Comparison of Two Phosphinidenes Binding to Silicon(IV)dichloride as well as to Silylene

Synthesis and Reactivity of the [NCCCO]- Cyanoketenate Anion

Cyanoketene is a fundamental molecule that is actively being searched for in the interstellar medium. Its deprotonated form (cyanoketenate) is a heterocumulene that is isoelectronic to carbon suboxide whose structure has been the subject of debate. However, the investigation of cyanoketene and its derivatives is hampered by the lack of practical synthetic routes to these compounds. We report the first synthesis of the cyanoketenate anion in [K(18-crown-6)][NCCCO] (1) as a stable molecule on a multigram scale in excellent yields (>90 %). The structure of this molecule is probed crystallographically and computationally. We also explore the protonation of 1, and its reaction with triphenylsilylchloride and carbon dioxide. In all cases, anionic dimers are formed. The cyanoketene could be synthesized and crystallographically characterized when stabilized by a N-heterocyclic carbene. The cyanoketenate is a very useful unsaturated building block containing N, C and O atoms that can now be explored with relative ease and will undoubtedly unlock more interesting reactivity.

Bicyclic (alkyl)(amino)carbene (BICAAC)-supported phosphinidenes

Herein, the synthesis and characterization of bicyclic (alkyl)(amino)carbene (BICAAC)-stabilized phosphinidenes (1-4) are reported. Compounds 1-3 were obtained by reacting trihalophosphine [PX3, X = Cl (1), Br (2), I (3)] with BICAAC in THF. A BICAAC-stabilized bis-phosphinidene (4) was obtained from the reduction of compound 2. All four compounds were characterized by X-ray crystallography and heteronuclear NMR spectroscopy. Theoretical calculations indicated the predominant C(carbene)P double bond characteristic in compounds 1-4.

Isolation of (Aryl)-(Imino) Phosphide and (Aryl)-(Phosphaalkene) Amide Complexes of Alkali Metals from Carbene-Phosphinidenes under Reductive-Thermal Rearrangements

Two-electron reduction of cyclic alkyl(amino) carbene (cAAC)-supported chloro-phosphinidene cAAC=P-Cl (1) followed by unprecedented thermal rearrangements afforded the alkali metal complexes of (aryl)-(cyclic alkyl(imino)) phosphides 3 a-3 c, 4 a-4 b through migration of the 2,6-diisopropylphenyl (dipp) group from N to the P centre, and the (aryl)-(cyclic alkyl(phosphaalkene)) amide 5 through cleavage of the CMe2 -N bond followed by energetically favoured 5-exo-tet ring-closure in the presence of the alkali metals Cs (3 a-3 c), K (4 a, 4 b), and Li (5). Compound 3 a was found to be photoluminescent (PL), emitting bright orange light under a laboratory UV lamp of wavelength 365 nm with PL quantum yield (ϕPL ) of 2.6 % (λem =600 nm), and an average lifetime (τ) of 4.8 μs. Reaction of 3 a with CuCl and AgOTf afforded (aryl)-(cyclic alkyl(imino)) phosphide-stabilized tetra-nuclear CuI (6), and octa-nuclear AgI (7) clusters, respectively. Moreover, complexes 3 a-3 c provided a direct route for the stabilization of cyclic alkyl(aminoboryl) phosphaalkenes 8 a-8 c when treated with 1-bromo-N,N,N',N'-tetraisopropylboranediamine.

Strain-Driven, Non-Catalysed Ring Expansion of Silicon Heterocycles

Silacycles are ubiquitous building blocks. Small silacycles can typically be expanded catalytically. A silirane, silirene and phosphasilirene as well as a siletane and a silolene were prepared starting from the base-free bromosilylene [(dtbp Cbz)SiBr] (dtbp Cbz=1,8-bis(3,5-ditertbutylphenyl)-3,6-ditertbutylcarbazolyl). As these heterocycles were derived from a dicoordinated silylene, they are susceptible to reactions with an external base. The three-membered silacycles readily undergo non-catalysed ring expansion reactions with isonitriles yielding the related four-membered silacycles. Surprisingly, the ring-expanded derivatives of the silirane undergo up to two further isomerisation reactions, first by enamine formation and then by another ring expansion. DFT computations were utilised to gauge the scope of this reactivity pattern. Three-membered silacycles should essentially universally undergo a ring expansion with isonitriles, while for four-membered silacycles, only very few instances are predicted to accommodate more challenging kinetic requirements of this ring expansion. Larger silacycles lack the ring strain energy required for this ring expansion reaction and are not expected to be expanded.

