Über metall-alkyl-verbindungen: XIV. Die kristallstrukturen von K[In(CH3)4], Rb[In(CH3)4] und Cs[In(CH3)4]

The crystal structure of KInMe₄ and CsInMe₄ have been determined from single crystal diffractometer data. Lattice parameters of RbInMe₄ obtained by powder methods are given. KInMe₄ and RbInMe₄ are isostructural (space group I4₁/amd), containing four formula units in the unit cell. CsInMe₄ belongs to space group P4? 2m with one formula unit per unit cell. Lattice parameters in Å: KInMe₄:a=9.904(2), c=8.132(2); RbInMe₄:a=10.208(2), c=8.146(2); CsInMe₄:a=7.459(1), c=4.163(1). All compounds consist of isolated alkali cations and tetrahedral InMe₄-anions. InC distances are 2.239(3) in KInMe₄ and 2.26(2) in CsInMe₄. The appearance of three different structure types of alkali metal tetramethyl indates is explained by the increasing alkali ion radii.