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A bulkytris(carbene)borate ligand allows several low-valent ironcarbonyl complexes to be isolated. One-electron reduction of the cationiciron(II) complex [PhB(MesIm)3Fe(CO)3][B(C6F5)4] (1) ([PhB(MesIm3)]−= phenyltris(1-mesitylimidazol-2-ylidene)borate)yields the low-spin (S= 1/2) iron(I) complex PhB(MesIm)3Fe(CO)2(2), as determined by structuraland spectroscopic methods. This complex can in turn be reduced toprovide the anionic dicarbonyl complex [K][PhB(MesIm)3Fe(CO)2] (3), which crystallizes as a dimer in whichthe potassium cation coordinates in a side-on fashion to one CO ligand.Protonation of 3yields the weakly acidic iron hydridePhB(MesIm)3Fe(CO)2H (4), whichcan also be isolated by treating the κ3-coordinatedalkylborohydrido complex PhB(MesIm)3Fe(κ3-BH(CH2CH3)3) (5) with CO. The strong donor ability of the tris(carbene)borate ligandresults in significant reduction of the CO bonds, as measured by IRspectroscopy. [ABSTRACT FROM AUTHOR]

Copolymers of methyl methacrylate and aryl-triazole based anion receptors were quantitatively analyzed. Transfer of structural features (1:1 and 2:1 complexes) and Cl- affinities from the parent receptors was demonstrated. Cl--induced cross-linking changed the polymer's hydrodynamic radius. Extraction of tetrapropylammonium Cl- from water to dichloromethane was enhanced over PMMA. [ABSTRACT FROM AUTHOR]

Anions stabilize stacking of C5-symmetric macrocycles, called cyanostars, into dimers in solution and herein we demonstrate this stacking in solid-state crystals. We further show that this guest binding can be applied as a route to bilayer growth at the solution--graphite interface. [ABSTRACT FROM AUTHOR]

Reacting (PNP)Ti=CHtBu(CH2tBu) with 2,2'-bipyridine (bipy) in cyclohexane or heptane results in dehydrogenation, cleanly producing cyclohexene and 1-heptene, respectively, and a TiII intermediate that is trapped by bipy to produce [(PNP)TiIII(CH2tBu)(bipy·-)] (1). This titanium(II) intermediate reduces the bipy ligand upon coordination to form a TiIII center, where the unpaired electron is antiferromagnetically coupled to the electron of the reduced [bipy·-] π-radical moiety, giving an overall diamagnetic species. Complex 1 has been characterized by NMR and UV-vis spectroscopies as well as single crystal X-ray diffraction studies. [ABSTRACT FROM AUTHOR]

Deprotonation of the parent titanium imido (tBunacnac)Ti ≡ NH(Ntolyl2) (tBunacnac- = [ArNCtBu]2CH; Ar = 2,6-1Pr2C6H3) with KCH2Ph forms a rare example of a molecular titanium nitride as a dimer, {[K][(tBunacnac)Ti≡N(Ntolyl2)]}2. From the parent imido or nitride salt, the corresponding aluminylimido- etherate adduct, (tBunacnac)TiN≡[AlMe2(OEt2)]-(Ntolyl2), can be isolated and structurally characterized. The parent imido is also a source for the related borylimido, (tBunacnac)Ti=NBEt2(Ntolyl2). [ABSTRACT FROM AUTHOR]

An unexpected doubling in redox storage emerging from a new pincer ligand upon bis-ligation of iron(II) is described. When tetrazine arms are present at the two ortho positions of pyridine, the resulting bistetrazinyl pyridine (btzp) pincer ligand displays a single one-electron reduction at ca. -0.85 V vs. Ag/AgCl. Complexation to iron, giving the cation Fe(btzp)2 2+, shows no oxidation but four reduction waves in cyclic voltammetry instead of the two expected for the two constituent ligands. Mossbauer, X-ray diffraction and NMR studies show the iron species to contain low spin Fe(II), but with evidence of back donation from iron to the pincer ligands. CV and UV-Vis spectroelectrochemistry, as well as titration studies as monitored by CV, electronic spectra and EPR reveal the chemical reversibility of forming the reduced species. DFT and EPR studies show varying degrees of delocalization of unpaired spin in different species, including that of a btzp-1 radical anion, partnered with various cations. [ABSTRACT FROM AUTHOR]

Synthesis and characterization of divalent nickel complexed by 2-pyridylpyrrolide bidentate ligands are reported, as possible precursors to complexes with redox active ligands. Varied substituents on the pyrrolide, two CF3 (L²), two tBu (L0), and one of each type (L¹) are employed and the resulting Ni(Ln)2 complexes show different Lewis acidity toward CO, H2O, tetrahydrofuran (THF), or MeCN, the L² case being the most acidic. Density functional theory calculations show that the frontier orbitals of all three Ni(Ln)2 species are localized at the pyrrolide groups of both ligands and Ni(Ln)2+ can be detected by mass spectrometry and in cyclic voltammograms (CVs). Following cyclic voltammetry studies, which show electroactivity primarily in the oxidative direction, reactions with pyridine N-oxide or Br2 are reported. The former yield simple bis adducts, Ni(L²)2(pyNO)2 and the latter effects electrophilic aromatic substitution of the one pyrrolide ring hydrogen for both chelates, leaving it brominated. [ABSTRACT FROM AUTHOR]

