Search

The 1967 attempt of structural analysis of the solid-state complex of caffeine and pyrogallol was a pioneering structural investigation in the supramolecular chemistry of caffeine, of what today would easily be considered an archetype of a model pharmaceutical cocrystal. Re-investigating this historically important system demonstrates that this long overlooked complex is most likely a tetrahydrate with a different structure and composition than initially proposed, and provides the crystal structure of the anhydrous cocrystal. [ABSTRACT FROM AUTHOR]

The frustrated Lewis pair (FLP) adducts PB{ECl2} (PB = iPr2P(C6H4)BCy2; Cy = cyclohexyl; E = Si, Ge) were used to access a bis(alkynyl)-functionalized silylene and a germylene; the goal behind preparing these species was to obtain new unsaturated main group polymers [E(C≡CSiMe3)2]n upon heating. While the silylene adduct PB{Si(C≡CSiMe3)2} was stable up to 150 °C, the heavier element congener PB{Ge(C≡CSiMe3)2} underwent a complicated rearrangement process accompanied by Cy-group migration and Ge(II)-alkyne coordination. Density functional theory computations were performed to understand the mechanistic pathway for the unusual rearrangement of PB{Ge(C≡CSiMe3)2}. [ABSTRACT FROM AUTHOR]

The solid-state reaction of the active pharmaceutical ingredient theophylline with citric acid is a well-established example of a mechanochemical reaction, leading to a model pharmaceutical cocrystal. Here, classical force field molecular dynamics was employed to investigate the molecular mixing and structural distortion that take place on the mechanically driven indentation of a citric acid nanoparticle on a slab of crystalline theophylline. Through non-equilibrium molecular dynamics simulations, a 6 nm diameter nanoparticle of citric acid was introduced onto an open (001) surface of a theophylline crystal, varying both the angle of incidence of the nanoparticle between 15° and 90° and the indentation speed between 1 m s−1 and 16 m s−1. This theoretical study enabled the evaluation of how these two parameters promote molecular mixing and overall structural deformation upon the mechanical contraction of theophylline and citric acid, both of which are important parameters underlying mechanochemical cocrystallisation. The results show that the angle of incidence plays a key role in the molecular transfer ability between the two species and in the structural disruption of the initially spherical nanoparticles. Changing the indentation speed, however, did not lead to a discernible trend in molecular mixing, highlighting the importance of the incident angle in mechanochemical events in the context of supramolecular chemistry, such as the disruption of the crystal structure and molecular transfer between molecular crystals. [ABSTRACT FROM AUTHOR]

An organometallic tetrahedron-shaped indium(I) tetramer [(MeIPrCH)In]4 (MeIPrCH = [(MeCNDipp)2CCH]-; Dipp = 2,6-iPr2C6H3) supported by anionic N-heterocyclic olefin (aNHO) ligands is reported. The monomeric unit of this species exhibits both Lewis acidic and basic character at indium, while the steric profile of the aNHO ligand enables isolation of a rare monomeric imide, RInNR'. [ABSTRACT FROM AUTHOR]

We report mild routes for the deposition of crystalline films of elemental tin via the formation and subsequent decomposition of unstable tin(II) hydrides. Specifically, we take advantage of efficient OtBu/H metathesis involving Sn(II) alkoxide precursors and the hydride source pinacolborane (HBpin); related -N(SiMe3)2/H exchange also afforded elemental tin as a final (insoluble) product. [ABSTRACT FROM AUTHOR]

The reactivity of [PB{SiX2}] (X = Cl, Br; PB = 1,2-iPr2(C6H4)BCy2; E = Si, Ge) adducts is described, with an initial focus on reduction attempts to access [PB{E}]x species; however, in all cases only free PB ligand was formed as the soluble product. Moreover, computations were performed to evaluate the energy penalty associated with EX2 dissociation from the PB chelates. Moving up the periodic table, the formal methylene adduct [PB{CH2}] was isolated and its reactivity was compared with its heavier element congeners of [PB{EH2}]. We also introduce new phosphine-borane frustrated Lewis pair (FLP) chelates and explore preliminary coordination chemistry with these ligands. [ABSTRACT FROM AUTHOR]

