The first adducts of NHCs (= N-heterocyclic carbenes) with aromatic polyphosphorus complexes are reported. The reactions of [Cp*Fe(h 5-P 5)] (1)(Cp* = pentamethyl-cyclopentadienyl) with IMe (= 1,3,4,5-tetramethylimidazolin-2-ylidene), IMes (= 1,3-bis(2,4,6-trimethylphenyl)-imidazolin-2-ylidene) and IDipp (= 1,3-bis(2,6-diisopropylphenyl)-imidazolin-2-ylidene) led to the corresponding neutral adducts which can be isolated in the solid state. However,i ns olution,t hey quicklyu ndergo ad issociative equilibrium between the adduct and 1 including the corresponding NHC. The equilibrium is influencedb yt he bulkiness of the NHC. [Cp''Ta (CO) 2 (h 4-P 4)] (Cp'' = 1,3-di-tertbutylcyclopentadienyl) reacts with IMe under Pa tom abstraction to give an unprecedented cyclo-P 3-containing anionic tantalum complex.D FT calculations shed light onto the energetics of the reaction pathways.
The redox chemistry of [Cp*Fe(η -As )] (1, Cp*=η -C Me ) has been investigated by cyclic voltammetry, revealing a redox behavior similar to that of its lighter congener [Cp*Fe(η -P )]. However, the subsequent chemical reduction of 1 by KH led to the formation of a mixture of novel As scaffolds with n up to 18 that are stabilized only by [Cp*Fe] fragments. These include the arsenic-poor triple-decker complex [K(dme) ][{Cp*Fe(μ,η -As )} ] (2) and the arsenic-rich complexes [K(dme) ] [(Cp*Fe) (μ,η -As )] (3), [K(dme) ] [(Cp*Fe) (μ,η -As )] (4), and [K(dme) ] [(Cp*Fe) (μ ,η -As )] (5). Compound 4 and the polyarsenide complex 5 are the largest anionic As ligand complexes reported thus far. Complexes 2-5 were characterized by single-crystal X-ray diffraction, H NMR spectroscopy, EPR spectroscopy (2), and mass spectrometry. Furthermore, DFT calculations showed that the intermediate [Cp*Fe(η -As )] , which is presumably formed first, undergoes fast dimerization to the dianion [(Cp*Fe) (μ,η -As )] .
The cothermolysis of As and [Cp″Zr(CO)] (Cp″ = η-CHtBu) results in the formation of [Cp″Zr(η-As)] (1) in high yields and the arsenic-rich complex [(Cp″Zr)(Cp″Zr)(μ,η-As)] (2) as a minor product. In contrast to yellow arsenic, 1 is a light-stable, weighable and storable arsenic source for subsequent reactions. The transfer reaction of 1 with [Cp‴Fe(μ-Br)] (Cp‴ = η-CHtBu) yields the unprecedented bond isomeric complexes [(Cp‴Fe)(μ,η-As)] (3a) and [(Cp‴Fe)(μ,η-cyclo-As)] (3b). In contrast, the analogous reaction with the Cp derivative [CpFe(μ-Br)] (Cp = η-C(CH(CH)) leads exclusively to the triple decker complex [(CpFe)(μ,η-As)] (4) possessing the tetraarsabutadiene-type ligand analogous to 3a. To elucidate the stability of the bonding isomers 3a and 3b, DFT calculations were performed. The oxidation of 4 with AgBF affords [(CpFe)(μ,η-As)][BF] (5), which is a product expanded by one arsenic atom, instead of the expected complex [(CpFe)(μ,η-cyclo-As)].
The synthesis of phosphines is based on white phosphorus, which is usually converted to PCl3, to be afterwards substituted step by step in a non-atomic efficient manner. Herein, we describe an alternative efficient transition metal-mediated process to form asymmetrically substituted phosphines directly from white phosphorus (P4). Thereby, P4 is converted to [Cp*Fe(η5-P5)] (1) (Cp* = η5-C5(CH3)5) in which one of the phosphorus atoms is selectively functionalized to the 1,1-diorgano-substituted complex [Cp*Fe(η4-P5R′R″)] (3). In a subsequent step, the phosphine PR′R″R‴ (R′ ≠ R″ ≠ R‴ = alky, aryl) (4) is released by reacting it with a nucleophile R‴M (M = alkali metal) as racemates. The starting material 1 can be regenerated with P4 and can be reused in multiple reaction cycles without isolation of the intermediates, and only the phosphine is distilled off.
The reaction behavior of [Cp2Mo2(CO)4(µ,η2:2-P2)] (1) and [(Cp’’Ta(CO)2(η4 P4)] (2), respectively, towards the anions OH- and tBu- are reported. While the reaction of 1 with KOH gives the anionic complex...
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