Ligand Dynamics in the Solid: Lithium‐fluorenide and Lithium‐benzo[b]fluorenide N,N,N′,N′‐Tetramethylethylenediamine (tmeda) Complexes

The dynamic behavior of the N,N,N′,N′‐tetramethylethylenediamine (tmeda) ligand has been studied in solid lithium‐fluorenide(tmeda) ( 3 ) and lithium‐benzo[b]fluorenide(tmeda) ( 4 ) using CP/MAS solid‐state ¹³C‐ and ¹⁵N‐NMR spectroscopy. It is shown that, in the ground state, the tmeda ligand is oriented parallel to the long molecular axis of the fluorenide and benzo[b]fluorenide systems. At low temperature (<250 K), the ¹³C‐NMR spectrum exhibits two MeN signals. A dynamic process, assigned to a 180° rotation of the five‐membered metallacycle (π‐flip), leads at elevated temperatures to coalescence of these signals. Line‐shape calculations yield ΔH^?=42.7 kJ mol^?1, ΔS^?=?5.3 J mol^?1 K^?1, and =44.3 kJ mol^?1 for 3 , and ΔH^?=36.8 kJ mol^?1, ΔS^?=?17.7 J mol^?1 K^?1, and =42.1 kJ mol^?1 for 4 , respectively. A second dynamic process, assigned to ring inversion of the tmeda ligand, was detected from the temperature dependence of T_1ρ, the ¹³C spin‐lattice relaxation time in the rotating frame, and led to ΔH^?=24.8 kJ mol^?1, ΔS^?=?49.2 J mol^?1 K^?1, and =39.5 kJ mol^?1 for 3 , and ΔH^?=18.2 kJ mol^?1, ΔS^?=?65.3 J mol^?1 K^?1, and =37.7 kJ mol^?1 for 4 , respectively. For (D₁₂)‐ 3 , the rotation of the CD₃ groups has also been studied, and a barrier E_a of 14.1 kJ mol^?1 was found.     

Luminescent Cyclometalated Alkynylplatinum(II) Complexes with a Tridentate Pyridine‐Based N‐Heterocyclic Carbene Ligand: Synthesis,Characterization, Electrochemistry,Photophysics, and Computational Studies

A new class of luminescent alkynylplatinum(II) complexes with a tridentate pyridine‐based N‐heterocyclic carbene (2,6‐bis(1‐butylimidazol‐2‐ylidenyl)pyridine) ligand, [Pt^II(C^N^C)(C?CR)][PF₆], and their chloroplatinum(II) precursor complex, [Pt^II(C^N^C)Cl][PF₆], have been synthesized and characterized. One of the alkynylplatinum(II) complexes has also been structurally characterized by X‐ray crystallography. The electrochemistry, electronic absorption and luminescence properties of the complexes have been studied. Nanosecond transient absorption (TA) spectroscopy has also been performed to probe the nature of the excited state. The origin of the absorption and emission properties has been supported by computational studies.     

Ligand Site Preference in Iron Tetracarbonyl Complexes Fe(CO)4L (L = CO,CS, N2, NO+, CN–, NC–, η2‐C2H4, η2‐C2H2, CCH2, CH2, CF2, NH3, NF3, PH3, PF3, η2‐H2)

