Stable Actinide π Complexes of a Neutral 1,4‐Diborabenzene

Abstract

The π coordination of arene and anionic heteroarene ligands is a ubiquitous bonding motif in the organometallic chemistry of d‐block and f‐block elements. By contrast, related π interactions of neutral heteroarenes including neutral bora‐π‐aromatics are less prevalent particularly for the f‐block, due to less effective metal‐to‐ligand backbonding. In fact, π complexes with neutral heteroarene ligands are essentially unknown for the actinides. We have now overcome these limitations by exploiting the exceptionally strong π donor capabilities of a neutral 1,4‐diborabenzene. A series of remarkably robust, π‐coordinated thorium(IV) and uranium(IV) half‐sandwich complexes were synthesized by simply combining the bora‐π‐aromatic with ThCl4(dme)2 or UCl4, representing the first examples of actinide complexes with a neutral boracycle as sandwich‐type ligand. Experimental and computational studies showed that the strong actinide–heteroarene interactions are predominately electrostatic in nature with distinct ligand‐to‐metal π donation and without significant π/δ backbonding contributions.

Actinide arene-metalates: ion pairing effects on the electronic structure of unsupported uranium–arenide sandwich complexes

“…The U1-(h 4 -C anth ) distances narrowly range from 2.638(5) to 2.676(6) A. Tetrahapto coordination of aromatic or carbocyclic ligands to the actinides is rare, but a handful of terminal cyclobutadienide complexes are known. [68][69][70][71] The U1-(h 4 -C anth ) distances in 1 18C6 $4THF are signicantly longer than the uranium-cyclobutadienide distances found in [Na ( 31 where the elongation of the thorium-arenide distances as compared to 1 18C6 $4THF possibly result from the slight size difference in the ionic radii between thorium and uranium (e.g., Th(IV), C.N. ¼ 6, r ¼ 0.94 A vs. U(IV), C.N.…”

“…In this case, the dbb-An bond was found to be strong, though, also primarily electrostatic in character. 31 In specic regards to thorium, Gambarotta and co-workers have reported the synthesis of the thorium naphthalenide complexes The latter is the only reported actinide-arenide sandwich complex; however, low yields and persistent impurities prevented characterization beyond the determination of its solidstate molecular structure.…”

cAAC‐Stabilized 9,10‐diboraanthracenes—Acenes with Open‐Shell Singlet Biradical Ground States

“…It should be noted that Harmansr elated NHC-stabilized derivative V (NHC = N-heterocyclic carbene,F igure 1) showed closedshell character, [19] which suggested that further fine-tuning of the acenes electronics is required to eventually prompt biradical formation, and to stabilize the resulting open-shell configuration. Due to their unique s donor and p acceptor capabilities,c AACs are powerful Lewis bases, [20] which have already proven their efficiencyinboron chemistry to support realization of uncommon and highly reactive,n eutral molecules [21] and radical species. [22] Fori nstance,d iborenes of the type (L)(ER)B = B(ER)(L) (ER = SBu, SPh, SePh) feature ac losed-shell ground state for L = NHC,w hile at riplet ground state was found for L = cAAC; both compounds show distinct differences in their geometries.…”

Actinide Arene-Metalates: Ion Pairing Effects on the Electronic Structure of Unsupported Uranium-Arene Sandwich Complexes

“…In this case, the dbb-An bond was found to be very strong, though, also primarily electrostatic in character. 29 In specific regards to thorium, Gambarotta and co-workers have reported the synthesis of the thorium naphthalene complexes 31 The latter is the only reported actinide-arene sandwich complex; however, low yields and persistent impurities prevented characterization beyond the determination of its solid-state molecular structure.…”