Transition metal complexes of the naked pnictide elements

Inorganic-organic hybrid Cu-dipyridyl semiconducting polymers based on the redox-active cluster [SFe3(CO)9]2-: filling the gap in iron carbonyl chalcogenide polymers

The construction of sulfur-incorporated cluster-based coordination polymers was limited and underexplored due to the lack of efficient synthetic routes. Herein, we report facile mechanochemical ways toward a new series of SFe3(CO)9-based dipyridyl-Cu polymers by three-component reactions of [Et4N]2[SFe3(CO)9] ([Et4N]2[1]) and [Cu(MeCN)4][BF4] with conjugated or conjugation-interrupted dipyridyl ligands, 1,2-bis(4-pyridyl)ethylene (bpee), 1,2-bis(4-pyridyl)ethane (bpea), 4,4'-dipyridyl (dpy), or 1,3-bis(4-pyridyl)propane (bpp), respectively. X-ray analysis showed that bpee-containing 2D polymers demonstrated unique SFe3(CO)9 cluster-armed and cluster-one-armed coordination modes via the hypervalent μ5-S atom. These S-Fe-Cu polymers could undergo flexible structural transformations with the change of cluster bonding modes by grinding with stoichiometric amounts of dipyridyls or 1/[Cu(MeCN)4]+. They exhibited semiconducting behaviors with low energy gaps of 1.55-1.79 eV and good electrical conductivities of 3.26 × 10-8-1.48 × 10-6 S cm-1, tuned by the SFe3(CO)9 cluster bonding modes accompanied by secondary interactions in the solid state. The electron transport efficiency of these polymers was further elucidated by solid-state packing, X-ray photoelectron spectroscopy (XPS), X-ray absorption near-edge spectroscopy (XANES), density of states (DOS), and crystal orbital Hamilton population (COHP) analysis. Finally, the solid-state electrochemistry of these polymers demonstrated redox-active behaviors with cathodically-shifted patterns compared to that of [Et4N]2[1], showing that their efficient electron communication was effectively enhanced by introducing 1 and dipyridyls as hybrid ligands into Cu+-containing networks.

Synthesis and Characterization of Novel Cobalt Carbonyl Phosphorus and Arsenic Clusters

Phosphorus- and arsenic-containing cobalt clusters are an interesting class of compounds that continue to provide new structures with captivating bonding patterns. Although the first members of this family were reported 45 years ago, the number of such species is still limited within the broad family of transition metal complexes bearing pnictogen atoms. Herein, we present the reaction of Co2(CO)8 as a cobalt source with a number of phosphorus- and arsenic-containing compounds under variable reaction conditions. These reactions result in various known and novel cobalt phosphorus and cobalt arsenic clusters in which different nuclearity ratios between P/As and Co exist. All those clusters were characterized by X-ray structural analysis and partly by IR, 31P{1H} NMR, EI-MS and elemental analysis. This comprehensive study is the first detailed study in this field that reveals the richness of compounds that could be obtained only by modifying the ratio of used reactants and the involved reaction conditions.

Supramolecular compounds assembled from the heteroleptic tetrahedral complex [{CpMo(CO)2}2(μ,η2-AsSb)] and metal salts

The reaction of the tetrahedral complex [{CpMo(CO)2}2(μ,η2-AsSb)] with CuI and AgI salts is presented which gives unprecedented neutral and cationic supramolecular aggregates featuring mixed As/Sb-donor molecules as ligands/linkers between metal ions.

Novel synthetic route towards heteroleptic pnictogen-rich organometallic-inorganic coordination compounds

The reaction of the Ag(I) dimer [Ag2(η2-A)2(μ,η1:η1-A)2][TEF]2 (A = [{CpMo(CO)2}2(μ,η2-P2)]) possessing labile η2-coordinated P2 ligands with the organometallic dipnictogen compounds [{CpMo(CO)2}2(μ,η2-EE')] (E = E' = As, Sb; E = P, E' = As, Sb) represents a facile synthetic route towards unprecedented heteroleptic pnictogen-rich supramolecular complexes. This method can also be extended to the analogous Cu(I) dimer and is studied by DFT computations.

Dimeric polybismuth heteroanion of [Rh@Bi10(RhCO)5]2- constructed using Bi10-bowl and square pyramidal Rh@(Rh-CO)5

Redox reaction of the monovalent Rh2(CO)4Cl2 and Binn- (n = 2, 3) from K5Bi4 in ethylenediamine (en) solution produced the decabismuthide-hexarhodium dianion [Rh@Bi10(RhCO)5]2- (1a) wherein a novel Bi10-bowl was constructed from oxidized 2Bi3/2Bi2 open triangles/dimers, which was stabilized by strong bonding to a reduced Rh@(RhCO)5 square pyramid. Two 1a dianons are held together by weak interactions (van der Waals forces and spatial resistance) to form a dimer [Rh@Bi10(RhCO)5]24- (1). The structure and bonding of the novel polybismuthide heteroanion 1 are discussed.

Unusual cleavage of phosphaalkynes triple bond in the coordination sphere of transition metals

The reaction of RCP (R = Me, tBu, iPr) with Co2(CO)8 and Fe2(CO)9 under mild conditions led to unpredictable fragmentations of the CP triple bond and subsequent formation of clusters with a dimeric Co3E (E = P and RC) and an Fe3P(CR) core, respectively.

