Triamidoamine–Uranium(IV)‐Stabilized Terminal Parent Phosphide and Phosphinidene Complexes

Reaction of [U(Tren^TIPS)(THF)][BPh₄] ( 1 ; Tren^TIPS=N{CH₂CH₂NSi(iPr)₃}₃) with NaPH₂ afforded the novel f‐block terminal parent phosphide complex [U(Tren^TIPS)(PH₂)] ( 2 ; U–P=2.883(2) Å). Treatment of 2 with one equivalent of KCH₂C₆H₅ and two equivalents of benzo‐15‐crown‐5 ether (B15C5) afforded the unprecedented metal‐stabilized terminal parent phosphinidene complex [U(Tren^TIPS)(PH)][K(B15C5)₂] ( 4 ; U?P=2.613(2) Å). DFT calculations reveal a polarized‐covalent U?P bond with a Mayer bond order of 1.92.     

Crystalline Diuranium Phosphinidiide and μ‐Phosphido Complexes with Symmetric and Asymmetric UPU Cores

Reaction of [U(Tren^TIPS)(PH₂)] ( 1 , Tren^TIPS=N(CH₂CH₂NSiPrⁱ₃)₃) with C₆H₅CH₂K and [U(Tren^TIPS)(THF)][BPh₄] ( 2 ) afforded a rare diuranium parent phosphinidiide complex [{U(Tren^TIPS)}₂(μ‐PH)] ( 3 ). Treatment of 3 with C₆H₅CH₂K and two equivalents of benzo‐15‐crown‐5 ether (B15C5) gave the diuranium μ‐phosphido complex [{U(Tren^TIPS)}₂(μ‐P)][K(B15C5)₂] ( 4 ). Alternatively, reaction of [U(Tren^TIPS)(PH)][Na(12C4)₂] ( 5 , 12C4=12‐crown‐4 ether) with [U{N(CH₂CH₂NSiMe₂Bu^t)₂CH₂CH₂NSi(Me)(CH₂)(Bu^t)}] ( 6 ) produced the diuranium μ‐phosphido complex [{U(Tren^TIPS)}(μ‐P){U(Tren^DMBS)}][Na(12C4)₂] [ 7 , Tren^DMBS=N(CH₂CH₂NSiMe₂Bu^t)₃]. Compounds 4 and 7 are unprecedented examples of uranium phosphido complexes outside of matrix isolation studies, and they rapidly decompose in solution underscoring the paucity of uranium phosphido complexes. Interestingly, 4 and 7 feature symmetric and asymmetric UPU cores, respectively, reflecting their differing steric profiles.     

Two‐Electron Reductive Carbonylation of Terminal Uranium(V) and Uranium(VI) Nitrides to Cyanate by Carbon Monoxide

Two‐electron reductive carbonylation of the uranium(VI) nitride [U(Tren^TIPS)(N)] ( 2 , Tren^TIPS=N(CH₂CH₂NSiiPr₃)₃) with CO gave the uranium(IV) cyanate [U(Tren^TIPS)(NCO)] ( 3 ). KC₈ reduction of 3 resulted in cyanate dissociation to give [U(Tren^TIPS)] ( 4 ) and KNCO, or cyanate retention in [U(Tren^TIPS)(NCO)][K(B15C5)₂] ( 5 , B15C5=benzo‐15‐crown‐5 ether) with B15C5. Complexes 5 and 4 and KNCO were also prepared from CO and the uranium(V) nitride [{U(Tren^TIPS)(N)K}₂] ( 6 ), with or without B15C5, respectively. Complex 5 can be prepared directly from CO and [U(Tren^TIPS)(N)][K(B15C5)₂] ( 7 ). Notably, 7 reacts with CO much faster than 2 . This unprecedented f‐block reactivity was modeled theoretically, revealing nucleophilic attack of the π* orbital of CO by the nitride with activation energy barriers of 24.7 and 11.3 kcal mol^?1 for uranium(VI) and uranium(V), respectively. A remarkably simple two‐step, two‐electron cycle for the conversion of azide to nitride to cyanate using 4 , NaN₃ and CO is presented.     

