Complexes of Co(II) and Zn(II) with N-(Thio)phosphorylthioureas AdNHC(S)NHP(O)(OiPr)2 and MeNHC(S)NHP(S)(OiPr)2

The reaction of the potassium salt of the N-(thio)phosphorylated thioureas AdNHC(S)NHP(O)(OiPr)₂ (HL^I , Ad = Adamantyl) and MeNHC(S)NHP(S)(OiPr)₂ (HL^II ) with Co(II) and Zn(II) in aqueous EtOH leads to [ML^I,II ₂] chelate complexes. They were investigated by UV-vis, ¹H and ³¹P NMR spectroscopy, and microanalysis. The molecular structures of [ML^I ₂] were elucidated by single crystal X-ray diffraction analysis. The metal centers in both complexes are found to be in a distorted-tetrahedral O₂S₂ environment formed by the C=S sulfur atoms and the P=O oxygen atoms of two deprotonated L^I ligands. The photoluminescence properties of [ZnL^II ₂] are also reported.     

Bismuth(V) iron(III) tris(phosphate) oxide

Bi^V_0.4Fe₃^IIIO(PO₄)₃ crystallizes with two Fe atoms (one on an inversion centre and one on a mirror plane) displaying octahedral geometry and a third Fe atom (on a mirror plane) with trigonal bipyramidal coordination. Fe atoms are seen in oxy­gen‐bridged chains. Bi^V atoms are found in the interstitial sites between these chains. Bi shows sevenfold coordination, with Bi—O distances between 2.357 (7) and 2.529 (6) Å.     

Tris(salicylhydroxamato)manganese(III)

Summary Hydroxamic acids show a degree of selectivity towards transition metal ions having symmetrical d-electron configuration, e.g. vanadium(V) (d⁰) and iron(III) (d⁶⁵). Hydroxamato complexes of metal ions having unsymmetrical d-electron distribution are rare. Thus for manganese(III) (d⁴) only some thiohydroxamato complexes⁽¹⁾ have been characterised so far. In this communication we report on the first synthesis of a salicylhydroxamato complex of manganese(III). Such investigations are of interest because these higher valent manganese complexes are potentially models for the water-splitting complex present in photosystem II⁽²).     

Osmium(II)-Phthalocyanine: Darstellung und Eigenschaften von Di(acido)phthalocyaninatoosmaten(II)

Osmium(II) Phthalocyanines: Preparation and Properties of Di(acido)phthalocyaninatoosmates(II) “H[Os(X)₂Pc^2?]” (X = Br, Cl) reacts in basic medium or in the melt with (ⁿBu₄N)X forming less stable, diamagnetic, darkgreen (ⁿBu₄N)₂[Os(X)₂Pc^2?]. Similar dicyano and diimidazolido(Im) complexes are formed by the reaction of “H[Os(Cl)₂Pc^2?]” with excess ligand in the presence of [BH₄]^?. The cyclic voltammograms show up to three quasireversible redoxprocesses: E_1/2(I) = 0.13 V (X = CN), ?0.03 V (Im), ?0.13 V (Br) resp. ?0.18 V (Cl) is metal directed (Os^II/III), E_1/2(II) = 0.69 V (Cl), 0.71 V (Br), 0.83 V (CN), 1.02 V (Im) is ligand directed (Pc^2?/?) and E_1/2(III) = 1.17 V (Cl) resp. 1.23 V (Br) is again metal directed (Os^III/IV). Between the typical “B” (～16.2 kK) and “Q” (～29.4 kK), “N regions” (～34.1 kK) up to seven strong “extra bands” of the phthalocyanine dianion (Pc^2?) are observed in the uv-vis spectrum. Within the row CN > Im > Br > Cl, most of the bands are shifted slightly, the “extra bands” considerably more to lower energy in correlation with E_1/2(I). The vibrational spectra are typical for the Pc^2? ligand with D_4h symmetry. M.i.r. bands at 514, 909, 1 173 and 1 331 cm^?1 are specific for hexa-coordinated low spin Os^II phthalocyanines. In the resonance Raman (r.r.) spectra polarized, depolarized or anomalously polarized deformation and stretching vibrations of the Pc^2? ligand will be selectively enhanced, if the excitation frequency coincides with “extra bands”. With excitation at ～19.5 kK the intensity of the symmetrical Os? X stretching vibration at 295 cm^?1 (X = Cl), 252 cm^?1 (X = Im) and 181 cm^?1 (X = Br) is r.r. enhanced, too. The asymmetrical Os? X stretching vibration is observed in the f.i.r. spectrum at 345 cm^?1 (X = CN), 274 cm^?1 (X = Cl), 261 cm^?1 (X = Im) and 200 cm^?1 (X = Br).     

