Coordination and Reactivity Studies of Titanium Complexes of Monoanionic Inversely Polarized Phosphaalkene–Ethenolate Ligands

Abstract

The synthesis and reactivity of the first series of monoanionic bidentate ligands containing an N-heterocyclic carbene−phosphinidene adduct and their corresponding half-metallocene titanium complexes were investigated. The structural characterization of 5a confirmed bidentate coordination through the phosphorus and oxygen atoms of the ligand, with evidence of significant electron delocalization over the ligand structure. The new titanium complexes produced polyethylene at room temperature and under 1 atm of ethylene at a rate of up to 9.2 kg PE mol Ti −1 h −1 .

Overview of the Synthesis and Catalytic Reactivity of Transition Metal Complexes Based on C═P Bond Systems

“…In summary, the titanium phosphaalkene complexes show promising activities in polymerizations of olefins under ambient and mild conditions. 54 3.2. Ruthenium.…”

“…Performed DFT calculation revealed that the compound with Ti–P bond is thermodynamically competitive to the compound with Ti–C bond, however, the energies of transition state predicted that experimentally observed complex (Ti–C–P–N) is certainly kinetically favored (ΔΔ E = 11.4 kJ·mol –1 ) . In 2020, Lavoie et al reported the first titanium complexes ( 5A and 6A ; Scheme ) with monoanionic bidentate ligands containing an N -heterocyclic carbene-phosphinidene adduct ( 5 and 6 ) …”

“…During the experiment, the titanium phosphaalkene complex converted over 165 mol of ethylene per mole of catalyst, which represented a rate of 9.3 kg PE/mol Ti/h. In summary, the titanium phosphaalkene complexes show promising activities in polymerizations of olefins under ambient and mild conditions …”

Lactide Polymerization Using Zinc Dichloride Complexes Containing a Neutral Bidentate Ligand with a Diacylated Cyclic Guanidine

“…Our group has been working with N-heterocyclic imines (NHI), a class of cyclic guanidines (and the related phosphorus analogues) derived from N-heterocyclic carbenes (NHC). − These N-heterocyclic imines provide means to control the Lewis acidity of the metal center and of the coordination sphere through the NHC “building block” and the substituents on the endocyclic nitrogen atoms. We thus became interested in preparing a series of neutral bidentate ligands containing an acylated cyclic guanidine donor connected to a second donor fragment ( 1a–c ; Scheme ).…”

A neutral analogue of a phosphamethine cyanine

“…Building on known protocols for the functionalisation of PH-bonds in primary imidazolio-phosphides ( IV , R′ = H) with strong electrophiles and base, 11,14 we set out to access a neutral analogue of III by condensation of 1 with bromoborane 2 in the presence of Et 3 N or DABCO ([2,2,2]-diazabicyclooctane). Borylated 3 was formed as anticipated, but the reaction was unselective, furnishing PH 3 , P 2 H 4 and imidazole/NHB-decorated derivatives thereof along with imidazolium ions and intractable solids as further products (Scheme 1).…”