Reactivity of [Ge9{Si(SiMe3)3}3]− Towards Transition-Metal M2+ Cations: Coordination and Redox Chemistry.

Recently the metalloid cluster compound [Ge9Hyp3]− ( 1; Hyp=Si(SiMe3)3) was oxidatively coupled by an iron(II) salt to give the largest metalloid Group 14 cluster [Ge18Hyp6]. Such redox chemistry is also possible with different transition metal (TM) salts TM2+ (TM=Fe, Co, Ni) to give the TM+ complexes [Fe(dppe)2][Ge9Hyp3] ( 3; dppe=1,2-bis(diphenylphosphino)ethane), [Co(dppe)2][Ge9Hyp3] ( 4), [Ni(dppe)(Ge9Hyp3)] ( 5) and [Ni(dppe)2(Ge9Hyp3)]+ ( 6). Such a redox reaction does not proceed for Mn, for which a salt metathesis gives the first open shell [Hyp3Ge9-M-Ge9Hyp3] cluster ( 2; M=Mn). The bonding of the transition metal atom to 1 is also possible for Ni (e.g., compound 6), in which one or even two nickel atoms can bind to 1. In contrast to this in case of the Fe and Co compounds 3 and 4, respectively, the transition-metal atom is not bound to the Ge9 core of 1. The synthesis and the experimentally determined structures of 2- 6 are presented. Additionally the bonding within 2- 6 is analyzed and discussed with the aid of EPR measurements and quantum chemical calculations. [ABSTRACT FROM AUTHOR]