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

Abstract

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 -In acetonitrile, compound 1 undergoes a base-promoted hydroalkylation reaction with potassium tert-butoxide and diphenylvinylphosphine to produce [{η 5 . 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 tertbutoxide 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.

Pentamethylcyclopentadienyl rhodium(III) trifluorovinyl phosphine complexes and attempted intramolecular dehydrofluorinative coupling of pentamethylcyclopentadienyl and trifluorovinyl phosphine ligands

“…This coordination chemical shift (Dd P ) is somewhat larger than that usually observed (ca. 35 ppm) for [Cp*RhCl 2 (PR 3 )] systems where PR 3 contains non-fluorinated groups, for example, Dd P for [Cp*RhCl 2 {PPh 2 (CH CH 2 )}] is 37.8 ppm [26]. It is however noted that complexes of other fluoro-organo substituted phosphines also display large Dd P values, for example Dd P for [Cp*RhCl 2 {PPh 2 (C 6 F 5 )}] is 45.1 ppm [21].…”

Diphenylvinylphosphine (DPVP) complexes containing the (η5-MeC5H4)Ru(ii) moiety: synthesis, characterization and reactionsDedicated to the late Professor Noel McAuliffe.

“…We have recently described the syntheses of tethered phosphinopropylcyclopentadiene 18 and phosphinopropylarene 19 compounds by hydroalkylation of coordinated DPVP. In an effort to extend the scope of the hydroalkylation reaction to the MeC 5 H 4 ring system we reacted complex 14 with KOBu t in refluxing acetonitrile and with the radical initiator azobisisobutyronitrile (AIBN) in refluxing benzene.…”

New cyclopentadienylethylphosphane chelate complexes with unsymmetrical phosphane substitution

“…The complexes were characterized spectroscopically. According to HMQC measurements 1 The syntheses as well as reactions of cyclopentadienyl or indenyl rhodium chelate complexes bearing a phosphane tether have been reported by Poilblanc et al, 50 Tani et al, [51][52][53][54][55][56] Nelson et al, 57,58 Saunders et al, [38][39][40][59][60][61] Hidai et al, 62 Jones et al, 63 Green et al, 64 Salzer et al, [65][66][67][68] Cole-Hamilton et al, 69 Lalinde et al, 70 and Whitby et al 71 In most cases the phosphane tether bears phenyl substituents, however, there are also some in which alkyl, pentafluorophenyl or more complicated substituents are present. To our knowledge there are no examples with tert-butyl substituents, which, according to our experience with cobalt complexes, increase the stability of the complexes and improve their crystallization properties.…”