Synthesis and structure of new neutral bimetallic platinum hydride complexes

Abstract

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(μ-H)(μ-C⋮CPh)Pt(C6F5)(PPh3)] (1b), containing (X-ray) a μ-η1:η2-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(μ-H)(μ(P)-η2-PPh3)Pt(C6F5)2] (2a), which finally rearranges quantitatively to form cis-[(C6F5)(PPh3)Pt(μ-H)(μ-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 η2-phenyl interaction, and 2c with a mixed pentafluorophenyl/hydride bridged system are reported. Similar hydride/chloride bridged diplatinum complexes [(C6F5)LPt(μ-H)(μ-Cl)Pt(C6F5)L] (3, L = PPh3; 4, L = PEt3), are also quantitatively formed by treatment of trans-[PtClHL2] 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 1H NMR spectroscopy.