Fine-Tuning of Metallaborane Geometries: Chemistry of Iridaboranes Derived from the Reaction of [(Cp*Ir)2HxCl4−x] (x=0-2; Cp*=η5-C5Me5) with LiBH4

Abstract

From reaction of [(Cp*Ir)2HxCl(4-x)] (x=1, 0) and LiBH4, arachno-[[Cp*IrH2]B3H7](1) is produced in moderate yield concurrently with [Cp*IrH4]. In contrast, reaction of [(Cp*Ir)2H2Cl2] with LiBH4 results in arachno-[[Cp*IrH]2(mu-H)B2H5] (3) in high yield at room temperature but a mixture of 1 and [[Cp*IrH]2(mu-H)BH4] (2) at 0 degrees C. BH3 x THF converts 1 to arachno-[(Cp*IrHB4H9] (4) and 2 to 3 with 1 as a minor product. Further, reaction of 3 with excess of BH3 x THF results in formation of nido-[[Cp*Ir]2-(mu-H)B4H7] (6) formed by loss of H2 from the intermediate arachno-[[Cp*IrH]2B4H8] (5). Reaction of 1 with [Co2(CO)8] permits the isolation of two metallaboranes, arachno-[[Cp*Ir(CO)]-B3H7] (7) and nido-[1-[Cp*Ir]-2,3-Co2-(CO)4(mu-CO)B3H7] (8). Treatment of 4 with [Co2(CO)8] gives only one single mixed-metal metallaborane nido-[1-[Cp*Ir]-2-Co(CO)3B4H7 (9) in high yield. Finally, pyrolysis of 8 results in loss of hydrogen and formation of pileo-[1-[Cp*Ir]-2,3-Co2(CO)5B3H5] (10) with a BH-capped square-pyramidal structure. With kinetic control rational synthesis of a variety metallaboranes has been achieved by varying the number of chlorides in the monocyclopentadienylmetal halide dimer, reaction temperature, types of monoborane, and metal fragment sources.

The Wade–Mingos rules in seven-vertex dimetallaborane chemistry: Hydrogen-rich Cp2M2B5H9 systems of the second and third row transition metals

“…Stable dimetallaboranes of nido-like stoichiometry resembling the original B n H nþ4 binary boranes that have been synthesized include the five-vertex derivatives Cp* 2 M 2 B 3 H 7 (M ¼ Co [12,13], Rh [14]), the six-vertex derivatives Cp* 2 M 2 B 4 H 8 (M ¼ Ir [15,16], Ru [17], and Re [18]), and the seven-vertex derivatives Cp* 2 M 2 B 5 H 9 (M ¼ Cr [19], Mo [19,20], W [21]), where Cp* ¼ h 5 -Me 5 C 5 . Hydrogen-richer seven-vertex systems Cp* 2 M 2 B 5 H 11 (M ¼ V [22], Ta [23,24] of arachno-like stoichiometry have also been synthesized.…”

Structure and decomposition of [HFe(CO)4(B2H5)], a revised behavior of an old uncharacterized complex

“…The distance d FeeH a ¼ 1:56 A is slightly longer than Fe-terminal hydrogen bonds in B and C ( [52]) and [Fe(CO) 4 ] fragments where the borane involves a mixed linking mode using a terminal hydrogen H a (of B 1 ) to build a bridged bond FeeH a eB 1 and a directly bonded B 2 eFe (Scheme 1). Nevertheless the BeB distance (1.907 A) which is longer than the usual bridged B 2 (m-H)M (M ¼ Ru) one (1.733e1.840) [13,16,20,53,54] in the complexed state, does not support this view. In the bimetallic species (C 5 Me) 2 Ta 2 (mBr) 2 (B 2 H 6 ) [55], the BeB bond exhibits a close distance to ours (1.88 A).…”

Six-Vertex Hydrogen-Rich Cp2M2B4H8 Dimetallaboranes of the Second- and Third-Row Transition Metals: Effects of Skeletal Electron Count on Preferred Polyhedra

“…In fact, Cp 2 Ir 2 B 4 H 8 is a transition-metal analogue of the known hexaborane 20 B 6 H 10 and is found experimentally to have a similar pentagonal-pyramidal structure. 24 In addition, the Cp 2 M 2 B 4 H 8 (M = Ru, Os) systems have the 14 Wadean skeletal electrons Figure 1. Removal of a vertex in various ways from seven-vertex deltahedra analogous to closo, isocloso, and oblatocloso deltahedra.…”