Steric effects in pyrrole-based mixed complex systems

✍ Scribed by B.S. Raghavendra; S. Gupta; R.H. Balundgi; A. Chakravorty

• Book ID: 104138269
• Publisher: Elsevier Science
• Year: 1976
• Tongue: English
• Weight: 418 KB
• Volume: 18
• Category: Article
• ISSN: 0020-1693
• DOI: 10.1016/s0020-1693(00)95614-7

✦ Synopsis

New systems of the type M(pyrenNRz)Br, M(pyrtn NRJBr (M = Cu, Ni), M(pyr)(pyrenNR,) (M = CM, Ni), Cu(pyr)(pyrtnNR,) (where Hpyr is pyrrole-2aldehyde, pyrenNR, is Schiff base of pyr and NR,CH, CH2NH, andpyrtnNR, is Schiff base ofpyr and NR2CH2 CH2CH2NH2) are reported. The first two systems are shown to have planar geometry in which pyrenNR, and pyrtnNR, act as tridentate ligands. On the basis of magnetic, spectral and X-ray powder diffraction studies on pure crystals and on solid solutions of nickel(II) and copper(H) species, it is concluded that M(pyr)(pyren NR,) has a I-coordinate grossly planar geometry in which the NR2 group of pyrenNR, fails to occupy a coordination position due to steric reasons. Models demonstrate that this steric difficulty should considerably decrease on replacement of pyrenNR, by pyrtnNR,.

Indeed the species Cu(pyr)(pyrtnNRJ have electronic spectra strongly suggestive of pentacoordination.