Issue 9, 2009

Metal-free dihydrogenactivation chemistry: structural and dynamic features of intramolecular P/B pairs

Abstract

Hydroboration of allyl(dimesityl)phosphane with HB(C6F5)2 gives the intramolecular five-membered P–B Lewis pair 7, that was characterized by X-ray diffraction. Similarly, HB(C6F5)2 addition to the substrates (mesityl)2P–CR[double bond, length as m-dash]CH2 (R = CH3, Ph) yield the corresponding (mesityl)2P(μ-CHRCH2)B(C6F5)2 products 9a (R = CH3) and 9b (R = Ph) that show a weak intramolecular P⋯B interaction. The activation energy of the (reversible) PB cleavage of these substrates was determined by dynamic 19F NMR spectroscopy (9a: ΔGinv (280 K) = 11.7 ± 0.4 kcal mol−1). Compounds 9b and 9c show similar values. Compound 9c was prepared by HB(C6F5)2 addition to (mesityl)2P–CH[double bond, length as m-dash]CHSiMe3. Compound 9a reacts rapidly with dihydrogen (2.5 bar) at room temperature in pentane to give the zwitterionic H2-activation product (mesityl)2PH+(μ-CHMeCH2)BH(C6F5)2 (11).

Graphical abstract: Metal-free dihydrogen activation chemistry: structural and dynamic features of intramolecular P/B pairs

Supplementary files

Article information

Article type
Paper
Submitted
10 Sep 2008
Accepted
07 Nov 2008
First published
20 Jan 2009

Dalton Trans., 2009, 1534-1541

Metal-free dihydrogen activation chemistry: structural and dynamic features of intramolecular P/B pairs

P. Spies, G. Kehr, K. Bergander, B. Wibbeling, R. Fröhlich and G. Erker, Dalton Trans., 2009, 1534 DOI: 10.1039/B815832K

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