0000000000026401
AUTHOR
Francesca Di Bianca
showing 18 related works from this author
Preparation and reactions of palladium(II) complexes with C2-bonded heteroaromatic ligands trans[PdCl(RN)(PPh3)2] (RN = 2-pyridyl, 2-pirazyl, 2-pyrim…
1986
Abstract The complexes trans -[PdCl(R N )(PPh 3 ) 2 ] (I) [R N = 2-pyridyl (2-Py), 2-pyrazyl (2-pyz), 2-pyrimidyl (2-pym) group] have been prepared in high yield by deprotonation with NEt 3 of the corresponding cationic compounds trans [PdCl(R N H) (PPh 3 ) 2 ] + (R N H = N -protonated C 2 -heteroaromatic ligand) in the presence of an excess of PPh 3 . In chlorinated solvents, complexes I undergo a slow reversible dimerization into the binuclear derivatives [PdCl(μ-R N )(PPh 3 )] 2 (II) (μ-R N = C 2 , N 1 -bridging ligand). From the 31 P NMR spectra in 1,2-dichloroethane the following dissociation constants were obtained: 1.9 mol 1 −1 (R N = 2-py), 5.1 × 10 −2 (2-pym), 6.6 × 10 −3 (2-pyz). …
Infrared and M�SSBAUER spectroscopic studies on complexes of Hal2SnIV moieties with tridentate ligands
1975
Novel complexes hal2Sntrid, where hal Cl, Br, and trid2− are dianions of „planar” tridentate ligands with ONO and SNO donor basic atoms, were synthesized and structurally investigated in the solid state mainly by far infrared and MOSSBAUER spectroscopy. Possible configurations were advanced and discussed, and it was concluded that the most probable is a monomeric trigonal bipyramidal structure for all compounds, although polymers, or dimers with O or Cl bridges, were not a priori excluded, in a special way for Br2Sntrid. Infrarot- und MOSSBAUER-spektroskopische Untersuchungen an Komplexen von Hal2SnIV mit dreizahnigen Liganden Neue Komplexverbindungen von Typ hal2Sntrid werden dargestellt (…
Reactions of α-diimino ligands with the chloro-bridged dimer [RhCl(COD)]2(COD=1,5-cyclooctadiene)
1988
Abstract The reactions of α-diimino ligands N - N ′ [ N - N ′= 2,2′-bipyridine (bipy), C 5 H 4 N2CHNR (R= C 6 H 4 OMe- p , PyCa), RNCHCHNR (R=C 6 H 4 - OMe- p , DAB)] with [RhCl(COD)] 2 give rise to stoichiometry, solvent, ligand, and temperature dependent equilibria. In general, the 1/1 ligand/dimer reaction yields the ionic product [Rh(COD)( N - N ′)] [RhCl 2 (COD)], at room temperature. For N - N ′=DAB, the ionic form is in equilibrium with the binuclear compound [{RhCl(COD)} (μ-DAB){RhCl(COD)}] (containing a σ σ,'- N , N ′ bridging α-diimine), which becomes the predominant species at low temperatures. In [Rh(COD)( N - N ′)] [RhCl 2 (COD)], a fast exchange of the Rh(COD) unit betwe…
Nucleophilic attack by 2-pyridylpalladium(II) and platinum(II) complexes on the organic chlorides ClCH2R (R COMe, CN, Ph, Cl)
1992
Abstract The 2-pyridyl complexes trans-[MCl(C5H4NC2)(PPh3)2] (M = Pd, 1a; M = Pt, 1b), [MCl(C5H4NC2)(dppe)] (M = Pd, 2a; M = Pt, 2b) and [M(dmtc)(C5H4NC2) (PPh3)] (M = Pd, 3a; M = Pt,3b) react with the chlorides ClCH2R(R COMe, CN, Ph) to give cationic products containing the 2-pyridylium ligands (1-CH2R)C5H4NC2. The rate of nucleophilic displacement of the chloride ion from ClCH2R depends on the central metal (Pt > Pd), on the coordination geometry (1 ~ 3) and on the substituent R (COMe > CN > Ph for the reactions with 3b). Like 1b and 2b, complex 3b also reacts with dichloromethane to give [Pt(dmtc){(1-CH2Cl)C5H4NC2}(PPh3)]+. The reaction of the binuclear compound [{PdCl(μ-C5H4NC2,…
Complexes of organometallic compounds
1972
Abstract The novel organobismuth(V) derivatives Ph 3 BiCl(Ox) and Ph 3 BiBr(Ox) (Ox − = 8-quinolinate) have been synthesized, and their configuration investigated in the solid state and in solution. The complexes are assumed to be octahedral in the solid, with Ox − acting as a chelating base and the halide atoms coordinating to bismuth. Tentative assignments of infrared bands in the 300–80 cm −1 region to BiHal and other skeletal modes are proposed. The main effect of solvents appears to be the weakening and breaking of BiN-bonds.
