A new approach to novel homobimetallic palladium complexes

Mononuclear trans-(PPh3)2Pd(I)(C6H4-4-I) (3), which is accessible by the oxidative addition of C6H4-1,4-I2 (2) to (Ph3P)4Pd (1), reacts with [AgOTf] (4) in a 1:1 molar ratio to give trans-(PPh3)2Pd(C6H4-4-I)(OTf) (5). Complex 5 affords on treatment with 0.5 equivalents of 4,4′-dicyanobiphenyl (6) homobimetallic trans-[(PPh3)2(C6H4-4-I)Pd ← Ntriple bond; length of mdashCsingle bondC6H4]2(OTf)2 (7). The latter species rearranges to give trans-[(PPh3)2(C6H4-4-PPh3)Pd ← Ntriple bond; length of mdashCsingle bondC6H4]2(OTf)4 (8) and [(PPh3)(C6H4-4-PPh3)Pd(μ-I)]2(OTf)2 (9), respectively. A possible mechanism for the formation of 8 and 9 will be presented. The solid-state structure of 8 is reported. In 8 two [trans-(PPh3)(C6H4-4-PPh3)Pd]2+ fragments are bridged by the 4,4′-dicyanobiphenyl unit.