Synthesis, Characterization, and Structure of Neutral and Anionic Complexes Containing Octahedral W(6)Te(8) Cluster...

The first examples of molecular telluride complexes, W(6)Te(8)L(6) [L =pyridine (py), piperidine (pip), and PEt(3)], and the reduced salt [Na(py)(6)](+)[W(6)Te(8)(py)(6)](-) were discovered. The amine complexes were prepared by reaction of W(6)Cl(12) with Na(2)Te or a Na(2)Te/Na(2)Te(2) mixture in the amine solvents, whereas W(6)Te(8)(PEt(3))(6) was established by displacement of pyridine in W(6)Te(8)(py)(6) by PEt(3). The cluster unit, W(6)Te(8), showed characteristic T(1u) W-Te stretching vibrations around 180-200 cm(-)(1). From XPS the W4f(7/2) binding energy of 30.8 eV for W(6)Te(8)L(6) compared favorably with values of 30.5 and 30.8 eV for the sulfide and selenide analogues, respectively. Crystallographic data for the three compounds on which structure analyses were performed are as follows: W(6)Te(8)(pip)(6).6pip, hexagonal, R&thremacr;, a = 17.738(6) Å, c = 24.318(10) Å, Z = 3; W(6)Te(8)(PEt(3))(6), monoclinic, C2/c, a = 24.724(6) Å, b = 19.716(4) Å, c = 13.543(9) Å, beta = 108.56(3) degrees, Z = 4; [Na(py)(6)](+)[W(6)Te(8)(py)(6)](-).py, triclinic, P&onemacr;, a = 12.433(3) Å, b = 12.760(2) Å, c = 12.882(2) Å, alpha = 96.78(1) degrees, beta = 100.03(1) degrees, gamma = 98.58(1) degrees, Z = 1. The average W-Te bond distance of 2.753 Å is very close to the average W-W bond distance of 2.748 Å in these telluride clusters. For the anionic complex, both the small distortion of the octahedral cluster unit and the shortening of the average W-W bond distance confirmed addition of the extra electron to a bonding orbital in the reduced 21e cluster unit. Extended Hückel MO calculations indicate that the structural distortion of the [W(6)Te(8)(py)(6)](-) anion arises from the Jahn-Teller effect on the (2)E(g) ground state. The unique cationic unit [Na(py)(6)](+) is the first documented example of a sodium ion octahedrally coordinated with six pyridine molecules.