Polyhfmn Vol. I, No. 2. pp. ISb161. 1982 0277-53871621020157~5~3.0010 Printed in Great Britain. Pergamon Press Ltd. zyxwvutsrq COMPLEXES OF l-METHYL4MERCAPTOPIPERIDINE WITH ZINC(H), CADMIUM(II) AND MERCURY(I1) HALIDES J. C. BAYON, I. CASALS, W. GAETE,* P. GONZALEZ-DUARTE and J. ROS Departament de Quimica Inorginica, Universitat Aut6noma de Barcelona, Bellaterra (Barcelona), Spain zyxwvutsrqponmlkjih (Received 8 July 1981; accepted for publication I3 August 1981) Abstract-The preparation of a series of complexes formed by I-methyl-4-mercaptopiperidine (AH) and divalent zinc, cadmium and mercury halides is reported together with some spectral and physical properties. The results of a crystallographic study allows to establish the structure of those of formula [M2(AH)&]H20 (M = Zn, Cd, Hg; X = Br, I) consisting of dimers and involving tetrahedral environment with sulphur-bridges for the metal atoms. _ Polymeric structures are proposed for the complexes of formulae Cd(AH)Cl* and Hg#l,(AH). INTRODUCTION As a part of our work on the coordination of y-mercap- toamines to metal ions we have reported some solid complexes formed by I-methyl-4-mercaptopiperidine recently. The crystal structure of the complex formed with cadmium perchlorate show that it is polymeric’ while the one formed with zinc chloride is dimeric.’ Taking into account that information relative to metal complexes of y-mercaptoamines is scarce and that mer- cury(I1) and thiol ligands give rise to a great diversity of structures- and in order to better understand the differences in coordination chemistry of the IIB elements we have undertaken a systematic study of the complexes of 1-methyl-4-mercaptopiperidine with the halides of these elements. We present in this paper good evidence of dimeric sulphur bridged tetraco-ordinated zinc, cad- mium and mercury atoms. Preparations EXPERIMENTAL I-Methyl-4_mercaptopiperidine(AH)and its hydrohalides were synthesized follow&g- a previ&sly reported method.’ The comolexes of emoirical formula IM~AH~XJHVO (where M = Cd@, Hg(I1);X = Br, I and AH denotes $e iwitierionic form of the ligand), [Cd(AH)C12] and [Hgz(AH)Cl,]were obtained in 10% methanolic solution by adding the appropriate metal(halide to the stoichiometric amount of the ligand. A slight excess of NaI was used in order to make HgI2 soluble. The complexes [M2(AH)&&H20 (where M = Zn(I1) and X = Br, I) were pre- pared analogously to the chloride derivative? In all cases the white crystalline products obtained (slightly yellow in the case of M = Hg(II) and X = I) were filtered off, washed with cold water, ethanol and ethyl ether and dried in uacuo. The complexes were analyzed as follows: S iodometrically or as barium sulphate; Zn as anthranilate; Cd with EDTA; Hg as [Cu en*][HgL]; Cl as AgCI; Br and I potentiometrically with AgNOs; C, H and N in a Perkin-Elmer 240 analyser. Results are given in Table I. Physical measurements The water content was determined by thermal gravimetric analysis and differential thermal analysis with a Netzch S.T.A. model 429 apparatus. Conductivity mdasurements were made on fresh solutions (l.lO-‘M) in DMF at 20°C with a Radiometer conductivity bridge type CDM3. The IR spectra were recorded in KCI, KBr or KI pellets or as Nujol mulls supported between thin polyethylene sheets on a Beckman IR-20A (400&250cm-‘) *Author to whom correspondence should be addressed. spectrophotometer. Powder diffraction patterns were recorded on a Philips X-ray Daractometer using the CuK, radiation. Mass spectra were recorded on a HP 5730A spectrometer with a 70 eV beam and at approx. lo-’ mm Hg pressure. RESULTSANDDISCUSSION X-Ray powder patterns indicate that these complexes of formula [M2(AH)2X.,]~H20 have the same structure as [Zn2(AH)4.&H20 already reported.’ The unit-cell dimensions have been calculated by least-squares methods and are given in Table 2. The other physical measurements are consistent with the results of the crystallographic study. Consequently, there can be little doubt that these halide complexes prepared in this work have a dimeric structure such as where the sulphur atoms of two ligand molecules in a zwitterionic form link two metal atoms. The co-ordination geometry around each metal atom is that of a distorted tetrahedron with two equivalent sulphur atoms and two non-equivalent halogen atoms. The water molecule is hydrogen bonded to two NH groups forming infinite chains in (010)directions and to two halogen atoms that belong to parallel chains. In agreement with their structure the values of the molar conductivities of [Mz(AHJzX4].Hz0 complexes in N,N-dimethylformamide solutions (Table 1) indicate that they are not electrolytes,8 except the complex [Zn2(AH)J41*H20 for which the value of AM = 126.30-l cm* mol-’ suggests that there is either some ionization or decomposition in this solvent. The most significant bands of the IR spectra of all the complexes obtained in this work together with the assignments made is given in Table 3. The differences observed between these spectra and the one of the corresponding halohydrated ligand are small. In the hydrated complexes absorptions due to v(OH) and v(NH) vibrations appear between 3600 and 26OOcm-‘. We have postulated previously* that the band cor- responding to v(NH) vibration is split up in two bands owing to Fermi resonance with the first overtone of the 6(CH2) vibration (1465cm-‘). In the region mentioned [Cd(AH)C121 and [Hg2(AH)CLI complexes show the ab- Poly Vol. 1. 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