Catecholate Complexes Research Articles

Zinc and cadmium complexes based on 3,6-di-tert-butyl-o-benzoquinone

Zinc and cadmium bis-o-semuquinolate and catecholate complexes are synthesized by the reduction of 3,6-di-tert-butyl-o-benzoquinone (3,6-Q) with amalgamated metals in a medium of various solvents. The oxidation of the metal catecholate derivatives results in the corresponding mono-o-semiquinone complexes, which undergo symmetrization to form the metal bis-o-semiquinolates. The molecular structures of the complexes (3,6-SQ)2Zn · Py, (3,6-SQ)2Zn · H2O, and (3,6-SQ)2Cd · α,α′-Bipy (3,6-SQ is the radical anion of 3,6-Q) are studied by X-ray diffraction analysis. Magnetochemical studies are carried out for the zinc and cadmium bis-o-semiquinone complexes.

Special features of photolytic transformation of tin heteropolymetallic catecholate complexes

The photolysis of bis(dicarbonylcyclopentadienyliron)(3,6-di-tert-butylcatecholato)tin(IV), bis(dicarbonylcyclopentadienylmolybdenum)(3,6-di-tert-butylcatecholato)tin(IV), and bis(dicarbonylcyclopentadienyltunsten)(3,6-di-tert-butylcatecholato)tin(IV) in solutions of saturated hydrocarbons was studied. Kinetic parameters of the transformation of these compounds under the action of a monochromatic radiation with a wavelength of 313 nm were determined. Products of their transformation formed in the course of the irradiation were identified, and the probable mechanism of their photodecomposition was proposed.

Binding of Catechols to Iron(III)–Octaethylporphyrin: An Experimental and DFT Investigation

AbstractThe synthesis, X‐ray structure, and properties of high‐spin, five‐coordinate catecholate complexes of (octaethylporphyrinato)iron(III), FeIII(OEP)(L) (L: catecholate monoanion), are reported here for the first time. In these complexes, catechol binds in an η1‐fashion as an axial ligand, which is supported by DFT calculations. The Fe–O–C angles of FeIII(OEP)(Hcat), FeIII(OEP)(4‐tBu‐Hcat), FeIII(OEP)(4‐NO2‐Hcat), and FeIII(OEP)(sal) are 119.5, 125.1, 122.2, and 124.3°, respectively. FeIII(OEP)(Hcat) has the smallest Fe–O–C angle in addition to the smallest dihedral angle of 26.2° between the planes of the porphyrin and axial catechol ligand among all phenolate complexes of iron(III)–porphyrins. In comparison to those of FeIII(OEP)(OPh) and FeIII(OEP)(4‐tBu‐Hcat), the Fe–O bond in FeIII(OEP)(Hcat) is elongated by 0.064 and 0.038 Å, respectively. This is due to the H‐bonding interactions in FeIII(OEP)(Hcat) and not caused by steric hindrance. In the 1H NMR spectra of the complexes, the signals of the ortho‐ and para‐protons of catechol are shifted upfield, whereas those of the meta‐protons are shifted downfield. The alternating shift pattern observed is due to negative and positive spin densities on the catechol carbon atoms and is indicative of π‐spin delocalization on the catecholato ligand. Electrochemical data reveal that the complexes undergo three one‐electron oxidations and a single one‐electron reduction. Based on spectroelectrochemical and DFT studies, the first oxidation is assigned to a catechol‐to‐semiquinone transformation and the second and third oxidations are found to be porphyrin‐ring‐centered.

Structure and Ultrafast Dynamics of the Charge-Transfer Excited State and Redox Activity of the Ground State of Mono- and Binuclear Platinum(II) Diimine Catecholate and Bis-catecholate Complexes: A Transient Absorption, TRIR, DFT, and Electrochemical Study

