A neutral tetraphosphacyclobutadiene ligand in cobalt(I) complexes

Functionalization of Tetraphosphido Ligands by Heterocumulenes

Although numerous polyphosphido complexes have been accessed through the transition-metal-mediated activation and functionalization of white phosphorus (P4), the selective functionalization of the resulting polyphosphorus ligands in these compounds remains underdeveloped. In this study, we explore the reactions between cyclotetraphosphido cobalt complexes and heterocumulenes, leading to functionalized P4 ligands. Specifically, the reaction of carbon disulfide (CS2) with [K(18c-6)][(Ar*BIAN)Co(η4-P4)] ([K(18c-6)]1, 18c-6 = [18]crown-6) affords the adduct [K(18c-6)][(Ar*BIAN)Co(η3:η1-P4CS2)] ([K(18c-6)]3), in which CS2 is attached to a single phosphorus atom (Ar* = 2,6-dibenzhydryl-4-isopropylphenyl, BIAN = 1,2-bis(arylimino)acenaphthene diimine). In contrast, the insertion of bis(trimethylsilyl)sulfur diimide S(NSiMe3)2 into a P-P bond of [K(18c-6)]1 yields [K(18c-6)][(Ar*BIAN)Co(η3:η1-P4SN2(SiMe3)2)] (K(18c-6)]4). This salt further reacts with Me3SiCl to form [(Ar*BIAN)Co(η3:η1-P4SN2(SiMe3)3] (5), featuring a rare azatetraphosphole ligand. Moreover, treatment of the previously reported complex [(Ar*BIAN)Co(η3:η1-P4C(O)tBu)] (2) with isothiocyanates results in P-C bond insertion, yielding [(Ar*BIAN)Co(η3:η1-P4C(S)N(R)C(O)tBu)] (6a,b; R = Cy, Ph).

Low-Valent Transition Metalate Anions in Synthesis, Small Molecule Activation, and Catalysis

This review surveys the synthesis and reactivity of low-oxidation state metalate anions of the d-block elements, with an emphasis on contributions reported between 2006 and 2022. Although the field has a long and rich history, the chemistry of transition metalate anions has been greatly enhanced in the last 15 years by the application of advanced concepts in complex synthesis and ligand design. In recent years, the potential of highly reactive metalate complexes in the fields of small molecule activation and homogeneous catalysis has become increasingly evident. Consequently, exciting applications in small molecule activation have been developed, including in catalytic transformations. This article intends to guide the reader through the fascinating world of low-valent transition metalates. The first part of the review describes the synthesis and reactivity of d-block metalates stabilized by an assortment of ligand frameworks, including carbonyls, isocyanides, alkenes and polyarenes, phosphines and phosphorus heterocycles, amides, and redox-active nitrogen-based ligands. Thereby, the reader will be familiarized with the impact of different ligand types on the physical and chemical properties of metalates. In addition, ion-pairing interactions and metal-metal bonding may have a dramatic influence on metalate structures and reactivities. The complex ramifications of these effects are examined in a separate section. The second part of the review is devoted to the reactivity of the metalates toward small inorganic molecules such as H2, N2, CO, CO2, P4 and related species. It is shown that the use of highly electron-rich and reactive metalates in small molecule activation translates into impressive catalytic properties in the hydrogenation of organic molecules and the reduction of N2, CO, and CO2. The results discussed in this review illustrate that the potential of transition metalate anions is increasingly being tapped for challenging catalytic processes with relevance to organic synthesis and energy conversion. Therefore, it is hoped that this review will serve as a useful resource to inspire further developments in this dynamic research field.

Cobalt-Mediated [3+1] Fragmentation of White Phosphorus: Access to Acylcyanophosphanides

