INTRAMOLECULAR [4-ALDER CYCLOADDITION OF A 2H-PHOSPHOLE TO COORDINATED UNSATURATED PHOSPHINES, PHOSPHOLES, AND AN ARSINE(2]DIELS)

Stereoselective [4+2] Diels-Alder cycloadditions occur between unsatur ated tertiary phosphine, phosphole, and arsine molybedenum carbonyl co mplexes, e.g., (Ph2E-trans-CH2CH=CHCH3)Mo(CO)(5) [E = P, As] and 3, 4- dimethyl-1-pbenylphosphole (DMPP). The coordinated DMPP undergoes a [1 , 5] phenyl migration at about 145 degrees C Frier to or concomitant w ith the [4+2] intramolecular cycloaddition reaction with the alkene mo iety of the dienophile to produce a new class of conformationally rigi d bidentate ligands containing the 1-phosphanorbornene bicyclic ring s ystem. The characteristic H-1, C-13{H-1}, and P-31{H-1} NMR spectrosco pic features of these compounds are described, Crystal structures of m ost of the new compounds are reported.