Synthesis of a new N,N 0 -ethane-1,2-bis(4-methoxyphenyl)carbothioamide ligand and its Cu(I) and Ag(I) complexes Nand K. Singh a, * , Mamata Singh a , Pratibha Tripathi a , Ajay K. Srivastava a , Ray J. Butcher b a Department of Chemistry, Banaras Hindu University, Varanasi 221 005, India b Department of Chemistry, Howard University, 525 College Street NW, Washington, DC 20059, USA Received 26 June 2007; accepted 23 September 2007 Available online 3 December 2007 Abstract [Cu(H 2 L)(PPh 3 ) 2 ]NO 3 Æ 0.5H 2 O(2) and [Ag(H 2 L)(PPh 3 ) 2 ]NO 3 Æ 0.5H 2 O(3) complexes of a new flexible thioamide ligand; N,N 0 -eth- ane-1,2-bis(4-methoxyphenyl)carbothioamide H 2 L(1) have been synthesized using PPh 3 as a coligand. The synthesized compounds have been characterized with the help of elemental analyses, IR, 1 H, 13 C and 31 P NMR spectroscopy. The ligand and its Cu(I) complex have been studied by single crystal X-ray crystallography. The ligand acts as a neutral S-donor and forms a nine-membered chelate ring in [Cu(H 2 L)(PPh 3 ) 2 ]NO 3 Æ 0.5H 2 O. The molecular packing is stabilized by an anionic cavity formed by intermolecular hydrogen bonding between the basal plane of the complex molecule and the nitrate ions. The square shaped columnar channel has dimensions of 5.489(25) [N(11)–H(11A)ÁÁÁO(13)ÁÁÁH(21A)N(21)] · 3.693(7) [N(11)–C(11)–C(21)–N(21)] A ˚ . Ó 2007 Elsevier Ltd. All rights reserved. Keywords: Thioamide ligand; b-Sheet hydrogen bonding; Cu(I) and Ag(I) complexes; Nine-membered chelate ring 1. Introduction The role of copper(I) is evident in several biologically important reactions [1–3], such as a dioxygen carrier and models for several enzymes [4]. Following our interest in the coordination properties of ligands containing the –NH–C(@S)– group, and their potential biological activity, which is probably related to their chelating ability towards vital metal ions, we have recently reported copper(II) and manganese(III) complexes of N 0 -[(2-hydroxyphenyl)carbo- thioyl]pyridine-2-carbohydrazide: a novel therapeutic agent for cancer [5]. The use of such Cu(II) systems is bound to involve the reduction of Cu(II) to Cu(I) in the cell (especially in the presence of S), thus the stability of the Cu(I) species is crucial to biological activity. However, the low solubility of copper (I and II) complexes has restricted us studying the structures from single crystal X- ray crystallography. The presence of tertiary phosphines are known to play an important role in enhancing the sol- ubility of Cu(I) compounds of heterocyclic thioamide ligands [6]. From the above viewpoints and with the aim of elucidat- ing the coordination geometry of ligands containing the –NH–C(@S)– moiety, N,N 0 -ethane-1,2-bis(4-methoxy- phenyl)carbothioamide and its Cu(I) and Ag(I) complexes with PPh 3 as a coligand, viz. [Cu(H 2 L)(PPh 3 ) 2 ]- NO 3 Æ 0.5H 2 O and [Ag(H 2 L)(PPh 3 ) 2 ]NO 3 Æ 0.5H 2 O, have been prepared and characterized. The ligand and the Cu(I) complex have been characterized by X-ray crystallography. 0277-5387/$ - see front matter Ó 2007 Elsevier Ltd. All rights reserved. doi:10.1016/j.poly.2007.09.035 * Corresponding author. Tel.: +91 542 2318529; fax: +91 542 2368127. E-mail address: nksingh@bhu.ac.in (N.K. Singh). www.elsevier.com/locate/poly Available online at www.sciencedirect.com Polyhedron 27 (2008) 375–382