Halogenid‐Ionen als Katalysator: Metallzentrierte C–C‐Bindungsknüpfung ausgehend von Acetontril

Halide Ions as Catalyst: Metalcentered C–C Bond Formation Proceeded from Acetonitril AlMe₃ reacts at 20 ?C in acetonitrile to the complex [Me₃Al(NCMe)] ( 1 ). By addition of cesium halides (X^– = F^–, Cl^–, Br^–) a trimerisation to the heterocycle [Me₂Al{HNC(Me)}₂C(CN)] ( 2 ) has been observed. The reaction might be carried out under catalytic conditions (1–2 mol% CsX). The gallium complex [Me₂Ga{HNC(Me)}₂ · C(CN)] ( 3 ), generated under similar reaction conditions, can be converted to the silylated compound [Me₂Ga{Me₃SiNC(Me)}₂C(CN)] ( 4 ) by successive treatment with two equivalents n‐butyllithium and Me₃SiCl. 3 reacts under hydrolysis conditions (1 M hydrochloric acid) to the iminium salt [{H₂NC(Me)}₂C(CN)]Cl ( 5 ). A mixture of H₂O, Ph₂PCl and 3 in THF/toluene leads in a unusual conversion to the diphospane derivative [Ph₂P–P(O)(Me₂GaCl)] ( 6 ). 1 , 2 , 4 , 5 and 6 have been characterized by NMR, IR and MS techniques. X‐ray structure analyses were performed with 1 , 2 , 4 and 6 · 0.5 toluene. According this 1 possesses an almost linear axis AlNCC [Al1–N1–C3: 179,5(2)?; N1–C3–C4: 179,7(4)?]. 2 is an AlN₂C₃ six‐membered heterocycle with two iminium fuctions. One N–H group is responsible for a intermolecular chain‐formation through hydrogen bridges to an adjacent nitrile group along the direction [010]. The basic structural motif of the heterocycle 3 has been maintained after silylation to 4 . In 6 · 0.5 toluene an unit Me₂GaCl, originated from 3 , is coordinated to the oxygen atom of the diphosphane oxide Ph₂P–P(O)Ph₂.     

Bis(β‐diketiminato) lanthanide amides: synthesis,structure and catalysis for the polymerization of l‐lactide and ε‐caprolactone

Treatment of the chlorides (L^2,6‐iPr2_Ph)₂LnCl (L^2,6‐iPr2_Ph = [(2,6‐ⁱPr₂C₆H₃)NC(Me)CHC(Me)N(C₆H₅)]^?) with 1 equiv. of NaNH(2,6‐ⁱPr₂C₆H₃) afforded the monoamides (L^2,6‐iPr2_Ph)₂LnNH(2,6‐ⁱPr₂C₆H₃) (Ln = Y ( 1 ), Yb ( 2 )) in good yields. Anhydrous LnCl₃ reacted with 2 equiv. of NaL^2,6‐iPr2_Ph in THF, followed by treatment with 1 equiv. of NaNH(2,6‐ⁱPr₂C₆H₃), giving the analogues (L^2,6‐iPr2_Ph)₂LnNH(2,6‐ⁱPr₂C₆H₃) (Ln = Sm ( 3 ), Nd ( 4 )). Two monoamido complexes stabilized by two L^2‐Me ligands, (L^2‐Me)₂LnNH(2,6‐ⁱPr₂C₆H₃) (L^2‐Me = [N(2‐MeC₆H₄)C(Me)]₂CH)^?; Ln = Y ( 5 ), Yb ( 6 )), were also synthesized by the latter route. Complexes 1 , 2 , 3 , 4 , 5 , 6 were fully characterized, including X‐ray crystal structure analyses. Complexes 1 , 2 , 3 , 4 , 5 , 6 are isostructural. The central metal in each complex is ligated by two β‐diketiminato ligands and one amido group in a distorted trigonal bipyramid. All the complexes were found to be highly active in the ring‐opening polymerization of L‐lactide (L‐LA) and ε‐caprolactone (ε‐CL) to give polymers with relatively narrow molar mass distributions. The activity depends on both the central metal and the ligand (Yb < Y < Sm ≈ Nd and L^2‐Me < L^2,6‐iPr2_Ph). Remarkably, the binary 3/benzyl alcohol (BnOH) system exhibited a striking ‘immortal’ nature and proved able to quantitatively convert 5000 equiv. of L‐LA with up to 100 equiv. of BnOH per metal initiator. All the resulting PLAs showed monomodal, narrow distributions (M_w/M_n = 1.06 ? 1.08), with molar mass (M_n) decreasing proportionally with an increasing amount of BnOH. The binary 4/BnOH system also exhibited an ‘immortal’ nature in the polymerization of ε‐CL in toluene. Copyright © 2014 John Wiley & Sons, Ltd.     

