Further studies into the reactivity and coordination chemistry of [Ge9]4− Zintl ions. The indium-containing anions [In(Ge9)2]5−, [(Ge9)2In(C6H5)]4− and [Ge9{In(C6H5)3}2]4−

Reactions between ethylenediamine solutions of K4Ge9 and triphenylindium yielded three novel Zintl ions, [In(Ge9)2]5− (1), [(Ge9)2In(C6H5)]4− (2), and [Ge9{In(C6H5)3}2}]4− (3). Species 1 exhibits an indium metal atom coordinated by two nine-atom germanium cages which bond to the central metal in an η3-mode. The “staggered” arrangement of the two clusters confers the indium metal centre an octahedral coordination geometry. Species 2 displays trigonal planar coordination around the indium atom with an [In(C6H5)]2+ moiety acting as a bridge between the two halves of a [Ge9–Ge9]6− dimer. Finally, species 3 is composed of a [Ge9]4− deltahedral Zintl ion acting as a Lewis base to two In(C6H5)3 moieties. All three anions were characterized in the solid-state by single-crystal X-ray diffraction in [K(2,2,2-crypt)]5[1]·2en, [K(2,2,2-crypt)]4[2]·3tol and [K(2,2,2-crypt)]4[3], respectively. The existence of the anions in solution was confirmed by electrospray mass-spectrometry. DFT level calculations were also conducted on all of the cluster anions.

Graphical abstractWe detail the synthesis of three Zintl ions, [In(Ge9)2]5− (1), [(Ge9)2In(C6H5)]4− (2), and [Ge9{In(C6H5)3}2}]4− (3). The anions were characterized by single-crystal X-ray diffraction in [K(2,2,2-crypt)]5[1]·2en, [K(2,2,2-crypt)]4[2]·3tol and [K(2,2,2-crypt)]4[3], respectively. The existence of the anions in solution was confirmed by electrospray mass-spectrometry. DFT level calculations are also reported.Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights► Three clusters ([In(Ge9)2]5−; [(Ge9)2In(C6H5)]4−; [Ge9{In(C6H5)3}2}]4−) are reported. ► All clusters were characterized by SXRD, ESI–MS and DFT calculations. ► [In(Ge9)2]5− displays an indium atom coordinated to two [Ge9]4– cluster anions. ► [(Ge9)2In(C6H5)]4− exhibits an [In(C6H5)]2+ moiety bridging a [Ge9–Ge9]6− dimer. ► [Ge9{In(C6H5)3}2}]4− is an example of a [Ge9]4− Zintl ion acting as a Lewis base.