The isolobal analogy that creates a surprising link between H and Ph3PAu has been used to prep. Ph3PAu "synthetic analogs" of transition metal hydrides to support expected, but crystallog. unconfirmed, hydride positions. The asym. 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 (Ph3
