A comparative study of the synthesis, stereochemical characterization and reactivity of new chiral ruthenium(II) complexes with (aminoferrocenyl)phosphine ligands. X-Ray crystal structure of RuClH(cod)(PTFA) and Ru(η3-C8H13)Cl(PPFA) [PTFA = 1-diphenylphosphino-2,3-endo-(α-dimethylamino)tetramethyleneferrocene and PPFA = 2-(1-dimethylaminoethyl)-1-diphenylphosphinoferrocene]†

Abstract

The (aminoferrocenyl)phosphine ligands 2-(1-dimethylaminoethyl)-1-diphenylphosphinoferrocene (PPFA), 1-diphenylphosphino-2,1'-(1-dimethylaminopropanediyl)ferrocene (PAPF), and 1-diphenylphosphino-2,3-endo-(α-dimethylamino)tetramethyleneferrocene (PTFA) were used to synthesise new ruthenium(II) complexes. Reaction of RuClH(bpzm)(cod) [bpzm = bis(pyrazol-1-yl)methane, cod = 1,5-cyclooctadiene] with PTFA, PAPF or PPFA gave rise to the new hydride complexes: RuClH(cod)(NP), NP = PTFA, 1; PAPF, 2; PPFA, 3. Complex 2 exists as two isomers with mutually trans hydride and chloride ligands that are oriented differently with respect to the aminophosphine ligand. It was not possible to isolate 3 in its pure form because it evolves in solution to Ru(η³-C₈H₁₃)Cl(PPFA) 4 as the final product. Reaction of RuCl₂(PPh₃)₃ with the (aminoferrocenyl)phosphine ligands gave RuCl₂(PPh₃)(PTFA) 5 and the known complex RuCl₂(PPh₃)(PPFA). The reaction with PAPF led to a complex mixture. Complex 5 did not react with H₂ (5 atm) or superhydride but reaction with KBH₄ in EtOH gave rise to one or two isomers of the hydride RuH(η²-BH₄)(PPh₃)(PTFA) 6. The fluxional behaviour of the BH₄ group was studied and, for the major isomer, two different energy barriers were found for the hydride scrambling process. A two-step mechanism is proposed. The molecular structures of 1 and 4 were determined by X-ray diffraction.