From Small Metal Clusters to Molecular Nanoarchitectures with a Core-Shell Structure: The Synthesis, Redox Fingerprint, Theoretical Analysis, and Solid-State Structure of [Co38As12(CO)50]4

The cluster [Co₃₈As₁₂(CO)₅₀]^4- was obtained by pyrolysis of [Co₆As(CO)₁₆]^-. The metal cage features a closed-packed core inside a Co/As shell that progressively deforms from a cubic face-centered symmetry. The redox and acid-base reactivities were determined by cyclic voltammetry and spectrophotometric titrations. The calculated electron density revealed the shell-constrained distribution of the atomic charges, induced by the presence of arsenic.

Synthesis of polyantimony ligand complexes starting from Cp*4Sb4

The reactivity of Cp*₄Sb₄ (1) towards ionic compounds and transition metal complexes with labile ligands was investigated in order to synthesize polyantimony ligand complexes. The silver salts [Ag][X] and the metalate Na[Cp*Mo(CO)₃] were primarily used, leading in the raction with Cp*₄Sb₄ to the formation of [Cp*₂Sb][X] (X = TEF (2a), FAL (2b)), [(Cp*Mo(CO)₃)₃(μ₃-Sb₃)] (3) and [Cp*Mo(CO)₂(η³-Sb₃)] (4), respectively. The reaction of 1 with the transition metal complexes [(Cp'''M)₂(tol)] leads to a degradation of the original Sb₄ unit and to the formation of [(Cp'''M)₄(μ₃-Sb)₄] (M = Ni (5); Co (6)). Towards [Cp^RFe(CO)₂]₂, substitutions on the antimony atoms were observed to give [{Cp^RFe(CO)₂}₄(μ₄-Sb₄)] (Cp^R = Cp'' (7a), Cp''' (7b)). All complexes were characterized by XRD and spectroscopic methods.

Structure-Property Relationships of Inorganic-Organic Hybrid Semiconducting Se-Fe-Cu-CO Polymers

A novel family of inorganic-organic-hybrid SeFe₃(CO)₉-dipyridyl two- and one-dimensional Cu polymers was synthesized via the three-component liquid-assisted grinding (LAG) of [Cu(MeCN)₄]⁺, inorganic cluster [SeFe₃(CO)₉]^2- (1), and rigid conjugated dipyridyls 4,4'-dipyridyl (dpy) and 1,2-bis(4-pyridyl)ethylene (bpee) or flexible conjugation-interrupted dipyridyls 1,2-bis(4-pyridyl)ethane (bpea) and 1,3-bis(4-pyridyl)propane (bpp). They included a cluster-linked 2D polymer, [(μ₄-Se)Fe₃(CO)₉Cu₂(MeCN)(dpy)_1.5]_n (1-dpy-2D), a cluster-pendant 1D chain, [(μ₃-Se)Fe₃(CO)₉Cu₂(dpy)₃]_n (1-dpy-1D), cluster-blocked 1D polymers, [(μ₃-Se)Fe₃(CO)₉Cu₂(L)]_n (1-L-1D, L = bpee, bpea), and a cluster-linked 2D polymer, [(μ₄-Se)Fe₃(CO)₉Cu₂(bpp)₂]_n (1-bpp-2D). The reversible dimensionality transformations of these three types of polymers accompanied by the change in coordination modes of 1 were achieved by the LAG addition of 1/[Cu(MeCN)₄]⁺ or dipyridyl ligands. These polymers were found to possess tunable low-energy gaps (1.49-1.72 eV) that increased in the order regarding their structural features: cluster-linked 1-dpy-2D and 1-bpp-2D, cluster-blocked 1-bpea-1D and 1-bpee-1D, and cluster-pendant 1-dpy-1D and [(μ₃-Se)Fe₃(CO)₉Cu₂(L)_2.5]_n (L = bpee, 1-bpee-2D; bpea, 1-bpea-2D), indicative of the importance of the participation of cluster 1. The measured electrical conductivities of 1-bpp-2D, 1-bpea-1D, and 1-dpy-1D were 3.13 × 10^-7, 2.92 × 10^-7, and 2.30 × 10^-7 S·cm^-1, respectively, which were parallel for the trend in their energy gaps, revealing semiconducting behaviors, supported by XPS, XANES, and DFT calculations. The surprising semiconductivity of the conjugation-interrupted bpp-linked 1-bpp-2D was mainly ascribed to electron transport via C-H···O(carbonyl) hydrogen bonds and aromatic C-H···π contacts within its closely packed 2D layers. Water-/light-stable polymers 1-bpp-2D, 1-bpea-2D, and 1-dpy-1D were also demonstrated to exhibit excellent pseudo-first-order photodegradation toward nitroaromatics and organic dyes, where cluster-linked polymer 1-bpp-2D performed the best, as predicted by its structural features and narrow energy gap.

