2011, Mücke, Philipp, Linseis, Michael, Zális, Stanislav, Winter, Rainer F.

The present account summarizes our work on mononuclear vinyl ruthenium complexes of the type RuCl(CHCHR′)(CO)(PR3)2L, divinyl-bridged diruthenium complexes {RuCl(CO)(PR3)2L}2(μ-CHCH-bridge-CHCH) and on heterobinuclear systems where only one of the two redox-active metal–organic moieties is of the vinyl ruthenium type. The favourable electrochemical properties of the {RuCl(CO)(PR3)2L(CHCH–) tag and the various spectroscopic handles offered by that unit provide detailed insights into the charge and spin delocalization over the {MCl(CO)(PR3)2L} and CHCHR′ constituents in their associated radical cations. They also offer a convenient means for measuring electronic coupling in the mixed-valent radical cations of the homo- and heterodinuclear vinyl-bridged complexes and, under favourable circumstances, on the rate of intramolecular electron transfer between the individual redox sites. Aspects of this work include examples of complexes showing time-dependent valence trapping, complexes aimed at delineating the efficiencies of through-space versus through-bond pathways for electron delocalization, complexes where electrostatic effects on the redox splitting ΔE1/2 dominate over those from the resonance contribution and systems that exhibit extensive charge and spin delocalization between two dislike endgroups despite their intrinsically different redox potentials.

2003, Hartmann, Stephan, Winter, Rainer F., Brunner, Birgit M., Sarkar, Biprajit, Knödler, Axel, Hartenbach, Ingo

We describe the allenylidene complexes [TpL2Ru=C=C=CPhR]+ SbF6− [Tp = HB(pz)3−, L2 = 2 PPh3 or 1,1′-bis(diphenylphosphanyl)ferrocene (dppf), R = Ph or ferrocenyl] and their spectroscopic and electrochemical characteristics. Three of these compounds possess redox-active, ferrocene-based substituents or ligands − that are oxidized at lower potentials than the ruthenium center itself − attached either to the terminal carbon atom of the allenylidene ligand or to the ruthenium atom. The Fc/Ph-substituted complexes 3a and 3b provide unique examples of hindered rotation of the allenylidene substituent around the M=C bond. For 3a (L2 = 2 PPh3), two isomers differing in the orientation of the vertically aligned, unsymmetrically substituted allenylidene ligand are discernible even at 388 K. The dppf-substituted congener 3b has the allenylidene ligand in a horizontal orientation and exhibits a rotational barrier, as determined by dynamic 31P NMR spectroscopy, of ΔG≠ = 47 kJ/mol at TC = 238 K. The changes in the spectroscopic and electrochemical properties upon replacement of the PPh3 by a dppf ligand and the Ph by an Fc moiety can be explained in terms of the bonding within these systems. These effects are attenuated when the ferrocene-based redox tags are oxidized, as shown by IR and UV/Vis spectroelectrochemistry. Thus, infrared spectroelectrochemistry reveals a blue shift of the allenylidene stretch upon oxidation of the dppf ligand, while oxidation of the ferrocene covalently linked to the unsaturated C3 ligand has the opposite effect. Oxidation of the ruthenium atom influences the bonding within the unsaturated ligand more profoundly. Results from IR spectroelectrochemistry point to a vinylidene structure in the RuIII state. Reduction enhances the contribution of alkynyl-type resonance forms to the overall bonding description, as also shown by IR spectroelectrochemistry. For the ferrocenyl-substituted allenylidene complexes, oxidation and reduction result in bleaching of the intense optical low-energy absorption band attributed to a ferrocenyl-to-allenylidene charge-transfer process. The EPR spectra of the paramagnetic reduced forms of these complexes also indicate spin delocalization into the aryl substituents attached to the allenylidene ligand. The complexes Tp(dppf)RuCl and [Tp(dppf)Ru=C=C=CPh2]+ SbF6− were also characterized by X-ray crystallography.

