A Zwitterionic Platinum Complex with a Carbene Ligand

The development of new materials suitable for electrooptical studies has recently received a great deal of attention. One strategy deals with the preparation of zwitterionic molecules which are provided with a very high ground-state dipole moment [1, 2]. Michl and coworkers have presented in 1999 a tropylium ylide [12-C7H6-CB11H11] with a dipole moment of 11.25 D and a first hyperpolarizability of 236 × 10−30 esu at 1064 nm [3]. Spencers group has studied polyhedral-based nonlinear optical materials on the basis of carborane substituted betains like 1,12[(C7H7)C2B10H10(C5H3Me2)] [4, 5]. Currently we are exploring the coordination chemistry of a new tin ligand, the stanna-closo-dodecaborate dianion. This heteroborate coordinates readily at transition metal centers and a variety of coordination compounds have been synthesized. In the square planar coordinated complexes of platinum(II) the heteroborate shows a strong trans influence [8]. Furthermore, stannaborate substituted phosphine complexes are selective catalysts in the hydroformylation of octene [9]. Since the stannaborate dianion [SnB11H11]2− is able to react as a monodentate ligand under replacement of a halide anion, this substitution results in the incorporation of a negative charge into the respective transition metal complex. Therefore, in reaction with cationic transition metal halides [LnPtCl] zwitterionic molecules of the type [(H11B11Sn)PtLn] can be synthesized [6 – 8]. Several of these polar transition metal complexes have been synthesized so far and the structures in the solid state