CATIONIC D(3)-D(3) DINUCLEAR COMPOUNDS OF TUNGSTEN - [W-2(O(2)CBU(T))(5)](-), WHERE X(-)=BF4- AND CF3SO3-()X()

Ditungsten hexapivalate, W-2(O(2)CBu(t))(6), and triethyloxonium tetra fluoroborate, Et(3)O(+)BF(4)(-), react in CH2Cl2 at room temperature t o yield the 1:1 complex [W-2(O(2)CBu(t))(5)][Bf(4)] (1), as a yellow c rystalline solid. A similar reaction involving trimethylsilyltrifluoro methane-sulfonate, TMS-OTf, yields [W-2(O(2)CBu(t))(5)][OTf] (2). Comp ounds 1 and 2 are 1:1 electrolytes in CH3CN but show ion pairing in TH F and CH2Cl2 solutions with the degree of ion pairing being greater fo r 2 than for 1. Only 1 is soluble in toluene. H-1 NMR spectroscopy sho ws there are 3 types of O(2)CBu(t) ligands in the integral ratio 1:2:2 which is consistent with the structure found in the solid stale for 1 which has a (W=W)(6+) unit, W-W=2.28(1) Angstrom supported by three b ridging pivalates and two chelating eta(2)-O(2)CBu(t) ligands. The loc al geometry about each tungsten is a distorted pentagonal pyramid, W=W O5, with relatively weak axial interactions (trans to the W=W bond) to the BF4- counter anions, W-F=2.50(1) Angstrom (av.). This leads to an infinite polymeric structure in the solid state. Crystal data for [W- 2(O(2)CBu(t))(5)][BF4] at -171 degrees C: a=29.44(1), b=36.05(1), c =2 0.80(1) Angstrom, beta=133.30(1)degrees, Z=16, D-calc=1.82 g cm(-3) an d space group C2/c.