Synthesis and reactions of heterobimetallic magnanese–palladium complexes. Crystal and molecular structure of [MnPdBr(CO)3-(µ-Ph2PCH2PPh2)2]

Abstract

Reaction of [MnX(CO)₅] with [Pd(dba)₂](dba = 1,5-diphenyl-1,4-pentadien-3-one) in hot toluene in the presence of Ph₂PCH₂PPh₂(dppm) affords [MnPdX(CO)₃(µ-dppm)₂][X = Cl (1), Br (2), or I (3)] in varying yield dependent upon X. Metathesis of complex (2) with NaX gives (3; X = I), (4; X = N₃), (5; X = NCO), and (6; X = SCN), and a reversible insertion of SnCl₂ into the PdCl bond of (1) affords (7; X = SnCl₃). Protonation of complexes (1)—(7) or of [Pd₂Cl₂(µ-dppm)₂] with HBF₄·Et₂O or CF₃CO₂H affords unstable cationic hydride complexes. Infrared, ¹H, ³¹P, and some ¹³C n.m.r. data of (1)—(7) and their protonated forms are given and discussed. The structure of complex (2) was established by a single-crystal X-ray diffraction study: the crystals are monoclinic, space group Cc, with a= 18.317(2), b= 13.412(2), c= 21.013(4)Å, and β= 111.75(1)°; refined to R 0.057 for 7 286 reflections [I 3σ(I)] collected by counter methods. The molecule consists of a near-planar Mn(CO)₃PdBr entity oriented perpendicular to the plane of the phosphorus atoms forming the (dppm)₂ framework. Including the Mn–Pd bond [2.810(2)Å], the palladium environment is square planar, but there is also evidence of an additional interaction involving a carbonyl. The manganese environment has an irregular six-co-ordinate geometry.