Theoretical study of primary and secondary deuterium equilibrium isotope effects for H2 and CH4 addition to trans-Ir(PR3)2(CO)X

Faraj Abu-Hasanayn; Karsten Krogh-Jespersen; Alan S Goldman

Theoretical study of primary and secondary deuterium equilibrium isotope effects for H₂ and CH₄ addition to trans-Ir(PR₃)₂(CO)X

Faraj Abu-Hasanayn, Karsten Krogh-Jespersen, Alan S Goldman

Rutgers University

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Abstract

Deuterium equilibrium isotope effects (EIE) for H₂ and H-CH₃ addition to Vaska-type complexes, transIr(PH₃)₂(CO)X (XM), have been determined using vibrational frequencies obtained from ab initio calculations on XM and on cis,trans-H₂Ir(PH₃)₂(CO)X (XMH₂). Inverse primary EIE values for H₂/D₂ addition to XM are computed to be 0.46 (X = Cl), 0.57 (X = CH₃), and 0.33 (X = H; 0.66 after statistical normalization) at 300 K. The EIE values and the computed enthalpy and entropy terms are consistent with several experimental studies. Secondary thermodynamic deuterium isotope effects for H₂ addition to XM are computed for X = H/D (α-EIE = 0.44; 0.88 after statistical normalization) and for X = CH₃/CD₃ (β-EIE = 0.86). Computations on the addition of CH₄/CH₃D or CH₄/CD₄ to HM reveal EIEs of 7.77 (1.94 per bond) and 3.64, respectively. These results are analyzed and discussed using equilibrium statistical mechanics.

Original language	English
Pages (from-to)	8019-8023
Number of pages	5
Journal	Journal of the American Chemical Society
Volume	115
Issue number	18
Publication status	Published - Sep 8 1993

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Abu-Hasanayn, F., Krogh-Jespersen, K., & Goldman, A. S. (1993). Theoretical study of primary and secondary deuterium equilibrium isotope effects for H₂ and CH₄ addition to trans-Ir(PR₃)₂(CO)X. Journal of the American Chemical Society, 115(18), 8019-8023.

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title = "Theoretical study of primary and secondary deuterium equilibrium isotope effects for H2 and CH4 addition to trans-Ir(PR3)2(CO)X",

abstract = "Deuterium equilibrium isotope effects (EIE) for H2 and H-CH3 addition to Vaska-type complexes, transIr(PH3)2(CO)X (XM), have been determined using vibrational frequencies obtained from ab initio calculations on XM and on cis,trans-H2Ir(PH3)2(CO)X (XMH2). Inverse primary EIE values for H2/D2 addition to XM are computed to be 0.46 (X = Cl), 0.57 (X = CH3), and 0.33 (X = H; 0.66 after statistical normalization) at 300 K. The EIE values and the computed enthalpy and entropy terms are consistent with several experimental studies. Secondary thermodynamic deuterium isotope effects for H2 addition to XM are computed for X = H/D (α-EIE = 0.44; 0.88 after statistical normalization) and for X = CH3/CD3 (β-EIE = 0.86). Computations on the addition of CH4/CH3D or CH4/CD4 to HM reveal EIEs of 7.77 (1.94 per bond) and 3.64, respectively. These results are analyzed and discussed using equilibrium statistical mechanics.",

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AU - Abu-Hasanayn, Faraj

AU - Krogh-Jespersen, Karsten

AU - Goldman, Alan S

PY - 1993/9/8

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N2 - Deuterium equilibrium isotope effects (EIE) for H2 and H-CH3 addition to Vaska-type complexes, transIr(PH3)2(CO)X (XM), have been determined using vibrational frequencies obtained from ab initio calculations on XM and on cis,trans-H2Ir(PH3)2(CO)X (XMH2). Inverse primary EIE values for H2/D2 addition to XM are computed to be 0.46 (X = Cl), 0.57 (X = CH3), and 0.33 (X = H; 0.66 after statistical normalization) at 300 K. The EIE values and the computed enthalpy and entropy terms are consistent with several experimental studies. Secondary thermodynamic deuterium isotope effects for H2 addition to XM are computed for X = H/D (α-EIE = 0.44; 0.88 after statistical normalization) and for X = CH3/CD3 (β-EIE = 0.86). Computations on the addition of CH4/CH3D or CH4/CD4 to HM reveal EIEs of 7.77 (1.94 per bond) and 3.64, respectively. These results are analyzed and discussed using equilibrium statistical mechanics.

AB - Deuterium equilibrium isotope effects (EIE) for H2 and H-CH3 addition to Vaska-type complexes, transIr(PH3)2(CO)X (XM), have been determined using vibrational frequencies obtained from ab initio calculations on XM and on cis,trans-H2Ir(PH3)2(CO)X (XMH2). Inverse primary EIE values for H2/D2 addition to XM are computed to be 0.46 (X = Cl), 0.57 (X = CH3), and 0.33 (X = H; 0.66 after statistical normalization) at 300 K. The EIE values and the computed enthalpy and entropy terms are consistent with several experimental studies. Secondary thermodynamic deuterium isotope effects for H2 addition to XM are computed for X = H/D (α-EIE = 0.44; 0.88 after statistical normalization) and for X = CH3/CD3 (β-EIE = 0.86). Computations on the addition of CH4/CH3D or CH4/CD4 to HM reveal EIEs of 7.77 (1.94 per bond) and 3.64, respectively. These results are analyzed and discussed using equilibrium statistical mechanics.

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