Salt Elimination Reactions Research Articles

Bismuth Bound to Transition Metals: Visible-Light-Induced Olefin Coordination, Reductive Elimination, and Oxidative Addition.

A series of dibenzobismepinyl (C14H10Bi) substituted transition metal complexes of the type [(C14H10Bi)M(CO)x(L)] (M = Mn, Co, Fe) was prepared in salt elimination reactions from a halobismepine and sodium metallates. Irradiation of these complexes with visible light has been investigated, aiming at the elimination of one carbonyl ligand and the concomitant coordination of the bismepine's olefin moiety to the transition metal center. The resulting complexes of the type [{κ2C,κ1Bi-(C14H10)Bi}M(CO)x-1(L)] (M = Co, Fe) have been isolated and fully characterized. When two dibenzobismepinyl units are positioned in the coordination sphere of an iron carbonyl complex fragment, reductive elimination / oxidative addition events of the dibismuthane (C14H10Bi)2 have been shown to be relevant. The analytical techniques applied in this work include (heteronuclear) NMR spectroscopy, elemental analysis, single-crystal X-ray diffraction analysis, UV/Vis spectroscopy, IR spectroscopy and (TD)-DFT calculations.

The synthesis, characterization, and thermal properties of a titanium (III) amidinate compound and its potential as a single chemical vapor deposition precursor for N/C-doped TiO2 film

A titanium(III) amidinate compound had been successfully obtained using a salt elimination reaction between TiCl3(3THF) and [Li(i Prn BuAMD)] in a 65% yield, and the characterization of the compound was conducted using various characterization methods. The reported compound’s thermal performances were studied through thermal gravimetric analysis (TGA), and the result indicated that the reported titanium(III) amidinate compound exhibited a suitable volatility, high thermal stability, and sufficient vapor pressure. Furthermore, film material deposit was performed in a CVD reactor under low pressure, and a N/C-doped TiO2 film was successfully deposited.

Crystalline Radical Anion of a Diboratriazole and Its Conversion to a Neutral Radical Driven by a Carbene.

One-electron reduction of diboratriazole 1 with potassium graphite (KC8) generates the radical anion 1•-•K+, which undergoes a salt (KCl) elimination reaction upon addition of an N-heterocyclic carbene (NHC) to afford the neutral diboratriazole radical 3. An X-ray diffraction analysis, electron paramagnetic resonance spectroscopy, and computational studies revealed that an unpaired electron in radical species 1•-•K+ and 3 is delocalized over the π-system of the B2N3 and carbene rings. Reversible oxidation of 3 gives rise to a diboratriazole cation 4 featuring a 6π aromatic character. Moreover, treating 1•-•K+ with a half equivalent of a bis(NHC) produces a biradical species 5, in which there is little interaction between two radical moieties separated by the bis(NHC) linker, suggesting the dis-biradical property. 5 undergoes stepwise and reversible two-electron oxidation, establishing three formal oxidation states.

Unique Double and Triple Decker Arrangements of Rare‐Earth 9,10‐Diborataanthracene Complexes Featuring Single‐Molecule Magnet Characteristics

AbstractHerein, we present the first report on the synthesis of rare‐earth complexes featuring a 9,10‐diborataanthracene ligand. This 14‐π‐electron ligand is highly reductive and was previously used in small‐molecule activation. Salt elimination reactions between dipotassium 9,10‐diethyl‐9,10‐diborataanthracene [K2(DEDBA)] and [LnIII(η8‐CotTIPS)(BH4)(thf)x] (CotTIPS=1,4‐(iPr3Si)2C8H6) in a 1 : 1 ratio yielded heteroleptic sandwich complexes [K(η8‐CotTIPS)LnIII(η6‐DEDBA)] (Ln=Y, Dy, Er). These compounds form Lewis‐base‐free one‐dimensional coordination polymers when crystallised from toluene. In contrast, reaction of [K2(DEDBA)] and [LnIII(η8‐CotTIPS)(BH4)(thf)x] in a 1 : 2 ratio led to the formation of heteroleptic triple‐decker complexes [(η8‐CotTIPS)LnIII(μ‐η6:η6‐DEDBA)LnIII(η8‐CotTIPS)] (Ln=Y, Dy, Er). Notably, these are not only the first lanthanide triple‐decker compounds featuring a six‐membered ring as a deck but also the first trivalent lanthanide triple‐decker featuring a heterocycle in the coordination sphere. Magnetic investigations reveal that [K(η8‐CotTIPS)LnIII(η6‐DEDBA)] (Ln=Dy, Er) and [(η8‐CotTIPS)ErIII(μ‐η6:η6‐DEDBA)ErIII(η8‐CotTIPS)] exhibit Single‐Molecule Magnet (SMM) behaviour. In the case of [(η8‐CotTIPS)LnIII(μ‐η6:η6‐DEDBA)LnIII(η8‐CotTIPS)] (Ln=Dy, Er), the introduction of a second near lanthanide ion results in strong antiferromagnetic interactions, allowing the enhancement of the magnetic characteristic of the system, compared to the quasi isolated counterpart. This research renews the overlooked coordination chemistry of the DBA ligand and expands it to encompass rare‐earth elements.

