Access to Bis-Silylene-Stabilized Group 13 Cations

Herein, we report the isolation of pyridine moiety-functionalized SiNSi pincer-based bis-silylene ligand (1) and its reactivity toward various halide precursors (X = Br and I) of group 13 elements (M = Al, Ga, and In). This gave us straightforward access to the SiNSi pincer-coordinated group 13 cations (2-7). These complexes are duly characterized by single-crystal X-ray diffraction studies, multinuclear magnetic resonance spectroscopy (1H, 13C, and 29Si), and high-resolution mass spectrometry techniques. Their electronic properties were further analyzed with the help of quantum chemical calculations.

Selective Hydrogen Isotope Exchange Catalysed by Simple Alkali-Metal Bases in DMSO

Dedicated to Proferssor Robert E. Mulvey on the occasion of his 65th birthday. Isotope Exchange processes are becoming the preferred way to prepare isotopically labelled molecules, avoiding the redesign of multistep synthetic protocols. In the case of deuterium incorporation, the most used strategy has employed transition metals, that offer high reactivity under mild reaction conditions. Despite their success, the trade-off is that these metals are precious, so expensive, and often exhibit high toxicity. Therefore, alternative transition-metal-free protocols would be a welcome addition to this field. In this report we show how the simple bases NaHMDS (HMDS=hexamethyldisilazide) and NaCH2SiMe3 can efficiently and selectively promote deuteration of a wide range of C(sp2)-H and C(sp3)-H bonds in DMSO-d6, providing an easy and direct access to deuterated compounds. Heterocycles, fluoroarenes, N-heterocyclic carbenes, amides and other aromatic molecules could be deuterated under mild conditions using catalytic amounts of base. Mechanistic studies along with the isolation and characterisation of reaction intermediates have flagged up the importance of the metalated substrate and metalated solvent in solution, establishing an equilibrium between these compounds is crucial for the success of this approach. An alkali-metal effect was observed, with heavier alkali-metal amides being more reactive at room temperature, but their lower stability at higher temperatures made sodium bases the optimal reagents for Hydrogen Isotope Exchange.

Reducing hybrid ligand-based alane and chasing aluminium(I): dialane and unusual transient dialumene

In this work, an alane, [DNIAlH2] (1) (DNI = 3,3-dimethyl-2-[2-methyl-2-(2,6-diisopropyl-aniline)ethenyl]-3H-indolenine), stabilised by a hybrid ligand was reduced by Jones's Mg(I) ([(MesBDIMg)2]) and Roesky's Al(I) ([DippBDIAl:]). The resulting dialane compound [{DNI(H)Al}2] (2) was characterised using NMR spectroscopy, mass spectrometry, DFT calculations and single-crystal XRD experiments. The reaction of aluminium dihydride [DNIAlH2] (1) with [DippBDIAl:] at high temperatures gives an intramolecular C(sp2)-H bond-activated compound 3. To study the monomeric hybrid ligand-based Al(I), characterisations and computational calculations were performed, which elucidate that compound 5, consisting of two inequivalent aluminium atoms in an Al2CN four-membered ring, resulting from the activation of a carbon-nitrogen bond in the reaction of [DNINa] with [(Cp*Al)4].

Dual Basicity and Nucleophilicity of Organosodium Reagents in Benzylic C-H Additions of Toluenes to Diarylethenes and Ketones

Profiting from the dual high basicity and nucleophilicity of organosodium complexes, here we report the stepwise lateral metalation of a wide range of alkyl arenes (MeAr), mediated by hydrocarbon-soluble NaCH2SiMe3 ⋅ PMDETA (PMDETA=N,N,N',N'',N''-pentamethyldiethylenetriamine), followed by nucleophilic addition to diarylethenes of the newly generated NaCH2Ar ⋅ PMDETA complexes. This method grants access to a range of functionalised hydrocarbons in excellent yields and can be upgraded to catalytic regimes when using trans-stilbene, a 10 mol% of the alkyl sodium base and toluene as a solvent. Extending this approach to aromatic ketones leads to the formation of stilbenes under mild reaction conditions, resulting from the deprotonative coupling of toluenes with ketones. Combining spectroscopic studies with the trapping and characterisation of key reaction intermediates, mechanistic insights have been gained, advancing the understanding of coordination effects in organosodium chemistry, and shedding light on their special reactivity profiles.

