122190-26-5Relevant articles and documents
1,5-Dihydropyrrol-2 ones from (1,4-diaza-1,3-diene)tricarbonyliron, (DAD)Fe(CO)3, and alkyne. 5. Spectroscopic and X-ray structural characterization of a bicyclo[2.2.1] complex resembling the initial cycloadduct. The C=N-Fe fragment in (DAD)Fe(CO)3 as an isolobal analogue of the classical 1,3-dipole azomethine ylide in 1,3-dipolar cycloaddition
Frühauf, Hans-Werner,Seils, Frank,Stam, Casper H.
, p. 2338 - 2343 (2008/10/08)
In solution, [biacetyl bis(4-methoxyanil)]Fe(CO)3 (1a) reacts instantly with dimethyl acetylenedicarboxylate, even at -90°C. Depending on the additional ligand offered, different products are isolated. Under 1 atm of CO, the expected 1,5-dihydropyrrol-2-one complex 3a is formed at room temperature from which the coordinated heterocycle can be displaced by using CO pressure (180 bar) at elevated temperature. When P(OMe)3 is offered instead, a ferrabicyclo[2.2.1] complex, 4a, can be isolated which is spectroscopically characterized (IR, FD-MS, and 1H, 13C, and 31P NMR). Above -20°C, 4a transforms into 5a, C28H33-N2O11PFe, of which the structure has been determined by single-crystal X-ray diffraction: space group P1, a = 11.833 (4) A?, b = 13.740 (2) A?, c = 11.607 (3) A?, α = 102.94 (2)°, β = 106.79 (2)°, γ = 76.54 (2)°, V = 1732.0 A?3, Z = 2, R = 0.048 (Rw = 0.075) for 5862 reflections with I > 2.5σ(I). In 5a the bicyclo[2.2.1] core of 4a is retained, while the phosphorus ligand has changed from a trivalent, 2e-donating phosphite in 4a to a covalently bound, pentavalent phosphonate in Sa. With the bicyclo[2.2.1] structure being established, the initial step in the reaction of (diazadiene)Fe(CO)3 complexes with dipolarophilic acetylenes is formulated in terms of an oxidative 1,3-dipolar cycloaddition of the alkyne to the C=N-Fe fragment. The isolobal analogy between the latter and the classic Huisgen 1,3-dipole R2C=N(R)-CR2 is demonstrated.
