Pedro T. Gomes

Polymerization with TMA‐protected polar vinyl comonomers. II. Catalyzed by nickel complexes containing α‐diimine‐type ligands

α-Diimine Ni complexes (7, 8) were used as catalyst precursors with MAO in co- and terpolymerization of ethylene/propylene/α-olefins with OH and COOH functional groups. Trimethylaluminium was used to protect the functional group of polar monomers. The presence of 5-hexen-1-ol seems to have no effect on the polymerization rate at all for the N,N′-bis(2,6-diisopropylphenyl) derivative 8 but caused activity decreases of about fivefold in copolymerization and around two times in terpolymerization for the N,N-dimesityl derivative 7. The effect levels off at higher polar comonomer concentration. This system, (7)/MAO, also incorporates well both 10-undecen-1-ol and 10-undecen-1-oic acid. The activities obtained with these α-diimine Ni complexes in co- and terpolymerization are three to twenty times higher than those obtained with group 4 Cp based complexes especially at concentrations of polar monomer in the feed higher than 80 mM.

Polymerization with TMA‐protected polar vinyl comonomers. I. Catalyzed by group 4 metal complexes with η5‐type ligands

This paper describes the use of several kinds of group IV Cp based catalyst systems, in the synthesis of co- and terpolymers of ethylene, propylene and α-olefins endowed with OH and COOH functional groups. The hydroxy monomers used were 5-hexen-1-ol (4) and 10-undecen-1-ol (5) and the carboxy monomer was 10-undecen-1-oic acid (6). The three catalyst systems used were the C 2 symmetric ansa-zirconocene (1) the in-site titanium complex (2) and the non-rigid zirconocene (3), all activated by methylaluminoxane. Trimethylaluminium was used to protect the functional group of polar monomers. The first two catalyst systems suffer similar activity loss in the presence of polar monomer whereas the third one exhibited better tolerance toward the hydroxyolefins. NMR and FTIR spectroscopies were used to characterize the polymerization products. All three catalyst systems afforded functionalized co- and terpolymers by direct polymerization of ethylene/propylene/hydroxy-a-olefins but only the catalyst system (1)/MAO displays appreciable activities for direct polymerization of ethylene, propylene and carboxy-α-olefins.

New tetradentate N,N,N,N-chelating α-diimine ligands and their corresponding zinc and nickel complexes: synthesis, characterisation and testing as olefin polymerisation catalysts

A series of zinc complexes of the general formula {[ZnCl(ArN=C(An)-C(An)=NAr)](+)}(2)[Zn(2)Cl(6)](2-) (where Ar = 2-(1-benzyl-1H-1,2,3-triazol-4-yl)phenyl 2a, 2-(1-(1-phenylethyl)-1H-1,2,3-triazol-4-yl)phenyl 2b, 2-(1-phenyl-1H-1,2,3-triazol-4-yl)phenyl 2c; An = acenaphthene backbone) were prepared by the condensation of acenaphthenequinone with the corresponding o-triazolyl-substituted anilines (2-(1-benzyl-1H-1,2,3-triazol-4-yl)aniline 1a, 2-(1-(1-phenylethyl)-1H-1,2,3-triazol-4-yl)aniline 1b, 2-(1-phenyl-1H-1,2,3-triazol-4-yl)aniline 1c) which were formed by the copper(I)-catalyzed Huisgen[3+2] dipolar cycloaddition between 2-ethynylaniline and the corresponding azides in high yields, using anhydrous ZnCl(2) as the metal template, in boiling glacial acetic acid. Zinc complexes of the type [ZnCl(ArN=C(An)-C(An)=NAr)](+)[ZnCl(3)(NCCH(3))](-) (4a-c) were synthesized by crystallisation of the corresponding complexes 2a-c in acetonitrile, at -20 °C. After removal of zinc dichloride from complexes 2a-c by the addition of potassium oxalate, in dichloromethane, the tetradentate N,N,N,N-chelating α-diimine ligands of the type ArN=C(An)-C(An)=NAr (5a-c) were obtained. The new ligand precursors and zinc complexes were characterised by elemental analysis, (1)H and (13)C{(1)H} NMR spectroscopy, two-dimensional NMR spectroscopy, and X-ray diffraction. Reaction of the ligand precursors 5a-c with [NiBr(2)(DME)], in dichloromethane, gave nickel complexes of the type [NiBr(2)(ArN=C(An)-C(An)=NAr)] (6a-c). The results of single crystal X-ray diffraction characterisation and magnetic susceptibility measurements demonstrated that nickel complexes 6a-c possess octahedral geometries around the nickel atoms with variable configurations, the Br atoms of which can be ionized when dissolved in methanol. In preliminary catalytic tests, complexes 6a-c revealed to be active as catalysts for the polymerisation of norbornene and styrene, when activated by cocatalyst MAO. The characterisation of the polymers by (1)H and (13)C{(1)H} NMR spectroscopy, gel permeation chromatography/size-exclusion chromatography (GPC/SEC) revealed that these polymers were formed by a coordination addition mechanism.

