88704-29-4Relevant academic research and scientific papers
Preparation and conformational dynamics of (C5Me5)Rh(PR′3)RX. Hindered rotation about rhodium-phosphorus and rhodium-carbon bonds
Jones, William D.,Feher, Frank J.
, p. 2376 - 2388 (2008/10/08)
Compounds with the general formula [C5Me5]RhXR(PR′3) have been prepared by the reactions of [C5Me5]Rh(PR′3)X2 and the corresponding Grignard or lithium reagent (X = Cl, Br, I; R = Me, C-C5H9, n-C3H7, CH2CMe3, C6H5, o-C6H4Me, m-C6H4Me, p-C6H4Me, 2,5-C6H3Me2, 3,5-C6H3Me2, 3,4-C6H3Me2, p-C6H4CF3, p-C6H4F, p-C6H4OMe, p-C6H4NMe2, CH=CH2, CMe=CH2, C=CHCH2CH2CH2, CH2C6H5; R′ = Me, C6H5, p-C6H4Me). The aryl derivatives show hindered rotation about the rhodium-aryl bond, with ΔH? = 9.8 ± 0.2 kcal/mol and ΔS? = -13.7 ± 0.6 eu for R′ = Me, X = Cl, and R = p-tolyl and ΔH? = 11.0 ± 0.2 kcal/mol and ΔS? = -9.8 ± 0.6 eu for R′ = C6D5, X = Br, and R = p-tolyl. ΔG? for this hindered rotation was determined for several of the above compounds. In addition, the triarylphosphine complexes also show hindered rotation about the metal-phosphorus bond with H? = 15.7 ± 0.2 kcal/mol and S? = -2.8 ± 0.2 eu (X = Br, R = C6D5, R′ = p-tolyl) and ΔH? = 14.3 ± 0.3 kcal/mol and ΔS? = -1.8 ± 1.2 eu for (C5Me5)Rh[P(p-tolyl)3]Br2. Both complete band shape analysis and spin saturation methods were used to determine rate constants. ΔG? for rotation about the metal-aryl bond is insensitive to the nature of the para substituent on the aryl group but shows a moderate halide dependence and a stronger phosphine dependence. Single-crystal X-ray structural parameters for [C5(CH3)5]Rh[P(C-H3) 3](C6H5)Br are a = 11.459 (12) A?, b = 9.008 (6) A?, c = 19.298 (13) A?, β = 90.03 (2)°, V = 1992 A?3, Z = 4, dcalcd = 1.57 g/cm3, space group P21/c, R = 4.68%, and Rw = 6.15% for the 2009 independent reflections with F2 ≥ 3σ(F2). The Rh-phenyl bond distance of 2.05 A? is typical for a rhodium sp2-carbon bond and does not suggest any unusual π-bonding between the metal and the phenyl ligand.
