SYNTHESIS AND CHEMISTRY OF 1,2-DIHYDRO-1,2-ARSAPHOSPHETES AND 1,3-ARSAPHOSPHOLIDE ANIONS

Several 1,2-dihydro-1,2-arsaphosphetes (1-3) were obtained by ring-exp ansion of phosphirenes with phenyldichloroarsine. Lithium cleavage of the P-As bond of these four-membered rings followed by reaction with d ichloromethane yielded the corresponding 1,3-arsaphosphol-4-enes (8-9) . Metallation at the CH2 central carbon of 9 followed by lithium cleav age of the two exocyclic P-Ph and As-Ph bonds produced the correspondi ng 4,5-diethyl-1,3-arsaphospholide ion 10 whose reaction with FeCl2 ga ve the 1,1'-diarsa-3,3'-diphosphaferrocene 11. Both 1 and 11 were char acterized by X-ray analysis but statistical disorders of the arsenic a nd phosphorus sites lowered the accuracy of the crystal data. A succes sful [4 + 2] cycloaddition reaction demonstrated the existence of an e quilibrium between the [W(CO)5]2 dicomplex of 1 and its 1-arsa-4-phosp hadiene counterpart at ca 120-degrees-C.