A Theoretical Study on the Mechanism of C2H4 Oxidation over a Neutral V3O8 Cluster

Density functional theory (DFT) calculations are used to investigate the reaction mechanism of V₃O₈+C₂H₄. The reaction of V₃O₈ with C₂H₄ produces V₃O₇CH₂+HCHO or V₃O₇+CH₂OCH₂ overall barrierlessly at room temperature, whereas formation of hydrogen‐transfer products V₃O₇+CH₃CHO is subject to a tiny overall free energy barrier (0.03 eV), although the formation of the last‐named pair of products is thermodynamically more favorable than that of the first two. These DFT results are in agreement with recent experimental observations. The (O_b)₂V(O_tO_t)^. (b=bridging, t=terminal) moiety containing the oxygen radical in V₃O₈ is the active site in the reaction with C₂H₄. Similarities and differences between the reactivities of (O_b)₂V(O_tO_t)^. in V₃O₈ and the small VO₃ cluster [(O_t)₂VO_t^.] are discussed. Moreover, the effect of the support on the reactivity of the (O_b)₂V(O_tO_t)^. active site is evaluated by investigating the reactivity of the cluster VX₂O₈, which is obtained by replacing the V atoms in the (O_b)₃VO_t support moieties of V₃O₈ with X atoms (X=P, As, Sb, Nb, Ta, Si, and Ti). Support X atoms with different electronegativities influence the oxidative reactivity of the (O_b)₂V(O_tO_t)^. active site through changing the net charge of the active site. These theoretical predictions of the mechanism of V₃O₈+C₂H₄ and the effect of the support on the active site may be helpful for understanding the reactivity and selectivity of reactive O^. species over condensed‐phase catalysts.     

A comparison of the unimolecular decomposition pathways of some C7 and C8 ions in the gas phase

[CnH_2n?3]⁺ and [C_nH_2n?4]⁺·(n = 7, 8) ions have been generated in the mass spectrometer from C_nH_2n?3 Br (n = 7, 8) precursors and from two steroids. The relative abundances of competing ‘metastable transitionss’ indicate (partial) isomerization to a common structure (or mixture of structures) prior to decomposition in most examples of all four types of ions. In contrast, [C₈H₁₀O]⁺· and [C₈H₁₂O]⁺· ions, generated from different sources as molecular ions and by fragmentation of steroids, do not decompose through common-intermediates.     

Kinetics and Mechanism of the Reduction of Chromium(VI) and Chromium(V) by D‐Glucitol and D‐Mannitol

The oxidation of D ‐glucitol and D ‐mannitol by Cr^VI yields the aldonic acid (and/or the aldonolactone) and Cr^III as final products when an excess of alditol over Cr^VI is used. The redox reaction occurs through a Cr^VI→Cr^V→Cr^III path, the Cr^VI→Cr^V reduction being the slow redox step. The complete rate laws for the redox reactions are expressed by: a) −d[Cr^VI]/dt {k_{M2 H} [H⁺]²+k_MH [H⁺]}[mannitol][Cr^VI], where k_{M2 H} (6.7±0.3)⋅10 M s⁻¹ and k_MH (9±2)⋅10 M s⁻¹; b) −d[Cr^VI]/dt {k_{G2 H} [H⁺]²+k_GH [H⁺]}[glucitol][Cr^VI], where k_{G2 H} (8.5±0.2)⋅10 M s⁻¹ and k_GH (1.8±0.1)⋅10 M s⁻¹, at 33°. The slow redox steps are preceded by the formation of a Cr^VI oxy ester with λ_max 371 nm, at pH 4.5. In acid medium, intermediate Cr^V reacts with the substrate faster than Cr^VI does. The EPR spectra show that five‐ and six‐coordinate oxo‐Cr^V intermediates are formed, with the alditol or the aldonic acid acting as bidentate ligands. Pentacoordinate oxo‐Cr^V species are present at any [H⁺], whereas hexacoordinate ones are observed only at pH<2 and become the dominant species under stronger acidic conditions where rapid decomposition to the redox products occurs. At higher pH, where hexacoordinate oxo‐Cr^V species are not observed, Cr^V complexes are stable enough to remain in solution for several days to months.     

