Triple Bonding to Tin: Synthesis and Characterization of the Square-Pyramidal Stannylyne Complex Cation [(dppe)2W⋮Sn−C6H3-2,6-Mes2]+ (dppe = Ph2PCH2CH2PPh2, Mes = C6H2-2,4,6-Me3)

Heavier tetrylene- and tetrylyne-transition metal chemistry: it's no carbon copy

Since the late 19th century, heavier tetrylene- and tetrylyne-transition metal chemistry has formed an important cornerstone in both main-group and organometallic chemistry alike. Driven by the success of carbene systems, significant efforts have gone towards the thorough understanding of the heavier group 14 derivatives, with examples now known from across the d-block. This now leads towards applications in cooperative bond activation, and moves ultimately towards well-defined catalytic systems. This review aims to summarise this vast field, from initial discoveries of tetrylene and tetrylyne complexes, to the most recent developments in reactivity and catalysis, as a platform to the future of this exciting, blossoming field.

Facile Access to Cationic Methylstannylenes and Silylenes Stabilized by E-Pt Bonding and their Methyl Group Transfer Reactivity

We describe a family of cationic methylstannylene and chloro- and azidosilylene organoplatinum(II) complexes supported by a neutral, binucleating ligand. Methylstannylenes MeSn:+ are stabilized by coordination to PtII and are formed by facile Me group transfer from dimethyl or monomethyl PtII complexes, in the latter case triggered by concomitant B-H, Si-H, and H2 bond activation that involves hydride transfer from Sn to Pt. A cationic chlorosilylene complex was obtained by formal HCl elimination and Cl- removal from HSiCl3 under ambient conditions. The computational studies show that stabilization of cationic methylstannylenes and cationic silylenes is achieved through weak coordination to a neutral N-donor ligand binding pocket. The analysis of the electronic potentials, as well as the Laplacian of electron density, also reveals the differences in the character of Pt-Si vs. Pt-Sn bonding. We demonstrate the importance of a ligand-supported binuclear Pt/tetrel core and weak coordination to facilitate access to tetrylium-ylidene Pt complexes, and a transmetalation approach to the synthesis of MeSnII :+ derivatives.

Reactivity Analysis of the [2 + 2] Cycloaddition between Group-6 ≡ Group-14 Triple-Bonded Complexes and Acetylene: Insights from Theoretical Studies

Theoretical examinations of reactivity for the formal [2 + 2] cycloaddition of Me-C≡C-Ph to Group-6(G6)≡Group-14(G14) triple-bonded organometallic complexes have been carried out using the M06-2X-D3/def2-TZVP level of theory. Our theoretical findings suggest that Me-C≡C-Ph can undergo adduct formation with all G6≡Si complexes, resulting in the generation of four-membered ring structures. However, among the W≡Group-14 complex reactants, only W≡Si-based, W≡Ge-based, and W≡Sn-based organometallic molecules are capable of undergoing a [2 + 2] cycloaddition reaction with Me-C≡C-Ph. Based on energy decomposition analysis, our theoretical investigations demonstrate that the bonding mechanism in such [2 + 2] cycloaddition reactions involves the creation of two dative bonds between singlet fragments (the donor-acceptor model), as opposed to two electron-sharing bonds between triplet fragments. In addition, the examinations based on the activation strain model indicate that the activation barrier of the [2 + 2] cycloaddition reaction is predominantly governed by the geometric deformation energy of the two reactants (G6≡G14-Rea and Me-C≡C-Ph). Our research using the M06-2X method shows that the barrier heights of [2 + 2] cycloaddition reactions between Me-C≡C-Ph and G6≡Si-Rea are dependent on the geometric changes occurring in both fragments during the transition states, consistent with Hammond's postulate.

