The infrared spectra of complexes with planar dithiooxamides X. The Cu(LH2)2X1 complexes

In this article, the preparation, X-ray powder results and vibrational properties of a new type of complex with planar dithiooxamides are discussed. In acetonitrile, Cu(I) can form complexes with the formula Cu(LH₂)₂X₁ (X = Cl, Br) where LH₂ is an N,N'-disubstituted dithiooxamide. Complexes with N,N'-dimethyldithiooxamide and N,N'-diethyldithiooxamide have been prepared. A thorough vibrational analysis with infrared and Raman techniques was performed, assisted by H/D and ⁶³Cu/⁶⁵Cu isotope substitution. The vibrational study indicates the presence of an inversion centre in the structure. This leads to the proposal of a very unusual six-coordinate structure for these compounds, with the two dithiooxamide ligands, having S-cis conformation, coordinated to the same copper and with the halogens bridged between two different copper atoms. Confirmation of this result was attempted by X-ray analysis, but although several methods were tried to obtain crystals, only powder X-ray data could be obtained, which could not give a definitive answer. Since such six-coordinate Cu(I) has never been described before, a less rigourous interpretation of the vibrational data was followed, leading to a square-pyramidal five-coordinate structure, with a rather weak bond between Cu(I) and a terminal halogen. The latter structure, with the data available up to now, seems a bit more likely, since five-coordination for Cu(I) has already been described.     

Synthesis,spectroscopy and thermal properties of the nickel(II), palladium(II) and copper(II) complexes of bis(aminoalkyl)-oxamides (=LH2) including the crystal structure of Cu2L(NO3)2

Summary The synthesis of the Ni^II, Pd^II and Cu^II complexes of N, N-bis(aminoalkyl)oxamides (LH₂) is described and structures are proposed on the basis of their physical and spectroscopic properties. With Ni^II and Pd^II only one complex is formed with general formula NiL or PdL, characterised by coordination through two deprotonated amide N-atoms and two terminal NH₂ groups. With Cu^II it proved possible to obtain three structurally different compounds, depending on the pH, with general formulae Cu(LH₂)X₂, Cu₂(L)X₂ and CuL in which X=Cl, Br or NO₃. The structure of [Cu₂(C₈O₂N₄H₁₆](NO₃)₂ was solved by means ofx-ray diffraction; Mr=451.33, monoclinic, space group P2₁/n, a=9.503(4), b=7.614(1), c=10.407(3) Å, =98.43(3)°, V=744.3(7)ų, Z=2, Dx=1.202 g cm^–3, =1.33 cm^–1, (MoK)=0.71073 Å, F(000)=520, room temperature, R=0.043, wR=0.047 for 1080 observed [I>-3(I)] not systematically absent reflections out of 1423 measurements and 137 variables. The compound has a conformational chair/boat disorder with 82% in the more stable chair form.     

Synthesis,spectroscopy and thermal properties of the nickel(II), palladium(II) and copper(II) complexes of oxalyldihydrazide

Summary The new complexes K₂[ML₂]·2H₂O (M=Ni, Cu), K₂[PdL₂]·H₂O, K₂[CuL₂(H₂O)₂]·H₂O, [Ni(LH₂)Cl₂]_x ·xH₂O and [Ni(LH₂)Br₂]_x·1,5xH₂O, where LH₂= oxalyldihydrazide, have been prepared. Emphasis has been put on determining the conditions for the synthesis of both deprotonated and non-deprotonated Ni^II complexes. They were characterized by analyses, conductivity measurements, thermogravimetry, magnetic susceptibility and spectroscopic methods like i.r. and far-i.r., diffuse reflectance u.v. vis, and e.s.r. Monomeric square planar and distorted octahedral structures were found for the deprotonated complexes in the solid state while the non-deprotonated Ni^II complexes appeared to be pseudo-tetrahedral polymers. The doubly deprotonated L²-ion exhibits a bidentate N(amide), N(amide)-coordination, while the neutral LH₂ molecule behaves as a N(amino), N(amino)-bidentate ligand forming polymeric structures. Vibrational analysis of the complexes was carried out, using hydrogen and metal isotopic substitution.     

Thermal analysis of dithiomalonamide complexes

Dithiomalonamide [H₂A, CH₂(CSNH₂)₂] and 2,2-dimethyldithiomalonamide [H₂B, C(CH₃)₂(CSNH₂)₂] can act as bidentate ligands and form stable, cationic 1∶2 complexes with general formula M₂(H₂L)₂X₂ [M=Ni²⁺, Pd²⁺, Pt²⁺;X=C1, Br, I; H₂L=H₂A, H₂B] in strong acidic medium. An elaborate thermal study is presented, based on results from elemental analyses and vibrational studies (IR and Raman spectroscopy). The H₂A complexes start to decompose by releasing two HX molecules whereafter a stable intermediate M(HA)₂ is formed. The H₂B complexes degrade in a different way; the metal-sulphur bond is broken and the ligand is expelled as a whole. Influences of the metal ion and of the halogenide counterions are investigated.     

