Linear homobimetallic palladium complexes with end-capped SC(O)Me units

Rigid-rod structured homobimetallic palladium complexes of type [{trans-(Me(O)CS-4-C6H4-C6H4)(Ph3P)2Pd}2(μ-N∩N)](OTf)2 (8a, μ-N∩N = 4,4′-bipyridine, bpy; 8b, μ-N∩N = C5H4N-CHN-NCH-C5H4N; 8c, μ-N∩N = C5H4N-CHCH-C6H4-CHCH-C5H4N; 8d, μ-N∩N = C5H4N-CHN-C6H4-NCH-C5H4N) were synthesized by the reaction of trans-[(Me(O)CS-4-C6H4-C6H4)(Ph3P)2Pd](OTf) (6) with 0.5 equivalents of N∩N (7a, N∩N = bpy; 7b, N∩N = C5H4N-CHN-NCH-C5H4N; 7c, N∩N = C5H4N-CHCH-C6H4-CHCH-C5H4N; 7d, N∩N = C5H4N-CHN-C6H4-NCH-C5H4N) in high yield. Complex 6 was accessible by the subsequent reaction of I-4-C6H4-C6H4-4′-SC(O)Me (2) with [(PPh3)4Pd] (3) to produce trans-[(I)(Me(O)CS-4-C6H4-C6H4)(Ph3P)2Pd] (4) which further reacted with AgOTf (5) to give 6.The structures of 4 and 8c in the solid state are reported. Most characteristic for these systems is the square-planer coordination geometry of palladium with trans-positioned PPh3 groups. This automatically positions the iodo ligand and the Me(O)CS-4-C6H4-C6H4 unit (complex 4) or the nitrogen donor atoms of the C5H4N-CHCH-C6H4-CHCH-C5H4N connectivity and the thio-acetyl group Me(O)CS-C6H4-C6H4 (complex 8c) trans to each other. In 8c a Pd–Pd separation of 20.156 Å is typical.The electrochemical redox behavior of 2, 4 and 8 is discussed.

The synthesis of trans-[(MeC(O)S-4-C6H4C6H4)(Ph3P)2Pd](X) (X = I, OTf) is discussed. Treatment of trans-[(C6H4C6H4-4-I)(Ph3P)2Pd](OTf) with the bidentate Lewis-bases N∩N (N∩N = 4,4′-bipyridine, C5H4N-CHN-NCH-C5H4N, C5H4N-CHCH-C6H4-CHCH-C5H4N, C5H4N-CHN-C6H4-NCH-C5H4N) in the ratio of 2:1 produced linear homobimetallic [{trans-(MeC(O)S-4-C6H4C6H4)(Ph3P)2Pd}2(μ-N∩N)](OTf)2. The electrochemical and molecular solid state behavior of these molecules is reported.Figure optionsDownload as PowerPoint slide