Electronic Structure and Donor Ability of an Unsaturated Triphosphorus-Bridged Dimolybdenum Complex

The triphosphorus complex [Mo₂Cp₂(μ-η³:η³-P₃)(μ-P^tBu₂)] was prepared in 83% yield by reacting the methyl complex [Mo₂Cp₂(μ-κ¹:η²-CH₃)(μ-P^tBu₂)(μ-CO)] with P₄ at 333 K, a process also giving small amounts of the methyldiphosphenyl complex [Mo₂Cp₂(μ-η²:η²-P₂Me)(μ-P^tBu₂)(CO)₂]. The latter could be better prepared by first reacting the anionic complex Na[Mo₂Cp₂(μ-P^tBu₂)(μ-CO)₂] with P₄ to give the diphosphorus derivative Na[Mo₂Cp₂(μ-η²:η²-P₂)(μ-P^tBu₂)(CO)₂] and further reaction of the latter with MeI. Density functional theory calculations on the title complex revealed that its triphosphorus group can be viewed as an allylic-like P₃^- ligand acting as a six-electron donor via the external P atoms, while coordination of the internal P atom involves donation from the π orbital of the ligand and back-donation to its π* orbital, both interactions having a weakening effect on the Mo-Mo and P-P connections. The reactivity of the title compound is dominated by the electron-donor ability associated with the lone pairs located at the P atoms. Its reaction with CF₃SO₃Me gave [Mo₂Cp₂(μ-η³:η³-P₃Me)(μ-P^tBu₂)](CF₃SO₃) as a result of methylation at an external atom of the P₃ ligand, while its reaction with [Fe₂(CO)₉] enabled the addition of one, two, or three Fe(CO)₄ fragments at these P atoms, but only the diiron derivative [Mo₂Fe₂Cp₂(μ-η³:η³:κ¹:κ¹-P₃)(μ-P^tBu₂)(CO)₈] could be isolated. This complex bears a Fe(CO)₄ fragment at each of the external atoms of the P₃ ligand, and the central P atom of the latter displays the lowest ³¹P chemical shift reported to date (δ_P -721.8 ppm). The related complexes [Mo₂M₂Cp₂(μ-η³:η³:κ¹:κ¹-P₃)(μ-P^tBu₂)(CO)₁₀] (M = Mo, W) were prepared by reacting the title compound with the corresponding [M(CO)₅(THF)] complexes in toluene, while reaction with [Mo(CO)₄(THF)₂] also enabled the formation of the heptanuclear derivative [Mo₇Cp₄(μ-η³:η³:κ¹:κ¹-P₃)₂(μ-P^tBu₂)₂(CO)₁₄]. The interatomic distances in the above compounds indicate that the central Mo₂P₃ skeleton of these molecules is little modified by the attachment of 16-electron M(CO)_n fragments at the external atoms of the P₃ ligand.

Metal carbonyl clusters of groups 8-10: synthesis and catalysis

In this review article, we discuss advances in the chemistry of metal carbonyl clusters (MCCs) spanning the last three decades, with an emphasis on the more recent reports and those involving groups 8-10 elements. Synthetic methods have advanced and been refined, leading to higher-nuclearity clusters and a wider array of structures and nuclearities. Our understanding of the electronic structure in MCCs has advanced to a point where molecular chemistry tools and other advanced tools can probe their properties at a level of detail that surpasses that possible with other nanomaterials and solid-state materials. MCCs therefore advance our understanding of structure-property-reactivity correlations in other higher-nuclearity materials. With respect to catalysis, this article focuses only on homogeneous applications, but it includes both thermally and electrochemically driven catalysis. Applications in thermally driven catalysis have found success where the reaction conditions stabilise the compounds toward loss of CO. In more recent years, MCCs, which exhibit delocalised bonding and possess many electron-withdrawing CO ligands, have emerged as very stable and effective for reductive electrocatalysis reactions since reduction often strengthens M-C(O) bonds and since room-temperature reaction conditions are sufficient for driving the electrocatalysis.

Versatile Coordination of AgI and CuI Ions towards cyclo-As5 Ligands

The reactions of the cyclo‐As₅ complex [Cp*Fe(η⁵‐As₅)] (B) with the Ag^I and Cu^I salts of the weakly coordinating anion (WCA) [FAl{OC₆F₁₀(C₆F₅)}₃]⁻ ([FAl]⁻) are studied. These reactions allow the synthesis of the mononuclear complexes [M(η⁵ : η²‐B)₂][FAl] (M=Ag (1), Cu (2)) when a ratio of B/M(FAl) 2 : 1 is used. Compound 1 shows an unusual disorder of the central Ag^I cation between two π‐coordinating cyclo‐As₅ ligands, which is absent in 2 pointing to a weak interaction of the Ag center towards the cyclo‐As₅ ligands in B. When the ratio of B/Ag(FAl) is changed to 3 : 1 or 1 : 1, the respective coordination compounds [Ag(η²‐B)₃][FAl] (3) and [Ag₂(η² : η²‐B)₂][FAl]₂ (4) are accessible. The coordination modes of the cyclo‐As₅ units in 1, 3 and 4 are all different, reflecting the adaptive coordination behavior of B towards Ag^I ions. The optimized geometries in the gas phase of 1–4 are determined by DFT calculations to support the bonding situation observed in their solid‐state structures.

