- Carbonyl complexes of noble metals with halide ligands II. Palladium(II): preparation of Pd2Br4(CO)2 and -: crystal structures of (X=Cl or Br)
-
The previously elusive Pd2Br4(CO)2 has been isolated, mixed with PdBr2, from the reaction of PdBr2 with CO under pressure.A centrosymmetric structure is suggested for it on the basis of IR spectral data in solution.Attempts to prepare the corresponding iodo carbonyl complex of palladium(II) failed.The anion - rapidly undergoes decarbonylation both in solution and in the solid state.The stabilities of the halocarbonyl complexes relative to those of the corresponding halides (PdX2 or Pd2X62-) appear to decrease in the sequence Cl > Br > I.The crystal and molecular structures of the - anions (X=Cl, Br) with + as counter-cation have been determined by X-ray diffraction.Crystal data for : monoclinic; space group, P21/n; a 18.231(10); b 8.889(4); c 14.978(8) Angstroem; β 104.88(2) deg; U 2346(2) Angstroem3; Z=4; Dc 1.368 g cm-3; μ(Mo-Kα) 11.29 cm-1; R=0.0397.Crystal data for *C2H2Cl4: triclinic; space group, P/1; a 16.667(10); b 10.376(8); c 9.644(7) Angstroem; α 74.27(3) deg; β 75.12(3) deg; γ 83.27(4) deg; U 1549(2) Angstroem3; Z=2 Dc 1.681 g cm-3; μ(Mo-Kα) 47.84 cm-1; R=0.0886.In both anions, which are essentially planar, the Pd-X bond trans to the CO ligand is not significantly different in length from the other two Pd-X distances.The overall idealized symmetry of the + cation changes from D2d to S4 when the counter-anion is changed from - to -.
- Andreini, Bianca Patrizia,Dell'Amico, Daniela Belli,Calderazzo, Fausto,Venturi, Maria Giovanna,Pelizzi, Giancarlo
-
-
Read Online
- Preparation, magnetic properties, and pressure-induced transitions of some MIIMIVF6 (MII = Ni, Pd, Cu; MIV = Pd, Pt, Sn) complex fluorides
-
MIIMIVF6 (MII = Ni, Pd, Cu; MIV = Pd, Pt) and PdSnF6 complex fluorides have been synthesized via different preparative methods using either BrF3 as oxidizer and solvent, or solid state reactions. For MII = Ni, Pd, the phases crystallize in the rhombohedral space group R3 (LiSbF6 type). Cationic ordering has been studied by X-ray diffraction and 119Sn Moessbauer resonance for PdSnF6. A lowering of symmetry has been observed when the involved divalent cation presents a Jahn-Teller configuration (CuII). Except for PdSnF6, which is paramagnetic down to 4 K, all compounds are Pd2F6-type ferromagnets at low temperature. This behavior has been related to the ordering between half-filled eg orbitals of the divalent cation and empty eg orbitals of the tetravalent cation. A drastic increase in conductivity has been observed under high pressures. In particular the insulator-semiconductor transition induced under pressure (up to 80 kbar) in Pd2F6 corresponds to a decrease of the electrical resistivity by six orders of magnitude. The assumption of an electronic transition induced under pressure from mixed oxidation states (MII + MIV) to an unique trivalent MIII oxidation state has been proposed.
- Tressaud,Bartlett
-
-
Read Online
- Ortho palladation and functionalization of L-phenylalanine methyl ester
-
The ortho-metalated complex (S,S)-[Pd2{κ2(C,N)- C6H4CH2CH(CO2Me)NH 2-2}2(μ-Br)2] (1b) can be prepared by refluxing in acetonitrile equimolecular amounts of Pd(OAc)2 and L-phenylalanine methyl ester hydrochloride, followed by addition of an excess of NaBr. Complex 1b reacts with 4-picoline to give the mononuclear derivative (S)-[Pd{κ2(CN)-C6H4CH 2CH(CO2Me)NH2-2}2Br(NC 5H4Me-4)] (2), whose crystal structure has been determined by X-ray diffraction. The precursor of 1b, (S,S)- [Pd2{κ2-(C,N)-C6H4CH 2CH(CO2Me)NH2-2}2(μ-Cl) 2] (1a), could not be isolated in a pure form, but it can be used as the starting material for the synthesis of functionalized derivatives of the phenylalanine methyl ester. Thus, CO and RNC (R = Xy, tBu) insert into the Pd-C bond of 1a to afford, after depalladation, (S)-1-oxo-3- (methoxycarbonyl)-1,2,3,4-tetrahydroisoquinoline (3) and (S)-l-R-3- (methoxycarbonyl)-3,4-dihydroisoquinolinium triflate (R = tBu (4), Xy (5)), respectively. Reaction of complex 1b with bromine or iodine affords trans-(S,S)-[PdBr2{NH2CH(CO2Me)CH 2C6H4-X-2}2] (X = Br (6), I (7)), which further reacts with 1, 10-phenanthroline (phen) to give [PdBr 2(phen)] and (S)-2-X-phenylalanine methyl ester (X = Br (8). I (9)).
- Vicente, Jose,Saura-Llamas, Isabel,Garcia-Lopez, Jose-Antonio,Calmuschi-Cula, Beatrice,Bautista, Delia
-
-
Read Online
- Unexpected isomerism in "[Pd(2,9-dimethylphenanthroline)X 2]" (X = Cl, Br, I) complexes: A neutral and an ionic form exist
-
Complexes of composition "[Pd(2,9-dimethylphenanthroline)X 2]" (X = Cl, Br, I) have long been known and they are used as precursors for the synthesis of other derivatives or as catalysts. In the previous literature, they have invariably been described as neutral square planar complexes, but we have found that a second ionic isomer also exists, having composition [Pd(Neoc)2X]2[Pd2X 6], and that the formation of this isomer occurs under a wider range of conditions than that of the neutral one. Retrospectively, the ionic isomer had surely been obtained in most previous reports even if formation of the neutral one was claimed. The Royal Society of Chemistry 2012.
- Rimoldi, Martino,Ragaini, Fabio,Gallo, Emma,Ferretti, Francesco,Macchi, Piero,Casati, Nicola
-
p. 3648 - 3658
(2012/05/20)
-
- Co-ordination Chemistry of Higher Oxidation States. Part 3. Palladium(IV) Complexes with Neutral Unidentate Ligands
-
Oxidation of with the corresponding halogen (X2) in carbon tetrachloride gave octahedral palladium(IV) anions n3, X=Cl; L=PEt2Ph, X=Br>.Attemps toprepare analogues with L=SbMe3, TeMe2, or dmso (dimethyl sulphoxide) failed.Neutral palladium (IV) complexes trans- (L=NMe3, Py, PPrn3, or AsMe2Ph, X= Cl; L=NMe3, X= Br) have been obtained from trans- and X2.The complexes were characterised by i.r. and electronic spectroscopy, and conductivity measurements, and their thermal decomposition examined by t.g.a.
- Gulliver, David J.,Levason, William
-
p. 1895 - 1898
(2007/10/02)
-
