Palladiumdichloride (ferrocenylethynyl)phosphanes and their use in Pd-catalyzed Heck-Mizoroki- and Suzuki-Miyaura carbon-carbon cross-coupling reactions

In this work the synthesis of phosphane selenides (FcCC)_nPh_3−nPSe (2a, n = 1; 2b, n = 2; 2c, n = 3; Fc = ferrocenyl, (η⁵-C₅H₄)(η⁵-C₅H₅)Fe) from (FcCC)_nPh_3−nP (1a, n = 1; 1b, n = 2; 1c, n = 3) and selenium is described to estimate the σ-donor properties of these systems by ³¹P{¹H} NMR spectroscopy. Progressive replacement of phenyl by ferrocenylethynyl causes a shielding of the phosphorus atom with increasing of the ¹J(³¹P-⁷⁷Se) coupling constants.The palladiumdichloride metal-organic complexes [((FcCC)_nPh_3−nP)₂PdCl₂] (3a, n = 1; 3b, n = 2; 3c, n = 3) have been used as (pre)catalysts in the Suzuki-Miyaura (reaction of 2-bromo-toluene (4a) and 4-bromo-acetophenone (4b), respectively, with phenyl boronic acid (5) to give 2-methyl biphenyl (6a) and 4-acetyl biphenyl (6b)) and in the Heck-Mizoroki reaction (treatment of iodobenzene (7) with tert-butyl acrylate (8) to give E-tert-butyl cinnamate (9)).The structures of molecules 1a, 1c, 2c, and 3c in the solid state were determined by single X-ray structure analysis showing that the structural parameters of these systems are unexceptional and correspond to those of related phosphanes, seleno phosphanes, and palladium dichloride complexes.     

Orthopalladation of phosphorus ylides in endo position with bidentate ligands

The ortho-metallated complexes [Pd₂{κ²(C,C)-C₆H₄(PPh₂CHC(O)C₆H₅R}₂(μ-Cl)₂] (R = Ph (1a), NO₂ (1b), Br (1c)) were prepared by refluxing equimolar mixtures of Ph₃PCHC(O)C₆H₅R, (R = Ph, NO₂, Br) and Pd(OAc)₂ in MeOH, followed by an excess of NaCl. The dinuclear complexes (1a-1c) react with silver trifluoromethylsulfonate and bidentate ligands [L = bipy (2,2′-bipyridine), phen (phenanthroline), dppe (bis(diphenylphosphino)ethane), dppp (bis(diphenylphosphino)propane)] giving the mononuclear stabilized orthopalladated complexes in endo position [Pd{κ²(C,C)-C₆H₄(PPh₂CHC(O)R}L](OTf) [R = Ph, L = phen (2a), bipy (3a), dppe (4a), dppp (5a); R = NO₂, L = phen (2b), bipy (3b), dppe (4b), dppp (5b); R = Br, L = phen (2c), bipy (3c), dppe (4c), dppp (5c); OTf = trifluoromethylsulfonate anion]. Orthometalation and ylidic C-coordination are demonstrated by an X-ray diffraction study of 2c and 3c. In the structures, the palladium atom shows a slightly distorted square-planar coordination geometry.     

Heterospin single-molecule magnets with extra-large anisotropic barrier

The mixtures of Co(X-hfpip)₂; X = I and H, and bisdiazo-dipyridine ligands, D2py₂(TBA), in 1:1 ratios gave the discrete cobalt complexes, 1 and 2, respectively. The molecular structures for 1 and 2 revealed by X-ray crystallography were cyclic 2:2 cobalt complexes formulated as [(Co(X-hfpip)₂)₂(D2py₂(TBA))₂], in which the cobalt units were compressed octahedra. After irradiation of the microcrystalline samples, the resulting Co-carbene complexes, 1c and 2c, showed SMM behaviors exhibiting slow magnetic relaxations. In dc and ac magnetic susceptibility experiments, the activation barrier, U_eff, for reorientation of the magnetic moment were estimated to be 139 and 135 K for 1c and 2c, respectively, and the hysteresis loops of the magnetization (the coercive force, H_c, and 26 and 15 kOe at 1.9 K for 1c and 2c, respectively) were observed. In addition, the values of the quantum tunneling time, τ_Q, were determined to be 1.1 × 10⁵ and 5.4 × 10⁵ s (t_1/2 = 21 and 104 h) for 1c and 2c, respectively, below 2.5 K.     