Octalithium, Tetrasodium, and Decalithium Compounds Based on Pyrrolyl Ligands: Synthesis, Structures, and Activation of the C-H Bonds of Pyrrolyl Rings and C═N Bonds of a Series of Ligands by Organolithium Reagents

The organometallic compounds of lithium ions have garnered continuous interest as indispensable precursors for the syntheses of organometallic complexes of main-group metals, transition metals, lanthanide metals, and actinide metals. In this work, we present a strategy for the preparation of a series of polynuclear lithium complexes. This methodology features the utilization of organolithium reagents both as metal sources to coordinate with the ligands and as nucleophilic reagents to undergo nucleophilic addition to the C═N bonds of the ligands. Reaction of a ligand HL1 [HL1 = 2-(((1-(2-(dimethylamino)ethyl)-1H-pyrrol-2-yl)methylene)amino)phenol] with n-BuLi produced complex [Li8(L1a)4]·1.5Tol (1·1.5Tol) [H2L1a = 2-((1-(1-(2-(dimethylamino)ethyl)-1H-pyrrol-2-yl)pentyl)amino)phenol]. One prominent feature regarding the formation of 1·1.5Tol is the occurrence of nucleophilic addition of n-BuLi to the C═N bond of HL1, leading to the generation of a new [L1a]2- ligand that contains both aminophenol and 1-(2-pyrrolyl)alkylamine scaffolds. The developed protocol can be adapted to a series of organolithium reagents. Compounds [Li8(L1b)4] (2) and [Li8(L1c)4] (3) were afforded by treatment of HL1 with sec-BuLi and LiCH2SiMe3, respectively. Reaction of an analogous ligand HL2 [HL2 = 2-(((1-(2-(dimethylamino)ethyl)-1H-pyrrol-2-yl)methylene)amino)-4-methylphenol] with n-BuLi generated compound [Li8(L2a)4] (4). C═N bond activation was not observed in the reaction of HL1 with NaOtBu, and the complex [Na4(L1)4]·Tol (5·Tol) was obtained. A decanuclear complex [Li10(L3a)2(L3b)2] (6) was also prepared via the reaction of HL3 [HL3 = 2-(2-((((1H-pyrrol-2-yl)methylene)amino)methyl)-1H-pyrrol-1-yl)-N,N-dimethylethan-1-amine] with t-BuLi. A remarkable feature in terms of the synthesis of 6 is the simultaneous occurrence of hydrogen atom abstraction from the C-H bond of the pyrrolyl ring and nucleophilic addition to the C═N bond of the HL3 ligand by t-BuLi. A series of amines containing biologically and physiologically important moieties were achieved by hydrolysis of the crude products from the reactions of the HL1-HL3 ligands and organolithium reagents. This work provides an efficient approach to high-nuclearity lithium compounds as well as a series of amines.

Highly Reactive Hydrocarbon Soluble Alkylsodium Reagents for Benzylic Aroylation of Toluenes using Weinreb Amides

Deaggregating the alkyl sodium NaCH₂ SiMe₃ with polydentate nitrogen ligands enables the preparation and characterisation of new, hydrocarbon soluble chelated alkylsodium reagents. Equipped with significantly enhanced metalating power over their organolithium counterparts, these systems can promote controlled sodiation of weakly acidic benzylic C-H bonds from a series of toluene derivatives under mild stoichiometric conditions. This has been demonstrated through the benzylic aroylation of toluenes with Weinreb amides, that delivers a wide range of 2-arylacetophenones in good to excellent yields. Success in isolating and determining the structures of key organometallic intermediates has provided useful mechanistic insight into these new sodium-mediated transformations.

