Synthesis and crystal structure of Poly(tetraphenylphosphonium (μ2-closo-decaborato)copper(I))

Interaction of dicopper(I)-decaborate Cu2B10H10 with tetraphenylphosphonium decaborate ((C6H5)(4)P)(2)(B10H10) afforded the title compound, Ph4P[Cu(B10H10)]. The compound has been characterized using elemental analysis, FTIR spectroscopy and X-ray crystallography. The asymmetric unit contains one-fourth of a Cu-I cation, one-fourth of a tetraphenylphosphonium cation and one-fourth of a decaborate dianion. The copper and phosphorus atoms are located on a four-fold rotation and a four-fold rotation-inversion axes, respectively. The dianion is disordered over four sites by a four-fold rotation axis and a glide plane. Decahydro-closo-decaborate dianion B10H102- acts as a bridge ligand through equatorial vertices. Each Cu-I centre coordinates two decaborate anions through 3c2e (CuHB) bonds to give a one-dimensional {[CuB10H10](-)}(n) chain Although a number of compounds with the {Cat[CuB10H10]}(n) composition (where Cat is any cation) and chain {[CuB10H10](-)}(n) anions are known, this coordination mode for borates has not been observed earlier. The ability of the decaborate dianion to act as a bridge ligand through various vertices and edges allows {[CuB10H10](-)}(n) anions to form a number of positional isomers. Relation between the coordination mode of closo-decaborate, the nature of cation and spatial features of polymer chain {[CuB10H10](-)}(n) in the structures of {Cat[CuB10H10]}(n) (where Cat = Cs+, Cu+, (CH3)(2)NH2+, (C2H5)(3)NH+ or Ph4P+) is discussed.