Synthesis, X-Ray Crystal Structure and Reactivity of Dichloro(phthalocyaninato) niobium(IV) (New Polymorph) and Trichloro(phthalocyaninato)niobium(V)

Dichloro(phthalocyaninato)niobium(IV), PcNbCl2, has been isolated as a new polymorph and its X-ray crystal structure solved. Crystals are triclinic: formula C32H16C2N8Nb, space group P1, cell parameters a = 8.707(2) Angstrom, b = 12.288(3) Angstrom, c = 12.801(3) Angstrom, alpha = 80.72(2)degrees, beta = 85.43(2)degrees, gamma = 76.62(2)degrees, V = 1313.7(6) Angstrom(3), Z = 2. The molecular structure closely resembles that already found for the monoclinic polymorph. Thus, Nb(IV) is six-coordinated in a cis arrangement, being displaced out of the inner N-4 Square planar system of the phthalocyanine ring by 0.898(1) Angstrom, towards the two chlorine atoms (average Nb-N-(Pc) bond distance: 2.130(15) Angstrom; Nb-Cl bond distances: 2.408(1) and 2.396(1) Angstrom; angle Cl1-Nb-Cl2: 80.7 degrees). The main difference between the two polymorphs is the different stacking of the molecules in the crystal lattice. PcNbCl3 is also triclinic: formula C32H16Cl3N8Nb, space group P1, cell parameters a = 12.086(2) Angstrom, b = 13.710(2) Angstrom c = 8.345(1) Angstrom, alpha = 93.49(2)degrees, beta = 100.95(2)degrees, gamma = 79.79(2)degrees, V = 1335.6(4) Angstrom(3), Z = 2. In the molecular structure the Pc chromophore and the three chlorine atoms are at opposite sites with respect to the Nb atom, which is seven coordinate (average Nb-N-(Pc) bond distance: 2.178(5) Angstrom; Nb-Cl bond distances: 2.482(1), 2.426(1) and 2.380(1) Angstrom; angles CI-Nb-Cl: 85.3(0), 80.3(0), and 76.5(0)degrees). The stability of PcNbCl2 and PcNbCl3 towards water has been examined. The reactivity of PcNbCl2 with pyrocathecol, oxalic acid, H2SO4 and iodine has also been examined and has led to the isolation and characterization of the following Nb(IV) and Nb(V) species: PcNbIV(cat), PcNbIV(oxal), (PcNbSO4)-S-IV, (PcNbCl2I)-Cl-V, PcNbV(cat)I.