J.A. Bertrand

Polynuclear copper(II) complexes with oxygen bridges: The relationship betweeen magnetic properties and structure

Abstract The structures of two copper(II) complexes of the general formula CuL (where L represents the dianion of H3CC(O)CH2C(CH3)N(CH2)nOH) have been determined by single-crystal X-ray diffraction studies. The compound with n = 2, abbreviated Cu(EIA), crystallizes as tetragonal crystalls (a = b = 14.46 A, c = 7.63 A) of space group P421c with two tetramers per unit cell (ϱobsd = 1.70; ϱcalcd = 1.71 g/cm3; the compound with n = 3, abbreviated Cu(PIA), crystallizes as monoclinic crystals (a = 5.98 A, b = 10.97 A, c = 14.42 A, and β = 106.75°) of space group P21/c, with two dimers per unit cell (ϱobsd = 1.61; ϱcalcd = 1.61 g/cm3). Both structures were solved from Patterson and electron density maps and refined by least-squares methods to conventional R values of 8.9% and 10.0% for Cu(EIA) and Cu(PIA), respectively. The two structures differ in the coordination about the bridging oxygens — in Cu(EIA) the oxygen is tetrahedrally coordinated and in Cu(PIA) the three — coordinate oxygen is planar. The fourth outer orbital of the planar oxygen and the dxz, dyz orbitals of copper can overlap to form a delocalized π-system; the pairing of electrons in delocalized π-orbitals is suggested as an explanation of the singlet ground state observed for most oxygen-bridged copper(II) complexes.

Sub-normal magnetic moments in copper (II) complexes: Five-coordinate copper in an oxygen-bridged dimer

Abstract The preparation, structure, and properties of a dimeric copper(II) compound, chloro-N-(2-hydroxypropyl)salicylaldimino copper(II), are reported. The compound, which has a magnetic moment of 1.1 B.M., crystallizes as brown, monoclinic crystals (a = 8.56(1) A; b = 12.35(2) A; c = 10.31(2) A; and β = 98.43(3)°) of space group P2 1 /c with two dimers per unit cell; the calculated density of 1.71 g/cm 3 agrees well with the observed density of 1.69 g/cm 3 . A total of 644 unique, non-zero reflections were collected (four-circle diffractometer); least-squares refinement with anisotrophic temperature parameters for copper and chlorine resulted in a conventional R value of 0.089. Each copper is five-coordinate (distorted trigonal bipyramid) and the phenolic oxygens are the bridging groups. The four-membered copper-oxygen ring is planar with a CuCu distance of 3.294(7) A; coordination of the bridging oxygen is also planar. The low magnetic moment is attributed to a π-interation delocalized over the four membered ring. For the atoms bonded to copper the bond distances and bond angles are: CuN (axial), 2.18(2) A; CuO (axial), 2.22(1) A; CuO (equatorial), 1.78(1) and 2.24(2) A; CuCl (equatorial), 2.12(1) A; NCuO (axial), 168.9(6)°; OCuO (equatorial), 123.4(7)°; ClCuO (equatorial), 126.2(5)° and 110.1(4)°.

Magnetic interaction in binuclear copper(II) complexes: Preparation and structure of the schiff base complex derived from pyrrole-2-carboxaldehyde and 3-aminopropanol

Abstract To obtain additional information about the relationship between magnetic properties and structure in oxygen-bridged complexes, the copper(II) complex of the Schiff base of pyrrole-2-carboxaldehyde and 3-aminopropanol was prepared. The complex, [Cu(C 8 H 10 N 2 O)] 2 , crystallizes as monoclinic crystals (a = 25.61A, b = 5.46A, c = 16.90A, β = 136.33°) of space group C2/c with 8 formula units (4 dimers) per unit cell (ϱ obsd = 1.73, ϱ calcd = 1.74 g/cm 3 ). A total of 858 unique, non-zero reflections were obtained from precession camera photographs; the structure was solved from Patterson and electron density maps and refined by least-squares methods to a ocnventional R value of 0.076. The coordination of copper is squareplanar and the coordination of the bridging oxygen is also planar. Within the planar four-membered copper-oxygen ring, the angle at copper is 76°; a molecular orbital treatment of the π-system suggests a relationship between this angle and the magnetic properties of binuclear copper(II) complexes.

The electronic structure of square-planar nickel(II) and copper(II) complexes

Abstract The polarized single crystal spectra of Ni(DACO) 2 (ClO 4 ) 2 2H 2 O and Cu(DACO)2· 2H 2 O indicate that the d orbital energy level order is d x 2 -y 2 >d xy >d xz , d yz >d z 2 in both cases. The simple vibronic selection rules for D 4h symmetry apply quite well and simple ligand field calculations fit the observed spectra reasonably well. The crystal structure of Ni(DACO) 2 (ClO 4 ) 2 ·2H 2 O has been determined. It crystallizes in the triclinic space group P 1 with a = 8.586(6), b = 9.324(2), c = 16.863(4)A, α = 156.34(2)°, β = 86.80(2)°, γ = 92.86°; V = 540.95A 3 one formula unit per unit cell. The structure was solved and refined by conventional techniques, based on 525 reflections measured with a scintillation counter (Mo Kα radiation); the final R value was 0.087. The coordination of the nickel is strictly planar and square within experimental error. The x axis positions are effectively blocked with no coordination in that direction. Thus the metal is effectively exactly D 4h square planar

The crystal and molecular structure of the tetrameric nickel(II) complex of 7-hydroxy-4-methyl-5-azahept-4-en-2-one, [Ni(C7H11NO2)(CH3OH)]4

Abstract The structure of the green methanolate of the nickel(III) complex of 7-hydroxy-4-methyl-5-azahept- 4-en-2-one (the dianion of the ligand is represented by EIA in formulas), Ni(EIA)(CH30H), has been determined by a single crystal X-ray diffraction study. The compound crystallizes as orthorhombic crystals (a = 12.319(4) A, b = 25.91(3) A, and c = 15.152(4) A of space group P212121 with 16 formula units (monomeric) per unit cell. The structure was solved by direct methods and refined by least-squares methods to R = 0.056 and Rw = 0.049 for 2829 independent, non-zero reflections. The structure consists of tetrameric, cubane-like complexes with alkoxide oxygen atoms and octahedrallycoordinated nickel(II) atoms at the corners of a cube. The cube is slightly distorted with eight short Ni-O distances (2.020-2.055 A] and two pairs of longer, mutually perpendicular Ni-O distances (2.112- 2.130 A).

