Reactions of Group 4 Amide Guanidinates with Dioxygen or Water. Studies of the Formation of Oxo Products

Living ring-opening polymerization of β-butyrolactone initiated by mononuclear zirconium compounds containing sterically hindered N,O-chelate and anionic dimethylamide ligands†

The ring-opening polymerization of β-lactones into polyhydroxyalkanoates (PHA), biodegradable polymers with high molecular weight and narrow polydispersity, is of significant interest. The mononuclear zirconium compound containing sterically hindered N,O-chelate and anionic dimethylamide ligands was used as an initiator for the polymerization of β-butyrolactone (BBL), resulting in polyhydroxylbutyrate (PHB) with a number-average molecular weight of 12 000 g mol⁻¹. Kinetic studies demonstrate a first-order dependence on β-butyrolactone (BBL) concentration at room temperature, accompanied by narrow molecular weight distributions (ca. 1.03–1.07), indicating a well-controlled living polymerization.

The ring-opening polymerization of β-lactones into polyhydroxyalkanoates (PHA), biodegradable polymers with high molecular weight and narrow polydispersity, is of significant interest.

Hydrolysis of organometallic and metal–amide precursors: synthesis routes to oxo-bridged heterometallic complexes, metal-oxo clusters and metal oxide nanoparticles

Organometallic and metal amide reagents react with –OH groups to generate metal–oxygen connectivity, yielding metal-oxo heterobimetallics, clusters and nanoparticles.

Syntheses and characterization of hepta-coordinated Group 4 amidinate complexes

Hepta-coordinated Group 4 amidinate complexes have been synthesized and characterized by ¹⁵N chemical shifts through ¹H–¹⁵N gHMBC NMR.

Density Functional Theory Study of the Reaction between d0 Tungsten Alkylidyne Complexes and H2O: Addition versus Hydrolysis

The reactions of early-transition-metal complexes with H₂O have been investigated. An understanding of these elementary steps promotes the design of precursors for the preparation of metal oxide materials or supported heterogeneous catalysts. Density functional theory (DFT) calculations have been conducted to investigate two elementary steps of the reactions between tungsten alkylidyne complexes and H₂O, i.e., the addition of H₂O to the W≡C bond and ligand hydrolysis. Four tungsten alkylidyne complexes, W(≡CSiMe₃)(CH₂SiMe₃)₃ (A-1), W(≡CSiMe₃)(CH₂^tBu)₃ (B-1), W(≡C^tBu)(CH₂^tBu)₃ (C-1), and W(≡C^tBu)(O^tBu)₃ (D-1), have been compared. The DFT studies provide an energy profile of the two competing pathways. An additional H₂O molecule can serve as a proton shuttle, accelerating the H₂O addition reaction. The effect of atoms at the α and β positions has also been examined. Because the lone-pair electrons of an O atom at the α position can interact with the orbital of the proton, the barrier of the ligand-hydrolysis reaction for D-1 is dramatically reduced. Both the electronic and steric effects of the silyl group at the β position lower the barriers of both the H₂O addition and ligand-hydrolysis reactions. These new mechanistic findings may lead to the further development of metal complex precursors.