Base-promoted hydroalkylation reactions of the eta(5)-C(5)Me(5) ligand coordinated to rhodium: Probing a mechanism. New compounds with the eta(5)-C(5)Me(4)CF(3) ligand

Dichloro(pentamethylcyclopentadienyl)rhodium(III) dimer, [{(eta(5)-C(5)Me(5))RhCl2}(2)] (1), reacts with diphenylvinylphosphine to produce [(eta(5)-C(5)Me(5))Rh{CH2CHP(C6H5)(2)}Cl-2] (2) and [(eta(5)-C(5)Me(5))Rh{CH2CHP(C6H5)(2)}Cl-2]X (3, X = Cl- (a), PF6- (b)). In acetonitrile, compound 1 undergoes a base-promoted hydroalkylation reaction with potassium tert-butoxide and diphenylvinylphosphine to produce [{eta(5)-C(5)Me(3)-1,3-[CH2CH2CH2P(C6H5)(2)](2)}RhCl]X (4, X = Cl- (a), PF6- (b), BPh(4)(-) (c)) and [{eta(5)-C(5)Me(3)-1,2-[CH2CH2CH2P(C6H5)(2)](2)}RhCl]X (5, X = Cl- (a), PF6- (b), BPh(4)(-) (c)). Compounds 4a-c and 5a-c contain chelating 1,3- and 1,2- his((diphenylphosphino)propyl)trimethylcyclopentadienide ligands. Compounds 2 and 3 are precursors on the pathway toward formation of 4a and 5a. Compound 1 reacts with allyldiphenylphosphine to produce [(eta(5)-C(5)Me(5))Rh{CH2CHCH2P(C6H5)(2)}Cl-2] (6) and [(eta(5)-C(5)Me(5))Rh{CH2CHCH2P(C6H5)(2)}Cl-2]X (7, X = Cl- (a), PF6- (b)). In acetonitrile, compound 1 reacts with allyldiphenylphosphine in the presence of potassium tert-butoxide to produce a complex mixture of products that may contain hydroalkylation adducts. Dichloro{(trifluoromethyl)tetramethylcyclopentadienyl}rhodium (III) dimer, [{(eta(5)-C(6)Me(4)CF(3))RhCl2}(2)] (8), reacts with diphenylvinylphosphine to produce [(eta(5)-C(6)Me(4)CF(3))Rh{CH2CHP(C6H5)(2)}Cl-2] (9), however the bis(phosphine) analog cannot be isolated or characterized. In refluxing ethanol, compound 8 reacts with diphenylvinylphosphine in the absence of potassium tert-butoxide to undergo hydroalkylation accompanied by conversion of the CF3 group into a carboethoxy functionality producing [{eta(5)-C-5(CO(2)Et)Me(3)-2-[CH2CH2CH2P(C6H5)(2)]}RhCl2] (10). Complexes 3b, 7b, and 10 were characterized by single-crystal X-ray crystallography.