Synthesis and Characterization of Tris(oxazolinyl)borato Copper(II) and Copper(I) Complexes

The reaction of To^MTl (To^M=tris(4,4-dimethyl-2-oxazolinyl)phenylborate) and CuBr₂ in benzene at 60 °C provides To^MCuBr ( 1 ) as an entry-point into tris(oxazolinyl)phenylborato copper chemistry. To^MCuO^tBu ( 2 ) and To^MCuOAc ( 3 ) are prepared by the reactions of To^MCuBr with KO^tBu and NaOAc, respectively. To^MCuO^tBu is transformed into (To^MCuOH)₂ ( 4 ) through hydrolysis. NMR, FT-IR, and EPR spectroscopies are used to determine the electronic and structural properties of these copper(II) compounds, and the solid-state structures were characterized by X-ray crystallography. Reduction of copper is observed upon treatment of To^MCuO^tBu with phenylsilane in an attempt to synthesize monomeric copper(II) hydride. To^MCu ( 5 ) and To^M₂Cu ( 6 ) were independently synthesized and characterized for comparison.     

Silver(I) ions-enhanced electrochemiluminescence of tris(2,2-bipyridyl)ruthenium(II)

In this paper, we demonstrate an electrochemiluminescence (ECL) enhancement of tris(2,2-bipyridyl)ruthenium(II) (Ru(bpy)₃²⁺) by the addition of silver(I) ions. The maximum enhancement factor of about 5 was obtained on a glassy carbon electrode in the absence of co-reactant. The enhancement of ECL intensity was possibly attributed to the unique catalytic activity of Ag⁺ for reactions between Ru(bpy)₃³⁺ with OH. The higher enhancement was observed in phosphate buffer solutions compared with that from borate buffer solutions. This resulted from the fact that formation of nanoparticles with large surface area in the phosphate buffer solution exhibited high catalytic activity. The amount of Ag⁺, solution pH and working electrode materials played important roles for the ECL enhancement. We also studied the effects of Ag⁺ on Ru(bpy)₃²⁺/tripropylamine and Ru(bpy)₃²⁺/C₂O₄²⁻ ECL systems.     

OsII-Phthalocyaninate(2−): Darstellung und Eigenschaften von (Halogeno)-(carbonyl)phthalocyaninato(2−)osmat(II)

Os^II Phthalocyaninates(2?): Synthesis and Properties of (Halo)(carbonyl)phthalocyaninato-(2?)osmate(II) Soluble, blue tetra(n-butyl)ammonium (halo)(carbonyl)phthalocyaninato(2?)osmate(II), (ⁿBu₄N)[Os(X)(CO)Pc^2?] (X = Cl, Br, I) is obtained by the reaction of [Os(THF)(CO)Pc^2?] (THF: tetrahydrofurane) with (ⁿBu₄N)X in THF. In the cyclovoltammograms there are three reversible electrode processes at ?1.21 ± 0.01, 0.18 ± 0.04 and 0.65 ± 0.01 V assigned to the three redox pairs Pc^2?/Pc^3?, Os^II/Os^III and Pc^2?/Pc^3?. In the electronic absorption spectra only the intense B and Q regions are observed at ～ 15800 resp. 27500, 33000 cm^?1. The infrared and resonance Raman spectra closely resemble those of other phthalocyaninates(2?) of low valent osmium. In the infrared spectrum v(C? O) is detected at 1896 ± 4 cm^?1 and v(Os? X) at 260 (X = Cl), 175 (X = Br) or 143 cm^?1 (X = I).     

