A K Fazlur Rahman

Title : Nucleophilic Addition Reactions to d9 Metal (Co, Rh, Ir) Stabilized Carbocations

Abstract:

Nucleophilic addition reactions to metal stabilized carbo-cations, such as, [(η5 -C5R5) (η2vinyl η3-cyclopentenyl)] +salts with various nucleophiles such as LiAlH4, MeLi, KCN, NaOMe, exclusively yields functionalized η2-vinyl η2-cyclopentene complexes, as the addition products in 70-80% yield.  These neutral nucleophilic addition products complexes are readily soluble in cyclohexane and ether. Nucleophilic addition reactions to cationic [(η5 -C5R5) (η2-vinyl η3-cyclopentenyl)] + are regio-selective and preferentially attacked the π-allyl unit not the π-vinyl unit of the carbocation fragment, seemingly followed the Davis, Green, Mingos rule, with a decrease by one unit of the hapticity of the ligand for example: η3 -allyl to η2 -olefin. The position of hydride attack was identified by reaction with LiBD4 and the Nu- appears exclusively to add in C4 carbon of the allylic unit with an exo attack with respect to the metal center suggesting a charge control pathway. DFT calculations were used to compare the nucleophilic reactivity of the coordinated vinyl cyclopentenyl cations coordinated to d9 metals going from 3d Co, 4d Rh and 5d Ir. All systems prefer exo attack at C4 position of the allylic cation, where the nucleophile prefers an attack to the allylic carbocation, from the opposite site of the metal fragment to minimize steric hindrance.

Biography:

Dr. Fazlur Rahman did his MA in Chemistry from Brandeis university and a Ph.D. from the Australian National University in Canberra, Australia. He did his post-doctoral works at the university of Tasmania, Australia, at the Ames National Laboratory, USA and at the University of Oklahoma, USA.  Dr. Rahman is the recipient of Southwest ACS regional Award in 2009, and the Oklahoma Chemist award in 2015. Dr. Rahman held visiting faculty positions at Texas A&M, University of Rochester, Cal-Tech, UC Berkeley, Free University of Berlin and Fried Schiller University, Rutgers University and at the Columbia University in NYC. He currently holds an endowed professorship and Sharkey’s Energy Foundation Chair in Chemistry at the Oklahoma School of Science and Mathematics. Rahman also worked as an affiliated Professor of Chemistry and Chemical Engineering at the with the University of Oklahoma where he teaches Organic chemistry as an adjunct Professor.