Yuji Matsushima

Synthesis of ruthenium complexes with planar-chiral cyclopentadienyl-pyridine or -phosphine bidentate ligands

Novel ruthenium complexes possessing planar-chiral cyclopentadienyl-pyridine or -phosphine bidentate ligands have been synthesized from (trisubstituted cyclopentadienyl)(benzene)ruthenium complexes. Co-ordination of the pyridyl group linked to a cyclopentadienyl ring through an ester bond is fairly weak, so that the pyridine dissociates from the central ruthenium atom in acetonitrile. In contrast, the phosphine ligand tightly co-ordinates to the ruthenium even in acetonitrile. Enantiomerically pure samples of planar-chiral cyclopentadienylphosphine complexes have been prepared by use of optically pure ruthenium complexes as a starting material. The molecular structure of a neutral ruthenium dithiocarbamate complex with the cyclopentadienylphosphine bidentate ligand has been determined by X-ray crystallography.

Stereoselective ligand-exchange reaction of planar-chiral cyclopentadienyl–ruthenium complexes: thermodynamic control of configuration at a stereogenic metal center

The reaction of planar-chiral cyclopentadienyl-ruthenium complexes with Bu4NI resulted in the formation of iodo complexes with high diastereoselectivity (up to >99%de). The stereochemistry of the ruthenium center in the starting material did not influence the diastereoselectivity of the products. Epimerization of a diastereomerically pure sample gave a mixture of two diastereomers in the same ratio as with the ligand-exchange reaction, suggesting that the selectivity is determined by the difference in thermodynamic stability between the diastereomeric pair of iodo complexes. The ratio of the products depends on the nature of the substituent on the cyclopentadienyl ring and P ligands on the ruthenium atom. A combination of small substituents on the cyclopentadienyl group and small P ligands with strong electron-donating ability favored the formation of 2-I. The bulkiness of the substituents on the cyclopentadienyl group or of the P ligands, and low electron-donating ability of the P ligands increased the ratio of 2-II complexes to 2-I isomer.

Highly selective induction of metal-centered chirality in the ligand exchange reaction of planar-chiral cyclopentadienyl–ruthenium complex bearing an anchor phosphine ligand

Treatment of planar-chiral cyclopentadienyl–phosphine ruthenium complexes with phosphine and phosphite induces metal-centered chirality with a high stereoselectivity (≳99 % de).

Synthesis and characterization of planar-chiral cyclopentadienylruthenium–vinylidene complexes

Abstract Enantiopure planar-chiral cyclopentadienylruthenium–vinylidene complexes, ( S Cl )- and ( R C1 )-[(η 5 -C 5 H 2 -1-COR 1 -2-Me-4-R 2 )Ru(PPh 3 ) 2 (CCHR 3 )][PF 6 ] ( 4 : R 1 =O-( l )- and O-( d )-menthyl; 8 : R 1 =NH t Bu. R 2 =Me, Ph; R 3 =Ph, H), were synthesized starting from [(η 5 -C 5 H 2 -1-COR 1 -2-Me-4-R 2 )Ru(η 6 -C 6 H 6 )][PF 6 ], and characterized by optical and spectra methods including 1 H, 13 C, and 31 P-NMR, and CD spectra. The reaction rate of [(η 5 -C 5 H 2 -1-CO 2 Et-2,4-Me 2 )Ru(PPh 3 ) 2 (MeCN) 3 ][PF 6 ] with phenylacetylenes leading to vinylidene complexes increases in the order: HCCC 6 H 4 NO 2 6 H 5 6 H 4 OMe. Analysis by cyclic voltammetry showed that trisubstituted cyclopentadienyl ligands C 5 H 2 -1-CO 2 Et-2-Me-4-R 2 (R 2 =Me, Ph, t Bu, Naph etc.) act as a weak electron-donor compared with non-substituted cyclopentadienyl one in ruthenium–phenylacetylide complexes.

Multiple ligand transfer to planar-chiral cyclopentadienylruthenium complexes inducing metal-centered chirality

Multiple ligand transfer reaction between planar-chiral cyclopentadienylruthenium complexes [Cp′Ru(AN)3][PF6] [(Cp′ = 1-(CO2Et)-2-Me-4-RC5H2, R = Me, Ph, But, AN = acetonitrile] and iron complexes CpFe(CO)(L)X (L = PMe3, PPh3; X = I, Br) results in formation of metal-centered chiral ruthenium complexes Cp′Ru(CO)(L)X with a diastereoselectivity (de) up to 68%.