Alfredo Musco

Structural and NMR spectroscopic characterization of η3-Benzyl palladium(II) complexes

Abstract η 3 -Benzyl palladium complexes have been prepared by insertion of styrene in the PdMe bond of the solvated cation [L 2 PdMe(solv)] + (L 2 = chelating ligand). The η 3 coordination of the benzyl ligand has been elucidated by X-ray structure determination and NMR spectroscopy. NMR studies have shown that [(η 3 -R-α-benzylPdL 2 ] + (R  Me or Et) undergo two dynamic processes in solution: η 3 - η 1 coordination of the benzyl group and ligand exchange of coordination sites. The TMEDA and DIPY complexes undergo a rapid and reversible reaction with carbon monoxide to yield (R-α-benzylCO)PdL 2 CO] + .

Synthesis and characterization of alkyl-substituted poly[E-1,2-(2,2′-dithienyl)ethylene]s

Abstract 3,3′-Dialkyl-substituted poly[ E -1,2-(2,2′-dithienyl)ethylene]s (PDTEs) have been synthesized and characterized. The polymers are sufficiently soluble in common organic solvents and have been structurally characterized by NMR and FT-IR spectroscopies. The polymers, doped via chemical or electrochemical process, show a strong electrochromic effect. The films of substituted polymer are blue in the reduced form whilst the doped materials are quite transparent in the visible spectral region.

Ambivalence of nucleophilic attack on central and terminal allyl carbon atoms of [(η3-allyl)ML2]+ (M Pd or Pt) complexes

The coordinated allyl group of complexes [(η3-allyl)ML2]+ (M  Pd or Pt) is shown experimentally to undergo nucleophilic attack on either central (Cc) or terminal (Ct) allyl carbon atoms. A new theoretical discussion is presented, showing that the feasibility of attack at the Cc atom is not as low as previously thought.

Crystallographic and nuclear magnetic resonance studies of carbonyl(η3-methylallyl)(trichlorostannyl) complexes of platinum(II) and palladium(II)

The complexes [M(η3-C4H7)(SnCl3)(CO)][C4H7= 2-methylallyl, M = Pt(1) or Pd(2)] have been prepared and characterized. Their solution behaviour has been studied by n.m.r. spectroscopy, the compounds being dynamic through dissociation of the CO ligand. The X-ray structures of (1) and (2) are reported. Complex (2) is the first mononuclear palladium carbonyl to be characterized by X-ray diffraction. The different stabilities of the two isostructural complexes are correlated with the subtle differences in bonding observed in the crystal structures.

Chemical and structural characterization of some π-allylic derivatives of rhodium(III)

Abstract The reaction of rhodium trichloride trihydrate and trans, trans, trans-1,5,9-cyclo- dodecatriene in boiling ethanol yields the red, diamagnetic dichloro(cyclododeca-1,5-dienyl)rhodium(III), insoluble in all common organic solvents. This compound is polymeric through chlorine bridges and reacts with many Lewis bases (e.g., carbon monoxide, amines, olefins) to give octahedral derivatives such as C12H19RhCl12B2 (B is a monodentate basic ligand). The chemical and structural characterization of this compound is reported through a study of its derivatives by X-rays, IR and NMR spectra and a possible mechanism is proposed.

Palladium(II) and platinum(II)η3-methylallyl trichlorotin complexes. Part 3. Crystal structure analysis of [Pt(η3-C4H7)(cod)]2[Pt(η3-C4H7)(SnCl3)3](cod = cyclo-octa-1,5-diene)

The dimer [{Pt(η3-C4H7)Cl}2] reacts with cyclo-octa-1,5-diene (cod) and SnCl2 to give [Pt(η3-C4H7)(cod)]2[Pt(η3-C4H7)(SnCl3)3](1). The compound crystallizes as discrete anionic and cationic platinum(II) complexes in space group P with a= 13.256(4), b= 19.960(4), c= 8.615(3)A, α= 101.75(2), β= 104.69(2), and γ= 86.62(2)°. The anionic complex displays a distorted square-pyramidal co-ordination while the two isostructural cations have irregular square-planar co-ordination. Analysis of bond distances using SnCl3 as a probe suggests that the trans influence of the methylallyl ligand is comparable to that of olefin ligands. While no n.m.r. data are available for (1) due to its very poor solubility, n.m.r. results for the palladium(II) analogue (2) obtained by the same synthetic route are compatible with the structure determined for (1).

Synthesis and characterization of alkyl-substituted poly(thiophene-2,5-diylvinylene)s

Abstract A new synthetic route for the preparation of poly(thiophene-2,5-diylvinylene)s consisting of the C-C coupling reaction of alkyl-substituted 2,5-diiodothiophene and E -1,2-bis(tri-n-butylstannyl)ethylene catalysed by palladium complexes is described. The resulting polymers are soluble. These materials have been extensively characterized by Fourier-transform infra-red and 13C nuclear magnetic resonance spectroscopy. The optical properties have been examined. The polymers are deep blue in the neutral state and transparent in the doped state. The solid-state structure of these materials will be discussed according to X-ray diffraction data.

Electromodulated absorption of alkyl substituted polythiophenes and polythienylenevinylenes

Abstract Electric field induced changes in the optical properties of alkyl substituted polytiiophenes and polythienylevinylenes are studied in the spectral region of the π-π ∗ electronic transition. The spectral shape and the magnitude of the electroabsorption (EA) signal are compared for mono- and di-alkyl substituted polythienylenevinylenes as well as for a well ordered poly(3-alkylthiophene). For all these polymers the induced absorption scales quadratically with the applied electric field and its lineshape is field invariant. For the well ordered poly(3-alkylthiophene) the EA spectrum resembles the first energy derivative of the unperturbed absorption, though there are several additional features. The EA spectra of the alkyl substituted polythienylenevinylenes do not however have a characteristic (e.g. first, second or third derivative) relationship to the unperturbed absorption.

A 13C and 31P N.M.R. Investigation of restricted rotation in [Pt(η3-allyl){P(cyclohexyl)3}2]+ [PF6]- and related compounds

Abstract The dynamic behaviour of [Pt(/gh3-allyl){P(cyclohexyl)3}2]+[PF6]- has been reinvestigated, and the earlier interpretation of restricted rotation about the Pt—P endorsed. The activation parameters were obtained. [Pt(/gh3-allyl)(PPri3)2]+[PF6]- behaves similarly, while it has not prove possible to stop the rotation in [Pt(/gh3-allyl){P(CH2Ph)3}2]+[PF6]-.

A rhodium(I)—iridium(III) hydrido-bridged phosphine complex

Abstract The new compound [(diphos)Rh(μ2-H)2IrH2(P{i-Pr}3)2] (II) (diphos 1 Ph2 PCH2 CH2 PPh2) was prepared from [Rh(diphos)(MeOH)2]+ and [IrH5(P{i-Pr}3)2] and characterized by NMR and X-ray methods.