Potassium-telluroether interactions: structural characterisation and computational analysis.

Dissolution of the potassium complex [K(ATe)(dme)] (1-Te) in THF, layering with hexanes, and cooling to -30 °C afforded X-ray quality crystals of [K(ATe)(THF)] (2-Te). The K-TeR distances in 2-Te are substantially shorter than those in 1-Te, and DFT and QTAIM calculations support the presence of K-TeR interactions, providing the first unambiguous examples of s-block-telluroether bonding. Attempts to prepare bulk quantities of 2-Te afforded [K(ATe)(THF)] (3-Te), and further drying yielded [K(ATe)(THF)] (4-Te) and [K(ATe)] (5-Te).

Silyl- and Germyl-Substituted Boranes: Synthesis and Investigation as Potential Atomic Layer Deposition Precursors.

Boranes featuring bulky hypersilyl or supersilyl groups and/or sterically unencumbered trimethylgermyl substituents were synthesized for investigation as potential precursors for atomic layer deposition (ALD) of elemental boron. The envisaged ALD process would employ a boron trihalide coreactant, exploiting the formation of strong silicon-halogen and germanium-halogen bonds as a driving force. The alkali metal silyl and germyl compounds hypersilyl lithium, {(MeSi)Si}Li(THF) (), supersilyl sodium, (BuSi)Na(THF) (, = 2-3), and trimethylgermyl lithium, {MeGeLi(THF)} (), were used for the synthesis of the silyl- and germyl-substituted boranes in this work.

Thorium(IV) and Uranium(IV) Thioether and Selenoether Complexes: Synthesis and An-ER (E = S, Se) Bonding Comparison.

Reactions of the rigid thioether- and selenoether-containing ligand salts [{Li(AE)}] (E = S or Se; AE = 4,5-bis(phenylchalcogenido)-2,7,9,9-tetramethylacridanide) with ThCl(dme) or UCl (for E = Se) afforded the actinide chalcogenoether complexes [(AE)ThCl] (E = S (), Se ()), and [(ASe)UCl] (). X-ray crystal structures of - revealed tetravalent actinide cations complexed to two κ-coordinated AE ligands, with Th-ER and U-ER distances below the sum of the covalent radii. Complexes - provide extremely rare examples of thorium-thioether, thorium-selenoether, and uranium-selenoether bonds, and and contain the shortest known Th-SR and Th-SeR distances.

A comparison of the coordination behaviour of RPCHBMe (R = Me Ph) ambiphilic ligands with late transition metals.

A new synthesis that avoids the use of MePH is reported for (MePCHBMe), and this method was extended to the synthesis of (PhPCHBMe). The ligand precursor (MePCHBMe) did not react with [{M(μ-Cl)(cod)}] (cod = 1,5-cyclooctadiene; M = Ir and Rh) or [PtCl(cod)] at room temperature. However, after 12-48 hours at 65-70 °C, these reactions afforded (a) [Ir(cod)(μ-Cl)(MePCHBMe)] (1), (b) an equilibrium mixture of (MePCHBMe), [{Rh(μ-Cl)(cod)}] and [Rh(cod)(μ-Cl)(MePCHBMe)] (2), and (c) -[Pt(μ-Cl)(MePCHBMe)] (3), respectively.

Reactions of [(dmpe)MnH(CH)] with hydrogermanes to form germylene, germyl, hydrogermane, and germanide complexes.

Reactions of the ethylene hydride complex -[(dmpe)MnH(CH)] (1) with secondary hydrogermanes HGeR at 55-60 °C afforded the base-free terminal germylene hydride complexes -[(dmpe)MnH(GeR)] (R = Ph; 2a, R = Et; 2b). Room temperature reactions of 2a or 2b with an excess of the primary hydrogermanes HGeR' (R' = Ph or Bu) afforded -[(dmpe)MnH(GeHR')] (R' = Ph; 3a, R' = Bu; 3b) in rapid equilibrium with small amounts of 2a/b, as well as the digermyl hydride complex -[(dmpe)MnH(GeHR')] {R' = Ph (4a) or Bu (4b)} and the -hydrogermane germyl complex -[(dmpe)Mn(GeHR')(HGeHR')] {R' = Ph (5a) or Bu (5b)}. Pure 3b was isolated from the reaction of 2b with HGeBu, whereas 3a decomposed readily in solution in the absence of free HGePh, and a pure bulk sample was not obtained.

