Thermal hydrosilylation of olefin with hydrosilane. Preparative and mechanistic aspects

The reaction of trichlorosilane (1a) at 250 °C with cycloalkenes, such as cyclopentene (2a), cyclohexene (2b), cycloheptene (2c), and cyclooctene (2d), gave cycloalkyltrichlorosilanes [C_nH_2n−1SiCl₃: n = 5 (3a), 6 (3b), 7 (3c), 8 (3d)] within 6 h in excellent yields (97-98%), but the similar reactions using methyldichlorosilane (1b) instead of 1a required a longer reaction time of 40 h and afforded cycloalkyl(methyl)dichlorosilanes [C_nH_2n−1SiMeCl₂: n = 5 (3e), 6 (3f), 7 (3g), 8 (3h)] in 88-92% yields with 4-8% recovery of reactant 2. In large (2, 0.29 mol)-scale preparations, the reactions of 2a and 2b with 1a (0.58 mol) under the same condition gave 3a and 3b in 95% and 94% isolated yields, respectively. The relative reactivity of four hydrosilanes [HSiCl_3−mMe_m: m = 0-3] in the reaction with 2a indicates that as the number of chlorine-substituent(s) on the silicon increases the rate of the reaction decreases in the following order: n = 3 > 2 > 1 ? 0. In the reaction with 1a, the relative reactivity of four cycloalkenes (ring size = 5-8) decreases in the following order: 2d > 2a > 2c > 2b. Meanwhile linear alkenes like 1-hexene undergo two reactions of self-isomerization and hydrosilylation with hydrosilane to give a mixture of the three isomers (1-, 2-, and 3-silylated hexanes). In this reaction, the reactivity of the terminal 1-hexene is higher than the internal 2- and 3-hexene. The redistribution of hydrosilane 1 and the polymerization of olefin 2 occurred rarely under the thermal reaction condition.     

Substituted lithiumtrimethylsiloxysilanides LiSiRR′(OSiMe3) - Investigations of their synthesis, stability and reactivity

The reactions of the trimethylsiloxychlorosilanes (Me₃SiO)RR′SiCl (1a-h: R′ = Ph, 1a: R = H, 1b: R = Me, 1c: R = Et, 1d: R = ⁱPr, 1e: R = ^tBu, 1f: R = Ph, 1g: R = 2,4,6-Me₃C₆H₂ (Mes), 1h: R = 2,4,6-(Me₂CH)₃C₆H₂ (Tip); 1i: R = R′ = Mes) with lithium metal in tetrahydrofuran (THF) at −78 °C and in a mixture of THF/diethyl ether/n-pentane in a volume ratio 4:1:1 at −110 °C lead to mixtures of numerous compounds. Dependent on the substituents silyllithium derivatives (Me₃SiO)RR′SiLi (2b-i), Me₃SiO(RR′Si)₂Li (3a-g), Me₃SiRR′SiLi (4a-h), (LiO)RR′SiLi (12e, 12g-i), trisiloxanes (Me₃SiO)₂SiRR′ (5a-i) and trimethylsiloxydisilanes (6f^∗, 6h^∗, 6i^∗) are formed. All silyllithium compounds were trapped with Me₃SiCl or HMe₂SiCl resulting in the following products: (Me₃SiO)RR′SiSiMe₂R″ (6b-i: R″ = Me, 7c-i: R″ = H), Me₃SiO(RR′Si)₂SiMe₂R″ (8a-g: R″ = Me, 9a-g: R″ = H), Me₃SiRR′SiSiMe₂R″ (10a-h: R″ = Me, 11a-h: R″ = H) and (HMe₂SiO)RR′SiSiMe₂H (13e, 13g-i). The stability of trimethylsiloxysilyllithiums 2 depends on the substituents and on the temperature. (Me₃SiO)Mes₂SiLi (2i) is the most stable compound due to the high steric shielding of the silicon centre. The trimethylsiloxysilyllithiums 2a-g undergo partially self-condensation to afford the corresponding trimethylsiloxydisilanyllithiums Me₃SiO(RR′Si)₂Li (3a-g). (Me₃)Si-O bond cleavage was observed for 2e and 2g-i. The relatively stable trimethylsiloxysilyllithiums 2f, 2g and 2i react with n-butyllithium under nucleophilic butylation to give the n-butyl-substituted silyllithiums ⁿBuRR′SiLi (15g, 15f, 15i), which were trapped with Me₃SiCl. By reaction of 2g and 2i with 2,3-dimethylbuta-1,3-diene the corresponding 1,1-diarylsilacyclopentenes 17g and 17i are obtained.X-ray studies of 17g revealed a folded silacyclopentene ring with the silicon atom located 0.5 Å above the mean plane formed by the four carbon ring atoms.     