Carbene-Anchored Boryl- and Stibanyl-Phosphaalkenes as Precursors for Bis-Phosphaalkenyl Dichlorogermane and Mixed-Valence AgI/AgII Phosphinidenide

Cyclic alkyl(amino) carbene (cAAC)-anchored boryl- and stibanyl-phosphaalkenes with general formula cAAC = P-ER₂ [E = B, R = (NⁱPr₂)₂ (3a-c); E = Sb, R = 2,4,6-triisopropylphenyl (5a-b)] have been synthesized and utilized as precursors for the bis-phosphaalkenyl dichlorogermane [(cAAC = P)₂GeCl₂] (6) and the first molecular example of a neutral polymeric mixed-valence Ag^I/Ag^II phosphinidenide complex [(cAACP)₂Ag₄^IAg^IICl₄]_n (7). All compounds have been characterized by single-crystal X-ray diffraction and further investigated by nuclear magnetic resonance (NMR), mass spectrometric analysis, and UV-vis/fluorescence measurements. The paramagnetic complex 7 has been characterized by ESR spectroscopy. Cyclic voltammetry studies of compounds 3/5 have suggested possible one-electron quasi-reversible reductions, indicating their redox noninnocent behavior in solution. Quantum chemical studies revealed the electron-sharing nature of the P-B and P-Sb σ bonds in compounds 3 and 5, and the polar C_cAAC = P bonds in compounds 3, 5, and 6 prevailing their phosphaalkene structures over phosphinidenes.

Insight into fragmentation of a phosphirane to form phosphinidene complexes: an illustration with the 1-phenylselenylphosphirane W(CO)5 complex

Density functional theory (DFT) calculations with 1-phenylselenylphosphirane complex 1 provide an insight into phosphirane fragmentation to phosphinidene complexes. FMO and ELF analyses show that the cleavage of two P-C σ bonds of phosphirane proceeds via an asynchronous concerted pathway. Transient [PhSeP-W(CO)₅] was generated by dissociation of 1 at 90 °C and trapped with different reagents. The 1-phenoxylphosphirane complex undergoes [1 + 2] retroaddition at a comparatively higher temperature which implies that the lone pair of the adjacent atom center of phosphorus plays a major role in phosphirane fragmentation.

Base-stabilized formally zero-valent mono and diatomic molecular main-group compounds

Various compounds are known for transition metals in their formal zero-oxidation state, while similar compounds of main-group elements are recently realized and limited to only a few examples. Lewis-base-stabilized mono and diatomic molecular species (B₂, C, C₂, Si, Si₂, Ge, Ge₂, Sn, P₂, As₂, Sb₂) represent groundbreaking examples of main-group compounds with formally zero-oxidation state. In recent years, the isolation of low-valent main-group compounds has attracted increasing attention of both experimental and theoretical chemists. This is not only due to their fascinating electronic structures and exceptional reactivities, but also their use as valuable precursors for the synthesis of exotic yet important chemical species. This has led to a better understanding of the intricate balance of the donor-acceptor properties of the ligand(s) used to stabilize elements in a formally zero-oxidation state. Owing to the unusual oxidation state of the central element, many compounds containing formally zero-valent elements can efficiently activate otherwise inert small molecules. This review describes the synthesis, characterization, and reactivity of reported mono and diatomic formal zero-oxidation state main-group compounds. This review also emphasizes the comparative description of systems where different ligands are used to stabilize an element in its formal zero-oxidation state.

