T. Boschi

Iron and ruthenium carbonyls of 2,3,5,6-tetrakis(methylene)bicyclo[2.2.2]octane. Crystal and molecular structure of (C12H14)Fe(CO)3

Abstract The reaction of 2,3,5,6-tetrakis(methylene)bicyclo[2.2.2]octane (1a) with Fe 2 (CO) 9 yields the two (η 4 -1,3-diene)Fe(CO) 3 isomers (2: exo; 3:endo) together with two bimetallic isomers (C 12 H 14 )[Fe(CO) 3 ] 2 (4:endo-exo; 5:diexo). The reaction of 1a with Ru 3 (CO) 12 yields the endo-(C 12 H 14 )Ru(CO) 3 (6) and endo, exo-(C 12 H 14 [Ru(CO) 3 ] 2 (7) complexes as the main products. The molecular structure of 3 has been determined by X-ray crystallography. The Fe(CO) 3 group is in the endo position with respect to the roof-shaped tetraene. The ligand is bound through one diene group to two basal positions of a tetragonal pyramidal Fe(CO) 3 L 2 moiety. Hydrogen atom positions have been determined (final residual R = 0.029). The dimensions for the 1,3-butadieneirontricarbonyl system, as found in this and 41 other structures, are summarized and discussed statistically. In this study the weighted averages for all structures show the threeCC distances to be of equal length and the FeC (inner) distance to be shorter than the FeC (outer) distance. The deviations of H(Z) and H(E) atoms from the butadiene plane, as found in this and 6 other structures having an exocyclic unsubstituted 1,3-diene group, are also discussed. Neither thermal epimerization of iron nor epimerization catalyzed by H + were found for complexes 2 – 7 whose structures in solution were deduced from their 1 H and 13 C NMR data on the basis of the known structure of 3.

Iron and Molybdenum Carbonyls of 5,6-Dimethylene-7-Oxabicyclo[2.2.1]Hept-2-Ene - Crystal and Molecular-Structure of (C8H8O)Fe2(Co)7

Abstract The photoreaction of 5,6-dimethylene-7-oxabicyclo [2.2.1]hept-2-ene(1) with Fe(CO)5 yields initially the dihapto-tetracarbonyl iron complex (3), which reacts further to give a dihapto-tetracarbonyl-tetrahapto- tricarbonyl complex (C8H8O)Fe2(CO)7 (4) The molecular structure of 4 has been determined by X-ray crystallagraphy. Both the Fe(CO)4 and Fe(CO)3 groups are in exo position with respect to the roof-shaped triene. The ligand is bound through its lone double bond to an equatorial position of a substituted trigonal-bipyramidal Fe(CO)4L moiety and through its diene group to two basal positions of a tetragonal pyramidal Fe(CO)3L2 moiety. Hydrogen atom positions have been determined in the last cycles (final residual R = 0.023). H(Z) atome deviate by 39° from the diene plane away from the metal and H(E) atoms deviate by 11° towards the metal. H atoms of the lone CC double bond deviate by 34° from the C(1)C(2)C(3)C(4) plane away fromthe metal. The structures of complexes 3,4 and(C8H8O)Mo(CO)3 (7) in solution were deduced fromtheir 1H NMR data and the unknown geometries of ligands 1 and 5,6-dimethylenebicyclo[2.2.1] hept-2-ene (2) were simulated by MINDO¦3. Deoxygenation of the ligand is observed in the presence of Fe2(CO)9 in benzene at 60 °C, giving o-quinodimethane complexes 5 and 6, 5 being also obtained by direct thermolysis of complex 4.

