Dimeric nitrogen bridges

The ligands (20) contain a coordination site such as pyridyl or amino nitrogen, or a hydroxyl oxygen. Complexes of (20 T = NH2 and n = 2) with iron(II) have been studied recently.65 A copper(II) dimer (with bridging oxime groups) of (20 T = OH, n = 2 or 3) was described by Ablov and coworkers66 in 1972 and its crystal structure has been elucidated67 in 1974. 

Another class of nitrogen-bridged expanded porphyrins was first reported in 1993 by Dolphin and coworkers. Referred to as porphocyanines, the first of these tetrapyrrolic expanded porphyrins to be reported was system 9.110. It was prepared via the oxidative dimerization (with loss of ammonia) of the bis(amino-methyl)dipyrrylmethane derivative 9.109, a precursor derived, in turn, from the bis(-cyano)-substituted dipyrrylmethane 9.108 (Scheme 9.2.2). ... 

Dinitrog en Complexes. The relative iaertness of molecular nitrogen is well known, however, some Cp —Zr compounds coordinate dinitrogen and substantially iacrease its reactivity. The nitrogen molecule can be coordinated either ia a terminal position or as a bridge ia dimeric stmctures. 

Copper(II) complexes of 2,6-lutidylphenylketone thiosemicarbazone, 38, have been prepared from copper(II) chloride and copper(II) bromide [186]. Similar to 2-pyridyl thiosemicarbazones, 38-H coordinates via the ring nitrogen, the azomethine nitrogen and the thiol sulfur based on infrared spectral assignments. Magnetic susceptibilities and electron spin resonance spectra indicate dimeric complexes and both are formulated as [Cu(38-H)A]2 with bridging sulfur atoms. The electronic spectra of both halide complexes show band maxima at 14500-14200 cm with shoulders at 12100 cm S which is consistent with a square pyramidal stereochemistry for a dimeric copper(II) center. 

To remove volatile impurities, the naterial was heated in vacuo at 135 °C. This treatment resulted in further condensation. Thus, the distillation residue was composed of a mixture of doubly-bridged dimers and tetramers, x = 1 and 2 as determined from the molecular weight, boron and nitrogen analyses and the volatile condensibles produced. 

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