Equilibrium geometries, bond dissociation energies and relative energies of axial and equatorial iron tetracarbonyl complexes of the general type Fe(CO)₄L (L = CO, CS, N2, NO⁺, CN^–, NC^–, η²‐C₂H₄, η²‐C₂H₂, CCH₂, CH₂, CF₂, NH₃, NF₃, PH₃, PF₃, η²‐H₂) are calculated in order to investigate whether or not the ligand site preference of these ligands correlates with the ratio of their σ‐donor/π‐acceptor capabilities. Using density functional theory and effective‐core potentials with a valence basis set of DZP quality for iron and a 6‐31G(d) all‐electron basis set for the other elements gives theoretically predicted structural parameters that are in very good agreement with previous results and available experimental data. Improved estimates for the (CO)₄Fe–L bond dissociation energies (D₀) are obtained using the CCSD(T)/II//B3LYP/II combination of theoretical methods. The strongest Fe–L bonds are found for complexes involving NO⁺, CN^–, CH₂ and CCH₂ with bond dissociation energies of 105.1, 96.5, 87.4 and 83.8 kcal mol^–1, respectively. These values decrease to 78.6, 64.3 and 64.2 kcal mol^–1, respectively, for NC^–, CF₂ and CS. The Fe(CO)₄L complexes with L = CO, η²‐C₂H₄, η²‐C₂H₂, NH₃, PH₃ and PF₃ have even smaller bond dissociation energies ranging from 45.2 to 37.3 kcal mol^–1. Finally, the smallest bond dissociation energies of 23.5, 22.9 and 18.5 kcal mol^–1, respectively are found for the ligands NF₃, N₂ and η²‐H₂. A detailed examination of the (CO)₄Fe–L bond in terms of a semi‐quantitative Dewar‐Chatt‐Duncanson (DCD) model is presented on the basis of the CDA and NBO approach. The comparison of the relative energies between axial and equatorial isomers of the various Fe(CO)₄L complexes with the σ‐donor/π‐acceptor ratio of their respective ligands L thus does not generally support the classical picture of π‐accepting ligands preferring equatorial coordination sites and σ‐donors tending to coordinate in axial positions. In particular, this is shown by iron tetracarbonyl complexes with L = η²‐C₂H₂, η²‐C₂H₄, η²‐H₂. Although these ligands are predicted by the CDA to be stronger σ‐donors than π‐acceptors, the equatorial isomers of these complexes are more stable than their axial pendants.     

Preparation and Characterization of Dinuclear Chromium(III) Complexes of a Hexadentate Tetraaza‐Dithiophenolate Ligand

The ability of the tetraaza‐dithiophenolate ligand H₂L² (H₂L² = N,N′‐Bis‐[2‐thio‐3‐aminomethyl‐5‐tert‐butyl‐benzyl]propane‐1,3‐diamine) to form dinuclear chromium(III) complexes has been examined. Reaction of Cr^IICl₂ with H₂L² in methanol in the presence of base followed by air‐oxidation afforded cis,cis‐[(L²)Cr^III₂(μ‐OH)(Cl)₂]⁺ ( 1a ) and trans,trans‐[(L²)Cr^III₂(μ‐OH)(Cl)₂]⁺ ( 1b ). Both compounds contain a confacial bioctahedral N₂ClCr^III(μ‐SR)₂(μ‐OH)Cr^IIIClN₂ core. The isomers differ in the mutual orientation of the coligands and the conformation of the supporting ligand. In 1a both Cl^? ligands are cis to the bridging OH function. In 1b they are in trans‐positions. Reaction of the hydroxo‐bridged complexes with HCl yielded the chloro‐bridged cations cis,cis‐[(L²)Cr^III₂(μ‐Cl)(Cl)₂]⁺ ( 2a ) and trans,trans‐[(L²)Cr^III₂(μ‐Cl)(Cl)₂]Cl ( 2b ), respectively. These bridge substitutions proceed with retention of the structures of the parent complexes 1a and 1b .     

Synthesis,Characterization and Crystal Structures of new Palladium(II) Complexes and the first Platinum(III) Complex Containing ATT (ATT = 6‐Aza‐2‐thiothymine)

Treatment of the ligand 6‐aza‐2‐thiothymine (ATT, HL, 1 ) with palladium chloride in methanol forms the ionic complex [(HL)₄Pd]Cl₂·8MeOH ( 2 ), while its reaction with palladium iodide in same solvent produces the neutral complex trans‐[(HL)₂PdI₂]·2MeOH ( 3 ) in high yields. The reaction of 1 with Na₂[PdCl₄] in the presence of sodium acetate in a molar ratio of 2:1:2 and with platinum(II) chloride in presence of sodium acetate led to the dimer tetranuclear complexes [(L₄Pd₂)NaCl]₂·8MeOH ( 4 ) and [L₄Pt₂Cl₂]·6MeOH·H₂O ( 5 ). The latter is the first Pt^III complex of the ligand. All complexes were characterized by elemental analyses and IR spectroscopy and the crystal structures of 2 , 3 , 4 and 5 are determined by single‐crystal X‐ray diffraction. Crystal data for 2 at ?80 °C: triclinic space group , a = 1006.6(1), b = 1006.9(1), c = 1158.1(1) pm, α = 85.20(1)°, β = 83.84(1)°, γ = 88.91(1)°, Z = 1, R₁ = 0.0278; for 3 at ?80 °C: triclinic space group , a = 490.5(1), b = 977.2(2), c = 1116.8(2) pm, α = 90.26(1)°, β = 102.33(1)°, γ = 96.08(1)°, Z = 1, R₁ = 0.0394; for 4 at ?80 °C: orthorhombic space group Ccca, a = 1791.7(2), b = 1874.1(2), c = 2044.0(1) pm, Z = 4, R₁ = 0.0341 and for 5 at ?80 °C: monoclinic space group P2₁/c, a = 1464.3(1), b = 2003.7(1), c = 1368.5(1) pm, β = 95.66(1)°, Z = 4, R₁ = 0.0429.     

