Octakis perchlorate

A number of methyl substituted PyO have been tried as ligands for coordination with the lanthanides. Depending on the position of the substituent, these ligands impart different degrees of steric strain for the formation of complexes. Since substituents in the 4 or 3 position do not introduce substantial steric hindrance to coordination, Harrison and Watson (160) could synthesize octakis-4-MePyO complexes. Subsequently, Koppikar and Soundararajan (161) could also synthesize octakis-3-MePyO complexes with lanthanide perchlorates. Complexes of 4-MePyO (162, 163) and 3-MePyO (164, 165) with lanthanide iodides and bromides also have a L M of 8 1. 

The complex octakis (pyridine-IV-oxide)La(III) perchlorate is an example involving eight unidentate ligands giving rise to a square antiprismatic structure with almost perfect D4 symmetry. Detailed coordinations suggest that the complex is distorted toward the cube. The molecular structure of [La(PyNO)8] is shown in Fig. 5.21. 

CftoHftoCl3LaN802o f Octakis(pyridine-N-oxide)lanthanum perchlorate (form i), 45B, 1225... 

CftoH8oClftC0202 6 f /i Bis(2(1H)-tetrahydropyrimidinone)-octakis(2(1H)-tetrahydropyrimidinone)dicobalt(II) perchlorate, 38B, 964 Cft oHg ftCrLiOg, Lithium tetrakis[bis(t-butyl)methoxo]chromate(III) tetrahydrofuran, 46B, 1161... 

The complex ion in octakis(pyridine-N-oxide)lanthanum(III) perchlorate (Al-Karaghouli and Wood, 1972a) is one of the very few examples of an eight-coordinate complex formed with monodentate ligands for which structural information is available. The complex ion is square antiprismatic and has almost perfect D4 symmetry. Consideration of the detailed coordination polyhedron suggests strongly that the ion is distorted toward the cube. 

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