Synthesis of Cobalt-Tin and -Lead Tetrylidynes-Reactivity Study of the Triple Bond

Tetrylidynes [TbbSn≡Co(PMe3 )3 ] (1 a) and [TbbPb≡Co(PMe3 )3 ] (2) (Tbb=2,6-[CH(SiMe3 )2 ]2 -4-(t-Bu)C6 H2 ) are accessed for the first time via a substitution reaction between [Na(OEt2 )][Co(PMe3 )4 ] and [Li(thf)2 ][TbbEBr2 ] (E=Sn, Pb). Following an alternative procedure the stannylidyne [Ar*Sn≡Co(PMe3 )3 ] (1 b) was synthesized by hydrogen atom abstraction using AIBN from the paramagnetic hydride complex [Ar*SnH=Co(PMe3 )3 ] (4) (AIBN=azobis(isobutyronitrile)). The stannylidyne 1 a adds two equivalents of water to yield the dihydroxide [TbbSn(OH)2 CoH2 (PMe3 )3 ] (5). In reaction of the stannylidyne 1 a with CO2 a product of a redox reaction [TbbSn(CO3 )Co(CO)(PMe3 )3 ] (6) was isolated. Protonation of the tetrylidynes occurs at the cobalt atom to give the metalla-stanna vinyl cation [TbbSn=CoH(PMe3 )3 ][BArF 4 ] (7 a) [ArF =C6 H3 -3,5-(CF3 )2 ]. The analogous germanium and tin cations [Ar*E=CoH(PMe3 )3 ][BArF 4 ] (E=Ge 9, Sn 7 b) (Ar*=C6 H3 (2,6-Trip)2 , Trip=2,4,6-C6 H2 iPr3 ) were also obtained by oxidation of the paramagnetic complexes [Ar*EH=Co(PMe3 )3 ] (E=Ge 3, Sn 4), which were synthesized by substitution of a PMe3 ligand of [Co(PMe3 )4 ] by a hydridoylene (Ar*EH) unit.

The Electronic Nature of Cationic Group 10 Ylidyne Complexes

We report a broad theoretical study on [(PMe3)3MER]+ complexes, with M = Ni, Pd, Pt, E = C, Si, Ge, Sn, Pb, and R = ArMes, Tbb, (ArMes = 2,6-dimesitylphenyl; Tbb = C6H2-2,6-[CH(SiMe3)2]2-4-tBu). A few years ago, our group succeeded in obtaining heavier homologues of cationic group 10 carbyne complexes via halide abstraction of the tetrylidene complexes [(PMe3)3M=E(X)R] (X = Cl, Br) using a halide scavenger. The electronic structure and the M-E bonds of the [(PMe3)3MER]+ complexes were analyzed utilizing quantum-chemical tools, such as the Pipek–Mezey orbital localization method, the energy decomposition analysis (EDA), and the extended-transition state method with natural orbitals of chemical valence (ETS-NOCV). The carbyne, silylidyne complexes, and the germylidyne complex [(PMe3)3NiGeArMes]+ are suggested to be tetrylidyne complexes featuring donor–acceptor metal tetrel triple bonds, which are composed of two strong π(M→E) and one weaker σ(E→M) interaction. In comparison, the complexes with M = Pd, Pt; E = Sn, Pb; and R = ArMes are best described as metallotetrylenes and exhibit considerable M−E−C bending, a strong σ(M→E) bond, weakened M−E π-components, and lone pair density at the tetrel atoms. Furthermore, bond cleavage energy (BCE) and bond dissociation energy (BDE) reveal preferred splitting into [M(PMe3)3]+ and [ER] fragments for most complex cations in the range of 293.3–618.3 kJ·mol−1 and 230.4–461.6 kJ·mol−1, respectively. Finally, an extensive study of the potential energy hypersurface varying the M−E−C angle indicates the presence of isomers with M−E−C bond angles of around 95°. Interestingly, these isomers are energetically favored for M = Pd, Pt; E = Sn, Pb; and R = ArMes over the less-bent structures by 13–29 kJ·mol−1.

Utilization of a Tris(carbene)borate Ligand for Umpolung Reactivity of a Nucleophilic Tin(II) Cation Salt

We show that a tris(carbene)borate (TCB) ligand, namely [PhB(^tBuIm)₃]^- ([PhB(^tBuIm)₃]^- = phenyltris(3-tert-butylimidazol-2-ylidene)borato), is capable of stabilizing an unprecedented nucleophilic Sn(II) cation salt. Unlike known Sn(II) cations, the strong electron-donating ability of [PhB(^tBuIm)₃]^- makes the cationic tin atom electron-rich, σ-donating yet slightly π-accepting, which allows for the ensuing facile oxidation with o-chloranil and S₈ as well as coordination with coinage metals. The former oxidations give the Sn(IV) cation salts, while the latter reactions produce the metal complexes. The electronic structures of these species are thoroughly probed by quantum chemical computations. These results uncover an added role for TCB ligands in isolating unprecedented p-block species.

