Monomeric Homoleptic (2‐Pyridylmethyl)(tert‐butyldimethylsilyl)amido Complexes of the Divalent Metals Mg,Mn, Fe,Co, and Zn

The transamination reaction of M[N(SiMe₃)₂]₂ with (2‐pyridylmethyl)(tert‐butyldimethylsilyl)amine yields the corresponding homoleptic metal bis[(2‐pyridylmethyl)(tert‐butyldimethylsilyl)amides] of Mg ( 1 ), Mn ( 2 ), Fe ( 3 ), Co ( 4 ) and Zn ( 5 ). All these compounds crystallize from hexane isotypic in the space group C2/c. From toluene the zinc derivative precipitates as toluene solvate 5 ·toluene. The molecular structures of these compounds are very similar with large NMN angles to the amide nitrogen atoms with NMN values of 148° ( 1 ) and 150° ( 5 ) for the diamagnetic compounds and 156° for the paramagnetic derivatives 2 and 3 . The Co derivative 4 displays a rather small NCoN angle of 142°. Different synthetic routes have been explored for compound 3 which is also available via the metallation reaction of bis(2,4,6‐trimethylphenyl)iron with (2‐pyridylmethyl)(tert‐butyldimethylsilyl)amine and via the metathesis reaction of lithium (2‐pyridylmethyl)(tert‐butyldimethylsilyl)amide with [(thf)₂FeCl₂]. In course of the metathesis reaction, an equimolar amount of lithium (2‐pyridylmethyl)(tert‐butyldimethylsilyl)amide and [(thf)₂FeCl₂] yields heteroleptic (2‐pyridylmethyl)(tert‐butyldimethylsilyl)amido iron(II) chloride ( 6 ) which crystallizes as a centrosymmetric dimeric molecule. The oxidative C‐C coupling reaction of 5 with Sn[N(SiMe₃)₂]₂ leads to the formation of tin(II) 1,2‐bis(2‐pyridyl)‐1,2‐bis(tert‐butyldimethylsilylamido)ethane, tin metal and Zn[N(SiMe₃)₂]₂.     

Synthese und Molekülstrukturen von N‐substituierten Diethylgallium‐2‐pyridylmethylamiden

Synthesis and Molekular Structures of N‐substituted Diethylgallium‐2‐pyridylmethylamides (2‐Pyridylmethyl)(tert‐butyldimethylsilyl)amine ( 1a ) and (2‐pyridylmethyl)‐di(tert‐butyl)silylamine ( 1b ) form with triethylgallane the corresponding red adducts 2a and 2b via an additional nitrogen‐gallium bond. These oily compounds decompose during distillation. Heating under reflux in toluene leads to the elimination of ethane and the formation of the red oils of [(2‐pyridylmethyl)(tert‐butyldimethylsilyl)amido]diethylgallane ( 3a ) and [(2‐pyridylmethyl)‐di(tert‐butyl)silylamido]diethylgallane ( 3b ). In order to investigate the thermal stability solvent‐free 3a is heated up to 400 °C. The elimination of ethane is observed again and the C‐C coupling product N, N′‐Bis(diethylgallyl)‐1, 2‐dipyridyl‐1, 2‐bis(tert‐butyldimethylsilyl)amido]ethan ( 4 ) is found in the residue. Substitution of the silyl substituents by another 2‐pyridylmethyl group and the reaction of this bis(2‐pyridylmethyl)amine with GaEt₃ yield triethylgallane‐diethylgallium‐bis(2‐pyridylmethyl)amide ( 5 ). The metalation product adds immediately another equivalent of triethylgallane regardless of the stoichiometry. The reaction of GaEt₃ with 2‐pyridylmethanol gives quantitatively colorless 2‐pyridylmethanolato diethylgallane ( 6 ).     

