Anionic Chains of Parent Pnictogenylboranes

We report on the synthesis and structural characterization of unprecedented anionic parent compounds of mixed Group 13/15 elements. The reactions of the pnictogenylboranes H₂E‐BH₂?NMe₃ ( 1 a =P, 1 b =As) with phosphorus and arsenic centered nucleophiles of the type [EH₂]^? (E=P, As) lead to the formation of compounds of the type [H₂E‐BH₂‐E′H₂]^? ( 2 : E=E′=P; 3 : E=E′=As; 4 : E=P, E′=As) containing anionic pnictogen–boron chain‐like units. Furthermore, a longer 5‐membered chain species [H₂As‐BH₂‐PH₂‐BH₂‐AsH₂]^? ( 5 ) and a cyclic compound [NHC^dipp‐H₂B‐PH₂‐BH₂‐NHC^dipp]⁺[P₅B₅H₁₉]^? ( 6 ) containing a n‐butylcyclohexane‐like anion were obtained. All the compounds have been characterized by X‐ray structure analysis, multinuclear NMR spectroscopy, IR spectroscopy, and mass spectrometry. DFT calculations elucidate their high thermodynamic stability, the charge distribution, and give insight into the reaction pathway.     

A Donor‐Stabilized Zwitterionic “Half‐Parent” Phosphasilene and Its Unusual Reactivity towards Small Molecules

The stabilization of the labile, zwitterionic “half‐parent” phosphasilene 4 L′Si?PH (L′=CH[(C?CH₂)CMe(NAr)₂]; Ar=2,6‐iPr₂C₆H₃) could now be accomplished by coordination with two different donor ligands (4‐dimethylaminopyridine (DMAP) and 1,3,4,5‐tetramethylimidazol‐2‐ylidene), affording the adducts 8 and 9 , respectively. The DMAP‐stabilized zwitterionic “half‐parent” phosphasilene 8 is capable of transferring the elusive parent phosphinidene moiety (:PH) to an unsaturated organic substrate, in analogy to the “free” phosphasilene 4 . Furthermore, compounds 4 and 8 show an unusual reactivity of the Si?P moiety towards small molecules. They are capable of adding dimethylzinc and of activating the S?H bonds in H₂S and the N?H bonds in ammonia and several organoamines. Interestingly, the DMAP donor ligand of 8 has the propensity to act as a leaving group at the phosphasilene during the reaction. Accordingly, treatment of 8 with H₂S affords, under liberation of DMAP, the unprecedented thiosilanoic phosphane LSi?S(PH₂) 16 (L=HC(CMe[2,6‐iPr₂C₆H₃N])₂). Compounds 4 and 8 react with ammonia both affording L′Si(NH₂)PH₂ 17 , respectively. In addition, the reaction of 8 with isoproylamine, p‐toluidine, and pentafluorophenylhydrazine lead to the corresponding phosphanylsilanes L′Si(PH₂)NHR (R=iPr 18 a ; R=C₆H₅?CH₃ 18 b , R=NH(C₆F₅) 18 c ), respectively.     

Group 13 Element Trihalide Complexes of Anionic N‐Heterocyclic Carbenes

A series of group 13 complexes of the general type [{(WCA‐IDipp)EX₃}Li(solv)] (E=B, Al, Ga, In; X=Cl, Br) that bear an anionic N‐heterocyclic carbene ligand with a weakly coordinating borate moiety (WCA‐IDipp, WCA=B(C₆F₅)₃ and IDipp=1,3‐bis(2,6‐diisopropylphenyl)imidazolin‐2‐ylidene) were prepared by the reaction of the respective group 13 trihalides (EX₃) with the lithium salt [(WCA‐IDipp)Li ? toluene]. The molecular structures of the BBr₃, AlCl₃, AlBr₃, GaCl₃ and InCl₃ adducts were established by X‐ray diffraction analyses, revealing the formation of coordination polymers linked by halide‐lithium interactions, except for the indium derivative, which consists of isolated [Li(THF)₄]⁺ and [(WCA‐IDipp)InCl₃]^? ions in the solid state.     