Heavy metalla vinyl-cations show metal-Lewis acid cooperativity in reaction with small molecules (NH3, N2H4, H2O, H2)

Halide abstraction from tetrylidene complexes [TbbE(Br)IrH(PMe3)3] [E = Ge (1), Sn (2)] and [Ar*E(Cl)IrH(PMe3)3] gives the salts [TbbEIrH(PMe3)3][BArF 4] [E = Ge (3), Sn (4)] and [Ar*EIrH(PMe3)3][BArF 4] [E = Ge (3'), E = Sn (4')] (Tbb = 2,6-[CH(SiMe3)2]2-4-(t-Bu)C6H2, Ar* = 2,6-Trip2C6H3, Trip = 2,4,6-triisopropylphenyl). Bonding analysis suggests their most suitable description as metalla-tetrela vinyl cations with an Ir[double bond, length as m-dash]E double bond and a near linear coordination at the Ge/Sn atoms. Cationic complexes 3 and 4 oxidatively add NH3, N2H4, H2O, HCl, and H2 selectively to give: [TbbGe(NH2)IrH2(PMe3)3][BArF 4] (5), [TbbE(NHNH2)IrH2(PMe3)3][BArF 4] [E = Ge (7), Sn (8)], [TbbE(OH)IrH2(PMe3)3][BArF 4] [E = Ge (9), Sn (10)], [TbbE(Cl)IrH2(PMe3)3][BArF 4] [E = Ge (11a), Sn (12a)], [TbbGe(H)IrH2(PMe3)3][BArF 4] (13), [TbbSn(μ-H3)Ir(PMe3)3][BArF 4] (14), and [TbbSn(H)IrH2(PMe3)3][BArF 4] (15). 14 isomerizes to give 15via an 1,2-H shift reaction. Hydride addition to cation 3 gives a mixture of products [TbbGeHIrH(PMe3)3] (16) and [TbbGeIrH2(PMe3)3] (17) and a reversible 1,2-H shift between 16 and 17 was studied. In the tin case 4 the dihydride [TbbSnIrH2(PMe3)3] (18) was isolated exclusively. The PMe3 and PEt3 derivatives, 18 and [TbbSnIrH2(PEt3)3] (19), respectively, could also be synthesized in reaction of [TbbSnH2]- with the respective chloride [(R3P) n IrCl] (R = Me, n = 4; R = Et, n = 3). Reaction of complex 19 with CO gives the substitution product [TbbSnIrH2(CO)(PEt3)2] (20). Further reaction with CO results in hydrogen transfer from the iridium to the tin atom to give [TbbSnH2Ir(CO)2(PEt3)2] (21). The reversibility of this ligand induced reductive elimination transferring 20 to 21 is shown.

Hydridotetrylene [Ar*EH] (E = Ge, Sn, Pb) coordination at tantalum, tungsten, and zirconium