Reactions of 1,4-diazubutadienes with chloro-bridged palladium(II) and platinum(II) allyl derivatives

Abstract The 1,4-diazabutadienes (or α-diimines) RNC(R′)C(R″)NR, DAB, (R = p -C 6 H 4 OMe, R′ = R″ = H, DAB I ; R = p -C 6 H 4 OMe, R′ = H, R″ = Me, DAB II ; R = p -C 6 H 4 OMe, R′ = R″ = Me, DAB III ; R = t-Bu, R′ = R″ = H, DAB IV ) react with the allylic compounds [PdCl(η 3 -2-Y-C 3 H 4 )] 2 (Y = H: all; Y = Me: Meall) and [PtCl(C 3 H 5 )] 4 in the presence of NaClO 4 yielding the cationic complexes [M(η 3 -2-Y-C 3 H 4 )(DAB)]ClO 4 (M = Pd, I; M = Pt, II). The 1 H and 13 C NMR spectra indicate a σ,σ′-N,N′ chelation of DAB. In the complexes with the asymmetric ligand DAB II a fast syn-syn, anti-anti , exchange of the allylic protons occurs at room temperature in CDCl 3 . In acetonitrile a partial dissociation of DAB is observed, with the following order of stability constants; DAB III > DAB I and Pt ⪢ Pd. In the absence of NaClO 4 , equilibria are established involving the starting reactant [PdCl(η 3 -Meall)] 2 , binuclear species {[PdCl(η 3 -Meall)] 2 (DAB)}, III (in which DAB acts as a bidentate bridging ligand) and ionic complexes [Pd(η 3 -Meall)(DAB)] + [PdCl 2 (η 3 -Meall)] − , IV. These equilibria were studied in various solvents by variable temperature 1 H NMR spectra, electronic spectra, molecular weight and conductivity measurements. The complexes III can be isolated as solids and are the predominant species in concentrated solution only with DAB I and DAB IV , both having R′ = R″ = H. With DAB III , the predominant species in CDCl 3 at −40 °C is a complex of type IV. A similar compound, [Pd(η 3 -Meall)(bipy)][PdCl 2 (η 3 -Meall)], is also obtained in the reaction with 2,2′-bipyridine.

Iron, molybdenum and tungsten carbonyls of 5,6,7,8-tetrakis(methylene)bicyclo[2.2.2]oct-2-ene. Crystal and molecular structure of (C12H12)Fe(CO)3

Abstract The reaction of 5, 6, 7, 8-tetrakis(methylene)bicyclo[2.2.2.]oct-2-ene (1) with Fe29CO)9 yields under various conditions the exo and endo-tetrahaptotri-carbonyliron complexes(2 and3) and the endo, exobis(tetrahaptotricarbonyliron) complex (4); with Fe(CO)39benzalacetone), 2 and the bis(exo-tetrahapto-tricarbonyliron) complex (5) are obtained. The little ligand reacts with M(CO)3(CH3CN)3 (M = Mo, W) giving respectively the hezahapto-tricarbonyl-molybdenum and -tugnsten complex (6, 7). Coordination of all five double bonds of the pentaene is achieved by reacting 2 with Mo9CO)3(CH3CN)3 giving the exo-tetrahapto-tricarbonyliron-hexahapto-tricarbonylmolybdenum complex (8). The structures of complexes 3–8 in solution were deduced from their NMR data and the molecular structure of 2 was determined by X-ray crystallography. The Fe(CO)3 group is in th eexo position with respect to the roof-shaped pentaene. The ligand is bound through one s-cis-butadiene group to two basal positions of a tetragonal pyramidal Fe(CO)3X2 moiety. Hydrogen atom positions were refined in the last cycles (final residual R = 0.023). H(Z) atoms deviate from the diene plane of the coordinated diene away from the metal by ∼42°, whereas H(E) atoms deviate towards the metal by ∼16°. Hybridization at the “inner” carbon atoms as well as at the carbon atoms of the other three double bonds does not differ significantly from sp2. Kinetic study of the cycloaddition reaction of a dienophile to the free 1, 3-diene system of the monometallic complexes shows that the rate with respect to that of the free ligand is not much affected by the presence of the metal.

Micelle‐Bound Metalloporphyrins as Highly Selective Catalysts for the Epoxidation of Alkenes

The porphyrin-surfactant interaction determines the activity of the title catalysts. Amphiphilic porphyrin derivatives (e.g. 1 with M=MnCl, R=CH2 CH2 (OCH2 CH2 )2 OH) are easy to prepare and can be included in micellar phases.

