Syntheses and structures of [Me2Si{As(PBu)3}2] and [(CyP)3SiMe2] (Cy = cyclohexyl, C6H11)

The reaction of the anion [(^tBuP)₃As]⁻ (1) with Me₂SiCl₂ results in nucleophilic substitution of the Cl⁻ anions, giving the di- and mono-substituted products [Me₂Si{As(P^tBu)₃}₂] (3a) and [Me₂Si(Cl){As(P^tBu)₃}] (3b). Analogous reactions of the pre-isolated [(CyP)₄As]⁻ anion (2) (Cy = cyclohexyl) with Me₂SiCl₂ produced mixtures of products, from which no pure materials could be isolated. However, reaction of 2 [generated in situ from CyPHLi and As(NMe₂)₃] gives the heterocycle [(CyP)₃SiMe₂] (4). The X-ray structures of 3a and 4 are reported.     

Synthesis, characterization, and catalytic activity of divalent organolanthanide complexes with new tetrahydro-2H-pyranyl-functionlized indenyl ligands

Two series of new divalent organolanthanide complexes with the general formula [η⁵:η¹-{1-R-3-(C₅H₉OCH₂)C₉H₅}]₂Ln^II (R = H, Ln = Yb (3); R = Me₃Si, Ln = Yb (4); R = H, Ln = Eu (5); R = Me₃Si, Ln = Eu (6)) were prepared by reactions of 2 equiv. of 1-R-3-(C₅H₉OCH₂)C₉H₆ (R = H (1), R = Me₃Si (2)) with the lanthanide(III) amides [(Me₃Si)₂N]₃Ln(μ-Cl)Li(THF)₃ (Ln = Yb, Eu) via a one-electron reductive elimination process. Recrystallization of 6 from n-hexane afforded [η⁵:η¹-(C₅H₉OCH₂C₉H₅SiMe₃)]₂Eu^II · (C₆H₁₄)_0.5 (7). All compounds were fully characterized by elemental analyses, and spectroscopic methods. The structures of complexes 4 and 7 were additionally determined by single-crystal X-ray analyses. The catalytic activity of the complexes on methyl methacrylate and ε-caprolactone polymerization was studied, and the temperatures, substituents on the indenyl ring, and solvents effects on the catalytic activity of the complexes were examined.     

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.     

Synthesis, characterization and molecular structure of the [(η-C6Me6)Ru(μ-N3)(N3)]2 complex and its reactions with some monodentate ligands

The reaction of complex [(η⁶-C₆Me₆)Ru(μ-Cl)Cl]₂ (1) with sodium azide yielded complexes of the composition [(η⁶-C₆Me₆)Ru(μ-N₃)(N₃)]₂ (2) and [(η⁶-C₆Me₆)Ru(μ-N₃)(Cl)]₂ (3), depending upon the reaction conditions. Complex 3 with excess of sodium azide in ethanol yielded complex 2. Complexes 2 and 3 undergo substitution reactions with monodentate ligands such as PPh₃, PMe₂Ph and AsPh₃ to yield monomeric complexes. The structure of complex 2 was determined by X-ray crystallography. All these complexes were characterized by micro analytical data and by FT-IR and FT-NMR spectroscopy. Complex 2 crystallizes in the monoclinic space group P2₁/n with a = 8.5370(11) Å, b = 16.192(2) Å, c = 10.4535(13) Å and β = 110.877(2)°.     

Syntheses and characterization of η-hexamethylbenzeneruthenium(II)-β-diketone complexes: their reactions with mono- and bidentate neutral ligands