Infrared photodissociation spectroscopy of heteronuclear group 15 metal-iron carbonyl cluster anions AmFe(CO)n- (A = Sb, Bi; m, n = 2, 3)

Heteronuclear group 15 metal-iron carbonyl cluster complexes of A_mFe(CO)_n^- (A = Sb, Bi; m, n = 2-3) were generated in the gas phase and studied by infrared photodissociation spectroscopy in the carbonyl stretching region. Their structures were determined by comparing the experimental spectra with predicted spectra derived from DFT calculations at the B3LYP and BP86 levels. All of the A_mFe(CO)_n^- cluster anions were determined to have Fe(CO)_n^- fragments with all of the CO ligands terminally bonded to the iron center, and they can be regarded as being formed via the interactions of the neutral group 15 metal clusters with the Fe(CO)_n^- fragments. Bonding analyses indicated that each A₂Fe(CO)_n^- (n = 2, 3) cluster anion contained two A-Fe single bonds and one A-A double bond. Each A₃Fe(CO)_n^- (n = 2, 3) cluster anion involved three A-Fe single bonds and three A-A single bonds. There is an isolobal relationship between the Fe(CO)₃^- group and the group 15 atoms. The substitution of an Fe(CO)₃^- group in place of one A atom in the tetrahedral A₄ molecule resulted in an A₃Fe(CO)₃^- cluster anion with the closed-shell electronic configuration for all the group 15 metals and iron atoms.

Mechanism for the Reaction of White Phosphorus with Cp2Cr2(CO)6 Leading Ultimately to the Triple-Decker Sandwich Cp2Cr2(μ-η5,η5-P5): A Theoretical Study

The experimentally known reaction of Cp₂Cr₂(CO)₆ with white phosphorus (P₄) to give CpCr(CO)₂(η³-P₃), Cp₂Cr₂(CO)₄(μ-η,²η²-P₂), and the triple-decker sandwich Cp₂Cr₂(μ-η,⁵η⁵-P₅) is of interest since the P₄ reactant having a tetrahedral cluster of four phosphorus atoms is converted to products having P₂, P₃, and P₅ ligands. The mechanism of this obviously complicated reaction can be dissected into three stages using a coupled cluster theoretical method that has been benchmarked with the P₂, Mn(CO)₅, and CpCr(CO)₃ dimerization processes. The first stage of the Cp₂Cr₂(CO)₆/P₄ reaction mechanism generates the unsaturated singlet intermediate Cp₂Cr₂(CO)₅ that combines with the P₄ reactant. Decarbonylation of the resulting Cp₂Cr₂(CO)₅(P₄) complex provides a singlet tetracarbonyl readily fragmenting into the stable triphosphacyclopropenyl complex CpCr(CO)₂(η³-P₃) and the chromium phosphide CpCr(CO)₂(P). The isomeric triplet tetracarbonyl Cp₂Cr₂(CO)₄(P₄), readily fragments into CpCr(CO)₂(η²-P₂), which can generate the stable diphosphaacetylene complex Cp₂Cr₂(CO)₄(η,²η²-P₂) as well as the pentamer [CpCr(CO)₂]₅(P₁₀). Combination of the coordinately unsaturated CpCr(CO)(η³-P₃) with CpCr(CO)₂(η²-P₂) can lead to a ring expansion. This generates the P₅ pentagonal ligand in a Cp₂Cr₂(CO)₃(P₅) precursor to the experimentally observed carbonyl-free triple-decker sandwich Cp₂Cr₂(μ-η,⁵η⁵-P₅) after three successive decarbonylations.

Mixed Organometallic-Organic Hybrid Assemblies Based on the Diarsene Complex [Cp2 Mo2 (CO)4 (μ,η2 -As2 )], AgI Salts and N-Donor Organic Molecules

The reaction of the organometallic diarsene complex [Cp2 Mo2 (CO)4 (η2 -As2 )] (1) with Ag[Al{OC(CF3 )3 }4 ] (Ag[TEF]) yielded the AgI monomer [Ag(η2 -1)3 ][TEF] (2). This compound exhibits dynamic behavior in solution, which allows directed selective synthesis of unprecedented organometallic-organic hybrid assemblies upon its reaction with N-donor organic molecules by a stepwise pathway, which is supported by DFT calculations. Accordingly, the reaction of 2 with 2,2'-bipyrimidine (L1) yielded the dicationic molecular compound [{(η2 -1)2 Ag}2 (μ-L1)][TEF]2 (3) or the 1D polymer [{(η2 -1)Ag}(μ-L1)]n [TEF]n (4) depending on the ratio of the reactants. However, its reactions with the pyridine-based linkers 4,4'-bipyridine (L2), 1,2-bis(4-pyridyl)ethylene (L3) and 1,2-bis(4-pyridyl)ethyne (L4) allowed the formation of the 2D polymers [{(η2 -1)Ag}2 (μ-Lx)3 ]n [TEF]2n [Lx=L2 (5), L3 (6), L4 (7), respectively]. Additionally, this concept was extended to step-by-step one-pot reactions of 1, [Ag(CH3 CN)3 ][Al{OC(CF3 )2 (CCl3 )}4 ] ([Ag(CH3 CN)3 ][TEFCl ]) and linkers L2-L4 to produce the 2D polymers [{(η2 -1)Ag}2 (μ,Lx)3 ]n [TEFCl ]2n [Lx=L2 (8), L3 (9), L4 (10), respectively].

