W2Cl4(NR(2))(2)(PR'(3))(2) molecules .4. A new synthetic route to products with a staggered conformation. Preparations and characterizations of W2Cl4(NR(2))(2)(PR'(3))(2) (R=Et, Bu, Hex; R'(3)=Me(3), Et(2)H) and an intermediate complex W2Cl4(NEt(2))(2)(NHEt(2))(2)

A new and convenient synthetic route to a series of W=W compounds with the general formula W2Cl4(NR(2))(2)(PR'(3))(2) has been developed. The method has been used in the preparation of W2Cl4(NR(2))(2)(PMe(3))(2) (R = Et (2), Bu (3), Hex (4)) and W2Cl4(NR(2))(2)(PEt(2)H)(2) (R = Et (5), Bu (6), Hex (7)). Treatment of W2Cl6(THF)(4) with the appropriate dialkylamine NHR(2) (R = Et, Bu, Hex) affords an intermediate species having the stoichiometry W2Cl4(NR(2))(2)(NHR(2))(2). This has been verified by single-crystal X-ray diffraction studies for W2Cl4(NEt(2))(2)(NHEt(2))(2) (1) with the following crystallographic parameters: orthorhombic space group Iba2, a = 11.6704(9) Angstrom, b = 13.336(1) Angstrom, c = 17.321(2) Angstrom, Z = 4. The structure of 1 reveals that the molecule itself deviates from an eclipsed conformation with retention of a strong intramolecular N-H ... Cl hydrogen bonding and the torsion angle involving the hydrogen bonded N and Cl atoms is 27.0 degrees. Each W atom is coordinated by a cis set of two Cl and two N atoms with a W-W distance of 2.3084(5) Angstrom. There is a 1.6% orientational disorder of the W-W unit. Subsequent addition of the monodentate phosphines (PMe(3) and PEt(2)H) to the intermediate complexes produces a variety of new W-2(6+) complexes W2Cl4(NR(2))(2)(PR'(3))(2), 2-7, in reasonable yields, depending on the choices of the amines and phosphines. The characterization of 2-7 has been accomplished using IR and H-1 and P-31{H-1} NMR spectroscopy and mass spectrometry. The crystal structures of 2, 3, 6, and 7 are fully described. Crystal data for these compounds are as follows: for 2, triclinic space group <P(1)over bar>, a = 9.568(2) Angstrom, b = 17.294(7) Angstrom, c = 17.418(5) Angstrom, alpha = 111.82(3)degrees, beta = 103.11(2)degrees, gamma = 90.72(3)degrees, Z = 4; for 3, <P(1)over bar>, a = 12.162(6) Angstrom, b = 14.955(4) Angstrom, c = 18.82 (1) Angstrom, alpha = 95.66(3)degrees, beta = 97.99(4)degrees, gamma = 91.26(3)degrees, Z = 4; for 6, monoclinic space group P2(1)/n, a = 17.970(3) Angstrom, b = 10.993(2) Angstrom, c = 20.689(4) Angstrom, beta = 115.43(1)degrees, Z = 4; for 7, P2(1)/c, a = 15.3937(7) Angstrom, b = 11.473(2) Angstrom, c = 24.977(3) Angstrom, beta = 92.33(1)degrees, Z = 4. The molecular structures of all these phosphine-containing complexes possess a common metal core unit and each entails an essentially staggered W2Cl4N2P2 conformation with the W atoms united by a triple bond (average W-W distance, 2.322 Angstrom). Each molecule adopts a cis configuration with the P and N atoms mutually cis on each W atom, consistent with the stereochemistry of the intermediate species W2Cl4(NR(2))2(NHR(2))2 formed in the first step.