SiP Double Bonds: Experimental and Theoretical Study of an NHC‐Stabilized Phosphasilenylidene

An experimental and theoretical study of the first compound featuring a Si?P bond to a two‐coordinate silicon atom is reported. The NHC‐stabilized phosphasilenylidene (IDipp)Si?PMes* (IDipp=1,3‐bis(2,6‐diisopropylphenyl)imidazolin‐2‐ylidene, Mes*=2,4,6‐tBu₃C₆H₂) was prepared by SiMe₃Cl elimination from SiCl₂(IDipp) and LiP(Mes*)SiMe₃ and characterized by X‐ray crystallography, NMR spectroscopy, cyclic voltammetry, and UV/Vis spectroscopy. It has a planar trans‐bent geometry with a short Si? P distance of 2.1188(7) Å and acute bonding angles at Si (96.90(6)°) and P (95.38(6)°). The bonding parameters indicate the presence of a Si?P bond with a lone electron pair of high s‐character at Si and P, in agreement with natural bond orbital (NBO) analysis. Comparative cyclic voltammetric and UV/Vis spectroscopic experiments of this compound, the disilicon(0) compound (IDipp)Si?Si(IDipp), and the diphosphene Mes*P?PMes* reveal, in combination with quantum chemical calculations, the isolobal relationship of the three double‐bond systems.     

Monomeric β-Diketiminato Group 13 Metal Dipnictogenide Complexes with Two Terminal EH2 Groups (E=P,As)

The pnictogenyl Group 13 compounds (Dipp₂Nacnac)M[E(SiMe₃)₂]Cl and (Dipp₂Nacnac)M(EH₂)₂ (Dipp₂Nacnac=HC[C(Me)N(Ar)]₂, Ar: Dipp=2,6-iPr₂C₆H₃; M=Al, Ga, In; E=P, As) were successfully synthesized. The salt metathesis between (Dipp₂Nacnac)MCl₂ and LiE(SiMe₃)₂ only led to monosubstituted compounds (Dipp₂Nacnac)M[E(SiMe₃)₂]Cl [E=P, M=Ga( 1 ), In ( 2 ); E=As, M=Ga ( 3 ), In ( 4 )], regardless of the stoichiometric ratios used. In contrast to the steric effect of the SiMe₃ groups in 1 – 4 , the reactions of the corresponding halides with LiPH₂⋅DME (or KAsH₂) facilely yielded the dipnictogenide compounds (Dipp₂Nacnac)M(EH₂)₂ (E=P, M=Al ( 5 ), Ga ( 6 ), In ( 7 ); E=As, M=Al ( 8 ), Ga ( 9 )), avoiding the use of flammable and toxic PH₃ and AsH₃ for their synthesis. The compounds 5 – 9 are the first examples of monomeric Group 13 diphosphanides and diarsanides in which the metal center is bound to two terminal PH₂ and AsH₂ groups, respectively. In contrast to the successful synthesis of the indium diphosphanide (Dipp₂Nacnac)In(PH₂)₂, the reaction of (Dipp₂Nacnac)InCl₂ with KAsH₂ led to an indium mirror due to the instability of the target product.     

Ruthenium Complexes of an Abnormally Bound,Anionic N‐Heterocyclic Carbene

The abnormally bound, anionic NHC–borane complex [Ru(IDipp‐BF₃)(p‐cymene)Cl]₂ ( 4 ; IDipp‐BF₃=1,3‐(2,6‐iPr₂C₆H₃)₂‐2‐BF₃(C₃HN₂)‐4‐yl) was synthesized by transmetalation from Li[(IDipp‐BF₃)₂Ag]. Addition of donors gave species of the form [Ru(IDipp‐BF₃)(p‐cymene)(L)Cl], whereas halide abstraction with Ag(Et₂O)[B(C₆F₅)₄] gave C?H activation of the methine position of the IDipp?BF₃ ligand.     

Theoretical assessing on the coordination mode and bonding in heteronuclear group‐13 dimetallocene

In this article, the coordination mode, the nature of metal–ligand interaction and dimetallic bonding in heteronuclear group‐13 dimetallocene (CpMM′CpI₂; Cp = C₅H₅, M/M′=B, Al, Ga, In, and Tl) have been investigated within the framework of the atoms in molecules theory, electron localization function, and energy decomposition analysis. The calculated results show that the symmetries of the title compounds, the coordination modes between the metal and ligand, the strength and nature of M‐ligand interaction and M M′ bond are well correlated with the periodicity changing of group‐13 metal atom going from the lighter to the heavier (B, Al, Ga, In, and Tl). The heavier group 13 metal atom is corresponding to the higher symmetry, stronger metal–ligand interaction, and weaker dimetallic bond. The covalent characters of both metal–ligand interaction and dimetallic bond are decreasing in the sequence of M′=Al, Ga, In, and Tl, for the same M atom.     

