Synthesis of Sterically Demanding Bis(phosphinimine) Dibenzofuran Ligands and Subsequent Zinc Metalation

Abstract

In light of previous success surrounding the use of bis(phosphinimine)dibenzofuran ligands for zinc-mediated lactide polymerization, a series of sterically demanding P=N pincer compounds have been prepared with important steric and electronic modifications at both P- and N-sites (L, 3a–d). These systems are highly crystalline and have been extensively characterized using multinuclear NMR spectroscopy, elemental analysis, and X-ray diffraction. The ligands can be transformed into their protonated analogues [HL][BArF4] (4a–d, [BArF4] = [B(m-(CF3)2-C6H3)4]) by reaction with Brookhart’s acid, and subsequently coordinated to zinc via an alkane elimination reaction with [ZnEt2] at ambient temperature to afford the corresponding [LZnEt][BArF4] cationic complexes 5a–d. In addition, an unusual chloridozinc species [LZnCl][BArF4] (5c′) has been isolated and structurally characterized, providing comparisons to previously established ligand sets with similar geometries.

Diphosphazide-Supported Trialkyl Thorium(IV) Complex

“…The Staudinger reaction, discovered in 1919, introduced the formation of a phosphinimine group (R 3 PNR′) via the reaction of a tertiary phosphine (R 3 P) with an organic azide (N 3 R′), resulting in concomitant loss of N 2 . Since its discovery, the phosphinimine functionality has been extensively utilized in coordination chemistry, largely due to the ease by which the steric and electronic properties can be fine-tuned by varying the phosphine and/or azide reactants. Notably, phosphinimines have been useful for supporting early transition metal olefin polymerization and rare earth metal ring-opening polymerization catalysts …”

Richard (Rick) Francis Langler Memorial Issue

“…Along with his co-workers from the University of Lethbridge, Paul describes the synthesis and characterisation of several sterically hindered bis(phosphinimine) dibenzofuran ligands followed by zinc metalation. [15] It is appropriate that long-time colleagues of Rick's, Steve Westcott, Christopher Vogels, Andreas Decken, and Felix Baerlocher, in addition to several undergraduate researchers, conclude this memorial issue with an article on the synthesis, characterisation, and antifungal activity of eight new fluoro-and methoxysubstituted benzodiazaborines. [16] …”