Cationic cyanobenzylpalladium(II) complexes. Synthesis and reactivity of the cyano group towards nucleophiles

Abstract The addition of alcohols, thiols, water and amines to the σ-coordinated CN group of cis -[Pd( o -CH 2 C 6 H 4 CN)L 2 ] 2 (BF 4 ) 2 (L 2 = 2PPh 3 , 1,2-bis(diphenylphosphino)ethene or -ethane) yields stable N-bonded iminoether, iminothioether, amide and amidine complexes,respectively. Thiophenols, ArSH (Ar = p -C 6 H 4 CH 3 , p -C 6 H 4 Br) break the σ-PdC bond, forming o -cyano toluene and complexes of the type [Pd(SAr)L 2 ] 2 (BF 4 ) 2 . The azido complex PdN 3 ( o -CH 2 C 6 H 4 CN)(Ph 2 PCH 2 CH 2 PPh 2 ) is stable in the solid state but in solution it undergoes an intramolecular 1,3-cycloaddition yielding the corresponding tetrazolate complex.

Cyanobenzylpalladium(II) complexes. Synthesis and spectroscopic properties

Abstract The oxidative addition of benzyl, o- , m- and p- cyanobenzyl chlorides to Pd(PPh 3 ) 4 yields trans- PdCl(CH 2 C 6 H 4 Y)(PPh 3 ) 2 (Y= H or CN) (1a-d). In solution, these complexes are in equilibrium with the dimers [PdCl(CH 2 C 6 H 4 Y)PPh 3 ] 2 (2a--d) which are obtained in quantitative yields upon shifting the equilibria by oxidation of the free PPh 3 with H 2 0 2 . PPh 3 in both the monomers and the dimers is readily displaced by bidentate ligands yielding PdCI(CH 2 C 6 -H 4 Y)(L-L) (3). Chloride abstraction from 3 gives dimeric cationic complexes [Pd(o-CH 2 C 6 H 4 CN)(L-L)] 2 (BF 4 ) 2 having a σ-coordinated CN group. Insertion of carbon monoxide in the PdC bonds is quantitative.

Synthesis of unsymmetrical porphyrin dimers containing β-octaalkyl and meso-tetraphenylporphyrin subunits

Methodology for synthesis of phenyl-linked unsymmetrical dimers containing 8,12-diethyl 2,3,7,12,13,17,18-hexamethylporphyrin and meso-tetraphenylporphyrin subunits is reported. Hetero metal complexes of these dimers can be prepared by following two different routes.

Dimethyldioxirane-Mn(Cl16)TDMPPCI porphyrin as efficient and chemoselective epoxidizing reagent of uracil derivatives

Abstract Dimethyldioxirane (DMDO) was employed as oxygen donor in metalloporphyrins catalyzed selective epoxidation of uracil derivatives.

First-row transition-metal complexes of corroles: synthesis and characterization of oxotitanium(IV) and oxovanadium(IV) complexes of β-alkylcorroles

Oxotitanium and oxovanadium β-alkylcorrolates have been synthesized by reaction of corroles H3L with different metal carriers. These complexes retain an aromatic π-electron system and exist as mononuclear species [MO(HL)] containing a MO double bond. Optical and NMR spectroscopy indicated reaction with base leading to the formation of anionic species [MOL]–. Titanyl corrolates represent the first examples of diamagnetic neutral complexes where the corrole acts as a dianionic ligand. Spectral characterization reveals that the location of the proton of HL is at the N22 or N23 inner nitrogen atoms and that the complexes are present in two tautomeric forms. In contrast to derivatives of Cr or Mo where the metals are in the +5 oxidation state, the EPR spectra of the vanadyl corrolates confirm the +4 oxidation state for the co-ordinated metal. These new complexes complete the series of first-row transition-metal derivatives of corrole.