Oxidative C‐C Coupling of Dilithium (2‐Pyridylmethanidyl)(tert‐butyldimethylsilyl)amide with White Phosphorus

(2‐Pyridylmethyl)(tert‐butyldimethylsilyl)amine ( 1 ) can be lithiated once or twice yielding lithium (2‐pyridylmethyl)(tert‐butyldimethylsilyl)amide ( 2 ) and dilithium (2‐pyridylmethanidyl)(tert‐butyldimethylsilyl)amide ( 3 ), respectively. The oxidation of 3 with white phosphorus yields dilithium 1,2‐dipyridyl‐1,2‐bis(tert‐butyldimethylsilylamido)ethane ( 4 ) which crystallizes after partial hydrolysis as an adduct of the form 2 · 4 .     

Synthese und Charakterisierung heterobimetallischer Bis(trimethylsilyl)phosphanide von Barium und Zinn

Synthesis and Characterization of Hetero-bimetallic Bis(trimethylsilyl)phosphanides of Barium and Tin The reaction of barium bis[bis(trimethylsilyl)amide] with one equivalent of bis(trimethylsilyl)phosphane in 1,2-dimethoxyethane (dme) yields the heteroleptic dimeric (dme)barium bis(trimethylsilyl)amide bis(trimethylsilyl)phosphanide. This colorless compound crystallizes in the monoclinic space group P2₁/n with a = 1 259.1(3), b = 1 822.7(4), c = 1 516.1(3) pm, β = 110.54(3)° and Z = 4. The central moiety of the centrosymmetric molecule is the planar Ba₂P₂-cycle with Ba? P-bond lengths of 329 and 334 pm. In the presence of bis[bis(trimethylsilyl)amino]stannylene hetero-bimetallic bis(trimethylsilyl)phosphanides of tin(II) and barium are isolated. If the reaction of Ba[N(SiMe₃)₂]₂ and Sn[N(SiMe₃)₂]₂ in the molar ratio of 1:2 with six equivalents of HP(SiMe₃)₂ is performed in toluene, barium bis{tin(II)-tris[bis(trimethylsilyl)phosphanide]} can be isolated. This compound crystallizes in the orthorhombic space group P2₁2₁2₁ with a = 1 265.1(1), b = 2 290.1(3), c = 2 731.9(3) pm and Z = 4. The anions {Sn[P(SiMe₃)₂]₃}^? bind as two-dentate ligands to the barium atom which shows the extraordinary low coordination number of four. The addition of tetrahydrofuran (thf) to the above mentioned reaction solution leads to the elimination of tris(trimethylsilyl)phosphane and the formation of thf complexes of barium bis{tin(II)-bis(trimethylsilyl)phosphanide-trimethylsilylphosphandiide}. The derivative crystallizes from toluene in the monoclinic space group P2₁/c with a = 1 301.9(2), b = 2 316.3(3), c = 3 968.7(5) pm, β = 99.29(1)° and Z = 8.     

Formation of an Imino‐Stabilized Cyclic Tin(II) Cation from an Amino(imino)stannylene

The novel amino(imino)stannylene 1 was prepared by conversion of HNIPr (NIPr=bis(2,6‐diisopropylphenyl)imidazolin‐2‐imino) with one equivalent of Lappert’s tin reagent (Sn[N(SiMe₃)₂]₂). Treatment of 1 with DMAP (4‐dimethylaminopyridine) yields its Lewis acid–base adduct 2 . The reaction of 1 with one equivalent of trimethylsilyl azide results in replacement of the amino group at the tin center by an N₃ substituent with concomitant elimination of N(SiMe₃)₃ to afford dimeric [N₃SnNIPr]₂ ( 3 ). Remarkably, the reaction of 1 with B(C₆F₅)₃ produces the novel tin(II) monocation 4 ⁺[MeB(C₆F₅)₃]^? comprising a four‐membered stannacycle through methyl‐abstraction from the trimethylsilyl group.     