Actinide–Pnictide (An−Pn) Bonds Spanning Non‐Metal,Metalloid, and Metal Combinations (An=U,Th; Pn=P,As, Sb,Bi)

The synthesis and characterisation is presented of the compounds [An(Tren^DMBS){Pn(SiMe₃)₂}] and [An(Tren^TIPS){Pn(SiMe₃)₂}] [Tren^DMBS=N(CH₂CH₂NSiMe₂Bu^t)₃, An=U, Pn=P, As, Sb, Bi; An=Th, Pn=P, As; Tren^TIPS=N(CH₂CH₂NSiPrⁱ₃)₃, An=U, Pn=P, As, Sb; An=Th, Pn=P, As, Sb]. The U−Sb and Th−Sb moieties are unprecedented examples of any kind of An−Sb molecular bond, and the U−Bi bond is the first two‐centre‐two‐electron (2c–2e) one. The Th−Bi combination was too unstable to isolate, underscoring the fragility of these linkages. However, the U−Bi complex is the heaviest 2c–2e pairing of two elements involving an actinide on a macroscopic scale under ambient conditions, and this is exceeded only by An−An pairings prepared under cryogenic matrix isolation conditions. Thermolysis and photolysis experiments suggest that the U−Pn bonds degrade by homolytic bond cleavage, whereas the more redox‐robust thorium compounds engage in an acid–base/dehydrocoupling route.     

Actinide–Pnictide (An−Pn) Bonds Spanning Non‐Metal,Metalloid, and Metal Combinations (An=U,Th; Pn=P,As, Sb,Bi)

The synthesis and characterisation is presented of the compounds [An(Tren^DMBS){Pn(SiMe₃)₂}] and [An(Tren^TIPS){Pn(SiMe₃)₂}] [Tren^DMBS=N(CH₂CH₂NSiMe₂Bu^t)₃, An=U, Pn=P, As, Sb, Bi; An=Th, Pn=P, As; Tren^TIPS=N(CH₂CH₂NSiPrⁱ₃)₃, An=U, Pn=P, As, Sb; An=Th, Pn=P, As, Sb]. The U?Sb and Th?Sb moieties are unprecedented examples of any kind of An?Sb molecular bond, and the U?Bi bond is the first two‐centre‐two‐electron (2c–2e) one. The Th?Bi combination was too unstable to isolate, underscoring the fragility of these linkages. However, the U?Bi complex is the heaviest 2c–2e pairing of two elements involving an actinide on a macroscopic scale under ambient conditions, and this is exceeded only by An?An pairings prepared under cryogenic matrix isolation conditions. Thermolysis and photolysis experiments suggest that the U?Pn bonds degrade by homolytic bond cleavage, whereas the more redox‐robust thorium compounds engage in an acid–base/dehydrocoupling route.     

Nature of the Arsonium‐Ylide Ph3As=CH2 and a Uranium(IV) Arsonium–Carbene Complex

Treatment of [Ph₃EMe][I] with [Na{N(SiMe₃)₂}] affords the ylides [Ph₃E=CH₂] (E=As, 1As ; P, 1P ). For 1As this overcomes prior difficulties in the synthesis of this classical arsonium‐ylide that have historically impeded its wider study. The structure of 1As has now been determined, 45 years after it was first convincingly isolated, and compared to 1P , confirming the long‐proposed hypothesis of increasing pyramidalisation of the ylide‐carbon, highlighting the increasing dominance of E⁺?C^? dipolar resonance form (sp³‐C) over the E=C ene π‐bonded form (sp²‐C), as group 15 is descended. The uranium(IV)–cyclometallate complex [U{N(CH₂CH₂NSiPrⁱ₃)₂(CH₂CH₂SiPrⁱ₂CH(Me)CH₂)}] reacts with 1As and 1P by α‐proton abstraction to give [U(Tren^TIPS)(CHEPh₃)] (Tren^TIPS=N(CH₂CH₂NSiPrⁱ₃)₃; E=As, 2As ; P, 2P ), where 2As is an unprecedented structurally characterised arsonium‐carbene complex. The short U?C distances and obtuse U‐C‐E angles suggest significant U=C double bond character. A shorter U?C distance is found for 2As than 2P , consistent with increased uranium‐ and reduced pnictonium‐stabilisation of the carbene as group 15 is descended, which is supported by quantum chemical calculations.     

