Acetylene binding to triphosphine-bridged, trirhodium chains. The preparation and X-ray crystal structure of the dimetalated olefin complex [Rh3(μ-(Ph2PCH2)2PPh) 2(μ-CO)(CO)(μ-Cl)-Clμ-CH3O2CC=CCO 2CH3][BPh4]

Alan L. Balch, L. Alan Fossett, John Linehan, Marilyn M. Olmstead

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[Rh3(dpmp)2(CO)3Cl2][BPh 4] (dpmp = bis[(diphenylphosphino)methyl]phenylphosphine) reacts with dimethyl acetylenedicarboxylate (CH3O2CC≡CCO2CH3) to yield major, brown and minor, violet isomers of [Rh3(dpmp)2(CO)2Cl2(μ-CH 3O2CC=CCO2CH3)][BPh4]. A similar reaction with diethyl acetylenedicarboxylate (CH3CH2O2CC≡CCO2CH 2CH3) yields only the brown form of [Rh3(dpmp)2(CO)2Cl2(μ-CH 3CH2O2CC=CCO2CH2CH 3)][BPh4]. With [Rh3(dpma)2(CO)3Cl2][BPh 4] (dpma = bis[(diphenylphosphino)methyl]phenylarsine) and CH3O2CC≡CCO2CH3, the brown form of [Rh3(dpma)2(CO)2Cl2(μ-CH 3O2CC=CCO2CH3)][BPh4] is obtained. Spectroscopic data (1H, 13C, and 31P NMR and infrared) indicate that the brown complexes contain a dimetalated olefin, two terminal carbon monoxide ligands, and nonequivalent ends to the triphosphine ligand: a structure with the dimetalated olefin spanning the Rh-Rh bond is proposed. [Rh3(dpmp)2(CO)2Cl2(μ-CH 3O2CC=CCO2CH3)][BPh4] undergoes stepwise substitution with iodide without major structural change. The minor, violet isomer of [Rh3(dpmp)2(CO)2Cl2(μ-CH 3O2CC=CCO2CH3)][BPh4] has been structurally characterized by X-ray crystallography. [Rh3[{(C6H5)2PCH2} 2PC6H6] 2(μ-CO)(CO)(μ-Cl)Cl(μ-CH3O2C 4O2CH3)][B(C6H5) 4]·3CH2Cl2 crystallizes from dichloromethane/ethyl ether in the triclinic space group P1 (no. 2) with two molecules per unit cell of dimensions a = 12.667 (8) Å, b = 16.787 (6) Å, c = 23.417 (6) A, α = 75.60 (2)°, β = 81.95 (4)°, and γ = 86.31 (4)° at 140 K. Least-squares refinement of 578 parameters using 7758 reflections yields R = 0.073. The structure consists of a triphosphine-bridged, trirhodium chain with a carbon monoxide and a dimetalated olefin bridging a nonbonded pair of rhodium ions (Rh⋯Rh = 3.410 (1) Å). This unit is linked to the third rhodium through the phosphine bridge and through a bridging chloride.

Original languageEnglish
Pages (from-to)691-698
Number of pages8
Issue number4
Publication statusPublished - 1986


ASJC Scopus subject areas

  • Inorganic Chemistry
  • Organic Chemistry

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