Guan D, Godard C, Polas SM, Tooze RP, Whitwood AC, Duckett SB. Using para hydrogen induced polarization to study steps in the hydroformylation reaction.
Dalton Trans 2019;
48:2664-2675. [PMID:
30702728 DOI:
10.1039/c8dt04723e]
[Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
A range of iridium complexes, Ir(η3-C3H5)(CO)(PR2R')2 (1a-1e) [where 1a, PR2R' = PPh3, 1b P(p-tol)3, 1c PMePh2, 1d PMe2Ph and 1e PMe3] were synthesized and their reactivity as stoichiometric hydroformylation precursors studied. Para-hydrogen assisted NMR spectroscopy detected the following intermediates: Ir(H)2(η3-C3H5)(CO)(PR2R') (2a-e), Ir(H)2(η1-C3H5)(CO)(PR2R')2 (4d-e), Ir(H)2(η1-C3H5)(CO)2(PR2R') (10a-e), Ir(H)2(CO-C3H5)(CO)2(PR2R') (11a-c), Ir(H)2(CO-C3H7)(CO)2(PR2R') (12a-c) and Ir(H)2(CO-C3H5)(CO)(PR2R')2 (13d-e). Some of these species exist as two geometric isomers according to their multinuclear NMR characteristics. The NMR studies suggest a role for the following 16 electron species in these reactions: Ir(η3-C3H5)(CO)(PR2R'), Ir(η1-C3H5)(CO)(PR2R')2, Ir(η1-C3H5)(CO)2(PR2R'), Ir(CO-C3H5)(CO)2(PR2R'), Ir(CO-C3H7)(CO)2(PR2R') and Ir(CO-C3H5)(CO)(PR2R')2. Their role is linked to several 18 electron species in order to confirm the route by which hydroformylation and hydrogenation proceeds.
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