title: Stabilizing high-valent metal ions with a ketimide ligand set: synthesis of Mn(N=C(t)Bu2)4.
abstract: Reaction of MnCl(2) with 4 equiv of Li(N=C(t)Bu(2)) generates [Li(THF)](2)[Mn(N=C(t)Bu(2))(4)] (1) in 80% yield. Oxidation of 1 with 0.5 equiv of I(2) produces [Li][Mn(N=C(t)Bu(2))(4)] (2) in 88% yield. Both complexes 1 and 2 exhibit tetrahedral structures about the Mn center in the solid-state, as determined by X-ray crystallography. Reaction of 2 with 12-crown-4 generates [Li(12-crown-4)(2)][Mn(N=C(t)Bu(2))(4)] (3) in 94% yield. Interestingly, in the solid-state, complex 3 exhibits a squashed tetrahedral structure about Mn. Addition of 1 equiv of I(2) to 1 generates the Mn(IV) ketimide, Mn(N=C(t)Bu(2))(4) (4), in 75% yield. Complex 4 was fully characterized, including analysis by X-ray crystallography and cyclic voltammetry. Like 3, complex 4 also exhibits a squashed tetrahedral structure in the solid-state. Interestingly, thermolysis of complex 4 at 50 °C for 6 h results in the formation of Mn(3)(N=C(t)Bu(2))(6) (6), which can be isolated in 49% yield. Also observed in the reaction mixture is pivalonitrile, isobutylene, and isobutene, the products of ketimide ligand oxidation. We have also synthesized the homoleptic Cr(IV) ketimide complex, Cr(N=C(t)Bu(2))(4) (5), and have analyzed its electrochemical properties with cyclic voltammetry.
authors.affiliation: Department of Chemistry and Biochemistry, University of California Santa Barbara, Santa Barbara California 93106, USA.
authors.forename: Richard A
authors.initials: RA
authors.lastname: Lewis
authors.forename: Guang
authors.initials: G
authors.lastname: Wu
authors.forename: Trevor W
authors.initials: TW
authors.lastname: Hayton
mesh_terms: D002857:Chromium / Q000737:chemistry / Q000378:metabolism; D056831:Coordination Complexes / Q000138:chemical synthesis* / Q000378:metabolism; D018360:Crystallography, X-Ray; D004563:Electrochemistry; D007477:Ions / Q000378:metabolism; D008024:Ligands; D008345:Manganese / Q000737:chemistry* / Q000378:metabolism; D008958:Models, Molecular; D015394:Molecular Structure; D009570:Nitriles / Q000138:chemical synthesis* / Q000378:metabolism; D010084:Oxidation-Reduction
chemical_list: D056831:Coordination Complexes; D007477:Ions; D008024:Ligands; D009570:Nitriles; D002857:Chromium; D008345:Manganese