Electron impact mass spectra of some nickel(II) and palladium(II) complexes of diphenylphosphinoacetone and 3-diphenylphosphinobutan-2-one

The electron impact mass spectral fragmentation of five newly synthesized Ni(II) and Pd(II) complexes of diphenylphosphinoacetone (HL), i.e. trans-[ NiCl₂(HL)₂] and trans-[PdCl₂(HL)₂] and their enolates cis-[NiL₂] and cis-[PdL₂] and the bis-enolate of 3-diphenylphosphinobutan-2-one (HLMe), trans-[Ni(LMe)₂], is discussed. The proposed fragmentation mechanisms and the ion structures were confirmed by high-resolution data for three of the compounds and by Ni and Pd isotope abundances. The results obtained reveal that a mass spectral differentiation is useful in the identification of these types of complexes. Especially with phosphinoenolate bis-chelates molecular ion peaks are observed.     

Cationic (fluoromesityl)palladium(II) complexes

Halide abstraction from [Pd(μ-Cl)(Fmes)(NCMe)]₂ (Fmes = 2,4,6-tris(trifluoromethyl)phenyl or nonafluoromesityl) with TlBF₄ in CH₂Cl₂/MeCN gives [Pd(Fmes)(NCMe)₃]BF₄, which reacts with monodentate ligands to give the monosubstituted products trans-[Pd(Fmes)L(NCMe)₂]BF₄ (L = PPh₃, P(o-Tol)₃, 3,5-lut, 2,4-lut, 2,6-lut; lut = dimethylpyridine), the disubstituted products trans-[Pd(Fmes)(NCMe)(PPh₃)₂]BF₄, cis-[Pd(Fmes)(3,5-lut)₂(NCMe)]BF₄, or the trisubstituted products [Pd(Fmes)L₃]BF₄ (L = CN^tBu, PHPh₂, 3,5-lut, 2,4-lut). Similar reactions using bidentate chelating ligands give [Pd(Fmes)(L-L)(NCMe)]BF₄ (L-L = bipy, tmeda, dppe, OPPhPy₂-N,N′, (OH)(CH₃)CPy₂-N,N′). The complexes trans-[Pd(Fmes)L₂(NCMe)]BF₄ (L = PPh₃, tht) (tht = tetrahydrothiophene) and [Pd(Fmes)(L-L)(NCMe)]BF₄ (L-L = bipy, tmeda) were obtained by halide extraction with TlBF₄ in CH₂Cl₂/MeCN from the corresponding neutral halogeno complexes trans-[Pd(Fmes)ClL₂] or [Pd(Fmes)Cl(L-L)]. The aqua complex trans-[Pd(Fmes)(OH₂)(tht)₂]BF₄ was isolated from the corresponding acetonitrile complex. Overall, the experimental results on these substitution reactions involving bulky ligands suggest that thermodynamic and kinetic steric effects can prevail affording products or intermediates different from those expected on purely electronic considerations. Thus,water, whether added on purpose or adventitious in the solvent, frequently replaces in part other better donor ligands, suggesting that the smaller congestion with water compensates for the smaller M-OH₂ bond energy.     

Palladium(II) and platinum(II) saccharinate complexes containing pyridine and 3-acetylpyridine: Synthesis, crystal structures, fluorescence and thermal properties

New palladium(II) and platinum(II) complexes of saccharinate (sac), trans-[Pd(py)₂(sac)₂] (1), cis-[Pt(py)₂(sac)₂] (2), trans-[Pd(3-acpy)₂(sac)₂] (3) and cis-[Pt(3-acpy)₂(sac)₂] (4) (py = pyridine and 3-acpy = 3-acetylpyridine) have been synthesized. Elemental analysis, UV-Vis, IR, NMR and TG/DTA characterizations have been carried out. The structures of 1-4 were determined by X-ray diffraction. The palladium(II) and platinum(II) ions are coordinated by two N-bonded sac ligands, and two nitrogen atoms of py or 3-acpy, forming a distorted square-planar geometry. The palladium(II) complexes (1 and 3) are trans isomers, while the platinum(II) complexes (2 and 4) are cis isomers. The mononuclear species in the solid state are connected by weak intermolecular C-H?O hydrogen bonds, C-H?π and π?π stacking interactions. The platinum(II) complexes show significant fluorescence at the room temperature.     

