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Intermetallic s̀ and ∞ Communication in Heterodinuclear μ‐Cyclooctatetraene Complexes
Author(s) -
Bögels Gerdjan,
Brussaard Hugo C.,
Hagenau Ute,
Heck Jürgen,
Kopf Jürgen,
van der Linden Johannes G. M.,
Roelofsen Annie
Publication year - 1997
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.19970030721
Subject(s) - cyclooctatetraene , ligand (biochemistry) , chemistry , cyclopentadienyl complex , steric effects , crystallography , pyridine , stereochemistry , metal , medicinal chemistry , molecule , biochemistry , receptor , organic chemistry , catalysis
The reaction of [(C 5 R 5 )Cr(∞ 6 ‐Cot)] (R = H, Me; Cot = cyclooctatetraene) with [(CO) 3 Fe(∞‐ cis ‐cyclooctene) 2 ] affords the heterodinuclear complexes [(C 5 R 5 )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, PR 3 (R = Me, Ph, OEt, F) to obtain [(C 5 R 5 )Cr{μ‐∞ 5 ( Cr ):∞ 3 ( Fe )‐Cot}Fe‐(CO) 2 PR 3 ] (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 C 5 Me 5 (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 31 P hyperfine coupling constants (hfcc). These can be explained by a superposition of two different electron spin transfer mechanisms, which include a s̀‐ and a π‐bonding mode between the Cr and Fe centers.