Treatment of [sigma:(eta 5)-(C9H6)C2B9H10]Zr(NMe2)(DME) with 2 equiv of guanidines (i) PrNHC(NR2)=N-i Pr (R = Me, Et) in refluxing toluene gave unprecedented complexes [eta:(sigma 5)-{2-[C=N-i Pr(NHi Pr)]C9H5}C2B9H10]eta(2)-[(i)112-(i PrN)(2)C(NR2)] (R = Me, Et). This communication describes the mechanism by which they are formed. Experimental results show that guanidinates are not inert ligands in the present cases that can undergo C-N bond cleavage to generate amido and carbodiimide that subsequently insert into the Zr-C bond to form the final product via 1,5-sigmatropic shift.