We use a gold nanoparticle synthesis as a model system to study the morphological and compositional changes in gold(III) precursor particles, while reduction is taking place during aging after mechanical activation. Scanning transmission electron microscopy coupled with a high-angle annular dark field detector revealed the nanoscale changes in particle morphology, while electron energy loss spectroscopy mapped the changes in the chemical landscape during the reduction process. Tracking a specific region of interest on the sample grid allowed for comparisons to be made of the same particles across a two day monitoring period. High-angle annular dark field images permitted the visualization of particle size reduction of the gold salt while electron energy loss spectroscopy captured the surprising mobility of the lighter chlorine and sodium ions in a solid matrix during the reduction process. This system offers unique insight into precursor particle reactivity in the solid phase, which is relevant for many mechanochemical and aging-based reactions. [ABSTRACT FROM AUTHOR]

We describe the application of a mild, molecular-based, hydride metathesis protocol for the preparation of metastable germanium(II) dihydrides with compositions approaching [GeH2]n. The common starting material for this work [Ge(OtBu)2] was prepared in a high yield and shown to undergo OtBu/H exchange at Ge with the hydride sources pinacolborane (HBpin), catecholborane (HBcat), and diisobutylaluminum hydride (DIBAL-H) to give the [GeH2]n materials as yellow to orange solids. Heating one of these [GeH2]n materials to 200 °C affords a narrowing of the optical band gap (from 2.5 eV) and the generation of amorphous Ge. Reaction of [Ge(OtBu)2] with excess H3B·SMe2 in toluene at 70 °C provides a convenient route to thin films of amorphous Ge, including its deposition onto soft substrates, such as polyethyleneterephthalate (PET). Accompanying computations give insight into the energetics of OtBu/H exchange at Ge, and reveal a general thermodynamic preference for branched structures of [GeH2]n oligomers over linear forms as the Ge chain becomes longer. We also show that [Ge(OtBu)2] is a suitable pre-catalyst for the borylation of aldehydes. [ABSTRACT FROM AUTHOR]

Adducts of the parent iminoborane isomers, HBNH and NBH2, have been prepared, each stabilized by the frustrated Lewis pair (FLP) chelate iPr2P(C6H4)BCy2 (PB). PB{HBNH} was accessed via dehydrohalogenation, while the corresponding isomer PB{NBH2} was obtained from the borylation of the formal nitrene-FLP complex PB{NH}. [ABSTRACT FROM AUTHOR]

Treatment of (PN)NiX (X = NHdipp or OtBu; PN = N-phosphinoamidinate ligand) with Me2PhSiH in benzene solvent afforded the crystallographically characterized, antifacial-coordinated, dinuclear species 1, the formation of which corresponds to the hitherto unknown net Ni–H addition of two equivalents of the putative (PN)NiH intermediate across C＝C units within a single benzene molecule. Computational analysis supports the view of 1 as being comprised of two cationic (PN)NiII fragments ligated by a substituted butadiene dianion μ2–η3:η3-C6H82− bridging group. Also described is the formation and characterization of three-coordinate (PN)Ni(alkyl) complexes stabilized by β-agostic (alkyl = Et, 2; n-Bu, 3; n-hexyl, 4) or γ-agostic (alkyl = neopentyl, 5) interactions, and our efforts to employ 2 and 3 as synthons for the generation of (PN)NiHvia β-hydride elimination. Notably, compound 5 represents both the first crystallographically characterized three-coordinate Ni-alkyl complex featuring a heterobidentate ligation, and the first neutral γ-agostic NiII-alkyl complex. [ABSTRACT FROM AUTHOR]

Polytellurophenes represent an emerging class of π-conjugated polymers that possess important characteristics for flexible electronics, such as narrow HOMO–LUMO gaps (Eg) and charge mobilities that can be orders of magnitude larger than their ubiquitous polythiophene counterparts. Herein we use the reactivity of pinacolboronate (BPin) groups attached to tellurophene scaffolds to directly prepare new 2,5-diiodinated monomers, which are then polymerized to afford new low Eg oligomers and polymers. Specifically, mixtures of (cycloalkyl)tellurophene oligomers (of 5 to 12 repeat units) with ring-fused 5- and 6-membered cyclic side chains were prepared via Yamamoto coupling, with a dramatic narrowing of band gap noted when less bulky 5-membered cycloalkyl side groups were present, due to enhanced tellurophene ring coplanarity. Grignard metathesis (GRIM) was also used to gain access to the first poly(3-aryltellurophene) with 94% regioregularity, along with a low Eg of 1.3 eV and an onset of light absorption at ca. 1000 nm. [ABSTRACT FROM AUTHOR]

