Transition Met. Chem., 21, 81 84 (1996) [Ni(S2CO)(dppe)] complexes 81 Investigation of { 1,2-bis(diphenylphosphino)ethane-P,P'} carbonato-S,S')-nickel(II) Zden~k Tr~vni~ek*, Richard Pastorek, Zden~k Sindehi~ and Roman Kli~ka Department of Inorganic and Physical Chemistry, Palack~ University, KlXi~kovskbho i0, 771 47 OIomouc, C Jaromir Marek Department of Inorganic Chemistry, Masaryk University, KotldlZskd 2, 6I I 37 Brno, Czech Republic Summary The reaction ofbis(iso-propylxauthato)nickel(II) with 1,2- bis(diphenylphosphino)ethane (dppe) in a 1 : 1 molar ratio affords [Ni(S2CO)(dppe)], which, on the basis of its mag- neto-chemical and spectral properties, has been charac- terized as a square-planar Ni complex. The complex was one-electron irreversibly oxidized at a potential of 0.673 V versus s.c.e. The crystal and molecular structure of a twinned crystal of the complex has been elucidated, and consists of two crystallographically independent mol- ecules inwhich each Ni atom is coordinated by two S atoms from the dithiocarbonate ligand and two P atoms from the dppe ligand in an approximately square-planar arrangement. Introduction It is known from the literature that square-planar nickel(II) xanthates of the type [Ni(RXa)21 (R = alkyl, Xa = $2CO -) react with dppe in three ways/~'2). Perpififin et al. ~1) studied the reactions of [Ni(RXa)2 ~ (R = Me, Et or cyclo-Hex) with dppe in a 1 : 1 molar ratio. The reactions led to formation of paramagnetic compounds with the composition [Ni(RXa)2(dppe)]. When the components were reacted in a non-sto~chiometric ratio (with an excess of dppe) the square-planar [Ni(S2CO)(dppe)] complex was formed. AIy et alJ 2) were also interested in reactions between [Ni(RXa)2 ] (R = Me, Et, n-Pr, n-Bu or cyclo- Hex) and dppe in a 1: 1 molar ratio. These yielded square- planar I-Ni(RXa)2(dppe)2 ] complexes, in which both the xanthates and diphosphine ligands arc coordinated as monodentate ligands. We present, in this paper, a physico-chemical study of [Ni(S2CO)(dppe)] as a product of the reaction between [Ni(i-PrXa)2] and dppe in a 1:1 molar ratio. Experimental All the chemicals used were of p.a. purity and were supplied by Lachema Brno Co., except for the dppe ligand (Fluka Co.). The C, H, S analyses were determined on an EAll08 instrument (Fisons). I.r. spectra were measured on a Specord M80 (Carl Zeiss) instrument, using the Nujol technique, in the 4000-400 cm- 1 region. U.v.-vis. spectra were recorded on a Specord M40 (Carl Zeiss) instrument in the 33000-11000cm -1 range. Magneto-chemical measurement~ were performed by the Faraday method at room temperature. The thermal decomposition (in air) was studied on a Q 1500 D Derivatograph (MOM * Author to whom ail correspondence should be directed, Budapest) instrument in the 20-900 ~ range. The molar conductivity, 2~, was measured on an OK 102/1 (Radel- kis) conductivity meter at 25~ in CH3NO > Elec- trochemical measurements were carried out on a Polarographic Analyser PA4 (Laboratorni pfistroje) in a three-electrode arrangement with Pt as the working electrode (surface area 0.32cna2), Pt foil with a large surface area as the auxiliary electrode with the potential referenced to a saturated calomel electrode (s.c.e.): polari- zation range, - 0 . 2 - + 0 . 8 V ; polarization scan rate, 0.005 V s - 1. The measurement was performed in DMSO in the presence of (MeaN)C1 (0.05 mot din-3) as support- ing electrolyte and with the concentration of the complex 7.65 x 10-Smoldm -3. The X-ray measurement was performed on a KUMA KM-4 four-circle diffractometer with ~c-axis geometry using a crystal with dimensions 0.4 x 0.3 x 0.2ram at 291(2)K. The experimental density was determined by floatation in aqueous KI solution. Graphite-mono- chromatized MoK~ radiation was used for data collec- tion. Because of problems with indexation of the orientation reflection's set, Duisenberg (3) indexing method was used. The method suggested that the crystal is a twin with twinning matrix: I 0.3 0.0 - 1 . 3 1 M I = 0.0 - 1 . 0 0.0 - 0 . 7 0.0 -0.3 where matrix M1 transforms indices (in raw form) of the first individual to those of the second. The twin assump- tion made it possible to index all 42 diffractions used for orientation and led to two orientation matrices confirm- ing twinning of the crystal. After refinement of both orientation matrices (we had 25 reflections in the range 10 ~ < 20 < 20 ~ for both individuals) the twinning matrix was.* I 0.30 0.00 -1. 3 0 1 M 2 = 0.00 -- 1.02 0.00| --0.72 0.00 --0.29_] with e.s.d.'s to the third significant figure. Because of the direct-space translation, vectors of two components of a twinned crystal are related by the term A 2 = M2A 1. An accidental overlapping of reflections from our twinned crystal occurred when two diffraction spots were separ- ated by less than the experimental resolution of the dif- fractometer. The degree of overlap of two reflections originating from two different twin components can be described by their distance, 6, in reciprocal space, which, on the basis of A2, is given by: 6 = l ( h 2 - h l ) a * + (k2 - kl)b~ + (Iz - ~)c~p, where h2, k 2 and 12 refer to the indices of a rcflection of the second subsystem, and hi, k 1 0340-4285 ~ 1996 Chapman & Halt