A Molecule Containing the OWOWO Unit. Synthesis, Structure, and Spectroscopy of W₂O₃(CH₂CMe₃)₆

Addition of excess water to W(CCMe₃)(CH₂CMe₃)₃yields pentane-soluble, water- and air-stable W₂O₃(CH₂CMe₃)₆(1). Anhydrous HCl reacts with 1 in the presence of Me₃SiCl to produce WONp₃Cl (2). W₂O₃(CH₂CMe₃)₆crystallizes in the trigonal system, space group [formula omitted], with a = 10.232 (2) Å, c = 61.446 (9) Å, V = 5571.1 ų, and Z = 6. The molecule, which has crystallographically imposed C₃symmetry, contains a linear O=W-O-W=O unit in which three neopentyl groups are trigonally disposed about each tungsten atom. The W=O bond lengths are 1.726 (10) and 1.689 (13) Å, the W(μ-O) distances are 1.923 (10) and 1.977 (10) Å, and the independent W-C bond lengths are 2.141 (9) and 2.127 (14) Å. The two ends of the molecule are twisted by 31.9 (5)° with respect to one another. Spectroscopic examination of 1 (and [¹⁸O]1) showed two IR active bands at 962 (905) (w) and 693 (668) (s) cm⁻¹ and two Raman active bands at 942 (894) (s) and 205 (205) (m) cm⁻¹ that we assign to the asymmetric W=O stretch, the asymmetric W-O-W stretch, the symmetric W=O stretch, and the symmetric W-O-W stretch, respectively. The calculated force constants are comparable to those reported for several rhenium(V) complexes containing a linear O=Re-O-Re=O backbone.