A new di(isopropoxy)boryl –B(OiPr)2 tellurophene precursor is described, from which several previously inaccessible phosphorescent borylated tellurophenes are formed via exchange of the –OiPr groups. One such tellurophene Mes(iPrO)B-Te-6-B(OiPr)Mes, bearing a sterically encumbered mesityl (Mes) substituent at each boron center, exhibits bright yellow-orange phosphorescence in the solid state at room temperature and in the presence of the known quencher O2. Furthermore, Suzuki–Miyaura cross-coupling between the newly prepared borylated tellurophenes and the test substrate 2-bromothiophene was examined with the pre-catalyst Cl(XPhos)Pd(aminobiphenyl). While more electron deficient boryl groups such as catecholatoboryl (–Bcat) yield significant protodeboronation in place of productive C–C bond formation, efficient formation of the desired thiophene-capped tellurophene thienyl-Te-6-thienyl was noted from tellurophenes bearing the readily accessible pinacolatoboryl (–Bpin) and 1,8-naphthalenediaminatoboryl (–Bdan) functional groups. These findings open the door for the efficient synthesis of aryl tellurophenes and polytellurophenes via the ubiquitous Suzuki–Miyaura coupling of borylated tellurophenes, which was previously hampered by protodeboronation. [ABSTRACT FROM AUTHOR]

The recently reported bulky N-heterocyclic carbene ITr (ITr = [(HCNCPh3)2C:]) was found to stabilize low-coordinate Ag(i) environments. These electrophilic species were crystallographically identified as the weak solvates [(ITr)Ag(sol)]+ (sol = PhF, MesH or CH2Cl2) and as a solvent-free dimer [(ITr)Ag]22+. The highly electrophilic nature of the [(ITr)Ag]+ cation was further demonstrated by the calculation of a very high methyl ion affinity (MIA) and the synthesis of [(ITr)Ag(PCO)] which features substantial side-on electron donation from a P–C π bond to Ag. [ABSTRACT FROM AUTHOR]

We report cationic complexes of arsenic and antimony with the tris(2-pyridyl)phosphine ligand. Chloride ion abstraction from AsCl3 using TMSOTf in the presence of the ligand gives [P(Pyr)3As][OTf]3, in which the trication adopts a C3v symmetric cage structure. The reaction proceeds via the intermediate [P(Pyr)3AsCl][OTf]2, which undergoes chloride exchange to give [P(Pyr)3As][OTf]3 and [P(Pyr)3AsCl2][OTf]. The rearrangement reaction has been supported by the isolation of the antimony mono fluoride derivative [P(Pyr)3SbF][OTf]2. The asymmetric axial lone pairs in derivatives of [P(Pyr)3Pn]3+ are electronically separated. The HOMO−1 (for arsenic) and HOMO (for antimony) represent the major contribution to the phosphine lone pair indicating the possibility for nucleophilic behaviour despite the +3 charge. Less accessible is the HOMO−7, which represents the lone pair at arsenic or antimony, respectively. [ABSTRACT FROM AUTHOR]

New complexes containing N-heterocyclic vinylene-stabilized [B2H5]+ fragments were prepared, and surprisingly it was found that the precursor N-heterocyclic olefins (NHOs) could promote the mild (room temperature) catalytic hydroborylation of ketones and aldehydes. This finding represents an important addition to the burgeoning field of non-metal mediated catalysis. [ABSTRACT FROM AUTHOR]

By investigating the coordination chemistry of a neutral N-heterocyclic olefin phosphine ligand, a new digold(i) chloride complex was discovered, demonstrating that mixed element (P/C) donor sites can be accessed at the same time. However attempts to extend this strategy for the preparation of heterobimetallic complexes featuring copper(i) and gold(i) centers with this mixed donor ligand were unsuccessful. The related monometallic copper(i) and gold(i) iodide complexes were discovered to be emissive in the solid state. [ABSTRACT FROM AUTHOR]

