The dinitrogen (N2)chemistry of lanthanides remains less developed compared to the d-block metals and lanthanide-promoted N2functionalization chemistry in well-defined lanthanide complexes remains elusive. Here we report the synthesis and characterization (SQUID, EPR, DFT, X-Ray) of the siloxide supported heterobimetallic (Tm/K) complexes[{KTm(OSi(OtBu)3)3}2(μ-η2:η2-N2)] (1)and[K3{Tm(OSi(OtBu)3)3}2(μ-η2:η2-N2)] (2). Complex2provides a rare example of a metal complex of the triply reducedN23-radical. The structure of2differs from the few previously reported N23-complexes as it presents two Tm and three K cations binding the N23-radical, facilitating N2functionalization. Notably, the K3Tm2-bound N23-moiety reacts with excess H+to form NH4Cl in 18% yield, and with MeOTf at room temperature to yield the dimethyl hydrazido complex[K2{Tm(OSi(OtBu)3)3}2(μ-(CH3)NN(CH3))] (3). Protonolysis of3yields MeHN-NMeH·2HCl in 18 % yield.