Molecular and Electronic Structures of Some Thiourea Complexes of Cobalt(II)

Abstract

Thiourea Complexes of Cobalt(II) 17 ions. Mo* 11 and Re111, which are the species formally present in the two cases, are isoelectronic (d4). However, if each were to adopt the other's structure, we should have [Mo3C112]6~a nd [Re6Cls]ll,+. The charges in both cases are quite high, and, in the former case, there is the added consideration that even the [Mo3-Cle]8core would have a substantial negative charge, so that it would be unlikely to combine with 3C1~to give [Mo3C1i2]6-.In summary, the combined requirements of filling only the bonding molecular orbitals and satisfying electrostatic requirements may place very severe restrictions on how many metal atom clusters are capable of existence. Nonetheless, chemical studies of the lower oxidation states of the heavier transition metals should be carried out with at least some alertness to the possibility of encountering further metal atom cluster compounds.

Ground electronic state description of thiourea coordination in homoleptic Zn2+, Ni2+ and Co2+ complexes using sulfur K-edge X-ray absorption spectroscopy

“…The SUMOs with e and b symmetries are split by approximately 0.1 eV; however, this is small enough for the ligand field stabilization energy to overcome the energy gain due to exchange stabilization that keeps the electron-electron repulsion minimal by forming three SUMOs. As detected experimentally (Cotton et al, 1964), the S = 1/2 spin ground state was estimated to be 0.74 eV and 0.48 eV higher than the S = 3/2 for the crystal structure and the optimized geometry (see below), respectively. The Co 3d-based SUMOs are followed by the C-S * orbitals.…”

“…The zinc(II) TU complex, Zn(TU) 4 (NO 3 ) 2 , was prepared by adding 3 mmol Zn(NO 3 ) 2 Á6H 2 O dissolved in 5 ml water to an aqueous solution of TU (12 mmol in 10 ml H 2 O) stirring at 65 C; colorless crystals were formed in the refrigerator overnight (Vega et al, 1978). Blue-green Co(TU) 4 (NO 3 ) 2 ÁH 2 O crystals were prepared in boiling n-butanol, following an earlier report (Cotton et al, 1964). Green nickel(II) TU crystals, Ni(TU) 6 (ClO 4 ) 2 , were prepared by refluxing a mixture of Ni(ClO 4 ) 2 Á6H 2 O and TU (1:6 mole ratio) in absolute ethanol (Frisch et al, 2009).…”

“…Thiourea [(H 2 N) 2 CS; TU] or thiocarbamide can be considered as a structurally versatile ligand in coordination complexes due to its simultaneous -donor and -acid characters that are manifested in the ability of TU to form hydrogen tautomers and electron resonance structures (Scheme 1). A thione or thiocarbonyl (C S) functional group is generally not considered to be a good donor to transition metal (TM) ions, yet TU forms well defined mononuclear complexes with zinc(II) (Vega et al, 1978), cobalt(II) (Cotton et al, 1964) and nickel(II) ions (Weininger et al, 1969). Formally, in [Ni(TU) 6 ] 2+ TU ligands coordinate via sulfur lone pairs in interactions forming a close-to-octahedral ligand environment around the nickel(II) ion.…”

Spectroscopic and Saturation Magnetization Properties of the Manganese- and Cobalt-Substituted Fur (Ferric Uptake Regulation) Protein from Escherichia coli

“…Table 1 reports the list of compounds and the experimental conditions for the XAS experiments. Compounds 2 , 4 , 10 , and 11 were synthesized according to published procedures [compound 2 , (); compound 4 , (); compound 10 , ( , ); compound 11 , ()], but their crystal structures differed from those previously described and have been solved by X-ray diffraction techniques: compound 2 : hexagonal space group P6 / mcc , a = b = 13.31630(10) Å, c = 21.2040(4) Å, V = 3256.23(7) Å 3 , all Co−N bond distances 2.135(3) Å; compound 4 : monoclinic space group C2 / c , a = 12.4294(11) Å, b = 11.0246(9) Å, c = 14.3292(12) Å, β = 107.6510(10)°, V = 1871.1(3) Å 3 , Co−N bond distances 2.108(2), 2.108(2), 2.179(2), 2.179(2) Å, Co−O bond distances 2.178(2), 2.178(2) Å; compound 10 : orthorhombic space group Pccn , a = 8.9541(2) Å, b = 9.46620(10) Å, c = 22.4304(4) Å, V = 1901.23(6) Å 3 , Co−S bond distances 2.3119(5), 2.3119(5), 2.3289(5), 2.3290(5) Å; compound 11 : monoclinic space group P2(1)/n , a = 7.9685(3) Å, b = 11.8701(3) Å, c = 11.4731(4) Å, β = 105.4120(10)°, V = 1046.18(6) Å 3 , Co−N bond distances 2.010(2), 2.013(2) Å, Co−Cl bond distances 2.2503(7), 2.2631(7) Å. Compounds 1 and 3 were specially synthesized for this study, and their structures have been solved by X-ray diffraction techniques: compound 1 : triclinic space group P-1 , a = 8.828(2) Å, b = 9.034(3) Å, c = 10.669(3) Å, α = 75.42(2)°, β = 83.13(2)°, γ = 62.73(2)°, V = 731.9(3) Å 3 , Co−N bond distances 2.163(2), 2.163(2), 2.187(2), 2.187(2), 2.194(2), 2.194(2) Å; compound 3 : tetragonal space group P4(2)/n , a = b = 13.5569(4) Å, c = 9.1426(4) Å, V = 1680.31(10) Å 3 , Co−Cl bond distances 2.477(2), 2.477(2) Å, Co−S bond distances 2.5123(13), 2.5124(13), 2.5590(13), 2.5590(13) Å.…”

Metal‐Organic Framework‐Derived Honeycomb‐Like Open Porous Nanostructures as Precious‐Metal‐Free Catalysts for Highly Efficient Oxygen Electroreduction

“…Therefore, the hydrophilic solution, whose volume is slightly less than the pore volume of the adsorbent, can totally and uniformly go inside the hydrophilic pores to avoid the deposition of guest precursors on the MOF outer surface. The encapsulated thiourea molecules would further coordinated to the Co(II) ions to form the [Co(TU) 4 ]Cl 2 compound, as evidenced by the color changes of the solid from light yellow to blue upon the encapsulation (Figure b and Figure S1, Supporting Information) …”