Despite recent advances in main group N-heterocyclic carbene (NHC) coordination chemistry, gallium hydrides remain, in large part, an unexplored area of research. In this paper we outline efficient routes to azide- and amido-functionalized gallium hydrides such as NHC·GaH2N3 and NHC·GaH2N(SiMe3)2 and explore these species as potential precursors to HGaNH complexes and bulk gallium nitride (GaN). [ABSTRACT FROM AUTHOR]

In this article our attempts to tune the color of luminescence within a new class of aggregation-induced emission (AIE) active tellurophenes is reported along with computational details that include spin–orbit coupling effects so as to better understand the nature of emission in the phosphorescent tellurophene (B-Te-6-B). Despite not meeting some of the initial synthetic targets, the emission within a borylated tellurophene can be altered with the addition of an N-heterocyclic carbene. [ABSTRACT FROM AUTHOR]

The synthesis of 16-electron complexes of the type (Cy-PSiP)RuX(L) (Cy-PSiP = κ3-(2-Cy2PC6H4)2SiMe) is reported. Treatment of (Cy-PSiP)H with one equiv. RuCl2(PPh3)3 in the presence of Et3N afforded a mixture of (Cy-PSiP)RuCl(PPh3) (1) and [(Cy-PSiP)RuCl]2 (2), which exists in a temperature-dependent equilibrium process involving reversible dissociation of PPh3 from 1 to form 2. While treatment of this equilibrium mixture with PMe3 afforded (Cy-PSiP)RuCl(PMe3) (3) cleanly, this product was more straightforwardly prepared by the addition of PMe3 to 2 (97% yield). Attempts to form an alkyl complex of the type (Cy-PSiP)RuMe(PMe3) via treatment of 3 with MeMgBr led to the dehydrogenation and cyclometalation of a cyclohexyl phosphino group to give the isolable 18-electron complex [MeSi(C6H4PCy2)(C6H4PCy(η3-C6H8))]RuPMe3 (4, 78% yield). The hydrido complex (Cy-PSiP)RuH(PMe3) (5) was identified as a minor by-product in this dehydrogenative process. Whereas simple 16-electron alkyl complexes of the type (Cy-PSiP)RuR(PMe3) remained elusive, the isolable allyl complex (Cy-PSiP)Ru(η3-C3H5) (9) was successfully prepared from 2 and (C3H5)MgCl (79% yield). Treatment of 3 with Me3SiN3 or NaN3 did not generate a five-coordinate azido species. However, the putative dinuclear complex [(Cy-PSiP)RuN3]2 (10) was observed to react with one equiv. of PMe3 to afford the isolable five-coordinate azido complex (Cy-PSiP)Ru(N3)(PMe3) (11; 94% yield). Crystallographic data for 3, 4, 5, 9 and 11 are presented. [ABSTRACT FROM AUTHOR]

Well-defined lanthanide polysulfide complexes containing S42− and S52− ligands, the samarium(iii) pentasulfide complex Sm(TpiPr2)(κ1-3,5-iPr2Hpz)(S5) and the tetrasulfide-bridged binuclear ytterbium(iii) complex (μ-S4)[Yb(TpiPr2)(κ1-3,5-iPr2Hpz)(κ2-3,5-iPr2pz)]2 (TpiPr2 = hydro-tris(3,5-diisopropylpyrazolyl)borate), have been synthesized and structurally characterized by single-crystal X-ray diffraction. [ABSTRACT FROM AUTHOR]

A general strategy for the synthesis of hindered N- and P-based donors is presented whereby the strongly electron releasing N-heterocyclic olefin (NHO) unit, IPr=CH–, (IPr=CH– = [(HCNDipp)2C=CH]−; Dipp = 3,6-iPr2C6H2) is linked to terminally bound phosphine and amine donors. Preliminary coordination chemistry is presented involving phosphine (IPr=CH)PR2 (R = iPr and Ph) and amine (IPr=CH)NMe2 ligands and the Lewis acids BH3 and AuCl. Interestingly, (IPr=CH)NMe2 binds AuCl through an exocyclic olefin unit, while the softer phosphorus centers in (IPr=CH)PR2 coordinate to yield Au–P linkages; thus the reported NHO-based ligands exhibit tunable binding modes to metals. [ABSTRACT FROM AUTHOR]

