Halide-exchange reactions of VCl4 or MoCl5 with dry HBr at temperatures between ca. -50 and +20-degrees-C afforded the corresponding bromides, VBr3 or MoBr4, in good yields, presumably via the formation of unstable higher-valent bromide intermediates which undergo spontaneous loss of bromine. In corresponding reactions with HI the exchange was incomplete and mixed halides were obtained. At room temperature the VCl4-HI system gave VCl3 in an almost quantitative yield. By reaction of MoBr4 with tetrahydrofuran (thf) [MoBr3(thf)3] was isolated and its crystal structure determined: orthorhombic, space group Pbcn (no. 60), a = 8.812(2), b = 13.882(5), c = 14.279(3) angstrom, z = 4, R = 0.063. The molecule has the usual meridional geometry, typical of other [MoX3(thf)3] derivatives (X = Cl or I).

LOW-TEMPERATURE SYNTHESES OF VANADIUM(III) AND MOLYBDENUM(IV) BROMIDES BY HALIDE EXCHANGE

CALDERAZZO, FAUSTO;PAMPALONI, GUIDO;
1993

Abstract

Halide-exchange reactions of VCl4 or MoCl5 with dry HBr at temperatures between ca. -50 and +20-degrees-C afforded the corresponding bromides, VBr3 or MoBr4, in good yields, presumably via the formation of unstable higher-valent bromide intermediates which undergo spontaneous loss of bromine. In corresponding reactions with HI the exchange was incomplete and mixed halides were obtained. At room temperature the VCl4-HI system gave VCl3 in an almost quantitative yield. By reaction of MoBr4 with tetrahydrofuran (thf) [MoBr3(thf)3] was isolated and its crystal structure determined: orthorhombic, space group Pbcn (no. 60), a = 8.812(2), b = 13.882(5), c = 14.279(3) angstrom, z = 4, R = 0.063. The molecule has the usual meridional geometry, typical of other [MoX3(thf)3] derivatives (X = Cl or I).
Calderazzo, Fausto; MAICHLE MOSSMER, C; Pampaloni, Guido; Straehle, J.
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Utilizza questo identificativo per citare o creare un link a questo documento: http://hdl.handle.net/11568/30207
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