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

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. Can. J. Chem. 62, 1705Chem. 62, (1984.Details of the synthesis, physical properties, and solid-state structure of [(C7Hr02)Ga(CH,)2I2 are reported. Crystals of bis(tropolonatodimethylgallium) are monoclinic, a = 10.2669(9), b = 9.3237(3), c = 10.867 l(10) A, P = 1 12.896(4)", Z = 2, space group P2,/t1 (22"C, X = 0.70930 A). The structure was solved by conventional heavy-atom techniques and was refined by full-matrix least-squares procedures to R = 0.034 and R,,. = 0.037 for 1746 reflections with I 2 3u(I). The centrosymmetric binuclear dimer features five-coordinate gallium atoms havlng irregular trigonal bipyramidal coordination geometry and a planar four-membered Ga20, ring. !mportant bond lengths (corrected for libra!~on) are Ga-O(equatoria1) = 1.972(2), Ga-O(axial) = 2.025(2) and 2.55 l(2) A, and Ga-C = 1.951 (4) and 1.954(4) A. [Traduit par le journal] Introduction As part of our continuing study of compounds containing five-coordinate gallium atoms ( I -6) we have synthesized and structurally characterized the compound bis(tropo1onatodi-methylgallium), [(C7H502)Ga(CH,)2]2. The choice of tropolone as the "active hydrogen" compound in this study was dictated by three considerations. Firstly, it was hoped to incorporate the tropolonato moiety in a mixed pyrazolyl gallate anionic ligand, secondly, we wished to extend our studies of five-coordinate gallium systems having three oxygen atoms in the coordination sphere about gallium and, finally, tropolone and its derivatives have been recently cited as antibiotic potentiators (7). Although the first objective was not fulfilled, the bis(tropo1onatodi-methylgallium) compound was isolated in high yield and shown to consist of dimer units in the solid state, displaying the familiar Ga202 central bridging unit and irregular trigonal bipyramidally coordinated gallium atoms. In dilute solution and in the gas phase, however, the compound exists solely as the monomeric species. ExperimentalAir-sensitive materials were handled in oxygen-free dry nitrogen. Tetrahydrofuran (THF) was dried by refluxing over sodium/benzophenone and used immediately following dist~llat~on. Tropolone (Aldrlch) was used as supplied. Tr~methylgall~um was prepared as described earher (8). 3,5-Dimethylpyrazole (pzUH) (Aldrich) and sodlum hydride (Alfa) were used as suppl~ed.Attempted preparation of Na'[Me2Gapz"(C,H,0,1]-Trimethylgallium (2.156 g, 18.8 mmol) in THF was added to Napz" (2.218 g, 18.8 mmol) (made from NaH + pzVH) in the same solvent.To the clear colorless solution of Na'[Me3GapzU]-so formed was added tropolone (2.293 g, 18.8 mmol) in THF. An immediate formation of yellowish precipitate was observed. The mixture was refluxed for approximately 40 h and then filtered. The pale yellow solid precipitate was isolated and shown by elemental analysis to be sodlum tropolonate, Na'C7HSO2-. The soluble reaction product from the reaction was shown to be the [Me,Ga(p-pzU)l2 dimer (9). Preparation of bis(tropolotzatodimethylgalliutn), [(C7H.~O~)Ga(CH.~)21~Trimethylgallium (1.945 g, 16.96 mmol) in...

Section: Fig I Stereoscopic View Of Bis(tropolonatodimethylgallium)supporting

confidence: 58%

Synthesis and structural characterization of bis(tropolonatodimethylgallium), [(C₇H₅O₂)Ga(CH₃)₂]₂