Despite the accessibility of numerous transition metal polyphosphido complexes through transition-metal-mediated activation of white phosphorus, the targeted functionalization of Pn ligands to obtain functional monophosphorus species remains challenging. In this study, we introduce a new [3+1] fragmentation procedure for cyclo-P4 ligands, leading to the discovery of acylcyanophosphanides and -phosphines. Treatment of the complex [K(18c-6)][(Ar*BIAN)Co(η4 -P4 )] ([K(18c-6)]3, 18c-6=[18]crown-6, Ar*=2,6-dibenzhydryl-4-isopropylphenyl, BIAN=1,2-bis(arylimino)acenaphthene diimine) with acyl chlorides results in the formation of acylated tetraphosphido complexes [(Ar*BIAN)Co(η4 -P4 C(O)R)] (R=tBu, Cy, 1-Ad, Ph; 4 a-d). Subsequent reactions of 4 a-d with cyanide salts yield acylated cyanophosphanides [RC(O)PCN]- (9 a-d- ) and the cyclo-P3 cobaltate anion [(Ar*BIAN)Co(η3 -P3 )(CN)]- (8- ). Further reactions of 4 a-d with trimethylsilyl cyanide (Me3 SiCN) and isocyanides provide insight into a plausible mechanism of this [3+1] fragmentation reaction, as these reagents partially displace the P4 C(O)R ligand from the cobalt center. Several potential intermediates of the [3+1] fragmentation were characterized. Additionally, the introduction of a second acyl substituent was achieved by treating [K(18c-6)]9b with CyC(O)Cl, resulting in the first bis(acyl)monocyanophosphine (CyC(O))2 PCN (10).

Direct Synthesis of Phosphoryltriacetates from White Phosphorus via Visible Light Catalysis

Organophosphorus compounds (OPCs) are widely used in many fields. However, traditional synthetic routes in the industry usually involve multistep and hazardous procedures. Therefore, it's of great significance to construct such compounds in an environmentally-friendly and facile way. Herein, a photoredox catalytic method has been developed to construct novel phosphoryltriacetates. Using fac-Ir(ppy)3 (ppy=2-phenylpyridine) as the photocatalyst and blue LEDs (456 nm) as the light source, white phosphorus can react with α-bromo esters smoothly to generate phosphoryltriacetates in moderate to good yields. This one-step approach features mild reaction conditions and simple operational process without chlorination.

Isolation and Reactivity of Homoleptic Diphosphene Lead Complexes

Due to their limited capacity for π-backdonation, isolation of π-complexes of main-group elements remains a great challenge. We report herein the synthesis of a homoleptic diphosphene lead complex (2) from the degradation of P4 with a bis(germylene)-stabilized Pb(0) complex. Structural and computational studies showed that 2 possesses significant π bonding interactions between Pb atom and diphosphene ligands, which is reminiscent of transition-metal diphosphene complexes. Consistent with its unique electronic structure, complex 2 can deliver Pb(0) atoms to perform redox reaction with an iminoquinone to produce a cyclic plumbylene (4) and perform 2,5-dimethyl-3,4-dimethylimidazol-1-ylidene (IMe2 Me2 ) induced phosphorus cation abstraction to give an anionic PbP3 complex (6).

Photochemical Benzylation of White Phosphorus

Organophosphorus compounds (OPCs) have wide application in organic synthesis, material sciences, and drug discovery. Generally, the vast majority of phosphorus atoms in OPCs are derived from white phosphorus (P4). However, the large-scale preparation of OPCs mainly proceeds through the multistep and environmentally toxic chlorine route from P4. Herein, we report the direct benzylation of P4 promoted by visible light. The cheap and readily available benzyl bromide was used as a benzylation reagent, and tetrabenzylphosphonium bromide was directly synthesized from P4. In addition, the metallaphotoredox catalysis strategy was applied to functionalize P4 for the first time, which significantly improved the application range of the substituted benzyl bromide.

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.

Haptotropism in a Nickel Complex with a Neutral, π-Bridging cyclo-P4 Ligand Analogous to Cyclobutadiene

Dedicated to Professor Manfred Scheer on the occasion of his 65th birthday The reaction of (1)Ni(η2 -cod), 2, incorporating a chelating bis(N-heterocyclic carbene) 1, with P4 in pentane yielded the dinuclear complex [(2)Ni]2 (μ2 ,η2  : η2 -P4 ), 3, formally featuring a cyclobutadiene-like, neutral, rectangular, π-bridging P4 -ring. In toluene, the butterfly-shaped complex [(1)Ni]2 (μ2 ,η2  : η2 -P2 ), 4, with a formally neutral P2 -unit was obtained from 2 and either P4 or 3. Computational studies showed that a haptotropic rearrangement involving two isomers of the μ2 ,η2  : η2 -P4 coordination mode and a low-energy μ2 ,η4  : η4 -P4 coordination mode, as previously predicted for related nickel cyclobutadiene complexes, could explain the coalescence observed in the low-temperature NMR spectra of 3. The insertion of the (1)Ni fragment into a P-P bond of P7 (SiMe3 )3 , forming complex 5 with a norbornane-like P7 ligand, was also observed.

