The synthesis of reduced coordination (less than 6), unchelated manganese oxygen cluster systems is described. Addition of phenols to Mn(NR 2) 2 (R = SiMe 3) results in protolytic amide ligand replacement, and represents the primary entry into the described chemistry. Addition of PhOH to Mn(NR 2) 2 results in the formation of the heteroleptic dimer Mn 2(μ-OPh) 2(NR 2) 2(THF) 2 (1). Usage of the sterically larger 2,6-diphenylphenol (Ph 2C 6H 3OH) as the ligand source results in the formation of a 3-coordinate heteroleptic dimer without THF coordination, Mn 2(μ-OC 6H 3Ph 2) 2(NR 2) 2 (2). Attempts to generate 2 in the presence of THF or Et 2O resulted in isolation of monomeric Mn(OC 6H 3Ph 2) 2L 2 (3, L = THF, Et 2O). Use of the sterically intermediate 2,4,6-trimethylphenol (MesOH) resulted in formation of the linear trinuclear cluster Mn 3(μ-OMes) 4(NR 2) 2(THF) 2 (4). Reaction of Mn(NR 2) 2 with PhOH in the presence of water, or reaction of 1 with water, results in the formation of a 5-coordinate, unchelated Mn-O cluster, Mn 8(μ 5-O) 2(μ-OPh) 12(THF) 6 (5). Preparation, structures, steric properties, and magnetic properties are presented. Notably, complex 5 exhibits a temperature-dependent phase transition between a 4-spin paramagnetic system at low temperature, and an 8-spin paramagnetic system at room temperature.
All Science Journal Classification (ASJC) codes
- Physical and Theoretical Chemistry
- Inorganic Chemistry