The isolobal analogy that creates a surprising link between H and Ph3PAu has been used to prepare Ph3PAu  �synthetic analogues� of transition metal hydrides to support expected, but crystallographically unconfirmed, hydride positions.  The asymmetric structure of the diiron hydrogenase enzyme active site, [FeFe]-H2ase eas, suggests a terminal (rather than bridging) hydride position is a requirement for catalytic activity.  Such asymmetry is also found in the all-carbonyl complexes HtFe(CO)4M(CO)5-, M = Cr, Mo, W, for which (Ph3PAu)tFe(CO)4M(CO)5- anions are also known.1 In both, the non-CO ligands are terminal.  In contrast, parent homobimetallic complexes (�-H)(�-CO)2[Fe(CO)3]2- and  (�-H)[M(CO)5]2- have only bridging hydrides, as seen in the usual biomimetic complexes derived for the [FeFe]-H2ase eas.  The requirement of asymmetry or polarized M-M' bonds sets the stage for defining new hydride complexes in bioorganometallic chemistry where bridging thiolate sulfur protonation may compete with metal-metal bond electrons, and terminal hydrides are gained only with difficulty. Arndt, L. W.;  Darensbourg, M. Y.; Fackler, J. P.; Lusk, R. J.; Marler, D. O.; Youngdahl, K. A.  J. Am. Chem. Soc. 1985 , 107, 7218-7219.

Rich man's proton: Triphenylphosphinegold as probe of hydride positions in organo- and bioorgano-metallic complexes

244th National Meeting (2012)

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