Conversion of E4 (E4 =P4 , As4 , AsP3 ) by Ni(0) and Ni(I) Synthons - A Comparative Study

The reactivity of white phosphorus and yellow arsenic towards two different nickel nacnac complexes is investigated. The nickel complexes [(L1 Ni)2 tol] (1, L1 =[{N(C6 H3 i Pr2 -2,6)C(Me)}2 CH]- ) and [K2 ][(L1 Ni)2 (μ,η1 : 1 -N2 )] (6) were reacted with P4 , As4 and the interpnictogen compound AsP3 , respectively, yielding the homobimetallic complexes [(L1 Ni)2 (μ-η2 ,κ1 :η2 ,κ1 -E4 )] (E=P (2 a), As (2 b), AsP3 (2 c)), [(L1 Ni)2 (μ,η3 : 3 -E3 )] (E=P (3 a), As (3 b)) and [K@18-c-6(thf)2 ][L1 Ni(η1 : 1 -E4 )] (E=P (7 a), As (7 b)), respectively. Heating of 2 a, 2 b or 2 c also leads to the formation of 3 a or 3 b. Furthermore, the reactivity of these compounds towards reduction agents was investigated, leading to [K2 ][(L1 Ni)2 (μ,η2 : 2 -P4 )] (4) and [K@18-c-6(thf)3 ][(L1 Ni)2 (μ,η3 : 3 -E3 )] (E=P (5 a), As (5 b)), respectively. Compound 4 shows an unusual planarization of the initial Ni2 P4 -prism. All products were comprehensively characterized by crystallographic and spectroscopic methods.

Rare-Earth-Silyl ate-Complexes Opening a Door to Selective Manipulations

The reactions of a number of rare-earth (RE) trichlorides and an oligosilanylene diide containing a siloxane unit in the backbone in DME are described. The formed products of the type [(DME)4·K][(DME)·RE(Cl)2{Si(SiMe3)2SiMe2}2O] (RE = Y, La, Ce, Pr, Sm, Tb, Dy, and Er) are disilylated dichloro metalate complexes and include the first examples of Si-La and Si-Pr compounds as well as the first structurally characterized example of a Si-Dy complex. A most intriguing aspect of the synthesis of these complexes is that they offer entry into a systematic study of the still largely unexplored field of silyl RE complexes by the possibility of ligand exchange reactions under preservation of the Si-RE interaction. This was demonstrated by the conversion of [(DME)4·K][(DME)·RE(Cl)2{Si(SiMe3)2SiMe2}2O] to [(DME)4·K][Cp2Y{Si(SiMe3)2SiMe2}2O].

Synthesis of Unprecedented 4d/4f-Polypnictogens

A series of 4d/4f-polyarsenides, -polyarsines and -polystibines was obtained by reduction of the Mo-pnictide precursor complexes [{Cpt Mo(CO)2 }2 (μ,η2:2 -E2 )] (E=As, Sb; Cpt =tBu substituted cyclopentadienyl) with two different divalent samarocenes [Cp*2 Sm] and [(CpMe4nPr )2 Sm]. For the reductive conversion of the Mo-stibide only one product was isolated, featuring a planar tetrastibacyclobutadiene moiety as an unprecedented ligand for organometallic compounds. For the corresponding Mo-arsenide a tetraarsacyclobutadiene and a second species with a side-on coordinated As2 2- anion was isolated. The latter can be considered as reaction intermediate for the formation of the tetraarsacyclobutadiene.

Fragmentation Mechanism of White Phosphorus: A Theoretical Insight into Multiple Cleavage/Formation of P-P and P-C Bonds

Molecular-level understanding of metal-mediated white phosphorus (P₄ ) activation is meaningful but challenging because of its direct relevance to the conversion of P₄ into useful organophosphorus compounds as well as the complicated and unforeseeable cleavage process of P-P bonds. The related study, however, has still rarely been achieved to date. Here, a theoretical insight into the step-by-step process of three P-P bond cleavage/four P-C bond formation for [P₃ +P₁ ]-fragmentation of P₄ mediated by lutetacyclopentadienes is reported. The unique charge-separated intermediate and the intermolecular cooperation between two lutetacyclopentadienes play a vital role in the subsequent P-P/P-C bond breaking/forming. It is found that, although the first P-C formation is involved in the assembly of the cyclo-P₃ [R₄ C₄ P₃ ]^- unit, the construction of the aromatic five-membered P₁ heterocycle [R₄ C₄ P]^- is completed prior to the cyclo-P₃ formation. The reaction mechanism has been carefully elucidated by analyses of the geometric structure, frontier molecular orbitals, bond index, and natural charge, which greatly broaden and enrich the general knowledge of the direct functionalization of P₄ .

