Daniel T. Yonemoto

Synthesis and characterization of 4,4′-methylenebis (2,6-di-tert-butylphenol) derivatives of a series of metal alkoxides and alkyls

Investigation of the coordination behavior of 4,4′-methylenebis(2,6-di-tert-butylphenol) (or H2-4DBP) with a series of metal alkoxides led to isolation of [(OR)3M]2(µ-4DBP), where M/OR = Ti/OBut (2), Ti/ONep (3), Zr/OBut (4), Hf/OBut (5), and [(py)(OR)3M]2(µ-4DBP) · py (5a), where py = pyridine and ONep = OCH2C(CH3)3. Metal alkyl derivatives of 4DBP were also studied and found to form similar di-substituted species: [(py)2(Et)Zn]2(µ-4DBP) · py (6), [(THF)3(Br)Mg]2(µ-4DBP) (7), [(THF)2(Br)Mg](µ-4DBP)[Mg(Br)(THF)3] · (THF, tol) (7a), and [(py)(R)2Al]2(µ-4DBP), where R = CH3 (8), Et (9), CH2CH(CH3)2 (10); tol = toluene and THF = tetrahydrofuran. All structures demonstrate the bridging nature of 4DBP and the ability to bind a variety of metal centers. Solution state NMR indicates that the structures of 2–10 are retained in solution. Thermal analyses indicate that 4DBP is preferentially lost during heating.

Synthesis and structural characterization of group 4 metal carboxylates for nanowire production.

The synthesis and characterization of a series of group 4 carboxylate derivatives ([M(ORc)4] where M = Ti, Zr, Hf) was undertaken for potential utility as precursors to ceramic nanowires. The attempted syntheses of the [M(ORc)4] precursors were undertaken from the reaction of [M(OBu(t))4] with a select set of carboxylic acids (H-ORc where ORc = OPc (O2CCH(CH3)2), OBc (O2CC(CH3)3), ONc (O2CCH2C(CH3)3)). The products were identified by single-crystal X-ray diffraction studies as [Ti(η(2)-OBc)3(OBu(t))] (1), [Zr2(μ3-O)(μ-OPc)4(μ,η(2)-OPc)(η(2)-OPc)]2 (2), [H]2[Zr(η(2)-OBc)2(OBc)2(OBc)2] (3), [Zr(μ-ONc)2(η(2)-ONc)2]2 (4), or [Hf(μ-ORc)2(η(2)-ORc)2]2 [ORc = OPc (5), OBc (6, shown), ONc (7)]. The majority of compounds (4-7) were isolated as dinuclear species with a dodecahedral-like (CN-8) bonding mode around the metals due to chelation and bridging of the ORc ligand. The two monomers (1 and 3) were found to adopt a capped trigonal prismatic and CN-8 geometry, respectively, due to chelating ORc and terminal ORc or OBu(t) ligands. The metals of the oxo-species 2 were isolated in octahedral and CN-8 arrangements. These compounds were then processed by electrospinning methods (applied voltage 10 kV, flow rate 30-60 μL/min, electric field 0.5 kV/cm), and wire-like morphologies were isolated using compounds 4, 6 (shown), and 7.

Synthesis and characterization of a series of rubidium aryloxide compounds

A series of rubidium aryloxides, [Rb(OAr)(solv) n ] x , was synthesized from the reaction of Rbo with a select set of 2-alkyl phenols [alkyl = methyl (H-oMP), iso-propyl (H-oPP), and tert-butyl (H-oBP)] and 2,6-di-alkyl phenols [alkyl = methyl (H-DMP), iso-propyl (H-DIP), and tert-butyl (H-DBP)]. The products were identified by single-crystal X-ray diffraction as [Rb5(μx-O)(ηx,μx-oMP)3] n (1), [Rb4(ηx,μx-oPP)4(py)] n (2), [Rb(μ3-oBP)(ηx-tol)]6 (3), [H]2[Rb7(O)(ηx,μ-DMP)7(py)2] n (4), and [Rb(η6,μ x -DIP)] n (5) (where ηx and μx indicate an undetermined amount of the specified interaction). Acceptable crystals of the DBP derivative could not be grown in our hands. In contrast to the solvated polymeric K and unsolvated Cs derivatives, the Rb derivatives were a mixture of solvated and unsolvated polymers and for the first time some were isolated with oxo ligands. NMR studies indicated that these compounds become smaller symmetric species upon dissolution.

