2-Butene Tetraanion Bridged Dinuclear Samarium(III) Complexes via Sm(II)-Mediated Reduction of Electron-Rich Olefins

Abstract

While reduction reactions are ubiquitous in chemistry, it is very challenging to further reduce electron-rich compounds, especially the anionic ones. In this work, the reduction of 1,3-butadienyl dianion, the anionic conjugated olefin, has been realized by divalent rare-earth metal compounds (SmI2), resulting in the formation of novel 2-butene tetraanion bridged disamarium­(III) complexes. Density functional theory (DFT) analyses reveal two features: (i) the single electron transfer (SET) from 4f atomic orbitals (AOs) of each Sm center to the antibonding π*-orbitals of 1,3-butadienyl dianion is feasible and the new HOMO formed by the bonding interaction between Sm 5d orbitals (AOs) and the π*-orbitals of 1,3-butadienyl dianion can accept favorably 2e– from 4f AOs of Sm­(II); (ii) the 2-butene tetraanionic ligand serves as a unique 10e– donating system, in which 4e– act as two σ-donation bonding interactions while the rest 6e– as three π-donation bonding interactions. The disamarium­(III) complexes represent a unique class of the bridged bis-alkylidene rare-earth organometallic complexes. The ligand-based reductive reactivity of 2-butene tetraanion bridged disamarium­(III) complexes demonstrates that 2-butene tetraanionic ligand serves as a 3e– reductant toward cyclooctatetraene (COT) to provide doubly COT-supported disamarabutadiene complexes. The reaction of the disamarium­(III) complexes with Cp*Li produces the doubly Cp*-coordinated Sm­(III) complexes via salt metathesis. In addition, the reaction with Mo­(CO)6 affords the oxycyclopentadienyl dinuclear complex via CO insertion.

The smallest 4f-metalla-aromatic molecule of cyclo-PrB2− with Pr–B multiple bonds

“…109,110 The insight of the characteristic high-lying 5d orbitals of the 4f-elements can provide guidance in preparing organometallic complexes with highly negatively charged organic ligands of rare-earth elements. 111,112…”

“…The present work also reveals that the high-lying 5d orbitals of the 4f-elements can facilitate the formation of the B 2 4tetraanion, which complete the isoelectronic B 2 4-, C 2 2and N 2 and O 2 2+ series. 109,110 The insight of the characteristic high-lying 5d orbitals of the 4f-elements can provide guidance in preparing organometalliccomplexes with highly negatively charged organic ligands of rare-earth elements 111,112.…”

C,C- and C,N-Chelated Organocopper Compounds

“…Although neutral N,N-chelated spiro copper complexes are relatively common, the anionic C,N- or C,C-cheated spiro counterparts are sporadic. As mentioned above, Xi’s group found that the C,C-bidentate ligand is an excellent platform to build up diversified coordination complexes across the periodic table [ 32 , 34 , 35 , 36 , 37 , 38 , 39 , 40 , 41 , 42 , 43 , 44 , 45 , 46 , 47 , 48 , 49 , 50 , 51 , 52 , 53 , 54 , 55 , 56 , 57 , 58 , 59 , 60 ]. The chelating effect increases the thermal stability of these organometallic species, facilitating isolation and following characterization.…”

Modulating the electronic properties of divalent lanthanoid complexes with subtle ligand tuning

“…[15][16][17][18] Ytterbium and samarium, which are the next most accessible in the divalent oxidation state, have also been investigated with particular focus on reactivity and small-molecule activation. [18][19][20] Despite the challenges with redox accessibility for the rest of the series, molecular species have been isolated for all of the divalent lanthanoid ions except Pm. 21,22 The electronic structure of the divalent lanthanoid ions differs from that of their trivalent counterparts, in the relatively low energy of the 5d orbitals.…”

“…15–18 Ytterbium and samarium, which are the next most accessible in the divalent oxidation state, have also been investigated with particular focus on reactivity and small-molecule activation. 18–20 Despite the challenges with redox accessibility for the rest of the series, molecular species have been isolated for all of the divalent lanthanoid ions except Pm. 21,22…”