Synthesis and characterization of new (N‐diphenylphosphino)‐isopropylanilines and their complexes: crystal structure of (Ph2P S)NH?C6H4?4?CH(CH3)2 and catalytic activity of palladium(II) complexes in the Heck and Suzuki cross‐coupling reactions

Three new (N‐diphenylphosphino)‐isopropylanilines, having isopropyl substituent at the carbon 2‐ (1) 4‐ (2) or 2,6‐ (3) were prepared from the aminolysis of chlorodiphenylphosphine with 2‐isopropylaniline, 4‐isopropylaniline or 2,6‐diisopropylaniline, respectively, under anaerobic conditions. Oxidation of 1,2 and 3 with aqueous hydrogen peroxide, elemental sulfur or gray selenium gave the corresponding oxides, sulfides and selenides (Ph₂P?E)NH? C₆H₄? 2‐CH(CH₃)₂, (Ph₂P?E)NH? C₆H₄? 4‐CH(CH₃)₂ and (Ph₂P?E)NH? C₆H₄? 2,6‐{CH(CH₃)₂}₂, where E = O, S, or Se, respectively. The reaction of [M(cod)Cl₂] (M = Pd, Pt; cod = 1,5‐cyclooctadiene) with two equivalents of 1,2 or 3 yields the corresponding monodendate complexes [M((Ph₂P)NH? C₆H₄? 2‐CH(CH₃)₂)₂Cl₂], M = Pd 1d, M = Pt 1e, [M((Ph₂P)NH? C₆H₄? 4‐CH(CH₃)₂)₂Cl₂], M = Pd 2d, M = Pt 2e and [M((Ph₂P)NH? C₆H₄? 2,6‐(CH(CH₃)₂)₂)₂Cl₂], M = Pd 3d, M = Pt 3e, respectively. All the compounds were isolated as analytically pure substances and characterized by NMR, IR spectroscopy and elemental analysis. Furthermore, representative solid‐state structure of [(Ph₂P?S)NH? C₆H₄? 4‐CH(CH₃)₂] (2b) was determined using single crystal X‐ray diffraction technique. The complexes 1d–3d were tested and found to be highly active catalysts in the Suzuki coupling and Heck reaction, affording biphenyls and stilbenes, respectively. Copyright © 2009 John Wiley & Sons, Ltd.     

Synthesis and structural characterization of diorganotin(IV) complexes with 2,6‐pyridinedicarboxylic acid

Two new diorganotin(IV) derivatives of 2,6‐pyridinedicarboxylic acid, {[Ph₂Sn(2,6‐C₅H₃N)(COO)₂][Na(2,6‐C₅H₃N)(COOH) (COO)(CH₃OH)₂]} ( 1 ) and [Me₂Sn(2,6‐C₅H₃N)(COO)₂(H₂O)]^•H₂O ( 2 ) were synthesized by the reaction of Ph₃SnCl and PhMe₂SnI with 2,6‐pyridinedicarboxylic acid, respectively in the presence of sodium methoxide or potassium iso‐propoxide. The prepared compounds were characterized by mass spectrometry, IR, ¹H, ¹³C and ¹¹⁹Sn NMR spectroscopies. The molecular structures of both complexes were determined by a single‐crystal X‐ray analysis. The X‐ray structure revealed pentagonal bipyramidal geometry around the tin atom for compound 1, which is incorporated with a hexacoordinated monosodium derivative of 2,6‐pyridinedicarboxylic acid. Complex 2 adopts a monomeric structure with two carboxylate oxygen atoms coordinated to tin in monodenate form from equatorial positions, and the coordination number is raised to six as the oxygen of water and pyridine nitrogen occupies the other equatorial positions of octahedron. Copyright © 2007 John Wiley & Sons, Ltd.     