Fe(II) and Co(II) pyridinebisimine complexes bearing different substituents on ortho- and para-position of imines: synthesis, characterization and behavior of ethylene polymerization

A series of 2,6-bis(imino)pyridyl iron(II) and cobalt(II) complexes [2,6-(ArNCMe)₂C₅H₃N]MCl₂ (Ar = 2,6-i-Pr₂C₆H₃, M = Fe: 3a, M = Co: 4a; Ar = 2,4,6-i-Pr₃C₆H₂, M = Fe: 3b, M = Co: 4b; Ar = 2,6-i-Pr₂-4-BrC₆H₂, M = Fe: 3c, M = Co: 4c; Ar = 2,4-i-Pr₂-6-BrC₆H₂, M = Fe: 3d, M = Co: 4d) has been synthesized, characterized, and investigated as precatalysts for the polymerization of ethylene in the presence of modified methylaluminoxane (MMAO). The substituents of pyridinebisimine ligands and their positions located significantly influence catalyst activity and polymer property. It is found that the catalytic activities of the iron complexes/MMAO systems are mainly dominated by electronical effect, while those of the cobalt complexes/MMAO systems are primarily controlled by hindering effect.     

Palladium(II) complexes containing a bulky pyridinyl N-heterocyclic carbene ligand: Preparation and reactivity

Coordination chemistry of a pyridine imidazole-2-ylidene ligand (pyN ˆC) with sterically hindered substituents toward palladium(II) metal ions has been investigated. The palladium carbene complex [(C-pyN ˆC)Pd(η³-allyl)Cl] (3) is prepared via the transmetallation from the corresponding silver carbene complexes with [ClPd(η³-allyl)]₂. Upon the abstraction of chloride, coordination of pyridinyl-nitrogen becomes feasible to form [C,N-(pyN ˆC)Pd(η³-allyl)](BF₄) (4). Ligand substitution reaction of 4 with triphenylphosphine results in the formation of [(C-pyN ˆC)Pd(PPh₃)(η³-allyl)](BF₄)], which the pyridinyl-nitrogen donor is substituted by the phosphine. This palladium complex appears to be base sensitive. Treatment of 4 with t-butoxide causes the decomposition to yield the metal nano-particles. Furthermore, de-complexation of 4 takes place under hydrogen atmosphere to generate the carbene precursor, 1-(6-mesityl-2-picolyl)-3-mesitylimidazolium salt. Nevertheless, the palladium complex 4 shows good catalytic activity on the Suzuki-Miyaura and Mizoroki-Heck reactions.     

Palladium and half sandwich ruthenium(II) complexes of selenated and tellurated benzotriazoles: Synthesis, structural aspects and catalytic applications

1-(Phenylselenomethyl)-1H-benzotriazole (L¹) and 1-(4-methoxyphenyltelluromethyl)-1H-benzotriazole (L²) have been synthesized by reacting 1-(chloromethyl)-1H-benzotriazole with in situ generated nucleophiles PhSe⁻ and ArTe⁻, respectively. The complexes of L¹ and L² with Pd(II) and Ru(II)(η⁶-p-cymene) have been synthesized. Proton, carbon-13, Se-77 and/or Te-125 NMR spectra authenticate both the ligands and their complexes. The single crystal structures of L¹, L² and [RuCl(η⁶-p-cymene)(L)][PF₆] (L = L¹: 3, L = L²: 4) have been solved. The Ru-Se and Ru-Te bond lengths have been found 2.4801(11) and 2.6183(10) Å, respectively. The palladium complexes, [PdCl₂(L)] (L = L¹: 1, L = L²: 2) have been explored for Heck and Suzuki-Miyaura C-C coupling reactions. The TON values are upto 95,000. The Ru-complexes have been found promising for catalytic oxidation of alcohols (TON ∼ 7.8-9.4 × 10⁴). The complexes of telluroether ligands are as efficient catalysts as those of selenoether ones and in fact better for catalytic oxidation.     

