Reactivity of Bulky Formamidinatosamarium(II or III) Complexes with C═O and C═S Bonds

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 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)Pr2-2,6)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)═(C6H5)C(Ph)2O}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(μ-η(2)(C,S):κ(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)2C2Ph}(thf)] 6 as a major product and light yellow unsolvated [Sm(DippForm)2{OC(Ph)2C2Ph}] 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 η(6)-bonded to potassium.

Reductive Trapping of [(OC)5W–W(CO)5]2− in a Mixed‐Valent SmII/III Calix[4]pyrrolide Sandwich

“…TheS m2ÀO4(isocarbonyl) bond is significantly shorter than Sm2ÀO3(thf). TheW1 ÀC49(isocarbonyl) (1.891-(8) )i ss lightly shorter than the W1ÀC(terminal carbonyl) bonds (2.004(10)-2.024 (9) ,r eflecting their greater Lewis Acidity than Sm II .E vidence of the presence of Sm II is provided by absorptions at 608 and 671 nm in the solid state visible spectrum of 1.These are assigned to f!dand metal to ligand charge transfer transitions of divalent samarium. [19] Further support for the presence of the divalent samarium comes from the reaction of 1 with benzophenone generating atransient purple/red color,consistent with the formation of aradical.…”

“…[7] Likewise, the less powerful reducing analogue YbCp* 2 has had some similar behavior, for example,t rapping of triiron-, [8a] hexairon-, [6] monocobalt-, [8b] and tricobalt [8c] carbonyl clusters.In seeking N-donor alternatives to the cyclopentadienyls for analogous purposes,w eh ave used the bulky [Sm-(DippForm) 2 2À from reaction with CS 2 . [9] In the search for another lanthanoid N-donor reductive trapping agent, we have now shown that the divalent samarium meso-octaethylcalix [4] [8b]…”

Potassium C–F Interactions and the Structural Consequences in N,N′-Bis(2,6-difluorophenyl)formamidinate Complexes

“…Not only does the anionic NCHN bite provide a variety of different nitrogen-based coordination modes (e.g., monodentate κ(N), bidentate κ(N,N ), or various bridging modes e.g., µ-1κ(N):2κ(N ), µ-1κ(N,N ):2κ(N,N ) to list a few) [6,7], the nitrogen-bound aromatic substituents can also provide additional coordination modes. The potential to form metal-arene interactions, such as η 6 coordination, has been largely observed in group one chemistry [8][9][10][11][12][13], though some examples are known in f -block chemistry [14]. In almost all examples of this aromatic coordination, the phenyl rings contained alkyl-substituents in either the 2,6 positions (e.g., iPr, Et, Me), or in the 2,4,6 positions (e.g., Me).…”

“…This contrasts the group one complexes of the non-fluorinated N,N′-di(aryl)formamidinate ligands [21][22][23], which readily retain coordinating solvent. Since then, we have expanded the use of fluorinated formamidinate ligands to f-block chemistry [9,16,17,[24][25][26][27][28], in a variety of different contexts [5]. One of the fluorinated formamidinate ligands used was N,N′-bis (2,6-difluorophenyl)formamidinate (DFForm) in both trivalent [16,17], and divalent [16] rare-earth complexes.…”

Activation of Heteroallenes COxS2–x (x = 0–2): Experimental and Theoretical Evidence of the Synthetic Versatility of a Bulky Guanidinato SmII Complex

“…[11][12][13][14][15][16][17][18][19][20][21][22][23][24] The metal as well as the steric and electronic contributions of the ligands influence the way conversion of CO 2 will proceed. Another nonnegligible factor is the solvent employed.…”