Roman Weimann

The influence of electronic and steric effects and the importance of polymerization conditions in the ethylene polymerization with zirconocene/MAO catalysts

Abstract A series of Cp′(C5H5)ZrCl12 and Cp2′ZrCl12 precatalysts (Cp′ = C5Me4H, C4Me4P, C5Me5) together with (C5H5)2ZrCl12 has been investigated in terms of steric and electronic variations and their catalytic activities in combination with methylalumoxane (MAO) towards the polymerization of ethylene are compared. The changes in the steric environment were evaluated on the basis of the structural data available and supplemented by theoretical structural studies on the semiempirical (ZINDO, EHMO) and density functional (DF) level. The X-ray structures of (C5Me4H)2ZrCl2 (3) and (C4Me4P)(C5H5)ZrCl2 (4) have been determined (3: orthorhombic, Cmcm, a = 6.714(4), b = 17.275(4) c = 15.643(5) A , Z = 4 ; 4: monoclinic, P21/c, a = 8.8791(5), b = 7.8051(8), c = 20.9215(10) A β = 94.422(4)° , Z = 4. 91Zr NMR data for the above series has been measured and is correlated to changes in the HOMO-LUMO gap available from electronic structure calculations. Under mostly homogeneous polymerization conditions, at very low zirconium concentrations the order of the catalytic activity found for ethylene polymerizations is (C5H5)2ZrCl2 > (C5Me4H)(C5H5)ZrCl2 > (C5Me5)(C5H5)ZrCl2 > (C4Me4P)(C5H5)ZrCl2 > (C5Me4H)2ZrCl2 > (C5Me5)2ZrCl2 > (C4Me4P)2ZrCl2, which for the most part is inversely proportional to the steric demand of the ring ligands in the metallocene precatalysts except for the phospholyl systems. The lower activities of the phospholyl vs. the tetra- and penta-methylcyclopentadienyl compounds might imply an electronic effect such that the electron withdrawing phosphorus substituent decreases the activity, although further studies are needed to clarify this situation. Emphasis is placed on the control of the polymerization conditions and evaluation of the time-activity profiles. At higher zirconium concentrations an increased precipitation of polyethylene takes place during the course of polymerization and results in a transfer to the heterogeneous phase with a diffusion controlled reaction rate thereby invalidating any activity-comparing studies.

1,4-Diaza-1,3-diene (DAD) complexes of early transition elements. Syntheses, structures and molecular dynamics of mono- and bis(η5-cyclopentadienyl)titanium-, zirconium- and hafnium(DAD) complexes. Crystal- and molecular structures of CpTi(DAD)CH2Ph, [CpTi(DAD)]2O, CpZr[(DAD)(N∩O)] and Cp2Hf(DAD)

