FT-IR Spectroscopic Study of M(Benzoic Acid) 2 Ni(CN) 4 Complexes (M = Ni, Cd, Co and Mn) Z. Kartal and S ¸.S ¸ent¨ urk Physics Department, Faculty of Arts and Sciences, Dumlupınar University, K¨ utahya, Turkey Reprint requests to Dr. Z. K; E-mail: zkartal@dumlupinar.edu.tr Z. Naturforsch. 60a, 285 – 288 (2005); received January 14, 2005 Complexes of M(benzoic acid) 2 Ni(CN) 4 (M = Ni, Cd, Co and Mn) are obtained for the first time. The observed spectra indicate that the obtained complexes are new examples of Hofmann-type com- plexes. — PACS NO: 33.20.Ea, 33.20.Tp Key words: Benzoic Acid; Infrared Spectroscopy; Tetracyanonickelate; Hofmann-type Compounds. 1. Introduction Many Hofmann-type complexes with the gen- eral formula ML 2 Ni(CN) 4 were produced by using N-donor ligand molecules such as ammonia [1], pyridine [2], and products of pyridine [3, 4]; O-donor ligand molecules such as water [5], dioxane [6], dimethylsulfoxide [7], urea [8], pyridine-1-oxide [9], and dimethylformamide [10]; S-donor ligand molecules such as 1,3-thiazolidin-2-thion [11] and dimethylthioformamide [12]. In the above formula, M is a transition metal atom having the valence +2, and L is either a bidentate or two monodentate molecules. In the present study we used for the first time benzoic acid (BA) as a ligand to produce new Hofmann-type complexes with the general formula M(BA) 2 Ni(CN) 4 (M = Ni, Cd, Co and Mn). These Fig. 1. The molecular structure of the benzoic acid monomer. 0932–0784 / 05 / 0400–0285 $ 06.00 c  2005 Verlag der Zeitschrift f¨ ur Naturforschung, T¨ ubingen · http://znaturforsch.com complexes were investigated in the infrared range of 4000 – 400 cm -1 . The BA molecule contains carboxyl groups, namely carbonyl and hydroxyl [13]. Each group (carbonyl and hydroxyl) contains an oxygen atom, which can donate electrons. BA has monomer and dimmer shapes [14]. The molecular structure of the monomer is shown in Figure 1. The electron density of the BA monomer was cal- culated at the restricted Hartree-Fock level using the PM3 method in the MOPAC 97 program package. The calculations indicate that the oxygen atom 9 has a higher electron density than the oxygen atom 8 and the hydrogen atom 15. Hence we expect that the bind- ing happens with the oxygen atom 9. There are vari- ous infrared spectroscopy studies reported for the BA molecule [14 – 19].