4-Chloro-5-methyl-3-diphenylphosphino-1-phenyl-1,2,3,6-tetrahydrophosphinine as a bidentate P-ligand in a cis chelate Pt(II) complex

Double deoxygenation of a 3-phosphinoxido-1,2,3,6-tetrahydrophosphine oxide (2) led to bisphosphine 3-2 with an inverted ring P atom. The reaction of bidentate P-ligand 3-2 with dichlorodibenzonitrilo platinum(II) yielded the mixture of a novel cis chelate complex (7 = PtCl₂(3-2)) and a cis bis(3-diphenylphosphino-1,2,3,6-tetrahydrophosphininyl) complex (8 = PtCl₂(η¹-5)₂) containing two units of monodentate P-ligand 5.     

Four-coordinate boron compounds derived from 2-(2-pyridyl)phenol ligand as novel hole-blocking materials for phosphorescent OLEDs

Four-coordinate boron compounds of Ph₂B · 1 (2) and (C₆F₅)₃B(1 · H) (3) were prepared from the reaction of 2-(2-pyridyl)phenol (1 · H) ligand with triarylborane starting materials, BPh₃ and B(C₆F₅)₃, respectively, and tested as hole-blocking layer (HBL) materials in phosphorescent OLEDs. While the crystal structure of 2 reveals the pseudo-tetrahedral geometry around the boron center with bidentate [N,O] chelation by 1, 3 is characterized as the zwitterionic four-coordinate system where the ligand 1 · H acts as monodentate [O] chelator with N-protonation. UV-Vis absorption and PL spectra of 2 and 3 are consistent with the ligand-centered, HOMO-LUMO electronic transitions with charge transfer from a phenoxide ring to a pyridine, which was further supported by time dependent DFT calculation for 2. Both compounds are found to possess the HOMO-LUMO energy gap of 3.1 eV appropriate for hole-blocking materials for phosphorescent OLEDs. The devices incorporating 2 and 3 as HBL materials displayed stable green phosphorescence of Ir(ppy)₃ (ppy = 2-phenylpyridine) with low turn-on voltage of 3.2 and 3.4 V, respectively, indicating that 2 and 3 function as HBL materials. Although both devices show the short lifetime (<1 h) probably owing to the low thermal stability, the device based on 2 displays better performances in terms of luminance, power and luminance efficiency, and external quantum efficiency in a wide range of current densities (0.1-100 mA/cm²) than the reference device incorporating BAlq as HBL materials.     

Synthesis, characterization and reactivity of tribenzylphosphine rhodium and iridium complexes

New rhodium and iridium complexes, with the formula [MCl(PBz₃)(cod)] [M = Rh (1), Ir (2)] and [M(PBz₃)₂(cod)]PF₆ [M = Rh (3), Ir (4)] (cod = 1,5-cyclooctadiene), stabilized by the tribenzylphosphine ligand (PBz₃) were synthesized and characterized by elemental analysis and spectroscopic methods. The molecular structures of 1 and 2 were determined by single-crystal X-ray diffraction. The addition of pyridine to a methanol solution of 1or 2, followed by metathetical reaction with NH₄PF₆, gave the corresponding derivatives [M(py)(PBz₃)(cod)]PF₆ [M = Rh (5), Ir (6)]. At room temperature in CHCl₃ solution, 4 converted spontaneously to the ortho-metallated complex [IrH(PBz₃)(cod){η²-P,C-(C₆H₄CH₂)PBz₂}]PF₆ (7) as a mixture of cis/trans isomers via intramolecular C-H activation of a benzylic phenyl ring. The reaction of 3 or 4 with hydrogen in coordinating solvents gave the dihydrido bis(solvento) derivative [M(H)₂(S)₂(PBz₃)₂]PF₆ (M = Rh, Ir; S = acetone, acetonitrile, THF), that transformed into the corresponding dicarbonyls [M(H)₂(CO)₂(PBz₃)₂]PF₆ by treatment with CO. Analogous cis-dihydrido complexes [M(H)₂(THF)₂(py)(PBz₃)₂]PF₆ (M = Rh, Ir) were observed by reaction of the py derivatives 5 and 6 with H₂.     

