Tripod ligands / Hindered rotation of vinylidene ligands / CpML 2 chelate ligands / Ruthenium / Carbenes / Carbene-type ligands / Cyclic voltammetry The tripodal ligand [CH 3 C(CH 2 C 5 H 4 )(CH 2 PPh 2 ) 2 ] -reacts C(OMe)Me (8), upon treatment with methanol. The vinylidene species 7 are deprotonated by NaOMe to produce with RuCl 2
the alkynyl compounds tripodCpL 2 RuCϵCR (9). Methylation of 9 with F 3 CSO 3 CH 3 results in the vinylidene derivatives substitution of the chlorine function with various nucleophiles LЈ to produce [tripodCpL 2 RuLЈ] + . The carbonyl LЈ = C=C(Me)R (R = tBu, 7d; R = Ph, 7e), having two organic substituents at the terminal carbon centre. For all vinylidene derivative (LЈ = CO) 2, isonitrile (LЈ = RNC) 3, nitrile compounds (LЈ = RCN) 4, and a tolane adduct (LЈ = η 2 -compounds with two different substituents at their terminal carbon atom, hindered rotation of the single-faced vinylidene PhCϵCPh) 5 are obtained when 1 is treated with the appropriate ligands in polar solvents. Halide acceptors (e.g.
π-ligand about its Ru-C bond is observed. Analysis by 31 P-NMR spectroscopic coalescence measurements as well as TlPF 6 ) are generally needed to promote these reactions. The cyanide derivative tripodCpL 2 RuCN (3a) is alkylated by line-shape analyses reveals activation enthalpies of around 40 kJmol -1 for this rotation, with small activation entropies of F 3 CSO 3 CH 3 to give the isonitrile derivative [tripodCpL 2 RuCNMe] + 3b. Terminal alkynes HCϵCR around ±10 Jmol -1 K -1 . Solid-state structures of nine compounds of the type [tripodCpL 2 RuLЈ] +n (n = 0, 1) produce vinylidene compounds [tripodCpL 2 RuLЈ] + , where LЈ = C=CHR (R = tBu, 7b; R = Ph, 7c), or allenylidene demonstrate the remarkable conformational rigidity of the tripodCpL 2 Ru template. They also show that the possible derivatives, LЈ = C=C=CPh 2 (6), depending on the nature of R (R = CPh 2 OH for synthesis of 6). Trimethylsilylacetylene strain imposed by linking the Cp ligand and the two donor groups L in one and the same chelate scaffolding does not gives the parent vinylidene species, LЈ = C=CH 2 (7a), which is transformed to the Fischer-type carbene compound, LЈ = appear to impose a serious steric strain on these templates.