Fixierung und Freisetzung von intakten E4-Tetraedern (E=P, As)

Binding, Release and Functionalization of Intact Pnictogen Tetrahedra Coordinated to Dicopper Complexes

The bridging MeCN ligand in the dicopper(I) complexes [(DPFN)Cu2 (μ,η1  : η1 -MeCN)][X]2 (X=weakly coordinating anion, NTf2 (1 a), FAl[OC6 F10 (C6 F5 )]3 (1 b), Al[OC(CF3 )3 ]4 (1 c)) was replaced by white phosphorus (P4 ) or yellow arsenic (As4 ) to yield [(DPFN)Cu2 (μ,η2  : η2 -E4 )][X]2 (E=P (2 a-c), As (3 a-c)). The molecular structures in the solid state reveal novel coordination modes for E4 tetrahedra bonded to coinage metal ions. Experimental data and quantum chemical computations provide information concerning perturbations to the bonding in coordinated E4 tetrahedra. Reactions with N-heterocyclic carbenes (NHCs) led to replacement of the E4 tetrahedra with release of P4 or As4 and formation of [(DPFN)Cu2 (μ,η1  : η1 -Me NHC)][X]2 (4 a,b) or to an opening of one E-E bond leading to an unusual E4 butterfly structural motif in [(DPFN)Cu2 (μ,η1  : η1 -E4 Dipp NHC)][X]2 (E=P (5 a,b), E=As (6)). With a cyclic alkyl amino carbene (Et CAAC), cleavage of two As-As bonds was observed to give two isomers of [(DPFN)Cu2 (μ,η2  : η2 -As4 Et CAAC)][X]2 (7 a,b) with an unusual As4 -triangle+1 unit.

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.

E4 Transfer (E=P, As) to Ni Complexes

The use of [Cp''2 Zr(η1:1 -E4 )] (E=P (1 a), As (1 b), Cp''=1,3-di-tert-butyl-cyclopentadienyl) as phosphorus or arsenic source, respectively, gives access to novel stable polypnictogen transition metal complexes at ambient temperatures. The reaction of 1 a/1 b with [CpR NiBr]2 (CpR =CpBn (1,2,3,4,5-pentabenzyl-cyclopentadienyl), Cp''' (1,2,4-tri-tert-butyl-cyclopentadienyl)) was studied, to yield novel complexes depending on steric effects and stoichiometric ratios. Besides the transfer of the complete En unit, a degradation as well as aggregation can be observed. Thus, the prismane derivatives [(Cp'''Ni)2 (μ,η3:3 -E4 )] (2 a (E=P); 2 b (E=As)) or the arsenic containing cubane [(Cp'''Ni)3 (μ3 -As)(As4 )] (5) are formed. Furthermore, the bromine bridged cubanes of the type [(CpR Ni)3 {Ni(μ-Br)}(μ3 -E)4 ]2 (CpR =Cp''': 6 a (E=P), 6 b (E=As), CpR =CpBn : 8 a (E=P), 8 b (E=As)) can be isolated. Here, a stepwise transfer of En units is possible, with a cyclo-E4 2- ligand being introduced and unprecedented triple-decker compounds of the type [{(CpR Ni)3 Ni(μ3 -E)4 }2 (μ,η4:4 -E'4 )] (CpR =CpBn , Cp'''; E/E'=P, As) are obtained.

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 .

Atom Exchange Versus Reconstruction: (Gex As4-x )x- (x=2, 3) as Building Blocks for the Supertetrahedral Zintl Cluster [Au6 (Ge3 As)(Ge2 As2 )3 ]3