Identification of Pt(II) and Pd(II) stereoisomeric complexes with aminobutyric acid by NMR and IR spectroscopy

Complexes of Pd(II) with aminobutyric acid AmH = NH₂CH(CH₂CH₃)COOH, namely, trans-[Pd(AmH)₂Cl₂] with monodentate (via the NH₂ group) AmH ligands and cis-, trans-Pd(Am)₂ with bidentate (via NH₂ and COO groups) ligands have been synthesized for the first time. Elemental analysis and IR and NMR spectroscopy were used to identify the synthesized compounds. The NMR spectra of the Pd(II) complexes were interpreted by comparing them with the NMR spectra of the analogous complexes of Pt(II). For Pt(II) and Pd(II) complexes with aminobutyric acid used as examples, an approach to identification of diastereomer bis-aminoacid complexes in specimens with racemic aminoacids by NMR spectroscopy is demonstrated.     

Coordination complexes of l-azetidine-2-carboxylic acid with platinum(II) and palladium(II)

Summary The complexes K[Pt(l-aze)Cl₂, [Pt(l-aze)₂] and [Pd(l-aze)₂] (l-aze = l-azetidine-2-carboxylate) were prepared. X-ray structures show that [Pt(l-aze)₂] and [Pd(l-aze)₂] are isomorphous, having a planar tetragonal geometry with a trans configuration around the Pt and Pd atoms. Slight puckerings of the MN(1)N(11)O(11) chelate ring (M = Pt or Pd) and the azetidine ring were observed. The circular dichroism (c.d.) spectra of the complexes in aqueous solution agree with the structures found in the solid state as far as the hexadecant rule is concerned, giving, for the trans configuration of [M(l-ia)₂] (where ia = imino acid), the profile of the c.d. signs for the three predominant d-d transitions as: +,-,-. I.r., conductivity and n.m.r. measurements are also reported and are in accord with the proposed structures.     

Calculations of microconstants and equilibrium formation constants for platinum(II) and palladium(II) halide complexes in solution

Distribution diagrams and formation functions for halide complexes [M(H₂O)_{4 ? n} Cl _n ]^{2 ? n} (M = Pt(II) or Pd(II)) and [PdCl_{4 ? n} Br _n ]^2? (n = 0?C4) in solution are analyzed in terms of the matrix model. Equilibrium constants for binding the first ligand $\left( {\bar K} \right)$ and corrections for the mutual influence between ligands (??) in the course of complex formation in solution are calculated. In examples analyzed, the substitution of chloride ion for water in the coordination sphere of platinum(II) and palladium(II) is an anti-cooperative process. The substitution of bromide ion for chloride ion in the coordination sphere of [PdCl₄]^2? is weakly cooperative. Quantum-chemical calculations show that platinum(II) and palladium(II) cis-bisaquadichloro complexes in the gas phase are thermodynamically less stable than trans-isomers. The cis-trans isomerization constants in the gas phase calculated by the DFT method and those found for solutions using the matrix model have the same order of magnitude.     

The Staudinger reaction of platinum(II)- and palladium(II)-coordinated 2-(azidomethyl)phenyl isocyanide. X-ray structure of trans-[PtCl{(H)}(PPh3)2][BF4] · CDCl3 · H2O