Coordination Behavior of a P4 -Butterfly Complex towards Transition Metal Lewis Acids: Preservation versus Rearrangement

The reactivity of the P4 butterfly complex [{Cp'''Fe(CO)2 }2 (μ,η1:1 -P4 )] (1, Cp'''=η5 -C5 H2 tBu3 ) towards divalent Co, Ni and Zn salts is investigated. The reaction with the bromide salts leads to [{Cp'''Fe(CO)2 }2 (μ3 ,η2:1:1 -P4 ){MBr2 }] (M=Co (2Co), Ni (2Ni), Zn (2Zn)) in which the P4 butterfly scaffold is preserved. The use of the weakly ligated Co complex [Co(NCCH3 )6 ][SbF6 ]2 , results in the formation of [{(Cp'''Fe(CO)2 )2 (μ3 ,η4:1:1 -P4 )}2 Co][SbF6 ]3 (3), which represents the second example of a homoleptic-like octaphospha-metalla-sandwich complex. The formation of the threefold positively charged complex 3 occurs via redox processes, which among others also enables the formation of [{Cp'''Fe(CO)2 }4 (μ5 ,η4:1:1:1:1 -P8 ){Co(CO)2 }][SbF6 ] (4), bearing a rare octaphosphabicyclo[3.3.0]octane unit as a ligand. On the other hand, the reaction with [Zn(NCCH3 )4 ][PF6 ]2 yields the spiro complex [{(Cp'''Fe(CO)2 )2 (μ3 ,η2:1:1 -P4 )}2 Zn][PF6 ]2 (5) under preservation of the initial structural motif.

Discrete and polymeric organometallic-organic assemblies based on the diarsene complex [(Cp)2Mo2(CO)4(μ,η2-As2)], AgPF6 and N-donor organic molecules

The first mixed-ligand self-assembly reactions of the diarsene complex [Cp₂Mo₂(CO)₄(μ,η²-As₂)] and N-donor organic molecules in the presence of AgPF₆ allow for the synthesis of two discrete and four polymeric supramolecular aggregates.

The Potential of the Diarsene Complex [(C5 H5 )2 Mo2 (CO)4 (μ,η2 -As2 )] as a Connector Between Silver Ions

The reaction of the organometallic diarsene complex [Cp₂Mo₂(CO)₄(μ,η²‐As₂)] (B) (Cp = C₅H₅) with Ag[FAl{OC₆F₁₀(C₆F₅)}₃] (Ag[FAl]) and Ag[Al{OC(CF₃)₃}₄] (Ag[TEF]), respectively, yields three unprecedented supramolecular assemblies [(η²‐B)₄Ag₂][FAl]₂ (4), [(μ,η¹:η²‐B)₃(η²‐B)₂Ag₃][TEF]₃ (5) and [(μ,η¹:η²‐B)₄Ag₃][TEF]₃ (6). These products are only composed of the complexes B and Ag^I. Moreover, compounds 5 and 6 are the only supramolecular assemblies featuring B as a linking unit, and the first examples of [Ag^I]₃ units stabilized by organometallic bichelating ligands. According to DFT calculations, complex B coordinates to metal centers through both the As lone pair and the As−As σ‐bond thus showing this unique feature of this diarsene ligand.

Low-Valent, Multiply Bonded, Trigonal-Planar Sb Complex: Rational Syntheses, Dual Acidic/Basic Properties, and Unexpected Semiconducting Characteristics

A 4-center, 6π-conjugated, multiply bonded trigonal-planar complex, [Sb{Cr(CO)₅}₃]^- (1), was synthesized via the hydride abstraction of [HSb{Cr(CO)₅}₃]^2- (1-H) with HBF₄·H₂O, with the release of high yields of H₂. The oxidation state of the Sb atom in [Et₄N][1] was well-defined as 0, which was evidenced by X-ray photoelectron spectroscopy and X-ray absorption near-edge structure. The distinct color-structure relationship of this low-valent Sb complex 1 toward a wide range of organic solvents was demonstrated, as interpreted by time-dependent density functional theory calculations, allowing the trigonal-planar 1 and the tetrahedral solvent adducts to be probed, revealing the dual acid/base properties of the Sb center. In addition, 1 showed pronounced electrophilicity toward anionic and neutral nucleophiles, even with solvent molecules, to produce tetrahedral complexes [(Nu)Sb{Cr(CO)₅}₃]^n- [1-Nu; n = 2, Nu = H, F, Cl, Br, I, OH; n = 1, Nu = PEt₃, PPh₃, N,N-dimethylformamide (DMF), acetonitrile (MeCN)]. On the contrary, the Fe/Cr hydride complex [HSb{Fe(CO)₄}{Cr(CO)₅}₂]^2- (2-H) was obtained by treating 1 with [HFe(CO)₄]^-. Upon hydride abstraction of 2-H with HBF₄·H₂O or [CPh₃][BF₄], a multiply bonded Fe/Cr trigonal-planar complex, [Sb{Fe(CO)₄}{Cr(CO)₅}₂]^- (2), was produced in which the oxidation coupling Sb₂-containing complexes [Sb₂Cr₄Fe₂(CO)₂₈]^2- (3-Cr) and [HSb₂Cr₃Fe₂(CO)₂₃]^- (3-H) were yielded as final products. Complex 3-Cr exhibited dual Lewis acid/base properties via hydridation and protonation reactions, to form 2-H or 3-H, respectively. Surprisingly, [Et₄N][1] possessed a low energy gap of 1.13 eV with an electrical conductivity in the range of (1.10-2.77) × 10^-6 S·cm^-1, showing that [Et₄N][1] was a low-energy-gap semiconductor. The crystal packing, crystal indexing, and density of states results of [Et₄N][1] further confirmed the efficient through-space conduction pathway via the intermolecular Sb···O(carbonyl) and O(carbonyl)···O(carbonyl) interactions of the 1D anionic zigzag chain of 1.