Copper Catalyzed Borylation of Alkynes: An Experimental Mechanistic Study

The copper catalyzed hydroboration of alkynes with B2pin2 was studied by in detail studies of individual relevant steps along the catalytic pathway. A number of reaction steps were retraced by in situ NMR spectroscopy as well as central intermediates and side-products were isolated and comprehensively characterized. A copper boryl complex is central to the catalytic process by inserting the terminal alkyne substrate into the B-Cu bond. The selectivity of this step - depending on the NHC auxiliary ligand - determines the α/β selectivity observed in the product. The latter complex is protonated by the auxiliary alcohol reagent resulting in hydroboration product formation and formation of a Cu alkoxido complex. Reaction of the latter with B2pin2 results in the regeneration of the central copper boryl complex. This alcoholysis step depends on the acidity of the alcohol, in particular on the relative acidity of the alcohol vs. the alkyne substrate. A number of side reactions leading to the hydrogenation product of the alkyne substrate and a bis hydroborated product were identified and studied in some detail. It is concluded that the performance of a particular catalytic system depends crucially on the relative acidities of the reagents and generalizations may be difficult.

Crystal structure and Hirshfeld surface analysis of dimeth-yl(phen-yl)phosphine sulfide

The title compound, C8H11PS, which melts below room temperature, was crystallized at low temperature. The P-S bond length is 1.9623 (5) Å and the major contributors to the Hirshfeld surface are H⋯H (58.1%), S⋯H/H⋯S (13.4%) and C⋯H/H⋯C contacts (11.7%).

Boron bis-(4-methylbenzoxazol-2-yl)-methanide complexes

Boron compounds have attracted the attention of chemists because of their unique catalytic properties and potential wider material applications. Although group 13 metal compounds, which are based on the bis-(benzoxazol-2-yl)-methane system (Box, ({NCOC6H4}2CH2)), have been reported in the last several years, boron containing Box compounds were still missing. Now we report their successful syntheses and spectroscopic characterisation in this work. The borane compound [({NCOC6H3}2CH)BH2] (1) and haloboranes [({NCOC6H3}2CH)BF2] (2), [({NCOC6H3}2CH)BCl2] (3) and [({NCOC6H3}2CH)BBr2] (4) were characterised in the solid state by single crystal X-ray diffraction and in solution by NMR techniques. In addition, the fluorescence properties of compounds 1-4 are communicated.

Deciphering Iron-Catalyzed C-H Amination with Organic Azides: N2 Cleavage from a Stable Organoazide Complex

Catalytic C-N bond formation by direct activation of C-H bonds offers wide synthetic potential. En route to C-H amination, complexes with organic azides are critical precursors towards the reactive nitrene intermediate. Despite their relevance, α-N coordinated organoazide complexes are scarce in general, and elusive with iron, although iron complexes are by far the most active catalysts for C-H amination with organoazides. Herein, we report the synthesis of a stable iron α-N coordinated organoazide complex from [Fe(N(SiMe3 )2 )2 ] and AdN3 (Ad=1-adamantyl) and its crystallographic, IR, NMR and zero-field 57 Fe Mössbauer spectroscopic characterization. These analyses revealed that the organoazide is in fast equilibrium between the free and coordinated state (Keq =62). Photo-crystallography experiments showed gradual dissociation of N2 , which imparted an Fe-N bond shortening and correspond to structural snapshots of the formation of an iron imido/nitrene complex. Reactivity of the organoazide complex in solution showed complete loss of N2 , and subsequent formation of a C-H aminated product via nitrene insertion into a C-H bond of the N(SiMe3 )2 ligand. Monitoring this reaction by 1 H NMR spectroscopy indicates the transient formation of the imido/nitrene intermediate, which was supported by Mössbauer spectroscopy in frozen solution.

A Neutral Planar Four-Membered Si2B2 2π-Aromatic Ring

The synthesis of the first inorganic four-membered neutral 2π-aromatic compound 2 is reported. This unique ring has been synthesized from a simple and straightforward reaction of amidinato-silylene with dichlorophenylborane, followed by the reduction with KC8 in THF. Compound 2 has been fully characterized by single-crystal X-ray diffraction (SC-XRD), NMR spectroscopy, and mass spectrometry. The computational calculations reveal that the Si2B2 ring is a π-delocalized system resulting from the interaction of pπ orbital of B and Si-N σ* orbitals having pseudo π symmetry. Compound 2 is the first known example of a neutral planar inorganic analogue of cyclobutenyl dication.