A series of mononuclear complexes of the type [Pt(Bu(2)cat)(4,4'-R(2)-bipy)] [where Bu(2)cat is the dianion of 3,5-(t)Bu(2)-catechol and R = H, (t)Bu, or C(O)NEt(2)] and analogous dinuclear complexes based on the "back-to-back" bis-catechol ligand 3,3',4,4'-tetrahydroxybiphenyl have been studied in detail in both their ground and excited states by a range of physical methods including electrochemistry, UV/vis/near-IR, IR, and electron paramagnetic resonance spectroelectrochemistry, and time-resolved IR (TRIR) and transient absorption (TA) spectroscopy. Density functional theory calculations have been performed to support these studies, which provide a detailed picture of the ground- and excited-state electronic structures, and excited-state dynamics, of these complexes. Notable observations include the following: (i) for the first time, the lowest-energy catecholate → bipyridine (bpy) ligand-to-ligand charge-transfer (LL'CT) excited states of these chromophores have been studied by TRIR spectroscopy, showing a range of transient bands associated with the bpy radical anion and semiquinone species, and back-electron-transfer occurring in hundreds of picoseconds; (ii) strong electronic coupling between the two catecholate units in the bridging ligand of the dinuclear complexes results in a delocalized, planar (class 3) "mixed-valence" catecholate(2-)/semiquinone(•-) state formed by one-electron oxidation of the bridging ligand; (iii) in the LL'CT excited state of the dinuclear complexes, the bridging ligand is symmetrical and delocalized, whereas the bpy radical anion is localized at one terminus of the complex. This study is the first example of an investigation of excited-state behavior in platinum(II) catecholate complexes, performed with the use of picosecond TRIR and femtosecond TA spectroscopy.

Electrochemical transformations of catecholate and o-amidophenolate complexes with triphenylantimony(V)

The electrochemical properties of catecholate and o-amidophenolate complexes with triphenylantimony(V) with various substituents in the aromatic ring were examined. Introduction of electron-donating groups into the catecholate ligand or replacement of an O atom (in catecholate) by a N atom (o-amidophenolate) stabilizes the monocationic forms of the complexes obtained by one-electron oxidation. Complexes with electron-withdrawing substituents undergo irreversible two-electron oxidation resulting in the elimination of o-quinone. Complexes containing electron-withdrawing ligands do not form o-semiquinones and are inert to atmospheric oxygen. According to electrochemical data, oxygen can be bound reversibly by catecholate complexes containing the electron-donating methoxy groups in the 3,6-di-tert-butylcatecholate ligand and o-amidophenolate derivatives with half-wave oxidation potentials lower than or equal to 0.70 V (vs. Ag/AgCl), which form relatively stable cationic complexes upon the oxidation.

Getting a grip on iron

Siderocalin (also known as lipocalin 2) is a component of the innate immune system that binds and sequesters bacterial iron compounds in the blood and urine. A new study identifies iron–catechol complexes as endogenous ligands for siderocalin, which can deliver the iron compounds to the kidney.

A Solution Study of Silica Condensation and Speciation with Relevance to in Vitro Investigations of Biosilicification

Requiring mild synthesis conditions and possessing a high level of organization and functionality, biosilicas constitute a source of wonder and inspiration for both materials scientists and biologists. In order to understand how such biomaterials are formed and to apply this knowledge to the generation of novel bioinspired materials, a detailed study of the materials, as formed under biologically relevant conditions, is required. In this contribution, data from a detailed study of silica speciation and condensation using a model bioinspired silica precursor (silicon catechol complex, SCC) is presented. The silicon complex quickly and controllably dissociates under neutral pH conditions to well-defined, metastable solutions of orthosilicic acid. The formation of silicomolybdous (blue) complexes was used to monitor and study different stages of silicic acid condensation. In parallel, the rates of silicomolybdic (yellow) complex formation, with mathematical modeling of the species present, was used to follow the solution speciation of polysilicic acids. The results obtained from the two assays correlate well. Monomeric silicic acid, trimeric silicic acids, and different classes of oligomeric polysilicic acids and silica nuclei can be identified and their periods of stability during the early stages of silica condensation measured. For experiments performed at a range of temperatures (273-323 K), an activation energy of 77 kJ.mol(-1) was obtained for the formation of trimers. The activation energies for the forward and reverse condensation reactions for addition of monomers to polysilicic acids (273-293 +/- 1 K) were 55.0 and 58.6 kJ.mol(-1), respectively. For temperatures above 293 K, these energies were reduced to 6.1 and 7.3 kJ.mol(-1), indicating a probable change in the prevailing condensation mechanism. The impact of pH on the rates of condensation were measured. There was a direct correlation between the apparent third-order rate constant for trimer formation and pH (4.7-6.9 +/- 0.1) while values for the reversible first-order rates reached a plateau at circumneutral pH. These different behaviors are discussed with reference to the generally accepted mechanism for silica condensation in which anionic silicate solution species are central to the condensation process. The results presented in this paper support the use of precursors such as silicon catecholate complexes in the study of biosilicification in vitro. Further detailed experimentation is needed to increase our understanding of specific biomolecule silica interactions that ultimately generate the complex, finely detailed siliceous structures we observe in the world around us.