The bis(η5‐cyclo­penta­dienyl)­methyl­zirconium(IV) methyl­tris­(penta­fluoro­phenyl)­borate ion pair

The title complex, [Zr(CH₃)(C₅H₅)₂][CH₃B(C₆F₅)₃], crystallizes as an ion pair linked through an unsymmetrical methyl bridge. The bridging Zr—Me distance [2.556 (2) Å] is significantly longer than the terminal Zr—Me distance [2.251 (3) Å], while the Zr—C—B angle approaches linearity [169.1 (2)°].     

Reaction of Pentelidene Complexes with Diazoalkanes: Stabilization of Parent 2,3‐Dipnictabutadienes

The reaction of the phosphinidene complex [Cp*P{W(CO)₅}₂] ( 1 a ) with diphenyldiazomethane leads to [{W(CO)₅}Cp*P=NN{W(CO)₅}=CPh₂] ( 2 ). Compound 2 is a rare example of a phosphadiazadiene ligand (R‐P=N?N=CR′R′′) complex. At temperatures above 0 °C, 2 decomposes into the complex [{W(CO)₅}PCp*{N(H)N=CPh₂)₂] ( 3 ), among other species. The reaction of the pentelidene complexes [Cp*E{W(CO)₅}₂] (E=P, As) with diazomethane (CH₂NN) proceeds differently. For the arsinidene complex ( 1 b ), only the arsaalkene complex 4 b [{W(CO)₅}₂{η^1:2‐(Cp*)As=CH₂}] is formed. The reaction with the phosphinidene complex ( 1 a ) results in three products, the two phosphaalkene complexes [{W(CO)₅}₂{η^1:2‐(R)P=CH₂}] ( 4 a : R=Cp*, 5 : R=H) and the triazaphosphole derivative [{W(CO)₅}P(Cp*)‐CH₂‐N{W(CO)₅}=N‐N(N=CH₂)] ( 6 a ). The phosphaalkene complex ( 4 a ) and the arsaalkene complex ( 4 b ) are not stable at room temperature and decompose to the complexes [{W(CO)₅}₄(CH₂=E?E=CH₂)] ( 7 a : E=P, 7 b : E=As), which are the first examples of complexes with parent 2,3‐diphospha‐1,3‐butadiene and 2,3‐diarsa‐1,3‐butadiene ligands.     

A DFT Quantum‐Chemical Study of Ion‐Pair Formation for the Catalyst Cp2ZrMe2 /MAO

A process of ion‐pair formation in the system Cp₂ZrMe₂/methylaluminoxane (MAO) has been studied by means of density functional theory quantum‐chemical calculations for MAOs with different structures and reactive sites. An interaction of Cp₂ZrMe₂ with a MAO of the composition (AlMeO)₆ results in the formation of a stable molecular complex of the type Al₅Me₆O₅Al(Me)O–Zr(Me)Cp₂ with an equilibrium distance r(Zr–O) of 2.15 Å. The interaction of Cp₂ZrMe₂ with “true” MAO of the composition (Al₈Me₁₂O₆) proceeds with a tri‐coordinated aluminum atom in the active site (OAlMe₂) and yields the strongly polarized molecular complex or the μ‐Me‐bridged contact ion pair ( d ) [Cp₂(Me)Zr(μMe)Al≡MAO] with the distances r(Zr–μMe) = 2.38 Å and r(Al–μMe) = 2.28 Å. The following interaction of the μ‐Me contact ion pair ( d ) with AlMe₃ results in a formation of the trimethylaluminum (TMA)‐separated ion pair ( e ) [Cp₂Zr(μMe)₂AlMe₂]⁺–[MeMAO]^– with r[Zr–(MeMAO)] equal to 4.58 Å. The calculated composition and structure of ion pairs ( d ) and ( e ) are consistent with the ¹³C NMR data for the species detected in the Cp₂ZrMe₂/MAO system. An interaction of the TMA‐separated ion pair ( e ) with ethylene results in the substitution of AlMe₃ by C₂H₄ in a cationic part of the ion pair ( e ), and the following ethylene insertion into the Zr–Me bond. This reaction leads to formation of ion pair ( f ) of the composition [Cp₂ZrCH₂CH₂CH₃]⁺–[Me‐MAO]^– named as the propyl‐separated ion pair. Ion pair ( f ) exhibits distance r[Zr–(MeMAO)] = 3.88 Å and strong C_γ‐agostic interaction of the propyl group with the Zr atom. We suppose this propyl‐separated ion pair ( f ) to be an active center for olefin polymerization.     

