30184-37-3Relevant academic research and scientific papers
First high-nuclearity palladium halide/carbonyl/phosphine cluster(1) (see abstract) containing an octacapped octahedral Pd6(μ 3-Pd)6(μ3-I)2 fragment: Structure-to-synthesis generation from different synthetic routes
Mednikov, Evgueni G.,Dahl, Lawrence F.
, p. 1557 - 1570 (2008/10/09)
The original synthesis and stereochemical characterization of the [Pd 12(μ3-I)2(μ4-I) 3(μ2-CO)6L6]+ monocation (1) (L = PEt3; [PF6]- salt) was an outgrowth of our investigation of the chemical behavior of two unusual thallium-palladium clusters: (μ6-Tl)[Pd3(CO) 3L3]2+ (2) which possesses a Pd 3TlPd3 sandwich framework, and [Tl2Pd 12(CO)9L9]2+ (3) which may be viewed as edge-fusions of three Pd5 trigonal bipyramids to a central Tl2Pd3 trigonal bipyramid. Room-temperature reactions of 2 and 3 with I2 in THF gave rise in each case to small yields (2(μ2-I)2I2L2 (7) and trans-PdI2L2 (8) (L = PEt3). The geometries and compositions of 1, 7, and 8 were unequivocally established from low-temperature CCD X-ray crystallographic determinations. 1 was characterized by solid-state/solution IR and multinuclear (31P, 13C, 1H) NMR spectra. The 12-atom metal-core architecture of this geometrically unprecedented Pd6(μ3-Pd) 6(μ3-I)2(μ4-I)3 kernel of 1 of crystallographic D3 (32) site symmetry may be envisioned as a distorted hexacapped octahedral Pd(oc)6Pd(cap) 6 core with its two metal-uncappedtrans octahedral Pd(oc)3 faces additionally capped by iodide μ3-I atoms. The three tetracapping μ4-I atoms are each coordinated to two Pd(oc) and two adjacent Pd(cap) atoms. A comparative geometrical/qualitative bonding analysis of the hexacapped octahedral Pd(oc)6Pd(cap)6 core in 1 with the structurally analogous cores in the recently reported Pd12 clusters, Pd12(μ2-CO)6(μ3-CO) 6(PR3)6 (R = n-Bu (4), Ph (5)), revealed significantly different architectural features but yet emphasized the importance of the Pd(cap) atoms in stabilizing the Pd(oc) octahedra in 1, 4, and 5. In fact, strong bonding interactions of the μ3-I and μ4-I atoms to the Pd12 polyhedron in 1 are evidenced by its black-violet crystals being air-stable for at least one month and by 1 dissolved in THF, acetone, or acetonitrile not undergoing decomposition to AgI upon addition of Ag(OAc). An exploration via the structure-to-synthesis approach of possible preparative pathways involving 14 different chemical reactions was carried out in order to isolate 1 in much higher yields. This systematic investigation demonstrated the importance of conproportionation reactions (i.e., Pd(0) + Pd(II) → Pd(1/2) in 1) utilizing the co-products trans-Pd 2(μ2-I)2I2L2 (7) and trans-PdI2L2 (8), in different chemical reactions as palladium(II) precursors; high yields of 1 (ca. 50% based upon 6) were obtained from conproportionation reactions in THF of palladium(0) Pd10(CO) 12L6 (6) with 7 in the presence of Pd(OAc)2 and (NBu4n)(PF6). The square-planar palladium(II) geometries of the iodide-bridged dimeric 7 and monomeric 8 are compared with each other and with those of the previous crystallographically determined 8 (at room temperature) and several crystallographically known analogues (with different phosphine ligands); corresponding molecular parameters were found to be in remarkably close agreement with distinct bond-length variations in bridging Pd-I(b) and terminal Pd-P bonds being readily attributed to the well-documented trans influence.