The complex [(η⁶-C₆Me₆)Ru(μ-Cl)Cl]₂1 react with sodium salts of β-diketonato ligands in methanol to afford the oxygen bonded neutral complexes of the type [(η⁶-C₆Me₆)Ru(κ²-O,O′-R¹COCHCOR²)Cl] {R¹, R² = CH₃ (2), CH₃, C₆H₅ (3), C₆H₅ (4), OCH₃ (5), OC₂H₅ (6)}. Complex 4 with AgBF₄ yields the γ-carbon bonded ruthenium dimeric complex 7. Complex 4 also reacts with tertiary phosphines and bridging ligands to yield complexes of the type [(η⁶-C₆Me₆)Ru(κ²-O,O′-C₆H₅COCHCOC₆H₅)(L)]⁺ (L = PPh₃ (8), PMe₂Ph (9)) and [{η⁶-C₆Me₆)Ru(κ²-O,O′-C₆H₅COCHCOC₆H₅)}₂(μ-L)] L = 4,4′-bipyridine (4,4′-bipy) (11), 1,4-dicyanobenzene (DCB) (12) and pyrazine (Pz) (13). Complexes 2-4 react with sodium azide to yield neutral complexes [(η⁶-C₆Me₆)Ru(κ²-O,O′-R¹COCHCOR²)N₃] {R¹, R² = CH₃ (10a), CH₃, C₆H₅ (10b), C₆H₅ (10c). All these complexes were characterized by FT-IR and FT-NMR spectroscopy as well as analytical data. The molecular structures of complexes [(η⁶-C₆Me₆)Ru(κ²-O,O′CH₃COCH-COC₆H₅)Cl] (3) and [(η⁶-C₆Me₆)Ru(κ²-O,O′-C₆H₅COCHCOC₆H₅] (4) were established by single crystal X-ray diffraction studies. The complex 3 crystallizes in the triclinic space group, [a = 7.9517(4), b = 9.0582(4) and c = 14.2373(8) Å, α = 88.442(3)°, β = 76.6.8(3)° and γ = 81.715(3)°. V = 987.17(9) ų, Z = 2]. Complex 4 crystallizes in the monoclinic space group, P2₁/c [a = 7.5894(8), b = 20.708(2) and c = 29.208(3) Å,β = 92.059(3)° V = 4587.5(9) ų, Z = 8].     

Arene ruthenium β-diketonato triazolato derivatives: Synthesis and spectral studies (β-diketones: 1-phenyl-3-methyl-4-benzoyl pyrazol-5-one, acetylacetone derivatives)

Mononuclear neutral arene ruthenium(II) β-diketonato complexes of the general formula (η⁶-arene)Ru(LL)Cl [LL = 1-phenyl-3-methyl-4-benzoyl pyrazol-5-one (L1), arene = C₆H₆ (1), p-ⁱPrC₆H₄Me (2), C₆Me₆ (3); arene = p-ⁱPrC₆H₄Me, LL = 1-benzoylacetone (L3) (8); arene = p-ⁱPrC₆H₄Me, LL = dibenzoylmethane (L4) (9)] have been synthesized and their subsequent substitution reactions with NaN₃ in alcohol at room temperature yielded the corresponding neutral terminal azido complexes (η⁶-arene)Ru(LL)N₃ [LL = 1-phenyl-3-methyl-4-benzoyl pyrazol-5-one (L1), arene = C₆H₆ (4), p-ⁱPrC₆H₄Me (6), C₆Me₆ (7); arene = p-ⁱPrC₆H₄Me, LL = dibenzoylmethane (L4) (10)] as well as a cationic complex [(η⁶-p-ⁱPrC₆H₄Me)Ru(L4) (PPh₃)]BF₄ (12) with PPh₃. The [3 + 2] cycloaddition reaction of selective azido complexes with the activated alkynes dimethyl and diethyl acetylenedicarboxylates produced the arene triazolato complexes [(η⁶-arene)Ru(LL){N₃C₂(CO₂R)₂}] [arene = p-ⁱPrC₆H₄Me, LL = L1, R = Me (13); arene = C₆Me₆, LL = L1, R = Me (14); arene = C₆Me₆, LL = acetyl acetone (L2), R = Me (15); arene = C₆Me₆, LL = L3, R = Me (16); arene = p-ⁱPrC₆H₄Me, LL = L1, R = Et (17); arene = C₆Me₆, LL = L1, R = Et (18); arene = C₆Me₆, LL = L2, R = Et (19); arene = C₆Me₆, LL = L3, R = Et (20)]. With fumaronitrile the reaction yielded the triazoles [(η⁶-arene)Ru(LL)(N₃C₂HCN)] [arene = p-ⁱPrC₆H₄Me, LL = L1 (21), arene = C₆Me₆, LL = L1 (22), arene = C₆Me₆, LL = L2 (23), arene = C₆Me₆, LL = L3 (24)]. In the above triazolato complexes only N(2) isomer was obtained. The complexes were characterized on the basis of spectroscopic data. Crystal structure of representatives complexes were determined by single crystal X-ray diffraction.     

