Quaternisation of 1, (k + 2)-diphosphabicyclo[k.1.0] alkanes 2, follow
ed by treatment of the monoquaternary salts with alkyllithium or Grign
ard reagents produces the cis-isomers of 1,n-disubstituted-1,n-diphosp
hacycloalkanes 3 exclusively; examples containing eight-, nine- and te
n-membered rings are described and the structures of two of these comp
ounds 3a and 3f have been determined.