The Polyhedral Metallaboranes Part II. Metallaborane Clusters with Eight Vertices and More

Fine Tuning of Metallaborane Geometries: Chemistry of Metallaboranes of Early Transition Metals Derived from Metal Halides and Monoborane Reagents

“…[1] The development of metallaborane chemistry has followed a similar pathway, with new species often obtained from conditions that favor the thermodynamic product, either through thermolysis or by simple metathesis reactions between a preformed polyborane anion and transition-metal halides. [2][3][4][5] Detailed investigations of the Co, [6] Rh, [7] Ir, [8,9] Fe, [10] Ru, [11] Re, [12,13] Cr, [14,15] Mo, [10,[16][17][18] W, [10,19,20] and Ta [21][22][23] systems reported to date reveal that metal identity affects products. For example, the earlier transition metals facilitate dehydrogenation leading to highly condensed clusters, such as closo-A C H T U N G -T R E N N U N G [(Cp*M) 2 B n H n + m ], (M = Re: [13] n = 7-10, m = 0; M = W: [12] n = 7, m = 2), whereas late transition elements form stable nido-or arachno-metallaboranes, such as nido-[(Cp*Ru) 2 B 10 H 16 ] [24] or arachno-1-[(Cp*IrH)B 4 H 9 ].…”

“…For example, the earlier transition metals facilitate dehydrogenation leading to highly condensed clusters, such as closo-A C H T U N G -T R E N N U N G [(Cp*M) 2 B n H n + m ], (M = Re: [13] n = 7-10, m = 0; M = W: [12] n = 7, m = 2), whereas late transition elements form stable nido-or arachno-metallaboranes, such as nido-[(Cp*Ru) 2 B 10 H 16 ] [24] or arachno-1-[(Cp*IrH)B 4 H 9 ]. [9] Metallaboranes that incorporate early transition metals are a sparsely explored area of cluster chemistry [2][3][4]25] and the challenge is to find synthetic routes. Traditionally, the focus has been on two broad but complementary approaches, namely a) insertion or fragmentation reactions of ready-assembled borane frameworks and b) condensation reactions of monoboron precursors [LiBH 4 ·thf] or [BH 3 ·thf].…”

“…[9] Metallaboranes that incorporate early transition metals are a sparsely explored area of cluster chemistry [2][3][4]25] and the challenge is to find synthetic routes. Traditionally, the focus has been on two broad but complementary approaches, namely a) insertion or fragmentation reactions of ready-assembled borane frameworks and b) condensation reactions of monoboron precursors [LiBH 4 ·thf] or [BH 3 ·thf]. Typically, products are isolated by chromatography from reaction mixtures in low yields, owing to the accessibility of several minima on the reaction pathway under the conditions employed.…”

“…Therefore, in contrast to tantalum and niobium, vanadium presented the possibility of examining not only the related species, but also new compounds. We present here the results of reaction of monocyclopentadienyl metal chlorides with monoborane reagents [LiBH 4 ·thf] or [BH 3…”

Boron Beyond the Icosahedral Barrier: A 16‐Vertex Metallaborane

“…Among the hundreds of metallaboranes and their derivatives reported by Fehlner and co-workers, [18] Kennedy, [19] and other groups, [20][21][22] only a few mono-or dimetallaboranes with 12 vertices [23] are known and none with more vertices. The lack of larger metallaboranes led us to renewed experimental efforts, and we recently reported the synthesis and structural characterization of dirhodium analogues of [B 8 H 12 ] and [B 10 H 14 ].…”