112173-11-2Relevant academic research and scientific papers
Steric effects on the ortho-metalation reactions at binuclear pyrazolyl-bridged rhodium compounds. Molecular structure of Rh2(3,5-dmpz)2[μ-P(o-C6F4)Ph 2]Br(CO)(η2-PCBr)(H2O) [3,5-dmpz = 3,5-dimethylpyrazolyl; PCBr = P(o-BrC6F4)Ph2]
Barceló, Francisco,Lahuerta, Pascual,Ubeda, M. Angeles,Foces-Foces, Concepción,Cano, Félix H.,Martínez-Ripoll, Martín
, p. 584 - 590 (2008/10/08)
Complexes of the type [Rh(Pz)(CO)(PCBr)]2 (Pz = pyrazolyl (pz), 1; 3-methylpyrazolyl (3-mpz), 2; 4-methylpyrazolyl (4-mpz), 3; PCBr = P(o-BrC6F4)Ph2) are obtained by reacting [Rh(Pz)(CO)2]2 with PCBr or Rh(acac)(CO)(PCBr) with HPz. The reaction between [Rh(3,5-dmpz)(CO)2]2, (3,5-dmpz = 3,5-dimethylpyrazolyl) with PCBr leads only to the isolation of Rh2(3,5-dmpz)2(CO)3(PCBr) (4); however, [Rh(3,5-dmpz)(CO)(PCBr)]2 (5) is obtained by reacting Rh(acac)(CO)(PCBr) with an excess of Na(3,5-dmpz). Complexes 1 and 2 undergo ortho-metalation by thermal reaction in refluxing xylene, leading to dirhodium(II) complexes Rh2(Pz)2(μ-PC)Br(CO)(η2-PCBr) (6 (Pz = pz) and 7 (Pz = 3-mpz); PC = P(o-C6F4)Ph2). 5 does not react under the same conditions, but the homologous, ortho-metalated compound with 3,5-dmpz, Rh2(3,5-dmpz)2(μ-PC)Br(CO)(η 2-PCBr)(H2O) (8), is obtained by reacting 4 and PCBr (1:1 molar ratio). The thermal reaction of 4 in refluxing xylene gives Rh2(3,5-dmpz)2(μ-PC)Br(CO)3 (9) as a major product. Compound 8 has been analyzed by X-ray diffraction. It crystallizes in the monoclinic P21/n space group, with cell parameters a = 13.8667 (4) A?, b = 26.0451 (14) A?, c = 14.4031 (4) A?, and β = 97.242 (2)°. The structure consists of a dinuclear unit, with a Rh-Rh bond distance of 2.583 (1) A?. Two 3,5-dmpz ligands are bridging the rhodium atoms (Rh1-N1 = 2.069 (5), Rh1-N11 = 2.045 (4), Rh2-N2 = 2.143 (5), Rh2-N12 = 2.054 (5) A?), and one ortho-metalated phosphine acts also as bridging ligand (Rh1-P1 = 2.278 (1), Rh2-C26 = 2.056 (5) A?). One bromine atom and one carbonyl ligand complete the coordination sphere around one metal (Rh1-Br1 = 2.697 (1), Rh1-C1 = 1.881 (5) A?). The coordination on the other rhodium atom is completed by a PCBr ligand that is bonded via its P and Br atoms in a η2-mode (Rh2-P2 = 2.291 (1), Rh2-Br2 = 2.644 (1) A?). The two Rh-Br distances are very similar, reflecting the strong ligation of the neutral bidentate phosphine.
