Copper() and silver() chemistry of vinyltrifluoroborate supported by a bis(pyrazolyl)methane ligand

Although unsaturated organotrifluoroborates are common synthons in metal-organic chemistry, their transition metal complexes have received little attention. [CH 2 (3,5-(CH 3 ) 2 Pz) 2 ]Cu(CH 2 &z.dbd;CHBF 3 ), (SIPr)Cu(MeCN)(CH 2 &z.dbd;CHBF 3 ) and [CH 2 (3,5-(CH 3 ) 2 Pz) 2 ]Ag(CH 2 &z.dbd;CHBF 3 ) represent rare, isolable molecules featuring a vinyltrifluoroborate ligand on coinage metals. The X-ray crystal structures show the presence of three-coordinate metal sites in these complexes. The vinyltrifluoroborate group binds asymmetrically to the metal site in [CH 2 (3,5-(CH 3 ) 2 Pz) 2 ]M(CH 2 &z.dbd;CHBF 3 ) (M = Cu, Ag) with relatively closer M-C(H) 2 distances. The computed structures of [CH 2 (3,5-(CH 3 ) 2 Pz) 2 ]M(CH 2 &z.dbd;CHBF 3 ) and M(CH 2 &z.dbd;CHBF 3 ), however, have shorter M-C(H)BF 3 distances than M-C(H) 2 . These molecules feature various inter- or intra-molecular contacts involving fluorine of the BF 3 group, possibly affecting these M-C distances. The binding energies of [CH 2 &z.dbd;CHBF 3 ] − to Cu + , Ag + and Au + have been calculated at the wB97XD/def2-TZVP level of theory, in the presence and absence of the supporting ligand CH 2 (3,5-(CH 3 ) 2 Pz) 2 . The calculation shows that Au + has the strongest binding to the [CH 2 &z.dbd;CHBF 3 ] − ligand, followed by Cu + and Ag + , irrespective of the presence of the supporting ligand. However, in all three metals, the supporting ligand weakens the binding of olefin to the metal. The same trends were also found from the analysis of the σ-donation and π-backbonding interactions between the metal fragment and the π and π* orbitals of [CH 2 &z.dbd;CHBF 3 ] − . Copper and silver complexes of vinyltrifluoroborate have been isolated and characterized using bis(pyrazolyl)methane, acetonitrile and N-heterocyclic carbene supporting ligands. Computational analysis of these systems includes gold as well.