Synthesis and structural characterization of hydroxyethyl- and alkoxyethyl-o-carboranes and their alkali and rare earth metal complexes

Facile and practical syntheses of 1,2-(HOCH2CH2)(2)-1,2-C2B10H10 (1), its derivatives 1,2-(ROCH2CH2)(2)-1,2-C2B10H10 (R = CH3 (2), CH2Ph (4)), and 1-(CH3OCH2CH2)-1,2-C2B10H11 (3) were reported. Treatment of 1 with excess K metal in THF gave, after fractional crystallization from acetone containing 18-crown-6 ether, two complexes, [{nido-(HOCH2CH2)(OCH2CH2)C2B10H10}{K(18-crown-6)}](n) (5) and [{nido-(HOCH2CH2)(2)C2B9H10}{K(18-crown-6)}](n) (6) in a molar ratio of 1:2. Reaction of 2 with MeOK in methanol afforded, after treatment with Me3NHCl, [Me3NH] [nido-(CH3OCH2CH2)(2)C2B9H10] (7). 2 reacted with excess Na metal in THF to yield [{eta(6)-[(CH3OCH2CH2)(2)C2B10H10]Na}{Na(THF)}](n) (8). Interactions of 2 with LnCl(3) in the presence of excess Li or Na metal gave, after recrystallization from a mixture of different solvents, half-sandwich 13-vertex closo-metallacarboranes [{eta(7)-[(CH3OCH2CH2)(2)C2B10H10]Er}{Na(CH3CN)(2)}](2) (9) and [{eta(7)-[(CH3OCH2CH2)(2)C2B10H10]Y}{Li(THF)(3)}](2) (10). Complexes [[{[eta(7)-(CH3OCH2CH2)C2B10H11]Er(THF)}{Na(CH3CN)(THF)}](2)](n) (11) and [{[eta(7)-(CH3OCH2CH2)C2B10H11]Y(THF)}{Na(THF)(3)}](2) (12) were prepared in a similar manner from the monosubstituted o-carborane 3, LnCl(3), and excess Na in THF. These complexes were characterized by various spectroscopic data, elemental analyses, and X-ray diffraction studies. Structural studies show that the Lewis base-functionalized sidearms have some effects on the coordination environments of the central metal atom through intramolecular interactions between the donor atoms of the sidearms and Lewis acidic metal ions, but do not change the gross structures of the 13-vertex lanthanacarboranes.