Synthesis and Structural Characterisation of Hafnium(IV) Mono‐ and Diphthalocyanines Obtained under Oxidation Conditions with Halogens

Abstract

New sandwich‐type hafnium(IV) diphthalocyaninato and hafnium(IV) monophthalocyaninato complexes were obtained in crystalline form under oxidation conditions with halogens. Partially oxidised by iodine, a sandwich‐type hafnium(IV) diphthalocyaninato complex with a composition of HfPc2I2 (Pc2– = phthalocyaninate) crystallizes in two crystalline modifications 1 and 2, depending on the thermal conditions. Both modifications are tetragonal and differ in the disordering model. Statistically, in both modifications, in two of three [HfPc2] sandwich units the closed‐shell d0 Hf4+ cation is sandwiched by a phthalocyaninato ligand (Pc2–) and a one‐electron‐oxidised Pc–· π‐radical ligand. The π‐radical character of the Pc–· ligand was detected by EPR spectroscopy. In 1, the Hf4+ and the symmetrical triiodide ions, which were detected by resonance Raman spectroscopy, are disordered in the crystal. However, in crystal 2, only the symmetrical I3– anions are disordered, but the Hf4+ cations are ordered. The hafnium(IV) monophthalocyanines with the composition of HfPcI2Pht (3) and HfPcBr2Pht (4) (Pht = phthalonitrile) are isostructural. The seven‐coordinate Hf4+ cation is surrounded by four isoindole N atoms of a Pc2– macrocycle, two halides (I– or Br–), and by a N atom of one of the two cyano groups of phthalonitrile. The last compound with a composition of HfPcCl2 (5) exists as a doubly bridged dimeric complex, bis[(μ2‐chlorido)chlorido(phthalocyaninato) hafnium(IV)], in which the coordination number seven of Hf4+ cations is achieved by four isoindole N atoms of Pc2–, two bridging, and one terminal Cl– ligand. The π–π interactions between the Pc macrocycles in the sandwich system [HfPc2] have an influence on the HOMO–LUMO transition, compared with the hafnium(IV) monophthalocyanines, and result in a blueshift of approximately 20 nm compared to that observed for hafnium(IV) monophthalocyanines.

Reducing zirconium(iv) phthalocyanines and the structure of a Pc4−Zr complex

“…1), similar to previously reported structures of analogous Zr(IV) and Hf(IV) porphyrins, 25,26 and nearly isostructural with the recently reported hafnium(IV) analogue. 32 The Zr-N bond lengths (2.203-2.231 Å) are longer than in the PcHf analogue (2.190(4)-2.208(4) Å) but shorter than in monomeric PcZr structures (∼2.34 Å), which generally have large axial ligands. The two non-coplanar PcZr moieties are connected by two nearly symmetrically bridging chlorides, with Zr-Cl1 and Zr-Cl1* bond lengths of 2.6422(14) and 2.6743(13) Å respectively; the terminal Zr-Cl bond length is substantially shorter, at 2.4268(16) Å.…”

“…This compound was prepared by a modification of a literature procedure. Calcd for C 32 Synthesis of 3-Li. The reaction mixture was heated to 230°C.…”

“…31 1-Chloronaphthalene (10 mL) was added to phthalonitrile (4.08 g, 24 mmol) and ZrCl 4 (0.932 g, 4.0 mmol) in a flask equipped with a stir bar and a reflux condenser. Calcd for C 32 Single crystal X-ray diffraction Suitable crystals of 1 and 3-Li were coated in paratone oil, mounted on a MiTeGen Micro Mount, and transferred to the cold stream (150 K) of the X-ray diffractometer. During heating the colour of the solution changed from beige to yellow, red, purple and finally deep blue.…”

From I‐Ligated and I‐Doped to O‐Ligated Hafnium(IV) Phthalocyaninate(2–) Complexes

“…[5] Hafnium and zirconium phthalocyanines as well as porphyrins are still intensively explored owing to their coordinative feature of the central metal, [6] and several of them have been prepared and characterized by spectroscopic and electrochemical methods. [11] The X-ray single-crystal analysis of this dichloridohafnium phthalocyanine complex clearly evidenced the great tendency of hafnium to achieve a coordination number higher than 6, which in a solid is realized by the dimerization of HfPcCl 2 and the formation of a bis[(μ 2 -chlorido)chloridophthalocyaninate(2-) hafnium(IV)] complex with two bifunctional and two terminal chloride atoms. [8] Owing to the coordinative feature of the central metal atoms and their tendency for high coordination numbers up to 8, zirconium(IV) and hafnium(IV) monophthalocyanines contain one or more additional out-of-plane ligand(s).…”

“…[9] An interesting example of hafnium(IV) monophthalocyanine is dichloridohafnium phthalocyanine, discovered over a decade ago [10] but only recently structurally characterized by us. [8,11] However, in solution, owing to their radical character, they might be active. However, in solution, and especially in O-donating solvents, the bis[(μ 2 -chlorido)chloridophthalocyaninate(2-) hafnium(IV)] dimeric complex transforms into the monomer with additional out-of-plane ligands owing to the oxophilic behaviour of hafnium.…”