A Synthetic, Structural, Spectroscopic, and Computational Study of Alkali Metal-Thioether, -Selenoether, and -Telluroether Interactions.

The rigid thioether- and selenoether-containing pro-ligands, 4,5-bis(phenylsulfido)-2,7,9,9-tetramethylacridan (H[AS] ()) and 4,5-bis(phenylselenido)-2,7,9,9-tetramethylacridan (H[ASe] ()), were deprotonated with one equiv of BuLi to afford dimeric lithium complexes [Li(AE)] (E = S (), Se ()) or with one equiv of KCHPh to afford the previously reported potassium complexes [K(AS)(dme)] () and [K(ASe)(dme)] (). Attempts to prepare a direct telluroether analogue of compounds - were unsuccessful. However, the bulky selenoether- and telluroether-containing pro-ligands 4,5-bis(2,4,6-triisopropylphenylselenido)-2,7,9,9-tetramethylacridan (H[ASe] ()) and 4,5-bis(2,4,6-triisopropylphenyltellurido)-2,7,9,9-tetramethylacridan (H[ATe] ()) were accessed via the reaction of 4,5-dibromo-2,7,9,9-tetramethylacridan with three equiv of BuLi, followed by the addition of two equiv of the corresponding diaryl dichalcogenide and quenching with dilute HCl.

Rare earth dialkyl cations and monoalkyl dications supported by a rigid neutral pincer ligand: synthesis and ethylene polymerization.

A palladium-catalyzed coupling reaction between 4,5-dibromo-2,7-di--butyl-9,9-dimethylxanthene and 2 equiv. of 1,3-diisopropylimidazolin-2-imine afforded the rigid neutral 2,7-di--butyl-4,5-bis(1,3-diisopropylimidazolin-2-imino)-9,9-dimethylxanthene (XII) pincer ligand. Reaction of XII with YCl(THF) provided [(XII)YCl] (1).

Group 3 dialkyl complexes of a rigid monoanionic NNN-donor pincer ligand: synthesis, structures, unexpected reactivity with CPh, and hydroamination catalysis.

Palladium-catalyzed coupling of 4,5-dibromo-2,7,9,9-tetramethylacridan with two equivalents of 1,3-diisopropylimidazolin-2-imine afforded 4,5-bis(1,3-diisopropylimidazolin-2-imino)-2,7,9,9-tetramethylacridan, H[AII]. Reaction of the H[AII] pro-ligand with one equivalent of [M(CHSiMe)(THF)] (M = Y or Sc) yielded the base-free neutral dialkyl complexes [(AII)M(CHSiMe)] {M = Y (1) and Sc (2)}. The rigid AII pincer ligand affords a similar steric profile to the previously reported XA pincer ligand, but is monoanionic rather than dianionic.

Ligand Determines the Stability of Paramagnetic Manganese(II) Hydrides of the Type -[MnH(L)(dmpe)] Where L is PMe, CH, or CO.

Paramagnetic metal hydride (PMH) complexes play important roles in catalytic applications and bioinorganic chemistry. 3d PMH chemistry has largely focused on Ti, Mn, Fe, and Co. Various Mn PMHs have been proposed as intermediates in catalysis, but isolated Mn PMHs are limited to dimeric high-spin Mn structures with bridging hydrides.

Uranium(iv) alkyl cations: synthesis, structures, comparison with thorium(iv) analogues, and the influence of arene-coordination on thermal stability and ethylene polymerization activity.

Reaction of [(XA)U(CHSiMe)] (1; XA = 4,5-bis(2,6-diisopropylanilido)-2,7-di--butyl-9,9-dimethylxanthene) with 1 equivalent of [PhC][B(CF)] in arene solvents afforded the arene-coordinated uranium alkyl cations, [(XA)U(CHSiMe)(η -arene)][B(CF)] {arene = benzene (2), toluene (3), bromobenzene (4) and fluorobenzene (5)}. Compounds 2, 3, and 5 were crystallographically characterized, and in all cases the arene is π-coordinated. Solution NMR studies of 2-5 suggest that the binding preferences of the [(XA)U(CHSiMe)] cation follow the order: toluene ≈ benzene > bromobenzene > fluorobenzene.

Coordination chemistry and structural rearrangements of the MePCHAlMe ambiphilic ligand.

