engleski

Adducts of bis(1,3-diphenyl-1,3-propanedioanto)cobalt(II) with 2,2"-bipyridine and 1,10-phenantroline. Solid state structure and EHMO calculation

The adducts of metal complexes are very suitable model system for investigation of molecular recognition and molecular association. Four-coordinated cobalt(II) complexes with various beta-diketones show pronounced tendency in increasing their coordination number from 4 to 6 by linking one or two additional molecules. The number of added molecules depends frequently on the number of ligating atoms. Molecules having one donor atom usually do not effect essentially the square-planar stereochemistry of starting Co(II) complex, and six-coordinated adduct results with added ligands in trans position to each other. One-donor atom ligands, however can lead to the conformational change if additional ligand-ligand interactions, other than simply Co-ligand, take place. Molecules possessing two favorable positioned donor atoms are of particular interest in adduct formation because they necessary give rise to the change in Co(II) square planar environment. In the reaction of bis(1,3-diphenyl-1,3-propanedionato)cobalt(II) with 2,2"-bipyridine and 1,10-phenantroline two novel compounds were prepared. The compounds were investigated by IR spectroscopy. Their thermal stability were determined by dynamic thermogravimetry and stereochemistry in the solid state by the X-ray diffraction. The EHMO calculations were performed to achieve better understanding of bonding and orbital overlaping. Both crystal structures are built up of discrete molecules attracted by van der Waals interactions only. In contrast to the compound with 1,10-phenantroline adduct with 2,2"-bipyridine crystallizes as acetone solvate. Both coordination polyhedra are severely distorted. Characteristic feature in both structures is the non-planarity of beta-diketone chelate ring caused by bulky 2,2"-bipyridine and 1,10-phenantroline.

adducts; cobalt(II) beta-diketonates; X-ray structure determination; EHMO calculation

nije evidentirano