Selective dismantling of closo-1,2-C2B10H12 to lower-cage dicarbaborane systems

1991 ◽  
Vol 56 (8) ◽  
pp. 1618-1635 ◽  
Author(s):  
Jaromír Plešek ◽  
Bohumil Štíbr ◽  
Xavier L. R. Fontaine ◽  
John D. Kennedy ◽  
Stanislav Heřmánek ◽  
...  
Keyword(s):  
Nmr Spectroscopy ◽  
Solution Structure ◽  
High Yield ◽  
Two Dimensional ◽  
Oxidizing Agents ◽  
Elimination Reactions

A modified, high-yield synthesis of the two isomeric nido twelve-vertex [C2B10H13]- anions, "reactive" [nido-7,9-C2B10H13]- and "unreactive" [nido-7,12-C2B10H13]-, has been developed. A solution structure for the reactive [nido-7,9-C2H10B13]- isomer is proposed on the basis of the result of two-dimensional 11B and 1H correlation NMR spectroscopy. It is concluded that there is a marked similarity between this species and the eleven-vertex congener [nido-7,8-C2B9H12]-. In accord with this parallel, the "reactive" twelve-vertex species is found to undergo selective boron-vertex elimination reactions in the presence of oxidizing agents. These reactions give excellent yields of smaller-cage nido dicarbaborane compounds, namely [nido-7,8-C2B9H12]-, [9-(SMe2)-nido-7,8-C2B9H11], and nido-5,6-C2B8H12. NMR spectroscopy assigns cluster 11B and 1H resonances for all the compounds isolated, and thence permits comparison with the equivalent shielding patterns of structurally related analogues such as [nido-7-CB10H13]- and [nido-7,9-C2B9H12]-.

Studies of the solution structure of the bleomycin A2-iron(II)-carbon monoxide complex by means of two-dimensional NMR spectroscopy and distance geometry calculations

1990 ◽  
Vol 112 (21) ◽  
pp. 7462-7474 ◽  
Author(s):  
Marcel A. J. Akkerman ◽  
Eric W. J. F. Neijman ◽  
Sybren S. Wijmenga ◽  
Cornelis W. Hilbers ◽  
Wolfgang Bermel
Keyword(s):  
Carbon Monoxide ◽  
Nmr Spectroscopy ◽  
Solution Structure ◽  
Distance Geometry ◽  
Two Dimensional

Nine- and Eight-Vertex Polyhedral Dicarbaborane Chemistry: New arachno and hypho Dicarbaboranes from arachno-4,5-C2B7H13: Isolation and Characterization of the [arachno-4,5-C2B7H12]- and [hypho-7,8-C2B6H13]- Anions, and of the Neutral Ligand Derivatives exo-6-(MeNC)-arachno-4,5-C2B7H11 and exo-5-L-hypho-4,9-C2B7H13 (L = NMe3 and NEt3)

1994 ◽  
Vol 59 (7) ◽  
pp. 1584-1595 ◽  
Author(s):  
Tomáš Jelínek ◽  
Josef Holub ◽  
Bohumil Štíbr ◽  
Xavier L. R. Fontaine ◽  
John D. Kennedy
Keyword(s):  
Nmr Spectroscopy ◽  
Selective Removal ◽  
High Yield ◽  
Two Dimensional ◽  
Neutral Ligand ◽  
Tertiary Amines ◽  
Proton Sponge ◽  
H Nmr ◽  
Isolation And Characterization

Deprotonation of neutral arachno-4,5-C2B7H13 (1) either with 1, 8-(NMe2)2C10H6 (proton sponge, PS) or with a mixture of aqueous K2CO3 and [NMe4]Cl leads to the isolation in high yield of the [arachno-4,5-C2B7H12]- anion (2). Isostructural with this anion is the ligand derivative exo-6-(MeNC)-arachno-4,5-C2B7H11 (3), which is prepared in 20% yield from the reaction between arachno-4,5-C2B7H13 and MeNC in dichloromethane. Under comparable conditions compound 1 with tertiary amines gives the first representatives of the nine-vertex hypho family of dicarbaboranes, the ligand derivatives exo-5-(NR3)-hypho-4,9-C2B7H13 (4a and 4b, where R = Me and Et, respectively) in moderate yields (20 - 55%), whereas the reaction between 1 and aqueous NaCN results in the selective removal of one boron vertex to yield the eight-vertex [hypho-7,8-C2B6H13]- anion (5) in 61% yield. All compounds isolated were characterized by 11B and 1H NMR spectroscopy, with two-dimensional and selective decoupling techniques giving unambiguous assignments.

scholarly journals Solution structure of the phosphocarrier protein HPr fromBacillus subtilisby two-dimensional NMR spectroscopy

1992 ◽  
Vol 1 (10) ◽  
pp. 1363-1376 ◽  
Author(s):  
Michael Wittekind ◽  
Ponni Rajagopal ◽  
Bruce R. Branchini ◽  
Jonathan Reizer ◽  
Milton H. Saier ◽  
...  
Keyword(s):  
Nmr Spectroscopy ◽  
Solution Structure ◽  
Two Dimensional

Solution structure of neuronal bungarotoxin determined by two-dimensional NMR spectroscopy: sequence-specific assignments, secondary structure, and dimer formation

Biochemistry ◽  
1991 ◽  
Vol 30 (20) ◽  
pp. 4901-4909 ◽  
Author(s):  
Robert E. Oswald ◽  
Michael J. Sutcliffe ◽  
Michelle Bamberger ◽  
Ralph H. Loring ◽  
Emory Braswell ◽  
...  
Keyword(s):  
Nmr Spectroscopy ◽  
Secondary Structure ◽  
Solution Structure ◽  
Two Dimensional ◽  
Dimer Formation
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