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17-electron chromium nitrosyl complexes

University of British Columbia

Reaction of [CpCr(NO)I]₂ with an excess of ammonia or allylamine yields the complex salts [CpCr(NO)L₂]⁺[I]⁻ (L = NH₃, NH₂C₃H₅) . Heating these salts results in loss of L and formation of the neutral complexes, CpCr(NO)(L)I. In contrast, reaction of [CpCr(NO)I]₂ with the bulkier amine NH₂CMe₃ affords CpCr(NO)(lS[NH₂CMe₃)I directly. Sequential reaction of CpCr(NO)( NH₂CMe₃)I or CpCr(NO)(P{OMe}3)I with AgPF₆ and further L affords, respectively, the salts [CpCr(NO)(L)₂]⁺[PF₆]⁻(L = NH₂CMe₃, L = P(OMe)₃). All these species exhibit room-temperature ESR spectra and magnetic moments consistent with their possessing 17-valence-electron configurations. Abstraction of a proton from the amine ligand of [CpCr(NO)L₂]+ and CpCr(NO)(L)I (L = amine) compounds results in the formation of amidebridged dimers [CpCr(NO)(NHR)]₂, which exist as mixtures of various cis- and /raws-isomers. Reduction of [CpCr(NO)(NH₃)₂]⁺ to an 18-electron configuration results in loss ofNH₃, so that CpCr(NO)(CO)₂ s formed in the presence of CO. In a reverse manner, oxidation of CpCr(NO)(CO)₂ in acetonitrile produces [CpCr(NO)(NCMe)₂]⁺[PF₆]-. These observations suggest that for CpCr(NO)L₂ complexes, a-basic ligands stabilize the 17-electron configurations of cations whereas π-acidic ligands stabilize the 18-electron configurations of the neutral congeners. This trend can be rationalized by the results of an Extended Hiickel molecular orbital analysis of the CpCr(NO) fragment and the interaction of its frontier orbitals with those of various ligands, L. [more abstract available; see pdf]

Thesis/Dissertation

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2009-02-19

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http://hdl.handle.net/2429/4804

Chemistry

University of British Columbia

UBCV

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