STRUCTURAL DETERMINATION AND ANALYSIS OF SOME NEW SCHIFF BASE AND TRIANGULO-TRIRUTHENIUM COMPOUNDS
| Presenter | : | YEAP CHIN SING |
| : | - | |
| Date | : | 28 / 10 / 2010 |
| Time | : | 3.00 PM |
| Venue | : | APPLIED PHYSICS LAB ( ROOM 249 ), SCHOOL OF PHYSICS |
| Sypnosis | : | X-ray diffraction technique is a very powerful and useful method to determine the accurate 3D structure of chemical compounds. It is very important to determine the structure of the compound for further development or studies onto the related fields. Schiff base and triangulo-triruthenium compounds were studied in this research. Schiff base compounds are interesting compounds due to their ease of synthesis and have a wide-range of applications. On the other hand, the triangulo-triruthenium clusters have wide-range variety of substitution such as mono-, bis-, and tri-substitute with group 15 ligands and they are also known for their interesting structural variations and related catalytic activity. Eight Schiff base compounds were studied in this research. They crystallized out in the common space groups, i.e. four compounds are in monoclinic C2/c, and one each in monoclinic Cc, P21 and Pn and triclinic . One Schiff base compound exists in a zwitterion form. The structures of two Schiff base compounds are disordered. One Schiff base compound is a racemic twin crystal. Water solvents exist in the asymmetric unit of two Schiff base compounds. The Schiff base compounds all exist in an E configuration with respect to the N=C. The average N=C double bond value is 1.282 Å. Eighteen triangulo-triruthenium complexes were studied in this research. All of them crystallized out in the common space group, i.e. seven compounds are in triclinic , another seven in monoclinic P21/c, two in monoclinic C2/c, and one each in orthorhombic Pbca and Pca21. The triangulo-triruthenium complex structures in four compounds are disordered. The asymmetric unit of eight compounds contains solvent molecules, e.g. water, dichloromethane or chloroform. All solvent molecules are disordered except for one of them. One triangulo-triruthenium compound is a racemic twin crystal and one triangulo-triruthenium compound is a pseudomerohedral twin crystal. In all triangulo-triruthenium complexes, the group 15 ligands occupy the equatorial position due to steric reaction. The effect of substitution results in significant differences in Ru—Ru bond lengths and carbonyl ligands bond lengths and angles. The average three Ru—Ru bond lengths are 2.840 Å, 2.860 Å and 2.878 Å. The axial Ru—C bonds are longer than the equatorial Ru—C bonds. The average axial Ru—C bond lengths is 1.931 Å and the average equatorial Ru—C bond lengths is 1.892 Å. The bond length of equatorial Ru—C when connected to the same Ru atom with the monodantate ligand is the shortest bond in most of the molecules. The average of these Ru—C bonds is 1.882 Å. The equatorial Ru—C—O angles are close to linear whereas the axial Ru—C—O angles are slightly bent. The average equatorial Ru—C—O angles is 177.1° and the axial Ru—C—O angles is 173.4°. Comparison between mono- and bis-substituted triangulo-triruthenium compounds and mono- and tri-substituted triangulo-triruthenium compounds showed that the substituted benzene rings are twisted as their dihedral angles differ when one/two ligand/ligands is/are coordinated to the other Ru atom/atoms. In addition, the carbonyl ligands are also coordinated at different angles. |
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