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 (similar to 40 degrees C) and short reaction times whereas the [Ge9Ni2(PPh3)](2-) ion (2) forms at higher temperatures (similar to 118 degrees 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 (13 C and 3 p). 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 [(GeNi)-Ni-10(PPh3)](2-) with an interstitial Ge. (c) 2005 Elsevier Ltd. All rights reserved.