A Functional Model of Extradiol-Cleaving Catechol Dioxygenases: Mimicking the 2-His-1-Carboxylate Facial Triad

The synthesis and characterization of an iron-catecholate model complex of a tridentate 2-N-1-carboxylate ligand derived from L-proline are reported. The X-ray crystal structure of the complex [(L)(3)Fe(3)(DBC)(3)] (1) (where L is 1-(2-pyridylmethyl)pyrrolidine-2-carboxylate and DBC is the dianion of 3,5-di-tert-butyl catechol) reveals that the tridentate ligand binds to the iron center in a facial manner and mimics the 2-his-1-carboxylate facial triad motif observed in extradiol-cleaving catechol dioxygenases. The iron(III)-catecholate complex (1) reacts with dioxygen in acetonitrile in ambient conditions to cleave the C-C bond of catecholate. In the reaction, an equal amount of extra- and intradiol cleavage products are formed without any auto-oxidation product. The iron-catecholate complex is a potential functional model of extradiol-cleaving catechol dioxygenases.

3,6-di-tert-butylcatecholates of triaryl antimony(V): NMR study and redox-transformations

Recently the ability of complexes of non-transition metals to reversibly add molecular oxygen was found by the example of о-amidophenolate and catecholate (Cat) complexes of triphenyl antimony(V) with donor methoxy groups in the 4 and 5 positions of the aromatic ring of the catecholate ligand [1, 2]. Variation in the nature of the substituents in the Cat ligand affects the reactivity of these compounds with respect to oxygen: The introduction of electron-withdrawing groups results in the formation of the air-stable catecholate s, whereas the presence of electron-donor groups makes it possible for these complexes to add molecular oxygen [3–7]. The investigation of electrochemical properties of the complexes has shown that the acceptor groups in the Cat ligand shift the oxidation potential of the catecholate to electropositive region (hamper the anodic process) and decrease the stability of the cationic complexes; the donor substituents, vice versa, facilitate oxidation of the Cat ligand with molecular oxygen (shift the oxidation potential to the cathode field), favoring interaction with oxygen. However, at present there are no data in the literature on the effect of the redox-inert organic fragments at the antimony atom on redox-transformations of the Cat ligand in complexes of the formula (Cat)SbAr3.

Fe L-edge X-ray absorption spectroscopy determination of differential orbital covalency of siderophore model compounds: electronic structure contributions to high stability constants.

Most bacteria and fungi produce low-molecular-weight iron chelators called siderophores. Although different siderophore structures have been characterized, the iron-binding moieties often contain catecholate or hydroxamate groups. Siderophores function because of their extraordinarily high stability constants (K(STAB) = 10(30)-10(49)) and selectivity for Fe(III), yet the origin of these high stability constants has been difficult to quantify experimentally. Herein, we utilize Fe L-edge X-ray absorption spectroscopy to determine the differential orbital covalency (i.e., the differences in the mixing of the metal d-orbitals with ligand valence orbitals) of a series of siderophore model compounds. The results enable evaluation of the electronic structure contributions to their high stability constants in terms of sigma- and pi-donor covalent bonding, ionic bonding, and solvent effects. The results indicate substantial differences in the covalent contributions to stability constants of hydroxamate and catecholate complexes and show that increased sigma as well as pi bonding contributes to the high stability constants of catecholate complexes.

Synthesis and Reactivity of Catecholate Complexes Containing Quadruply Bonded Metal Ions

Quadruply bonded metal complexes of rhenium and molybdenum have been prepared with tetrachlorocatechol. Structural characterization on the [Re(2)(Cl(4)Cat)(4)](2-) anion has shown that it consists of distorted square-planar Re(Cl(4)Cat)(2) units linked by a short (2.2067 A) quadruple Re-Re bond. The addition of tetrachlorocatechol to molybdenum acetate was used to prepare the isoelectronic molybdenum analogue "[Mo(2)(Cl(4)Cat)(4)](4-)". This complex was found to be far more reactive than the rhenium dimer. A dimer containing a Mo-Mo double bond, [(Cl(4)Cat)(2)Mo(mu-O)(mu-OCH(3))Mo(Cl(4)Cat)(2)](3-), was obtained as the methanolysis product of the complex formed initially, and the oxomolybdenum(V) monomer [MoO(Cl(4)Cat)(2)](-) was formed under more oxidative conditions. Both complexes are oxygen-sensitive, giving [MoO(2)(Cl(4)Cat)(2)](2-) as the final air-stable complex product.

