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Cerebral oximetry using near-infrared spectroscopy (NIRS) allows for continuous monitoring of cerebral perfusion and immediate treatment of hemodynamic perturbations. In configurations used in current clinical practice, NIRS optodes are placed on the patient`s forehead and cerebral oxygen saturation (ScO2 ) is determined in bilateral frontal cortical samples. However, focal cerebral ischemic lesions outside of the NIRS field of view may remain undetected. The objective of this observational case-series study was to investigate ScO2 measurements in patients with acute iatrogenic stroke not located in the frontal cortical region. Adult patients undergoing cardiac surgery with cardiopulmonary bypass or interventional cardiology procedures and suffering stroke in the early postoperative period were identified from the Bernese Stroke Registry and analyzed for their intraoperative ScO2 values and brain imaging data. Main outcome measures were the ScO2 values, computed tomography and magnetic resonance imaging findings. In six patients, the infarct areas were localized in the vascular territories of the posterior and/or dorsal middle cerebral arteries. One patient had watershed stroke and another one excellent collaterals resulting in normal cerebral blood volume and only subtle decrease of cerebral blood flow in initially critically perfused watershed brain areas. Intraoperative ScO2 values were entirely unremarkable or nonindicative for brain damage. Our results indicate that uneventful intraoperative NIRS monitoring does not exclude severe cerebral ischemia due to the limited field of view of commercially available NIRS devices. False negative NIRS may occur as a consequence of stroke localized outside the frontal cortex.

BACKGROUND AND PURPOSE Randomized controlled trials have shown that bridging endovascular therapy (EVT) after intravenous thrombolysis (IVT) therapy improves outcome in patients with stroke with large-artery anterior circulation stroke compared with IVT alone. It remains unknown whether IVT adds any benefit to EVT in these patients. The aim of this study was to assess recanalization rates and thrombus dislocation before initiation of EVT in patients receiving bridging therapy. METHODS All patients in the Bernese stroke registry (2008-2015) in whom bridging therapy was considered were included in this analysis. Relevant recanalization before EVT, thrombus dislocation and increase in thrombus load between initial and control imaging were assessed retrospectively. RESULTS A total of 319 patients were included. Relevant recanalization before EVT occurred in 8.8% and thrombus dislocation in 7.2% of patients before EVT. Recanalization rates were significantly higher in distal compared with large and more proximal vessel occlusions of the anterior circulation (occlusion of internal carotid artery, 5.4%; middle cerebral artery segment M1, 8.1%; middle cerebral artery segment M2, 17.6%) and in drip-and-ship patients compared with mother-ship patients. In multivariable regression analysis the occlusion site was the only independent predictor of relevant recanalization before EVT (P = 0.046). CONCLUSIONS Relevant recanalization after IVT and prior to EVT in patients receiving bridging therapy was highly dependent on the occlusion site. These findings suggest that future randomized controlled trials should consider occlusion site and treatment paradigm to specify patients who benefit most from bridging therapy in comparison to EVT or IVT alone.

BACKGROUND AND PURPOSE Patients with prior stroke within 3 months have been mostly excluded from randomized thrombolysis trials mainly because of the fear of an increased rate of symptomatic intracerebral hemorrhage (sICH). The aim of this study was to compare baseline characteristics and clinical outcome of thrombolyzed patients who had a previous stroke within the last 3 months with those not fulfilling this criterion (comparison group). METHODS In all, 1217 patients were included in our analysis (42.2% women, mean age 68.8 ± 14.4 years). RESULTS Patients with previous stroke within the last 3 months (17/1.4%) had more often a basilar artery occlusion (41.2% vs. 10.8%) and less frequently a modified Rankin scale (mRS) score 0-1 prior to index stroke (88.2% vs. 97.3%) and a higher mean time lapse from symptom onset to thrombolysis (321 min vs. 262 min) than those in the comparison group. Stroke severity was not different between the two groups. Rates of sICH were 11.8% vs. 6%. None of the sICHs and only one asymptomatic intracerebral hemorrhage occurred in the region of the former infarct. At 3 months, favorable outcome (mRS ≤ 2) in patients with previous stroke within 3 months was 29.4% (vs. 48.9%) and mortality 41.2% (vs. 22.7%). CONCLUSIONS In patients with prior stroke within the last 3 months, none of the sICHs and only one asymptomatic intracerebral hemorrhage occurred in the region of the former infarct. The high mortality was influenced by four patients, who died until discharge due to acute major index stroke. It is reasonable to include these patients in randomized clinical trials and registries to assess further their thrombolysis benefit-risk ratio.

PURPOSE: To evaluate the diagnostic accuracy of in situ postmortem multislice computed tomography (MSCT) and magnetic resonance imaging (MRI) in the detection of primary traumatic extra-axial hemorrhage. MATERIALS AND METHODS: Thirty forensic neurotrauma cases and 10 nontraumatic controls who underwent both in situ postmortem cranial MSCT and MR imaging before autopsy were retrospectively reviewed. Both imaging modalities were analyzed in view of their accuracy, sensitivity, and specificity concerning the detection of extra-axial hemorrhage. Statistical significance was calculated using the McNemar test. kappa values for interobserver agreement were calculated for extra-axial hemorrhage types and to quantify the agreement between both modalities as well as MRI, CT, and forensics, respectively. RESULTS: Analysis of the detection of hemorrhagic localizations showed an accuracy, sensitivity, and specificity of 89%, 82%, and 92% using CT, and 90%, 83%, and 94% using MRI, respectively. MRI was more sensitive than CT in the detection of subarachnoid hemorrhagic localizations (P = 0.001), whereas no significant difference resulted from the detection of epidural and subdural hemorrhagic findings (P = 0.248 and P = 0.104, respectively). Interobserver agreement for all extra-axial hemorrhage types was substantial (CT kappa = 0.76; MRI kappa = 0.77). The agreement of both modalitites was almost perfect (readers 1 and 2 kappa = 0.88). CONCLUSION: CT and MRI are of comparable potential as forensic diagnostic tools for traumatic extra-axial hemorrhage. Not only of forensic, but also of clinical interest is the observation that most thin blood layers escape the radiological evaluation.

Cognitive functions in the child's brain develop in the context of complex adaptive processes, determined by genetic and environmental factors. Little is known about the cerebral representation of cognitive functions during development. In particular, knowledge about the development of right hemispheric (RH) functions is scarce. Considering the dynamics of brain development, localization and lateralization of cognitive functions must be expected to change with age. Twenty healthy subjects (8.6–20.5 years) were examined with fMRI and neuropsychological tests. All participants completed two fMRI tasks known to activate left hemispheric (LH) regions (language tasks) and two tasks known to involve predominantly RH areas (visual search tasks). A laterality index (LI) was computed to determine the asymmetry of activation. Group analysis revealed unilateral activation of the LH language circuitry during language tasks while visual search tasks induced a more widespread RH activation pattern in frontal, superior temporal, and occipital areas. Laterality of language increased between the ages of 8–20 in frontal (r = 0.392, P = 0.049) and temporal (r = 0.387, P = 0.051) areas. The asymmetry of visual search functions increased in frontal (r = −0.525, P = 0.009) and parietal (r = −0.439, P = 0.027) regions. A positive correlation was found between Verbal‐IQ and the LI during a language task (r = 0.585, P = 0.028), while visuospatial skills correlated with LIs of visual search (r = −0.621, P = 0.018). To summarize, cognitive development is accompanied by changes in the functional representation of neuronal circuitries, with a strengthening of lateralization not only for LH but also for RH functions. Our data show that age and performance, independently, account for the increases of laterality with age. Hum Brain Mapp, 2009. © 2008 Wiley‐Liss, Inc.

