Crystal and Molecular Structure of 4,4-Dimethyl-2,2-diphenyl-1,3-dioxa-4-azonia-2- boranatacyclopentane

Self Cite

. Can. J. Chem. 60,2957Chem. 60, (1982. There are two crystalline modifications of (acetylacetonato)diphenylboron: triclinic, a = 8.3557(8), b = 9.3519(8), c = 9.6103 (9) A, a = 96.094(5), P = 94.904(6), y = 93.489(6)", Z = 2, space group PT, and monoclinic, a = 11.6329(11), b = 17.1628(8), c = 7.6542(6) A, P = 97.669(4)", Z = 4, space group P2, lc. Crystals of (tropolonato)diphenylboron are monoclinic, a = 12.1596(5), b = 10.2614(4), c = 12.4883(6) A, P = 100.965(2)",Z = 4, spacegroup P2,lc. All threestructures were solvedby direct methodsandwere refined by full-matrix least-squares procedures to R values of 0.046,0.041, and 0.035 for 2465, 2124, and 1722 reflections with 12 3o(I) respectively. Each structure consists of discrete molecules containing tetrahedrally coordinated boron atoms, both the acetylacetonato and tropolonato moieties being delocalized and symmetric. The chelate rings in both forms of (acety1acetonato)-diphenylboron have distorted B-envelope conformations while the chelate ring in (tropo1onato)diphenylboron is essentially planar.The mean l3-0 and B-C distances (corrected for libration) are: 1.543(4) and 1.605(4) A in triclinic, 1.533(3) and 1.607(4) A in monoclinic (acetylacetonato)diphenylboron, and 1.555(11) and 1.605(6) A in (tropolonato)diphenyIboron. Chem. 60, 2957Chem. 60, (1982. L'(acCty1acCtonato)diphenylbore se prCsente sous deux formes cristallines: (a) une forme triclinique appartenant au groupe Chaque structure comprend des molCcules discretes contenant des atomes de bore coordonnts de f a~o n tetraedrique, les deux unites acetylacCtonato et tropolonato Ctant symttriques et dClocalistes. Les cycles du chelate dans les deux formes d'(acttylacttonato) diphtnylbore ont des conformations du type enveloppe B dCformees tandis que le cycle du chClate dans le (tropolonato) diphenylbore est essentiellement plan. Les distances moyennes l3-0 et B-C (corrigkes pour la libration) sont IntroductionExperimental AS part of a continuing study of the molecular The compounds were prepared by reacting (2-aminoethanostructures of organoboron compounds (1-1 1) we 1ato)diphenylboron with the appropriate chelating agent in now report the crystal and molecular structures of ethanollacetone (1:l). With the exception of the solvent used, the procedure is identical to that previously reported for both 1 the acet~lacetOne and trO~O1One esters d i~h e n~l -(12) and 2 (16). Two crystalline modifications of 1 were obtainborinic acid. Both (acety1acetonato)diphenyl-ed. Colorless crvstals of the triclinic form were isolated directly boron, 1, and (tropolonato)diphenylboron~ 2, are stabilized by both intramolecular 0 + B interactions and by electron delocalization in the chelate rings. The chemical and physical properties of these compounds are well documented (12-17 and references therein).'References 1-11 list previous papers in this series.I from the reaction mixture and recrystallization from acetonk afforded colorless crystals of the monoclinic form. High-quality pale yellow crystals of 2 were isolated di...

“…Differences between chemically equivalent B-C distances have been observed earlier (3,5,6,28). The geometry of the B-substituted phenyl rings is as expected (28).…”

Section: Fig 1 Stereoscopic Views Of the Triclinic (Top)supporting

confidence: 59%

Structural studies of organoboron compounds. XII. Crystal and molecular structures of (acetylacetonato)diphenylboron and (tropolonato)diphenylboron

Rettig¹,

Trotter²

1982

Self Cite

“…The phenolic 0-B distances of 1.500(4) and 1.506(3) in 2 and 5 respectively as well as those of 1.530(2)-1.565 (2) in the acetylacetone and tropolone esters of diphenylborinic acid (1) are significantly longer th?n those in 1. The two equal C-B dist!nces (mean 1.599(1) A) are the same as that in 4 (1.599(2) A), but shorter than those in other compounds containing tetrahedral boron, which range from 1.603(5) A in 2 to 1.639 (8) A in 6 (23). The bonds C(2)-C(7), C(9)-C(14), C(1)-0(1), and C(8)-O(3) are all significantly longer than their counterparts in 2 and 5 indicating a lesser contribution from resonance form 16 than from comparable forms contributing to the structures of 2 and 5.…”

