Ligand-stabilization of an unusual square-based pyramidal geometry of Cd(n) and Zn(n) in an heterometallic {MPt2S2} core (M = Cd, Zn)

Abstract

Two heterometallic complexes, [Pt2MCl(bipy)(PPh3)4(μ3-S) 2][PF6] (M = Zn, 2, Cd, 3) were synthesized from [Pt2(PPh3)4(μ-S)2] and characterized by single-crystal X-ray diffraction and electrospray ionization mass spcctrometry. Two unusual square-based pyramidal (sbp) Zn(n) and Cd(n) structures are evident. VT 31P-{1H} NMR studies showed that 2 and 3 are fluxional at rt whereby rapid ligand exchange takes place by a non-dissociative mechanism. At intermediate temperatures, this motion slows down to a flipping movement of the {Pt2S2} ligand. At 183 K, all four phosphines are inequivalent in a distorted sbp model similar to that observed in the solid state. Nonlocal density functional theory calculations reveal that the formation of a trigonal bipyramidal intermediate in the fluxional process is favored over that of the tetrahedral species for both 2 and 3. The M-C1 (M = Zn, Cd) bonds are notably strong. © The Royal Society of Chemistry 2000.