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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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Article information


Submitted
04 Sep 2009
Accepted
02 Nov 2009
First published
11 Jan 2010

Dalton Trans., 2010,39, 1962-1971
Article type
Paper

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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