Addition of carbon nucleophiles to the allenylidene ligand of [Ru(η5-C5H5)(C=C=CPh2)(CO)(PiPr3)]BF4:: Synthesis of new organic ligands by formal C-C coupling between mutually inert fragments

EHT-MO Calculations on the model cation [Ru(eta(5)-C5H5)(C=C=CH2)(CO)(PH3)](+) (1a) suggest that 23% and 31% of the LUMO and 26% of the HOMO of [Ru(eta(5)-C5H5)(C=C=CPh2)(CO)((PPr3)-Pr-i)]BF4 (1) are located on C-alpha, C-gamma, and C-beta of the allenylidene ligand, respectively, On the basis of these results, we report a new synthetic strategy for the preparation of compounds resulting from the formal addition of phenylacetylene, acetone, and methane to the allenylidene of 1. Treatment of 1 with LiC=CPh leads to the allenyl complex Ru(eta(5)-C5H5){C(C=CPh)=C=CPh2}(CO)((PPr3)-Pr-i) (2) and the alkynyl derivative Ru(eta(5)-C5H5){C=C-C(Ph)(2)C=Cph}(Co)((PPr3)-Pr-i) (3), The reaction of 2 with HBF4 affords the substituted carbene compound [Ru(eta(5)-C5H5){C(C=CPh)CH=CPh2}(CO)((PPr3)-Pr-i)]BF4 (4), which is a result from the formal addition of phenylacetylene to the C-alpha-C-beta double bond of the allenylidene of 1, The molecular structure of 4 has been determined by X-ray crystallography. The geometry around the ruthenium center is close to octahedral with the cyclopentadienyl ligand occupying three sites of a face. The Ru=C bond length is 2.004(5) Angstrom. In the presence of KOH, complex 1 reacts with acetone to give Ru(eta(5)-C5H5){C=C-C(Ph)(2)CH2C(O)CH3}(CO)((PPr3)-Pr-i). (5). The reaction of 5 with HBF4 leads to the unsaturated cyclic carbene complex [Ru(eta(5)-C5H5){CCH2C(Ph)(2)CH=C(CH3)O}(CO)((PPr3)-Pr-i)]BF4 (6). Complex 5 also reacts with 2 equiv of CF3-CO2D to give [Ru(eta(5)-C5H5){CCD2C(Ph)(2)CH=C(CH3)O}(CO)((PPr3)-Pr-i)](CF3CO2) (6-d(2)) and CF3CO2H, and the reaction of Ru(eta(5)-C5H5){C=C-C(Ph)(2)CD2C(O)CD3}(CO)((PPr3)-Pr-i) (5-d(5)) with 2 equiv of HBF4 affords [Ru(eta(5)-C5H5){CCH2C(Ph)(2)CD=C(CD3)O}(CO)((PPr3)-Pr-i)]BF4 (6-d(4)) and DBF4. On the basis of these isotope labeling experiments, the mechanism for the addition of acetone to the allenylidene Ligand of 1 is discussed, Complex 1 also reacts with Na(acac) and CH3Li. The reaction with Na(acac) leads to Ru(eta(5)-C5H5){C=C-C(Ph)(2)CH[C(O)CH3](2)}(CO)((PPr3)-Pr-i) (7), while the treatment of 1 with CH3Li gives a mixture of Ru(eta(5)-C5H5){C(CH3)=C=CPh2}(CO)((PPr3)-Pr-i) (8) and Ru(eta(5)-C5H5){C=C-C(Ph)(2)CH3}(CO)((PPr3)-Pr-i) (9). Complex 9 reacts with HBF4 to afford [Ru(eta(5)-C5H5){C=CHC(Ph)(2)CH3}(CO)((PPr3)-Pr-i)]BF4 (10), which is a result of the formal addition of a C-H bond of methane to the C-beta-C-gamma double bond of the allenylidene of 1.