Boron Compounds with Macrocyclic Structures

A further example of a macrocyclic ring system with boron that is related to the structures of the metallocyclophanes mentioned before is compound 68 that can be prepared via condensation between two bis(borazaphenanthrene) molecules. 

The compounds [CymB(Pz)3]Tl (136) and [FcB(Pz)3]Tl show polymeric structures, with bridging B(Pz)3 fragments in the solid state. This is a result of unfavorable steric interaction between the substituent on boron and the hydrogen atoms on the pyrazolyl ring 5-position. The structure of [Cym B(Pz)3]Tl is somewhat related, but it adopts a macrocyclic tetrameric structure rather than a linear polymeric structure. Ligands with secondary donors on the backbone may form additional bonds to the thallium atom. For example, in [HB(3-(2-pyridyl)Pz)3]Tl, weak TF"N interactions between pyridyl nitrogens and the T1 atom have been observed. HB(3-(2-MeOC6Fl4)Pz)3]Tl features close intramolecular TF 0 interactions. ... 

The subphthalocyanine (SubPc) macrocycles have been received a great deal of attention because of their interesting optical properties and their utility in the synthesis of asymmetrical non-planar phthalocyanines " SubPc compounds consist of three coupled isoindole units with a boron atom at the centre. One component of this series is the sub-2,3-boronnaphthalocyanine chlorine (subBClNPc) compound, Figure 14.31. This compound has been considered in this chapter since it represents a new challenge in the optic of the surface vibrational studies because of the structure of this compound is conic, as in the case of the sub-2,3-boronphthalocyanine chlorine macrocycle, instead of the planar structure of the naphtalocyanine complexes already mentioned. ... 

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