Organophosphorus compounds -: Part 164.: 2,4-disubstituted 1,3-diphosphacyclobutadienes:: generation and trapping reactions

1lambda(3),3lambda(3)-Diphosphacyclobutadienes have been specifically generated for the first time through hexachloroethane-induced extrusion of the organophosphorus ligands from dimeric zirconocene-phosphaalkyne complexes. The species were chemically characterized indirectly by reactions with appropriate trapping reagents. Thus, the use of bis(acceptor)-substituted alkynes gave rise to 2,5-diphosphabenzvalenes, whereas reactions with N-methylmaleinimide and donor -substituted alkynes such as bis(diethylamino)acetylene resulted in the fort-nation of 1,3-diphospha-Dewar-benzenes. Representatives of both classes of compounds were analyzed by X-ray crystallography. Kinetically stabilized phosphaalkynes reacted similarly to furnish tetraphosphabishomoprismanes through a sequence of [4 + 2] and [2 + 2 + 2] cycloaddition processes. (C) 2002 Elsevier Science B.V. All rights reserved.