Unsaturated hetero chains, VIII - First metal complexes of oligonitrile ligands: Palladium(II) complexes of N-methoxycarbonyl- and N-thiobenzoyl-1,3,5,7-tetraazaoctatetraenes

Two mononuclear six-membered chelate PdCl2 complexes 2a, b of the two diffe rent types of tetrameric oligonitriles la, b have been synthesized. Both co ntain square-planar palladium(II) with a cis arrangement of the chloride at oms. In complex 2a of the omega-amino-substituted N-methoxycarbonyl oligoni trile la the metal center is coordinated by the nitrogen atoms N1 and N3. W ithin the chelate ring alternating bond lengths for the C-N bonds are obser ved, whereas the noncomplexed, more flattened part of the oligonitrile chai n shows almost equal C-N bond lengths, indicating strong donor-acceptor int eractions involving the terminal amino group and the N3-Pd moiety of the mo lecule. The complex 2b is derived from the thiobenzoyl ligand 1b bearing a terminal (R)-fenchylidene group. In 2b the sulfur atom S1 and the nitrogen atom N2 are involved in complexation. In contrast to 2a, strong bond-length alternation is observed in 2b for the complexed and the non-complexed part of the Ligand. From the NMR spectra of both complexes no indication for a migration of the PdCl2 unit along the chain could be derived.