Pincer‐Type Heck Catalysts and Mechanisms Based on PdIV Intermediates: A Computational Study

Pincer‐type palladium complexes are among the most active Heck catalysts. Due to their exceptionally high thermal stability and the fact that they contain Pd^II centers, controversial Pd^II/Pd^IV cycles have been often proposed as potential catalytic mechanisms. However, pincer‐type Pd^IV intermediates have never been experimentally observed, and computational studies to support the proposed Pd^II/Pd^IV mechanisms with pincer‐type catalysts have never been carried out. In this computational study the feasibility of potential catalytic cycles involving Pd^IV intermediates was explored. Density functional calculations were performed on experimentally applied aminophosphine‐, phosphine‐, and phosphite‐based pincer‐type Heck catalysts with styrene and phenyl bromide as substrates and (E)‐stilbene as coupling product. The potential‐energy surfaces were calculated in dimethylformamide (DMF) as solvent and demonstrate that Pd^II/Pd^IV mechanisms are thermally accessible and thus a true alternative to formation of palladium nanoparticles. Initial reaction steps of the lowest energy path of the catalytic cycle of the Heck reaction include dissociation of the chloride ligands from the neutral pincer complexes [{2,6‐C₆H₃(XPR₂)₂}Pd(Cl)] [X=NH, R=piperidinyl ( 1 a ); X=O, R=piperidinyl ( 1 b ); X=O, R=iPr ( 1 c ); X=CH₂, R=iPr ( 1 d )] to yield cationic, three‐coordinate, T‐shaped 14e^? palladium intermediates of type [{2,6‐C₆H₃(XPR₂)₂}Pd]⁺ ( 2 ). An alternative reaction path to generate complexes of type 2 (relevant for electron‐poor pincer complexes) includes initial coordination of styrene to 1 to yield styrene adducts [{2,6‐C₆H₃(XPR₂)₂}Pd(Cl)(CH₂?CHPh)] ( 4 ) and consecutive dissociation of the chloride ligand to yield cationic square‐planar styrene complexes [{2,6‐C₆H₃(XPR₂)₂}Pd(CH₂?CHPh)]⁺ ( 6 ) and styrene. Cationic styrene adducts of type 6 were additionally found to be the resting states of the catalytic reaction. However, oxidative addition of phenyl bromide to 2 result in pentacoordinate Pd^IV complexes of type [{2,6‐C₆H₃(XPR₂)₂}Pd(Br)(C₆H₅)]⁺ ( 11 ), which subsequently coordinate styrene (in trans position relative to the phenyl unit of the pincer cores) to yield hexacoordinate phenyl styrene complexes [{2,6‐C₆H₃(XPR₂)₂}Pd(Br)(C₆H₅)(CH₂?CHPh)]⁺ ( 12 ). Migration of the phenyl ligand to the olefinic bond gives cationic, pentacoordinate phenylethenyl complexes [{2,6‐C₆H₃(XPR₂)₂}Pd(Br)(CHPhCH₂Ph)]⁺ ( 13 ). Subsequent β‐hydride elimination induces direct HBr liberation to yield cationic, square‐planar (E)‐stilbene complexes with general formula [{2,6‐C₆H₃(XPR₂)₂}Pd(CHPh?CHPh)]⁺ ( 14 ). Subsequent liberation of (E)‐stilbene closes the catalytic cycle.     

The Synthesis,Characterisation, and Reactivity of Some Polydentate Phosphinoamine Ligands with Benzene‐1,3‐diyl and Pyridine‐2,6‐diyl Backbones

The polydentate phosphinoamines 1,3‐{(Ph₂P)₂N}₂C₆H₄ and 2,6‐{(Ph₂P)₂N}₂C₅H₃N have been prepared in a single step from the reaction of the amines 1,3‐(NH₂)₂C₆H₄ or 2,6‐(NH₂)₂C₅H₃N with Ph₂PCl in presence of Et₃N (1 : 4 : 4 molar ratio) in CH₂Cl₂. Reaction of 1,3‐{(Ph₂P)₂N}₂C₆H₄ or 2,6‐{(Ph₂P)₂N}₂C₅H₃N with elemental sulfur or selenium in CH₂Cl₂ affords the corresponding tetrasulfide or tetraselenide, respectively, in good yield. The complexes [1,3‐{Mo(CO)₄(Ph₂P)₂N}₂(C₆H₄)] and [2,6‐{Mo(CO)₄(Ph₂P)₂N}₂(C₅H₃N)] were prepared from the reaction of these phosphinoamines with [Mo(CO)₄(nbd)] (nbd=norbornadiene) in toluene, and the structure of the latter complex has been determined by single‐crystal X‐ray diffraction analysis.     

