Gold(I) complexes with PO and P–OH functionalised phosphorus ligands

P-coordination of anionic phosphonite [(R2O)R1PO]− or phosphite [(RO)2PO]− ligands to (triorganophosphine)gold(I) units leads to neutral molecules with an unsymmetrical P–Au–P′ axis and a PO function. A general synthetic route starts from (R3P)AuMe precursors and the corresponding primary phosphonites (R2O)R1P(O)H or secondary phosphites (RO)2P(O)H, respectively. The gold(I) phosphonites (R3P)AuP(O)R1(OR2) (1a–d) undergo a ligand redistribution in solution, establishing equilibria that involve ionic isomers of the type [(R3P)2Au]+[Au{P(O)R1(OR2)}2]− as demonstrated by NMR spectroscopy. In the complexes Ph2P(OH)AuCl (2), Ph2P(OH)AuGeCl3 (3), [Ph2P(OH)]2Au+X−, with X−=ClO4 − (4a), SbF6 − (4b), BF4 − (4c), TfO− (4d) and (MeO)2P(OH)AuCl (5) the phosphinous acid and the phosphorous acid diester, respectively, are coordinated to gold(I) as neutral ligands with a P–OH function, respectively. The combination of the anionic phosphite and neutral ester ligands in the same molecule leads to the formation of compounds [(RO)2P(OH)AuP(O)(OR)2]n (6a–c), which oligomerise via cooperative action of hydrogen and aurophilic bonding as determined by single-crystal X-ray diffraction and NMR measurements. The degree of oligomerisation depends largely on the steric effect of the R groups. Compound 6b is a dimer, while compound 6a is a polymer. The crystal structure of the phosphite complex [(Me3P)AuP(O)(OMe)2]n (7) contains a chain of neutral monomeric units associated solely via aurophilic contacts.