154860-74-9Relevant academic research and scientific papers
Direct synthesis and reactivity of unsupported (η3-oxaallyl)rhodium(I) complexes
Slough, Greg A.,Hayashi, Randy,Ashbaugh, John R.,Shamblin, Sheri L.,Aukamp, Amy M.
, p. 890 - 898 (2008/10/08)
Addition of 2 equiv of K+PhC(O)CH2- to [(Ph3P)2RhCl]2 (1) gave the monomeric (η3-oxaallyl)rhodium complex (Ph3P)2Rh(η3-CH2C(O)Ph) (3). Reaction of 1 with K+t-BuC(O)CH2-produced a similar oxaallyl complex (6), which was characterized by spectroscopic methods and by X-ray crystallography. Both 3 and 6 showed dynamic NMR spectra which equilibrated the methylene protons at 25°C. A general methodology for the preparation of (η3-oxaallyl)rhodium complexes was developed by starting from [(COD)RhCl]2 (7) and 4 equiv of phosphine. Complexes (Et3P)2Rh(η-CH2C(O)Ph) (8) and (Et3P)2Rh((Z)-η3-CH3CHC(O)-t-Bu) (10) were prepared by this methodology. No fluxional behavior was observed with either 8 or 10. Oxaallyl 8 reacted rapidly with CO and t-BuNC to produce the η1-oxygen-bound rhodium enolates trans-(Et3P)2(CO)Rh(OC(Ph)CH2) (12) and trans-(Et3P)2(t-BuNC)Rh(OC(Ph)CH2) (13). However, unlike complex 8, oxaallyl 6 added 2 equiv of t-BuNC, giving a trigonal-bipyramidal carbon-bound rhodium enolate complex (16). Notable differences in reactivity between rhodium oxaallyl and rhodium allyl complexes are explained in terms of enhanced stability of the η1-oxygen-bound rhodium complex relative to the η1-allyl complex.
