Note The cyanocarbanion (C[C(CN) 2 ] 3 ) 2 as monodentate ligand: Synthesis, structure and magnetic properties of [Mn 2 (bpym) 3 (tcpd) 2 (H 2 O) 2 ] (tcpd 2 = (C[C(CN) 2 ] 3 ) 2 and bpym = 2,2 0 -bipyrimidine) Franck The ´tiot a , Smaı ¨l Triki a, * , Jean Sala-Pala a , Ste ´phane Golhen b a UMR CNRS 6521, Chimie, Electrochimie Mole ´culaires, Chimie Analytique, Universite ´ de Bretagne Occidentale, 6 Avenue Victor Legorgeu, CS 93837 29238, BP 809, 29285 Brest Cedex 3, France b UMR CNRS 6511, L.C.S.I.M., Universite ´ de Rennes 1, CS 74205, 35042 Rennes Cedex, France Received 16 February 2005; accepted 25 April 2005 Abstract One-pot reaction between MnCl 2 Æ4H 2 O, K 2 tcpd (tcpd 2 = [C 10 N 6 ] 2 = (C[C(CN) 2 ] 3 ) 2 = 2-dicyanomethylene-1,1,3,3-tetracyano- propanediide anion) and 2,2 0 -bipyrimidine (bpym = C 8 H 6 N 4 ) in aqueous solution yields the new compound [Mn 2 (bpym) 3 (tcpd) 2 (H 2 O) 2 ] (1). The molecular structure of 1 consists of a centrosymmetrical binuclear complex which includes unprecedented unidentate tcpd ligands with two bidentate and a bis-chelate bpym units. Examination of the intermolecular distances reveals that the dinuclear units are held together by hydrogen bonds involving coordinated water molecules and two nitrile groups of the tcpd ligand, giving rise to a 2D structure overall. Variable-temperature magnetic susceptibility data show the occurrence of slight antiferromagnetic coupling (J = 0.58 cm 1 ) between the Mn(II) ions through bridging bpym (the exchange Hamiltonian being defined as b H ¼2J b S A  b S B ). Ó 2005 Elsevier B.V. All rights reserved. Keywords: Polynitrile ligands; Binuclear complexes; Crystal structures; Magnetic properties 1. Introduction Polynitrile anions [1] (Scheme 1) have received, in the last few years, considerable interest in the field of coor- dination chemistry and molecular materials [2–9]. These organic anions are interesting for their ability to act with various coordination modes and for their high electronic delocalization [2–15]. Thus, their reactions with transi- tion metal ions afford binary compound displaying fas- cinating molecular extended and discrete structures with various and unusual magnetic properties [3,4]. To explore the influence of a second ligand on the network structures and on the electronic properties of these binary systems, we focused our interest on the use of the p-conjugated bridging molecules (Scheme 1). In this context, the bis-chelating 2,2 0 -bipyrimidine (bpym) ligand, which is known to transmit antiferro- magnetic coupling between paramagnetic centers sepa- rated by more than 5.5 A ˚ [16,17], is a particularly interesting choice. The recently reported results ob- tained for dca/bpym [11–14] and for dcne/bpym [15] mixed ligand complexes revealed that such combina- tions afford a rich variation in molecular architectures. The combination of dca with bpym as ligands afforded 1D, 2D and 3D derivatives: [M(dca) 2 (bpym)(H 2 O)] (M = Mn, Fe, Co) and [Mn(dca) 2 (bpym)] have 1D structures [12–14], [M 2 (dca) 4 (bpym)] Æ H 2 O (M = Fe, 0020-1693/$ - see front matter Ó 2005 Elsevier B.V. All rights reserved. doi:10.1016/j.ica.2005.04.030 * Corresponding author. Tel.: +33 2 9801 6146; fax: +33 2 9801 6594. E-mail addresses: triki@univ-brest.fr, smail.triki@univ-brest.fr (S. Triki). www.elsevier.com/locate/ica Inorganica Chimica Acta 358 (2005) 3277–3282