Five-coordinate gold(III) complexes of the Kläui ligands [(η⁵-C₅H₅)Co{P(O)(OR)₂}₃]− (R°=°Me, Et)

Abstract

The reactions of cycloaurated gold(III) dichloride complexes [LAuCl₂] (L°=°2-C₆H₄CH₂NMe₂ or 2-C₆H₄PPh₂ NPh) with monoanionic tripodal oxygen donor Kläui ligands [(η⁵-C₅H₅)Co{P(O)(OR) ₂}₃]− (R°=°Me or Et) results in the formation of cationic gold(III) salts [LAu{OP(OR) ₂}₃Co(η⁵-C₅H₅)]+. An X-ray structure determination on [(2-C₆H₄PPh₂ NPh)Au{OP(OR) ₂}₃Co(η⁵-C₅H₅)]BF₄shows that the Kläui ligand coordinates strongly to the gold through two oxygen atoms, and weakly through the third, giving the gold(III) a distorted square pyramidal geometry. This is the first structurally characterised example of this geometry for gold(III) with ligands other than those containing rigid bipyridine or phenanthroline backbones. In solution at room temperature there is rapid interchange (on the NMR timescale) between the oxygen atoms of the Kläui ligands, which is frozen out on cooling.