Unique Double and Triple Decker Arrangements of Rare-Earth 9,10-Diborataanthracene Complexes Featuring Single-Molecule Magnet Characteristics.

Herein, we present the first report on the synthesis of rare-earth complexes featuring a 9,10-diborataanthracene ligand. This 14-π-electron ligand is highly reductive and was previously used in small-molecule activation. Salt elimination reactions between dipotassium 9,10-diethyl-9,10-diborataanthracene [K2(DEDBA)] and [LnIII(η8-CotTIPS)(BH4)(thf)x] (CotTIPS=1,4-(iPr3Si)2C8H6) in a 1 : 1 ratio yielded heteroleptic sandwich complexes [K(η8-CotTIPS)LnIII(η6-DEDBA)] (Ln=Y, Dy, Er). These compounds form Lewis-base-free one-dimensional coordination polymers when crystallised from toluene. In contrast, reaction of [K2(DEDBA)] and [LnIII(η8-CotTIPS)(BH4)(thf)x] in a 1 : 2 ratio led to the formation of heteroleptic triple-decker complexes [(η8-CotTIPS)LnIII(μ-η6:η6-DEDBA)LnIII(η8-CotTIPS)] (Ln=Y, Dy, Er). Notably, these are not only the first lanthanide triple-decker compounds featuring a six-membered ring as a deck but also the first trivalent lanthanide triple-decker featuring a heterocycle in the coordination sphere. Magnetic investigations reveal that [K(η8-CotTIPS)LnIII(η6-DEDBA)] (Ln=Dy, Er) and [(η8-CotTIPS)ErIII(μ-η6:η6-DEDBA)ErIII(η8-CotTIPS)] exhibit Single-Molecule Magnet (SMM) behaviour. In the case of [(η8-CotTIPS)LnIII(μ-η6:η6-DEDBA)LnIII(η8-CotTIPS)] (Ln=Dy, Er), the introduction of a second near lanthanide ion results in strong antiferromagnetic interactions, allowing the enhancement of the magnetic characteristic of the system, compared to the quasi isolated counterpart. This research renews the overlooked coordination chemistry of the DBA ligand and expands it to encompass rare-earth elements.

Synthesis, Structural Characterization, and Magnetic Properties of Lanthanide Arsolyl Sandwich Complexes.

A series of trivalent lanthanide sandwich complexes [(η5-C4R4As)Ln(η8-C8H8)] using three different arsolyl ligands are reported. The complexes were obtained via salt elimination reactions between potassium arsolyl salts and lanthanide precursors [LnI(COT)(THF)2] (Ln = Sm, Dy, Er; COT = η8-C8H8). The resulting compounds exhibit classical sandwich complex structures with one notable exception. Characterization was conducted in both the solid state using single-crystal X-ray diffraction and in solution for the Sm compounds using NMR spectroscopy. Furthermore, the magnetic properties of an Er complex were investigated, revealing distinctive single-molecule-magnet behavior characterized by an energy barrier of Ueff = 323.3 K. Theoretical calculations were employed to support and interpret the experimental findings, with a comparative analysis performed against previously reported complexes.

