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Selective Homo- and Heterodehydrocouplings of Phosphines Catalyzed by Rhodium Phosphido Complexes

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journal contribution
posted on 25.10.2006, 00:00 by Li-Biao Han, T. Don Tilley
Reactions of the rhodium complex (dippe)Rh(η3-CH2Ph) (1, dippe = iPr2PCH2CH2PiPr2) with ArPH2 (Ar = Ph, Mes) proceed via P−H oxidative additions to the phosphido complexes (dippe)Rh(μ-PHAr)2Rh(dippe) (3a, Ar = Ph; 3b, Ar = Mes). The corresponding reaction of Ph2PH occurs similarly, via the intermediate (dippe)Rh(PPh2)PHPh2 (4), to (dippe)Rh(μ-PPh2)2Rh(dippe) (3c). Complexes 3ac and 4 are catalysts for the catalytic dehydrodimerizations of the corresponding phosphines to diphosphanes. Complex 1 is a more active dehydrocoupling catalyst, and substituent effects suggest that the active catalyst is mononuclear. Efficient dehydrocouplings of 2-EtC6H4PH2, 2-iPrC6H4PH2, and 2,4,6-iPr3C6H2PH2 were also observed. Complex 1 also catalyzes the heterocoupling of Ph2PH with PhSH (to Ph2P−SPh), and stoichiometric reactions in this system allowed isolation of (dippe)Rh(μ-SPh)2Rh(dippe) (6) and (dippe)Rh(SPh)PHR2 (7a, R2PH = MesPH2; 7b, R2PH = Ph2PH).