Assembly and incorporation of a CO2Me group into a bridging vinyliminium ligand in a diiron complex

The diiron complex [Fe2{m-l1(O):h1(C):h3(C)eC(N(Me)(Xyl))C(H)]C(Me)C(O)OMe}(m-CO)(Cp)2] (2) has been obtained from the diiron bridging vinyliminium [Fe2{m-h1:h3eC(Me)]C(H)C]N(Me)(Xyl)}(m-CO) (CO)(Cp)2][SO3CF3] (1; Xyl ¼ 2,5-C6H3Me2) upon treatment with NaH in the presence of CH2]C]CMe2, followed by chromatography on alumina with MeOH as eluent. The reaction consists in the incorporation of a methylcarboxylate unit, assembled from CO and MeO, into the bridging vinyliminium ligand. The resulting complex 2 exhibits a C4 fragment bridging the two iron centres through the carbonyl oxygen atom and the allylidene moiety. The X-ray molecular structure of 2 has been determined

N,N-Dialkylcarbamato Derivatives of Niobium and Tantalum as Precursors to Metal-Functionalized Silica Surfaces

Chemical implantation of Group 5 cations [Nb(III), Nb(V), and Ta(V)] has been carried out under mild conditions by the reaction of N,N-dialkylcarbamato derivatives M(O2CNR2)n (M = Nb, Ta) with silanol groups of amorphous silica, carbon dioxide, and secondary amine being released in the process. The amount of supported cations depends on the metal and on the initial number of N,N-dialkylcarbamato ligands on M; partial reduction to the +4 oxidation state occurs in the case of Nb(O2CNR2)5

Addition of Alkynes to Zwitterionic mu -Vinyliminium Diiron Complexes: New Selenophene (Thiophene) and Vinyl Chalcogenide Functionalized Bridging Ligands

Zwitterionic vinyliminium complexes [Fe2{u-eta1:eta3-C(R’)=C(E)C=N(Me)(R)}(-CO)(CO)(Cp)2][SO3CF3] (R = R’ = Me, E = Se, 1a; R = Xyl R’ = Tol, E = Se, 1b; R = Xyl, R’ = Tol, E = S, 2a; R = Xyl, R’ = Tol, E = S, 2b; Tol = 4-MeC6H4, Xyl = 2,6-Me2C6H3), undergo alkyne addition by different reaction modes. Complexes 1a and 2a undergo 1,3 dipolar cycloaddition with alkynes [HCCCO2Me, and C2(CO2Me)2], affording new 1-(2-amino)-seleno(thio)phene-alkylidene diiron complexes [Fe2{μ-1(N):1(C):1(C):-C(R’)CEC(CO2Me)=C(R’’)CN(Me)(R)}(μ-CO)(CO)(Cp)2] (R = R’ = Me, E = Se, R’’ = CO2Me, 3a; R = R’ = Me, E = Se, R’’ = H, 3b; R = Me, R’ = Tol, E = S, R’’ = CO2Me, 4). The hemilabile character of the bridging ligand in 3a is investigated by reaction with CNBut, which replace NMe2 coordination affording [Fe2{μ-C(Me)CSeC(CO2Me)=C(CO2Me)CN(Me)2}(μ-CO)(CO)(CNBut)(Cp)2] (5). Complexes 2a, 2b react with two equivalents of HCCCO2Me, leading to the formation in formation of [Fe2{-1(O):1(C):3(C)-C(CCCO2Me)C(R’)C(SCH=CHCO2Me)CON(Me)(Xyl)}(-CO)(Cp)2] (R’ = Tol, 6a; R’ = Me, 6b). Finally, complexes 1b, 2a and 2b react with different alkynes, in the presence of NH4PF6, affording the vinyl sufide and vinyl selenide vinyliminium complexes [Fe2{μ-1:3-C(R’)=C(ECR’’=CHCO2Me)C=N(Me)(Xyl)}(μ-CO)(CO)(Cp)2][PF6] (R’ = Tol, E = S, R’’= H, 7a; R’ = Me, E = S, R’’ = H, 7b; R’ = Tol, E = S, R’’= CO2Me, 7c; R’ = Me, E = S, R’’= CO2Me, 7d; R’ = Tol, E = Se, R’’= H, 8a; R’ = Tol, E = Se, R’’= CO2Me, 8b). The molecular structures of 3a, 5, and 6b have been elucidated by X-ray diffraction