PURPOSE: The aim of this retrospective study was to determine optimal duplex sonographic criteria for use in our institution for diagnosing severe carotid stenoses and to correlate those findings with angiographic measurements obtained by the European Carotid Surgery Trial (ECST), North American Symptomatic Carotid Endarterectomy Trial (NASCET), and Common Carotid (CC) methods of grading carotid stenoses. METHODS: We analyzed the angiographic data using the ECST, NASCET, and CC methods and compared the results with the duplex sonographic findings. We then calculated the sensitivity, specificity, positive and negative predictive values, and accuracy of the duplex sonographic method. Taking these parameters into account, the optimal intrastenotic peak systolic velocity (PSV) and end diastolic velocity (EDV) were derived for diagnosing severe stenoses according to the 3 angiographic methods. RESULTS: Optimal PSV and EDV values for diagnosing a 70% or greater stenosis in our laboratory were as follows: with the NASCET method of angiographic grading of stenoses, PSV 220 cm/second or greater and EDV 80 cm/second or greater, and with the ECST and CC methods, PSV 190 cm/second or greater, and EDV 65 cm/second or greater. The optimal PSV and EDV for diagnosing a stenosis of 80% or greater with the ECST grading method were 215 cm/second or greater and 90 cm/second or greater, respectively. CONCLUSIONS: Duplex sonography is a sensitive and accurate tool for evaluating severe carotid stenoses. Optimal PSVs and EDVs vary according to the angiographic method used to grade the stenosis. They are similar for stenoses 70% or greater with the NASCET method and for stenoses 80% or greater with the ECST method.

To increase the intraoperative safety factor and to acquire anatomic assistance during revision endoscopic sinus surgery (RESS), we used an optical computer-aided surgery (CAS) system that we developed collaboratively in Bern, Switzerland. During 1 year, 25 RESSs were performed with CAS: recurrent polyposis (n = 20), recurrent frontal recess stenosis (n = 3), and recurrent frontal recess stenosis with mucocele (n = 2). These patients were compared with a control group of 10 patients undergoing RESS without CAS. The same surgeon (M.C.) performed all operations, and there were no minor or major complications in either group. The clinical inaccuracy of our system is between 0.5 and 2 mm with paired-point and surface matching. The navigation system is an important aid to surgeons in identifying anatomic landmarks that are typically difficult to visualize in this type of surgery, thus reducing the stress placed on the surgeon.

The purpose of this study was to determine whether the age at onset of temporal lobe epilepsy influences hippocampal volume. Fifteen right-handed patients with medically intractable partial complex epilepsy of temporal origin were studied in quantified magnetic resonance imaging (MRI) and neuropsychological tests. In seven patients (mean age: 24 years) epilepsy began before the age of three (? YOUNG), in eight patients (mean age: 29 y) after the age of three (= OLDER). Education, social integration, duration of epilepsy and seizure frequency were equal in YOUNG and OLDER. The mean hippocampal volume, after normalization to total intracranial volume was for the right and for the left side smaller in YOUNG than in OLDER (p ≤ 0.02). The side-to-side asymmetry of absolute hippocampal volume was in patients with left-side focus more pronounced in YOUNG than in OLDER (p < 0.03). The number of patients with right-side focus was too small for statistical analysis. Results of neuropsychological testing showed no significant differences between YOUNG and OLDER. Onset-age of epilepsy before three years is associated with a higher risk of bilateral hippocampal hypotrophy and unilateral hippocampal asymmetry. Performance in neuropsychological testing seems not to be significantly influenced by hippocampal volume or age at onset.

A method for monitoring eye movements in humans during functional MRI is presented. It is based on the acquisition of electro-oculographic (EOG) signals near one eye. EOG potentials were amplified and converted into an optical signal just outside the head coil. An optical fiber was used for signal transmission from inside the magnet bore to the control room. The EOG sensor was tested during EPI sequences at 1.5 Tesla without contamination of the MR signal. Some flow related artifacts on the EOG were observed inside the magnet, but no additional interactions from the MR sequence. An analysis of the latency, direction, and amplitude of the saccadic eye movements was possible.

Reactions of some primary and secondary Δ4‐, Δ5‐ and Δ6‐alkenols with thallium triacetate (TTA) in benzene, acetic acid and chloroform as solvent have been investigated. When terminally unsubstituted Δ4‐alkenols, such as 4‐penten‐1‐ol (5a) and 5‐hexen‐2‐ol (5b), are treated with TTA in benzene, β‐acetoxylated tetrahydrofurans 8a and 8b are obtained. However, when the reaction is carried in acetic acid the products are both regioisomers, i.e. five‐ and six‐membered cyclic ethers (8a, 8b, 7a and 7b). 4‐Methyl‐4‐penten‐1‐ol (5c) is converted in benzene into a mixture of products (8c and 7c) in which the tetrahydropyran derivative 7c is predominant, and in acetic acid it is the sole cyclization product. Terminally dialkylated alkenols, such as 5‐methyl‐4‐hexen‐1‐ol (1b) and 6‐methyl‐5‐hepten‐2‐ol (1c), are converted into β‐acetoxylated (4b and 4c) and unsaturated cyclic ethers (9a and 9b), in both cases of the tetrahydrofuran type. 5‐Hexen‐1‐ol (10) and 6‐hepten‐1‐ol (11) cyclize to the corresponding six‐ (13) and seven‐membered cyclic ether (14), respectively. Organothallium intermediates have been isolated and identified in the cases of alcohols 5a, 5c and 10, proving that the TTA addition to the double bond has originally obeyed the Markovnikov rule.

The regioselectivity in cyclofunctionalization of some acyclic olefinic alcohols with benzeneselenenyl halides (PhSeCl and PhSeBr) at different temperatures (−78°C, O°C and room temperature) is investigated. It has been found that Δ4- and Δ5- alkenols are converted into five- and/or six-membered cyclic phenyl selenoethers, the yield of which decreases with increasing reaction temperature. PhSeCl has been found to be more efficient than PhSeBr in the cyclization reactions.

Twofold lithiation of dibenzofuran (6) and dibenzothiophene (12) with n-butyllithium/N,N,N′,N′-tetramethylethylenediamine (TMEDA) in n-hexane or n-pentane followed by the reaction with chlorodiphenylphosphine yielded the title compounds 4 and 5, respectively, The monophosphines 4-(diphenylphosphino)dibenzofuran (11) and 4-(diphenylphosphino)dibenzothiophene (15) were obtained analogously via the monolithium compounds 9 and 14 of the heteroarenes. In the case of dibenzofuran (6), it was shown that mono- and dilithiation is controlled by temperature.