Kinetics of iron oxidation upon polyphenol binding

Polyphenol prevention of iron-mediated DNA damage occurs primarily through iron binding. Once bound, iron in the Fe(2+)-polyphenol complex autooxidizes to Fe(3+) in the presence of O(2). To determine the correlation between the rate of Fe(2+)-polyphenol autooxidation and polyphenol antioxidant ability, kinetic studies at pH = 6.0 in the presence of oxygen were performed using UV-vis spectrophotometry. Initial rates of iron-polyphenol complex oxidation for epigallocatechin gallate (EGCG), methyl-3,4,5-trihydroxybenzoate (MEGA), gallic acid (GA), epicatechin (EC), and methyl-3,4-dihydroxybenzoate (MEPCA) were in the range of 0.14-6.7 min(-1). Polyphenols with gallol groups have faster rates of iron oxidation than their catechol analogs, suggesting that stronger iron binding results in faster iron oxidation. Concentrations of polyphenol, Fe(2+), and O(2) were varied to investigate the dependence of the Fe(2+)-polyphenol autooxidation on these reactants for MEGA and MEPCA. For these analogous gallate and catecholate complexes of Fe(2+), iron oxidation reactions were first order in Fe(2+), polyphenol, and O(2), but gallate complexes show saturation behavior at much lower Fe(2+) concentrations. Thus, gallol-containing polyphenols promote iron oxidation at a significantly faster rate than analogous catechol-containing compounds, and iron oxidation rate also correlates strongly with polyphenol inhibition of DNA damage for polyphenol compounds with a single iron-binding moiety.

白金カテコラート錯体組み込みによる新たなベンゾアヌレンジカチオン発生法：初の１０π芳香族デヒドロベンゾ[12]アヌレンジカチオン

白金カテコラート錯体組み込みによる新たなベンゾアヌレンジカチオン発生法：初の１０π芳香族デヒドロベンゾ[12]アヌレンジカチオン

Intermetallic Communication in Titanium(IV) Ferrocenyldiketonates

A tetradentate bis(ferrocenyldiketonate) ligand, Fc(2)BobH(2), is prepared via Claisen condensation of acetylferrocene and 2,2'-biphenyldiacetyl chloride, and is metalated with titanium(IV) isopropoxide to give (Fc(2)Bob)Ti(O(i)Pr)(2) in good yield. The isopropoxide groups are replaced with di(4-nitrophenyl)phosphate groups on treatment with the corresponding acid, and with chlorides on treatment with trimethylsilyl chloride. Metathesis with catechol leads to the bis(o-hydroxyphenoxide) complex rather than the chelating catecholate complex. Hydrolysis selectively gives the mu-oxo trimer (Delta,Delta,Delta)/(Lambda,Lambda,Lambda)-{(Fc(2)Bob)Ti(mu-O)}(3). The solid-state structures of the mu-oxo trimer and the bis(o-hydroxyphenoxide) complex show that the ferrocene substituents are oriented proximal to the biphenyl backbone rather than pointed out toward the exogenous groups. The complexes show dramatic changes in color depending on the bound anions, ranging from the red isopropoxide (lambda(max) = 489 nm) to the green bis(di(4-nitrophenyl)phosphate) (lambda(max) = 653 nm). The oxidation potentials of the ferrocenes show modest shifts based on the titanium environment, but the redox potentials of the two ferrocenes are never separated by more than 60 mV. These results and those of density-functional theory (DFT) calculations indicate that the titanium interacts principally with the lowest unoccupied molecular orbital (LUMO) of the ferrocenyldiketonate and very little with its highest occupied molecular orbital (HOMO).

