Metal-Templated Diyne Cyclodimerization and Cyclotrimerization

Reaction of [Pt(CH3)2(COD)] (COD = 1,5-cyclooctadiene) with Ph2PC⋮CC⋮CPPh2 led to a mixture of [{Pt(CH3)2}2(μ-Ph2PC4PPh2)2] (1) and [{Pt(CH3)2}3(μ-Ph2PC4PPh2)3] (2). Reaction of [PtCl2(COD)] with Ph2PC⋮CC⋮CPPh2 led to a mixture of the thermally unstable compounds [{PtCl2}2(μ-Ph2PC4PPh2)2] (3) and [{PtCl2}3(μ-Ph2PC4PPh2)3] (4) which transform into [{PtMe2}2{μ-C8(PPh2)4}] (5) and [{PtMe2}3{μ3-C12(PPh2)6}] (6) containing 8-membered diene−diyne and 12-membered triene−triyne rings, respectively. Compound 2 can be converted to [{PtMe2}3{C12(PPh2)6}] (7) by heating with CuCl at 80 °C, while 1 can be heated without significant cycloaddition.