Synthesis and molecular structures of dinuclear complexes with 1,2-dihydro-1,2-diphenyl-naphtho[1,8-c,d]1,2-diphosphole as a bridging ligand

A bisphosphine in which a PhP-PPh bond bridges 1,8-positions of naphthalene, 1,2-dihydro-1,2-diphenyl-naphtho[1,8-cd]-1,2-diphosphole (1), was used as a bridging ligand for the preparation of dinuclear group 6 metal complexes. Free trans-1, a more stable isomer having two phenyl groups on phosphorus centers mutually trans with respect to a naphthalene plane, was allowed to react with two equivalents of M(CO)₅(thf) (M = W, Mo, Cr) at room temperature to give dinuclear complexes (OC)₅M(μ-trans-1)M(CO)₅ (M = W (2a), Mo (2b), Cr (2c)). The preparation of the corresponding dinuclear complexes bridged by the cis isomer of 1 was also carried out starting from the free trans-1 in the following way. Mono-nuclear complexes M(trans-1)(CO)₅ (M = W (3a), Mo (3b), Cr (3c)) which had been prepared by a reaction of trans-1 with one equivalent of the corresponding M(CO)₅(thf) (M = W, Mo, Cr) complex, were heated in toluene, wherein a part of the trans-3a-c was converted to their respective cis isomer M(cis-1)(CO)₅. Each cis trans mixture of the mono-nuclear complexes 3a-c was treated with the corresponding M(CO)₅(thf) to give a cis trans mixture of the respective dinuclear complexes 2a-c. The cis isomer of the ditungsten complex 2a was isolated, and its molecular structure was confirmed by X-ray analysis, showing a shorter W?W distance of 5.1661(3) Å than that of 5.8317(2) Å in trans-2a.     

Carbonyl complexes of manganese, rhenium and molybdenum with 2-pyridylimino acid ligands

[MBr(CO)₃{κ²(N,O)-pyca}] [M = Mn(1a), Re(1b), pyca = pyridine-2-carboxaldehyde] and [MoCl(η³-C₃H₄Me-2)(CO)₂{κ²(N,O)-pyca}] (1c) react with aminoacid β-alanine to give the corresponding iminopyridine complexes 2a-2c. The same method affords the iminopyridine derivatives from γ-aminobutyric acid (GABA) (3a-3c) and 3-aminobenzoic acid (4a-4c). For complexes 2a-2c, 3a, 3c and 4a, the solid state structures have been determined by X-ray crystallography, revealing interesting differences in their hydrogen-bonding patterns in solid state.     

Palladium(II)/allylpalladium(II) complexes with xanthate ligands: Single-source precursors for the generation of palladium sulfide nanocrystals

In an effort to find simple and common single-source precursors for palladium sulfide nanostructures, palladium(II) complexes, [Pd(S₂X)₂] (X = COMe (1), COⁱPr (2)) and η³-allylpalladium complexes with xanthate ligands, [(η³-CH₂C(CH₃)CR₂)Pd(S₂X)] (R = H, X = COMe (3); R = H, X = COEt (4); R = H, X = COⁱPr (5); R = CH₃, X = COMe (6)), have been investigated. The crystal structures of [Pd(S₂X)₂] (X = COMe (1), CoⁱPr (2)) and [(η³-CH₂C(CH₃)CH₂)Pd(S₂COMe)] (3) have been established by single crystal X-ray diffraction analysis. The complexes, 1, 2 and 3 all contain a square planar palladium(II) centre. In the allyl complex 3, this is defined by the two sulfurs of the xanthate and the outer carbons of the 2-methylallyl ligand, while in the complexes, 1 and 2 it is defined by the four sulfur atoms of the xanthate ligand. Thermogravimetric studies have been carried out to evaluate the thermal stability of η³-allylpalladium(II) analogues. The complexes are useful precursors for the growth of nanocrystals of PdS either by furnace decomposition or solvothermolysis in dioctyl ether. The solvothermal decomposition of complexes in dioctyl ether gives a new metastable phase of PdS which can be transformed to the more stable tetragonal phase at 320 °C. The nanocrystals obtained have been characterized by PXRD, SEM, TEM and EDX.     

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.     

The (phosphino)tetraphenylborate ligand in ruthenium-arene chemistry

The synthesis of a series of anionic half-sandwich ruthenium-arene complexes [E][RuCl₂(η⁶-p-cymene){PR₂(p-Ph₃BC₆H₄)}] (E = Bu₄N⁺: R = Ph, 1a, ⁱPr, 1b or Cy, 1c; E = bis(triphenylphosphine)iminium or PNP⁺: R = Ph, 1a′, ⁱPr, 1b′ or Cy, 1c′) are reported. X-ray crystallographic studies of 1a′ and 1b′ confirmed the three-legged piano-stool coordination geometry. In solution, complexes 1a-c and 1a′-c′ are proposed to form monomer-dimer equilibria as a result of chloride ligand dissociation. Complexes 1a-c and 1a′-c′ also form the formally neutral zwitterionic complexes [RuCl(L)(η⁶-p-cymene){PR₂(p-Ph₃BC₆H₄)}] (L = pyridine: R = Ph, 2a, ⁱPr, 2b or Cy, 2c; L = MeCN: R = Ph, 3a, ⁱPr, 3b or Cy, 3c) via chloride ligand abstraction using AgNO₃ or MeOTf.     