In a reaction of tantalocene trihydride with the low valent aryl tin cation [Ar*Sn(C₆H₆)][Al(OC{CF₃}₃)₄] (1a) the hydridostannylene complex [Cp₂TaH₂–Sn(H)Ar*][Al(OC{CF₃}₃)₄] (2) was synthesized. Hydride bridged adducts [Cp₂WH₂EAr*][Al(OC{CF₃}₃)₄] (E = Sn 3a, Pb 3b) were isolated as products of the reaction between Cp₂WH₂ and cations [Ar*E(C₆H₆)][Al(OC{CF₃}₃)₄] (E = Sn 1a, Pb 1b). The tin adduct 3a exhibits a proton migration to give the hydridostannylene complex [Cp₂W(H) Created by potrace 1.16, written by Peter Selinger 2001-2019 ]]> Sn(H)Ar*][Al(OC{CF₃}₃)₄] 4a. The cationic complex 4a is deprotonated at the tin atom in reaction with base ^MeNHC at 80 °C to give a hydrido-tungstenostannylene [Cp₂W(H)SnAr*] 5a. Reprotonation of metallostannylene 5a with acid [H(Et₂O)₂][BAr^F] provides an alternative route to hydridotetrylene coordination. Complex 4a adds hydride to give the dihydrostannyl complex [Cp₂W(H)–SnH₂Ar*] (7). With styrene 4a shows formation of a hydrostannylation product [Cp₂W(H)Sn(CH₂CH₂Ph)Ar*][Al(OC{CF₃}₃)₄] (8). The lead adduct 3b was deprotonated with ^MeNHC to give plumbylene 5b [Cp₂W(H)PbAr*]. Protonation of 5b with [H(Et₂O)₂][Al(OC{CF₃}₃)₄] at −40 °C followed by low temperature NMR spectroscopy indicates a hydridoplumbylene intermediate [Cp₂W(H)Pb(H)Ar*]⁺ (4b). Hydrido-tungstenotetrylenes of elements Ge (5c), Sn (5a) and Pb (5b) were also synthesized reacting the salt [Cp₂W(H)Li]₄ with organotetrylene halides. The metallogermylene [Cp₂W(H)GeAr*] (5c) shows an isomerization via 1,2-H-migration to give the hydridogermylene [Cp₂WGe(H)Ar*] (9), which is accelerated by addition of AIBN. 9 is at rt photochemically transferred back to 5c under light of a mercury vapor lamp. Zirconocene dihydride [Cp₂ZrH₂]₂ reacts with tin cation 1a to give the trinuclear hydridostannylene adduct 10 [({Cp₂Zr}₂{μ-H})(μ-H)₂μ-Sn(H)Ar*][Al(OC{CF₃}₃)₄]. Deprotonation of 10 was carried out using benzyl potassium to give neutral [({Cp₂Zr}₂{μ-H})(μ-H)μ-Sn(H)Ar*] (11). 11 was also obtained from the reaction of low valent tin hydride [Ar*SnH]₂ with two equivalents of [Cp₂ZrH₂]₂. The trihydride Ar*SnH₃ reacts with half of an equivalent of [Cp₂ZrH₂]₂ under evolution of hydrogen and formation of a dihydrostannyl complex 13 [Cp₂Zr(μ-H)SnH₂Ar*]₂ and with further equivalents of Ar*SnH₃ to give bis(hydridostannylene) complex [Cp₂Zr{Sn(H)Ar*}₂].

Low valent cations of tin and lead were used to form hydridotetrylene coordination compounds. The mobility of the hydrogen substituent was investigated in deprotonation equilibria as well as in 1,2-H-shift reactions.

Chemistry of the Bis(imine)-Based Tetradentate Ligand Stabilized Group 14 E(II) Cations (E=Ge and Sn)

The ambiphilic Ge(II) and Sn(II) cationic species have been reported to be isolated through kinetic or thermodynamic stabilizations. Nonetheless, steric congestion or excessive coordination of donor atoms to the cationic center concurrently disfavors its prompt reactivity. Our research in this field revolves around the utilization of structurally non-rigid bis(imine) based tetradentate supporting ligands for the stabilization of Ge(II) and Sn(II) cationic species. Such E(II) cationic systems have been advantaged due to inherent flexibility present at the ligand backbone allowing disposal of E(II) orbitals through geometric rearrangements for further reactivity. The bifunctionality present in the ligand enables the first examples of Ge(II) bis-monocations. Furthermore, the redox-active nature of the ligand encourages participation in chemical transformations. In this personal account we have provided a detailed discussion of our published work in this direction in the last five years.

Accessing cationic tetrylene-nickel(0) systems featuring donor-acceptor E-Ni triple bonds (E = Ge, Sn)

We describe facile synthetic methods for accessing linear cationic tetrylene nickel(0) complexes [^SiiPDippE·Ni(PPh₃)₃]⁺ (E = Ge (4) and Sn (5); ^SiiPDipp = [(iPr₃Si)(Dipp)N]^-), which feature donor-acceptor E-Ni triple bonds. These species are readily accessed in a one-pot protocol, combining the bulky halo-tetrylenes ^SiiPDippECl (E = Ge (1) and Sn (2)), Ni(cod)₂, PPh₃, and Na[BAr^F₄]. Given the diamagnetic nature of 4 and 5, they each contain a formal zero-valent Ni centre, making the E-M triple bonds in these complexes unique compared to previously reported metal tetrylidyne complexes, which typically feature covalent/ionic bonding. In-depth computational analyses of these species further support triple bond character in their E-Ni interactions.