The use of weakly coordinating anions BArF4 (where ArF = 3,5-(CF3)2C6H3) and CB11H12 allows one to access clean reactions of the [(PNP)Pd]+ fragment (PNP = bis(2-iPr2P4--Me-phenyl)amido) with the B-H bond in catecholborane (CatBH) and catecholdiboron (CatBBCat). In both cases, a net heterolytic cleavage of B-H or B-B takes place, with the nitrogen atom of PNP being a recipient of a boryl fragment. The resultant products [(PN(BCat)P)PdH]+ (2) and [(PN(BCat)P)PdBCat]+ (3) were isolated as either BArF4 or CB11H12 salts and fully characterized. They are susceptible to hydrolysis, with the B-N bond hydrolyzing selectively and rapidly at RT to give [(PN(H)P)PdH]+ (1) and [(PN(H)P)PdBCat]+ (4). Notably, 4 and 2 are isomers, but they do not interconvert even under thermolysis at 90 ¼C. The Pd-B bond in 4 can be further hydrolyzed more slowly, to give 1. On the other hand, a Pd-B bond was formed from the Pd-H bond in 2 by reaction with excess CatBH (and evolution of H2), producing 3. [ABSTRACT FROM AUTHOR]

Terminal oxo and sulfido complexes in the form of (nacnac) V=E(Ntol2) (nacnac = [ArNC(CH3)]2CH−, Ar=2,6-(CHMe2)2C6H3, Ntol2 = −N(C6H4-4-Me), E = O (1), S (2)) were isolated from treatment of the masked three-coordinate vanadium(II) complex, (nacnac)V(Ntol2), with C5H5NO and S8, respectively. Both vanadium(IV) species, 1 and 2, have been characterized by room temperature X-band EPR spectroscopic studies, and in the case of complex 1, a single crystal molecular structure confirmed the presence of a terminal oxo moiety. Moreover, reaction of (nacnac)V(Ntol2) with diphenyl–disulfide and diphenyl–diselenide results in the reductive cleavage of these compounds to produce the vanadium(III) complexes (nacnac)V(XPh)(Ntol2) (X = S, (3), Se (4)). A molecular structure of the phenylsulfide complex, 3, confirmed formation of the d2 complex resulting from reductive cleavage of the S–S bond. [Copyright &y& Elsevier]

The (PNP)Rh fragment, where PNP is the bis(o-diisopropylphosphinophenyl)amide “pincer” ligand, has been shown to undergo a series of silicon−halogen oxidative addition reactions. (PNP)Rh(SPri2) (1) reacted with certain silyl halides with formation of (PNP)Rh(Silyl)(Hal) and release of SPri2. The reactions with 1.1 equiv of Me3Si-I, Cl3Si-Cl, or MeCl2Si-Cl proceeded to completion, the reactions with 1.1 equiv of Me2ClSi-Cl or Me3Si-Br produced an equilibrium mixture of (PNP)Rh(Silyl)(Hal) and (PNP)Rh(SPri2) (1), and the reaction with Me3Si-Cl did not proceed at all. (PNP)Rh(SiMe3)(Cl) was instead prepared via the reaction of (PNP)Rh(Me)(CH2Ph) with Me3Si-Cl, which proceeds with concomitant elimination of ethylbenzene. The reaction of (PNP)Rh(SPri2) (1) with Me2SiHCl led to the exclusive formation of (PNP)Rh(SiMe2Cl)(H) (14), containing a borderline Si···H contact. (PNP)Rh(SPri2) (1) and (PNP)Rh(SiMe2Cl)(Cl) (7) displayed similar rates in the reaction with PhBr that results in (PNP)Rh(Ph)(Br), presumably via the rate-limiting elimination of either SPri2or Me2SiCl2. [ABSTRACT FROM AUTHOR]

We have developed a short and practical first synthesis of methyl l-hydroxy-6-oxo-2-cyclohexenecarboxylate (2), which has been known as a component of salicortin and tremulacin since 1970. Birch reduction of the SEM ether of methyl salicylate followed by oxidation of the intermediate enolate with (—)-camphorsulfonyloxaziridine afforded the SEM enol ether of 2. Hydrolysis of the SEM enol ether afforded 2. We did not observe the dimerization of either racemic or optically enriched 2 to give idesolide (1). [ABSTRACT FROM AUTHOR]

Palladium(II) complexes of the PCHP pincer ligand were prepared from PdCl2, a “proto-pincer” P2CH2, and base. The resulting (PCHP)PdCl was converted to (PCHP)PdOTf. (PCHP)PdCl did not react with NaN(SiMe3)2but produced (PCHP)PdR (R Me, Et, Ph) upon reaction with the corresponding organolithium, Grignard, or organozinc reagent. Trityl cation abstracted a hydride from (PCHP)PdCl to yield cationic Pd carbene complex (P2C)PdCl. Analysis of the structural data points to minimal -interaction between the carbene center and palladium. [ABSTRACT FROM AUTHOR]

Reductive alkylation of 5-methoxy-1-tetralone (6) with 2,3-dibromopropene gave an equilibrium mixture of bicyclic diones 7(51%) and 8(35%). Radical cyclization of 7afforded tricyclic dione 5(84%), which was reduced, cyclized, and dehydrated to give tetracyclic alkene 13in 63% yield. Allylic oxidation of 13with SeO2and activated MnO2afforded enone 2in 85% yield, thereby completing a short formal synthesis of (±)-platensimycin. [ABSTRACT FROM AUTHOR]

Reaction of CO2 with a Pd(I)--Pd(I) dimer supported by amido/ bis(phosphine) pincer PNP ligands produces free CO in the presence of Me3SiCl and Me3SiOTf. [ABSTRACT FROM AUTHOR]

Photolysis of (FPNP)Pd–Et in the presence of Et2Zn leads to the formation of (FPNP)Pd–Zn–Pd(PNPF), the first example of a compound with a covalent Pd–Zn bond. [ABSTRACT FROM AUTHOR]