Heterotrimetallic clusters with U-Ni-Ge and U-Ni-Sn units

Metal-metal bonds in complexes with d-block transition metals are common; but those with metal–metal bonds involving both p-, d-, and f-block metals are extremely rare. Here, we report two examples of heterotrimetallic clusters featuring U-Ni-Ge and U-Ni-Sn units. The heterotrimetallic clusters [(CH2OCH2CH2NPiPr2)2U(µ-Ni)(GePh3)(µ-Cl)]2 (2) and [(CH2OCH2CH2NPiPr2)2U(µ-Ni)(SnPh3)(µ-Cl)]2 (3) were synthesized by the salt elimination reactions of [(CH2OCH2CH2NPiPr2)2UCl(µ-Ni)(µ-Cl)]n (1) with Ph3SnK or Ph3GeLi, respectively. Complexes 2 and 3 were fully characterized by single crystal X-ray diffraction, elemental analysis, UV–Vis-NIR and SQUID. Theoretical studies at the DFT level showed that the Ni-Ge and Ni-Sn bonding interactions are polarized toward Ge and Sn. In both cases, the covalent part of the bonding is controlled by the atomic orbital overlap rather than by the energy difference. This study provides a new opportunity to explore the property of heterometallic clusters with diversified metal–metal bonds.

Tetravalent Uranium and Thorium Complexes: Elucidating Disparate Reactivities of AnIVCl2 (An = U, Th) Supported by a Pyridine-Decorated Dianionic Ligand.

Although synthesis, reactivity, and bonding of U(IV) and Th(IV) complexes have been extensively studied, direct comparison of fully analogous compounds is rare. Herein, we report corresponding complexes 1-U and 1-Th, in which U(IV) and Th(IV) are supported by the tetradentate pyridine-decorated dianionic ligand N2NN' (1,1,1-trimethyl-N-(2-(((pyridin-2-ylmethyl)(2-((trimethylsilyl)amino)benzyl)amino)methyl)phenyl)silanamine). Although 1-U and 1-Th are structurally very similar, they display disparate reactivities with TMS3SiK (tris(trimethylsilyl)silylpotassium). The reaction of (N2NN')UCl2 (1-U) and 1 equiv of TMS3SiK in THF unexpectedly formed [Cl(N2NN')U]2O (2-U) featuring an unusual bent U-O-U moiety. In contrast, a salt elimination reaction between (N2NN')ThCl2 (1-Th) and 1 equiv of TMS3SiK led to thorium complex 2-Th, in which the pyridyl group has undergone a 1,4-addition nucleophilic attack. Complex 2-Th serves as a synthon for preparing dimetallic bis-azide complex 3-Th by reaction with NaN3. The complexes were characterized by X-ray crystal diffraction, solution NMR, FT-IR, and elemental analysis. Computations of the formation mechanism of 2-U from 1-U suggest reduced U(III) as a key intermediate for promoting the cleavage of the C-O bonds of THF. The inaccessible nature of Th(III) as an intermediate oxidation state explains the very different reactivity of 1-Th versus 1-U. Given that reactants 1-U and 1-Th and products 2-U and 2-Th all comprise tetravalent actinides, this is an unusual case of very disparate reactivity despite no net change in the oxidation state. Complexes 2-U and 3-Th provide a basis for the synthesis of other dinuclear actinide complexes with novel reactivity and properties.

Anilidophosphine ligand supported praseodymium and terbium phosphaethynolate complexes: Synthesis, characterization, and DFT calculations

The 2-phosphaethynolate has received particular attention and displayed various reaction patterns due to its ambident property. In this work, the reactivity of monoanionic bidentate anilidophosphine PN ligand (PN: N-(2-(diisopropylphosphanyl)-4-methylphenyl)-2,4,6-trimethyl anilide) supported (PNMe3)2PrIIICl (2A) and (PNMe3)2TbIIICl (2B) with NaOCP(dioxane)2.5 by salt elimination reaction is described. The reactions yield corresponding praseodymium and terbium phosphaethynolate complexes: (PNMe3)2PrIIIOCP (3A) and (PNMe3)2TbIIIOCP (3B), respectively. These two complexes feature a preferential O-bound terminal adduct. Magnetic data analysis reveals that praseodymium and terbium chloride and phosphaethynolate complexes showed a strong temperature dependence. All the complexes have been characterized by various measurement means, including NMR, UV spectroscopies, FT-IR spectrum as well as X-ray single crystal crystallography. For comparison, bond analyses of all the complexes collected from experimental and computational approaches are conducted in detail.