Synthesis and electrochemical properties of new cobalt and manganese phthalocyanine complexes tetra-substituted with 3,4-(methylendioxy)-phenoxy

The synthesis and electrochemical properties of new cobalt and manganese phthalocyanine complexes, tetra-substituted with 3,4-(methylendioxy)-phenoxy at the peripheral (complexes 3 and 5) and non-peripheral (complexes 4 and 6) positions, are reported. Complexes 3 and 4 showed Q-band absorption, in DMF, at 668 and 686 nm, respectively while Q-band due to complexes 5 and 6 appeared at 732 and 760 nm, respectively in CHCl₃. All the complexes showed well resolved redox processes attributed to both metal and ring based processes. Complexes 3 and 4 showed four redox processes, labeled I, II, III and IV. For complex 3, process I (Co^IPc⁻²/Co^IPc⁻³) was observed at −1.45 V, II (Co^IIPc⁻²/Co^IPc⁻²) at −0.38 V, III (Co^IIIPc⁻²/Co^IIPc⁻²) at +0.49 V and IV (Co^IIIPc⁻¹/Co^IIIPc⁻²) at +0.97 V versus Ag|AgCl. Similar processes were observed for complex 4 at −1.36 V, −0.27 V, +0.56 V, +1.03 V versus Ag|AgCl, respectively. Complexes 5 and 6 showed two redox processes (I and II). For complex 5, these processes appeared at −0.79 V (Mn^IIPc⁻²/Mn^IIPc⁻³, I) and −0.07 V versus Ag|AgCl (Mn^IIIPc⁻²/Mn^IIPc⁻², II), while for complex 6, they were observed at −0.86 V and −0.04 V versus Ag|AgCl. Spectroelectrochemistry was used to probe and confirm the origin of these processes.     

A combined experimental and theoretical study of metallic salts of thiapentadienyl, sulfinylpentadienyl and butadienesulfonyls

Alternative methods for the synthesis of the following acyclic salts (CH₂CHCHCHS)M [M = K, 1(K); Na, 1(Na); Li, 1(Li)], (CH₂CHCHCHSO)M [M = K, 2(K); Na, 2(Na)], (CH₂CHCHCHSO₂)M [M = K, 3(K); Na, 3(Na); Li, 3(Li)], (CH(Me)CHC(Me)CHSO₂)M [Me5-syn, M = K, 9(K); Na, 9(Na); Li, 9(Li), (CH(Me)CHCHC(Me)S)M [Me5-syn, M = K, 10(K); Na, 10(Na); Me5-anti, M = K, 11(K); Na, 11(Na)] are described, as a result of the activation of C-S bond in dihydrothiophenes by deprotonation with different bases. The effect of methyl substituents in the dihydrothiophenes is significant, which modifies considerably the choice of the base. The influence of the reaction conditions, type of solvent, base and dihydrothiophenes is analyzed. The NMR spectroscopy, including NOESY, ROESY and difference NOE establish the preferred U conformation for all derivatives, and support a delocalization of charge on the thiapentadienyl (1M) and sulfinylpentadienyl (2M) complexes. However, a conjugated diene structure is proposed on the butadienesulfonyl compounds (3M), in which the negative charge is delocalized in the SO₂ fragment and stabilized with the corresponding cations (M = K, Na and Li). In presence of traces of base, compounds 3M suffer a rearrangement, to the most stable S conformer, 13M. The stability of 3M depends on the size of the cation, the greater the size, the greater stability. Furthermore, a theoretical study shows that electronic and geometrical properties (energy conformers, charge distributions and relative stabilities) of the thiapentadienyl, sulfinylpentadienyl and butadienesulfonyl anions and their corresponding metal salts 1M-3M (M = Li, Na and K) shows to be in good agreement with the experimental findings.     

