Iridium-catalyzed Borylation of Pyrene: Irreversibility and the Influence of Ligand on Selectivity

The iridium-catalyzed borylation of pyrene, using 4,4′-dimethyl-2,2′-bipyridine as the ligand, in the presence of t-BuOK, gave a mixture of 2,4,7,9-tetrakis(Bpin)pyrene (c4) and its 2,4,7,10-isomer (m4) in a 2.2:1 ratio, and the selectivity of the Ir-catalyzed borylation of pyrene is kinetically determined and can be influenced to some extent by the nature of the ligand

Heterometallic cubane-type clusters containing group 13 and 16 elements

Heterometallic cubane-type clusters were synthesized from the reaction of group 6 and 8 metallaboranes using transition-metal carbonyl compounds. Structural and spectroscopic study revealed the existence of novel “capped-cubane” geometry. In addition, the crystal structure of these clusters distinctly confirms the presence of boride unit as one of the vertices. These clusters possess 60 cluster valence electrons (cve) and six metal–metal bonds. A plausible pathway for the formation of ruthenium-capped cubane has been described

Ring expansion of a Cp moiety upon CO insertion: Synthesis and characterization of [(η⁶-C₆H₅OCo)Co₃(CO)₉]

Reaction of [(CpV)2(B2H6)2], 1 (Cp = η5-C5H5) with four equivalents of [Co2(CO)8] or [Co4(CO)12] in hexane at 70 °C leads to the isolation of the tetranuclear carbonyl cluster, [(η6-C6H5OCo)Co3(CO)9], 2 in modest yield. The geometry of 2 is similar to that of [Co4(CO)12] where all the four Co atoms are arranged in a tetrahedral geometry. The apical cobalt atom in 2 is coordinated to C6H5O ring in a η6-fashion and the other three cobalt atoms are each coordinated to three carbonyl ligands. Compound 2 has been characterized in solution by IR, 1H, 13C NMR and mass spectrometry and the structural types were unequivocally established by crystallographic analysis

Metallaheteroborane clusters of group 5 transition metals derived from dichalcogenide ligands

Treatment of group 5 metal polychlorides such as, [CpnMCl4-x] (M = V: n, x = 2; M = Nb: n = 1, x = 0), or [Cp∗TaCl4] (Cp = η5–C5H5, Cp∗ = η5-C5Me5), with [LiBH4·THF] followed by thermolysis in the presence of diphenyl diselenide yielded metallaheteroborane clusters [{CpV(μ-SePh)} 2 (μ-Se)], 1 [(CpNb)2B4H9(μ-SePh)], 2 and [(Cp∗Ta)2B4H11(SePh)], 3 in modest yields. Compound 1 is an organovanadium selenolato cluster in which two (CpV) moieties bridged by (μ-Se) and two (μ-SePh) ligands. Compound 2 exhibits a bicapped tetrahedral core with one (μ-SePh) ligand. 3 is a tantalahexaborane cluster in which one of the terminal BH protons is substituted by SePh. Compounds 1–3 have been characterized by mass spectrometry, 1H, 11B, 13C NMR spectroscopy, and the geometric structures were unequivocally established by crystallographic analysis of 1–3

From metallaborane to borylene complexes: syntheses and structures of triply bridged ruthenium and tantalum borylene complexes

Reaction of [1,2-(Cp*RuH)₂B₃H₇] (1; Cp*=η⁵-C₅Me₅) with [Mo(CO)₃(CH₃CN)₃] yielded arachno-[(Cp*RuCO)₂B₂H₆] (2), which exhibits a butterfly structure, reminiscent of 7 sep B₄H₁₀. Compound 2 was found to be a very good precursor for the generation of bridged borylene species. Mild pyrolysis of 2 with [Fe₂ (CO)₉] yielded a triply bridged heterotrinuclear borylene complex [(μ₃-BH)(Cp*RuCO)₂ (μ-CO){Fe(CO)₃}] (3) and bis-borylene complexes [{(μ₃-BH)(Cp*Ru)(μ-CO)}₂Fe₂ (CO)₅] (4) and [{(μ₃-BH)(Cp*Ru)Fe(CO)₃}₂ (μ-CO)] (5). In a similar fashion, pyrolysis of 2 with [Mn₂(CO)10] permits the isolation of μ₃-borylene complex [(μ₃-BH)(Cp*RuCO)₂ (μ-H)(μ-CO){Mn(CO)₃}] (6). Both compounds 3 and 6 have a trigonal-pyramidal geometry with the μ₃-BH ligand occupying the apical vertex, whereas 4 and 5 can be viewed as bicapped tetrahedra, with two μ₃-borylene ligands occupying the capping position. The synthesis of tantalum borylene complex [(μ₃-BH)(Cp*TaCO)₂ (μ-CO){Fe(CO)₃}] (7) was achieved by the reaction of [(Cp*Ta)₂B₄H₈ (μ-BH₄)] at ambient temperature with [Fe₂ (CO)₉]. Compounds 2–7 have been isolated in modest yield as yellow to red crystalline solids. All the new compounds have been characterized in solution by mass spectrometry; IR spectroscopy; and ¹H, ¹¹B, and ¹³C NMR spectroscopy and the structural types were unequivocally established by crystallographic analysis of 2–6

Efficient Synthesis of Aryl Boronates via Zinc-Catalyzed Cross-Coupling of Alkoxy Diboron Reagents with Aryl Halides at Room Temperature

A zinc­(II)/NHC system catalyzes the borylation of aryl halides with diboron (4) reagents in the presence of KOMe at rt. This transformation can be applied to a broad range of substrates with high functional group compatibility. Radical scavenger experiments do not support a radical-mediated process

Reusable Fe2O3-nanoparticle catalysed efficient and selective hydroboration of carbonyl compounds

The first Fe2O3-nanoparticle catalysed hydroboration of aromatic and aliphatic aldehydes and ketones with HBpin (pin = OCMe2CMe2O) is reported. The reaction proceeds under mild conditions (room temperature) and is moderately sensitive to air. This process is applicable to a broad range of substrates with high functional group compatibility. Moreover, aldehydes are selectively hydroborated over other reducible functional groups, such as ketone, nitrile, hydroxide, alkene, amide, ester, nitro and halide groups

Condensed tantalaborane clusters: synthesis and structures of [(Cp*Ta)₂B₅H₇{Fe(CO)₃}₂] and [(Cp*Ta)₂B₅H₉{Fe(CO)₃}₄]

The reaction of [(Cp*Ta)₂B₄H₉(μ-BH₄)] (1; Cp* = η⁵-C₅Me₅) with [Fe₂(CO)₉] in hexane yielded [(Cp*Ta)₂B₅H₇{Fe(CO)₃}₂] (2) and [(Cp*Ta)₂B₅H₉{Fe(CO)₃}₄] (3) in moderate yield. Cluster 2 represents the first example of a bicapped pentagonal-bipyramidal metallaborane with a deformed equatorial plane, and 3 can be described as a fused cluster in which two pentagonal-bipyramidal units are fused through a common 3-vertex triangular face. Compounds 2 and 3 have been characterized by mass spectrometry and IR, ¹H, ¹¹B, and ¹³C NMR spectroscopy, and the geometric structures were unequivocally established by crystallographic analysis