Bonding in Phosphanylphosphinidene Complexes of Transition Metals and their Correlation with Structures, 31 P NMR Spectra, and Reactivities

A Carbene‐Stabilized Boryl‐Phosphinidene

Herein, the synthesis and characterization of the carbene‐stabilized boryl phosphinidenes 1–3 are reported. Compounds 1–3 are obtained by reacting Me‐cAAC=PK (Me₂‐cAAC=dimethyl cyclic(alkyl)(amino)carbene) and dihaloaryl borane in toluene. All three compounds were characterized by X‐ray crystallography. Quantum mechanical studies indicated that these compounds have two lone pairs on the P center viz., an σ‐type lone pair and a “hidden” π‐type lone pair. Hence, these compounds can act as double Lewis bases, and the basicity of the π‐type lone pair is higher than the σ‐type lone pair.

Palladium(II) complexes of bis(diphosphene) with different coordination behaviors

Organophosphorus compounds possessing a P-P double-bond character are intriguing materials in coordination chemistry because it is possible to form a variety of coordination modes from the π-bond in addition to the lone pairs. We report herein the complexation of a new bidentate ligand, ethylene-tethered bis(binaphthyldiphosphene) (S,S)-2, with palladium(II) species. The reaction of (S,S)-2 with [Pd(π-allyl)(cod)](SbF₆) and PdCl₂(cod) afforded η¹/η¹-bis(diphosphene) complex 7 and η¹-diphosphene/η²-phosphanylphosphide complex 8, respectively. The latter was characterized by a chloride migration from the palladium atom to a phosphorus atom due to the high electron-accepting character of the PP moiety. Theoretical calculations revealed the migration process and nature of complex 8.

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.

Synthesis and versatile reactivity of scandium phosphinophosphinidene complexes

M=E/M≡E multiple bonds (M = transition metal, E = main group element) are of significant fundamental scientific importance and have widespread applications. Expanding the ranges of M and E represents grand challenges for synthetic chemists and will bring new horizons for the chemistry. There have been reports of M=E/M≡E multiple bonds for the majority of the transition metals, and even some actinide metals. In stark contrast, as the largest subgroup in the periodic table, rare-earth metals (Ln) were scarcely involved in Ln=E/Ln≡E multiple bonds. Until recently, there were a few examples of rare-earth monometallic alkylidene, imido and oxo complexes, featuring Ln=C/N/O bonds. What are in absence are rare-earth monometallic phosphinidene complexes with Ln=P bonds. Herein, we report synthesis and structure of rare-earth monometallic phosphinidene complexes, namely scandium phosphinophosphinidene complexes. Reactivity of scandium phosphinophosphinidene complexes is also mapped out, and appears to be easily tuned by the supporting ligand.

The Reactivity of Phosphanylphosphinidene Complexes of Transition Metals Toward Terminal Dihaloalkanes

The reactivities of phosphanylphosphinidene complexes [(DippN)₂W(Cl)(η²-P–PtBu₂)]⁻ (1), [(pTol₃P)₂Pt(η²-P=PtBu₂)] (2), and [(dppe)Pt(η²-P=PtBu₂)] (3) toward dihaloalkanes and methyl iodide were investigated. The reactions of the anionic tungsten complex (1) with stochiometric Br(CH₂)_nBr (n = 3, 4, 6) led to the formation of neutral complexes with a tBu₂PP(CH₂)₃Br ligand or neutral dinuclear complexes with unusual tetradentate tBu₂PP(CH₂)_nPPtBu₂ ligands (n = 4, 6). The methylation of platinum complexes 2 and 3 with MeI yielded neutral or cationic complexes bearing side-on coordinated tBu₂P–P-Me moieties. The reaction of 2 with I(CH₂)₂I gave a platinum complex with a tBu₂P—P—I ligand. When the same dihaloalkane was reacted with 3, the P—P bond in the phosphanylphosphinidene ligand was cleaved to yield tBu₂PI, phosphorus polymers, [(dppe)PtI₂] and C₂H₄. Furthermore, the reaction of 3 with Br(CH₂)₂Br yielded dinuclear complex bearing a tetraphosphorus tBu₂PPPPtBu₂ ligand in the coordination sphere of the platinum. The molecular structures of the isolated products were established in the solid state and in solution by single-crystal X-ray diffraction and NMR spectroscopy. DFT studies indicated that the polyphosphorus ligands in the obtained complexes possess structures similar to free phosphenium cations tBu₂P⁺=P−R (R = Me, I) or (tBu₂P⁺=P)₂.

The phosphanylphosphinidene complexes of tungsten and platinum as building blocks for syntheses of polydentate phosphorus ligands.

Diphosphination of CO2 and CS2 mediated by frustrated Lewis pairs – catalytic route to phosphanyl derivatives of formic and dithioformic acid

The first example of CO₂ diphosphination is described.

The new diphosphanylphosphido complexes of tungsten(vi) and molybdenum(vi). Their synthesis, structures and properties

We report on the reactivity of R2P-P(Li)-PR'2 (R = tBu, iPr, R' = NEt2, iPr) towards diimido complexes [(dippN)2MCl2·dme] (M = Mo, W and dipp = 2,6-iPr2C6H3). A series of new complexes with diphosphanylphosphido ligands R2P-P-PR'2 were isolated. The solid-state structures of [(dippN)2M(Cl)(1,2-η-iPr2P-P-PiPr2)] (2Mo and 2W) and [(dippN)2M(Cl){1,2-η-tBu2P-P-P(NEt2)2}] (3Mo and 3W) were established by single-crystal X-ray diffraction analysis and indicate a side-on geometry of the R2P-P-PR'2 moiety. 3W and 3Mo are the first triphosphorus complexes with the amido ligand NEt2 on the P atom. [(dippN)2M(Cl)(1,2-η-tBu2P-P-PtBu2)] (1Mo and 1W) and 3Mo and 3W display similar side-on geometry in solution and in the solid state. By contrast, 2Mo and 2W reveal a dynamic behavior in solution. For the first time, the reactivity of diphosphanylphosphido complexes towards different nucleophiles was studied. The complexes react with the phosphorus nucleophile Ph2PLi, yielding phosphanylphosphinidene complexes [(dippN)2M(Cl)(η2-P-PR2)]- Li+ (M = Mo, W) together with related diphosphanes R'2P-PPh2. Carbon nucleophile MeLi does not yield [(dippN)2M(Cl)(η2-P-PR2)]- Li+ but substitutes a Cl ligand at the metal center. Moreover, we compare the coordination of the R2P-P-PR'2 moiety to different metal centers based on DFT methods.