84774-75-4Relevant academic research and scientific papers
Preparation and structural dynamics of phosphine-bridged trirhodium chains. Observation of facile bridge/terminal interchange of anionic ligands or carbon monoxide
Balch, Alan L.,Fossett, L. Alan,Guimerans, Rosalvina R.,Olmstead, Marilyn M.,Reedy Jr., Philip E.,Wood, Fred E.
, p. 1248 - 1253 (2008/10/08)
The preparations of the trirhodium chain compounds [Rh3(μ-dpmp)2(CO)3X2][BPh 4] (dpmp is bis((diphenylphosphino)-methyl)phenylphosphine; X = Cl-, Br-, I-, N3-, NCO-) and [Rh3(μ-dpma)2(CO)3X2] [BPh4] (dpma is bis((diphenylphosphino)-methyl)phenylarsine; X = Cl-, Br-, I-) are reported. Infrared and multinuclear (1H, 31P, 13C) NMR spectra along with the previously reported X-ray crystallographic data on [Rh3(μ-dpmp)2(CO)3(μ-Cl)Cl]+ and [Rh3(μ-dpmp)2(μ-CO)(CO)2(μ-I) 2]+ allow these cations to be sorted into three classes. All classes contain a Rh3(dpmp)2 or Rh3(dpma)2 core with trans P-Rh-P and As-Rh-As units. The cations [Rh3(μ-dpmp)2(CO)3(μ-X)X]+ (X = Cl-, N3-, NCO-) and [Rh3(μ-dpma)2(CO)3(μ-X)X]+ (X = Cl-, Br-) possess a structure with one bridging X and only terminal carbonyls. In solution these undergo rapid bridge/terminal halide exchange. The cations [Rh3(μ-dpmp)2(μ-CO)(CO)2(μ-I) 2]+ and [Rh3(μ-dpma)2(μ-CO)(CO)2(μ-I) 2]+ both possess a static structure in solution that is the same as the solid-state structure. One Rh-Rh unit is bridged by a carbonyl and an iodide. That iodide is close to the third rhodium, which is also bridged to the central rhodium by a shorter iodide bridge. The structure of [Rh3(μ-dpmp)2(μ-CO)(CO)2Br 2]+ is unique. In solution it undergoes rapid bridge/terminal carbonyl exchange, which leaves one of the terminal carbonyl groups unaffected. This cation crystallizes in two modifications, a violet one without a bridging carbonyl and a tan one with an apparent structure similar to that found in solution.
X-ray crystal structure and structural dynamics of [Ir3{μ-(Ph2PCH2)2AsPh} 2(μ-CO)2(CO)2(μ-Cl)Cl]+ and related rhodium complexes
Balch, Alan L.,Fossett, L. Alan,Guimerans, Rosalvina R.,Olmstead, Marilyn M.,Reedy Jr., Philip E.
, p. 1397 - 1404 (2008/10/08)
The preparation of the tetracarbonyl complexes [Ir3(μ-dpma)2(μ-CO)2(CO) 2(μ-X)X][BPh4], [Rh3(μ-dpma)2(μ-CO)2(CO) 2(μ-I)I][BPh4] and [Rh3(μ-dpmp)2(μ-CO)2(CO) 2(μ-X)X][BPh4] (dpma = bis((diphenylphosphino)methyl)phenylarsine; dpmp = bis((diphenylphosphino)methyl)phenylphosphine; X = Cl, Br, I) is reported. Infrared and electronic spectral data indicate that all have a common structure. [Ir3;{μ((C6H5)2PCH 2)2AsC6H5}2(μ-CO) 2(CO2)2(μ-Cl)Cl][B(C6H 5)4]·2CH2Cl2 crystallizes from dichloromethane/ether in the triclinic space group P1 (No. 2) with a = 12.789 (3) A?, b = 16.936 (4) A?, c = 23.874 (6) A?, α = 87.80 (2)°, β = 68.69 (2)°, γ = 77.05 (2)° at 140 K. Least-squares refinement of 493 parameters using 8413 reflections yields R = 0.083, Rw = 0.090. The structure of the cation has the two dpma ligands in a fully extended trans alignment. The three iridium atoms are nearly linear (Ir-Ir-Ir angle 166.0 (1)°) with Ir-Ir bonds of nearly equal lengths, 2.887 (1) and 2.842 (1) A?. One Ir-Ir bond is bridged by a chloride and a carbonyl ligand in a double-A-frame arrangement while the other Ir-Ir bond is bridged by a carbonyl ligand. A nearly statistical disorder in the crystal packing exchanges the sites of the bridging chlorine and the terminal chlorine. Multinuclear (31P, 1H, and 13C) NMR spectra of these tetracarbonyls in dichloromethane solution indicate that they have a time-averaged, symmetrical structure that renders the two end P2Ir environments equivalent. A dynamic process involving bridge/terminal halide interchange is proposed to explain these spectra.