Abstract Treatment of CpTiCl3 and CpZrCl3(THF)2 with one equivalent magnesium in the presence of 1,4-diaza-1,3-dienes (R1NCR2CR2NR1 (R1,R2-DAD; R1=C6H4-2-Me, C6H4-4-Me, C6H4-4-OMe, R2=H, Me, Ph) yields the monomeric titanium complexes CpTi(R1,R2-DAD)Cl (2, R1=C6H4-4-OMe, R2=H; 3, R1=C6H4-2-Me, R2=Me; 4, R1=C6H4-4-OMe, R2=Me; 5, R1=C6H4-4-Me, R2=Ph), and the chloro bridged dimeric zirconium complexes [CpZr(R1,R2-DAD)Cl]2 (6, R1=C6H4-4-OMe, R2=H; 7, R1=C6H4-4-OMe, R2=Me; 8, R1=C6H4-4-Me, R2=Ph). Both the half-sandwich complexes of DAD ligands bearing alkyl (3, 4 and 7) and aryl (5, 8) substituents at the inner carbon atoms and the complexes without substituents at this DAD positions (2, 6) prefer the σ2,π-coordination geometry with a supine conformation of the heterodiene. Alkylation of the new half-sandwich DAD complexes with one equivalent of PhCH2MgCl or one equivalent of MeMgI affords the benzyl and methyl derivatives CpM(R1,R2-DAD)CH2Ph (9, M=Ti, R1=C6H4-4-OMe, R2=Me; 10, M=Zr, R1=C6H4-4-OMe, R2=Me) and CpZr(R1,R2-DAD)Me (11, R1=C6H4-4-Me, R2=Ph). An X-ray study of the benzyl derivative 9 reveals that the alkylation does not change appreciably the DAD bonding parameters in comparison with the starting chloride complex 4. The monomeric half-sandwich zirconium complex CpZr(R1,R2-DAD)(N∩O) (12, R1=C6H4-4-OMe, R2=H) which has been prepared by reaction of 6 with the chelating acetylacetoneiminate compound Na[(C6H4-4-Me)NC(Me)-CHC(Me)O] (Na[N∩O]) as well as the oxygen bridged complex [CpTi(R1,R2-DAD)]2O (13, R1=C6H4-2-Me, R2=Me) which has been formed by hydrolysis of 3 also keep the supine conformation of the heterodiene ligand with respect to the Cp group. Temperature dependent NMR spectra of a series of different titanocene DAD complexes Cp2Ti(R1,R2-DAD) (R1=Ph, C6H4-2-Me, C6H4-4-Me, C6H4-4-OMe, 1-C10H7, R2=Me; 14–18) have been used to estimate the energy barrier of the thermal induced inversion of the folded diazametallacyclopentene rings and to identify rotameric isomers derived from restricted rotation of the C6H4-2-Me and the 1-C10H7 group about the NCipso bond of the DAD ligand. Accordingly, complexes 16 and 18 and also the half-sandwich complexes 3 and 13 adopt mixtures of meso and rac rotamers. Finally, the crystal structure of Cp2Hf(R1,R2-DAD) (21, R1=R2=Ph) is reported.

The chemistry of 1,3,5-triazacyclohexane complexes 5: cationic zinc(II) alkyl complexes of N-alkylated 1,3,5-triazacyclohexanes and 13-benzyl-1,5,9-triazatricyclo[7.3.1.05,13]-tridecane

Abstract Diethylzinc reacts with hydroperchlorates of N-alkylated 1,3,5-triazacyclohexanes (R 3 TAC; R = methyl (Me), benzyl (Bz), isopropyl ( i Pr)) and with the hydrotetrafluoroborate of 1,3,5-tris-( para -fluorobenzyl)-1,3,5-triazacyclohexane (FBz 3 TAC) to give the corresponding cationic zinc ethyl complexes [(R 3 TAC)Zn(Et)][X] (X = ClO 4 − , BF 4 − ). Similar complexes were obtained from diethylzinc treated with [HNMe 2 Ph][BF 4 ] or [HNMe 2 Ph][B(C 6 F 5 ) 4 ](Et 2 O) in the presence of R 3 TAC (R = Bz, FBz, s-1-phenylethyl (s-PhMeCH)). A product of decomposition of [(Bz 3 TAC)Zn(Et)][ClO 4 ] was analyzed by X-ray diffraction. The structures of [({s-PhMeCH} 3 TAC)Zn(Et)][BF 4 ] an [(FBz 3 TAC)Zn(Et)][BF 4 ] were estimated using nuclear Overhauser enhancement spectroscopy. Protonolysis of diethylzinc with [HNMe 2 Ph][BF 4 ] in the presence of 13-benzyl-1,5,9-triazatricyclo[7.3.1.0 5,13 ]-tridecane (BzTATC) yielded the complex [(BzTATC)Zn(Et)][BF 4 ].

SYNTHESIS AND ESR-CHARACTERIZATION OF RADICAL ANION COMPLEXES OF LANTHANUM. X-RAY CRYSTAL STRUCTURE OF THE MIXED BIPY, BIPY-1 COMPLEX OF LANTHANUM(III ) LAI2(BIPY)(BIPY)(DME) : EVIDENCE FOR AN INTER-LIGAND CHARGE TRANSFER

