Positional isomers of mononuclear silver(I) anionic complex [Ag(Ph3P)2[B10H10−xClx]]− (x = 0 or 1) with apically and equatorially coordinated decahydrido-closo-decaborate and 2-chlorononahydrido-closo-decaborate ligands

Abstract

Attempts to separate the two dianions [B10H10]2− and [B10H9Cl]2− from mixtures with silver nitrate and PPh3 gave two novel compounds, [Ag(PPh3)4][Ag(PPh3)2[B10H9.15Cl0.85]] (1) and [Ag(PPh3)4][Ag(PPh3)2[B10H9.5Cl0.5]] (2), instead. They were selectively prepared using different synthetic approaches: 1 was prepared by the reaction of a mixture of [B10H10]2− and [B10H9Cl]2− salts [Bu4N]2[B10H10−xClx] (x=0, 1) with AgNO3 followed by dissolution of the resulting precipitate in an acetonitrile solution in an excess of PPh3, whereas 2 was prepared by the reaction of the same mixture [Bu4N]2[B10H10−xClx] with AgNO3 and an excess of PPh3 in a DMF solution. The X-ray diffraction studies showed that complex anions [Ag(Ph3P)2[B10H10−xClx]]− in 1 and 2 are positional isomers with the 10-vertex boron cluster ligands coordinating silver atoms by an apical and an equatorial edge, respectively. Crystals 1 and 2 are isostructural; in both, the anionic silver(I) complexes with [B10H10]2− and [B10H9Cl]2− cocrystallize in the same lattice. The chlorine substituents are not involved in silver coordination. Anionic complex in 2 provides the first example of silver(I) decahydrido-closo-decaborate with uncoordinated apical boron atoms of the boron cage. Possible mechanisms of the formation of complexes 1 and 2 are supposed.