Facile Access to Mono- and Dinuclear Heteroleptic N‑Heterocyclic Silylene Copper Complexes

Reaction of the heteroleptic N-heterocyclic chlorosilylene L­(Cl)­Si: (<b>1</b>; L = PhC­(N<i>t</i>Bu)₂) with [Cu­(tmeda)­(CH₃CN)]­[OTf] (<b>2</b>; tmeda = <i>N,N</i>,<i>N</i>′,<i>N</i>′-tetramethylethylenediamine, OTf = OSO₂CF₃ (triflate)) affords the Cu­(I) complex [L­(Cl)­Si:→Cu­(tmeda)]­[OTf] (<b>3</b>) in high yield as the first example of a heteroleptic N-heterocyclic silylene copper complex. Similarly, the reaction of L­(O<i>t</i>Bu)­Si: (<b>4</b>; L = PhC­(N<i>t</i>Bu)₂) with <b>2</b> affords [L­(O<i>t</i>Bu)­Si: → Cu­(tmeda)]­[OTf] (<b>5</b>) and that of L­(NMe₂)­Si: (<b>6</b>) with <b>2</b> leads to [L­(NMe₂)­Si:→Cu­(tmeda)]­[OTf] (<b>7</b>). Complex <b>3</b> shows a rather strong interaction in the solid state between the O atom of the triflate anion and the three-coordinate Cu­(I) center with a Cu···O distance of 2.312 Å. In contrast, complex <b>7</b> features only a weak interaction (ca. 3.28 Å), while in complex <b>5</b> the cation and anion are fully separated. Strikingly, the reaction of the chelating oxo-bridged silylene :Si­(L)­(μ₂-O)­(L)­Si: (<b>8</b>) with the copper source [Cu­(CH₃CN)₄]­[OTf] (<b>9</b>) affords the dinuclear complex salt [Cu₂{η¹:η¹-LSi­(μ₂-O)­SiL}₂]­[OTf]₂ (<b>10</b>), featuring a novel metallacyclooctane dication, selectively in a good yield. Complex <b>10</b> also exhibits a very strong interaction between the copper centers in the dication and the oxygen atoms of triflate anions in the solid state, evidenced by a Cu···O separation of only 2.141 Å. All complexes were fully characterized

Highly Electron-Rich Pincer-Type Iron Complexes Bearing Innocent Bis(metallylene)pyridine Ligands: Syntheses, Structures, and Catalytic Activity

The first neutral bis­(metallylene)­pyridine pincer-type [<b>ENE</b>] ligands (E = Si^II, Ge^II) were synthesized, and their coordination chemistry and reactivity toward iron was studied. First, the unprecedented four-coordinate complexes <b>κ</b>^<b>2</b><i><b>E,E</b></i>′-<b>[ENE]­FeCl</b>_<b>2</b> were isolated. Unexpectedly and in contrast to other related pyridine-based pincer-type Fe­(II) complexes, the N atom of pyridine is reluctant to coordinate to the Fe­(II) site due to the enhanced σ-donor strength of the E atoms, which disfavors this coordination mode. Subsequent reduction of <b>κ</b>^<b>2</b><i><b>Si,Si</b></i>′<b>-[SiNSi]­FeCl</b>_<b>2</b> with KC₈ in the presence of PMe₃ or direct reaction of the [<b>ENE</b>] ligands using Fe­(PMe₃)₄ produced the highly electron-rich iron(0) complexes <b>[ENE]­Fe­(PMe</b>_<b>3</b><b>)</b>_<b>2</b>. The reduction of the iron center substantially changes its coordination features, as shown by the results of a single-crystal X-ray diffraction analysis of <b>[SiNSi]­Fe­(PMe</b>_<b>3</b><b>)</b>_<b>2</b>. The iron center, in the latter, exhibits a pseudosquare pyramidal (PSQP) coordination environment, with a coordinative (pyridine)­N→Fe bond, and a trimethylphosphine ligand occupying the apical position. This geometry is very unusual for Fe(0) low-spin complexes, and variable-temperature ¹H and ³¹P NMR spectra of the <b>[ENE]­Fe­(PMe</b>_<b>3</b><b>)</b>_<b>2</b> complexes revealed that they represent the first examples of configurationally stable PSQP-coordinated Fe(0) complexes: even after heating at 70 °C for >7 days, no changes are observed. The substitution reaction of <b>[ENE]­Fe­(PMe</b>_<b>3</b><b>)</b>_<b>2</b> with CO resulted in the isolation of <b>[ENE]­Fe­(CO)</b>_<b>2</b> and the hitherto unknown <b>κ</b>^<b>2</b><i><b>E,E</b></i>′<b>-[ENE]­Fe­(CO)</b>_<b>2</b><b>L</b> (L = CO, PMe₃) complexes. All complexes were fully characterized (NMR, MS, XRD, IR, and ⁵⁷Fe Mössbauer spectroscopy), showing the highest electron density on the iron center for pincer-type complexes reported to date. DFT calculations and ⁵⁷Fe Mössbauer spectroscopy confirmed the innocent behavior of these ligands. Moreover, preliminary results showed that these complexes can serve as active precatalysts for the hydrosilylation of ketones