Facile Synthesis of the Dicyanophosphide Anion via Electrochemical Activation of White Phosphorus: An Avenue to Organophosphorus Compounds

Organophosphorus compounds (OPCs) have gained tremendous interest in the past decades due to their wide applications ranging from synthetic chemistry to materials and biological sciences. We describe herein a practical and versatile approach for the transformation of white phosphorus (P₄) into useful OPCs with high P atom economy via a key bridging anion [P(CN)₂]^-. This anion can be prepared on a gram scale directly from P₄ through an electrochemical process. A variety of OPCs involving phosphinidenes, cyclophosphanes, and phospholides have been made readily accessible from P₄ in a two-step manner. Our approach has a significant impact on the future preparation of OPCs in laboratory and industrial settings.

Recent advances in the domain of Cyclic (alkyl)(amino) carbenes

Isolation of cyclic (alkyl) amino carbenes (cAACs) in 2005 has been a major achievement in the field of stable carbenes due to their better electronic properties. cAACs and bicyclic(alkyl)(amino)carbene (BicAAC) in essence are the most electrophilic as well as nucleophilic carbenes are known till date. Due to their excellent electronic properties in terms of nucleophilic and electrophilic character, cAACs have been utilized in different areas of chemistry, including stabilization of low valent main group and transition metal species, activation of small molecules, and catalysis. The applications of cAACs in catalysis have opened up new avenues of research in the field of cAAC chemistry. This review summarizes the major results of cAAC chemistry published until August 2021.

Synthesis and Characterization of Super Bulky β-Diketiminato Group 1 Metal Complexes

Sterically bulky β-diketiminate (or Nacnac) ligand systems have recently shown the ability to kinetically stabilize highly reactive low-oxidation state main group complexes. Metal halide precursors to such systems can be formed via salt metathesis reactions involving alkali metal complexes of these large ligand frameworks. Herein, we report the synthesis and characterization of lithium and potassium complexes of the super bulky anionic β-diketiminate ligands, known [TCHPNacnac]− and new [TCHP/DipNacnac]− (ArNacnac = [(ArNCMe)2CH]−) (Ar = 2,4,6-tricyclohexylphenyl (TCHP) or 2,6-diisopropylphenyl (Dip)). The reaction of the proteo-ligands, ArNacnacH, with nBuLi give the lithium etherate compounds, [(TCHPNacnac)Li(OEt2)] and [(TCHP/DipNacnac)Li(OEt2)], which were isolated and characterized by multinuclear NMR spectroscopy and X-ray crystallography. The unsolvated potassium salts, [{K(TCHPNacnac)}2] and [{K(TCHP/DipNacnac)}∞], were also synthesized and characterized in solution by NMR spectroscopy. In the solid state, these highly reactive potassium complexes exhibit differing alkali metal coordination modes, depending on the ligand involved. These group 1 complexes have potential as reagents for the transfer of the bulky ligand fragments to metal halides, and for the subsequent stabilization of low-oxidation state metal complexes.

Directed Design of a AuI Complex with a Reduced Mesoionic Carbene Radical Ligand: Insights from 1,2,3-Triazolylidene Selenium Adducts and Extensive Electrochemical Investigations

Carbene-based radicals are important for both fundamental and applied chemical research. Herein, extensive electrochemical investigations of nine different 1,2,3-triazolylidene selenium adducts are reported. It is found that the half-wave potentials of the first reduction of the selones correlate with their calculated LUMO levels and the LUMO levels of the corresponding triazolylidene-based mesoionic carbenes (MICs). Furthermore, unexpected quasi-reversibility of the reduction of two triazoline selones, exhibiting comparable reduction potentials, was discovered. Through UV/Vis/NIR and EPR spectroelectrochemical investigations supported by DFT calculations, the radical anion was unambiguously assigned to be triazoline centered. This electrochemical behavior was transferred to a triazolylidene-type MIC-gold phenyl complex resulting in a MIC-radical coordinated AuI species. Apart from UV-Vis-NIR and EPR spectroelectrochemical investigations of the reduction, the reduced gold-coordinated MIC radical complex was also formed in situ in the bulk through chemical reduction. This is the first report of a monodentate triazolylidene-based MIC ligand that can be reduced to its anion radical in a metal complex. The results presented here provide design principles for stabilizing radicals based on MICs.