Synthesis, structure and reactivity of μ3-SnH capped trinuclear nickel cluster

Treatment of the trichlorotin-capped trinuclear nickel cluster, [Ni₃(dppm)₃(μ₃-Cl)(μ₃-SnCl₃)], 1, with 4 eq. NaHB(Et)₃ yields a μ₃-SnH capped trinuclear nickel cluster, [Ni₃(dppm)₃(μ₃-H)(μ₃-SnH)], 2 [dppm = bis(diphenylphosphino)methane]. Single-crystal X-ray diffraction, nuclear magnetic resonance (NMR) spectroscopy, and computational studies together support that cluster 2 is a divalent tin hydride. Complex 2 displays a wide range of reactivity including oxidative addition of bromoethane across the Sn center. Addition of 1 eq. iodoethane to complex 2 releases H₂ (g) and generates an ethyltin-capped nickel cluster with a μ₃-iodide, [Ni₃(dppm)₃(μ₃-I)(μ₃-Sn(CH₂CH₃))], 4. Notably, insertion of alkynes into the Sn–H bond of 2 can be achieved via addition of 1 eq. 1-hexyne to generate the 1-hexen-2-yl-tin-capped nickel cluster, [Ni₃(dppm)₃(μ₃H)(μ₃-Sn(C₆H₁₁))], 5. Addition of H₂ (g) to 5 regenerates the starting material, 2, and hexane. The formally 44-electron cluster 2 also displays significant redox chemistry with two reversible one-electron oxidations (E = −1.3 V, −0.8 V vs. Fc^0/+) and one-electron reduction process (E = −2.7 V vs. Fc^0/+) observed by cyclic voltammetry.

The synthesis, structure, and reactivity of a μ₃-SnH capped trinuclear nickel cluster, [Ni₃(dppm)₃(μ₃-H)(μ₃-SnH)], is reported. This complex undergoes oxidative addition chemistry, alkyne insertion, and subsequent hydrogenation.

Synthesis and Hydrogenation of Heavy Homologues of Rhodium Carbynes: [(Me3 P)2 (Ph3 P)Rh≡E-Ar*] (E=Sn, Pb)

Tetrylidynes [(Me3 P)2 (Ph3 P)Rh≡SnAr*] (10) and [(Me3 P)2 (Ph3 P)Rh≡PbAr*] (11) are accessed for the first time via dehydrogenation of dihydrides [(Ph3 P)2 RhH2 SnAr*] (3) and [(Ph3 P)2 RhH2 PbAr*] (7) (Ar*=2,6-Trip2 C6 H3 , Trip=2,4,6-triisopropylphenyl), respectively. Tin dihydride 3 was either synthesized in reaction of the dihydridostannate [Ar*SnH2 ]- with [(Ph3 P)3 RhCl] or via reaction between hydrides [(Ph3 P)3 RhH] and 1 / 2  [(Ar*SnH)2 ]. Homologous lead hydride [(Ph3 P)2 RhH2 PbAr*] (7) was synthesized analogously from [(Ph3 P)3 RhH] and 1 / 2  [(Ar*PbH)2 ]. Abstraction of hydrogen from 3 and 7 supported by styrene and trimethylphosphine addition yields tetrylidynes 10 and 11. Stannylidyne 10 was also characterized by 119 Sn Mössbauer spectroscopy. Hydrogenation of the triple bonds at room temperature with excess H2 gives the cis-dihydride [(Me3 P)2 (Ph3 P)RhH2 PbAr*] (12) and the tetrahydride [(Me3 P)2 (Ph3 P)RhH2 SnH2 Ar*] (14). Complex 14 eliminates spontaneously one equivalent of hydrogen at room temperature to give the dihydride [(Me3 P)2 (Ph3 P)RhH2 SnAr*] (13). Hydrogen addition and elimination at stannylene tin between complexes 13 and 14 is a reversible reaction at room temperature.