Structural Diversity in Molecular Nickel Phosphide Carbonyl Nanoclusters

The reaction of [Ni₆(CO)₁₂]^2– as a [NBu₄]⁺ salt in CH₂Cl₂ with 0.8 equiv of PCl₃ afforded [Ni₁₄P₂(CO)₂₂]^2–. In contrast, the reactions of [Ni₆(CO)₁₂]^2– as a [NEt₄]⁺ salt with 0.4–0.5 equiv of POCl₃ afforded [Ni_22–xP₂(CO)_29–x]^4– (x = 0.84) or [Ni₃₉P₃(CO)₄₄]^6– by using CH₃CN and thf as a solvent, respectively. Moreover, by using 0.7–0.9 mol of POCl₃ per mole of [NEt₄]₂[Ni₆(CO)₁₂] both in CH₃CN and thf, [Ni_23–xP₂(CO)_30–x]^4– (x = 0.82) was obtained together with [Ni₂₂P₆(CO)₃₀]^2– as a side product. [Ni_23–xP₂(CO)_30–x]^4– (x = 0.82) and [Ni₂₂P₆(CO)₃₀]^2– were separated owing to their different solubility in organic solvents. All the new molecular nickel phosphide carbonyl nanoclusters were structurally characterized through single crystal X-ray diffraction (SC-XRD) as [NBu₄]₂[Ni₁₄P₂(CO)₂₂] (two different polymorphs, P2₁/n and C2/c), [NEt₄]₄[Ni_23–xP₂(CO)_30–x]·CH₃COCH₃·solv (x = 0.82), [NEt₄]₂[Ni₂₂P₆(CO)₃₀]·2thf, [NEt₄]₄[Ni_22–xP₂(CO)_29–x]·2CH₃COCH₃( x = 0.84) and [NEt₄]₆[Ni₃₉P₃(CO)₄₄]·C₆H₁₄·solv. The metal cores’ sizes of these clusters range from 0.59 to 1.10 nm, and their overall dimensions including the CO ligands are 1.16–1.63 nm. In this respect, they are comparable to ultrasmall metal nanoparticles, molecular nanoclusters, or atomically precise metal nanoparticles. The environment of the P atoms within these molecular Ni–P–CO nanoclusters displays a rich diversity, that is, Ni₅P pentagonal pyramid, Ni₇P monocapped trigonal prism, Ni₈P bicapped trigonal prism, Ni₉P monocapped square antiprism, Ni₁₀P sphenocorona, Ni₁₀P bicapped square antiprism, and Ni₁₂P icosahedron.

Five new molecular nickel phosphide carbonyl clusters have been obtained displaying overall sizes in the range 1.16−1.63 nm and very diverse environments for the phosphide atoms.

Manganese Telluride Carbonyl Complexes: Facile Syntheses and Exotic Properties-Reversible Transformations, Hydrogen Generation, Paramagnetic, and Semiconducting Properties

A novel family of five Mn-Te-CO complexes was prepared via facile syntheses: mono spirocyclic [Mn₄Te(CO)₁₆]^2- (1), four-membered Mn₂Te₂ ring-type [Mn₂Te₂(CO)₈]^2- (2), hydride-containing square pyramidal [HMn₃Te₂(CO)₉]^2- (3), and dumbbell-shaped [Mn₆Te₆(CO)₁₈]^4- (4) and [Mn₆Te₁₀(CO)₁₈]^4- (5). Electron-precise complexes 4 and 5 exhibit unusual paramagnetism arising from two types of Mn atoms in different oxidation states, as determined by X-ray photoelectron spectroscopy, electron paramagnetic resonance, and density functional theory (DFT) calculations. The structural transformations from small-sized Mn₄Te 1 and Mn₂Te₂ 2 to the largest Mn₆Te₁₀ 5 were controllable, the off/on magnetic-switched transformation between HMn₃Te₂ 3 and 5 was reversible, and the magnetic transformation between Mn₆Te₆ 4 and 5 was observed. Interestingly, the reversible dehydridation and hydridation between the HMn₃Te₂-based cluster 3 and [Mn₃Te₂(CO)₉]^- were successfully accomplished, in which the release of a high yield of H₂ was detected by gas chromatography. In addition, upon the addition of CO, cluster 3 first forms a carbonyl-inserted intermediate [HMn₃Te₂(CO)₁₀]^2- (3'), detected by the high resolution ESI-MS, which is readily transformed to a dimeric dihydrido cluster [{HMn₃Te₂(CO)₁₀}₂]^2- (6) with the introduction of O₂. These low- to high-nuclearity complexes exhibit rich redox properties with semiconducting behavior in solids, possessing low but tunable energy gaps (1.06-1.62 eV) due to efficient electron transport via nonclassical C-H···O(carbonyl) interactions. The structural nature, reversible structural transformations, controllable on/off magnetic switches, electron communication networks, and associated chemical properties for hydrogen generation are discussed in detail and supported by DFT calculations, density of states, band structures, and noncovalent interaction analyses.

