Linear homobimetallic palladium complexes Heinrich Lang a, * , Deeb Taher a , Bernhard Walfort a , Hans Pritzkow b a Technische Universita ¨ t Chemnitz, Fakulta ¨t fu ¨ r Naturwissenschaften, Institut fu ¨ r Chemie, Lehrstuhl Anorganische Chemie, Straße der Nationen 62, 09111 Chemnitz, Germany b Anorganisch-chemisches Institut, Ruprecht-Karls-Universita ¨ t Heidelberg, Im Neuenheimer Feld 270, 69120 Heidelberg, Germany Received 7 April 2006; received in revised form 10 May 2006; accepted 16 May 2006 Available online 3 June 2006 Abstract The oxidative addition of C 6 H 4 -1,4-I 2 (1) to Pd(PPh 3 ) 4 (2) gives mononuclear trans-(Ph 3 P) 2 Pd(C 6 H 4 -4-I)(I) (3), which can be con- verted to trans-(Ph 3 P) 2 Pd(C 6 H 4 -4-I)(OTf) (5) by its reaction with [AgOTf] (4). Complex 5 can be used in the high-yield preparation of a series of unique cationic mono- and dinuclear palladium complexes of structural type [trans-(Ph 3 P) 2 Pd(C 6 H 4 -4-I)(L)] + (7, L=C 4 H 4 N 2 ; 9a, L=C 5 H 4 N-4-C„N; 9b, L=N„C-4-C 5 H 4 N) and [trans-(C 6 H 4 -4-I)(Ph 3 P) 2 Pd  N \ N ! Pd(PPh 3 ) 2 (C 6 H 4 -4-I)] 2+ (14a,N \ N=C 6 H 4 -1,4-(C„N) 2 ; 14b,N \ N = (C 6 H 4 -4-C„N) 2 ; 14c,N \ N = 4,4 0 -bipyridine (=bipy)). Complexes 7, 9 and 14 rearrange in solution to give [trans-(Ph 3 P) 2 Pd(C 6 H 4 -4-PPh 3 )(L)] 2+ (10,L=C 4 H 4 N 2 ; 12a,L=C 5 H 4 N-4-C„N; 12b,L=N„C-4-C 5 H 4 N) and [trans-(C 6 H 4 -4-PPh 3 )(Ph 3 P) 2 Pd  N \ N ! Pd(PPh 3 ) 2 (C 6 H 4 -4-PPh 3 )] 4+ (15a,N \ N=C 6 H 4 -1,4-(C„N) 2 ; 15b,N \ N = (C 6 H 4 -4-C„N) 2 ) along with {[(Ph 3 P) 2 (Ph 3 P-4-C 6 H 4 )Pd(l-I)] 2 } 2+ (11). The solid state structures of 3, 9a, 10, 11 and 15b are reported. Most characteristic for all complexes is the square-planar coordination geometry of palladium with trans-positioned PPh 3 ligands. In 3 the iodide and the 4-iodo-benzene are linear oriented laying with the palladium atom on a crystallographic C 2 axes. In 9a this symmetry is broken by steric interactions of the PPh 3 ligands with the 4-cyano- pyridine and 4-iodobenzene groups. Compound 11 contains two l-bridging iodides with different Pd–I separations showing that the C 6 H 4 PPh þ 3 ligand induces a stronger trans-influence than PPh 3 . In 15b, the Ph 3 PC 6 H 4 APd  N„CAC 6 H 4 AC 6 H 4 AC„N ! PdAC 6 H 4 PPh 3 building block is rigid-rod structured with the C 6 H 4 units perpendicular oriented to the Pd coordination plane, while the biphenylene connecting moiety is in-plane bound. Ó 2006 Elsevier B.V. All rights reserved. Keywords: Palladium; Homobimetallic; Lewis-bases; 1-Dimensional complexes; X-ray structure 1. Introduction There is a wide interest in the synthesis of one-dimen- sional molecules [1], because they possess considerable attention in, for example, the developing field of molecular electronics [2]. The ability of molecular wires is to transport in a very efficient way electrons through the wire between two redox-active fragments [3]. The properties of such complexes depend on the nature of the redox termini and the p-conjugated linking units [4]. The use of redox-active organometallic building blocks assembled with all-carbon chains [5], or hetero atom consisting units [6], offer a fasci- nating perspective for the design of nanoscopic molecular devices. However, it appeared that, when the chain length of the bridging unit is increased, the synthesis of the com- pounds becomes more difficult and the stability of the com- pounds decreases [6]. Out of this reason, we decided to systematically study homobimetallic late-transition metal complexes in which the organometallic fragments are bridged by p-conjugated nitrogen-containing Lewis-bases of different length [6,7]. This would enable us to prepare in a straightforward manner linear transition metal complexes. 0022-328X/$ - see front matter Ó 2006 Elsevier B.V. All rights reserved. doi:10.1016/j.jorganchem.2006.05.034 * Corresponding author. Tel.: +49 371 531 1673; fax: +49 371 531 1833. E-mail address: heinrich.lang@chemie.tu-chemnitz.de (H. Lang). www.elsevier.com/locate/jorganchem Journal of Organometallic Chemistry 691 (2006) 3834–3845