Magnesium complexes containing β-ketiminate and β-diketiminate ligands with dimethylamino substituents on the ligand core nitrogen atoms

Abstract

Treatment of dibutylmagnesium with two equivalents of 4-(2,2-dimethylhydrazino)dimethylhydrazone-3-penten-2-one (L 1H) in diethyl ether afforded Mg(L 1) 2 (76%), which contains η 2-L 1 ligands with tetrahedral coordination at the magnesium ion. Similar treatment of dibutylmagnesium with 4-(2,2-dimethylhydrazino)-3-penten-2-one (L 2H) or 5-(2,2-dimethylhydrazino)-2,6-dimethyl-4-hepten-3-one (L 3H) and 4- tert-butylpyridine (4-tBupy) in diethyl ether afforded the octahedral complexes Mg(L 2) 2(4-tBupy) 2 (85%) and Mg(L 3) 2(4-tBupy) 2 (79%). Treatment of dibutylmagnesium with two equivalents of L 2H or L 3H in the absence of 4-tBupy afforded [Mg(L 2) 2] 2 and Mg(L 3) 2, however, these complexes were difficult to isolate due to the sticky nature of the crude products. A better synthetic approach entailed sublimation of Mg(L 2) 2(4-tBupy) 2 or Mg(L 3) 2(4-tBupy) 2 at 95–100 °C/0.05 Torr, which afforded [Mg(L 2) 2] 2 (94%) and Mg(L 3) 2 (80%) as colorless crystalline solids that were easily isolated. Treatment of [MgCp(CH 3)(OEt 2)] 2 with two equivalents each of 4-tBupy and L 1H afforded MgCp(L 1)(4-tBupy) (65%). Similar treatment of [MgCp(CH 3)(OEt 2)] 2 with two equivalents of L 2H or L 3H afforded the dimeric complexes [MgCp(L 2)] 2 (81%) and [MgCp(L 3)] 2 (84%), respectively. [MgCp(L 2)] 2 and [MgCp(L 3)] 2 decompose upon attempted sublimation at 125–130 °C/0.05 Torr to afford Cp 2Mg (47–53%) and [Mg(L 2) 2] 2 (67%) or Mg(L 3) 2 (74%). The X-ray crystal structures of Mg(L 1) 2, Mg(L 3) 2(4-tBupy) 2, [Mg(L 2) 2] 2, Mg(L 3) 2, MgCp(L 1)(4-tBupy), [MgCp(L 2)] 2, and [MgCp(L 3)] 2 are described. The thermal stability and volatility of the complexes were determined through preparative sublimation experiments. Many of the complexes sublime without decomposition at moderate temperatures and low pressures, and thus represent new potential precursors for thin film growth using chemical vapor deposition and related techniques.