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

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.