SILICON AND ZINC COORDINATION TO PERIPHERAL CATECHOL SITES OF 16,17,23,24-OCTAHYDROXYPHTHALOCYANINATO)NICKEL(II) - PHTHALOCYANINE COORDINATION CHEMISTRY AT THE EDGE

.10.16,17,23,24-Octahydroxyphthalocyaninato)nickel (NiPc(OH)(8)) has b een prepared by demethylation of (octamethoxyphthalocyaninato)nickel(I I). Silylation of peripheral oxygen atoms using dimethyl-tert-butylsil yl chloride gave NiPc(OSi(t-Bu)Me-2)(8) as a convenient precursor to N iPc(OH)(8) with high solubility in hydrocarbon solvents. The coordinat ion properties of peripheral catechol sites were investigated by treat ing NiPc(OH)s with Tp(Cum,Me)Zn(OH). A model study was first carried o ut by adding 5,6-dihydroxyphthalimide (H(2)PhtCat) to Tp(Cum,Me)Zn(OH) . Partial deprotonation occurred to give Tp(Cum,Me)Zn(HPhtCat). Furthe r deprotonation with NMe4(OH) gave (NMe4)[Tp(Cum,ME)Zn(PhtCat)] as the methanol solvate. H-1 NMR spectra recorded on Tp(Cum,Me)Zn(HPhtCat) s how sharp resonances for equivalent arms of the Tp(Cum,Me) ligand, whi le Tp(Cum,Me) resonances for (NMe4)[Tp(Cum,Me)Zn(PhtCat)] appear broad ened by slow site exchange about the strongly chelated catecholate lig and. Similarly, the reaction between NiPc(OH)(8) and Tp(Cum,Me)Zn(OH) occurred with partial deprotonation to give NiPc(OH)(4)(OZnTp(Cum,Me)) (4) Structural characterization on crystals obtained from acetonitrile showed that Zn ions bond to single ring oxygen atoms at two sites and that they chelate to adjacent oxygen atoms at the other two ring site s. Cumenyl i-propyl substituents of the Tp(Cum,Me) ligands form hydrop hobic pockets above and below the central metal of the phthalocyanine ring. These sites are occupied by acetonitrile solvent molecules posit ioned with hydrogen atoms directed toward the Ni atom in the crystal s tructure of the complex obtained by crystallization from a dichloromet hane/acetonitrile solution. Addition of base to NiPc(OH)(4)(OZnTp(Cum, Me))(4) results in deprotonation of the remaining four OH groups and s ubstantial red shifts for electronic transitions in the 400 and 600 nm regions of the phthalocyanine ring. Broadened H-1 NMR resonances for arms of the Tp(Cum,Me) ligands point to a chelated structure for the Z n atoms of (NMe4)(4)[NiPc(O(2)ZnTp(Cum,Me))(4)].