The scandium complex bearing both methylidene and phosphinidene ligands, [(LSc) 2 (μ 2-CH 2)(μ 2-PDIPP)] (L = [MeC(NDIPP)CHC(NDIPP)Me] − , DIPP = 2,6-(i Pr) 2 C 6 H 3) (2), has been synthesized, and its reactivity has been investigated. Reaction of scandium methyl phosphide [LSc(Me){P(H)DIPP}] with 1 equiv of scandium dimethyl complex [LScMe 2 ] in toluene at 60 °C provided complex 2 in good yield, and the structure of complex 2 was determined by single-crystal X-ray diffraction. Complex 2 easily undergoes nucleophilic addition reactions with CO 2 , CS 2 , benzonitrile, and tert-butyl isocyanide. In the above reactions, the unsaturated substrates insert into the Sc−C(methylidene) bond to give some interesting dianionic ligands while the Sc−P(phosphinidene) bond remains untouched. The bonding situation of complex 2 was analyzed using DFT methods, indicating a more covalent bond between the scandium ion and the phosphinidene ligand than between the scandium ion and the methylidene ligand. ■ INTRODUCTION Alkylidene (or carbene) and phosphinidene complexes of transition metals have attracted intense interest and been extensively studied in the past decades. 1,2 The research on such complexes has revealed rich reactivity and applications in group-transfer and catalytic reactions. One exception is those complexes with rare-earth metal (Sc, Y, and lanthanide metal) ions. Rare-earth metal ions are among the hardest Lewis acids, whereas alkylidene and phosphinidene ligands are soft Lewis bases; thus, the rare-earth metal−alkylidene (or phosphini-dene) coordination is mismatched based on the Pearson's HSAB principle. 3 Up to now, the rare-earth metal alkylidene and phosphinidene complexes remain limited. 4−6 The reactivity study showed that most of the rare-earth metal alkylidene and phosphinidene complexes can react as the alkylidene or phosphinidene transfer agents with ketones to give alkenes or phosphaalkenes. 4 It was also found that some of the rare-earth metal alkylidene and phosphinidene complexes undergo nucleophilic addition reactions with unsaturated substrates, such as CO, isocyanate, carbodiimide, and isocyanide. 5k,l,6f,g We have developed a type of β-diketiminato based tridentate ligands, which can stabilize a series of rare-earth metal dialkyl complexes, 7 and a scandium terminal imido complex. 8 Recently, we obtained a scandium bridged phosphinidene complex [{MeC(NDIPP)CHC(Me)NCH 2 CH 2 N(i Pr) 2 }Sc{μ-PC 6 H 3-(2,6-Me 2)}] 2 (DIPP = 2,6-(i Pr) 2 C 6 H 3)), in which the pendant arm of the tridentate ligand is not coordinated to the scandium ion due to the phosphinidene ligand having a strong tendency to bridge two or more rare-earth metal centers. 6f Thus, we carried out a study to synthesize a scandium phosphinidene complex supported by the bulky β-diketiminato ligand, [MeC(NDIPP)CHC(NDIPP)Me] − (DIPP = 2,6-(i Pr) 2 C 6 H 3). 9 During this study, we obtained an unprecedented scandium complex which bears both phosphinidene and methylidene ligands. This scandium methylidene phosphini-dene complex reacts with a variety of unsaturated small molecules, and favoring reaction with the methylidene ligand over the phoshinidene ligand. ■ RESULTS AND DISCUSSION A salt elimination reaction of scandium methyl chloride [LSc(Me)Cl] (L = [MeC(NDIPP)CHC(NDIPP)Me] − , DIPP = 2,6-(i Pr) 2 C 6 H 3) 10 with 1 equiv of K[P(H)DIPP] in toluene at room temperature yielded a scandium methyl phosphide [LSc(Me){P(H)DIPP}] (1) in 85% yield. Complex 1 was