Halide‐Free Diarylcalcium Complexes—Syntheses,Structures, and Stability

A general procedure was developed for the synthesis of diarylcalcium complexes by addition of KOtBu to arylcalcium iodides in THF. Intermediate arylcalcium tert‐butanolate dismutates immediately leading to insoluble tert‐butanolate precipitates of calcium. Depending on the steric demand and denticity of additional neutral aliphatic azabases, mononuclear or dinuclear complexes trans‐[Ca(α‐Naph)₂(thf)₄] ( 1 ), [Ca(β‐Naph)₂(thf)₄] ( 2 ), [Ca(Tol)₂(tmeda)]₂ ( 3 ), [Ca(Ph)₂(tmeda)]₂ ( 4 ), [Ca(Ph)₂(pmdta)(thf)] ( 5 ), [Ca(hmteta)(Ph)₂] ( 6 ), and [Ca([18]C‐6)(Ph)₂] ( 7 ) were isolated (Naph=naphthyl; meda=N,N,N′,N′‐tetramethylethylenediamine; pmdta= N,N,N′,N′′,N′′‐pentamethyldiethylenetriamine; hmteta=N,N,N′,N′′,N′′′,N′′′‐hexamethyltriethylenetetramine). The Ca?C bond lengths vary between 250.8 and 263.5 pm, the ipso‐carbon atoms show low‐field‐shifted resonances in the ¹³C NMR spectra.     

Reaktionen von Lanthanoidhalogeniden mit Alkalibenzylverbindungen. Darstellung und Kristallstrukturen von [(tmeda)(C6H5CH2)2Y(μ-Br)2Li(tmeda)], [(tmeda)2SmBr(μ-Br)2Li(tmeda)] und [(dme)2SmBr(μ-Br)]2

Reactions of Lanthanide Halides with Alkalibenzyl Compounds. Synthesis and Crystal Structures of [(tmeda)(C₆H₅CH₂)₂Y(μ-Br)₂Li(tmeda)], [(tmeda)₂SmBr(μ-Br)₂Li(tmeda)] and [(dme)₂SmBr(μ-Br)]₂ Alkali-benzyl compounds react via a metathesis reaction with lanthanide halides to benzyl complexes of the rare earths. Reaction of [(C₆H₅CH₂)Li(tmeda)] with YBr₃ leads to the complex [(tmeda)Y(C₆H₅CH₂)₂ (μ-Br)₂Li(tmeda)] 1 , in which Yttrium and lithium are linked via two bromide bridges. However, the reaction of [(C₆H₅CH₂)Li(tmeda)] with SmBr₃ in toluene/tmeda leads under reduction of the Sm ion to the compound [(tmeda)₂SmBr(μ-Br)₂Li(tmeda)] 2 . 2 reacts with DME to yield the dimeric compound [(dme)₂SmBr(μ-Br)]₂ 3 . The structures of 1 – 3 were determined by X-ray single crystal structure analysis:

• 1: Space group P2₁/c, Z = 4, a = 829.5(6) pm, b = 1477.9(11) pm, c = 2575.0(10) pm, β = 92.03(6)°,
• 2: Space group P2₁, Z = 2, a = 954,7(3) pm, b = 1338.5(6) pm, c = 1244.9(5) pm, β = 107.51(3)°,
• 3: Space group P1 , Z = 1, a = 797.2(7) pm, b = 818.3(7) pm, c = 1169.7(8) pm, α = 100.96(6)°, β = 92.03(6)°, γ = 91.75(7)°.

     

On the Solution Behaviour of Benzyllithium⋅(−)‐Sparteine Adducts and Related Lithium Organyls – A Case Study on Applying 7Li,15N{1H} HMQC and Further NMR Methods,Including Some Investigation into Asymmetric Synthesis

