Decachloro-closo-decaborate anion in copper(II) complexation reactions with N-donor ligands: 35 Cl NQR and X-ray studies V.V. Avdeeva a,⇑ , E.A. Kravchenko a , A.A. Gippius b,c , A.V. Vologzhanina d , E.A. Malinina a , S.V. Zhurenko b , G.A. Buzanov a , N.T. Kuznetsov a a Kurnakov Institute of General and Inorganic Chemistry, Russian Academy of Sciences, Leninskii pr. 31, 119991 Moscow, Russia b Lomonosov Moscow State University, Department of Physics, 119991 Moscow, Russia c Shubnikov Institute of Crystallography, Russian Academy of Sciences, Leninskii pr. 58, 119333 Moscow, Russia d Nesmeyanov Institute of Organoelement Compounds, Russian Academy of Sciences, ul. Vavilova 28, 119991 Moscow, Russia article info Article history: Received 22 November 2016 Accepted 4 February 2017 Available online 17 February 2017 Keywords: Decachloro-closo-decaborate anion 35 Cl NQR spectroscopy X-ray diffraction Copper Complexation abstract Copper(II) complexation reactions with neutral N-donor ligands (Bipy, Phen, NH 3 ) in the presence of the bulky decachloro-closo-decaborate dianion were studied. Copper(II) complexes can be prepared from copper(II) salts or copper(I) salts by redox reactions proceeding in air. The complexes [Cu(Bipy) 3 ] [B 10 Cl 10 ]2CH 3 CN (12CH 3 CN), [Cu(Bipy) 3 ][B 10 Cl 10 ]2Bipy (12Bipy), [Cu(Bipy) 2 Cl] 2 [B 10 Cl 10 ]2DMF (22DMF), [Cu(Phen) 2 Cl] 2 [B 10 Cl 10 ]DMSO1.25H 2 O(3DMSO1.25H 2 O) and [Cu(NH 3 ) 4 (CH 3 CN) 2 ][B 10 Cl 10 ] (4) were prepared and characterized by X-ray diffraction as well as IR and 11 B NMR spectroscopies. Complexes 12CH 3 CN, 22DMF, and 4 were also studied using 35 Cl NQR spectroscopy. Secondary interac- tions were selected from all the interatomic contacts found in these crystals by X-ray diffraction. Hydrogen N–HCl–B, C–HCl–B and pp (B–ClC) secondary bonds were identified in all the com- pounds, the spectroscopic data being generally in accordance with the results of the X-ray diffraction. Ó 2017 Elsevier Ltd. All rights reserved. 1. Introduction The polyhedral boron clusters [B n H n ] 2 (n = 6–12) [1] are very interesting compounds in boron chemistry. They form numerous substituted derivatives with a number of substituents varying from 1 to n [2]. In addition, they are able to act as inner-sphere ligands, forming different bonds with metal atoms (direct B–M bonds, B–H–M bonds with bridging H atoms, (B)H–M with the B atom not coordinated to the metal and three-centered two-electron bonds (BHM) with all three atoms involved in bonding) [3]. In addition, they tend to participate in secondary X–HH–B (X = C, N, O) interactions (dihydrogen bonds) with organic molecules, organic cations or solvent molecules available from the corresponding reaction mixtures [4]. Complexation reactions of copper proceeding in the presence of boron clusters and organic ligands are of particular interest because this metal has two stable oxidation states (1+ and 2+). For copper complexation, a number of copper(I) [5], copper(II), and copper(I,II) complexes [6] with the [B 10 H 10 ] 2 anion and organic ligands L (L = Phen (1,10-phenanthroline), Bipy (2,2 0 -bipyr- idyl), 2,2 0 -bipyridylamine, 5 N-phenanthridine) have been isolated. The reaction conditions, namely temperature, solvent, reagent ratio, atmosphere (nitrogen or air), and the presence of an addi- tional organic ligand L have an effect on the reaction pathway of the complexation reactions and the structure of the obtained prod- ucts. Taking into account the known information about the reactiv- ity of boron clusters in complexation reactions, one can select the appropriate conditions to prepare compounds with the desired structures and properties. It is interesting to know whether substituted derivatives of the decahydro-closo-decaborate anion participate in secondary bond- ing. Among the variety of substituted derivatives, the perhalo- genated anion [B 10 Cl 10 ] 2 was chosen because of its stability and ease of preparation. The chemistry of [B 10 Cl 10 ] 2 is fragmentally studied. It was found that it can stabilize the binuclear copper complex [Co 2 (m-Cl) 2 (Phen) 4 ] 2+ due to its greater weight as com- pared to the [B 10 H 10 ] 2 and [B 12 H 12 ] 2 anions [7]. The silver(I) complex [Ag(NH 3 ) 2 ] 2 [B 10 Cl 10 ] [8] and the salts R 2 [B 10 Cl 10 ] [8,9] (R = Et 3 NH + , Ph 4 P + , Cs + ,K + ) were studied by X-ray diffraction as well as IR and 35 Cl NQR spectroscopies. The [B 10 Cl 10 ] 2 anion was found to participate in numerous secondary interactions with organic cations or solvent molecules and 35 Cl NQR spectroscopy has proved to be a powerful tool for their detection. http://dx.doi.org/10.1016/j.poly.2017.02.015 0277-5387/Ó 2017 Elsevier Ltd. All rights reserved. ⇑ Corresponding author. E-mail address: avdeeva.varvara@mail.ru (V.V. Avdeeva). Polyhedron 127 (2017) 238–247 Contents lists available at ScienceDirect Polyhedron journal homepage: www.elsevier.com/locate/poly