Iron-Gallium and Cobalt-Gallium Tetraphosphido Complexes

The synthesis and characterization of two heterobimetallic complexes [K([18]crown-6){(η4-C14H10)Fe(μ-η4:η2-P4)Ga(nacnac)}] (1) (C14H10 = anthracene) and [K(dme)2{(η4-C14H10)Co(μ-η4:η2-P4)Ga(nacnac)}] (2) with strongly reduced P4 units is reported. Compounds 1 and 2 are prepared by reaction of the gallium(III) complex [(nacnac)Ga(η2-P4)] (nacnac = CH[CMeN(2,6-iPr2C6H3)]2) with bis(anthracene)ferrate(1-) and -cobaltate(1-) salts. The molecular structures of 1 and 2 were determined by X-ray crystallography and feature a P4 chain which binds to the transition metal atom via all four P atoms and to the gallium atom via the terminal P atoms. Multinuclear NMR studies on 2 suggest that the molecular structure is preserved in solution.

Functionalization of Pentaphosphorus Cations by Complexation

The chemistry of polyphosphorus cations has rapidly developed in recent years, but their coordination behavior has remained mostly unexplored. Herein, we describe the reactivity of [P5 R2 ]+ cations with cyclopentadienyl metal complexes. The reaction of [CpAr Fe(μ-Br)]2 (CpAr =C5 (C6 H4 -4-Et)5 ) with [P5 R2 ][GaCl4 ] (R=iPr and 2,4,6-Me3 C6 H2 (Mes)) afforded bicyclo[1.1.0]pentaphosphanes (1-R, R=iPr and Mes), showing an unsymmetric "butterfly" structure. The same products 1-R were formed from K[CpAr ] and [P5 R2 ][GaCl4 ]. The cationic complexes [CpAr Co(η4 -P5 R2 )][GaCl4 ] (2-R[GaCl4 ], R=iPr and Cy) and [(CpAr Ni)2 (η3:3 -P5 R2 )][GaCl4 ] (3-R[GaCl4 ]) were obtained from [P5 R2 ][GaCl4 ] and [CpAr M(μ-Br)]2 (M=Co and Ni) as well as by using low-valent "CpAr MI " sources. Anion metathesis of 2-R[GaCl4 ] and 3-R[GaCl4 ] was achieved with Na[BArF24 ]. The P5 framework of the resulting salts 2-R[BArF24 ] can be further functionalized with nucleophiles. Thus reactions with [Et4 N]X (X=CN and Cl) give unprecedented cyano- and chloro-functionalized complexes, while organo-functionalization was achieved with CyMgCl.

Direct functionalization of white phosphorus with anionic dicarbenes and mesoionic carbenes: facile access to 1,2,3-triphosphol-2-ides

A series of unique C₂P₃-ring compounds [(ADC^Ar)P₃] (4) are readily accessible in an almost quantitative yield by the direct functionalization of white phosphorus (P₄) with appropriate anionic dicarbenes [Li(ADC^Ar)].

A series of unique C₂P₃-ring compounds [(ADC^Ar)P₃] (ADC^Ar = ArC{(DippN)C}₂; Dipp = 2,6-iPr₂C₆H₃; Ar = Ph 4a, 3-MeC₆H₄4b, 4-MeC₆H₄4c, and 4-Me₂NC₆H₄4d) are readily accessible in an almost quantitative yield by the direct functionalization of white phosphorus (P₄) with appropriate anionic dicarbenes [Li(ADC^Ar)]. The formation of 1,2,3-triphosphol-2-ides (4a–4d) suggests unprecedented [3 + 1] fragmentation of P₄ into P₃⁺ and P^–. The P₃⁺ cation is trapped by the (ADC^Ar)^– to give 4, while the putative P^– anion reacts with additional P₄ to yield the Li₃P₇ species, a useful reagent in the synthesis of organophosphorus compounds. Remarkably, the P₄ fragmentation is also viable with the related mesoionic carbenes (iMICs^Ar) (iMIC^Ar = ArC{(DippN)₂CCH}, i stands for imidazole-based) giving rise to 4. DFT calculations reveal that both the C₃N₂ and C₂P₃-rings of 4 are 6π-electron aromatic systems. The natural bonding orbital (NBO) analyses indicate that compounds 4 are mesoionic species featuring a negatively polarized C₂P₃-ring. The HOMO–3 of 4 is mainly the lone-pair at the central phosphorus atom that undergoes σ-bond formation with a variety of metal-electrophiles to yield complexes [{(ADC^Ar)P₃}M(CO)_n] (M = Fe, n = 4, Ar = Ph 5a or 4-Me-C₆H₄5b; M = Mo, n = 5, Ar = Ph 6; M = W, n = 5, Ar = 4-Me₂NC₆H₄7).