Synthesis of allyl- and aryl-iminopyrrolyl complexes of nickel

The 2-iminopyrrole ligand precursors 2-C4H3NH[(R)CN(2,4,6-C6H2Me3)] (R = H, I; R = Me, II) were synthesised and react with NaH to give the corresponding sodium salts 1 and 2, respectively. Salt 2 reacts with [NiPhBr(PPh3)2] to yield [NiPh(acetiminopyrrolyl)(PPh3)] 3. Ligand precursors II and 2 react, respectively, with equimolar amounts of [NiMe2(TMEDA)] and [NiBr2(NCMe)2] to give [Ni(acetiminopyrrolyl)2] 4. Both 1 and 2 react with [Ni(η3-C3H5)(μ-Br)]2 to give complexes [Ni(η3-C3H5)(iminopyrrolyl)] 5 and 6. The crystal structures of ligand precursor II and of complex 3 are reported and compared. Complex 3 was tested for catalytic activity for the oligomerisation of ethylene and showed only moderate activity.

Synthesis of novel polyurethanes from sugars and 1,6-hexamethylene diisocyanate

Abstract Synthesis of two new polyurethanes was accomplished by reaction of 1,6-hexamethylene diisocyanate with the sugars methyl 2,6-di-O-pivaloyl-α- d -glucopyranoside (1) and methyl 4,6-O-benzylidene-α- d -glucopyranoside (2) catalysed by 1,4-diazabicyclo[2.2.2]octane. The polymers 4 and 5 obtained were characterised by physical and spectroscopic methods.

A path-following preview controller for autonomous air vehicles

An operating concept and a laboratory analysis methodology were developed and tested to examine how four-dimensional trajectory analysis methods could support higher levels of automation for separation assurance in the National Airspace System. Real-time simulations were conducted in which a human controller generated conflict resolution trajectories using an automated trial planning resolution function, but only in response to conflicts detected and displayed by an automatic conflict detection function. Objective metrics were developed to compare aircraft separation characteristics and flying time efficiency under automated operations to that of today’s operations using common airspace and traffic scenarios. Simulations were based on recorded air traffic data from Fort Worth and Cleveland Centers and conducted using today’s and nearly two-times today’s traffic levels. Results suggest that a single controller using trajectory-based automation and data link communication of control clearances to aircraft could manage substantially more traffic than they do now with improved route efficiency while maintaining separation. The simulation and analysis capability provides a basis for further analysis of semi-automated, or fully automated, separation assurance concepts.

