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Issue 30, 2013
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Identification of non-classical C–H⋯M interactions in early and late transition metal complexes containing the CH(ArO)3 ligand

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Abstract

The fully optimised DFT structure of the d0 complex [{CH(ArO)3}Ti(NEt2)] (2) at the B3LYP level compares well with the distorted tetrahedral geometry shown by the X-ray crystal structure. QTAIM analysis of the electron density associated with the C–H⋯Ti interaction shows a well defined bond critical point, a bond path between the hydrogen and titanium centres and a negative value for the energy density indicative of covalency. A natural bond orbital (NBO) picture of the interaction shows that the C–H σ bond electron density donates to a d hybrid orbital on the metal in a linear fashion. Calculated IR and NMR data for the components of the interaction are consistent with experiment. The computed structures for [{CH(ArO)3}Ti(OPh)] (3), [{CH(ArO)3}Zr(NEt2)] (4), [{CH(ArO)3}Hf(NEt2)] (5), show tetrahedral geometries and QTAIM and NBO properties similar to (2). [{CH(ArO)3}Mo(NEt2)] (6) shows distortion of the tripodal ligand and a reduced C–H⋯M bond angle with properties more consistent with a C–H⋯M side-on donor interaction. In [{CH(ArO)3}Fe(NEt2)] (7) the C–H⋯M bond angle is linear and involves a donor interaction. An energy minimised structure maintaining the three fold coordination to the tripodal ligand was not obtained for [{CH(ArO)3}Ni(NEt2)]2− but changing from a diethyl amide ligand to phenolato gave energy minimised [{CH(ArO)3}Ni(OPh)]2− (8). This structure shows a distorted square planar geometry with a substantially bent phenoxo ligand and a near linear C–H⋯M covalent interaction with donor and back bonding properties. The work shows that linear C–H⋯M interactions can have both agostic and weak hydrogen bond-like covalency.

Graphical abstract: Identification of non-classical C–H⋯M interactions in early and late transition metal complexes containing the CH(ArO)3 ligand

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Publication details

The article was received on 19 Apr 2013, accepted on 08 Jun 2013 and first published on 10 Jun 2013


Article type: Paper
DOI: 10.1039/C3DT51028J
Citation: Dalton Trans., 2013,42, 10939-10951
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    Identification of non-classical C–H⋯M interactions in early and late transition metal complexes containing the CH(ArO)3 ligand

    M. Lein, J. A. Harrison and A. J. Nielson, Dalton Trans., 2013, 42, 10939
    DOI: 10.1039/C3DT51028J

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