Formation,Dynamic Behavior,and Chemical Transformation of Pt Complexes with a Rotaxane‐like Structure

The reaction of [Pt(CH₂COMe)(Ph)(cod)] (cod=1,5‐cyclooctadiene) with (ArCH₂NH₂CH₂‐C₆H₄COOH)⁺(PF₆)^? (Ar=4‐tBuC₆H₄ or 9‐anthryl) in the presence of cyclic oligoethers such as dibenzo[24]crown‐8 (DB24C8) and dicyclohexano[24]crown‐8 (DC24C8) produces {(ce)[ArCH₂NH₂CH₂C₆H₄COOPt(Ph)(cod)]}⁺(PF₆)^? (ce=DB24C8 or DC24C8, Ar=4‐tBuC₆H₄ or 9‐anthryl) with interlocked structures. FABMS and NMR spectra of a solution of these compounds indicate that the Pt complexes with a secondary ammonium group and DB24C8 (or DC24C8) make up the axis and cyclic components, respectively. Temperature‐dependent ¹H NMR spectra of a solution of {(DB24C8)[4‐tBuC₆H₄CH₂NH₂CH₂‐C₆H₄COOPt(Ph)(cod)]}⁺(PF₆)^? ({(DB24C8)[ 4 ‐H]}⁺(PF₆)^?) show equilibration with free DB24C8 and the axis component. The addition of DB24C8 to a solution of {(DC24C8)[ 4 ‐H]}⁺(PF₆)^? causes partial exchange of the macrocyclic component of the interlocked molecules, giving a mixture of {(DC24C8)[ 4 ‐H]}⁺(PF₆)^?, {(DB24C8)[ 4 ‐H]}⁺(PF₆)^?, and free macrocyclic compounds. The reaction of 3,5‐Me₂C₆H₃COCl with {(DB24C8)[ 4 ‐H]}⁺(PF₆)^? affords the organic rotaxane {(DB24C8)(4‐tBuC₆H₄CH₂NH₂CH₂‐C₆H₄COOCOC₆H₃Me₂‐3,5)}⁺(PF₆)^? through C? O bond formation between the aroyl group and the carboxylate ligand of the axis component. The addition of 2,2′‐bipyridine (bpy) to a solution of {(DB24C8)[ 4 ‐H]}⁺(PF₆)^? induces the degradation of the interlocked structure to form a complex with trigonal bipyramidal coordination, [Pt(Ph)(bpy)(cod)]⁺(PF₆)^?, whereas the reaction of bpy with [Pt(OCOC₆H₄Me‐4)(Ph)(cod)] produces the square‐planar complex [Pt(OCOC₆H₄Me‐4)(Ph)(bpy)].     

Synthesis and Structure of (N,)C,N‐chelated Organoantimony(III) and Bismuth(III) Cations and Isolation of Their Adducts with Ag[CB11H12]

