Ligand and metal-centered chemistry of binuclear nickel complexes

Jin Kang Gong, Purdue University

Abstract

The reaction of Ni(COD)$\sb2$, dppm and LX$\sb2$ (L = CO, CNMe, SO, CNC$\sb6$H$\sb5$; X = CO, CNMe, Cl, Br) leads to a convenient but effective route to synthesize a series of binuclear diphosphine nickel complexes with different bridging ligands. The binuclear nickel complexes prepared are in three different geometries, "cradle", "A-frame", and "mixed" geometries. "Cradle" is d$\sp{20}$ dimer preferred geometry while "A-frame" and "mixed geometry" are adopted by d$\sp{18}$ species. Complex (3) which is a "mixed geometry" has an interesting spin equilibrium in solution and is paramagnetic in the solid form. Spectroscopic data such as VT $\sp{31}$P$\{\sp1$H$\}$ NMR, EPR and magnetic susceptibility are presented. Ni$\sb2$($\mu$-CO)(CO)$\sb2$(dppm)$\sb2$ (1) can undergo (i) ligand centered reaction chemistry with strong Lewis acids to form adducts, Ni$\sb2$($\mu$-CO(AlR$\sb3$))(CO)$\sb2$(dppm)$\sb2$ (7, 8), (ii) metal centered reaction with H$\sp+$ to form a cationic dimer with a bridging hydride, (Ni$\sb2$($\mu$-H)(CO)$\sb2$(dppm)$\sb2$) $\sp+$ (9, 10), (iii) substitution reaction with Me$\sb3$P = CH$\sb2$ to form Ni$\sb2$($\mu$-CO)(PMe$\sb3$)$\sb2$(dppm)$\sb2$ (11) and (iv) transmetallation with (Pd(CNMe)$\sb4$) (PF$\sb6$) $\sb2$ to form mixed-metal complex (NiPd(CNMe)$\sb3$(dppm)$\sb2$) (PF$\sb6$) $\sb2$ (12). Complex (2), Ni$\sb2$($\mu$-CNMe)(CNMe$\sb2$(dppm)$\sb2$ reacts with HgCl$\sb2$ to give an extraordinary tetrametallation product ( (Ni$\sb2$($\mu$-CNMe)(CNMe)$\sb4$(dppm)$\sb2$) $\sb2$Hg) (NiCl$\sb4$) (13). The center mercury (II) ion coordinated only by four nickel atoms. The bonding may be viewed similarly to that of a linear bis($\pi$-complex). Complex (15), (Ni(CH$\sb2$Ph$\sb2$PCH$\sb2$PPh$\sb2$)$\sb2$) (Br$\sb2$) is the reaction product of Ni(COD)$\sb2$, dppm and CH$\sb2$Br$\sb2$. The double insertion of carbene into nickel phosphorus bonds results in the formation of nickel ylide. Complex (15) can undergo deprotonation with NaNH$\sb2$ to form Ni(CH$\sb2$Ph$\sb2$PCHPPh$\sb2$)$\sb2$ (16), which reform (15) by reacting with 2 eq. HBr.

Degree

Ph.D.

Advisors

Kubiak, Purdue University.

Subject Area

Chemistry

COinS