Metalla carboranes

Scheme 3.2-24. Reaction of 44 with BBr3 gives a mixture of closo-carboranes 45, 46 and 47, and with FeCI2 the metalla-carborane/sandwich complex 48.

C in the presence of a catalytic amount of a Lewis base such as dimethylether, (CH3)20. In addition to the gas-phase pyrolysis of diborane, B10H14 can be prepared by a solution-phase process developed at Union Carbide Corp. Decaborane is a key intermediate in the preparation of many carboranes and metalla derivatives. As of this writing, this important compound is not manufactured on a large scale in the western world and is in short supply. Prices for decaborane in 1991 were up to 10,000/kg. 

The first definitive crystal structures of the group 14 c/oso-metalla-carboranes were those reported by Hosmane and co-workers (38-41) from the reactions involving the monoanion of m do-2-[(CH3)3Si]-3-(R)-2,3-C2B4H6 [R = (CH3)3Si, CH3, H] with SnCl2 in THF (C4H80) to produce the corresponding stannacarboranes (see Scheme 3). The structures of the complexes (Figs. 13-15) show Sn2+ to occupy an apical position in... 

Fig. 5-18i,13 has been followed in recent years by studies of early transition metal-carboranes as catalysts for olefin polymerization.14 In these applications, the metalla-carborane species resemble their metallocene-based analogues however, there are other areas, such as the construction of new types of electronic, magnetic, and optical materials, in which the unique structural and other characteristics of metalla-carboranes may be put to use. Venus flytrap linked-dicarbollide ligands such as that shown encapsulating a Co3+ ion in Fig. 5-18f have been prepared as a possible way to bind radiotransition metals to tumor-associated monoclonal antibodies for purposes of diagnosis and therapy.15... 

This review covers the 2000 hterature of carboranes and metallacarboranes and follows essentially the same format as adopted in previous years. Selected heteroboranes of the other members of Group 4 (e.g. Sn) are also included. Carborane complexes are ordered by their formula, with metal complexes included in a separate, appropriately ordered, section. Those complexes with both a carbon and another heteroatom in the cage have been included in the appropriate section on the basis of the carbon atom count. Exo metalla-sub-stituted carboranes are included in the appropriate carborane section. The literature pubhshed has been searched using Web of Science, CAS and the Cambridge Crystallographic Database. Due to space hmitations, descriptions of specific results are kept to a minimum, with the reader directed to the original paper for more information. 

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