Reaktionen des diphosphen-komplexes (CO)5CrPhPPPhCr(CO)5

Cage-size effects on the encapsulation of P2 by fullerenes

The classic pnictogen dichotomy stands for the great contrast between triply bonding very stable N₂ molecules and its heavier congeners, which appear as dimers or oligomers. A banner example involves phosphorus as it occurs in nature as P₄ instead of P₂ , given its weak π-bonds or strong σ-bonds. The P₂ synthetic value has brought Lewis bases and metal coordination stabilization strategies. Herein, we discuss the unrealized encapsulation alternative using the well-known fullerenes' capability to form endohedral and stabilize otherwise unstable molecules. We chose the most stable fullerene structures from C_n (n = 50, 60, 70, 80) and experimentally relevant from C_n (n = 90 and 100) to computationally study the thermodynamics and the geometrical consequences of encapsulating P₂ inside the fullerene cages. Given the size differences between P₂ and P₄ , we show that the fullerenes C₇₀ -C₁₀₀ are suitable cages to side exclude P₄ and host only one molecule of P₂ with an intact triple bond. The thermodynamic analysis indicates that the process is favorable, overcoming the dimerization energy. Additionally, we have evaluated the host-guest interaction to explain the origins of their stability using energy decomposition analysis.

Synthesis of distibiranes and azadistibiranes by cycloaddition reactions of distibenes with diazomethanes and azides

Cycloaddition reactions of distibene [L(Me2N)GaSb]2 (L = HC[C(Me)NDipp]2; Dipp = 2,6-i-Pr2C6H3)[double bond, length as m-dash] with a series of organoazides RN3 (R = Ph, p-CF3Ph, 1-adamantyl (ada)) yielded azadistibiranes [L(Me2N)GaSb]2NR (R = Ph 1, p-CF3Ph 2, ada 3), whereas Me3SiN3 reacted with insertion into one Ga-Sb bond and formation of L(Me2N)GaSbSb(NSiMe3)Ga(NMe2)L (4). Analogous compounds 5 and 6 formed after heating of 1 and 2 above 60 °C. Prolonged heating of 5 resulted in a [2 + 2] cycloaddition accompanied by elimination of LGa(NMe2)2 and formation of tetrastibacyclobutane 7, while the reaction of 5 with a second equivalent of PhN3 gave heteroleptic azadistibirane 9, which isomerized at elevated temperature to distibene 10. Cycloaddition also occurred in reactions of [L(X)GaSb]2 (X = NMe2, OEt, Cl) with Me3Si(H)CN2, yielding distibiranes [L(X)GaSb]2C(H)SiMe3 (X = NMe211, OEt 12, Cl 13). Compounds 1-13 were characterized by IR, UV-Vis and NMR spectroscopy and sc-XRD. The mechanism of the reaction of [L(Me2N)GaSb]2 with PhN3 and Me3SiN3 and the electronic nature of the resulting compounds were studied by DFT calculations.

Molecular 1,1'-bifunctional mixed-valence P-P compounds, enabled through metal complexation

Mixed-valence compounds feature the same atoms but in different formal oxidation states. This research field is largely dominated by metal-based solid-state chemistry and has been intensively studied in recent years. By contrast, the situation is different for molecular main group element compounds and to establish 1,1'-bifunctional groups remained a particular challenge. Here a detailed study on 1,1'-bifunctional mixed-valence main group compounds possessing a P-P bond is presented, and the fundamental role of the metal complex fragments is discussed. Based on the generation of a transient phosphanylidene-phosphinidenoid complex a dinuclear diphosphene complex was obtained possessing an unprecedented ambident reactivity, i.e., 1,2-addition or 1,1-addition products were obtained depending on the nature of the reagent. The 1,1-addition products represent stable hitherto unknown 1,1'-bifunctional phosphanylidene-phosphorane complexes which have been confirmed by X-ray diffraction studies. Detailed state-of-the-art DFT calculations provide insight into bonding and reaction pathways.

Reactivity enhancement of a diphosphene by reversible N-heterocyclic carbene coordination

Diphosphene TerMesP = PTerMes (1; TerMes = 2,6-Mes2C6H3; Mes = 2,4,6-Me3C6H2) and NHCMe42 (NHCMe4 = 1,3,4,5-tetramethylimidazol-2-ylidene) exist in an equilibrium mixture with the NHCMe4 -coordinated diphosphene 3. While uncoordinated 1 is inert to hydrolysis, the NHC adduct 3 readily undergoes hydrolysis to afford a phosphino-substituted phosphine oxide with the liberation of NHCMe4 . On this basis, conditions suitable for the catalytic use of NHCMe4 were identified. Similarly, while the hydrogenation of free diphosphene 1 with H3N·BH3 is very slow, 3 reacts instantaneously with H3N·BH3 at room temperature to afford a dihydrodiphosphane.

Triple-Bond Reactivity of Diphosphorus Molecules

We report a mild method for generating the diphosphorus molecule or its synthetic equivalent in homogeneous solution; the P2 allotrope of the element phosphorus is normally obtained only under extreme conditions (for example, from P4 at 1100 kelvin). Diphosphorus is extruded from a niobium complex designed for this purpose and can be trapped efficiently by two equivalents of an organic diene to produce an organodiphosphorus compound. Diphosphorus stabilized by coordination to tungsten pentacarbonyl can be generated similarly at 25 degrees C, and in this stabilized form it still efficiently consumes two organic diene molecules for every diphosphorus unit.