The Zintl anion (Ge2 As2 )2- represents an isostructural and isoelectronic binary counterpart of yellow arsenic, yet without being studied with the same intensity so far. Upon introducing [(PPh3 )AuMe] into the 1,2-diaminoethane (en) solution of (Ge2 As2 )2- , the heterometallic cluster anion [Au6 (Ge3 As)(Ge2 As2 )3 ]3- is obtained as its salt [K(crypt-222)]3 [Au6 (Ge3 As)(Ge2 As2 )3 ]⋅en⋅2 tol (1). The anion represents a rare example of a superpolyhedral Zintl cluster, and it comprises the largest number of Au atoms relative to main group (semi)metal atoms in such clusters. The overall supertetrahedral structure is based on a (non-bonding) octahedron of six Au atoms that is face-capped by four (Gex As4-x )x- (x=2, 3) units. The Au atoms bind to four main group atoms in a rectangular manner, and this way hold the four units together to form this unprecedented architecture. The presence of one (Ge3 As)3- unit besides three (Ge2 As2 )2- units as a consequence of an exchange reaction in solution was verified by detailed quantum chemical (DFT) calculations, which ruled out all other compositions besides [Au6 (Ge3 As)(Ge2 As2 )3 ]3- . Reactions of the heavier homologues (Tt2 Pn2 )2- (Tt=Sn, Pb; Pn=Sb, Bi) did not yield clusters corresponding to that in 1, but dimers of ternary nine-vertex clusters, {[AuTt5 Pn3 ]2 }4- (in 2-4; Tt/Pn=Sn/Sb, Sn/Bi, Pb/Sb), since the underlying pseudo-tetrahedral units comprising heavier atoms do not tend to undergo the said exchange reactions as readily as (Ge2 As2 )2- , according to the DFT calculations.

A General Pathway to Heterobimetallic Triple-Decker Complexes

A systematic study on the reactivity of the triple‐decker complex [(Cp’’’Co)₂(μ,η⁴:η⁴‐C₇H₈)] (A) (Cp’’’=1,2,4‐tritertbutyl‐cyclopentadienyl) towards sandwich complexes containing cyclo‐P₃, cyclo‐P₄, and cyclo‐P₅ ligands under mild conditions is presented. The heterobimetallic triple‐decker sandwich complexes [(Cp*Fe)(Cp’’’Co)(μ,η⁵:η⁴‐P₅)] (1) and [(Cp’’’Co)(Cp’’’Ni)(μ,η³:η³‐P₃)] (3) (Cp*=1,2,3,4,5‐pentamethylcyclopentadienyl) were synthesized and fully characterized. In solution, these complexes exhibit a unique fluxional behavior, which was investigated by variable temperature NMR spectroscopy. The dynamic processes can be blocked by coordination to {W(CO)₅} fragments, leading to the complexes [(Cp*Fe)(Cp’’’Co)(μ₃,η⁵:η⁴:η¹‐P₅){W(CO)₅}] (2 a), [(Cp*Fe)(Cp’’’Co)(μ₄,η⁵:η⁴:η¹:η¹‐P₅){(W(CO)₅)₂}] (2 b), and [(Cp’’’Co)(Cp’’’Ni)(μ₃,η³:η²:η¹‐P₃){W(CO)₅}] (4), respectively. The thermolysis of 3 leads to the tetrahedrane complex [(Cp’’’Ni)₂(μ,η²:η²‐P₂)] (5). All compounds were fully characterized using single‐crystal X‐ray structure analysis, NMR spectroscopy, mass spectrometry, and elemental analysis.

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.

Samarium Polyarsenides Derived from Nanoscale Arsenic

Zintl phases of arsenic and molecular compounds containing Zintl-type polyarsenide ions are of fundamental interest in basic and applied sciences. Unfortunately, the most obvious and reactive arsenic source for the preparation of defined molecular polyarsenide compounds, yellow arsenic As₄ , is very inconvenient to prepare and neither storable in pure form nor easy to handle. Herein, we present the synthesis and reactivity of elemental As⁰ nanoparticles (As⁰ _Nano , d=7.2±1.8 nm), which were successfully utilized as a reactive arsenic source in reductive f-element chemistry. Starting from [Cp*₂ Sm] (Cp*=η⁵ -C₅ Me₅ ), the samarium polyarsenide complexes [(Cp*₂ Sm)₂ (μ-η² :η² -As₂ )] and [(Cp*₂ Sm)₄ As₈ ] were obtained from As⁰ _nano , thereby generating the largest molecular polyarsenide of the f-elements and circumventing the use of As₄ in preparative chemistry.