The Influence of β-diiminato Ligands on As4 Activation by Cobalt Complexes

In a systematic study of the activation of As₄, three [LCo(tol)] (L=β‐diiminato) complexes have revealed different steric and electronic influences. 2,6‐Diisopropylphenyl (Dipp) and 2,6‐dimethylphenyl (dmp) flanking groups were used, one of the ligands with H backbone substituents (β‐dialdiminate L⁰) and two with Me substituents (β‐diketiminates L³ and L¹). In the reaction with As₄, different dinuclear products [(LCo)₂As₄] (LM=L⁰ (1), L¹ (2), L³ (3)) were isolated, with all showing differently shaped [Co₂As₄] cores in the solid state: octahedral in 1, prismatic in 2, and asterane‐like in 3. Thermal treatment of 3 leads to the abstraction of one arsenic atom to yield [(L³Co)₂As₃] (4). All products were comprehensively characterized by single‐crystal X‐ray diffraction, FD‐MS, and ¹H NMR spectroscopy. A rational explanation for the different reactivity is also proposed and DFT calculations shed light on the nature of the highly flexible [Co₂As₄] cores.

Mono- and dinuclear tetraphosphabutadiene ferrate anions

Reduction of [Cp^ArFe(μ-Br)]₂ (1, Cp^Ar = C₅(C₆H₄-4-Et)₅) by potassium napthalenide, followed by the addition of white phosphorus, affords [K(18-c-6){Cp^ArFe(η⁴-P₄)}] (2, 18-c-6 = [18]crown-6), which features a planar cyclo-P₄^2- ligand. The related diiron complex [Na₂(THF)₅(Cp^ArFe)₂(μ,η^4:4-P₄)] (3) was obtained by reducing 1 with sodium amalgam in the presence of P₄. Protonation of 3 affords [Na(THF)₃][(Cp^ArFe)₂(μ,η^4:4-P₄)(H)] (4), while the reaction of 3 with trimethylchlorosilane gives the nortricyclane compound P₇(SiMe₃)₃ as the main product.

Sterically induced reductive linkage of iron polypnictides with bulky lanthanide complexes by ring-opening of THF

Reduction of [Cp*Fe(η⁵-E₅)] (E = P, As) with divalent lanthanide reagents usually leads to reduction of [Cp*Fe(η⁵-E₅)] followed by a Ln-E bond formation. In contrast, by using the sterically encumbered reagent [(DippForm)₂Sm(thf)₂] (DippForm = {(2,6-ⁱPr₂C₆H₃)NC(H)[double bond, length as m-dash]N(2,6-ⁱPr₂C₆H₃)}^-), ring-opening of thf and reduction of the polypnictide is observed. This leads to two new 3d/4f polyphosphide or polyarsenide complexes [(DippForm)₂Sm(Cp*Fe)E₅{(CH₂)₄O}{(DippForm)₂Sm(thf)}], in which [(DippForm)₂Sm(thf)₂] and [Cp*Fe(η⁵-E₅)] are linked by a ring-opened thf molecule and no Ln-E bond formation is observed.

Synthesis and Reactivity of an End-Deck cyclo-P4 Iron Complex

Reduction of the Fe^II complex [(^Ph PP₂^Cy )FeCl₂ ] (2) generated an electron-rich and unsaturated Fe⁰ species, which was reacted with white phosphorus. The resulting new complex, [(^Ph PP₂^Cy )Fe(η⁴ -P₄ )] (3), is the first iron cyclo-P₄ complex and the only known stable end-deck cyclo-P₄ complex outside Group V. Complex 3 features an Fe^II center, as shown by Mössbauer spectroscopy, associated to a P₄^2- fragment. The distinct reactivity of complex 3 was rationalized by analysis of the molecular orbitals. Reaction of complex 3 with H⁺ afforded the unstable complex [(^Ph PP₂^Cy )Fe(η⁴ -P₄ )(H)]⁺ (4), whereas with CuCl and BCF, the complexes [(^Ph PP₂^Cy )Fe(η⁴ :η¹ -P₄ )(μ-CuCl)]₂ (5) and [(^Ph PP₂^Cy )Fe(η⁴ :η¹ -P₄ )B(C₆ F₅ )₃ ] (6) were formed.

