K. Maitra et al., INTRAMOLECULAR [4-ALDER CYCLOADDITION OF A 2H-PHOSPHOLE TO COORDINATED UNSATURATED PHOSPHINES, PHOSPHOLES, AND AN ARSINE(2]DIELS), Journal of the American Chemical Society, 119(51), 1997, pp. 12560-12567
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.