The synthesis and structures of a series of lanthanide(II) and lanthanide(III) complexes supported by the amido ligand N(SiMe3)Ar were described. Several lanthanide(III) amide chlorides were synthesized by a metathesis reaction of LnCl(3) with lithium amide, including {[(C6H5)(Me3Si)N](2)YbCl(THF)}(2)center dot PhCH3 , [(C6H3-Pr-i(2)-2,6)(SiMe3)N](2)YbCl(mu-Cl)Li(THF)(3)center dot PhCH3 , [(C6H3-Pr-i(2)-2,6)(SiMe3)N]YbCl2(THF)(3) , and [(C6H3-Pr-i(2)-2,6)(SiMe3)N](2)SmCl3Li2(THF)(4) . The reduction reaction of with Na-K alloy afforded bisamide ytterbium(II) complex [(C6H5)(Me3Si)N](2)Yb(DME)(2). The same reaction for Sm gave an insoluble black powder. An analogous samarium(II) complex [(C6H5)(Me3Si)N](2)Sm(DME)(2) was prepared by the metathesis reaction of SmI2 with NaN(C6H5)(SiMe3). The reduction reaction of ytterbium chloride with Na-K alloy afforded monoamide chloride {[(C6H3-Pr-i(2)-2,6)(SiMe3)N]Yb(mu-Cl)(THF)(2)}(2), which is the first example of ytterbium(II) amide chloride, formed via the cleavage of the Yb-N bond. The same reduction reaction of gave a normal bisamide complex [(C6H3-Pr-i(2)-2,6)(SiMe3)N](2)Sm(THF)(2) via Sm-Cl bond cleavage. This is the first example for the steric effect on the outcome of the reduction reaction in lanthanide(II) chemistry. can also be synthesized by the Na/K alloy reduction reaction of . All of the complexes were fully characterized including X-ray diffraction for.