Synthesis, Reactivity and Coordination Chemistry of Group 9 PBP Boryl Pincer Complexes: [(PBP)M(PMe3)n] (M = Co, Rh, Ir; n = 1, 2)

The unsymmetrical diborane(4) derivative [(d(CH2P(iPr)2)abB)-Bpin] (1) proved to be a versatile PBP boryl pincer ligand precursor for Co(I) (2a, 4a), Rh(I) (2-3b) and Ir(I/III) (2-3c, 5-6c) complexes, in particular of the types [(d(CH2P(iPr)2)abB)M(PMe3)2] (2a-c) and [(d(CH2P(iPr)2)abB)M-PMe3] (2b-c). Whilst similar complexes have been obtained before, for the first time, the coordination chemistry of a homologous series of PBP pincer complexes, in particular the interconversion of the five- and four-coordinate complexes 2a-c/3a-c, was studied in detail. For Co, instead of the mono phosphine complex 2a, the dinitrogen complex [(d(CH2P(iPr)2)abB)Co(N2)(PMe3)] (4a) is formed spontaneously upon PMe3 abstraction from 2a in the presence of N2. All complexes were comprehensively characterised spectroscopically in solution via multinuclear (VT-)NMR spectroscopy and structurally in the solid state through single-crystal X-ray diffraction. The unique properties of the PBP ligand with respect to its coordination chemical properties are addressed.

A Carbene-Stabilized Boryl-Phosphinidene

Herein, the synthesis and characterization of the carbene-stabilized boryl phosphinidenes 1-3 are reported. Compounds 1-3 are obtained by reacting Me-cAAC=PK (Me2 -cAAC=dimethyl cyclic(alkyl)(amino)carbene) and dihaloaryl borane in toluene. All three compounds were characterized by X-ray crystallography. Quantum mechanical studies indicated that these compounds have two lone pairs on the P center viz., an σ-type lone pair and a "hidden" π-type lone pair. Hence, these compounds can act as double Lewis bases, and the basicity of the π-type lone pair is higher than the σ-type lone pair.

A Sodium Sodate as Precursor for Lanthanide Bis(4-R-benzoxazol-2-yl)methanide Single-Molecule Magnets

From the sodium sodate precursor [(Na(thf)₆][Na{(4-Me-NCOC₆H₃)₂CH}₂] (1) three isostructural dinuclear lanthanide complexes [(μ-Cl)Ln^III{(4-MeNCOC₆H₃)₂CH}₂]₂ with Ln = Gd (2), Dy (3), and Er (4) based on the N,N'-chelating monoanionic bis(4-methylbenzoxazol-2-yl)methanide ligand (titled "Mebox") were synthesized and characterized by X-ray diffraction and magnetic measurements. The sodium precursor 1 was analyzed via X-ray diffraction and diffusion-ordered NMR spectroscopy experiments (DOSY-NMR) in order to investigate its aggregation in solution and the solid state. The sodium analog [(thf)₃Na(NCOC₆H₄)₂CH] (1') based on the bis(benzoxazol-2-yl)-methanide ligand (titled "box") was prepared and analyzed for comparison reasons. From the lanthanide derivatives 2-4, the Dy^III complex 3 displays slow relaxation of magnetization at zero field, with a relaxation barrier of U = 315.7 cm^-1. The coupling strength between the two lanthanide centers was estimated with the Gd^III equivalent 2, giving a weak antiferromagnetic coupling of J = -0.035 cm^-1.

Alkali Metal Based Triimidosulfite Cages as Versatile Precursors for Single-Molecule Magnets

Based on the potassium [{S(tBuN)2 (tBuNH)}2 K3 (tmeda)-K3 {(HNtBu)(NtBu)2 S}2 ] (1) and sodium precursors [S(tBuN)3 (thf)3 -Na3 SNa3 (thf)3 (NtBu)3 S] (2), [S(tBuN)3 (thf)3 Na3 {(HNtBu)(NtBu)2 S}] (3) and [(tmeda)3 S-{Na3 (NtBu)3 S}2 ] (4) the syntheses and magnetic properties of three mixed metal triimidosulfite based alkali-lanthanide-metal-cages [(tBuNH)Dy{K(0.5tmeda)}2 {(NtBu)3 S}2 ]n (5) and [ClLn{Na(thf)}2 {(NtBu)3 S}2 ] with Ln=Dy (6), Er (7) are reported. The corresponding potassium (1) and sodium (2-4) based cages are characterized through XRD and NMR experiments. Preventing lithium chloride co-complexation led to a significant increase of SMM performance to previously reported sulfur-nitrogen ligands. The subsequent DyIII -complexes 5 and 6 display slow relaxation of magnetization at zero field, with relaxation barriers U=77.0 cm-1 for 5, 512.9 and 316.3 cm-1 for 6, respectively. Significantly, the latter complex 6 also exhibits a butterfly-shaped hysteresis up to 7 K.

