From the addition of Na/Hg (1 equiv) to a WC14 slurry in THF (THF = tetrahydrofuran) was obtained the green crystalline compound NaW2Cl7(THF)5 in 60-70% recrystallized yields. The compound has been shown to involve a confacial bioctahedral W2C17(THF)2" anion coordinated to a (THF)3Na+ cation via two chloride ligands that are terminally bonded to W atoms. The W-W distance 2.4028 (15) A is essentially identical with that seen in other W2X91 23' anions (X = Cl or Br) and is indicative of strong t2g3-t2g3 M-M bonding. The compound provides a useful synthetic starting material for metathetic reactions involving Li-X leading to the known X3W=WX3 compounds where X = CH2-í-Bu, NMe2, and O-z-Bu. The latter are obtained in 60-80% yield based on W by either sublimation or crystallization. The compound NaW2Cl7(THF)5 bears a striking similarity in terms of both its preparation and its reactivity to the compound formulated as W2C16(THF)4 by Schrock, Sturgeoff, and Sharp,48 though it is not presently known how the two are related. Crystal data for NaW2Cl7(THF)

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Hydrocarbon solutions of W2(p-CSiMe3),X4(W-W) compounds, where X = CH2SiMe3 and 0-i-Pr, have been found to react with diphenyldiazomethane, N2CPh2, at room temperature to give the 1:l adducts W2(p-CSiMe3)2X4(N2CPh2) (1, X = CH2SiMe3; 2, X = 0-i-Pr). The dinuclear center of the alkylidyne compound acts as a source of electrons reducing the diazoalkane to a NNCPh2 hydrazonido(2-) ligand. Both compounds have been characterized by 'H, I3C, and IR spectroscopy. The molecular structure of W2(p-CSiMe3)2(CH2SiMe3)4(N2CPhz) (1) shows that NNCPh2 is terminally bound to one W atom resulting in a pseudo-trigonal-bipyramidal geometry at that W atom wherein the coordinated NNCPh2 ligand and one of the alkylidyne bridges occupy the axial positions. The other W atom is in a pseudotetrahedral environment. The W-N distance of 1.767 (10) 8, together with the WNN angle of 158.2 (8)" suggests partial donation of the nitrogen lone pair to give significant WEN character. Thermolysis of 1 at 120 "C in toluene solution results in loss of Si(CH3)4 (1 equiv) and generates, via C-H bond activation, a compound which we formulate, on the basis of 'H and 13C NMR spectroscopic data, as (Me3SiCH2)2W(p-CSiMe3)2W-(CH2SiMe3) (NN=C(Ph)-o-C6H4). At no time was alkylidene formation observed from either thermolysis or photolysis of solutions of 1. On the basis of low-temperature 'H NMR, 13C NMR, and IR spectroscopic data, we formulate that 2 is structurally related to 1. The molecule is fluxional on the 'H NMR time scale due to a pseudorotational process occurring about the trigonal-bipyramidal W atom, AG*,t = 13.4 kcal/mol. Neither thermolysis at 120 "C nor photolysis of hydrocarbon solutions of 2 generate alkylidene-containing products, but rather dissociation of N2CPh2 occurs with regeneration of W2(p-CSiMe3)2(0-i-Pr)4. Crystal data for 1 at -159 O C : a = 21.163 (5) A, b = 22.639 (4) A, c = 10.403 (1) A, / 3 = 91.73 (l)", 2 = 4, dCdcd = 1.441 g ~m -~, and space group P2,/a.

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