2D ⁷Li,¹⁵N heteronuclear shift correlation through scalar coupling has successfully been applied to several lithium organyls consisting of polydentate N ligands such as N,N,N′,N′‐tetramethylethylenediamine (tmeda), N,N,N′,N′,N′′‐pentamethyldiethylentriamine (pmdta) and (?)‐sparteine. Structural insights on the conformation of benzyllithium ? pmdta ( 5 ) in a toluene solution and the strength of ion pairing in combination with PGSE NMR measurements, ¹H,¹H‐NOESY and ¹H,⁷Li‐HOESY experiments are presented. By studying in detail the formation of 5 in solution, a transient species has been observed for the first time and assigned to a pre‐complex of nBuLi and pmdta. In addition, the solution behaviour of the complex formed between benzyllithium and (?)‐sparteine ( 8 ) has been studied by PGSE and multinuclear NMR spectroscopy. The straightforward synthesis and first applications in asymmetric lithiations are also reported, which show that the new system benzyllithium ? (?)‐sparteine ( 8 ) provide poorer enantioselective induction than the classical nBuLi ? (?)‐sparteine ( 6 ). The results were supported by deprotonation experiments confirming that the formation of 8 relies on two relevant factors, namely temperature and lithiating reagent. The existence of 8 may thus interfere with the asymmetric induction when the system nBuLi ? (?)‐sparteine is used in the enantioselective deprotonations of N‐Boc‐N‐(p‐methoxyphenyl)‐benzylamine conducted in toluene.     

Heterobimetallische Komplexe von Lithium,Aluminium und Gold mit dem N‐[2‐N′,N′‐(Dimethylaminoethyl)‐N‐methyl‐aminoethyl]‐ferrocenyl‐Liganden (η5‐C5H5)Fe{η5‐C5H3[CH(CH3)N(CH3)CH2CH2NMe2]‐2}

Heterobimetallic Complexes of Lithium, Aluminum, and Gold with the N ‐[2‐ N ′, N ′‐(dimethylaminoethyl)‐ N ‐methyl‐aminoethyl]‐ferrocenyl Ligand (η⁵‐C₅H₅)Fe{η⁵‐C₅H₃[CH(CH₃)N(CH₃)CH₂CH₂NMe₂]‐2} N‐[2‐N′,N′‐(dimethylaminoethyl)‐N‐methyl‐aminoethyl]ferrocene FcN,NH ( 1 ) reacts with ⁿBuLi under formation of the lithium organyl (FcN,N)Li ( 2 ). At reactions of 2 with AlBr₃ and AuCl · PPh₃ the heterobimetallic organo derivatives (FcN,N)AlBr₂ ( 3 ), (FcN,N)Au · PPh₃ ( 4 ) are formed. A detailed characterization of 2 – 4 was carried out by single crystal x‐ray analyses as well as by NMR and Mößbauer spectroscopy.     

Mononuclear Formamidinate Complexes of Lithium and Sodium

Treatment of N,N′‐bis(aryl)formamidines (FXylH = N,N′‐bis(2,6‐dimethylphenyl)formamidine, FEtH = N,N′‐bis(2,6‐diethylphenyl)formamidine, FisoH = N,N′‐bis(2,6‐diisopropylphenyl)formamidine) with nBuLi in the presence of tmeda (= N,N,N′,N′‐tetramethylethylenediamine) led to deprotonation of the amidine affording [Li(FXyl)(tmeda)] ( 1 ), [Li(FEt)(tmeda)] ( 2 ) and [Li(Fiso)(tmeda)] ( 3 ) respectively. Similar treatment of FXylH and FisoH with [Na{N(SiMe₃)₂}] in THF and pmdeta (= N,N,N′,N″,N″‐pentamethyldiethylenetriamine) yielded [Na(FXyl)(pmdeta)] ( 4 ) and [Na(Fiso)(pmdeta)] ( 5 ). All complexes were characterised by spectroscopy (NMR and IR) and X‐ray crystallography. Due to the bulkiness of the formamidinate ligands and the multidentate nature of the supporting neutral amine ligands (tmeda and pmdeta), all compounds were mononuclear with η²‐chelating formamidinate ligands in the solid state.     

Synthesis,X-ray structural and DFT studies of n-membered ring P,C-chelated complexes of Pd(II) and Pt(II) derived from unsymmetrical phosphorus ylides and application of Pd(II) complexes as catalyst in Suzuki reaction

