Reaktionen von Cyclooctin mit Nickel‐Verbindungen

Abstract

Von Umsetzungen des Cyclooctins mit Nickel‐Verbindungen erwartete man Hinweise auf den Mechanismus der Cyclooctatetraen‐Synthese. Während mit Nickelcyanid nur das trimere Cyclooctin 1 resultierte, lieferte die Reaktion mit Nickelacetylacetonat die Addukte 2 und 3. Mit Nickelbromid und ‐jodid erhielt man außer 1 die Cyclobutadien‐Komplexe 4 und 5, deren Stabilität es unwahrscheinlich erscheinen ließ daß sie Zwischenstufen der Trimerisierung darstellen. Während mit Nickeltetracarbonyl bei Raumtemperatur eine CO‐Einschiebung zu 6 erfolgte, konnte bei 0° ein Primärkomplex 8 gefaßt werden, dessen Reaktivität Hinweise auf den Mechanismus der Trimerisation gab.

Isolation of intermediates in the dicobalt octacarbonyl-catalyzed cyclotrimerization of cyclooctyne. Crystal and molecular structure of a cobaltacyclopentadiene complex

“…Chunky orange crystals of Co2(CO)5(C8H12)2 suitable for X-ray diffraction studies were grown from «-hexane by slow evaporation at 4 °C. The crystal selected for the experiment was an eight-sided prism with faces (100), (100), (010), (010), (001), (001), (10 ), and (101). Preliminary photographs indicated that the complex crystallizes in the triclinic crystal system; there was no evidence of diffraction symmetry higher than C,(I).…”

“…The packing of the two molecules in the unit cell is shown in C(l), C(8), C(9), C (16) -0.2800*-0.7289Z-0.6248Z-C(l), C(8), C(9), C(16), Co(l) -0.1696*-0.8155T-0.5534Z-C(l), C(2), C(7), C(8),C(9), C (10), C(ll), C(15), C(16) -0.2566*-0.7530T -0.6059Z -C(l), C (16) (1)°, C(16)-Co(2)-C(21) = 169.9 (1)°]. The distance Co(l)-Co(2) of 2.4738 (7) A is within the range expected for a metal-metal single bond; this must be present if each metal atom is to have a rare gas configuration.…”

“…Caled for C24H36: C, 88.81; H, 11.19. Found: C,88.95; H, 11.08. Elution with benzene gave two bands, the faster moving of which afforded yellow plates identified as bis(hexamethylene)-l,4-benzoquinone, [C8H12CO]2 (0.045 g, 5%): mp 148-149 °C (lit.13 mp 148 °C); IR (Nujol) 1640 cm"1 MC=0)] (lit.13 1640 cm"1); mass spectrum m/e (relative intensity) 274 (67), 272 (100), 244 (10), 229 (14), 216 (9), 215 (10), 203 (12), 201 (9), 189 (12), 187 (14), 175 (13), 173 (11), 161 (14), 159 (10), 147 (9), 145 (10), 131 (11), 117 (12), 105 (18), 91 (59), 79 (30), 77 (34). Anal.…”

The oligomerization of acetylenes induced by metals of the nickel triad

“…Nickel(n) complexes are apparently the active catalysts in the cyclooctatetraene synthesis 6 , but relatively little work has appeared on other such reactions, though Wittig 7 has obtained cyclobutadiene complexes in low yields by dimerization of cyclooctyne with nickel halides. Part of the problern appears to be due to the low solubility of common nickel(n) salts in organic solvents which do not complex strongly and to the high affinity of nickel(n) for oxy-ligands.…”