Synthesis, molecular structure, and C-C coupling reactions of carbeneruthenium(II) complexes with C5H5Ru(==CRR′) and C5Me5Ru(=CRR′) as molecular units

The ethene derivatives [(eta(5)-C5R5)RuX(C2H4)(PPh3)], with R=H and Me, which have been prepared from the eta(3)-allylic compounds [(eta(5)-C5R5)-Ru(eta(3)-2-MeC3H4)(PPh3)] (1, 2) and acids HX under an ethene atmosphere, are excellent starting materials for the synthesis of a series of new halfsandwich-type ruthenium(II) complexes. The olefinic ligand is replaced not only by CO and pyridine, but also by internal and terminal alkynes to give (for X = Cl) alkyne, vinylidene, and allene compounds of the general composition [(eta(5)-C5R5)RuCl(L)(PPh3)] with L = C-2(CO2Me)(2), Me3SiC2CO2Et, C=CHCO2R, and C3H4. The allenylidene complex [(eta(5)-C5H5)RuCl(=C=C=CPh2)- (PPh3)] is directly accessible from I (R=H) in two steps with the propargylic alcohol HCdropCC(OH)Ph-2 as the precursor. The reactions of the ethene derivatives [(eta(5)-C5H5)RuX(C2H4)-(PPh3)] (X=Cl, CF3CO2) with diazo compounds RR'CN2 yield the corresponding carbene complexes [(eta(5)-C5R5)-RuX(=CRR')(PPh3)], while with ethyl diazoacetate (for X = Cl) the diethyl maleate compound [(eta(5)-C5H5)RuCl-{eta(2)-Z-C2H2(CO2Et)(2)}(PPh3)] is obtained. Halfsandwich-type ruthenium(II) complexes [(eta(5)-C5R5)RuCl(=CHR')-(PPh3)] with secondary carbenes as ligands, as well as cationic species [(eta(5)-C5H5)Ru(=CPh2)(L)(PPh3)]X with L=CO and CNtBu and X=AlCl4 and PF6, have also been prepared. The neutral compounds [(eta(1)-C5H5)-RuCl(=CRR')(PPh3)] react with phenyllithium, methyllithium, and the vinyl Grignard reagent CH2=CHMgBr by displacement of the chloride and subsequent C-C coupling to generate halfsandwich-type ruthenium(II) complexes with eta(3)-benzyl, eta(3)-allyl, and substituted olefins as ligands. Protolytic cleavage of the metal-allylic bond in [(eta(5)-C5H5)-Ru(eta(3)-CH2CHCR2)(PPh3)] with acetic acid affords the corresponding olefins R2C=CHCH3. The by-product of this process is the acetato derivative [(eta(5)-C5H5)Ru(kappa(2)-O2CCH3)(PPh3)], which can be reconverted to the carbene complexes [(eta(5)-C5H5)RuCl(=CR2)(PPh3)] in a one-pot reaction with R2CN2 and Et3NHCl.