2000, Winter, Rainer F., Scheiring, Thomas

Isomerically pure nitrile complexes cis-[Ru(dppm)2Cl(NCR)]+ (2 a–d) are formed upon chloride displacement from cis-[Ru(dppm)2Cl2] (1) or, alternatively, by ligand substitution from the acetonitrile complex 2 a. This latter approach does also allow for the introduction of pyridine (3 a,b), heptamethyldisilazane (4) or isonitrile ligands (5). All complexes are obtained as the configurationally stable cis-isomers. Only cis-[Ru(dppm)2Cl(CNtBu)]+ slowly isomerizes to the trans from. The solid state structures of the CH3CN, C2H5CN and the trans-tBuNC complexes were established by X-ray crystallography. Electrochemical investigations of the nitrile complexes 2 a–d show in addition to a chemically reversible one-electron oxidation an irrversible reduction step. In CH2Cl2 solution, cis- and trans-[Ru(dppm)2Cl2] have been identified as the final products of the electrochemically induced reaction sequence.

2010, Záli , Stanislav, Winter, Rainer F., Kaim, Wolfgang

This review provides an overview of density functional theory (DFT) calculations in a consequence with spectroelectrochemical measurements on mononuclear and symmetrically or unsymmetrically bridged di- and tetranuclear ruthenium complexes of vinyl and TCNX ligands. The DFT approach is used for the calculations of molecular structures, vibrational frequencies, electronic and electron paramagnetic resonance (EPR) spectral data. DFT calculations enable us to identity the primary redox site and the electron and spin-density distribution between the individual components for the individual redox congeners. The DFT technique reproduces the spectral properties of the presented complexes and their radical ions. The generally close correspondence between experimental and quantum chemical results demonstrate that modern DFT is a powerful tool to address issues like ligand non-innocence and electron and spin delocalization in systems containing both redox-active metal ions and redox-active ligands.

2001, Hartmann, Stephan, Winter, Rainer F., Schiering, Thomas, Wanner, Matthias

Allylferrocenylselenide (2) is prepared from diferrocenyldiselenide (1Se) which was characterized along with its sulfur analog 1S by X-ray structure analysis. In the crystal lattice the packing is determined by ‘point-to-face’ CHcdots, three dots, centeredπ interactions with close contacts between the CH π donors and cyclopentadienyl rings as the π acceptors. Compound 2 is then used in the trapping of the primary butatrienylidene intermediate trans-[ClRu(dppm)2=C=C=C=CH2]+. The isolated product, trans-[Cl(dppm)2Ru=C=C=C(SeFc)(C4H7)]+ (3) (Fc=ferrocenyl), represents the first seleno-substituted allenylidene complex to be reported to date. Compound 3 is formed in a sequence involving regioselective addition of the selenium nucleophile to Cγ followed by hetero-Cope-rearrangement of the allyl vinyl substituted SeR3+ cation. Its spectroscopic properties place 3 at an intermediate position between sulfur and arene substituted all-carbon allenylidene complexes of the same metal fragment. The selenoallenylidene complex 3 contains a redox active ferrocenyl substituent attached to the heteroatom giving rise to reversible electrochemistry. ESR spectroscopy proves that electron transfer occurs from this site and its effect on the spectroscopic properties of 3 is probed by combining electrochemistry and IR or UV–vis/NIR spectroscopy by in situ techniques. In contrast, the reversible reduction primarily involves the allenylidene ligand as ascertained by ESR spectroscopy. In situ spectro-electrochemical techniques reveal how the reduction affects the bonding within the unsaturated ligand.

2010, Ott, Ingo, Kowalski, Konrad, Gust, Ronald, Maurer, Jörg, Mücke, Philipp, Winter, Rainer F.

Two ethylene linkednext term binuclear previous termmixednext term ferrocene/ruthenium complexes were biologically investigated in comparison to structurally related mononuclear ferrocene or ruthenium species with styryl substituents or ligands. Results indicated that the electron distribution (but not the redox potential), cellular uptake and (to some minor extent) anti-estrogenic effects were the key contributors to antiproliferative effects observed in tumor cell lines.

2000, Winter, Rainer F., Brunner, Birgit, Scheiring, Thomas

cis-[RuCl2(depe)2] (1) (depe=Et2PC2H4PEt2) is obtained in excellent yield and high isomeric purity by the reaction of [RuCl2(DMSO)4] with two equivalents of depe in acetone or ethyl acetate under reflux conditions. One of the chloride ligands is labile and readily displaced by CH3CN to afford the cationic monosubstitution product cis-[RuCl(CH3CN)(depe)2]+(2), which was isolated as the PF6 − salt. The X-ray crystal structure of 1 was determined. The redox properties of 1 and 2 as well as the chloride displacement from 1 by CH3CN were studied by cyclic and square wave voltammetry.