Various Coordinations in (η2-Alkene)(η5-cyclopentadienyl)organylnickel(II) Complexes A series of (η2-alkene)(η5-cyclopentadienyl)organylnickel(II) complexes with substituted cyclopentadienyl ligands is synthesized in order to compare the structures, the thermal stabilities, and chemical reactivities. In (allyl)(η5-Cp')Ni compounds the allyl moiety is η3-coordinated when Cp'=C5H5, C5Me5 (1), C5Ph5 (2), indenyl (3), [Hydridotri(pyrazolyl)borato] (4) (as an equivalent of the cyclopentadienyl ligand), and [C5H4((CH2)3CHCH2)] (22). It is found that the [(η2-alkene)alkyl(η5-Cp')nickel] compounds [Cp'=C5Me5; alkeneC2H4, alkyl=Me (10), Et (9) or alkene=(1 – 2-η2)-1,3-butadiene, alkyl=Me (11); Cp'=C5Ph5; alkene=C2H4, alkyl=Me (12)] are thermally more stable and less reactive than their η5;- C5H5 analogues; the largest increase in thermal stability is observed when the η5-Cp' and the η2-alkene functions are connected by substitution of the cyclopentadienyl ligand with an alkenyl group of suitable chain length. In the case of compounds of the general type [(η5-C5R4((CH2)nCHCH2))-(ligand)Ni(II)] with Ph3P as the ligand these complexes are cationic [RH, n=3 (14+) or RMe, n=2 (17+)]. On the other hand, the compounds with anionic ligands are neutral complexes (RH, n=3, ligand=methyl (19), ethyl (20), isopropyl (21) or RMe, n=3 and ligand=iodide (24), bromide (25), methyl (26), ethyl (27)]. In 14+, 17+, 19 – 21 and 24 – 27 the CC bond of the alkenyl group is η2-coordinated to the nickel atom. X-ray structures have been determined for 4 and 25.

Das schwerlosliche „Anthracenmagnesium” 1a ⋅ n THF reagiert in THF mit Dialkylaluminiumhydriden zu den Magnesium-μ-(9,10-dihydro-9,10-anthrylen)-dialkylhydridoaluminaten 2a – c, mit Aluminiumtrihydrid zum entsprechenden -trihydridoaluminat 2d und mit Ethoxydiethyl-aluminium zum -ethoxydiethylaluminat 6. Die Konstitutionen der Komplexe 2a – c und 6 in THF wurden mittels NMR-Spektroskopie bestimmt. Nach dem Ergebnis der Rontgenstrukturanalyse von 2b (Alkyl = Et) besetzen Al und Mg im 9,10-Dihydro-9,10-anthrylen-System axiale Positionen, und es besteht bindende Wechselwirkung zwischen dem Mg⊕-Kation und dem Hydridwasserstoff des Aluminat-Anions. Analoge Komplexe 3 mit Trialkylaluminium lassen sich nur erhalten, wenn 1a ⋅ n THF mit mindestens (n + 1) AlR3 (R = Me, Et) in nicht-Lewis-basischen Losungsmitteln umgesetzt wird. Ether spalten die Komplexe 3 wieder in Trialkylaluminium-etherat, z. B. 4 oder 5, und 1a. In Diethylether ist letzteres nicht stabil und zerfallt in Magnesium und Anthracen. Magnesium-μ-(9,10-dihydro-9,10-anthrylene)-aluminates; Complexes of “Anthracenemagnesium” The relatively insoluble “anthracenemagnesium” 1a ⋅ n THF reacts in THF with dialkylaluminium hydrides to give magnesium-μ-(9,10-dihydro-9,10-anthrylene)-dialkylhydridoaluminates 2a – c, with aluminium trihydride the corresponding -trihydridoaluminate 2d and with ethoxydiethylaluminium the -ethoxydiethylaluminate 6. The structures of the compounds 2a – c and 6 dissolved in THF were determined by NMR spectroscopy. An X-ray crystallographic investigation of 2b (alkyl = ethyl) shows that Al and Mg occupy axial positions in a 9,10-dihydro-9,10-anthrylene system. The Mg⊕ cation interacts with the hydride of the aluminate anion. Analogous complexes 3 with trialkylaluminium can only be obtained if 1a ⋅ n THF is reacted with (n + 1) AIR3 (R = methyl, ethyl) in non-Lewis base solvents. Ether cause the cleavage of 3 into trialkylaluminium etherate, e. g. 4 or 5, and 1a, which is unstable in diethyl ether and decomposes into magnesium and anthracene.

Es wird die Addition von in 1- und/oder 3-Stellung substituierten Allylmagnesiumverbindungen (ClMgCHR3CHCRlR2; 1 -4)an Olefine (CH2CHR4; 8,13,20,27) im Temperaturbereich 20- 130°C in polaren und unpolaren Reaktionsmedien untersucht. Die 3-Alkyl-2-propenyl-magnesiumhalogenide addieren sich dabei entweder mit C-1 oder C-3 des Alkenylrestes an die CC-Bindung, wobei Verbindungen des Typs CIMgCH2CHR4CHR3CHCR1R2 (9,14,21) bzw. CIMgCH2CHR4CR1R2CHCHR3 (11,16,23,32 und 33) entstehen. Die Selektivitat zugunsten der Anlagerung mit C-3 nimmt mit zunehmender Temperatur und sterischem Anspruch des Alkens ab. Neben der normalen (Metall-an-C-1)-Addition wird auch (Metall-an-C-2)-Addition beobachtet, die bei Additionen an Styrol (27) uberwiegt. - Auser den unterschiedlichen Additionsrichtungen des Metalls und den alternativen Angriffen des Alkenylrestes werden noch Gerustumlagerungen beobachtet, die uber die intramolekulare Bildung von Cyclobutylmethylmetall verlaufen. Nach Addition von 1 oder 2 an I-Octen (20) und Hydrolyse lassen sich die Methylcyclobutanderivate 69 bzw. 59 und 62 nachweisen. Der Unterschied an freier Enthalpie zwischen primaren und sekundaren Alkylmagnesiumchloriden wird zu —3 bis —4 kcal.mo1−1 abgeschatzt. Der Gewinn an freier Enthalpie beim Ubergang sekundarer und tertiarer 4-Alkenylmagnesiumverbindungen in primares Cyclobutylmethylmagnesium last sich zur Synthese von Cyclobutylderivaten des Magnesiums nutzen. - 2-Butenylmagnesiumchlorid (1) und Bicyclo[2.2.l]hept-2-en (73) bilden bei 40°C das 1 : 1 -Addukt 76, das beim Erhitzen zum Tricyclus 78 cyclisiert. Weiter finden Isomerisierungen als auch Offnung eines gesattigten Fu,nfringes zum 1-[3-(1-Propenyl)cyclo-pentyl]allylmagnesiumchlorid (88) statt. - Erstmals konnte eine intramolekulare Cyclisierung einer 4-Alkenylmagnesiumverbindung 36 zu einer Cyclopentylmagnesiumverbindung 84 nachgewiesen werden. - Aus Octadienylenmagnesium 98 und Athylen (8) werden uberwiegend Clo-Cyclopentanderivate (z. B. 100) neben wenig offenkettigem Clz-Alkadien erhalten. Aus 2,7-Dimethyl-2,6-octadienylenmagnesium (92) und 8 entstehen dagegen mehr 1 :2-Addukte (z. B. 95). Addition of Organomagnesium Halides to CC Bonds, VII. - Reactions of 1- and 3-Sub-stituted Allylmagnesium Halides with Olefins The addition of allylmagnesium compounds substituted in position 1 and/or 3 (CIMgCHR3CH CR1R2; 1-4) to olefins (CH2CHR4; 8,13,20,27) has been investigated. The reactions were carried out in polar and non-polar media and within a temperature range of 20–130°C. The 3-alkyl-2-propenylmagnesium halides add of either C-1 or C-3 of the alkenyl group to the C C-bond, giving CIMgCH2CHR4CHR3CH CR1R2 (9,14,21) or CIMgCH2CHR4CRl-R2CHCHR3 (11,16, 23, 32 and 33), respectively. The selectivity in favour of addition with C-3 decreases with increasing temperature and bulk of the alkene. Besides normal metal-to-C-1 addition metal-to-C-2 addition is also observed and predominates in the case of additions to styrene (27). - Apart from the various directions of addition of the metal and the alternative attack of the alkenyl group, skeletal rearrangements are also observed which proceed via intermediate formation of cyclobutylmethylmetal. Addition of 1 or 2 to 1-octene (20) followed by hydrolysis leads to the methylcyclobutane derivatives 69 or 59 and 62, respectively. The difference in free enthalpy between primary and secondary alkylmagnesium chloride is estimated to be — 3 to — 4 kcal 'mol−1. The gain in free enthalpy on conversion of secondary or tertiary 4-alkenyl- into primary cyclobutylmethylmagnesium can be utilized for the synthesis of cyclobutyl derivatives of magnesium. - At 40°C 2-butenylmagnesium chloride (1) and bicyclo[2.2.1]hept-2-en (73) form the 1:l-adduct 76, which on heating is cyclized to the tricycle78. Isomerizations occur as well as an opening reaction of the saturated five membered ring to give 1-[3-(l-propenyl)cyclopentyl]allylmagnesium chloride (88). - The first intra- molecular cycloaddition of a 4-alkenylmagnesium 36 to give a cyclopentylmagnesium compound 84 has been demonstrated. Starting from octadienylenemagnesium 98 and ethylene (8) mainly Clo-cyclopentane derivatives (e. g. 100) are formed together with small amounts of open chain Clz-alkadienes. On reaction of 2,7-dimethyl-2,6-octadienylenemagnesium (92) with 8 1 :2 adducts predominate (e. g. 95).