Computational Study on the Stacking Interaction in Catechol Complexes

The stability and electron density topology of catechol complexes (dimers and tetramer) were studied using the MPW1B95 functional. The QTAIM analysis shows that both dimers (face to face and C-H/pi one) display a different electronic origin. The formation of the former is accompanied by a significant change in the values of atomic electron dipole and quadrupole components, flattening the most diffuse part of the electron density distribution toward the molecular plane. A small electron population transfer is observed between catechol monomers connected by C-H/pi interactions, whose QTAIM characterization does not differ from that of a weak hydrogen bond. Cooperative effects in the tetramer on binding energies are small and negligible for bond properties and charge transfer. Nevertheless, they are significant on atomic electron populations.

Electrochemical studies of the nickel catecholate complexes for detection of sulphur dioxide gas

Nickel catecholate complexes, bis(diphenylphosphino)ethanenickelcatecholate [(dppe)NiO 2C 6H 34-R 1] R 1 = CH 3 ( 1), C(CH 3) 3 ( 2), H ( 3) and F ( 4)] were studied using CV and SWV techniques between −1.5 and +1.5 V at 50 mV s −1 in cathodic and anodic sweeps. Glassy carbon electrode was used with 0.1 M tetrabutylammonium tetrafluroborate (TBATFB) in CH 2Cl 2. Complexes 1– 4 before addition of SO 2, showed approximately reversible behaviour ( i pa/ i pc ≈ 1 and Δ E ≈ 77–88 mV); oxidation peaks observed between +313 and +524 mV, reduction peaks between +225 and +436 mV, depending on the substituent on the ligand. Detection limit 0.01 ppm, linear range 0.01–20 ppm, sensitivity 0.02 ppm/mV (with SWV) were obtained. The complexes 1 and 2 could be used as voltammetric sensors while complexes 3 and 4 would be suitable as amperometric sensors, for monitoring industrial SO 2 emissions.

Dioxygenase catalysis by d 0 metal–catecholate complexes containing vanadium and molybdenum with H 2(3,5-DTBC) and H 2(3,6-DTBC) substrates

Facile synthetic dioxygenases, catalysts that can split O 2 and place both oxygen atoms selectively into 2 olefins to yield 2 epoxides or into 2 C–H bonds to yield 2 alcohols, remain a “Holy Grail” of oxidation catalysis. Recently, it was shown that [VO(3,5-DTBC)(3,5-DBSQ)] 2 (where 3,5-DTBC and 3,5-DBSQ are 3,5-di- tert-butylcatecholate and 3,5-di- tert-butylsemiquinone, respectively) is the catalytic-cycle resting state of a record catalytic lifetime catechol dioxygenase catalyst (100,000 total catalytic turnovers) for the substrate 3,5-di- tert-butylcatechol, H 2(3,5-DTBC) [C.-X. Yin, R.G. Finke, J. Am. Chem. Soc. 127 (2005) 9003–9013]. Herein we show that the precatalyst V(3,6-DTBC) 2(3,6-DBSQ) also gives dioxygenase products for the substrate H 2(3,5-DTBC), notably the same dioxygenase products in similar yields as seen for [VO(3,5-DTBC)(3,5-DBSQ)] 2. EPR studies show that the same g = 2.003–2.004 species are present in solution throughout the oxidation reaction for both [VO(3,5-DTBC)(3,5-DBSQ)] 2 and V(3,6-DTBC) 2(3,6-DBSQ). The similar products, product yields, and EPR spectra observed suggest that both [VO(3,5-DTBC)(3,5-DBSQ)] 2 and V(3,6-DTBC) 2(3,6-DBSQ) are feeding into the same catalytic cycle. In addition we have expanded the substrates to include H 2(3,6-DTBC), a substrate of interest for its higher symmetry, structurally simplified organic products and steric hindrance expected to favor the formation of monomeric metal–catecholate complexes. The precatalysts [VO(3,5-DTBC)(3,5-DBSQ)] 2 and V(3,6-DTBC) 2(3,6-DBSQ) were examined with H 2(3,6-DTBC) and found to give the same intradiol and extradiol dioxygenase products in the same yields. EPR studies of [VO(3,5-DTBC)(3,5-DBSQ)] 2 and V(3,6-DTBC) 2(3,6-DBSQ) with H 2(3,6-DTBC) show that the same spectra are observed throughout the oxidation, but at different reaction times. These EPR observations, along with the product studies, suggest that [VO(3,5-DTBC)(3,5-DBSQ)] 2 and V(3,6-DTBC) 2(3,6-DBSQ) have a common mechanistic cycle en route to the H 2(3,6-DTBC) dioxygenase products, albeit a mechanism different than that observed for H 2(3,5-DTBC) based on observed EPR spectra and differing product distributions. We also show that oxidation catalysis with [MoO(3,5-DTBC) 2] 2 follows primarily an oxidase path leading to the undesired benzoquinone autoxidation products for both H 2(3,5-DTBC) and H 2(3,6-DTBC) and with reaction times one to two orders of magnitude longer than seen for the vanadium precatalysts. The dramatic difference in product distribution and slower rate for [MoO(3,5-DTBC) 2] 2, along with its lack of a semiquinone ligand in at least this precatalyst, suggests the hypothesis that the d 0 vanadium(V) bonded to a semiquinone ligand in [VO(3,5-DTBC)(3,5-DBSQ)] 2 and V(3,6-DTBC) 2(3,6-DBSQ) is a necessary component of these dioxygenase precatalysts able to produce primarily dioxygenase products.