Abstract The reaction of [LaI2(THF)3]2[C10H8] with excess of 2,2′-bipyridine (bipy) in DME or THF results in the formation of mixed radical anion ligand/neutral ligand complexes [LaI2(bipy(0))(bipy(−1))(L)n (DME)(1) and (THF)2 (2), whereas a reactant reactant ratio of 1:2 generates the mono-bipy complex [LaI2(bipy)(DME)2] (3). ESR and IR spectroscopic data show a fast shuttle electron transfer (SIET) between the neutral and the radical anion of bipy in1 and2. The X-ray structure shows1 to be monoclinic, space group P2/c, Z = 2, with a = 10.0320(12), b = 9.7510(11), c = 16.296(8)A˚, β = 90.43(2)°. The structure was refined toR = 0.0360 for 2562 observed reflections (1 > 2σ(1)). It shows the lanthanum atom eight-coordinated by two iodine, two oxygen and four nitrogen atoms.

Sol-gel entrapped lipophilic and hydrophilic ruthenium-, rhodium-, and iridium-phosphine complexes as recyclable isomerization catalysts

Abstract The phosphinated complexes RuCl 2 (PPh 3 ) 3 , 1 , RhCl(PPh 3 ) 3 , 2 , IrCl(CO)(PPh 3 ) 2 , 3 , their water soluble sulfonated analogs RuCl 2 [Ph 2 P(3-C 6 H 4 SO 3 Na)] 2 · 4H 2 O, 4 , RhCl[Ph 2 P(3-C 6 H 4 SO 3 Na)] 3 · 4H 2 O, 5 , IrCl(CO)[Ph 2 P(3-C 6 H 4 SO 3 Na)] 2 , 6 , as well as the dirhodium compounds trans -[Rh(CO)(PPh 3 )(μ-pz)] 2 , 7 , and trans -[Rh(CO)(PPh 3 )(μ-Cl)] 2 , 9 were entrapped physically in SiO 2 sol-gel matrices. Replacement of the PPh 3 ligands in the two latter complexes by Ph 2 P(CH 2 ) 2 Si(OEt) 3 groups enabled to bind of the dirhodium complexes chemically to the matrix backbone via the silyloxy functions. The activity of the immobilized complexes as allylbenzene isomerization catalysts was studied and compared. Entrapped complex 4 was found to be most efficient catalyst.

First structural characterization of a zinc-bis(dialkylamide) compound:

Abstract The reaction of two molar equivalents of with ZnCl2 in diethyl ether yields the title compound 1, which was characterized by 1H, 13C and 14N NMR, melting point, elemental analysis, mass spectrometry and single crystal X-ray diffraction. The structural characterization permits the first direct comparison of di(aryl)amide and di(triorganoslyl)amide examples with a di(alkyl)amide composition, thereby probing the nature of the ZnN interaction.

Intramolekular stabilisierte gallium- und indiumorganyle: Synthese und röntgenstrukturanalyse repräsentativer bis- und tris[3-(dialkylamino) propyl]gallium- und -indium-derivate

Abstract The intramolecularly stabilized organogallium and organoindium compounds ClGa(CH 2 CH 2 CH 2 NMe 2 ) 2 ( 1 ), RIn(CH 2 CH 2 CH 2 NMe 2 ) 2 (R = Cl, Br, I, CN, SCN, CF 3 CC, MeCC, Me 3 SiCC, C 6 F 5 O, CF 3 CO 2 , CF 3 , i C 3 F 7 ,( 2a–13a ), RIn(CH 2 CH 2 CH 2 NEt 2 ) 2 (R = Cl, I, CN, CF 3 CC, MeCC, Me 3 SiCC, C 6 F 5 O, CF 3 CO 2 ( 2b , 4b , 5b , 7b–11b ) ClGa(C 6 H 4 CH 2 NMe 2 -2) 2 ( 14 ), ClIn(C 6 H 4 CH 2 NMe 2 -2) 2 ( 15 ), and ClIn[CH 2 CH 2 CH 2 N(CH 2 ) 5 ] 2 ( 16 ) a well as the homoleptic compounds GaR 3 (R = CH 2 CH 2 CH 2 NMe 2 ( 17 ), CH 2 CHMeCH 2 NMe 2 ( 18 ), C 6 H 4 CH 2 NMe 2 -2 ( 19 ) and In(CCCF 3 ) 3 (THF) 2 ( 20 ) have been synthesized from gallium trichloride or indium trichloride and the corresponding ω-aminoorganyl lithium compounds, by the reaction of 2a and 2b with the appropriate RLi, or from Cd(CH 2 CH 2 CH 2 NMe 2 ) 2 and RInBr 2 (R = CF 3 , i C 3 F 7 ). The 1 H-, 13 C-NMR and mass spectra of the new compounds as well as the X-ray crystal structure analyses of 1 , 4a , 14 , 17 , 19 and 20 are reported and discussed.