Section: Resultsmentioning

confidence: 70%

Structural studies of organoboron compounds. XIII. Preparation and crystal and molecular structure of bis[(salicylaldoximato(2−))phenylboron]

Rettig¹,

Trotter²

1983

Self Cite

. Can. J. Chem. 61, 206 (1983) The reaction of (C6HS)?BOH with salicylaldoxime yielded [ ( C~H S N O~) B C~H~]~ via a boron-carbon bond cleavage rtaction. Crystals of bis[(salicylaldoximato(2-))phenylboron] are triclinic, a-= 9.219(1), b = 11.240(1), c = 12.086(1) A, a = 100.682(7), P = 112.224(6), y = 92.189(7)", Z = 2, space group P 1. The structure was solved by direct methods and was refined by full-matrix least-squares procedures to R = 0.036 and R,,. = 0.049 for 3433 reflections with 1 2 3u(1). The molecule, which has approximate Cz symmetry. contains a system of five fused six-membered rings including the first crystallographically characterized BzNZOz ring. The compound is stabilized both by intramolecular N -z B coordination and by resonance delocalization and contains boron atoms in a distorted tetrahedral environment. Bond lengjhs (corrected for libration) are: 0-B, 1.469(2)-1.488(2), N-B, 1.602(2) and 1.575(2), C-B, 1.598 (2) Intensities were measured with graphite-monochromated Mo-Ka radiation (h = 0.71073 A) on an Enraf-Nonius CAD4-F diffractometer. An w-1.330 scan at 1.12-6.71' min-' over a range of (0.58 + 0.35 tan 0) degrees in w (extended by 25% on both sides for background measurement) was employed. Data were measured to 20 = 55". The intensities of three check reflections, measured every 3600 s throughout the data collection, remained constant to within 3%.

“…The iminium structure 2b-d or 4a is also supported by the 'H-nmr spectrum, which shows a low field shift of the N-methyl protons at 6 = 3.70 ppm which can be compared with the values for N-methyl protons in nitrones 6 (R = Me) of 3.70 ppm. Formally 4a can be derived by the elimination of R-H from the boron-nitrogen betaine 5 (26,37), the structure of which has been confirmed by X-ray analysis of the diphenylboron derivative (38). Structure 5 may also be regarded as a formal reduction derivative of 4a.…”

mentioning

confidence: 94%

Crystal and molecular structure of difluoroboron N-methylacethydroxamate (2,2-difluoro-4,5-dimethyl-1,3-dioxa-4-azonia-2-boranatacyclopent-4-ene)

Rettig¹,

Trotter²,

Kliegel³

et al. 1977

Self Cite

(1977). Metal hydroxamates are well known (1 1-15), but structural formulations are (as with hydroxamic acid or hydroxamate anions) still subject to some controversy (6,15). Spectroscopic data do not provide sufficient information for a definitive formulation. Evidence for at least partial C-N double bond and C-O single bond character is mainly given by X-ray crystallographic studies of organotin (16-18), iron (19), and zinc (20) complexes of hydroxamic acids and a nickel thiohydroxamate (15,21). Chelated protons are also easiiy displaced by "pseudometal" cations (22) X,Bf which are well established (23-27) as remarkable acceptors in the formation of chelate complexes. The bidentale dianionic ligand in Id should be well suited for the synthesis of boron chelates and in fact hydroxamic acids and their N-substituted derivatives readily form X,B-chelates 2 (8,9,26,(28)(29)(30)(31).' The uv spectrum of the anion 3 suggests the presence of C=N double bonding (8, 9 ) whereas for a cyclic thiohydroxamate the thione form, analogous to 2a, is favored but not unambiguously proven (30). With the assumption that a betainic structure 4a represents the best formal description of the chelates 2a-d, the study of complexes of Nsubstituted2 hydroxamic acids with electronaccepting boron compounds seemed very useful. One of the simplest molecules of this type is the N-methylacethydroxamate of the extremely electron-deficient difluoroborenium ion ( 2 or 4, R = R' = Me, X = F). The ir spectrum of Nmethylacethydroxamic acid (1. R = R' = Me) (32) displays an absorption around 1625 cm-' which can be assigned to C=O of the hydroxamic or to C=N of the hydroximic form (33). In the difluoroboron chelate 2 or 4a this band is shifted to a higher frequency (about 1675 cm-l) into the region of C=Nf vibrations of iminium salts, which is a general effect (34) associated with quaternization of a C=N group. The iminium structure 2b-d or 4a is also supported by the 'H-nmr spectrum, which shows a low field shift of the N-methyl protons at 6 = 3.70 ppm which can be compared with the values for N-methyl protons in nitrones 6 (R = Me) of 3.70 ppm. (6 (ppm) for N-methyl protons in N-methyl-C