2D polymeric cadmium(II) complexes containing 1,3-imidazolidine-2-thione (Imt) ligand, [Cd(Imt)(H2O)2(SO4)]n and [Cd(Imt)2(N3)2]n
Graphical abstract
Introduction
Cadmium(II) is known to form a wide variety of 1:1 to 1:4 complexes with thiones (L), with the structural arrangements generally based on tetrahedral and octahedral coordination environments. The 1:1 complexes [1], [2], [3], [4] for example, [Cd(Tu)(H2O)2(SO4)]n [2] and [Cd(MeImt)(SeCN)2]n [4] (MeImt = N-methylimidazolidine-2-thione) usually exist in the polymeric form. The structures of the 1:2 complexes such as, [Cd(Tu)2X2] [5], [Cd(Dmtu)2X2] [6], [7], [Cd(Tmtu)2X2] [8], [9], [10] or [Cd(Imt)2X2] [11], [12] (X = Cl, Br, I) are the most common and often consist of discrete monomeric molecules with a tetrahedrally [5], [6], [7], [8], [9], [10], [11], [12], [13], [14], [15], [16], [17], [18], [19], [20], [21] (or octahedrally [22], [23]) coordinated Cd(II) ion. In some cases, polymeric species are formed through bridging sulfur or nitrogen atoms [21], [24], [25], [26], [27], [28], [29], e.g., [Cd(Metu)2(SCN)2]n [24] and [Cd(Imt)2(SCN)2]n [25]. The 1:3 compounds are rare. The crystal structure of [Cd(Tu)3(SO4)] shows that the molecule is a dimer, and the coordination around the metal atom is intermediate between square pyramidal and trigonal bipyramidal [30]. Another such compound is known in the form of a co-crystal of [Cd(Tu)2(H2O)4]SO4 and [Cd(Tu)3(H2O)3]SO4 [31]. The complexes with a Cd:thione ratio of 1:4 may be ionic or nonionic. In the ionic complexes like [Cd(2-mercaptopyridine)4](NO3)2 [32] or [Cd(Diaz)4]SO4 (Diaz = 1,3-diazinane-2-thione) [33], the Cd(II) atom possesses a tetrahedral environment. The molecular species for instance, [Cd(Diaz)4Cl2] [34] display a distorted octahedral geometry around the metal ion [29], [34], [35]. These structural studies show that thioureas or thiones coordinate to cadmium(II) via the sulfur atom. We have reported earlier the crystal structures of several cadmium(II) complexes of heterocyclic thiones [4], [5], [6], [7], [8], [9], [10], [14], [15], [16], [17], [23], [24], [33], [34], [35]. To investigate further about the structural aspects of such complexes, we report in this work the spectroscopic data and X-ray structures of two new 2D polymeric cadmium(II) complexes of imidazolidine-2-thione (Imt), [Cd(Imt)(H2O)2(SO4)]n (1) and [Cd(Imt)2(N3)2]n (2). The main goal of the present study is to exploit the effect of binding flexibility of sulfate and azide ions for the preparation of Cd-Imt polymers.
Section snippets
Materials
Cadmium sulfate (CdSO4·8/3H2O) and NaN3 were obtained from Merck Chemical Company, Germany. Imidazolidine-2-thione was prepared according to the method reported in the literature [36].