Die Umsetzung von CpZrCl3 (6) mit Allylmagnesiumchlorid liefert Tris(allyl)(η5-cyclopentadienyl)zirconium (7a). Durch eine Komproportionierung mit 6 wird daraus CpZr(allyl)Cl2 (9a) zuganglich, dessen Reaktion mit „Butadien-Magnesium” das (η3-Allyl)(η4-butadien)(η5-cyclopentadienyl)zirconium (12a) in guter Gesamtausbeute ergibt. 12a zeigt dynamische NMR-Spektren. Es wird daraus eine Aktivierungsbarriere der Automerisierung des Allylliganden von ΔG = 19 kcal/mol abgeleitet. Die Photolyse von 12a bei tiefer Temperatur liefert 13a. Nach den NMR-Spektren, insbesondere den 1H-NMR-NOE-Differenzspektren, unterscheiden sich die Isomeren 12a und 13a durch die relative Anordnung der drei π-Liganden zueinander. Die Struktur beider Verbindungen leitet sich von einer quadratisch-pyramidalen Geometrie ab. In 12a offnen sich beide offenkettigen 4π-Liganden zur apikalen Cp-Gruppierung, in 13a offnen sie sich zur Basis des pyramidalen Gerustes. 13a lagert sich in einer thermisch induzierten Reaktion zu 12a um (ΔG = 22 kcal/mol). Zwei chirale Metallkomplex-Systeme analoger Struktur, (η4-Butadien)(η5 -cyclopentadienyl)(η3-1-methylallyl)zirconium (12 b/13 b) und (η3-Allyl)-(η5-cyclopentadienyl)(η4-isopren) zirconium (12c/13c), wurden durch analoge Reaktionsfolgen hergestellt. Die Aktivierungsbarrieren der degenerierten Allylumlagerung wie der Isomerisierung sind in der gleichen Grosenordnung wie beim Stammsystem 12a/13a. Formation of Chiral Mono(η5-cyclopentadienyl)zirconium(II) Complexes Treatment of CpZrCl3 (6) with allylmagnesium chloride yields tris(allyl)(η5-cyclopentadienyl)-zirconium (7a). Its comproportionation reaction with 6 makes CpZr(allyl)Cl2 (9a) available. The reaction of 9a with “butadiene-magnesium” proceeds to (η3-allyl)(η4-butadiene)(η5-cyclopentadienyl) zirconium (12a) in a high overall yield. 12a exhibits dynamic NMR spectra. From their analysis an activation barrier of ΔG = 19 kcal/mol is derived for the automerization reaction of the allyl ligand. Photolysis of 12a at low temperature yields 13a. According to the NMR spectra, especially the 1H NMR NOE difference spectra, the isomers 12a and 13a are distinguished by the relative arrangement of the three π-ligands. The structure of both compounds is derived from a square-pyramidal geometry. In 12a both open-chain 4π-ligands open themselves in a direction towards the apical Cp-moiety, in 13a their open sides point to the basis of the pyramidal skeleton. 13a rearranges to 12a in a thermally induced reaction (ΔG = 22 kcal/mol). Two chiral transition metal complex systems of analogous structures, (η4-butadiene)(η5-cyclopentadienyl)(η3-1 -methylallyl)zirconium (12b/13b) and (η3-allyl(η5-cyclopentadienyl)(η4isoprene)-zirconium (12c/13c), have been obtained by similar reaction sequences. The activation barriers of the degenerate allyl rearrangement as well as the isomerization reaction are of the same order of magnitude as found for their parent system 12a/13a.