Kinetics and mechanism of acid and base hydrolysis ofcis-chloro-(benzotriazole)bis(ethylenediamine)cobalt(III) andcis-chloro-(N-methylbenzotriazole)bis(ethylenediamine)cobalt(III) cations

Summary The kinetics of acid hydrolysis ofcis-[CoCl(btzH)(en)₂]²⁺ andcis-[CoCl(btzMe)(en)₂]²⁺ complexes (where btzH = benzotriazole, btzMe =N-methylbenzotriazole and en = ethylenediamine) have been investigated in HClO₄ at ionic strength 1 = 0.25 mol dm^–3 in the 30–40° range. In the 1.0 x 10^–1 to 1.0 X 10^–3 mol dm^–3 acid strength range, the rate of aquation of the [CoCl(btzH)(en)₂]²⁺ cation follows the relationship:-d ln[complex]/dt = k₁ + k₂K_NH[^H+]^–1, where k₁ and k₂ are aquation rate constants of the acid independent and acid dependent steps respectively, and K_NH is the acid dissociation constant of the coordinated benzotriazole.cis-[CoCl(btzMe)-(en)₂]²⁺ undergoes acid independent hydrolysis presumably due to the absence of a labile N-H proton. The base hydrolysis could be followed for thecis-[CoCl(btzMe)(en)₂]²⁺ complex only by measuring hydrolysis rates at 0°.     

Ruthenium(II)-Phthalocyaninate(1–): Darstellung und Eigenschaften von (Halogeno)(carbonyl)phthalocyaninato(1–)ruthenium(II)

Ruthenium(II)-Phthalocyaninates(1–): Synthesis and Properties of (Halo)(carbonyl)phthalocyaninato(1–)ruthenium(II) Brown-violet (halo)(carbonyl)phthalocyaninato(1–)ruthenium(II), [Ru(X)(CO)Pc^?] (X = Cl, Br) is prepared by oxidation of [Ru(X)(CO)Pc^2?]^? with the corresponding halogen or dibenzoylperoxide. The eff. magnetic moment μ_eff = 1.74 (X = Cl), 1.68 μ_B (Br) confirms the presence of a low-spin Ru^II complex of the Pc^? radical. Accordingly, only the first ring oxidation at ～0.64 V and the first ring reduction at ～ ?1.19 V is observed in the cyclovoltammogram of [Ru(X)(CO)Pc^2?]^?. The UV-VIS-NIR spectra characterizing a monomeric Pc^? radical with intense π-π* transitions at 14500, 19800, 25100 and 33900 cm^?1 are compared with those of [Ru(Cl)₂Pc^?] and of monomeric as well as dimeric [Zn(Cl)Pc^?]. The IR and resonance Raman(RR) spectra are characteristic for a Pc^? radical, too. Diagnostic in-plane vibrations of the Pc^? ligand are in the IR spectrum at 1071, 1359, 1445 cm^?1 and in the RR spectrum (λ₀ = 488.0 nm) at 567, 1597 cm^?1. v(C? O) at 1950 cm^?1 and v(Ru? X) at 260 (X = Cl) resp. 184 cm^?1 (X = Br) are observed only in the IR spectrum.     

Ruthenium(II)-Phthalocyanine: Darstellung und Eigenschaften von Di(halogeno)phthalocyaninatoruthenat(II)

Ruthenium(II) Phthalocyanines: Preparation and Properties of Di(halo)phthalocyaninatoruthenate(II) [Ru(Py)₂Pc^2?] reacts with molten (ⁿBu₄N)X forming stable, green (ⁿBu₄N)₂[Ru(X)₂Pc^2?] (X = Cl, Br). The cyclovoltammogram shows a quasireversible redoxprocess for the metal oxidation at E_1/2(I) = ?0.02 V (X = Cl) resp. 0.05 V (X = Br) and for the first ringoxidation at E_1/2(II) = 0.70 V. The typical π-π*-transitions (B < Q < N) of the phthalocyanine dianion (Pc^2?) are observed in the uv-vis spectrum. With respect to Ru^III phthalocyanines B is shifted significantly to higher, Q, N to lower energy. The strong extra-band at 24.2 kK is diagnostic for these Ru^II phthalocyanines. The vibrational spectra are typical for the Pc^2? ligand with D_4h symmetry, too, and bands at 513, 909, 1 171 und 1 329 cm^?1 in the m.i.r. spectrum are specific for hexa-coordinated low spin Ru^II. In the Raman spectrum with excitation at ～480 nm the intensity of the totally symmetrical Ru? X stretching vibration at 266 cm^?1 (X = Cl) resp. 168 cm^?1 (X = Br) together with a progression of up to three overtones is selectively resonance Raman enhanced. The asymmetrical Ru? X stretching vibration is observed in the f.i.r. spectrum at 272 cm^?1 (X = Cl) resp. 215 cm^?1 (X = Br).     

