Facile reduction of tungsten halides with nonconventional, mild reductants. I. Tungsten tetrachloride: Several convenient solid-state syntheses, a solution synthesis of highly reactive (WCl4)(x), and the molecular structure of polymeric tungsten tetr

摘要

Polymeric (WCl4)(x) has been prepared in crystalline form from WCl6 by three new, safer solid-state approaches via mercury (in 83% yield), bismuth (82% yield), or antimony (97% yield) reduction. A modification of a published procedure for reduction of WCl6 with red phosphorus, which improves (WCl4)(x) purity, is also described. Highly reactive (WCl4)(x) powder can be prepared in 99% yield via tin reduction of WCl6 in 1,2-dichloroethane. (WCl4)(x) powder was readily converted in high yields to the known WCl4(MeCN)(2) and W2Cl4(OMe)(4)(HOMe)(2). The molecular structure of (WCl4)(x), as determined by single-crystal X-ray diffractometry, consists of a polymer of opposite-edge-sharing bioctahedra with alternating short (W(1)-W(1A), 2.688(2) Angstrom) and long (W(1)... W(1B), 3.787(3) Angstrom) tungsten-tungsten distances. The acute W(1)-Cl(2)-W(1A) angle (69.4(2)degrees), obtuse Cl(1)-W(1)-W(1A) angle (94.99(12)degrees), short axial Cl(1)... Cl(1A) nonbonded distance (3.085(10) Angstrom, substantially less than twice the Cl van der Waals radius); and short W(1)-W(1A) distance are consistent with a strong W(1)-W(1A) interaction best described as a W=W bond for this d(2)-d(2) compound. Crystal data: Cl4W, a = 11.782(3) Angstrom, b = 6.475(1) Angstrom c = 8.062(2) Angstrom, beta = 131.14(1)degrees, V = 463.2(2) Angstrom(3), monoclinic, C2/m, Z = 4. [References: 53]