Calcium Hydride Cation [CaH]+ Stabilized by an NNNN‐type Macrocyclic Ligand: A Selective Catalyst for Olefin Hydrogenation

Reaction of dibenzyl calcium complex [Ca(Me₄TACD)(CH₂Ph)₂], containing the neutral NNNN‐type macrocyclic ligand Me₄TACD (Me₄TACD=1,4,7,10‐tetramethyl‐1,4,7,10‐tetraazacyclododecane), with triphenylsilane gave the cationic dinuclear calcium hydride [Ca₂H₂(Me₄TACD)₂](PhCHSiPh₃)₂ which was characterized by NMR spectroscopy and single‐crystal X‐ray diffraction. The cation can be regarded as the ligand‐stabilized dimeric form of hypothetical [CaH]⁺. Hydrogenolysis of benzyl calcium cation [Ca(Me₄TACD)(CH₂Ph)(thf)]⁺ gave dicationic calcium hydrides [Ca₂H₂(Me₄TACD)₂][BAr₄]₂ (Ar=C₆H₄‐4‐^tBu; C₆H₃‐3,5‐Me₂) containing weakly coordinating anions. In THF, they catalyzed the isotope exchange of H₂ and D₂ to give HD and the hydrogenation of unactivated 1‐alkenes.     

Aminodiphenylphosphanes: Isotope‐induced chemical shifts 1Δ14/15N(31P), coupling constants 1J(31P,15N), and chemical shifts δ15N and δ31P

A series of aminodiphenylphosphanes 1 [Ph₂P‐N(H)tBu ( a ), ‐NEt₂ ( b ), ‐NiPr₂ ( c )], 2 [Ph₂P‐NHPh ( a ), ‐NH‐2‐pyridine ( b ), ‐NH‐3‐pyridine ( c ), ‐NH‐4‐pyridine ( d ), NH‐pyrimidine ( e ), NH‐2,6‐Me₂‐C₆H₃ ( f ), NH‐3‐Me‐2‐pyridine ( g )], 3 [Ph₂P‐N(Me)Ph ( a ), ‐NPh₂ ( b )], and N‐pyrrolyldiphenylphosphane 4 (Ph₂P‐NC₄H₄) was prepared and studied by NMR (¹H, ¹³C, ³¹P, ¹⁵N NMR) spectroscopy. The isotope‐induced chemical shifts ¹Δ^14/15N(³¹P) were determined at natural abundance of ¹⁵N by using HEED INEPT experiments. A dependence of ¹Δ^14/15N(³¹P) on the substituents at nitrogen was found (alkyl < H < aryl; increasingly negative values). The magnitude and sign of the coupling constants ¹J(³¹P,¹⁵N) (positive sign) are dominated by the presence of the lone pair of electrons at the phosphorus atom. The X‐ray structural analysis of 2b is reported, showing the presence of dimers owing to intermolecular hydrogen bridges in the solid state. © 2001 John Wiley & Sons, Inc. Heteroatom Chem 12:542–550, 2001     

7‐{Di­phenyl­[(tri­phenyl­phos­phine)­aurio]­phos­phine(1+)‐P}‐8‐methyl‐7,8‐dicarba‐nido‐undecaborate(1–) dichloro­methane hemi­solvate

The title compound, 7‐[(Ph₂P)Au(PPh₃)]‐8‐(CH₃)‐7,8‐nido‐C₂B₉H₁₀]·­0.5CH₂Cl₂ or [Au(C₁₅H₂₃B₉P)­(C₁₈H₁₅P)]·­0.5CH₂Cl₂, is the first reported gold derivative of the ligand [7‐­(Ph₂P)‐8‐(CH₃)‐7,8‐nido‐C₂B₉H₁₀]^?. It has a mono­nuclear structure with the gold centre in an essentially linear coordination [P—Au—P 174.041 (15)°]. The open C₂B₃ face contains one H atom that is strongly bonded to the central B atom and semi‐bridging to a neighbouring B atom [B—H distances 1.070 (16) and 1.45 (3) Å].     

