Gas-phase functionalized carbon-carbon coupling reactions catalyzed by Ni (II) complexes.

Gas-phase C-C coupling reactions mediated by Ni (II) complexes were studied using a linear quadrupole ion trap mass spectrometer. Ternary nickel cationic carboxylate complexes, [(phen)Ni (OOCR1 )]+ (where phen = 1,10-phenanthroline), were formed by electrospray ionization. Upon collision-induced dissociation (CID), they extrude CO2 forming the organometallic cation [(phen)Ni(R1 )]+ , which undergoes gas-phase ion-molecule reactions (IMR) with acetate esters CH3 COOR2 to yield the acetate complex [(phen)Ni (OOCCH3 )]+ and a C-C coupling product R1 -R2 . These Ni(II)/phenanthroline-mediated coupling reactions can be performed with a variety of carbon substituents R1 and R2 (sp3 , sp2 , or aromatic), some of them functionalized. Reaction rates do not seem to be strongly dependent on the nature of the substituents, as sp3 -sp3 or sp2 -sp2 coupling reactions proceed rapidly. Experimental results are supported by density functional theory calculations, which provide insights into the energetics associated with the C-C bond coupling step.