Alkali Metal and Alkaline Earth Metal Complexes with the Bis(borane‐diphenylphosphanyl)amido Ligand – Synthesis,Structures, and Catalysis for Ring‐Opening Polymerization of ϵ‐Caprolactone

The syntheses of lithium and alkaline earth metal complexes with the bis(borane‐diphenylphosphanyl)amido ligand ( 1 ‐ H ) of molecular formulas [{κ²‐N(PPh₂(BH₃))₂}Li(THF)₂] ( 2 ) and [{κ³‐N(PPh₂(BH₃))₂}₂M(THF)₂] [(M = Ca ( 3 ), Sr ( 4 ), Ba ( 5 )] are reported. The lithium complex 2 was obtained by treatment of bis(borane‐diphenylphosphanyl)amine ( 1 ‐ H ) with lithium bis(trimethylsilyl)amide in a 1:1 molar ratio via the silylamine elimination method. The corresponding homoleptic alkaline earth metal complexes 3 – 5 were prepared by two synthetic routes – first, the treatment of metal bis(trimethylsilyl)amide and protio ligand 1 ‐ H via the elimination of silylamine, and second, through salt metathesis reaction involving respective metal diiodides and lithium salt 2 . The molecular structures of lithium complex 2 and barium complex 5 were established by single‐crystal X‐ray diffraction analysis. In the solid‐state structure of 2 , the lithium ion is ligated by amido nitrogen atoms and hydrogen atoms of the BH₃ group in κ²‐coordination of the ligand 1 resulting in a distorted tetrahedral geometry around the lithium ion. However, in complex 5 , κ³‐coordination of the ligand 1 was observed, and the barium ion adopted a distorted octahedral arrangement. The metal complex 5 was tested as catalyst for the ring opening polymerization of ?‐caprolactone. High activity for the barium complex 5 towards ring opening polymerization (ROP) of ?‐caprolactone with a narrow polydispersity index was observed. Additionally, first‐principle calculations to investigate the structure and coordination properties of alkaline earth metal complexes 3 – 5 as a comparative study between the experimental and theoretical findings were described.     

Pentamethylcyclopentadienyl Halfsandwich Complexes of Vanadium and Tantalum with Amido‐, Imido‐ Nitrido‐ and Azido Ligands

Lithium bis(trimethylsilyl)amide, LiN(SiMe₃)₂, reacts with Cp*V(O)Cl₂ and Cp*TaCl₄ to give trimethylsilylimido complexes such as [Cp*V(NSiMe₃)(μ‐NSiMe₃)]₂ ( 7 ) and Cp*Ta(Cl)(NSiMe₃)[N(SiMe₃)₂] ( 19 ), respectively. Substitution of the chloro ligand in 19 by anionic groups leads to complexes with 3 different N‐containing ligands, Cp*Ta(X)(NSiMe₃)[N(SiMe₃)₂] (X = N₃ ( 20 ) or NPEt₃ ( 21 )). Complex 7 is air‐ and moisture‐sensitive, and several derivatives containing oxo and trimethylsiloxy ligands have been identified. Trimethylsilyl azide, Me₃Si‐N₃, is able to replace the oxygen‐containing ligands for azido ligands. The two complete series of bis(azido)‐bridged complexes, [Cp*VCl_n(N₃)_2‐n(μ‐N₃)]₂ (n = 2, 1, 0) and [Cp*TaCl_n(N₃)_3‐n(μ‐N₃)]₂(n = 3, 2, 1, 0), are accessible from the reactions of Cp*VCl₃ and Cp*TaCl₄, respectively, with trimethylsilyl azide. A bis(nitrido)‐bridged azido‐vanadium complex, [Cp*V(N₃)(μ‐N)]₂ ( 18 ), has also been obtained and structurally characterized.     