(Aceto­nitrile)­[2,6‐bis­(pyrazol‐1‐yl)­pyridine](isonicotin­amide)copper(II)–tetra­fluoro­borate–aceto­nitrile (1/2/2)

Molecules of the title compound, [Cu(C₂H₃N)(C₁₁H₉N₅)(C₆H₆N₂O)](BF₄)₂·2C₂H₃N, comprise (aceto­nitrile)[2,6‐bis(pyrazol‐1‐yl)­pyridine](isonicotin­amide)copper(II) cations, tetra­fluoro­borate anions and lattice aceto­nitrile mol­ecules. The cations have distorted square‐pyramidal geometries in which the N₃‐donor, viz. 2,6‐bis­(pyrazol‐1‐yl)­pyridine, and the N‐donor, viz. the isonicotin­amide ligand, occupy the four basal positions, with the coordinated aceto­nitrile N‐donor atom occupying the apical position. Pairs of cations are linked by N—H?F hydrogen bonds through tetra­fluoro­borate anions, forming centrosymmetric dimers, which are further linked by C—H?O hydrogen bonds into two‐dimensional undulating sheets, three of which interpenetrate to generate a two‐dimensional network.     

Tripodale Bis(2,6‐iminophosphoranyl)pyridin‐Liganden: Eisen‐ und Cobalt‐Komplexe mit Potential in der Ethen‐Polymerisation

Tripodal Bis(2,6‐iminophosphoranyl)pyridine Ligands: Iron and Cobalt Complexes with a Potential in Ethene Polymerisation By Staudinger Reaction of bis‐2,6‐diphenylphosphanyl‐pyridine with aryl‐, alkyl‐ and silylazides tripodal ligands L = 2,6‐(Ph₂P=NR)₂C₅H₃N (R = Ph 1 a , Mes 1 b , Ad  1 c , SiMe₃ 1 d ) are synthesized. The reaction of ligand 1 b  with equimolar amounts of [CoCl₂(THF)₂] and [FeCl₂(THF)_1.5] in THF does not lead to the expected neutral complexes [(k³‐L)MCl₂] but to coordination compounds of the composition L₂(CoCl₂)₃ ( 2 a ) und L(FeCl₂)₂ ( 3 ). By using acetonitrile as solvent or by crystallisation of 2 a from hot acetonitrile the cationic complex [(k³‐L)CoCl(MeCN)]Cl ( 2 b ) is formed as a second product. The molecular structure 2 b has been characterized by an X‐ray single crystal structure analysis (triclinic, P1, Z = 2, a = 1299.8(1), b = 1488.8(2), c = 1674.2(2) pm, α = 82.911(13)°, β = 76.715(12)°, γ = 72.758(11)°). A preliminary test with 3 shows, that coordination compounds of the ligand system introduced here have potential as catalysts in methyl alumoxane mediated ethene polymerisation.     

β‐Diketiminatoytterbium aryloxides: synthesis,structural characterization,and catalytic activity for addition of amines to carbodiimides

The steric effect of an aryloxido group on the synthesis and molecular structures of ytterbium aryloxides supported by β‐diketiminato ligand L (L = [N(2,6‐Me₂C₆H₃)C(Me)]₂CH^?) is reported. Reactions of β‐diketiminatoytterbium dichloride, LYbCl₂(THF)₂, with NaOAr¹ in THF (Ar¹ = [2,6‐^tBu₂‐4‐MeC₆H₂], THF = tetrahydrofuran) at 60°C gave the corresponding ytterbium complexes LYb(OAr¹)Cl(THF) ( 1 ) and LYb(OAr¹)₂ (1), depending on the molar ratio of dichloride to sodium aryloxide, respectively, while the same reactions with NaOAr² and NaOAr³ (Ar² = [2,6‐ⁱPr₂C₆H₃], Ar³ = [2,6‐Me₂C₆H₃]) in 1:1 or 1:2 molar ratio in THF afforded only bisaryloxide complexes LYb(OAr²)₂(THF) (1) and LYb(OAr³)₂(THF) ( 4 ) in good yields, respectively. Complexes 1 , 2 , 3 , 4 were fully characterized, including X‐ray crystal structure analyses. All the complexes are efficient pre‐catalysts for the catalytic addition of amines to carbodiimides giving guanidines. Copyright © 2013 John Wiley & Sons, Ltd.     