Reaction of 2 equivalents of (MePCHAlMe) with [{RhCl(cod)}] (cod = 1,5-cyclooctadiene) afforded [{κ,-(MeAl)ClMeAl(CHPMe)}Rh(cod)] (1), which features a κ-coordinated bis(phosphino)aluminate anion. In compound 1, an Al-Cl substituent bridges to a molecule of AlMe, which could be removed to provide [{κ,-ClMeAl(CHPMe)}Rh(cod)] (2). By contrast, reaction of 1 equiv.

Uranium(IV) Thio- and Selenoether Complexes: Syntheses, Structures, and Computational Investigation of U-ER Interactions.

Rigid thioether- and selenoether-containing pincer proligands H[AS ] (1) and H[ASe ] (2) were synthesized, and deprotonation provided the potassium salts [K(AS )(dme)] (3) and [K(ASe )(dme) ] (4). Reaction of two equivalents of 3 or 4 with [UI (dioxane) ] afforded the uranium thioether complex [(AS ) UI ] (5) and the first example of a uranium-selenoether complex, [(ASe ) UI ] (6). X-ray structures revealed distorted square antiprismatic geometries in which the AE ligands are κ -coordinated.

Reactions of [(dmpe)MnH(CH)]: synthesis and characterization of manganese(i) borohydride and hydride complexes.

Reactions of trans-[(dmpe)MnH(CH)] (1) with BH(NMe), 9-BBN, and HBMes yielded the manganese(i) borohydride complexes [(dmpe)Mn(μ-H)BR] (3: R = H, 4: R = CH, 5: R = Mes). The reaction of 1 with BH(NMe) proceeds via ethylene substitution. By contrast, a detuerium labelling study indicates that the reaction of 1 with HBMes involves initial isomerization of 1 to an unobserved 5-coordinate ethyl intermediate, [(dmpe)MnEt], which reacts with the hydroborane to afford EtBR and [(dmpe)MnH], followed by reaction with a second equivalent of hydroborane to generate 5 (an analogous pathway is likely followed for other base-free hydroboranes such as 9-BBN).

Interconversion and reactivity of manganese silyl, silylene, and silene complexes.

Manganese disilyl hydride complexes [(dmpe)MnH(SiHR)] ( : R = Ph, : R = Bu) reacted with ethylene to form silene hydride complexes [(dmpe)MnH(RHSi[double bond, length as m-dash]CHMe)] ( : R = Ph, : R = Bu). Compounds reacted with a second equivalent of ethylene to generate [(dmpe)MnH(REtSi[double bond, length as m-dash]CHMe)] ( : R = Ph, : R = Bu), resulting from apparent ethylene insertion into the silene Si-H bond. Furthermore, in the absence of ethylene, silene complex slowly isomerized to the silylene hydride complex [(dmpe)MnH([double bond, length as m-dash]SiEt Bu)] ( ).

Thorium(iv) alkyl and allyl complexes of a rigid NON-donor pincer ligand with flanking 1-adamantyl substituents.

Palladium-catalyzed coupling of 1-adamantylamine (2 equiv.) with 4,5-dibromo-2,7-di-tert-butyl-9,9-dimethylxanthene afforded the proligand 4,5-bis(1-adamantylamino)-2,7-di-tert-butyl-9,9-dimethylxanthene, H2[XAd] (1), which upon deprotonation with excess KH or KCH2Ph in THF or dme generated [{K(THF)3}2(XAd)] (2a) and [K2(XAd)(dme)] (2b). Subsequent reaction of in situ generated 2a or 2b with [ThCl4(dme)2] yielded [(XAd)ThCl4K2]·x(dme) (3; x = 0.

Manganese Silylene Hydride Complexes: Synthesis and Reactivity with Ethylene to Afford Silene Hydride Complexes.

Reaction of the ethylene hydride complex trans-[(dmpe) MnH(C H )] (1) with Et SiH at 20 °C afforded the silylene hydride [(dmpe) MnH(=SiEt )] (2 a) as the trans-isomer. By contrast, reaction of 1 with Ph SiH at 60 °C afforded [(dmpe) MnH(=SiPh )] (2 b) as a mixture of the cis (major) and trans (minor) isomers, featuring a Mn-H-Si interaction in the former. The reaction to form 2 b also yielded [(dmpe) MnH (SiHPh )] (3 b); [(dmpe) MnH (SiHR )] (R=Et (3 a) and Ph (3 b)) were accessed cleanly by reaction of 2 a and 2 b with H , and the analogous reactions with D afforded [(dmpe) MnD (SiHR )] exclusively.

Cyclometalation and coupling of a rigid 4,5-bis(imino)acridanide pincer ligand on yttrium.