Synthesis,Spectral, Valence‐Bond Parameters,and Single Crystal X‐ray Structural Studies on [Ni(dnpdtc)(PPh3)(NCS)] and [Ni(dnpdtc)(PPh3)(CN)]

Two new nickel complexes withplanar surrounding of Ni [Ni(dnpdtc)(PPh₃)(NCS)] (1) and [Ni(dnpdtc)(PPh₃)(CN)] (2) (dnpdtc=N, N‐dipropyldithiocarbamate) were prepared from the parent dithiocarbamate and were characterized by elemental analysis, electronic, IR and NMR spectra. The structures of both the complexes were determined by single crystal X‐ray crystallography. Thioureide stretching vibrations occur at 1528 cm^‐1 and 1521 cm^‐1 for 1 and 2 respectively. Large ³¹P chemical shifts were observed for the two compounds. A significant asymmetry in Ni—S bond distances was observed in compound 1 [2.1700(16) and 2.2251(17)Å] whereas in compound 2 the bond distances were almost similar [2.2100(14) and 2.2122(13)Å]. A marginal difference was observed with respect to the thioureide bond distances [1.340(6)Å for 1 and 1.312(5)Å for 2 ]. The observation clearly supports the less effective trans influence of SCN^— over PPh₃. However, PPh₃ and CN^— show almost similar trans influence.     

Nature of the Arsonium-Ylide Ph3As=CH2 and a Uranium(IV) Arsonium–Carbene Complex

Treatment of [Ph₃EMe][I] with [Na{N(SiMe₃)₂}] affords the ylides [Ph₃E=CH₂] (E=As, 1As ; P, 1P ). For 1As this overcomes prior difficulties in the synthesis of this classical arsonium-ylide that have historically impeded its wider study. The structure of 1As has now been determined, 45 years after it was first convincingly isolated, and compared to 1P , confirming the long-proposed hypothesis of increasing pyramidalisation of the ylide-carbon, highlighting the increasing dominance of E⁺−C⁻ dipolar resonance form (sp³-C) over the E=C ene π-bonded form (sp²-C), as group 15 is descended. The uranium(IV)–cyclometallate complex [U{N(CH₂CH₂NSiPrⁱ₃)₂(CH₂CH₂SiPrⁱ₂CH(Me)CH₂)}] reacts with 1As and 1P by α-proton abstraction to give [U(Tren^TIPS)(CHEPh₃)] (Tren^TIPS=N(CH₂CH₂NSiPrⁱ₃)₃; E=As, 2As ; P, 2P ), where 2As is an unprecedented structurally characterised arsonium-carbene complex. The short U−C distances and obtuse U-C-E angles suggest significant U=C double bond character. A shorter U−C distance is found for 2As than 2P , consistent with increased uranium- and reduced pnictonium-stabilisation of the carbene as group 15 is descended, which is supported by quantum chemical calculations.     

