Mono-alkylated bisphosphines as dopants for ESI-MS analysis of catalytic reactions?

Dalton Transactions Pub Date: 2009-10-14 DOI: 10.1039/B913225B

Abstract

Bisphosphines Ph2P(CH2)nPPh2 (n = 1, 2, 4, 6) may be easily monobenzylated to generate cationic phosphine/phosphonium ligands [Ph2P(CH2)nPPh2CH2Ph]+. These ligands may be doped into a catalytic reaction involving neutral complexes with labile phosphine ligands, and replacement of a neutral phosphine with a charged analogue renders the resulting complex amenable to electrospray ionisation mass spectrometry (ESI-MS). Examination of olefin hydrogenation with Wilkinson's catalyst, RhCl(PPh3)3, revealed that this approach yielded rapid identification of all off-cycle solution species as well as catalyst poisons. Reactive intermediates could be generated using collision-induced dissociation (CID) of a triphenylphosphine ligand to make three-coordinate RhClP2 species, and these react with alkenes in the gas phase to form RhClP2(alkene). The solution speciation and gas phase behaviour revealed by ESI-MS match closely to what is already known about the system from kinetic and NMR studies.

Graphical abstract: Mono-alkylated bisphosphines as dopants for ESI-MS analysis of catalytic reactions
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