Preparation and characterization of sodium heptachloropentakis(THF)ditungstate(1-). A synthetically useful precursor for X3W.tplbond.WX3 compounds where X = CH2-tert-Bu, NMe2 and O-tert-Bu

From the addition of Na/Hg (1 equiv) to a WCl/sub 4/ slurry in THF (THF = tetrahydrofuran) was obtained the green crystalline compound NaW/sub 2/Cl/sub 7/(THF)/sub 5/ in 60-70% recrystallized yields. The compound has been shown to involve a confacial bioctahedral W/sub 2/Cl/sub 7/(THF)/sub 2//sup -/ anion coordinated to a (THF)/sub 3/Na/sup +/ 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 W/sub 2/X/sub 9//sup 3 -/ anions (X = Cl or Br) and is indicative of strong t/sub 2g//sup 3/-t/sub 2g//sup 3/ M-M bonding. The compound provides a useful synthetic starting material for metathetic reactions involving Li-X leading to the known X/sub 3/W identical with WX/sub 3/ compounds where X = CH/sub 2/-t-Bu, NMe/sub 2/, and O-t-Bu. The latter are obtained in 60-80% yield based on W by either sublimation or crystallization. The compound NaW/sub 2/Cl/sub 7/(THF)/sub 5/ bears a striking similarity in terms of both its preparation and its reactivity to the compound formulated as W/sub 2/Cl/sub 6/(THF)/sub 4/ by Schrock, Sturgeoff, and Sharp, though it is not presently known how the two are related. Crystal data for NaW/sub 2/Cl/sub 7/(THF)/submore » 5/ at -151/sup 0/C: a = 18.817 (7) A, b = 8.397 (3) A, c = 20.964 (10) A, ..beta.. = 107.09 (3)/sup 0/, Z = 4, V = 3166.2 (1) A/sup 3/, d/sub calcd/ = 2.097 g cm/sup -3/, space group P2/sub 1//c. 20 references, 4 figures, 6 tables.« less