SYNTHESIS AND STRUCTURAL STUDIES OF BIMETALLIC DITHIOCYANATE DISELENOCYANATE AND RELATED COMPLEXES

>M(NCS)(NCSe)M'(SeCN)(SCN)< [M=Co(II), Ni(II); M' =Hg(II), Cd(II), Zn(II)] have been synthesized and studied by elemental analysis, magnetic moment, and electronic and infrared spectral measurements. These studies indicate that the structure of these compounds is basically similar to >M(NCS)2M'(SCN)2< and >M(NCSe)2M'(SeCN)2<; however, their properties are intermediate to these two compounds. On reaction with pyridine, polymeric bridged complexes of the type >(py)2M(NCS)(NCSe)M'(SeCN)(SCN)< are formed when M =Co(II) or Ni(II) and M'=Hg(II) and cationic-anionic type complexes are formed when M=Co(II) or Ni(II) and M'=Cd(II) or Zn(II). With 2, 2′-bipyridine, monomeric bridged complexes are formed when M'=Hg(II), and cationic-anionic complexes are formed when M'=Cd(II) or Zn(II). All the complexes of triphenylphosphine are monomeric bridged. The total softness values of (M-N4) and (M'-X4) units (X=S, Se) for different M and M' in >M(NCS)2M'(SCN)2<, >M(NCSe)2M'(SeCN)2<, and >M(NCS)(NCSe)-M'(SeCN)(SCN)< have been calculated, viz., in the case of >M(NCS)(NCSe)M'(SeCN)(SCN)<: E‡(M-N4)=En‡(M)+2Em‡(NCS)+2Em‡(NCSe) and E‡(M'-X4)=En‡(M')+2Em‡(SCN)+2Em‡(SeCN), where En‡(M) is the softness value of metal ion and Em‡ is the softness value of anion. The difference of total softness of the (M-N4) and (M'-X4) unit has been derived and designated by A[(M'-X4) - (M-N4)]. On relating Δ[(M'-X4) - (M-N4)] with the stability of the thio or selenocyanate bridge, we get the following order: >M(NCSe)2M'(SeCN)2< > >M(NCS)(NCSe)M'-(SeCN)(SCN)< > >M(NCS)2M'(SCN)2<. © 1978, American Chemical Society. All rights reserved.