2-(Azidomethyl)phenyl isocyanide, 2-(CH₂N₃)C₆H₄NC (AziNC), coordinates to some cationic Pt(II) and Pd(II) species to afford isocyanide complexes of the type trans-[MCl(AziNC)(PPh₃)₂][BF₄] (M=Pt, l; Pd, 2). AziNC is coordinated also in some neutral Pt(II) and Pd(II) species such as [MCl₂(AziNC)₂] (M=Pt, 3; Pd, 4) derived from the reactions of 2 equiv. of AziNC with [PtCl₂(COD)] and [PdCl₂(MeCN)₂], respectively. Complexes 1 and 2 react with 1 equiv. of PPh₃ affording the heterocyclic carbene complexes trans-[MCl{(H)}(PPh₃)₂][BF₄] (M=Pt, 5; Pd, 6). Complexes 3 and 4 react with 1 equiv. of PPh₃ displacing the isocyanide with the formation of the complexes cis-[MCl₂(AziNC)(PPh₃)] (M=Pt, 7; Pd, 8). These latter ones react with 2 equiv. of PPh₃ affording as the final products the cationic carbene species trans-[MCl{(H)}(PPh₃)₂][Cl] (M=Pt, 9; Pd, 10). Complex 5 was also characterized by single crystal X-ray diffraction. The carbene complex is square-planar and the angle formed between the platinum square plane and the heterocyclic carbene ligand is 87.9(2)°. The C(1)-N(1) and C(1)-N(2) bond distances in the latter of 1.32(2) and 1.30(2) Å, respectively, are short for a single bond and indicate extensive π-bonding between the nitrogen atoms and the carbene carbon.     

Thermally-reversible photoisomerization of trans-dinitrobis(tri-N-propylphosphine)palladium(II)

UV irradiation of trans-dinitrobis(tri-n-propylphosphine)palladium(II) in MeOH yields a photostationary trans-cis mixture which reverts quantitatively in the dark to the trans-form. The cis-isomer, which can be isolated in crystalline form by irradiation of trans-species in n-hexane, has been characterized by UV, IR ¹H and ³¹P NMR spectroscopy. Irradiation of a 1/1 mixture of trans-[(PBu₃ⁿ)₂Pd(NO₂)₂] and trans-[(PPr₃ⁿ)₂Pd(NO₂)₂] gives almost entirely a 1/1 mixture of the corresponding cis-isomer, indicating an intramolecular process.     

Mixed dimethyl sulfoxide-thiocarbamic ester complexes of platinum(II) halides

Summary The platinum(II) halidecis-[Pt(DMTC)(DMSO)X₂] andcis-[Pt(DETC)(DMSO)X₂](X=Cl or Br; DMSO=dimethyl sulfoxide; DMTC=EtOSCN-Me₂; DETC=EtOSCNEt₂) adducts and the platinum(II) and palladium(II) halide adducts,trans-[M(DETC)₂X₂] (M=Pt or Pd; X=Cl or Br), have been prepared. The complexes were characterized by i.r., and¹H and¹³Cn.m.r. spectroscopy. Both DMTC and DETC coordinate through the sulphur atoms. The 1:2 DETC complexes present the usualtrans configuration, whereas the presence of DMSO favourscis geometry in the mixed species.     

Synthesis and structure of highly substituted pyrazole ligands and their complexes with platinum(II) and palladium(II) metal ions

Reaction of 3-methoxycarbonyl-2-methyl- or 3-dimethoxyphosphoryl-2-methyl-substituted 4-oxo-4H-chromones 1 with N-methylhydrazine resulted in the formation of isomeric, highly substituted pyrazoles 4 (major products) and 5 (minor products). Intramolecular transesterification of 4 and 5 under basic conditions led, respectively, to tricyclic derivatives 7 and 8. The structures of pyrazoles 4a (dimethyl 2-methyl-4-oxo-4H-chromen-3-yl-phosphonate) and 4b (methyl 4-oxo-2-methyl-4H-chromene-3-carboxylate) were confirmed by X-ray crystallography. Pyrazoles 4a and 4b were used as ligands (L) in the formation of ML₂Cl₂ complexes with platinum(II) or palladium(II) metal ions (M). Potassium tetrachloroplatinate(II), used as the metal ion reagent, gave both trans-[Pt(4a)₂Cl₂] and cis-[Pt(4a)₂Cl₂], complexes with ligand 4a, and only cis-[Pt(4b)₂Cl₂] isomer with ligand 4b. Palladium complexes were obtained by the reaction of bis(benzonitrile)dichloropalladium(II) with the test ligands. trans-[Pd(4a)₂Cl₂] and trans-[Pd(4b)₂Cl₂] were the exclusive products of these reactions. The structures of all the complexes were confirmed by IR, ¹H NMR and FAB MS spectral analysis, elemental analysis and Kurnakov tests.     