A versatile strategy for the formation of hydride-bridged actinide-iridium multimetallics.

Reaction of the potassium pentamethylcyclopentadienyl iridate tris-hydride K[IrCp*H3] with UCl4 and ThCl4(DME)2 led to the complete replacement of the halide ligands to generate multimetallic complexes U{(μ-H)3IrCp*}4 (1) and Th{[(μ-H2)(H)IrCp*]2[(μ-H)3IrCp*]2} (2), respectively. These analogues feature a significant discrepancy in hydride bonding modes; 1 contains twelve bridging hydrides while 2 contains ten bridging hydrides and two terminal, Ir-bound hydrides. Use of a U(iii) starting material, UI3(1,4-dioxane)1.5, resulted in the octanuclear complex {U[(μ2-H3)IrCp*]2[(μ3-H2)IrCp*]}2 (3). Computational studies indicate significant bonding character between U/Th and Ir in 1 and 2, with f-orbital involvement in the singly-occupied molecular orbitals of the uranium species 1. In addition, these studies attribute the variation in hydride bonding between 1 and 2 to differences in dispersion effects.

Comparison of group 4 and thorium M(IV) substituted cyclopentadienyl silanide complexes.

We report the synthesis and characterisation of a series of M(IV) substituted cyclopentadienyl hypersilanide complexes of the general formula [M(CpR)2{Si(SiMe3)3}(X)] (M = Hf, Th; CpR = Cp', {C5H4(SiMe3)} or Cp'', {C5H3(SiMe3)2-1,3}; X = Cl, C3H5). The separate salt metathesis reactions of [M(CpR)2(Cl)2] (M = Zr or Hf, CpR = Cp'; M = Hf or Th, CpR = Cp'') with equimolar K{Si(SiMe3)3} gave the respective mono-silanide complexes [M(Cp')2{Si(SiMe3)3}(Cl)] (M = Zr, 1; Hf, 2), [Hf(Cp'')(Cp'){Si(SiMe3)3}(Cl)] (3) and [Th(Cp'')2{Si(SiMe3)3}(Cl)] (4), with only a trace amount of 3 presumably formed via silatropic and sigmatropic shifts; the synthesis of 1 from [Zr(Cp')2(Cl)2] and Li{Si(SiMe3)3} has been reported previously. The salt elimination reaction of 2 with one equivalent of allylmagnesium chloride gave [Hf(Cp')2{Si(SiMe3)3}(η3-C3H5)] (5), whilst the corresponding reaction of 2 with equimolar benzyl potassium yielded [Hf(Cp')2(CH2Ph)2] (6) together with a mixture of other products, with elimination of both KCl and K{Si(SiMe3)3}. Attempts to prepare isolated [M(CpR)2{Si(SiMe3)3}]+ cations from 4 or 5 by standard abstraction methodologies were unsuccessful. The reduction of 4 with KC8 gave the known Th(III) complex, [Th(Cp'')3]. Complexes 2-6 were characterised by single crystal XRD, whilst 2, 4 and 5 were additionally characterised by 1H, 13C{1H} and 29Si{1H} NMR spectroscopy, ATR-IR spectroscopy and elemental analysis. In order to probe differences in M(IV)-Si bonds for d- and f-block metals we studied the electronic structures of 1-5 by density functional theory calculations, showing M-Si bonds of similar covalency for Zr(IV) and Hf(IV), and less covalent M-Si bonds for Th(IV).

Anionic Magnesium and Calcium Hydrides: Transforming CO into Unsaturated Disilyl Ethers

AbstractThe synthesis, characterisation and reactivity of two isostructural anionic magnesium and calcium complexes is reported. By X‐ray and neutron diffraction techniques, the anionic hydrides are shown to exist as dimers, held together by a range of interactions between the two anions and two bridging potassium cations. Unlike the vast proportion of previously reported dimeric group 2 hydrides, which have hydrides that bridge two group 2 centres, here the hydrides are shown to be “terminal”, but stabilised by interactions with the potassium cations. Both anionic hydrides were found to insert and couple CO under mild reaction conditions to give the corresponding group 2 cis‐ethenediolate complexes. These cis‐ethenediolate complexes were found to undergo salt elimination reactions with silyl chlorides, allowing access to small unsaturated disilyl ethers with a high percentage of their mass originating from the C1 source CO.

