Shuzo Shibata

The molecular structure of acetylacetone as studied by gas-phase electron diffraction

Abstract The molecular structure of the enol form of gaseous acetylacetone has been determined from electron diffraction data. The molecular skeleton is planar but it is not symmetric. The bond distances in the ring are r g (CO) = 1.243 ± 0.002 A, r g (CO) = 1.319 ± 0.003 A, r g (CC) = 1.382 ± 0.007, r g (CC) = 1.430 ± 0.008 A, r g (OH) = 1.049 ± 0.015 A and r g (O⋯O) = 2.512 ± 0.008 A. The hydrogen atom of the internal hydrogen bond lies 0.45 ± 0.08 A out of the molecular plane with the OHO angle of 137 ± 7°.

Ab initio study on the charge-transfer complexes of boron trihalide with ammonia, trimethylamine, phosphine and trimethylphosphine

Abstract The charge-transfer complexes between the donors DX 3 (D = N or P, X = H of CH 3 ) and the acceptors AY 3 (A = B, Y = H or halogen) were studied by ab initio calculation. The optimized structures of these complexes were almost in agreement with the experiments. Good correlation was found between the D-A distances and the formation energy of the complexes and the structural changes of the acceptors and donors by the complex formation were found to be deeply related to the charge transfer.

Molecular structures of dipivaloylmethane complexes of lanthanides of samarium to holmiun as determined by gas electron diffraction

Abstract The molecular structures of six Ln(dpm) 3 (Ln = Sm, Eu, Gd, Tb, Dy and Ho; dpm = (CH 3 ) 3 CCOCHCOC(CH 3 ) 3 ) have been determined by gas-phase eletron diffraction. The experimental data are consistent with a trigonal prismatic structure with the slightly pitched OLnO planes. The observed LnO distances show the predicted lanthanide contraction: r a (SmO) = 2.278(7) A to r a (HoO) = 2.226(8) A. The OLnO and the pitch angles also depend on the atomic number. The structural parameters of the dpm ligand are as follows (average values with stranded deviations): r a (CO) = 1.279(8) A, r a (CC r ) = 1.411(12) A, r a (CC t ) = 1.523(19) A, r a (C t C m = 1.548(9) A, r a (O…O) = 2.716(23)A, ∠OCC r = 124.5(6)°, ∠CC r C′ = 122.2(5)° and ∠C r CC t = 117.6(9)°.

Molecular structure of tris(dipivaloylmethanato)-praseodymium (III) as studied by gas electron diffraction

Abstract The molecular structure of tris(dipivaloylmethanato)erbium has been determined by gas-phase electron diffraction. The experimental data are consistent with a monomeric trigonal prismatic structure. The structural parameters are as follows: ra(ErO) = 2.218 ± 0.005, ra(CO) = 1.274 ± 0.004, ra(CCring) = 1.405 ± 0.006, ra(CCtext) = 1.513 ± 0.014, ra(CCmeth) = 1.550 ± 0.006 A, and ∠OErO = 75.0 ± 0.5°. The folding of the ligand about the OO axis is 22.2 ± 1.5°, and the t-butyl groups rotate freely.

Temperature effects of the molecular structure of dimethyl ether—boron trifluoride as studied by gas-phase electron diffraction

Abstract The molecular structure of dimethyl ether—boron trifluoride (CH 3 ) 2 O·BF 3 has been studied at temperatures of 16, 30 and 70°C by gas-phase electron diffraction. The molecule exists in a staggered conformation with an O—B distance of 1.75 ± 0.02 A, an angle between the O—B bond and the COC plane of 40 ± 8° and an FBF angle of 117 ± 2° at each temperature. However, the F—B and C—O distances are found to decrease with increasing temperature, and appear to converge to the corresponding values of the component molecules. The temperature dependence of the B—F and C—O distances is surprisingly large, compared with those in other molecules.

The molecular structures of complexes of pyridine with boron trifluoride, boron trichloride and boron tribromide as studied by gas phase electron diffraction

Abstract The molecular structures of pyridine complexes with boron trifluoride, boron trichloride and boron tribromide have been determined from gas electron-diffraction data. The molecular parameters of the boron trifluoride complex are r g (NB) = 1.669(7) A, r g (BF) = 1.366(2) A, ∠FBF = 113.3(4)°, r g (CN) = 1.345(6) A and r g (CC) = 1.382(4) A. The corresponding values for the boron trichloride complex are 1.706(12) A, 1.830(3) A, 112.5(3)°, 1.360(10) A and 1.390(6) A, and those of boron tribromide complex are 1.694(17) A, 1.986(3) A, 111.9(3)°, 1.362(12) A and 1.392(8) A. On complex formation the structure change of the acceptor molecules is much larger than that of the donor molecule and increases with the increase of atomic number of the halogen atoms.

Molecular structure of gaseous copper nitrate as studied by electron diffraction

Abstract The molecular structure of copper nitrate has been reinvestigated by gaseous electron diffraction. The experimental data were found to be consistent with a square-planar arrangement of the oxygen atoms of two bidentate nitrate groups. The bond distances and angles were determined as follows: CuO = 1.946 ± 0.003 A, NO(coordinated) = 1.298 ± 0.003 A, NO(terminal) = 1.205 ± 0.005 A, OCuO = 67.8 ± 0.2°. The sample of copper nitrate was also found to be considerably decomposed by heating at 150°C.

Molecular structure of gaseous copper(I) trifluoroacetate as determined by electron diffraction

Abstract The molecular structure of gaseous copper(I) trifluoroacetate was determined by electron diffraction. The molecule is dimeric and its skeleton is essentially planar. The molecular parameters and the uncertainties are r g (CuCu) = 2.566 ± 0.018 A, r g (CuO) = 1.874 ± 0.002 A, r g (CO) = 1.253 ± 0.004 A r g (CC) = 1.542 ± 0.005 A, r g (CF) = 1.333 ± 0.003 A and ∠OCuO′ = 170.3 ± 0.6°. The rotational barrier height of the CF 3 group is 5.9 ± 2.5 kJ mol −1 , and the minimum of the barrier is at the position such that one of the CF bonds lies on the plane perpendicular to the ring.

Ab initio MO study of the geometries of four-coordinated zinc, copper and nickel acetylacetone complexes

Abstract Ab initio SCF MO calculations on the four-coordinated acetylacetone complexes of Zn(II), Cu(II) and Ni(II) have indicated that the conformation of the Zn complex is tetrahedral and those of the Cu and Ni complexes are square-planar which is in agreement with the experimental results. The metal—oxygen bond is predominantly ionic, and the main factor determining the conformation of the complexes is the interaction between the positive holes in the metal d shell and the negative charges on the oxygen ligand atoms.