Ferrocenylpyrazole—A versatile building block for hydrogen-bonded organometallic supramolecular assemblies Tomoyuki Mochida a,b, * , Fumiko Shimizu a , Hirotaka Shimizu a , Kazuya Okazawa a , Fuminori Sato c , Daisuke Kuwahara c a Department of Chemistry, Faculty of Science, Toho University, Miyama, Funabashi, Chiba 274-8510, Japan b Research Center for Materials with Integrated Properties, c/o Faculty of Science, Toho University, Japan c The University of Electro-Communications, Chofu, Tokyo 182-8585, Japan Received 1 September 2006; received in revised form 7 November 2006; accepted 7 November 2006 Available online 16 November 2006 Abstract The crystal architectures of 5-ferrocenylpyrazole (1) and its metal complexes were investigated. Compound 1 can form non-solvated and chloroform-solvated crystals. In both cases, 1 forms a zigzag one-dimensional architecture via NHN hydrogen bonds. The hydro- gen bond exhibits a twofold disorder, which was shown to be static by solid-state 13 C NMR. In the solvated crystal, the chloroform is released at 415 K, associated with melting of the crystal. The reaction of 1 with metal salts provided metal-centered ferrocenyl clusters [Zn(NO 3 ) 2 (1) 4 ](4), [Co(NO 3 ) 2 (1) 4 ](5), [CoCl 2 (1) 4 ](6), [Zn(NCS) 2 (1) 2 ](7), cis-[Pt(NH 3 ) 2 (1) 2 ](PF 6 ) 2 (8), and trans-[Pt(NH 3 ) 2 (1) 4 ](PF 6 ) 2 (9). In all of these complexes, 1 acts as a monodentate ligand. In 4, 5, and 7, the multinuclear units are joined via hydrogen bonds to form supramolecular chains. Two polymorphs were found for the crystals of 4. Both are composed of the same hydrogen-bonded chains, but their arrangements are different. 5-Ferrocenyl-1-tritylpyrazole (2) and 4-ferrocenyl-1-methylpyrazole (3) were also crystallographi- cally characterized. Ó 2006 Elsevier B.V. All rights reserved. Keywords: Crystal structure; Hydrogen bond; Pyrazole; Ferrocene; Metal complex 1. Introduction Various organometallic supramolecular assemblies have been reported to date [1–3]. In the construction of supra- molecular assemblies, hydrogen bonds and coordination bonds play essential roles. Our approach toward the study of organometallic supermolecules is to introduce heteroaryl substituents into ferrocenes, which has led to the design of versatile ligands such as 5-ferrocenylpyrimidine (FcPM) [4] and relevant ligands [5]. FcPM gives various assembled structures when combined with transition metal salts, and its combination with hydrogen-bond donors leads to hydrogen-bonded supermolecules with various dimensions [4d]. We also prepared ferrocenyl tetrazoles and triazoles, which exhibit one-dimensional crystal architecture based on weak NHC hydrogen bonds [6]. In this study, to real- ize the synergy of hydrogen bonds and coordination bonds in an organometallic molecular assembly, we designed 5- ferrocenylpyrazole (FcPz, 1). Pyrazole derivatives form intriguing hydrogen-bonded assemblies, such as chains, cyclic tetramers, trimers, and dimers (Fig. 1a), and they often show disorder with respect to their NH protons [7]. The hydrogen bond in pyrazoles has drawn attention in terms of intermolecular proton transfer [8]. Furthermore, pyrazole derivatives are versatile ligands [9] that can act as monodentate ligands in their neutral form (Fig. 1a) and as bidentate bridging ligands in the form of pyrazolate 0022-328X/$ - see front matter Ó 2006 Elsevier B.V. All rights reserved. doi:10.1016/j.jorganchem.2006.11.011 * Corresponding author. Address: Department of Chemistry, Faculty of Science, Toho University, Miyama, Funabashi, Chiba 274-8510, Japan. Tel./fax: +81 47 472 4406. E-mail address: mochida@chem.sci.toho-u.ac.jp (T. Mochida). www.elsevier.com/locate/jorganchem Journal of Organometallic Chemistry 692 (2007) 1834–1844