Isostructural σ-hydrocarbyl phospholide complexes of uranium, neptunium, and plutonium

Abstract

σ-hydrocarbyl complexes of the form [M(η5-PC4Me4)2(μ-η1:η6-CH2Ph)2K(η6-arene)] (M = La, Ce, Pr, U, Np, Pu; arene = benzene or toluene) were synthesised in one-pot reactions from [MI3(THF)4], or [U(BH4)3(toluene)] (M =...

Carbene Complexes of Plutonium: Structure, Bonding, and Divergent Reactivity to Lanthanide Analogs

“…The carbene center in 2Pu adopts a planar (∑∠ = 359.7(4)°) T-shaped geometry with a P–C–P angle of 170.8(4)°, which is statistically indistinguishable from the corresponding angle of 170.4(5)° in 2Np and close to the values of 167.6(4)° for 2Pr and 165.2(2)° for 2Sm . The PuC BIPM distance in 2Pu of 2.422(6) Å is the shortest Pu–C distance of any type to date, the previous being a Pu–CH 2 bond length of 2.542(19) Å in [{η 5 -P(CMeCMe) 2 } 2 ­Pu(μ-η 6 -CH 2 C 6 H 5 ) 2 K], and there are no other PuC double bonds reported for comparison. However, by the 3σ-criterion the PuC distance in 2Pu is indistinguishable to the NpC BIPM distance of 2.425(7) Å in 2Np .…”

“…The P–C BIPMH –P angle of 135.8(2)° is typical of the “open book” conformation of (BIPM TMS H) 1– . The Pu–C BIPMH distance in 1Pu of 2.732(4) Å is long compared to the sum of the single bond covalent radii of Pu and C (2.47 Å) but can be compared to the few examples of crystallographically authenticated formal Pu–C σ-bonds that include [K­(2.2.2-cryptand)]­[(η 5 -C 5 H 4 SiMe 3 ) 3 ­Pu­(η 1 -C 5 H 4 SiMe 3 )] (2.740(5) Å), [(η 5 -C 5 H 5 ) 2 Pu­(μ-η 1 :η 5 -C 5 H 5 )] n (2.830(12) and 2.888(12) Å), [(η 5 -C 5 H 5 ) 3 Pu­(CNCy)] (2.58(3) Å), and [{η 5 -P­(CMeCMe) 2 } 2 ­Pu­(μ-η 6 -CH 2 C 6 H 5 ) 2 K] (2.542(19) and 2.614(19) Å) . The iodide-bridged dimeric structure of 1Pu does not have any isostructural trivalent f-element (BIPM TMS H) 1– complexes for direct comparison, but for dimeric trivalent actinide complexes with (BIPM TMS H) 1– we previously reported [(BIPM TMS H)­Np­(Cl)­(μ-Cl) 3 Np­{(μ-Cl)­Li­(DME)­(OEt 2 )}­(BIPM TMS H)], which exhibits Np–C BIPMH distances of 2.831(4) and 2.838(4) Å.…”

“…The preceding survey emphasizes the dominance of multihapto π-bonded ligands in organo-Pu chemistry . There are only four formally σ-bonded complexes to date, ,,, and each of those is derived from potentially η n >1 -ligands. It hence follows that there are no Pu–C multiple (alkylidene, Fischer carbene) or dative N-heterocyclic carbene (NHC) bonds, despite the mature nature of carbene chemistry generally.…”

“…While the first organo-Pu complex, [Pu­(C 5 H 5 ) 3 ], was first reported in 1965, this compound was only structurally authenticated, as [(η 5 -C 5 H 5 ) 2 Pu­(μ-η 1 :η 5 -C 5 H 5 )] n , in 2018, although [Pu­{η 5 -C 5 H 3 (SiMe 3 ) 2 } 3 ] and [K­(2.2.2-cryptand)]­[Pu­{η 5 -C 5 H 3 (SiMe 3 ) 2 } 3 ] were reported in 2017. Subsequently, [K­(2.2.2-cryptand)]­[(η 5 -C 5 H 4 SiMe 3 ) 3 Pu­(η 1 -C 5 H 4 SiMe 3 )], [(η 5 -C 5 Me 5 ) 2 PuI­(THF)], [(η 5 -C 5 H 5 ) 3 Pu­(CNCy)], [{η 5 -P­(CMeCMe) 2 } 2 Pu­(μ-η 6 -CH 2 C 6 H 5 ) 2 K], and [{Pu­(η 5 -C 5 H 4 SiMe 3 ) 3 } 2 (4,4′-bipy)] emerged between 2020 and 2023. Following the report of the structure of uranocene in 1969, [Pu­(η 8 -C 8 H 8 ) 2 ] appeared in 1970, though it was not structurally characterized until 2020 .…”

“…The only structurally characterized Pu-arene complex is [{C 6 H 4 -1,4-(C 6 H 4 -2-NDipp) 2 }­PuI­(THF)] (Dipp = 2,6-diisopropylphenyl) reported in 2023. Though there are prior reports of Pu-alkyls being prepared, for example, [Pu­{CH­(SiMe 3 ) 2 } 3 ], the only structurally authenticated Pu–C σ-bonds are in the aforementioned η 1 -ligated complexes [{η 5 -P­(CMeCMe) 2 } 2 Pu­(μ-η 6 -CH 2 C 6 H 5 ) 2 K], [K­(2.2.2-cryptand)]­[(η 5 -C 5 H 4 SiMe 3 ) 3 Pu­(η 1 -C 5 H 4 SiMe 3 )], and [(η 5 -C 5 H 5 ) 2 Pu­(μ-η 1 :η 5 -C 5 H 5 )] n and the isonitrile complex [(η 5 -C 5 H 5 ) 3 Pu­(CNCy)] . It is hence the case that unambiguously structurally authenticated organo-Pu complexes that provide metal–ligand bond metrics all date from 2017 onward, which stands in contrast to the analogous U and neptunium (Np) organometallics whose structural chemistry spans six and four decades, respectively. − …”