Intermetallic s̀ and ∞ Communication in Heterodinuclear μ‐Cyclooctatetraene Complexes

Structure and Reactivity of Early−Late Heterobimetallic Complexes

“…The chromium−iron distances are around 3.0 Å in all these complexes. Solid solution EPR spectra are consistent with the unpaired electron residing primarily on the chromium center in a d z 2 -type orbital ( g iso = 1.991−1.995, a ( 53 Cr) = 18.9−19.0 G): hyperfine coupling to the hydrogens of the η 5 -cyclooctatetraene ligand ( a ( 1 H) = 3.2−5.4 G) and to the phosphorus center (when present, a ( 31 P) = 13.3−34.2 G) is also observed (see section IV.B) 9 Crystal structure of [Cp*Cr(μ-cot)Fe(CO) 3 ].…”

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9 Crystal structure of [Cp*Cr(μ-cot)Fe(CO) 3 ]. Reprinted with permission from ref . Copyright 1997 Wiley-VCH Verlag GmbH.

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“…The authors propose a spin delocalization mechanism involving both σ- and π-interactions between the two metal centers (see Figure ). Spin transfer through the bridging ligand was formally excluded 54 Proposed spin delocalization mechanism in [(C 5 R 5 )Cr(μ-cot)Fe(CO) 2 (PR 3 )].…”

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54 Proposed spin delocalization mechanism in [(C 5 R 5 )Cr(μ-cot)Fe(CO) 2 (PR 3 )]. Redrawn from ref .

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“…The chromium−iron complexes [(C 5 R 5 )Cr(μ-η 5 Cr ,η 3 Fe -cot)Fe(CO) 3 ] show reversible oxidation processes at −0.10 V (R = H) and −0.20 V (R = Me), as well as irreversible oxidations at potential greater than +0.54 V. Reduction of these complexes occurs at around −2.5 V: this is reversible for R = H but not for R = Me, where an EC process appears to be involved. Replacement of a carbonyl ligand with a phosphine leads to a shift in the oxidation potentials of more than −0.25 V. However, [(C 5 R 5 )Cr(μ-η 5 Cr ,η 3 Fe -cot)Fe(CO) 2 (PF 3 )] presents a reversible oxidation at −0.15 V, an indication of the high π-acidity of PF 3 …”