apical nitrogen of 1H, where carbon-nitrogen bond formation occurs with a low-energy barrier. In the case of aryl isocyanides, the resulting complex incorporates additional isocyanide molecules leading to a carbon-carbon coupling. With ketones, the high oxophilicity of titanium promotes the unusual total cleavage of the carbon-oxygen double bond.

Two-electron reductive carbonylation of terminal uranium(V) and uranium(VI) nitrides to cyanate by carbon monoxide

Two-electron reductive carbonylation of the uranium(VI) nitride [U(Tren(TIPS))(N)] (2, Tren(TIPS)=N(CH2CH2NSiiPr3)3) with CO gave the uranium(IV) cyanate [U(Tren(TIPS))(NCO)] (3). KC8 reduction of 3 resulted in cyanate dissociation to give [U(Tren(TIPS))] (4) and KNCO, or cyanate retention in [U(Tren(TIPS))(NCO)][K(B15C5)2] (5, B15C5=benzo-15-crown-5 ether) with B15C5. Complexes 5 and 4 and KNCO were also prepared from CO and the uranium(V) nitride [{U(Tren(TIPS))(N)K}2] (6), with or without B15C5, respectively. Complex 5 can be prepared directly from CO and [U(Tren(TIPS))(N)][K(B15C5)2] (7). Notably, 7 reacts with CO much faster than 2. This unprecedented f-block reactivity was modeled theoretically, revealing nucleophilic attack of the π* orbital of CO by the nitride with activation energy barriers of 24.7 and 11.3 kcal mol(-1) for uranium(VI) and uranium(V), respectively. A remarkably simple two-step, two-electron cycle for the conversion of azide to nitride to cyanate using 4, NaN3 and CO is presented.

Reactivity of nitrido complexes of ruthenium(VI), osmium(VI), and manganese(V) bearing Schiff base and simple anionic ligands

Nitrido complexes (M≡N) may be key intermediates in chemical and biological nitrogen fixation and serve as useful reagents for nitrogenation of organic compounds. Osmium(VI) nitrido complexes bearing 2,2':6',2″-terpyridine (terpy), 2,2'-bipyridine (bpy), or hydrotris(1-pyrazolyl)borate anion (Tp) ligands are highly electrophilic: they can react with a variety of nucleophiles to generate novel osmium(IV)/(V) complexes. This Account describes our recent results studying the reactivity of nitridocomplexes of ruthenium(VI), osmium(VI), and manganese(V) that bear Schiff bases and other simple anionic ligands. We demonstrate that these nitrido complexes exhibit rich chemical reactivity. They react with various nucleophiles, activate C-H bonds, undergo N···N coupling, catalyze the oxidation of organic compounds, and show anticancer activities. Ruthenium(VI) nitrido complexes bearing Schiff base ligands, such as [Ru(VI)(N)(salchda)(CH3OH)](+) (salchda = N,N'-bis(salicylidene)o-cyclohexyldiamine dianion), are highly electrophilic. This complex reacts readily at ambient conditions with a variety of nucleophiles at rates that are much faster than similar reactions using Os(VI)≡N. This complex also carries out unique reactions, including the direct aziridination of alkenes, C-H bond activation of alkanes and C-N bond cleavage of anilines. The addition of ligands such as pyridine can enhance the reactivity of [Ru(VI)(N)(salchda)(CH3OH)](+). Therefore researchers can tune the reactivity of Ru≡N by adding a ligand L trans to nitride: L-Ru≡N. Moreover, the addition of various nucleophiles (Nu) to Ru(VI)≡N initially generate the ruthenium(IV) imido species Ru(IV)-N(Nu), a new class of hydrogen-atom transfer (HAT) reagents. Nucleophiles also readily add to coordinated Schiff base ligands in Os(VI)≡N and Ru(VI)≡N complexes. These additions are often stereospecific, suggesting that the nitrido ligand has a directing effect on the incoming nucleophile. M≡N is also a potential platform for the design of new oxidation catalysts. For example, [Os(VI)(N)Cl4](-) catalyzes the oxidation of alkanes by a variety of oxidants, and the addition of Lewis acids greatly accelerates these reactions. [Mn(V)(N)(CN)4]2(-) is another highly efficient oxidation catalyst, which facilitates the epoxidation of alkenes and the oxidation of alcohols to carbonyl compounds using H2O2. Finally, M≡N can potentially bind to and exert various effects on biomolecules. For example, a number of Os(VI)≡N complexes exhibit novel anticancer properties, which may be related to their ability to bind to DNA or other biomolecules.

