Bis(2,4,6-tri-tert-butylphenyl)phosphavinylidene(oxo)phosphorane (1) (Mes* = 2,4,6-tri-tert-butylphenyl), the first 1λ5σ3,3λ3σ2-diphosphaallene, has been synthesised by addition of the phosphaalkenyllithium Mes*P=C(Li)Cl to dichlorophosphane oxide Mes*P(O)Cl2. Compound 1 is stable in the solid-state but undergoes a slow intramolecular cyclisation in solution by addition of a C–H bond of an orthotert- butyl group to the σ3-P=C double bond.

Dimesitylfluoro(trichloromethyl)germane 1 has been synthesized from difluorodimesitylgermane, chloroform and n-butyllithium. Addition of n-butyllithium to compound 1 gave the lithium derivative 2 which behaves as a synthetic equivalent of the C,C-dichlorogermene Mes2Ge=CCl2. Warming 2 to room temperature afforded the 1,2-digermylalkene 6 possibly by an unprecedented [1,3]-Cl shift from the transient germene 12. Addition of tert-butyllithium to 6

New 1,3-digermacyclobutanes, with two exocyclic C=PMes* bonds, and the corresponding first bis(methylenethioxo)phosphoranes with CP=(S)Mes* moieties have been synthesized.