Edge-bridging structure

The edge-bridging structure leading to a stoichiometry M4L6 is now well established and is frequently referred to as the adamantyl structure. Saalfrank has studied this structure type using ligands of the general type 45 ... 

Figure 29 Connectivities of tetrahedral clusters the edge-bridging structure (left) and the face-bridging structure (right)—only one ligand is shown and the fourth metal ion lies behind the centre of the ligand.

The alkyl-bridged structures can also be described as comer-protonated cyclopropanes, since if the bridging C—C bonds are considered to be fully formed, there is an extra proton on the bridging carbon. In another possible type of structure, called edge-protonated cyclopropanes, the carbon-carbon bonds are depicted as fully formed, with the extra proton associated with one of the bent bonds. MO calculations, structural studies under stable-ion conditions, and product and mechanistic studies of reactions in solution have all been applied to understanding the nature of the intermediates involved in carbocation rearrangements. 

Fig. 5.4 View of the structure and intercluster connectivity of the [(ZreBjClia] structure, and mixed halide derivative, respectively. Edge-bridging chlorines are...

Reduction of [W4S6Cl2(PMe2Ph)6] (see Section IV,A) with excess Na/Hg in thf at room temperature gives [W4( t2-S)6(PMe2Ph)4] in 10% yield (94). The structure consists of an almost regular tetrahedron of W(III) atoms with each edge bridged by 2-S atom (Fig. 19). The six... 

Pd7(CO)7(PMe3)7] has been isolated from the reaction of (23) with CO.115 This cluster has a monocapped octahedral structure with one phosphine attached to each Pd atom. Four of the carbonyl ligands bridge the octahedral faces, while the other carbonyls edge bridge (Pd—Pd 2.79(2) A). 

General formula central Ligand positions bridging face edge terminal Structure/ section number... 

The idealized structure of the [ Ag6(SPh)8]2 cage is (6e) with the four central Ag atoms trigonally coordinated, and the two outer Ag atoms almost linearly coordinated.29 The edge-bridged tetrahedron of metal atoms occurs in [Au6(Ph2PCH2CH2CH2PPh2)4]2+ but the loosely connected metal array is distorted due to the absence of Au—Au bonding.220... 

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