Synthesis of closo-1,2-H₂C₂B₈Me₈ and 1,2-H₂C₂B₈Me₇X (X = I and OTf) Dicarbaboranes and Their Rearrangement Reactions

Abstract

Methyl-camouflaged dicarbaboranes closo-1,2-and 1,10-H 2 C 2 B 8 Me 8 have been prepared in high yields either from nido-5,6-H 2 C 2 B 8 H 10 or closo-1,2-H 2 C 2 B 8 H 8 via electrophilic methylation reactions and cluster-rearrangement methods. Prepared were also monosubstituted derivatives of general formulation closo-H 2 C 2 B 8 Me 7 −X (X = I or OTf). The permethylated compounds exhibit extreme air stability in comparison to unprotected counterparts as a consequence of rigid, egg-shaped hydrocarbon structures incorporating inner C 2 B 8 carborane scaffolding. The structures of all compounds isolated were confirmed unambiguously by multinuclear ( 11 B, 1 H, 13 C, and 19 F) NMR measurements, supported by X-ray diffraction analyses and geometry optimization methods on several compounds.

Thiaboranes on Both Sides of the Icosahedral Barrier: Retaining and Breaking the Barrier with Carbon Functionalities

“…Consequently, the methylated borons in the 11 B NMR spectrum of 7,8,9,10,11,12‐Me 6 ‐ closo ‐1‐SB 11 H 5 are significantly paramagnetically deshielded to high frequencies (i. e. downfield‐shifted) with respect to the parent compound (−5.6 ppm for B(7–11), 18.2 ppm for B(12)). This quantitatively agrees with the trend observed for methylated carbaboranes . In contrast, the borons of the pentagonal belt directly adjacent to sulfur are more shielded (i. e. upfield shifted) than in the parent compound (−5.2 ppm for B(2–6)) …”

“…This quantitatively agrees with the trend observed for methylated carbaboranes. [30,31,32] In contrast, the borons of the pentagonal belt directly adjacent to sulfur are more shielded (i. e. upfield shifted) than in the parent compound (À 5.2 ppm for B (2)(3)(4)(5)(6)). [26] Nido Thiaborane Clusters…”

“…After column chromatography on silica gel using hexane as an eluent, 0.210 g (85 % yield based on the starting 1-SB 11 H 11 ) of 7,8,9,10,11,12-Me 6closo-1-SB 11 H 5 were obtained as a white powder, as unambiguously verified by the ab initio/GIAO/NMR structural tool (see Table 3 and refs. [5,14,[30][31][32] as other examples of this structural methodology). Its purity > 98 % was assessed by GC MS. Figure 5.…”

Protonation of dppbz- and binap-ligated rhodathiaboranes yielding proton, hydride and hydrogen exchange

“…The bridging B6-O1 distance in the rhodathiaborane cage-triflate bond measures 1.514(5) Å, slightly exceeding the mean value of 1.469 Å observed across six triflate-ligated polyhedral boron-containing compounds deposited in the Cambridge Structural Database (CSD). [37] Conversely, the S-O1 length at 1.520(3) Å closely approximates the mean value of 1.524 Å for this B-O-S bridging linkage observed in substituted decaborane and carborane clusters analysed crystallographycally [49][50][51][52][54].The introduction of the CF3-SO3 group breaks the symmetry present in parent cluster 2 and the dppbz ligand tilts slightly in derivative 7 to mitigate steric hindrance from the triflate substituent.…”