Issue 39, 2007

Insertion reactions of dicyclohexylcarbodiimide with aminoboranes, -boryls and -borylenes

Abstract

Insertion reactions of dicyclohexylcarbodiimide with aminoboranes and with aminoboryl and -borylene transition metal complexes have been examined as potential routes to new boron-containing ligand systems. Reactions with systems containing two-coordinate boron centres are found to be significantly more facile than those with three-coordinate substrates. Thus, reaction of (dicyclohexylamino)boron dichloride (1a) with dicyclohexylcarbodiimide over 36 h at 50 °C generates the (structurally authenticated) guanidinate complex Cy2NC(NCy)2BCl2 (2a) via insertion into the BN bond. By contrast, the corresponding reaction with the cationic aminoborylene complex [CpFe(CO)2(BNCy2)]+[BArf4] (4a) proceeds rapidly at ca. −30 °C, via initial insertion into the FeB bond to give [CpFe(CO)2C(NCy)2BNCy2]+[BArf4] (5a). Consistent with related studies, a key factor in facilitating such insertion chemistry is thought to be the formation of an initial donor/acceptor complex between the diimide and the group 13 centre. Thus, DFT studies suggest that [CpFe(CO)2B(NCy2)(CyNCNCy)]+[BArf4] is a potential intermediate in the reaction of 4a with CyNCNCy, and that further reaction to give the observed product, 5a, is strongly exergic (−183 kJ mol−1). By contrast, DFT calculations for the alternative isomer [CpFe(CO)2B(CyN)2CNCy2]+[BArf4] (5a′), formed by BN insertion, suggest that it is 112 kJ mol−1 less stable than 5a. Such experimental and computational findings imply that under reaction conditions where a suitable isomerisation pathway is available, cationic complexes such as 5a′, which contain a four-membered boron-donor heterocycle are likely to be disfavoured with respect to alternative C-bound isomers.

Graphical abstract: Insertion reactions of dicyclohexylcarbodiimide with aminoboranes, -boryls and -borylenes

Supplementary files

Article information

Article type
Paper
Submitted
19 Jun 2007
Accepted
19 Jul 2007
First published
08 Aug 2007

Dalton Trans., 2007, 4405-4412

Insertion reactions of dicyclohexylcarbodiimide with aminoboranes, -boryls and -borylenes

G. A. Pierce, N. D. Coombs, D. J. Willock, J. K. Day, A. Stasch and S. Aldridge, Dalton Trans., 2007, 4405 DOI: 10.1039/B709249K

To request permission to reproduce material from this article, please go to the Copyright Clearance Center request page.

If you are an author contributing to an RSC publication, you do not need to request permission provided correct acknowledgement is given.

If you are the author of this article, you do not need to request permission to reproduce figures and diagrams provided correct acknowledgement is given. If you want to reproduce the whole article in a third-party publication (excluding your thesis/dissertation for which permission is not required) please go to the Copyright Clearance Center request page.

Read more about how to correctly acknowledge RSC content.

Social activity

Spotlight

Advertisements