Molecular hydrogen complexes of the transition metals. 2. Preparation, structure, and reactivity of W(CO)3(PCy3)2 and W(CO)3(P-iso-Pr3)2, .eta.2-H2 complex precursors exhibiting metal.cntdot..cntdot..cntdot.hydrogen-carbon interaction.

The synthesis, reactivity, and molecular structures of coordinatively and electronically unsaturated complexes M(CO)/sub 3/(PR/sub 3/)/sub 2/ (M = Mo, W; R = Cy, i-Pr) are described. Ligands that bind reversibly to W(CO)/sub 3/(PCy/sub 3/)/sub 2/ include H/sub 2/, N/sub 2/, C/sub 2/H/sub 4/, H/sub 2/O, ROH, and thiophene; irreversibly bound ligands are MeCN, pyridine, NH/sub 3/, CyNH/sub 2/, and PR/sub 3/. The structures of W(CO)/sub 3/(PCy/sub 3/)/sub 2/ and W(CO)/sub 3/(P(i-Pr)/sub 3/)/sub 2/ involve incipient intramolecular oxidative addition of a distal phosphine C-H bond to the metal. The three-center M...H-C interaction in W(CO)/sub 3/(PCy/sub 3/)/sub 2/ has W-H(11a)-C(11) = 127.6/sup 0/, W-C(11) = 2.945 (6) A, and W-H(11a) approx. 2.27 A. Crystal data for W(CO)/sub 3/(PCy/sub 3/)/sub 2/ are the following: space group P1, a = 10.300 (1) A, b = 12.675 (2) A, c = 15.473 (1) A, ..cap alpha.. = 91.44 (1)/sup 0/, ..beta.. = 90.37 (1)/sup 0/, ..gamma.. = 103.99 (1)/sup 0/, Z = 2, rho(calcd) = 1.34 g cm/sup -3/, R = 0.025, 6211 reflections. Crystal data for W(CO)/sub 3/(P-i-Pr/sub 3/)/sub 2/ are the following: P2/sub 1//m, a = 8.425 (1) A, b = 13.375 (2) A, c = 12.039 (2) A, ..beta.. = 109.58 (1)/supmore » 0/, Z = 2, rho(calcd) = 1.53 g cm/sup -3/, R = 0.034, 2212 reflections. Since these molecules add dihydrogen to form stable eta/sup 2/-H/sub 2/ complexes, they afford an unprecedented opportunity to observe both H-H and C-H bond activation at a single metal center.« less