Self-assembly of organooxotin(IV) clusters with Schiff-base-containing-triazole from hydrolysis or solvothermal synthesis: Crystal structures, hydrogen bonds, C-H?π stacking and S?S interaction

Eight new organostannoxane-based multiredox assemblies containing-Schiff-base-triazole ligand peripheries have been readily synthesized by hydrolysis or solvothermal synthetic routes. The reactions of the diorganotin dichloride with the Schiff-base-containing-triazole ligand afford the following types: [(Me₂Sn)₂O₂(Ln)]₂ (n = 1, for 1) [(Me₂Sn)₂O(RO)(Ln)]₂ (R = Et, n = 2, for 2; R = Me, n = 3, for 3), [(n-Bu₂Sn)₂O₂(Ln)]₂ (n = 1, for 4; n = 2, for 5; n = 3, for 6) and [(Me₂Sn)₂Ln₂O]₂ · L (n = 2; L = H₂O for 7, L = CH₃OH for 8). All the complexes were characterized by elemental analysis, IR, ¹H, ¹³C and ¹¹⁹Sn spectra analyses. Except for complexes 4 and 6, the other complexes are also characterized by X-ray crystallography diffraction analyses. Complexes 1-3 and 5 show similar structures containing a Sn₄O₄ ladder-shaped skeleton in which the N atom from a corresponding thione-form deprotonated Schiff base coordinated to the exo tin atoms in monodentate chelating agent. Complex 7 and 8 show a novel framework containing a Sn₂O₂ symmetrical core with two N atoms from triazole moiety coordinated to tin atoms. Weak but significant intermolecular hydrogen bondings, C-H?π stacking or non-bonded S?S interaction lead to aggregation and self-assembly of these complexes into 1D, 2D or 3D supramolecular frameworks.     

Reactions of trimethylsiloxychlorosilanes with lithium metal - On the mechanism of the formation of trimethylsiloxysilyllithium compounds LiSiRR’(OSiMe3)

The reaction pathway for the formation of the trimethylsiloxysilyllithium compounds (Me₃SiO)RR′SiLi (2a: R = Et, 2b: R = ⁱPr, 2c: R = 2,4,6-Me₃C₆H₂ (Mes); 2a-c: R′ = Ph; 2d: R = R′ = Mes) starting from the conversion of the corresponding trimethylsiloxychlorosilanes (Me₃SiO)RR′SiCl (1a-d) in the presence of excess lithium in a mixture of THF/diethyl ether/n-pentane at −110 °C was investigated.The trimethylsiloxychlorosilanes (Me₃SiO)RPhSiCl (1a: R = Et, 1b: R = ⁱPr, 1c: R = Mes) react with lithium to give initially the trimethylsiloxysilyllithium compounds (Me₃SiO)RPhSiLi (2a-c). These siloxysilyllithiums 2 couple partially with more trimethylsiloxychlorosilanes 1 to produce the siloxydisilanes (Me₃SiO)RPhSi-SiPhR(OSiMe₃) (Ia-c), and they undergo bimolecular self-condensation affording the trimethylsiloxydisilanyllithium compounds (Me₃SiO)RPhSi-RPhSiLi (3a-c). The siloxydisilanes I are cleaved by excess of lithium to give the trimethylsiloxysilyllithiums (Me₃SiO)RPhSiLi (2). In the case of the two trimethylsiloxydisilanyllithiums (Me₃SiO)RPhSi-RPhSiLi (3a: R = Et, 3b: R = ⁱPr) a reaction with more trimethylsiloxychlorosilanes (Me₃SiO)RPhSiCl (1a, 1b) takes place under formation of siloxytrisilanes (Me₃SiO)RPhSi-RPhSi-SiPhR(OSiMe₃) (IIa: R = Et, IIb: R = ⁱPr) which are cleaved by lithium to yield the trimethylsiloxysilyllithiums (Me₃SiO)RPhSiLi (2a, 2b) and the trimethylsiloxydisilanyllithiums (Me₃SiO)RPhSi-RPhSiLi (3a, 3b). The dimesityl-trimethylsiloxy-silyllithium (Me₃SiO)Mes₂SiLi (2d) was obtained directly by reaction of the trimethylsiloxychlorosilane (Me₃SiO)Mes₂SiCl (1d) and lithium without formation of the siloxydisilane intermediate. Both silyllithium compounds 2 and 3 were trapped with HMe₂SiCl giving the products (Me₃SiO)RR′Si-SiMe₂H and (Me₃SiO)RPhSi-RPhSi-SiMe₂H.     

