Optical Resolution of π-Thiophene Complexes (C₆Me₆)Ru(2-RC₄H₃S)²⁺and Related Studies

Abstract

Diastereomeric iminium thiolato complexes were prepared by the addition of S-(−)-α-methylbenzylamine to the π-thiophene complexes [(C6Me6)Ru(2-RC4H3S)]2+, where R = Me (1 2+), CH2OH (3 2+), and 2-C4H3S (6 2+). After chromatographic separation, the diastereomers were treated with HOTf to generate optically pure π-thiophene complexes. The absolute configuration of [(C6Me6)RuSCMeC2H2(CHNHCHMePh)]OTf, (−)-2(OTf), was determined by a single-crystal X-ray diffraction; the monohydrate crystallized in the acentric space group P212121. Acetone solutions of (−)-1 2+ and (−)-3 2+ are optically stable for days in solution (25 °C), while the bithiophene complex was unstable with respect to dissociation of the bithiophene ligand. Optical resolution of [(cymene)Os(2-MeC4H3S)](OTf)2 was not possible due to the instability of the iminium thiolato. Base hydrolysis of (−)-1 2+ gave the formyl thiolato complex (−)-9 kin, which isomerized to (+)-9 therm with inversion of configuration at Ru, as indicated by circular dichroism measurements. The methyl ester of the amino acid (l)-phenylalanine was shown to add to (C6Me6)Ru(C4H4S)2+ to give a 2:1 mixture of diastereomeric iminium thiolato complexes.

Thiophenes in Organotransition Metal Chemistry: Patterns of Reactivity

“…There is no evidence in these amine reactions for a thioimine product analogous to 48 . The reaction of (η 6 -C 6 Me 6 )Ru(η 5 -2-MeT) 2+ with the chiral primary amine (Ph)(Me)(H)CNH 2 gives two diastereomers of the syn isomer of the iminium-thiolate complex analogous to 50 . Partial separation of these diastereomers and treatment with CF 3 SO 3 H converts them to partially resolved (η 6 -C 6 Me 6 )Ru(η 5 -2-MeT) 2+ .…”

Synthesis, characterization, electropolymerization, and possible utilities of a new ruthenium–thiophene complex

“…On the basis of previous results regarding the obtaining of ruthenium complexes with coordinated thiophenes, the synthesis of the new complex 1 was tested by the reaction of [RuCl 2 ( p ‐cymene)] 2 in CH 2 Cl 2 with AgOSO 2 CF 3 to generate in situ [Ru( p ‐cymene)](OSO 2 CF 3 ) 2 ; this was followed by the addition of thiophene (Scheme ). Because certain triflate salts are usually hygroscopic, one often needs to exchange the counterion of the hexafluorophosphate triflate.…”

“…[18][19][20][21][22][23] By the 1980s, metal-thiophene interaction had aroused great interest, 24,25 and thiophenes showed four bonding modes to metals, 26,27 g 5 being the most common coordination mode. In this respect, the studies of Rauchfuss and coworkers [27][28][29][30][31][32] on [Ru(g 5 -thiophene)(g 6 -arene)] structures were important. These compounds proved to be susceptible to base-catalyzed hydrolysis and aminolysis, and this led to CAS bond breakage.…”