Structure and reactivity of sterically hindered lithium amides and their diethyl etherates: crystal and molecular structures of [Li{N(SiMe3)2}(OEt2)]2 and tetrakis(2,2,6,6-tetramethylpiperidinatolithium)

1983 ◽  
Vol 105 (2) ◽  
pp. 302-304 ◽  
Author(s):  
Michael F. Lappert ◽  
Martin J. Slade ◽  
Anirudh Singh ◽  
Jerry L. Atwood ◽  
Robin D. Rogers ◽  
...  
Keyword(s):  
Molecular Structures ◽  
Crystal And Molecular Structures ◽  
Lithium Amides ◽  
Sterically Hindered

Structural studies of organoboron compounds LIX. Reaction of two sterically hindered N,N′-dihydroxyaminals with phenylboronic acid, and the crystal and molecular structures of the resulting 1,3,5-trioxa-6,8-diaza-2,4-diboracyclooctanes and one of the adducts

1993 ◽  
Vol 71 (12) ◽  
pp. 2129-2138 ◽  
Author(s):  
Wolfgang Kliegel ◽  
Gottfried Lubkowitz ◽  
Steven J. Rettig ◽  
James Trotter
Keyword(s):  
Bond Order ◽  
Phenylboronic Acid ◽  
Direct Methods ◽  
Molecular Structures ◽  
Structural Studies ◽  
Bond Orders ◽  
Space Group ◽  
Crystal And Molecular Structures ◽  
Transannular Interaction ◽  
Sterically Hindered

The syntheses of the sterically hindered N,N′-dihydroxyaminals; N,N′-bis(1-ethoxycarbonyl-1-methylethyl)-N,N′-dihydroxymethanediamine, 1b, and N,N′-bis(1,1-dimethylethyl)-N,N′-dihydroxymethanediamine, 1c, and their reactions with phenylboronic acid to yield the 1,3,5-trioxa-6,8-diaza-2,4-diboracyclooctanes 3 and 4, respectively, are described. Crystals of 1b are tetragonal, a = 18.413(1), c = 9.867(2) Å, Z = 8, space group I41; those of 3 are monoclinic, a = 20.420(4), b = 8.272(4), c = 17.851(5) Å, β = 117.34(1)°, Z = 4, space group C2/c; and those of 4 are monoclinic, a = 9.493(4), b = 16.202(4), c = 14.783(3) Å, β = 101.90(2)°, Z = 4, space group P21/c. The structures were solved by direct methods and were refined by full-matrix least-squares procedures to R = 0.034, 0.039, and 0.040 (Rw = 0.035, 0.034, and 0.036) for 1550, 1438, and 2187 reflections with I ≥ 3σ(F2), respectively. In the solid state, both 3 and 4 exhibit transannular [Formula: see text] interactions. In 3 there are two identical (by symmetry) interactions with [Formula: see text] Å that have estimated bond orders of 0.06, while the single transannular interaction in 4 has N—B = 1.953(3) Å and a bond order of about 0.3. The intermediate-strength transannular interaction in 4 is the first to be reported for this type of molecule.

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