Es wurde eine Reihe von Organyleisen-Komplexen des Types Cp(L)2FeR (Cp = C5H5, C5H4Me, C5Me5; L = PhnMe3−nP, n = 0−3) (R = Me, Et, Bu, Ph, CH2CH2Ph, CHCH2) teilweise uber die entsprechenden Eisenchloride (1–7) und Organomagnesium-Verbindungen, zum anderen Teil aus Cp(COD)FeLi (8, 9), Organohalogenid und Phosphan dargestellt. Die thermische Stabilitat der Ethyleisen-Komplexe 17–24 gegenuber s-H-Eliminierung zu den (η2-Ethylen)eisenhydriden 37–39 bzw. den Verbindungen Cp(L)2FeH (40–48) nimmt mit der Basizitat des Phosphanliganden zu, jedoch mit zunehmender Methylsubstitution am Cp-Liganden ab. Die Vinyleisenverbindugen 29–32, 54, 55 reagieren mit Ethylen unter Insertion in die Vinyl-Fe-Bindung. Nach Isomerisierung entstehen die (η3-Crotyl)eisen-Komplexe 56–61. Als bei 20°C stabile (η1, η2-Alkenyl)eisen-Verbindungen wurden Cp(Me3P)Fe−[CH2]3−CH CH2(CpC5H5 (62), C5Me5 (63) und (c5Me5)(ME3P)Fe−oC6H4CH2CH2 (67) isoliert. Organyl Complexes of (η-Cyclopentadienyl)(triorganophosphane)iron A series of organyliron complexes of the type Cp(L)2FeR (Cp = C5H5, C5H4Me, C5Me5; L = PhnMe3−nP, n = 0−3) (R = Me, Et, Bu, Ph, CH2CH2Ph, CHCH2) have been prepared either from the corresponding iron chlorides (1–7) and organomagnesium compounds or from Cp(COD)FeLi (8, 9), organic halide, and phosphane. The thermal stability of the ethyliron complexes 17–24 towards β-H elimination (to give the (η2-ethylene)iron hydrides 37–39 or the Cp(L)2FeH compounds 40–48) increases with the basicity of the phosphane ligand and decreases with increasing methyl-substitution of the Cp ligand. The vinyliron compounds 29–32, 54 and 55 react with ethylene with insertion into the vinyl–Fe bond to give the (η3-crotyl)iron complexes 56–61 as the result of isomerization. The (η1, η2-alkenyl)iron compounds Cp(Me3P)Fe−[CH2]3−CHCH2(CpC5H5 (62), C5Me5 (63) and (C5Me5)(Me3P)Fe−o-C6H4CH2CHCH2 (67) were isolated and are stable at 20°C.

Das bei der Umsetzung von Nickelocen (1) mit Organylmagnesiumhalogenid bzw. Organyllithium primar entstehende (Cyclopentadienyl)organylnickel A last sich durch Komplexierung an die C = C-Bindung eines Olefins stabilisieren. Unterhalb ca. −30°C lassen sich mit Organyllithium die (η2-Alken)(η5-cyclopentadienyl)organylnickel-Komplexe 2a–j (Alken: Ethylen), 7–14 (Alken: Propen) sowie die Methylnickel-Derivate gleichen Typs 15–17 und 22–25 mit verschiedenartigen Alkenen erhalten. Bei Butadien komplexiert nur eine C = C-Bindung zu 18, bei unsymmetrisch substituierten Butadienen ist dies die geringer substituierte Bindung. — Rotation des Alkens um die Koordinationsbindungsachse bedingt temperaturabhangige NMR-Spektren; bei Alkenen der Typen CH2=CHR und CH2=CR1R2 sind bei ca. −60°C zwei Rotamere beobachtbar. Die Fahigkeit der Organyl-Nickel-Bindung zur Addition an komplexiertes Ethylen sinkt in der Reihe Ph-Ni (zu 28) < c-C3H5–Ni (zu 29 < Me-Ni (zu 2e). 2d katalysiert bei 120°C die Oligomerisierung von Ethylen zu einem Gemisch von Buten, Hexen und Octen. (η2-Alkene)(η5-cyclopentadienyl)organylnickel Complexes The (cyclopentadienyl)organylnickel species A, which is formed by reaction of nickelocene (1) with organolithium or organomagnesium halides, can be stabilized by complexation to the C = C bond of an olefin. Below ca. −30°C, the organyllithium compounds react with 1 and olefins to give the (η2-alkene)(η5-cyclopentadienyl)organylnickel complexes 2a–j (alkene: ethylene), 7–14 (alkene: propene) as well as the related methylnickel derivatives 15–17 and 22–25 with alkenes of different types. —Only one C=C bond of butadiene complexes to give 18, while in the case of substituted 1,3-alkadienes the least substituted double bond is complexed. Temperature dependent NMR spectra are observed; in the case of the CH2=CHR and CH2=CR1R2 complexes as the result of rotation of the alkene around the coordination axis two rotamers can be observed at ca. −60°C. The ability of the organylnickel bond to add to complexed ethylene decreases in the order Ph-Ni (to 28) < c-C3H5–Ni (to 29) < Me-Ni (to 2e). 2d catalyzes the oligomerisation of ethylene at 120°C to give a mixture of butene, hexene, and octene.

Ausgehend von (-)-(1S,5S)-β-Pinen und von (+)-(1R,5R)-α-Pinen gewinnt man in 3- bzw. 5 stufigen Synthesen die im Titel genannten Nickelkomplexe. Die Halogenide eignen sich zur Racemattrennung chiraler Phosphine. Die Struktur des (+)-Bis(π-pinenyl)nickels ergibt sich aus einer dreidimensionalen Rontgenstrukturanalyse. Allyl Metal-Compounds, I. - (-)- and (+)-π-Pinenylnickel Halides and (-)- and (+)-Bis(π- pinenyl)nickel - Molecular and Crystal Structure of (+)-Bis(π-pinenyl)nickel The title compounds have been prepared by three and five stage syntheses starting from (-)-(1S,5S)-β-pinene and (+)-(1R,5R)-α-pinene, respectively. The halides may be used to separate racemic mixtures of chiral phosphines. The structure of (+)-bis(π-pinenyl)nickel has been determined by a three dimensional X-ray analysis.

Die Dithia[3.3]phane 5–8 mit Naphthalin und Pyridin- bzw. Pyrazin-Einheiten liesen sich durch Reaktion mit Alkalimetall-bis(trimethylsilyl)amiden und Methylierung der Thiolat-Anionen in guten Ausbeuten zu den bis(methylthio)substituierten [2.2]Phanen 9–12 ringverengen. Mit Lithium-bis(trimethylsilyl)amid in Tetrahydrofuran wurden als Hauptprodukte die Stereoisomeren 9a–12a erhalten, wahrend die Natrium-Base in Toluol uberwiegend zu 9b–11b und 12b/c fuhrte. Transanular Interaction in [m.n]Phanes, 31. S-Analogous Wittig-Ether Rearrangement of Thioethers in Dithia[3.3]phanes by means of Alkali Metal Bis(trimethylsilyl)amides The dithia[3.3]phanes 5–8 containing naphthalene and pyridine or pyrazine units were ring-contracted by reaction with alkali metal bis(trimethylsilyl)amides and subsequent methylation of the thiolate anions giving the bis(methylthio) substituted [2.2]phanes 9–12 in high yields. With lithium bis(trimethylsilyl)amide in tetrahydrofuran the stereoisomers 9a–12a were obtained as the main products whereas the sodium base in toluene yielded mainly 9b–11b and 12b/c.

The 1H NMR spectra of various alkyl substituted η3-allyl transition metal complexes (MNi, Ru) have been analysed. The chemical shifts of the η3-allyl protons can be calculated using additive increments; the values of the syn and anti vicinal proton-proton coupling constants approach each other on alkyl substitution of the η3-allyl group.

