Joachim Sieler

Aktivierung von Kohlendioxid an Übergangsmetallzentren: Selektive Cooligomerisation mit Hexin(−3) durch das Katalysatorsystem Acetonitril/Trialkylphosphan/Nickel(0) und Struktur eines Nickel(0)-Komplexes mit side-on gebundenem Acetonitril

Abstract CO 2 reacts with hexyne(−3) in a catalytic reaction under formation of tetraethyl-2-pyrone, when the catalytic system alkyl 3 P/acetonitrile/nickel(0) is used. The selectivity of this homogeneous-catalytic reaction can be increased to values of 96% when phosphanes of high basicity and small cone angle are used. The investigation of the system Ni(COD) 2 /tricyclohexylphosphane/acetonitrile shows that acetonitrile can act as ligand in complexes of nickel(0). A yellow-brown tetranuclear complex was isolated, the structure of which was determined by X-ray diffraction studies. Acetonitrile acts as bridging ligand and is coordinated alkyne-analogously to one nickel center with its triple bond. The free electron pair of the nitrogen atom is bonded to a second nickel atom. Some reaction steps of this selective catalytic reaction are discussed. This reaction represents the first example of a selective homogeneous-catalytic co-oligomerization between CO 2 and an unsaturated substrate which takes place under CC linkage with a 3 d -transition metal.

COMPLEXES OF COPPER(II) ACETATE WITH NICOTINAMIDE : PREPARATION, CHARACTERIZATION AND FUNGICIDAL ACTIVITY; CRYSTAL STRUCTURES OF CU2(O2CCH3)4(NIA) AND CU2(O2CCH3)4(NIA)2

Abstract Three new copper (II) acetate complexes with nicotinamide (nia) were synthesized analyzed and characterized by standard chemical and physical methods and tested for fungicidal activity The crystal and molecular structures of the compounds [Cu2 (O2CCH3)4 (nia)] (1B) and [Cu2 (O2CCH3)4 (nia)2] (2) were determined by X-ray diffraction Both consist of binuclear units of bridging tetracarboxylate type however they differ in the bonding mode of nicotinamide molecules They are bonded at the apical positions of the dimers and connect them in an infinite chain in 1B On the other hand the dimers remain isolated in the structure of the compound 2 It seems that compound 1B is the first example where a nicotinamide molecule acts as a bidentate bridging ligand The results of EPR spectra agree with the dimeric nature of the complexes Dissolved in water or DMSO the compounds completely stop mycelial growth at a concentration of 50×10−3 mol l−1 Less concentrated solutions (up to 10×10−3 mol l−1) show weaker fungicidal activity.

Komplexkatalyse: LVII. Vereinfachte Synthese des Nd(π-C3H5)3·C4H8O2 nach der Grignard-Methode und Darstellung der neuen Allylneodym(III)-Komplexe [Nd(π-C5Me5)(π-C3H5)2·C4H8O2] und [Nd(π-C3H5)Cl(THF)5]B(C6H5)4·THF als Präkatalysatoren für die stereospezifische Butadienpolymerisation

Abstract For the tris(allyl)neodymium(III) compound [Nd(π-C 3 H 5 ) 3 ·Dioxan] ( 1a ) an essentially more simple synthesis by the Grignard method is reported. Therewith also further allylneodymium compounds as potential complex catalysts for the stereospecific butadiene polymerization become accessible more easily. As a new bis(allyl)- and a new mono(allyl)neodymium(III) compound the neutral complex [Nd(π-C 5 Me 5 )(π-C 3 H 5 ) 2 ·Dioxan] ( 2a ) and the cationic complex [Nd(π-C 3 H 5 )Cl(THF) 5 ]B(C 6 H 5 ) 4 ·THF ( 3a ) are described, respectively; both were characterized by X-ray crystal structure analysis. Whereas from 2a highly active catalyst systems for butadiene polymerization can be obtained by combination with proper Lewis acids like methylaluminoxane (MAO), 3a proved to be unsuitable for catalyst generation. The conclusions concerning the catalytic structure–reactivity relationship are discussed briefly.

Aktivierung von CO2 an Übergangsmetallzentren : Zum Ablauf der homogen-katalytischen Bildung von 2-Pyron aus Kohlendioxid und Hex-3-in an Nickel(0)-Fragmenten

IR-investigations of the catalytic formation of tetraethyl-2-pyrone from hex-3-yne and CO2 at (TMED)Ni0- or (COD)Ni0 centres show that in the first step of this reaction the nickel(0) complex reacts under oxidative coupling with both CO2 and alkyne to afford the five-membered metallacycle A. The alternative route, the oxidative coupling of two alkynes at nickel(0), can be excluded. Complex A reacts in a second step with a further molecule alkyne to yield compound B, which undergoes a reductive elimination forming the 2-pyrone C. The insertion of CO2 into A and the “reductive disproportionation of CO2 at (TMED)Ni0 are deactivation reactions of the catalytic cycle forming the trimeric carbonato complex D and the Ni0 compound E bearing diethylmaleic anhydride. The structure of complex A was determined by X-ray analysis.

