Crystal structure and EPR/ENDOR study of the nonplanar system bis(tetraphenylarsonium) bis(maleonitriledithiolato)zincate(II) doped with copper(II) (original) (raw)

1986, Inorganic Chemistry

A single-crystal EPR and I3C ENDOR study on bis(tetrapheny1arsonium) bis(maleonitriledithiolato)cuprate(II), [ (C , H ,) , A S ]~[ C U (~~~)~] , and the crystal and molecular structure of the corresponding zinc host complex are reported. [(C,H,),A~],[zn(mnt)~] crystallizes in the monoclinic crystal system, space group P2,/c, with Z = 4, a = 17.559 (3) A, b = 16.828 (3) A, c = 18.542 (2) A, and p = 110.43 (1)'. The coordination of the Zn ion by the four sulfur atoms is almost tetrahedral. The angle between the ligand planes is 84". From EPR and ENDOR measurements, the structure of the incorporated [Cu(mnt),12anions is determined. The themselves planar [Cu(mnt),12-anions do not accept the structure of the host. Instead, an angle of 30" between the ligand planes has been found by EPR and of 30 or 46" with I3C ENDOR on the ring-carbon atoms. Comparison of the experimental EPR parameters with the parameters that are computed from the results of extended Hiickel molecular orbital calculations for various molecular geometries suggests an angle of approximately 30". The EPR line width decreases exponentially with decreasing temperature, down to 150 K. It points to an activated process with an activation energy of 3.9 kcal/mol. Experimental Section A. Preparation of Complexes and Single Crystals. Na2mnt was prepared according to the method of Bahr and Schleizer.21s22 The synthesis was performed with "C-enriched CS2 (enrichment 35%)23 in order to obtain mnt2-complexes in which the chelate ring atoms are 13C-labeled. Yellow [(C,H,),A~]~[2n(mnt)~] was prepared as described by Gray et al.24 Brown [(C,H,),AS]~[~~CU(~~~)~] was synthesized in the same manner with use of ,,Cu-enriched CuCI2.2H2O (97.8% ,,Cu, 2.2% ,%). Green single crystals containing 2 mol % of the paramagnetic copper(I1)