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

Abstract The electrochemical synthesis of Sc(OMe) 3 ( 1 ), Sc(OEt) 3 ( 2 ) and Sc 5 O(OPr i ) 13 ( 3 ) was carried out via anodic oxidation of scandium metal in aliphatic alcohols. X-ray single crystal study showed 3 to be analogous to the known isopropoxides of Y, Er, Yb and In. The interaction of 3 with excess ROH (R=Me, Et, Bu n , Bu s , Bu t ) gives non-volatile amorphous 1 , 2 and Sc(OBu n ) 3 ( 4 ), and volatile Sc 5 O(OBu s ) 13 ( 5 ) and Sc 5 O(OPr i ) 8 (OBu t ) 5 ( 6 ). Oxoalkoxides Sc 5 O(OPr i ) 8 (OR) 5 (R=Bu n 7 , Me 8 ) were obtained on reaction of 3 with n-ROH in 1:5 ratio. The mass spectral study shows 5 is an individual compound, whereas 6 – 8 in the gas phase consist of a number of aggregates with different extents of substitution for OPr i groups, Sc 5 O(OR) n (OPr i ) 13− n : for R=Bu t n ≤5, for R=Bu n n ≤8, and for R=Me n ≤12. The maximal intensity in the spectrum of 6 is observed for Sc 5 O(OPr i ) 10 (OBu t ) 2 + , and in the spectra of 7 and 8 for Sc 5 O(OPr i ) 12− n (OBu n ) n + , n =4, 5, and Sc 5 O(OPr i ) 9 (OMe) 3 + respectively. The presence of the Sc 5 O(OMe) 12 + ion in the spectrum of 8 indicates the possibility of replacing all the OPr i in the pentanuclear core and demonstrates the existence of a ‘volatile scandium methoxide’ in the gas phase. Study of the complex formation of Sc(OR) 3 with Al(OR) 3 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(OPr i ) 4 ] 3 ( 11 ) can be obtained only on exchange reaction of ScCl 3 with KAl(OPr i ) 4 . The results obtained indicate rather high stability of the [Sc 5 O(OR) 8 ] core for primary and secondary R.