Ligand properties of boryl ligands in bis-boryl rhodium(III) complexes: a case study

The oxidative addition of five diborane(4) derivatives, symmetrical and unsymmetrical, to [Rh(PMe₃)₃Cl] was studied. Only for the more electron poor diboron derivatives, B₂cat₂, B₂pin₂ and catB-Bpin the resulting octahedral bis-boryl complexes [(PMe₃)₃Rh(boryl)₂Cl] were obtained, while for the more electron rich congeners only the equilibrium oxidative addition (catB-Bdmab) or no significant reaction (pinB-Bdmab) was observed (pin = (OCMe₂)₂, cat = 1,2-O₂C₆H₄, dmab = 1,2-(NMe)₂C₆H₄). By abstraction of the chlorido ligand with NaBArF (BArF = tetrakis-[3,5-bis-(trifluormethyl)-phenyl]-borat) in the presence of a neutral ligand (L = PMe₃, MeCN, MeNC) the corresponding cationic octahedral complexes [(PMe₃)₃Rh(boryl)₂L]⁺ were obtained. All isolated complexes were fully characterised including single crystal X-ray diffraction and heteronuclear, temperature dependent NMR spectroscopy. Whilst the complexes [(PMe₃)₃Rh(boryl)₂Cl] and [(PMe₃)₃Rh(boryl)₂L]⁺ show many similarities, their detailed structural and spectroscopic properties depend crucially on the properties of both boryl ligands.

Isolation and Properties of the Long Elusive Deep Blue Soluble [K3 {(Nt Bu)3 S}2 ]. Cage Radical

The reaction of potassium metal with sulfurtriimide S(Nt Bu)3 (II) gives the long elusive deep blue cage radical [K3 {(Nt Bu)3 S}2 ]. (1_K) that crystallizes at -35 °C from toluene solution. The subsequent physical characterization via X-ray structure analysis, UV/Vis-, and EPR spectroscopy from solution reveals the existence of one unpaired electron delocalized within the whole cage, i.e. coupling with the six nitrogen atoms, as well as the three potassium atoms caped by the two SN3 ligands. The present X-ray structure analysis further supports previous assumptions made on the parent compound 1_Li obtained from [Li4 {(Nt Bu)3 S}2 ] (I) and finally elucidates the structural arrangement of the SN3 caps and alkali metals in such radical cage species.

High yield of a variety of silicon-boron radicals and their reactivity

Herein we report stable silicon-boron radicals of composition LSi(NMe2)-B(Br)Tip (1), LSi(NMe2)-B(I)Tip (2) LSi(tBu)-B(I)Tip (3) [L=PhC(NtBu)2]. They were prepared in high yield using a one-pot reaction of LSiR, X2BTip, and KC8...

Stabilization of Reactive Nitrene by Silylenes without Using a Reducing Metal

Herein, we report the stabilization of nitrene reagents as the source of a nitrogen atom to synthesize nitrogen-incorporated R1 LSi-N←SiLR2 (1) [L=PhC(NtBu)2 ; R1 =NTMS2 , R2 =NTMS]. Compound 1 is synthesized by reacting LSi(I)-SiI L with 3.1 equivalents of Me3 SiN3 at low temperature to afford a triene-like structural framework. Whereas the reaction of the LSi(I)-SiI L with 2.1 equivalents of Me3 SiN3 at room temperature produced silaimine 2 with a central four-membered Si2 N2 ring which is accompanied by a silylene LSi and a cleaved silylene fragment. 1 further reacts with AgOTf at room temperature to yield compound 3 which shows coordination of nitrene to silver with the triflate salt. The compounds 1 and 2 were fully characterized by NMR, mass spectrometry, and X-ray crystallographic analysis. The quantum mechanical calculations reveal that compounds 1 and 2 have dicoordinated monovalent N atoms having two active lone pairs of electrons. These lone pairs are stabilized by hyperconjugative interactions.

