Issue 25, 2015

Iminoborylene complexes: evaluation of synthetic routes towards BN-allenylidenes and unexpected reactivity towards carbodiimides

Abstract

The synthetic and reaction chemistries of cationic iminoborylene complexes [LnM[double bond, length as m-dash]B[double bond, length as m-dash]N[double bond, length as m-dash]CR2]+, which feature a unique heterocumulene structure, have been systematically investigated. Precursors of the type CpFe(CO)2B(Cl)NCAr2 (Ar = p-Tol/Mes, 5c/d) have been generated by B-centred substitution chemistry using CpFe(CO)2BCl2 and suitable lithiated ketimines – a reaction which is found to be highly sensitive to the steric bulk at both the metal fragment and the ketimino group. Carbonyl/phosphine exchange (using PCy3 or PPh3), followed by halide abstraction allows for the generation of the cationic iminoborylenes [CpFe(PR3)(CO)(BNCAr2)]+[BArX4] (R = Cy, Ar = p-Tol/Mes, 12c/d; R = Ph, Ar = Mes, 13d; ArX = 3,5-X2C6H3 where X = Cl, CF3) which have been characterized spectroscopically and by X-ray crystallography. The reactivity of these iminoborylene systems towards a range of nucleophiles and unsaturated substrates has been investigated. The latter includes the first examples of M[double bond, length as m-dash]B metathesis reactivity with a carbodiimide, and results in Fe[double bond, length as m-dash]B cleavage and formation of the isonitrile complexes [CpFe(PCy3)(CO)(CNR)]+[BArCl4] (R = iPr/Cy, 16/17).

Graphical abstract: Iminoborylene complexes: evaluation of synthetic routes towards BN-allenylidenes and unexpected reactivity towards carbodiimides

Associated articles

Supplementary files

Article information

Article type
Paper
Submitted
12 Jan 2015
Accepted
10 Feb 2015
First published
11 Feb 2015
This article is Open Access
Creative Commons BY license

Dalton Trans., 2015,44, 11294-11305

Author version available

Iminoborylene complexes: evaluation of synthetic routes towards BN-allenylidenes and unexpected reactivity towards carbodiimides

J. Niemeyer, M. J. Kelly, I. M. Riddlestone, D. Vidovic and S. Aldridge, Dalton Trans., 2015, 44, 11294 DOI: 10.1039/C5DT00131E

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