PSb+P Ligand: Platform for a Stibenium to Transition-Metal Interaction

The coordination chemistry of cationic divalent pnictogen ligands, such as nitrenium and phosphenium, has been well-explored in recent years. However, corresponding studies of a heavier congener, stibenium ion, are rare. To better facilitate a Sb⁺-metal interaction, a tridentate P-Sb⁺-P ligand with two phosphine buttresses was designed and synthesized, and its coordination chemistry toward late transition metals was investigated. The stibenium ligand was delivered as an activated P(SbCl)P-AgOTf complex (2) that releases AgCl and the P-Sb⁺-P ligand upon the treatment with transition metals. Reacting 2 with Rh(I) and Ir(I) metals yielded the anticipated stibenium-transition-metal complexes [(Rh(COD)Cl)₂(μ-PSb⁺P)] OTf ([3][OTf]) and [(Ir(COD)Cl)₂(μ-PSb⁺P)] OTf ([4][OTf]). The M-Sb⁺-M bridging structure was confirmed by single-crystal X-ray crystallography, and the bonding situation was examined computationally. Theoretical studies revealed the presence of three-center delocalized M-Sb⁺-M bonding interactions in [3][OTf] and [4][OTf].

The Potential of Molybdenum Complexes Bearing Unsubstituted Heterodiatomic Group 15 Elements as Linkers in Supramolecular Chemistry

The reactions of tetrahedral molybdenum complexes bearing unsubstituted heterodiatomic Group 15 elements, [Cp₂ Mo₂ (CO)₄ (μ,η² :η² -PE)] (Cp=C₅ H₅ ; E=As (1), Sb (2)), with Cu^I halides afforded seven unprecedented neutral supramolecular assemblies. Depending on the Mo₂ PE units and the Cu^I halide, the oligomers [⟨{Cp₂ Mo₂ (CO)₄ }{μ₄ ,η² :η² :η² :η¹ -PE}⟩₄ ⟨{CuX}{Cu(μ-X)}⟩₂ ] (E=As (X=Cl (3), Br (4)); E=Sb (X=Cl (6), Br (7))) or the 1D coordination polymers [{Cp₂ Mo₂ (CO)₄ }{μ₄ ,η² :η² :η¹ :η¹ -PAs}{Cu(μ-I)}]_n (5) and [{Cp₂ Mo₂ (CO)₄ }{μ₄ ,η² :η² :η² :η¹ -PSb}₂ {Cu(μ-X)}₃ ]_n (X=I (8), Br (9)) are accessible. These solid-state aggregates are the first and only examples featuring the organometallic heterodiatomic Mo₂ PE complexes 1 and 2 as linking moieties. DFT calculations demonstrate that complexes 1 and 2 present a unique class of mixed-donor ligands coordinating to Cu^I centers via the P lone pair and the P-E σ-bond, revealing an unprecedented coordination mode.

Antimony(i) → Pd(ii) complexes with the (μ-Sb)Pd2 coordination framework

The reaction of the antimony(i) compound ArSb (1) (where Ar = C₆H₃-2,6-(CH[double bond, length as m-dash]NtBu)₂) with various dimeric allyl palladium(ii) complexes [Pd(η³-allyl)(μ-X)]₂ (where allyl = C₃H₅ or C₃H₄Me; X = Cl or CF₃CO₂) in a 1 : 1 stoichiometric ratio gave unique complexes with the μ-ArSb moiety bridging two palladium fragments, i.e. [{Pd(η³-C₃H₅)Cl}₂(μ-ArSb)] (2), [{Pd(η³-C₃H₄Me)Cl}₂(μ-ArSb)] (3) and [{Pd(η³-C₃H₅)(CF₃CO₂)}₂(μ-ArSb)] (4). Compound 1 serves formally as a 4e donor in 2-4. The treatment of 2 with another equivalent of ArSb led to the formation of the [Pd(η³-C₃H₅)(Cl)(μ-ArSb)] complex (5), proving that 1 is able to function as a 2e donor in target complexes as well. The structures of 2-5 were described in detail both in solution (NMR and mass spectrometry) and in the solid state (single crystal X-ray diffraction analysis). DFT methods were used to compare bonding in the 1 : 1 (5) and 1 : 2 (2) complexes. Furthermore, a comprehensive ¹²¹Sb Mössbauer spectroscopic investigation of complexes 2 and 5 along with parent ArSbCl₂ (6) and 1 was performed. For comparison, complexes [Fe(CO)₄(ArSb)] (7) and [Mo(CO)₅(ArSb)] (8) were also included in this study.

