Structure, chemical bonding and properties of Sr2Rh2In3 and Sr3Ir4Sn4

New compounds Sr2Rh2In3 and Sr3Ir4Sn4 were synthesized by reacting the elem ents in glassy carbon crucibles under an argon atmosphere in a high-frequen cy furnace. X-rap diffraction of powders and single crystals yielded C2/m, mC14, a=1101.9(1) pm, b =427.18(5) pm, c= 793.01(7) pm, beta = 115.40(1)deg rees, wR2=0.0480, 708 F-2 values and 24 parameters for Sr2Rh2In3 (new struc ture-type) and 1 (4) over bar 3m, cl22, a=807.88(7), wR2=0.0236, 165 F-2 va lues and ten parameters for Sr3Ir4Sn4 (Na3Pt4Ge4-type), Common to both comp ounds is the formation of transition metal indium(tin) polyanions, [Rh2In3] and [Ir4Sn4], which extend two-dimensionally for Sr2Rh2In3 but three-dimen sionally for Sr2Ir4Sn4. According to semi-empirical band structure calculat ions the strongest bonding interactions are found For the Rh-In and Ir-Sn c ontacts. All Rh-Rh and Ir-Ir bonding and antibonding states were found to b e tilled, which is not surprising for a formal d(10)-d(10) interaction. Acc ording to magnetic susceptibility measurements Sr2Rh2In3 is a Pauli paramag net and a metallic conductor with room temperature values of -1.8x10(-9) m( 3)/mol and 415+/-20 mu Omega cm, respectively. (C) 2000 Elsevier Science Lt d. All rights reserved.