N-methyl-2,2′-bipyridylium ion (bpyMe) complexes: Synthesis and cyclometallation of [Pd(bpyMe)2Cl2]2+

On prolonged heating in water Pd(bpyMe)Cl₃ (bpyMe = N-methyl-2,2′-bipyridylium cation) cyclometallates to give monomeric Pd(bpyMe-H)Cl₂, whereas the immediate products are a mixture of trans-[Pd(bpyMe)₂Cl₂]²⁺ and anionic palladium species. [Pd(bpyMe)₂Cl₂]²⁺ was synthesised directly from Na₂PdCl₄ and on heating gives Pd(bpyMe-H)Cl₂ with the elimination of bpyMe and H⁺.     

A study of the reactions of methionine- and histidine-containing peptides with palladium(II) complexes: The key role of steric crowding on palladium(II) in the selective cleavage of the peptide bond

¹H NMR spectroscopy was applied to study the reactions of palladium(II) complexes, cis-[Pd(dpa)Cl₂] and cis-[Pd(dpa)(H₂O)₂]²⁺ (dpa is 2,2′-dipyridylamine acting as a bidentate ligand) with the dipeptides methionylglycine (Met-Gly) and histidylglycine (His-Gly), and the N-acetylated derivatives of these dipeptides, MeCOMet-Gly and MeCOHis-Gly. All reactions were carried out in the pH range 2.0–2.5 with equimolar amounts of the palladium(II) complex and the peptide at two different temperatures, 25 and 60 °C. In the reactions of cis-[Pd(dpa)Cl₂] and cis-[Pd(dpa)(H₂O)₂]²⁺ with Met-Gly and His-Gly, no hydrolysis of the peptide bond was observed. The final product in these reactions was the [Pd(dpa)₂]²⁺ complex. The square-planar structure of this complex was confirmed by X-ray analysis. The reaction of the cis-[Pd(dpa)(H₂O)₂]²⁺ complex with the MeCOHis-Gly and MeCOMet-Gly peptides under the previously mentioned experimental conditions was remarkably selective in the cleavage of the amide bond involving the carboxylic group of methionine in the side chain. The modes of coordination of cis-[Pd(dpa)Cl₂] and cis-[Pd(dpa)(H₂O)₂]²⁺ in the reactions with the non-acetylated peptides and the total steric inhibition of the hydrolytic reaction between cis-[Pd(dpa)(H₂O)₂]²⁺ and MeCOHis-Gly can be attributed to the steric bulk of the palladium(II) complex. This finding should be taken into consideration in designing new palladium(II) complexes for the regioselective cleavage of peptides and proteins.     

Transition-Metal Complexes with Bidentate Ligands Spanning trans-Positions. IX. Preparation and 1H-NMR. Studies of complexes [MX2(1)] and [M′Cl(CO)(1)] (M = Pd,Pt; M′ = Rh,Ir; X = Cl,Br, I; 1 = 2, 11-Bis-(diphenylarsinomethyl)benzo[c]phenanthrene) and crystal and molecular structure of [PtCl2(1)]

The preparation of the bidentate ligand 2, 11-bis(diphenylarsinomethyl)benzo-[c]-phenanthrene ( 1 ) is described. This ligand reacts with appropriate substrates to give mononuclear square planar complexes of type [MX₂( 1 )] (M = Pd, Pt; X = Cl, Br, I) and [M′Cl(CO)( 1 )] (M′ = Rh, Ir) in which ligand 1 spans trans-positions. This is confirmed by the crystal structure of [PtCl₂( 1 )]. ¹H-NMR. spectra of the complexes are discussed and compared with those of model compounds trans-[MCl₂( 12 )₂] (M = Pd, Pt) and [M'Cl(CO)( 12 )₂] (M′ = Rh, Ir; 12 = AsBzPh₂).     