The treatment of N,C,N‐chelated antimony(III) and bismuth(III) chlorides [C₆H₃‐2,6‐(CH=NR)₂]MCl₂ [R = tBu and M = Sb ( 1 ) or Bi ( 2 ); R = Dmp and M = Sb ( 3 ) or Bi ( 4 )] (Dmp = 2,6‐Me₂C₆H₃) with one molar equivalent of Ag[CB₁₁H₁₂] led to a smooth formation of corresponding ionic pairs {[C₆H₃‐2,6‐(CH=NR)₂]MCl}⁺[CB₁₁H₁₂]^– [R = tBu and M = Sb ( 7 ) or Bi ( 8 ), R = Dmp and M = Sb ( 9 ) or Bi ( 10 )]. Similarly, the reaction of C,N‐chelated analogues [C₆H₂‐2‐(CH=NDip)‐4,6‐(tBu)₂]MCl₂ [M = Sb ( 5 ) or Bi ( 6 ), Dip = 2′,6′‐iPr₂C₆H₃] gave compounds {[C₆H₂‐2‐(CH=NDip)‐4,6‐(tBu)₂]MCl}⁺[CB₁₁H₁₂]^– [M = Sb ( 11 ) or Bi ( 12 )]. All compounds 7 – 12 were characterized with ¹H, ¹¹B and ¹³C{¹H} NMR spectroscopy, ESI‐mass spectrometry, IR spectroscopy, and molecular structures of 7 – 9 and 12 were determined by the help of single‐crystal X‐ray diffraction analysis. In contrast, all attempts to cleave also the second M–Cl bond in 7 – 12 using another molar equivalent Ag[CB₁₁H₁₂] remained unsuccessful. Nevertheless, the reaction between 7 (or 8 ) and Ag[CB₁₁H₁₂] produced unprecedented adducts of both reagents namely {[C₆H₃‐2,6‐(CH=NtBu)₂]SbCl}₂²⁺[Ag₂(CB₁₁H₁₂)₄]^2– ( 13 ) and {[C₆H₃‐2,6‐(CH=NtBu)₂]BiCl}⁺[Ag(CB₁₁H₁₂)₂]^– ( 14 ) in a reproducible manner. The molecular structures of these sparingly soluble compounds were determined by single‐crystal X‐ray diffraction analysis.     

A study of the structures of decomposing and non-decomposing [C4H5N]+˙ ions formed from different neutral species

[C₄H₅N]^+˙ ions have been generated from eleven neutral species. From a study of their metastable transitions and the translational energy released in the fragmentation in which C₂H₂ is lost, it is concluded that [C₄H₅N]^+˙ ions with sufficient energy to decompose do so from a common structure or mixture of structures when they are generated from crotonitrile, allyl cyanide, cyclopropyl cyanide, methacrylontrile, pyrrole, 2-, 3- and 4-hydroxypyridines and 2-aminopyridine. The [C₄H₅N]^+˙ ions formed from allyl isocyanide decompose from a different structure and those given by cyclopropyl isocyanide appear to decompose from a mixture of the two structures. Non-decomposing [C₄H₅N]^+˙ ions were investigated by means of their collision induced decomposition spectra using a B/E linked scan. Six different structures or mixtures of structures are suggested to explain these observations.     

Ligand‐to‐Ligand Charge‐Transfer Transitions of Platinum(II) Complexes with Arylacetylide Ligands with Different Chain Lengths: Spectroscopic Characterization,Effect of Molecular Conformations,and Density Functional Theory Calculations

