Recent progress in the chemistry of lanthanide-ligand multiple bonds

Lewis‐Acid Stabilized Organoimide Complexes of Divalent Samarium, Europium, and Ytterbium

“…The SiPh 3 ligand backbone in samarium(II) imide complex 2-Sm led to the same solid-state structure as detected for Yb II congener 2-Yb b ,e xcept that both Sm II centers are coordinated by two thf molecules in an overall slightly distorted octahedral ligand environment( Figure 6). The SmÀN bond lengths involving the m 3 -bridging imido ligandsa re in the range of 2.551(2) to 2.567(2) ( Table 1), which is longer than those found for terminally coordinated silylamido ligands in [(thf) 2 Sm{N(SiMe 3 ) 2 } 2 ] [42] (SmÀN, 2.442(9) and2 .424 (9) ), but shorter than the average SmÀNb ond lengths of the m 2 -bridging silylamido ligandsi nt rimeric [(thf) 2 (4) and 2.951(4) ,T CyTAC = 1,3,5-tricyclohexyl-1,3,5-triazacyclohexane), [44] indicating relativelyw eak bonding between Sm II and the Lewis acid AlMe 3 .…”

“…The recents urge of interest in organo rare-earth metal imide chemistry is particularly due to gaining ab etter understanding of the chemical bonding in such long-time elusive compounds, but also with av iew to the potentiale mergenceo fu nprecedented reactivity in organic or inorganic transformations. [1,2] In previouss tudies, various synthesis strategies have been launched to generate Ln III imide species, in whicht he lanthanide centers adopt their most prominent oxidation state + 3. These strategies include intramolecular protonolysisr eactions of alkyl-amide complexes [(L)Ln(R)(NHR')], [3][4][5] Lewis base-induced deprotonation of lanthanide amide complexes [(L) 2 Ln{NH(R')}], [6][7][8] organoaluminum-assisted deprotonation, [9][10][11][12][13] 1,2-addition of LnÀHo rL n ÀCb onds across NC unsaturated substrates, [14][15][16] salt metathesis of lanthanide halides with magnesium phenylimidea st ransfer reagent, [17] reductive cleavage of azobenzene by redox-active metal centers, [18][19][20] and transformation of rare-earth metal methylidene species with compounds carrying NÀH, N=Co rN =Nf unctional groups.…”

Chasing Multiple Bonding Interactions between Alkaline‐Earth Metals and Main‐Group Fragments

“…Althoughn eutral N-o rO-chelatingl igands, such as tmeda or dme, are knownt os tabilize heteroleptic complexes [(L)Ae(R')(EH)], [29] highly polarized and basic ligands E 2À formed via intramolecular deprotonation, displayapronounced bridging tendency. [14][15][16][17][18] Compared with the corresponding chemistry of trivalent rare-earth metals,w hich is also largely dominat-ed by ionic/non-orbital interactions but allows fort he implementation of an anionic ancillary ligand, [14][15][16][17][18] the isolation of monomeric and terminal complexes [(L)Ae=E] is therefore further complicated in case of Ae 2 + complexes. However,p erforming the reactions in polar ethereal solvents usually leads to the formation of donor solvent-coordinated products [(do) z Ae(E)] x .A na dditional advantage of the latter approach arises from the insolubility of many Ae precursors of the type [AeR' 2 ]i na liphatic or aromatic solvents, whereas they often are readily soluble in polar ethereal solvents (highionicity).…”

“…[2][3][4][5][6] Being well-established for d-transition metals (even commercially applied) [7][8][9][10][11][12] and the 5f-element uranium, [13] derivatives of the 4f elements (lanthanides) emerged as av ibrant field only during the past 10 years. [14][15][16][17][18] Ar espective alkaline-earth (Ae) metal chemistry hasr emained underdeveloped. This is surprising since the organometallic chemistry of the Group 2m etals, particularly with regard to the higher homologs, has witnessed remarkable progress, triggered by promising applications in catalysis [19] and the globali ssue of hydrogen storage.…”

“…Crystallographicallyauthenticated homometallic Ae organoimides. The complexes were prepared via protonolysis approach e,u sing dialkylmagnesium compounds(13,(15)(16)(17)(18)(19), Grignard reagents (14)ord ibenzylcalcium(21). Compound 20 was obtainedf rom ar edox transfer using [Bi(Cl)(m-NTer)] 2 .…”