Abstract
The Zintl anion (Ge(2) As(2) )(2-) represents an isostructural and isoelectronic binary counterpart of yellow arsenic, yet without being studied with the same intensity so far. Upon introducing [(PPh(3) )AuMe] into the 1,2-diaminoethane (en) solution of (Ge(2) As(2) )(2-) , the heterometallic cluster anion [Au(6) (Ge(3) As)(Ge(2) As(2) )(3) ](3-) is obtained as its salt [K(crypt-222)](3) [Au(6) (Ge(3) As)(Ge(2) As(2) )(3) ]⋅en⋅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 (Ge(x) As(4-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 (Ge(3) As)(3-) unit besides three (Ge(2) As(2) )(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) (Ge(3) As)(Ge(2) As(2) )(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 pseudo-tetrahedral units comprising heavier atoms do not tend to undergo the said exchange reactions as readily as (Ge(2) As(2) )(2-) , according to the DFT calculations.