Imidosulfonate scorpionate ligands in lanthanide single-molecule magnet design: slow magnetic relaxation and butterfly hysteresis in [ClDy{Ph2PCH2S(NtBu)3}2]

Single-molecule magnets (SMMs) harbour vast opportunities for potential pioneering applications upon optimization like big data storage and quantum computing. Lanthanides were found to be highly suitable candidates in the design of such molecules, as they intrinsically hold a large unquenched orbital momentum and a strong spin-orbit coupling, warranting a high magnetic anisotropy. An indispensable element in successfully tailoring SMMs is the ligand design. Polyimido sulfur ligands offer a promising choice because the polar S⁺-N^--bond facilitates both electronic and geometric adaptability to various f-metals. In particular, the acute N-Ln-N bite angle generates advantageous magnetic properties. The [Ph₂PCH₂S(NtBu)₃]^- anion, introduced from [(thf)₃K{Ph₂PCH₂S(NtBu)₃}] (2) to a series of complexes [ClLn{Ph₂PCH₂S(NtBu)₃}₂] with Ln = Tb (3a), Dy (3b), Er (3c), Ho (3d), and Lu (3e), provides tripodal shielding of the metal's hemisphere as well as a side-arm donation of a soft phosphorus atom. For the Tb and Er complexes 3a and 3d, slow magnetic relaxation (U_eff = 235 and 34.5 cm^-1, respectively) was only observed under an applied dc field. The dysprosium congener 3b, however, is a true SMM with relaxation at zero field (U_eff = 66 cm^-1) and showing a butterfly hysteresis close to 3.5 K. Upon magnetic dilution with the diamagnetic and isostructural lutetium complex 3e or application of a magnetic field, the energy barrier to spin reversal is increased to 74 cm^-1.

Enhancing Steric Hindrance via Ligand Design in Dysprosium Complexes: From Induced Slow Relaxation to Zero-Field Single-Molecule Magnet Properties

The synthesis and magnetic characterization of three novel Dy compounds, [Dy{PPh₂S(N^tBu)₂}₂(μ-Cl₂)Li(THF)₂] (1), [Dy{PhS(N^tBu)₂}₂(μ-Cl₂)Li(THF)₂] (2), and [Dy{MeS(N^tBu)₃}₂(μ-Cl₂)Li(THF)₂] (3), based on the sulfur-nitrogen ligands RS(N^tBu)_x^- (where R = PPh₂, x = 2 for (1); R = Ph, x = 2 for (2); and R = Me, x = 3 for (3)) are reported. They represent rare examples of lanthanide-based complexes containing sulfur-nitrogen ligands, whose suitability to enhance the magnetic anisotropy in 3d metals was only recently established. Changes in the ligand field environment drastically affect the magnetic properties, with compounds 1 and 2 displaying field-induced single-molecule magnet (SMM) behavior, while compound 3 shows slow relaxation at zero field. These trends strongly suggest that ligand engineering strategies toward linear dysprosium complexes, similar to those for dysprosocenium complexes, should enhance the SMM performances of SN-based lanthanide compounds.

Slow Magnetic Relaxation in Mono- and Bimetallic Lanthanide Tetraimido-Sulfate S(NtBu)4 2- Complexes

Lanthanide ions are particularly well-suited for the design of single-molecule magnets owing to their large unquenched orbital angular momentum and strong spin-orbit coupling that gives rise to high magnetic anisotropy. Such nanoscopic bar magnets can potentially revolutionize high-density information storage and processing technologies, if blocking temperatures can be increased substantially. Exploring non-classical ligand scaffolds with the aim to boost the barriers to spin-relaxation are prerequisite. Here, the synthesis, crystallographic and magnetic characterization of a series of each isomorphous mono- and dinuclear lanthanide (Ln=Gd, Tb, Dy, Ho, Er) complexes comprising tetraimido sulfate ligands are presented. The dinuclear Dy complex [{(thf)2 Li(NtBu)2 S(tBuN)2 DyCl2 }2  ⋅ ClLi(thf)2 ] (1c) shows true signatures of single-molecule magnet behavior in the absence of a dc field. In addition, the mononuclear Dy and Tb complexes [{(thf)2 Li(NtBu)2 S(tBuN)2 LnCl2 (thf)2 ] (2b,c) show slow magnetic relaxation under applied dc fields.

