Z. Naturforsch. 2015; 70(8)b: 541–546 Muhammad Nawaz Tahir, Anvarhusein A. Isab, Fozia Afzal, Kashif Raza, Shah Muhammad, Muhammad Hanif, Sajjad Ahmad, Tahira Gul and Saeed Ahmad* Synthesis and characterization of silver(I) complexes of thioureas and thiocyanate: crystal structure of polymeric (1,3-diazinane-2-thione) thiocyanato silver(I) DOI 10.1515/znb-2014-0263 the sulfur coordination to silver(I). The appearance of a Received October 27, 2014; accepted April 2, 2015 band around 2100 cm–1 in the IR and a resonance around 125 ppm in the 13C NMR spectrum indicates the binding of thiocyanate to silver(I). Abstract: Silver(I) complexes of thioureas and thiocy- anate, [(Tu)AgSCN], [(Metu)AgSCN], [(Dmtu)AgSCN], Keywords: silver(I) complexes; spectroscopy; thioureas; [(Tmtu)(AgSCN)1.5], [(Imt)AgSCN], and [(Diaz)AgSCN] thiocyanate; X-ray structure. (where Tu = thiourea, Metu = N-methylthiourea, Dmtu = N,N′-dimethylthiourea, Tmtu = N,N,N′,N′- tetramethylthiourea, Imt = 1,3-imidazolidine-2-thione, and Diaz = 1,3-diazinane-2-thione), have been prepared 1 Introduction and characterized by elemental analysis, IR and NMR The complexation of thiones towards metal ions such as spectroscopy, and thermal analysis. The crystal structure copper(I) and silver(I) has received considerable impor- of one of them, [(Diaz)Ag(SCN)] (1), was determined by tance in view of their variable bonding modes, structural X-ray crystallography. The crystal structure of 1 shows diversity, and promising biological implications [1–10]. that the complex exists in the form of a chain-like poly- Our interest in these ligands is because of their relevance mer comprising [Ag(μ -Diaz)(μ -SCN)] units. The silver 2 2 to biological systems [3, 4], and consequently, we have atoms are bridged by μ -thione sulfur atoms of Diaz and 2 been investigating the coordination chemistry of > C = S μ -thiocyanate sulfur atoms. Thereby each silver atom 2 ligands with d10 metal ions in an attempt to assess their adopts a distorted tetrahedral coordination environment modes of binding and to study their physical properties comprising four sulfur atoms, two from thione and two [10–18]. Several complexes of thiones with silver cyanide from thiocyanate ligands. An upfield shift in the > C = S have been prepared and characterized using NMR spec- resonance of thiones in 13C NMR and a downfield shift troscopy and X-ray crystallography. These studies have in the N–H resonance in 1H NMR are consistent with shown that some of these compounds exist as mononu- clear species LAgCN, while others exist in the ionic form + – *Corresponding author: Saeed Ahmad, Department of Chemistry, [AgL2] [Ag(CN)2] [7, 11–13]. However, the reports about University of Engineering and Technology, Lahore 54890, Pakistan, the coordination of thiones with silver thiocyanate are Tel.: +92-333-5248570, E-mail: [email protected] still limited [19–21]. Therefore, in the present paper, we Muhammad Nawaz Tahir: Department of Physics, University of report the synthesis of some new [(thioamide)(AgSCN) ] Sargodha, Sargodha, Pakistan n Anvarhusein A. Isab: Department of Chemistry, King Fahd University (n = 1 or 1.5) complexes, which have been characterized of Petroleum and Minerals, Dhahran 31261, Saudi Arabia by IR, 1H and 13C NMR spectroscopy, and thermal analysis. Fozia Afzal, Kashif Raza, Muhammad Hanif and Tahira Gul: The crystal structure of one of these compounds, [(Diaz) Department of Chemistry, University of Engineering and Technology, Ag(SCN)], is also presented. The structure of the Imt Lahore 54890, Pakistan complex was also determined, but it was found to be the Shah Muhammad: Department of Chemical Engineering, University of Engineering and Technology, Lahore 54890, Pakistan same as an already reported one, [(Imt)2Ag(SCN)] [19, 20]. Sajjad Ahmad: Department of Chemistry, Quaid-i-Azam University, The structures of thioamides used in this study are shown Islamabad, Pakistan in Scheme 1. 