The Synthesis,Vibrational Spectra,Electronic Spectra,and Thermal Analysis of Some Mixed Complexes with Planar Dithiooxamides

Planar Pd(LH)₂ complexes (LH₂ = H₂N C S C S N H₂, CH₃HNCSCSNHCH₃) form mixed polymeric complexes with Ni(II), Cu(II), Zn(II) and Cd(II) in alcalic media, where the planar Pd(LH)₂ complexes act as tetradentates with N-coordination. The electronic spectra and thermal behaviour are discussed, a thorough investigation of the i.r. spectra is presented and special attention has been given to the H/D, CH₃/CD₃ and ⁵⁸Ni/⁶²Ni, ⁶³Cu/⁶⁵Cu and ⁶⁴Zn/⁶⁸Zn isotopic shifts.     

The vibrational analysis of someN- andN,N′-monosubstituted oxamide complexes

Summary The vibrational spectra of someN- andN-N-monosubstituted oxamide complexes with Ni^II are presented. The vibrational analysis is given for a planarC _2h structure for eight isotopes of theN-methyloxamide derivative. The Et, Pr, Bu, cyclo-Pr and i-Bu derivatives give analogous complexes. Octahedral Ni^II complexes have been prepared withN,N-di-methyloxamide.Presented in part at XX I.C.C.C. Calcutta 1980.     

Catena-μ-(3,5-diamino-1,2,4-triazole N1, N3)-bis(thiocyanato-N) cadmium(II): Synthesis,crystal and molecular structure,and infrared and Raman characterization

The title compound (C₆H₁₀CdN₁₂S₂) was prepared and characterized by means of X-ray, Raman, and IR measurements. The crystals are orthorhombic:Pbcn, (No. 60),a=9.558(2),b=9.491(2),c=15.898(2) Å,Z=4. The structure was solved by the heavy-atom method, and least-squares refinement of structural parameters led toR=0.021 (R _w =0.020) for 863 independent reflections. The compound exhibits two-dimensional Cd(II) networks, with the 1,2,4-triazole molecule acting as a bidentate bridging ligand. The structure consists of centrosymmetric units, in which the cadmium atoms are coordinated in distorted octahedral geometries by six nitrogen atoms. Each cadmium atom is linked by four 1,2,4-triazole molecules, and two thiocyanate ions complete the octahedral coordination around the metal. Each 1,2,4-triazole molecule bridges two cadmium atoms. The NH and NH₂ groups of the guanazole unit are involved in intermolecular hydrogen bonds. Infrared and Raman bands are diagnostic of the coordination environments around the metal atoms.     

Thermal analysis of oxathioamidate complexes

Oxathioamidates (CSNR₁ R ₂COOKR ₁=R ₂=H (A),R ₁=H andR ₂=CH₃ (B),R ₁,=R ₂=CH₃ (C)) can act as O, S donors and form pentaatomic ring systems with divalent metals (M(II)=Mn, Fe, Co, Ni, Cu, Zn). Vibrational spectra and thermal analysis provide information on the amount and nature of associated water molecules. The dehydration of MA₂(H₂O)₂ (M=Mn, Fe, Co, Ni) can be very well explained by the C.F.S.E. (crystal field stabilization energy) for weak field octahedral complexes. The complexes with ligand A and B decompose to form polymers by deprotonation on the thioamide group. The proposed structures are confirmed by the vibrational spectra. For ligand C no stable intermediates are formed during heating, degradation proceeds until metal sulphide remains.The N.F.W.O. is thanked for the financial support towards the spectroscopic and thermal equipment. The authors are very grateful to Ing. J. Janssens for the TG/DTA measurements.     

Determination of the crystal structure and the spectroscopic data of Pd(N,N′ -dicyclopentyldithiooxamide)2

Summary The title compound exhibits a PdS₄ coordination geometry, demonstrated by crystallographic and n.m.r. measurements. The bond distances and valence angles of the complex are discussed using the information provided by i.r. measurements. Despite the strong S,S steric hindrance in the compound, the C-C bond distance is shorter in the complex than in the free ligand. The i.r. spectra also provide evidence for strong intramolecular hydrogen bonds.     

Normal coordinate analysis of malononitriles: III. The valence force field of malononitrile and its deuterated derivatives

The procedure of Becher and Mattes [1] has been applied to the calculation of the valence force field for malononitrile H₂C(CN)₂ and its deuterated derivatives, HDC(CN)₂ and D₂C(CN)₂. The results have been localized in the space of the real solutions of the inverse vibrational eigenvalue problem. The convergence of the method has been demonstrated. The average deviation between observed and calculated frequencies on isotopic substitution is less than 1 %.