Bis(4-benzhydryl-benzoxazol-2-yl)methane - from a Bulky NacNac Alternative to a Trianion in Alkali Metal Complexes

A novel sterically demanding bis(4-benzhydryl-benzoxazol-2-yl)methane ligand 6 (4-BzhH2 BoxCH2 ) was gained in a straightforward six-step synthesis. Starting from this ligand monomeric [M(4-BzhH2 BoxCH)] (M=Na (7), K (81 )) and dimeric [{M(4-BzhH2 BoxCH)}2 ] (M=K (82 ), Rb (9), Cs (10)) alkali metal complexes were synthesised by deprotonation. Abstraction of the potassium ion of 8 by reaction with 18-crown-6 resulted in the solvent separated ion pair [{(THF)2 K@(18-crown-6)}{bis(4-benzhydryl-benzoxazol-2-yl)methanide}] (11), including the energetically favoured monoanionic (E,E)-(4-BzhH2 BoxCH) ligand. Further reaction of 4-BzhH2 BoxCH2 with three equivalents KH and two equivalents 18-crown-6 yielded polymeric [{(THF)2 K@(18-crown-6)}{K@(18-crown-6)K(4-Bzh BoxCH)}]n (n→∞) (12) containing a trianionic ligand. The neutral ligand and herein reported alkali complexes were characterised by single X-ray analyses identifying the latter as a promising precursor for low-valent main group complexes.

Trigonal Planar Iron(II) and Cobalt(II) Complexes Containing [RS(NtBu)3]n- (R = NtBu, n = 2; CH2PPh2, n = 1) as Acute Bite-Angle Chelating Ligands: Soft P Donor Proves Beneficial to Magnetic Co Species

We prepared four new complexes, 4a,b and 5a,b, from polyimido sulfur-centered ligands with Fe^II and Co^II amides. Their molecular structures were elucidated by single-crystal X-ray diffraction. Cobalt magnetic investigations and multiconfigurational calculations provided insight into magneto-structural correlations between the acute N,N' chelating bite angle and P-side arm donation. The deviation from an ideal trigonal planar geometry and the magnetic performance correlated in an unprecedented manor. Mononuclear cobalt species 4b and 5b showed slow magnetic relaxation under a small applied dc field with energy barriers of up to 33.0 and 21.9 cm^-1, respectively. Although they possess some of the largest zero-field splitting parameters among three-coordinate cobalt single-ion magnets, both theory and experiment suggest that the high rhombicity (E/D) hampers large effective energy barriers to spin reversal at zero field from being obtained.

New Members of the Cinchona Alkaloids Family: Assembly of the Triazole Heterocycle at the 6' Position

The substance class of the well-known Cinchona alkaloids is widened by 6′-Amino-cinchonine and 6′-Amino-cinchonidine, novel compounds which incorporate a primary amino function in the quinolinic ring system. These key intermediates open the field for a range of fruitful chemistry. Here is described a short and direct pathway for the synthesis of triazole containing derivatives of the above-mentioned substances using the [3 + 2] Huisgen cycloaddition. For this purpose, the amines were first converted into the corresponding azides. Based on this, non-substituted and silyl-protected triazoles were synthesized as examples. Furthermore, didehydrated derivatives of quincorine and quincoridine were used as addition partners, resulting in compounds that carry the quinuclidine ring of the cinchona alkaloids at both ends. Some of these compounds were examined radiographically to investigate the position of the quinuclidine ring to the triazole. The solid-state structures of compounds 10, 11 and 28 were determined by X-ray diffraction analyses.

Group 13 Heavier Carbene Analogues Stabilized by the Bulky Bis(4-benzhydryl-benzoxazol-2-yl)methanide Ligand

On the basis of the bulky bis(4-benzhydryl-benzoxazyl-2-yl)methane ligand (^4-BzhH2Box₂CH₂), neutral monovalent group 13 complexes [M₁₃(^4-BzhH2Box₂CH)] [M₁₃ = Tl (1), In (2), or Ga (3)] have been synthesized by salt metathesis reaction of the corresponding potassium or sodium precursor and TlOTf, InOTf, or "GaI". The diiodido gallium species [GaI₂(^4-BzhH2Box₂CH)] (3a) was realized as a byproduct once the synthesis of 3 was carried out at higher temperatures. The synthesis of [AlI₂(^4-BzhH2Box₂CH)] (6) as a potential precursor for an aluminum(I) congener was accomplished by two alternative synthetic routes. During one of those procedures, [AlMe₂(^4-BzhH2Box₂CH)] (4) was synthesized in good yields by deprotonation with an AlMe₃ solution (method A). Subsequently, 4 was converted to the monoiodinated species [AlMeI(^4-BzhH2Box₂CH₂)] (5) using 1 equiv of I₂ or to 6 by iodination with 2 equiv of I₂ at 70 °C for 4 days. As an alternative, complex 6 could be prepared by iodination of 1 equiv of I₂ and [AlH₂(^4-BzhH2Box₂CH)] (7), which was previously obtained by facile reaction of ^4-BzhH2Box₂CH₂ and AlH₃NMe₂Et. All main products 1-7 were completely characterized by nuclear magnetic resonance spectroscopy, mass spectrometry, elemental analysis, and single-crystal X-ray structure determination. Alane 7 was additionally analyzed by solid-state fluorescence spectroscopy. Density functional theory calculations on [M₁₃(^4-BzhH2Box₂CH)] [M₁₃ = Tl (1), In (2), Ga (3), or Al] revealed that the complexes consist of monovalent group 13 cations coordinated by an anionic (^4-BzhH2Box₂CH) ligand similar to metallacycles incorporating a NacNac ligand.

