The construction of supramolecules or extended frameworks based on coordination and organometallic complexes is one of the major areas of current research in inorganic and organometallic chemistry. Nevertheless, this approach has received little attention in the field of organobismuth ± transition-metal complexes; such complexes are of great importance mainly due to their potential applications as catalysts in olefin oxidation and ammoxidation [3] and as precursors to a variety of electronic materials. Bismuth has been shown to form the polymer [Et 2 Bi(OAr)] I in which the alkoxide ligand bridges the Et 2 Bi groups giving a helical chain with no direct Bi À Bi interaction. [5] For the Bi-Fe-CO system, the polymer [{PhCH 2 NMe 3 }{(m-H)Fe 2 (CO) 6 Bi 2 (m-Cl) 2 }] I was
In an attempt to pinpoint the source of the oxide in the hexameric structures, we repeated the preparation of 2 in a vial connected through a heated capillary to a Hiden Analytical Quadrupole mass spectrometer (Warrington, England). After the addition of THF, the reaction mixture was heated and the volatile products blown into the mass spectrometer were subjected to selective ion mass (SIM) analysis. This confirmed the presence of ethylene (parent peak at 28 amu; daughter fragments at 27, 26, and 25 amu). Ethylene is commonly extruded during THF-cleavage processes, [10] so the origin of the O 2À ions in 2 is almost certainly from THF. Fragmentation of THF is a complex matter, the outcome of which can differ depending on many variables such as the metal and the nature of the organyl assailant. Hard organolithium bases are known to deprotonate THF at the aposition, before undergoing a [p4sp2s] cycloreversion to afford enolate ™CH 2 CHÀO À ∫ and ethylene. [11] There are also precedents for THF fragmentation leading to M-O-M bridges in organolanthanide chemistry, [12] and to O 2À in other metal [13] and metalloidal [14] systems. Here the heterobimetallic nature of the inverse crown ether system exacerbates the complexity of the THF fragmentation process, a sign of which is that the filtrates left following the isolation of 2 and 3 darken and degrade to viscous oils in a matter of days. However the salient point is that both new compounds can be prepared reproducibly in a pure crystalline form, and isolated for future synthetic exploration, before the onset of this degradation.
Experimental Section
2 and 3: In a typical preparation, BuNa, Bu 2 Mg, and the relevant amine (5:5:15 mmol) were mixed together in a hydrocarbon solution under a protective argon atmosphere. Dry, distilled THF (5 mL, 62 mmol) was then added and the solution warmed for 30 min. Cooling the solution on the bench (for 2) or in the refrigerator at À 26 8C (for 3) afforded colorless crystals of 2 or 3. Yields of first batches isolated were typically 18 or 11 %, respectively. No further solids could be isolated due to degradation of the filtrate solutions. M.p. 330 8C (decomp) and 258 8C (decomp), respectively. Satisfactory analyses (C, H, N) were obtained for both compounds.