Pyridineselenolate complexes of copper and indium: Precursors to CuSex and In2Se3

The pyridineselenolate (2-Se-NC5H4, (SePy)) and the 3-(trimethylsilyl)pyridineselenolate (3-Me(3)Si-2-Se-NC5H4 (SePy*)) ligands form air-stable homoleptic coordination compounds of Cu(I){[Cu(SePy)](4) (1) and [Cu(SePy*)](4) (2)} and In(III) {In(SePy)(3) (3) and In(SePy*)(3) (4)}. Mass spectroscopic characterization of the Cu(I) compounds indicated a tetrametallic core, and this was confirmed with a single-crystal X-ray structural characterization of crystalline 1 and 2, which both contain a tetrametallic cluster of Cu(I) ions bound to two doubly bridging Se atoms and a pyridine nitrogen. The Cu coordination sphere is completed with two strong Cu-Cu bonds and one weaker Cu-Cu interaction. The indium compounds 3 and 4 are each distorted fac-octahedral molecules with chelating SePy ligands. These compounds are useful low-temperature precursors to the binary selenides. Both 3 and 4 sublime intact; 3 thermally decomposes to give In2Se3. The Cu clusters do not sublime intact but still decompose to give metal selenide phases: 2 decomposes to give pure alpha-CuSe at low temperatures and increasing amounts of Cu2-xSe at elevated temperatures, while 3 decomposes to give a mixture of CuSe phases at all temperatures. Crystal data (Mo K alpha: 1, 153(5) K; 2-4, 293(2) K) are as follows: 1, monoclinic space group C2/c, a = 20.643(5) Angstrom, b = 16.967(2) Angstrom, c = 16.025(2) Angstrom, beta = 114.16(2)degrees, Z = 8; 2, tetragonal space group I4(1)/a, a = 14.756(3) Angstrom, c = 19.925(3) Angstrom, Z = 4; 3, trigonal space group P (3) over bar c1, a = 13.352(2) Angstrom, c = 13.526(2) Angstrom, Z = 4; 4, monoclonic space group P2(1)/c, a = 9.793(1) Angstrom, b = 20.828(6) Angstrom, c = 16.505(1) Angstrom, beta = 96.69(1)degrees, Z = 4.