Reactivity patterns of the unsaturated Os(0) species Os(NO)(CO)(PBut2Me)2+

Abstract

OsHCl(CO)L₂ (L=PBu₂^tMe) is transformed to OsCl(NO)(CO)L₂ by p-MeC₆H₄SO₂N(NO)Me. Chloride removal with NaBAr₄^′ [Ar′=3,5-(CF₃)₂C₆H₃] yields the nonplanar, unsaturated Os(0) compound [Os(NO)(CO)L₂]BAr₄^′, which is shown to be more reactive towards oxidative addition than its Ru analog. It adds H₂, and the resulting Os(H)₂(NO)(CO)L₂⁺ shows broad coalesced hydride NMR signals at 25°C but inequivalent sites (¹H NMR spectra) at -32°C. This cation is deprotonated by NEt₃ to give trigonal bipyramidal OsH(NO)(CO)L₂. The cation Os(NO)(CO)L₂⁺ adds CO. Reaction of Os(NO)(CO)L₂⁺ with PhC₂H gives first a 1:1 adduct, then the oxidative addition product OsH(C₂Ph)(NO)(CO)L₂⁺, then the vinylidene complex Os(CCHPh)(NO)(CO)L₂⁺; a mixture of these cations can be deprotonated by NEt₃ to give Os(CCPh)(CO)(NO)L₂. Reaction of Os(NO)(CO)L₂⁺ with Me₃SiC3CSiMe₃ gives Os[CC(SiMe₃)₂](NO)(CO)L₂⁺, which can be doubly hydrolyzed to give Os(CCH₂)(NO)(CO)L₂⁺. HCCH forms an η²-HCCH adduct, which does not isomerize to Os(CCH₂)(CO)(NO)L₂⁺ even at 60°C.