Rettig¹,

Storr²,

Trotter³

1984

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“…The B-C bonds are es2entially equal in the two structures, mean B-C = 1.600(4) A. These distances are in good agreement with those observed for other resonance-stabilized five-membered 0,O-chelates of diphenylboron (in 8 (X = Ph) 0-B = 1.548(2) and 1.552(2), B-C = 1.609 (2), and in (tropolonato)diphenylboron (36) 0-B = 1.544(2) and 1.565(2), B-C = 1.599(2) and 1.61 l(3) A) and similar to those in the two crystalline forms of (acetylacetonato)diphenylboron (36) The equatorially substituted cyclohexane ring has a regular chair con<ormation and normal geometry (mean C-C = 1.529(7) A, mean C-C-C = 1 1 1.2(7)"). Of the four Bphenyl rings in the two structures, three are slightly but significantly non-planar while the other (C(12) ring in 6b) is planar within experimental error (x2 = 32.5, 35.0, 55.4, and 5.7, maximum deviation from the mean plane 0.015(2) A).…”

Section: Resultsmentioning

confidence: 58%

Structural studies of organoboron compounds. XVIII. Crystal and molecular structures of 2,2-diphenyl-1,3-dioxa-3a-azonia-2-borataindan and 4-cyclohexyl-6-methyl-2,2-diphenyl-1,3-dioxa-3a-azonia-2-borataindan

Kliegel¹,

Nanninga²,

Rettig³

et al. 1983

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. 61, 2493 (1983). The crystal structures of 2,2-d1phenyl-l,3-dioxa-3a-azonia-2-borataindan, 6a, and 4-cyclohexyl-6-methyl-2,2-d~phenyl-1,3-dioxa-3a-azonia-2-borataindan, 6b, reported here represent the first crystallographic examples of coordination complexes of the anionic ligand derivedo from 2-hydroxypyridine N-oxide. Crystals of 6a are monoclinic, a = 11.5210(13), 6 = 10.2860(8), c = 12.7354(15) A, P = olO1 .878(5)", Z = 4, space group P 2 , l c ; and those of 6b are monoclin~c, a = 8.5047 (8)

“…These distortions involve distances and angles in the B3O3 ring as well as the planarity of the boroxine ring, reducing the symmetry of the anion to approximately Cz, . (20)(21)(22)(23)(24)(25)(26)(27). In further support of the a-bonding argument, the longer of the two bonds (B(2)-O(1)) is observed where there is a larger local deviation from planarity (see Table 4).…”

Section: X-ray Crystallographic Analysismentioning

confidence: 99%

Structural studies of organoboron compounds. XXII. Preparation and crystal and molecular structure of tetramethylammonium-2,4,6,6-tetraphenyl-1,3,5-trioxa-2,4- dibora-6-boratacyclohexane

Kliegel¹,

Motzkus²,

Rettig³

et al. 1985

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Details of the preparation and physical properties of (Me4N)+ (Ph4BS03) -are given. Crystals of tetramethylammonium 2,4,6,6-tetraphenyl-I ,3,5-trioxa-2,4-dibora-6-boratacyclohexane are orthorhombic, a = 18.130(2), b = 11.9745(7), c = 12.5187(5) A, Z = 4, space group P n a 2 , . The structure was solved by direct methods and was refined by full-matrix least-squares procedures to R = 0.056 and R,,. = 0.064 for 1460 reflections with I 2 2u(l). The crystal structure consists of discrete tetramethylammonium cations and tetraphenylboroxinate anions, the first such anion to be structurally characterized. Introduction X-ray crystallographic analyses of heterocyclic boron compounds containing BOBON ring systems such as 1 (1) and 2 (2) or of polycyclic compounds such as 3, which contain the same BOBON ring system (3-5), reveal a remarkably short B-0 distance between the tricoordinated boron atom and the oxygen atom within the B(S~')-O-B(S~') moiety in each case. This indicates a strong pp(n)-interaction between the tricoordinate boron atom and the oxygen atom (6, 7) at this site of the BOBON ring which represents an anhydridic bond between a boronic acid and a tetracoordinated borinic (1 and 2) or boronic acid (3). Replacement of the N-0 unit (hydroxylamine component) in 1 or 2 by an 0-B-0 unit (a second boronic acid component) should lead to a boroxine ring system with one negatively charged tetrahedral boron atom and two very short B-0 bonds of the type described above (cf.