Bonding and stability of donor ligand-supported heavier analogues of cyanogen halides (L')PSi(X)(L)

Fluoro- and chloro-phosphasilynes [X-Si[triple bond, length as m-dash]P (X = F, Cl)] belong to a class of illusive chemical species which are expected to have Si[triple bond, length as m-dash]P multiple bonds. Theoretical investigations of the bonding and stability of the corresponding Lewis base-stabilized species (L')PSi(X)(L) [L' = cAACMe (cyclic alkyl(amino) carbene); L = cAACMe, NHCMe (N-heterocyclic carbene), PMe3, aAAC (acyclic alkyl(amino) carbene); X = Cl, F] have been studied using the energy decomposition analysis-natural orbitals for chemical valence (EDA-NOCV) method. The variation of the ligands (L) on the Si-atom leads to different bonding scenarios depending on their σ-donation and π-back acceptance properties. The ligands with higher lying HOMOs prefer profoundly different bonding scenarios than the ligands with lower lying HOMOs. The type of halogen (Cl or F) on the Si-atom was also found to have a significant influence on the overall bonding scenario. The reasonably higher value and endergonic nature of the dissociation energies along with the appreciable HOMO-LUMO energy gap may corroborate to the synthetic viability of the homo and heteroleptic ligand-stabilized elusive PSi(Cl/F) species in the laboratory.

Synthesis and Reactivity of Heteroleptic Ga-P-C Allyl Cation Analogues

Oxidative addition of cyclic alkyl(amino)carbene-coordinated phosphinidenes (Me cAAC)PX to LGa affords gallium-coordinated phosphinidenes LGa(X)-P(Me cAAC) (L=HC[C(Me)N(2,6-i-Pr2 C6 H3 )]2 ; X=Cl 1, Br 2), which react with NaBArF 4 and LiAl(ORF )4 to [LGaP(Me cAAC)][An] (An=B(C6 H3 (CF3 )2 )4 3, B(C6 F5 )4 4, Al(OC(CF3 )3 )4 5). The cations in 3-5 show substantial Ga-P double bond character and represent heteronuclear analogues of allyl cations according to quantum chemical calculations. The reaction of 4 with 4-dimethylaminopyridine (dmap) to adduct 6 confirms the strong electrophilic nature of the gallium center, whereas 5 reacts with ethyl isocyanate with C-C bond formation to the γ-C atom of the β-diketiminate ligand and formation of compound 7.

Synthesis and Coordination Behavior of a New Hybrid Bidentate Ligand with Phosphine and Silylene Donors

This work describes the synthesis and coordination behavior of a new mixed-donor ligand PhC(NtBu)2 SiC6 H4 PPh2 (1) containing both silylene and phosphine donor sites. Ligand 1 was synthesized from a reaction of ortho-lithiated diphenylphosphinobenzene (LiC6 H4 PPh2 ) with chlorosilylene (PhC(NtBu)2 SiCl). Treatment of 1 with Se and GeCl2 resulted in SiIV compounds 2 and 3 by selective oxidation of the silylene donor. This strong σ-donor ligand induces dissociation of CuCl and PhBCl2 leading to formation of ionic complexes 4 and 5 respectively. The reaction of 1 with ZnCl2 and AlCl3 resulted in the formation of chelate complexes 5 and 7, respectively, while treatment with EtAlCl2 and GaCl3 forms monodentate complexes 8 and 9. X-ray analysis of 4 showed that the copper is in the spiro center of the two five-membered rings. Moreover, the copper(I)chloride has not been oxidized but dissociates to Cu+ and [CuCl2 ]- . All the compounds are well characterized by mass spectrometry, elemental analysis, NMR spectroscopy, and single-crystal X-ray diffraction studies.

