15550-00-2Relevant academic research and scientific papers
Kinetic studies of some substituted hexarhodium carbonyl clusters
Babij, Claudia,Farrar, David H.,Koshevoy, Igor O.,Poe, Anthony J.,Tunik, Sergey P.
, p. 116 - 122 (2007/10/03)
Reactions of the halides X- (X- = chloride, bromide or iodide) with the substituted cluster Rh6(CO)15(PPh 3) in oxygen-free chloroform lead to [Rh5(CO) 14(PPh3)]-, Rh(CO)2(PPh 3)2X and [Rh(CO)2X2]- in the molar ratios 2 : 1 : ～13, Oxidation by the solvent is assumed to lead to most of the Rh(I) product, and the stoichiometry for reactions with I - can be defined as 4Rh6(CO)15(PPh 3) + 27I- + 12CHCl3 → 2[Rh 5(CO)14(PPh3)]- + Rh(CO) 2(PPh3)2I + 13[Rh(CO)2I 2]- + 6C2H2Cl4 + 4CO + 12Cl-. This can be rationalized quite simply with the aid of a few generally justifiable assumptions. Rate constants for reactions with bromide increase to a limiting value with increasing [Br-] in a way that shows that breaking of one Rh-Rh bond, with an unusual closo to nido structural change, is rate determining. This opening of the cluster might be spontaneous or solvent induced. To complete the reaction, the bromide has to compete with the reverse nido to closo change. The same closo to nido change is also a major rate determining step for reactions with P(OPh)3 in oxygen-free solutions, and for reactions with bromide in oxygenated solutions in the presence of trifluoroacetic and some other acids. The limiting rates increase slightly with increasing basicity of the ligands P(p-XC6H 4)3 along the series X = F3C, Cl, F, H and MeO. Activation parameters for these reactions are reported.
Rhodium(I) complexes with OPPy2Ph and OPPy3 (Py = 2-pyridyl), and their behavior in hydrogenation reactions
Casares, Juan A.,Espinet, Pablo,Martín-Alvarez, José M.,Espino, Gustavo,Pérez-Manrique, Mercedes,Vattier, Florencia
, p. 289 - 296 (2007/10/03)
The reaction of [Rh2(μ-Cl)2(COD)2] (COD = 1,5-cyclooctadiene) or [Rh2(μ-Cl)2(TFB)2] (TFB = tetrafluorobenzobicyclo[2.2.2]octatriene) with the N-donor chelating ligand OPPy2Ph (Py = 2-pyridyl) in the presence of T1BF4 affords cationic complexes [Rh(diene)(OPPy2Ph)](BF4) (1, diene: COD; 2, diene: TFB). Compounds 1 or 2 react with CO to give [Rh(CO)2(OPPy2Ph)](BF4) (4), which is also obtained by treatment of [Rh2(μ-Cl)2(CO)4] with OPPy2Ph and T1BF4. In a similar way, the complexes [Rh(diene)(OPPy3)](BF4) (5, diene: COD; 6, diene: TFB) are obtained when using OPPy3; they react with CO to give [Rh2(μ-CO)3 (OPPy3)2](BF4)2 (9). The behavior of the complexes in solution is reported. The complexes with OPPy3, 5 and 6, show equivalence of the three Py groups in their NMR spectra. Complex 5 is square-planar in the solid state, and in solution, and the uncoordinated and coordinated Py groups undergo fast exchange in solution. Complex 6 is pentacoordinated in the solid state and in solution, and its Py groups exchange their coordination sites in a fast topomerization process. The single-crystal X-ray structures of 5 and 6 have been solved. The behavior of 1 and 5 as catalysts in hydrogenation reactions of cyclohexene, acetone, and cyclohexanone is also reported.
Mechanistic Studies of the Carbonylation of Nitrobenzene Catalysed by the -/bipy System. X-Ray Structure of ; + = (PPh3)2N+; bipy = 2,2'-bipyridyl>
Ragaini, Fabio,Cenini, Sergio,Demartin, Francesco
, p. 1467 - 1468 (2007/10/02)
Reaction of with C6H3Cl2NO2 gives , the X-ray structure of which is reported together with its reactivity.
