SHORT COMMUNICATION DOI: 10.1002/ejic.200600029 Two Novel 5f–3d Bimetallic Cyano-Bridged Complexes Lin-Ping Zhang, [a,b] Peter A. Tanner,* [c] and Thomas C. W. Mak [a] Keywords: Cyano bridge / Transition metal / Uranium / Electronic structure Bimetallic cyano-bridged uranyl Co and uranyl Fe com- pounds crystallize in the same space group but are not iso- morphous and each comprises two different types of uranyl ion. The spectroscopic consequences with regard to band in- Introduction There has been considerable interest in 3d–4f bimetallic cyano-bridged complexes due to their catalytic, semicond- uctive and magnetic properties. [1] Du et al. [2] have listed an- other 15 applications. Although there have been several re- ports of 3d–5f complexes, [3] attention has not been directed towards cyano-bridged 3d–5f complexes, so that we decided to synthesize such complexes comprising the uranyl ion, be- cause the electronic structure and spectroscopy of this acti- nide ion are well-documented. [4] Two novel complexes in- volving also the coordination of dimethylformamide (dmf) and aqua ligands to U VI are reported herein: [UO 2 (H 2 O) 4 - (dmf) 2 ] 0.5 ·{UO 2 [M(CN) 6 ](dmf) 2 }, M = Co (1), Fe (2) and their spectroscopic properties have been investigated. Results and Discussion Crystal Structures Compound 1 comprises two ionic components (Figure 1, a). The anionic component is a cyano-bridged infinite layer in which the U VI cation is seven-coordinate in a pentagonal- bipyramidal geometry, bonding to two oxygen atoms [U1– O1, 1.727(7) Å, U1–O2, 1.761(7) Å], two dmf molecules [U1–O3, 2.325(6) Å, U1–O4, 2.359(5) Å], and three cyanide groups from different [Co(CN) 6 ] 3– ions [U1–N1, 2.494(6) Å, U1–N2a, 2.499(6) Å, U1–N5b, 2.492(6) Å]. The Co III cat- [a] The Department of Chemistry, The Chinese University of Hong Kong, Shatin, New Territories, Hong Kong S.A.R., P.R. China [b] College of Chemistry and Chemical Engineering, Donghua University, West Yan-an Road 1882, Shanghai 20051, P.R. China [c] Department of Biology and Chemistry, City University of Hong Kong, Tat Chee Avenue, Kowloon, Hong Kong S.A.R., P.R. China Fax: +852-2788-7406 E-mail: bhtan@cityu.edu.hk Supporting information for this article is available on the WWW under http://www.eurjic.org or from the author. Eur. J. Inorg. Chem. 0000, 0–0 © 0000 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim 1 b/ i tensities and positions for the transitions at these different uranyl ion sites are novel and are rationalized. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006) ion is octahedrally coordinated by six cyanide groups (Co– C, 1.884–1.904 Å), with three of them connecting three different U VI cations. The U VI ions bridge other [Co(CN) 6 ] 3– ions through cyanide groups, forming an infi- nite two-dimensional anionic layer parallel to the bc plane (Figure 2, a). The cationic component comprises discrete centrosymmetric [UO 2 (H 2 O) 4 (dmf) 2 ] 2+ cations, situated above and below the anionic layer, each forming O–H···N interactions with it. This U VI cation is eight-coordinate in a hexagonal bipyramidal geometry, being coordinated by Figure 1. Atom labeling in the asymmetric unit: (a) [UO 2 (H 2 O) 4 - (dmf) 2 ] 0.5 ·{UO 2 [Co(CN) 6 ](dmf) 2 } (1); (b) [UO 2 (H 2 O) 4 (dmf) 2 ] 0.5 · {UO 2 [Fe(CN) 6 ](dmf) 2 }(2).