### Abstract

Microwave spectra of seven isotopomers of tetracarbonyldihydroiron were measured in the 4-16 GHz range using a Flygare-Balle type microwave spectrometer. Measured transitions were fit using a rigid rotor Hamiltonian with five independent distortion constants. Structural parameters from a least-squares fit to the rotational constants are r(Fe-H) = 1.576(64) Å, r(Fe-C1) = 1.815(54) Å, r(Fe-C3 = 1.818(65) Å, r(C1-O1) = 1.123(80) Å, r(C3-O3) = 1.141(74) Å, <(H-Fe-H) 88.0(2.8)°, <(C1-Fe-C2) = 154.2(4.2)°, <(C3-Fe-C4) = 99.4(4.3)°, <(Fe-C1-O1) = 172.5(5.6)°, and <(Fe-C3-O3) 177.8(6.8)°. All of the carbonyl groups are bent slightly toward the hydrogen atoms. The least-squares-determined structural parameters are in excellent agreement with the substitution coordinates determined from the Kraitchman equations, the structural parameters calculated using density functional theory, and the previously published electron diffraction data. The C(2v) molecular symmetry is consistent with the results ofthe microwave data and with theoretical calculations. All of the analyses show that the H atoms are separated by about 2.2 Å, and this indicates that the complex is clearly a 'classical dihydride' rather than an η^{2}-'dihydrogen' complex. Structural parameters obtained from a density functional theory calculation agreed with measured values to within 2%. The density functional theory analysis of the anharmonicity in the Fe-H symmetric stretching potential is shown to support the observed deuterium isotope effects observed for the hydrogen atom coordinates. The anharmonicity effects are larger for the Fe-H stretching coordinate than for the <H-Fe-H interbond angle. The r_{0}(Fe-D) bond lengths were observed to be 0.05(4) Å shorter than the r_{0}(Fe-H) bond lengths.

Original language | English (US) |
---|---|

Pages (from-to) | 6774-6780 |

Number of pages | 7 |

Journal | Journal of the American Chemical Society |

Volume | 120 |

Issue number | 27 |

DOIs | |

State | Published - Jul 15 1998 |

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### ASJC Scopus subject areas

- Chemistry(all)

### Cite this

**Molecular structure of tetracarbonyldihydroiron : Microwave measurements and density functional theory calculations.** / Drouin, Brian J.; Kukolich, Stephen G.

Research output: Contribution to journal › Article

*Journal of the American Chemical Society*, vol. 120, no. 27, pp. 6774-6780. https://doi.org/10.1021/ja9741584

}

TY - JOUR

T1 - Molecular structure of tetracarbonyldihydroiron

T2 - Microwave measurements and density functional theory calculations

AU - Drouin, Brian J.

AU - Kukolich, Stephen G

PY - 1998/7/15

Y1 - 1998/7/15

N2 - Microwave spectra of seven isotopomers of tetracarbonyldihydroiron were measured in the 4-16 GHz range using a Flygare-Balle type microwave spectrometer. Measured transitions were fit using a rigid rotor Hamiltonian with five independent distortion constants. Structural parameters from a least-squares fit to the rotational constants are r(Fe-H) = 1.576(64) Å, r(Fe-C1) = 1.815(54) Å, r(Fe-C3 = 1.818(65) Å, r(C1-O1) = 1.123(80) Å, r(C3-O3) = 1.141(74) Å, <(H-Fe-H) 88.0(2.8)°, <(C1-Fe-C2) = 154.2(4.2)°, <(C3-Fe-C4) = 99.4(4.3)°, <(Fe-C1-O1) = 172.5(5.6)°, and <(Fe-C3-O3) 177.8(6.8)°. All of the carbonyl groups are bent slightly toward the hydrogen atoms. The least-squares-determined structural parameters are in excellent agreement with the substitution coordinates determined from the Kraitchman equations, the structural parameters calculated using density functional theory, and the previously published electron diffraction data. The C(2v) molecular symmetry is consistent with the results ofthe microwave data and with theoretical calculations. All of the analyses show that the H atoms are separated by about 2.2 Å, and this indicates that the complex is clearly a 'classical dihydride' rather than an η2-'dihydrogen' complex. Structural parameters obtained from a density functional theory calculation agreed with measured values to within 2%. The density functional theory analysis of the anharmonicity in the Fe-H symmetric stretching potential is shown to support the observed deuterium isotope effects observed for the hydrogen atom coordinates. The anharmonicity effects are larger for the Fe-H stretching coordinate than for the <H-Fe-H interbond angle. The r0(Fe-D) bond lengths were observed to be 0.05(4) Å shorter than the r0(Fe-H) bond lengths.

AB - Microwave spectra of seven isotopomers of tetracarbonyldihydroiron were measured in the 4-16 GHz range using a Flygare-Balle type microwave spectrometer. Measured transitions were fit using a rigid rotor Hamiltonian with five independent distortion constants. Structural parameters from a least-squares fit to the rotational constants are r(Fe-H) = 1.576(64) Å, r(Fe-C1) = 1.815(54) Å, r(Fe-C3 = 1.818(65) Å, r(C1-O1) = 1.123(80) Å, r(C3-O3) = 1.141(74) Å, <(H-Fe-H) 88.0(2.8)°, <(C1-Fe-C2) = 154.2(4.2)°, <(C3-Fe-C4) = 99.4(4.3)°, <(Fe-C1-O1) = 172.5(5.6)°, and <(Fe-C3-O3) 177.8(6.8)°. All of the carbonyl groups are bent slightly toward the hydrogen atoms. The least-squares-determined structural parameters are in excellent agreement with the substitution coordinates determined from the Kraitchman equations, the structural parameters calculated using density functional theory, and the previously published electron diffraction data. The C(2v) molecular symmetry is consistent with the results ofthe microwave data and with theoretical calculations. All of the analyses show that the H atoms are separated by about 2.2 Å, and this indicates that the complex is clearly a 'classical dihydride' rather than an η2-'dihydrogen' complex. Structural parameters obtained from a density functional theory calculation agreed with measured values to within 2%. The density functional theory analysis of the anharmonicity in the Fe-H symmetric stretching potential is shown to support the observed deuterium isotope effects observed for the hydrogen atom coordinates. The anharmonicity effects are larger for the Fe-H stretching coordinate than for the <H-Fe-H interbond angle. The r0(Fe-D) bond lengths were observed to be 0.05(4) Å shorter than the r0(Fe-H) bond lengths.

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U2 - 10.1021/ja9741584

DO - 10.1021/ja9741584

M3 - Article

AN - SCOPUS:0032528230

VL - 120

SP - 6774

EP - 6780

JO - Journal of the American Chemical Society

JF - Journal of the American Chemical Society

SN - 0002-7863

IS - 27

ER -