The molecular structure of high‐spin (S = ) manganese(II) phthalocyanine in tetrabutylammonium bromido(phthalocyaninato)manganese(II)

The title complex salt, (C₁₆H₃₆N)[MnBr(C₃₂H₁₆N₈)] or (TBA)[Mn^IIBr(Pc)] (TBA is tetrabutylammonium and Pc is phthalocyaninate), has been obtained as single crystals by the diffusion technique and its crystal structure was determined using X‐ray diffraction. The high‐spin (S = ) [Mn^IIBr(Pc)]⁻ macrocycle has a concave conformation, with an average equatorial Mn—N(Pc) bond length of 2.1187 (19) Å, an axial Mn—Br bond length of 2.5493 (7) Å and with the Mn^II cation displaced out of the 24‐atom Pc plane by 0.894 (2) Å. The geometry of the Mn^IIN₄ fragment in [Mn^IIBr(Pc)]⁻ is similar to that of the high‐spin (S = ) manganese(II) tetraphenylporphyrin (TPP) in [Mn^II(1‐MeIm)(TPP)] (1‐MeIm is 1‐methylimidazole).     

Ethylene dicysteine (EC) and ethyl cysteinate dimer (ECD) complexes of Ga(III) and In(III)

Ethylene dicysteine (EC) and ethyl cysteinate dimer (ECD) complexes of⁶⁷Ga and¹¹¹In were prepared and the complexation yield and radiochemical purity estimated by paper chromatography, paper electrophoresis and solvent extraction into chloroform.¹¹¹In-EC was found to be anionic, whereas¹¹¹In-ECD was neutral. EC complexes of⁶⁷Ga and¹¹¹In were stable upto 6 hours and expectedly less lipophilic than ECD complexes. ECD complexes of⁶⁷Ga and¹¹¹In were unstable in aqueous medium, but highly stable in chloroform. The utility of the work for stabilisation of products as organic extract and the possible role and limitation for the development of new⁶⁸Ga radiopharmaceuticals and of bifunctional chelating agent (BCA) for¹¹¹In are discussed.     

Thallium(II) in the chemically induced thallium(I)-Thallium(III) exchange

The rate of the electron exchange between thallium(I) and thallium(III) induced by iron(II) has been measured at various concentrations of Tl(I), Tl(III), and Fe(II).²⁰⁴Tl tracer, initially in the Tl(I) state, was used. Exchange induced by the separation method was less than 0.01%. The mechanism earlier discussed is $$\begin{gathered} Tl^{III} + Fe^{II} \rightleftharpoons Tl^{II} + Fe^{III} \left( {k_1 ,k_{ - 1} } \right) \hfill \\ Tl^{II} + Fe^{II} \rightharpoonup Tl^I + Fe^{III} \left( {k_2 } \right) \hfill \\ *Tl^I + Tl^{II} \rightleftharpoons *Tl^{II} + Tl^I \left( {k_I } \right) \hfill \\ *Tl^{II} + Tl^{III} \rightleftharpoons *Tl^{III} + Tl^{II} \left( {k_{III} } \right), \hfill \\ \end{gathered} $$ which provides an exchange path in addition to the two-electron reaction^*Tl^I+Tl^III?^*Tl^III+Tl^I (k_ex). The rate law deduced from this mechanism agrees with experiment over a limited range of conditions but fails to account for the observed effect at low concentrations of Tl(I). The additional rate can be represented by inclusion of a term in which the rate of the induced exchange is independent of the concentration of Tl(I). When treated according to the resulting complete rate law the data are consistent with earlier photochemical studies. The present results in combination with other data give k₂=3·10⁶ M^?1·sec^?1 in 1M perchloric acid at 25°C. This is in satisfactory agreement with a recent pulse radiolysis measurement as well as with independent flash photolysis studies.     