Tris[bis(trimethysilyl)amido]zinkate von Lithium und Calcium

Tris[bis(trimethylsilyl)amido]zincates of Lithium and Calcium Calcium-bis[bis(trimethylsilyl)amide] and Bis[bis(trimethylsilyl)amido]zinc yield in 1,2-dimethoxyethane quantitatively Calcium-bis{tris[bis(trimethylsilyl)- amido]zincate} · 3DME. When THF is chosen as a solvent, the two reactants and the zincate form a temperature-independent equilibrium, whereas in benzene no reaction occurs. The tris[bis(trimethylsilyl)amido]zincate anion displays characteristic ¹³C{¹H) and ²⁹Si{¹H] chemical shifts of 7 and ?8 ppm, respectively; the nature of the solvent, the cation and the complexating ligands don't influence the IR nor NMR data of the zincate anion and thus verify that [Ca(DME)₃]²⁺ and {Zn[N(SiMe_{3 2}]₃}^? appear as solvent separated ions, which is also confirmed by their insolubility in hydrocarbons.     

Yttrium bis(alkyl) and bis(amido) complexes bearing N,O multidentate ligands. Synthesis and catalytic activity towards ring‐opening polymerization of L‐lactide

Methoxy‐modified β‐diimines HL ¹ and HL ² reacted with Y(CH₂SiMe₃)₃(THF)₂ to afford the corresponding bis(alkyl)s [L¹Y(CH₂SiMe₃)₂] ( 1 ) and [L²Y(CH₂SiMe₃)₂] ( 2 ), respectively. Amination of 1 with 2,6‐diisopropyl aniline gave the bis(amido) counterpart [L¹Y{N(H)(2,6‐iPr₂? C₆H₃)}₂] ( 3 ), selectively. Treatment of Y(CH₂SiMe₃)₃(THF)₂ with methoxy‐modified anilido imine HL ³ yielded bis(alkyl) complex [L³Y(CH₂SiMe₃)₂(THF)] ( 4 ) that sequentially reacted with 2,6‐diisopropyl aniline to give the bis(amido) analogue [L³Y{N(H)(2,6‐iPr₂? C₆H₃)}₂] ( 5 ). Complex 2 was “base‐free” monomer, in which the tetradentate β‐diiminato ligand was meridional with the two alkyl species locating above and below it, generating tetragonal bipyramidal core about the metal center. Complex 3 was asymmetric monomer containing trigonal bipyramidal core with trans‐arrangement of the amido ligands. In contrast, the two cis‐located alkyl species in complex 4 were endo and exo towards the O,N,N tridentate anilido‐imido moiety. The bis(amido) complex 5 was confirmed to be structural analogue to 4 albeit without THF coordination. All these yttrium complexes are highly active initiators for the ring‐opening polymerization of L ‐LA at room temperature. The catalytic activity of the complexes and their “single‐site” or “double‐site” behavior depend on the ligand framework and the geometry of the alkyl (amido) species in the corresponding complexes. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 5662–5672, 2007     

New Sn(IV) and Ti(IV) bis(trimethylsilyl)amides in d,l-lactide polymerization, SEM characterization of polymers

Ring-opening polymerization of d,l-lactide initiated with new chlorotris(bis(trimethylsilyl) amido) tin(IV), tetrakis(bis(trimethylsilyl)amido) tin(IV) and titanium(IV) was investigated. New complexes reveal practically quantitative conversion degrees and produced polymers with higher molecular weight with respect to reference alkoxo-species.The X-ray crystal structure of chlorotris(bis(trimethylsilyl)amido) tin (IV) was investigated. Axial enantiomerism of [SnCl{N(SiMe₃)₂}₃] molecules in solution was studied by high-field dynamic NMR, the value of Gibbs activation energy ΔG^‡ = 59.5 kJ/mol.Field emission SEM investigation of bulk polymer samples and thin films on conductive Al foil revealed a stratified fibrous textures in the bulk polymers, as well as nanoscaled topographical features due to coils and entanglements of individual macromolecules in thin films.     