η1,η2-4-Alkenylnickel-Komplexe wie 1 isomerisieren bei 70°C uber einen βH-Eliminierungsmechanismus zu den entsprechenden isomeren η3-Allynickel-Komplexen wie z. B. 2, 3. Einbindung der Atome C-1 und C-2 des Alkenylliganden in einen aromatischen Ring in 10 oder in ein Cyclopropylsystem in 11–17 erhoht die Stabilitat gegen βH-Eliminierung. 1H NMR- und Kristallstrukturuntersuchungen (an 17) beweisen die Molekulstruktur von 11–17. Durch PMe3 wird die CC-Bindung aus der Koordination mit Ni verdrangt. Es entstehen die 1:1-Komplexe 18–22. Analoge η1, η2-Alkenylnickel-Verbindungen mit um ein Glied kurzerer oder langerer Kette sind nicht stabil. Die 3-Alkenylkomplexe lagern sich - abhangig von der Substitution an der CC-Bindung - in den η3-Cyclopentenyl-Komplex 26 bzw. die offenkettige (η3-3-Vinylallyl)nickel-Verbindung 28 um. Aus 5-Alkenylnickel entstehen die Kohlenwasserstoffe 29–31, deren Bildung diskutiert wird. η1,η2-4-Alkenyl(η5-cyclopentadienyl)nickel Complexes η1,η2-4-Alkenylnickel complexes such as 1 isomerize at 70°C through a βH-elimination mechanism to give the corresponding η3-allylnickel compounds. Incorporation of the atoms C-1 and C-2 of the alkenyl ligand into an aromatic ring (in 10) or into a cyclopropyl system (in 11–17) increases the stability with respect to βH-elimination. 1H NMR investigations and a crystal structure determination (of 17) establish the molecular structure of 11–17. Reaction with PMe3 results in displacement of the CC bond from nickel and formation of the 1:1 complexes 18–22. Analogous η1,η2-alkenyl compounds having chains one member shorter or longer are not stable: the 3-alkenyl compounds rearrange (dependent on the substituents at the CC bond) to η3-cyclopentenyl (26) or to an open chain vinyl-substituted η3-allylnickel complex 28, while the 5-alkenylnickel system gives the hydrocarbons 29–31, the formation of which is discussed.

Die 2-Alkenylmagnesiumhalogenide 1–6 reagieren zu uber 90% regioselektiv mit Butadien unter Metall-an-C-2-Addition bei gleichzeitiger Allylinversion und 2,4-Metallverschiebung zu den 1:1-Addukten 32, 38, 44, 13, 20 und 26. Beim Isopren uberwiegt die Metalladdition an das geringer substituierte C-Atom 3. Man erhalt hauptsachlich die Verbindungen 50, 56, 62, 68 und 76. — Mit Uberschus an 1,3-Dien reagieren die 1:1-Addukte weiter zu 1:2-Produkten, die rasch durch intramolekulare Mg - C-Addition in die 2,4-Divinylcyclohexylmethylverbindungen 112, 114, 116, 118 und 120 bzw. bei Isopren in die 2,4-Diisopropenylcyclohexylmethylmagnesiumverbindungen 122, 124, 126, 128 und 130 ubergehen. Bei den Reaktionen von 2-Methyl-2-propenylmagnesiumchlorid (2) oder 1-Methyl-2-butenylmagnesiumchlorid (3) werden mit Uberschus an Butadien die 1:3-Verbindungen 132 bzw. 134 gebildet. Das cyclische 1:3-Addukt 137 entsteht auch aus tert-Butylmagnesiumchlorid und Butadien. Addition of Organomagnesium Halides to C = C Bonds, XI. — Reactions of Grignard Compounds with Butadiene and Isoprene The 2-alkenylmagnesium halides 1–6 react with more than 90% regioselectivity with butadiene via metal-to-C-2 addition and simultaneous inversion of the 2-alkenyl group, followed by a 2,4-metal shift to give the 1:1-addition products 32, 38, 44, 13, 20 and 26. With isoprene, the metal in 1–5 predominantly adds to the less substituted C-atom 3 to give the 1:1-adducts 50, 56, 62, 68 and 76. — In the presence of an excess of 1,3-diene the 1:1-adducts react further to give 1:2-addition products which undergo fast intramolecular cyclization to the 2,4-divinylcyclohexylmethyl compounds 112, 114, 116, 118 and 120, and, in the case of isoprene, the 2,4-diisopropenylcyclohexylmethyl compounds 122, 124, 126, 128 and 130, respectively. Reaction of 2-methyl-2-propenylmagnesium chloride (2) or 1-methyl-2-butenylmagnesium chloride (3) with an excess of butadiene affords the 1:3-adducts 132 and 134, respectively, as cyclohexylmethyl-magnesium compounds. The cyclic 1:3-adduct 137 is also formed on reaction of tert-butylmagnesium chloride with butadiene.

Natrium-1-alkine NaC CR (1a: R = H, 1b : R = Me, lc: R = At, 1d: R = iPr, 1e: R = tBu) reagieren in flussigem Ammoniak mit Allylchlorid (2a), 2-Methylallylchlorid (2b), 2-Butenylchlorid (2c) sowie mit 3-Methyl-2-butenylbromid (2d) in unterschiedlichen Ausbeuten zu verschiedenen Gemischen von isomeren Monoallylierungsprodukten 3–6, Diallylierungsprodukten 7–10 und Triallylierungsprodukten 11, 12 der 1-Alkine (vgl. Schema A und Tabelle 1). 41 Verbindungen konnten mit Hilfe der 1H-NMR-Spektren (vgl. Tabellen 5–7) sicher identifiziert werden: 14 nicht konjugiert ungesattigte Verbindungen vom Typ 3, 7 und 11 (vgl. Tabelle 2), 18 konjugiert ungesattigte Verbindungen vom Typ 4, 6, 8, 10 und 12 (vgl. Tabelle 3) sowie 9 Kohlenwasserstoffe mit Allenstruktur vom Typ 5 und 9 (vgl. Tabelle 4). – In uber 80proz. Reinheit sind praparativ unmittelbar zuganglich: 2-Hepten-5-in (3b3), 2-Methyl-2-hepten-5-in (3b4), 5-Methyl-1,2,4-hexatrien (5a4), I-Penten-3-in (6a1), 2-Hexen-4411 (6a3), 5-(1-Propenyl)-2-octen-6-in(7b3), 3-Vinyl-1,2,5-hexatrien (9a1)J – Die Kohlenwasserstoffe trans-3c3, trans-3e3. 5c3, 4C2, 5a1, 5a2, 5a4, 6a2, 6a4, 7e1, 7c2. 7d2, E-8e1, 9a1 Mcis-l0e1, llc1, 11d1 11e1, Z/E-l2b1 und Z/E-l2e1 wurden – meist durch praparative Gaschromatographie (pGC) – in Reinheitsgraden von uber 98 % isoliert. -4-Methyl- 3-penten-1-in (4a2), 3-Hexen-1-in (4a3), 2-Methyl-2-hepten-4-in (4c2, 6b4) und 2-Methyl-2- hexen-4-in (6a4) liesen sich mit Natriumamid in flussigem Ammoniak in zu uber 95 0,; reine, konjugierte Alkenine isomerisieren. Die Natrium-triathyl(alkeniny1)borate 15 und 16 erhalt man aus 4a2 bzw. 4a3 mit Na(At3BH) in hohen Ausbeuten. Die Hydroborierungen von 4a2 und von 2,6,6-Trimethyl-3-hepten-4-in(4e2) mit Athyldiboran liefern bei nur kleiner Regioselektivitat jeweils zwei Alkadienyldiathylborane 17 und 18 bzw. 19 und 20.

