A hydrogen bonded heme-Fe(III)-O(2)(-) adduct is stabilized and characterized using resonance Raman and EPR spectroscopy. The low O-O vibrations of this complex are quite different from those reported for other heme-Fe(III)-O(2)(-) adducts.

Four planar-chiral, enantiomerically pure ferrocene dibromides (3 R1R2 ; [(CHR 1 R 2 )BrH 3 C 5 ] 2 Fe) equipped with two CHR 1 R 2 groups in α position to bromine were synthesized. From the four C 2 symmetrical species, two are already known [CHR 1 R 2 = CHMe 2 (3 MeMe ), CHEt 2 (3 EtEt )] and two are new compoundsThe dibromides 3 R1R2 were in situ converted into dilithio ferrocene derivatives and reacted with Cl 2 BNiPr 2 resulting in mixtures of bora[1]-ferrocenophanes (4 R1R2 ) and 1,1′-bis(boryl)ferrocenes (5 R1R2 ). The aim of this investigation was to test the hypothesis that the alkyl group that is oriented approximately perpendicular to the Cp ring, i.e., R 2 , affects the outcome of the salt-metathesis reaction. The obtained product ratios 4 R1R2 :5 R1R2 were determined by 1 H NMR spectroscopy and revealed that systems with the same R 2 group gave similar 4 R1R2 :5 R1R2 ratios (1.0:0.51 and 1.0:0.49 for R 2 = Me; 1.0:0.30 and 1.0:0.27 for R 2 = Et), confirming the hypothesis. Shown by DFT calculations (B3PW91/6-311+G(d,p)), reaction paths resulting in either product 4 R1R2 or product 5 R1R2 are both concerted steps.

A series of new boron-bridged [1]ferrocenophanes ([1]FCPs) was prepared by salt-metathesis reactions between enantiomerically pure dilithioferrocenes and amino(dichloro)boranes (Et2 NBCl2 , iPr2 NBCl2 , or tBu(Me3 Si)NBCl2 ). The dilithioferrocenes were prepared in situ by lithium-bromine exchange from the respective planar-chiral dibromides (Sp ,Sp )-[1-Br-2-(HR2 C)H3 C5 ]2 Fe (R=Me or Et). In most of the cases, mixtures of the targeted [1]FCPs 4 and the unwanted 1,1'-bis(boryl)ferrocenes 5 were formed. The product ratio depends on the bulkiness of the amino group, the speed of addition of the amino(dichloro)borane, the alkyl group on Cp rings, and in particular on the reaction temperature. The formation of strained [1]FCPs is strongly favored by increased reaction temperatures. Secondly, CHEt2 groups at Cp rings favored the formation of the targeted [1]FCPs stronger than CHMe2 groups. These discoveries open up new possibilities to further suppress the formation of unwanted byproducts by a careful choice of the reaction temperature and through tailoring the bulkiness of CHR2 groups on ferrocene. Thermal ring-opening polymerizations of selected boron-bridged [1]FCPs gave metallopolymers with a Mw of 10 kDa (GPC).

A series of [1]­ferrocenophanes ([1]­FCPs) bridged by boron, carbon, silicon, phosphorus, and sulfur, respectively, were investigated by DFT calculations. A comparison of measured molecular structures with calculated structures showed that the applied B3PW91/6-311+G­(d,p) level of theory provides realistic molecular geometries. Geometry optimization of carbon-bridged [1]­FCPs (ER x = CH2, CMe2) revealed that these unknown species with tilt angles α of 38.5° may be sufficiently stable to allow isolation, given sufficient kinetic stability. In order to measure the amount of strain in [1]­FCPs, a hypothetical 1,2-addition of a C–H group of FeCp2 across the E–Cipso bond of a [1]­FCP to give a bis­(ferrocenyl)­species was investigated. The calculated reaction enthalpies were compared to experimental ΔH ROP values as obtained from differential scanning calorimetry (DSC) measurements.

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