Metal complexes of N-benzamidoporphyrin: (N-benzimido-meso-tetraphenylporphyrinato)(methanol)zinc(II) methanol solvate and (acetato)(N-benzamido-meso-tetraphenylporphyrinato)cadmium(II) benzene solvate

Article abstract of DOI:10.1021/ic0207202

The crystal structures of N-benzamido-meso-tetraphenylporphyrin (NHCOC₆H₅-Htpp; 1), (N-benzimido-meso-tetraphenylporphyrinato)(methanol)zinc(II) [Zn(N-NCOC₆H₅-tpp)(MeOH); 2(MeOH)], and (acetato)(N-benzamido-meso-tetraphenylporphyrinato)cadmium(II) [Cd(N-NHCOC₆H₅-tpp)(OAc); 3] were established. The coordination sphere around Zn²⁺ ion in 2(MeOH) is a distorted trigonal bipyramid with N(2), N(5), and O(2) lying in the equatorial plane, whereas, for Cd²⁺ ion in 3, it is a sitting-atop derivative with a distorted trigonal bipyramidal geometry in which the apical site is occupied by atoms N(2) and O(2). Cd in 3 acquires five-coordination with five strong bonds [Cd(1)-N(1) = 2.319(5) A?, Cd(1)-N(2) = 2.252(5) A?, Cd(1)-N(3) = 2.332(5) A?, Cd(1)-0(2) = 2.292(5) A?, and Cd(1)-O(3) = 2.317(5) A?] and with one secondary intramolecular interaction [Cd(1)?N(4)]. The porphyrin ring in these two complexes is distorted to a large extent. The plane of the three pyrrole nitrogen atoms [i.e., N(1)-N(3)] strongly bonded to Zn²⁺ in 2(MeOH) and to Cd²⁺ in 3 is adopted as a reference plane 3N. For the Zn²⁺ complex, the pyrrole nitrogen bonded to the benzamido (BA) ligand lies in a plane with a dihedral angle of 33.8° with respect to the 3N plane, but for the Cd²⁺ complex, this dihedral angle is found to be 31.4°. In the former complex, Zn²⁺ and N(5) are located on the different side at -0.08 and 1.39 A from its 3N plane, and in the latter one, Cd²⁺ and N(5) are also located on the different side at 1.08 and -1.51 A? from its 3N plane. VT NMR (¹H and ¹³C) studies of 3 show that the acetate acts as a bidentate ligand and the OAc^- exchange does not occur in CD₂Cl₂. Moreover, the NH proton [i.e., H(5)] of 3 in CD₂Cl₂ is observed as a sharp singlet at δ = -1.13 ppm with Δν1/2 = 4 Hz at 20 °C indicating that the intermolecular proton exchange between water and NH proton is rapid.