Steric and electronic control of an ultrafast isomerization

Abstract

Synthetic control and the influence of steric and electronic factors on the ultrafast (picosecond) isomerization of penta-coordinate ruthenium dithietene complexes (Ru((CF3)2C2S2)(CO)(L)2, where L = a monodentate phosphine ligand) is reported.

Full Conformational Analyses of the Ultrafast Isomerization in Penta-coordinated Ru(S2C2(CF3)2)(CO)(PPh3)2: One Compound, Two Crystal Structures, Three CO Frequencies, 24 Stereoisomers, and 48 Transition States

“…Isomers , 6 ( III L U P P P P ), , 10 ( III L U P P P M ), and 12 ( III L U P M P M ) have an equatorial CO with the alternative ruthenium stereochemistry III . The calculated average C–C and C–S bond distances for all the isomers ( 1 – 12 ) of 1.377 and 1.735 Å, respectively (Figure ), are in good accord with the dithiolate (two electron-reduced) character of the ligand (C–C and C–S bond distances of 1.337 and 1.761 Å), which yields a Ru­(II) d assignment for all the isomers 1 – 12 , in excellent agreement with the experiment …”

“…In a previous study, three ν CO bands near 1980, 1960, and 1940 cm –1 were observed in solution . DFT calculations show that the scaled ν CO frequencies for isomers 1 (1957 cm –1 ), 4 (1956 cm –1 ), 9 (1955 cm –1 ), 11 (1954 cm –1 ), and 12 (1954 cm –1 ) are in good agreement with the experimentally observed ν CO band at 1960 cm –1 , as are the scaled ν CO frequencies for isomers 2 (1940 cm –1 ), 3 (1942 cm –1 ), 5 (1943 cm –1 ), and 8 (1939 cm –1 ) with the reported ν CO band near 1940 cm –1 .…”

“…Isomerization of Ru­(S 2 C 2 (CF 3 ) 2 )­(CO)­(PPh 3 ) 2 as previously described . Although the structure of 0-b in ChemDraw (above) seems to be TBP with axial PPh 3 groups, their DFT optimized structure for 0-b is closer to a distorted SP with an apical S, as indicated by the two greatest valence angles (S–Ru–C = 178.1° and P–Ru–P = 163.6°).…”

“…The more-stable orange isomer was found to have the CO ligand in the apical position while the violet isomer had the CO in the equatorial position . Recently, the stereodynamics of this ruthenium complex and related ones have been characterized by using both Fourier transform and two-dimensional (2D) infrared (IR) spectroscopy . In dichloromethane solutions, three individual carbonyl stretching frequencies (ν CO ) in the vicinity of 1960, 1940, and 1980 cm –1 were observed.…”

Chelating Phosphine–N-Heterocyclic Carbene Platinum Complexes via Catalytic Asymmetric Hydrophosphination and Their Cytotoxicity Toward MKN74 and MCF7 Cancer Cell Lines

“…This strong affinity originates from the soft–soft interaction between the C- and P-donors with platinum and helps in the formation of kinetically inert bonds, which inhibit ligand dissociation and slow the formation of highly electrophilic complexes that may otherwise induce undesirable effects as these complexes react indiscriminately with biological molecules . Substituents on both NHCs and phosphines can also be modified readily so as to fine-tune the extent of steric interaction with other ligands around the coordination sphere of platinum …”