326868-98-8Relevant academic research and scientific papers
Spectroscopic and computational studies of a Ni+-CO model complex: Implications for the acetyl-CoA synthase catalytic mechanism
Craft, Jennifer L.,Mandimutsira, Beaven S.,Fujita, Koyu,Riordan, Charles G.,Brunold, Thomas C.
, p. 859 - 867 (2008/10/08)
The four-coordinate Ni+ complex [PhTtBu]NilCO, where PhTtBu = phenyltris((tert-buthylthio)methyl) borate (a tridentate thioether donor ligand), serves as a possible model for key Ni-CO reaction intermediates in the acetyl-CoA synthase (ACS) catalytic cycle. Resonance Raman, electronic absorption, magnetic circular dichroism (MCD), variable-temperature variable-field MCD, and electron paramagnetic resonance spectroscopies were utilized in conjunction with density functional theory and semiemperical INDO/S-Cl calculations to investigate the ground and excited states of [PhTtBu]NilCO. These studies reveal extensive Ni+ → CO π-back-bonding interactions, as evidenced by a low C-O stretching frequency (1995 cm-1), a calculated C-O stretching force constant of 15.5 mdyn/A (as compared to kCO(free CO) = 18.7 mdyn/A), and strong Ni+ → CO charge-transfer absorption intensities. Calculations reveal that this high degree of π-back-bonding is due to the fact that the Ni+ 3d orbitals are in close energetic proximity to the CO π* acceptor orbitals. In the ACS paramagnetic catalytic cycle , the high degree of π-back-bonding in the putative Ni+-CO intermediate (the NiFeC species) is not expected to preclude methyl transfer from CH3-CoFeSP.
