Atom Exchange Versus Reconstruction: (GexAs4-x)x-(x=2, 3) as Building Blocks for the Supertetrahedral Zintl Cluster [Au6(Ge3As)(Ge2As2)3]3-

The Zintl anion (Ge2As2)(2) represents an isostructural and isoelectronic binary counterpart of yellow arsenic, yet without being studied with the same intensity so far. Upon introducing [(PPh3)AuMe] into the 1,2-diaminoethane (en) solution of (Ge2As2)(2-), the heterometallic cluster anion [Au-6(Ge3As)(Ge2As2)(3)](3)- is obtained as its salt [K(crypt-222)](3)[Au-6(Ge3As)(Ge2As2)(3)]center dot en center dot 2 tol (1). The anion represents a rare example of a superpolyhedral Zintl cluster, and it comprises the largest number of Au atoms relative to main group (semi)metal atoms in such clusters. The overall supertetrahedral structure is based on a (non-bonding) octahedron of six Au atoms that is face-capped by four (GexAs4-x)(x-) (x= 2, 3) units. The Au atoms bind to four main group atoms in a rectangular manner, and this way hold the four units together to form this unprecedented architecture. The presence of one (Ge3As)(3-) unit besides three (Ge2As2)(2-) units as a consequence of an exchange reaction in solution was verified by detailed quantum chemical (DFT) calculations, which ruled out all other compositions besides [Au-6(Ge3As)(Ge2As2)(3)](3-). Reactions of the heavier homologues (Tt(2)Pn(2))(2-) (Tt= Sn, Pb; Pn= Sb, Bi) did not yield clusters corresponding to that in 1, but dimers of ternary nine-vertex clusters, {[AuTt(5)Pn(3)](2)}(4-) (in 2-4; Tt/Pn= Sn/Sb, Sn/Bi, Pb/Sb), since the underlying pseudotetrahedral units comprising heavier atoms do not tend to undergo the said exchange reactions as readily as (Ge2As2)(2-), according to the DFT calculations.