Magnesium amido N-heterocyclic carbene complexes

Magnesium dications bind strongly to a tridentate anionic dicarbene ligand L = [N{CH2CH2(CNCHCHNMes)}(2)] forming dinuclear and trinuclear Mg complexes with some particularly short Mg-C bonds. Treatment of the proligand H4LCl3 with three equivalents of methyl magnesium chloride or benzyl magnesium chloride affords Mg-3(HL)Cl-6 in high yield. A suspension of 1 in thf was heated to 80 degrees C for 2 h to affordMg(2)(L)Cl-3, consistent with the loss of one equivalent of MgCl2, and the deprotonation of the remaining acidic NH, lost as HCl gas. Treatment of Mg3(HL) Cl6 with one equivalent of KC8 results in deprotonation of the ligand amine NH to afford Mg-3(L)Cl-5; treatment with a second equivalent forms the radical anion of the complex, K[Mg3(L) Cl5], which decomposes upon storage, precluding its structural characterisation. The acidic NH proton of the ligand in Mg-3(HL)Cl-6 can also be removed by deprotonation with Li{N(SiMe3)(2)}; additional equivalents of which also exchange the magnesium-bound chlorides for silylamido ligands, affording Mg-2(L)Cl2N '' and Mg-2(L)Cl(N '')(2), which have both been characterised by single-crystal X-ray diffraction studies.