Reaction of the Pincer‐type Ligand {2, 6‐[P(O)(OEt)2]2‐4‐tert‐Bu‐C6H2}— with [Ph3C]+[PF6]—. Unprecedented Rearrangement and Carbon‐Carbon Bond Formation

The reaction of the organolithium derivative {2, 6‐[P(O)(OEt)₂]₂‐4‐tert‐Bu‐C₆H₂}Li ( 1 ‐Li) with [Ph₃C]⁺[PF₆]^— gave the substituted biphenyl derivative 4‐[(C₆H₅)₂CH]‐4′‐[tert‐Bu]‐2′, 6′‐[P(O)(OEt)₂]₂‐1, 1′‐biphenyl ( 5 ) which was characterized by ¹H, ¹³C and ³¹P NMR spectroscopy and single crystal X‐ray analysis. Ab initio MO‐calculations reveal the intramolecular O···C distances in 5 of 2.952(4) and 2.988(5)Å being shorter than the sum of the van der Waals radii of oxygen and carbon to be the result of crystal packing effects. Also reported are the synthesis and structure of the bromine‐substituted derivative {2, 6‐[P(O)(OEt)₂]₂‐4‐tert‐Bu]C₆H₂}Br ( 9 ) and the structure of the protonated ligand 5‐tert‐Bu‐1, 3‐[P(O)(OEt)₂]₂C₆H₃ ( 1 ‐H). The structures of 1 ‐H, 5 , and 9 are compared with those of related metal‐substituted derivatives.     

Synthesis and Structures of Homoleptic Methyl‐ and Phenylthiomethylaluminium Complexes [Al(CH2SR)3](R = Me,Ph)

Sulfur‐substituted methylmercury compounds [Hg(CH₂SR)₂]( 1a, R = Me; 1b, R = Ph ) react with aluminium amalgam in refluxing toluene with transmetallation to give homoleptic tris(thiomethyl)aluminium complexes [Al(CH₂SR)₃]( 2a, R = Me; 2b, R = Ph ) (degree of conversion: >80%, isolated yields: 2a 63%, 2b 41%). Their identities were confirmed by NMR spectros‐copy (¹H, ¹³C) and X‐ray crystal structure analyses. In crystals of compound 2a the aluminium atoms possess a trigonal‐bipyramidal arrangement with the coordination polyhedron defined by three carbon and two sulfur atoms. Two of the three CH₂SMe ligands are bridging ligands (μ‐η²; 1kC:2kS), the third one is terminal bound (η¹; kC). The structure is polymeric. Crystals are threaded by helical chains built up of six‐membered Al₂C₂S₂ rings. Crystals of 2b are built up of centrosymmetrical dimers with six‐membered Al₂C₂S₂ rings having bridging CH₂SPh ligands (μ‐η²; 1kC:2kS). On each Al atom two terminal (η¹; kC)CH₂SPh ligands are bound. They exhibit quite different Al‐C‐S angles (116.7(4) and 106.5(3)?). Similar values (114.32115.7? and 109.52109.9?) were found in ab initio calculations of model compounds [{Al(CH₂SR)₃}₂]( 3a, R=H; 3b, R=Me; 3c, R=CH=CH₂ ). A conformational energy diagram for rotation of one of the terminal CH₂SH ligand in the parent compound 3a around the Al‐C bond is discussed in terms of repulsive interactions of lone electron pairs of sulfur atoms.     