Coordination chemistry of 2,6-dimethanol pyridine with early transition metal alkoxide compounds

The coordination behavior of the 2,6-dimethanol pyridine (H2-pdm) with Group 4 and 5 metal alkoxides was undertaken through a series of alcoholysis reactions. The products were crystallographically identified as: (OR)2M(μ2-pdm)[(μ-pdm)M(OR)2]2 (M = Ti, OR = OPri (1 · py), ONep (2 · HONep, tol); Zr, OBut (3)), [M3(μ3-pdm)(μ-pdm)2(μ-ONep)2(ONep)4] (M = Zr (4), Hf (5)), [M(μ-pdm)(OR)3]2 [M/OR = Nb/OEt (6), and Ta/ONep (7)] where μ = η1,η1,η2(O,N,O′), μ2 = η2,η1,η2(O,N,O′), μ3 = η1,η1,η3(O,N,O′), OEt = OCH2CH3, OPri = OCH(CH3)2, OBut = OC(CH3)3, and ONep = OCH2C(CH3)3. For each complex, pdm was a bichelating (O,N,O′) ligand generating trinuclear species coupled with a variety of additional bridging modes: μ, μ2, and μ3. Further analyses by multinuclear and DOSY NMR studies indicated that the structures were retained in solution. Graphical abstract The coordination behavior of 2,6-dimethanolpyridine (H2-pdm) with Group 4 and 5 metal alkoxides was crystallographically determined. The pdm ligand was found to undergo a variety of tridentate, bridging coordination configurations: (OR)2 M(μ2–pdm)[(μ–pdm)M(OR)2]2 (shown), M3(μ3–pdm)(μ–pdm)2(OR)6, or [M(μ–pdm)(OR)3]2.

2-(2-Hydroxy-4-methoxybenzoyl)benzoic acid derivatives of Group 4 metal alkoxides

Continued exploration of the coordination behavior of derivatives of 2-benzophenone-based ligands with metal alkoxides ([M(OR)4]) was undertaken from the reaction of 2-(2-hydroxy-4-methoxybenzoyl)benzoic acid (H2-OBzA) with a series of Group 4 precursors. The products of these reactions were identified as: [(OR)2Ti(μ-(c,c-OBzA))]2 (OR = OCHMe2 (OPri; 1 •2tol); OCMe3 (OBut; 2 •THF); OCH2CMe3 (ONep; 3)), [[(OPri)3Ti(μ-OPri)Ti(OPri)2]2(μ-(μc,μ-OBzA))2]2 (4), [(ONep)3Zr(μ-ONep)2Zr(ONep)2]2(μ-(c,μ-OBzA)2) (5 •tol), [(py)(OBut)3Zr]2(μ-(c,c-OBzA)) (6), [(OBut)2Hf(μ-OBut)]2(μ-(c,η1-OBzA)) (7) where ‘c’ = chelating or η2; ‘μ’ = bridging or η1,η1(O,O’); and μc = bridging chelating or η1,η1(O,O’); η2 : η1. The metal centers for each of these compounds adopt a pseudo-octahedral geometry employing the OBzA ligand in numerous binding modes. The different functional oxygens (carboxylate, hydroxyl, and carbonyl) were employed in a variety of coordination modes for 1–7. The complexity of these OBzA-modified compounds is driven by a combination of the coordination behavior of the OBzA moieties, the size of the metal cation, and the pendant chain of the OR ligand. Solution NMR indicates a complex structure exists in solution that was considered to be consistent with the solid-state structure. Graphical Abstract