An unusual product formation is observed for the insertion reaction of the thermally stable silylene Si[(NCH₂Bu^t)₂C₆H₄-1,2] [abbrev. as Si(NN)] into the carbon–halogen bond of alkyl or aryl halides RHal (Hal = Cl, Br). In general, depending on the halogen, the reaction either results in a disilane of type (NN)Si(Hal)-(R)Si(NN) for Hal = Cl or a mixture of disilane and the monosilane (NN)Si(R)(Hal) for Hal = Br. The results are put into context to previously suggested mechanisms. The disilane (NN)Si(Hal)-(R)Si(NN) (Hal = Cl or Br) is thermally labile and mild thermolysis yields the corresponding monosilane (NN)Si(R)(Hal) and silylene 1. Additionally, strong evidence is presented for a radical pathway for the reaction of 1 and RHal.