Stoichiometric Hydrosilylation of Nitriles with Hydrido(hydrosilylene)tungsten Complexes: Formation of W−Si−N Three-Membered Ring Complexes and Their Unique Thermal Behaviors

Reactions of hydrido(hydrosilylene)tungsten complexes, Cp‘(CO)2(H)WSi(H)[C(SiMe3)3], with nitriles (MeCN, tBuCN) at 60 °C gave hydrosilylation products, Cp‘(CO)2W[κ2(N,Si)-Si(H)(NCHR‘){C(SiMe3)3}] (R‘ = Me, tBu), with a novel W−Si−N three-membered ring structure. The product of the hydrosilylation of tBuCN underwent reversible rearrangement at 70 °C to a silylene complex, Cp‘(CO)2(H)WSi(NCHtBu)[C(SiMe3)3], which was a major component in equilibrium. A reaction mechanism for the hydrosilylation involving coordination of nitriles to the silylene ligand and subsequent migration of the hydrido ligand to the nitrile carbon was proposed

Synthesis of Cationic Diiron Complexes Bridged by a Base-Stabilized Gallium Atom [Fp₂(μ-Ga·Do₂)]⁺X^- (Fp = (η-C₅H₅)Fe(CO)₂, Do₂ = 2,2‘-Bipyridine, <i>N,N,N</i><i>‘</i><i>,N</i><i>‘</i>-Tetramethylethylenediamine, 1,10-Phenanthroline, (4-(Dimethylamino)pyridine)₂, X^- = [Fp₂GaCl₂]^-, BPh₄^-)

Addition of 2,2‘-bipyridine (bpy) to an acetonitrile solution of Fp2GaCl (1:  Fp = CpFe(CO)2; Cp = η-C5H5) afforded quantitatively a salt consisting of a diiron cation bridged by a Ga·bpy fragment [Fp2(μ-Ga·bpy)]+ ([2a]+) and a μ-GaCl2 diiron anion [Fp2(μ-GaCl2)]- ([3]-). The reaction of 1 with Do2 (Do2 = N,N,N‘,N‘-tetramethylethylenediamine (tmeda), 1,10-phenanthroline (phen), and (4-(dimethylamino)pyridine)2 (= dmap2)) in the presence of 1 equiv of NaBPh4 in acetonitrile afforded [Fp2(μ-Ga·Do2)]+BPh4- (Do2 = tmeda (2b), phen (2c), and (dmap)2 (2d)). Cation [2a−d]+ is the first example of a dinuclear complex bridged by a base-coordinated gallium atom Ga·Do2 (Do = Lewis base). X-ray crystal structure analysis of [2a][3]·CH3CN revealed that the Fe−Ga bond lengths (2.3969(16) and 2.4037(14) Å) in [2a]+ are shorter than those of [3]- (2.4234(13) and 2.4359(15) Å), but within the range previously observed for Fp−gallyl complexes (2.36−2.46 Å). The Ga−Cl bonds in [3]- (2.3259(19) and 2.3537(19) Å) are longer than those of known chlorogallyl complexes (2.18−2.29 Å)

Reactions of Hydrido(hydrosilylene)tungsten Complexes with α<i>,</i>β-Unsaturated Carbonyl Compounds: Selective Formation of (η³-Siloxyallyl)tungsten Complexes

Hydrido(hydrosilylene)tungsten complexes (C5Me4R)(CO)2(H)WSi(H)[C(SiMe3)3] [R1 = Me (1a), R1 = Et (1b)] reacted with α,β-unsaturated carbonyl compounds RC(O)CHCHR (R2 = Me, R3 = H or Ph; R2 = OMe, R3 = H) at room temperature to give exo-anti (η3-siloxyallyl)tungsten complexes (C5Me4R1)(CO)2W[η3-R3HCCHCR2OSiH2{C(SiMe3)3}] almost quantitatively and regioselectively. Possible reaction mechanisms involving a [2+4] cycloaddition process are proposed

Synthesis of Cationic Diiron Complexes Bridged by a Base-Stabilized Gallium Atom [Fp₂(μ-Ga·Do₂)]⁺X^- (Fp = (η-C₅H₅)Fe(CO)₂, Do₂ = 2,2‘-Bipyridine, <i>N,N,N</i><i>‘</i><i>,N</i><i>‘</i>-Tetramethylethylenediamine, 1,10-Phenanthroline, (4-(Dimethylamino)pyridine)₂, X^- = [Fp₂GaCl₂]^-, BPh₄^-)

