The rare-earth-metal organic cyclo-P-4 complex (LY center dot DMAP)(2)[1,2-R-2-cyclo-P-4] (2, L = N,N'-2,6-diisopropylphenyl-1,4-diazabutadiene, DMAP = 4-N,N'-dimethylpyridine, R = CH2C6H4NMe2-2) was synthesized by direct functionalization of P-4 using the rare-earth-metal alkyl complex LYR(THF) (1) for the first time. Further investigations indicated that three selective conversions of the cyclo-P-4 species have been realized by alkyl migration. Complex 2 was slowly transformed into a R2P-substituted cyclo-P-3 cluster (LY center dot DMAP)(2)[cyclo-P3PR2] (3) under heating conditions. The reaction of 2 with 1 equiv of KR gave the unsubstituted cyclo-P-3 complex (LY center dot THF)(2)[cyclo-P-3]K (4) in quantitative yield, accompanied by the elimination of the organophosphorus compound PR3 (5). Treatment of 2 with HMPA afforded the structurally characterized Zintl-type P-7 complex (LY center dot HMPA)(3)P-7 (6). The formation of complexes 3, 4, and 6 revealed that unusual alkyl migrations in the polyphosphorus complexes occurred in these reactions, and the transformations from cyclo-P-4 into cyclo-P-3 also provided a new insight into the stepwise degradation of P-4 using metal complexes.