Synthesis of [Cd(Imt)(H2O)2(SO4)]n (1) and [Cd(Imt)2(N3)2] (2)
Complex 1 was prepared by adding 0.10 g (1.0 mmol) Imt in 15 mL methanol to an aqueous solution (5 mL) of cadmium sulfate (0.26 g, 1.0 mmol) and stirring the mixture for 30 min. Mixing resulted in a colorless solution. The clear solution was kept at room temperature for crystallization. As a result, a white
X-ray structure studies
The molecular structure of compound 1 is illustrated in Fig. 1. Selected bond angles and distances are given in Table 2. The compound crystallizes in Pbca space group in the form of a 2D polymer comprising of [Cd(Imt)(H2O)2(SO4)] units (Fig. 2). The 2D wavy network is characterized by 12-membered ring motifs [CdOSO]3, where the cadmium ion is hexa-coordinate as [Cd(Imt)(OH2)2(OSO3)3]. It is bonded to two water molecules in a cis position, the sulfur atom of the terminal imidazolidine-2-thione
Conclusion
This paper describes the synthesis and structural characterization of two cadmium(II) complexes of 1,3-imidazolidine-2-thione (Imt), [Cd(Imt)(H2O)2(SO4)]n (1) and [Cd(Imt)2(N3)2]n (2). The X-ray structures of the complexes show that both of them exist in the form of two dimensional polymers with each cadmium atom being octahedrally coordinated. The polymers are assembled through triply-bridging sulfate and doubly-bridging, μ(1,3) azide ions in case of 1 and 2 respectively. The 2D polymers are
Acknowledgement
The Deanship of Scientific Research, Prince Sattam bin Abdulaziz University, Al-Kharj, Saudi Arabia is gratefully acknowledged for supporting this work through Project No. 2016/01/6822.
References (50)
- et al.
Complexes of heterocyclic thiones and group 12 metals: Part VI. Preparation and characterization of complexes of cadmium(II) halides with 1-methylimidazoline-2(3H)-thione, 1,3-thiazolidine-2-thione and 1,3-benzothiazoline-2-thione. Crystal structures of polymeric (1,3-thiazolidine-2-thione)cadmium(II) chloride, bis(1,3-thiazolidine-2-thione)cadmium(II) iodide and monomeric bis(1-methylimidazoline-2(3H)-thione)cadmium(II) bromide
Inorg. Chim. Acta
(2004) - et al.
A novel polymeric Cd[SSe2N2] central core five-coordinate complex: synthesis, X-ray structure and 113Cd, 77Se CP MAS NMR characterization of catena(bis(μ2-selenocyanato-N,Se)(N,N’-dimethylimidazolidine-2-thione-S)-cadmium(II))
Inorg. Chem. Commun.
(2008) - et al.
New cadmium chloride complexes with imidazolidine-2-thione and its derivatives: X-ray structures, solid state and solution NMR and antimicrobial activity studies
Polyhedron
(2007) - et al.
Synthesis, crystal structures, and spectroscopic characterization of the neutral monomeric tetrahedral [M(Diap)2(OAc)2]. H2O complexes (M = Zn, Cd; Diap = 1,3-diazepane-2-thione; OAc = acetate) with N–H–-O and O–H–-O intra- and intermolecular hydrogen bonding interactions
Inorg. Chim. Acta
(2007) - et al.
Synthesis and characterization of some N-alkyl/aryl and N,N’-dialkyl/aryl thiourea cadmium(II) complexes: the single crystal X-ray structures of [CdCl2(CS(NH2)NHCH3)2]n and [CdCl2(CS(NH2)NHCH2CH3)2]
Polyhedron
(2003) - et al.
N,N’-Diisopropyl- and N,N’-dicyclohexylthiourea cadmium(II) complexes as precursors for the synthesis of CdS nanoparticles
Polyhedron
(2007) - et al.
The crystal structure of a five coordinated cadmium(II) complexes: tristhiourea-cadmium sulphate
Inorg. Chim. Acta
(1969) - et al.
Synthesis and crystal structures of cadmium(II) complexes of 1,3-diazinane-2-thione (diaz); [Cd(diaz)4Cl2], [Cd(diaz)2(NCS)2] and [Cd(diaz)2(N3)2]n
Inorg. Chim. Acta
(2018) - et al.
Synthesis, structural characterization and thermal analysis of a high nitrogen-contented cadmium(II) coordination polymer based on 1,5-diaminotetrazole
J. Mol. Struct.
(2011) - et al.
Two new polymeric cadmium(II) complexes containing end-to-end bridging azido or thiocyanato ligands with different topologies
Polyhedron
(2003)