Bulky Amido Ligands in Rare Earth Chemistry — Syntheses,Structures, and Catalysis

The amido metal chemistry of the rare earth elements is a rapid developing area in coordination chemistry. Especially bulky mono and bidentate amido and amidinates have been introduced as ligands in rare earth chemistry. Due to these sterically demanding ligands, the coordination numbers of the rare earth elements are significantly reduced. This article focuses on two of these bulky ligand systems: bis(trimethylsilyl)amide and aminotroponiminates. The homoleptic bis(trimethylsilyl)amides of rare earth elements, [Ln{N(SiMe₃)₂}₃], are well established compounds in synthetic chemistry. Therefore, this article reviews recent progress in the catalytic application of these compounds. In the second part of this research report, it is shown that N, N′‐disubstituted aminotroponiminates and mono bridged bisaminotroponiminates can be used as cyclopentadienyl alternatives. Achiral and chiral aminotroponiminates have been used. The structural properties, reactivities as well as the catalytic and synthetic applications of the aminotroponiminates complexes will be outlined in this article.     

Structural and Mechanistic Insights into s‐Block Bimetallic Catalysis: Sodium Magnesiate‐Catalyzed Guanylation of Amines

To advance the catalytic applications of s‐block mixed‐metal complexes, sodium magnesiate [NaMg(CH₂SiMe₃)₃] ( 1 ) is reported as an efficient precatalyst for the guanylation of a variety of anilines and secondary amines with carbodiimides. First examples of hydrophosphination of carbodiimides by using a Mg catalyst are also described. The catalytic ability of the mixed‐metal system is much greater than that of its homometallic components [NaCH₂SiMe₃] and [Mg(CH₂SiMe₃)₂]. Stoichiometric studies suggest that magnesiate amido and guanidinate complexes are intermediates in these catalytic routes. Reactivity and kinetic studies imply that these guanylation reactions occur via (tris)amide intermediates that react with carbodiiimides in insertion steps. The rate law for the guanylation of N,N′‐diisopropylcarbodiimide with 4‐tert‐butylaniline catalyzed by 1 is first order with respect to [amine], [carbodiimide], and [catalyst], and the reaction shows a large kinetic isotopic effect, which is consistent with an amine‐assisted rate‐determining carbodiimide insertion transition state. Studies to assess the effect of sodium in these transformations denote a secondary role with little involvement in the catalytic cycle.     

Effect of Chelate Ring Size in Iron(II) Isothiocyanato Complexes with Tetradentate Tripyridyl‐alkylamine Ligands on Spin Crossover Properties

Iron(II) complexes of the type [Fe(L)(NCS)₂] with tetradentate ligands L are well known to show spin crossover properties. However, this behavior is quite sensitive in regard to small changes of the ligand system. Starting from the thoroughly investigated complex [Fe(tmpa)(NCS)₂] [tmpa = tris(2‐pyridylmethyl)amine, also abbreviated as tpa in the literature] we modified the ligand by increasing systematically the chelate ring sizes from 5 to 6 thus obtaining complexes [Fe(pmea)(NCS)₂], [Fe(pmap)(NCS)₂], and [Fe(tepa)(NCS)₂] [pmea = N,N‐bis[(2‐pyridyl)methyl]‐2‐(2‐pyridyl)ethylamine, pmap = N,N‐bis[2‐(2‐pyridyl)ethyl]‐(2‐pyridyl)methylamine, and tepa = tris[2‐(2‐pyridyl)ethyl]amine]. All complexes were structurally characterized and spin crossover properties were investigated using Mößbauer spectroscopy, magnetic measurements, and IR/Raman analyses. The results demonstrated that only the iron complexes with tmpa and pmea showed spin crossover properties, whereas the complexes with the ligands pmap and tepa only formed high spin complexes. Furthermore, DFT calculations supported these findings demonstrating again the strong influence of ligand environment. Herein the effect of increasing the chelate ring sizes in iron(II) isothiocyanato complexes with tetradentate tripyridyl‐alkylamine ligands is clearly demonstrated.     

