Altering Charges on Heterobimetallic Transition‐Metal Carbonyl Clusters

The homoleptic group 5 carbonylates [M(CO)(6)](−) (M=Nb, Ta) serve as ligands in carbonyl‐terminated heterobimetallic Ag(m)M(n) clusters containing 3 to 11 metal atoms. Based on our serendipitous [Ag(6){Nb(CO)(6)}(4)](2+) (4 a (2+)) precedent, we established access to such Ag(m)M(n) clusters of the composition [Ag(m){M(CO)(6)}(n)](x) (M=Nb, Ta; m=1, 2, 6; n=2, 3, 4, 5; x=1−, 1+, 2+). Salts of those molecular cluster ions were synthesized by the reaction of [NEt(4)][M(CO)(6)] and Ag[Al(OR(F))(4)] (R(F)=C(CF(3))(3)) in the correct stoichiometry in 1,2,3,4‐tetrafluorobenzene at −35 °C. The solid‐state structures were determined by single‐crystal X‐ray diffraction methods and, owing to the thermal instability of the clusters, a limited scope of spectroscopic methods. In addition, DFT‐based AIM calculations were performed to provide an understanding of the bonding within these clusters. Apparently, the clusters 3 (+) (m=6, n=5) and 4 (2+) (m=6, n=4) are superatom complexes with trigonal‐prismatic or octahedral Ag(6) superatom cores. The [M(CO)(6)](−) ions then bind through three CO units as tridentate chelate ligands to the superatom core, giving overall structures related to tetrahedral AX(4) (4 (2+)) or trigonal bipyramidal AX(5) molecules (3 (+)).