Trapping of a Highly Bent and Reduced Form of 2‐Phosphaethynolate in a Mixed‐Valence Diuranium–Triamidoamine Complex

The chemistry of 2‐phosphaethynolate is burgeoning, but there remains much to learn about this ligand, for example its reduction chemistry is scarce as this promotes P‐C‐O fragmentations or couplings. Here, we report that reduction of [U(Tren^TIPS)(OCP)] (Tren^TIPS=N(CH₂CH₂NSiPrⁱ₃)₃) with KC₈/2,2,2‐cryptand gives [{U(Tren^TIPS)}₂{μ‐η²(OP):η²(CP)‐OCP}][K(2,2,2‐cryptand)]. The coordination mode of this trapped 2‐phosphaethynolate is unique, and derives from an unprecedented highly reduced and highly bent form of this ligand with the most acute P‐C‐O angle in any complex to date (P‐C‐O ? ≈127°). The characterisation data support a mixed‐valence diuranium(III/IV) formulation, where backbonding from uranium gives a highly reduced form of the P‐C‐O unit that is perhaps best described as a uranium‐stabilised OCP^2?. radical dianion. Quantum chemical calculations reveal that this gives unprecedented carbene character to the P‐C‐O unit, which engages in a weak donor–acceptor interaction with one of the uranium ions.     

Vierkernige Clusterkomplexe vom Typ [MM′(AuPR3)2(μ‐H)(μ‐PCy2)(μ4‐PCy)(CO)6] (M,M′ = Mn,Re; R = Ph,Cy, Et): Synthese,Struktur und Topomerisierung

Tetranuclear Cluster Complexes of the Type [MM′(AuR₃)₂(μ‐H)(μ‐PCy₂)(μ₄‐PCy)(CO)₆] (M,M′ = Mn, Re; R = Ph, Cy, Et): Synthesis, Structure, and Topomerisation The dirhenium complex [Re₂(μ‐H)(μ‐PCy₂)(CO)₇(ax‐H₂PCy)] ( 1 ) reacts at room temperature in thf solution with each two equivalents of the base DBU and of ClAuPR₃ (R = Ph, Cy, Et) in a photochemical reaction process to afford the tetranuclear clusters [Re₂(AuPR₃)₂(μ‐H)(μ‐PCy₂)(μ₄‐PCy)(CO)₆] (R = Ph ( 2 ), Cy ( 3 ), Et ( 4 )) in yields of 35–48%. The homologue [Mn₂(μ‐H)(μ‐PCy₂)(CO)₇(ax‐H₂PCy)] ( 5 ) leads under the same reaction conditions to the corresponding products [Mn₂(AuPR₃)₂(μ‐H)(μ‐PCy₂)(μ₄‐PCy)(CO)₆] (R = Ph ( 6 ), Et ( 8 )). Also [MnRe(μ‐H)(μ‐PCy₂)(CO)₇(ax/eq‐H₂PCy)] ( 9 ) reacts under formation of [MnRe(AuPR₃)₂(μ‐H)(μ‐PCy₂)(μ₄‐PCy)(CO)₆] (R = Ph ( 10 ), Et ( 11 )). All new cluster complexes were identified by means of ¹H‐NMR, ³¹P‐NMR and ν(CO)‐IR spectroscopic measurements. 2 , 4 and 10 have also been characterized by single crystal X‐ray structure analyses with crystal parameters: 2 triclinic, space group P 1, a = 12.256(4) Å, b = 12.326(4) Å, c = 24.200(6) Å, α = 83.77(2)°, β = 78.43(2)°, γ = 68.76(2)°, Z = 2; 4 monoclinic, space group C2/c, a = 12.851(3) Å, b = 18.369(3) Å, c = 40.966(8) Å, β = 94.22(1)°, Z = 8; 10 triclinic, space group P 1, a = 12.083(1) Å, b = 12.185(2) Å, c = 24.017(6) Å, α = 83.49(29)°, β = 78.54(2)°, γ = 69.15(2)°, Z = 2. The trapezoid arrangement of the metal atoms in 2 and 4 show in the solid structure trans‐positioned an open and a closed Re…Au edge. In solution these edges are equivalent and, on the ³¹P NMR time scale, represent two fluxional Re–Au bonds in the course of a topomerization process. Corresponding dynamic properties were observed for the dimanganese compounds 6 and 8 but not for the related MnRe clusters 10 and 11 . 2 and 4 are the first examples of cluster compounds with a permanent Re–Au bond valence isomerization.     

