Rigid-rod structured palladium complexes

Mononuclear and homobimetallic palladium complexes of structural type [trans-(Me(O)CS-4-C6H4)(Ph3P)2Pd(N∩N)]OTf (8a, N∩Ndouble bond; length as m-dashC4H4N2; 8b, N∩Ndouble bond; length as m-dashC5H4N-4-Ctriple bond; length of mdashN) and {[trans-(Me(O)CS-4-C6H4)(Ph3P)2Pd]2N∩N}(OTf)2 (9a, N∩N = 4,4′-bipyridine (=bipy); 9b, N∩N = C6H4-1,4-(Ctriple bond; length of mdashN)2; 9c, N∩N = (C6H4-4-Ctriple bond; length of mdashN)2) are accessible by the reaction of trans-(Ph3P)2Pd(C6H4-4-SC(O)Me)(OTf) (6) with 1 or 0.5 equivalents of the Lewis-bases N∩N (7a, N∩N = C4H4N2; 7b, N∩N = C5H4N-4-Ctriple bond; length of mdashN; 7c, N∩N = bipy; 7d, N∩N = C6H4-1,4-(Ctriple bond; length of mdashN)2; 7e, N∩N = (C6H4-4-Ctriple bond; length of mdashN)2) in high yield. Complex 6 can be prepared in a two-step synthesis procedure. Oxidative addition of I-1-C6H4-4-SC(O)Me (2) to Pd(PPh3)4 (3) gives trans-(Ph3P)2Pd(C6H4-4-SC(O)Me)(I) (4), which further reacts with [AgOTf] (5) to afford 6. The formation of 8 and 9 strongly depends on the size of the Lewis-bases N∩N. It is obvious that the co-ordination of the second N-ligated site of 8a or 8b to a further bulky[(PPh3)2Pd(C6H4-4-SC(O)Me)]+ unit is not possible. In contrast, more extended N∩N species such as 7c–7e will result in the formation of linear structured homobimetallic 9a–9c. The solid-state structures of 4 and 4 · CH2Cl2 are reported. Complex 4 is packed in the orthorhombic space group Pbca . The assembly of dichloromethane into the crystal lattice breaks the symmetry, whereby 4 · CH2Cl2 crystallises in the triclinic space group View the MathML sourceP1¯. In both modifications a square-planar palladium(II) ion is present, with the iodo atom and the Me(O)CS-C6H4 unit trans-positioned. The different crystal packing has no significant influence onto the geometry around the d8-configurated palladium atoms.