The reaction of N,N'-dicyclohexylcarbodiimide (DCCI) with [Cp(2)Yb(o-H(2)NC(6)H(4)S)](2) (Cp = C(5)H(5)) () forms the monomer product Cp(2)Yb[SC(6)H(4)N[double bond, length as m-dash]C(NHCy)(2)] (), indicating that the adjacent NH(2) group can add to the C[double bond, length as m-dash]N double bonds of carbodiimide to construct a neutral guanidine group. When DCCI reacts with [Cp(2)Y(o-H(2)NC(6)H(4)S)](2).2THF (), a dimer product [CpY(mu-eta(2):eta(1)-SC(6)H(4)N[double bond, length as m-dash]C(NHCy)NCy)(THF)](2) () was isolated, through the amino group addition and cyclopentadienyl elimination. Interestingly, on treatment of with one or two equivalent of (i)PrN[double bond, length as m-dash]C[double bond, length as m-dash]N(i)Pr at the same conditions gave an amino group partial addition product CpY(THF)[mu-eta(2):eta(1)-SC(6)H(4)N[double bond, length as m-dash]C(NH(i)Pr)N(i)Pr)](mu-eta(2):eta(1)-SC(6)H(4)NH(2))YCp(2).THF (), where only one NH(2) group can add to the C[double bond, length as m-dash]N double bonds of carbodiimide molecule, another one is remained. However, when we extended this reaction to the gadolinium complex, a novel co-crystalline compound {Cp(2)Gd[SC(6)H(4)N[double bond, length as m-dash]C(NHCy)(2)]}.{CpGd(THF)[mu-eta(2):eta(1)-SC(6)H(4)N[double bond, length as m-dash]C(NHCy)NCy)][mu-eta(2):eta(1)-SC(6)H(4)NH(2)]GdCp(2).THF} () was obtained from the reaction of [Cp(2)Gd(o-H(2)NC(6)H(4)S)](2) () with DCCI. In order to investigate the sequence of addition and the elimination of the cyclopentadienyl group, a deprotonation reaction of the addition product has also been studied. Reaction of CpYb[SC(6)H(4)NC(NH(i)Pr)(2)](2)(THF) (), formed by reaction of Cp(3)Yb with two equivalent of o-aminothiophenol, and subsequently with 2 equiv. of (i)PrN[double bond, length as m-dash]C[double bond, length as m-dash]N(i)Pr, with one equiv. of Cp(3)Yb gave a cyclopentadienyl elimination product [CpYb(mu-eta(2):eta(1)-SC(6)H(4)N[double bond, length as m-dash]C(NH(i)Pr)N(i)Pr)(THF)](2) (). This result reveals that addition of the NH(2) group to carbodiimide is prior to the elimination of cyclopentadienyl group. All of new compounds have been characterized by elemental analysis and spectroscopic properties. The solid-state structures of complexes , and were determined by single-crystal X-ray diffraction.