Synthesis and single crystal X‐ray determination of the Schiff base 1‐[(2‐isopropyl‐5‐methylphenoxy)hydrazono] ethyl ferrocene

The reaction of acetylferrocene [Fe(η‐C₅H₅)(η‐C₅H₄COCH₃)] (1) with (2‐isopropyl‐5‐methylphenoxy) acetic acid hydrazide [CH₃C₆H₃CH(CH₃)₂OCH₂CONHNH₂] (2) in refluxing ethanol gives the stable light‐orange–brown Schiff base 1‐[(2‐isopropyl‐5‐methylphenoxy)hydrazono] ethyl ferrocene, [CH₃C₆H₃CH(CH₃)₂OCH₂CONHN?C(CH₃)Fe(η‐C₅H₅)(η‐C₅H₄)] (3). Complex 3 has been characterized by elemental analysis, IR, ¹H NMR and single crystal X‐ray diffraction study. It crystallizes in the monoclinic space group P2₁/n, with a = 9.6965(15), b = 7.4991(12), c = 29.698(7) Å, β = 99.010(13) °, V = 2132.8(7) ų, D_calc = 1.346 Mg m^?3; absorption coefficient, 0.729 mm^?1. The crystal structure clearly shows the characteristic [N? H···O] hydrogen bonding between the two adjacent molecules of 3. This acts as a bidentale ligand, which, on treatment with [Ru(CO)₂Cl₂] _n, gives a stable bimetallic yellow–orange complex (4). Copyright © 2002 John Wiley & Sons, Ltd.     

An Inverted‐Sandwich Diuranium μ‐η5:η5‐Cyclo‐P5 Complex Supported by U‐P5 δ‐Bonding

Reaction of [U(Tren^TIPS)] [ 1 , Tren^TIPS=N(CH₂CH₂NSiiPr₃)₃] with 0.25 equivalents of P₄ reproducibly affords the unprecedented actinide inverted sandwich cyclo‐P₅ complex [{U(Tren^TIPS)}₂(μ‐η⁵:η⁵‐cyclo‐P₅)] ( 2 ). All prior examples of cyclo‐P₅ are stabilized by d‐block metals, so 2 shows that cyclo‐P₅ does not require d‐block ions to be prepared. Although cyclo‐P₅ is isolobal to cyclopentadienyl, which usually bonds to metals via σ‐ and π‐interactions with minimal δ‐bonding, theoretical calculations suggest the principal bonding in the U(P₅)U unit is polarized δ‐bonding. Surprisingly, the characterization data are overall consistent with charge transfer from uranium to the cyclo‐P₅ unit to give a cyclo‐P₅ charge state that approximates to a dianionic formulation. This is ascribed to the larger size and superior acceptor character of cyclo‐P₅ compared to cyclopentadienyl, the strongly reducing nature of uranium(III), and the availability of uranium δ‐symmetry 5f orbitals.     

Technetium Complexes with 2‐Mercapto‐methyltetrazolate

2‐Mercapto‐methyltetrazolate, Smetetraz^–, acts as monoanionic, monodentate ligand in a number of technetium compounds. Anionic Tc^V complexes of the types [TcO(Smetetraz)₄]^– and [TcN(Smetetraz)₄]^2– are formed when (Bu₄N)[Tc^VOCl₄] or (Bu₄N)[Tc^VINCl₄], respectively, react with Na(Smetetraz). Reduction of the metal takes place in the latter case. (Bu₄N)₂[TcN(Smetetraz)₄] crystallises in the monoclinic space group Pc (a = 9.701(5), b = 17.570(5), c = 16.821(10) Å, β = 96.50(3)°, Z = 2). The Tc atom is situated 0.580(3) Å above the basal plane of a square pyramid which is formed by the sulfur atoms and the nitrido ligand as its apex. The Tc–S bond lengths lie between 2.384(3) and 2.410(3) Å. [Tc(PPh₃)(Smetetraz)₃(CH₃CN)] is formed during the reaction of [TcCl₃(PPh₃)₂(CH₃CN)] with NaSmetetraz as blue needles with co‐crystallised solvent toluene (space group C2/c, a = 24.188(4), b = 14.373(1), c = 25.617(5) Å, β = 109.48(1)°, Z = 8). The metal atom is coordinated by PPh₃ and CH₃CN in the axial position of a trigonal bipyramid. All three aryl rings are on the sterically less strained side of the plane defined by the sulfur atoms. The Tc–S bond lengths range between 2.233(2) and 2.247(2) Å.     

