Systematic Metallaborane Chemistry

Abstract

Monocyclopentadienyl metal chlorides of transition metals of groups 5-9 react with monoboranes (LiBH 4 or BH 3 THF) to give metallaboranes (and LiCl or BH 2 Cl). The composition of the metallaborane produced depends on the nuclearity of the metal complex, the number of chlorides (oxidation state of the metal), and the monoborane used. For both monoboranes, a monocyclopentadienyl metal polyborohydride is implicated as the key intermediate, which is competitively converted into either a metal hydride or a metallaborane. The comparative reaction chemistry of these metallaboranes exhibits a dependence on transition metal properties for borane addition, metal fragment addition, and dihydrogen elimination. In addition, base degradation and small molecule reactivity promise similar metal dependencies. These observations suggest that control of borane chemistry with transition metals, analogous to that achieved in organometallic chemistry, can be realized.

Cross-cluster transition-metal bonding in oblato-nido dimetallaboranes unveiled by topological analysis

“…The idea behind the DI decomposition [26] is immediately visible when comparing Eqs. (2) and (6) with Eq. (7) after the integration over another domain.…”

“…There are today over hundred molecular dimetallaboranes, which have been synthesized and characterized with nearly all the transition metals (T), both early and late metals (see for example Fehlner et al [1][2][3]). They constitute a class of compounds which has revealed numerous possibilities for the way metal and borane fragments interact to generate novel structures, demonstrating the important role for the transition metal in the structural arrangements which are observed.…”

“…Density functional theory (DFT) calculations have been able to sort out this apparent systematic rule deviation [7], but the proximity of the two metal atoms on opposite sides in the flattened direction allows some speculation about the nature of T-T interaction. This has been tackled several times in the literature using MO analysis [1,2,7,8,[12][13][14][15][16][17][18][19][20]. However, whereas the conclusions seem to fully converge with some studies evidencing a single T-T bond [7], some others suggest a formal internal T-T double bond [8].…”

An Efficient Route to Group 6 and 8 Metallaborane Compounds: Synthesis of arachno‐[Cp*Fe(CO)B3H8] and closo‐[(Cp*M)2B5H9] (M = Mo, W)

“…[9] Fehlner et al showed that the addition of monoboranes (LiBH 4 ·thf, BH 3 ·thf, or BHCl 2 ·SMe 2 ) to monocyclopentadienylmetal chlorides, [Cp*MCl] n , is an excellent method for the preparation of metallaboranes containing transition metals ranging from groups 5 to 9. [10] Despite having welldeveloped routes to metallaboranes of second to third row transition metals of group 5 to 9, there are not many suitable synthetic routes are available for first row transition metals. The synthetic route depends on the selective conversion of metal polyborohydrides to metallaboranes by hydrogen elimination.…”

Reactions of small boranes with ruthenium phosphine hydrides: Oligomerisation of monoborane-tetrahydrofuran to a nido-hexaruthenaborane

“…Previously we have reported the synthesis of [Mo(g-C 5 H 5 ) 2 (H)B 2 H 5 ], [arachno-2-Mo(g-C 5 H 5 )(g 5 :g 1 -C 5 H 4 )B 4 H 7 ] and [closo-1-Mo(g-C 5 H 5 )(g 2 :g 3 -C 3 H 3 )C 2 B 3 -H 5 ] from [Mo(g-C 5 H 5 ) 2 H 2 ] and BH 3 AE thf as well as the synthesis of [arachno-2-W(PMe 3 ) 3 [1][2][3]. In the last 12-13 years Fehlner and co-workers have used the reagent BH 3 AE thf to systematically produce a range of metallaboranes, often in good yields, using mainly cyclopentadienyl metal chlorides as precursors [4]. Most of these metallaboranes are closo and contain two metal atoms.…”