The phosphonium salts [Ph₂P(CH₂)_nPPh₂CH₂C(O)C₆H₄-m-OMe]Br (n = 1 (S₁) and n = 2 (S₂)) were synthesized in the reaction of bis(diphenylphosphino)methane (dppm) and bis(diphenylphosphino)ethane (dppe) with 2-bromo-3?-methoxy acetophenone, respectively. Further treatment with NEt₃ gave the phosphorus ylides Ph₂P(CH₂)_nPPh₂C(H)C(O)C₆H₄-m-OMe (n = 1 (Y₁) and n = 2 (Y₂)). These ligands were treated with [MCl₂(cod)] (M = Pd or Pt; cod = 1,5-cyclooctadiene) to give the P, C-chelated complexes, [MCl₂(Ph₂P(CH₂)_nPPh₂C(H)C(O)C₆H₄-m-OMe)] (n = 1, M = Pd (3), Pt (4), and n = 2, M = Pd (5), Pt (6)). These compounds were characterized by elemental analysis, spectroscopic methods, UV–visible, and fluorescence emission spectra. Further, the structures of complexes 3 and 6 were characterized crystallographically. The palladium complexes 3 and 5 proved to be excellent catalysts for the Suzuki reactions of various aryl chlorides. Also, a theoretical study on the structure of complexes 3–6 has been investigated at the BP86/def2-SVP level of theory. The strength and nature of donor?acceptor bonds between the phosphorus ylides (L) and MCl₂ fragment in the [LMCl₂] (M = Pd, Pt, L = Y₁, Y₂) were studied by NBO and energy decomposition analysis (EDA), as well as their natural orbitals for chemical valence variation (EDA-NOCV).     

Ruthenium(II) complexes of aroylhydrazones: structural,electrochemical and electrostatic interactions with DNA

Four Ru(II) complexes with tridentate ligands viz. (4-hydroxy-N′-(pyridin-2-yl-ethylene) benzohydrazide [Ru(L¹)(PPh₃)₂(Cl)] (1), N′-(pyridin-2-yl-methylene) nicotinohydrazide [Ru(L²)(PPh₃)₂(Cl)] (2), N′-(1H-imidazol-2-yl-methylene)-4-hydroxybenzohydrazide [Ru(L³)(PPh₃)₂(Cl)] (3), and N′-(1H-imidazol-2-yl-methylene) nicotinohydrazide [Ru(L⁴)(PPh₃)₂(Cl)] (4) have been synthesized and characterized. The methoxy-derivative of L³H (abbreviated as L³H*) exists in E configuration with torsional angle of 179.4° around C₇-N₈-N₉-C₁₀ linkage. Single crystal structures of acetonitrile coordinated ruthenium complexes of 1 and 3 having compositins as [Ru(L¹)(PPh₃)₂(CH₃CN)]Cl (1a) and [Ru(L³)(PPh₃)₂(CH₃CN)]Cl (3a) revealed coordination of tridentate ligands with significantly distorted octahedral geometry constructed by imine nitrogen, heterocyclic nitrogen, and enolate amide oxygen, forming a cis-planar ring with trans-placement of two PPh₃ groups and a coordinated acetonitrile. Ligands (L¹H-L⁴H) and their ruthenium complexes (1–4) are characterized by ¹H, ¹³C, ³¹P NMR, and IR spectral analysis. Ru(II) complexes have reversible to quasi-reversible redox behavior having Ru(II)/Ru(III) oxidation potentials in the range of 0.40–0.71 V. The DNA binding constants determined by absorption spectral titrations with Herring Sperm DNA (HS-DNA) reveal that L⁴H and 1 interact more strongly than other ligands and Ru(II) complexes. Complexes 1–3 exhibit DNA cleaving activity possibly due to strong electrostatic interactions while 4 displays intercalation.     

Pyrrole Denitrogenation and Fragmentation of Tetramethylethylenediamine Promoted by a NbII Cluster

A nitrogen center was abstracted from a pyrrolyl ring to form the dinuclear nitrido- and dienyl-bridged complex 1 during the reaction of [{(tmeda)Nb^IICl}₂(μ-Cl)₃Li(tmeda)] with the lithium salt of 2,5-dimethylpyrrole (tmeda=N,N,N′,N′-tetramethylethylenediamine). A second product from this reaction is the amido-carbene-hydride niobium complex 2 , which likewise forms under C−N bond cleavage.     