The reactivity of tungsten carbonyl adducts of Group 14 element (Ge, Sn and Pb) dihalides towards the metal-based donors (η5-C5H5)Rh(PMe2Ph)2 and Pt(PCy3)2 was examined. When (η5-C5H5)Rh(PMe2Ph)2 was treated with the Lewis acid supported Ge(ii) complex, THF·GeCl2·W(CO)5, cyclopentadienyl ring activation occurred, whereas the analogous Lewis acidic units SnCl2·W(CO)5 and PbCl2 form direct adducts with the Rh complex to yield Rh–Sn and Rh–Pb dative bonds. Attempts to prepare metal coordinated element(ii) hydrides by adding hydride sources to the above mentioned rhodium–E(ii) halide complexes were unsuccessful; in each case insoluble products were formed along with regeneration of free (η5-C5H5)Rh(PMe2Ph)2. In a parallel study, ECl2·W(CO)5 (E = Ge or Sn) groups were shown to participate in E–Cl oxidation addition chemistry with (Cy3P)2Pt to give the formal Pt(ii) complexes ClPt(PCy3)2ECl·W(CO)5. [ABSTRACT FROM AUTHOR]

Reactions of polydentate phosphines with sources of Pn3+ (Pn = P, As, Sb, Bi) yield complexes of Pn1+ (Pn = P, As) or Pn3+ (Pn = Sb, Bi) acceptors. The distinction between coordination of a phosphine center to Pn and oxidation of a phosphine ligand is dependent on Pn. The first structurally verified triphosphine complexes of Sb(iii) and Bi(iii) acceptors are reported. [ABSTRACT FROM AUTHOR]

The series of homoleptic lanthanide(ii) “bent sandwich-like” hydro-tris(pyrazolyl)borate complexes Ln(TpiPr2)2 (Ln = Sm (1), Eu (2), Tm (3), Yb (4); TpiPr2 = hydro-tris(3,5-diisopropylpyrazolyl)borate) has been completed by the synthesis of the hitherto unknown europium and ytterbium derivatives 2 and 4. Both compounds were prepared in high yields by treatment of LnI2(THF)2 (Ln = Eu, Yb) with 2 equiv. of KTpiPr2 in a THF solution. Although the molecules are sterically highly congested, an X-ray diffraction study of bright red 4 revealed a similar bent B–Yb–B arrangement (151.1° and 153.9°, two independent molecules) as in the previously investigated Sm(ii) and Tm(ii) complexes 1 and 3. An initial reactivity study showed a very different behavior with acetonitrile. While 2 and 4 proved to be unreactive toward acetonitrile, the more strongly reducing Sm(ii) complex 1 yielded two new products. The major product was the dark green-black acetonitrile solvate SmII(TpiPr2)2·CH3CN (5), while the second product, the colorless (TpiPr2)SmIII(3,5-iPr2pz)2(NCCH3) (6) with two 3,5-diisopropyl-pyrazolate ligands, resulted from oxidation of samarium to the trivalent state and degradation of a TpiPr2 ligand. Disappointingly, from the most reducing Tm(ii) complex 3 only the ligand fragmentation product pyrazabole, [HB(3,5-iPr2pz)2]2 (7), could be isolated and the fate of the Tm containing by-product(s) remains unknown. The new compounds 4–6 were structurally authenticated through single-crystal X-ray diffraction. The europium compound 2 shows an extremely bright yellow emission in solution, which can be observed also at daylight excitation, as well as in the solid state. The high intensity is even remarkable when compared to other Eu(ii) containing materials. The photoluminescence was investigated with the conclusion that the rigidity of this complex is responsible for these outstanding luminescence properties. [ABSTRACT FROM AUTHOR]