Reactivity with electrophiles of imido groups supported on trinuclear titanium systems

Several trinuclear titanium complexes bearing amido μ-NHR, imido μ-NR, and nitrido μn-N ligands have been prepared by reaction of [{Ti(η(5)-C5Me5)(μ-NH)}3(μ3-N)] (1) with 1 equiv of electrophilic reagents ROTf (R = H, Me, SiMe3; OTf = OSO2CF3). Treatment of 1 with triflic acid or methyl triflate in toluene at room temperature affords the precipitation of compounds [Ti3(η(5)-C5Me5)3(μ3-N)(μ-NH)2(μ-NH2)(OTf)] (2) or [Ti3(η(5)-C5Me5)3(μ3-N)(μ-NH)(μ-NH2)(μ-NMe)(OTf)] (3). Complexes 2 and 3 exhibit a fluxional behavior in solution consisting of proton exchange between μ-NH2 and μ-NH groups, assisted by the triflato ligand, as could be inferred from a dynamic NMR spectroscopy study. Monitoring by NMR spectroscopy the reaction course of 1 with MeOTf allows the characterization of the methylamido intermediate [Ti3(η(5)-C5Me5)3(μ3-N)(μ-NH)2(μ-NHMe)(OTf)] (4), which readily rearranges to give 3 by a proton migration from the NHMe amido group to the NH imido ligands. The treatment of 1 with 1 equiv of Me3SiOTf produces the stable ionic complex [Ti3(η(5)-C5Me5)3(μ3-N)(μ-NH)2(μ-NHSiMe3)][OTf] (5) with a disposition of the nitrogen ligands similar to that of 4. Complex 5 reacts with 1 equiv of [K{N(SiMe3)2}] at room temperature to give [Ti3(η(5)-C5Me5)3(μ3-N)(μ-N)(μ-NH)(μ-NHSiMe3)] (6), which at 85 °C rearranges to the trimethylsilylimido derivative [Ti3(η(5)-C5Me5)3(μ3-N)(μ-NH)2(μ-NSiMe3)] (7). Treatment of 7 with [K{N(SiMe3)2}] affords the potassium derivative [K{(μ3-N)(μ3-NH)(μ3-NSiMe3)Ti3(η(5)-C5Me5)3(μ3-N)}] (8), which upon addition of 18-crown-6 leads to the ion pair [K(18-crown-6)][Ti3(η(5)-C5Me5)3(μ3-N)(μ-N)(μ-NH)(μ-NSiMe3)] (9). The X-ray crystal structures of 2, 5, 6, and 8 have been determined.

Copper(I) and silver(I) complexes supported by the tridentate [{Ti(η(5)-C5Me5)(μ-NH)}3(μ3-N)] metalloligand

