4-COORDINATE GOLD(I), SILVER(I), AND COPPER(I) COMPLEXES WITH A LARGE-SPAN CHIRAL DITERTIARY PHOSPHINE LIGAND

The ligand L = Ph2PCH2CHEtOPPh2 (R,S) with two chemically different do nor sites and a center of chirality in the middle of the loop connecti ng the phosphorus atoms has been chosen for the preparation of a serie s of gold(I), silver(I), and copper(I) complexes. The ligand-to-metal ratio was allowed to vary between 2:1, 1:1, and 1:2. The 1:1 complexes [LAuX](2) with X = Cl, Br, I, and SCN have been found to be component s of solution equilibria (in di- or trichloromethane) of various cycli c dinuclear isomers involving also several complexes generated in liga nd redistribution processes. However, single crystals (X = Cl, Br) obt ained from these solutions are composed solely of centrosymmetrical di mers where the two metal atoms are part of 12-membered rings and are b ridged transannularly by two halogen atoms. By symmetry, the metal bri dging by the two ligands L follows a head-to-tail pattern and involves a pair of enantiomers of L. The silver compound [LAgClO4](2) has an a nalogous structure with the silver atoms attaining coordination number 4 by perchlorate bridging. The copper complex [LCuCl](2) is a tricycl ic binuclear compound where each copper atom is chelated by an individ ual ligand L and doubly halogen bridged with the second metal atom. Th e 2:1 complex [L2Au]Cl is assigned a bis-chelated structure with the t etracoordinated metal atom as a spiro center of two six-membered rings . The solution P-31 NMR spectra show the presence of various stereoiso mers which are readily identified via the strong couplings mediated by the metal center. Only small J(P, P') values would be expected for P- P' coupling along the ligand PCCOP' loops. The spectrum of the dinucle ar 1:2 complex L(AuCl)(2) features only two singlet P-31 resonances.