Base-Promoted Hydroalkylation Reactions of the η5-C5Me5Ligand Coordinated to Rhodium: Probing a Mechanism. New Compounds with the η5-C5Me4CF3Ligand

Dichloro(pentamethylcyclopentadienyl)rhodium(III) dimer, [{(η 5 -C 5 Me 5 )RhCl 2 } 2 ] ( 1 ), reacts with diphenylvinylphosphine to produce [(η 5 -C 5 Me 5 )Rh{CH 2 CHP(C 6 H 5 ) 2 }Cl 2 ] ( 2 ) and [(η 5 -C 5 Me 5 )Rh{CH 2 CHP(C 6 H 5 ) 2 } 2 Cl]X ( 3, X = Cl - ( a ), PF 6 - ( b )). In acetonitrile, compound 1 undergoes a base-promoted hydroalkylation reaction with potassium tert -butoxide and diphenylvinylphosphine to produce [{η 5 -C 5 Me 3 -1,3-[CH 2 CH 2 CH 2 P(C 6 H 5 ) 2 ] 2 }RhCl]X ( 4, X = Cl - ( a ), PF 6 - ( b ), BPh 4 - ( c )) and [{η 5 −C 5 Me 3 -1,2-[CH 2 CH 2 CH 2 P(C 6 H 5 ) 2 ] 2 }RhCl]X ( 5, X = Cl - ( a ), PF 6 - ( b ), BPh 4 - ( c )). Compounds 4a − c and 5a − c contain chelating 1,3- and 1,2- bis((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 [(η 5 -C 5 Me 5 )Rh{CH 2 CHCH 2 P(C 6 H 5 ) 2 }Cl 2 ] ( 6 ) and [(η 5 -C 5 Me 5 )Rh{CH 2 CHCH 2 P(C 6 H 5 ) 2 } 2 Cl]X ( 7, X = Cl - ( a ), PF 6 - ( 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, [{(η 5 -C 5 Me 4 CF 3 )RhCl 2 } 2 ] ( 8 ), reacts with diphenylvinylphosphine to produce [(η 5 -C 5 Me 4 CF 3 )Rh{CH 2 CHP(C 6 H 5 ) 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 CF 3 group into a carboethoxy functionality producing [{η 5 -C 5 (CO 2 Et)Me 3 -2-[CH 2 CH 2 CH 2 P(C 6 H 5 ) 2 ]}RhCl 2 ] ( 10 ). Complexes 3b, 7b, and 10 were characterized by single-crystal X-ray crystallography.