A Novel Tripodal Ligand Containing Three Different N‐Heterocyclic Donor Functions and Its Application in Catechol Dioxygenase Mimicking

We describe a novel chiral ligand, L, in which three different N-donor functions are linked to a methoxymethine unit: a methylpyrazole derivative, a methylimidazole unit, and a pyridyl residue. Complexes with FeCl(2), FeBr(2), and FeCl(3) have been synthesized and fully characterized, including with respect to their molecular structures. While in combination with FeCl(3) L coordinates in a tripodal fashion, with FeX(2) (X = Cl, Br) it binds only through two functions and the pyridyl unit remains dangling. For potential modelling of intradiol and extradiol catechol dioxygenase reactivity, the complexes [LFeCl(2)], 1, and [LFeCl(3)], 3, have been treated with 3,5-di-tert-butylcatechol, triethylamine, and O(2). Both complexes yielded similar results in such investigations, since the LFe(II)-catecholate complex reacts with O(2) through one-electron oxidation in the first step. Employing 3 in acetonitrile solution, intradiol cleavage occurred, although the undesired quinone was formed as the main product. If reagents were added (NaBPh(4), H(+)) or reaction conditions were chosen (CH(2)Cl(2) instead of CH(3)CN as the solvent) that made the coordination sphere at the iron centre more accessible for a third substrate donor function, an alternative reaction route, presumably involving O(2) binding at the metal, became more important, which led to extradiol cleavage. In the extreme case (CH(2)Cl(2) as the solvent and with the addition of NaBPh(4)), mainly the extradiol cleavage products were formed; the intradiol products were only observed as side products then and quinone formation became negligible. Protonated base functions in the second coordination sphere increased the efficiency of extradiol cleavage only slightly. The obtained results are in line with current understanding of the function of intradiol/extradiol dioxygenases.

Analysis of the supramolecular structures of Sb(III) and Sb(V) catecholate complexes from the viewpoint of ligand solid angles

The ligand solid angle approach has been successfully applied to the analysis of the catecholate complexes of Sb(III) and Sb(V). The Sb(III) complexes possess an electron lone pair that influences their molecular structure but does not behave as a classic “ligand” when intermolecular interactions are concerned. The Sb(III) complexes in solid state form numerous intermolecular interactions that effectively increase metal shielding, and herein we analyze the effects of the lone pair of electrons on the complex coordination geometry. In the five-coordinate R3CatSb(V) complexes (Cat = catecholate ligand, R = Ph, Me, Cl) the metal is shielded by 87(3)% and multiple intermolecular contacts are observed. The central metal in the six-coordinate antimony(V) complexes R3CatSb(V) · L is shielded to the extent of 89(2)% and no strong attractive intermolecular interactions are detected in solid state. Thus, the metal shielding in excess of 85% is required to prevent complex dimerization or additional ligation of the central atom by a nucleophile.

Radical polymerization of styrene in the presence of Tin(IV) catecholate complexes

The synthesis of PS in the presence of diethyl(3,6-di-tert-butylcatecholato)tin(IV) tetrahydrofuranate and diphenyl(3,6-di-tert-butylcatecholato)tin(IV) tetrahydrofuranate has been studied. It has been found that such tin catecholates can act as chain length regulators in the polymerization of styrene and ensure a linear increase in molecular mass with conversion. Using the macroinitiators obtained in the presence of diphenyl(3,6-di-tert-butylcatecholato)tin(IV) tetrahydrofuranate, the postpolymerization of styrene has been carried out.