Synthese und charakterisierung von Cp2∗M(DAD)-komplexen (M = Y oder La) : Molekülstruktur von Cp2∗Y[N(C6H4-4-Me) = C(Ph)C(Ph) = N(C6H4-4-Me)]

Zusammenfassung The treatment of ( η 5 -C 5 Me 5 ) 2 La( μ -Cl) 2 K(dme) 2 ( 3 ) with an equimolar amount of Na 2 (DAD) [DAD = (Ph)N=C(Ph)C(Ph)=N(Ph)] in the presence of DAD or with two equivalents of Na(DAD) results in the formation of the ionic complex [Na(DAD)][( η 5 -C 5 Me 5 ) 2 La(DAD)] ( 4 ), which has been characterized by IR and NMR spectroscopy. Complex 4 exhibits dynamic NMR spectra indicating rapid migration of the ( η 5 -C 5 Me 5 ) 2 La unit from one side of the reduced DAD ligand to the other. ( η 5 -C 5 Me 5 ) 2 Y( μ -Cl) 2 Li(OEt 2 ) 2 ( 5 ) reacts with Na(DAD) [DAD= (Me-4-C 6 H 4 )-N=C(Ph)C(Ph)=N(Me-4-C 6 H 4 )] to yield dark-red crystals of the complex ( η 5 -C 5 Me 5 ) 2 Y(DAD) ( 6 ). Complex 6 is monoclinic, of space group C 2/ c (No. 15), with Z = 4, with a = 1345.2(3), b = 1702.9(2) and c = 1811.3(2) pm and with β = 106.73(1)°. The structure was refined to R = 0.040 for 2399 observed reflections ( F 0 > 4 σ ( F 0 )). The DAD ligand in 6 is reduced to the radical anion and forms a planar five-membered Y(N-C-C-N) ring.

Organometallic compounds of the lanthanides. CIII Mixed sandwich complexes of the 4f elements: synthesis and crystal structure of (ν8-cyclooctatetraenyl)(ν5-2,5-di-tert.-butylpyrrolyl) samarium, -thulium, and -lutetium☆

[(ν8-C8H8)Ln(μ-Cl)(THF)]2 (Ln = Sm, Tm, Lu) reacts with Na[pyr∗] (pyr∗ = NC4H2tBu2-2,5) to form [(ν8-C8H8)Ln(ν5-pyr∗)(THF)x] (Ln = Sm 1, x = 1; Ln = Tm 2, Lu 3, x = 0). The novel sandwich compounds have been characterized by C,H,N analysis, mass spectrometry and NMR spectroscopy. Additionally, an X-ray structural analysis of 1 was performed. The crystals of 1 are monoclinic, space group P21/c with a = 11.131(2) A, b = 20.023(3) A, c = 20.118(5) A, β = 91.16(2)°, V = 4482.8(14) A3and Z = 4. The final refinement resulted in R1 = 3.09% (I>2σ(I)).

Die 1,3-diphenylcyclopentadienylkomplexe von Natrium, Indium(I), Thallium(I) und Eisen(II): Röntgenstrukturanalyse von Tl(C5H3Ph2)(THF) und Fe(C5H3Ph2)2

Abstract 1,4-Diphenylcyclopentadiene (1) reacts with TlOC2H5 or NaNH2 to give the corresponding half-sandwich complexes Na(C5H3Ph2) (2) and Tl(C5H3Ph2) (4). 2 reacts with InCl to form In(C5H3Ph2) (3), and 2 as well as 4 react with FeCl2 to form Fe(C5H3Ph2)2 (5). The 1H, 13C NMR and mass spectra of the new compounds, as well as the X-ray crystal structure analyses of 4 and 5, are reported and discussed.