Lithiated γ-O-functionalized propyl phenyl sulfides and sulfones of the type Li[CH(SOxPh)CH2CH2OR] (x = 0, 2). [Li{CH(SPh)CH2CH2Ot-Bu}(tmeda)] – A structurally characterized organolithium inner complex

Lithiation of O-functionalized alkyl phenyl sulfides PhSCH₂CH₂CH₂OR (R = Me, 1a; i-Pr, 1b; t-Bu, 1c; CPh₃, 1d) with n-BuLi/tmeda in n-pentane resulted in the formation of α- and ortho-lithiated compounds [Li{CH(SPh)CH₂CH₂OR}(tmeda)] (α-2a–d) and [Li{o-C₆H₄SCH₂CH₂CH₂OR)(tmeda)] (o-2a–d), respectively, which has been proved by subsequent reaction with n-Bu₃SnCl yielding the requisite stannylated γ-OR-functionalized propyl phenyl sulfides n-Bu₃SnCH(SPh)CH₂CH₂OR (α-3a–d) and n-Bu₃Sn(o-C₆H₄SCH₂CH₂CH₂OR) (o-3a–d). The α/ortho ratios were found to be dependent on the sterical demand of the substituent R. Stannylated alkyl phenyl sulfides α-3a–c were found to react with n-BuLi/tmeda and n-BuLi yielding the pure α-lithiated compounds α-2a–c and [Li{CH(SPh)CH₂CH₂OR}] (α-4a–b), respectively, as white to yellowish powders. Single-crystal X-ray diffraction analysis of [Li{CH(SPh)CH₂CH₂Ot-Bu}(tmeda)] (α-2c) exhibited a distorted tetrahedral coordination of lithium having a chelating tmeda ligand and a C,O coordinated organyl ligand. Thus, α-2c is a typical organolithium inner complex.Lithiation of O-functionalized alkyl phenyl sulfones PhSO₂CH₂CH₂CH₂OR (R = Me, 5a; i-Pr, 5b; CPh₃, 5c) with n-BuLi resulted in the exclusive formation of the α-lithiated products Li[CH(SO₂Ph)CH₂CH₂OR] (6a–c) that were found to react with n-Bu₃SnCl yielding the requisite α-stannylated compounds n-Bu₃SnCH(SO₂Ph)CH₂CH₂OR (7a–c). The identities of all lithium and tin compounds have been unambiguously proved by NMR spectroscopy (¹H, ¹³C, ¹¹⁹Sn).     

Syntheses and characterizations of 5-nitro-2-(3′,5′-di(trifluoromethyl)phenyl)pyridyl-containing iridium(III) complexes and the two-band white photoluminescence properties in solution

A derivative of 2-phenylpyridine (Hppy), 5-nitro-2-(3′,5′-di(trifluoromethyl)phenyl)pyridine (HL), is prepared. The L-containing cyclometalated iridium(III) complexes with mono- and bidentate ancillary ligands, [Ir(L)₂(PPh₃)Cl] (1) and [Ir(L)₂(pic)] (2, pic = picolinic acid), are synthesized and characterized. The photoluminescence (PL) spectra of 1 and 2 in CH₂Cl₂ solutions show emission maxima at 558 and 560 nm, corresponding to yellow light emission with the Commission Internationale de L’éclairage (CIE) coordinates of (0.45, 0.54) and (0.46, 0.52), respectively. However, the luminescence intensity of 2 with PL quantum yield of 0.71 is obviously stronger that of 1 with PLQY of 0.19. The two-band white PL properties of 2 and [Ir(dfppy)₂(PPh₃)(NCS)] (3, dfppy = 2-(4,6-difluorophenyl)pyridine) with efficient blue light emission are investigated. The CH₂Cl₂ solutions of 2 and 3 in the molar ratio of 1?:?5 show white light emission with the CIE coordinates of (0.33, 0.41).     

Synthesis, characterization and Schlenk equilibrium studies of methylmagnesium compounds with O- and N-donor ligands - the unexpected behavior of [MgMeBr(pmdta)] (pmdta = N,N,N′,N″,N″-pentamethyldiethylenetriamine)

