A Phospha-Wittig Route to 5-Phosphaphenanthrene

The reaction of tributylphosphane with a 7-(2′-formyl-2-biphenylyl)phosphanorbornadiene P-W(CO) 5 complex leads to the 5-phosphaphenanthrene P-W(CO) 5 complex via an intramolecular phospha-Wittig condensation. This complex is stable enough for detection by 31 P NMR spectroscopy but cannot be isolated due to its high reactivity. It is trapped by addition of MeOH or cycloaddition with 2,3-dimethylbutadiene or a nitrileimine. The adducts were characterized by X-ray crystal structure analysis. Graphical The reaction of 4 with tributylphosphane at room temperature gives phosphaphenanthrene complex 5 , which can be detected by 31 P NMR and trapped by addition, and [2+4] or [2+3] cycloaddition.