The crystal and molecular structure of dichlorobis(triphenylphosphine oxide)copper(II)

Abstract The structure of dichlorobis(triphenylphosphine oxide)- copper(II) has been determined by a single-crystal x-ray diffraction study. The compound crystallizes as orthorhombic crystals (a=31.961(4) A, b=20.839(4) A, and c=9.886(2) A of space group Fdd2 with eight molecules per unit cel (ϱobs=1.40(2) g/cm3; ϱcalc= 1.38 g/cm3). The structure was solved from Patterson and electron density maps and refined by least- squares methods to a conventional R value of 0.044 for 1386 independent, non-zero reflections. The complex has 2-fold symmetry and the coordination about copper is a slightly elongated tetrahedron with a Cu- Cl distance of 2.170(2) A and a Cu-0-distance of 1.958(4) A; the Cu-0-P angle is 150.9.(3).

Square-planar nickel(II) in an oxygen-bridged dimer

The structure of the complex of nickel(II) and the dianion of CH 3 C(O)CH 2 C(CH 3 NCH 2 CH 2 OH has been determined by a single-crystal X-ray diffraction study: the ligand (hereafter abbreviated EIA), obtained by the condensation of 2,4-pentanedione and 2-aminoethanol, forms a 1:1 complex with nickel(II). The compound crystallizes a monoclinic crystals (a = 16.99(2) A, b = 7.45(1) A, c = 14.02(2) A, and β = 112.93(4)°) of space group C2/c with eight formula units (four dimers) per unit cell (ϱ obsd. = 1.61 g/cm 3 ; ϱ calcd. = 1.62 g/cm 3 ). The structure was solved from Patterson and electron density maps and refined by least-squares methods to a conventional R value of 6.6% for 884 independent, non-zero reflections. The structure consists of oxygen-bridged dimers with square-planar coordination about the nickel; the four-membered nickel-oxygen ring is considerably bent. In the coordination sphere of nickel, the NiO bonds vary from 1.81 to 1.88 A and the NiN distance is 1.85 A.

Preparation and structure of chloro(bis{salicylideniminephenyl}disulfido)iron(III)

Abstract Chloro(bis{o-salicylideniminephenyl}disulfido)iron (III), Fe(C 26 H 18 N 2 S 2 O 2 )Cl, has been prepared and its crystal structure determined from precession camera data. The compound crystallized in space group P2 1 /c (a = 10.02(2) A , b = 21.76(4) A , c = 11.06(2) A , and β = 96.17(10)· at 25°C using Zr filtered Mo Kα radiation) with four formula units per unit cell (ρ calcd = 1.52 gcm −3 ; ρ obsd = 1.55(2)gcm −3 ). The structure, which was refined to a conventional R value of 0.096 by full-matrix least-squares refinement, consists of monomeric iron(III) complexes with octahedral coordination. The disulfide functions as a pentadentate ligand and is coordinated through two nitrogens, two oxygens, and one sulfur atom; the chloride ion occupies the sixth coordination position. The magnetic moment, 5.90 B.M., is normal for a high-spin octahedral iron(III) complex.

The structure of μ4-oxo-hexa-μ-bromo-tetra[amminecopper(II)]

Abstract The structure of Cu 4 OBr 6 (NH 3 ) 4 has been determined by a single-crystal X-ray diffraction study. The compound crystallizes as tetragonal crystal (a = 9.004(10) A, c = 9.731(13) A) of space group P42 1 c with two molecules per unit cell (d calc. = 3.44 g/cm 3 ; d obs = 3.35 g/cm 3 . The structure, which is similar to that found for other μ 4 -oxo complexes, consists of a central oxide ion coordinated tetrahedrally to four copper(II) ions; the copper(II) ions are bridged in pairs by the six bromide ions and the ammonia molecules complete the trigonal-bipyramidal coordination of the copper(II) ions. The average interatomic distances are: CuCu, 3.12 A; CuO, 1.93 A; CuBr, 2.54 A, CuN, 1.98 A; The CuBrCu angle is 76.5°.

The structure of K2BaCo(NO2)6 at 233°K.: a static Jahn-Teller distortion

Abstract The structure of K 2 BaCo(NO 2 ) 6 has been determined at 233°K; the crystals, which are cubic at room temperature, are orthorhombic, space group Fmmm, at 233°K with a =10.51(3) A, b =10.68(3) A, an c = 10.51(3) A. The hexanitrocobaltate(II) ion, which appears to be octahedral with a cobalt-nitrogen distance of 1.98(2) A at room temperature, is elongated along one axis to give cobalt-nitrogen distances of 1.90(2) A, 1.94(6) A, and 2.10(2) A. The results are indicative of a dynamic Jahn-Teller distortion at room temperature and a static Jahn-Teller distortion at 233°K; the elongation along one axis is the type of distortion observed for most complexes of copper(II).