Cyclometallated thiosemicarbazone palladium(II) compounds: The first crystal and molecular structures of mononuclear complexes with a η-diphosphine ligand

Treatment of the thiosemicarbazones 2-XC₆H₄C(Me)NN(H)C(S)NHR (R = Me, X = F, a; R = Et, X = F, b; R = Me, X = Cl, c; R = Et, X = Br, d) with potassium tetrachloropalladate(II) in ethanol, lithium tetrachloropalladate(II) in methanol or palladium(II) acetate in acetic acid, as appropriate, gave the tetranuclear cyclometallated complexes [Pd{2-XC₆H₃C(Me)NNC(S)NHR}]₄ (1a-1d). Reaction of 1a-1d with the diphosphines Ph₂PCH₂PPh₂ (dppm), Ph₂P(CH₂)₂PPh₂ (dppe), Ph₂P(CH₂)₃PPh₂ (dppp) or trans-Ph₂PCHCHPPh₂ (trans-dpe) in 1:2 molar ratio gave the dinuclear cyclometallated complexes [{Pd[2-XC₆H₃C(Me)NNC(S)-NHR]}₂(μ-diphosphine-P,P)] (2a-5a, 3b, 3d, 4c, 5c). Reaction of 1a, 1b with the short-bite or long-bite diphosphines, dppm or cis-dpe, in a 1:4 molar ratio gave the mononuclear cyclometallated complexes [Pd{2-XC₆H₃C(Me)NNC(S)NHR}(diphosphine-P)] (6a, 6b, 7a). The molecular structure of ligand a and of complexes 1a, 3d, 5a, 5c, 6a, 6b and 7a have been determined by X-ray diffraction analysis. The structure of complex 7a shows that the long-bite cis-bis(diphenylphosphino)ethene phosphine appears as monodentate with an uncoordinated phosphorus donor atom.     

Aqueous syntheses of [(Cp-R)M(CO)3] type complexes (Cp = cyclopentadienyl, M = Mn, Tc, Re) with bioactive functionalities

We describe reactions of [^99mTc(H₂O)₃(CO)₃)]⁺ (1) with Diels-Alder products of cyclopentadiene such as “Thiele’s acid” (HCp-COOH)₂ (2) and derivatives thereof in which the corresponding [(Cp-COOH)^99mTc(CO)₃)] (3) complex did form in water. We propose a metal mediated Diels-Alder reaction mechanism. To show that this reaction was not limited to carboxylate groups, we synthesized conjugates of 2 (HCp-CONHR)₂ (4a-c) (4a, R = benzyl amine; 4b, R = N_α-Boc-l-2,3-diaminopropionic acid and 4c, R = glycine). The corresponding ^99mTc complexes [(4a)^99mTc(CO)₃)] 6a, [(4b)^99mTc(CO)₃)] 6b and [(4c)^99mTc(CO)₃)] 6c have been prepared along the same route as for Thiele’s acid in aqueous media demonstrating the general applicability of this synthetic strategy. The authenticity of the ^99mTc complexes on the no carrier added level have been confirmed by chromatographic comparison with the structurally characterized manganese or rhenium complexes.Studies of the reaction of 1 with Thiele’s acid bound to a solid phase resin demonstrated the formation of [(Cp-COOH)^99mTc(CO)₃)] 3 in a heterogeneous reaction. This is the first evidence for the formation of no carrier added ^99mTc radiopharmaceuticals containing cyclopentadienyl ligands via solid phase syntheses. Macroscopically, the manganese analogue 5a and the rhenium complexes 5b-c have been prepared and characterized by IR, NMR, ESI-MS and X-ray crystallography for 5a (monoclinic, P2₁/c, a = 9.8696(2) Å, b = 25.8533(4) Å, c = 11.8414(2) Å, β = 98.7322(17)°) in order to unambiguously assign the authenticity of the corresponding ^99mTc complexes.     

