Syntheses and characterization of dinuclear palladium and platinum complexes with a single unsupported bridging group. Crystal structure of [{C6H3(CH2NMe2)2-o,o′}Pd(µ-Cl)Pd{C6H3(CH2NMe2)2-o,o′}]BF4

Abstract

Reaction of cationic [M{C₆H₃(CH₂NMe₂)₂-o,o′}(H₂O)_n]Y (M = Pd or Pt; n= 1, Y = BF₄; M = Pt, n= 0, Y = O₃SCF₃) with neutral [MX{C₆H₃(CH₂NMe₂)₂-o,o′}](M = Pd or Pt; X = halide or CN) gives novel homo- and hetero-dinuclear complexes possessing a single unsupported halide or cyanide bridge. The complexes have been characterized by i.r., ¹H n.m.r., and elemental analyses. A single-crystal X-ray structure determination has been carried out on the palladium species [{C₆H₃(CH₂NMe₂)₂-o,o′Pd(µ-Cl)Pd{C₆H₃(CH₂NMe₂)₂-o,o′}] BF₄[a= 11.163(1), b= 21.347(2), c= 12.246(4)Å, β= 91.48(2)°, and Z= 4; R= 0.042 for 5 077 reflections]. The cation consists of two Pd{C₆H₃(CH₂NMe₂)₂-o,o′} units sharing a single bridging chlorine atom. Both Pd^II centres have a slightly distorted square-planar co-ordination sphere. Each Pd atom is surrounded by a carbon atom and two mutually trans N atoms of the terdentate ligand and the bridging chlorine atom. Dihydride-bridged complexes [(C₆H₃(CH₂NMe₂)₂-o,o′}M(µ-H)₂Pt(PPh₃)₂]BF₄(M = Pd or Pt) have been prepared by using a procedure in which a reactive hydride is generated in situ from the reaction of a Pt⁰ phosphine species and gaseous H₂ in the presence of [M(C₆H₃(CH₂NMe₂)₂-o,o′}]BF₄(M = Pd or Pt). From ¹H n.m.r. these complexes are anticipated to have a geometry in which there is both a four- and a five-co-ordinate centre. The reaction of [Pt{C₆H₃(CH₂NMe₂)₂-o,o′}]O₃SCF₃ and [Pt(O₂CH){C₆H₃(CH₂NMe₂)₂-o,o′}] in benzene afforded the monohydride-bridged complex [{C₆H₃(CH₂NMe₂)₂-o,o′}Pt(µ-H)Pt{C₆H₃(CH₂NMe₂)₂-o,o′}]O₃SCF₃. Attempts to synthesize the palladium analogue were not successful.