Synthesis of neutral and cationic monocyclopentadienyl alkyl niobium and tantalum complexes

Compound [NbCp′Me₄] (Cp′ = η⁵-C₅H₄SiMe₃, 1) reacted with several ROH compounds (R = tBu, SiiPr₃, 2,6-Me₂C₆H₃) to give the derivatives [NbCp′Me₃(OR)] (R = tBu 2a, SiiPr₃2b, 2,6-Me₂C₆H₃2c). The diaryloxo tantalum compound [TaCp^∗Me₂(OR)₂] (Cp^∗ = η⁵-C₅Me₅, R = 2,6-Me₂C₆H₃3) was obtained by reaction of [TaCp^∗Cl₂Me₂] with 2 equiv of LiOR (R = 2,6-Me₂C₆H₃). Abstraction of one methyl group from these neutral compounds 1-3 with the Lewis acids E(C₆F₅)₃ (E = B, Al) gave the ionic derivatives [NbCp′Me₂X][MeE(C₆F₅)₃] (X = Me 4-E. X = OR; R = SiiPr₃5b-E, 2,6-Me₂C₆H₃5c-E. E = B, Al) and [TaCp^∗Me(OR)₂][MeE(C₆F₅)₃] (R = 2,6-Me₂C₆H₃6-E; E = B, Al). Polymerization of MMA with the aryloxoniobium compound 2c and Al(C₆F₅)₃ gave syndiotactic PMMA in a low yield, whereas the tetramethylniobium compound 1 and the diaryloxotantalum derivative 3 were inactive.     

Mono and dinuclear half-sandwich platinum group metal complexes bearing pyrazolyl-pyrimidine ligands: Syntheses and structural studies

Reactions of 0.5 eq. of the dinuclear complexes [(η⁶-arene)Ru(μ-Cl)Cl]₂ (arene = η⁶-C₆H₆, η⁶-p-ⁱPrC₆H₄Me) and [(Cp∗)M(μ-Cl)Cl]₂ (M = Rh, Ir; Cp∗ = η⁵-C₅Me₅) with 4,6-disubstituted pyrazolyl-pyrimidine ligands (L) viz. 4,6-bis(pyrazolyl)pyrimidine (L1), 4,6-bis(3-methyl-pyrazolyl)pyrimidine (L2), 4,6-bis(3,5-dimethyl-pyrazolyl)pyrimidine (L3) lead to the formation of the cationic mononuclear complexes [(η⁶-C₆H₆)Ru(L)Cl]⁺ (L = L1, 1; L2, 2; L3, 3), [(η⁶-p-ⁱPrC₆H₄Me)Ru(L)Cl]⁺ (L = L1, 4; L2, 5; L3, 6), [(Cp∗)Rh(L)Cl]⁺ (L = L1, 7; L2, 8; L3, 9) and [(Cp∗)Ir(L)Cl]⁺ (L = L1, 10; L2, 11; L3, 12), while reactions with 1.0 eq. of the dinuclear complexes [(η⁶-arene)Ru(μ-Cl)Cl]₂ and [(Cp∗)M(μ-Cl)Cl]₂ give rise to the dicationic dinuclear complexes [{(η⁶-C₆H₆)RuCl}₂(L)]²⁺ (L = L1, 13; L2, 14; L3, 15), [{(η⁶-p-ⁱPrC₆H₄Me)RuCl}₂(L)]²⁺ (L = L1, 16; L2, 17; L3, 18), [{(Cp∗)RhCl}₂(L)]²⁺ (L = L1, 19; L2, 20; L3, 21) and [{(Cp∗)IrCl}₂(L)]²⁺ (L = L1 22; L2, 23; L3 24). The molecular structures of [3]PF₆, [6]PF₆, [7]PF₆ and [18](PF₆)₂ have been established by single crystal X-ray structure analysis.     