Tetraimido Sulfuric Acid H2 S(NtBu)4 -Valence Isoelectronic to H2 SO4

The valence isoelectronic imido analog H2 S(NtBu)4 (1) of sulfuric acid H2 SO4 was synthesized, isolated, and characterized by NMR spectroscopy and high-resolution X-ray charge density analysis. The latter reveals strongly polarized Sδ+ -Nδ- bonds with virtually no double bond character. The easy-to-polarize S-N bonds are an advantageous and versatile feature of sulfur nitrogen ligands, which enables them to adapt to different electron requirements of various metal cations.

Exchange Coupling in Binuclear Manganese and Cobalt Complexes with the Tetraimido Sulfate Anion [S(NtBu)4]2

The (hetero)bimetallic complexes [Cl₂Mn(NtBu)₂S(tBuN)₂Mn{ClLi(THF)₃}₂] (1), [(acac)Co(NtBu)₂S(tBuN)₂Co(acac)] (2), and [(acac)Co(NtBu)₂S(tBuN)₂Li(THF)₂] (3), with THF = tetrahydrofuran and acac = acetylacetonate [H₂C(C(O)Me)₂], were synthesized and investigated for their magnetic properties. While the two different Mn^II sites in 1 gave a weak coupling of J = -1.00 cm^-1, we could observe an appreciable antiferromagnetic coupling of J = -6.08 cm^-1 between the two Co^II cations in 2, proving the tetraimido sulfate anion to be a challenging but promising linker to enhance magnetic communication between paramagnetic centers. The heterobimetallic complex 3 seems a versatile platform for magnetically interesting d/d, f/d, or f/f mixed-metal complexes.

Stability and decomposition of copper(i) boryl complexes: [(IDipp)Cu–Bneop], [(IDipp*)Cu–Bneop] and copper clusters

Synthesis and characterisation of NHC copper boryl complexes [(NHC)Cu–Bneop] and their decomposition to low-valent copper clusters.

Mixed Low-Valent Alanes from the Bis(4-methyl-benzoxazol-2-yl)methanide Ligand

Within this work, an aluminum dihydride complex ([(^4-MeBox₂CH)AlH₂]) (1) based on the bis(4-methyl-benzoxazol-2-yl)methanide ligand was synthesized and characterized by spectroscopic methods (NMR, ATR-IR, and fluorescence), DSC (differential scanning calorimetry), mass spectrometry (LIFDI), and single crystal X-ray diffraction. The reactivity of alane 1 was investigated toward the reducing agents [^DippNacNacAl^I] and [(^MesNacNacMg^I)₂], which gave the dialane compounds [(^4-MeBox₂CH)HAl^II-Al^IIH(^DippNacNac)] (2) and [{(^4-MeBox₂CH)Al^IIH}₂] (4a), respectively. Furthermore, dialuminoxanes [{(^4-MeBox₂CH)AlH}₂(μ-O)] (4b) and [({(^MesNacNac)Mg}₂(μ-H)){H₃Al^II-Al^IIH(^4-MeBox₂CH)}] (4c) were isolated as byproducts, with 4b co-crystallizing with 4a. The hydricity of both hydrides in the mixed-ligated dialane 2 were examined by a reaction with 1 equiv of trityl borate ([Ph₃C][B(C₆F₅)₄]), which resulted in [(^4-MeBox₂CH)HAl^II-Al^II(^DippNacNac)][B(C₆F₅)₄] (3). Due to the formation of 4b, complex 1 was reacted with 0.5 equiv of water, which causes the likely synthesis of insoluble oligomeric alumoxanes. To prevent this reaction and support the formation of well-defined dialumoxanes, 1 was initially converted to [(^4-MeBox₂CH)(DippO)AlH] (5) by the deprotonation of 2,6-diisopropylphenol (propofol). This sterically encumbered compound 5 was subsequently reacted with 0.5 equiv of water, which resulted in defined molecules of [{(^4-MeBox₂CH)(DippO)Al}₂(μ-O)] (6). All these compounds exemplify the versatility of the ^4-MeBox₂CH ligand in low-valent aluminum chemistry.