MgMe₂ (1) was found to react with 1,4-diazabicyclo[2.2.2]octane (dabco) in tetrahydrofuran (thf) yielding a binuclear complex [{MgMe₂(thf)}₂(μ-dabco)] (2). Furthermore, from reactions of MgMeBr with diglyme (diethylene glycol dimethyl ether), NEt₃, and tmeda (N,N,N′,N′-tetramethylethylenediamine) in etheral solvents compounds MgMeBr(L), (L = diglyme (5); NEt₃ (6); tmeda (7)) were obtained as highly air- and moisture-sensitive white powders. From a thf solution of 7 crystals of [MgMeBr(thf)(tmeda)] (8) were obtained. Reactions of MgMeBr with pmdta (N,N,N′,N″,N″-pentamethyldiethylenetriamine) in thf resulted in formation of [MgMeBr(pmdta)] (9) in nearly quantitative yield. On the other hand, the same reaction in diethyl ether gave MgMeBr(pmdta) · MgBr₂(pmdta) (10) and [{MgMe₂(pmdta)}₇{MgMeBr(pmdta)}] (11) in 24% and 2% yield, respectively, as well as [MgMe₂(pmdta)] (12) as colorless needle-like crystals in about 26% yield. The synthesized methylmagnesium compounds were characterized by microanalysis and ¹H and ¹³C NMR spectroscopy. The coordination-induced shifts of the ¹H and ¹³C nuclei of the ligands are small; the largest ones were found in the tmeda and pmdta complexes. Single-crystal X-ray diffraction analyses revealed in 2 a tetrahedral environment of the Mg atoms with a bridging dabco ligand and in 8 a trigonal-bipyramidal coordination of the Mg atom. The single-crystal X-ray diffraction analyses of [MgMe₂(pmdta)] (12) and [MgBr₂(pmdta)] (13) showed them to be monomeric with five-coordinate Mg atoms. The square-pyramidal coordination polyhedra are built up of three N and two C atoms in 12 and three N and two Br atoms in 13. The apical positions are occupied by methyl and bromo ligands, respectively. Temperature-dependent ¹H NMR spectroscopic measurements (from 27 to −80 °C) of methylmagnesium bromide complexes MgMeBr(L) (L = thf (4); diglyme (5); NEt₃ (6); tmeda (7)) in thf-d₈ solutions indicated that the deeper the temperature the more the Schlenk equilibria are shifted to the dimethylmagnesium/dibromomagnesium species. Furthermore, at −80 °C the dimethylmagnesium compounds are predominant in the solutions of Grignard compounds 4-6 whereas in the case of the tmeda complex7 the equilibrium constant was roughly estimated to be 0.25. In contrast, [MgMeBr(pmdta)] (9) in thf-d₈ revealed no dismutation into [MgMe₂(pmdta)] (12) and [MgBr₂(pmdta)] (13) even up to −100 °C. In accordance with this unexpected behavior, 1:1 mixtures of 12 and 13 were found to react in thf at room temperature yielding quantitatively the corresponding Grignard compound 9. Moreover, the structures of [MgMeBr(pmdta)] (9c), [MgMe₂(pmdta)] (12c), and [MgBr₂(pmdta)] (13c) were calculated on the DFT level of theory. The calculated structures 12c and 13c are in a good agreement with the experimentally observed structures 12 and 13. The equilibrium constant of the Schlenk equilibrium (2 9c ? 12c + 13c) was calculated to be K_gas = 2.0 × 10⁻³ (298 K) in the gas phase. Considering the solvent effects of both thf and diethyl ether using a polarized continuum model (PCM) the corresponding equilibrium constants were calculated to be K_thf = 1.2 × 10⁻³ and K_ether = 3.2 × 10⁻³ (298 K), respectively.     

Syntheses of the Antimonides R2Sb− (R = Ph,Mes, tBu,tBu2Sb) and Sb73− by Reactions of Organoantimony Hydrides or cyclo‐(tBuSb)4 with Li,Na, K,or BuLi

Reactions of R₂SbH with BuLi at ?70 °C in tetrahydrofuran (thf) lead to [R₂SbLi(thf)₃] [R = Ph ( 1 ) or R = Mes ( 2 )]. The antimonides [tBu₂SbK(pmdeta)] ( 3 ) (pmdeta = pentamethyldiethylenetriamine), [Li(tmeda)₂][tBu₄Sb₃]·benzene ( 4 ) (tmeda = tetramethylethylenediamine), and [tBu₄Sb₃Na(tmeda, thf)] ( 5 ) result from the reduction of cyclo‐(tBuSb)₄ by Li, Na, or K with pmdeta or tmeda in thf. The primary stibanes RSbH₂ [R = Mes ( 6 ), 2‐(Me₂NCH₂)C₆H₂ ( 7 )] are synthesized by reactions of RSbCl₂ with LiAlH₄. PhSbH₂ reacts with BuLi, and tmeda in toluene to give [Sb₇Li₃(tmeda)₃]·toluene ( 8 ). [Sb₇Na₃(pmdeta)₃]·toluene ( 9 ) is obtained from PhSbH₂, Na in liqu. NH₃, pmdeta and toluene. Crystal structures are reported for 1 – 5 and 9 .     