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.

Coordination Behavior of [Cp''2 Zr(η1:1 -P4 )] towards Different Lewis Acids

A detailed method for the preparation of [Cp''₂ Zr(η^1:1 -P₄ )] (1) is presented. The coordination behavior of 1 towards Lewis acidic transition metal complexes of tungsten, manganese, and iron, respectively, and main group compounds (AlMe₃ , AlEt₃ ) was investigated in detail by computational and experimental studies. In doing so, a series of unprecedented complexes with different coordination modes and multiple coordination numbers of the tetraphosphabicyclo[1.1.0]butane framework were synthesized. All products, as well as the starting materials, were comprehensively characterized by NMR spectroscopy, mass spectrometry, elemental analysis, and single crystal X-ray structural analysis.

Different Reactivity of As4 towards Disilenes and Silylenes

The activation of yellow arsenic is possible with the silylene [PhC(NtBu)₂ SiN(SiMe₃ )₂ ] (1) and the disilene [(Me₃ Si)₂ N(η¹ -Me₅ C₅ )Si=Si(η¹ -Me₅ C₅ )N(SiMe₃ )₂ ] (3). The reaction of As₄ with 1 leads to the unprecedented As₁₀ cage compound [(LSiN(SiMe₃ )₂ )₃ As₁₀ ] (2; L=PhC(NtBu)₂ ) with an As₇ nortricyclane core stabilized by arsasilene moieties containing silicon(II)bis(trimethylsilyl)amide substituents. In contrast, the compound [Cp*{(SiMe₃ )₂ N}SiAs]₂ (4) containing a butterfly-like diarsadisilabicyclo[1.1.0]butane unit is formed by the reaction of As₄ with the disilene 3. Both compounds were characterized by single-crystal X-ray diffraction analysis, NMR spectroscopy, and mass spectrometry. The reaction outcomes demonstrate the different reaction behavior of yellow arsenic (As₄ ) compared to white phosphorus (P₄ ) in the reactions with the corresponding silylenes and disilenes.

Nacnac-Cobalt-Mediated P4 Transformations

A comparison of P4 activations mediated by low-valent β-diketiminato (L) cobalt complexes is presented. The formal Co0 source [K2 (L3 Co)2 (μ2 :η1 ,η1 -N2 )] (1) reacts with P4 to form a mixture of the monoanionic complexes [K(thf)6 ][(L3 Co)2 (μ2 :η4 ,η4 -P4 )] (2) and [K(thf)6 ][(L3 Co)2 (μ2 :η3 ,η3 -P3 )] (3). The analogue CoI precursor [L3 Co(tol)] (4 a), however, selectively yields the corresponding neutral derivative [(L3 Co)2 (μ2 :η4 ,η4 -P4 )] (5 a). Compound 5 a undergoes thermal P atom loss to form the unprecedented complex [(L3 Co)2 (μ2 :η3 ,η3 -P3 )] (6). The products 2 and 3 can be obtained selectively by an one-electron reduction of their neutral precursors 5 a and 6, respectively. The electrochemical behaviour of 2, 3, 5 a, and 6 is monitored by cyclic voltammetry and their magnetism is examined by SQUID measurements and the Evans method. The initial CoI -mediated P4 activation is not influenced by applying the structurally different ligands L1 and L2 , which is proven by the formation of the isostructural products [(LCo)2 (μ2 :η4 ,η4 -P4 )] [L=L3 (5 a), L1 (5 b), L2 (5 c)].

