Structural Properties of Bis(hexacarbonyldicobalt) Complexes with Heteroatoms Next to the Former Triple Bonds − A Contribution to the Mechanism of the Pauson−Khand Reaction

Abstract

The bis(hexacarbonyldicobalt) complexes of cyclic diynes with sila-, thia-and selena-substituted acetylene units have been isolated. The structural features of these complexes have been elucidated by means of X-ray diffraction analyses on single crystals. In three cases (24Ј, 25Ј and 29Ј) the X-ray investigations show bis(pentacarbonyldicobalt) complexes instead of bis(hexacarbonyldicobalt) ones. Their empty coor-

In Pursuit of an Acetylenedithiolate Synthesis

“…A comparable ratio of the carbon-sulfur bond lengths was observed in cyclic poly-(alkyne thioethers). [13] The remarkably short alkyne-sulfur bonds are in accordance with extensive structural data for alkynyl sulfides published by Gleiter [3a,13] and others. [14] Short C(sp)-X distances generally reflect the dependence of the bond length from the hybridization at the carbon center.…”

“…Crystallization was achieved by cooling a sat-urated benzene solution (30 mg 3c/mL benzene). 13 Trimethylsilylethynyl Trimethylsilylethyl Sulfide (4): Sulfide 4 was prepared as described for 1a by using trimethylsilylacetylene (10 mL, 71 mmol), diethyl ether (100 mL), n-butyllithium (10  in n-hexane, 7.1 mL), sulfur (2.27 g, 71 mmol), and finally 2-trimethylsilylethylbromide (11.2 mL, 12.9 g, 71 mmol) as the alkylating agent. Extraction of the crude product with n-hexane (80 mL and 3 ϫ 20 mL), filtration, and removal of the solvent in vacuo yielded 4 (14.0 g, 86 %) analytically pure as a light yellow oil.…”

Synergetic Effects of Oxidative and Coordinative Promotors to Increase the Yield of a Twofold Pauson−Khand Reaction

“…The slightly higher yields for 25 and 26 than 27 and 28 might be traced back to only one transannular CoϪS bond in the dithia complexes relative to the tetrathia complexes in which two strong transannular CoϪS bonds are assumed. [16] The very similar behavior of the one-sided donor-substituted diynes 18Ϫ19 as compared with 20Ϫ21, which have donor substituents on both sides of the alkyne units, indicates that polar effects, as discussed controversially in the literature, [18,19] are of no importance. In 7 and 15Ϫ17, the PausonϪKhand reaction is initiated either thermally (protocol A) or oxidatively by DMSO (protocol B).…”

“…[16] Similarly, for complex 14, generated from 1,4,7-trithiacyclotrideca-9,11-diyne and two equivalents of Co 2 (CO) 8 , one CO Scheme 3 Scheme 4 in the pseudoaxial position of one [C 2 Co 2 (CO) 6 ] cluster is also replaced by a sulfur center. [17] Spurred by these results we decided to compare the outcome of PausonϪKhand reactions with cyclic diynes and cyclic thiadiynes with ethylene as the olefinic component under four different reaction protocols.…”

Das Koordinationsverhalten des Acetylendisulfids Bis(benzylthio)acetylen gegenüber nullwertigen Metallkomplexen des W, Co und Pt/The Coordination Behavior of the Acetylenedisulfide Bis(benzylthio)acetylene with Zero-valent Metal Complexes of W, Co and Pt

“…Dass die darauf folgende reduktive Entfernung von Benzyl-Gruppen zu η 2 -Alkinkomplexen des Acetylendithiolats führen kann, ist bereits an einem ausgewählten Beispiel gezeigt worden [3]. 0932-0776 / 07 / 0500-0669 $ 06.00 © 2007 Verlag der Zeitschrift für Naturforschung, Tübingen · http://znaturforsch.com Hier berichten wir über die Synthese und Charakterisierung von η 2 -Alkinkomplexen des Liganden Bis- 6 ]-Einheit gegenüber bemerkenswerten zyklischen Bis{bis(alkylthio)acetylenen} [5]. Darüber hinaus berichten wir über Versuche, die Benzylgruppen in den dargestellten Komplexen reduktiv zu entfernen.…”