Solid-State Isolation of Cyclic Alkyl(Amino) Carbene (cAAC)-Supported Structurally Diverse Alkali Metal-Phosphinidenides

Cyclic alkyl(amino) carbene (cAAC)-supported, structurally diverse alkali metal-phosphinidenides 2-5 of general formula ((cAAC)P-M)_n (THF)_x [2: M=K, n=2, x=4; 3: M=K, n=6, x=2; 4: M=K, n=4, x=4; 5: M=Na, n=3, x=1] have been synthesized by the reduction of cAAC-stabilized chloro-phosphinidene cAAC=P-Cl (1) utilizing metallic K or KC₈ and Na-naphthalenide as reducing agents. Complexes 2-5 have been structurally characterized in solid state by NMR studies and single crystal X-ray diffraction. The proposed mechanism for the electron transfer process has been well-supported by cyclic voltammetry (CV) studies and Density Functional Theory (DFT) calculations. The solid state oligomerization process has been observed to be largely dependent on the ionic radii of alkali metal ions, steric bulk of cAAC ligands and solvation/de-solvation/recombination of the dimeric unit [(cAAC)P-M(THF)_x ]₂ .

The chemistry of phosphirane-substituted phosphinidene complexes

Thermolysis of the 1,1'-biphosphirane pentacarbonylmetal complex offers access to 3,4-dihydro-1,2-diphosphete and diphosphorus (P2) intermediates. A control reaction proves that this step-wise reaction is initiated by the dissociation of a W(CO)5 group. DFT calculations predict that further transformations proceed via a transient phosphiranylphosphinidene complex. The formation of the 3,4-dihydro-1,2-diphosphete derivative is thermodynamically favored, while a kinetic process provides the diphosphorus (P2) complex.

1,2-Diaza-4-phospholide complexes of chromium(ii): dipotassium organochromates behaving as single-molecule magnets

The 1,2-diaza-4-phospholide (dp^-) dipotassium ate complexes of chromium(ii) {[(η¹-N-3,5-tBu₂dp)₄Cr][(η⁵-(N,N,C,C,P))₂-K(η¹-O-THF)₂]₂} (5) and {[(η¹-N-3,5-Ph₂dp)₄Cr][(η⁵-(N,N,C,C,P))₂-K(η¹-O-THF)₂]₂}_∞ (6) were synthesized and characterized by X-ray single crystal structure analysis. Complex 5 with a near-square planar geometry at the chromium(ii) ion was unambiguously characterized by the high field electron paramagnetic resonance (HF-EPR) technique and magnetic measurements, revealing that it is a field-induced single-molecule magnet (SMM).

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.

Low-Valent Group 14 Phosphinidenide Complexes [({SIDipp}P)2 M] Exhibit P-M pπ-pπ Interaction (M=Ge, Sn, Pb)

Herein, the synthesis of new low-valent Group 14 phosphinidenide complexes [({SIDipp}P)2 M] exhibiting P-M pπ-pπ interactions (SIDipp=1,3-bis(2,6-diisopropylphenyl)-imidazolidin-2-ylidene, M=Ge, Sn, Pb), is presented. These compounds were investigated by means of structural, spectroscopic, and quantum-chemical methods. Furthermore, the monosubstituted compounds [(SIDippP)MX]2 (M=Sn, X=Cl; M=Pb, X=Br) are presented, which show dimeric structures instead of multiple bonding interaction.

Transition-Metal-Like Reversible Cycloadditions of [tBuSP-W(CO)5 ] with Alkenes and Alkynes

tert-Butylthiophosphinidene complex [tBuSP-W(CO)₅ ] was generated by dissociation of 1-(tert-butylthio)phosphirane-W(CO)₅ complex under mild conditions. The formation of transient [tBuSP-W(CO)₅ ] was indicated by trapping reactions with 2,3-dimethyl-1,3-butadiene, alkynes, phenanthrene-9,10-dione, and methanol. The LUMO of [MeSP-W(CO)₅ ] is significantly lower in energy than those of [Me₂ NP-W(CO)₅ ], [MeOP-W(CO)₅ ], and [Me₂ PP-W(CO)₅ ]. The HOMO of [MeSP-W(CO)₅ ] contains a significant contribution from the in-plane lone pair of P and the LUMO shows a typical π* characteristic. Since stabilized by sulfur lone pair and coordinated by W(CO)₅ , [tBuSP-W(CO)₅ ] undergoes facile and reversible cycloadditions with alkenes and alkynes.