Synthesis of the pentacarbonyl(chalcocarbonyl)chromium(0) complexes,Cr(CO)5(CX) (X = S,Se)

The arene complexes, (η⁶-C₆H₆)Cr(CO)₂(CX) (X = S, Se), react with excess CO gas under pressure in tetrahydrofuran at about 60° C to produce the Cr(CO)₅(CX) complexes in high yield. The IR and NMR (¹³C and ¹⁷O) spectra of these complexes are in complete accord with the expected C_4v molecular symmetry. Like the analogous W(CO)₅(CS) complex, both compounds react with cyclohexylamine to give Cr(CO)₅(CNC₆H₁₁). However, while W(CO)₅(CS) undergoes stereospecific CO substitution with halide ions (Y^? to form trans-[W(CO)₄(CS)Y]^?, the two chromium chalcocarbonyl complexes apparently undergo both CO and CX substitution to afford mixtures of [Cr(CO)₅Y]^? and trans-[Cr(CO)₄(CX)Y]^?.     

Heterovalent trinuclear Co(III)-Co(II)-Co(III) complexes with N-(2-Carboxyethyl)salicylaldimines

The heterovalent trinuclear cobalt complexes [Co₂^IIIL₄ ⁱ · Co^II(H₂O)₄] · nXmY (L ⁱ are deprotonated Schiff bases derived from substituted salicylaldehydes and β-alanine; i = 1–3) were obtained and characterized. An X-ray diffraction study of the trinuclear cobalt complex with N-(2-carboxyethyl)salicylaldimine showed that the central Co(II) ion and the terminal Co(III) ions are linked by bridging carboxylate groups. Either terminal Co(III) atom is coordinated to two ligand molecules. They form an octahedral environment consisting of two azomethine N atoms, two phenolate O atoms, and two O atoms of two carboxylate groups. The central Co(II) atom is coordinated to four water molecules and to two O atoms of two bridging carboxylate ligands involved in the coordination sphere of the terminal Co(III) atoms.     

Ruthenium(III)-Phthalocyanine: Darstelllung und Eigenschaften von Di(halogeno)phthalocyaninato(1−)ruthenium(III), [Ru(X)2Pc] (X = Cl,Br, I)

Ruthenium(III) Phthalocyanines: Synthesis and Properties of Di(halo)phthalocyaninato(1?)ruthenium(III) Di(halo)phthalocyaninato(1?)ruthenium(III), [Ru(X)₂Pc^?] (X = Cl, Br, I) is prepared by oxidation of [Ru(X)₂Pc^2?]^? (Cl, Br, OH) with halogene in dichloromethane. The magnetic moment of [Ru(X)₂Pc^?] is 2,48 μ_B (X = Cl) resp. 2,56 μ_B (X = Br) in accordance with a systeme of two independent spins (low spin Ru^III and Pc^?: S = 1/2). The optical spectra of the red violet solution of [Ru(X)₂Pc^?] (Cl, Br) are typical for the Pc^? ligand with the “B” at 13.5 kK, “Q₁” at 19.3 kK and “Q₂ region” at 31.9 kK. Sytematic spectral changes within the iron group are discussed. The presence of the Pc^? ligand is confirmed by the vibrational spectra, too. Characteristic are the metal dependent bands in the m.i.r. spectra at 1 352 and 1 458 cm^?1 and the strong Raman line at 1 600 cm^?1. The antisymmetric Ru? X stretch (v_as(Ru? X)) is observed at 189 cm^?1 (X = I) resp. 234 cm^?1 (X = Br). There are two interdependent bands at 295 and 327 cm^?1 in the region expected for v_as(Ru? Cl) attributed to strong interaction of v_as(Ru? Cl) with an out-of-plane Pc^? tilting mode of the same irreducible representation. Only the symmetric Ru? Br stretch at 183 cm^?1 is selectively enhanced in the resonance-Raman(RR) spectra. The Raman line at 168 cm^?1 of the diiodo complex is assigned to loosely bound iodine. The broad band at 978 cm^?1 in the RR spectra of the dichloro complex is due to an intraconfigurational transition within the electronic ground state of low spin Ru^III split by spin orbit coupling.     

