Copper(i) and silver(i) 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. [CH2(3,5-(CH3)(2)Pz)(2)]Cu(CH2 = CHBF3), (SIPr)Cu(MeCN)(CH2 = CHBF3) and [CH2(3,5-(CH3)(2)Pz)(2)]Ag(CH2 = CHBF3) 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 [CH2(3,5-(CH3)(2)Pz)(2)]M(CH2 = CHBF3) (M = Cu, Ag) with relatively closer M-C(H)(2) distances. The computed structures of [CH2(3,5-(CH3)(2)Pz)(2)]M(CH2 = CHBF3) and M(CH2 = CHBF3), however, have shorter M-C(H)BF3 distances than M-C(H)(2). These molecules feature various inter- or intra-molecular contacts involving fluorine of the BF3 group, possibly affecting these M-C distances. The binding energies of [CH2 = CHBF3](-) 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 CH2(3,5-(CH3)(2)Pz)(2). The calculation shows that Au+ has the strongest binding to the [CH2 = CHBF3](-) 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 sigma-donation and pi-backbonding interactions between the metal fragment and the pi and pi* orbitals of [CH2 = CHBF3](-).

Automated summary

This study synthesized and studied the structures and interactions of vinyltrifluoroborate ligands in metal complexes, revealing asymmetric binding between metal and carbon, as well as the influence of supporting ligands on the binding between ligands and metals.