Distortions from trigonal prismatic geometry for several structurally characterized clathrochelate complexes: significance of π-backbonding on clathrochelate coordination geometry

• Published in: Inorganica Chimica Acta 1996-01, Vol.241 (2), p.21-30
• Main Authors: Kubow, Stephen A., Takeuchi, Kenneth J., Grzybowski, Joseph J., Jircitano, Alan J., Goedken, Virgil L.
• Format: Article
• Language: English
• Subjects: Clathrochelate complexes; Cobalt complexes; Crystal structures; Iron complexes; Ruthenium complexes
• ISSN: 0020-1693; 1873-3255
• DOI: 10.1016/0020-1693(95)04720-4

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-cyclohexanedione dioximato (C 6H 8N 2O 2); n-Bu = n-butyl) are presented. The data display an unexpected trend in distortion from trigonal prismatic geometry (Co(7.0°) < Ru(12.0°) < Fe(20.3°)), which is different from that predicted by ligand field stabilization energy (LFSE) factors (Co < Fe < Ru). It appears that LFSE considerations in combination with π-backbonding effects are necessary to interpret the ϕ values of the three complexes, where the unusually small distortion for the ruthenium complex is a result of strong π-backbonding, evidenced by the unusually short RuN av distance (1.972(4) Å). Crystal data: all three compounds are monoclinic, space group C2/ c. Compound CoC 26H 42B 2N 6O 6 : a = 22.878(6), b = 15.026(2), c = 18.047(6) A ̊ , β = 109.95(2)°, V = 5831.6(5) A ̊ 3, Z = 8, R = 5.9, N obs = 3346 . Compound FeC 26H 42B 2N 6O 6 : a = 23.046(3), b = 14.920(2), c = 18.064(4) A ̊ , β = 107.87(2)°, V = 5911.6(5) A ̊ 3, Z = 8, R = 5.4, N obs = 4687 . Compound RuC 26H 42B 2N 6O 6 : a = 22.966(5), b = 14.951(2), c = 18.125(6) A ̊ , β = 107.39(2)°, V = 5942(6) A ̊ 3, Z = 8, R = 4.4, N obs = 4493 .