Abstract
Paradoxically, N- and O-donor substituted tri-arylphosphanes are shown to be weaker donors than PPh3 when binding the soft Lewis acid moiety [PPh2]+. This arises from internal solvation and rehybridisation at phosphorus, precluding chelation and increasing steric demand, in direct contrast to coordination modes observed for metal complexes.
Highlights
N- and O-donor substituted tri-arylphosphanes are shown to be weaker donors than PPh3 when binding the soft Lewis acid moiety [PPh2]+. This arises from internal solvation and rehybridisation at phosphorus, precluding chelation and increasing steric demand, in direct contrast to coordination modes observed for metal complexes
We describe the synthesis of a family of simple donor functionalised phosphane-derived phosphane–phosphenium salts; the effect of donor substitution on the overall donor strength and resultant cation stability is discussed
The reaction with Me3SiOTf or GaCl3 likewise resulted in clean chloride abstraction and the quantitative formation of the desired triflate or [GaCl4]− salts except for 1c which gave complex mixtures for both reagents
Summary
Donor-substituted phosphanes – surprisingly weak Lewis donors for phosphenium cation stabilisation†. N- and O-donor substituted tri-arylphosphanes are shown to be weaker donors than PPh3 when binding the soft Lewis acid moiety [PPh2]+. This arises from internal solvation and rehybridisation at phosphorus, precluding chelation and increasing steric demand, in direct contrast to coordination modes observed for metal complexes. We describe the synthesis of a family of simple donor functionalised phosphane-derived phosphane–phosphenium salts; the effect of donor substitution on the overall donor strength and resultant cation stability is discussed
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