THERMAL-REACTIONS OF N,N-DIMETHYL-1,2-ETHANEDIAMINE COMPLEXES OF NICKEL(II) IN THE SOLID-STATE

Complexes [NiL2(H2O)X]X·nH2O (L=N,N-dimethyl-1,2-ethanediamine; n=0 when X=BF4; n=1 when X=Br; n=3 when X= CI), [NiL2(H2O)Y]·nH2O (n=2 when Y= SeO4; n=5 when Y=SO4), [NiL2(H2O)2]-(NO3)2·H2O and [NiL2] (ClO4)2 have been synthesized and investigated thermally in the solid state. The complexes [NiL2(H2O)Cl]Cl·3H2O, [NiL2(H2O)Br]Br·H2O, [NiL2(H2O)(SO4)]·5H2O, and [NiL2(H2O(SeO4)]·2H2O possess trans octahedral geometry and undergo deaquation-anation associated with trans → cis isomerization upon heating in the solid state whereas on deaquation the complex [NiL2(H2O)2](NO3)2·H2O retains its trans octahedral configuration. The complex [NiL2(H2O)(BF4)](BF4) possesses cis octahedral geometry and on thermal deaquation it transforms to a square planar complex. The complex [NiL2](ClO4)2 is square planar and undergoes a yellow→red thermochromic phase transition on heating (203-216°C; ΔH=6.9 kj mol-1). The red isomer is also square planar. The species [NiLCl2], [NiL(SO4)] and NiL0.33Cl2 have been synthesized pyrolytically in the solid state from their corresponding parent diamine complexes. The complexes [NiLCl2] and [NiL(SO4)] possess octahedral geometry. NiL0.33Cl2 possesses an unusually high magnetic moment (4.1 BM at 28°C). © 1990 The Chemical Society of Japan.