Chiral Benzamidinate Ligands in Rare‐Earth‐Metal Coordination Chemistry

The treatment of the recently reported potassium salt (S)‐N,N′‐bis‐(1‐phenylethyl)benzamidinate ((S)‐KPEBA) and its racemic isomer (rac‐KPEBA) with anhydrous lanthanide trichlorides (Ln=Sm, Er, Yb, Lu) afforded mostly chiral complexes. The tris(amidinate) complex [{(S)‐PEBA}₃Sm], bis(amidinate) complexes [{Ln(PEBA)₂(μ‐Cl)}₂] (Ln=Sm, Er, Yb, Lu), and mono(amidinate) compounds [Ln(PEBA)(Cl)₂(thf)_n] (Ln=Sm, Yb, Lu) were isolated and structurally characterized. As a result of steric effects, the homoleptic 3:1 complexes of the smaller lanthanide atoms Yb and Lu were not accessible. Furthermore, chiral bis(amidinate)–amido complexes [{(S)‐PEBA}₂Ln{N(SiMe₃)₂}] (Ln=Y, Lu) were synthesized by an amine‐elimination reaction and salt metathesis. All of these chiral bis‐ and tris(amidinate) complexes had additional axial chirality and they all crystallized as diastereomerically pure compounds. By using rac‐PEBA as a ligand, an achiral meso arrangement of the ligands was observed. The catalytic activities and enantioselectivities of [{(S)‐PEBA}₂Ln{N(SiMe₃)₂}] (Ln=Y, Lu) were investigated in hydroamination/cyclization reactions. A clear dependence of the rate of reaction and enantioselectivity on the ionic radius was observed, which showed higher reaction rates but poorer enantioselectivities for the yttrium compound.     

Carbenhomologe Verbindungen von Germanium,Zinn und Blei mit 2‐substituierten N‐Pyrrolyl‐Liganden

Carbene Homologues of Germanium, Tin, and Lead with 2‐substituted N ‐Pyrrolyl Ligands A series of germylenes, stannylenes, and plumbylenes could be prepared by reacting the appropriate bis(trimethylsilyl)amino‐substituted carbene homologue E[N(SiMe₃)₂]₂ (E = Ge, Sn, and Pb) with an α‐carbonyl substituted pyrrole derivative under elimination of bis(trimethylsilyl)amine. The isolated compounds have been analysed spectroscopically, and the resulting NMR and IR data were contrasted with parameters obtained from quantumchemical calculations. The good agreement between experimental and theoretical results gives us the opportunity to discuss the vibrations in more detail, particularly those in which the group 14 element is involved. X‐ray crystal structure analyses obtained for five examples show the title compounds essentially to be monomers with primary E–N bonds and, in addition to that, coordinative E ← O contacts.     

Synthesis and Thermal Decomposition of Heavy Tetrylenes Bearing N-Aminocarbazolyl Substituents

The synthesis of the N-aminocarbazole R-NH₂ ( 2 ) is reported. Subsequent reaction with bis[bis(trimethylsilyl)amido]tetrylenes E[N(SiMe₃)₂]₂ (E=Ge, Sn, or Pb) allowed the isolation of formal hydrazidotetrylene derivatives, R−N(H)EN(SiMe₃)₂ ( 3 ) that includes the first example of a hydrazidoplumbylene to date. Thermal decomposition of these compounds resulted in the elimination of “NH” and afforded the tetrylenes R-EN(SiMe₃)₂ ( 4 ).     