Stereo and regioselectivity in the phenylation of cationic allylpalladium(II) α-diimine complexes by tetraphenylborate anion
1993
The reaction of the cationic complex [Pd(4-methoxy-1,3-η3-cyclohexenyl)(py-2-CHNC6H4OMe-4)]+ (1) with BPh4− in the presence of fumaronitrile yields trans-3-methoxy-6-phenylcyclohexene (2a) and trans-4-methoxy-3-phenylcyclohexene (2b), in ca. 1 : 1 molar ratio. The trans stereochemistry of these products implies that the phenylation of the allyl ligand involves prior transfer of a phenyl group from BPh4− to the metal, followed by reductive coupling of the organic moieties. In the reactions of [Pd(η3-1,1-R1,R2-C3H3)(NN′)]+ (3) [NN′ 4-MeOH4C6NCHCHNC6H4OMe-4; py-2-CHNR (R C6H4OMe-4, Me, or CMe3), 2,2′-bipyridine (bipy); R1 H, R2 Ph, Me; R1 R2 Me; with BPh4− in the presence of …
Reactions of pyridine-2-carbaldimines with chloro-bridged palladium(II) and platinum(II) 2-methylallyl dimers. Solution behaviour of the cationic com…
1987
Abstract The reactions of pyridine-2-carbaldimines, py-2- CHNR (R = C6H4OMe-p, Me), with allylic dimers [MCl(n3-2-MeC3H4)]2 give rise to stoichiometry, concentration, solvent and temperature dependent equilibria, in which the cationic complexes [M(n3- 2-MeC3H4)(py-2-CHNR)]+ and the anion [MCl2(n3- 2-MeC3H4)]- or Cl- are involved. In general, the ligand/dimer reaction (1/1 molar ratio) yields the ionic products [M(n3-2-MeC3H4)(py-2-CHNR)]- [MCl2(n3-2-MeC3H4)], which can be isolated as solids, whereas the same reaction in a 1/0.5 molar ratio yields the species [M(n3-2-MeC3H4 )(py-2-CH NR)] Cl, which can be studied only in solution, but are easily converted into [M(n3-2-MeC3H4)(py-2-CH NR…
Coordination properties of imino(2-pyridyl)methylpalladium(II) compounds. Preparation and thermal rearrangement of binuclear adducts with palladium(I…
1988
Abstract The imino(2-pyridyl)methylpalladium(II) compound py-2-C(R′)NR (R = C 6 H 4 OMe-p, R′ = trans-PdCl(PPh 3 ) 2 ) reacts with [PdCl 2 (CH 2 CHPh)] 2 , [PdCl 2 - (NCMe) 2 ], and K[PtCl 3 (CH 2 CH 2 )] to give binuclear complexes [MCl 2 {py-2- C(R′)NR}] (M = Pd, Pt), in which the α-diimino group acts as a chelating bidentate ligand. In hot 1,2-dichloroethane, these complexes undergo a PPh 3 and chloride ligand exchange at rates which depend markedly on the metal M (Pd ⪢ Pt), to yield the new derivatives [MCl(PPh 3 ){py-2-C(cis-PdCl 2 (PPh 3 ))NR}]. The ligand exchange is followed by a much slower decomposition to [MCl 2 (PPh 3 ) 2 ]. Labile intermediates of the same type, [MCl(PPh …
Solution behaviour and relative stability of the complexes [MCl2(RNCHCHNR)] and [MCl2(py-2-CHNR)] (M=Pd, Pt;R=C6H4OMe-p)
1988
Abstract Even though the α-diimino complexes [MCl 2 (RNCHCHNR)] and [MCl 2 (py-2-CHNR)] (M=Pd, Pt;R=C 6 H 4 OMe- p ) are poorly soluble in chlorinated solvents, such as chloroform and 1,2-dichloroethane, or in acetonitrile, the electronic and 1 H NMR spectra indicate that these compounds are generally present as undissociate monomers with σ, σ′- N,N′ chelate N-ligands in dilute solutions. Only for [PdCl 2 (RNCHCHNR)], some dissociation of the α-diimine occurs in acetonitrile. In dimethylsulfoxide, where the solubility is much higher, no dissociation is observed for the pyridine-2-carbaldimine complexes [MCl 2 (py-2-CHNR)], whereas the 1,2-bis(imino) ethane derivatives [MCl 2 (RNCH…
