The Structure of Cluster Compounds of Transition Metals and the Limits of Applicability of the Electron Counting Rules for Polyhedral Molecules

Synthesis and Molecular Structure of Tetraruthenium Cluster Isomers with Different Electron Counts

“…In compound 2 the organic moiety apparently donates 6 electrons via 2 σ interactions with the hinge atoms and 2 π interactions with the wingtip atoms. This gives the cluster 62 valence electrons, which is satisfactory for the butterfly cluster 10b…”

“…As mentioned above, the ligand in compound 1 can be thought to donate a total of four electrons to the cluster framework via interactions with the hinge atoms and the wingtip ruthenium atoms. Thus, the cluster has a total of 60 valence electrons, two less than the 62 valence electrons required for the butterfly structure . If it is viewed as a closo -octahedral cluster (M 4 C 2 ), it has 66 valence electrons, which is satisfactory for the four-metal/two-carbon geometry.…”

“…The two clusters share the same Ru 4 (CO) 12 core and differ in the opening angle. While the conversion from a tetrahedral cluster with a 60-electron count to a planar rhombus (64 electrons) across an average butterfly (62 electrons) has been widely studied, the effect of varying the angle of the butterfly on the frontier orbitals of the cluster has received much less attention. A Walsh diagram for the transformation of a closed butterfly into an open one is shown in Figure .…”

A hydrocarbon dication with nonplanar hexacoordinated carbon

“…5 The boron and metal atom environments provide for the formation of multicentre bonds of carbon and its nonclassical stereochemistry. Attention was focused on compounds containing hexacoordinated carbon centres such as exemplified by carboranes 1-3 6 isoelectronic with the icosahedric borane B 12 H 12 2-, carbide clusters 4 5,7 and the hexaaurated dication C(AuPPh 3 ) 6 2+ . 8 The ab initio calculation performed at different levels of approximation predicts the stability of other molecules and ions with hexacoordinated carbon centres: CLi 6 n (n = 0, 2+), 9 CH 6 2+ , 10 cation carbene 5 11 and dication 6, which was the only experimentally observed species with a hexacoordinated carbon atom.…”

Octacoordinated Carbon in a Boron-Carbon Cage

“…The heptacoordination of carbon in organoboron systems 1 [4] and 2 [5] predicted by quantumchemical calculations is currently the record hypercoordination for carbon bound to an array of main-group elements. At the same time, octacoordinated carbon in nickel and cobalt carbide clusters [C · Ni 8 (CO) 16 ] 2-and [C · Co 8 (CO) 18 ] 2-with a tetragonal antiprism structure 3 has long been known [6,7]. In organic or organometallic systems, as well as in clusters of main-group elements, octacoordinated carbon has been neither theoretically predicted nor experimentally found.…”