A Convenient Route to Mixed Pnictogenylboranes

We report on the synthesis and characterization of mixed pnictogenylboranes. The substitution of the Lewis base SMe₂ in (OC)₅W–PH₂BH₂–SMe₂ ( 2 ) by different pnictogenylboranes ER₂BH₂–LB (E=P, As, Sb) leads to the Lewis acid/base stabilized butane analogue (OC)₅W–PH₂BH₂ER₂BH₂–LB ( 3 a , b : E=P; R=H, SiMe₃; LB=NMe₃; 4 a , b : E=As; R=H, SiMe₃; LB=NMe₃; 5 : E=Sb; R=SiMe₃; LB=NHC^Me). All of these compounds were characterized by single‐crystal X‐ray structure analysis, mass spectrometry, NMR, and IR spectroscopy. In addition, the very unstable phosphanylborane chain PH₂BH₂PH₂BH₂–NMe₃ ( 1 ) was synthesized. DFT calculations provide insight into the thermodynamics of these reactions.     

Isolation and Characterization of Lewis Base Stabilized Monomeric Parent Stibanylboranes

The synthesis of the Lewis base stabilized monomeric parent compound of stibanylboranes, “H₂Sb? BH₂”, is reported. Through a salt metathesis route, the silyl‐substituted compounds (Me₃Si)₂Sb? BH₂?LB (LB=NMe₃, NHC^Me) were synthesized as representatives of derivatives with a Sb? B σ bond. Under very mild conditions, they could be transformed into the target compounds Me₃N?H₂B? HSb? BH₂?NMe₃ and H₂Sb? BH₂?NHC^Me, respectively. The products were characterized by X‐ray structure analysis, NMR spectroscopy, IR spectroscopy, and mass spectrometry. DFT calculations give further insight into the stability and bonding of these unique compounds.     

Coordination and Activation of AlH and GaH Bonds

The modes of interaction of donor‐stabilized Group 13 hydrides (E=Al, Ga) were investigated towards 14‐ and 16‐electron transition‐metal fragments. More electron‐rich N‐heterocyclic carbene‐stabilized alanes/gallanes of the type NHC?EH₃ (E=Al or Ga) exclusively generate κ² complexes of the type [M(CO)₄(κ²‐H₃E?NHC)] with [M(CO)₄(COD)] (M=Cr, Mo), including the first κ² σ‐gallane complexes. β‐Diketiminato (′nacnac′)‐stabilized systems, {HC(MeCNDipp)₂}EH₂, show more diverse reactivity towards Group 6 carbonyl reagents. For {HC(MeCNDipp)₂}AlH₂, both κ¹ and κ² complexes were isolated, while [Cr(CO)₄(κ²‐H₂Ga{(NDippCMe)₂CH})] is the only simple κ² adduct of the nacnac‐stabilized gallane which can be trapped, albeit as a co‐crystallite with the (dehydrogenated) gallylene system [Cr(CO)₅(Ga{(NDippCMe)₂CH})]. Reaction of [Co₂(CO)₈] with {HC(MeCDippN)₂}AlH₂ generates [(OC)₃Co(μ‐H)₂Al{(NdippCme)₂CH}][Co(CO)₄] ( 12 ), which while retaining direct Al?H interactions, features a hitherto unprecedented degree of bond activation in a σ‐alane complex.     

