THE ISOLATION AND CHARACTERIZATION OF METAL METHYLENE COMPOUNDS, (MCH(2), M = CHROMIUM, MANGANESE, IRON, COBALT, NICKEL, COPPER, ZINC), VIA FTIR MATRIX ISOLATION SPECTROSCOPY (INFRARED)

[摘要] The reactions of atomic metal with diazomethane in cryogenic matrices have been studied using Fourier Transform infrared spectroscopy. Chromium, manganese, iron, cobalt, nickel, and copper atoms were found to react spontaneously with diazomethane in argon matrices to form the simple unligated metal methylene, MCH$sb 2$, the dinitrogen coordinated metal methylene, N$sb 2$MCH$sb 2$, and metal-diazomethane complexes, M(CH$sb 2$N$sb 2$). Only the Zn(CH$sb 2$N$sb 2)$ complex was spontaneously formed in the zinc reaction. Metal methylene species, isolated as (N$sb 2$)$sb{m x}$MCH$sb 2$ where x $ge$ 1, were also found in nitrogen matrices. The reaction products, especially the metal methylene, were identified and characterized by isotopic studies using carbon-13 enriched, deuterated and partially deuterated diazomethane, and by normal coordinate analysis. Reactions of these matrix isolated species such as oxidative-addition, reductive-elimination, and hydrogen rearrangement can be photolytically induced. Photolysis of most M(CH$sb 2$N$sb 2)$ complexes leads to the insertion products, MCH$sb 2$ and N$sb 2$MCH$sb 2$, through a oxidative-addition reaction. ZnCH$sb 2$ was obtained by irradiating Zn(CH$sb 2$N$sb 2)$ with $lambdage$ 500nm. UV photolysis of FeCH$sb 2$ and ZnCH$sb 2$ causes a hydrogen migration to occur to form HFeCH and HZnCH, respectively. The metal-carbon stretching force constants shows that $pi$ bonding in MCH$sb 2$ and HMCH is significant and indicates metal-carbon double and triple bonds, respectively. MCH$sb 2$ and N$sb 2$MCH$sb 2$ species, except for copper, were found to be reactive toward hydrogenation to form CH$sb 4$ and M. The isolation of CH$sb 3$MH and (N$sb 2$)CH$sb 3$MH from the reactions with iron and cobalt indicates that hydrogenation occurs first by hydrogenating the M=C bond to form CH$sb 3$MH /or (N$sb 2$)CH$sb 3$MH as an intermediate and then giving CH$sb 4$ and M via a reductive-elimination reaction. The matrix reactions of various metal methylene with water in argon matrices have also been investigated. Only FeCH$sb 2$ was found to react with H$sb 2$O spontaneously. The regiospecific reaction which yields CH$sb 3$FeOH indicates that the methylene carbon in FeCH$sb 2$ is nucleophilic.

[发布机构] Rice University