Pseudohalide complexes of tricyclopentadienyl cerium(IV) and bisindenyl cerium(IV)

Advances in f-element cyanide chemistry

“…Following these results, the homoleptic lanthanide cyanides [Ln (CN) x ] ∞ (x = 3 and Ln = Ce, Pr, Sm, Eu, Ho, Yb, or x = 2 and Ln = Sm, Eu, Yb) were obtained by either of two ways: treatment of metal turnings with Hg(CN) 2 in liquid NH 3 gave impure products whereas electrolysis of metal pieces in the presence of HCN in liquid ammonia afforded the pure compounds in low yields. 27 The tris(cyclopentadienyl) and bis-(indenyl) cerium(IV) complexes [Ce(Cp) 3 (CN)] (Cp = η-C 5 H 5 ) and [Ce(C 9 H 7 ) 2 (CN) 2 ] were reported in 1972, 28 but these results were strongly questioned. 29 30 Other syntheses of the tris(cyclopentadienyl) derivatives [U(C 5 H 4 R) 3 (CN)] were proposed afterwards (Scheme 1): from salt metathesis reactions of [U(C 5 H 4 R) 3 Cl] (R = H, Me) with alkali metal cyanides in aqueous solution or acetonitrile, 31 oxidation of [U(C 5 H 4 R) 3 ] (R = H, t Bu) with nitrile 32 or isonitrile molecules, 30,31 and addition of N n Bu 4 CN to the cationic precursors [U(C 5 H 4 R) 3 ][BPh 4 ] (R = t Bu, SiMe 3 ).…”

“…Following these results, the homoleptic lanthanide cyanides [Ln (CN) x ] ∞ (x = 3 and Ln = Ce, Pr, Sm, Eu, Ho, Yb, or x = 2 and Ln = Sm, Eu, Yb) were obtained by either of two ways: treatment of metal turnings with Hg(CN) 2 in liquid NH 3 gave impure products whereas electrolysis of metal pieces in the presence of HCN in liquid ammonia afforded the pure compounds in low yields. 27 The tris(cyclopentadienyl) and bis-(indenyl) cerium(IV) complexes [Ce(Cp) 3 (CN)] (Cp = η-C 5 H 5 ) and [Ce(C 9 H 7 ) 2 (CN) 2 ] were reported in 1972, 28 but these results were strongly questioned. 29 The first organouranium cyanide complexes [U(Cp) 2 (CN)] and [U(Cp) 3 (CN)] were synthesized in 1974 by protonolysis of [U(Cp) 3 ] and [U(Cp) 4 ] with HCN in benzene, as well as [Ln(Cp) 2 (CN)] from [Ln(Cp) 3 ] (Ln = Nd, Yb).…”

Existence and Stability of Lanthanide−Main Group Element Multiple Bonds. New Paradigms in the Bonding of the 4f Elements. A DFT Study of Cp2CeZ (Z = F+, O, NH, CH-, CH2) and the Ligand Adduct Cp2Ce(CH2)(NH3)

“…A notable exception is cerium, for which the +4 oxidation state is also possible. [36][37][38][39][40][41][42][43][44][45] The high propensity of lanthanide elements to achieve high coordination numbers requires the use of bulky ligands in order to prevent oligomerization (e.g. to achieve compounds such as I).…”

“…been devoted to the synthesis, structure, and reactivity of Ln(III) and Ln(II) compounds, cyclopentadienyl derivatives have also been proven to exist for the +4 oxidation state. [36][37][38][39][40][41][42][43][44][45] These systems, or analogues with more sterically encumbered cyclopentadienyl rings, could therefore provide access to the target compounds. The field of chemistry has provided many examples of reactive transition metal complexes whose chemistry has languished when the heavier congeners of the series have been targeted.…”

“…In this respect, the lanthanide elements are rather limited, with most lanthanides preferring the trivalent oxidation state. A notable exception is cerium, for which the +4 oxidation state is also possible. − The high propensity of lanthanide elements to achieve high coordination numbers requires the use of bulky ligands in order to prevent oligomerization (e.g., to achieve compounds such as I ). − We therefore considered the bis(cyclopentadienyl)cerium(IV) system as a possible synthetic target for isolating a terminal metal−ligand multiple-bonding interaction and set out to perform computational analyses of Cp 2 CeZ compounds (where Z is a divalent element or group) to assess the nature of chemical bonding and ascertain whether multiple metal−ligand bonding seemed feasible.…”