Transition metal chemistry of heavier group 14 congener triple-bonded complexes: syntheses and reactivity

The diversification and synthetic utility of carbyne complexes in organometallic chemistry and catalysis are well recognized, but the syntheses of related heavier group 14 alkylidyne complexes are a recent advancement. A wide range of metal-ylidyne M[triple bond, length as m-dash]E (E = Si-Pb) complexes were synthesized and characterized spectroscopically. The synthetic methodology generally involves elimination or substitution chemistry between metallates and suitable group 14 precursors. The reluctance in forming triple bonded complexes makes this field quite fascinating and challenging. This article gives a brief overview of the pioneering reports followed by detailed information on the latest developments of complexes having a triple bond between a metal and heavier group 14 elements (Si, Ge, Sn, and Pb). Their synthesis and chemistry of the earlier reports followed by recent progress in this field will be discussed. Furthermore, their unique structures and bonding properties will be described based on spectroscopic and theoretical studies.

Functionalization of N2 via Formal 1,3-Haloboration of a Tungsten(0) σ-Dinitrogen Complex

Boron tribromide and aryldihaloboranes were found to undergo 1,3-haloboration across one W-N≡N moiety of a group 6 end-on dinitrogen complex (i.e. trans-[W(N2 )2 (dppe)2 ]). The N-borylated products consist of a reduced diazenido unit sandwiched between a WII center and a trivalent boron substituent (W-N=N-BXAr), and have all been fully characterized by NMR and IR spectroscopy, elemental analysis, and single-crystal X-ray diffraction. Both the terminal N atom and boron center in the W-N=N-BXAr unit can be further derivatized using electrophiles and nucleophiles/Lewis bases, respectively. This mild reduction and functionalization of a weakly activated N2 ligand with boron halides is unprecedented, and hints at the possibility of generating value-added nitrogen compounds directly from molecular dinitrogen.

Hydridoorganostannylene Coordination: Group 4 Metallocene Dichloride Reduction in Reaction with Organodihydridostannate Anions

Organodihydridoelement anions of germanium and tin were reacted with metallocene dichlorides of Group 4 metals Ti, Zr and Hf. The germate anion [Ar*GeH2 ]- reacts with hafnocene dichloride under formation of the substitution product [Cp2 Hf(GeH2 Ar*)2 ]. Reaction of the organodihydridostannate with metallocene dichlorides affords the reduction products [Cp2 M(SnHAr*)2 ] (M=Ti, Zr, Hf). Abstraction of a hydride substituent from the titanium bis(hydridoorganostannylene) complex results in formation of cation [Cp2 M(SnAr*)(SnHAr*)]+ exhibiting a short Ti-Sn interaction. (Ar*=2,6-Trip2 C6 H3 , Trip=2,4,6-triisopropylphenyl).

Triple bonds of niobium with silicon, germaniun and tin: the tetrylidyne complexes [(κ3-tmps)(CO)2Nb[triple bond, length as m-dash]E-R] (E = Si, Ge, Sn; tmps = MeSi(CH2PMe2)3; R = aryl)

