PREPARATION AND CHARACTERIZATION OF M2(SEAR)6 AND MIXED-LIGAND M2(OR)2(SEAR')4 SPECIES (M = MO, W)

Toluene solutions of M2(NMe2)6 (M = Mo, W) react with mesitylene selenol (Ar'SeH) to give M2(SeAr')6 complexes. Mo2(OR)6 (R = (t)Bu) react with excess (> 6 fold) Ar'SeH to give Mo2(SeAr')6, whilst W2(OR)6(py)2 (OR)6(py)2 (R = (i)Pr, CH2(t)Bu) react with excess (> 6 fold) Ar'SeH to give W2(OR)2(SeAr')4. Reaction of mo2(OPR(i)6 with ar' SeH produces Mo2(OPR(i))2(SeAr`)4 which crystallizes in two different space groups. These arene-selenato complexes are air-stable and insoluble in common organic solvents. X-ray crystallographic studies revealed that the Mo2(SeAr')6 and W2(SeAr')6 compounds are isostructural in the solid state and adopt ethane-like staggered configurations with the following important structural parameters, M-M (W-W/Mo-Mo) 2.3000(11)/2.2175(13) angstrom, M-Se 2.430 (av.)/2.440 (av.) angstrom, M-M-Se 97.0-degrees (av.)degrees. In the solid state W2(O(i)Pr)2(SeAr')4 adopts the anti-configuration with crystallographically imposed C(i) symmetry and W-W 2.3077(7) angstrom, W-Se 2.435 (av.) angstrom, W-O 1.858(6) angstrom; W-W-Se 100.27(3)-degrees, 93.8(3)-degrees and W-W-O 108.41(17)-degrees. Mo2(OPr(i))2(SeAr')4 crystallizes in both P1bar and A2/a space groups in which the molecules are isostructural with each other and the tungsten analogue. Important bond lengths and angles are Mo-Mo 2.180(24) angstrom, Mo-Se 2.432(av.) angstrom, Mo-O 1.872(9) angstrom, Mo-Mo-Se 99.39(9)-degrees, 94.71(8)-degrees, Mo-Mo-O-107.55(28)-degrees.