Deacon, Glen B., Junk, Peter C., Wang, Jun, and Werner, Daniel (2014) Reactivity of bulky formamidinatosamarium(II or III) complexes with C=O and C=S bonds. Inorganic Chemistry, 53 (23). pp. 12553-12563.

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Abstract

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 CS(2) are discussed. Treatment of the tris(formamidinato)samarium(III) complex [Sm(DippForm)(3)] 1 (DippForm = N,N'-bis(2,6-diisopropylphenyl)formamidinate, (CH(NC(6)H(3)-^iPr(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){μ-OC(Ph)═(C(6)H(5))C(Ph)(2)O}Sm(DippForm)(2)] (C(6)H(5)= 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 OCPh(2) 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)(μ-η2(C,S):κ(S',S")-SCSCS(2)] 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)C(2)Ph}(thf)] 6 as a major product and light yellow unsolvated [Sm(DippForm)(2){OC(Ph)(2)C(2)Ph}] 7 as a minor product. Molecular structures of complexes (2, 4–7) show that κ(N,N') bonding between a DippForm and samarium atom exists in all compounds, but in 2, DippForm also bridges K and Sm by 1κ(N):2κ(N') bonding and two 2,6-diisopropylphenyl groups are η6-bonded to potassium.

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