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Issue 8, 2010
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Reactions of alkynes with phosphido niobocenes: a combined experimental and theoretical study

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Abstract

The reactions of phosphido complexes [Nb(η5-C5H4SiMe3)2(L)(PPh2)] [L = CO (1), CNxylyl (2), CNCy (3)] with alkynes have been carried out. The new diphenylphosphinoalkenyl niobocene complexes [Nb(η5-C5H4SiMe3)21-C–C(CO2CH3)[double bond, length as m-dash]C(R)PPh2)(CO)] [R = H (4), CH3 (5)] and [Nb(η5-C5H4SiMe3)21-C–C(CO2R)[double bond, length as m-dash]C(CO2R)PPh2)(CO)] [R = CH3, (6), R = tBu, (7)] were successfully synthesized by the reaction of 1 with methyl propiolate (HC[triple bond, length as m-dash]CCO2CH3) or methyl 2-butynoate (CH3C[triple bond, length as m-dash]CCO2CH3) and dimethyl 2-butynedioate [(CH3 O2C)C[triple bond, length as m-dash]C(CO2CH3)] or di(tert-butyl) 2-butynedioate [(tBuO2C)C[triple bond, length as m-dash]C(CO2tBu)], respectively. However, reaction was not observed with more electron-rich alkynes. Complex 2 reacted with methyl propiolate, methyl 2-butynoate (MeC[triple bond, length as m-dash]CCO2Me) or di(tert-butyl) 2-butynedioate to give surprising new heteroniobacycle complexes [Nb(η5-C5H4SiMe3)21-C–C([double bond, length as m-dash]NXylyl)C(R1)[double bond, length as m-dash]C(R2)PPh21-P)] [R1 = H, R2 = CO2Me (8); R1 = Me, R2 = CO2Me (9); R1 = CO2tBu, R2 = CO2tBu (10)]. Finally, the phosphido complexes 2 and 3 reacted with phenylacetylene (PhC[triple bond, length as m-dash]CH) to give new diphenylphosphinoalkenyl niobocene derivatives [Nb(η5-C5H4SiMe3)21-C–C(C6H5)[double bond, length as m-dash]C(H)PPh2)(CNR)] [R = xylyl (11), Cy (12)]. All of these compounds were characterized by NMR spectroscopy and the molecular structure of 8 was determined by single-crystal X-ray diffraction studies. Theoretical studies were also carried out by means of density functional theory (DFT) calculations on the insertions of alkynes into the Nb–P bond in the phosphido niobocenes.

Graphical abstract: Reactions of alkynes with phosphido niobocenes: a combined experimental and theoretical study

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Publication details

The article was received on 04 Sep 2009, accepted on 02 Nov 2009 and first published on 11 Jan 2010


Article type: Paper
DOI: 10.1039/B918298E
Dalton Trans., 2010,39, 1962-1971

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    Reactions of alkynes with phosphido niobocenes: a combined experimental and theoretical study

    A. Antiñolo, S. García-Yuste, I. L. Solera, A. Otero, J. C. Pérez-Flores, R. Reguillo-Carmona, E. Villaseñor, E. Santos, E. Zuidema and C. Bo, Dalton Trans., 2010, 39, 1962
    DOI: 10.1039/B918298E

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