HEXAAMIDOSTANNATES(IV) OF THE ALKALI-METALS POTASSIUM, RUBIDIUM AND CESIUM, M(2)[SN(NH2)(6)] (M=K,RB,CS), SYNTHESIS AND CRYSTAL-STRUCTURES

Hexaamidostannates(IV) of the alkali metals potassium, rubidium and ca esium were prepared by the reaction of tetraphenyl tin with alkali ami des in an autoclave made of stainless steel at 385 K with ammonia as s olvent. Single crystals were obtained in the form of colourless, trans parent hexagonal plates. Their structures were solved by X-ray methods including all hydrogen positions for K-2[Sn(NH2)(6)] in the space gro up R (3) over bar with Z=3 (hexagonal setting), and for Rb-2[Sn(NH2)(6 )] and Cs-2[Sn(NH2)(6)] in the space group P (3) over bar with Z=1. K- 2[Sn(NH2)(6)] a = 6.337(4) Angstrom, c = 19.769(5) Angstrom, F-0(2) gr eater than or equal to 3 sigma(F-0(2)) = 869, N(var.) = 22, R/R(w) = 0 .019/0.022 Rb-2[Sn(NH2)(6)] a = 6.669(2) Angstrom, c = 5.771(1) Angstr om, F-0(2) greater than or equal to 3 sigma(F-0(2)) = 245, N(var.) = 2 3, R/R(w) = 0.022/0.029 Cs-2[Sn(NH2)(6)] a = 6.879(1) Angstrom, c = 5. 850(1) Angstrom, F-0(2) greater than or equal to 3 sigma(F-2(0)) = 734 , N(var.) = 23, R/R(w) = 0.018/0.018 Both structure types contain isol ated octahedra units [Sn(NH2)(6)](2-). Potassium is coordinated trigon al anti-prismatically by 6 amide ions, rubidium and caesium anti-cuboc tahedrally by 12 amide ions. The orientation of the hydrogen atoms is related to the size of the alkali metal ions.