Synthesis and characterization of thioaldehyde hydride derivatives of permethyltantalocene. Investigations of their equilibration with thiolates and the stereochemistry of alkyl migrations from sulfur to tantalum

C−S Bond Cleavage in CpRu(PPh3)2SCH2CHCH2To Give the Trimer (CpRu)3(μ3-S)2(μ-SCH2CHCH2)

“…A possible reaction sequence might involve loss of PPh 3 and C−S bond cleavage to give a coordinatively unsaturated ruthenium sulfide species, CpRu(PPh 3 )(S), which could aggregate to give 6 . Similar species have been reported such as Cp* 2 Ta(CH 2 R)(S) and Cp* 2 Zr(py)(S) . The formation of the dimer Cp*Ir(PMe 3 )(μ 2 -S)IrCp*, which is postulated to involve aggregation of the species Cp*Ir(PMe 3 )(S) obtained via dehalogenation of Cp*Ir(PMe 3 )(SH)Cl, is particularly relevant to the results reported here.…”

Olefination and group transfer reactions of an electron deficient tantalum methylidene complex

“…The carbon atoms of the methylene and the methyl group were refined as one full occupancy carbon (C12); see X-ray details for further information. Compound 14 is one of only a few g 2 -thioformaldehyde complexes known for early metals (Ta, 41 Zr 42 and Ti 43 ). In addition, 14 is thermally robust; no changes were observed upon prolonged heating at 135 • C. This behavior contrasts to that of other tantalum thioaldehydes, Cp 2 Ta(SCHR)H, which undergo facile migrations to the more thermodynamically stable terminal sulfido alkyl complexes, Cp 2 Ta(S)CH 2 R. 44 Carbon-sulfur bond cleavage of a different kind occurs in the reaction of 1 with triphenylmethanethiol, to form the terminal sulfido complex 15 and triphenylethane (eqn (3)).…”

“…When b-hydrogens are present on the thiolate ligand, b-hydride elimination to thioformaldehyde is favored. 41 In the case of a tertiary substituted thiolate group, carbon-sulfur cleavage is preferred. 48, 49 The latter is consistent with the proposed mechanism for the reaction between 1 and Ph 3 CSH.…”

Niobium and Tantalum

“…For example, carbonylation of Cp*TaMe 2 (bipy) affords Cp*Ta(r) 2 -O=CMe 2 )(CO)(bipy) 94 while nascent [Cp* 2 TaMe] (in equilibrium with Cp* 2 Ta(=CH 2 )H) reacts with MeOH to afford the hydrido formaldehyde complex Cp 2 *Ta(r| 2 -O=CH 2 )H. 109 ' 226 Similarly, treatment of the [Cp* 2 Ta(=C=CH 2 )H « * Cp* 2 TaCH=CH 2 ] equilibrium mixture with thiols HSCH 2 R affords the T I 2 -thioaldehyde compounds Cp* 2 Ta(r| 2 -S=CHR)H (for R = H, Ph, Bz, or CH 2 Bu l ) which constitute the kinetic product of this reaction. 140 Upon heating these compounds, equilibrium concentrations of [Cp* 2 TaSCH 2 R] are generated, which undergo a rate-determining a-alkyl elimination to afford Cp* 2 Ta(=S)CH 2 R. The complexes Ta(r| 2 -O=CH 2 )(silox) 3 and Ta(ri 2 -O=CHEt)-(silox) 3 are available either from carbonylation of TaH 2 (silox) 3 3 Green, Gibson, and co-workers have prepared and examined a series of complexes in which the ri 2 ligand constitutes a cyclometallated PMe 3 ligand, either r| 2 -CH 2 PMe 2 (formally alkyl carbon) or r| -CHPMe 2 (formally alkylidene carbon). For example, Green et al 454 reported a series of lower-valent tantalum compounds from reducing TaCl 5 in liquid PMe 3 using sodium sand.…”