Rare Neutral Diphosphine Complexes of Scandium(III) and Yttrium(III) Halides

Reaction of Me2PCH2CH2PMe2 or o-C6H4(PMe2)2 (L–L)
with a suspension of ScI3 or YI3 in MeCN solution
under rigorously anhydrous and oxygen-free conditions produced the
highly unusual complexes [ScI3(L–L)2],
[YI3(Me2PCH2CH2PMe2)2], and [YI3{o-C6H4(PMe2)2}2MeCN].
X-ray crystal structures reveal that the scandium complexes adopt
seven-coordinate, pentagonal-bipyramidal geometries with chelating
diphosphines, while the eight-coordinate [YI3{o-C6H4(PMe2)2}2MeCN] is dodecahedral. The complexes were characterized by microanalysis
and IR and multinuclear NMR spectroscopy. Solid-state NMR data (45Sc, 89Y, 31P) and variable-temperature
solution NMR data (1H, 31P­{1H}, 45Sc) are presented and compared, leading to the conclusion
that the same species are present in both the solid state and CH2Cl2 solution. Attempts to prepare complexes with
other scandium halides and with aryl diphosphines and o-C6H4(AsMe2)2 are briefly
described.