Syntheses,Spectroscopic, Structural,Fluorescent and Thermal Properties of Bis(saccharinato)copper(II) Complexes with two Bis(pyridylamine) Ligands

Two new copper(II) complexes of saccharinate (sac) with bis(2‐pyridylmethyl)amine (bpma) and N,N′‐bis[1‐(pyridin‐2‐yl)ethylidene]ethane‐1,2‐diamine (bapen), [Cu(bpma)(sac)₂] · H₂O ( 1 ) and [Cu(bapen)(sac)₂] ( 2 ), were synthesized and characterized by elemental analysis, TG‐DTA, X‐ray diffraction, and UV/Vis and IR spectroscopy, respectively. In 1 , the copper(II) ion is coordinated by two N‐bonded sac ligands, and three nitrogen atoms of bpma, in a distorted square‐pyramidal coordination arrangement, whereas the arrangement around the copper ion in 2 is a distorted octahedron with two N‐coordinated sac ligands and a tetradentate bapen ligand. In addition to hydrogen bonding involving the water molecule in 1 , the mononuclear species of 1 and 2 are further connected by weak intermolecular C–H ··· π and C–H ··· O interactions to form a three‐dimensional network. Both complexes are luminescent at room temperature and their emissions seem to be due to ligand‐based π–π* transitions.     

Synthesis and Characterization of the Zinc Amides: [EtZnL]2 and [ZnL2] (L = N,N‐dimethyl(N′‐trimethylsilyl)ethane‐1,2‐diaminate)

The ligand N,N‐dimethyl(N′‐trimethylsilyl)ethane‐1,2‐diamine (HL) was treated with ZnEt₂ in varying stoichiometric ratios to synthesize [EtZnL]₂ and [ZnL₂] complexes. Crystal data: [EtZnL]₂, monoclinic, P2₁/n, a = 10.0149(5) Å, b = 8.0296(3) Å, c = 16.1689(8) Å, β = 91.715(2)°. [ZnL₂], monoclinic, P2₁/n, a = 8.8457(3) Å, b = 15.4249(6) Å, c = 16.0121(7) Å, β = 92.656(1)°. The former complex is an amido nitrogen bridged dimer with distorted tetrahedral stereochemistry of the zinc atom and the latter is a distorted tetrahedral monomer based on amide/amine chelation.     

Iron‐Promoted ortho‐ and/or ipso‐Hydroxylation of Benzoic Acids with H2O2

Regioselective hydroxylation of aromatic acids with hydrogen peroxide proceeds readily in the presence of iron(II) complexes with tetradentate aminopyridine ligands [Fe^II(BPMEN)(CH₃CN)₂](ClO₄)₂ ( 1 ) and [Fe^II(TPA)(CH₃CN)₂](OTf)₂ ( 2 ), where BPMEN=N,N′‐dimethyl‐N,N′‐bis(2‐pyridylmethyl)‐1,2‐ethylenediamine, TPA=tris‐(2‐pyridylmethyl)amine. Two cis‐sites, which are occupied by labile acetonitrile molecules in 1 and 2 , are available for coordination of H₂O₂ and substituted benzoic acids. The hydroxylation of the aromatic ring occurs exclusively in the vicinity of the anchoring carboxylate functional group: ortho‐hydroxylation affords salicylates, whereas ipso‐hydroxylation with concomitant decarboxylation yields phenolates. The outcome of the substituent‐directed hydroxylation depends on the electronic properties and the position of substituents in the molecules of substrates: 3‐substituted benzoic acids are preferentially ortho‐hydroxylated, whereas 2‐ and, to a lesser extent, 4‐substituted substrates tend to undergo ipso‐hydroxylation/decarboxylation. These two pathways are not mutually exclusive and likely proceed via a common intermediate. Electron‐withdrawing substituents on the aromatic ring of the carboxylic acids disfavor hydroxylation, indicating an electrophilic nature for the active oxidant. Complexes 1 and 2 exhibit similar reactivity patterns, but 1 generates a more powerful oxidant than 2 . Spectroscopic and labeling studies exclude acylperoxoiron(III) and Fe^IV?O species as potential reaction intermediates, but strongly indicate the involvement of an Fe^III? OOH intermediate that undergoes intramolecular acid‐promoted heterolytic O? O bond cleavage, producing a transient iron(V) oxidant.