Synthesis and structure of Os(η2-3,3-diphenylcyclopropene)Cl(NO)(PPh3)2 and the ring-opening reactions of the π-bound cyclopropene with acids

Reaction between the zerovalent nitrosyl complex, OsCl(NO)(PPh3)3 and 3,3-diphenylcyclopropene yields the robust π-adduct, Os(η2-3,3-diphenylcyclopropene)Cl(NO)(PPh3)2 (1), the crystal structure of which reveals the chloride and nitrosyl ligands located mutually trans and the Os, the two PPh3 ligands and the double bond of the cyclopropene, all lying in one plane. Treatment of 1 with the acids HX (X = Cl, O2CCF3) brings about a ring-opening of the cyclopropene ring (perhaps via an intermediate diphenylvinyl carbene complex) with the organic moiety remaining bound to osmium and with ultimate formation of the σ-diphenylallyl complexes, Os(CH2CHdouble bond; length as m-dashCPh2)Cl2(NO)(PPh3)2 (2) and Os(CH2CHdouble bond; length as m-dashCPh2)Cl(O2CCF3)(NO)(PPh3)2 (3), respectively. A crystal structure determination for 2 has been obtained.