Herein we detail the synthesis and characterisation of a series of zirconium compounds featuring the bis(amido)silyl ligand [iPr2Si(NDipp)2]2− (Dipp = 2,6-diisopropylphenyl). The functionalisation of bis(amido)silyl zirconium halide complexes with a variety of nucleophiles, such as LiNMe2, LiBH4 and MeLi, was explored and the resulting products showed a propensity to form anionic zirconate salts when the syntheses were carried out in THF. One of the zirconate products, [iPr2Si(NDipp)2]Zr(NMe2)2·ClLi(THF)3, has the ability to catalyse the dehydrocoupling of primary and secondary amine-boranes at room temperature in aromatic solvents. [ABSTRACT FROM AUTHOR]

The zirconium-mediated syntheses of pinacolboronate (BPin) appended benzo[b]tellurophenes and two phenyl/BPin substituted tellurophene isomers with different colors of emission have been achieved. These species are new additions to an emerging class of inorganic heterocycles that display visible phosphorescence in the solid state under ambient conditions. [ABSTRACT FROM AUTHOR]

Although the use of ball milling to induce reactions between solids (mechanochemical synthesis) can provide lower-waste routes to chemical products by avoiding solvent during the reaction, there are further potential advantages in using one-pot multistep syntheses to avoid the use of bulk solvents for the purification of intermediates. We report here two-step syntheses involving formation of salen-type ligands from diamines and hydroxyaldehydes followed directly by reactions with metal salts to provide the corresponding metal complexes. Five salen-type ligands 2,2'-[1,2-ethanediylbis[(E)-nitrilomethylidyne]]bisphenol, 'salenH2', 1; 2,2'-[(±)-1,2-cyclohexanediylbis-[(E)-nitrilomethylidyne]]bis-phenol, 2; 2,2'-[1,2-phenylenebis( nitrilomethylidyne)]-bis-phenol, 'salphenH2' 3; 2-[[(2-aminophenyl)imino]methyl]-phenol, 4; 2,2'-[(±)-1,2-cyclohexanediylbis[(E)-nitrilomethylidyne]]-bis[4,6-bis(1,1-dimethylethyl)]-phenol, 'Jacobsen ligand', 5) were found to form readily in a shaker-type ball mill at 0.5 to 3 g scale from their corresponding diamine and aldehyde precursors. Although in some cases both starting materials were liquids, ball milling was still necessary to drive those reactions to completion because precipitation of the product and or intermediates rapidly gave in thick pastes which could not be stirred conventionally. The only ligand which required the addition of solvent was the Jacobsen ligand 5 which required 1.75 mol equivalents of methanol to go to completion. Ligands 1-5 were thus obtained directly in 30-60 minutes in their hydrated forms, due to the presence of water by-product, as free-flowing yellow powders which could be dried by heating to give analytically pure products. The one-armed salphen ligand 4 could also be obtained selectively by changing the reaction stoichiometry to 1 : 1. SalenH2 1 was explored for the onepot two-step synthesis of metal complexes. In particular, after in situ formation of the ligand by ball milling, metal salts (ZnO, Ni(OAc)2·4H2O or Cu(OAc) 2·H2O) were added directly to the jar and milling continued for a further 30 minutes. Small amounts of methanol (0.4-1.1 mol equivalents) were needed for these reactions to run to completion. The corresponding metal complexes [M(salen)] (M = Zn, 6; Ni, 7; or Cu, 8) were thus obtained quantitatively after 30 minutes in hydrated form, and could be heated briefly to give analytically pure dehydrated products. The all-at-once 'tandem' synthesis of [Zn(salen)] 6 was also explored by milling ZnO, ethylene diamine and salicylaldehyde together in the appropriate mole ratio for 60 minutes. This approach also gave the target complex selectively with no solvent needing to be added. Overall, these syntheses were found to be highly efficient in terms of time and the in avoidance of bulk solvent both during the reaction and for the isolation of intermediates. The work demonstrates the applicability of mechanochemical synthesis to one-pot multi-step strategies. [ABSTRACT FROM AUTHOR]

