The Group 5 pentahalides MX5 (M = Nb, Ta; X = Cl, Br), 1, react with a variety of epoxides (1,2-epoxybutane, styrene oxide, 2,3-dimethyl-2,3-epoxybutane, epoxycyclohexane, ethylene oxide) in a 1:3 molar ratio to afford the dinuclear dihalide-tris(2-haloalcoholato) complexes [MX2(OR)2(μ-OR)]2 [M = Nb, X = Cl, R = –CH(Et)CH2Cl, 2a; M = Nb, X = Cl, R = –CH2CH(Ph)Cl, 2b; M = Nb, X = Cl, R = –C(Me)2C(Me)2Cl, 2c; M = Nb, X = Br, R = –CH2CH(Ph)Br, 2d; M = Nb, X = Br, R = –C(Me)2C(Me)2Br, 2e; M = Ta, X = Cl, R = –CH(Et)CH2Cl, 2f; M = Ta, X = Cl, , 2g; M = Ta, X = Br, R = –CH2CH2Br, 2h], in moderate to good yields. The products, 2a–h, result from multiple epoxide insertion into metal–halide bonds, and the reactions involving 1,2-epoxybutane and styrene oxide proceed with high regioselectivity. The molecular structure of 2h has been elucidated by X-ray diffraction. Differently, NbF5 adds one equivalent of 2,3-dimethyl-2,3-epoxybutane to give the monomer NbF5[OC(Me)(But)], 3, in high yield, as a result of epoxide to ketone isomerization. The reactions of MF5 (M = Nb, Ta) with other epoxides proceed non-selectively according to various pathways, including formation of C–O and C–F bonds and C–C and C–H cleavages.

Epoxide Ring Opening and Insertion into the M–X Bond of Niobium and Tantalum Pentahalides: Synthesis of Dihalide-tris(2-haloalcoholato) Complexes

MARCHETTI, FABIO;PAMPALONI, GUIDO;
2009

Abstract

The Group 5 pentahalides MX5 (M = Nb, Ta; X = Cl, Br), 1, react with a variety of epoxides (1,2-epoxybutane, styrene oxide, 2,3-dimethyl-2,3-epoxybutane, epoxycyclohexane, ethylene oxide) in a 1:3 molar ratio to afford the dinuclear dihalide-tris(2-haloalcoholato) complexes [MX2(OR)2(μ-OR)]2 [M = Nb, X = Cl, R = –CH(Et)CH2Cl, 2a; M = Nb, X = Cl, R = –CH2CH(Ph)Cl, 2b; M = Nb, X = Cl, R = –C(Me)2C(Me)2Cl, 2c; M = Nb, X = Br, R = –CH2CH(Ph)Br, 2d; M = Nb, X = Br, R = –C(Me)2C(Me)2Br, 2e; M = Ta, X = Cl, R = –CH(Et)CH2Cl, 2f; M = Ta, X = Cl, , 2g; M = Ta, X = Br, R = –CH2CH2Br, 2h], in moderate to good yields. The products, 2a–h, result from multiple epoxide insertion into metal–halide bonds, and the reactions involving 1,2-epoxybutane and styrene oxide proceed with high regioselectivity. The molecular structure of 2h has been elucidated by X-ray diffraction. Differently, NbF5 adds one equivalent of 2,3-dimethyl-2,3-epoxybutane to give the monomer NbF5[OC(Me)(But)], 3, in high yield, as a result of epoxide to ketone isomerization. The reactions of MF5 (M = Nb, Ta) with other epoxides proceed non-selectively according to various pathways, including formation of C–O and C–F bonds and C–C and C–H cleavages.
Marchetti, Fabio; Pampaloni, Guido; Zacchini, S.
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Utilizza questo identificativo per citare o creare un link a questo documento: http://hdl.handle.net/11568/205090
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