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Supplementary Material Available: Bond lengths (Table IV); valence angles (Table V); dihedral angles (Table VI) of 13, 14, and 8, including corresponding values calculated by the MM2 method for 6, 7, and 8; standard deviations of the calculated structural parameters of 6, 7, and 8 from the observed values (Table VII); listings of final atomic coordinates of 13,14, and 8 (Table VIII); thermal parameters (Tables IX and X) (l7 pages).Ordering information is given on any current masterhead page.