Anionic Magnesium and Calcium Hydrides: Transforming CO into Unsaturated Disilyl Ethers.

The synthesis, characterisation and reactivity of two isostructural anionic magnesium and calcium complexes is reported. By X-ray and neutron diffraction techniques, the anionic hydrides are shown to exist as dimers, held together by a range of interactions between the two anions and two bridging potassium cations. Unlike the vast proportion of previously reported dimeric group 2 hydrides, which have hydrides that bridge two group 2 centres, here the hydrides are shown to be "terminal", but stabilised by interactions with the potassium cations. Both anionic hydrides were found to insert and couple CO under mild reaction conditions to give the corresponding group 2 cis-ethenediolate complexes. These cis-ethenediolate complexes were found to undergo salt elimination reactions with silyl chlorides, allowing access to small unsaturated disilyl ethers with a high percentage of their mass originating from the C1 source CO.

Chromium-Based Complexes Bearing N-Substituted Diphosphinoamine Ligands for Ethylene Oligomerization.

A range of novel N-substituted diphosphinoamine (PNP) ligands Ph2PN(R)PPh2 [R = F2CHCH2 (1); R = Me2CHCH2 (2); R = Me2CHCH2CH2 (3)] have been synthesized via one-step salt elimination reaction. The ligand-coordinated chromium carbonyls [Ph2PN(R)PPh2]Cr(CO)4 (4–6) were further synthesized, and X-ray crystallography analysis of complex 6 revealed the κ2-P,P bidentate binding mode of Cr center and the molecular structure of PNP ligand 3. Then the catalytic ethylene oligomerization behaviors of PNP ligands 1–3 bridging chromium chloride complexes {[Ph2PN(R)PPh2]CrCl2(μ-Cl)}2 (7–9) were further discussed in depth. Experimental results showed that complex 7 with the strong electron-withdrawing F2CHCH2 group can promote the nonselective ethylene oligomerization, while both complex 8 and complex 9 with the electron-donating Me2CHCH2 and Me2CHCH2CH2 groups can significantly enhance the selective ethylene tri/tetramerization. The good catalytic activity of 198.3 kg/(g Cr·h), the selectivity toward 1-hexene and 1-octene of 76.4%, and the low PE content of 0.2% were simultaneously achieved with the Al/Cr molar ratio of 600 using the complex 8/MMAO system at 45 °C and 45 bar. These excellent results were mainly attributed to the fact that the β-branching of bridging ligand 2 increased the steric bulk of the N-moiety for complex 8.

Heterobimetallic-Mediated Dinitrogen Functionalization: N-C Bond Formation at Rhenium-Group 9 Diazenido Complexes.

We report the synthesis and characterization of rhenium-group 9 heterobimetallic diazenido species (η5-Cp)Re(μ-BDI)(μ-N2)M(η4-COD) (1-M, M = Ir or Rh, Cp = cyclopentadienide, BDI = N,N'-bis(2,6-diisopropylphenyl)-3,5-dimethyl-β-diketiminate, COD = 1,5-cyclooctadiene), formed from salt elimination reactions between Na[(η5-Cp)Re(BDI)] and [MCl(η4-COD)]2. Additionally, we find that these same reagents react under an argon atmosphere to instead produce bridging hydride complexes (BDI)Re(μ-η5:η1-C5H4)(μ-H)M(η4-COD) (2-M), which undergo rearrangements upon protonation to form the alternative bridging hydrides [(η5-Cp)Re(μ-BDI)(μ-H)M(η4-COD)][(B(m-C6H3(CF3)2)4)] (3-M). Further, we demonstrate the first example of N-C bond formation at a heterobimetallic dinitrogen complex through reactions of 1-M and methyl triflate, which produces the alkylated species [(η5-Cp)Re(μ-N(Me)N)(μ-BDI)M(η4-COD)][OTf] (4-M, OTf = trifluoromethanesulfonate). A combination of spectroscopic studies, X-ray structural analysis, and computational investigations is discussed as an aid to understanding the modes of dinitrogen activation within these unique heterobimetallic complexes.

