Platinum-indium polyanions in the structures of LaPtIn4 and LnPtIn(3) (Ln = La, Ce, Pr, Nd, Sm) and structure refinement of Ce2Pt2In

The title compounds were prepared by reacting the elements in an are-meltin g furnace and subsequent annealing. The LaRuSn3 type structure of the new c ompounds LnPtIn(3) (Ln = La, Ce, Pr, Nd, Sm) was refined from single crysta l X-ray data for LaPtIn3: Pm3n, a = 980.4(2)pm, wR2 = 0.0271, 399 F-2 value s, 15 variables. Striking structural motifs of LaPtIn3 are condensed distor ted trigonal [PtIn6] prisms with Pt-In distances of 269 pm. The lanthanum a toms occupy large cavities within the polyhedral network. Besides Pt-In bon ding In-In bonding also plays an important role in LaPtIn3 with In-In dista nces of 299 and 327 pm. The La1 position is occupied only to 91%, resulting in a composition La-0.98(1)PtIn3. The La1 atoms show an extremely large di splacement parameter indicating a rattling of these atoms in the In-12 cage s. The so far most indium rich compound in the ternary system lanthanum-pla tinum-indium is LaPtIn4 which was characterized on the basis of Guinier pow der data: YNiAl4-type, Cmcm, a = 455.1(2) pm, b = 1687.5(5) pm, and c = 738 .3(2) pm. The platinum atoms in LaPtIn4 center trigonal prisms with the com position [La2In4]. Together with the indium atoms the platinum atoms form a complex three-dimensional [PtIn4] polyanion in which the lanthanum atoms o ccupy large hexagonal tubes. The structure of Ce2Pt2In is confirmed: Mo2FeB 2-type, P4/mbm, a = 779.8(1) pm, c = 388.5(1) pm, wR2 = 0.0466, 433 F-2 val ues, 12 parameters. It is built up from CsCl and AlB2 related slabs with th e compositions CeIn and CePt2, respectively. Chemical bonding in the [PtIn3 ] and [PtIn4] polyanions of LaPtIn3 and LaPtIn4 is discussed.