Crystals of (salicylaldox~mato-0,N)diphenylboron are triclin~c, n = 10.125(2), O = 10.797(1), c = 14.760(2) A, a = 89.05(1), P = 86.98(1), y = 83.18(1)", Z = 4, space group P i . The structure was solved by direct methods and was refined by full-matrix least-squares procedures to R = 0.040 and R,, = 0.048 for 4145 reflections with 1 2 3a(l). The structure consists of two crystallographically independent, but essentially identical, molecules linked by strong 0-H...O hydrogen bonds to form continuous spirals along the n axis. The PhzB moiety is chelated by the phcnol~c oxygen and oxime nitrogen atoms of the ligand resulting in the formation of a non-planar six-membered chelate ring. Important libration-corrected mean bond lengths are 0-B = 1.516 (1)

Crystals of diphenylboron N-methylacethydroxamate are orthorhombic, a = 12.5478(8), b = 7.8735(3), c = 13.6809(5) Å, Z = 4, space group Pnam. The structure was solved by direct methods and was refined by full-matrix least-squares procedures to R = 0.037 and Rw = 0.054 for 1265 reflections with I ≥ 3σ(I). The molecule features a five-membered BO2CN ring which lies in the crystallographic mirror plane. The carbon and nitrogen atoms of the heterocyclic ring are positionally disordered. Mean bond lengths (corrected for libration) are: O—B, 1.550(2), B—C, 1.609(2), O—C/N, 1.340(3), C—N, 1.300(2), C/N—CH, 1.470(2), and C—C(phenyl), 1.394(8) Å.

. Can. J. Chem. 64, 1855 (1986). The title compound was prepared according to the literature in order to determine whether it has a bicyclic cage structure resulting from intramolecular 0 --+ B coordination or a monocyclic boronate structure incorporating a trigonal planar boron atom. Crystals or 5-methyl-5-nitro-2-phenyl-l,3-dioxa-2-boracyclohexane are orthorhombic, a = 17.2358(4), b = 6.5007(2), c = 9.9225(3) A, Z = 4, space group Pnam. The structure was solved by direct methods and was refined by full-matrix least-squares procedures to R = 0.064 and R,. = 0.070 for 798 reflections with 1 r 3u(I). The nlolecule actually has Cl symmetry but, in the solid state, is located at a site of crystallographic C, symmetry. In order to maintain the apparent mirror symmetry the nitro oxygen atoms are disordered over two mirror-related rotational positions around the C(2)-N bond. The molecule was found to have a monocyclic boronate structure, in agreement with earlier predictions. Tile six-membered heterocyclic ring has a "semi-planar" conformation. Bond distances and angles are normal. [Traduit par la revue]

Es werden Borchelate 2 -6 aus N-Alkyl-bzw. N-Arylhydroxamsauren 1 und verschiedenen Borverbindungen, die fur eine Chelatbildung mit zweizahnigen Liganden geeignet sind, dargestellt. Die spektroskopischen Daten stehen im Einklang mit der cyclischen B,N-Betainstruktur von 2 -6 und reflektieren sowohl die Lewis-Aciditat der chelatisierten Borenium-Ionen als auch das Ausman der Elektronendelokalisierung in den Hydroxamat-Liganden. Boron Chelates of N-Substituted Hydroxamic AcidsBoron chelates 2 -6 are synthesized from N-alkyl-or N-arylhydroxamic acids 1 and various boron compounds that are capable of being chelated by bidentate ligands. The spectroscopic data correspond to the cyclic B,N-betaine structure of 2 -6 and reflect the Lewis acidity of the chelated borenium ions as well as the extent of electron delocalization in the hydroxamate ligands.Im Verlauf unserer Untersuchungen der B,N-Betainstruktur von Hydroxamsaure-Borchelaten -3, haben wir verschiedene Borchelate von N-alkylierten bzw. N-arylierten Hydroxamsauren dargestellt. Die ersten Verbindungen dieses Typs waren von Urnland und Mitarbb. mit dem Diphenylb~rchelat~) und dem Difluorborchelat5) der N-Phenylbenzohydroxamsaure vorgestellt worden. Eine massenspektrometrische Charakterisierung beider Verbindungen folgte spater6). In neueren Arbeiten wurden dann ein Difluorborchelat 2, und ein Diphenylborchelat 3, der N-Methylacetohydroxamsaure jeweils mit Rantgenstrukturanalyse beschrieben und weiterhin einige Difluorborchelate als Kontrollsynthone fur Photocy~lisierungen~) und fur die Gewinnung spektroskopischer Vergleichsdaten beim Studium protonierter Hydroxamsauren * -lo) eingesetzt.Die Borchelate 2-6 , in denen das Proton der N-substituierten Hydroxamsaure 1 durch ein Borenium-Ion (X,B') ersetzt ist, lassen sich am zutreffendsten mit der Grenzformulierung D charakterisieren, da nach den rontgenkristallographischen Befunden2s3) die B,N-Betainform D die Bindungszustande des Resonanzhybrids (C ++ D) am besten wiedergibt. Monzyk und Crumbliss haben an Eisen(II1)-hydroxamaten gezeigt, daR die Komplexstabilitat wesentlich durch die Elektronendonorfahigkeit des N-Substituenten (R') beeinflufit wird, wobei sowohl induktive als auch Resonanz-Effekte die Delokalisie-0 Verlag Chemie GmbH, D

Can. J. Chem. 54,3142 (1976). Crystals of 8,8-dimethyl-3,5-diphenyl-2,4,6-trioxa-l-azonia-3-bora-5-boranatabicyclo[3.3.O]-octane are monoclinic, cr = 22.323(1), b = 9.555(1), c = 16.0027(6) A, p = 109.055(4)", Z = 8, space group C2/c. The structure was solved by direct methods and was refined by full-matrix least-squares procedures to a final R of 0.048 and R , of 0.066 for 2629 reflections with I 2 3o(I).The central part of the molecule consists of two fused five-membered rings. One of them is a familiar BOCCN ring while the other is a novel and nearly planar BOBON ring containing one tetrahedral boron atom and one trigonal planar boron atom.