The complexes [Pt(tBu₃tpy){C?C(C₆H₄C?C)_n?1R}]⁺ (n=1: R=alkyl and aryl (Ar); n=1–3: R=phenyl (Ph) or Ph‐N(CH₃)₂‐4; n=1 and 2, R=Ph‐NH₂‐4; tBu₃tpy=4,4’,4’’‐tri‐tert‐butyl‐2,2’:6’,2’’‐terpyridine) and [Pt(Cl₃tpy)(C?CR)]⁺ (R=tert‐butyl (tBu), Ph, 9,9’‐dibutylfluorene, 9,9’‐dibutyl‐7‐dimethyl‐amine‐fluorene; Cl₃tpy=4,4’,4’’‐trichloro‐2,2’:6’,2’’‐terpyridine) were prepared. The effects of substituent(s) on the terpyridine (tpy) and acetylide ligands and chain length of arylacetylide ligands on the absorption and emission spectra were examined. Resonance Raman (RR) spectra of [Pt(tBu₃tpy)(C?CR)]⁺ (R=n‐butyl, Ph, and C₆H₄‐OCH₃‐4) obtained in acetonitrile at 298 K reveal that the structural distortion of the C?C bond in the electronic excited state obtained by 502.9 nm excitation is substantially larger than that obtained by 416 nm excitation. Density functional theory (DFT) and time‐dependent DFT (TDDFT) calculations on [Pt(H₃tpy)(C?CR)]⁺ (R= n‐propyl (nPr), 2‐pyridyl (Py)), [Pt(H₃tpy){C?C(C₆H₄C?C)_n?1Ph}]⁺ (n=1–3), and [Pt(H₃tpy){C?C(C₆H₄C?C)_n?1C₆H₄‐N(CH₃)₂‐4}]⁺/+H⁺ (n=1–3; H₃tpy=nonsubstituted terpyridine) at two different conformations were performed, namely, with the phenyl rings of the arylacetylide ligands coplanar (“cop”) with and perpendicular (“per”) to the H₃tpy ligand. Combining the experimental data and calculated results, the two lowest energy absorption peak maxima, λ₁ and λ₂, of [Pt(Y₃tpy)(C?CR)]⁺ (Y=tBu or Cl, R=aryl) are attributed to ¹[π(C?CR)→π*(Y₃tpy)] in the “cop” conformation and mixed ¹[d_π(Pt)→π*(Y₃tpy)]/¹[π(C?CR)→π*(Y₃tpy)] transitions in the “per” conformation. The lowest energy absorption peak λ₁ for [Pt(tBu₃tpy){C?C(C₆H₄C?C)_n?1C₆H₄‐H‐4}]⁺ (n=1–3) shows a redshift with increasing chain length. However, for [Pt(tBu₃tpy){C?C(C6H4C?C)_n?1C₆H₄‐N(CH₃)₂‐4}]⁺ (n=1–3), λ₁ shows a blueshift with increasing chain length n, but shows a redshift after the addition of acid. The emissions of [Pt(Y₃tpy)(C?CR)]⁺ (Y=tBu or Cl) at 524–642 nm measured in dichloromethane at 298 K are assigned to the ³[π(C?CAr)→π*(Y₃tpy)] excited states and mixed ³[d_π(Pt)→π*(Y₃tpy)]/³[π(C?C)→π*(Y₃tpy)] excited states for R=aryl and alkyl groups, respectively. [Pt(tBu₃tpy){C?C(C₆H₄C?C)_n?1C₆H₄‐N(CH₃)₂‐4}]⁺ (n=1 and 2) are nonemissive, and this is attributed to the small energy gap between the singlet ground state (S₀) and the lowest triplet excited state (T₁).     

Synthesis and Structure of Lanthanide Sandwich Complexes with Mixed Cyclooctatetraenyl and Chelating Substituted‐indenyl Ligands

Two types of sandwich complexes (η⁵‐MeOCH₂CH₂C₉H₆) Ln (η⁸‐C₈H₈) (THF)_n [Ln=La (1), Nd(2), n=0; Sm(3), Dy (4) and Er (5). n = l] and (η⁵‐C₄H₇OCH₂C₉H₆)Ln(η⁸‐C₈H₈) (THF) [Ln = La (6), Nd(7). Sm(8). Dy (9) and Er (10)] were synthesized by the reactions of LnCl₃ with equivalent mole of K₂C₈H₈, followed by treatment with corresponding potassium salt of ether‐substituted indenide. The molecular structures of 3 and 8 were determined by single crystal X‐ray diffraction. (η⁵ ‐MeOCH₂CH₂C₉H₆) Sm (η⁸‐C₈H₈) (THF) (3) monoclinic. Pt₁/c, a = 1.4793(3) nm, b = 0.8716 (2) nm, c = 1.6149 (3) nm, β = 98. 17(3), V = 2.0612(7) nm³, Z = 4, R(F)=0.0362. (η⁵‐C₄H₇OCH₂C₉H₆)Sm(η⁸‐C₈H₈)(THF) (8) orthorhombic. p2₁2₁2₁. a = 0.8754(2) nm, b = 1.1000(2) nm, c = 2.3117 (5) nm, V = 2.2260(8) nm³, Z=4, R(F) =0.0497.     

