Synthesis, Structure and Reactivity of Homo- and Heterobimetallic Complexes of the General Formula [Cp*Ru(μ-Cl)3ML] [LM = (arene)Ru, Cp*Rh, Cp*Ir]

Synthesis, structures, and reactivity of isomers of [RuCp*(1,4-(Me2N)2C6H4)]2

[RuCp*(1,3,5-R₃C₆H₃)]₂ {Cp* = η⁵-pentamethylcyclopentadienyl, R = Me, Et} have previously been found to be moderately air stable, yet highly reducing, with estimated D⁺/0.5D₂ (where D₂ and D⁺ represent the dimer and the corresponding monomeric cation, respectively) redox potentials of ca. -2.0 V vs. FeCp₂^+/0. These properties have led to their use as n-dopants for organic semiconductors. Use of arenes substituted with π-electron donors is anticipated to lead to even more strongly reducing dimers. [RuCp*(1-(Me₂N)-3,5-Me₂C₆H₃)]⁺PF₆^- and [RuCp*(1,4-(Me₂N)₂C₆H₄)]⁺PF₆^- have been synthesized and electrochemically and crystallographically characterized; both exhibit D⁺/D potentials slightly more cathodic than [RuCp*(1,3,5-R₃C₆H₃)]⁺. Reduction of [RuCp*(1,4-(Me₂N)₂C₆H₄)]⁺PF₆^- using silica-supported sodium-potassium alloy leads to a mixture of isomers of [RuCp*(1,4-(Me₂N)₂C₆H₄)]₂, two of which have been crystallographically characterized. One of these isomers has a similar molecular structure to [RuCp*(1,3,5-Et₃C₆H₃)]₂; the central C-C bond is exo,exo, i.e., on the opposite face of both six-membered rings from the metals. A D⁺/0.5D₂ potential of -2.4 V is estimated for this exo,exo dimer, more reducing than that of [RuCp*(1,3,5-R₃C₆H₃)]₂ (-2.0 V). This isomer reacts much more rapidly with both air and electron acceptors than [RuCp*(1,3,5-R₃C₆H₃)]₂ due to a much more cathodic D₂˙⁺/D₂ potential. The other isomer to be crystallographically characterized, along with a third isomer, are both dimerized in an exo,endo fashion, representing the first examples of such dimers. Density functional theory calculations and reactivity studies indicate that the central bonds of these two isomers are weaker than those of the exo,exo isomer, or of [RuCp*(1,3,5-R₃C₆H₃)]₂, leading to estimated D⁺/0.5D₂ potentials of -2.5 and -2.6 V vs. FeCp₂^+/0. At the same time the D₂˙⁺/D₂ potentials for the exo,endo dimers are anodically shifted relative to those of [RuCp*(1,3,5-R₃C₆H₃)]₂, resulting in much greater air stability than for the exo,exo isomer.

Pentamethylcyclopentadienyl half-sandwich hydrazine complexes of ruthenium: preparation and reactivity

The preparation and selective oxidation of hydrazine complexes of ruthenium stabilised by a pentamethylcyclopentadienyl fragment are described. The formation of the sandwich complex [Ru(η⁵-C₅Me₅)(η⁶-C₆H₆)]BPh₄ through the oxidation of coordinate phenylhydrazine is also reported.

Synthesis, Reactivity, Spectroscopic Characterization, X-ray Structures, PGSE, and NOE NMR Studies of (η5-C5Me5)-Rhodium and -Iridium Derivatives Containing Bis(pyrazolyl)alkane Ligands

Rhodium(III) and iridium(III) complexes containing bis(pyrazolyl)methane ligands (pz = pyrazole, L' in general; specifically, L1 = H2C(pz)2, L2 = H2C(pzMe2)2, L3 = H2C(pz4Me)2, L4 = Me2C(pz)2), have been prepared in a study exploring the reactivity of these ligands toward [Cp*MCl(mu-Cl)]2 dimers (M = Rh, Ir; Cp* = pentamethylcyclopentadienyl). When the reaction was carried out in acetone solution, complexes of the type [Cp*M(L')Cl]Cl were obtained. However, when L1 and L2 ligands have been employed with excess [Cp*MCl(mu-Cl)]2, the formation of [Cp*M(L')Cl][Cp*MCl3] species has been observed. PGSE NMR measurements have been carried out for these complexes, in which the counterion is a cyclopentadienyl metal complex, in CD2Cl2 as a function of the concentration. The hydrodynamic radius (rH) and, consequently, the hydrodynamic volume (VH) of all the species have been determined from the measured translational self-diffusion coefficients (Dt), indicating the predominance of ion pairs in solution. NOE measurements and X-ray single-crystal studies suggest that the [Cp*MCl3]- approaches the cation, orienting the three Cl-legs of the "piano-stool" toward the CH2 moieties of the bis(pyrazolyl)methane ligands. The reaction of 1 equiv of [Cp*M(L')Cl]Cl or [Cp*M(L')Cl][Cp*MCl3] with 1 equiv of AgX (X = ClO4 or CF3SO3) in CH2Cl2 allows the generation of [Cp*M(L')Cl]X, whereas the reaction of 1 equiv of [Cp*M(L')Cl] with 2 equiv of AgX yields the dicationic complexes [Cp*M(L')(H2O)][X]2, where single water molecules are directly bonded to the metal atoms. The solid-state structures of a number of complexes were confirmed by X-ray crystallographic studies. The reaction of [Cp*Ir(L')(H2O)][X]2 with ammonium formate in water or acetone solution allows the generation of the hydride species [Cp*Ir(L')H][X].