Metallaboranes

Transition-Element Metallaboranes. The transition-metal hydroborate cluster, HMn2(CO) Q(BH2)2, containing a moiety, which is... 

The first closo metaHaborane complexes prepared (159) were the nickelaboranes [< /(9j 0-( q -C H )Ni(B22H22)] and closo-l]l- r]-Q ]) -l]l-53i] pri Q [55266-88-1] (Fig. 13). These species are equivalent to closo-C ]]ri ][ i closo-Q, p5 2 by tbe electron-counting formaUsm. The mixed bimetallic anion [ /(9j (9-(Tj -C H )2CoNi(B2QH2Q)] and other related species were reported later (160). These metallaboranes display remarkable hydrolytic, oxidative, and thermal stabiUty. 

Main Group Element Metallaboranes. A variety of metaHaborane clusters, which incorporate main group metals in vertex positions of polyhedral metaHaborane clusters, have been reported. Examples are (BH BeB H Q (165), MgB2QH22 20(C2H )2 (166), [(CH2)HgB2QH22]A (167),... 

The volatile, air-sensitive Hquid species (CH3)2AlB3Hg and (CH3)2GaB3Hg are prepared by the direct reaction of the corresponding main group metal hahde and salts of the [B3Hg] ion, in the absence of solvent (178). The reaction of (CH3)2AlB3Hg and A1(BH 3 results in the species (BH 2AlB3Hg. These small metallaboranes are fluxional in solution and have limited thermal stability at room temperature. 

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... 

Table 9. Metallaboranes with Three Boron Atoms...

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... 

Group 7 metallaboranes formed by monoboron addition to CpMX 155... 

Metallaborane cluster complexes of the post-transition metals 167... 

This chapter deals with metallaborane chemistry and covers the period from 1994 to 2004. In many respects the format is the same as adopted by Barton and Srivastava in COMC (1995).1... 

Many reviews and book chapters have appeared over the period 1994-2004 on the subject of metallaborane chemistry or related topics (i.e., electronic structures of metallaboranes). Of particular note (in loose chronological order) are ... 

The use of metalloorganic precursors for depositing inorganic electronic materials, encompassing the deposition of borides from metallaboranes or related complexes.2... 

A comprehensive summary of the theoretical contributions over the past 40 years towards the understanding of the relationship between two-dimensional aromaticity (hydrocarbons) and the electronic structure of three-dimensional deltahedral boranes. Note in particular that rearrangement processes and the isocloso problem in metallaboranes have also been discussed.11... 

The structural and electronic factors that influence metallaboranes of the earlier transition metals.14... 

This section reviews the developments in the chemistry of monoborane complexes of the transition metals especially borohydride and hydridoborate complexes. Although such complexes are not strictly metallaboranes in the sense that they are not cluster species, they are included here as they share many similarities with polyborane species of the transition metals such as three-center two-electron bonding. Additionally, as will be shown in Section 3.04.3.1 borohydride species can also be intermediates in the formation of larger M By clusters. In this chapter, three-coordinate monoborane species, which are best considered as cr-complexes between a transition metal and HBR2 or metal-boryl (M-B) species, are not considered. 

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