An infrared spectroscopic study of dianiline-metal(ii) tetracyanometalate complexes
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The results of an IR spectroscopie study are presented for six new dianiline metal tetracyanometalate complexes, M(an)2M'(CN)4 (M = Mn, Fe, Co or Cu and M'= Ni; M = Ni or Cd and M' = Pt; an = aniline). Their structure consists of polymeric layers of (M-M'(CN)4)∞ with the aniline molecules bound directly to metal (M). For these series of isomorphous complexes there is a correlation between the shifts of some aniline bands on coordination and the strength of metal-nitrogen bonding measured by the v(M-N) value. Low temperature (83 K) data are also reported and it is noted that whilst the aniline ring and CH mode frequencies are virtually insensitive to temperature, the NH2 wagging, NH2 rocking and the metal-ligand stretching v(M-N) frequencies increase with decreasing temperature, whilst the v(NH2) modes decrease with decreasing temperature. The vibrational frequencies of the M'(CN)4 group are also temperature dependent and increase in value upon cooling the sample to 83 K. The changes are thought to be due to a slight contraction in the cavity size with decreasing temperature. The relationship between these complexes and Hofmann-type aniline clathrates, M(NH3)2M'(CN)4 · 2 an, is indicated.