Treatment of Silylene-Phosphinidene with Chalcogens Resulted Exclusively in the Formation of Silicon-Bonded Chalcogens

Chalcogen-bonded silicon phosphinidenes LSi(E)-P-Me cAAC (E=S (1); Se (2); Te (3); L=PhC(NtBu)2 ; Me cAAC=C(CH2 )(CMe2 )2 N-2,6-iPr2 C6 H3 )) were synthesized from the reactions of silylene-phosphinidene LSi-P-Me cAAC (A) with elemental chalcogens. All the compounds reported herein have been characterized by multinuclear NMR, elemental analyses, LIFDI-MS, and single-crystal X-ray diffraction techniques. Furthermore, the regeneration of silylene-phosphinidene (A) was achieved from the reactions of 2-3 with L'Al (L'=HC{(CMe)(2,6-iPr2 C6 H3 N)}2 ). Theoretical studies on chalcogen-bonded silicon phosphinidenes indicate that the Si-E (E=S, Se, Te) bond can be best represented as charge-separated electron-sharing σ-bonding interaction between [LSi-P-Me cAAC]+ and E- . The partial double-bond character of Si-E is attributed to significant hyperconjugative donation from the lone pair on E- to the Si-N and Si-P σ*-molecular orbitals.

In situ synthesis of BiOCl nanosheets on three-dimensional hierarchical structures for efficient photocatalysis under visible light

Assembling two-dimensional (2D) nanomaterials into three-dimensional (3D) hierarchical structures with novel functions is challenging and has attracted considerable attention. However, it is quite difficult to obtain complex 3D architectures of 2D materials with a uniform and intact structure using traditional methods, such as hydrothermal/solvothermal methods and direct precipitation methods. Here, we use butterfly wing scales as bio-templates to prepare 3D hierarchical BiOCl/Au wing scales for plasmonic photocatalysis. The as-prepared materials exhibit excellent photodegradation of rhodamine B (RhB) under visible light. The degradation rates of BiOCl microspheres and BiOCl and BiOCl/Au butterfly wing scales are 48.8%, 72.6%, and 93.8%, respectively, within 20-min illumination at the same loading capacities. This excellent performance of BiOCl/Au is attributed to the coupling of enhanced carrier separation efficiency and the effect of localized surface plasmon resonance (LSPR) aroused by 3D metallic structures. This study provides a relatively facile method to obtain complex 3D constructure of 2D materials. It also demonstrates a nature-led route to prepare highly efficient plasmonic photocatalysts.

Isolation of base stabilized fluoroborylene and its radical cation

Herein, we report the synthesis and characterization of the metal free low valent fluoroborylene [(Me-cAAC)₂BF] (1) stabilized by cyclic (alkyl)(amino) carbene (cAAC). The fluoroborylene 1 is obtained by the reductive defluorination of Me-cAAC:BF₃ with 2.0 equivalents of KC₈ in the presence of 1.0 equivalent of Me-cAAC. Due to its highly electron rich nature, 1 underwent one-electron oxidation with 1.0 equivalent of lithium tetrakis(pentafluorophenyl)borate [LiB(C₆F₅)₄] to form the radical cation [(Me-cAAC)₂BF]˙⁺[B(C₆F₅)₄]^- (2). DFT studies suggested that the lone pair of electrons is localized on the boron atom in 1, which explains its unprecedented reactivity. Both compounds 1 and 2 were characterized by X-ray crystallography. The radical cation 2 was studied by EPR spectroscopy.

