Facile Synthesis of Linear and Cyclic Poly(diphenylacetylene)s by Molybdenum and Tungsten Catalysis

Abstract

Improved methods for the synthesis of linear and cyclic poly(diphenylacetylene)s by polymerization of the corresponding diphenylacetylenes using MoCl₅ - and WCl₄ -based catalytic systems have been developed. MoCl₅ induces migratory insertion polymerization of diphenylacetylenes in the presence of arylation reagents such as Ph₄ Sn and ArSnⁿ Bu₃ to produce cis-stereoregular linear poly(diphenylacetyelene)s with high molecular weights (number-average molar mass (M_n )=30,000-3,200,000) in good yields (up to 98 %). On the other hand, WCl₄ induces ring expansion polymerization of diphenylacetylenes in the presence of Ph₄ Sn or reducing reagents to produce cis-stereoregular cyclic poly(diphenylacetylene)s with high molecular weights (M_n =20,000-250,000) in moderate to good yields (up to 90 %). Both catalytic systems are applicable to the polymerization of various diphenylacetylenes having polar functional groups such as esters that are not efficiently polymerized by conventional methods using WCl₆ -Ph₄ Sn and TaCl₅ -ⁿ Bu₄ Sn systems.

Keywords: Diphenylacetylenes; Molybdenum; Polymerization; Polymers; Tungsten.