Titanium complexes bearing aromatic-substituted β-enaminoketonato ligands: Syntheses, structure and olefin polymerization behavior

A series of titanium complexes [(Ar)NC(CF₃)CHC(R)O]₂TiCl₂ (4b: Ar = -C₆H₄OMe(p), R = Ph; 4c: Ar = -C₆H₄Me(p), R = Ph; 4d: Ar = -C₆H₄Me(o), R = Ph; 4e: Ar = α-Naphthyl, R = Ph; 4f: Ar = -C₆H₅, R = t-Bu; 4g: Ar = -C₆H₄OMe(p); R = t-Bu; 4h: Ar = -C₆H₄Me(p); R = t-Bu; 4i: Ar = -C₆H₄Me(o); R = t-Bu) has been synthesized and characterized. X-ray crystal structures reveal that complexes 4b, 4c and 4h adopt distorted octahedral geometry around the titanium center. With modified methylaluminoxane (MMAO) as a cocatalyst, complexes 4b-c and 4f-i are active catalysts for ethylene polymerization and ethylene/norbornene copolymerization, and produce high molecular weight polyethylenes and ethylene/norbornene alternating copolymers. In addition, the complex 4c/MMAO catalyst system exhibits the characteristics of a quasi-living copolymerization of ethylene and norbornene with narrow molecular weight distribution.     

2-Arylnaphthoxazole-derived palladium(II) complexes as phosphine-free catalysts for Heck reactions

Four air- and moisture-stable new palladium(II) complexes 2a–2c and 4 have been synthesized from easily available 2-arylnaphthoxazole derivatives. The detailed structures of 2c and 4 have been determined by single-crystal X-ray analysis. The Pd–N, Pd–C bonds in palladacycle complexes 2a–2c and the Pd–N, Pd–O bonds in complex 4 form the basis for five- and six-membered chelate rings, respectively. These complexes were applied as efficient phosphine-free catalysts for Heck reactions with aryl bromides and ethyl acrylate. Typically, in the presence of two equivalent n-Bu₄NBr, using 0.01% of palladacycle complex 2c as catalyst and two equivalent of K₂CO₃ as base in DMF at 140 °C provided coupled products in moderate to high yields.     

Synthesis, photophysical and electrophosphorescent properties of mononuclear Pt(II) complexes with arylamine functionalized cyclometalating ligands

Four cyclometalated Pt(II) complexes, i.e., [(L²)PtCl] (1b), [(L³)PtCl] (1c), [(L²)PtCCC₆H₅] (2b) and [(L³)PtCCC₆H₅] (2c) (HL² = 4-[p-(N-butyl-N-phenyl)anilino]-6-phenyl-2,2′-bipyridine and HL³ = 4-[p-(N,N′-dibutyl-N′-phenyl)phenylene-diamino]-phenyl-6-phenyl-2,2′-bipyridine), have been synthesized and verified by ¹H NMR, ¹³C NMR and X-ray crystallography. Unlike previously reported complexes [(L¹)PtCl] (1a) and [(L¹)PtCCC₆H₅] (2a) (HL¹ = 4,6-diphenyl-2,2′-bipyridine), intense and continuous absorption bands in the region of 300-500 nm with strong metal-to-ligand charge transfer (¹MLCT) (dπ(Pt) → π^∗(L)) transitions (ε ∼ 2 × 10⁴ dm³ mol⁻¹ cm⁻¹) at 449-467 nm were observed in the UV-Vis absorption spectra of complexes 1b, 1c, 2b and 2c. Meanwhile, with the introduction of electron-donating arylamino groups in the ligands of 1a and 2a, complexes 1b and 2b display stronger phosphorescence in CH₂Cl₂ solutions at room temperature with bathochromically shifted emission maxima at 595 and 600 nm, relatively higher quantum yields of 0.11 and 0.26, and much longer lifetimes of 8.4 and 4.5 μs, respectively. An electrochromic film of 1b-based polymer was obtained on Pt or ITO electrode surface, which suggests an efficient oxidative polymerization behavior. An orange multilayer organic light-emitting diode with 1b as phosphorescent dopant was fabricated, achieving a maximum current efficiency of 11.3 cd A⁻¹ and a maximum external efficiency of 5.7%. The luminescent properties of complexes 1c and 2c are dependent on pH value and solvent polarity, which is attributed to the protonation of arylamino units in the C^N^N cyclometalating ligands.     

