The preparation of a new heterobimetallic samarium(II) formamidinate complex and selected reactions of samarium(II) complexes and one samarium(III) formamidinate complex with benzophenone or CS2 are discussed. Treatment of the tris(formamidinato)samarium(III) complex [Sm(DippForm)3] 1 (DippForm = N,N'-bis(2,6-diisopropylphenyl)formamidinate, (CH(NC6H3-(i)Pr-2-2,6)(2)) with potassium graphite in toluene yielded the dark brown heterobimetallic formamidinatosamarium(II)/potassium complex [KSm(DippForm)(3)](n) 2. Divalent 2, a Lewis base solvent free homoleptic species, differs significantly from the related heteroleptic formamidinatosamarium(II) complex [Sm(DippForm)(2)(thf)(2)] 3 with respect to its constitution, structure, and reactivity toward benzophenone. While 2 reacts giving complex 1, the reaction of 3 with benzophenone generates the highly unusual [Sm(DippForm)(2)(thf){mu-OC(Ph)-(C6H5)C(Ph)(2)O}Sm(DippForm)(2)] (C6H5 = 1,4-cyclohexadiene-3-yl-6-ylidene) 4. The formation of 4 highlights a rare C-C coupling between a carbonyl carbon and the carbon at the para position of a phenyl group of the OCPh2 fragment. An analogous reaction of [Yb(DippForm)(2)(thf)(2)] gives an isostructural complex 4Yb. 3 reacts with carbon disulfide forming a light green dinuclear formamidinatosamarium(III) complex [{Sm(DippForm)(2)(thf)}(2)(mu-eta(2)(C,S):kappa(S',S?)-SCSCS2)] 5 through an unusual C-S coupling induced by an amidinatolanthanoid species giving the thioformylcarbonotrithioate ligand. The trivalent organometallic [Sm(DippForm)(2)(CCPh)(thf)] complex activates the C-O bond of benzophenone by an insertion reaction, forming the light yellow [Sm(DippForm)(2){OC(Ph)(2)C2Ph}(thf)] 6 as a major product and light yellow unsolvated [Sm(DippForm)(2){OC(Ph)(2)C2Ph}] 7 as a minor product. Molecular structures of complexes (2, 4-7) show that kappa(N,N') bonding between a DippForm and samarium atom exists in all compounds, but in 2, DippForm also bridges K and Sm by 1 kappa(N):2 kappa(N') bonding and two 2,6-diisopropylphenyl groups are eta(6)-bonded to potassium.