Alkali metal ion catalyzed carbon dioxide chemistry of low valent transition metal isocyanide complexes
Abstract
The reaction of the tetrakis (aryl Isocyanide) complex Ni(CNAr)$\sb4$ (Ar = 2,6-dimethylphenyl) with carbon dioxide in the presence of Li$\sp+$ leads to the formation of Ni(CO)$\sb2$(CNAr)$\sb2$ and the arylisocyanate, ArN=C=O. The tetrakis (methyl isocyanide) complex Ni(CNMe)$\sb4$ reacts similarly with carbon dioxide in the presence of Li$\sp+$ to produce Ni(CO)$\sb2$(CNMe)$\sb2$. $\sp{13}$C-labeling studies indicate that the carbonyl ligands of Ni(CNR)$\sb4$ are produced by multiple bond metatheses between CO$\sb2$ and CNR (R = methyl, 2,6-dimethylphenyl), not by deoxygenation of CO$\sb2$. The reaction of Ni(CNAr)$\sb4$ with $\rm\sp{13}CO\sb2$ gave Ni(CO)$\sb2$(CNAr)$\sb2$ and ArN=$\sp{13}$C=O. The reaction of Ni($\sp{13}$CNMe)$\sb4$ with CO$\sb2$ gave Ni($\sp{13}$CO)$\sb2$(CNMe)$\sb2$. The reactions are catalytic and first order in (Li$\sp+$) over the range of (Li$\sp+$) /Ni(CNAr)$\sb4$:0.01-20. Kinetic studies indicate that the rate of reaction of Ni(CNAr)$\sb4$ with CO$\sb2$ is first order in (CO$\sb2$). The reaction order in Ni(CNAr)$\sb4$ is complex. At high (Li$\sp+$) and high (CO$\sb2$), the reaction rate is second order in (Ni(CNAr)$\sb4$), but the rate saturates and becomes nearly independent of (Ni(CNAr)$\sb4$) at low (Li$\sp+$) and low (CO$\sb2$). There are two main unknown points concerning reactions of Ni(CNAr)$\sb4$ (Ar=2,6-dimethylphenyl) and Ni(CNMe)$\sb4$ with CO$\sb2$ in the presence of Li$\sp+$ that are either novel or previously unknown: the reaction involves a multiple bond metathesis exchange of an alkyl or aryl imido group of an isocyanide ligand and an O-atom of CO$\sb2$; and, more importantly, these multiple bond metathesis reactions are catalyzed by Li$\sp+$ ions. This catalyzed multiple bond metathesis reaction was applied to binuclear isocyanide complexes of nickel(0) and iridium(o) with epoxides instead of CO$\sb2$.
Degree
Ph.D.
Advisors
Kubiak, Purdue University.
Subject Area
Chemistry|Organic chemistry
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