Nido-carborane ligands

Metallacarboranes have both metal and carbon atoms in the cage skeleton. In contrast to the metallaboranes, syntheses of metallacarboranes via low- or room-temperature metal insertion into carborane anions in solution are more controllable, usually occurring at a well-defined QB, open face and forming a single isomer. Other preparative routes, such as metal insertion into neutral carboranes at high temperature, involve more complex processes and tend to give less clean-cut results, and such approaches are rarely employed today. Typical syntheses that are based on readily available 11-vertex and 7-vertex nido-carborane ligands are as shown ... 

By contrast with the established coordination chemistry of the nido-1 ligand, the analogous nido-7,9-C2lN>Yl ligand, derived by deboronation of "meta-carborane" 1,7-C2BioHi2 has been less widely studied. The few studies that have been... 

This outlines the approach we have adopted. We begin with a nido 7,8-C2B9 carborane ligand with bulky substituents (usually Ph groups) attached to the cage C... 

There are now at least a dozen synthetic routes to metallocarboranes including (i) coordination using nido-carborane anions as ligands, (ii) polyhedral expansion reactions, (iii) polyhedral contraction reactions, (iv) polyhedral subrogation and (v) thermal metal transfer reactions. These first five routes were all devised by... 

Phosphorus-substituted carborane ligands can be mono-, bi-, or multidentate when they react with a metal center. Factors affecting this behavior include the structural features of the carborane cage (i.e., whether it is the ortho, meta, or para isomer, or has the closo or nido structure), the substitution pattern of the carborane cluster, the number and kind of donor atoms, and the electronic and steric properties of the ligand. All these factors have an influence on the catalytic activity of the metal complex. For example, the carborane cluster can act as an electron acceptor or electron donor at the phosphorus atom [22,29]. The donor atoms adjacent to phosphorus can act as labile ligands that block the coordination site at the metal until a substrate approaches. In nido cluster compounds, the metal ion can bind in two ways through the phosphorus substituent or by the decapped face of the cluster, whereby the former option is the most stable. In nido-carborme chemistry, B-H-Rh and... 

The interest in organometallic carboranes is due to their close electronic similarity with the cyclopentadienide ligand as shown (Hawthorne et al. 1988) in a study of the frontier orbital of the nido-carborane (C2R2B9H9) (R = H or a cage carbon) and of the... 

Homoleptic gold(III) derivatives with dithiolate, ligands of the type [Au(S-S)2] are well known and are usually prepared from [AuC14] with the dithiol some examples are with 1,2-benzene dithiolate, maleonitriledithiolate, dmit, and so on, [164, 336]. Similar complexes have been reported for bidentate sulfur ligands such as dithiocarbamates, dithiophosphates, and so on, [41]. Other derivatives as the trinuclear species [Au(C6F5)(S2C6H4)]3 [337] or the complex with one nido and one closo-carborane dithiolate are known [338]. Figure 1.72 collects some of these complexes. 

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