The length, strength and polarity of metal–carbon bonds: dialkylzinc compounds studied by density functional theory calculations, gas electron diffraction and photoelectron spectroscopy

Arne Haaland; Jennifer C. Green; G. Sean McGrady; Anthony J. Downs; Emanuel Gullo; Mark J. Lyall; Jessima Timberlake; Andrey V. Tutukin; Hans Vidar Volden; Kari-Anne Østby

doi:10.1039/B306840B

The length, strength and polarity of metal–carbon bonds: dialkylzinc compounds studied by density functional theory calculations, gas electron diffraction and photoelectron spectroscopy†

Arne Haaland,*^a Jennifer C. Green,*^b G. Sean McGrady,‡*^c Anthony J. Downs,^b Emanuel Gullo,^c Mark J. Lyall,^b Jessima Timberlake,^b Andrey V. Tutukin,^a Hans Vidar Volden^a and Kari-Anne Østby^a

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* Corresponding authors

^a Department of Chemistry, University of Oslo, Box 1033, Blindern, N-0315 Oslo, Norway
E-mail: arne.haaland@kjemi.uio.no

^b Inorganic Chemistry Laboratory, University of Oxford, South Parks Road, Oxford, UK
E-mail: jennifer.green@chemistry.oxford.ac.uk

^c Department of Chemistry, King's College London, Strand, UK

Abstract

The molecular structures and thermodynamic functions of seven dialkyl zinc compounds, R₂Zn, R = Me, Et, i-Pr, t-Bu, n-Pr, neopentyl and the silaneopentyl Me₃SiCH₂, of the parent hydrocarbons RH and of the radicals R have been determined by density functional theory calculations at the B3LYP/SDD level. The molecular structures of the i-Pr, t-Bu, neo-Pe and Me₃SiCH₂ derivatives have been determined by gas electron diffraction. Me₂Zn, Et₂Zn, t-Bu₂Zn and neo-Pe₂Zn have been studied by photoelectron spectroscopy and the ionisation energies calculated. Both experimental and calculated Zn-C bond distances were found to increase in the order Me₂Zn ≈ (Me₃SiCH₂)₂Zn < Et₂Zn ≈ n-Pr₂Zn ≈ neo-Pe₂Zn < i-Pr₂Zn < t-Bu₂Zn.

Calculated mean bond rupture enthalpies indicate that the strength of the Zn–C bonds decrease in the same order, viz. Me₂Zn ≈ (Me₃SiCH₂)₂Zn > Et₂Zn ≈ n-Pr₂Zn ≈ neo-Pe₂Zn > i-Pr₂Zn > t-Bu₂Zn.

Both bond lengths and bond strengths were found to be strongly correlated with the inductive Taft constant I, indicating that the bond strength increases and the bond length decreases with increasing electron withdrawing power of the alkyl group. Evidence from the literature indicates that bond strengths and bond lengths in homoleptic alkyl derivatives of the main group metals in Groups 12, 13 and 14 and of the transition elements in Group 4 vary in the same manner.

$Graphical abstract: The length, strength and polarity of metal–carbon bonds: dialkylzinc compounds studied by density functional theory calculations, gas electron diffraction and photoelectron spectroscopy$

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The length, strength and polarity of metal–carbon bonds: dialkylzinc compounds studied by density functional theory calculations, gas electron diffraction and photoelectron spectroscopy†

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The length, strength and polarity of metal–carbon bonds: dialkylzinc compounds studied by density functional theory calculations, gas electron diffraction and photoelectron spectroscopy

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