Preparation and Fluxional Behavior of New Rhodiacyclopentadiene Complexes Containing Trifluorophosphine

M. A. Bennett; R. N. Johnson; T. W. Turney

doi:10.1021/ic50155a022

Preparation and Fluxional Behavior of New Rhodiacyclopentadiene Complexes Containing Trifluorophosphine

M. A. Bennett, R. N. Johnson, T. W. Turney

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11 Citations (Scopus)

Abstract

Dimethyl acetylenedicarboxylate, CH₃O₂CC₂CO₂CH₃, and methyl propiolate, HC₂CO₂CH₃ (ac), react with dirhodium octakis(trifluorophosphine), Rh₂(PF₃)₈ below room temperature to give red complexes of empirical formula Rh₂(PF₃)₅(ac)₂ (1, ac = CH₃O₂CC₂CO₂CH₃; 2, ac = HC₂CO₂CH₃). Above room temperature explosive polymerization of the acetylenes ensues. The complexes are assigned a metallocyclopentadiene structure (F₃P)₃Rh(μ-C₄X₂Y₂)Rh(PF₃)₂ (X = Y = CO₂CH₃; X = CO₂CH₃, Y = H) on the basis of ¹H and ¹⁹F NMR spectra and a preliminary single-crystal X-ray study of the bis(triphenylphosphine) complex of 2, the acetylene units in 2 being arranged in a “head-to-tail” manner. The Rh(PF₃)₃ unit in 1 and 2 shows fluxional behavior in the ¹⁹F NMR spectra while the Rh(PF₃)₃ unit remains essentially unchanged, and an intramolecular tritopal rearrangement is suggested. Line shape analysis gives the free energy of activation (ΔG^‡) of the process in 1 and 2 as ca. 10.5 kcal/mol.

Original language	English
Pages (from-to)	107-110
Number of pages	4
Journal	Inorganic Chemistry
Volume	15
Issue number	1
DOIs	https://doi.org/10.1021/ic50155a022
Publication status	Published - 1 Jan 1976
Externally published	Yes

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title = "Preparation and Fluxional Behavior of New Rhodiacyclopentadiene Complexes Containing Trifluorophosphine",

abstract = "Dimethyl acetylenedicarboxylate, CH3O2CC2CO2CH3, and methyl propiolate, HC2CO2CH3 (ac), react with dirhodium octakis(trifluorophosphine), Rh2(PF3)8 below room temperature to give red complexes of empirical formula Rh2(PF3)5(ac)2 (1, ac = CH3O2CC2CO2CH3; 2, ac = HC2CO2CH3). Above room temperature explosive polymerization of the acetylenes ensues. The complexes are assigned a metallocyclopentadiene structure (F3P)3Rh(μ-C4X2Y2)Rh(PF3)2 (X = Y = CO2CH3; X = CO2CH3, Y = H) on the basis of 1H and 19F NMR spectra and a preliminary single-crystal X-ray study of the bis(triphenylphosphine) complex of 2, the acetylene units in 2 being arranged in a “head-to-tail” manner. The Rh(PF3)3 unit in 1 and 2 shows fluxional behavior in the 19F NMR spectra while the Rh(PF3)3 unit remains essentially unchanged, and an intramolecular tritopal rearrangement is suggested. Line shape analysis gives the free energy of activation (ΔG‡) of the process in 1 and 2 as ca. 10.5 kcal/mol.",

author = "Bennett, {M. A.} and Johnson, {R. N.} and Turney, {T. W.}",

year = "1976",

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doi = "10.1021/ic50155a022",

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AU - Johnson, R. N.

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PY - 1976/1/1

Y1 - 1976/1/1

N2 - Dimethyl acetylenedicarboxylate, CH3O2CC2CO2CH3, and methyl propiolate, HC2CO2CH3 (ac), react with dirhodium octakis(trifluorophosphine), Rh2(PF3)8 below room temperature to give red complexes of empirical formula Rh2(PF3)5(ac)2 (1, ac = CH3O2CC2CO2CH3; 2, ac = HC2CO2CH3). Above room temperature explosive polymerization of the acetylenes ensues. The complexes are assigned a metallocyclopentadiene structure (F3P)3Rh(μ-C4X2Y2)Rh(PF3)2 (X = Y = CO2CH3; X = CO2CH3, Y = H) on the basis of 1H and 19F NMR spectra and a preliminary single-crystal X-ray study of the bis(triphenylphosphine) complex of 2, the acetylene units in 2 being arranged in a “head-to-tail” manner. The Rh(PF3)3 unit in 1 and 2 shows fluxional behavior in the 19F NMR spectra while the Rh(PF3)3 unit remains essentially unchanged, and an intramolecular tritopal rearrangement is suggested. Line shape analysis gives the free energy of activation (ΔG‡) of the process in 1 and 2 as ca. 10.5 kcal/mol.

AB - Dimethyl acetylenedicarboxylate, CH3O2CC2CO2CH3, and methyl propiolate, HC2CO2CH3 (ac), react with dirhodium octakis(trifluorophosphine), Rh2(PF3)8 below room temperature to give red complexes of empirical formula Rh2(PF3)5(ac)2 (1, ac = CH3O2CC2CO2CH3; 2, ac = HC2CO2CH3). Above room temperature explosive polymerization of the acetylenes ensues. The complexes are assigned a metallocyclopentadiene structure (F3P)3Rh(μ-C4X2Y2)Rh(PF3)2 (X = Y = CO2CH3; X = CO2CH3, Y = H) on the basis of 1H and 19F NMR spectra and a preliminary single-crystal X-ray study of the bis(triphenylphosphine) complex of 2, the acetylene units in 2 being arranged in a “head-to-tail” manner. The Rh(PF3)3 unit in 1 and 2 shows fluxional behavior in the 19F NMR spectra while the Rh(PF3)3 unit remains essentially unchanged, and an intramolecular tritopal rearrangement is suggested. Line shape analysis gives the free energy of activation (ΔG‡) of the process in 1 and 2 as ca. 10.5 kcal/mol.

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JO - Inorganic Chemistry

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Preparation and Fluxional Behavior of New Rhodiacyclopentadiene Complexes Containing Trifluorophosphine

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