Synthesis of new chloro methyl niobium and tantalum complexes with silyl-cyclopentadienyl ligands: X-ray crystal structure of [Ta{η-C5H3(SiMe3)2}Cl2Me2]

Trichloro methyl [Nb{η⁵-C₅H₃(SiXMe₂)(SiMe₃)}Cl₃Me] (X = Cl, 2; Me, 3), dichloro dimethyl [Nb{η⁵-C₅H₃(SiXMe₂)(SiMe₃)}Cl₂Me₂] (X = Cl, 4; Me, 5) and tetramethyl [Nb{η⁵-C₅H₃(SiXMe₂)(SiMe₃)}Me₄] (X = Me, 6; Cl, 7) niobium complexes were synthesized by treatment of starting tetrachloro derivatives [Nb{η⁵-C₅H₃(SiXMe₂)(SiMe₃)}Cl₄] (X = Cl, 1a; Me, 1b) with dimethyl zinc or chloro methyl magnesium in different proportions and conditions. A mixture of trichloro methyl and dichloro dimethyl tantalum complexes [Ta{η⁵-C₅H₃(SiClMe₂)(SiMe₃)}Cl_4−xMe_x] (x = 1, 8; 2, 9) in a 2:1 molar ratio was obtained in the reaction of [Ta{η⁵-C₅H₃(SiClMe₂)(SiMe₃)}Cl₄] (1c) with 0.5 equivalents of ZnMe₂ in toluene at low temperature. 8 could be isolated as single compound when 1 equivalent of 1c was added to the mixtures of 8 and 9, while the reaction of 1c with 1.5 equivalents of dimethyl zinc gave 9 as unitary product. However, [Ta{η⁵-C₅H₃(SiMe₃)₂}Cl₄] (1d) reacts with 0.5 equivalents of alkylating reagent giving the trichloro methyl compound [Ta{η⁵-C₅H₃(SiMe₃)₂}Cl₃Me] (10) in good yield. On the other hand, [Ta{η⁵-C₅H₃(SiMe₃)₂}Cl₄] (1d) reacts with 2 equivalents of MgClMe in hexane at room temperature giving a mixture of dichloro dimethyl and chloro trimethyl complexes[Ta{η⁵-C₅H₃(SiMe₃)₂}Cl_4−xMe_x] (x = 2, 11; 3, 12), while the use of 4 equivalents of MgClMe converts 1c into the tetramethyl derivative [Ta{η⁵-C₅H₃(SiClMe₂)(SiMe₃)}Me₄] (13). Finally, a tetramethyl tantalum complex [Ta{η⁵-C₅H₃(SiMe₃)₂}Me₄] (14) was prepared by reaction of [Ta{η⁵-C₅H₃(SiXMe₂)(SiMe₃)}Cl₄] (X = Cl, 1c; Me, 1d) with 5 (X = Cl) or 4 (X = Me) equivalents of MgClMe in diethyl ether (X = Cl) or hexane (X = Me), respectively, as solvent. All the complexes were studied by IR and NMR spectroscopy and the molecular structure of the complex 11 was determined by X-ray diffraction methods.     

Spectral, structural and DFT studies of platinum group metal 3,6-bis(2-pyridyl)-4-phenylpyridazine complexes and their ligand bonding modes