A Tale of Biphenyl and Terphenyl Substituents for Structurally Diverse Ketiminato Magnesium, Calcium and Germanium Complexes

In this paper, we have used two N,O-ketiminato ligands (L1 and L2) with biphenyl and terphenyl substituent on the nitrogen atom. Deprotonation of L1 with KN(SiMe₃ )₂ and subsequent reaction with MgI₂ led to a homoleptic dinuclear magnesium complex (1) with a Mg₂ O₂ four-membered ring. Deprotonation with nBuLi and subsequent reaction with MgI₂ afforded a unusual dinuclear magnesium complex (2) with a Mg₂ O₂ ring. Extension of the ligand for calcium resulted in a trinuclear calcium complex (3) with six four-membered Ca₂ O₂ rings. We could not isolate any chelating complex when L2 was used as a ligand, and only oxygen bound magnesium (4) and calcium (5) adducts were isolated. DFT studies were performed to understand this dissimilar behavior. More diverse results were obtained when lithiated L1 and L2 were treated with germanium dichloride. We were able to stabilize a monomeric germylene monochloride (7) with L1. However, with L2, an unusual ligand scrambling, and a C-C coupling take place, leading to the formation of a secondary carbocation with GeCl₃ - as a counter-anion (8). Besides, a germanium dichloride adduct (9) bound to the oxygen center of the ligand was obtained as the minor product.

Crystal structure of 2-methyl-1,2,3,4-tetra-hydro-iso-quinoline trihydrate

The crystal structure of the title compound, C10H13N·3H2O, a heterocyclic amine, was determined in the presence of water. The compound co-crystallizes with three water mol-ecules in the asymmetric unit, which leads to the formation of hydrogen bonding in the crystal.

Terminal versus Bridging Boryl Coordination in N-Heterocyclic Carbene Copper(I) Boryl Complexes: Syntheses, Structures, and Dynamic Behavior

The B-B bond activation of the diborane(4) derivatives B₂cat₂ with the copper(I) alkoxido complex [(SIDipp)Cu-O tBu] delivers, depending on the solvent, either the linear boryl complex [(SIDipp)Cu-Bcat] from PhMe or the μ-boryl complex [((SIDipp)Cu)₂Bcat][cat₂B] from THF. The relevant conversion of the linear boryl complex to the μ-boryl complex occurs in the polar solvent via formal boryl anion abstraction by the Lewis acid catB-O tBu, concomitantly formed during the B-B activation. With Lewis acids such as BPh₃ or [CPh₃][BArF] (reversible), boryl abstraction from the linear complexes [(SIDipp)Cu-Bcat] or [(SIDipp)Cu-Bdmab] occurs and results in the μ-boryl complexes [((SIDipp)Cu)₂Bcat/dmab][Ph₃B-Bcat/dmab] and [((SIDipp)Cu)₂Bcat][BArF]. The formation of [((SIDipp)Cu)₂Bcat][cat₂B] is generally accompanied by the concomitant formation of the μ-hydrido complex [((SIDipp)Cu)₂H][cat₂B]. The spiroborate [cat₂B]^- is formed from the initially formed Lewis acid/base adduct [catB-B(O tBu)cat]^- presumably in a process that involves the glass surface of the reaction vessel. All complexes are thoroughly characterized structurally as well as spectroscopically, in particular with respect to the dynamic behavior of the μ-boryl complexes in solution.

Isolation of base stabilized fluoroborylene and its radical cation

Herein, we report the synthesis and characterization of the metal free low valent fluoroborylene [(Me-cAAC)₂BF] (1) stabilized by cyclic (alkyl)(amino) carbene (cAAC). The fluoroborylene 1 is obtained by the reductive defluorination of Me-cAAC:BF₃ with 2.0 equivalents of KC₈ in the presence of 1.0 equivalent of Me-cAAC. Due to its highly electron rich nature, 1 underwent one-electron oxidation with 1.0 equivalent of lithium tetrakis(pentafluorophenyl)borate [LiB(C₆F₅)₄] to form the radical cation [(Me-cAAC)₂BF]˙⁺[B(C₆F₅)₄]^- (2). DFT studies suggested that the lone pair of electrons is localized on the boron atom in 1, which explains its unprecedented reactivity. Both compounds 1 and 2 were characterized by X-ray crystallography. The radical cation 2 was studied by EPR spectroscopy.