19624-67-0Relevant articles and documents
Gold(I) complexes with bidentate tertiary phosphine ligands: Formation of annular vs. tetrahedral chelated complexes
Berners-Price, Susan J.,Sadler, Peter J.
, p. 3822 - 3827 (2008/10/08)
Titrations of gold(I) complexes [(AuCl)2(P-P)] with ligand (P-P) were studied by 31P NMR for the bidentate tertiary phosphine ligands Ph2P(CH2)nPPh2, where n = 1 (dppm), 2 (dppe), 3 (dppp), and 4 (dppb), cis-Ph2PCH=CHPPh2 (dppey), Ph2P(CH2)2PEt2 (eppe), and Et2P(CH2)2PEt2 (depe). Bis-chelated four-coordinate gold(I) phosphine complexes [Au(P-P)2]+ containing either five- or six-membered chelate rings (n = 2 or 3) all exhibited exceptionally high thermodynamic and kinetic stabilities in solution. The species containing phenyl-substituted phosphines existed in CDCl3 solutions at Au:P-P ratios of less than 1:1. They were isolated and characterized with Cl- as the counteranion. [Au(depe)2]+ existed in solution at Au:depe ratios >1:1 and was isolable as a PF6- or SbF6- salt. Four-coordinate complexes containing either four- (n = 1) or seven-membered (n = 4) chelate rings were not observed as stable species in CDCl3 solutions. The solution behavior of species with a 1:1 Au:P-P ratio was also investigated by 31P NMR. In D2O the 31P NMR spectrum of the 1:1 Au:eppe species consisted of two overlapping AA′BB′ multiplets corresponding to the two isomers of the annular complex [Au2(eppe)2]2+. The isomer containing two Et2P-Au-PPh2 linkages (X) predominated by 2:1 over the other isomer (Y). For the ligands dppe and eppe, the 1:1 Au:P-P complexes were stable in aqueous solution but were involved in dissociative equilibria in CDCl3 with ring-closed species. The analogous complexes of depe, dppm, and dppb appeared to be stable in chloroform. These observations are discussed in terms of a destabilization of the annular [Au2(P-P)2]2+ complexes by steric effects.