An extremely rigid NNN-donor proligand, 4,5-bis{(diphenylmethylene)amino}-2,7,9,9-tetramethylacridan, H[AIm2] was prepared in five steps starting from 5-methyl-2-aminobenzoic acid and 4-bromotoluene. Reaction of intensely orange H[AIm2] with LiCH2SiMe3 formed deep blue Li(x)[AIm2]x (x = 2 in the solid state), while reaction with [Y(CH2SiMe3)3(THF)2] (0.5 equiv.

Synthesis and platinum complexes of an alane-appended 1,1'-bis(phosphino)ferrocene ligand.

An aryldimethylalane-appended analogue of 1,1'-bis(diphenylphosphino)ferrocene, FcPPAl, was prepared, and reaction with [Pt(nb)3 ] (nb=norbornene) afforded [Pt(η(2) -nb)(FcPPAl)] (1). Heating a solution of 1 to 80 °C resulted in crystallization of [{Pt(FcPPAl)}2 ] (2), whereas treatment of 1 with C2 H4 , C2 Ph2 , H2 , or CO provided [PtL(FcPPAl)] [L=C2 H4 (3), C2 Ph2 (4)], [PtH2 (FcPPAl)] (5), and [Pt(CO)(FcPPAl)] (6). In all complexes, the FcPPAl ligand is coordinated through both phosphines and the alane.

Platinum complexes of a borane-appended analogue of 1,1'-bis(diphenylphosphino)ferrocene: flexible borane coordination modes and in situ vinylborane formation.

A bis(phosphine)borane ambiphilic ligand, [Fe(η(5) -C5 H4 PPh2 )(η(5) -C5 H4 PtBu{C6 H4 (BPh2 )-ortho})] (FcPPB), in which the borane occupies a terminal position, was prepared. Reaction of FcPPB with tris(norbornene)platinum(0) provided [Pt(FcPPB)] (1) in which the arylborane is η(3) BCC-coordinated. Subsequent reaction with CO and CNXyl (Xyl=2,6-dimethylphenyl) afforded [PtL(FcPPB)] {L=CO (2) and CNXyl (3)} featuring η(2) BC- and η(1) B-arylborane coordination modes, respectively.

The transcription factors IRF8 and PU.1 negatively regulate plasma cell differentiation.

Activated B cells undergo immunoglobulin class-switch recombination (CSR) and differentiate into antibody-secreting plasma cells. The distinct transcriptomes of B cells and plasma cells are maintained by the antagonistic influences of two groups of transcription factors: those that maintain the B cell program, including BCL6 and PAX5, and plasma cell-promoting factors, such as IRF4 and BLIMP-1. We show that the complex of IRF8 and PU.

The BTB-ZF transcription factor Zbtb20 is driven by Irf4 to promote plasma cell differentiation and longevity.

The transcriptional network regulating antibody-secreting cell (ASC) differentiation has been extensively studied, but our current understanding is limited. The mechanisms of action of known "master" regulators are still unclear, while the participation of new factors is being revealed. Here, we identify Zbtb20, a Bcl6 homologue, as a novel regulator of late B cell development.

Oct2 and Obf1 as Facilitators of B:T Cell Collaboration during a Humoral Immune Response.

The Oct2 protein, encoded by the Pou2f2 gene, was originally predicted to act as a DNA binding transcriptional activator of immunoglobulin (Ig) in B lineage cells. This prediction flowed from the earlier observation that an 8-bp sequence, the "octamer motif," was a highly conserved component of most Ig gene promoters and enhancers, and evidence from over-expression and reporter assays confirmed Oct2-mediated, octamer-dependent gene expression. Complexity was added to the story when Oct1, an independently encoded protein, ubiquitously expressed from the Pou2f1 gene, was characterized and found to bind to the octamer motif with almost identical specificity, and later, when the co-activator Obf1 (OCA-B, Bob.

Germinal center-independent, IgM-mediated autoimmunity in sanroque mice lacking Obf1.

Mice homozygous for a point mutation in the Rc3h1 gene encoding Roquin1, designated sanroque mice, develop a severe antibody-mediated autoimmune condition. The disease is T-cell intrinsic, exacerbated by macrophage-intrinsic defects and driven by excessive T follicular helper cell generation and spontaneous germinal centre (GC) formation. This culminates in abnormally high numbers of plasma cells secreting high-affinity autoreactive immunoglobulin G (IgG).