An NHC-Stabilized H2GeBH2 Precursor for the Preparation of Cationic Group 13/14/15 Hydride Chains

The synthesis, characterization and reactivity studies of the NHC-stabilized complex IDipp ⋅ GeH₂BH₂OTf ( 1 ) (IDipp=1,3-bis(2,6-diisopropylphenyl)imidazolin-2-ylidene) are reported. Nucleophilic substitution of the triflate (OTf) group in 1 by phosphine or arsine donors provides access to the cationic group 13/14/15 chains [IDipp ⋅ GeH₂BH₂ERR¹R²]⁺ ( 2 E=P; R, R¹=H; R²=^tBu; 3 E=P; R=H; R¹, R²=Ph; 4 a E=P; R, R¹, R²=Ph; 4 b E=As; R, R¹, R²=Ph). These novel cationic chains were characterized by X-ray crystallography, NMR spectroscopy and mass spectrometry. Moreover, the formation of the parent complexes [IDipp ⋅ GeH₂BH₂PH₃][OTf] ( 5 ) and [IDipp ⋅ GeH₃][OTf] ( 6 ) were achieved by reaction of 1 with PH₃. Accompanying DFT computations give insight into the stability of the formed chains with respect to their decomposition.     

Studien zur Reaktion von [Me2AlP(SiMe3)2]2 mit basenstabilisierten Organogalliumchloriden und ‐hydriden

Investigations on the Reactivity of [Me₂AlP(SiMe₃)₂]₂ with Base‐stabilized Organogalliumhalides and ‐hydrides [Me₂AlP(SiMe₃)₂]₂ ( 1 ) reacts with dmap?Ga(Cl)Me₂, dmap?Ga(Me)Cl₂, dmap?GaCl₃ and dmap?Ga(H)Me₂ with Al‐P bond cleavage and subsequent formation of heterocyclic [Me₂GaP(SiMe₃)₂]₂ ( 2 ) as well as dmap?AlMe_xCl_3?x (x = 3 8 ; 2 3 ; 1 4 ; 0 5 ). The reaction between equimolar amounts of dmap?Al(Me₂)P(SiMe₃)₂ and dmap?Ga(t‐Bu₂)Cl yield dmap?Ga(t‐Bu₂)P(SiMe₃)₂ ( 6 ) and dmap?AlMe₂Cl ( 3 ). 2 – 8 were characterized by NMR spectroscopy, 2 and 6 also by single crystal X‐ray diffraction.     

Lewis acid stabilized group 13–15 element analogs of ethylene

Stabilization of hydrogen-substituted group 13–15 compounds H₂EE′H₂ (E = B, Al, Ga; E′ = P, As, Sb) by Lewis acids is considered at B3LYP/def2-TZVP, B3LYP-D3/def2-TZVP and M06-2X/def2-TZVP levels of theory. It is shown, that for many Lewis acids additional reactivity beyond the DA complex formation with H₂EE′H₂ monomer is expected. In case of complexation with E(C₆F₅)₃, F/H exchange reactions with group 13 bound hydrides are predicted to be exothermic and accompanied by the activation energies which are smaller than dissociation of the complex into components. In case of complex formation with transition metal (TM) carbonyls, additional O → Al, TM–C → Al interactions are observed, which in several cases lead to cyclic structures. The most promising candidates for the experimental studies have been identified. Synthetic approaches to the most promising LA-only stabilized compounds are recommended.     

New Trinuclear Complexes of Group 6, 8, and 9 Metals with a Triply Bridging Borylene Ligand

Trinuclear complexes of group 6, 8, and 9 transition metals with a (μ₃‐BH) ligand [(μ₃‐BH)(Cp*Rh)₂(μ‐CO)M′(CO)₅], 3 and 4 ( 3 : M′=Mo; 4 : M′=W) and 5 – 8 , [(Cp*Ru)₃(μ₃‐CO)₂(μ₃‐BH)(μ₃‐E)(μ‐H){M′(CO)₃}] ( 5 : M′=Cr, E=CO; 6 : M′=Mo, E=CO; 7 : M′=Mo, E=BH; 8 : M′=W, E=CO), have been synthesized from the reaction between nido‐[(Cp*M)₂B₃H₇] (nido‐ 1 : M=Rh; nido‐ 2 : M=RuH, Cp*=η⁵‐C₅Me₅) and [M′(CO)₅ ? thf] (M′=Mo and W). Compounds 3 and 4 are isoelectronic and isostructural with [(μ₃‐BH)(Cp*Co)₂(μ‐CO)M′(CO)₅], (M′=Cr, Mo and W) and [(μ₃‐BH)(Cp*Co)₂(μ‐CO)(μ‐H)₂M′′H(CO)₃], (M′′=Mn and Re). All compounds are composed of a bridging borylene ligand (B?H) that is effectively stabilized by a trinuclear framework. In contrast, the reaction of nido‐ 1 with [Cr(CO)₅ ? thf] gave [(Cp*Rh)₂Cr(CO)₃(μ‐CO)(μ₃‐BH)(B₂H₄)] ( 9 ). The geometry of 9 can be viewed as a condensed polyhedron composed of [Rh₂Cr(μ₃‐BH)] and [Rh₂CrB₂], a tetrahedral and a square pyramidal geometry, respectively. The bonding of 9 can be considered by using the polyhedral fusion formalism of Mingos. All compounds have been characterized by using different spectroscopic studies and the molecular structures were determined by using single‐crystal X‐ray diffraction analysis.     

