The twotrans-[NiL2(NCS)2] (L =N,N-dimethyl-1,3-propanediamine) isomers in the solid state and in solution

Summary Two complextrans-NiL₂ (NCS)2] (L =N, N-dimethyl-1,3-propanediamine) synthesised from solution in two isomeric forms (1) and (2), exhibit similar colours, magnetic moments and electronic spectra, but differ in their i.r. spectra and x-ray powder diffraction patterns. We suggest they possesstrans- chair-chair andcis-chair-chair chelate conformations, respectively. Complexes (1) (2) isomerise (temperature range 382–397.5 K; H = 5.12 kJ mol^–1) in the solid state. Isomer (2) is converted into isomer (1) upon recrystallisation from chloroform. Thetrans-[NiL₂NCSe)₂] complex does not isomerise upon heating. The compound [NiL(NCS)₂], prepared by thermal decomposition of [NiL₂(NCS)₂], possesses octahedral polymeric structure in which the diamine is chelated and all the thiocyanato groups are bridging.