Characterization of Anilinepentacyanoferrate (II) and (III)

The anilinepentacyanoferrate (II) complex has been characterized in aqueous solution. The complex exhibits a predominant ligand field transition at λ_max = 415 nm with ?_max = 494 M^?1 cm^?1. The corresponding Fe(III) complex displays a strong absorption at λ_max = 700nm(?_max = 1.61×10⁴ M^?1 sec^?1) which can be assigned as a ligand to metal charge transfer transition. The rate constants of formation and dissociation for the Fc(II) complex are (3.14±0.18)×10² M^?1W^?1 and 0.985±0.005 sec^?1, respectively, at μ = 0.10 M LiClO₄, pH = 8 and T = 25°C. The cyclic voltammetry of the complex shows that a reversible redox process is observed with E_1/2 value of 0.51±0.01 V vs. NHE at μ = 0.10 M LiClO₄, pH = 8 and T = 25°C. The kinetic study of the oxidation of the Fe(II) complex by ferricyanide ion yielded the rate constant of the reaction k_et = (1.43±0.04)x10 M sec^?1 at μ = 0.10 M LiClO₄, pH = 8 and T = 25°C.     

Kinetics of acid- and iron(III)-catalysed aquation of cis-(salicylato)-(methyl/ethylamine) bis(ethylenediamine)cobalt(III)

Summary The kinetics of spontaneous, acid- and Fe^III-catalysed aquation of cis-[Co(en)₂(RNH₂)(SalH)]²⁺ complexes (R = Me, Et; SalH = C₆H₄(OH)CO _inf2 ^sup- ) were studied in acid perchlorate medium, I = 1.5 mol dm^–3 (NaClO₄) at 70–80°C. The Fe^III-catalysed aquation proceeds via formation of a binuclear species, the evidence of which follows from aquation, complexation and equilibrium studies. The spontaneous aquation rate shows steric acceleration with the increase of the nonlabile amine chain length, while that of acid- and Fe^III-catalysed aquation shows the opposite trend. An attempt is made to explain the discrepancy in the rate on the basis of solvent cosphere effects.     

Ferrate(VI) and ferrate(V) oxidation of cyanide,thiocyanate, and copper(I) cyanide

Cyanide (CN⁻), thiocyanate (SCN⁻), and copper(I) cyanide (Cu(CN)₄³⁻) are common constituents in the wastes of many industrial processes such as metal finishing and gold mining, and their treatment is required before the safe discharge of effluent. The oxidation of CN⁻, SCN⁻, and Cu(CN)₄³⁻ by ferrate(VI) (Fe^VIO₄²⁻; Fe(VI)) and ferrate(V) (Fe^VO₄³⁻; Fe(V)) has been studied using stopped-flow and premix pulse radiolysis techniques. The rate laws for the oxidation of cyanides were found to be first-order with respect to each reactant. The second-order rate constants decreased with increasing pH because the deprotonated species, FeO₄²⁻, is less reactive than the protonated Fe(VI) species, HFeO₄⁻. Cyanides react 10³–10⁵ times faster with Fe(V) than with Fe(VI). The Fe(V) reaction with CN⁻ proceeds by sequential one-electron reductions from Fe(V) to Fe(IV) to Fe(III). However, a two-electron transfer process from Fe(V) to Fe(III) occurs in the reaction of Fe(V) with SCN⁻ and Cu(CN)₄³⁻. The toxic CN⁻ species of cyanide wastes is converted into relatively non-toxic cyanate (NCO⁻). Results indicate that Fe(VI) is highly efficient in removing cyanides from electroplating rinse water and gold mill effluent.     

Base hydrolysis ofcis-(methyl/ethylamine)bis(ethylenediamine) (salicylato)cobalt(III) complexes

The kinetics of the base hydrolysis ofcis-[Co(en)₂(RNH₂)-(SalH)]²⁺ (R=Me or Et; SalH=HOC₆H₄CO ₂ ⁻ ) were investigated in aqueous ClO ₄ ⁻ in the 0.004–0.450 mol dm⁻³ [OH⁻] range, I=0.50 mol dm⁻³ at 30–40°C. The phenoxide species is hydrolysed via [OH⁻]-independent and [OH⁻]-dependent paths, the latter being first order in [OH⁻]. The high rate of alkali-independent hydrolysis of the phenoxide species is associated with high ΔH^≠ and ΔS^≠ values, in keeping with the SNICB mechanism involving an amido conjugate base generated by the phenoxide-assisted NH-deprotonation of the coordinated amine. The [OH⁻]-dependent path also involves the conventional SN₁ CB mechanism. The rate constant, k₁, for the SNICB path exhibits a steric acceleration with the increasing size of the non-labile alkylamine, whereas the rate constant, k₂, for the SN₁CB path shows a reverse trend. TMC 2578