The synthesis, x-ray crystal structure, and solution characterization of a bis(diphosphine)-bridged dirhodium(I) complex containing a Rh2P4 six-membered ring

The preparation of [{Rh(cod)}2(μ-L¹)2][BF4] 2 (1) from (CH2CMe=CH2P)2 (L¹) and [Rh(cod)2]-BF4 (cod = cyclo-octa-1,5-diene) is described. The compound crystallizes in the monoclinic space group P21/c (C⁵2h), with a = 9.650(1), b = 11.609(1), c = 21.884(3) Å, β = 117.07(1)°, and Z = 2. The structure was refined to R = 0.033 for 3 434 reflections. The solid-state structure shows two diphosphine ligands L¹ bridging two rhodium(I) atoms to form a six-membered Rh2P4 ring in a chair conformation. Solution studies (¹H and ¹³C-{¹H} variable-temperature n.m.r. spectra) exhibit characteristics of a ring inversion equilibrium with ΔG271 = 14.0(0.2) kcal mol^-1. Computer simulation of the ³¹P-{¹H} n.m.r. spectrum is used to analyse the internuclear couplings of the AA′A″A‴XX′ pattern (A = ³¹P, X = ¹⁰³Rh). The bridging diphosphine ligands exhibit a deshielding effect on the trans olefinic carbon atoms of cod in (1) which is in the range normally found for phosphine ligands.

Duke Scholars

Author Alvin L. Crumbliss Chemistry

Author Andrew T. McPhail Chemistry