DISTORTIONS FROM TRIGONAL PRISMATIC GEOMETRY FOR SEVERAL STRUCTURALLYCHARACTERIZED CLATHROCHELATE COMPLEXES - SIGNIFICANCE OF PI-BACKBONDING ON CLATHROCHELATE COORDINATION GEOMETRY
Sa. Kubow et al., DISTORTIONS FROM TRIGONAL PRISMATIC GEOMETRY FOR SEVERAL STRUCTURALLYCHARACTERIZED CLATHROCHELATE COMPLEXES - SIGNIFICANCE OF PI-BACKBONDING ON CLATHROCHELATE COORDINATION GEOMETRY, Inorganica Chimica Acta, 241(2), 1996, pp. 21-30
The crystallographic data for several clathrochelate complexes of the
form [M(NOX)(3)(B-n-Bu)(2)] (where M = Co, Fe, Ru; NOX = 1,2- cyclohex
anedione dioximato (C6H8N2O2); n-Bu = n-butyl) are presented, The data
display an unexpected trend in distortion from trigonal prismatic geo
metry (Co(7.0 degrees) < Ru(12.0 degrees) < Fe(20.3 degrees)), which i
s different from that predicted by ligand field stabilization energy (
LFSE) factors (Co < Fe < Ru). It appears that LFSE considerations in c
ombination with pi-backbonding effects are necessary to interpret the
theta values of the three complexes, where the unusually small distort
ion for the ruthenium complex is a result of strong pi-backbonding, ev
idenced by the unusually short Ru-N-av distance (1.972(4) Angstrom). C
rystal data: all three compounds are monoclinic, space group C2/c. Com
pound CoC26H42B2N6O6: a = 22.878(6), b = 15.026(2), c = 18.047(6) Angs
trom, beta = 109.95(2)degrees, V = 5831.6(5) Angstrom(3), Z = 8, R = 5
.9, N-obs = 3346. Compound FeC26H42B2N6O6: a = 23.046(3), b = 14.920(2
), c = 18.064(4) Angstrom, beta = 107.87(2)degrees, V = 5911.6(5) Angs
trom(3), Z = 8, R = 5.4, N-obs = 4687. Compound RuC26H42B2N6O6: a = 22
.966(5), b = 14.951(2), c = 18.125(6) Angstrom, beta = 107.39(2)degree
s, V = 5942(6) Angstrom(3), Z = 8, R = 4.4, N-obs = 4493.