Synthesis and reactivity of asymmetrically substituted ansa-bridged zirconocene complexes: X-ray crystal structures of [Zr{R(H)C(η-C5Me4)(η-C5H4)}Cl2] (R = Bu, Bu) and [Zr{Bu(H)C(η-C5Me4)(η-C5H4)}(CH2Ph)2]

The dialkyl complexes, (R = Prⁱ, R′ = Me (2a), CH₂Ph (3a); R = Buⁿ, R′ = Me (2b), CH₂Ph (3b); R = Bu^t, R′ = Me (2c), CH₂Ph (3c); R = Ph, R′ = Me (2d), CH₂Ph (3d)), have been synthesized by the reaction of the ansa-metallocene dichloride complex, [Zr{R(H)C(η⁵-C₅Me₄)(η⁵-C₅H₄)}Cl₂] (R = Prⁱ (1a), Buⁿ (1b), Bu^t (1c), Ph (1d)), and two molar equivalents of the alkyl Gringard reagent. The insertion reaction of the isocyanide reagent, CNC₆H₃Me₂-2,6, into the zirconium-carbon σ-bond of 2 gave the corresponding η²-iminoacyl derivatives, [Zr{R(H)C(η⁵-C₅Me₄)(η⁵-C₅H₄)}{η²-MeCNC₆H₃Me₂-2,6}Me] (R = Prⁱ (4a), Buⁿ (4b), Bu^t (4c), Ph (4d)). The molecular structures of 1b, 1c and 3b have been determined by single-crystal X-ray diffraction studies.     

Normal and abnormal carbene complexes derived from thiazole: Preparation and a preliminary investigation of their relative catalytic performance

Readily prepared 2-, 4- and 5-bromo-3-methyl thiazolium triflates react by oxidative substitution with M(PPh₃)₄ (M = Ni or Pd) to furnish five of the expected normal and abnormal cationic thiazolylidene complexes (1a, 1b, 2a, 2b, and 3b). Carbene complex formation is accompanied by a ca. 40 ppm downfield shift of the α-N carbene carbons in Pd complexes 1 and 2 in their ¹³C NMR spectra but the chemical shift of C(carbene) in the abnormal3b (δ 135.7) is particularly low. Crystal and molecular structures of complexes 1a, 2b, and 3b all indicate a square planar arrangement of the ligands around the central metal atoms. The new complexes catalyse Suzuki-Miyaura aryl coupling.     

High-pressure NMR study of migratory CO-insertion in palladium-methyl complexes modified with Cs-symmetrical 1,4-diphosphines

Carbonylation of the palladium complexes [PdCH₃(P^∧P′)Cl] (P^∧P′ = 1a, 1b, 1c, 1d, 1e) and [PdCH₃(P^∧P′)(CH₃CN)](OTf) was investigated by means of high-pressure NMR with the determination of the half-life times t_1/2. The results were rationalized on the basis of the electronic properties of the diphosphines and the nature of the solvento ligand in the first coordination sphere. The crystal structures of the complexes [Pd(1b)Cl₂] and [Pd(1b)(H₂O)₂](OTf)₂ are described (1b = 1-(diphenylphosphinomethyl)-2-[bis(3- trifluoromethylphenyl)phosphinomethyl]benzene).     

Five-membered ring chelate complexes of Ni(II), Pd(II) and Pt(II) derived of di-(2-pyridyl)-N-ethylimine

Cis-diaquobis{di-(2-pyridyl)-N-ethylimine}nickel(II) chloride (2) was obtained from the reaction of di-(2-pyridyl)-N-ethylimine (1) and [NiCl₂dppe] [dppe = cis-1,2-bis(diphenylphosphino)ethylene] in a 2:1 ratio in hot acetonitrile. Cis-dichloro{di-(2-pyridyl)-N-ethylimine}palladium(II) (3) and cis-dichloro{di-(2-pyridyl)-N-ethylimine}platinum(II) (4) complexes were obtained from the reaction of MCl₂ (M = Pd, Pt) and (1) in equimolar ratio in hot acetonitrile. Compounds 1–4 were characterized by IR spectroscopy, elemental analysis, and mass spectrometry; the complexes 3 and 4 were characterized in solution by NMR. In addition, solid state structures of compounds 1–4 were determined using single crystal X-ray diffraction analyses. X-ray diffraction data of the complexes 3 and 4 showed a distorted square planar local geometry at palladium and platinum atoms with the chlorine atoms in a cis-coordination; in 2 a local octahedral geometry at nickel atom was observed. Complexes 3 and 4 are arranged as dimers with a M?M distance of 3.4567(4) Å (M = Pd) and 3.4221(4) Å (M = Pt), respectively; 2 consists of units linked by intermolecular hydrogen bonding.