The reaction of YbI2with KTpMe2gives (TpMe2)YbI(THF)2(1-Yb) as a thermally unstable product. Use of the more hindered KTptBu,Megave (TptBu,Me)LnI(THF)n(Ln = Sm, n= 2, 2-Sm; Ln = Yb, n= 1, 2-Yb). The crystal structures of both these compounds are reported. Adducts with neutral ligands such as pyridines and isonitriles can be prepared and the crystal structures of [(TptBu,Me)YbILn] (L = CNtBu, n= 1; L = 3,5-lutidine, n= 2) are described. 2-Smcan be oxidized using AgBPh4to give [(TptBu,Me)SmI(THF)2]BPh4. Compounds 2-Smand 2-Ybare useful starting materials for the preparation of heteroleptic compounds by metathesis with appropriate potassium reagents. The preparations and characterization of the hydrocarbyls (TptBu,Me)Ln{CH(SiMe3)2} (Ln = Sm, 5-Sm; Yb, 5-Yb) and [(TptBu,Me)Ln{CH2(SiMe3)}(THF)] (Ln = Yb, 6a-Yb) and the triethylborohydrides [(TptBu,Me)Ln(HBEt3)(THF)n] (Ln = Sm, n= 0, 7-Sm; Yb, n= 1, 7-Yb) are reported, as well as the crystal structures of 5-Smand 5-Yb, and the THF adducts 6a-Yband [(TptBu,Me)Sm{CH(SiMe3)2}(THF)], 5a-Sm. [ABSTRACT FROM AUTHOR]

Monophosphines of the type PhxPAr3-x (x = 0, 1 or 2, Ar = o-N-methylanilinyl) and the diphosphine, Ar2PCH2PAr2 (mapm) have been synthesized for use as chelating and/or bridging P,N-ligands within mono- and binuclear rhodium(I) complexes, respectively. The previously prepared phosphines, PhxPAr'3-x (x = 0, 1 or 2, Ar' = o-N,N-dimethylanilinyl) and Ar'2PCH2PAr'2 (dmapm), have also been used to prepare analogous mono- and binuclear complexes. Variable temperature 1HNMR spectroscopy of the mononuclear complexes, [RhCl(CO)(L)] (L = PhPAr2, PhPAr'2, PAr3 and PAr'3), and line-shape analyses of the resultant spectra indicate the substantially increased lability of the N,N-dimethylanilinyl donors relative to the related monomethylanilinyl groups. X-Ray structural analyses of the mononuclear complexes suggest that the enhanced Type II hemilability in the dimethylanilinyl complexes compared to their monomethyl analogues results from increased steric interactions involving the coordinated dimethylanilinyl substituents. In the case of the binuclear, dmapm-bridged compound [Rh2Cl2(CO)2(μ-dmapm)], there are additional transannular repulsions between the chloro ligand on one metal and the coordinated dimethylanilinyl group on the other, which result in a Rh-Rh separation of over 4.1Å . For the analogous mapm-bridged species, the transannular interactions between the chloro ligands and the amine hydrogens are in fact attractive, resulting in a much closer Rh-Rh separation (3.450Å ). The chloride substituents of [Rh2Cl2(CO)2(μ-mapm)] can be replaced to generate the complexes, [Rh2(X)2(CO)2(μ-mapm)] (X = I, CF3SO3, CH3CO2), the last of which also exhibits pronounced transannular hydrogen-bonding interactions in the solid state. [ABSTRACT FROM AUTHOR]

Remote coordination of a Ru(hfac)2 moiety to a chelating N-benzyl tetrazine lowers the C-N homolytic bond dissociation enthalpy by approximately 20 kJ mol-1. The significant bond strength perturbation is believed to arise as a consequence of metal-ligand redox non-innocence. [ABSTRACT FROM AUTHOR]

Reactivity studies of a Pd(II)--verdazyl complex reveal novel ligandcentred reduction processes which trigger pseudo-reductive elimination at Pd. Reaction of the complexwithwater induces a ligand-centred redox disproportionation. The reduced verdazyl ligands can also be reversibly protonated. [ABSTRACT FROM AUTHOR]

Reactions of trimethylphosphine or diphosphines with SbCl3in the presence of AlCl3or Me3SiSO3CF3give ligand stabilized stibenium and stibinidenium cations. The geometry at each antimony center reveals a variety of environments for antimony that describes new bonding and highlights new directions in the chemistry of the pnictogen elements. [ABSTRACT FROM AUTHOR]