Interaction of t-butyl isocyanide with methyl compounds of tungsten, rhenium, zirconium, titanium, and tantalum. The X-ray crystal structures of W–N(But)CMe2(Me)(NBut)[N(But)CMeCMe2] and its hydrogen chloride adduct. t-Butyl isocyanide complexes of molybdenum(0), ruthenium(II), and rhodium(I)

Abstract

The interaction of t-butyl isocyanide with the following methyl compounds leads to the formation of insertion products in which methyl groups are transferred to the isocyanide ligand: hexamethyltungsten, hexamethylrhenium, tetraneopentylzirconium, bis(η-cyclopentadienyl)dimethyltitanium, and dichlorotrimethyltantalum. For WMe₆, a unique transfer of five methyl groups occurs to give the complex [graphic omitted]Me₂(Me)(NBu^t)[N(Bu^t)CMeCMe₂](1) whose structure has been determined by X-ray crystallography. Crystals of (1) are triclinic, space group P, with a= 8.829(2), b= 10.265(1), c= 14.324(5)Å, α= 90.87(2), β= 101.47(2), γ= 82.44(2)°, and Z= 2. The structure was solved by the heavy-atom method and refined to R= 0.057 for 4 069 observed [l > 1.5σ(l)] diffractometer data. The W–N and W–C bond lengths in the azatungstacyclopropane unit are 1.91(1) and 2.20(1)Å, the W–C(Me) distance is 2.10(1)Å, and the remaining W–N distances are 1.76(1)Å to the t-butylamide, and 1.94(1)Å to the alkylalkeneamide. All W–N bonds are presumed to be strengthened by π-bonding. The complex (1) reacts with three mol of hydrogen chloride to give the salt (2) whose structure has also been determined by X-ray methods and shown to be [Me₂CC(Me)NH₂Bu^t][[graphic omitted]Me₂(Me)(NBu^t)Cl₃]. Crystals of (2) are also triclinic, space group P, with a= 11.178(2), b= 12.730(2), c= 12.155(2)Å, α= 84.21 (2), β= 111.31 (2), γ= 97.59(2)°, and Z= 2. The structure was solved by the heavy-atom method and refined to R= 0.077 for 4 559 observed data. The identification of the components of the structure was complicated by disorder. The main points of interest in the structure are the protonation of the N atom of the azatungstacyclopropane ring leading to an increase in the W–N bond length in the ligand and the shortening of the Bu^tN(1)→W bond relative to that in compound (1). The t-butyl isocyanide complexes Mo(CNBu^t)₆, RuH₂(PMe₃)₂(CNBu^t)₂, and RhMe(CnBu^t)₄ were also synthesised. Infrared and ¹H, ¹³C, and ³¹P n.m.r. spectra of the compounds are reported.