Reactions of dimethyl- and diphenyl-mercury with dihalobis(isocyanide)palladium(II) complexes

The reaction of cis-[PdCl₂(CNR)₂] (R = Ph, p-MeC₆H₄, p-MeOC₆H₄) and trans-[PdI₂(CNPh)₂] with HgR′₂ (R′ = Me, Ph) followed by addition of PPh₃ (Pd/PPh₃, $\text{1}\text{2}$) gives complexes of the type trans- [PdX {C(=NR)C(R′)=NR}(PPh₃)₂] (X = Cl, I) I as main products. These bis(imino) compounds may result from double insertion of the coordinated isocyanides into a PdR′ σ-bond. NaBPh₄ was also found to act like HgPh₂ as a good phenylating agent towards coordinated isocyanide. The reactions of I with methanolic HClO₄ yield cationic compounds: trans- [PdX{C(NHR)C(R′)=NR}(PPh₃)₂]ClO₄; the protonated bis(imino) group may also be formulated as {C(=NR)C(R′)NHR} and a fast equilibrium between the two forms probably exists in solution. The factors influencing the reaction with HgR′₂ and spectroscopic data (IR and ¹H NMR) for the complexes are reported and discussed.     

Preparation and properties of dinitrogen trimethylphosphine complexes of molybdenum and tungsten—II: Synthesis and crystal structures of [MCl(N2)(PMe3)4] (M = Mo,W) and trans-[MoCl2(PMe3)4]

Sodium amalgam reduction of the complexes [MCl₃(PMe₃)₃] (M = Mo, W) in tetrahydrofuran, under dinitrogen, yields dark red-brown suspensions from which red-orange crystals of composition trans-[MCl(N₂)· (PMe₃)₄] can be collected. Spectroscopic and chemical evidence indicate the compounds are best formulated as mixtures of trans-[M(N₂)₂(PMe₃)₄] and trans-[MCl₂(PMe₃)₄] species, but attempts to isolate the pure bis(dinitro derivatives have proved unsuccessful. Single crystals of analytical composition [MCl(N₂)(PMe₃)₄] have been studied by X-ray crystallography, and the structure of trans-[MoCl₂(PMe₃)₄] has been determined for comparison. trans-[MCl(N₂)(PMe₃)₄] (M = Mo, W) and trans-[MoCl₂(PMe₃)₄] are all isostructural, crystallizing in the tetragonal space group I$\text{4}$2 trans-[MoCl(N₂)(PMe₃)₄] has a = 9.597(5), b = 12.294(6) Å, D_c = 1.36g cm^?3 Z = 2 and was refined to a final R value of 0.021 based on 319 independent observed reflections. The tungsten analogue has a = 9.573(4), b = 12.278(5) Å, D_c = 1.63g cm^?3 for Z = 2 and was refined to R = 0.19 with 322 independent observed reflections. trans-[MoCl₂(PMe₃)₄] has cell parameters a = 9.675(5), b = 12.311(6) Å D_c = 1.36 g cm^?3 for Z = 2 and was refined to R = 0.043 with 316 independent observed reflections. In each case the metal atom resides on a crystallographic $\text{4}$2m position. For trans-[MoCl(N₂)(PMe₃)₄] (M = Mo, W) the chlorine and dinitrogen ligands are disordered. M-N distances of 2.08(1) ? (M = Mo) and 2.04(2) ? (M = W) and M-Cl bond lengths of 2.415(8) Å (M = Mo) and 2.46(1) Å (M = W) are observed. In trans-[MoCl₂(PMe₃)₄], where there is no disorder, the Mo-Cl distance is 2.420(6) Å.     

