Pseudohalogeno-bonding of thallium(III) porphyrins, stabilisation of isocyano bonding. Crystal structure of isocyano(5,10,15,20-tetraphenylporphyrinato)thallium(III)

Abstract

Thallium(III) porphyrin complexes of the type [Tl(por)X][por = 5,10,15,20-tetraphenyl-(tpp) or 2,3,7,8,12,13,17,18-octaethyl-porphyrinate(2–)(oep); X = N₃, SCN or NC] have been prepared. The stereochemistry of the metal has been established by IR and ¹H NMR spectroscopy and isocyano bonding in [Tl(tpp)(NC)] confirmed by X-ray diffraction methods using Mo-Kα radiation. Crystals are monoclinic, space group P2₁/n, with a= 10.061(8), b= 16.161(12), c= 21.173(15)Å, β= 90.80(6)° and Z= 4; R= 0.023 and R′= 0.028 for 4833 observed reflections. The thallium atom is five-co-ordinated by the four nitrogen atoms (N_p) of the porphyrin plane and one nitrogen atom, N(25), of the isocyano group: mean Tl–N_p 2.222(10), Tl–N(25) 2.260(3)Å, N(25)–Tl–N_p 110.4(1) Tl–N(25)–C(26) 175.3(4)°.