Synthesis of cAAC stabilized biradical of "Me2Si" and "Me2SiCl" monoradical from Me2SiCl2 - an important feedstock material

The cyclic alkyl(amino) carbene (cAAC) coordinated biradical of dimethylsilicon was isolated as (cAAC)2Me2Si (1), (cAAC = C(CH2)(CMe2)2N-2,6-i-Pr2C6H3), synthesized from the reduction of Me2SiCl2 using two equivalents of KC8 in the presence of two equivalents of cAAC. The reduction of Me2SiCl2 by one equivalent of KC8 in the presence of one equivalent of cAAC resulted in the stable dimethylsiliconchloride monoradical (cAAC)Me2SiCl (2).

Stable cyclic (alkyl)(amino)carbene (cAAC) radicals with main group substituents

Recent attempts to isolate cyclic (alkyl)(amino)carbene stabilized radicals of p-block elements have been described here.

Isolation and characterization of stable radicals has been a long-pursued quest. While there has been some progress in this field particularly with respect to carbon, radicals involving heavier p-block elements are still considerably sparse. In this review we describe our recent successful efforts on the isolation of stable p-block element radicals particularly those involving aluminum, silicon, and phosphorus.

Synthesis of Cyclic Alkyl(amino) Carbene Stabilized Silylenes with Small N-Donating Substituents

Lewis base cAACs stabilized monomeric silylenes with halogen or methyl substituents at the silicon center have not been reported due to the strong σ-donor and π-acceptor character of cAAC. To prepare these monomeric silylenes, we used the silicon(IV) precursors 5 and 6 with a nitrogen donor group L (L=o-C₆ H₄ NMe₂ ). The cAAC-stabilized (cAAC=C(CH₂ )(CMe₂ )₂ N-Ar, Ar=2,6-iPr₂ C₆ H₃ ) silylenes LSiCl(cAAC) (7) and LSiMe(cAAC) (8) were synthesized by reduction of LSiCl₃ and LSiMeCl₂ with two equivalents of KC₈ in the presence of one equivalent of cAAC, respectively. Compounds 7 and 8 were characterized by single-crystal X-ray crystallography, NMR spectroscopy, and elemental analysis. Compounds 7 and 8 are stable in the solid state as well as in solution at room temperature for at least four months under inert conditions.

Oxidation of a phosphinidene oxide: formation of a dioxaphosphirane oxide with oxygen scrambling

The oxidation of a prototypical phosphinidene oxide FP[double bond, length as m-dash]O has been studied in O2-doped Ar and N2 matrices at 10 K. Upon 266 nm laser irradiation, FP[double bond, length as m-dash]O combines with O2 and yields the cyclic peroxide, dioxaphosphirane oxide FP([double bond, length as m-dash]O)(O2). Unexpected oxygen scrambling occurs during the oxygenation as evidenced by the observation of a 1 : 2 mixture of FP([double bond, length as m-dash]16O)(18O18O) and FP([double bond, length as m-dash]18O)(16O18O) when 18O2 was used. Quantum chemical calculations suggest that the scrambling happens via the intermediacy of the low-lying triplet FPO3 by passing minimum energy crossing points (MECPs). In addition, inorganic dioxophosphorane FP([double bond, length as m-dash]O)2 has been also identified among the oxidation products of FP[double bond, length as m-dash]O.

Methoxyphosphinidene and Isomeric Methylphosphinidene Oxide

A rare oxyphosphinidene (Me-OP) has been generated in the triplet ground state through either photolysis (266 nm) or flash-vacuum pyrolysis (FVP, 700 °C) of methoxydiazidophosphine MeOP(N₃)₂. Upon ArF laser irradiation (193 nm), an unprecedented isomerization from Me-OP to the long-sought methylphosphinidene oxide (Me-PO) occurs in cryogenic Ne- and N₂-matrices. Alternatively, the latter can be efficiently generated through photolysis (193 nm) or FVP (ca. 700 °C) of methylphosphoryl diazide MeP(O)(N₃)₂, in which the elusive nitrene intermediate MeP(O)(N₃)N in the triplet ground state has been also observed by IR (with ¹⁵N-labeling) and EPR (| D/ hc| = 1.545 cm^-1 and | E/ hc| = 0.003 95 cm^-1) spectroscopy.