Darstellung und Struktur der Zweikernigen tert-Butyliminovanadium(IV)-Komplexe [(μ?NtC4H9)2V2(CH2CMe3)2X2] (X = OtC4H9, CH2CMe3)

Synthesis and Molecular Structure of the Binuclear tert-Butyliminovanadium(IV) Complexes [(μ-N^tC₄H₉)₂V₂(CH₂CMe₃)₂X₂] (X = O^tC₄H₉, CH₂CMe₃) Syntheses of the neopentylvanadium(V) compounds ^tC₄H₉N?V(CH₂CMe₃)_3?n(O^tC₄H₉)_n (n = 0 ( 7 ), 1 ( 6 ), 2) are described. 6 and 7 decompose by irradiation splitting off neopentane and yielding the binuclear diamagnetic neopentylvanadium(IV) complexes [(μ-N^tC₄H₉)₂V₂(CH₂CMe₃)₂X₂] [X = O^tC₄H₉ ( 8 ), CH₂CMe₃ ( 11 )]. All compounds obtained are characterized by ¹H and ⁵¹V NMR spectroscopy. 8 has been found by X-ray diffraction analysis to be a binuclear complex with bridging tert-butylimino ligands and a vanadium—vanadium single bond. The complexes ^tC₄H₉N?V(CH₂C₆H₅)(O^tC₄H₉)₂ and [(μ-N^tC₄H₉)₂V₂(CH₂SiMe₃)₂(O^tC₄H₉)₂] ( 10 ) have been also prepared; the crystal structure of 8 and 10 are nearly identical.     

Kinetics and mechanism of silver(I) catalysed autoxidation of aqueous sulphur(IV) in acetate buffered medium

The kinetics of the silver(I) catalysed autoxidation of aqueous sulphur(IV) an acetate buffered medium obey the rate law: –d[S^IV]/dt = D[Ag^I][S^IV]²[H⁺]^–1/(B+C[S^IV]). The rate is independent of [O₂] but strongly inhibited by EtOH. A free radical mechanism is proposed.     

On the formation of anisole from phenoxyacetamides

A major fragmentation route of N-t-butyl-N-isopropyl-and N-ethylphenoxyacetamide is the formation of [C₇H₈O]⁺. Deuterium labeling implicates hydrogen transfer from nitrogen in all three species and from the t-butyl groups of the t-butylamide. The anisole structure is assigned to the [C₇H₈O]⁺· ion on the basis of its secondary fragmentation.     

CARBODIPHOSPHAN (2.4.6-tBu3C6H2[sbnd]P[dbnd]2)C: REAKTION MIT ELEKTROPHILEN

Abstract

The reaction of Ar[sbnd]P[dbnd]C[dbnd]P[sbnd]Ar (Ar=2.4.6-^tBu₃C₆H₂) with electrophiles (H⁺, S₈) proceeds at the phosphorus atom with subsequent cyclisation of an o-^tbutyl group.     

Thermal reactions of ethane-d6–acetylene and D2–acetylene mixtures behind shock waves

A study of the thermal decomposition of an acetylene–ethane-d₆ mixture indicates that the rate constant for hydrogen abstraction from acetylene by methyl is more than 20 times less than for abstraction from ethane. Isotopic exchange is initiated by a rapid reaction between product D atoms and C₂H₂. A series of experiments involving the reactions of a D₂–acetylene mixture indicated that a molecular exchange process was also occurring, and it was shown that d[C₂HD]/dt = k[D₂]^0.7[C₂H₂]^0.3, effective activation energy = 15.8 kcal/mol. This mechanism made an insignificant contribution to isotope exchange in C₂H₂–C₂D₆ mixtures.     

Gossypol clathrates: Structure and thermal behavior of the gossypol acridine complex

The natural compound gossypol forms a stable clathrate with acridine. The composition of the clathrate is C₃₀H₃₀O₈·0.5C₁₃H₉N. The unit cell is monoclinic, C2/c space group, a = 11.3213(3) ?, b = 30.5957(13) ?, c = 17.0824(4) ?, γ = 94.153(2)°, V = 5901.5(3) ?³, M = 1153.24, Z = 8, d _x = 1.369 g/cm³, and R = 0.0413 for 4726 reflections. The structure of the clathrate allows one to refer this compound to the ethyl acetate isomorphic host-guest group of gossypol complexes.     

