Pseudohalogeno Complexes of Sterically Hindered Tripyrrinatopalladium (TrpyPd) Fragments

Abstract

AbstractEight new pseudohalogeno complexes of sterically hindered TrpyPd fragments 4–11 have been prepared by salt metathesis in one step from known trifluoroacetates TrpyPdOAcF 1–3, using sodium salts of N3, NCO, NCS, NCSe, dicyanamide (dca) and tricyanomethanide (tcm) anions. Despite the propensity of the co‐ligands to bind to two or more metal centres in a bridging coordination mode all new complexes have been shown by NMR spectroscopy to be essentially monomeric in solution. X‐ray diffraction studies performed on TrpyPdNCS(6), TrpyPddca(8), TrpyPddca(9), and TrpyPdtcm(10) revealed the presence of two different conformers in the solid state, one with a helically distorted Trpy backbone for 6 and 10, and one with an almost planar tripyrrole but a tetrahedral distortion of the PdII coordination, a so‐called pseudoplanar form, for 8 and 9. Interestingly the helical forms are also detected by unusual wavenumbers for the νCN stretching bands in their IR spectra. The reason for the occurrence of two different conformers in the solid state appears to be the crystal packing which depends mainly on the shape of the anionic co‐ligand and on the presense of alkyl groups on the TrpyPd fragment.