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Issue 11, 2013
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Hetero-dehydrocoupling of silanes and amines by heavier alkaline earth catalysis

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Abstract

The homoleptic alkaline earth hexamethyldisilazides, [M{N(SiMe3)2}2]2 (1: M = Mg; 2: M = Ca; 3: M = Sr), have been demonstrated as active pre-catalysts for the cross-dehydrocoupling of Si–H and N–H bonds under mild (25–60 °C) conditions. The reactions are applicable to the coupling of a wide variety of amine and silane substrates and are proposed to occur via a sequence of discrete Si–H/M–N and N–H/M–H metathesis steps. Whereas reactions of dialkyl group 2 species with 2,6-di-iso-propylaniline and phenylsilane delivered a series of well-defined compounds consistent with this rationale, kinetic analysis of the cross-coupling of diethylamine with diphenylsilane provided evidence for a more complex and subtly variable mechanistic landscape. Although reactions performed with all three pre-catalysts presented a number of common features, in every case the calcium species, 2, was found to provide notably superior catalytic activity, an order of magnitude higher than both 1 and 3 and in excess of many previously described benchmark transition metal- or f-element-mediated processes. Variations in overall reaction order, mode of pre-catalyst activation and the nature of the rate determining process are postulated to arise as a consequence of the marked change in M2+ radius and resultant charge density as group 2 is descended.

Graphical abstract: Hetero-dehydrocoupling of silanes and amines by heavier alkaline earth catalysis

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Supplementary files

Article information


Submitted
27 Jun 2013
Accepted
13 Aug 2013
First published
14 Aug 2013

Chem. Sci., 2013,4, 4212-4222
Article type
Edge Article

Hetero-dehydrocoupling of silanes and amines by heavier alkaline earth catalysis

M. S. Hill, D. J. Liptrot, D. J. MacDougall, M. F. Mahon and T. P. Robinson, Chem. Sci., 2013, 4, 4212
DOI: 10.1039/C3SC51797G

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