THE TUNGSTEN-TUNGSTEN TRIPLE BOND .19. PREPARATION AND CHARACTERIZATION OF W-2(6+)-CONTAINING COMPOUNDS SUPPORTED BY AMIDE/ALKOXIDE AND TRIFLUOROMETHANESULFONATE LIGANDS

The compound W2(NMe2)4(OTf)2 (1), where OTf is the trifluoromethanesulfonate anion, O3SCF3-, has been prepared from the reaction between W2(NMe2)6 and Me3SiOTf (2equiv) in hexane at room temperature (22-degrees-C). Compound I is also formed in the reaction between W2Cl2(NMe2)4 and AgOTf (2 equiv) in THF but in lower yield. Crystal data for I at -153-degrees-C: a = 7.650 (2) angstrom, b = 18.012 (5) angstrom, c = 8.849 (2) angstrom, beta = 109.33 (1)-degrees, Z = 2, d(calcd) = 2.43 g cm-3, and space group P2(1)/n. Compound I contains an anti-W2O2N4 core with W-W = 2.292 (2) angstrom, W-O = 2.07 (1) angstrom, W-N = 1.92 (1) angstrom (average), W-W-O = 102.0 (4)-degrees, and W-W-N = 101.2 (5)-degrees (average). Compound I and PMe3 (2-4 equiv) react in toluene to give W2(NMe2)3(OTf)3(PMe3)2 (II) and W2(NMe2)6 by ligand redistribution reactions. Crystal data for II at -172-degrees-C: a = 14.097 (3) angstrom, b = 14.651 (3) angstrom, c = 11.752 (2) angstrom, alpha = 107.48 (1)-degrees, beta = 93.61 (1)-degrees, gamma = 91.27 (1)-degrees, Z = 2, d(calcd) = 1.98 g cm-3, and space group P1BAR. The molecular structure of II contains roughly square planar WON2P and WO2NP units united by a W=W bond of length 2.324 (1) angstrom. The W2O3N3P2 unit is staggered. The W-O distance, 2.205 (9) angstrom, is longer when supported by two attendant NMe2 ligands, W-N = 2.00 (1) angstrom (average). Conversely, the shorter W-O distances, 2.13 (1) angstrom (average), associated with the W(NMe2)(OTf)2(PMe3) moiety are supported by a shorter W-N bond, 1.92 (1) angstrom. Attempts to prepare W2(O-t-Bu)4(OTf)2 from the reaction between W2(O-t-Bu)6 and Me3SiOTf (2 equiv) at room temperature yield a green crystalline compound that we formulate as [W(O-t-Bu)2(OTf)]n, where n = even. The latter compound is thermally unstable at room temperature and decomposes slowly in solution at -25-degrees-C. Addition of PMe3 (2-4 equiv) to the compound [W(O-t-Bu)2(OTf)]n yields W2(O-t-Bu)4(OTf)2(PMe3)2 (III) in high yields. Compound III is soluble in THF, very sparingly soluble in toluene, and insoluble in hexane. Compound III crystallizes with molecules of THF in the lattice. The molecular structure contains two roughly square planar WO3P units, W-O(OTf) and 2.19 (2) and 2.21 (1) angstrom, W-O(O-t-Bu) = 1.88 (2) angstrom (average), W-P = 2.46 (1) angstrom (average), and W-W = 2.421 (1) angstrom. Crystal data for III at -176-degrees-C: a = 15.226 (2) angstrom, b = 21.562 (2) angstrom, c = 15.689 (2) angstrom, Z = 4, d(calcd) = 1.70 g cm-3, and space group P2(1)2(1)2(1).