Condensed Al-6 rings in the subiodides La3Al2I2 and La2Al2I

The subiodides La3Al2I2 and La2Al2I are reported. The compounds were prepar ed from stoichiometric mixtures of lanthanum, aluminium, and LaI3 under Ar atmosphere in sealed Ta ampoules at 920-950 degreesC and 980-1000 degreesC, respectively. La3Al2I2 crystallizes in space group C2/m with a=19.73(2) An gstrom, b=4.318(1)Angstrom, c=12.348(9)Angstrom and beta= 121.49(3)degrees, La2Al2I in p6(3)/mmc with a = 4.3718(8)Angstrom and c = 17.605(2) A (isoty pic with Gd2Fe2I). Both structures are characterized by sheets of trigonal prisms formed by th e La atoms centered by aluminium, the latter being arranged in Al-6 rings. These rings are connected to chains in La3Al2I2 (d(Al(2)-Al(2)) = 2.550(4) Angstrom and 2.615(2) Angstrom, respectively) and layers (d(Al-Al)= 2.533(1 ) Angstrom) in La2Al2I. Both compounds are metallic conductors. The electro nic structure of both compounds is discussed based on band structure calcul ations.