METALLACARBORANE COMPLEXES AS GUEST FOR CYCLODEXTRINS - MOLECULAR-STRUCTURE OF THE INCLUSION COMPLEX CS[CLOSO-3,3,3-(CO)3-3,1,2-REC2B9H11.ALPHA-CD].8H2O

Inclusion complexes of the metallacarboranes Cs[closo-3,3,3-(CO)3-3,1,2,-MC2B9H11] (M = Mn, Re) with alpha- and beta-cyclodextrin have been prepared in aqueous solution to yield Cs[closo-3,3,3-(CO)3-3,1,2-MC2B9H113.alpha-CD] [M = Mn (1a), M = Re (2a)] and Cs(closo-3,3,3-(CO)3-3,1,2-MC2B9H11.beta-CD] [M = Mn (1b), M = Re (2b)]. The binding constants of these inclusion complexes have been determined by NMR studies. Very strong binding was observed in aqueous solution with beta-cyclodextrin as host, and the binding constants obtained for 1b and 2b were 1080 (+/- 150) and 942 (+/- 73) M-1, respectively, in D2O/DMSO-d6 (50:50 volume ratios). The single-crystal X-ray diffraction study of 2a.8H2O is reported. Crystal data for 2a.8H2O: C41H71B9CsReO33 + 8H2O, orthorhombic, P2(1)2(1)2(1), a = 13.705 (1) angstrom, b = 20.280 (2) angstrom, c = 23.384 (2) angstrom, V = 6499 angstrom-3, Z = 4, D(calcd) = 1.689 g cm-3, T = 188 K, lambda = 0.709 26 angstrom, crystal size 0.4 x 0.3 x 0.1 mm, mu = 25.29 cm-1. Of the 6432 unique reflections measured, in the range theta < 28-degrees, 3960 were considered observed (I > 3-sigma(I)). The final R factor was R = 0.075, R(w) = 0.085.