Isolation of N-Heterocyclic Carbene-Stabilized Phosphorus and Arsenic Mononitride

Phosphorus mononitride (PN) and arsenic mononitride (AsN) species supported by two different N-heterocyclic carbenes were prepared: The reaction of [(IDipp)NSiMe₃] [IDipp = 1,3-bis(2,6-diisopropylphenyl)imidazolin-2-ylidene] with PCl₃ or AsCl₃ afforded the dichlorides [(IDipp)NECl₂] (E = P, As) and, after the addition of IMes [IMes = 1,3-bis(2,4,6-trimethylphenyl)imidazolin-2-ylidene], the cationic chloro species [(IDipp)NE(Cl)(IMes)]Cl (E = P, As), which were reduced with potassium graphite (KC₈) to yield the neutral compounds [(IMes)PN(IDipp)] and [(IMes)AsN(IDipp)], which exhibit the typical trans-bent geometry of dicarbene-dielement species in the solid state according to single-crystal X-ray diffraction.     

Quantum chemistry investigation of electronic structure and NMR spectral characteristics for fluorides of dialkylamidosulfoxylic acids and related compounds

The parent (H₂N? S? F) and N,N‐dialkyl‐substituted fluorides of amidosulfoxylic acid (R₂N? S? F, R?Me or R₂N?Morph) as well as the related compounds X? S? F (X?CH₃, OH, F, SiH₃, PH₂, SH, Cl) have been investigated with quantum chemical calculations at the ab initio (MP2) level of approximation. The geometries, electronic structures, molecular orbital (MO) energies and NMR chemical shift values have been calculated to evaluate the role and extent of the polarization and delocalization effects in forming of the high‐field fluorine NMR resonances within the series of interest. The δF magnitudes for all investigated fluorides of amidosulfoxylic acid as well as the δN value calculated for Me₂N? S? F are in the good agreement with the ¹⁹F and ¹⁴N NMR chemical shift values measured experimentally. For the parent compounds, H₂N? S? F and H₂N? SO₂? F, the orientation of principal axes of the magnetic shielding tensors and the corresponding principal σ_ii values along these axes have been qualitatively interpreted basing on the analysis of the MO interactions in the presence of the rotating magnetic field. Copyright © 2009 John Wiley & Sons, Ltd.     

Diisobutyl(phosphanyl)alan: ein einfaches PH2‐Transferreagens zur Synthese von polyphosphanylierten Verbindungen des Siliciums und Germaniums

Diisobutyl(phosphaneyl)alane: a Simple PH₂‐Transfer Reagent for the Synthesis of Polyphosphaneyl Compounds of Silicon and Germanium Introduction of PH₃ into a solution of diisobutylaluminium hydride in hexane furnishes, under evolution of H₂, the title compound [iBu₂AlPH₂]₃ ( 4 ). The alane 4 is probably trimer in noncoordinating solvents such as hydrocarbons and shows only a marginal tendency in such solutions to undergo dissociation. A nucleophilic transfer of the PH₂ group in 4 onto E–X‐compounds of group 14 elements (E = Si, Ge; X = Cl) succeeds only in the presence of THF which transforms 4 to the corresponding monomeric, THF‐solvated alane 5 . The latter is a remarkable mild phosphaneylation reagent, which facilitates access to Si(PH₂)₄ ( 1 ), Ge(PH₂)₄ ( 2 ), MeSi(PH₂)₃ ( 6 ), and EtSi(PH₂)₃ ( 7 ) more efficiently.     

