Synthesis and Characterization of the Complexes of Pentane-

Two mononuclear complexes, [Ni(acac)2].0.5CH3OH (1) and[Co(acac)2NO3].2H2O (2) (acac = pentane-2,4-dione), have been synthesized and characterized by single crystal X-ray analysis. Complex 1 crystallizes in the monoclinic space group P2(1)/c with a = 9.295(4), b = 11.450(5), c = 12.974(6) A, V = 1379.1(11) A(3),beta = 92.854(7), and Z = 4. Complex 2 crystallizes in the triclinic space group P(-1) with a= 8.153(9), b = 9.925(11), c = 10.355(12), V = 746.3(15) A(3), alpha = 70.530(16), beta =71.154(15), gamma = 80.698(16) and Z = 2. Complex 1 has a one-dimensional chain-like structure, which is extended by weak hydrogen contacts, while complex 2 shows a three-dimensional network structure.


Introduction
The d-transition metal -β-diketone compounds were used extensively as starting materials in the early days of metallocene chemistry [1].Currently complexes containing the pentanedionato ligand have been the focus of much investigation as electroluminescent materials [2][3], presumably due to their ease of preparation, high stability and high volatility in comparison to other chelate complexes [5][6].The pentanedionato ligand possesses a rather complicated coordination behavior toward redoxactive and inactive transition metal ions because it can exist in various protonated forms [7].Studies on the structures of pentanedionato complexes and the characterization are becoming of more and more interest to chemists and biochemists [8][9].Herein we present two new complexes, [Ni(acac) 2 ] 2 •0.5CH 3 OH (1) and [Co(acac) 2 NO 3 ]•2H 2 O (2), and describe their syntheses and crystal structures.

Results and Discussion
2,4-Pentanedionato complexes of cobalt were usually obtained adventitiously from the attempted preparation of cobalt(II)-Schiff bases, presumably due to Co(II) redox-activity.It is usually difficult to produce single crystals of these kinds of compounds, but we have found that large crystals of these two complexes can be readily obtained using the hydrothermal method.Both complexes are soluble in common polar organic solvents, such as DMSO, DMF, EtOH, MeCN and Me 2 CO, but poorly soluble in water and MeOH.1.855( 5)   The crystallography data reveal that complexes 1 and 2 have similar mononuclear molecular structures, as shown in Figures 1 and 3, respectively.The mononuclear nickel(II) complex 1 consists of a nickel atom, two pentane-2,4-dione anions and one uncoordinated molecule of CH 3 OH.The molecular structure is thus essentially the same as that reported for this complex by Zhou [9], but without coordinated water.The central nickel(II) atom is united by four oxygen donors of two dichelating pentane-2,4-dione anions.The NiO 4 core involving the central atom is a well-defined plane.Compound 2 is a mononulear cobalt complex.The average Co-O bond distance of 1.909(4) Å is in good agreement with the corresponding Co-O distance reported in the literature (average 1.919(3) Å, [9]).In reference [8] the Co atom is described as being located on a centre of symmetry and consequently the two chelate rings are coplanar.The cobalt oxygen bond length is 1.917(3) Å.There are weak hydrogen contacts of 3.072 (7) Å between the oxygen atoms from the ligands.The central Co atom has a slightly distorted octahedral coordination geometry and is hexacoordinated by four oxygen donors, two of which are from a di-chelating pentane-2,4-dione anion and the other two from a dichelating nitrate anion.The three diagonal angles in the Co octahedrons are 169.76°,165.34° and 178.3°, respectively.The O-H•••O hydrogen bonds link the symmetry related molecules to form a network (Figures 2, 4 and Table 3).

Data collection, Crystal Structure Determination and Refinement
A yellow crystal of 1 (approximate dimensions of 0.30 x 0.24 x 0.20 mm) and a brown-red crystal of 2 (approximate dimensions of 0.42 x 0.37 x 0.31 mm) were mounted on a CCD area detector equipped with graphite-monochromated Mo Kα (λ = 0.71073 Å) radiation at 293 K for 1 and 298 K for 2 using the ω/2θ scan mode.A total of 2434 reflections for 1 and 2546 reflections for 2 were collected in the range of 2.19 o < θ < 25.02 o for 1 and 2.64 o < θ < 25.02 o for 2, of which 1231 for 1 and 2024 for 2 were unique.The data sets were corrected for Lorentz -polarization effects, and a MULTI-SCANE absorption correction was applied (T min = 0.6766 and T max = 0.7654 for 1; T min = 0.6344 and T max = 0.7088 for 2).The structures were solved by direct methods.The remaining non-hydrogen atoms were located by use of successive difference Fourier maps and full-matrix least-squares refinement.All standard deviations (esds) (except the esd in the dihedral angle between two leastsquare planes) were estimated using the full covariance matrix.The cell esds were taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they were defined by crystal symmetry.An approximate (isotropic) treatment of cell esds was used for estimating esds involving least square planes.The weighted R-factor (Rw) and goodness of fit (S) are based on F 2 , conventional R-factors are based on F, with F set to zero for negative F 2 .The threshold expression of I > 2σ (I) is used only for calculating Rfactors (gt) etc., and is not relevant to the choice of reflections for refinement.R-factors based on F 2 are statistically about twice as large as those based on F, and R-factors based on ALL data will be even larger.The final R 1 (R 1 = ∑||F o | -|F c ||/∑||F o |) value for 1 was 0.0554 for 173 parameters and 1231 observed reflections (I > 2σ(I)); and the final R 1 for 2 was 0.0520 for 204 parameters and 522 observed reflections (I > 2σ(I)).All calculations were carried on a Bruker SMART computer using the SHELXS and SHELXL programs and published scattering factors.Crystallographic data for the complexes reported in this paper have been deposited with the Cambridge Crystallographic Data Centre (CCDC 233227 for complex 1 and CCDC 233226 for complex 2; these data can be obtained free of charge via www.ccdc.cam.ac.uk/conts/retrieving.html (or from the CCDC, 12 Union Road, Cambridge CB2 1EZ, U.K.; fax +44 1223 336033; e-mail: deposit@ccdc.cam.ac.uk).

Figure 4 .
Figure 4.The crystal packing for 2 viewed along the b-axis, showing intermolecular O-H•••O hydrogen bonds as dashed lines.

Table 1
Crystallographic and experimental data for complexes 1 and 2