Synthesis of [(Me₃SiNCH₂CH₂)₃N]^3- and [(C₆F₅NCH₂CH₂)₃N]^3- Complexes of Molybdenum and Tungsten That Contain CO, Isocyanides, or Ethylene

Abstract

Paramagnetic complexes of the type [N3N]MoL ([N3N]3- = [(Me3SiNCH2CH2)3N]3-; L = CO, RNC, C2H4) have been prepared by displacing dinitrogen from [N3N]Mo(N2). [N3N]Mo(CO) was reduced by magnesium powder in the presence of Me3SiCl to yield the diamagnetic oxycarbyne complex [N3N]Mo⋮COSiMe3, while oxidation of [N3N]Mo(CN-t-Bu) with [Cp2Fe]OTf yielded {[N3N]Mo(CN-t-Bu)}OTf. Thermolysis of [N3N]Mo(CN-t-Bu) resulted in loss of a t-Bu radical to yield [N3N]Mo(CN), which was structurally characterized. [N3NF]ML ([N3NF]3- = [(C6F5NCH2CH2)3N]3-; M = Mo, W; L = CO, RNC) complexes have been prepared by one-electron reduction of [N3NF]M(OTf) in the presence of L. An X-ray study of [N3NF]W(CN-t-Bu) showed it to contain a bent isocyanide ligand. Anionic CO complexes were prepared by the two-electron reduction of [N3NF]M(OTf) in the presence of CO. An X-ray study of {[N3NF]W(CO)2}Na(ether)3 revealed it to have a pseudo-octahedral structure in which sodium is bound to the CO trans to the amine donor atom. Treatment of {[N3NF]M(CO)}- complexes with Me3SiCl gave oxycarbyne complexes [N3NF]M⋮COSiMe3. Reaction of [N3NF]WCO with V(Mes)3(THF) yielded [N3NF]W(CO)V(Mes)3, the structure of which was determined in an X-ray study. Cationic [N3NF]3- complexes could be prepared that contain up to 3 equiv of isocyanide. An X-ray study of {[N3NF]W(CN-t-Bu)3}BPh4 showed it to be a seven-coordinate species with one isocyanide located in the equatorial plane and the other two isocyanide ligands in the apical pocket. Reduction of [N3NF]W(OTf) under ethylene gave [N3NF]W(C2H4), which could be oxidized to yield diamagnetic {[N3NF]W(C2H4)}OTf.