Synthesis and fluxional behaviour of new “heavy fluorous” cyclopentadienes

The new “heavy fluorous” cyclopentadienes C₅H_6−n[M(C₂H₄C₆F₁₃)₃]_n (M = Si, n = 1 (3); n = 2 (4) and M = Sn, n = 1 (10)) were synthesized by reaction of cyclopentadienyl lithium with BrSi(C₂H₄C₆F₁₃)₃ (2) or commercial BrSn(C₂H₄C₆F₁₃)₃. Fluorous cyclopentadienes prepared in this manner contain three or six C₆F₁₃ groups, which significantly increase their solubility in perfluorinated solvents. They also provide intermediates for titanium complexes suitable for fluorous biphase catalysis. All three isomers of silylcyclopentadienes 3 and 4 were identified and fully characterized by two dimensional NMR spectroscopy, which was performed at low temperature. The allylic isomers 3a and 4a undergo degenerate metallotropic rearrangement. This fluxional behaviour was compared with the behaviour of previously prepared cyclopentadienes 6 and 7 (C₅H_6−n[SiMe₂(C₂H₄C₈F₁₇)]_n where n = 1, 2, respectively). The presence of allylic isomers 6a and 7a was further confirmed by Diels-Alder cycloaddition of the strong dienophile tetracyanoethylene (TCNE), providing compounds 8 and 9.     

Effect of π-accepting substituent on the reactivity and spectroscopic characteristics of triarylbismuthanes and triarylbismuth dihalides

Competitive chlorination of p-substituted triarylbismuthanes 1 [(p-XC₆H₄)₃Bi; a: X = OMe, c: Cl, d: CO₂Et, e: CF₃, f: CN, g: NO₂] and trimesitylbismuthane (2,4,6-Me₃C₆H₂)₃Bi 1h by sulfuryl chloride was carried out against 1b (X = H) and the effect of these substituents on the formation of triarylbismuth dichlorides 2 was studied. The relative ratios 2/2b decreased with increasing electron-withdrawing ability of the substituents (2a/2b = 53/47, 2c/2b = 33/67, 2d/2b = 35/65, 2e/2b = 29/71, 2f/2b = 16/84, 2g/2b = 0/100, 2h/2b = 46/54), indicating a lowering of reactivity of the lone pair on the bismuth atom. Pd-Catalyzed degradation of 2a-g and their difluorides 3 giving biaryls 4 was promoted by the electron-withdrawing p-substituents in the equatorial aryl groups but suppressed by the more electronegative fluorine atoms in the apical positions. This is in fairly good accord with the stability of the trigonal bipyramidal geometry. The ¹³C NMR study of 1-3 showed that the signals due to the ipso carbons (C1) attached to the bismuth atom shift downfield with increasing electron-withdrawing nature of the p-substituents. No such tendency was observed in other aromatic ring carbons. The electronic effect on the C1 atoms, similar to that on the chlorination of 1 and degradation of 2 and 3, indicates the significant participation of the C1 atoms in these reactions through the Bi-C1 bonds.     

Carbonylation of four-membered ruthenium and osmium metallacycles incorporating an orthometallated phenolic function: New acylruthenium and arylosmium complexes

The solution reaction of Ru(QL¹)(PPh₃)₂(CO)Cl (3) and Os(QL¹)(PPh₃)₂(CO)Br (4) with carbon monoxide at one atmosphere pressure has respectively afforded the orange acylruthenium system Ru(QL²)(PPh₃)₂(CO)Cl (5) and the yellow arylosmium dicarbonyl system Os(QL³)(PPh₃)₂(CO)₂Br (6) in excellent yields. (QL¹ is C₆H₂O-2-CHNHC₆H₄Q(p)-3-Me-5, QL² is C₆H₂(CO-1)O-2-CHNHC₆H₄Q(p)-3-Me-5 and QL³ is C₆H₂OH-2-CHNC₆H₄Q(p)-3-Me-5 and Q is Me, OMe and Cl.) It is proposed that in the case of 3 a dicarbonyl complex similar to 6 is formed as an intermediate which rapidly undergoes aryl migration with concomitant phenolato coordination furnishing 5. The stability of 6 is consistent with the greatly diminished ability of osmium in promotion of migratory reactions. In the reaction 4 → 6 the Os-O(phenolato) bond is cleaved and the Schiff base moiety undergoes iminium-phenolato → imine-phenol tautomerization. The observed cis geometry of 6 may arise by a concerted route involving edge displacement of the halide ligand. The crystal and molecular structure of 5(Q = Cl) has revealed the presence of a distorted octahedral RuC₂P₂OCl coordination sphere and a highly planar acyl chelate ring characterized by a Ru-C distance of 2.013(4) Å. In the hydrogen bonded zwitterionic iminium-phenolato ring the N ? O distance is 2.561(6) Å. The acyl complexes of type 5 display an MLCT band near 500 nm which is absent in 6. The Schiff base CN stretch in 5 (∼1630 cm⁻¹) is significantly higher than that in 6 (∼1600 cm⁻¹) which displays two strong CO stretches near 2020 and 1940 cm⁻¹ (cis-Os(CO)₂ configuration). A single ³¹P NMR signal occurs in both 5 and 6 near 37 and −6 ppm, respectively (trans-M(PPh₃)₂ configuration). The voltammetric reduction potentials of the M^III/M^II couple is observed near 1.0 and 0.8 V vs. SCE in 5 and 6, respectively. Both are significantly higher than those in parent complexes (3 and 4) due to stabilization of the bivalent state upon carbonylation.     

