Scandium alkoxides: the first mixed-ligand alkoxides containing the [M5O(OR)(8)] core, scandium alkoxoaluminates

The electrochemical synthesis of Sc(OMe)(3) (1), Sc(OEt)(3) (2) and Sc5O(OP ri)(13) (3) was carried out via anodic oxidation of scandium metal in aliph atic alcohols. X-ray single crystal study showed 3 to be analogous to the k nown isopropoxides of Y, Er, Yb and In. The interaction of 3 with excess RO H (R=Me, Er, Bu-n, Bu-s, Bu-t) gives non-volatile amorphous 1, 2 and Sc(OBu n), (4), and volatile Sc5O(OBus)(13) (5) and Sc5O(OPri)(8)(OBut)(5) (6). Ox oalkoxides Sc5O(OPri)(8)(OR)(5) (R = Bu-n 7, Me 8) were obtained on reactio n of 3 with n-ROH in 1:5 ratio. The mass spectral study shows 5 is an indiv idual compound, whereas 6-8 in the gas phase consist of a number of aggrega tes with different extents of substitution for OPri groups, Sc5O(OR)(n)(OPr i)(13-n): for R=Bu-t n less than or equal to 5, for R = Bu-n n less than or equal to 8, and forR=Me n less than or equal to 12. The maximal intensity in the spectrum of 6 is observed for Sc5O(OPri)(10)(OBut)(2)(+), and in the spectra of 7 and 8 for Sc5O(OPri)(12-n)(OBun)(n)(+), n=4, 5, and Sc5O(OPri )(9)(OMe)(3)(+) respectively. The presence of the Sc5O(OMe)(12)(+) ion in t he spectrum of 8 indicates the possibility of replacing all the OPri in the pentanuclear core and demonstrates the existence of a 'volatile scandium m ethoxide' in the gas phase. Study of the complex formation of Sc(OR), with AI(OR), has shown that 2 and 4 form volatile Sc[Al(OR)(4)](3), R=Et 9, Bu-n 10, while 3 does not react under these conditions. Sc[Al(OPri)(4)](3) (11) can be obtained only on exchange reaction of ScCl3 with KAl(OPri)(4). The results obtained indicate rather high stability of the [Sc5O(OR)(8)] core f or primary and secondary R. (C) 2000 Elsevier Science Ltd All rights reserv ed.