Reactions of 3,6-bis(2-pyridyl)-4-phenylpyridazine (L^ph) with [(η⁶-arene)Ru(μ-Cl)Cl]₂ (arene = C₆H₆, p-ⁱPrC₆H₄Me and C₆Me₆), [(η⁵-C₅Me₅)M(μ-Cl)Cl]₂, (M = Rh and Ir) and [(η⁵-Cp)Ru(PPh₃)₂Cl] (Cp = C₅H₅, C₅Me₅ and C₉H₇) afford mononuclear complexes of the type [(η⁶-arene)Ru(L^ph)Cl]PF₆, [(η⁵-C₅Me₅)M(L^ph)Cl]PF₆ and [(Cp)Ru(L^ph)(PPh₃)]PF₆ with different structural motifs depending on the π-acidity of the ligand, electronic properties of the central metal atom and nature of the co-ligands. Complexes [(η⁶-C₆H₆)Ru(L^ph)Cl]PF₆1, [(η⁶-p-ⁱPrC₆H₄Me)Ru(L^ph)Cl]PF₆2, [(η⁵-C₅Me₅)Ir(L^ph)Cl]PF₆5, [(η⁵-Cp)Ru(PPh₃)(L^ph)]PF₆, (Cp = C₅H₅, 6; C₅Me₅, 7; C₉H₇, 8) show the type-A binding mode (see text), while complexes [(η⁶-C₆Me₆)Ru(L^ph)Cl]PF₆3 and [(η⁵-C₅Me₅)Rh(L^ph)Cl]PF₆4 show the type-B binding mode (see text). These differences reflect the more electron-rich character of the [(η⁶-C₆Me₆)Ru(μ-Cl)Cl]₂ and [(η⁵-C₅Me₅)Rh(μ-Cl)Cl]₂ complexes compared to the other starting precursor complexes. Binding modes of the ligand L^ph are determined by ¹H NMR spectroscopy, single-crystal X-ray analysis as well as evidence obtained from the solid-state structures and corroborated by density functional theory calculations. From the systems studied here, it is concluded that the electron density on the central metal atom of these complexes plays an important role in deciding the ligand binding sites.     

Syntheses and characterization of mono and dinuclear complexes of platinum group metals bearing benzene-linked bis(pyrazolyl)methane ligands

Reaction of the benzene-linked bis(pyrazolyl)methane ligands, 1,4-bis{bis(pyrazolyl)-methyl}benzene (L1) and 1,4-bis{bis(3-methylpyrazolyl)methyl}benzene (L2), with pentamethylcyclopentadienyl rhodium and iridium complexes [(η⁵-C₅Me₅)M(μ-Cl)Cl]₂ (M = Rh and Ir) in the presence of NH₄PF₆ results under stoichiometric control in both, mono and dinuclear complexes, [(η⁵-C₅Me₅)RhCl(L)]⁺ {L = L1 (1); L2 (2)}, [(η⁵-C₅Me₅)IrCl(L)]⁺ {L = L1 (3); L2 (4)} and [{(η⁵-C₅Me₅)RhCl}₂(μ-L)]²⁺ {L = L1 (5); L2 (6)}, [{(η⁵-C₅Me₅)IrCl}₂(μ-L)]²⁺ {L = L1 (7); L2 (8)}. In contrast, reaction of arene ruthenium complexes [(η⁶­arene)Ru(μ-Cl)Cl]₂ (arene = C₆H₆, p-ⁱPrC₆H₄Me and C₆Me₆) with the same ligands (L1 or L2) gives only the dinuclear complexes [{(η⁶-C₆H₆)RuCl}₂(μ-L)]²⁺ {L = L1 (9); L2 (10)}, [{(η⁶-p-ⁱPrC₆H₄Me)RuCl}₂(μ-L)]²⁺ {L = L1 (11); L2 (12)} and [{(η⁶-C₆Me₆)RuCl}₂(μ-L)]²⁺ {L = L1 (13); L2 (14)}. All complexes were isolated as their hexafluorophosphate salts. The single-crystal X-ray crystal structure analyses of [7](PF₆)₂, [9](PF₆)₂ and [11](PF₆)₂ reveal a typical piano-stool geometry around the metal centers with six-membered metallo-cycle in which the 1,4-bis{bis(pyrazolyl)-methyl}benzene acts as a bis-bidentate chelating ligand.     