Reduction of [Cp*Sb]4 with Subvalent Main-Group Metal Reductants: Syntheses and Structures of [(L1 Mg)4 (Sb4 )] and [(L2 Ga)2 (Sb4 )] Containing Edge-Missing Sb4 Units

[Cp*Sb]₄ (Cp*=C₅ Me₅ ) reacts with [L¹ Mg]₂ and L² Ga with formation of [(L¹ Mg)₄ (μ₄ ,η^1:2:2:2 -Sb₄ )] (L¹ =iPr₂ NC[N(2,6-iPr₂ C₆ H₃ )]₂ , 1) and [(L² Ga)₂ (μ,η^2:2 -Sb₄ )] (L² =HC[C(Me)N(2,6-iPr₂ C₆ H₃ )]₂ , 2). The cleavage of the Sb-Sb and Sb-C bonds in [Cp*Sb]₄ are the crucial steps in both reactions. The formation of 1 occurred by elimination of the Cp* anion and formation of Cp*MgL¹ , while 2 was formed by reductive elimination of Cp*₂ and oxidative addition of L² Ga to the Sb₄ unit. 1 and 2 were characterized by heteronuclear NMR spectroscopy and single-crystal X-ray diffraction, and their bonding situation was studied by quantum chemical calculations.

{[CuSn5 Sb3 ](2-) }2 : A Dimer of Inhomogeneous Superatoms

Reaction of the binary Zintl anion (Sn2 Sb2 )(2-) with the β-diketiminato complex [LCu(NCMe)] (L=nacnac=[(N(C6 H3 (i) Pr2 -2,6)C(Me))2 CH](-) ) in ethylenediamine or DMF affords the ternary cluster dimer {[CuSn5 Sb3 ](2-) }2 (1) as its [K(crypt-222)](+) salt. The chemical formulation of 1 is supported by energy-dispersive X-ray spectroscopy (EDX) and quantum chemical calculations. Each monomeric part of the dimer represents a trimetallic "[CuSn5 Sb3 ](2-) " cluster, with an architecture in between a tricapped trigonal prism and a capped square antiprism. As shown by quantum chemical investigations, the presence of Sb atoms and, in particular, of Cu atoms in the cluster skeleton makes the monomeric unit behave like an inhomogeneous superatom, which clearly prefers to dimerize, thereby producing a relatively short, yet virtually non-bonding Cu⋅⋅⋅Cu distance.

Influence of the nacnac Ligand in Iron(I)-Mediated P4 Transformations

A study of P4 transformations at low-valent iron is presented using β-diketiminato (L) Fe(I) complexes [LFe(tol)] (tol=toluene; L=L(1) (1 a), L(2) (1 b), L(3) (1 c)) with different combinations of aromatic and backbone substituents at the ligand. The products [(LFe)4 (μ4 -η(2) :η(2) :η(2) :η(2) -P8 )] (L=L(1) (2 a), L(2) (2 b)) containing a P8 core were obtained by the reaction of 1 a,b with P4 in toluene at room temperature. Using a slightly more sterically encumbered ligand in 1 c results in the formation of [(L(3) Fe)2 (μ-η(4) :η(4) -P4 )] (2 c), possessing a cyclo-P4 moiety. Compounds 2 a-c were comprehensively characterized and their electronic structures investigated by SQUID magnetization and (57) Fe Mössbauer spectroscopy as well as by DFT methods.

A Gallium-Substituted Distibene and an Antimony-Analogue Bicyclo[1.1.0]butane: Synthesis and Solid-State Structures

RGa {R=HC[C(Me)N(2,6-iPr2C6H3)]2} reacts with Sb(NMe2)3 with insertion into the Sb-N bond and elimination of RGa(NMe2)2 (2), yielding the Ga-substituted distibene R(Me2N)GaSb=SbGa(NMe2 )R (1). Thermolysis of 1 proceeded with elimination of RGa and 2 and subsequent formation of the bicyclo[1.1.0]butane analogue [R(Me2N)Ga]2Sb4 (3).

Attenuated Organomagnesium Activation of White Phosphorus

Sequential reactions between a 2,6-diisopropylphenyl-substituted β-diketiminato magnesium n-butyl derivative and P₄ allow the highly discriminating synthesis of unusual [nBu₂P₄]²⁻ and [nBu₂P₈]²⁻ cluster dianions.