The First Naked Bismuth-Chalcogen Metal Carbonyl Clusters: Extraordinary Nucleophilicity of the Bi Atom and Semiconducting Characteristics

Mixed bismuth-chalcogen-iron clusters [{EFe₃(CO)₉}Bi]^- [E = Te (1a) or Se (1b)] were produced via the reduction of BiCl₃ with [EFe₃(CO)₉]^2- under mild conditions. X-ray analysis showed that both clusters 1a and 1b had a square-pyramidal geometry, where the naked Bi and chalcogen both adopted a distorted trigonal-pyramidal configuration with a stereoactive lone pair. Complexes 1a and 1b can be further functionalized by methylation and metalation, which permits the nucleophilicity of the 6s/5s and 6s/4s lone pairs to be compared. In the metalation, the 6s pair of the Bi atom in 1a and 1b had an extraordinary nucleophilicity toward the unsaturated Cr(CO)₅ fragment, even in the presence of the more chemically active 5s or 4s pair, whereas in the case of methylation, only the 4s pair of Se could be selectively alkylated. Upon oxidation of 1a and 1b with suitable oxidizing agents, NaBiO₃ or K₂SeO₃, Bi-E bonded tetrahedral complexes [{EFe₂(CO)₆}Bi]^- [E = Te (4a) or Se (4b)] were formed by the elimination of one Fe(CO)₃ vertex. X-ray photoelectron spectroscopy, X-ray absorption near-edge structure, and density functional theory (DFT) calculations showed that all of the Bi atoms in these complexes had oxidation states close to +1. Due to the electropositive character of the Bi atom, pronounced induced Bi···E inter- and intramolecular interactions were evident in 1a (1b), 4a (4b), and the metalated 3a (3b), where their linear-like ···Bi···E··· or zigzag-like ···Bi-E··· (E = Te or Se) chain or the Bi···E···E···Bi (E = Te or Se) dimeric chain can further expand into the two-dimensional network via nonclassical C-H···O(carbonyl) interactions, supported by noncovalent interaction index and DFT calculations. These positively charged Bi-induced Bi···E (E = Te or Se) and carbonyl-aided weak interactions can facilitate efficient electron transport within these ternary Bi-E-Fe or quaternary Bi-E-Fe-Cr cluster-based frameworks, resulting in semiconducting behavior with surprising ultranarrow energy gaps of 1.01-1.21 eV.

The Triple-Decker Complex [Cp*Fe(µ,η⁵:η⁵-P₅)Mo(CO)₃] as a Building Block in Coordination Chemistry

Although the triple-decker complex [Cp*Fe(µ,η⁵:η⁵-P₅)Mo(CO)₃] (2) was first reported 26 years ago, its reactivity has not yet been explored. Herein, we report a new high-yielding synthesis of 2 and the isolation of its new polymorph (2’). In addition, we study its reactivity towards Ag^I and Cu^I ions. The reaction of 2 with Ag[BF₄] selectively produces the coordination compound [Ag{Cp*Fe(µ,η⁵:η⁵-P₅)Mo(CO)₃}₂][BF₄] (3). Its reaction with Ag[TEF] and Cu[TEF] ([TEF]⁻ = [Al{OC(CF₃)₃}₄]⁻) leads to the selective formation of the complexes [Ag{Cp*Fe(µ,η⁵:η⁵-P₅)Mo(CO)₃}₂][TEF] (4) and [Cu{Cp*Fe(µ,η⁵:η⁵-P₅)Mo(CO)₃}₂][TEF] (5), respectively. The X-ray structures of compounds 3–5 each show an M^I ion (M^I = Ag^I, Cu^I) bridged by two P atoms from two triple-decker complexes (2). Additionally, four short M^I···CO distances (two to each triple-decker complex 2) participate in stabilizing the coordination sphere of the M^I ion. Evidently, the X-ray structure for compound 3 shows a weak interaction of the Ag^I ion with one fluorine atom of the counterion [BF₄]⁻. Such an Ag···F interaction does not exist for compound 4. These findings demonstrate the possibility of using triple-decker complex 2 as a ligand in coordination chemistry and opening a new perspective in the field of supramolecular chemistry of transition metal compounds with phosphorus-rich complexes.

Metal carbonyl cluster-based coordination polymers: diverse syntheses, versatile network structures, and special properties

This highlight surveys recent progress in groups 6–10 metal carbonyl cluster-based coordination polymers, focusing on diverse synthetic strategies, versatile structures, structural transformations, and semiconducting as well as magnetic properties.

[Bi7M3(CO)3]2− (M = Co, Rh): a new architype of 10-vertex deltahedral hybrids by the unprecedented polycyclic η5-coordination addition of Bi73− and trimetallic fragments

A new prototype of 10-vertex deltahedral clusters, [Bi₇M₃(CO)₃]²⁻ (M = Co, 1a; M = Rh, 2a), have been synthesized and characterized, resulting from the unprecedented polycyclic η⁵-coordination addition of a Bi₇³⁻ cage and trimetallic fragments.

[(η3-Bi3)2(IrCO)6(μ4-Bi)3]3−: a new archetype of a 15-vertex deltahedral hybrid from Bixx−-coordination aggregation of cationic [IrCO]+ units

The first Zintl-deltahedral metal carbonyl hybrid [(η³-Bi₃)₂(IrCO)₆(μ₄-Bi)₃]³⁻ was obtained by a new synthetic methodology, namely the Bi_x^x−-coordination aggregation of [Ir(CO)]⁺ to trigonal prismatic [Ir(CO)]₆⁶⁺.

Coordinated “Naked” Pnicogenes and Catalysis

Diphosphorous (P2) side-on coordinated to a dicobalt (Co–Co) moiety was described 45 years ago. This discovery had several links to actual problems of homogeneous molecular catalysis. The new type of organometallic complexes induced several ingenious new ramifications in main-group/transition metal cluster chemistry in the last decades. The present review traces the main lines of these research results and their contacts to actual problems of industrial catalysis.