Reactivity of carbon suboxide toward As and P stabilized ylides. Crystal and molecular structure of CH2{C(=O) [C(=AsPh3) (COOMe)]}2

The reactions of carbon suboxide, C3O2, with a series of stabilized triphenylarsoranes, Ph3As=CHX (X = CN, COOMe, COMe, COPh, COC6H4-p-OMe), yield two different kinds of cmpounds. When X = CN, COOMe the reaction proceeds in a 2:1 ratio (ylide: C3C2) yielding open-chain maloni bis-ylidic compounds (1a,b) whereas in the cases of X = COMe, COPh, COC6H4-p-OME only 1:1 cyclic zwitterionic compounds (2a-c) are obtained. The crystal structure of the bis-ylidic compound 1b has been determined. The crystalas are monoclinic, space group C2/c with . The molecular parameters are consistent with an important contribution of the dipolar form −OC=CAs+. Carbon suboxide has been reactde also with Ph3P=CHX (X = COC6H4-p-OMe, COOMe) giving the cyclic zwitterionic compounds 3 when X = COC6H4-p-OME, whereas when X = COOMe a mixture of products has been obtained.