The Synthesis of Molybdenum and Tungsten Dinitrogen Complexes

The free ligand is stable to the atmosphere and can be stored indefinitely. It is soluble in nonpolar solvents, for example, benzene, toluene, and halohydro-carbons, and to a lesser extent in acetonitrile. It is insoluble in primary alcohols and water. The nmr spectrum in CDC13 consists of a simple four-line spectrum 2.12 (12H), 4.87 (2H), 6.98 (8H), 12.58 (broad, 2N—H) ppm. The compound melts sharply at 243°. The electronic spectrum contains the following absorptions 340 (emax = 39,700), 269 (emax = 15,100), 255 nm (emax = 18,400). 

Submitted by JONATHAN R. DILWORTH and RAYMOND L. RICHARDS Checked by GRACE J.-J. CHENt and JOHN W. McDONALDt 

A preparation of fra/ -[Mo(N2)2(dppe)2] (dppe = Ph2PCH2CH2PPh2) that uses triethylaluminum as reductant has already been reported in Inorganic Syntheses,3 but it is less convenient and gives much lower yields than that described below. Other reported methods, using sodium amalgam as reductant, involve a more difficult work-up procedure.4 

Conventional Schlenk-type glassware5 is used in the procedures described below and unless otherwise stated, all manipulations are carried out under nitrogen. All solvents are anhydrous and are freshly distilled under nitrogen prior to use. Solutions are stirred with a magnetic stirrer bar unless otherwise stated. 

Mo Cl5 + excess CH3CN— [MoCl4(CH3CN)2] + chlorinated organic products 

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Displacement of ligating dinitrogen by isocyanides constitutes a convenient route for the preparation of isocyanide complexes. The first isocyanide complexes prepared by this route involve a molybdenum(0) or tungsten(0) electron-rich metal site, and the general method for their synthesis is given below. 

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