The formation of ferrocenyl-functionalized iron and cobalt carbonyl clusters is reported, based on a reaction of FcPCl 2 (3) (Fc = Fe(η 5 -C 5 H 5 )(η 5 -C 5 H 4 )) with Fe 2 (CO) 9 and Co 2 (CO) 8 , respectively. Therein, nido-Fe 3 (CO) 9 (μ 3 -PFc) 2 (4) and nido-Co 4 (CO) 10 (μ 3 -PFc) 2 (5) clusters were obtained as the first diferrocenyl-substituted carbonyl clusters with a symmetrical cluster core. Cluster 4 shows two reversible one-electron processes within the anodic region, based on Fc/Fc + redox events, as well as two processes in the cathodic region. In situ IR and electron paramagnetic resonance (EPR) measurements of all electronic states confirmed an Fc-based oxidation and a core-based reduction. On the basis of the results of a single-crystal X-ray analysis of structures of 4 and 5, computational studies of the highest occupied molecular orbital−lowest unoccupied molecular orbital energies, the spin density, quantum theory of atom-in-molecule delocalization indices, and the atomic charges were performed to explain the experimental results. The latter revealed a reorganization of the cluster core upon reduction and the existence of weak P•••P interactions in 4 and 5. Ferrocenyl-related redox processes, occurring reversibly in case of 4, were absent for 5, due to a different distribution of the HOMO energies. EPR measurements furthermore confirmed the core-based radical anion and the formation of a decomposition product at potentials lower than [M] 2− (M = Fe, Co).
The reaction chemistry of Fe 2 (CO) 9 (10) with ferrocenenyl dichlorophosphines of different substitution is discussed. Single FcPCl 2 , (5) as well as 1,1'-( 6) and 1,2-( 9) difunctionalized phosphines were used, of which 6 and 9, were prepared in a novel straightforward synthetic process. Substrate 5 gave butterfly-shaped Fe 2 (CO) 6 (μ 2 -Cl)(μ 2 -PFcCl) and Fe 2 (CO) 6 (μ 2 -PFcR 1 )(μ 2 -PFcR 2 ) (R 1 , R 2 = Cl, H). In addition, nido-Fe 3 (CO) 10 (μ 3 -PFc) and nido-Fe 3 (CO) 9 (μ 3 -PFc) 2 were obtained. 1,1'-Functionalized 6 bridges both ends of the Fe 2 (CO) 6 entity. Therein, the so far smallest non-binding P•••P distance (2.7674(12) Å) between both 1,1'-substituents is observed. Additionally, an 'organometallic octabisvalene', containing two [2]ferrocenophane entities was obtained. The eight-membered cyclic structure is twisted by 35.31(9)°regarding their ferrocenyl axis. Usage of 1,2-(PCl 2 ) 2 functionalized 9 produced two isomers of a PÀ P connected dimer, which coordinates towards two independent Fe 2 (CO) 6 fragments in a novel μ,μ',k 8 or bis(μ,k 4 ) fashion, resulting in a meso isomer with a planar core, and a racem mixture, possessing a pocket-type structure. The latter shows the so far shortest observed P•••P distance of 2.950(7) Å between two ortho P atoms of a ferrocenyl backbone. The results confirm that the geometric properties of ferrocenyls featuring 1,1'-and 1,2-substitution patterns are not comparable with phenyl-based analogues. X-ray single crystal solid state structures, and DFT calculations were carried out.
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