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Metallaboranes from Metal Carbonyl Compounds and Their Utilization as Catalysts for Alkyne Cyclotrimerization
Author(s) -
Anju V. P.,
Barik Subrat Kumar,
Mondal Bijnaneswar,
Ramkumar V.,
Ghosh Sundargopal
Publication year - 2014
Publication title -
chempluschem
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.801
H-Index - 61
ISSN - 2192-6506
DOI - 10.1002/cplu.201400013
Subject(s) - cyclopentadienyl complex , alkyne , moiety , chemistry , catalysis , reactivity (psychology) , metal , photodissociation , valence (chemistry) , ligand (biochemistry) , boron , valence electron , main group element , metal carbonyl , medicinal chemistry , nuclear magnetic resonance spectroscopy , molecule , yield (engineering) , photochemistry , stereochemistry , transition metal , organic chemistry , electron , materials science , medicine , biochemistry , physics , alternative medicine , receptor , pathology , quantum mechanics , metallurgy
The photolysis of [M 2 (CO) 10 ] (M=Re or Mn) with BH 3 ⋅thf at room temperature yields arachno ‐1 and 2 , [(CO) 8 M 2 B 2 H 6 ] ( 1 : M = Re, 2 : M = Mn). Both the compounds show a butterfly structure with seven skeletal electron pairs and 42 valence electrons. This result presents a new method for general access to low‐boron‐content metal–boron compounds without the cyclopentadienyl ligand at the metal centers. This new synthetic route is superior to the existing procedures because it avoids the use of [LiBH 4 ] and metal polychlorides, for which the synthesis is very tedious. Compound 1 catalyzes the cyclotrimerization of a series of internal and terminal alkynes to yield mixtures of 1,3,5‐ and 1,2,4‐substituted benzenes. The reactivity of 1 with alkynes demonstrates for the first time that the introduction of the [B 2 H 6 ] moiety into the [Re 2 (CO) 10 ] framework significantly enhances the catalytic activity. Note that [Re 2 (CO) 10 ] catalyzes the same set of alkynes under harsh conditions over a prolonged period of time. Quantum‐chemical calculations using DFT methods are applied to afford further insight into the electronic structure, stability, and bonding of 1 and 2 . All the compounds are characterized by IR and 1 H, 11 B, and 13 C NMR spectroscopy, and the geometry of 1 is established unambiguously through crystallographic analysis.