1,5-Diazacyclooctane, nickel complexes

A second example relates to the complex bis(l,5-diazacyclooctane)nickel(II) (Fig. 6.6). A crystal structure analysis of this complex revealed apparently planar NCCCN moieties with unusual bond lengths and angles 231. A molecular mechanics analysis of the same complex showed that these moieties are puckered and concluded that the crystal structure result was a consequence of conformational disorder, the refined geometry corresponding to an average of two puckered conformations (see Fig. 6.6)T24]. 

Herein we review results with the neutral complex, N,N -bis(mercaptoethyl)-l,5-diazacyclooctane-nickel(II), or (bme-daco)NiH, 1, to yield N-(mercaptoethyl)-N -(sulfinatoethyl)-l,5-diazacyclooctanenickel(II), or (me s e - d ac 0)Ni 11, 2 and N,N -bis(sulfinatoethyl)-l,5-diazacyclooctanenickel(II), or (bse-daco)NiH, 3, Scheme III. The mechanistic implications of isotopic labelling experiments as well as spectroscopically observed intermediates are discussed. 

Using the knowledge that sterically blocking the axial positions in square planar systems effectively prevents an octahedral configuration from forming, nickel(II) and copper(II) complexes of a secondary mediumring diamine, 1,5-diazacyclooctane (daco), were synthesized (Figure 9) (67). 

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