Formamidinium Salts of Low Valent Metal Halide Anions MX3 – (M = Ge, Sn) and M2X6 2– (M = Ga, In)

Abstract

Abstract Tetramethylformamidinium trichlorogermanite, [CH(NMe2)2][GeCl3], tetramethylformamidinium trichlorostannite, [CH(NMe2)2][SnCl3], bis-(tetramethylformamidinium hexaiododigallate, [CH(NMe2)2]2[Ga2I6] and bis-(tetramethylformamidinium hexachlorodiindate, [CH(NMe2)2]2[In2Cl6] have been prepared by the reactions between tetramethylformamidinium chloride, [CH(NMe2)2]Cl, and the corresponding low valent halides GeCl2 (as dioxane adduct), SnCl2, “GaI” and InCl. Their crystal structures have been determined by single crystal X-ray diffraction. [CH(NMe2)2][GeCl3] aggregates in a centrosymmetric dimeric structure, in which two trigonal pyramidal GeCl3 units are connected together by two weak Ge···Cl bonds and each Ge atom is bonded to one cation by a weak Ge···N contact. Two sets of weak hydrogen bonds C-H···Cl are observed with bond lengths of 2.87(2) Å and 2.85(2) Å . In [CH(NMe2)2][SnCl3], the SnCl3 − units adopts a (3+3) coordination with three normal Sn-Cl bonds and three weak Sn···Cl contacts. [CH(NMe2)2]2[Ga2I6] and [CH(NMe2)2]2[In2Cl6] contain metal-metal bonded anions with distorted staggered ethane-like conformations. The metal-metal bond lengths are 2.423(1) Å (Ga-Ga) and 2.719(1) Å (In-In). Their Raman spectra contain intense bands at 118.7 cm−1(Ga-Ga) and 174.7 cm−1(In-In) associated with metal-metal stretching modes.