Unprecedented functionalized products with an η(4)-P5 ring are obtained by the reaction of [Cp*Fe(η(5)-P5)] (1; Cp*=η(5)-C5Me5) with different nucleophiles. With LiCH2SiMe3 and LiNMe2, the monoanionic products [Cp*Fe(η(4)-P5CH2SiMe3)](-) and [Cp*Fe(η(4)-P5NMe2)](-), respectively, are formed. The reaction of 1 with NaNH2 leads to the formation of the trianionic compound [{Cp*Fe(η(4)-P5)}2N](3-), whereas the reaction with LiPH2 yields [Cp*Fe(η(4)-P5PH2)](-) as the main product, with {[Cp*Fe(η(4)-P5)]2PH}(2-) as a byproduct. The calculated energy profile of the reactions provides a rationale for the formation of the different products.
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.
A comparison of P4 activations mediated by low‐valent β‐diketiminato (L) cobalt complexes is presented. The formal Co0 source [K2(L3Co)2(μ2:η1,η1‐N2)] (1) reacts with P4 to form a mixture of the monoanionic complexes [K(thf)6][(L3Co)2(μ2:η4,η4‐P4)] (2) and [K(thf)6][(L3Co)2(μ2:η3,η3‐P3)] (3). The analogue CoI precursor [L3Co(tol)] (4 a), however, selectively yields the corresponding neutral derivative [(L3Co)2(μ2:η4,η4‐P4)] (5 a). Compound 5 a undergoes thermal P atom loss to form the unprecedented complex [(L3Co)2(μ2:η3,η3‐P3)] (6). The products 2 and 3 can be obtained selectively by an one‐electron reduction of their neutral precursors 5 a and 6, respectively. The electrochemical behaviour of 2, 3, 5 a, and 6 is monitored by cyclic voltammetry and their magnetism is examined by SQUID measurements and the Evans method. The initial CoI‐mediated P4 activation is not influenced by applying the structurally different ligands L1 and L2, which is proven by the formation of the isostructural products [(LCo)2(μ2:η4,η4‐P4)] [L=L3 (5 a), L1 (5 b), L2 (5 c)].
The reduction of [Cp'''Ni(η(3) -P3 )] (1; Cp'''=η(5) -1,2,4-tBu3 C5 H2 ) with potassium produces the complex anion [(Cp'''Ni)2 (μ,η(2:2) -P8 )](2-) (2), which contains a realgar-like P8 unit. The anionic triple-decker sandwich complex [(Cp'''Ni)2 (μ,η(3:3) -P3 )](-) (3) with a cyclo-P3 middle deck is obtained when 1 is treated with NaNH2 as a nucleophile. Na[3] can subsequently be oxidized with AgOTf to the neutral triple-decker complex [(Cp'''Ni)2 (μ,η(3:3) -P3 )] (4). In contrast, 1 reacts with LiPPh2 to give the anionic compound [(Cp'''Ni)2 (μ,η(2:2) -P6 PPh2 )](-) (5), a complex containing a bicyclic P7 fragment capped by two Cp'''Ni units. Protonation of Li[5] with HBF4 leads to the neutral complex [(Cp'''Ni)2 (μ,η(2:2) -(HP6 PPh2 )] (6). Adding LiNMe2 to 1 results in [Cp'''Ni(η(2) -P3 NMe2 )](-) (7) becoming accessible, a complex which forms as a result of nucleophilic attack at the cyclo-P3 ring of 1. The complexes K2 [2], Na[3], 4, 6, and Li[7] were fully characterized and their structures determined by single-crystal X-ray diffraction.
. Die berechneten Energieprofile der Reaktionen liefern eine Erklärung für die Bildung der unterschiedlichen Produkte.Ferrocen, der erste metallorganische Sandwichkomplex, der vor über 60 Jahren entdeckt wurde, ist eine erprobte vielseitige und wichtige Verbindung in der Chemie. Während zu Beginn der Ferrocenchemie extensive Reaktivitätsstudien durchgeführt wurden, [1] wird es gegenwärtig breit in der Polymerchemie genutzt, [2] für die asymmetrische Katalyse [3] oder für medizinische Anwendungen.[4] Eine der bemerkenswertesten Reaktionen von Ferrocen ist die mit starken metallorganischen Basen, wie Organolithiumverbindungen, [5,6] die zur Deprotonierung der C 5 H 5 -Einheit und damit zu Mono-und Dilithioferrocenen führt. Dies zeigt, dass das Reaktionsverhalten von Ferrocen gegenüber Nukleophilen durch den C 5 H 5 -Liganden dominiert wird. Das ähnlichste Polyphosphorderivat ist Pentaphosphaferrocen [Cp*Fe(h 5 -P 5 )] (Cp* = h 5 -C 5 Me 5 ) (1). [7] Wir und die Gruppe um Scherer sind an der Reaktivität von 1 interessiert, und es konnte gezeigt werden, dass die cylco-P 5 -Einheit an Übergangsmetall-carbonyle koordinieren kann, wobei Tripeldecker-Komplexe und andere metallorganische Verbindungen mit verzerrten P 5 -Einheiten gebildet werden, [8] und an Kupfer(I)-Halogenide, was zur Entstehung von 1D-und 2D-Polymeren [9] oder sogar sphärischen Fulleren-artigen Superbällen führt.[10] Die [12] Jedoch fehlt in der Chemie von 1 dessen Reaktivität gegenüber Hauptgruppennukleophilen, um seine Reaktivität im Vergleich mit seinem Kohlenstoffanalogon Ferrocen besser zu verstehen. Dichtefunktionaltheoretische Rechnungen an 1 zeigen, dass die LUMO-und LUMO + 1-Orbitale hauptsächlich an den P-Atomen des cyclo-P 5 -Liganden lokalisiert sind, was auch für die positive Ladung gilt.[13] Daher konnte man vermuten, dass der nukleophile Angriff am cyclo-P 5 -Liganden erfolgt. Hier berichten wir erstmals über die Reaktivität von Pentaphosphaferrocen gegenüber Hauptgruppen-Nukleophilen, die zu einer beispiellosen Funktionalisierung des cyclo-P 5 -Liganden führt. Durch diese Ergebnisse wird dieses Molekül zu einem wertvollen Ausgangsstoff in der metallorganisch basierten Hauptgruppenchemie.Das Vermischen einer grünen Lçsung von 1 und
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