Cationic benzyl nickel complexes as homogeneous catalysts for styrene oligomerization. X-ray crystal structure of [Ni(η3-CH2C6H5)(PPh3)2]PF6 · CH2CI2 *

Abstract New cationic complexes [Ni(η3-CH2C6H5)(PPh3)2]PF6 (3) and [Ni(η3-CH2C6H5)((+)-DIOP)]PF6 (4) were synthesized from the corresponding neutral compounds [Ni(η3-CH2C6H5)X(PR3)2] (X = Cl, Br), by metathetical halide abstraction with TIPF6. Complex 3 was characterized by X-ray crystallography and shown to have a distorted square-planar geometry with the benzylic group coordinated in a quasi-allylic fashion. Crystals are monoclinic, space group P21/n, a = 11.798(5), b = 19.251(2), c = 18.561(3) A, β = 93.03°, V = 4208.6 A3. Solution NMR studies showed benzyl fluxionality and phosphine lability in compound 3, but not in 4. The latter one is catalytically inactive towards styrene oligomerization, whereas 3 produces styrene oligomers ( M ¯ n ≈ 1000 ) with 67% isotactic content. Although [Ni(η3-CH2C6H5)CI(PCy3)] and trans[Ni(Cl)(H)(PCy3)2] are inactive, addition of TlPF6 induced catalytic activity with formation of highly isotactic (90%) styrene oligomers with similar M ¯ n and a different terminal group.

Ansa-bridged η-cyclopentadienyl imido and amido derivatives of titanium, zirconium, niobium and molybdenum

Abstract An improved synthesis of the ligand precursor {[C5H4(SiMe3)](CH2)3N(SiMe3)2} is described. It has been used to prepare the compounds {Ti[η:σ-C5H4(CH2)3N(SiMe3)]Cl2}, {Ti[η-C5H4(CH2)3(μ-N)]Cl}2, {Zr[η:σ-C5H4(CH2)3N(SiMe3)](SMe2)Cl2}, {Zr[η:σ-C5H4(CH2)3N(SiMe3)]Cl2} and {Mo[η:σ-C5H4(CH2)3N(SiMe3)](PMe3)Cl2}. The zirconium compounds together with methylaluminoxane act as catalysts for ethylene and propylene polymerisation.

Synthesis and characterisation of ring-coupled cyclopentadienyl and indenyl bimetallic derivatives of nickel

Abstract The reaction of NiCl2(PPh3)2 with 0.5 equivalents of the salts Li2[CMe2(C5H4)2] (1), Li2[CMe2(C9H6)2] (2) or Li2[(C5H4)CMe2(C9H6)] (3) is an efficient route to the synthesis of ring-coupled cyclopentadienyl and indenyl homobimetallic nickel derivatives. The new binuclear complexes [Cl(PPh3)Ni{μ-(η-C5H4)CMe2(η-C5H4)}Ni(PPh3)Cl] (4), [(PPh3)2Ni{μ-(η-C5H4)CMe2(η-C5H4)}Ni(PPh3)2][PF6]2 (5), [(PPh3)2Ni{μ-(η-C9H6)CMe2(η-C9H6)}Ni(PPh3)2][PF6]2 (6), [Cl(PPh3)Ni{μ-(η-C5H4)CMe2(η-C9H6)}Ni(PPh3)Cl] (7), [(PPh3)2Ni{μ-(η-C5H4)CMe2(η-C9H6)}Ni(PPh3)Cl][PF6] (8), [(PPh3)2Ni{μ-(η-C5H4)CMe2(η-C9H6)}Ni(PPh3)2][PF6]2 (9) have been prepared and characterised. The X-ray crystal structure of 5 is reported.

A vision-based system for early fire detection

This paper presents a video-based early fire detection system. Focus is given to the challenges related to the actual deployment of the vision system. Most importantly, background subtraction is performed in a windowed way for improved accuracy, an attentive mechanism is employed to focus a computationally expensive frequency analysis of potential fire regions, interaction with a people detection and tracking system is included so as to enable model-based false alarms rejection, a new colour-based model of fires appearance as well as a new Wavelet-based model of fires frequency signature are proposed, and the camera-world mapping is approximated according to a GPS-based learning calibration process. An average success rate of 92.7% at a processing rate of 10 Hz shows the applicability of the model to real-life applications.