Monomers, dimers, and trimers: Reactivity studies of nickel with small molecules

Kevin Stanley Ratliff, Purdue University

Abstract

The reaction of nickelocene with the isocyanides CNR, (R = methyl, butyl, t-butyl, phenyl, benzyl, xylyl), results in the nickel zero monomers Ni(CNR)$\sb4$. The nickel monomers react with carbonyl sulfide and carbon dioxide. The nature of the reactions is bond cleavage where one of the double bonds of the heteroallene is cleaved. A catalyst in the form of alkalai metal ions is necessary to achieve a reaction with carbon dioxide. The bridging nitrosyl complex (Ni$\sb2$($\mu$-NO)(CNMe)$\sb2$(dppm)$\sb2$) $\sp+$ has been prepared. The stable dinickel complexes Ni$\sb2$($\mu$-L)(CNMe)(dppm)$\sb2$, (L = CNMe, CNMe(H)$\sp+$, NO$\sp+$), are used to explore how bridging small molecules effect the metal atoms themselves. The nature of the HOMO and LUMO of these complexes changes drastically when the bridging ligand is changed. The degree of metal-metal bonding is also affected by the bridging ligand with the most Lewis acidic ligand forcing the strongest bond. Transmetallation of Ni$\sb2$(CNMe)$\sb3$(dppm)$\sb2$ with Pt(dppm)Cl$\sb2$ forms the strongly bonded Ni-Pt heterobimetallic complex (NiPt($\mu$-CNMe)(CNMe)(dppm)$\sb2$Cl) (Cl). The complex is a rare example of a heterodinuclear nickel-platinum complex. The complex undergoes a facile conversion to (NiPt(CNMe)$\sb3$(dppm)$\sb2$) (PF$\sb6$) $\sb2$ which has a much weaker Ni-Pt interaction. Preparation of this complex completes the series of the previously prepared complexes ((Ni-M)(CNMe)$\sb3$(dppm)$\sb2$) (PF$\sb6$) $\sb2$, (M = Ni, Pd). The trinuclear complex (Ni$\sb3$($\mu\sb3$-CNMe)($\mu\sb3$-I)(CNMe)$\sb2$(dppm)$\sb2$) (I) is prepared from the metallation of Ni$\sb2$(CNMe)$\sb3$(dppm)$\sb2$ with NiI$\sb2$. The complex contains an unprecedented symmetric linear $\mu\sb3$-$\eta\sp1$ capping isocyanide. The complex undergoes reactions with numerous small molecules. The redox chemistry of the trinickel core is very versatile. The similar complex (Ni$\sb3$($\mu\sb3$-CNMe($\mu\sb3$-I)(dppm)$\sb3$) (I) also contains a symmetric linear $\mu\sp3$-$\eta\sp1$ capping isocyanide. The complex undergoes a reversible one electron reduction to the neutral cluster. The complex is an electrocatalyst in the reduction of carbon dioxide to carbon monoxide and carbonate.

Degree

Ph.D.

Advisors

Kubiak, Purdue University.

Subject Area

Chemistry

COinS