The hypervalent phosphorous compound, ,8-dioxa-1-phosphabicyclo-3.3.0
octa-2,4,6-triene (ADPO) forms adducts with chromium, tungsten, nicke
l and palladium metal centers. All four new adducts contain tetrahedra
l phosphorous atoms as a result of folding the ADPO unit. Tis folding
of the planar 10-P-3 ADPO and 8-P-3 ADPO and the strength of the phosp
horous-metal interaction. In the case of a homoleptic palladium(II) co
mplex, dimerization of the coordinated ADPO unit was observed.