Aggregation and Degradation of White Phosphorus Mediated by N‐Heterocyclic Carbene Nickel(0) Complexes

The reaction of zerovalent nickel compounds with white phosphorus (P₄) is a barely explored route to binary nickel phosphide clusters. Here, we show that coordinatively and electronically unsaturated N‐heterocyclic carbene (NHC) nickel(0) complexes afford unusual cluster compounds with P₁, P₃, P₅ and P₈ units. Using [Ni(IMes)₂] [IMes=1,3‐bis(2,4,6‐trimethylphenyl)imidazolin‐2‐ylidene], electron‐deficient Ni₃P₄ and Ni₃P₆ clusters have been isolated, which can be described as superhypercloso and hypercloso clusters according to the Wade–Mingos rules. Use of the bulkier NHC complexes [Ni(IPr)₂] or [(IPr)Ni(η⁶‐toluene)] [IPr=1,3‐bis(2,6‐diisopropylphenyl)imidazolin‐2‐ylidene] affords a closo‐Ni₃P₈ cluster. Inverse‐sandwich complexes [(NHC)₂Ni₂P₅] (NHC=IMes, IPr) with an aromatic cyclo‐P₅^? ligand were identified as additional products.     

Transition-Metal-Mediated Functionalization of White Phosphorus

Recently there has been great interest in the reactivity of transition-metal (TM) centers towards white phosphorus (P₄). This has ultimately been motivated by a desire to find TM-mediated alternatives to the current industrial routes used to transform P₄ into myriad useful P-containing products, which are typically indirect, wasteful, and highly hazardous. Such a TM-mediated process can be divided into two steps: activation of P₄ to generate a polyphosphorus complex TM-P_n, and subsequent functionalization of this complex to release the desired phosphorus-containing product. The former step has by now become well established, allowing the isolation of many different TM-P_n products. In contrast, productive functionalization of these complexes has proven extremely challenging and has been achieved only in a relative handful of cases. In this review we provide a comprehensive summary of successful TM-P_n functionalization reactions, where TM-P_n must be accessible by reaction of a TM precursor with P₄. We hope that this will provide a useful resource for continuing efforts that are working towards this highly challenging goal of modern synthetic chemistry.     

Activation of Small Molecules by Phosphorus Biradicaloids

The reactivity of biradicaloid [P(μ‐NTer)]₂ was employed to activate small molecules bearing single, double, and triple bonds. Addition of chalcogens (O₂, S₈, Se_x and Te_x) led to the formation of dichalcogen‐bridged P₂N₂ heterocycles, except from the reaction with molecular oxygen, which gave a P₂N₂ ring featuring a dicoordinated P^III and a four‐coordinated P^V center. In formal [2πe+2πe] addition reactions, small unsaturated compounds such as ethylene, acetylene, acetone, acetonitrile, tolane, diphenylcarbodiimide, and bis(trimethylsilyl)sulfurdiimide are readily added to the P₂N₂ heterocycle of the biradicaloid [P(μ‐NTer)]₂, yielding novel heteroatom cage compounds. The synthesis, reactivity, and bonding of the biradicaloid [P(μ‐NTer)]₂ were studied in detail as well as the synthesis, properties, and structural features of all addition products.     

Probing the Structure,Dynamics, and Bonding of Coinage Metal Complexes of White Phosphorus

A series of cationic white phosphorus complexes of the coinage metals Au and Cu have been synthesised and characterised both in the solid state and in solution. All complexes feature a P₄ unit coordinated through an edge P?P vector (η²‐like), although the degree of activation (as measured by the coordinated P?P bond length) is greater in the gold species. All of the cations are fluxional on the NMR timescale at room temperature, but in the case of the gold systems fluxionality is frozen out at ?90 °C. Electronic structure calculations suggest that this fluxionality proceeds via an η¹‐coordinated M?P₄ intermediate.     

