Synthesis and structure of new neutral bimetallic platinum hydride complexes

The reactions of mononuclear hydride complexes trans-[PtHXL2] with the solvated species cis-[Pt(C6F5)(2)(thf)(2)] constitute a simple methodology to high-yield synthesis of dinuclear compounds with a mixed bridging system H/X. Thus, trans-[Pt(C=CPh)H(PPh3)(2)] reacts readily with, cis-[Pt(C6F5)(2)(thf)(2)] to give trans-[(C6F5)(PPh3)Pt(mu-H)(mu-C=CPh)Pt(C6F5)(PPh3)] (1b), containing (X-ray) a mu-eta(1):eta(2)-C=CPh alkynyl ligand. trans-[Pt(C6F5)H(PPh3)(2)] reacts with cis-[Pt(C6F5)(2)(thf)(2)] under mild conditions to afford initially the 1:1 adduct trans,cis-[(C6F5)(PPh3)Pt(mu-H)(mu(P)-eta(2)-PPh3)Pt(C6F5)(2)] (2a), which finally rearranges quantitatively to form cis-[(C6F5)(PPh3)Pt(mu H)(mu-C6F5)Pt(C6F5)(PPh3)] (2c). The crystal structures of 2a, a compound displaying an unusual PPh3 bridging ligand via the P donor atom and an eta(2)-phenyl interaction, and 2c with a mixed pentafluorophenyl/hydride bridged system are reported. Similar hydride/chloride bridged diplatinum complexes [(C6F5)LPt(mu-H)(mu-Cl)Pt(C6F5)L] (3, L = PPh3; 4, L = PEt3), are also quantitatively formed by treatment of trans-[PtClHl(2)] with cis-[Pt(C6F5)(2)(thf)(2)] in CHCl3. Both complexes are obtained as trans isomers (3b and 4b), but their NMR data in CD3COCD3 indicate that they are present as a mixture of trans (3b, 4b) and cis (3c, 4c) isomers. Slow crystallization of 3b (CH2Cl2/hexane) in the presence of light gave crystals of the cis isomer 3c (X-ray), which is also quantitatively formed by photolysis of 3b. The presence of hydride bridging ligands in all complexes 1-4 is unambiguously confirmed by H-1 NMR spectroscopy.