Understanding the Subtleties of Frustrated Lewis Pair Activation of Carbonyl Compounds by N‐Heterocyclic Carbene/Alkyl Gallium Pairings

This study reports the use of the trisalkylgallium GaR₃ (R=CH₂SiMe₃), containing sterically demanding monosilyl groups, as an effective Lewis‐acid component for frustrated Lewis pair activation of carbonyl compounds, when combined with the bulky N‐heterocyclic carbene 1,3‐bis(tert‐butyl)imidazol‐2‐ylidene (ItBu) or 1,3‐bis(tert‐butyl)imidazolin‐2‐ylidene (SItBu). The reduction of aldehydes can be achieved by insertion into the C=O functionality at the C2 (so‐called normal) position of the carbene affording zwitterionic products [ItBuCH₂OGaR₃] ( 1 ) or [ItBuCH(p‐Br‐C₆H₄)OGaR₃] ( 2 ), or alternatively, at its abnormal (C4) site yielding [aItBuCH(p‐Br‐C₆H₄)OGaR₃] ( 3 ). As evidence of the cooperative behaviour of both components, ItBu and GaR₃, neither of them alone are able to activate any of the carbonyl‐containing substrates included in this study NMR spectroscopic studies of the new compounds point to complex equilibria involving the formation of kinetic and thermodynamic species as implicated through DFT calculations. Extension to ketones proved successful for electrophilic α,α,α‐trifluoroacetophenone, yielding [aItBuC(Ph)(CF₃)OGaR₃] ( 7 ). However, in the case of ketones and nitriles bearing acidic hydrogen atoms, C?H bond activation takes place preferentially, affording novel imidazolium gallate salts such as [{ItBuH}⁺{(p‐I‐C₆H₄)C(CH₂)OGaR₃}^?] ( 8 ) or [{ItBuH}⁺{Ph₂C=C=NGaR₃}^?] ( 12 ).     

Singlet-triplet splitting of divalent five-membered fused rings C<Subscript>12</Subscript>H<Subscript>8</Subscript>M (M = C,Si, Ge,Sn, and Pb): Application in nanocomplex synthesis

Energy differences, ΔX _s−t (X = E, H, and G) (ΔX _s−t = X(singlet) − X(triplet)) between singlet (s) and triplet (t) states of C₁₂H₈M were calculated at B3LYP/6-311+G*. The DFT calculations indicated that the ΔG _s−t between singlet (s) and triplet (t) states of C₁₂H₈M were increased from M = C to M = Pb. The ΔG _s−t of C₁₂H₈M was compared with its analogue C₄H₄M through replacement of heavy atoms from M = C to M = Pb. Configurations of the electrons in orbitals (σ² or π²) for the singlet state of C₁₂H₈M were discussed.     

Metastable ion decomposition and collisional activation mass spectra of 1,2,3-triarylpropen-1-ones

Substituents have been found to have a marked influence on the metastable ion decompositions and collisionally activated (CA) fragmentations of the M⁺˙ ion of a number of 1,2,3-triarylpropen-1-ones. An attempt has been made to confirm the structures of the rearrangement ions, [C₁₄H₁₀]⁺˙, [C₁₃H₁₁]⁺˙, [C₁₃H₉]⁺ and [C₁₂H₈]⁺˙ by comparison of their CA spectra with those of the corresponding ions produced from reference compounds. The results imply that [C₁₄H₁₀]⁺˙ and the M⁺˙ ions of phenanthrene and diphenylacetylene have a common structure, [C₁₃H₉]⁺ and the fluorenyl cation have a common structure and [C₁₂H₈]⁺˙ and biphenylene molecular ion have a common structure. The available data indicate that the ion at m/z 167 consists of a mixture of structures, likely possibilities being diphenylmethyl, phenyltropylium and dihydrofluorenyl cations.     

