Boron coordination compounds derived from 2-phenyl-benzimidazole and 2-phenyl-benzotriazole bidentate ligands Adriana Esparza-Ruiz a , Adrián Peña-Hueso a , Heinrich Nöth b , Angelina Flores-Parra a, * , Rosalinda Contreras a, * a Department of Chemistry, Cinvestav, AP 14-740, CP 07000, México DF, Mexico b Department Chemie, Ludwig-Maximiliams Universität, Butenandt-Strasse 5-13 (Haus D), D-81377 Munich, Germany article info Article history: Received 12 June 2009 Received in revised form 8 July 2009 Accepted 9 July 2009 Available online 18 July 2009 Keywords: Organoboron 2-Phenyl-benzimidazole 2-Phenyl-benzotriazole Coordination compounds 11 B and 19 F NMR abstract The syntheses and structural analyses of a series of boron heterocycles derived from 2-(1H-benzimidazol- 2-yl)-phenylamine (1), 2-(1H-benzimidazol-2-yl)-phenol (2), 2-(1H-benzimidazol-2-yl)-benzenedisulfide (3), 2-[3-(1,1,1,3,-tetramethyl-butyl)-phenyl]-2H-benzotriazole (4), 2-[3,5-bis-(1-methyl-1-phenylethyl)- phenyl]-2H-benzotriazole (5) and (C 6 H 5 ) 2 BOH or BF 3 OEt 2 are reported. The new boron compounds: diphenyl-[2-(1H-benzimidazol-2-yl-jN)-phenylamide-jN]-boron (6), diphenyl-[2-(1H-benzimidazol-2- yl-jN)-phenolate-jO]-boron (7), diphenyl-[2-(1H-benzimidazol-2-yl-jN)-benzenethiolate-jS]-boron (8), diphenyl-[2-(2H-benzotriazol-2-yl-jN)-4-(1,1,3,3-tetramethyl-butyl)-phenolate-jO]-boron (9), diphenyl-[2-(2H-benzotriazol-2-yl-jN)-4,6-(1-methyl-1-phenylethyl)-phenolate-jO]-boron (10), difluoro- [2-(1H-benzimidazol-2-yl-jN)-phenolate-jO]-boron (11), difluoro-[2-(2H-benzotriazol-2-yl-jN)-4- (1,1,3,3-tetramethylbutyl)-phenolate-jO]-boron (12) and difluoro-[2-(2H-benzotriazol-2-yl-jN)-4, 6-(1-methyl-1-phenylethyl)-phenolate-jO]-boron (13) have four fused rings, with boron included in a six-membered ring and bound to N, O or S atoms and strongly coordinated by a nitrogen atom from the imidazole or triazole rings. Their structures are zwitterionic, with a negative charge on the boron and a delocalized positive charge on the ligand. Compounds 6–12 were studied by NMR, IR, mass spec- trometry, and 6–10 and 12 by X-ray diffraction analyses. Ó 2009 Elsevier B.V. All rights reserved. 1. Introduction There is considerable structural and biological interest in the study of aromatic six-membered ring compounds containing boron [1–4]. We have studied this kind of boron heterocycles derived from guanidinobenzimidazole [5], uroylbenzimidazole [6] and imidazole [7]. Herein, we report the syntheses and structural analyses of heterocyclic compounds derived from [BPh 2 ] + or [BF 2 ] + groups and 2-phenyl-benzimidazole and 2-phenyl-benzotriazole derivatives. The high Lewis acidity of these boron groups make them excellent models for transition metal coordination, with the advantage that they form diamag- netic molecules easily analyzed by NMR techniques. The chosen bidentate ligands were compounds 1–5, Scheme 1. Comparison of benzimidazole and benzotriazole derivatives as coordinating molecules is interesting because the presence of a third nitro- gen in the triazole, rather than a carbon in the imidazole, affects the resonance contributors and has an impact in the stability of the new heterocycles. Some of the starting ligands have been used before to prepare coordination compounds. Ligand 1 has been widely used for the preparation of a series of transition metal coordination compounds [8,9], whereas, compound 2 has been employed as a ligand for transition [10–13] and lanthanides metals [14]. The structural analysis of disulfide 3 has been recently reported [15]. Compound 4 has been used in the synthesis of Re(I) compounds [16]. Deriva- tives of compound 5 and elements of group 4 have been employed as catalysing agents [17]. Compounds 1 and 2 have been used to prepare phosphorus heterocycles [18,19]. Haloboron heterocycles derived from compound 2 are known. It was proposed that two benzimidazole ligands were coordinated to a BBr þ 2 , through the imidazole nitrogen atom, however their structural characterization was not completed [20]. Planar diaminoboranes from ligand 1 have been prepared [21]. 2. Results and discussion The reactions of compounds 1–5 with BPh 2 OH and BF 3 OEt afforded the new boron compounds 6–13, which were analyzed by NMR, IR, mass spectrometry, and 6–10 and 12 by X-ray diffrac- tion. The reactions of 1 and 3 with BF 3 OEt gave a mixture of com- pounds that were not isolated neither properly assigned, Scheme 1. 0022-328X/$ - see front matter Ó 2009 Elsevier B.V. All rights reserved. doi:10.1016/j.jorganchem.2009.07.029 * Corresponding authors. E-mail address: aflores@cinvestav.mx (R. Contreras). Journal of Organometallic Chemistry 694 (2009) 3814–3822 Contents lists available at ScienceDirect Journal of Organometallic Chemistry journal homepage: www.elsevier.com/locate/jorganchem