Synthesis,Structure, Chemical and Energetic Characterization of 1,3‐Dinitramino‐2‐nitroxy‐propane

The title compound, 1,3‐dinitramino‐2‐nitroxy‐propane ( 1 ) was prepared in high yield (85 %) and characterized by multinuclear NMR (¹H, ¹³C, ¹⁴N) and vibrational (IR, Raman) spectroscopy. The molecular structure in the solid state was elucidated by single crystal X‐ray diffraction. 1 crystallizes in the orthorhombic space group P_nma with a crystal density of ρ = 1.798 g cm^?3. Compound 1 melts at 166 °C and decomposes at 168 °C. The impact (7 J), friction (96 N) and electrostatic discharge sensitivities (0.6 J) were determined experimentally. The detonation parameters of 1 were calculated using a combined quantum chemical (CBS‐4M) calculation and a chemical equilibrium calculation based on the steady‐state model of detonation: Q = ?5998 kJ kg^?1, P = 339 kbar, D = 8895 m s^?1. The experimentally determined detonation velocity (fiber optic method) agrees well with the calculated values. In comparison with picric acid (PA) and nitropenta (PETN), compound 1 shows superior detonation characteristics when detonated in a confined space.     

Effects on Coordination of Thioether Sites. 4. Structural Analysis of η3-Tripodal Ligand Manganese(I) Complexes

Crystal structures of a series of manganese(I) complexes containing tripodal ligands were determined. For [η³-{CH₃C(CH₂PPh₂)₂(CH₂SPh)-P,P′,S}Mn(CO)₃]PF₆ ( 1 ): a = 10.856(3) Å, b = 19.698(3) Å, c = 17.596(5) Å, β = 96.17(2)°, monoclinic, Z = 4, P2₁/c, R(F_o) = 0.068, R_w(F_o) = 0.055 for 3617 reflections with I_o > 2σ(I_o). For [η³-{CH₃C(CH₂PPh₂)(CH₂SPh)₂-P,P′,S}Mn(CO)₃]PF₆ ( 2 ): a = 9.890(2) Å, b = 20.403(4) Å, c = 10.269(3) Å, β = 117.44(2)°, monoclinic, Z = 2, P2_l, R(F_o) = 0.050, R_w(F_o) = 0.037 for 1760 reflections with I_o > 2σ(I_o). For [η³-{CH₃C(CH₂PPh₂)₂(CH₂S)-P,P′,S}Mn(CO)₃] ( 4 ): a = 8.191(7) Å, b = 10.495(3) Å, c = 19.858(6) Å, α = 99.61(2)°, β = 96.17(2)°, γ = 92.70(4)°, triclinic, Z = 2, P-I, R(F_o) = 0.048, R_w(F_o) = 0.039 for 2973 reflections with I_o > 2σ(I_o). There is no significant difference in the bond lengths of Mn-S bonds among three species in their crystal structures [2.325(2) Å in 1; 2.358(4) in 2; 2.380(2) in 4], but the better donating ability of thiolate in complex 4 appears on the lower frequencies of its carbonyl stretching absorptions.     

Metathetical Reactions in the System Na(K)PF6 – LiBF4 – Aprotic Media

¹⁹F NMR spectroscopy, X‐ray powder diffraction, elemental analysis, and ab initio quantum chemical calculations were used to study metathetical reactions between potassium or sodium hexafluorophosphate and lithium tetrafluoroborate in a mixture of propylene carbonate (PC) – dimethyl carbonate (DMC). It was shown that the increase in size of the cations in the second coordination sphere from Na⁺ to K⁺ results in an increase of the equilibrium conversion. This is in agreement with the influence of the cation size on the solubility of tetrafluoroborates in the media investigated.     

Copper(I) and Gold(I) Complexes with N,N′‐Bis(diphenylphosphino)‐2,6‐diaminopyridine as Ligand: Synthesis and Molecular Structures

Reaction of CuI with 1 or 2 equivalent(s) N,N′‐Bis(diphenylphosphino)‐2,6‐diaminopyridine (BDDP) gives two different complexes, [Cu(I)μ‐(BDDP‐κP,N_py)]₂ ( 1 ) and [Cu(BDDP‐κP,N_py)₂]I ( 2 ), in high yields. The determination of the molecular structure show that both Cu^I atoms are tetrahedrally coordinated, rather than a square‐planar geometry reported for Cr⁰, Ni^II‐BDDP complexes before, which contains a planar tridentate chelate ring system. The introduction of AuCl(tht) (tht = tetrahydrothiophene) into [Cu(BDDP‐κP,N_py)₂]I leads unexpectedly to the formation of a digold complex 2,6‐[(ClAuPh₂P)HN]₂C₅H₃N and dimeric [Cu(I)μ‐(BDDP‐κP,N_py)]₂.     

