NO binds to unsaturated Os(IV) polyhydrides as a redox reagent

Reaction of Os(H)3ClL2(Ldouble bond; length as m-dashPiPr3) with equimolar NO occurs via a detectable paramagnetic species, to form OsCl(NO)L2 + H2, then Os(H)2Cl(NO)L2, together with the product of halogen transfer, OsHCl2(NO)L2. For comparison, equimolar NO and the dichloride Os(H)2Cl2L2 react to give OsHCl2(NO)L2. DFT(PBE) calculations on potential radical intermediates reveal cases where spin density is on NO (vs. on Os), and show how coordinated H2 can lead to the observed halogen transfer.