(ν5-Cp)methylnickel-Komplexe mit verschiedenartigen CC-Bindungssystemen in 1-Alkenen (4), in Olefinen mit interner Doppelbindung (2, 3), α,ω-Alkadienen (5) sowie in Cycloalkenen (6) und Cycloalkapolyenen sechs- (7, 8), acht- (9) und zwolfgliedriger Ringe (10–12) wurden durch Umsetzung von Nickelocen (1) mit Methyllithium in Gegenwart dieser Olefine erhalten. Olefine mit mehreren CC-Bindungen sind im Normalfall nur einfach komplexiert. Bei 1,3-Cyclohexadien werden zusatzlich, bei 1,5-Cyclooctadien ausschlieslich die Komplexe 13, 14 erhalten, bei denen an jede CC-Bindung ein CpNi-methyl koordiniert ist. Thermolyse der ν2-1,3-Alkadien-Verbindungen 15–17 fuhrt unter Ethan-abspaltung zu zweikernigen (CpNi)2-ν4-Alkadien-Komplexen 18–20. (ν5-Cyclopentadienyl)methylnickel Complexes with Single and Multiple Double-Bond Systems The reaction of nickelocene (1) with methyllithium in the presence of a variety of olefins has been studied and complexes have been isolated involving 1-alkenes (4), olefins with internal double bonds (2, 3), α,ω-alkadienes (5), as well as cycloalkenes (6) and the cycloalkapolyenes with six- (7, 8), eight- (9), and twelve-membered rings (10–12). Single complexation is generally observed also when more than one CC bond is present. In the case of 1,3-cyclohexadiene an additional complex is formed in which each CC bond is coordinated to a CpNi-methyl moiety, and in the case of 1,5-cyclooctadiene this is the only type of complex isolated (13,14). Thermolysis of the ν2-1,3-alkadiene compounds 15–17 results in elimination of ethane to give the binuclear (CpNi)2 -ν4-alkadiene complexes 18–20.

Die Synthese des 7,7-Bis(trimethylsilyl)cyclopropabenzols (2), ausgehend von Cyclopropabenzol (1), wird beschrieben. Die oxidative Addition von 2 an Tris(ethen)nickel(0) (3) in Gegenwart von chelatisierenden Aminliganden liefert unter Insertion der Nickel-atome in eine der CC-Einfachbindungen des Cyclopropabenzol-Dreiringes Nickelacyclobutabenzole des Typs 4. In einer Ligandenaustauschreaktion last sich das Tetramethylethylendiamin im Komplex 4a durch Phosphorliganden glatt unter Bildung von Nickelacyclobutabenzolen des Typs 5 verdrangen. – Von 4a wurde eine Rontgenstrukturanalyse ausgefuhrt. The synthesis of 7,7-bis(trimethylsilyl)cyclopropabenzene (2) from cyclopropabenzene (1) is reported. The oxidative addition of 2 to tris(ethene)nickel(0) (3) in the presence of chelating ligands occurs with insertion of the nickel atom into the CC-single bond of the cyclopropabenzene three-membered ring to give nickelacyclobutabenzene derivatives 4, Ligand exchange of the tetramethylethylenediamine in 4a by phosphorus ligands occurs smoothly to give nickelacyclobutabenzene species. 5. – An X-ray structure analysis of 4a was performed.

Es werden verschiedene Darstellungsmethoden fur Alkenyl-η5-cyclopentadienylnickel-Komplexe, namlich Umsetzung von Nickelocen (1) mit Alkenylmagnesiumhalogeniden 2, 23 und 30 oder mit Isopropylmagnesiumbromid (5) und Alkadienen 6-8, 17, 20, 31, 32, exo-Methylencyclopropanen 27, 28 oder -cyclobutan (15) beschrieben. — Die η1, η2-4-Alkenylnickel-Komplexe 3, 9-12, 18a, 33 und 34 sind gegen β-H-Eliminierung stabil; allerdings nimmt ihre Stabilitat mit zunehmender Substitution am C-5 der C C-Bindung ab. Die η1, η2-3-Alkenylnickel-Komplexe isomerisieren in die η3-Allylnickel-Verbindungen 13, 14, 19, 21, 22, 24, 35, wenn nicht die β-H-Eliminie-rung durch Dimethylsubstitution wie in 29 verhindert wird. 5-Alkenylnickel-Komplexe isomerisieren in die stabileren η1, η2-4-Alkenylnickel-Verbindungen. η1, η2-Alkenylnickel Complexes A variety of methods are described for the preparation of alkenyl-η5-cyclopentadienylnickel complexes in which nickelocene (1) is either reacted with the alkenylmagnesium halides 2, 23 and 30 or with isopropylmagnesium bromide (5) and the alkadienes 6-8, 17, 20, 31, 32 as well with the exo-methylenecyclopropanes 27, 28 or exo-methylenecyclobutane (15). — The η1, η2-4-alkenylnickel complexes 3, 9-12, 18a, 33 and 34 are stable to β-H-elimination, the stability decreasing with increasing substitution at C-5 of the C C bond. The η1, η2-3-alkenylnickel complexes isomerize in the absence of dimethyl-substitution of the β-carbon atom (which hinders β-H elimination, e. g. 29) to the η3-allylnickel complexes 13, 14, 19, 21, 22, 24 and 35. 5-Alkenylnickel complexes isomerize to the more stable η1, η2-4-alkenyl analogues.

„Anthracenmagnesium” bzw. dessen 9,10-Bis(trimethylsilyl)-Derivat 6 reagieren in vielfaltiger Weise mit Organoaluminium-Verbindungen. Die Umsetzung von „Anthracenmagnesium” mit R3Al (R = Me, Et) in Toluol bzw. mit Et2AlOEt in THF ergibt die Magnesium-μ-(9,10-dihydro-9,10-anthrylen)-aluminat-Komplexe 1, 2 bzw. 10. Aus 6 und Me3Al entsteht dagegen der 1:2-Komplex 7. Die Reaktion von 1 mit MeAlCl2 fuhrt zu 9,10-Bis(dimethylaluminio)-9,10-dihydroanthracen (3), das in den THF-Komplex 4 ubergefuhrt werden kann. 6 reagiert mit Et2AlCl, abhangig vom Molverhaltnis, entweder zum Chloromagnesiumaluminat-Komplex 8 oder zur monomeren Ethylaluminium-Verbindung 9. – Nach dem Ergebnis von Strukturanalysen besetzen in 10 Mg und Al, in 4 zwei Al axiale Positionen im 9,10-Dihydro-9,10-anthrylen-Rest. Das Mg ist durch Bindung an C-9, an den Sauerstoff der EtOAl-Gruppe in 10 sowie an drei THF verzerrt trigonal-bipyramidal koordiniert. 9,10-Dihydro-9,10-anthrylene Compounds of Aluminium „Anthracene magnesium” and the 9,10-bis(trimethylsilyl) derivative 6 react with organoaluminium compounds in a number of different ways. The magnesium-μ-(9,10-dihydro-9,10-anthrylene)-aluminate complexes 1, 2, and 10 are formed in the reaction of „anthracene magnesium” with R3Al (R = Me, Et) in toluene or with Et2AlOEt in THF. 6 reacts, in contrast, with Me3Al to give the 1:2 complex 7. The reaction of 1 with MeAlCl2 gives 9,10-bis(dimethylaluminio)-9,10-dihydroanthracene (3) or its THF adduct 4.6 reacts with Et2AlCl, depending on the molar ratio, to give either the chloromagnesium-aluminate 8 or the monomeric ethylaluminium compound 9. According to X-ray structure analyses, Mg and Al in 10 as well as both Al in 4 occupy axial positions in the 9,10-dihydro-9,10-anthrylene group. The Mg occupies a distored trigonal bipyramidal coordination with bonds to C-9, to the oxygen of the EtOAl group in 10, and to three THF molecules.

