Synthesis and characterization of the [Ni6Ge13(CO)5]4− and [Ge9Ni2(PPh3)]2− Zintl ion clusters

Reactions between K4Ge9, Ni(CO)2(PPh3)2, and 2,2,2-crypt in ethylenediamine solutions give two different products depending on reaction conditions. The [Ni6Ge13(CO)5]4− ion (1) is formed at low temperatures (∼40 °C) and short reaction times whereas the [Ge9Ni2(PPh3)]2− ion (2) forms at higher temperatures (∼118 °C). Both complexes were isolated as [K(2,2,2-crypt)]+ salts and characterized by single-crystal X-ray diffraction, electrospray mass spectrometry (ESI-MS) and NMR studies (13C and 31P). 1 has a hypo-closo cluster electron count (Wades Rules) and adopts an interpenetrating biicosahedral structure with 17 vertices and 2 interstitials, which is unique in transition metal Zintl ion clusters. 2 also has a hypo-closo cluster electron count but displays an open, nido-like 10-vertex structure with a Ni interstitial. The composition of 2 was established through ESI-MS studies and corrects an earlier report that characterized the cluster as [Ge10Ni(PPh3)]2− with an interstitial Ge.

Graphical abstractReactions between K4Ge9, Ni(CO)2(PPh3)2, and 2,2,2-crypt in ethylenediamine solutions give the [Ni6Ge13(CO)5]4− ion (see structure) at low temperatures (∼40 °C) and the [Ge9Ni2(PPh3)]2− ion at higher temperatures (∼118 °C). The biicosahedral structure of the [Ni6Ge13(CO)5]4− ion is unique in Zintl cluster chemistry.Figure optionsDownload full-size imageDownload as PowerPoint slide