Reactivity of 2,3-bis(2-pyridyl)pyrazine with [Re2(CO)8(CH3CN)2]: Molecular structures of [Re2(CO)8(C14H10N4)] and [Re2(CO)8(C14H10N4)Re2(CO)8]

The reaction of the labile compound [Re₂(CO)₈(CH₃CN)₂] with 2,3-bis(2-pyridyl)pyrazine in dichloromethane solution at reflux temperature afforded the structural dirhenium isomers [Re₂(CO)₈(C₁₄H₁₀N₄)] (1 and 2), and the complex [Re₂(CO)₈(C₁₄H₁₀N₄)Re₂(CO)₈] (3). In 1, the ligand is σ,σ′-N,N′-coordinated to a Re(CO)₃ fragment through pyridine and pyrazine to form a five-membered chelate ring. A seven-membered ring is obtained for isomer 2 by N-coordination of the 2-pyridyl groups while the pyrazine ring remains uncoordinated. For 2, isomers 2a and 2b are found in a dynamic equilibrium ratio [2a]/[2b]  =  7 in solution, detected by ¹H NMR (−50 °C, CD₃COCD₃), coalescence being observed above room temperature. The ligand in 3 behaves as an 8e-donor bridge bonding two Re(CO)₃ fragments through two (σ,σ′-N,N′) interactions. When the reaction was carried out in refluxing tetrahydrofuran, complex [Re₂(CO)₆(C₁₄H₁₀N₄)₂] (4) was obtained in addition to compounds 1-3. The dinuclear rhenium derivative 4 contains two units of the organic ligand σ,σ′-N,N′-coordinated in a chelate form to each rhenium core. The X-ray crystal structures for 1 and 3 are reported.     

Pyridine derived N-heterocyclic germylenes: A density functional perspective

Three novel germanimines, 2-, 3-, and 4-germapyridines (1, 2, and 3, respectively) along with their isomeric germylenes, are compared and contrasted at B3LYP/AUG-cc-pVTZ//B3LYP/6-31+G^∗ level of theory. From a thermodynamic viewpoint, two germylenes out of a total of eight singlet minima, 1H-2-germapyridine-2-ylidene (1a) and 1H-4-germapyridine-4-ylidene (3a), are found 29.2 and 15.4 kcal/mol more stable than their corresponding aromatic germapyridine isomers, respectively. Indeed, 1a is the global minimum on the potential energy surface of cyclic C₄NGeH₅ with a singlet-triplet energy gap larger than that of Herrmann’s germylene, i.e. 57.4 vs. 49.7 kcal/mol. From a kinetic viewpoint, the calculated energy barrier for 1,2-H shift of 1a to 1 is 70.8 kcal/mol compared to more prohibitive 92.5 kcal/mol for 1,4-H shift of 3a to 3. No GeGe doubly bonded minimum structure is found as dimer for 1a. The doubly bonded dimer of 3a is 11.2 kcal/mol less stable than its two separate monomers. This study signifies the thermodynamic and kinetic stabilities of divalent 1a and 3a hoping to prompt the experimental attentions toward them.     

Syntheses and structures of non-symmetric guanidinato zirconium and hafnium complexes and their catalytic behavior for ethylene polymerization

Equivalent addition reactions of PhN(Li)SiMe₃ to nitriles, RCN (R = dimethylamido, 1-piperidino), generated non-symmetric guanidinato lithium [(Et₂O)LiN(SiMe₃)C(NMe₂)N(Ph)]₂ (1) or [(THF)LiN(SiMe₃)C(NMe₂)N(Ph)]₂ (2) and [(Et₂O)LiN(SiMe₃)C(N(CH₂)₅)N(Ph)]₂ (5) which further reacted with zirconium or hafnium tetrachloride to form Zr and Hf guanidinato complexes with the general formula [PhNC(R)NSiMe₃]₃MCl (R = dimethylamido, M = Zr (3), Hf (4); R = 1-piperidino, M = Zr (6), Hf (7)). Complexes 1-4, 6 and 7 were well characterized by ¹H, ¹³C NMR and microanalysis, the single crystal X-ray diffraction analysis data for complexes 1, 3, 4 and 7 were also provided. Furthermore, complexes 3, 4, 6 and 7 were found to be active for ethylene polymerization. The influences of cocatalyst, pressure, reaction temperature and Al/M ratio on activity were investigated.     

