Synthetic Control of Heteroatonvcontaining Dynamic Complexes by Taking Advantage of Kinetic Stabilization

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The main purposes of this project are the development of novel ligands bearing steric protection group and their application toward the synthesis and isolation of novel dynamic complexes bearing unique chemical bonds between heteroatoms. We have succeeded in the synthesis of the extremely bulky bidentate ligand, {Bbt(Me)PCH_2}_2 (1), and its platinum complex, [PtCl_2(1)](2). In this year, we attempted to synthesize the corresponding zero valent platinum complex, [Pt(1)](3), which should be a good precursor for the unprecedented platinum complex bearing a Pt=S double bond, [PtS(1)]. Although reduction of 2 using sodium shot or lithium naphthalenide was attempted, no evidence for the generation of 3 was observed. On the other hand, we succeeded in the synthesis of a new lithium β-diketiminate bearing Tbt and mesityl (Mes) groups, [Li{TbtNC(Me)CHC(Me)NMes}] (4), which is the first heteroatomrdonor-free monomeric lithium β-diketiminate. Lithium β-diket-iminate 4 reacted with MCl_4(thf)_2 (M = Ti, Zr, Hf) to give the corresponding group 4 metal complexes [M{TbtNC(Me)CHC(Me)NMes}(thf)n] (5a : M = Ti, n = 0, 5b : M = Zr, n = 1, 5c : M = Hf, n = 1), respectively. The reduction of 5a-c with KC_8 in the presence of tmeda and LiCl was found to afford unexpected imido complexes [M(NTbt)-{MesNC(Me)CHC(Me)}(μ-Cl)_2Li(tmeda)] (6a : M = Ti, 6b : M = Zr, 6c : M = Hf) in good yields. The treatment of hafnium complex 6c in benzene with KC_8 gave imido complex [HfCl(NTbt)- {MesNC(Me)CHC(Me)}(thf] (7c) in 82% yield in the absence of additives. These imido complexes 6a-c and 7c are most likely formed via the corresponding divalent group 4 metal complexes.