N,C "Rollover" cyclometalated platinum(II) hydrides: Mono- and polynuclear derivatives

N,C cyclometalated platinum(II) hydrides were obtained by reaction of the "rollover" derivatives [Pt(N'-C(3))(Cl)(L)] (N-CH= 6-tert-butyl- and 6-phenyl-2,2'-bipyridine; L = DMSO, 3,5-Me-2-pyridine, PPh3) with Na[BH4]. Mono- or polynuclear hydrides, [Pt(N'-C(3))(H)(L)] or [Pt(N'-C(3))(mu-H)](n), are formed depending on the nature of the neutral ligand, L. The unsaturated 14-electron fragments [Pt(N'-C(3))(mu-H)] assemble to form oligomers with bridging hydrides. Spectroscopic characterization provides evidence for tetramers both in solution (H-1 NMR) and in vapor phase (ESI-MS). In the tetrameric systems the 2e-3c Pt-H-Pt bond is cleaved by pi-acceptor ligands such as Ph3P and CO to give stable mononuclear hydrides.