Steric and electronic effects in stabilizing allyl-palladium complexes of “P-N-P” ligands, X2PN(Me)PX2 (X = OC6H5 or OC6H3Me2-2,6)

The chemistry of η³-allyl palladium complexes of the diphosphazane ligands, X₂PN(Me)PX₂ [X = OC₆H₅ (1) or OC₆H₃Me₂-2,6 (2)] has been investigated.The reactions of the phenoxy derivative, (PhO)₂PN(Me)P(OPh)₂ with [Pd(η³-1,3-R′,R″-C₃H₃)(μ-Cl)]₂ (R′ = R″ = H or Me; R′ = H, R″ = Me) give exclusively the palladium dimer, [Pd₂{μ-(PhO)₂PN(Me)P(OPh)₂}₂Cl₂] (3); however, the analogous reaction with [Pd(η³-1,3-R′,R″-C₃H₃)(μ-Cl)]₂ (R′ = R″ = Ph) gives the palladium dimer and the allyl palladium complex [Pd(η³-1,3-R′,R″-C₃H₃)(1)](PF₆) (R′ = R″ = Ph) (4). On the other hand, the 2,6-dimethylphenoxy substituted derivative 2 reacts with (allyl) palladium chloro dimers to give stable allyl palladium complexes, [Pd(η³-1,3-R′,R″-C₃H₃)(2)](PF₆) [R′ = R″ = H (5), Me (7) or Ph (8); R′ = H, R″ = Me (6)].Detailed NMR studies reveal that the complexes 6 and 7 exist as a mixture of isomers in solution; the relatively less favourable isomer, anti-[Pd(η³-1-Me-C₃H₄)(2)](PF₆) (6b) and syn/anti-[Pd(η³-1,3-Me₂-C₃H₃)(2)](PF₆) (7b) are present to the extent of 25% and 40%, respectively. This result can be explained on the basis of the steric congestion around the donor phosphorus atoms in 2. The structures of four complexes (4, 5, 7a and 8) have been determined by X-ray crystallography; only one isomer is observed in the solid state in each case.     

Heterocyclic thioamides of copper(I): Synthesis and crystal structures of copper complexes with 1,3-imidazoline-2-thiones in the presence of triphenyl phosphine

Reaction of copper(I) chloride with 1,3-imidazoline-2-thione (imzSH) in the presence of Ph₃P in 1:2:2 or 1:1:2 (M:L:PPh₃) molar ratios yielded a compound of unusual composition, [Cu₂(imzSH)(PPh₃)₄Cl₂] · CH₃OH (1), whose X-ray crystallography has shown that its crystals consist of four coordinated [CuCl(1κS-imzSH)(PPh₃)₂] (1a), and three coordinated [Cu(PPh₃)₂Cl] (1b) independent molecules in the same unit cell. In contrast, crystals of complexes of copper(I) bromide/iodide are formed by single molecules of [CuBr(1κS-imzSH)(PPh₃)₂] · H₂O (2) and [CuI(1κS-imzSH)(PPh₃)₂] (3), respectively, similar to molecule 1a. The related ligand, 1,3-benzimidazoline-2-thione (bzimSH) formed a complex [CuBr(1κS-bzimSH)(PPh₃)₂] · CH₃COCH₃ (4), similar to 2. The formation of 1a and 1b has been also revealed by NMR spectroscopy. The NMR spectra of 2–4 also showed weak signals indicating formation of compounds similar to 1b. It reveals that the lability of the Cu–S bond varies in the order: Cl ? Br ∼ I. Weak interactions {e.g. C–H?π electrons of ring, –NH?halogens/oxygen, C–H?halogens/oxygen, π?π (between rings)} have played an important role in building 2D chains of complexes 1–4.     

