Formation of the intermetalloid cluster [AgSn₁₈]^7--the reactivity of coinage metal NHC compounds towards [Sn₉]^4-

In recent years the formation of intermetalloid clusters by reacting homoatomic tetrel cluster anions with transition metal complexes has become a promising synthetic route. Nevertheless a better understanding of the processes occurring in solution is necessary. Here we present a series of novel polyanionic coinage metal NHC Zintl clusters [NHC^DippM(η⁴-Sn₉)]^3- (M: Cu, Ag, Au; Dipp: diisopropylphenyl) which are obtained at low temperatures from the reaction of K₄Sn₉ with NHC^DippMCl (M: Cu-Au) in liquid ammonia. For M = Ag a larger intermetalloid Ag^I-bridged nonastannide dimer [(η⁴-Sn₉)Ag(η¹-Sn₉)]^7- is also formed. The stepwise formation of the intermetalloid cluster [AgSn₁₈]^7- is discussed and compared with that of previously reported intermetalloid stannides.