Dimeric and trimeric diorganosilicon chalcogenides (PhRSiE)2,3 (E = S, Se, Te; R = Ph, Me)

Ph₂SiCl₂ and PhMeSiCl₂ react with Li₂E (E = S, Se, Te) under formation of trimeric diorganosilicon chalcogenides (PhRSiE)₃ (R = Ph: 1a-3a, R = Me: cis/trans-4a (E = S), cis/trans-5a (E = Se)). In case of E = S, Se dimeric four-membered ring compounds (PhRSiE)₂ (R = Ph: 1b-2b, R = Me: cis/trans-4b (E = S), cis/trans-5b (E = Se)) have been observed as by-products. 1a-5b have been characterized by multinuclear NMR spectroscopy (¹H, ¹³C, ²⁹Si, ⁷⁷Se, ¹²⁵Te). Four- and six-membered ring compounds differ significantly in ²⁹Si and ⁷⁷Se chemical shifts as well as in the value of ¹J_SiSe.The molecular structures of 2a, 3a and trans-5a reported in this paper are the first examples of compounds with unfused six-membered rings Si₃E₃ (E = Se, Te). The Si₃E₃ rings adopt twisted boat conformations. The crystal structure of 3a reveals an intermolecular Te-Te contact of 3.858 Å which yields a dimerization in the solid state.     

Ruthenium(II), rhodium(III) and iridium(III) based effective catalysts for hydrogenation under aerobic conditions

The new cationic mononuclear complexes [(η⁶-arene)Ru(Ph-BIAN)Cl]BF₄ [η⁶-arene = benzene (1), p-cymene (2)], [(η⁵-C₅H₅)Ru(Ph-BIAN)PPh₃]BF₄ (3) and [(η⁵-C₅Me₅)M(Ph-BIAN)Cl]BF₄ [M = Rh (4), Ir (5)] incorporating 1,2-bis(phenylimino)acenaphthene (Ph-BIAN) are reported. The complexes have been fully characterized by analytical and spectral (IR, NMR, FAB-MS, electronic and emission) studies. The molecular structure of the representative iridium complex [(η⁵-C₅Me₅)Ir(Ph-BIAN)Cl]BF₄ has been determined crystallographically. Complexes 1–5 effectively catalyze the reduction of terephthaldehyde in the presence of HCOOH/CH₃COONa in water under aerobic conditions and, among these complexes the rhodium complex [(η⁵-C₅Me₅)Rh(Ph-BIAN)Cl]BF₄ (4) displays the most effective catalytic activity.     

Syntheses, crystal structures and DFT studies of [Me3EM(CO)5] (E = Sb, Bi; M = Cr, W), cis-[(Me3Sb)2Mo(CO)4], and [Bu3BiFe(CO)4]

Syntheses of [Me₃SbM(CO)₅] [M = Cr (1), W (2)], [Me₃BiM(CO)₅] [M = Cr (3), W (4)], cis-[(Me₃Sb)₂Mo(CO)₄] (5), [^tBu₃BiFe(CO)₄] (6), crystal structures of 1-6 and DFT studies of 1-4 are reported.     

A novel series of iridium complexes with alkenylquinoline ligands: Theoretical study on electronic structure and spectroscopic property

The ground and the lowest-lying triplet excited state geometries, electronic structures, and spectroscopic properties of a novel series of neutral iridium(III) complexes with cyclometalated alkenylquinoline ligands [(C^N)₂Ir(acac)] (acac = acetoylacetonate; C^N = 2-[(E)-2-phenyl-1-ethenyl]pyridine (pep) 1; 2-[(E)-2-phenyl-1-ethenyl]quinoline (peq) 2; 1-[(E)-2-phenyl-1-ethenyl]isoquinoline (peiq) 3; 2-[(E)-1-propenyl]pyridine (pp) 4; 2-[(E)-1-fluoro-1-ethenyl]pyridine (fpp) 5) were investigated by DFT and CIS methods. The highest occupied molecular orbital is composed of d(Ir) and π(C^N) orbital, while the lowest unoccupied molecular orbital is dominantly localized on C^N ligand. Under the TD-DFT with PCM model level, the absorption and phosphorescence in CH₂Cl₂ media were calculated based on the optimized ground and triplet excited state geometries, respectively. The calculated lowest-lying absorptions at 437 nm (1), 481 nm (2), 487 nm (3), 422 nm (4), and 389 nm (5) are attributed to a {[d_x²-y²(Ir) + d_xz(Ir) + π(C^N)] → [π∗(C^N)]} transition with metal-to-ligand/intra-ligand charge transfer (MLCT/ILCT) characters, and the calculated phosphorescence at 582 nm (1), 607 nm (2), 634 nm (3), 515 nm (4), and 491 nm (5) can be described as originating from the ³{[d_x²-y²(Ir) + d_xz(Ir) + π (C^N)] [π∗(C^N)]} excited state with the ³MLCT/³ILCT characters. The calculated results revealed that the phosphorescent color of these new Ir(III) complexes can be tuned by changing the π-conjugation effect strength of the C^N ligand.     

