Additive Character of Electron Donation by Methyl Substituents within a Complete Series of Polymethylated [1-(eta(6)-MenC6H6-n)-closo-1,2,3-FeC2B9H11] Complexes. Linear Correlations of the NMR Parameters and Fe-II/III Redox Potentials with the Number of Arene Methyls
Abstract
A systematic method for the incorporation of the {(eta(6)-Me(n)C(6)H(6-n))Fe} fragment into the dicarbollide cage was developed based on reactions between [(eta(6)-Me(n)C(6)H(6-n),)(2)Fe][PF(6)](2) salts (1) and Tl(2)[nido-7,8-C(2)B(9)H(11)]. These reactions proceed with elimination of one arene ligand to generate a complete series of the neutral [1-(eta(6)-Me(n)C(6)H(6-n))-closo-1,2,3-FeC(2)B(9)H(11)] (2) complexes with n=1-6 in yields ranging 15 70% depending on the arene.
Correlations between selected and (11)B NMR parameters and the Fe(II/III) redox potentials and the number of arene methyls for complexes 2 are linear. These facts establish direct evidence for a strictly additive character of electron donation by the methyl substituents to the arene ring and further to the Fe center and the second (dicarbollide) ligand.