From Unsymmetrically Substituted Benzamidinato and Guanidinato Dichlorohydridosilanes to Novel Hydrido N‑Heterocyclic Silylene Iron Complexes

Starting from the unsymmetric N,N′-substituted thiourea compounds (R)­N­(H)­C­(S)­N­(H)­(^<i>t</i>Bu) (<b>1</b>, R = Dipp: 2,6-^<i>i</i>Pr₂-C₆H₃; <b>2</b>, R = 1-adamantyl), the corresponding asymmetric carbodiimines (R)­NCN­(^<i>t</i>Bu) (<b>3</b>, R = Dipp; <b>4</b>, R = 1-adamantyl) are readily accessible in high yields upon reduction with LiHMDS (Li­[N­(SiMe₃)₂]). The reaction of compound <b>3</b> with PhLi followed by SiCl₄ afforded, in a one-pot reaction, the asymmetric benzamidinato-stabilized trichlorosilane [PhC­{(N^<i>t</i>Bu)­(NDipp)}]­SiCl₃ (<b>5</b>). Similarly, silanes [PhC­{(N^<i>t</i>Bu)­(NDipp)}]­SiHCl₂ (<b>6</b>), [(NMe₂)­C­{(N^<i>t</i>Bu)­(NDipp)}]­SiHCl₂ (<b>7</b>), and [PhC­{(N^<i>t</i>Bu)­(NAd)}]­SiHCl₂ (<b>8</b>) could also be isolated. All novel trichloro- or dichlorohydridosilanes were fully spectroscopically characterized and studied by single-crystal X-ray diffraction analyses, the latter revealing in all cases a distorted-trigonal bipyramidal five-coordinate silicon center. The reactions of silanes <b>5</b>–<b>8</b> with K₂[Fe­(CO)₄] were also explored: In the case of the reaction of silane <b>5</b> with K₂[Fe­(CO)₄], no reaction was observed even after prolonged heating. However, in the case of the silanes <b>6</b>–<b>8</b>, the selective formation of the corresponding hydrido Si^II:→Fe⁰ complexes [[R¹C­{(N^<i>t</i>Bu)­(NR²)}]­(H)­Si:→Fe­(CO)₄] (<b>9</b>, R¹ = Ph, R² = Dipp; <b>10</b>, R¹ = NMe₂, R² = Dipp; <b>11</b>, R¹ = Ph, R² = 1-adamantyl) could be achieved. Complexes <b>9</b>–<b>11</b> represent unprecedented hydrido-N-heterocyclic silylene complexes, bearing asymmetric ligand backbones. Complexes <b>9</b>–<b>11</b> were fully spectroscopically characterized, and in addition the single-crystal X-ray structure analysis of compound <b>10</b> is reported

From a Zwitterionic Phosphasilene to Base Stabilized Silyliumylidene-Phosphide and Bis(silylene) Complexes

The reactivity of ylide-like phosphasilene <b>1</b> [LSi­(TMS)P­(TMS), L = PhC­(N<i>t</i>Bu)₂] with group 10 d¹⁰ transition metals is reported. For the first time, a reaction of a phosphasilene with a transition metal that actually involves the silicon–phosphorus double bond was found. In the reaction of <b>1</b> with ethylene bis­(triphenylphosphine) platinum(0), a complete silicon–phosphorus bond breakage occurs, yielding the unprecedented dinuclear platinum complex <b>3</b> [LSi­{Pt­(PPh₃)}₂P­(TMS)₂]. Spectroscopic, structural, and theoretical analysis of complex <b>3</b> revealed the cationic silylene (silyliumylidene) character of the silicon unit in complex <b>3</b>. Similarly, formation of the analogous dinuclear palladium complex <b>4</b> [LSi­{Pd­(PPh₃)}₂P­(TMS)₂] from tetrakis­(triphenylphosphine) palladium(0) was observed. On the other hand, in the case of bis­(cyclooctadiene) nickel(0) as starting material, a distinctively different product, the bis­(silylene) nickel complex <b>5</b> [{(LSi)₂P­(TMS)}­Ni­(COD)], was obtained. Complex <b>5</b> was fully characterized including X-ray diffraction analysis. Density functional theory calculations of the reaction mechanisms showed that the migration of the TMS group in the case of platinum and palladium was induced by the oxidative addition of the transition metal into the silicon–silicon bond. The respective platinum intermediate <b>2</b> [LSi­{Pt­(TMS)­(PPh₃)}­P­(TMS)] was also experimentally observed. This is contrasted by the reaction of nickel, in which the equilibrium of phosphasilene <b>1</b> and the phosphinosilylene <b>6</b> [LSiP­(TMS)₂] was utilized for a better coordination of the silicon­(II) moiety in comparison with phosphorus to the transition metal center

