Bond angle of isothiocyanate. Molecular network of cobalt(II) isothiocyanate with bis(3-pyridyl)dialkylsilanes q Tae Hwan Noh, Jae Hong Kim, Young-A Lee 1 , Hongsuk Suh, Ok-Sang Jung * Department of Chemistry, Center for Plastic Information System, Pusan National University, Pusan 609-735, South Korea Received 4 November 2003; revised 9 December 2003; accepted 11 December 2003 Abstract The reaction of Co(NCS) 2 with L produces the coordination polymers of [Co(NCS) 2 L 2 ] unit (L ¼ bis(3-pyridyl)cyclotetramethylenesilane (bpcms) and bis(3-pyridyl)dimethylsilane (bpdms)). Each L linker connects two cobalt(II) ions defining the edges of a 32-membered [Co II ] 4 , thus forming a 2D grid sheet structure. The local geometry of the cobalt(II) ion is an octahedral arrangement with two NCS groups in trans position and four pyridine units in a propeller fashion building the basal plane. Difference between dimethyl and cyclotetramethylene moieties of two spacer ligands induces delicate structural difference. The Co– N – CS angle of [Co(NCS) 2 (bpdms) 2 ] is severely bent (Co – N – C ¼ 153.9(2)8) in contrast to the corresponding angle (Co–N–C ¼ 180.08) of [Co(NCS) 2 (bpdms) 2 ]. The degree of the Co–N–CS angle seems to be determined by steric or packing effects rather than electronic effects. q 2003 Elsevier B.V. All rights reserved. Keywords: Cobalt(II) complexes; Coordination polymers; Isothiocyanate; Bis(3-pyridyl)dimethylsilane; Bis(3-pyridyl)cyclotetramethylenesilane; Crystal structures 1. Introduction Metal-based coordination polymers have emerged as new motifs of molecular architecture due to both aesthetic facet and potential applicability such as electrical conductivity, molecular magnet, host – guest chemistry, crystal bending effect, and catalysis [1–9]. The new motifs can be designed by selecting the coordination geometry of central metals, the structure of spacer ligands, the kinds of counterions, and reaction conditions [10–14]. Among diverse elegant efforts to find key factors in the development of rational infinite structures, the use of unique spacers that can bridge two or more metal centers is of current interest. The appropriate angle and flexible components of the spacers play an important role as a rational design strategy [15–19]. In this context, recently, silicone-containing bipyridyl spacers have been explored for a remarkable class of materials containing diverse architectures and functions [20–24]. In order to investigate delicate structural differences of coordination polymers including the bond angle of Co II –N–CS induced by the difference between bis(3-pyridyl)cyclotetramethyle- nesilane (bpcms) and bis(3-pyridyl)dimethylsilane (bpdms), we report the results on the synthesis and structural properties of Co(NCS) 2 with bpdms or bpcms. The two silicon- containing bipyridyl ligands are similar in general structure, bite length, and potential bidentate, but slightly different in conformational rigidity around the Si atom. On the other hand, the NCS moiety is one of the interesting ambidentate ligands [25]. 0022-2860/$ - see front matter q 2003 Elsevier B.V. All rights reserved. doi:10.1016/j.molstruc.2003.12.009 Journal of Molecular Structure 691 (2004) 165–169 www.elsevier.com/locate/molstruc q Supplementary data associated with this article can be found, in the online version, at doi:10.1016/j.molstruc.2003.12.009 1 Present address: Department of Chemistry, University of Rochester, Rochester, NY 14627, USA. * Corresponding author. Tel.: þ 82-51-510-2591; fax: þ82-51-516-7421. E-mail address: oksjung@pusan.ac.kr (O.-S. Jung).