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

Abstract

. 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...

Synthesis and structural characterization of glycinatodimethylgallium, (C2H4NO2)Ga(CH3)2

“…2 and Table 5). The monomer units show no tendency to associate via formation of a (Ga-0)2 four-membered ring system as was found previously in the solid-state structures of numerous five-coordinate gallium complexes (3,12), or to form a polymeric chain via. weak Ga-0 bonding to the "uncoordiCan.…”

Synthesis, characterization, and structural studies of gallium citrate complexes

“…The central four-membered ring is exactly planar, while the five-membered chelate rings are significantly non-planar (x2 = 166) although each of these rings, as well as tbe entire fused ring system, is planar to within +0.046(6) A. The Ga-0 distances inv~lving the bridging alkoxide 0 atom (1.950(3) and 2.103(3) A, respectively, for equatorial and axial bonds) are comparable to those observed in other dimeric alkoxo-bridged species, the corresponding ranges being 1.91 l(3)-1.960(8) and 2.018(2)-2.078(3) A (16 …”

“…The dimerization occurs via the formation of a central four-membered Ga,02 ring, the Ga atoms attaining 5-coordination in a trigonal-bipyramidal fashion with the two coordination polyhedra sharing an axial-equatorial edge as in numerous previous examples (16). It is interesting that the outer ester groups do not chelate the gallium atoms.…”

Coordination compounds containing a novel tridentate pyrazolylgallate ligand. X-ray structures of Me2Ga(μ-OH)(μ-Me2pz)GaMe2•HOCH2Me2pz and [Me2Ga(pz)(OCH2pz)]2Ni (pz = N2C3H3)

“…Thus the 'H nmr spectrum gives singlets for both the -Gable2 and -CH2-protons, a pattern inconsistent with a fac coordination for the ligand. (14,(25)(26)(27).…”

“…An equimolar amount of 1-hydroxymethylpyrazole (0.502 g, 5.12 mmol) in THF was added to a THF solution of Na'Me3Gapz- (14) and the mixture was refluxed overnight. The resultant clear solution was cooled and made up to standard volume with THF for use in subsequent reactions.…”