η5-Phospholylgallium: The First Monomeric Polyhapto Compound between a Phospholyl Ligand and a Main Group Metal

Monomeric polyhapto-bound phospholyl compounds were hitherto unknown for the main group elements. Use of a solution of metastable GaBr has allowed the synthesis of monomeric η⁵-phospholylgallium, which has been characterized by X-ray structure analysis as the Cr(CO)₅ complex 1 .     

Synthesis and Structural Characterization of Cationic Complexes with Hexacoordinate Silicon(IV) and Three Bidentate 1‐Oxopyridine‐2‐olato(1–) Ligands

The cationic complexes with hexacoordinate silicon(IV), tris[1‐oxopyridine‐2‐olato(1–)]silicon(IV) trifluoromethanesulfonate ( 4 ), 4 · ¹/₂ C₅H₅NO₂, tris[1‐oxopyridine‐2‐olato(1–)]silicon(IV) ethyl sulfate–ethanol ( 5 · EtOH), and tris[1‐oxopyridine‐2‐olato(1–)]silicon(IV) isopropyl sulfate ( 6 ), were synthesized. The identities of 4 , 4 · ¹/₂ C₅H₅NO₂, 5 · EtOH, and 6 were established by elemental analyses (C, H, N, S), mass‐spectrometric studies (FAB MS) as well as solid‐state (²⁹Si) and solution (¹H, ¹³C, ¹⁹F, ²⁹Si) NMR experiments. In addition, 4 · ¹/₂ C₅H₅NO₂ was structurally characterized by single‐crystal X‐ray diffraction.     

Synthesis of Heteroleptic Cerium(IV) Complexes Using a Heptadentate (N4O3) Tripodale Schiff‐base Ligand

The Cerium(IV) complexes [{N[CH₂CH₂N=CH(2‐O‐3,5‐^tBu₂C₆H₂)]₃}CeCl] ( 1 ) and [{N[CH₂CH₂N=CH(2‐O‐3,5‐^tBu₂C₆H₂)]₃}Ce(NO₃)] ( 2 ) were derived from the condensation of tris(2‐aminoethyl)amine and 3,5‐di‐tert‐butylsalicylaldehyde and the appropriate Ce starting material CeCl₃(H₂O)₆ and (NH₄)₂[Ce(NO₃)₆], respectively. Single crystal X‐ray diffraction studies reveal monomeric complexes.     

A Facile Synthesis of New Pyrazolo[3,4‐d]pyrimidine Derivatives via a One‐Pot Four‐Component Reaction with Sodium Acetate Supported on Basic Alumina as Promoter

An efficient one‐pot procedure for the synthesis of 3‐amino‐6‐aryl‐2‐phenylpyrazolo[3,4‐d]pyrimidine derivatives, through the reaction of aldehydes, malononitrile, benzamidine hydrochloride, and hydrazine hydrate in the presence of basic alumina‐supported sodium acetate (AcONa/Al₂O₃) under reflux conditions, is reported. This protocol has some advantages, including the use of a simple and one‐pot synthetic approach to attain pyrazolo[3,4‐d]pyrimidine directly from four readily available starting materials, simple workup, high overall yields of the products, and the simultaneous conversion of a NO₂ to an amino group, offering an opportunity to synthesize more complex structures.     

Synthesis and Characterization of Some New Zinc(II) Complexes Incorporating Heterocyclic Thiophosphates as a Ligand

New tetracoordinated complexes of Zn (II) have been synthesized by the reaction between zinc chloride and 3-methyl-2-benzothiazolylidenamido-thiophosphoryl dichloride (L₁), (3-methyl-2-benzothiazolylidenamido)-bis-(diethylamido)thiophosphate (L₂), 3-benzyl-2-benzothiazolylidenamido thiophosphoryl dichloride (L₃), and (3-benzyl-2-benzothiazolylidenamido)-bis-(diethyl-amido) thiophosphate (L₄) in a 1:1 ratio. The complexes have been isolated and characterized by elemental analysis, electrical conductivity, and mass and IR spectral studies. The stability constants of these complexes also have been determined in aqueous solution by spectrophotometric methods.