Protonation and methylation reactions of 2-pyridyl-palladium(II) and -platinum(II) complexes
1983
Abstract The reactions of strong acids HX and HClO4 with the 2-pyridyl complexes [PdX(μ-C5H4N-C2,N)(PPh3)]2 (X = Cl, Br), trans-[PdCl(C5H4N-C2)(PEt3)2] and [PdCl(C5H4N-C2)(dppe)] yield the N-protonated derivatives cis-[PdX2-(C5H5N-C2)(PPh3)], trans-[PdCl(C5H5N-C2)(PEt3)2]ClO4 and [PdCl-(C5H5N-C2)(dppe)]ClO4, respectively. The terminal 2-pyridyl group of trans-[PdCl(C5H4N-C2)(PEt3)2] and [PdCl(C5H4N-C2)(dppe)] also reacts with Me2SO4/NaClO4 to give trans-[PdClC5H4(l-Me)N-C2(PEt3)2]ClO4 and [PdClC5H4(l-Me)N-C2(dppe)]ClO4. Analogous N-protonation or N-methylation reactions occur with trans-[PtBr(C5H4N-C2)(L)2] (L = PEt3, PPh3). The complexes trans-[MX(C5H5N-C2)(PMe2Ph)2]ClO4 (M = Pd, X = Cl an…
Coordination properties of imino(2-pyridyl)methylpalladium(II) compounds. Reactions with the chloride-bridged allyl dimers [MCl(η3-2-MeC3H4)]2 (MPd,…
1990
Abstract The imino(2-pyridyl)methylpalladium(II) compounds py-2-CR 1 NR [R 1 = trans -PdCl(PPh 3 ) 2 , R = C 6 H 4 OMe- p ( Ia ), Me ( Ib ), CMe 3 ( Ic ); R 1 = Pd(dmtc)(PPh 3 ), R = C 6 H 4 OMe- p ( Id )] react with [MCl(η 3 - 2-MeC 3 H 4 )] 2 (M = Pd, Pt) in a molar ratio 1/0.5 and in the presence of NaClO 4 to yield the binuclear cationic complexes II , [M(η 3 -2-MeC 3 H 4 )(py-2-CR 1 NR)]ClO 4 , where the α-diimino group acts as σ,σ N , N ′ chelating ligand. In the absence of NaClO 4 and with a molar ratio 1/1, the reaction leads initially to formation of a ionic intermediate A , [M(η 3 - 2-MeC 3 H 4 )(py-2-CR 1 NR)] [MCl 2 (η 3 -2-MeC 3 H 4 )], which subsequently undergoes exchange …
Mechanism of oxidative allyl transfer from allylic ammonium cations to palladium(0) α-diimine complexes
1996
Abstract The palladium(0) complex [Pd(η2-fn)(NN′)] (1, fn = fumaronitrile; NN′ = C5H4N-2-CH=NC6H4OME-4) reacts slowly and reversibly with A + CH 2 CH=CH 2 (2a, A = NEt 3 ; 2 b , A = C 5 H 5 N ) to yield the cationic η3-allypalladium(II) derivative [ Pd (η[ 3 - C 3 H 5 )( N N ′)] + (3) the free amine A and fn. The equilibrium constant Ke is (2.6 ± 0.1) × 10−3 for 2a and 1.0 ± 0.4 for 2b. Kinetic studies of these oxidative allyl-transfer reactions show that the rates increase with increasing concentration of 2 and with decreasing concentration of fn. A stepwise mechanism is proposed which involves slow and reversible displacement of fn by 2 to give a labile intermediate [ Pd (η 2 - CH…
Phenylation of cationic allylpalladium(II) complexes by tetraphenylborate anion. A mechanistic study
1990
Abstract The mechanism of the reaction of allyl complexes [Pd(η3-2-R′C3H4)(NN′)]+ (NN′ = α-diimine ligand) wiht BPh4− in the presence of activated olefins (ol), yielding the products [Pd(η2-ol)(NN′)] and PhCH2C(R′)CH2, has been investigated. The results are interpreted in terms of extensive association between the cationic substrate and the BPh4− anion in a tight ion-pair, followed by rate-determining phenyl transfer to the palladium center and fast reductive elimination of allylbenzene.