Tri­benzyl{η5‐[2‐(p‐tolyl)­prop‐2‐yl]­cyclo­penta­dienyl}­zirconium

The title compound, [Zr(C₇H₇)₃(C₁₅H₁₇)], (I), crystallizes from light petroleum with two independent mol­ecules in the asymmetric unit. Whereas in the parent mol­ecule, Zr(η⁵‐C₅H₅)(CH₂Ph)₃, all three Zr—CH₂Ph angles are equal, in (I), they differ significantly. In spite of their different environments, both independent mol­ecules in (I) exhibit a small, an expected, and a large Zr—CH₂Ph angle. The angles are similar to those of the closely related tri­benzyl­[η⁵‐(benzyl­di­methyl­silyl)­cyclo­penta­dienyl]­zirconium complex. The smallest Zr—CH₂Ph angle and the consequently relatively short Zr?C_ipso distance are indicative of η²‐bonding of the benzyl group.     

Darstellung und Kristallstruktur der Addukte [DB-18C6] · CH3CN · CH3CSOH und [DC-18C6](CH3CSOH)2 sowie der salzartigen Verbindungen [Cs(B-15C5)2]CH3CSS und [Cs(DB-18C6)]2S5(DMF)21)

Synthesis and Crystal Structure of the Adducts [DB-18C6] · CH₃CN · CH₃CSOH and [DC-18C6](CH₃CSOH)₂ as well as of the Salt-like Compounds [Cs(B-15C5)₂]CH₃CSS and [Cs(DB-18C6)]₂S₅(DMF)₂¹) The reaction products of crown ethers, cesium, and sulfur in aprotic solvents like acetonitrile and dimethylformamide strongly depend on the reaction conditions. Using CH₃CN as a solvent, sometimes neutral host-guest adducts crystallize only, e.g., [dibenzo-18C6] · CH₃CN · CH₃CSOH (monoclinic, S. G. P2₁/c, Z = 4, a = 9.73(1) Å, b = 22.03(1) Å, c = 11.86(1) Å, β = 91.8(1)°) or [dicyclohexyl-18C6](CH₃CSOH)₂ (monoclinic, S. G. P2₁/n, Z = 2, a = 7.75(1) Å, b = 10.32(1) Å, c = 17.73(1) Å, β = 95.7(1)°). The monothioacetic acid, CH₃CSOH, must be regarded as the first product of the hydrolysis of CH₃CN. Furthermore, another product of this kind of hydrolysis, CH₃CSSH, is obtained too. Therefore, we also obtain the salt-like compound [Cs(benzo-15C5)₂]CH₃CSS (monoclinic, S. G. C2/c, Z = 4, a = 16.05(1) Å, b = 16.73(1) Å, c = 13.11(1) Å, β = 106.3(1)°). If the solvent DMF is used, the pentasulfide [Cs(dibenzo-18C6)]₂S₅(DMF)₂ crystallizes (monoclinic, S. G. P2₁/n, Z = 4, a = 14.79(1) Å, b = 14.24(1) Å, c = 25.74(1) Å, β = 92.7(1°. The S₅^2? anions show the cis-conformation.     