Polarographic Behavior of Bivalent Germanium in Alkaline Solution

Bivalent germanium was polarographically studied in sodium hydroxide solution at various concentrations. A well-defined reduction wave with half-wave potential varying from ?0.90 to ?0.98 volt vs. S.C.E. was observed for 1×10^?4 M Ge(II) in concentration range of 0.2 to 2.0 F with respect to NaOH, and from ?0.70 to ?0.88 volt vs. S.C.E. in the pH range 9.0–12.1 at 25°. The value of i_d/C is 5.43 μα/mM and that of i_d/C m^for t^1/8 is 5.21. Dependence of E_1/2 upon pH is expressed by —E_1/2 =0.18+0.058 pH. Experimental result suggests that the reaction proceeds in two-steps involving an irreversible two-electron reduction: Ge(OH)₂+OH^?→HGeO₂^?+H₂O and HGeO₂^?+H₂O+2e→Ge⁰+3OH^?.     

The Reactivity of Isomeric Nitrenium Lewis Acids with Phosphines,Carbenes, and Phosphide

Alkylation of spiro[fluorene-9,3’-indazole] at N(1) and N(2) with tBuCl affords the nitrenium cations [C₆H₄N₂(tBu)C(C₁₂H₈)][BF₄], 1 and 2 , respectively. Compound 1 converts to 2 over the temperature range 303–323 K with a free energy barrier of 28±5 kcal mol⁻¹. Reaction of 1 with PMe₃ afforded the N-bound phosphine adduct [C₆H₄N(tBu)N(PMe₃)C(C₁₂H₈)]BF₄] 3 . However, phosphines attack 2 at the para-carbon atom of the aryl group with concurrent cleavage of N(2)−C(1) bond and proton migration to C(1) affording [(R₃P)C₆H₃NN(tBu)CH(C₁₂H₈)][BF₄] (R=Me 4 , nBu 5 ). Analogous reactions of 1 and 2 with the carbene SIMes prompt attack at the para-carbon with concurrent loss of H^. affording the radical cation salts [(SIMes)C₆H₃N(tBu)NC(C₁₂H₈)^.][BF₄] 6 and [(SIMes)C₆H₃NN(tBu)C(C₁₂H₈)^.][BF₄] 7 , whereas reaction of 2 with BAC gives the Lewis acid-base adduct, [C₆H₄N(BAC)N(tBu)C(C₁₂H₈)][BF₄] 8 . Finally, reactions of 1 and 2 with KPPh₂ result in electron transfer affording (PPh₂)₂ and the persistent radicals C₆H₄N(tBu)NC(C₁₂H₈)^. and C₆H₄NN(tBu)C(C₁₂H₈)^.. The detailed reaction mechanisms are also explored by extensive DFT calculations.     

One-and two-dimensional silver-tetramethylpyrazine coordination polymers with uncoordinated anions: Synthesis and structure of [Ag(Me4Pyz)]PF6 and [Ag2(Me4Pyz)3](BF4)2·H2O

Coordination polymers [Ag(Me₄Pyz)] PF₆(I) and [Ag₂(Me₄Pyz)₃](BF₄)₂·H₂O (II) have been synthesized, and their structures have been determined. The crystals of I are monoclinic, space group C2/c, a = 9.440(2) ?, b = 10.587(2) ?, c = 13.165(3) ?, β= 107.19(3)°, V = 1257.0(5) ?³, d = 2.056 g/cm³, Z = 4. The crystals of II are monoclinic, space group P2₁/n, a = 13.062(3) ?, b = 12.259(2) ?, c = 18.996(4) ?, β = 97.73(3)°, V = 3014.1(11)?³, ρ = 1.798 g/cm³, Z = 4. The structure of I is built of linear polymeric cations [Ag(C₈H₁₂N₂)] _∞ ⁺ and octahedral anions [PF₆]⁻. Upon the interaction of tetramethylpyrazine molecule with Ag⁺ ions, intersecting polymeric chains [Ag(C₈H₁₂)] _∞ ⁺ (1D polymer) are formed extending in mutually perpendicular diagonal directions. The structure of II consists of layers (2D polymers) formed by fused sixmembered rings. These rings consist of Ag⁺ ions linked by bridging ligands Me₄Pyz. Original Russian Text ? Yu.V. Kokunov, Yu.E. Gorbunova, 2007, published in Zhurnal Neorganicheskoi Khimii, 2007, Vol. 52, No. 5, pp. 743–750.