Intermolecular alkynyl ligand transfer in palladium(II) and platinum(II) complexes with -C≡CCOOR and -C≡CPh ligands. Relative stability of the alkynyl complexes and conproportionation of dialkynyl and diiodo complexes of these metals
Osakada, Kohtaro,Hamada, Makiko,Yamamoto, Takakazu
, p. 458 - 468 (2008/10/08)
An equimolar reaction of trans-Pd(C≡CCOOMe)2(PEt3)2 with trans-PdI2(PEt3)2 catalyzed by CuI causes conproportionation of the complexes at room temperature, producing trans-PdI(C≡COOMe)(PEt3)2 in 88% yield, while the reaction without CuI catalyst gives the monoalkynylpalladium complex in approximately 2% yield after a prolonged period. Similar reactions of trans-Pd(C≡CPh)2(PEt3)2 with trans-PdI2(PEt3)2 with and without CuI catalyst give the alkynyl ligand transfer reaction product trans-PdI(C≡CPh)(PEt3)2 in 95% and 33% yields, respectively. CuI-catalyzed conproportionation of trans-Pt(C≡CPh)2(PEt3)2 and trans-PtI2(PEt3)2 occurs more slowly than the corresponding reactions of the Pd complexes; trans-Pt(C≡CCOOMe)2(PEt3)2 does not react with the diiodoplatinum complex even in the presence of CuI. The alkynyl ligand transfer reaction from trans-Pd(C≡CCOOMe)2(PEt3)2 to trans-PtI2(PEt3)2 occurs in the presence of CuI catalyst, affording a mixture of several organopalladium and -platinum complexes. The main Pd complex in the reaction mixture is trans-PdI(C≡CCOOMe)(PEt3)2, while the Pt-containing product is composed of trans-Pt (C≡CCOOMe)2(PEt3)2, trans-PtI(C≡CCOOMe)(PEt3)2, and trans-PtI2(PEt3)2 in an approximate 1:2:1 molar ratio. Mixing of trans-Pd(C≡CCOOMe)2(PEt3)2, trans-PdI2(PEt3)2, and trans-PtI2(PEt3)2 results in the formation of trans-PdI(C≡CCOOMe)(PEt3)2 in a high yield, while the alkynyl ligand transfer from Pd to Pt complexes is almost negligible. trans-PtI2-(PEt3)2 catalyzes the alkynyl ligand transfer between the dialkynyl- and diiodopalladium-(II) complexes and remains unchanged in the reaction mixture.
THERMAL STABILITY OF ORGANOPALLADIUM COMPOUNDS: NONRADICAL METHYL ELIMINATION FROM
Morvillo, A.,Turco, A.
, p. 431 - 438 (2007/10/02)
The thermolysis of the palladium complexes 2> (X = Br, I, CN; Me = CH3, CD3) in decalin or toluene under argon, in the temperature range 120-160 deg C, produces methane, ethane and ethylene, in ratios which vary with the temperature.Deuterium labelling shows that the methane is mainly formed through intramolecular abstraction of hydrogen from the phosphine ligands by the coordinated methyl group and not through homolytic fission of the Pd-Me bond.The thermal stability and the decomposition mechanisms of the organopalladium complexes are compared with those of the platinum analogues, which are remarkably more stable.At the higher temperatures, the thermal decomposition involves cleavage of the P-Et bonds in the phosphine ligands, and this leads to the formation of ethane and ethylene.The rate of generation of methane from the Pd-Me moieties is increased by a factor of 10 by the presence of an excess of dioxygen.Deuterium isotopic labelling shows that the rate increase is accompanied by a change from an intramolecular to a radical mechanism involving the abstraction of hydrogen by the methyl groups.
Preparation of highly reactive metal powders. Preparation, characterization, and chemistry of iron, cobalt, nickel, palladium, and platinum microparticles
Kavaliunas, Arunas V.,Taylor, Ashley,Rieke, Reuben D.
, p. 377 - 383 (2008/10/08)
Anhydrous metal halides of iron, cobalt, nickel, palladium, and platinum are readily reduced in glyme or THF with lithium in the presence of a small amount of naphthalene and yield finely divided, black metal powders of exceptional reactivity. Metal powders of Fe and Co react with C6F5X (X = Br, I) to yield solvated M(C6F5)2 and MX2. Powders of palladium and platinum react with C6F5I to yield solvated M(C6F5)I (M = Pd, Pt). Nickel powder reacts with C6F5I to yield the solvated species Ni(C6F5)2 and NiI2, however, with C6F5Br the product is solvated Ni(C6F5)Br. In most cases the metal powders are sufficiently reactive that a stoichiometric amount of C6F5X to the metal powder is used. The coordinated ether of all of these organometallic compounds is exceptionally labile and is displaced with a variety of ligands: phosphines, amines, sulfides, isocyanides, diolefins, and carbon monoxide. Many of the resultant compounds are novel and most are obtained in high yields. Palladium metal powder to which has been added 2,2′-bipyridine (bpy) reacts with iodobenzene to yield Pd(C6H5)I(bpy). Surface analyses including ESCA and BET were carried out on the highly reactive Ni, Pt, and Pd metal powders.