542 M.N. Tahir et al.: Synthesis and characterization of silver(I) complexes of thioureas and thiocyanate CH CH3 CH3 CH3 CH3 3 H N NH H N NH HN NH N N 2 2 2 CH H3C 3 S S S S Thiourea (Tu) N-Methylthiourea (Metu) N,NÄ-Dimethylthiourea (Dmtu) N,NNÄ NÄ-Tetramethylthiourea (Tmtu) HN NH HN NH S S 1,3-Imidazolidinene-2-thione (Imt) 1,3-Diazinane-2-thione (Diaz) Scheme 1: Structures of the ligands used in the study. mixing of thiones to AgNO resulted in colorless solutions, 2 Experimental section 3 while for Dmtu, Diaz, and Imt white precipitates formed on mixing. The mixtures were stirred for 15 min and then 2.1 Chemicals one equivalent KSCN solution was added. The addition of KSCN to Tu, Metu, and Tmtu solutions resulted in white AgNO was a product of Panreac Química S.A. 3 precipitates, while in the case of the 2:1 system of Dmtu, ( Castellar del Vallès, Spain). KSCN was obtained Diaz, or Imt:Ag(I), a colorless solution was obtained, from Merck (Darmstadt, Germany). N-Methylthiourea which upon evaporation of some solvent yielded white (Metu), N,N′-dimethylthiourea (Dmtu), and N,N,N′,N′- precipitates. The white precipitates of the 1:1 mixture of tetramethylthiourea (Tmtu) were obtained from Acros Dmtu and Ag(I) did not dissolve on addition of KSCN and Organics (Pittsburgh, PA, USA). Imidazolidine-2-thione therefore the product was collected from the filtrate (the (Imt) and 1,3-diazinane-2-thione (Diaz) were synthesized residue was discarded). The white precipitates in all cases according to the procedures described in the literature [16]. were filtered, washed with methanol, and air dried. The product yield is about 40–50 %, except for the 1:1 system of Diaz:Ag(I), for which it is only 15 %. The elemental 2.2 Preparation of (thione)–AgSCN analysis and melting points of the complexes are given in complexes Table 1. The complexes were prepared by adding 1 or 2 mmolar solutions of Dmtu, Tmtu, and Diaz (for Tu, Metu, and Imt 2.3 Spectroscopic data complexes only 2 mmolar) in methanol (Tu in water and –1 Imt in acetonitrile) to 0.17 g AgNO3 (1 mmol) in metha- IR (KBr pellet, cm ): AgSCN, ν = 2142; [(Tu)Ag(SCN)], ν = nol followed by the addition of an aqueous solution of 705, 2099, 3190, 3383 (Tu, ν = 732, 3156, 3365); [(Metu) 0.10 g KSCN (1 mmol). In the case of Tu, Metu, and Tmtu, Ag(SCN)], ν = 627, 2110, 3375, 3177 (Metu, ν = 634, 3163, Table 1: Elemental analysis and melting points of the complexes. Complexes Found (calcd.) in % m.p. (°C) C H N S [(Tu)Ag(SCN)] 9.6 (9.9) 1.4 (1.7) 15.6 (17.4) 24.9 (26.5) 154–156 [(Metu)Ag(SCN)] 14.5 (14.1) 2.4 (2.4) 15.8 (16.4) 25.6 (25.0) 119–121 [(Dmtu)Ag(SCN)] 18.4 (17.8) 3.2 (3.0) 15.0 (15. 6) 22.7 (23.7) 111–118 [(Tmtu)(AgSCN)1.5] 18.7 (20.5) 2.7 (3.1) 12.1 (12.9) 20.5 (21.0) 206–207 [(Diaz)Ag(SCN)] 21.9 (21.3) 3.1 (2.9) 14.0 (14.9) 21.8 (22.7) 119–121 M.N. Tahir et al.: Synthesis and characterization of silver(I) complexes of thioureas and thiocyanate 543 3245); [(Dmtu)Ag(SCN)], ν = 638, 2096, 3226 (Dmtu, Table 2: Crystal structure data for compound 1. ν = 641, 3203); [(Tmtu)(AgSCN)1.5], 610, 2105 (Tmtu, ν = Formula C H AgN S 622); [(Diaz)Ag(SCN)], ν = 520, 2100, 3250 (Diaz, ν = 510, 5 8 3 2 M 282.13 3200). – 1H NMR (500 MHz, DMSO, 24 °C, TMS, ppm): r Crystal system Monoclinic [(Tu)Ag(SCN)], δ = 7.65, 8.10 (Tu, δ = 6.98, 7.25); [(Metu) Space group C2/c Ag(SCN)], δ = 2.78, 2.79, 7.88, 8.42, 8.61 (Metu, δ = 2.68, a, Å 20.542(2) 2.87, 6.95, 7.45, 7.65); [(Dmtu)Ag(SCN)], δ = 2.80, 3.04, 8.13, b, Å 13.7782(11) c, Å 6.7186(6) 8.43 (Dmtu, δ = 2.85, 7.38); [(Imt)2Ag(SCN)], δ = 3.70, 8.75 β (Imt, δ = 3.62, 7.98); [(Diaz)Ag(SCN)], δ = 1.78, 3.22, 8.66 , deg 106.569(5) V, Å3 1822.7(3) δ = 13 (Diaz, 1.75, 3.15, 7.81). – C NMR (125.65 MHz, DMSO, Z 8 TMS, ppm): [(Tu)Ag(SCN)], δ = 178.7, 124.5 (Tu, δ = 183.81); –3 ρcalcd., g cm 2.056 –1 [(Metu)Ag(SCN)], δ = 30.2, 31.5, 124.6, 175.4, 179.4 (Metu, μ(MoKα), mm 2.610 δ = 29.9, 31.1, 181.1, 184.1); [(Dmtu)Ag(SCN)], δ = 29.6, 32.1, F(000), e 1104 3 124.3, 176.1 (Dmtu, δ = 30.7, 182.7); [(Imt) Ag(SCN)], δ = Crystal size, mm 0.34 × 0.18 × 0.16 2 Temperature, K 296(2) 44.7, 126.8, 179.5 (Imt, δ = 44.0, 183.4); [(Diaz)Ag(SCN)], δ = Radiation: λ, Å MoKα; 0.71073 18.2, 40.0, 124.5, 169.38 (Diaz, δ = 19.2, 39.8, 175.6). 2θ range, deg 2.069–26.494 h,k,l limits –25:24/–17:17/–8:8 Refl. total/unique/Rint 1886/1886/– 2.4 IR and thermal measurements Reflections observed with I > 2σ(I) 1352 Data/ref. parameters 1886/101 R /wR (I < 2σ(I)) 0.0398/0.0981 The solid-state IR spectra of the ligands and their thiocy- 1 2 R1/wR2 (all data) 0.0630/0.1105 anato silver(I) complexes were recorded on a Perkin-Elmer Goodness of fit (F2) 1.093 FTIR 180 spectrophotometer using KBr pellets over the Largest diff.