Metal Complexes of the Perfluorinated Trityl Alkoxide [(C6F5)3CO]−

AbstractHerein we investigate sodium, magnesium, zinc, titanium, silver and thallium complexes based on the perfluorinated trityl alcohol (C6F5)3COH (1) with respect to their structural motifs. The coordination compounds were prepared by alkane or salt elimination reactions in non‐polar solvents. XRD analysis revealed a monomeric structure for Ti[OC(C6F5)3]2[OCH(CH3)2]2 (2), dimers for [Mg(OC(C6F5)3)2]2 (3), [Zn(OC(C6F5)3)Et]2 (4) and [Tl(OC(C6F5)3)]2 (5) as well as tetrameric structural motifs for the homoleptic sodium and silver compounds with the general formula [M(OC(C6F5)3)]4: A distorted [NaO]4 cube is observed for [Na(OC(C6F5)3)]4 (6) whereas [Ag(OC(C6F5)3)]4 (7) exhibits a planar [AgO]4 square. Metal fluorine contacts play an important role in all molecular structures presented herein.

Introduction of plumbole to f-element chemistry.

Herein, we present the synthesis and characterization of heteroleptic lanthanide complexes bearing a dianionic η5-plumbole ligand in their coordination sphere. The reaction proceeds via a salt elimination reaction between the dilithioplumbole ([Li(thf)]2[1,4-bis-tert-butyl-dimethylsilyl-2,3-bis-phenyl-plumbolyl] = [Li2(thf)2(η5-LPb)]) and specifically designed [Ln(η8-COTTIPS)BH4] precursors (Ln = lanthanide, La, Ce, Sm, Er; COTTIPS = 1,4-bis-triisopropylsilyl-cyclooctatetraenyl), that are capable of stabilizing a planar plumbole moiety in the coordination sphere of different trivalent lanthanide ions. In-depth ab initio calculations show that the aromaticity of the dianionic plumbole is retained upon coordination. Electron delocalization occurs from the plumbole HOMO to an orbital of mainly d-character at the lanthanide ion. The magnetic properties of the erbium congener were investigated in detail, leading to the observation of magnetic hysteresis up to 5 K (200 Oe s−1), an unequivocal proof for single molecule magnet behavior in this system. The magnetic behavior of the erbium species can be modulated by manipulating the position of the lithium cation in the complex, which directly influences the bonding metrics in the central [(η5-LPb)Er(η8-COTTIPS)]− fragment. This allowed us to assess a fundamental magneto-structural correlation in an otherwise identical inner coordination sphere.

S‐ and p‐Block Dinuclear Metal(loid) Complexes Bearing 1,4‐Phenylene and 1,4‐Cyclohexylene Bridged Bis(amidinate) Ligands

Treating two 2,6‐diisopropylphenyl (Dip) substituted, 1,4‐phenylene or 1,4‐cyclohexylene bridged, bis(amidine)s, viz. C6Hn{[Dip(H)N](DipN=)C}2‐1,4 (n = 4 (PhAmid2H2) or 10 (CyAmid2H2)), with groups 1 and 2 alkyl complexes, proceeded via alkane elimination and the formation of the lithium and magnesium bis(amidinate) complexes, [{(THF)2Li}2(µ‐PhAmid2)], [{(THF)3K(µ‐PhAmid2)K}∞], [(Et2O)IMg(µ‐PhAmid2)MgI(OEt2)2], and [{(Et2O)2IMg}2(µ‐CyAmid2)]. The crystal structures of the complexes reveal variable modes of coordination at the metal centre. Two lithium bis(amidinate) compounds have been utilized in salt elimination reactions with group 13 and 14 halides, yielding a series of bis(amidinato) aluminum(III), silicon(IV), germanium(II) and tin(II) halide complexes, viz. [(I2Al)2(µ‐PhAmid2)], [(X3Si)2(µ‐PhAmid2)] (X = Cl, Br or Cl/H), [(ClM)2(µ‐PhAmid2)] (M = Ge or Sn), and [(ClGe)2(µ‐CyAmid2)]. Attempts to reduce the bis(amidinato) metal(loid) halide complexes with a series of s‐block metal reducing agents have been carried out, with the aim of obtaining dinuclear or polymeric bis(amidinato) metal(I) systems. However, these reductions typically led to intractable mixtures of products. In other attempted reductions, treating [(Cl2HSi)2(µ‐PhAmid2)] with two N‐heterocyclic carbenes (NHCs), :C{(RNCMe)2} (R = Me (TMC) or Pri (IPrIMe)) led to single dehydrochlorination reactions, affording the cyclohexa‐2,5‐diene‐1,4‐diylidene bridged bis(diamide) silicon(IV) complexes, [{(NHC)Cl2Si}{µ‐(DipN)2C=(C6H4)=C(NDip)2}{SiHCl(NHC)}] (NHC = TMC or IPrIMe), in which the bis(amidinate) ligand has been transformed into a tetra(amide).

