Structural studies of organoboron compounds LXIV. Boron chelate formation with glycolohydroxamic acids, and the crystal and molecular structure of 5-(1-hydroxycyclohexyl)-2,2-diphenyl-1,3-dioxa-4-azonia-2-borata-4-cyclopentane

A diphenylboron chelate of anN-alkyl-2,2-diarylglycolohydroxamic acid

“…The Xray analysis con®rms the molecular structure (II), a typical hydroxamatoboron complex, the general geometry of which is very similar to that of related compounds (Kliegel et al, 1996, and references therein;Kliegel et al, 2001). The preference of the hydroxamate group as the ligand for the Ph 2 B + ion is in agreement with the ®ndings for the diphenylboron chelates of hydroxamic acids containing additional 2-hydroxy groups as possible nucleophilic ligands in the carbonic acid part (Kliegel et al, 1996) or in the hydroxylamine part (Kliegel, Schumacher, Tajerbashi et al, 1991).…”

Diphenylboron chelate of an 3-hydroxy-N-(2-hydroxyalkyl)hydroxamic acid

“…1). The detailed structure of the chelate ring system in (II) is very similar to that found in related hydroxamatoboron chelates (Kliegel et al, 1996(Kliegel et al, , 2001(Kliegel et al, , 2002, and references therein), the BONCO ring having a slight B-envelope conformation [dihedral angle magnitudes 1.5 (3)±6.9 (3) ]. The short C1Ð N1 bond distance of 1.297 (3) A Ê corresponds to a high amount of double-bond character, with a %-bond order of around 0.8, similar to the hydroxamatoboron complex reported recently (Kliegel et al, 2002).…”

“…Comparable to the latter is also the retention of about 50% of the double-bond character of the C1ÐO2 carbonyl bond of the hydroxamate moiety. The two OÐB bonds show a difference of 0.030 A Ê between the longer (C)OÐB bond [1.569 (5) A Ê ] and the shorter (N)OÐB bond [1.539 (4) A Ê ]; this difference lies in the normal range 0.001± 0.035 A Ê found in other hydroxamatoboron complexes (Kliegel et al, 1996(Kliegel et al, , 2001.…”

“…In the course of our research on the formation of boron complexes with functionally modi®ed hydroxamic acids (Kliegel et al, 1996(Kliegel et al, , 2001(Kliegel et al, , 2002, and references therein), the tetradentate ligand (I), obtained from (AE)tropic acid and 1-(N-hydroxyaminomethyl)cyclohexanol, was reacted with diphenylborinic acid (anhydride).…”

An OBONC five-membered heterocycle

“…The molecule of (II)•EtOH contains a five-membered O-B-O-N═C ring, which is nearly planar [slight B-envelope, with dihedral angles with magnitudes in the range 0.2 to 3.5 (2)°], similar to the geometry in related substances (Rettig et al, 1977(Rettig et al, , 1978Kliegel et al, 1983Kliegel et al, , 1990Kliegel et al, , 1996Kliegel, Schumacher et al, 1991;. The short C-N bond [1.301 2 45.3 (w 1/2 = 214 Hz): ratio of peak areas 20:1 [the main peak at 14.1 p.p.m.…”