Acceptorless, intramolecular, alkyl dehydrogenation in the solid-state in a rhodium phosphine complex; reversible uptake of three equivalents of H 2 per molecule

Article abstract of DOI:10.1039/b718615k

Addition of H₂ to the phosphine alkene ligated complex [Rh(dppe)(PCyp₂Cyp′)][BArF4] 1 (Cyp = cyclo-C₅H ₉; Cyp′ = cyclo-C₅H₇, Ar^F = 3,5-(CF₃)₂C₆H₃) in the solid state results in hydrogenation of the alkene and uptake of two further equivalents of H₂ to afford the dihydride-dihydrogen complex [Rh(dppe)(PCyp ₃)(H)₂(η²-H₂)][BArF4] 2. Placing 2 under a vacuum or argon results in sequential loss of H₂ and dehydrogenation of one of the cyclopentyl rings to reform 1. The hydrogenation-dehydrogenation cycle has been repeated 5 times without apparent degradation and has been followed by solid-state ³¹P{¹H} NMR spectroscopy. Intermediates on this process have been trapped using acetonitrile to give stable complexes that have been characterised in solution. We have previously shown that this hydrogenation-dehydrogenation process also happens in the solution-state; and evidence is presented that shows that, apart from a subtle difference, the same overall transformation occurs in the solid-state. The Royal Society of Chemistry and the Centre National de la Recherche Scientifique.