Herein we report the synthesis and full characterization (NMR and solid-state structures) for a series of Zr(IV), Hf(IV), and Al(III) salalen complexes, together with salen bimetallic counterparts. With the salalen ligand, 1H 2 , monometallic complexes were observed in solution and solid state. Complex Zr(1)(O i Pr) 2 was able to produce isotactic polylactide (PLA) from rac-lactide (P m up to 0.85) in solution at 50 °C; in the melt (130 °C) this reduced to ca. 0.75. Al(1)Me was significantly less active and produced PLA with only a very modest isotactic enchainment (P m ≈ 0.6). Zr(1)(O i Pr) 2 was also able to produce copolymers with lactide and ε-caprolactone, producing copolymers of a "blocky" nature.

A series of monometallic and bimetallic Al(iii) complexes with substituted naphthyl based Schiff base ligands have been prepared and characterised. When 1-aminonaphthalene based ligands were reacted with AlMe3 monometallic complexes were isolated, however, with 1,5 and 1,8-diaminonaphthalene based ligands bimetallic complexes were formed. In all cases 4-coordinate tetrahedral Al(iii) centres were observed in the solid state and in solution. There was little difference in rate of polymerisation of rac-lactide between the monometallic and bimetallic complexes based on 1,5-diaminonaphthalene. However, for the 1,8-diaminonaphthalene the complex was an order of magnitude faster than the monometallic and the analogous 1,5-system. Moreover, this complex was active at room temperature, which is rare for aluminium initiators, and PLA with a high degree (Pm = 0.82) of isotacticity was observed.

This paper describes the preparation and comprehensive characterization of a series of water-soluble cationic silver(I)-centered complexes featuring the hemilabile P, N-ligand known as 3,7-dimethyl-1,3,5-triaza-7-phosphabicyclo[3.3.1]nonane (herein abbreviated as PTN(Me)) and differing types of monoanionic counterions including known biologically active sulfadiazine and triclosan. The complexes primarily differed though the number of coordinating PTN(Me) ligands. The bis-substituted Ag(I) complexes revealed P, N bidentate coordination, while the only P-monocoordination of the metal center was observed for the tris-substituted systems. The bis-ligated silver compounds were observed to quickly degrade upon photoexposure or in contact with air. In contrast, the tris-ligated complexes demonstrated greater stability, in particular, a high resistance to photo-decomposition. Calculated geometry optimized models using the density functional theory method (BP86) revealed for the bis-substituted PTN(Me) Ag(I) species that the total enthalpy of the tetrahedral C-symmetric structure is marginally lower by -0.6 kcal mol compared to the planar C structure, which is analogous for the corresponding [Au(PTN(Me))] complex with Δ H = -0.5 kcal mol. Hence both types of complexes feature free rotation of the PTN ligand about the M-P bond axis. This series of Ag(I) and bis-PTN(Me) Au(I) complexes were evaluated using the agar well diffusion test for potential antimicrobial and antifungal activity. The nature of the counterion was found to have a strong correlation with the area of microbiological growth inhibition. Silver(I) complexes bearing the deprotonated triclosan as the counterion demonstrated the greatest activity, with large zones of growth inhibition, with the tris-ligated triclosan complex obtaining of a high clearance of 42 mm against the Gram-negative Escherichia coli. In contrast, the previously reported [Au(PTN(Me))]Cl complex demonstrated activity only against E. coli, which is lower than that observed for the silver(I) PTN(Me) species.

Two series of ligands based on diaminocyclohexane (DACH) have been prepared and successfully complexed to AlIII and ZnII metal centres. Solution and solid‐state studies reveal a tendency to form mono‐ or bis‐ligated forms depending on the steric bulk of the ligand. These complexes have been tested for their ability to ring open rac‐lactide. AlIII based complexes generally gave atactic PLA after a polymerisation time of 1–2 days. The ZnII complexes, were found to be more active and furnished PLA with a slight heterotactic bias.