A systematic, efficient approach to first complexes containing a triple bond between niobium and the elements silicon, germanium or tin is reported. The approach involves a metathetical exchange of the niobium-centered nucleophile (NMe4)[Nb(CO)4(κ2-tmps)] (1) (tmps = MeSi(CH2PMe2)3) with a suitable organotetrel(ii)halide. Compound 1 was obtained from (NMe4)[Nb(CO)6] and the triphosphane tmps by photodecarbonylation. Reaction of 1 with the disilene E-Tbb(Br)Si[double bond, length as m-dash]Si(Br)Tbb in the presence of 4-dimethylaminopyridine afforded selectively the red-brown silylidyne complex [(κ3-tmps)(CO)2Nb[triple bond, length as m-dash]Si-Tbb] (2-Si, Tbb = 4-tert-butyl-2,6-bis(bis(trimethylsilyl)methyl)phenyl). Similarly, treatment of 1 with E(ArMes)Cl (E = Ge, Sn; ArMes = 2,6-mesitylphenyl) afforded after elimination of (NMe4)Cl and two CO ligands the deep magenta colored germylidyne complex [(κ3-tmps)(CO)2Nb[triple bond, length as m-dash]Ge-ArMes] (3-Ge), and the deep violet, light-sensitive stannylidyne complex [(κ3-tmps)(CO)2Nb[triple bond, length as m-dash]Sn-ArMes] (3-Sn), respectively. Formation of 3-Sn proceeds via the niobiastannylene [(κ3-tmps)(CO)3Nb-SnArMes] (4-Sn), which was detected by IR and NMR spectroscopy. The niobium tetrylidyne complexes 2-Si, 3-Ge and 3-Sn were fully characterized and their solid-state structures determined by single-crystal X-ray diffraction studies. All complexes feature an almost linear tetrel coordination and the shortest Nb-E bond lengths (d(Nb-Si) = 232.7(2) pm; d(Nb-Ge) = 235.79(4) pm; d(Nb-Sn) = 253.3(1) pm) reported to date. Reaction of 3-Ge with a large excess of H2O afforded upon cleavage of the Nb-Ge triple bond the hydridogermanediol Ge(ArMes)H(OH)2. Photodecarbonylation of [CpNb(CO)4] (Cp = η5-C5H5) in the presence of Ge(ArMes)Cl afforded the red-orange chlorogermylidene complex [Cp(CO)3Nb[double bond, length as m-dash]Ge(ArMes)Cl] (5-Ge). The molecular structure of 5-Ge features an upright conformation of the germylidene ligand, a trigonal-planar coordinated Ge atom, and a Nb-Ge double bond length of 251.78(6) pm, which lies in-between the Nb-Ge triple bond length of 3-Ge (235.79(4) pm) and a Nb-Ge single bond length (267.3 pm). Cyclic voltammetric studies of 2-Si, 3-Ge, and 3-Sn reveal several electron-transfer steps. One-electron oxidation and reduction of the germylidyne complex of 3-Ge in THF are electrochemically reversible suggesting that both the radical cation and radical anion of 3-Ge are accessible species in solution.

Reactive p-block cations stabilized by weakly coordinating anions

The chemistry of the p-block elements is a huge playground for fundamental and applied work. With their bonding from electron deficient to hypercoordinate and formally hypervalent, the p-block elements represent an area to find terra incognita. Often, the formation of cations that contain p-block elements as central ingredient is desired, for example to make a compound more Lewis acidic for an application or simply to prove an idea. This review has collected the reactive p-block cations (rPBC) with a comprehensive focus on those that have been published since the year 2000, but including the milestones and key citations of earlier work. We include an overview on the weakly coordinating anions (WCAs) used to stabilize the rPBC and give an overview to WCA selection, ionization strategies for rPBC-formation and finally list the rPBC ordered in their respective group from 13 to 18. However, typical, often more organic ion classes that constitute for example ionic liquids (imidazolium, ammonium, etc.) were omitted, as were those that do not fulfill the - naturally subjective -"reactive"-criterion of the rPBC. As a rule, we only included rPBC with crystal structure and only rarely refer to important cations published without crystal structure. This collection is intended for those who are simply interested what has been done or what is possible, as well as those who seek advice on preparative issues, up to people having a certain application in mind, where the knowledge on the existence of a rPBC that might play a role as an intermediate or active center may be useful.

Dispersion-Corrected Relativistic Density Functional Theory (DFT) Calculations of Structure and (119)Sn Mössbauer Parameters for M≡SnR Bonding in Filippou's Stannylidyne Complexes of Molybdenum and Tungsten

