Triruthenium [(dppe)(2)Ru{-C≡C-1,4-C(6)H(2)-2,5-R(2)-CH═CH-RuCl(CO)(P(i)Pr(3))(2)}(2)](n+) (4a, R = H; 4b, R = OMe) containing unsymmetrical (ethynyl)(vinyl)phenylene bridging ligands and displaying five well-separated redox states (n = 0-4) are compared to their bis(alkynyl)ruthenium precursors (dppe)(2)Ru{-C≡C-1,4-C(6)H(2)-2,5-R(2)-C≡CR'} (2a,b: R' = TMS; 3a,b: R' = H) and their symmetrically substituted bimetallic congeners, complexes {Cl(dppe)(2)Ru}(2){μ-C≡C-1,4-C(6)H(2)-2,5-R(2)-C≡C} (A(a), R = H; A(b), R = OMe) and {RuCl(CO)(P(i)Pr(3))(2)}(2){μ-CH═CH-1,4-C(6)H(2)-2,5-R(2)-CH═CH} (V(a), R = H; V(b), R = OMe) as well as the mixed (ethynyl)(vinyl)phenylene bridged [Cl(dppe)(2)Ru-C≡C-1,4-C(6)H(4)-CH═CH-RuCl(CO)(P(i)Pr(3))(2)] (M(a)). Successive one-electron transfer steps were studied by means of cyclic voltammetry, EPR and UV-vis-NIR-IR spectroelectrochemistry. These studies show that the first oxidation mainly involves the central bis(alkynyl) ruthenium moiety with only limited effects on the appended vinyl ruthenium moieties. The second to fourth oxidations (n = 2, 3, 4) involve the entire carbon-rich conjugated path of the molecule with an increased charge uniformly distributed between the two arms of the molecules, including the terminal vinyl ruthenium sites. In order to assess the charge distribution, we judiciously use (13)CO labeled analogues to distinguish stretching vibrations due to the acetylide triple bonds and the intense and charge-sensitive Ru(CO) IR probe in different oxidation states. The comparison between complex pairs 4a,b(n+) (n = 0-3), A(a,b)(n+) and V(a,b)(n+) (n = 0-2) serves to elucidate the effect of the methoxy donor substituents on the redox and spectroscopic properties of these systems in their various oxidation states and on the metal/ligand contributions to their frontier orbitals.

Diruthenium complexes (X)(dppe) 2 Ru-CtC-1,4-C 6 H 4 -CHdCH-RuCl(CO)(P i Pr 3 ) 2 (X = Cl, 1a; X = CtCPh, 1b) containing an unsymmetrical (ethynyl)(vinyl)phenylene bridging ligand are compared to their symmetrical 1,4-bis(ethynyl)phenylene-and 1,4-divinylphenylene-bridged congeners and their mononuclear alkynyl precursors. Electrochemical and UV/vis/NIR, IR, and EPR spectroscopic studies on the neutral complexes and their various oxidized forms indicate bridging ligand-centered oxidation processes and uniform charge and spin delocalization over both dislike organoruthenium moieties despite differences in their intrinsic redox potentials. Comparison between the chloro and the phenylacetylide-terminated derivatives 1a,b suggests further that the conjugated organometallic π-system extends over the entire unsaturated backbone including the terminal ligand at the alkynyl ruthenium site. This paves the way to even more extended π-conjugated organoruthenium arrays for long-range electronic interactions.

Vinylbenzoate-bridged diruthenium complexes (RHC=CH)(CO)(P(i)Pr(3))(2)Ru(mu-4-OOCC(6)H(4)-CH=CH)RuCl(CO)(P(i)Pr(3))(2) (R = Ph, 3a or CF(3), 3b) and vinylpyridine-bridged (eta(6)-p-cymene)Cl(2)Ru(mu-NC(5)H(4)-4-CH=CH)RuCl(CO)(P(i)Pr(3))(2) (3c) have been prepared from their monoruthenium precursors and investigated with respect to the sequence of the individual redox steps and electron delocalization in their partially and fully oxidized states. Identification of the primary redox sites rests on the trends in redox potentials and the EPR, IR and Vis/NIR signatures of the oxidized radical cations and is correctly reproduced by quantum chemical investigations. Our results indicate that the trifluoropropenyl complex 3b has an inverse FMO level ordering (Ru1-bridge-Ru2 > terminal vinyl-Ru1 site) when compared to its styryl substituted counterpart 3a such that the primary oxidation site in these systems can be tuned by the choice of the terminal alkenyl ligand. It is further shown that the vinylbenzoate bridge is inferior to the vinylpyridine one with regard to charge and spin delocalization at the radical cation level. According to quantum chemical calculations, the doubly oxidized forms of these complexes have triplet diradical ground states and feature two interconnected oxidized vinyl ruthenium subunits.

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New doubly functionalized pentafulvenes are easily obtained by a regioselective one-pot reaction of sodium cyclopentadienide with imidoyl chlorides of different electrophilicity. Under thermodynamic control, benzimidoyl chlorides as electrophiles afford hydrogen-bridged 6-arylamino-2-benzimidoylfulvenes, whereas under kinetic control trifluoroacetimidoyl chlorides afford nonhydrogen-bridged 6-arylamino-3-imidoylfulvenes. Structurally, these show that the bis(imidoyl)(pentamethyl)ruthenocenes are novel redox-active metalloligands and reveal the strongly electron-withdrawing effect of the appended imine moieties. All new compounds were fully characterized by spectroscopic methods and by a total of 11 single-crystal X-ray analyses.

As we have recently shown, the doubly substituted [1,2‐O,O]H, [1,2‐O,N]H, [1,2‐N,N]H, and [1,3‐N,N]H pentafulvenes are convenient N/O‐functionalized cyclopentadienide (Cp) precursors. Deprotonation of the pentafulvenes by potassium hydride followed by reaction with [Cp*RhCl2]2 or [Cp*IrCl2]2 gave access to the first functionalized rhodocenium and iridocenium salts that contain two acyl and/or imidoyl substituents. These air‐stable compounds represent interesting bis(acyl/imidoyl) or mixed acyl/imidoyl metalloligand systems that combine an axially shielding, electrochemically active metallocene moiety with directly attached, conjugating oxygen and/or nitrogen donor sites. The structural properties of these novel metallocene metalloligands in solution and in the solid state were studied by NMR spectroscopy (1H, 13C, 103Rh) and by single‐crystal structure analysis. The electrochemical investigations on complexes 5a, 6b, and 7a showed the effect of the appended functional groups on the potential and on the reversibility of the rhodocenium/rhodocene reduction and provided evidence for the dimerization that followed the reduction. Further redox processes that were due to the heteroatom functions included the stepwise reduction of the 1,2‐diketo entity of 5a and the oxidation of the 1,2‐diimino moiety of 7a.