Butterfly clusters

Synthesis of ji-Acetylene Tetracobaltodecacarbonyl Clusters - Butterflies [(CO)8Co4( r-CO)2]( r-C2R2) (R = CH2OH, CH2SCMe3) [75o]... 

The removal of one or more vertices from a closo polyhedral system leaves the number of skeletal bonding MOs unchanged thus, a 6-vertex closo cluster (octahedral, as in Fig. 5-5), a 5-vertex nido cluster (square pyramidal), and a 4-vertex arachno cluster (butterfly or square planar, depending on whether adjacent or nonadjacent vertices are removed from the octahedron) all have 6 bonding MOs and hence require 7 bonding electron pairs. Expressed in terms of the number of vertices n, this equals n+1, n+2, n+3, and n+4 pairs for closo, nido, arachno, and hypho clusters, respectively. 

The derivatives of the inorganic phosphorus acids are usually intractable powders which are unsuitable for X-ray diffraction, but those of the organic phosphorus acids are often crystalline and a series of complex solid-state structures which have been described as drums, cubes, oxygen-capped clusters, butterfly formations, crowns, and extended clusters32-51 have been identified. 

For tetranuclear cluster complexes, three stmcture types are observed tetrahedral open tetrahedral (butterfly) or square planar, for typical total valence electron counts of 60, 62, and 64, respectively. The earliest tetracarbonyl cluster complexes known were Co4(CO)22, and the rhodium and iridium analogues. The... 

In the families of heptanuclear clusters, two geometries are found the capped octahedron that is typical for 98-valence electrons, and the vertex-sharing open tetrahedral (butterfly) stmctures typical for 106-valence electrons. An example of the former is Osy(CO)22 (51) an example of the latter is [H2AuOsg(CO)2Q] (52). In the AuOs cluster anion, the gold atom is at the vertex-sharing position. 

A structural variation shows the borido cluster d HFe4(CO),2(Et3PAu)2B, where the B atom is within bonding contact of all six metal atoms and the two Au atoms symmetrically bridge the wingtips of the butterfly-shaped complex ... 

The 8V+ 2 rule has been completely substantiated by the calculated ground state geometries of tetramers in Table 2 [7], The cluster (lOe) is linear [11]. The Si/" cluster (18e) has a butterfly structure (Dp [18],... 

Butterfly Cluster Complexes of the Group VIII Transition Metals Sargeson, Alan M., see Hendry, Philip Sanon, G., see Fleischauer, P. D. Sawyer, Donald T., see Sobkowiak, Andrzej Sawyer, Jeffery F., and Gillespie, Ronald J., The Stereochemistry of SB (HI) 35 437... 

Interest in the organotin derivatives of the acids and thioacids of phosphorus arises from their potential biological action and the wide variety of structures that have been identified by X-ray diffraction. These structures are often particularly complex when the compounds are derived from the partially hydrolyzed mono- or diorganotin compounds, and words such as cubes, drums, crowns, butterflies, clusters, oxygen-capped clusters, and extended clusters have been use to describe them. References to the early work are given in Ref 351, and a recent review is available.352... 

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