Synthesis and Structure of Unprecedented Samarium Complex with Bulky Bis‐iminopyrrolyl Ligand via Intramolecular C=N Bond Activation

An unprecedentate samarium complex of the molecular composition [{κ³‐{(Ph₂CH)N=CH}₂C₄H₂N)}{κ³‐{(Ph₂CHN=CH)(Ph₂CHNCH)C₄H₂N}Sm}₂] ( 2 ), which was isolated by the reaction of a potassium salt of 2,5‐bis{N‐(diphenylmethyl)‐iminomethyl}pyrrolyl ligand [K(THF)₂{(Ph₂CH)N=CH}₂C₄H₂N)] ( 1 ) with anhydrous samarium diiodide in THF at 60 °C through the in situ reduction of imine bond is presented. The homoleptic samarium complex [[κ³‐{(Ph₂CH)–N=CH}₂C₄H₂N)]₃Sm] ( 3 ) can also be obtained from the reaction of compound 1 with anhydrous samarium triiodide (SmI₃) in THF at 60 °C. The molecular structures of complexes 2 and 3 were established by single‐crystal X‐ray diffraction analysis. The molecular structure of complex 2 reveals the formation of a C–C bond in the 2,5‐bis{N‐(diphenylmethyl)iminomethyl}pyrrole ligand moiety (Ph₂Py^–). However, complex 3 is a homoleptic samarium complex of three bis‐iminopyrrolyl ligands. In complex 2 , the samarium ion adopts an octahedral arrangement, whereas in complex 3 , a distorted three face‐centered trigonal prismatic mode of nine coordination is observed around the metal ion.     

Acetato(N‐phenylpyridine‐2‐carboxamidato‐κ2N,N)(N‐phenylpyridine‐2‐carboxamide‐κ2N1,O)copper(II)

The title complex, [Cu(C₁₂H₉N₂O)(C₂H₃O₂)(C₁₂H₁₀N₂O)], is a neutral Cu^II complex with a primary N₃O₂ coordination sphere. The Cu centre coordinates to both a deprotonated and a neutral molecule of N‐phenylpyridine‐2‐carboxamide and also to an acetate anion. The coordination around the metal centre is asymmetric, the deprotonated ligand providing two N donor atoms [Cu—N = 1.995 (2) and 2.013 (2) Å] and the neutral ligand providing one N and one O donor atom to the coordination environment [Cu—N = 2.042 (2) Å and Cu—O = 2.2557 (19) Å], the fifth donor being an O atom of the acetate ion [Cu—O = 1.9534 (19) Å]. The remaining O atom from the acetate ion can be considered as a weak donor atom [Cu—O = 2.789 (2) Å], conferring to the Cu complex an asymmetric octahedral geometry. The crystal structure is stabilized by intermolecular N—H...O, C—H...O and C—H...π interactions.     

Structural Study of Nickel(II), Copper(II), and Palladium(II) Complexes of 2‐Pyridineformamide 3‐Hexamethyleneiminylthiosemicarbazone

Reduction of 2‐cyanopyridine by sodium in the presence of 3‐hexamethyleneiminylthiosemicarbazide produces 2‐pyridineformamide 3‐hexamethyleneiminylthiosemicarbazone, HAmhexim. Complexes with nickel(II), copper(II) and palladium(II) have been prepared and the following complexes structurally characterized: [Ni(Amhexim)OAc], [{Cu(Amhexim)}₂C₄H₄O₄]·2DMSO·H₂O, [Cu(HAmhexim)Cl₂] and [Pd(Amhexim)Cl]. Coordination is via the pyridyl nitrogen, imine nitrogen and thiolato or thione sulfur atom when coordinating as the anionic or neutral ligand, respectively. [{Cu(Amhexim)}₂C₄H₄O₄] is a binuclear complex with the two copper(II) ions bridged by the succinato group in [Cu‐(HAmhexim)Cl₂] the Cu atom is 5‐coordinate and close to a square pyramid structure and in [Ni(Amhexim)OAc] and [Pd(Amhexim)Cl] the metal atoms are planar, 4‐coordinate.     

A square‐planar NiII complex with an asymmetric coordination of a novel polynucleative 2,6‐diacetylpyridine bis{[2‐(hydroxyimino)propanoyl]hydrazone} ligand

The title compound, (2,6‐diacetylpyridine bis{[2‐(hydroxyimino)propanoyl]hydrazone}(2−))nickel(II) dimethyl sulfoxide solvate monohydrate, [Ni(C₁₅H₁₇N₇O₄)]·C₂H₆OS·H₂O, represents the first example of square‐planar N₄ coordination via N atoms with four different functions, namely amide, azomethine, hydroxyimino and pyridine. The coordination polyhedron of the central Ni atom has a slightly distorted square‐planar geometry. The 2,6‐diacetylpyridine bis{[2‐(hydroxyimino)propanoyl]hydrazone} ligand forms one six‐ and two five‐membered chelate rings, and a pseudo‐chelate ring through an intramolecular hydrogen bond with an amide group as donor and a deprotonated hydroxyimino group as acceptor, resulting in a pseudomacrocyclic arrangement.     

