Tungsten coordination chemistry of 1,4-bisdiphenylphosphinobutadiyne — Synthesis of coordination macrocycles and factors controlling diyne cycloaddition

Abstract

The 1:1 reaction of [W(CO)4(2-picoline)2] (1) with Ph2PCtriple bondC-Ctriple bondCPPh2 (2) led to {[cis-W(CO)4]2(µ-Ph2PC4PPh2)2} (3), in which two bis(diphenylphosphino)butadiyne ligands bridge two tetracarbonyltungsten centres. Reaction of 1 with excess 2 led to [cis-W(CO)4(Ph2PC4PPh2-κ1-P)2] (4), in which two dangling bis-phosphines are coordinated to one metal centre, and reaction of 2 with two equivalents of 1 led to {[W(2-picoline)(CO)4]2(µ-Ph2PC4PPh2)} (5), in which one ligand bridges two tungsten centres. Combination of 4 and 5 led to the trimeric complex {[cis-W(CO)4]3(µ-Ph2PC4PPh2)3} (6), in which three tetracarbonyltungsten centres are bridged by three bisdiphenylphosphinobutadiyne ligands. The dimeric complex 3 showed no reactivity towards alkyne cycloaddition; however, the trimeric complex 6 undergoes cycloaddition at moderate temperatures to form {[W(CO)4]3[µ3-C12(Ph2P)6]} (8), which contains a cyclododecatrienetriyene ring. Comparison of structural data for the template complexes 3 and 6, as well that of previously described platinum template complexes, suggests that alkyne cycloaddition reactions are favoured by proximity of the alkynyl carbons α to phosphorus in adjacent ligands.Key words: coordination chemistry, diyne, cycloaddition, templated reaction, tungsten.