Synthesis and crystal structures of boratranes with methyl substituents on the atrane cage

Three monomeric boratranes B[(OCH₂CH₂)_nN(CH₂CMe₂O)_3−n] (n = 0, 1; n = 1, 2; n = 2, 3) have been synthesized by the reaction of B(OMe)₃ with a series of triethanolateamines such as [(OCH₂CH₂)_nN(CH₂CMe₂O)_3−n]³⁻ (n = 0, L1; n = 1, L2; n = 2, L3), where the number of CMe₂ groups adjacent to the OH functionality varied from 3 (L1H₃) to 2 (L2H₃) to 1 (L3H₃). These boratranes 1-3 have been characterized by solution ¹H, ¹³C{¹H} and ¹¹B NMR, and the crystal structures of 1 and 2 have been determined by single crystal X-ray diffraction.     

Two-electron reductive reactivity of trivalent uranium tetraphenylborate complexes of (C5Me5) and (C5Me4H)

The reductive reactivity of the (BPh₄)¹⁻ ligand in pentamethylcyclopentadienyl [(C₅Me₅)₂U][(μ-η²:η¹-Ph)₂BPh₂] (1) was compared with that of the tetramethyl analog, [(C₅Me₄H)₂U][(μ-η⁶:η¹-Ph)(μ-η¹:η¹-Ph)BPh₂] (2) using PhSSPh as a probe to determine if the mode of (BPh₄)¹⁻ bonding affected the reduction. Both complexes act as two-electron reductants to form (C₅Me₄R)₂U(SPh)₂ [R = Me, 3; H, 4], but only in the R = H case could the product be crystallographically characterized. An improved synthesis of 1 from [(C₅Me₅)₂UH]₂ (5) and [Et₃NH][BPh₄] is also reported as well as its reaction with MeCN that provides another route to the unusual, parallel-ring, uranium metallocene [(C₅Me₅)₂U(NCMe)₅][BPh₄]₂ (6).     

o-Phenylene-bridged Cp/amido titanium and zirconium complexes and their polymerization reactivity

o-Phenylene-bridged trimethylcyclopentadienyl/amido titanium complexes [(η⁵-2,3,5-Me₃C₅H)C₆H₄NR-κN]TiCl₂ (18, R = CH₃; 19, R = CH₂CH₃; 20, R = CH₂C(CH₃)₃; 21, R = CH₂(C₆H₁₁)) and zirconium complexes {[(η⁵-2,3,5-Me₃C₅H)C₆H₄NR-κN]ZrCl-μCl}₂ (22, R = CH₃; 23, R = CH₂CH₃; 24, R = CH₂C(CH₃)₃; 25, R = CH₂(C₆H₁₁); 26, R = C₆H₁₁; 27, R = CH(CH₂CH₃)₂) are prepared via a key step of the Suzuki-coupling reaction between 2-dihydroxyboryl-3-methyl-2-cyclopenten-1-one (2) and the corresponding bromoaniline compounds. The molecular structures of titanium complexes 18 and 19 and dinuclear zirconium complexes 24 and 26 were confirmed by X-ray crystallography. The Cp(centroid)-Ti-N and Cp(centroid)-Zr-N angles are smaller, respectively, than those observed for the Me₂Si-bridged complex [Me₂Si(η⁵-Me₄C₅)(N^tBu)]TiCl₂ and its Zr-analogue, indicating that the o-phenylene-bridged complexes are more constrained than the Me₂Si-bridged complex. Titanium complex 19 exhibits comparable activity and comonomer incorporation to the CGC ([Me₂Si(η⁵-Me₄C₅)(N^tBu)]TiCl₂) in ethylene/1-octene copolymerization. Complex 19 produces a higher molecular-weight polymer than CGC.