Activation of Open‐Cage Fullerenes with Ruthenium Carbonyl Clusters

Reactions of the open‐cage fullerene C₆₃NO₂(Py)(Ph)₂ ( 1 ) with [Ru₃(CO)₁₂] produce [Ru₃(CO)₈(μ,η⁵‐C₆₃NO₂(Py)(Ph)₂)] ( 2 ), [Ru₂H(CO)₃(μ,η⁷‐C₆₃N(Py)(Ph)(C₆H₄))] ( 3 ), and [Ru(CO)(Py)₂₍η³‐C₆₃NO₂(Py)(Ph)₂)] ( 4 ), in which the orifice sizes are modified from 12 to 8, 11, and 15‐membered ring, through ruthenium‐mediated C?O and C?C bond activation and formation.     

Direct Synthesis of Phospholyl Lithium from White Phosphorus

The selective construction of P?C bonds directly from P₄ and nucleophiles is an ideal and step‐economical approach to utilizing elemental P₄ for the straightforward synthesis of organophosphorus compounds. In this work, a highly efficient one‐pot reaction between P₄ and 1,4‐dilithio‐1,3‐butadienes was realized, which quantitatively affords phospholyl lithium derivatives. DFT calculations indicate that the mechanism is significantly different from that of the well‐known stepwise cleavage of P?P bond in P₄ activation. Instead, a cooperative nucleophilic attack of two C Li bonds on P₄, leading to simultaneous cleavage of two P?P bonds, is favorable. This mechanistic information offers a new view on the mechanism of P₄ activation, as well as a reasonable explanation for the excellent yields and selectivity. This method could prove to be a useful route to P₄ activation and the subsequent production of organophosphorus compounds.     

Selective Functionalization of P4 by Metal‐Mediated CP Bond Formation

A new and selective one‐step synthesis was developed for the first activation stage of white phosphorus by organic radicals. The reactions of NaCp^R with P₄ in the presence of CuX or FeBr₃ leads to the clean formation of organic substituted P₄ butterfly compounds Cp^R₂P₄ (Cp^R: Cp^BIG=C₅(4‐nBuC₆H₄)₅ ( 1 a ), Cp′′′=C₅H₂tBu₃ ( 1 b ), Cp*=C₅Me₅ ( 1 c ) und Cp^4iPr=C₅HiPr₄ ( 1 d )). The reaction proceeds via the activation of P₄ by Cp^R radicals mediated by transition metals. The newly formed organic derivatives of P₄ have been comprehensively characterized by NMR spectroscopy and X‐ray crystallography.     

Systematic reactions of [Pt(PF3)4

Tetrahedral [Pt(PF(3))(4)] reacts with H(+) to form trigonal bipyramidal [Pt(PF(3))(4)H](+). This in turn looses PF(3) to form square-planar [Pt(PF(3))(3)H](+). The complex [Pt(PF(3))(4)] can be oxidized with AsF(5) to form the square-planar complex, [Pt(PF(3))(4)](2+), which can be more conveniently obtained from PtF(4) and PF(3) in HF/SbF(5) solution. [Pt(PF(3))(4)](2+) reacts with F(-) in HF under cluster formation to [Pt(4)(PF(3))(8)H](+).     

Synthesis and Characterization of Stable Phosphorus Carbabetaines

Phosphorus 1,3‐ and 1,4‐carbabetaines with ′P(+)−C−C(−)′ and ′P(+)−C−C−C(−)′ structures, respectively, in which the carbanion moiety was significantly stabilized by two trifluoromethylsulfonyl groups, have been synthesized and characterized. Analysis of their X‐ray crystal structures revealed that any attractive interactions between the anionic and cationic moieties were negligibly weak. This result was corroborated by using natural bond orbital (NBO) and Bader′s quantum theory of atoms in molecules (QTAIM) models. In contrast, performing the same analysis of a known 1,3‐carbabetaine equivalent, which can be drawn as a ′P(+)−C−C=C−O(−)′ resonance structure, revealed pronounced charge‐transfer interactions between the anionic and cationic moieties.