Hydrogenation of Aryldiazenido Complexes. Synthesis and Structure of trans-Hydrido(acetone phenylhydrazone)bis(triphenylphosphine)platinum(II) Tetrafluoroborate

The compound formulated as Pt(BF4)(NNAr)(PPh3)2, Ar = C6H5, p-FC6H4, can be hydrogenated in a variety of solvents under mild conditions using no additional catalyst. In ethanol the hydrazine complex [PtH(H2NNHAr)(PPh3)2]-[BF4] is formed, while in the presence of acetone the corresponding hydrazone complex results. The ready availability of a coordination site on the Pt(NNAr)(PPh3)2 unit must play a key role in the easy activation of molecular hydrogen which leads to these hydrazine derivatives. The hydrazone complex trans-[PtH(PhHNNC3H6)(PPh3)2][BF4]-C6H6 crystallizes in space group C2h5-P21/c with a = 13.403 (4) Å, b = 20.949 (5) Å, c = 16.535 (4) Å, β = 91.24 (1)°, V= 4641 Å3, and Z = 4. The structure has been determined from 5635 unique x-ray reflections and refined to a conventional R index of 0.046. The coordination geometry about the platinum atom is square planar with trans phosphine groups. The hydrazone group is bound to the platinum atom through the sp2 hydridized nitrogen atom.