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

OsHCl(CO)L-2 (L = (PBu2Me)-Me-t) is transformed to OsCl(NO)(CO)L-2 by p-MeC6H4SO2N(NO)Me. Chloride removal with NaBAr'(4) [Ar' = 3,5-(CF3)(2)C6H3] yields the nonplanar, unsaturated Os(o) compound [Os(NO)(CO)L-2]BAr'(4), which is shown to be more reactive towards oxidative addition than its Ru analog. It adds H-2, and the resulting Os(H)(2)(NO)(CO)L-2(+) shows broad coalesced hydride NMR signals at 25 degrees C but inequivalent sites (H-1 NMR spectral at - 32 degrees C. This cation is deprotonated by NEt3 to give trigonal bipyramidal OsH(NO)(CO)L-2. The cation Os(NO)(CO)L-2(+) adds CO. Reaction of Os(NO)(CO)L-2(+) with PhC2H gives first a 1 : 1 adduct, then the oxidative addition product OsH(C2Ph)(NO)(CO)L-2(+), then the vinylidene complex Os(CCHPh)(NO)(CO)L-2(+); a mixture of these cations can be deprotonated by NEt3 to give Os(CCPh)(CO)(NO)L-2. Reaction of Os(NO)(CO)L-2(+) with Me3SiC=CSiMe3 gives Os[CC(SiMe3)(2)](NO)(CO)L-2(+), which can be doubly hydrolyzed to give Os(CCH2)(NO)(CO)L-2(+). HCCH forms an eta(2)-HCCH adduct, which does not isomerize to Os(CCH2)(CO)(NO)L-2(+) even at 60 degrees C.