Preparation, crystal structures and spectroscopic properties of a series of cobalt(III) phosphine complexes: trans- and cis-[Co(dtc) 2 (PMe 3-nPh n) 2] + (dtc = N,N-dimethyldithiocarbamate; n = 0, 1, 2 or 3)

Takayoshi Suzuki, Shinsaku Kashiwamura, Kazuo Kashiwabara

Research output: Contribution to journalArticle

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Abstract

A series of new cobalt(III) phosphine complexes of trans-[Co(dtc) 2 (PMe 3-nPh n) 2]BF 4 (dtc = N,N-dimethyldithiocarbamate; n = 0, 1, 2 or 3) and cis-[Co(dtc) 2(PMe 3 or PMe 2Ph) 2](BF 4 or PF 6) have been prepared and their crystal structures and spectroscopic properties have been investigated. It is found that the Co-S bond lengths vary with steric and electronic factors of the P-ligands; i.e. (1) the intramolecular π-π stacking interaction between the dtc plane and the phenyl ring of the P-ligand, and (2) the electronic trans influence of the trans-positioned P-ligand. The strength of electronic trans influence decreases as PMe 3 > PMe 2Ph > P(OCH 2) 3CEt in accordance with the order of σ-donicity strengths. In the series of trans-isomers, the electronic trans influence is competitive with the steric requirement of the phosphine to elongate the mutually trans Co-P bonds. The steric trans influence via the equatorial dtc ligands for such an elongation of the Co-P bonds seems to be negligible, which is in sharp contrast to the situation for via pentane-2,4-dionate (acac) ligands in the analogous complexes, trans-[Co(acac) 2 (PMe 3-nPh n) 2]PF 6. This is probably due to the compactness of dtc and the resulting open space at the Co atom. The fact that the Co-P bond lengths in the dtc complexes are shorter than those in the acac complexes is reflected in the larger stability toward hydrolysis of the dtc complexes. In the UV-vis absorption spectra, the degenerate splitting component (a 1E g) of the first d-d transition band of trans-[Co(dtc) 2 (PMe 3-nPh n) 2] + is observed at almost the same position (within 300 cm -1) as that of the corresponding acac complexes, while the transition energies of the P-to-Co LMCT of these two series of complexes are rather different (at least 2700 cm -1) from each other. Furthermore, the first and the second d-d transition bands of cis-[Co(dtc) 2(PMe 3 or PMe 2Ph) 2] + are observed at lower energy than those of cis-[Co(dtc) 2{P(OMe) 3} 2 + in spite of a weaker σ-donor of phosphite. The separation of the first and the second d-d transition bands of the P(OMe) 3 complex is remarkably smaller than the separation of the bands of the PMe 3 one, being indicative of a further reduction of the interelectronic repulsion in the P(OMe) 3 complex.

Original languageEnglish
Pages (from-to)2349-2359
Number of pages11
JournalBulletin of the Chemical Society of Japan
Volume74
Issue number12
DOIs
Publication statusPublished - Dec 2001
Externally publishedYes

ASJC Scopus subject areas

  • Chemistry(all)

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