R(6)TT'(2), new variants of the Fe(2)P structure type. Sc(6)TTe(2) (T = Ru, Os, Rh, Ir), Lu(6)MoSb(2), and the anti-typic Sc(6)Te(0.80)Bi(1.68).
The Fe(2)P structure (P62m) features two 3-fold Fe positions and both 2-fold and 1-fold P sites, and variations in occupancies of the latter pair yield the reported diversity of results. The known Sc(6)TTe(2) examples for T = Fe-Ni are herein extended to four heavier transition metal T derivatives. An attempt to synthesize bismuth analogues led to the novel inverse derivative in which fractional Te (vice T) occupies the smaller tricapped trigonal prismatic (TTP) Sc polyhedron, and Bi rather than Te occurs in the larger TTP of Sc, with parallel reversal of polarity in the bonding. The reported Lu(8)Te, which is distributed as Lu(6)TeLu(2), is the only example in which a transition metal occupies the normal 2-fold P or Te non-metal position, with corresponding large effects on the bonding. Lutetium otherwise does not form R(6)TTe(2) analogues, but the novel Lu(6)MoSb(2) isotype occurs instead. Extended Hückel calculations are presented for five examples, and the structural and bonding regularities and varieties are discussed further.
Chen
Ling
L
Department of Chemistry, Iowa State University, Ames, Iowa 50011, USA.
Corbett
John D
JD