Synthesis and structures of the [benzamidinato]3- complexes Li3(tmeda)(L1)]2 and [Li(thf)4][Li5(L2)(OEt2)2] [L1 = N(SiMe3)C(Ph)N(SiMe3) and L2 = N(SiMe3)C(C6H4-4)NPh

Reduction at ambient temperature of each of the lithium benzamidinates [Li(L(1))(tmeda)] or [{Li(L(2))(OEt(2))(2)}(2)] with four equivalents of lithium metal in diethyl ether or thf furnished the brown crystalline [Li(3)(L(1))(tmeda)] (1) or [Li(thf)(4)][Li(5)(L(2))(2)(OEt(2))(2)] (2), respectively. Their structures show that in each the [N(R(1))C(R(3))NR(2)](3-) moiety has the three negative charges largely localised on each of N, N' and R = Aryl); a consequence is that the "aromatic" 2,3- and 5,6-CC bonds of R(3) approximate to being double bonds. Multinuclear NMR spectra in C(6)D(6) and C(7)D(8) show that 1 and 2 exhibit dynamic behaviour. [The following abbreviations are used: L(1) = N(SiMe(3))C(Ph)N(SiMe(3)); L(2) = N(SiMe(3))C(C(6)H(4)Me-4)N(Ph); tmeda = (Me(2)NCH(2)-)(2); thf = tetrahydrofuran.] This reduction is further supported by a DFT analysis.     

Studies of η5-cyclichydrocarbon ruthenium(II) complexes containing para-amino-N-(pyrid-2-ylmethylene)phenylamine ligand: molecular structure of [(η5-C5H5)Ru(PPh3)(C5H4NCH=N-C6H4-p-NH2)]BF4

Reaction of [(η⁵-Cp)Ru(PPh₃)₂Cl] (1) with excess para-amino-N-(pyrid-2-ylmethylene)-phenylamine ligand (app) in methanol in the presence of NH₄BF₄ leads to the formation of [η⁵-CpRu(PPh₃)(aap)]BF₄ (6BF₄). Similarly, [(η⁵-ind)Ru(PPh₃)₂(CH₃CN)]BF₄ (4BF₄) and [(η⁵-Cp*)Ru(PPh₃)₂(CH₃CN)]BF₄ (5BF₄) react with app to yield the cationic complexes [(η⁵-ind)Ru(PPh₃)(app)]BF₄ (7BF₄) and [(η⁵-Cp*)Ru(PPh₃)(app)]BF₄ (8BF₄), respectively. The complexes were characterized by analysis and spectroscopic data. The structure of a representative complex (6BF₄) was established by single-crystal X-ray methods.     

Synthesis,spectroscopic investigation,structural characterization,and DFT calculations of [ReX2(N2COPh)(CH3PhCN)(PPh3)2] (X=Cl,Br)

Reactions of [ReX₂(η ²-N₂COPh-N′,O)(PPh₃)₂] with 3-methylbenzonitrile give two iso-structural complexes, [ReX₂(N₂COPh)(CH₃PhCN)(PPh₃)₂] (X?=?Cl, Br). The crystal and molecular structures of [ReCl₂(N₂COPh)(CH₃PhCN)(PPh₃)₂] (1) and [ReBr₂(N₂COPh)(CH₃PhCN)(PPh₃)₂]?·?CH₂Cl₂ (2) were determined. The electronic structures were examined with density functional theory (DFT). The spin-allowed electronic transitions were calculated with the time-dependent DFT method, and the UV-Vis spectrum has been discussed.     

