|Budget Amount *help
¥1,800,000 (Direct Cost : ¥1,800,000)
Fiscal Year 1999 : ¥600,000 (Direct Cost : ¥600,000)
Fiscal Year 1998 : ¥1,200,000 (Direct Cost : ¥1,200,000)
The cold ESI, operating ionization under low temperature was recently developed in our laboratory and proved to be effective to preserve thermally unstable compounds unchanged. Some significant spectra were obtained form MeMgCl, MeMgBr, EtMgCl, EtMgBr, PhMgCl t-BuMgCl, AllyMgCl and i-PrMgCl in tetrahydrofuran (THF) solution using the cold ESI. The characteristic ion peaks consistent with these three spectra of m/z 529, 601 and 673 indicate the ion species of [NMgィイD22ィエD2ClィイD23ィエD2(THF)ィイD2nィエD2]ィイD1+ィエD1 formed based on the atomic nitrogen attached break down products. The [RMgィイD22ィエD2ClィイD23ィエD2(THF)ィイD2nィエD2-H]ィイD1+ィエD1 ion peaks directly related to the corresponding Grignard species are definitely observed in EtMgCl and PhMgCl. The isotopic ion peak patterns as well as MS/MS analysis detecting sequential THF cleavage from the parent ion suggest these ion structures. Following equilibrium is then derived.
3RMgX(THF)ィイD2nィエD2【double arrow】RィイD22ィエD2Mg + RMgィイD22ィエD2XィイD23ィエD2(THF)ィイ
On the other hand, X-ray crystallographic analyses were undertaken. We determined the crystal structures of 2[MgィイD22ィエD2ClィイD23ィエD2(THF)ィイD26ィエD2]・[PhィイD24ィエD2MgィイD22ィエD2ClィイD22ィエD2] obtained from PhMgCl, and [MgィイD22ィエD2ClィイD23ィエD2(THF)ィイD26ィエD2]・[t-BuMgClィイD22ィエD2(THF)] from t-BuMgCl. The structure of dimagnesium cationic species included in the both crystals obtained from PhMgCl and t-BuMgCl was solved. This cationic species [MgィイD22ィエD2ClィイD23ィエD2(THF)ィイD26ィエD2]ィイD1+ィエD1 which is detected in the Grignard reagent for the first time has rarely observed. The first crysta lstructure of RMgX without solvent molecule was observed. In case of the crystal obtained from t-BuMgCl, monomeric structure (t-BuMgClィイD22ィエD2THF) was observed together with the cationic species. These constitutions were thought to be included in the Schlenk equilibrium.
8PhMgCl(THF)ィイD2nィエD2 【double arrow】2PhィイD22ィエD2Mg + 2[(MgィイD22ィエD2ClィイD23ィエD2)(THF)ィイD26ィエD2]ィイD1+ィエD1 + [PhィイD24ィエD2MgィイD22ィエD2ClィイD22ィエD2]ィイD12-ィエD1 (eq. 2)
5t-BuMgCl(THF)ィイD2nィエD2 【double arrow】 2t-BuィイD22ィエD2Mg + [(MgィイD22ィエD2ClィイD23ィエD2)(THF)ィイD26ィエD2]ィイD1+ィエD1 + [t-BuMgClィイD22ィエD2(THF)]ィイD1-ィエD1 (eq. 3)
Other crystal structures of Grignard species have also been investigated in the same manner for comparison. In case of MeMgCl, the crystal structure of MeィイD22ィエD2MgィイD24ィエD2ClィイD26ィエD2(THF)ィイD26ィエD2 included in Schlenk equilibrium was found.
6MeMgCl(THF)ィイD2nィエD2 【double arrow】 2MeィイD22ィエD2Mg + MeィイD22ィエD2MgィイD24ィエD2ClィイD26ィエD2(THF)ィイD26ィエD2 (eq. 4) Less