An NMR spectroscopic study of the reactions of (2-(2-methoxyethoxy)ethyl)diphenylphosphine with rhodium(I) olefin complexes

Article abstract of DOI:10.1016/0022-328X(90)80180-8

The reactions of Ph2P(CH2CH2O)2CH3 (I) with <(cod)Rh(μ-Cl)>2 and <(coe)2Rh(μ-Cl)>2 (cod = 1,5-cyclooctadiene, coe = cis-cyclooctene) and of Ph2PMe with <(coe)2Rh(μ-Cl)>2 have been studied using 31P and 13C NMR spectroscopy.These studies indicate that the two Rh complexes give quite different reaction products.The reaction of I with <(cod)Rh(μ-Cl)>2 at a Rh/I ratio of 1/1 yields (cod)RhCl (II).Increasing the Rh/I ratio in this solution to 1/2 results in the formation of ClRh3 (III), but not of any complexes with two I's coordina ted to Rh.A complex with two I's attached to the Rh can be formed by first reacting II with AgBF4 to form <(cod)Rh>BF4 (IV) and then by reacting IV with a second equivalent of I to form <(cod)Rh2>BF4 (V).The reaction of <(coe)2Rh(μ-Cl)>2 with Ph2PMe yields <(coe)(Ph2PMe)Rh(μ-Cl)>2 (VI) at a Rh/Ph2PMe ratio of 1/1, <(Ph2PMe)2Rh(μ-Cl)>2 (VII) at a Rh/Ph2PMe ratio of 1/2 and ClRh(Ph2PMe)3 (VIII) at a Rh/Ph2PMe ratio of 1/3.The reaction of<(coe)2Rh(μ-Cl)>2 with I gives a different product, <Rh(μ-Cl)>2 (IX) at a Rh/I ratio of 1/1, but similar products at Rh/I ratios of 1/2, <2Rh(μ-Cl)>2 (XI) and 1/3, III.The differences in the reaction products are due to the fact that the bidentate cod ligand coordinates much more strongly to the Rh than do either the bridging chlorine of the monodentate coe ligand.Thus, the reactions of <(cod)Rh(μ-Cl)>2 with phosphines initially involve displacement of the bridging chloride, but those of <(coe)2Rh(μ-Cl)>2 with phosphines initially involve loss of the coe ligand.The weak Rh-coe bond allows I to function as a chelating P/O-ligand in IX.