A Monoaryllead Trichloride That Resists Reductive Elimination

Transmetallation of Pb(OAc)₄ with R₂Hg ( 1 ), followed by treatment with HCl in Et₂O, provided RPbCl₃ ( 2 ), the first kinetically stabilized monoorganolead trihalide that resists reductive elimination under ambient conditions. The kinetic stabilisation relies on an intramolecularly coordinating O‐donor substituent (R=6‐Ph₂P(O)‐Ace‐5‐). The gram‐scale preparation of 2 was key for the synthesis of unsymmetrically substituted diaryllead dichlorides RR′PbCl₂ ( 3 a , R′=Ph; 3 b , R′=4‐MeOC₆H₄; 3 c , R′=4‐Me₂NC₆H₄).     

Synthesis and Structures of RhI and IrI Complexes Supported by N‐Heterocyclic Carbene‐Phosphinidene Adducts

N‐Heterocyclic carbene‐phosphinidene adducts of the type (IDipp)PR [R = Ph ( 5 ), SiMe₃ ( 6 ); IDipp = 1,3‐bis(2,6‐diisopropylphenyl)imidazolin‐2‐ylidene] were used as ligands for the preparation of rhodium(I) and iridium(I) complexes. Treatment of (IDipp)PPh ( 5 ) with the dimeric complexes [M(μ‐Cl)(COD)]₂ (M = Rh, Ir; COD = 1,5‐cyclcooctadiene) afforded the corresponding metal(I) complexes [M(COD)Cl{(IDipp)PPh}] [M = Rh ( 7 ) or Ir ( 8 )] in moderate to good yields. The reaction of (IDipp)PSiMe₃ ( 6 ) with [Ir(μ‐Cl)(COD)]₂ did not yield trimethylsilyl chloride elimination product, but furnished the 1:1 complex, [Ir(COD)Cl{(IDipp)PSiMe₃}] ( 9 ). Additionally, the rhodium‐COD complex 7 was converted into the corresponding rhodium‐carbonyl complex [Rh(CO)₂Cl{(IDipp)PPh}] ( 10 ) by reaction with an excess of carbon monoxide gas. All complexes were fully characterized by NMR spectroscopy, microanalyses, and single‐crystal X‐ray diffraction studies.     

Group 13 Ligand Supported Heavy‐Metal Complexes: First Structural Evidence for Gallium–Lead and Gallium–Mercury Bonds

Heavy‐metal complexes of lead and mercury stabilized by Group 13 ligands were derived from the oxidative addition of Ga(ddp) (ddp=HC(CMeNC₆H₃‐2,6‐iPr₂)₂, 2‐diisopropylphenylamino‐4‐diisopropyl phenylimino‐2‐pentene) with corresponding metal precursors. The reaction of Me₃PbCl and Ga(ddp) afforded compound [{(ddp)Ga(Cl)}PbMe₃] ( 1 ) composed of Ga? Pb^IV bonds. In addition, the monomeric plumbylene‐type compound [{(ddp)Ga(OSO₂CF₃)}₂Pb(thf)] ( 2 a ) with an unsupported Ga‐Pb^II‐Ga linkage was obtained by the reaction of [Pb(OSO₂CF₃)₃] with Ga(ddp) (2 equiv). Compound 2 a falls under the rare example of a discrete plumbylene‐type compound supported by a nonclassical ligand. Interesting structural changes were observed when [Pb(OSO₂CF₃)₃] ? 2 H₂O was treated with Ga(ddp) in a 1:2 ratio to yield [{(ddp)Ga(μ‐OSO₂CF₃)}₂(OH₂)Pb] ( 2 b ) at below ?10 °C. Compound 2 b consists of a bent Ga‐Pb‐Ga backbone with a bridging triflate group between the Ga? Pb bond and a weakly interacting water molecule at the gallium center. Similarly, the reaction of mercury thiolate Hg(SC₆F₅) with Ga(ddp) (2 equiv) produced the bimetallic homoleptic compounds anti‐[{(ddp)Ga(SC₆F₅)}₂Hg] ( 3 a ) and gauche‐[{(ddp)Ga(SC₆F₅)}₂Hg] ( 3 b ), respectively, with a linear Ga‐Hg‐Ga linkage. Compounds 1 – 3 were structurally characterized and these are the first examples of compounds comprised of Ga? Pb^II, Ga? Pb^IV, and Ga? Hg bonds.