Synthesis and molecular studies of half-sandwich arene ruthenium and Cp*Rh/Cp*Ir complexes containing (3-picolyl)thiourea derivatives as N,S-bidentate donor ligands Mahesh Kalidasan 1 • R. Nagarajaprakash 2 • Kollipara Mohan Rao 1 Received: 21 March 2015 / Accepted: 7 May 2015 / Published online: 28 May 2015 Ó Springer International Publishing Switzerland 2015 Abstract Series of mononuclear complexes of arene Ru and Cp*Rh/Cp*Ir complexes containing (3-picolyl)thiourea derivative ligands, of general formulae [(g 6 -arene)R- u(L)Cl]Cl and [Cp*M(L)Cl]Cl {L = benzoyl(3-picoy- lyl)thiourea, arene = benzene (1); p-cymene (2) and M = Rh (3); Ir (4); L = 1,3-bis(3-picolyl)thiourea, arene = benzene (5); p-cymene (6) and M = Rh (7); Ir (8)}, have been synthesized and characterized by spectroscopic meth- ods. X-ray crystallographic studies of complexes (2)–(5), (7), and (8) reveal a typical piano-stool geometry around the metal center with a six-membered metallacycle, in which L acts as an N,S-chelating ligand. Intramolecular N–HÁÁÁS, SÁÁÁO, and N–HÁÁÁN interactions are found to play a sig- nificant role in the molecular structures. Introduction The chemistry of arene Ru and Cp*Rh/Cp*Ir complexes is well established. Nevertheless, new synthetic routes in- volving mild reaction conditions, high yields, stable com- plexes, and solubility under aqueous conditions are still desirable [1, 2]. These complexes have numerous appli- cations as catalysts for various organic transformations [3– 5], as sensors in supramolecular chemistry [6], and as products with biological properties [7, 8]. Thiourea and its derivatives are potentially very versatile ligands, widely used in many fields including the pharma- ceutical industry due to their anticancer, antimicrobial, an- tibacterial, and antimalarial properties [9–11]. There are able to act as neutral, monoanionic, or dianionic ligands to co- ordinate to a range of metal centers. For example, N-alkyl- benzoylthiourea ligands can give stable complexes with various transition metals including Cu and Ni in which they act as bidentate O,S donor ligands [12, 13]. In addition, the presence of hard nitrogen and soft sulfur donor atoms pro- vides a multitude of bonding possibilities; moreover, an additional donor group such as pyridyl residue in the ligand can change the coordination behavior of benzoyl thiourea to act as a N,S-bidentate ligands [14, 15]. As part of our research on half-sandwich complexes, we have previously synthesized arene Ru and Cp*Rh/Cp*Ir complexes with various bidentate NN, NO, and OO donor ligands [16]. To the best of our knowledge among various N-donor derivatives, there is no report currently available on arene Ru and Cp*Rh/Cp*Ir complexes with benzoyl(3- picolyl)thiourea and 1,3-bis(3-picolyl)thiourea ligands. Thus, we now report the synthesis of a series of mononu- clear half-sandwich complexes of arene Ru(II), Cp*Rh(III) and Cp*Ir(III) with bidentate ligands, as shown in Fig. 1. Experimental Physical methods and materials All reagents were purchased from commercial sources and used as received. RuCl 3 ÁnH 2 O, RhCl 3 ÁnH 2 O, and IrCl 3 ÁnH 2 O were purchased from Arora Matthey, 2-amino- 3-picoline was obtained from Aldrich, and benzoyl chloride and KSCN were acquired from Merck. The solvents were & Kollipara Mohan Rao mohanrao59@gmail.com 1 Department of Chemistry, North Eastern Hill University, Shillong 793 022, India 2 Department of Chemistry, Pondicherry University, Puducherry 605014, India 123 Transition Met Chem (2015) 40:531–539 DOI 10.1007/s11243-015-9946-x