A Soft Grip: Magnesium Complexes with a Phosphine‐Modified Phosphonium Diylidic Lewis Base

Simple strategies to obtain magnesium complexes with the soft chelating diylidic ligand [Ph₂PCHPPh₂(fluorenylidene)]^? (dppmflu^?) were developed to evaluate the influence of the hard acid (cation) and soft base (anion) mismatch on the stability and reactivity of the formed derivatives. Deprotonation of the precursor Ph₂PCH₂PPh₂(flu) (dppmfluH) by an alkylmagnesium derivative or magnesium amide provided access to [{Mg(dppmflu)(μ‐nBu)}₂], [Mg(dppmflu){N(SiMe₃)₂}], and [{Mg(dppmflu)(μ‐Me)}₂], which were used as starting materials for further investigations. The reaction of [{Mg(dppmflu)(μ‐nBu)}₂] with PhSiH₃ in the presence of THF allowed isolation of the magnesium hydride complex [{Mg(dppmflu)(μ‐H)(thf)}₂] without a stabilizing nitrogen donor ligand. Prolonged heating enforced ligand redistribution and [{Mg(dppmflu)(μ‐H)(thf)}₂] was converted to [Mg(dppmflu)₂] and MgH₂. The homoleptic derivative [Mg(dppmflu)₂], in which the magnesium center is in a very soft ligand environment, can open a THF molecule by frustrated Lewis pair reactivity to give [{Mg(dppmflu)(μ‐OC₄H₈dppmflu)}₂].     

Synthesis and Structure of the Tetrameric [Cp*V(μ‐F)2]4 (Cp* = C5Me5); Preparation of the Imido Molybdenum Fluoride [(2,6‐i‐Pr2C6H3N)2MoF2] · THF and the Structural Investigation of [(2,6‐i‐Pr2C6H3N)6Mo4(μ3‐F)2Me2(μ‐O)4]

Treating [Cp*V(μ‐Cl)₂]₃ (Cp* = C₅Me₅) and [(2,6‐i‐Pr₂C₆H₃N)₂MoMe₂], respectively, with Me₃SnF afforded the title compounds [Cp*V(μ‐F)₂]₄ ( 1 ) and [(2,6‐i‐Pr₂C₆H₃N)₂MoF₂] · THF ( 2 ). 1 has a tetrameric structure, in which four V atoms can be regarded as being arranged at the vertices of a distorted tetrahedron, with four long edges bridged by one F atom and each of the other two short edges bridged by two F atoms with a mean V–F bond length of 2.00 Å. A hydrolyzed product of 2 , [(2,6‐i‐Pr₂C₆H₃N)₆Mo₄(μ₃‐F)₂Me₂(μ‐O)₄] ( 3 ) was characterized by elemental analyses and X‐ray single crystal study. The X‐ray diffraction analysis reveals that 3 has a unique tetranuclear structure, containing two five and two six coordinated Mo atoms connecting each other by four μ‐O and two μ₃‐F atoms. The geometries around the two Mo atoms can be described having distorted trigonal bipyramidal and distorted octahedral coordination spheres, respectively. The Mo–(μ‐O) bond lengths are 1.813 Å (average) for five coordinated Mo atoms and 2.030 Å (average) for those of six coordinated, respectively, indicating an additional π bonding between five coordinated Mo atoms and the μ‐O atoms. The Mo–(μ₃‐F) distances range from 2.291 to 2.352 Å.     

Synthese und Struktur von Ruthenium(II)‐Komplexen mit Triazenido‐ und Pentaazadienido‐Liganden

