Alkyl, alkylidene, and alkylidyne complexes of osmium(VI)

Article abstract of DOI:10.1021/ja00122a010

Addition of dialkylzinc reagents to [PPh₄]₂[OsO₂Cl₄] gives OsO₂R₂ complexes (R = neopentyl, neophyl, or (trimethylsilyl)methyl). The reaction between OsO₂(CH₂-t-Bu)₂ and 2 equiv of Ta(CH-t-Bu)(CH₂-t-Bu)₃ gave syn,anti-Os(CH₂-t-Bu)₂(CH₂-t-Bu)₂, while [OsO₂(CH₂SiMe₃)₂]_n reacted to give a 1:1 mixture of syn,anti-Os(CH-t-Bu)₂(CH₂SiMe₃)₂ and anti,anti-Os(CH-t-Bu)₂(CH₂SiMe₃)₂. Isolated anti,anti-Os(CH-t-Bu)₂(CH₂SiMe₃)₂ was shown in an X-ray study to be a distorted tetrahedron in which the two neopentylidene ligands lie in the same plane. Extended Hückel calculations performed on Os(CH₂)₂(CH₃)₂ suggest that the HOMO is an orbital of primarily of character that lies between and in the plane of the OsC₂ fragment, the LUMO is the π* system of the bis(methylidene), and the HOMO-1 and HOMO-2 are bonding combinations of the tem. Os(CH-t-Bu)₂(CH₂-t-Bu)₂ reacts with neat trimethylphosphine to give Os(PMe₃)₃(η²-t-BuC≡C-t-Bu) which was shown in an X-ray study to be a pseudotetrahedral species in which C≡C = 1.30 (1) ?. syn,anti-Os(CH-t-Bu)₂(CH₂-t-Bu)₂ reacts with pyridinium triflate in the presence of pyridine to yield Os(C-t-Bu)(CH₂-t-Bu)₂(py)₂(OTf), while OsO₂(CH₂-t-Bu)₂ reacts with 1 equiv of Ta(CH-t-Bu)(py)₂X₃ (X = Cl, Br) to form Os(C-t-Bu)(CH₂-t-Bu)(py)₂X₂. Os(C-t-Bu)(CH₂-t-Bu)₂L (L = O-t-Bu or N(SiMe₃)₂), Os(C-t-Bu)(CH₂-t-Bu)₂{CpCo[P(O)(OEt)₂] ₃}, and Os(C-t-Bu)(CH₂-t-Bu)₂[HB(pyrazolyl)₃] could all be prepared from Os(C-t-Bu)(CH₂-t-Bu)₂(py)₂(OTf). An X-ray study of Os(C-t-Bu)(CH₂-t-Bu)₂(HBpz₃) showed it to be a pseudooctahedral molecule in which Os≡C = 1.73(2) ?.