Copper(I) and silver(I) ionic compounds [(L)M{(μ(3)-NH)(3)Ti(3)(η(5)-C(5)Me(5))(3)(μ(3)-N)}][O(3)SCF(3)] containing [MTi(3)N(4)] cube-type cations have been prepared by reaction of [(CF(3)SO(2)O)M{(μ(3)-NH)(3)Ti(3)(η(5)-C(5)Me(5))(3)(μ(3)-N)}] (M = Cu (2), Ag (3)) with a variety of donor molecules L. Treatment of complexes 2 and 3 with NH(3) in toluene at room temperature gives the ammonia adducts [(H(3)N)M{(μ(3)-NH)(3)Ti(3)(η(5)-C(5)Me(5))(3)(μ(3)-N)}][O(3)SCF(3)] (M = Cu (4), Ag (5)), whose X-ray crystal structures reveal two cube-type cations associated through hydrogen bonding interactions between the ammine ligands and one oxygen atom of each trifluoromethanesulfonate anion. Analogous treatment of 2 and 3 with 1 equiv of pyridine, 2,6-dimethylphenylisocyanide, tert-butylisocyanide, or triphenylphosphane gives the ionic compounds [(L)M{(μ(3)-NH)(3)Ti(3)(η(5)-C(5)Me(5))(3)(μ(3)-N)}][O(3)SCF(3)] (L = py, M = Cu (6), Ag (7); L = CNAr, M = Cu (8), Ag (9); L = CNtBu, M = Cu (10), Ag (11); L = PPh(3), M = Cu (12), Ag (13)). The reactions of 2 and 3 with methylenebis(diphenylphosphane) (dppm) in a 1:1 ratio lead to the single-cube complexes [(dppm)M{(μ(3)-NH)(3)Ti(3)(η(5)-C(5)Me(5))(3)(μ(3)-N)}][O(3)SCF(3)] (M = Cu (14), Ag (15)), whereas in a 2:1 ratio give the bisphosphane-bridged double-cube compounds [{M(μ(3)-NH)(3)Ti(3)(η(5)-C(5)Me(5))(3)(μ(3)-N)}(2)(μ-dppm)][O(3)SCF(3)](2) (M = Cu (16), Ag (17)). Similarly, treatment of 2 or 3 with a half equivalent of ethane-1,2-diylbis(diphenylphosphane) (dppe) affords double-cube derivatives [{M(μ(3)-NH)(3)Ti(3)(η(5)-C(5)Me(5))(3)(μ(3)-N)}(2)(μ-dppe)][O(3)SCF(3)](2) (M = Cu (18), Ag (19)). The X-ray crystal structures of 4, 5, 10, 14, 15, and 18 have been determined.

Electrophilic attack on trinuclear titanium imido-nitrido systems

Alkylation of [{Ti(η(5)-C(5)Me(5))(μ-NH)}(3)(μ(3)-N)] with MeOTf occurs at the imido ligands to produce the methylamido derivative [Ti(3)(η(5)-C(5)Me(5))(3)(μ(3)-N)(μ-NH)(2)(μ-NHMe)(OTf)] which readily rearranges to form the methylimido complex [Ti(3)(η(5)-C(5)Me(5))(3)(μ(3)-N)(μ-NH)(μ-NH(2))(μ-NMe)(OTf)].

Observation of the inverse trans influence (ITI) in a uranium(V) imide coordination complex: an experimental study and theoretical evaluation

An inverse trans influence has been observed in a high-valent U(V) imide complex, [(((Ad)ArO)(3)N)U(NMes)]. A thorough theoretical evaluation has been employed in order to corroborate the ITI in this unusual complex. Computations on the target complex, [(((Ad)ArO)(3)N)U(NMes)], and the model complexes [(((Me)ArO)(3)N)U(NMes)] and [(NMe(3))(OMe(2))(OMe)(3)U(NPh)] are discussed along with synthetic details and supporting spectroscopic data. Additionally, the syntheses and full characterization data of the related U(V) trimethylsilylimide complex [(((Ad)ArO)(3)N)U(NTMS)] and U(IV) azide complex [(((Ad)ArO)(3)N)U(N(3))] are also presented for comparison.

A new double-cube nitride complex containing titanium and potassium

The reaction of the imide-nitride complex [{Ti(η(5)-C(5)Me(5))(μ-NH)}(3)(μ(3)-N)] with potassium iodide in pyridine at room temperature affords the adduct di-μ-iodido-1:1'κ(4)I-bis{tri-μ(3)-imido-1:2:3κ(3)N;1:2:4κ(3)N;1:3:4κ(3)N-μ(3)-nitrido-2:3:4κ(3)N-tris[2,3,4(η(5))-pentamethylcyclopentadienyl](pyridine-1κN)-tetrahedro-potassiumtrititanium(IV)}, [K(2)Ti(6)(C(10)H(15))(6)I(2)N(2)(NH)(6)(C(5)H(5)N)(2)] or [(C(5)H(5)N)(μ-I)K{(μ(3)-NH)(3)Ti(3)(η(5)-C(5)Me(5))(3)(μ(3)-N)}](2). The crystal structure contains two [KTi(3)N(4)] cube-type units held together by two bridging I atoms. There is a centre of inversion located in the middle of this unprecedented discrete K(2)I(2) unit. The geometry around K is best described as distorted trigonal prismatic, with three imide groups, two bridging I atoms and one pyridine ligand.