Cationoid rearrangements in reactions of perfluoro-1-arylbenzocyclobutenes with antimony pentafluoride

In the presence of antimony pentafluoride at 130 °C, the four-membered ring of perfluoro-1-(2-ethylphenyl)benzocyclobutene (2) undergoes cleavage, forming perfluoro-2-ethyl-2′-methyldiphenylmethane (5). Compound 5 is converted, under the action of SbF₅ at 170 °C, to perfluoro-8,9-dimethyl-1,2,3,4-tetrahydrofluorene (8). Perfluoro-1-(4-ethylphenyl)benzocyclobutene (3) remains unchanged at 130 °C, whereas at 170 °C it gives a mixture of perfluorinated 4′-ethyl-2-methyldiphenylmethane (9), 6-ethyl-1,2,3,4-tetrahydroanthracene (11) and 2-ethyl-9,10-dihydroanthracene (12). When heated with SbF₅ at 170 °C, perfluoro-1-phenylbenzocyclobutene (1) remains unchanged. Solution of compounds 2, 3, 5 and 9 in SbF₅-SO₂ClF generated the perfluorinated 1-(2-ethylphenyl)-1-benzocyclobutenyl (29), 1-(4-ethylphenyl)-1-benzocyclobutenyl (30), 2-ethyl-2′-methyldiphenylmethyl (31) and 4′-ethyl-2-methyldiphenylmethyl (32) cations, respectively.     

Quantum chemical study of ethylene addition to group-7 oxo complexes MO2(CH3)(CH2) (M = Mn, Tc, Re)

Quantum chemical calculations using DFT at the B3LYP level have been carried out for the reaction of ethylene with the group-7 compounds ReO₂(CH₃)(CH₂) (Re1), TcO₂(CH₃)(CH₂) (Tc1) and MnO₂(CH₃)(CH₂) (Mn1). The calculations suggest rather complex scenarios with numerous pathways, where the initial compounds Re1-Mn1 may either engage in cycloaddition reactions or numerous addition reactions with concomitant hydrogen migration. There are also energetically low-lying rearrangements of the starting compounds to isomers which may react with ethylene yielding further products. The [2 + 2]_Re,C cycloaddition reaction of the starting molecule Re1 is kinetically and thermodynamically favored over the [3 + 2]_C,O and [3 + 2]_O,O cycloadditions. However, the reaction which leads to the most stable product takes place with initial rearrangement to the dioxohydridometallacyclopropane isomer Re1a that adds ethylene with concomitant hydrogen migration yielding Re1a-1. The latter reaction has a slightly higher barrier than the [2 + 2]_Re,C cycloaddition reaction. The direct [3 + 2]_C,O cycloaddition becomes more favorable than the [2 + 2]_M,C reaction for the starting compounds Tc1 and Mn1 of the lighter metals technetium and manganese but the calculations predict that other reactions are kinetically and thermodynamically more favorable than the cycloadditions. The reactions with the lowest activation barriers lead after rearrangement to the ethyl substituted dioxometallacyclopropanes Tc1a-1 and Mn1a-1. The manganese compound exhibits an even more complex reaction scenario than the technetium compounds. The thermodynamically most stable final product of ethylene addition to Mn1 is the ethoxy substituted metallacyclopropane Mn1a-2 which has, however, a high activation barrier.     

Iron(0) and ruthenium(0) complexes with tridentate phosphonite ligands and their potential for ketene formation from methyl iodide, CO and a base

