Binding of isocyanides to five-coordinate, durene-capped hemes

Abstract

This paper is dedicated to Professor Do~iglas E. Ryan on the occasiorl of his 65th birthday SHANTHA DAVID, BRIAN R. JAMES, and DAVID DOLPHIN. Can. J. Chem. 65, 1098Chem. 65, (1987. Solution data at 20°C are presented for the binding of t-butylisocyanide and tosylmethylisocyanide (TMIC) to the five-coordinate hemes Fe(porp)(CyzIm), where CyrIm = 1,5-dicyclohexylimidazole and porp = the dianion of some durene-capped porphyrins with variable length linking methylene straps on either side of the durene moiety (4/4, 515, or 7/7 methylenes). The 'BuNC and TMIC ligands are used to probe the steric nature of the distal binding site under the cap, in particular the respective "central" and "peripheral" effects as defined by Traylor et al. The binding constants range from 1.1 X 10' M-' for the 7/7-TMIC system to immeasurably small for the 4/4-'BuNC system, this range spanning data reported in the literature for related anthracene-and adamantane-capped systems.SHANTHA DAVID, BRIAN R. JAMES et DAVID DOLPHIN. Can. J. Chem. 65, 1098 (1987). On rapporte des donnkes relatives 2 la complexation des isocyanures de tert-butyle et de tosylmCthyle (ICTM) avec des hkmes penta-coordonnCes Fe(porp)(CyrIm) dans lesquels CyzIm = dicyclohexyl-1,5 imidazole et porp = le dianion de porphyrines acappCes~ par un durene rattach6 par des unitis mCthylCniques de longueurs variables (4/4, 5/5 ou 717 mkthylenes). On a utilisC les ligands tert-BuNC et ICTS comme sondes pour la nature stCrique du site de complexation <<distal,, et en particulier pour les effets res ectifs <<centrals et <<pCriphkraln dCf nis par Traylor et ses collaborateurs. Les constantes de complexation