Synthesis of ylideplatinum(II) complexes via α-functionalised alkylplatinum(II) intermediates and some comparative data on palladium(II) complexes; X-ray structure of trans-[Pt(CH2PEt3)I(PEt3)2]I

The reaction of [Pt(PEt₃)₃] with CH₂I₂ affords trans-[Pt(CH₂PEt₃)I(PEt₃)₂]I and is believed to proceed via the α-functionalised alkyl cis-[Pt(CH₂I)I(PEt₃)₂], because similar ylides are obtained from cis- or trans-[PT(CH₂X)(PPh₃)₂X] (XCl, Br, or I) with PR₃ (PEt₃, PBu₃ⁿ, PMePh₂, PEtPh₂, or PPh₃); cis-[Pd(CH₂I)-I(PPh₃)₂] does not react with excess PPh₃, but with PEt₃ yields trans-[Pd(CH₂PEt₃)I(PPh₃)₂]I; the X-ray structure of trans-[Pt(CH₂PEt₃)I(PEt₃)₂]I (current R = 0.045) shows PtP(1) 2.332(7), PtP(2) 2.341(8), PtC 2.08(2), and PtI 2.666(2) Å, and angles (a) C(1)PtI, P(1), P(2): 176.9(8), 91.6(6), 93.4(6), (b) IPtP(1), P(2): 87.1(2), 88.5(2), and (c) P(1)P(2), 166.8(3), and (d) PtC(1)P(3), 118(1)°.     

Photochemistry of planar four-co-ordinate palladium(II) complexes—III. Photosynthesis and crystal structure of [Pd2(PPr3n2(NCS)(SCN)2(μ-CN)]

U.V. irradiation of MeOH and CH₃CN solutions of trans-[Pd(PPr₃ⁿ)₂(NCS)₂] causes a stepwise photochemical reaction. When the solvent is CH₃CN the photoproduct can be conveniently isolated in a crystalline form. This compound has been shown, by X-ray analysis, to be a cyano bridged palladium(II) complex.     

Intramolecular metallation of o-carboranylphosphine-palladium(II) and -platinum(II) complexes

Preparation of trans-[P^cb₂MCl₂]-type complexes (P^cb= o-HCB₁₀H₁₀CCH₂PPh₂ M = Pd, Pt), which readily undergo intramolecular metallation through the BH bonds of the carborane cage to form exocyclic compounds involving a $\text{PCCBM}$ bond system, is described. Both monomeric compounds, trans-[MCl(B-P)P^cb], and bridged complexes, such as [Pd₂Cl₂(BP)₂], are formed, where (BP) is intramolecular-metallated carborane phosphine. The bridging bond is readily cleaved under the action of various ligands (pyridine, PEt₃, etc.) to form monomeric compounds.     

Synthesis and characterization of some trans-hydridomethylbis(phosphine)-platinum(II) and -palladium(II) complexes

Several trans-hydridomethylbis(phosphine)-platinum(II) and -palladium(II) complexes have been made by the reaction: trans-M(H)Cl(PR₃)₂ + CH₃MgBr → trans-M(CH₃)(PR₃)₂ + MgClBr and their structures determined by ¹H NMR and IR spectroscopy. The complexes in which M  Pt and R  Cy (cyclohexyl) or i-Pr (isopropyl) are very stable in the solid state and in solution, while the compounds in which M  Pt, R  Et (ethyl) and M  Pd, R  i-Pr slowly decompose either in the solid state or in solution. The compound in which M  Pd and R  Cy was not isolated but was identified in solution.     

Synthesis of the cyanamide-derived bis(cyanoimido) complexes trans-[M(NCN)2(Ph2PCH2CH2PPh2)2] (M = Mo or W) and crystal structure of the molybdenum compound

Reaction of cyanamide (NCNH₂) with trans-[M(N₂)₂(dppe)₂] (M = Mo or W, dppe = PH₂PCH₂CH₂PPh₂) leads to the formation of the bis(cyanoimido) complexes trans-[M(NCN)₂(dppe)₂]. The crystal structure of trans-[Mo(NCN)₂(dppe)₂] has been determined by an X-ray diffraction study.