title: Synthesis, structure, and magnetic studies of manganese-oxygen clusters of reduced coordination number, featuring an unchelated, 5-coordinate octanuclear manganese cluster with water-derived oxo ligands.
abstract: 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(2)C(6)H(3)OH) as the ligand source results in the formation of a 3-coordinate heteroleptic dimer without THF coordination, Mn(2)(μ-OC(6)H(3)Ph(2))(2)(NR(2))(2) (2). Attempts to generate 2 in the presence of THF or Et(2)O resulted in isolation of monomeric Mn(OC(6)H(3)Ph(2))(2)L(2) (3, L = THF, Et(2)O). 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.
authors.affiliation: Department of Chemistry, Temple University, 1901 N. 13th Street, Philadelphia, Pennsylvania 19122, USA.
authors.forename: Sandeep K
authors.initials: SK
authors.lastname: Kondaveeti
authors.forename: Shivaiah
authors.initials: S
authors.lastname: Vaddypally
authors.forename: Carol
authors.initials: C
authors.lastname: Lam
authors.forename: Daigorou
authors.initials: D
authors.lastname: Hirai
authors.forename: Ni
authors.initials: N
authors.lastname: Ni
authors.forename: Robert J
authors.initials: RJ
authors.lastname: Cava
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Zdilla