Organometallic Cerium Complexes from Tetravalent Coordination Complexes

Abstract

Dedicated to Professor Jean-Claude Bünzli on the occasion of his 65th birthday were isolated. However, the salt metathesis of cerium triflate with KL provided a simple route to [CeL 4 ], which was significantly improved if an external oxidant, benzoquinone, was included in the mixture to maintain oxidation-state integrity. Likewise, the salt metathesis of cerium triiodide with KL and added benzoquinone provided a straightforward route to [CeL 4 ].

Covalency in CeIV and UIV Halide and N‐Heterocyclic Carbene Bonds

“…[32][33][34][35][36][37] The first Ce IV cyclopentadienyl complex [38] was the tris(cyclopentadienyl)-supported Ce IV isopropoxide (D) reported by Marks et al, [39] closely followed by the crystallographically characterised tert-butoxide analogue reported by Evans et al [40] We have demonstrated the synthesis of [CeL 4 ] (L= OCMe 2 CH 2 (CNCHCHNiPr); E). [41,42] The Ce IV ion is supported by two bound and two unbound unsaturated backbone NHC ligands and is the only example of a Ce IV À C two-electron s bond.…”

Synthesis and Characterization of Cerium(IV) Metallocenes

“…Ce(IV) alkoxides are well suited for this purpose and reports of Ce(IV) alkoxides exist where these have exhibited utility as precursors in CVD applications [15] and in ring-opening polymerization of lactide [16]. The synthesis of Ce(IV) organometallic complexes, however, is limited by the lack of available starting materials and this has constrained the growth and development of traditional organometallic chemistry and reactivity using this high-oxidation state lanthanide [17]. Two main approaches exist as entry points into Ce(IV) chemistry; the oxidation of Ce(III) compounds and the use of materials such as Ce(OPr [22].…”

Lanthanide/actinide differentiation with sterically encumbered N-heterocyclic carbene ligands

“…It has been demonstrated that a single NHC ligand can afford a modest degree of selectivity for U III over Ce III in the complexes Cp* 2 MI, forming [Cp* 2 UI(NHC)] in preference to [Cp* 2 CeI(NHC)] by a 4 : 1 ratio (Cp* = η 5 -C 5 Me 5 ). 28 We also showed that using a bidentate NHC-alkoxide as the sole ligand for Ce or U resulted in dramatically different structures; the Ce IV complex CeL 4 (L = [OCMe 2 CH 2 {CNCHCHN i Pr}]) 29,30 is sixcoordinate in the solid state with two bound and two free NHC groups, whereas the uranium complex, expected to be isostructural, is seven-coordinate with three bound and one free NHC groups. 31 Since then, we have reported the synthesis of saturated-backbone analogues of these bidentate alcoholfunctionalised proligands [HL R ] (R = P denotes iso-propyl; R = M denotes Mes, 2,4,6-trimethylphenyl; R = D denotes Dipp, 2,6-di-isopropylphenyl).…”