Synthesis and Crystal Structure of Ruthenium(II) Complexes with Triazenido and Pentaazadienido Ligands The ruthenium(II) triazenido complex [RuCl(ClC₆H₄N₃C₆H₄Cl)(p‐cymene)] ( 1 ) is obtained by the reaction of silver bis(p‐chlorphenyl)triazenid with [RuCl₂(p‐cymene)]₂ in CH₂Cl₂, and forms air stable, orange yellow crystals. It crystallizes as 1 ·CH₂Cl₂ in the orthorhombic space group Pbca with the lattice parameters a = 3134.3(3), b = 2105.7(2), c = 769.15(4) pm and Z = 8. In the diamagnetic mononuclear complex 1 the chelating triazenido ligand coordinates with the atoms N(1) and N(3). p‐Cymene binds η⁶ with its C₆ ring. The reaction of the etherphosphane complex [RuCl₂(Ph₂PCH₂C₄H₇O₂)₂] with 1, 3‐bis(p‐tolyl)triazenid in THF yields the complex [RuCl(tolyl‐N₃‐tolyl)(Ph₂PCH₂C₄H₇O₂)₂] ( 2 ). 2 forms monoclinic, red crystals with the space group P2₁/c and a = 1521.0(2), b = 1451.8(2), c = 2073.7(2) pm, β = 99.29(1)° and Z = 4. It is air stable and diamagnetic. The triazenide ion coordinates with the atoms N(1) and N(3). One of the two etherphosphane ligands is chelating and coordinates with the P atom and one O atom, while the other ligand binds in a monodentate fashion with its P atom, resulting in a coordination number of six for the Ru^II. [Ag(tolyl‐N₅‐tolyl)]₂ reacts in THF with [RuCl₂(C₆H₆)]₂ to afford the air stable, diamagnetic pentaazadienido complex [RuCl(tolyl‐N₅‐tolyl)(C₆H₆)] ( 3 ). 3 forms monoclinic, red crystals with the space group P2₁/c and a = 1462.4(1), b = 1056.51(8), c = 1371.4(1) pm, β = 114.36(1)° and Z = 4. The chelating pentaazadienido ligand coordinates with the atoms N(1) and N(3) at the divalent Ru atom. The benzene molecule binds η⁶ with its π system.     

Tunable Fluorophores Based on 2‐(N‐Arylimino)pyrrolyl Chelates of Diphenylboron: Synthesis,Structure, Photophysical Characterization,and Application in OLEDs

Reactions of 2‐(N‐arylimino)pyrroles (HNC₄H₃C(H)?N‐Ar) with triphenylboron (BPh₃) in boiling toluene afford the respective highly emissive N,N′‐boron chelate complexes, [BPh₂{κ²N,N′‐NC₄H₃C(H)?N‐Ar}] (Ar=C₆H₅ ( 12 ), 2,6‐Me₂‐C₆H₃ ( 13 ), 2,6‐iPr₂‐C₆H₃ ( 14 ), 4‐OMe‐C₆H₄ ( 15 ), 3,4‐Me₂‐C₆H₃ ( 16 ), 4‐F‐C₆H₄ ( 17 ), 4‐NO₂‐C₆H₄ ( 18 ), 4‐CN‐C₆H₄ ( 19 ), 3,4,5‐F₃‐C₆H₂ ( 20 ), and C₆F₅ ( 21 )) in moderate to high yields. The photophysical properties of these new boron complexes largely depend on the substituents present on the aryl rings of their N‐arylimino moieties. The complexes bearing electron‐withdrawing aniline substituents 17 – 20 show more intense (e.g., ?_f=0.71 for Ar=4‐CN‐C₆H₄ ( 19 ) in THF), higher‐energy (blue) fluorescent emission compared to those bearing electron‐donating substituents, for which the emission is redshifted at the expense of lower quantum yields (?_f=0.13 and 0.14 for Ar=4‐OMe‐C₆H₄ ( 15 ) and 3,4‐Me₂‐C₆H₃ ( 16 ), respectively, in THF). The presence of substituents bulkier than a hydrogen atom at the 2,6‐positions of the aryl groups strongly restricts rotation of this moiety towards coplanarity with the iminopyrrolyl ligand framework, inducing a shift in the emission to the violet region (λ_max=410–465 nm) and a significant decrease in quantum yield (?_f=0.005, 0.023, and 0.20 for Ar=2,6‐Me₂‐C₆H₃ ( 13 ), 2,6‐iPr₂‐C₆H₃ ( 14 ), and C₆F₅ ( 21 ), respectively, in THF), even when electron‐withdrawing groups are also present. Density functional theory (DFT) and time‐dependent DFT (TD‐DFT) calculations have indicated that the excited singlet state has a planar aryliminopyrrolyl ligand, except when prevented by steric hindrance (ortho substituents). Calculated absorption maxima reproduce the experimental values, but the error is higher for the emission wavelengths. Organic light‐emitting diodes (OLEDs) have been fabricated with the new boron complexes, with luminances of the order of 3000 cd m^?2 being achieved for a green‐emitting device.