XLVII. Darstellung und Charakterisierung einiger anionischer Allylneodym(III)-Komplexe als Katalysatoren für die stereospezifische Butadienpolymerisation: Li[Nd(η3-C3H5)4] · 1,5Dioxan, Li[Nd(π-C5H5)(η3-C3H5) 3] · 2Dioxan und Li[Nd(η5-C5Me5)(η3-C3H53] · 3Dimethylglykolether☆

Abstract For the already known tetrakis(allyl) complex Li[Nd( η 3 -C 3 H 5 ) 4 ] · 1.5dioxane 2 an essentially improved method of preparation from anhydrous NdCl 3 and LiC 3 H 5 · dioxane 1 in dimethylglycolether (DMGE) was found. By partial protolysis with cyclopentadiene and pentamethyl cyclopentadiene from 2 the complexes Li[Nd( π -C 5 H 5 )( η 3 -C 3 H 5 ) 3 ] · 2dioxane 3 and Li[Nd( η 5 -C 5 Me 5 )( η 3 -C 3 H 5 ) 3 ] · 4 were obtained. 3 can also be synthesized from η 5 -C 5 H 5 NdCl 2 · 3THF and 1 in tetrahydrofurane (THF), whereas η 5 -C 5 Me 5 NdCl 2 · 3THF reacts to 2 under these conditions. The new compounds 3 and 4 were characterized by elemental analyses, IR and 1 H-NMR spectroscopy and 4 also by X-ray crystal structure analysis. In comparison with 2 , complexes 3 and 4 show different catalytic properties with respect to the stereospecific polymerization of butadiene. The catalytic reactivity depends obviously on, how far a dissociation of the complexes with formation of LiC 3 H 5 takes place under the reaction conditions. By addition of proper acceptor or donor molecules, like BEt 3 , Ph 2 SnCl 2 , Et 2 AlCl and THF or dipiperidylethane, the reactivity can be controlled accordingly.

One- and two-dimensional coordination polymers of 3,3′,5,5′-tetramethyl-4,4′-bipyrazolyl, a new perspective crystal engineering module

Abstract The coordination polymers based upon new bidentate ligand 3,3′,5,5′-tetramethyl-4,4′-bipyrazolyl (4,4′-bpz) have been prepared and characterized by means of X-ray analysis. In all compounds Ag(4,4′-bpz)NO3·CH3OH (1), Cd(4,4′-bpz)(C3H7OH)(NO3)2 (2), Cd(4,4′-bpz)2(NO3)2 (3), Cu(4,4′-bpz)2(H2O)(BF4)2·0.5C6H5Br (4), and Cu(4,4′-bpz)2(H2O)(HCOO)2·2.5HCONH2 (5) the molecules of bipyrazolyl act as bridging neutral groups and connect two metal atoms at the distances of 9.58–10.25 A. Complexes 1 and 2 exhibit one-dimensional polymeric structure, while compounds 3–5 exist as two-dimensional polymers, containing layers of four-connected coordination nets. In structures 4 and 5 the layers are interlinked by means of hydrogen bonding involving counter anions, which lead to formation of three-dimensional open networks capable of incorporation of hydrophilic (5) or hydrophobic (4) guest molecules. Geometry of coordination polymer in these cases is significantly dominated by the angular structure of 4,4′-bpz ligand, while structure of the coordination net in 3 is very similar for analogues containing linear 4,4′-bipyridine bridges.

Aktivierung von kohlendioxid an übergangsmetallzentren: Metallaringschluss mit dicyclopentadien am elektronenreichen nickel(0)-komplexrumpf als topo- und stereoselektive reaktion

Abstract CO 2 reacts with dicyclopentadiene (dcp) at the complex moiety (bipy)Ni 0 to form a five-membered nickelacycle as the result of a topo- and stereo-selective coupling reaction (reaction of the norbornene part, exo position). X-Ray analysis of the compound shows a planar configuration around the central atom with a NiC σ-bond length of 1.929 A and a monodentate carboxylato group (NiO distance: 1.845 A). The structure of the nickelacycle is compared with those of similar compounds formed by oxidative coupling of CH 3 CHO or PhCHNPh with CO 2 at electron-rich nickel(0) moieties. Relations between structure and reactivity are investigated.

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.

Metallacyclen aus CO2 und dimethylbutadien am komplexrumpf (L)Ni0: Struktur und reaktivität als funktion der neutralliganden L

Abstract (L) Ni(CH 2 C(CH 3 )C(CH 3 )CH 2 COO) can be synthesized either by the oxidative coupling of CO 2 and diene at the complex moiety (L)Ni, or by the exchange of neutral ligands in metallacycle I (L = N, N ′-tetramethylene diamine (TMED)). X-ray analyses of the compounds with L = Ph 3 P and Cy 3 P show that the C 5 O chains are bonded similarly, with an η 3 -allyl- and a monodentate carboxylate group at the ends of the chains. Thermal investigations and reactions with π-acceptor ligands were carried out as a function of the neutral ligands L. The reaction of I with π-acidic 1,4-diazadienes leads to 3,4-dimethyl-penta(2,4)dienecarboxylic acid and simulates a partial step of a possible catalytic cycle: oxidative coupling - reductive elimination under H-shift.

Molybdenum tetracarbonyl complexes with functionalised aminophosphine ligands: cis-[Mo(CO)4(PPh2NHR)2] (R=Ph, But) — molecular structures of PMes2NHPh (Mes=2,4,6-Me3C6H2), PPh2NHBut and cis-[Mo(CO)4(PPh2NHBut)2]

Abstract The aminophosphines PPh2NHR [R=Ph (1a), But (1b)] react readily with cis-[Mo(CO)4(NCEt)2] to give cis-[Mo(CO)4(PPh2NHR)2] [R=Ph (2), But (3)] in high yield, while the bulky aminophosphine PMes2NHPh (1c) (Mes=2,4,6-Me3C6H2), obtained from LiNHPh and PMes2Cl, does not react even at elevated temperature. Compounds 1c, 2 and 3 were characterised spectroscopically (IR; 1H, 31P, 13C NMR), 2 and 3 also by MS, and crystal structure determinations were carried out on 1b, 1c and 3; for 3, this showed the presence of the cis isomer. Complexes 2 and 3 do not react with [Cp2ZrCl2]/NEt3 or with [Cp2ZrMe2].