Metal alkyl-arenes and processes for the preparation thereof

Metal alkyl-arene, (η6-arene)2AlqXrRs (I) M (η6-arene)AlqXrRs (Ia) wherein: M = Zr, Hf, or mixts. thereof, preferably zirconium; arene represents a benzene, or a benzene 10 substituted with from 1 to 6 linear or branched C1-C6 alkyl groups, or mixts. thereof; X represents a halogen atom selected from chlorine, bromine, fluorine, iodine, preferably chlorine; R represents a linear or branched C1-C15 alkyl group; q is a no. ranging from 2 to 6, preferably 3 for a metal alkyl-arene I, 2 for a metal alkyl-arene Ia; r is a no. ranging from 1 to 20, preferably 9 for a metal alkyl-arene Ia, 6 for a metal alkyl-arene Ia; s is a no. ranging from 1 to 6, preferably 2. Said metal alkyl-arene can be advantageously used for the prepn. of solid components of catalysts for the (co)polymn. of α-olefin

Chemical Implantation of Group 4 Cations on Silica via Cyclopentadienyl- and N,N-Dialkylcarbamato Derivatives

Chemical implantation of Group 4 cations [Ti(III), Ti(IV), Zr(IV), Hf(IV)] has been carried out under mild conditions by the reaction of polycyclopentadienyl- (MCpn; M = Ti, n = 3, 4; M = Zr, Hf, n = 4), mixed cyclopentadienyl/N,N-dialkylcarbamato (MLx(O2CNEt2)y; M = Ti, L = Cp, C5Me5 (Cp*), x = 2, y = 1; M = Hf, L = Cp, x = 1, y = 3), and N,N-dialkylcarbamato (M(O2CNR2)n, M = Ti, n = 3, R = iPr; M = Ti, Hf, n = 4, R = Et; M = Zr, n = 4, R = iPr) derivatives, with the silanol groups of amorphous silica. Cyclopentadiene/ pentamethylcyclopentadiene and/or carbon dioxide and the secondary amine are released in the process. The amount of implanted cations depends on the metal and on the ligands, the pentamethylcyclopentadienyl complex being less reactive than the unsubstituted congener. The starting complexes and the final products have been characterized by EPR or by 13C CP-MAS NMR spectroscopy

Metal alkyl-arenes and processes for the preparation thereof

Metal alkyl-arene, (η6-arene)2AlqXrRs (I) M (η6-arene)AlqXrRs (Ia) wherein: M = Zr, Hf, or mixts. thereof, preferably zirconium; arene represents a benzene, or a benzene 10 substituted with from 1 to 6 linear or branched C1-C6 alkyl groups, or mixts. thereof; X represents a halogen atom selected from chlorine, bromine, fluorine, iodine, preferably chlorine; R represents a linear or branched C1-C15 alkyl group; q is a no. ranging from 2 to 6, preferably 3 for a metal alkyl-arene I, 2 for a metal alkyl-arene Ia; r is a no. ranging from 1 to 20, preferably 9 for a metal alkyl-arene Ia, 6 for a metal alkyl-arene Ia; s is a no. ranging from 1 to 6, preferably 2. Said metal alkyl-arene can be advantageously used for the prepn. of solid components of catalysts for the (co)polymn. of α-olefins

Ring Opening Polymerization of rac-Lactide by Group 4 Tetracarbamato Complexes: Activation, Propagation and Role of The Metal

A series of group 4 metal tetracarbamates M(O(2)CNR(2))(4) (M = Ti, R = Et, ; M = Zr, R = Et, ; (i)Pr, ; M = Hf, R = Et, ; R = (i)Pr, ) were studied as catalytic precursors in the solution polymerization of rac-lactide. The titanium complex but not the zirconium and hafnium ones increase the activity by addition of (i)PrOH. The structure of the carbamato ligand markedly influences the molar mass of polymer; the complexes with isopropyl carbamato ligands produced PLA with molar masses up to 94000 g mol(-1). The main mechanistic aspects of the initial stages of the polymerization reactions were outlined by spectroscopic and computational analyses. In the case of zirconium and hafnium complexes, an interaction between a carbamato ligand and the CH unit of one lactide molecule is established at room temperature. This interaction is followed by the high temperature proton transfer from the lactide to the carbamato O-atom, affording a catalytic active alkoxy complex with release of CO(2) and NHR(2). The polymerization mediated by Ti(O(2)CNEt(2))(4) involves the release of a radical fragment [O(2)CNEt(2)]˙, with consequent generation of a Ti(iii) center. The propagating chain is an alcoholate ligand coordinated to a Ti(iv) centre and containing a radical mainly localized at the tail of the chain (DFT, EPR)