Reactivity of bulky Ln(ii) amidinates towards P4, As4, and As4S4

The reduction of P₄, As₄ and As₄S₄ (realgar) with [(DippForm)₂Ln(thf)₂] (Ln = Sm, Yb) led to the first, purely f-element containing inverse inorganic sandwich complexes [{(DippForm)₂Sm}₂(μ²-η⁴:η⁴-E₄)] (E = P, As) and the unusual species [{(DippForm)(DippForm-AsS₂)}Ln(thf)].

Selective Derivatization of a Hexaphosphane from Functionalization of White Phosphorus

The reaction of LGa (L = Dipp(4-(Dipp-imino)pent-2-en-2-yl)amide; Dipp: 2,6-diisopropylphenyl) and white phosphorus was revisited. A plethora of unprecedented polyphosphanes in addition to the known monoinserted product LGaP₄ (1) are observed. An optimized synthesis of the hitherto unknown hexaphosphane (LGa)₂P₆ (3) is presented, and its subsequent selective derivatization with Brønsted acids, MeOTf, Ph₂ECl (E = P, As), and NaOCP provides access to a wealth of functionalized hexa- and heptaphosphanes.

The Charge Transfer Approach to Heavier Main-Group Element Radicals in Transition-Metal Complexes

The Co^II and Fe^II complexes 1Co and 1Fe with a coordinated phosphorus radical were easily obtained through a charge-transfer approach from the M^I precursors LM^I (tol) (M=Co, Fe; L=CH(MeC=NDipp)₂ , Dipp=2,6-iPr₂ C₆ H₃ ) to the diazafluorenylidene-substituted phosphaalkene 1. Structural, magnetic, and computational studies on 1Co and 1Fe indicate a weak antiferromagnetic interaction between the high-spin M^II ion and the phosphorus radical, resulting in a triplet and quartet ground state, respectively. Complexes 1Co and 1Fe are the first examples of phosphorus-radical-coordinated transition-metal complexes synthesized by charge transfer, providing a new approach to access radicals of heavier main-group elements.

Metalate-Mediated Functionalization of P4 by Trapping Anionic [Cp*Fe(CO)2(η1-P4)]- with Lewis Acids

The development of selective functionalization strategies of white phosphorus (P4) is important to avoid the current chlorinated intermediates. The use of transition metals (TMs) could lead to catalytic procedures, but these are severely hampered by the high reactivity and unpredictable nature of the tetrahedron. Herein, we report selective first steps by reacting P4 with a metal anion [Cp*Fe(CO)2]- (Cp*=C5(CH3)5), which, in the presence of bulky Lewis acids (LA; B(C6F5)3 or BPh3), leads to unique TM-substituted LA-stabilized bicyclo[1.1.0]tetraphosphabutanide anions [Cp*Fe(CO)2(η1-P4⋅LA)]-. Their P-nucleophilic site can be subsequently protonated to afford the transient LA-free neutral butterflies exo,endo- and exo,exo-Cp*Fe- (CO)2(η1-P4H), allowing controllable stepwise metalate-mediated functionalization of P4.

A New Domain of Reactivity for High-Valent Dinuclear [M(μ-O)2 M'] Complexes in Oxidation Reactions

The strikingly different reactivity of a series of homo- and heterodinuclear [(MIII )(μ-O)2 (MIII )']2+ (M=Ni; M'=Fe, Co, Ni and M=M'=Co) complexes with β-diketiminate ligands in electrophilic and nucleophilic oxidation reactions is reported, and can be correlated to the spectroscopic features of the [(MIII )(μ-O)2 (MIII )']2+ core. In particular, the unprecedented nucleophilic reactivity of the symmetric [NiIII (μ-O)2 NiIII ]2+ complex and the decay of the asymmetric [NiIII (μ-O)2 CoIII ]2+ core through aromatic hydroxylation reactions represent a new domain for high-valent bis(μ-oxido)dimetal reactivity.