Investigations on organoantimony compounds
1976
Abstract Diorganoantimony(V) complexes of the type R 2 SbClTrid (R = Me, Ph) containing dianionic, potentially tridentate Schiff-base ligands with ONO donor atoms (Trid 2− ) have been prepared and characterized. IR and NMR data suggest an octahedral coordination environment for the antimony atom with meridional arrangement of the ONO ligand atoms and a linear CSbC skeleton.
Five-coordinate complexes of palladium(ii) and platinum(ii) with α-diimine and 1,5-cyclooctadiene ligands
2001
The five-coordinate complexes [PtMe(cod)(N–N′)]BF4 [cod = η2,η2-cyclooctadiene, N–N′ = (6-R2)C5H3N-2-CHNR1 (R1 = C6H4OMe-4, R2 = H (1), Me (2); R1 = CMe3, R2 = H (3), Me (4); R1 = (R)-bornyl, R2 = Me (5))] are readily obtained from the reaction of [PtClMe(cod)] with N–N′ in the presence of NaBF4. The preparation of [PtMe(cod)(6)]BF4 (6 = 4-MeOC6H4NCHCHNC6H4OMe-4), [PdMe(cod)(N–N′)]BF4 and [PtCl(cod)(N–N′)]BF4 (N–N′ = 2, 4) requires chloride abstraction by AgBF4 from [PtClMe(cod)], [PdClMe(cod)] and [PtCl2(cod)], respectively, followed by coordination of N–N′. The NMR spectral data suggest a trigonal-bipyramidal structure with chelating cod and N–N′ ligands, where the α-diimine and one CC bo…
Isomer Distribution and Interconversion in Cationic Allylpalladium(II) Complexes with 2-(Iminomethyl)pyridine Ligands
1997
The complexes [Pd(η3-allyl)(N-N‘)]ClO4 [allyl = 2-butenyl or 3-methyl-2-butenyl, N-N‘ = C5H3(6-R)N-2-CHNR‘ (R = H, R‘ = Me, CMe3, C6H4OMe-4; R = Me, R‘ = C6H4OMe-4) and C5H4N-2-CH2NMe2] are present in solution with different isomers, the structures of which may be assigned by an 1H NMR criterion based on chemical shift changes of the pyridine H(6) and/or of the allylic methyl protons, as confirmed also by 2D 1H NMR spectra. The isomer distribution depends mainly on the steric requirements of both the allyl and N-N‘ ligands: for [Pd(η3-3-methyl-2-butenyl)(N-N‘)]ClO4 the predominant isomer (ca. 100%) has a structure with the allylic methyl groups cis to the coordinated pyridine nitrogen when…
Preparation and reactions of 1-methylpyrid-6-one-2-yl compounds of palladium(II) and platinum(II)
1984
Abstract The compounds trans -[MCl{(1-Me)C 5 H 3 (6-O)N- C 2 }(L) 2 ] (M = Pd, Pt; L = PPh 3 , PMe 2 Ph), can be prepared from the reaction of the corresponding 1-methyl-6-chloro-2-pyridylium cationic complexes, trans -[MCl{(1-Me)C 5 H 3 (6-Cl)N- C 2 }(L) 2 ]ClO 4 , with a mixture of acetic acid, ethanol, and triethylamine in the molar ratio M/MeCO 2 H/EtOH/NEt 3 of 1/3/3/4. The rate is slow compared to that of the 1-methyl-2-chloropyridinium cation under similar conditions, and is markedly affected by the steric and electronic effects of the trans -MCl(L) 2 unit. The novel 1-methylpyrid-6-one-2-yl derivatives have been characterized by conventional spectroscopic techniques and by reactions…
N-protonated 2-pyridylnickel(II) complexes insertion of isocyanides into the nickel2-pyridyl bond
1987
The reaction of the binuclear complex [NiCl(μ-2-py)(PPh3)]2 (μ-2-py = μ-C5H4N-C2,N) with the phosphines L (L = PPh3, PMePh2, PMe2Ph or PEt3) or dppe (= 1,2-bis(diphenylphosphino)ethane) in the presence of HClO4 yields the N-protonated 2-pyridyl derivatives trans-[NiCl(2-pyH)(L)2]ClO4 or [NiCl(2-pyH)(dppe)] ClO4 (2-pyH = C5H5N-C2) with a square-planar coordination around the nickel(II) center. These products are largely associated through hydrogen bonding between the NH group and the perchlorate anion, both in the solid and in chlorinated solvents. The configuration in solution has been studied by 1H and 31P NMR spectroscopy. In the complex trans-[NiCl(2-pyH)(PMe2Ph)2]ClO4, the planar 2-pyH…