Chloride Metathesis and Dimethylamide Transfer in the Reaction of TaCl(NMe2)4 with ZnMe2 and MeMgCl: Spectroscopic Studies and X-ray Diffraction Structures of TaCl(Me)(NMe2)3 and ZnCl2(NHMe2)2

Abstract  

Treatment of TaCl(NMe₂)₄ with ZnMe₂ in pentane furnishes a mixture of TaCl(Me)(NMe₂)₃, TaMe(NMe₂)₄, and Ta(NMe₂)₅ as the principal reaction products based on ¹H NMR spectroscopy. Depending upon the work-up conditions employed, the compounds TaCl(Me)(NMe₂)₃ and ZnCl₂(NHMe₂)₂ have been isolated and their molecular structures established by X-ray crystallography. TaCl(Me)(NMe₂)₃ crystallizes in the orthorhombic space group Pna2₁, a = 13.644(4) ?, b = 12.934(4) ?, c = 6.992(2) ?, V = 1233.9(7) ?³, Z = 4, and d _calc = 1.958 Mg/m³; R = 0.0316 and wR ₂ = 0.0707 for 2630 reflections with I > 2σ(I). The molecular structure of TaCl(Me)(NMe₂)₃ consists of a trigonal bipyramidal core and contains axial and equatorial chlorine and methyl groups, respectively. ZnCl₂(NHMe₂)₂ crystallizes in the orthorhombic space group P2₁2₁2₁, a = 5.759(1) ?, b = 10.810(2) ?, c = 15.174(3) ?, V = 944.1(3) ?³, Z = 4, d _calc = 1.593 Mg/m³; R = 0.0213 and wR ₂ = 0.0494 for 1872 reflections with I > 2σ(I). ZnCl₂(NHMe₂)₂ exhibits a tetrahedral motif and represents the first reported four-coordinate zinc(II) compound containing acyclic monodentate secondary amine groups. The reaction between TaCl(NMe₂)₄ and MeMgCl afforded a mixture of tantalum products, of which TaCl(Me)(NMe₂)₃ and Ta(NMe₂)₅ were found as the major products by ¹H NMR spectroscopy.