Titanium(IV) Chelates Containing Binegative Ligands

Abstract

The reaction of titanium(IV) alkoxides in 1:1 stoichiometry with 2-methyl-2,4-pen tan ediol, pyrocatechol, salicylic acid, or , '-diphenylmethylenediphosphinic acid yields chelates of the form Ti(BB)(OR)z, where BB represents the binegative bidentate ligands involved and R is ethyl or isopropyl. A similar reaction with 1,3-propanediol does not produce Ti-(OCaHeOXORk, but instead Ti(OCsHeOk and Ti(ORk are recovered. The Ti(BB)(ORk derivatives are all associated

Michaelis-Arbuzov rearrangement

“…The reaction of a phosphonite with a dihalide may result in the formation of either esters of haloalkylphosphinic acids114,115 or of diphosphinic acids. [116][117][118] The latter can also be prepared by the reaction of alkyl halides on diphosphinites.119 Similarly the reaction of diphosphonites and dihalides yields polyphosphonites. 120 Likewise, co-haloalkyl phosphonite esters yield cyclic phosphinates121,122 (68) by intramolecular rearrangement; e.g.…”

Polyesters

“…5, 80 On the other hand, when exchange is possible the catalytic effect does not depend on the nature of the ligands [Ti(OBu n )4 has the same catalytic activity as Ti(OPr i )4] unless the ligands resulting from the exchange are too bulky; in this latter case they can hinder coordination with the metal resulting in a decrease of catalytic effectiveness."? However, many experimental results suggest that the behavior of these catalysts in the reacting system is rather more complex.…”

Catecholate complexes of zirconium: synthesis, spectroscopic characterization and polymerization studies

“…It is understood that the nuclearity of the metal complex is basically dependent on these ancillary ligands and that the catalyst nuclearity plays a crucial role in the coordination–insertion growth mechanism. In 1966, Dahl's group reported Ti complexes comprising the catechol ligand . But they did not test the catalytic activity of these complexes towards the ROP of cyclic esters and LA.…”