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A range of ligands based upon 2-(aminomethyl)piperidine have been successfully complexed to Mg(ii), Zn(ii) and group IV metal centres. These complexes have been characterised both in solution and solid state with different coordination geometries realised dependant on the nature of the ligand. For the Mg(ii) and Zn(ii) complexes, M(1–2)2, were isolated and analysed by DOSY NMR spectroscopy. These ligands also furnished diastereomeric group IV complexes, M(1–2)2(OiPr)2. Group IV salalen and salan complexes, M(4–5)(OR)2 were also found to be diastereomeric in nature, with either β-cis or α-cis geometriesrespectively. The tridentate ligand, 6H2, yielded five coordinate complexes with both Ti(iv) and Zr(iv). All complexes were screened for the ring opening polymerisation of rac-lactide under both solvent and melt conditions. For the Mg(ii) and Zn(ii) complexes, good activity was observed with Zn(1–2)2 demonstrating immortal polymerisation characteristics. [ABSTRACT FROM AUTHOR]

We report the rationalised design of aluminium initiators and their application for ROP of rac-lactide (rac-LA). A very minor change to the ligand backbone (imine reduction) to give secondary amines was found to have a dramatic effect on activity and selectivity with isotactic PLA being realised. [ABSTRACT FROM AUTHOR]

Five new lithium aryloxide complexes stabilised by polyamine ligands have been synthesised by simple deprotonation reactions of the parent aryl alcohols H–OAr [OAr = OC6H5, OC6H2-2,4,6-(Me)3and OC6H2-2,6-(tBu)2-4-(Me)] with LiN(SiMe3)2in the presence of the Lewis bases N,N,N′,N′-tetramethylethylenediamine (TMEDA) and N,N,N′,N′′,N′′-pentamethyldiethylenetriamine (PMDETA). All the compounds have been characterised by multinuclear NMR and X-ray crystallographic studies. The PMDETA derivative of the phenol adopts a tetrameric ladder-like structural motif in the solid state, exhibiting an unusual bridging coordination mode of the N-donor ligand. The 2,4,6-trimethylphenol derivatives exhibit dimeric (TMEDA), and tetrameric (PMDETA) structural motifs in the solid state. Meanwhile, the TMEDA and PMDETA derivatives of the sterically hindered 2,6-di-tert-butyl-4-methylphenol exhibit a rare monomeric structural motifs, which appears to remain unaltered in C6D6solution. [ABSTRACT FROM AUTHOR]

Abstract: In this paper we investigate the coordination of various oximes (COH) with titanium(IV). We have chosen three ligands (1H2–3H2) with a phenolic moiety and one ligand 4H with a pyridine group. It was shown that ligands 1H2 to 3H2 react with Ti(O i Pr)4 to form complexes with a generic formula Ti3(L)2(O i Pr)8, where each oxime bridges between the three titanium centres. Interestingly, these complexes are clusters made up of three titanium atoms, with one titanium centre sitting above the other two. This titanium centre can be thought of as a trapped Ti(O i Pr)4 molecule, 1H and 13C NMR spectroscopy indicates that the solid-state structures are maintained in solution. Subtle differences between the three X-ray structures are discussed. Ligand 4H readily reacts with Ti(O i Pr)4 forming a dimeric species, Ti2(4)4(O i Pr)4, where the titanium centres are linked by bridging isopropoxide moieties. [Copyright &y& Elsevier]

The first examples of Group 1 metal complexes of tris(2-dimethylaminoethyl)amine (Me6TREN) are reported including monomeric sodium complexes containing η4-bound ligands, suggesting their potential use in alkali-metal-mediated synthetic applications. [ABSTRACT FROM AUTHOR]

The reaction of bismuth amides or alkoxides with phenolic ligand precursors yields Bi complexes of aminetris(phenoxide)s, one of which was characterized by X-ray crystallography, revealing monomeric Bi units of the tetradentate NO3 ligand further associated via a symmetrical toluene bridge into a bis(bismuth)toluene inverted-sandwich complex. Synthesis of the analogous Sb complex suggests a markedly different geometric and electronic environment at the metal center, as evidenced by the solid-state molecular structure. Density functional theory calculations of the sandwich bismuth arene complex indicate the presence of a weak σ*-2π interaction. [ABSTRACT FROM AUTHOR]