Metallacarboranes synthesis

Serendipitous insertion of CsHs- into the metallaborane Cp 2Cr2B4Fl8 gave the triple-decker sandwich 122 in low yield.140 This compound can be described as an eight-vertex Cr2C2B4 c/ara-metallacarborane cluster, and its preparation is notable as one of the few examples of metallacarborane synthesis from a metallaborane precursor (rather than by the usual metal insertion into a carborane), an approach first demonstrated by Grimes and co-workers in the 1970s.34,141,141a... 

Metal-vapor synthesis also prepares metallaboranes and metallacarboranes with oxidation of the metal. Thermally generated Ni, Co and Fe atoms react with the nido-carborane 2,6-C2B7H, and either cyclopentadiene, toluene, mesitylene, or... 

The synthesis of new materials having novel electronic or optical properties is of great current interest. One approach to the synthesis of such materials is to systematically link small sandwich units together to form an extended multi-decker sandwich system. Immediately following the discovery of the triple-decker structure of the Cp3Ni2+ complex in early 1970s,181 Grimes and co-workers synthesized the first neutral triple-decker metallacarborane sandwich compound. Most of the subsequent research in this field, some of which has been described... 

Tetracarbaboranes, which contain four carbon atoms in a single polyhedral skeleton, were rare until the discovery (129) of the metallacarborane-mediated synthesis of (CH3)4C4BgH8 [58815-26-2]. 

Linear polarization, and NLO properties, 12, 102 Linear polymers, siloxanes, synthesis, 3, 660 Linkage isomerism, for photochromic behavior, 1, 245 Linked cages, metallacarboranes, 3, 245 Linkers, traceless, chromium carbonyls as, 5, 251 Lipids, in bioorganometallic chemistry, 1, 904 Liquefied noble gases, in low-temperature infrared studies, 1, 264... 

In contrast to the rather rich and varied chemistry reported for aluminacarboranes, only limited information is available on the heavier group 13 metallacarboranes. The preparation of closo-l-C2H5-GaC2B9Hn by Hawthorne and co-workers (18,19) was described earlier [see Eq. (2)]. Grimes et al. (30) have reported the synthesis of c/oso-l-(CH3)-l,2,3-GaC2B4H6 and l-(CH3)-l,2,3-InC2B4H6 by the gas-phase reaction of Ga(CH3)3 and In(CH3)3 with C2B4H8. Reaction conditions and yields are... 

The C-Si(CH3)3-substituted stannacarboranes have been found to be useful starting materials for the synthesis of the other metallacarboranes. The apical tin is loosely ligated and can be replaced by other metal groups. For example, the reaction of Os3(CO)12 with c/-Sn[(CH3)3Si]2-C2B4H4 in the absence of solvent yields l-Os(CO)3-2,3-[(CH3)3Si]2C2B4H4 (50) in essentially quantitative yield [see Eq. (7)], while direct reaction of... 

The 11-vertex dianion, named dicarbollide (from the Spanish olla, pot) has a pentagonal C2B3 open face that is analogous to C5Hj, a fact that led directly to the synthesis of metallacarboranes (following section). 

In conclusion, we have demonstrated that the reactions of metal amide bonds, M-NR2, with acidic hydrogen atoms of wVfo-carboranes provide an attractive route to the synthesis of metallacarboranes of the early/middle transition elements. The structural preferences of the amide ligands in the products provide us with valuable lessons on the relationship between electronic and molecular structures. Early transition metal... 

The structures of a representative cross-section of known carboranes are shown in Figures 3.2-3.6. Though many new carboranes have been synthesized and characterized since the borane/carborane structural pattern was hrst described,these have tended to consolidate rather than greatly extend the picture. A little progress has been made with the synthesis of macropoly-hedral borane clusters in which fused smaller polyhedra share edges or faces.This area need not concern us here, as it almost exclusively involves boranes and metallaboranes rather than carboranes and metallacarboranes. 

Carboranes - polyhedral boranes containing carbon in the framework - have been known for over 35 years, and their intrinsic stability, versatility, structural variety, and electronic properties have been put to use in a number of diverse areas, [1] for example in the synthesis of extraordinarily heat-stable polymers, in BNCT (boron neutron capture therapy), as ligands in metallacarborane catalysts, as com-plexing agents for extraction of metal ions, as precursors to ceramics, conducting polymers, and nonlinear optical materials, as anticancer... 

Wang X, Sabat M, Grimes RN (1995) Organotransition-metal metallacarboranes directed synthesis of carborane-end-capped multidecker sandwiches. J Am Chem Soc 117 12227-12234... 

In the area of synthesis, the structural and theoretical framework contributed by Lipscomb provided a foundation for the monumental synthetic work of M. F. Hawthorne and his students, who transformed boron cluster chemistry first by their synthesis of the polyhedral borane anions BioHio and Bi2Hi2 (30) and later by the synthesis of metallacarboranes (31). In our own laboratory, considerations of charge distribution in borane anions (14) prompted us to explore reactions of transition metal ions with small borane and carborane anions (32). This, in turn, led to a number of advances including the first closed polyhedral metallaboranes (33), the discovery of metal-induced oxidative cage fusion (34), and the synthesis of B12H16, the only neutral Bi2 hydride, via metal-promoted fusion of BeHQ (35)... 

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