(119)Sn Mössbauer isomer shift (IS) and quadrupole splitting (ΔEQ) for M≡SnR bonding in metal-stannylidyne complexes trans-[Cl(PMe3)4Mo≡Sn-R] (1), trans-[Cl(PMe3)4W≡Sn-R] (2), trans-[Cl(dppe)2Mo≡Sn-R] (3), trans-[Cl(dppe)2W≡Sn-R] (4), [(dppe)2Mo≡Sn-R](+) (5), [(dppe)2W≡Sn-R](+) (6) (R = C6H3-2,6-Mes2) have been investigated for the first time. Calculations of optimized structures and (119)Sn Mössbauer parameters were carried out at the DFT/TPSS-D3(BJ)/TZVPP/ZORA level of theory. The calculated geometry parameters of stannylidyne complexes of molybdenum and tungsten (1-6) are in good agreement with experimental values of W-Sn and Sn-C bond distances. The calculated values of the isomer shift for the complexes (1-6) are almost same to the experimental values (within ±0.1 mm/s). Experimental values (ISexptl, 2.38-2.50 mm/s) and calculated values (IScalcd, 2.37-2.49 mm/s) of isomer shifts indicate that the oxidation state of tin in the studied complexes with M≡Sn-R bonding is Sn(II). The variations of ISexptl, as a function of Sn s electrons (Ns(Sn)), also exhibit a linear trend. (IS = 0.477Ns(Sn) - 1.888, R(2) = 0.9973). Calculated values of isomer shift (IScalcd) using the linear regression with the Ns(Sn) electron density are in excellent concord with the ISexptl.The calculated values of nuclear quadrupole splitting parameters (ΔEQ(calcd)) of (119)Sn using the relation ΔEQ(calcd) = (0.540 + 0.28) V are in agreement with the experimental values.

Stepwise isolation of low-valent, low-coordinate Sn and Pb mono- and dications in the coordination sphere of platinum

Synthetic access to low-coordinate Pb mono- and dications is in general impeded due to their poor solubility and highly electrophilic nature. However, the electrophilicity of these cations can be tamed by attaching them to electron-rich transition metals. Following this principle we have isolated low-valent Pb mono- ([(Cy3P)2Pt-PbCl]2[AlCl4]2, 8a) and dications ([(Cy3P)2Pt(Pb)][AlCl4]2, 11) in the coordination sphere of platinum. The same approach then has been implemented for the isolation of analogous low-valent Sn mono- (7a) and dications (10). An energy decomposition analysis (EDA-NOCV) was performed to investigate the nature of Pt-Pb and Pb-Cl bonding in [(Cy3P)2Pt(PbCl2)] (2), 8a and 11. The results show that the Pt-Pb bonds in 8a and 11 are electron-sharing in nature, whereas that of the precursor 2 is a dative bond. The breakdown of attractive interactions in 2, 8a and 11 reveals that the ionic interactions in the analyzed Pt-Pb and Pb-Cl bonds are always stronger than the covalent interactions, except for the Pb-Cl bond in 8a. The calculated D3 dispersion energies show that dispersion interactions play a key role in the thermodynamic stability of 2, 8a and 11.

Accessing heavy allyl-analogous [(TerN)2E]− (E = Sb, Bi) ions and their reactivity towards ECl3

Highly reactive heavy heteroatom allyl analogues were obtained by reduction of 1,3-dichloro-cyclo-1,3-dipnicta-2,4-diazanes.

Cations and dications of heavier group 14 elements in low oxidation states

This review gives an introduction to the synthesis, properties, and reactivity of the cations and dications of the heavier group 14 elements in their low oxidation state.

Reactions of a tungsten-germylyne complex with α,β-unsaturated ketones: complete cleavage of the W≡Ge bond and formation of two types of η3-germoxyallyl tungsten complexes

Germylyne complex Cp*(CO)2W≡Ge{C(SiMe3)3} (1) reacted with two molecules of RC(O)CH═CH2 (R = Me, Et) to give η(3)-allyl complexes, in which an oxagermacyclopentene framework was bound to an η(3)-allyl ligand through an oxygen atom. In the reaction with α-Me-substituted MeC(O)C(Me)═CH2, 1 reacted with only one molecule of the substrate to give another type of η(3)-allyl complex, in which a five-membered oxagermacyclopentenyl ring was coordinated to the W center in an η(3) fashion. Both reactions resulted in unprecedented complete cleavage of a W≡Ge triple bond.

Assessment of density functionals and paucity of non-covalent interactions in aminoylyne complexes of molybdenum and tungsten [(η5-C5H5)(CO)2MEN(SiMe3)(R)] (E = Si, Ge, Sn, Pb): a dispersion-corrected DFT study

Geometries, bonding analysis and dispersion interactions in aminoylyne complexes of molybdenum and tungsten have been investigated using different density functionals.