Synthesis and reactions of some tris(2-methylphenyl)silanolatometal compounds. Crystal and molecular structures of [Ta{OSi(C6H4Me-2)3}Cl4]·1.5Et2O and [Ta{OSi(C6H4Me-2)3}Me3Cl]

Abstract

The reactions of HfCl₄, NbCl₅, TaCl₅ and WCl₆ with Li[OSi(C₆H₄Me-2)₃] in 1 : 1 molar ratios afforded the compounds [Hf{OSi(C₆H₄Me-2)₃}Cl₄]·Li(Et₂O)₂1, [Nb{OSi(C₆H₄Me-2)₃}Cl₄]·1.5Et₂O 2, [Ta{OSi(C₆H₄Me-2)₃}Cl₄]·1.5Et₂O 3 and Si(C₆H₄Me-2)₃Cl respectively. The reactions of 3 with MgMeX (X = Cl or l) under a range of conditions were explored. Thus the compounds [Ta{OSi(C₆H₄Me-2)₃}Me₃X]4(X = Cl), and the corresponding isomorphous mixture 4a having chloride and iodide present in the ratio 2 : 1, [{Ta[OSi(C₆H₄Me-2)₃]Me₃}₂]5 and [Ta{OSi(C₆H₄Me-2)₃}₂Me₂Cl]6 have been prepared and characterised. Compound 6 was also prepared form [Ta{OSi(C₆H₄Me-2)₃}₂Cl₃]7. X-Ray structures of compound 3, and the isomorphous mixture 4a have been determined. Compound 3 is octahedral with the siloxy and ether groups mutually trans with Ta–O distances of 1.812(3)(siloxy) and 2.263(3)Å(ether); Ta–Cl 2.328–2.356(1). Compound 4a is five-co-ordinate trigonal bipyramidal with the siloxy and halide axial: Ta–O 1.1856(5), Ta–Cl/l 2.37(1)/2.674(6), and equatorial Ta–C 2.11–2.17(1)Å.