Different coordination modes of a tripod phosphine in gold(I) and silver(I) complexes

Abstract

The following gold(I) and silver(I) complexes of the tritertiary phosphine 1,1,1-tris(diphenylphosphinomethyl)ethane, tripod, have been synthesised: Au3(tripod)X3 [X = Cl (1), Br (2), I (3)]; [Au3(tripod)2Cl2]Cl (4); Au(tripod)X [X = Br (5), I (6)]; Ag3(tripod)(NO3)3 (7), Ag(tripod)NO3 (8). They were characterized by X-ray diffraction (complexes 2, 3 and 4), 31P NMR spectroscopy, electrospray and FAB mass spectrometry and infrared spectroscopy. Complexes 2 and 3 show a linear coordination geometry for Au(I), with relatively short Au-P bond distances. Complex 3 has a Au···Au intramolecular distance of 3.326 Å, while complex 2 had a short Au···Au intermolecular interaction of 3.048 Å. Complexes 4-6 were found by 31P NMR spectroscopy studies to contain a mixture of species in solution, one of which crystallised as [Au3(tripod|)2Cl2]Cl which was shown by X-ray diffraction to contain both tetrahedral and linear Au(I), the first example of a Au(I) complex containing such a mixture of geometries. The reaction of [Au3(tripod)Cl3] (1) with tripod led successfully to the formation of [Au3(tripod)(-)2Cl2]+ and [Au3(tripod)3Cl]2+. The silver(I) complexes, 7 and 8 appear to contain linear and tetrahedral Ag(I), respectively.