An efficient route to the novel tridentate phosphine ligands RP[CH₂CH₂CH₂P(OR′)₂]₂ (I: R = Ph; R′ = i-Pr; II: R = Cy; R′ = i-Pr; III: R = Ph; R′ = Me and IV: R = Cy; R′ = Me) has been developed. The corresponding ruthenium and iron dicarbonyl complexes M(triphos)(CO)₂ (1: M = Ru; triphos = I; 2: M = Ru; triphos = II; 3: M = Ru; triphos = III; 4: M = Ru; triphos = IV; 5: M = Fe; triphos = I; 6: M = Fe; triphos = II; 7: M = Fe; triphos = III and 8: M = Fe; triphos = IV) have been prepared and fully characterized. The structures of 1, 3 and 5 have been established by X-ray diffraction studies. The oxidative addition of MeI to 1-8 produces a mixture of the corresponding isomeric octahedral cationic complexes mer,trans-(13a-20a) and mer,cis-[M(Me)(triphos)(CO)₂]I (13b-20b) (M = Ru, Fe; triphos = I-IV). The structures of 13a and 20a (as the tetraphenylborate salt (21)) have been verified by X-ray diffraction studies. The oxidative addition of other alkyl iodides (EtI, i-PrI and n-PrI) to 1-8 did not afford the corresponding alkyl metal complexes and rather the cationic octahedral iodo complexes mer,cis-[M(I)(triphos)(CO)₂]I (22-29) (M = Ru, Fe; triphos = I-IV) were produced. Complexes 22-29 could also be obtained by the addition of a stoichiometric amount of I₂ to 1-8. The structure of 22 has been verified by an X-ray diffraction study. Reaction of 13a/b-20a/b with CO afforded the acetyl complexes mer,trans-[M(COMe)(triphos)(CO)₂]I, 30-37, respectively (M = Ru, Fe; triphos = I-IV). The ruthenium acetyl complexes 30-33 reacted slowly with 2-tert-butylimino-2-diethylamino-1,3-dimethylperhydro-1,3,2-diazaphosphorine (BEMP) even in boiling acetonitrile. Under the same conditions, the deprotonation reactions of the iron acetyl complexes 34-37 were completed within 24-40 h to afford the corresponding zero valent complexes 5-8. It was not possible to observe the intermediate ketene complexes. Tracing of the released ketene was attempted by deprotonation studies on the labelled species mer,trans-[Fe(COCD₃)(triphos)(CO)₂]I (38) and mer,trans-[Fe(¹³COMe)(triphos)(CO)₂]I (39).     

Synthesis,structure and properties of [ML(NO3)2]: M = Co,Ni, Cu; L = N-(2-pyridylethyl)pyridine-2-carbaldimine

Syntheses of complexes of the type [ML(NO₃)₂], where M = Co(II), Ni(II), and Cu(II), L = N-(2-pyridylethyl)pyridine-2-carbaldimine, a tridentate ligand, are described. They were characterized by elemental analysis, spectral, magnetic, thermal studies, and X-ray crystallography. In the cobalt (1), nickel (2), and copper (3) complexes, the bivalent metal ion is coordinated by the three nitrogen atoms of the tridentate L with two pyridine-N groups occupying trans positions. Amongst the two nitrates one coordinates in a bidentate fashion while the other adopts a monodentate fashion. The X-band EPR spectra of 1, 2, and 3 in the polycrystalline state and in acetonitrile solution at 77 K are reported. Room temperature vibrating sample magnetometer data of 1, 2, and 3 afforded μ_eff values respectively of 3.928, 3.897, and 1.952 BM. The thermal stability order is 1 > 2 > 3, showing a reverse Irving-Williams trend.     

Influence of sterically non-hindering methyl groups on adsorption properties of two classical zinc and copper MOF types

The metal-organic frameworks (three-dimensional porous coordination polymers) [Zn₄O(Me₄BPDC)₃] × 9 DMF, 2 · 9 DMF and [Cu₂(Me₄BPDC)₂] × 9 DMF, 3 · 9 DMF are representatives of the classical Zn-IRMOF series and Cu paddle-wheel complexes with H₂Me₄BPDC = 2,2′,6,6′-tetramethyl-4,4′-biphenyldicarboxylic acid, 1. The dicarboxylate linker of 1 is a representative of the non-planar biphenyl ligand family, known as an efficient scaffold for chiral molecules. There is a 90° twist angle between the phenyl rings in 1, dictated by the methyl groups, which leads to assembly of doubly interpenetrated pcu-a (in 2) and nbo-a (in 3) nets under low temperature solvothermal conditions in dimethylformamide (DMF). Activation by degassing (to yield 2), exchange with methanol or tetrahydrofuran and subsequent evacuation at elevated temperatures (to yield 3^I) gave materials with BET surface areas of 1735 m²/g (2) and 1041 m²/g (3^I). Adsorbed quantities of H₂ were 1.26 wt% (2) and 1.02 wt% (3^I) (77 K, 1 bar), CO₂ 30.8 cm³/g (2) and 50 cm³/g (3^I) (273 K, 1 bar) and CH₄ 12.9 cm³/g (2) and 11.4 cm³/g (3^I) (273 K, 1 bar). The H₂ and CO₂ sorption values for 2 are similar to those of MOF-5 (IRMOF-1) with its almost doubled BET surface area. An increase is found concerning the adsorbed amounts of N₂, H₂, and CO₂ for 3^I compared to related doubly interpenetrated nbo-a-type MOF-601, MOF-602, MOF-603 ([Cu₂L₂] with L = 2,2′-R₂-4,4′-biphenyldicarboxylate, R = CN, Me, I, respectively).