Synthesis and Reactions of Tungsten Alkylidene Complexes That Contain the 2,6-Dichlorophenylimido Ligand

Abstract

Tungsten alkylidene complexes that contain the 2,6-dichlorophenylimido ligand (NArCl), W(NArCl)(CHCMe3)(ORF6)2 and W(NArCl)(CHCMe3)(Biphen)(THP) (ORF6 = OCMe(CF3)2; Biphen2- = 3,3‘-di-t-Bu-5,5‘,6,6‘-tetramethyl-1,1‘-biphenyl-2,2‘-diolate; THP = tetrahydropyran), have been prepared from W(NArCl)(CHCMe3)(OSO2CF3)2(dme). Reaction of W(NArCl)(CHCMe3)(ORF6)2 with excess ethylene gave the tungstacyclobutane complex W(NArCl)(ORF6)2(C3H6), while reaction of W(NArCl)(CHCMe3)(ORF6)2 with internal olefins gave the dimer, [W(μ-NArCl)(ORF6)2]2. W(NArCl)(CHCMe3)(Biphen)(THP) reacted with excess ethylene to give W(NArCl)(Biphen)(C3H6), which yielded W(NArCl)(Biphen)(C2H4)(THF) upon addition of THF. The tungstacyclopentane complex, W(NArCl)(Biphen)(C4H8), was formed upon treatment of W(NArCl)(Biphen)(C2H4)(THF) with ethylene. W(NArCl)(Biphen)(C3H6) decomposed to yield (inter alia) the dimeric, heterochiral methylidene complex, [W(NArCl)(Biphen)(μ-CH2)]2, which decomposed further to yield homochiral [W(NArCl)(Biphen)]2(μ-CH2CH2). Finally, [W(NArCl)(Biphen)]2(μ-CH2CH2) loses ethylene reversibly to yield [W(NArCl)(Biphen)]2, which could not be isolated in pure form. {W(μ-NArCl)[OC(CF3)2Me]2}2, W(NArCl)(Biphen)(C3H6), W(NArCl)(Biphen)(C2H4)(THF), W(NArCl)(Biphen)(C4H6), [W(NArCl)(Biphen)(μ-CH2)]2, and [W(NArCl)(Biphen)]2(μ-CH2CH2) were characterized through X-ray studies.