Addition of 2,2‘-bipyridine (bpy) to an acetonitrile solution of Fp2GaCl (1:  Fp = CpFe(CO)2; Cp = η-C5H5) afforded quantitatively a salt consisting of a diiron cation bridged by a Ga·bpy fragment [Fp2(μ-Ga·bpy)]+ ([2a]+) and a μ-GaCl2 diiron anion [Fp2(μ-GaCl2)]- ([3]-). The reaction of 1 with Do2 (Do2 = N,N,N‘,N‘-tetramethylethylenediamine (tmeda), 1,10-phenanthroline (phen), and (4-(dimethylamino)pyridine)2 (= dmap2)) in the presence of 1 equiv of NaBPh4 in acetonitrile afforded [Fp2(μ-Ga·Do2)]+BPh4- (Do2 = tmeda (2b), phen (2c), and (dmap)2 (2d)). Cation [2a−d]+ is the first example of a dinuclear complex bridged by a base-coordinated gallium atom Ga·Do2 (Do = Lewis base). X-ray crystal structure analysis of [2a][3]·CH3CN revealed that the Fe−Ga bond lengths (2.3969(16) and 2.4037(14) Å) in [2a]+ are shorter than those of [3]- (2.4234(13) and 2.4359(15) Å), but within the range previously observed for Fp−gallyl complexes (2.36−2.46 Å). The Ga−Cl bonds in [3]- (2.3259(19) and 2.3537(19) Å) are longer than those of known chlorogallyl complexes (2.18−2.29 Å)

Reactions of Hydrido(hydrosilylene)tungsten Complexes with α<i>,</i>β-Unsaturated Carbonyl Compounds: Selective Formation of (η³-Siloxyallyl)tungsten Complexes

Hydrido(hydrosilylene)tungsten complexes (C5Me4R)(CO)2(H)WSi(H)[C(SiMe3)3] [R1 = Me (1a), R1 = Et (1b)] reacted with α,β-unsaturated carbonyl compounds RC(O)CHCHR (R2 = Me, R3 = H or Ph; R2 = OMe, R3 = H) at room temperature to give exo-anti (η3-siloxyallyl)tungsten complexes (C5Me4R1)(CO)2W[η3-R3HCCHCR2OSiH2{C(SiMe3)3}] almost quantitatively and regioselectively. Possible reaction mechanisms involving a [2+4] cycloaddition process are proposed

Cationic Metallogermylene and Dicationic Dimetallodigermenes: Synthesis by Chloride Abstraction from <i>N</i>‑Heterocyclic Carbene-Stabilized Chlorometallogermylenes

Reaction of NHC-stabilized dichlorogermylenes (NHC = <i>N</i>-heterocyclic carbene) with an anionic tungsten complex produced NHC-stabilized chlorometallogermylenes. Subsequent chloride abstraction from the products with NaBAr₄ (Ar = 3,5-(CF₃)₂C₆H₃) gave a cationic metallogermylene or dicationic dimetallodigermenes

Stoichiometric Hydrosilylation of Nitriles with Hydrido(hydrosilylene)tungsten Complexes: Formation of W−Si−N Three-Membered Ring Complexes and Their Unique Thermal Behaviors

Reactions of hydrido(hydrosilylene)tungsten complexes, Cp‘(CO)2(H)WSi(H)[C(SiMe3)3], with nitriles (MeCN, tBuCN) at 60 °C gave hydrosilylation products, Cp‘(CO)2W[κ2(N,Si)-Si(H)(NCHR‘){C(SiMe3)3}] (R‘ = Me, tBu), with a novel W−Si−N three-membered ring structure. The product of the hydrosilylation of tBuCN underwent reversible rearrangement at 70 °C to a silylene complex, Cp‘(CO)2(H)WSi(NCHtBu)[C(SiMe3)3], which was a major component in equilibrium. A reaction mechanism for the hydrosilylation involving coordination of nitriles to the silylene ligand and subsequent migration of the hydrido ligand to the nitrile carbon was proposed

A Tantalum(V) Carbene Complex: Formation of a Carbene−Bis(phenoxide) Ligand by Sequential Proton and Hydride Abstraction

Proton and subsequent hydride abstraction from the bis(phenoxide) ligand of the trimethyltantalum(V) complex affords a cationic tantalum(V) carbene complex, in which two phenoxide groups are linked to the carbene center. The electrophilic nature of the carbene functionality is demonstrated by the reaction with PPh3

A Tantalum(V) Carbene Complex: Formation of a Carbene−Bis(phenoxide) Ligand by Sequential Proton and Hydride Abstraction

Proton and subsequent hydride abstraction from the bis(phenoxide) ligand of the trimethyltantalum(V) complex affords a cationic tantalum(V) carbene complex, in which two phenoxide groups are linked to the carbene center. The electrophilic nature of the carbene functionality is demonstrated by the reaction with PPh3

Selective and Stepwise Bromodemethylation of the Silyl Ligand in Iron(II) Silyl Complexes with Boron Tribromide

Treatment of Cp*(CO)2FeSiMe2R (Cp* = C5Me5, R = Me and Ph) with 1 equiv of BBr3 at room temperature afforded Cp*(CO)2FeSiBrMeR (R = Me and Ph) and MeBBr2 in high yields via bromodemethylation of the silyl ligand. Cp*(CO)2FeSiBrMeR (R = Me and Ph) was further converted to Cp*(CO)2FeSiBr2R (R = Me and Ph) quantitatively on addition of another equivalent of BBr3 and heating. Treatment of Cp*(CO)2FeSiMe2SiMe3 with 1 equiv of BBr3 at room temperature led to selective bromodemethylation at the α-silicon atom to produce Cp*(CO)2FeSiBrMeSiMe3, which was also converted to Cp*(CO)2FeSiBr2SiMe3 on heating with another equivalent of BBr3 at 40 °C in quantitative yield. The solid-state structure of Cp*(CO)2FeSiBr2SiMe3 was confirmed by X-ray crystal structure determination