Syntheses,characterization, and crystal structures of ruthenium(II)/(III) complexes with tridentate salicylaldiminato ligands

Treatment of [Ru(PPh₃)₃Cl₂] with one equivalent of tridentate Schiff base 2-[(2-dimethylamino-ethylimino)-methyl]-phenol (HL) in the presence of triethylamine afforded a ruthenium(III) complex [RuCl₃(κ²-N,N-NH₂CH₂CH₂NMe₂)(PPh₃)] as a result of decomposition of HL. Interaction of HL and one equivalent of [RuHCl(CO)(PPh₃)₃], [Ru(CO)₂Cl₂] or [Ru(tht)₄Cl₂] (tht = tetrahydrothiophene) under different conditions led to isolation of the corresponding ruthenium(II) complexes [RuCl(κ³-N,N,O-L)(CO)(PPh₃)] (2), [RuCl(κ³-N,N,O-L)(CO)₂] (3), and a ruthenium(III) complex [RuCl₂(κ³-N,N,O-L)(tht)] (4), respectively. Molecular structures of 1·CH₂Cl₂, 2·CH₂Cl₂, 3 and 4 have been determined by single-crystal X-ray diffraction.     

Nucleophilic Aromatic Addition Reactions of the Metallabenzenes and Metallapyridinium: Attacking Aromatic Metallacycles with Bis(diphenylphosphino)methane to Form Metallacyclohexadienes and Cyclic η2‐Allene‐Coordinated Complexes

The reactions of phosphonium‐substituted metallabenzenes and metallapyridinium with bis(diphenylphosphino)methane (DPPM) were investigated. Treatment of [Os{CHC(PPh₃)CHC(PPh₃)CH}Cl₂(PPh₃)₂]Cl with DPPM produced osmabenzenes [Os{CHC(PPh₃)CHC(PPh₃)CH}Cl₂{(PPh₂)CH₂(PPh₂)}]Cl ( 2 ), [Os{CHC(PPh₃)CHC(PPh₃)CH}Cl{(PPh₂)CH₂(PPh₂)}₂]Cl₂ ( 3 ), and cyclic osmium η²‐allene complex [Os{CH?C(PPh₃)CH?(η²‐C?CH)}Cl₂{(PPh₂)CH₂(PPh₂)}₂]Cl ( 4 ). When the analogue complex of osmabenzene 1 , ruthenabenzene [Ru{CHC(PPh₃)CHC(PPh₃)CH}Cl₂(PPh₃)₂]Cl, was used, the reaction produced ruthenacyclohexadiene [Ru{CH?C(PPh₃)CH?C(PPh₃)CH}Cl{(PPh₂)CH₂(PPh₂)}₂]Cl₂ ( 6 ), which could be viewed as a Jackson–Meisenheimer complex. Complex 6 is unstable in solution and can easily be convert to the cyclic ruthenium η²‐allene complexes [Ru{CH?C(PPh₃)CH?(η²‐C?CH)}Cl{(PPh₂)CH₂(PPh₂)}₂]Cl₂ ( 7 ) and [Ru{CH?C(PPh₃)CH?(η²‐C?CH)}Cl₂{(PPh₂)CH₂(PPh₂)}₂]Cl ( 8 ). The key intermediates of the reactions have been isolated and fully characterized, further supporting the proposed mechanism for the reactions. Similar reactions also occurred in phosphonium‐substituted metallapyridinium [OsCl₂{NHC(CH₃)C(Ph)C(PPh₃)CH}(PPh₃)₂]BF₄ to give the cyclic osmium η²‐allene‐imine complex [OsCl₂{NH?C(CH₃)C(Ph)?(η²‐C?CH)}{(PPh₂)CH₂(PPh₂)}(PPh₃)]BF₄ ( 11 ).     

The Nitrogen‐Assisted Triphenylphosphine Displacement of Methylpyridine Ligand in Palladium(II) Complex: Crystal Structures of [Pd(PPh3)2{η1‐C5H3N(CH3)}(Br)] and [Pd(PPh3)Br]2{μ,η2‐C5H3N(CH3)}2

Treatment of Pd(PPh₃)₄ with 2‐bromo‐4‐methylpyridine, C₅H₃N(CH₃)Br, in dichloromethane at ?20 °C causes the oxidative addition reaction to produce the palladium complex [Pd(PPh₃)₂ {η¹‐C₅H₃N(CH₃)}(Br)], 2 , by substituting two triphenylphosphine ligands. In a dichloromethane solution of complex 2 at room temperature for 3 h, it undergoes displacement of the triphenylphosphine ligand to form the dipalladium complex [Pd(PPh₃)Br]₂{μ,η²‐C₅H₃N(CH₃)}₂, 3 , in which the two 4‐methylpyridine ligands coordinated through carbon to one metal center and bridging the other metal through the nitrogen atom. Complexes 2 and 3 are characterized by X‐ray diffraction analyses.