Cu(I) Complexes of Multidentate N,C,N- and P,C,P-Carbodiphosphorane Ligands and Their Photoluminescence

A series of dinuclear copper(I) N,C,N- and P,C,P-carbodiphosphorane (CDP) complexes using multidentate ligands CDP(Py)2 (1) and (CDP(CH2PPh2)2 (13) have been isolated and characterized. Detailed structural information was gained by single-crystal XRD analyses of nine representative examples. The common structural motive is the central double ylidic carbon atom with its characteristic two lone pairs involved in the binding of two geminal L-Cu(I) fragments at Cu–Cu distances in the range 2.55–2.67 Å. In order to enhance conformational rigidity within the characteristic Cu–C–Cu triangle, two types of chelating side arms were symmetrically attached to each phosphorus atom: two 2-pyridyl functions in ligand CDP(Py)2 (1) and its dinuclear copper complexes 2–9 and 11, as well as two diphenylphosphinomethylene functions in ligand CDP(CH2PPh2)2 (13) and its di- and mononuclear complexes 14–18. Neutral complexes were typically obtained via the reaction of 1 with Cu(I) species CuCl, CuI, and CuSPh or via the salt elimination reaction of [(CuCl)2(CDP(Py)2] (2) with sodium carbazolate. Cationic Cu(I) complexes were prepared upon treating 1 with two equivalents of [Cu(NCMe)4]PF6, followed by the addition of either two equivalents of an aryl phosphine (PPh3, P(C6H4OMe)3) or one equivalent of bisphosphine ligands bis[(2-diphenylphosphino)phenyl] ether (DPEPhos), 4,5-bis(diphenylphosphino)-9,9-dimethylxanthene (XantPhos), or 1,1′-bis(diphenyl-phosphino) ferrocene (dppf). For the first time, carbodiphosphorane CDP(CH2PPh2)2 (13) could be isolated upon treating its precursor [CH(dppm)2]Cl (12) with NaNH2 in liquid NH3. A protonated and a deprotonated derivative of ligand 13 were prepared, and their coordination was compared to neutral CDP ligand 13. NMR analysis and DFT calculations reveal that the most stable tautomer of 13 does not show a CDP (or carbone) structure in its uncoordinated base form. For most of the prepared complexes, photoluminescence upon irradiation with UV light at room temperature was observed. Quantum yields (ΦPL) were determined to be 36% for dicationic [(CuPPh3)2(CDP(Py)2)](PF6)2 (4) and 60% for neutral [(CuSPh)2(CDP(CH2PPh2)2] (16).

Synthesis and Structural Diversity of Triaryl(phenylethyl)silanes

Starting from trichloro(phenylethyl)silane, six differently fluorinated triaryl(phenylethyl)silanes were synthesized by salt elimination reactions and their structures were determined by X-ray diffraction analysis. Tris(pentafluorophenyl)(phenylethyl)silane reveals a folded structure due to intramolecular π-stacking interactions, while those with a lower degree of fluorination show either intermolecular π-stacking or no interplay between the aryl groups. A similar folded structure was observed for (4-methylphenethyl)tris(pentafluorophenyl)silane and [2-(naphth-2-yl)ethyl]tris(pentafluorophenyl)silane, both generated from the corresponding trichlorosilanes. In contrast, the inversely fluorinated [2-(pentafluorophenyl)ethyl]triphenylsilane only revealed intermolecular π-stacking interactions. Compounds with tetrafluoropyridyl substituents behave differently; with these compounds, π-stacking is only observed between the fluorinated units. All compounds were analyzed by NMR and IR spectroscopy, elemental analyses and single-crystal X-ray diffraction, and found to have strong H/C/N/F···F and N···C contacts.