Date Available

12-7-2011

Year of Publication

2008

Document Type

Thesis

Degree Name

Master of Science (MS)

College

Arts and Sciences

Department/School/Program

Chemistry

Faculty

Dr. Stephen M. Holmes

Faculty

Dr. Robert B. Grossman

Abstract

The syntheses, structures, and magnetic properties of a series of di/trivalent hydridotris(3,5-dimethylpyrazol-1-yl)borate (Tp*) cyanomanganates were investigated. Treatment of manganese(III)acetylacetonate with KTp* followed by tetra(ethyl)- ammonium cyanide affords [NEt4][(Tp*)MnII(acac)(CN)] (1). Attempts to oxidize 1 with iodine affords {(Tp*)MnII(κ2O-acac-CN)}n (7); a minor complex {[NEt4][(Tp*)MnII(κ2O-acac-3-CN)]2(µ-CN) (8) was also isolated.

The manganese(II) complex [NEt4][(Tp*)MnII(κ2O-acac-3-CN)(κ1N -3-NC-acac)] (2) was obtained via treatment of Mn(3-acacCN)3 with KTp* and [NEt4]CN. [NEt4]2[MnII(CN)4] (3) was prepared via treatment of Mn(OTf)2 with excess [NEt4]CN. [NEt4][(Tp*)MnIII(CN)3] (4), is prepared via treatment of 4 with Mn(3-acacCN)3, KTp* and excess [NEt4]CN. [PPN][(Tp*)MnIII(CN)3] (5) is obtained via treatment of [PPN]3[MnII(CN)6] with (Tp*)SnBu2Cl.

Combination of 4 with [MnII(bipy)2(OH2)2][OTf]2 afforded a tetranuclear rectangular cluster {MnIII 2MnII 2} (9). At low temperature, {MnIII2NiII2} (10) was prepared via treatment of 4 and [Ni(II)(bipy)2(H2O)2][OTf]2. Treatment of 4 with [CoII(bipy)2(OH2)2][OTf]2 at low temperature failed to give the desired {MnIII2CoII2} complex.

Magnetic measurements indicate that 1, 2, and 7 contain high-spin isotropic MnII with no long-range magnetic order observed for 7 (T > 2 K); 4 contains low-spin MnIII that likely adopt an isotropic 3A2 spin ground state. Surprisingly 9 and 10 do not exhibit slow relaxation of the magnetization (for T > 1.8 K) despite the presence of significant molecular anisotropy.

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