From a Zwitterionic Phosphasilene to Base Stabilized Silyliumylidene-Phosphide and Bis(silylene) Complexes

The reactivity of ylide-like phosphasilene <b>1</b> [LSi­(TMS)P­(TMS), L = PhC­(N<i>t</i>Bu)₂] with group 10 d¹⁰ transition metals is reported. For the first time, a reaction of a phosphasilene with a transition metal that actually involves the silicon–phosphorus double bond was found. In the reaction of <b>1</b> with ethylene bis­(triphenylphosphine) platinum(0), a complete silicon–phosphorus bond breakage occurs, yielding the unprecedented dinuclear platinum complex <b>3</b> [LSi­{Pt­(PPh₃)}₂P­(TMS)₂]. Spectroscopic, structural, and theoretical analysis of complex <b>3</b> revealed the cationic silylene (silyliumylidene) character of the silicon unit in complex <b>3</b>. Similarly, formation of the analogous dinuclear palladium complex <b>4</b> [LSi­{Pd­(PPh₃)}₂P­(TMS)₂] from tetrakis­(triphenylphosphine) palladium(0) was observed. On the other hand, in the case of bis­(cyclooctadiene) nickel(0) as starting material, a distinctively different product, the bis­(silylene) nickel complex <b>5</b> [{(LSi)₂P­(TMS)}­Ni­(COD)], was obtained. Complex <b>5</b> was fully characterized including X-ray diffraction analysis. Density functional theory calculations of the reaction mechanisms showed that the migration of the TMS group in the case of platinum and palladium was induced by the oxidative addition of the transition metal into the silicon–silicon bond. The respective platinum intermediate <b>2</b> [LSi­{Pt­(TMS)­(PPh₃)}­P­(TMS)] was also experimentally observed. This is contrasted by the reaction of nickel, in which the equilibrium of phosphasilene <b>1</b> and the phosphinosilylene <b>6</b> [LSiP­(TMS)₂] was utilized for a better coordination of the silicon­(II) moiety in comparison with phosphorus to the transition metal center

From Bis(silylene) and Bis(germylene) Pincer-Type Nickel(II) Complexes to Isolable Intermediates of the Nickel-Catalyzed Sonogashira Cross-Coupling Reaction

The first [ECE]­Ni­(II) pincer complexes with E = Si^II and E = Ge^II metallylene donor arms were synthesized via C–X (X = H, Br) oxidative addition, starting from the corresponding [EC­(X)­E] ligands. These novel complexes were fully characterized (NMR, MS, and XRD) and used as catalyst for Ni-catalyzed Sonogashira reactions. These catalysts allowed detailed information on the elementary steps of this catalytic reaction (transmetalation → oxidative addition → reductive elimination), resulting in the isolation and characterization of an unexpected intermediate in the transmetalation step. This complex, {[ECE]­Ni acetylide → CuBr} contains both nickel and copper, with the copper bound to the alkyne π-system. Consistent with these unusual structural features, DFT calculations of the {[ECE]­Ni acetylide → CuBr} intermediates revealed an unusual E–Cu–Ni three-center–two-electron bonding scheme. The results reveal a general reaction mechanism for the Ni-based Sonogashira coupling and broaden the application of metallylenes as strong σ-donor ligands for catalytic transformations

Living Well With Kidney Disease and Effective Symptom Management: Consensus Conference Proceedings

Chronic kidney disease (CKD) confers a high burden of uremic symptoms that may be underrecognized,underdiagnosed, and undertreated. Unpleasant symptoms, such as CKD-associated pruritus andemotional/psychological distress, often occur within symptom clusters, and treating 1 symptom maypotentially alleviate other symptoms in that cluster. The Living Well with Kidney Disease and EffectiveSymptom Management Consensus Conference convened health experts and leaders of kidney advocacygroups and kidney networks worldwide to discuss the effects of unpleasant symptoms related to CKD onthe health and well-being of those affected, and to consider strategies for optimal symptom management.Optimizing symptom management is a cornerstone of conservative and preservative management whichaim to prevent or delay dialysis initiation. In persons with kidney dysfunction requiring dialysis (KDRD),incremental transition to dialysis and home dialysis modalities offer personalized approaches. KDRD isproposed as the preferred term given the negative connotations of“failure”as a kidney descriptor, and thesuccess stories in CKD journeys. Engaging persons with CKD to identify and prioritize their personal valuesand individual needs must be central to ensure their active participation in CKD management, includingKDRD. Person-centered communication and care are required to ensure diversity, equity, and inclusion;education/awareness that considers the health literacy of persons with CKD; and shared decision-makingamong the person with CKD, care partners, and providers. By putting the needs of people with CKD,including effective symptom management, at the center of their treatment, CKD can be optimally treated ina way that aligns with their goals.</p