Michael Luke Neville

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.

Structural Properties of the Acidification Products of Scandium Hydroxy Chloride Hydrate.

The structural properties of a series of scandium inorganic acid derivatives were determined. The reaction of Sc(0) with concentrated aqueous hydrochloric acid led to the isolation of [(H2O)5Sc(μ-OH)]24Cl·2H2O (1). Compound 1 was modified with a series of inorganic acids (i.e., HNO3, H3PO4, and H2SO4) at room temperature and found to form {[(H2O)4Sc(κ(2)-NO3)(μ-OH)]NO3}2 (2a), [(H2O)4Sc(κ(2)-NO3)2]NO3·H2O (2b) (at reflux temperatures), {6[H][Sc(μ-PO4)(PO4)]6}n (3), and [H][Sc(μ3-SO4)2]·2H2O (4a). Additional organosulfonic acid derivatives were investigated, including tosylic acid (H-OTs) to yield {[(H2O)4Sc(OTs)2]OTs}·2H2O (4b) in H2O and [(DMSO)3Sc(OTs)3] (4c) in dimethyl sulfoxide and triflic acid (H-OTf) to form [Sc(H2O)8]OTf3 (4d). Other organic acid modifications of 1 were also investigated, and the final structures were determined to be {([(H2O)2Sc(μ-OAc)2]Cl)6}n (5) from acetic acid (H-OAc) and [Sc(μ-TFA)3Sc(μ-TFA)3]n (6) from trifluoroacetic acid (H-TFA). In addition to single-crystal X-ray structures, the compounds were identified by solid-state and solution-state (45)Sc nuclear magnetic resonance spectroscopic studies.

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

Scandium separation from tungsten crucibles

The first step in an attempt to isolate Sco from a Wo crucible was explored by soaking the samples in a series of organic (HOAc) and inorganic (HCl, H2SO4, H3PO4, HNO3) acids. All samples, except the HOAc, yielded a powder. The weight loss suggests that HNO3 is the most efficient solvent; however, the powders were tentatively identified by PXRD and found to contain both W and Sc by-products. The higher weight loss may also indicate dissolution of the Wo crucible, which was further evidenced upon visual inspection of the crucible. The H3PO4 acid soak yielded the cleanest removal of Sc from the crucible. More work to understand the separation of the Sco from the Wo crucible is necessary but the acid routes appear to hold promise under not as of yet established criteria.