Cyanoscorpionates: New structural motifs for transition metal complexes and coinage metal polymers
New complexes have been synthesized of scorpionate ligands with cyano substituents in the 4-positions of the pyrazoles and tert-butyl substituents in the 3-positions of the pyrazoles. Reaction of Co²⁺,Mn²⁺, and Ni(cyclam)²⁺ (cyclam=1,4,8,11-tetraazacyclotetradecane) salts with KTpt-Bu,4CN in a 1:2 ratio produced new octahedral metal complexes of the form (Tpt-Bu,4CN)₂ML₄ (L₄=(H₂O)₄, (H₂O)₂(MeOH)₂, or cyclam). Unlike the sandwich complexes previously isolated with TpPh,4CN, the crystal structures showed none of the pyrazole nitrogen atoms coordinated to the metal. Rather, the metal is coordinated to one CN nitrogen atom from each ligand, with two Tp anions coordinated trans to each other around the metal center. This leaves the Tp pyrazole nitrogen atoms open for another metal to coordinate, which could to lead to heterometallic complexes, new coordination polymers, as well as the framework for supramolecular complexes. Attempts to insert metal ions into the pyrazole coordination pockets of these complexes have to date been unsuccessful. However, these attempts resulted in new Cu(I) and Ag(I) coordination polymers of the cyano-substituted scorpionate ligands as well as several new metal complexes of 3-tert-butyl- 4-cyanopyrazole. The newly isolated Tpt-Bu,4CNCu(I) polymer has the same structure as the one previously synthesized except for the acetonitrile which is crystallized in the lattice. This is a very good indication that there is some type of channel or pocket within the lattice which was not previously recognized. The newly isolated Tpt-Bu,4CNAg(I) polymers show various coordination motifs giving rise to different structural networks.