ISSN:
0947-6539
Keywords:
bridging ligands
;
cyclooctatetraene
;
EPR spectroscopy
;
heterodinuclear complexes
;
structure elucidation
;
Chemistry
;
General Chemistry
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
Notes:
The reaction of [(C5R5)Cr(∞6-Cot)] (R = H, Me; Cot = cyclooctatetraene) with [(CO)3Fe(∞-cis-cyclooctene)2] affords the heterodinuclear complexes [(C5R5)Cr{μ-∞5(Cr):∞3(Fe)-Cot}Fe(CO)3] (R = H: 1, R = Me: 2) in quite good yields. One of the CO ligands in 1 and 2 can be easily substituted by a phosphane ligand, PR3 (R = Me, Ph, OEt, F) to obtain [(C5R5)Cr{μ-∞5(Cr):∞3(Fe)-Cot}Fe-(CO)2PR3] (R = H, R = Me: 3a; R = H, R = Ph: 3b; R = Me, R = Me: 4a; R = Me, R = Ph: 4b; R = Me, R = OEt: 4c; R = Me, R = F: 4d). The X-ray structure determinations of 2, 3a, and 4c showed exclusively synfacial coordination of the two metal ligand moieties, despite the bulky C5Me5 (Cp*) ligand in 2 and 4c. However, the steric demand of Cp* gives rise to structural distortions in 2 and 4c, compared to the Cp-containing products 1 and 3a, and an elongation of the Cr-Fe distance from 293 pm to 303 and 304 pm, respectively. The heterodinuclear complexes were investigated by cyclic voltammetry and ESR spectroscopy in order to elucidate the role of the permethylation of the cyclopentadienyl ligand and the influence of phosphane ligands with different π-accepting abilities. The ESR spectroscopic results reveal surprisingly large 31P hyperfine coupling constants (hfcc). These can be explained by a superposition of two different electron spin transfer mechanisms, which include a s̰- and a π-bonding mode between the Cr and Fe centers.
Additional Material:
5 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/chem.19970030721
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