A series of complexes with π-conjugated carbon chains terminated by bipyridyl moieties has been prepared. These allenylidene complexes were derived from 9-hydroxy-9-ethynyl-4,5-diazafluorene, the preparation of which is reported; the new allenylidene complexes are highly colored with the cumulated carbon chain terminating in a bipyridyl unit providing a site for further coordination. The synthesis, characterization, and X-ray structure determination of trans-[MCl(P∩P) 2 dCdCd(4,5-diazafluoren-9-yl)]PF 6 (M ) Ru, P∩P ) bis(diphenylphosphino)methane (dppm), 1,2-bis(diphenylphosphino)ethane (dppe), 1,2-bis(dimethylphosphino)ethane (dmpe); M ) Os, P∩P ) dppm) are described. The effect of the variation in metal and ligand on electronic and electrochemical characteristics of these complexes has been investigated by using UV-vis, solution electrochemistry, and a combination of these techniques in spectroelectrochemical experiments. DFT calculations have been performed on trans-[RuCl(P∩P) 2 dCdCd(4,5-diazafluoren-9-yl)] q (P∩P ) dppm, bis(dimethylphosphino)methane (dmpm); q ) -1, 0, +1, +2) and subsequently solvent-corrected calculations with use of COSMO were also undertaken to examine the nature of electronic transitions in various oxidation states.

Reactions of the transition metal halide complexes [MXL2(Cp)] (M = Fe, X = I, L2 = dppe; M = Ru, X = Cl, L = PPh3; M = Os, X = Br, L = PPh3; Cp = η-C5H5) with the alkynol HCCCH(OH)(Fc) (1) (Fc = ferrocenyl) in the presence of TlBF4 gave the monosubstituted allenylidene complexes [M(CCCHFc)L2(Cp)][BF4] (2a: M = Ru, L = PPh3; 3: M = Fe, L2 = dppe; 4: M = Os, L = PPh3). Similarly, the reaction of 1 with [RuCl(PPh3)2(Cp)] and NH4PF6 in methanol gave [Ru(CCCHFc)(PPh3)2(Cp)][PF6] (2b). These highly colored compounds were characterized by spectroscopic and electrochemical techniques and in the case of 2b by a single-crystal X-ray structure determination. Cyclic voltammetry in MeCN in the presence of [nBu4N][ClO4] at 100 mV·s−1 shows a reversible ferrocenyl-based one-electron oxidation, in addition to irreversible oxidation and reduction processes. The NMR spectra of 2b show complex behavior at low temperature, attributed to temperature-dependent chemical shifts and correlated motions of the allenylidene ligand and the ferrocenyl substituent.

No abstract

The open, planar Ru 4 C 2 compounds [Ru 4 (µ 4 -CC)(η-C 5 H 4 R) 2 (µ-CO) 2 (CO) 8 ] (R ) H, Me) react with the activated electron-deficient alkyne dimethyl acetylenedicarboxylate, (CO 2 Me) 2 C 2 (DMAD), to afford a number of products. One of these was found to contain a metallacyclopentadiene ligand ligated at the 1-and 2-positions by Ru(η-C 5 H 4 R) groups, and another was a new Ru 2 compound resulting from the coupling of DMAD, C 2 , and CO to produce a five-carbon chain.a C(100) is the centroid of the Cp rings; primed atoms are related by the intramolecular 2-axis.