Synthesis and Thermal Behaviour of Compounds in the System [Ph4P]Cl/BiCl3 and the Crystal Structures of [Ph4P]3[Bi2Cl9] · 2 CH2Cl2 and [Ph4P]2[Bi2Cl8] · 2 CH3COCH3

Six polynuclear chlorobismuthates are formed in the reaction between BiCl₃ and Ph₄PCl by variation of the molar ratio of the educts, the solvents and the crystallisation methods: [Ph₄P]₃[Bi₂Cl₉] · 2 CH₂Cl₂, [Ph₄P]₃[Bi₂Cl₉] · CH₃COCH₃, [Ph₄P]₂[Bi₂Cl₈] · 2 CH₃COCH₃, [Ph₄P]₄[Bi₄Cl₁₆] · 3 CH₃CN, [Ph₄P]₄[Bi₆Cl₂₂], and [Ph₄P]₄[Bi₈Cl₂₈]. We report the crystal structure of [Ph₄P]₃[Bi₂Cl₉] · 2 CH₂Cl₂ which crystallises with triclinic symmetry in the S. G. P1 No. 2, with the lattice parameters a = 13.080(3) Å, b = 14.369(3) Å, c = 21.397(4) Å, α = 96.83(1)°, β = 95.96(1)°, γ = 95.94(2)°, V = 3943.9(1) ų, Z = 2. The anion is formed from two face‐sharing BiCl₆‐octahedra. [Ph₄P]₂[Bi₂Cl₈] · 2 CH₃COCH₃ crystallises with monoclinic symmetry in the S. G. P2₁/n, No. 14, with the lattice parameters a = 14.045(5) Å, b = 12.921(4) Å, c = 17.098(3) Å, β = 111.10(2)°, V = 2894.8(2) ų, Z = 2. The anion is a bi‐octahedron of two square‐pyramids, joined by a common edge. The octahedral coordination is achieved with two acetone ligands. [Ph₄P]₄[Bi₄Cl₁₆] · 3 CH₃CN crystallises in the triclinic S. G., P1, No. 2, with the lattice parameters a = 14.245(9) Å, b = 17.318(6) Å, c = 24.475(8) Å, α = 104.66(3)°, β = 95.93(3)°, γ = 106.90(4)°, V = 5486(4) ų, Z = 2. Two Bi₂Cl₈ dimers in syn‐position form the cubic anion. Lattice parameters of [Ph₄P]₃[Bi₂Cl₉] · CH₃COCH₃ are also given. The solvated compounds are desolvated at approximately 100 °C. [Ph₄P]₃[Bi₂Cl₉] · 2 CH₂Cl₂ and [Ph₄P]₃[Bi₂Cl₉] · CH₃COCH₃ show the same sequence of phase transitions after desolvation. All compounds melt into a liquid in which some order is observed and transform on cooling into the glassy state.     

N‐Heterocyclic Phosphenium,Arsenium, and Stibenium Ions as Ligands in Transition Metal Complexes: A Comparative Experimental and Computational Study

Reaction of 2‐chloro‐1,3,2‐diazaarsolenes and ‐diazaphospholenes with Tl[Co(CO)₄] gives instable complexes of type [Co(ER₂)(CO)₄] which decarbonylated to yield [Co(ER₂)(CO)₃]. Spectroscopic and X‐ray diffraction studies revealed that the tetracarbonyl complexes can be formulated as ion pair for E = P and as covalent metalla‐arsine for E = As, and the tricarbonyl complexes as carbene‐like species with a formal E=Co double bond. A similar reactivity towards Tl[Co(CO)₄] was also inferred for 1,3,2‐diazastibolenes although the products were not isolable and their constitution remained uncertain. Evaluation of structural and computational data suggests that the weak and polarized Co–As bond in [Co(AsR₂)(CO)₄] can be characterized as an “inverse” M→L donor‐acceptor bond. The computational studies disclosed further η²(EN)‐coordination of the EN₂C₂ heterocycle as an alternative to the formation of a carbene‐like structure for [Co(ER₂)(CO)₃]. The η²‐complex is less stable for E = P but close in energy for E = As and more stable than the carbene‐like complex for E = Sb.