Allylmagnesiumhalogenide 1 (la mit CI, 1b mit Br) sowie deren 2-Methylderivate 2 addieren sich an Athylen, 1-Alkene, Butadien, Styrol und gespannte Cycloalkene. Die Reaktionen von 1 und 2 mit Athylen, Styrol und Bicyclo[2.2.l]hept-2-en sowie von 2 mit Propen und I-Octen sowie von 1 mit Butadien fuhren in masigen bis guten Ausbeuten zu den 1 :1-Addukten 3, 5, 6, 8, 20,21,22,23,24,25 und 50, die nach Hydrolyse als Kohlenwasserstoffe identifiziert wurden. Die Additionen verlaufen in Cyclohexan und Diathylather leichter als in Tetrahydrofuran. Die Anlagerung von l a an 1-Octen fuhrt uberwiegend zum 2:1-Addukt 15, das sich teilweise durch intramolekulare Mg-C-Addition an die Doppelbindung in ein Cyclohexylmethylderivat umlagert. Bei der Reaktion von 1 und 2 mit Styrol erhalt man nach Hydrolyse ein 22: 78- bzw. 21 :79-Gemisch der Olefine 20 und 22 bzw. 21 und 23 entsprechend der Anlagerung von Metall an C-1 und C-2 des Styrols. Die Addition von 1 und 2 an Butadien fuhrt hauptsachlich zu den 1 : 2-Addukten 32 bzw. 45, die durch intramolekularen Ringschlus, mit dem eine Umwandlung der 2-Alkenyl- in eine primare Alkylmagnesiumverbindung 31 4 3 2 bzw. 4445) verbunden ist, der Weiterreaktion von 31 bzw. 44 mit Butadien grostenteils entzogen werden. Die 1 :3-Addukte, z. B. 48, entstanden nur in geringer Menge. Die Reaktion von 2 mit uberschussigem Bicyclo[2.2.l]hept-2-en fuhrt, zunachst nach 1 : 1-Addition zu 50, als Folge mehrerer Umlagerungen und Offnung eines Funfrings zum 1 :2-Addukt 58. Beim Erhitzen von 50 auf 85°C erfolgt Isomerisierung zu 53 und teilweise dessen Ringoffnung zu 54. Addition of Organomagnesium Halides to CC Bonds, VI1). - Reactions of Allylmagnesium Halides with Olefins Allylmagnesium halides 1 (la with CI,1 b with Br) and the 2-methyl derivative 2 add to ethylene, I -alkenes, butadiene, styrene and strained cycloalkenes. The reactions of 1 and 2 with ethylene, styrene and bicyclo[2.2.l]hept-2-ene as well as those of 2 with propene and I-octene, and of 1 with butadiene produce the 1 : l adducts 3, 5, 6, 8, 20, 21, 22, 23, 24, 25 and 50, respectively, which have been identified after hydrolysis as hydrocarbons. The additions proceed more readily in cyclohexane and diethyl ether than in tetrahydrofuran. Addition of 1a to I-octene produces mainly the 2: 1 adduct 15, which undergoes partial rearrangement to a cyclohexylmethyl derivative as a result of an intramolecular Mg-C addition. Reaction of 1 and 2 with styrene followed by hydrolysis produces a 22: 78 and a 21 : 79 mixture, respectively, of the olefins 20 and 22 and the olefins 21 and 23 corresponding to metal to C-1 and metal to C-2 addition to styrene. Addition of 1 and 2 to butadiene leads to the 1:2 adducts 32 and 45 respectively; intramolecular ring closure precludes reaction with further butadiene. The cyclization is accompanied by conversion of the 2-alkenyl- into a primary alkylmagnesium compound (31 32 and 44 45, resp.). The 1 : 3 adducts, e. g. 48 are not formed in significant amounts. The reaction of 2 with excess bicyclo[2.2.1]hept-2-ene produces mainly the 1 :2 adduct 58 as a result of several rearrangements of the 1 : 1 adduct 50 and the subsequent opening of one five-membered ring. On heating to 85°C 50 isomerizes to 53, and some degree of ring opening of 53 to 54 occurs.

Nickelocen (1) reagiert in Ether/THF (ca. 5:1) mit den 2-Alkenylmagnesiumverbindungen 2 – 5 und 11 im Molverhaltnis Ni/Mg - R = 1 glatt zu den η3-Allyl-η5-cyclopentadienylnickel-Komplexen 6 – 9 und 12. Analoge Verbindungen 14 – 19 entstehen bei gleichzeitiger Einwirkung von Isopropyl- oder Isobutylmagnesiumhalogeniden und 1,3-Dien auf 1. Mit unsymmetrisch substituierten 1,3-Dienen entstehen Mischungen isomerer Allylkomplexe, die beim Erhitzen auf 90°C in Gleichgewichtsgemische der syn-anti-Isomeren und bei 120°C in solche der Allyl-Isomeren ubergehen. Reactions of Nickelocene with Organomagnesium Halides and Preparation of η3-Allyl-η5-cyclopentadienylnickel Complexes Nickelocene (1) reacts in ether/THF (ca. 5:1) with the 2-alkenylmagnesium compounds 2 – 5 and 11 in a molar ratio Ni/Mg - R = 1 to give the η3-allyl-η5-cyclopentadienylnickel complexes 6 – 9 and 12. Analogous compounds 14 – 19 are formed by the reaction of isopropyl- or isobutylmagnesium halide and 1,3-dienes with 1. Mixtures of isomeric allyl complexes are formed in the reaction of unsymmetrically substituted 1,3-dienes. The mixtures of syn-anti isomers equilibrate at 90°C. At 120°C an equilibration between the allylic isomers occurs.

The Stevens rearrangement of the triarylphosphorusylids R3 P=CHR′ (III) (R′ = H, CH3, C2 H5) to diarylbenzylphosphines (V) is catalyzed by nickel complexes (e.g., (COD)2 Ni (I)). Attempts to prepare trimesitylphosphine-methylene result in direct formation of dimesityl (mesitylmethyl) phosphine (XII) — the first recorded direct Stevens rearrangement of a phosphorusylid. Phosphorusylids react with nickeltetracarbonyl without rearrangement to give complexes of the type R3P=CHa · Ni(CO)3 (XIV). The structure of XIV has been established by the IR and NMR spectra and confirmed by an X-ray structural determination.1 The ylid is bonded to the nickel through the C-atom with resulting hybridization from sp2 towards sp3.