TRANSITION-METAL SUBSTITUTED DIPHOSPHENES .24. CHELETROPIC [1+4] CYCLOADDITION OF AZODICARBOXYLIC ESTERS AND AMIDES TO THE METAL SUBSTITUTED DIPHOSPHENE (ETA-5-C5ME5)(CO)2FE-P=P-MES-STAR (MES-STAR = 2,4,6TBU3C6H2) - STRUCTURE OF (ETA-5-C5ME5)(CO)2FE-P(= P-MES-STAR[N(CO2ET)N=C(OET)O]

The diphosphenyl complex (eta(5)-C5Me5)(CO)2Fe-P = P-Mes* (1) (Mes* = 2,4,6(t)Bu3C6H2) reacts with equimolar amounts of the azo compounds R(O)C-N = N-C(O)R (2a: R = OEt; 2b: R = O-tBu; 2c: R = OCH2C6H5; 2d: R = NC5H10) in a cheletropic [1 + 4] cycloaddition to afford stereoselectively the metal substituted oxadiazaphospholenes (eta(5)-C5Me5)(CO)2Fe-P(= P-Mes*){N[C(O)R]N = C(R)O} (3a-d). The products have been characterized by elemental analysis as well as by spectroscopic data (IR, H-1, C-13, P-31 NMR, MS). The molecular structure of 3a has been elucidated by single crystal X-ray analysis.