Nickel complexes neutral 1,3-diketones

Template reactions between malonaldehydes and diamines in the presence of copper(II), nickel(II) or cobalt(II) salts yield neutral macrocyclic complexes (equation 15).99-102 Both aliphatic102 and aromatic101 diamines can be used. In certain cases, non-macrocyclic intermediates can be isolated and subsequently converted into unsymmetrical macrocyclic complexes by reaction with a different diamine (Scheme ll).101 These methods are more versatile and more convenient than an earlier template reaction in which propynal replaces the malonaldehyde (equation 16).103 This latter method can also be used for the non-template synthesis of the macrocyclic ligand in relatively poor yield. A further variation on this reaction type allows the use of an enol ether (vinylogous ester), which provides more flexibility with respect to substituents (equation 17).104 The approach illustrated in equation (15), and Scheme 11 can be extended to include reactions of (3-diketones. The benzodiazepines, which result from reaction between 1,2-diaminobenzenes and (3-diketones, can also serve as precursors in the metal template reaction (Scheme 12).101 105 106 The macrocyclic complex product (46) in this sequence, being unsubstituted on the meso carbon atom, has been shown to undergo an electrochemical oxidative dimerization (equation 18).107... 

As the nickel component of the Ziegler-Natta type systems, Ni(II) carboxylates, j8-diketonates, )3-dlthiodiketonates, and phosphine complexes are frequently used, but organonickel compounds [NiXRL] or Ni(0) derivatives have also been thoroughly investigated ". The neutral rj -allyl complexes [ NiX(i7 —C3H5))2] and... 

These macrocyclic compounds interact with nickel(II), cobalt(II) and iron(II) salts, yielding neutral complexes [M(L46)] [16]. The H NMR spectra of H2L46 and of its nickel(II) complex, and the X-ray structure analysis of [Fe(L46)], where R = -(CH2)7CH3, R = -C14H10, showed that the L46B structure is present both in complexes and in the metal-free macrocycle [18], Attempts to carry out thermal isomerization of L46B into the so far undiscovered isomeric structure L46A failed [16], Also of note is that the initial 1,2-dihydrazones of cyclic a-diketones (from H NMR spectra evidence) have syn, anti structures (Eq. 2.10) [16J. 

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