Reactivity of P2N2 and P2N2H4 towards C7H8M(CO)4 (M = Cr, Mo). X-ray structure of fac-(CO)3Mo[PN2P(O)]

The interaction of C7H8M(CO)4(M = Cr, Mo) with half an equivalent of P2N2(P2N2= N,N′-bis[o-(diphenylphosphino)benzylidene]ethylenediamine) in THF at ambient temperature gives [cis-(CO)4M]2(P2N2) (I, M = Cr; II, M = Mo) in high yield. The interaction of C7H8M(CO)4with 1 equivalent of P2N2in refluxed THF gives [cis-(CO)4M]2(P2N2), fac-(CO)3M(PN2P) (III, M = Cr; IV, M = Mo) and fac-(CO)3M [PN2P(O)] (V, M = Mo). The yield of the products depends on the length of the reaction time. For a short reaction time the major product is [cis-(CO)4M]2(P2N2), whereas for a long reaction time fac-(CO)3M(PN2P) is the major product. However, the interaction of C7H8Cr(CO)4with 1 equivalent of P2N2H4(P2N2H4= N,N′-bis[o-(diphenylphosphino)benzyl]ethylenediamine) in refluxed THF produces [cis-(CO)4Cr]2(P2N2H4) (VI as the only isolated product in high yield. Prolonged refluxing of [cis-(CO)4M]2(P2N2) with P2N2in THF does not give fac-(CO)3M(PN2P). In solution IV slowly oxidizes to V, whose structure has been determined by X-ray crystallography.