Regioselective bis-functionalization of endohedral dimetallofullerene, La2@C80: extremal La-La distance

Bis-functionalization of endohedral metallofullerene La(2)@C(80) by carbene addition is reported herein. Adducts were characterized using spectroscopic and single-crystal X-ray structure analyses. Crystallographic data for bisadduct La(2)@C(80)(CClPh)Ad (3, Ad = adamantylidene) revealed that both carbene additions occur at the 6,6-bond junction on the C(80) cage with ring cleavages and that La atoms are positioned collinearly with spiro carbons. It is noteworthy that the La-La distance in 3 is highly elongated by carbene bis-functionalization compared to the distance in pristine La(2)@C(80) and reported functionalized derivatives. The metal positions were confirmed through density functional calculations.     

Metal atoms collinear with the spiro carbon of 6,6-open adducts, M2@C80(Ad) (M = La and Ce, Ad = adamantylidene)

The photochemical reaction of M2@C80 (M = La and Ce) with 2-adamantane-2,3'-[3H]-diazirine (1) affords the corresponding adducts by carbene addition. The adducts were characterized by spectroscopic and single-crystal X-ray structure analyses. Crystallographic data for the adduct La2@C80(Ad) (2, Ad = adamantylidene) reveal that the two La atoms are collinear with the spiro carbon of the 6,6-open adduct. It is noteworthy that the La-La distance is highly elongated by the addition of carbene. Paramagnetic 13C NMR spectral analysis of the adduct Ce2@C80(Ad) (3) indicates that the two Ce atoms are also collinear with the spiro carbon at room temperature in solution. The unique metal positions were confirmed by density functional calculations.     

Synthesis and structural characterization of endohedral pyrrolidinodimetallofullerene: La2@C80(CH2)2NTrt

The endohedral pyrrolidinodimetallofullerene, La2@C80(CH2)2NTrt (Trt = triphenylmethyl), was successfully synthesized and characterized. X-ray crystallographic and NMR spectroscopic analyses reveal that two La atoms in the 6,6-adduct are localized at the stable site on the mirror plane. Theoretical calculation also suggests the localization of two La atoms in the 6,6-adduct.     

New dinuclear nickel(II) complexes: synthesis, structure, electrochemical, and magnetic properties

The reaction of [NiBr(2)(bpy)(2)] (bpy = 2,2'-bipyridine) with organic phosphinic acids ArP(O)(OH)H [Ar = Ph, 2,4,6-trimethylphenyl (Mes), 9-anthryl (Ant)] leads to the formation of binuclear nickel(II) complexes with bridging ArP(H)O(2)(-) ligands. Crystal structures of the binuclear complexes [Ni(2)(μ-O(2)P(H)Ar)(2)(bpy)(4)]Br(2) (Ar = Ph, Mes, Ant) have been determined. In each structure, the metal ions have distorted octahedral coordination and are doubly bridged by two arylphosphinato ligands. Magnetic susceptibility measurements have shown that these complexes display strong antiferromagnetic coupling between the two nickel atoms at low temperatures, apparently similar to binuclear nickel(II) complexes with bridging carboxylato ligands. Cyclic voltammetry and in situ EPR spectroelectrochemistry show that these complexes can be electrochemically reduced and oxidized with the formation of Ni(I),Ni(0)/Ni(III) derivatives.     

Synthesis and Ligand Substitution Reactions of a Mesitylphosphido-Bridged Platinum(II) Dimer

The stable primary phosphine complexes trans-M(PH(2)Mes)(2)Cl(2) (1, M = Pd; 2, M = Pt; Mes = 2,4,6-(t-Bu)(3)C(6)H(2)) were prepared from Pd(PhCN)(2)Cl(2) and K(2)PtCl(4), respectively. Reaction of Pt(COD)Cl(2) (COD = 1,5-cyclooctadiene) with less bulky arylphosphines gives the unstable cis-Pt(PH(2)Ar)(2)Cl(2) (3, Ar = Is = 2,4,6-(i-Pr)(3)C(6)H(2); 4, Ar = Mes = 2,4,6-Me(3)C(6)H(2)). Spontaneous dehydrochlorination of 4 or direct reaction of K(2)PtCl(4) with 2 equiv of PH(2)Mes gives the insoluble primary phosphido-bridged dimer [Pt(PH(2)Mes)(&mgr;-PHMes)Cl](2) (5), which was characterized spectroscopically, including solid-state (31)P NMR studies. The reversible reaction of 5 with PH(2)Mes gives [Pt(PH(2)Mes)(2)(&mgr;-PHMes)](2)[Cl](2) (6), while PEt(3) yields [Pt(PEt(3))(2)(&mgr;-PHMes)](2)[Cl](2) (7), which on recrystallization forms [Pt(PEt(3))(&mgr;-PHMes)Cl](2) (8). Complex 5 and PPh(3) afford [Pt(PPh(3))(&mgr;-PHMes)Cl](2) (9). Addition of 1,2-bis(diphenylphosphino)ethane (dppe) to 5 gives the dicationic [Pt(dppe)(&mgr;-PHMes)](2)[Cl](2) (10-Cl), which was also obtained as the tetrafluoroborate salt 10-BF(4)() by deprotonation of [Pt(dppe)(PH(2)Mes)Cl][BF(4)] (11) with Et(3)N or by reaction of [Pt(dppe)(&mgr;-OH)](2)[BF(4)](2) with 2 equiv of PH(2)Mes. Complexes 8, 9, and 10-Cl.2CH(2)Cl(2).2H(2)O were characterized crystallographically.     

Tunable charge-transport properties of I(h)-C80 endohedral metallofullerenes: investigation of La2@C80, Sc3N@C80, and Sc3C2@C80

Fullerene crystals or films have drawn much interest because they are good candidates for use in the construction of electronic devices. The results of theoretical calculations revealed that the conductivity properties of I(h)-C(80) endohedral metallofullerenes (EMFs) vary depending on the encapsulated metal species. We experimentally investigated the solid-state structures and charge-carrier mobilities of I(h)-C(80) EMFs La(2)@C(80), Sc(3)N@C(80), and Sc(3)C(2)@C(80). The thin film of Sc(3)C(2)@C(80) exhibits a high electron mobility μ = 0.13 cm(2) V(-1) s(-1) under normal temperature and atmospheric pressure, as determined using flash-photolysis time-resolved microwave conductivity measurements. This electron mobility is 2 orders of magnitude higher than the mobility of La(2)@C(80) or Sc(3)N@C(80).     

A monomeric thallium(I) amide in the solid state: synthesis and structure of TlN(Me)ArMes2 (ArMes2 = C6H3-2,6-Mes2)

Reaction of TlCl and [LiN(Me)Ar(Mes)2](2) [Ar(Mes)2 = C(6)H(3)-2,6-(C(6)H(2)-2,4,6-Me(3))(2)] in Et(2)O generated the thallium amide, TlN(Me)Ar(Mes)2 (1). X-ray data showed that it has a monomeric structure with an average Tl-N distance of 2.364(3) Angstroms. There was also a Tl-arene approach [Tl-centroid = 3.026(2) Angstroms (avg)] to a flanking mesityl ring from the terphenyl substituent. DFT calculations showed that this interaction is weak and supported essentially one coordination for thallium. The electronic spectrum of 1 is hypsochromically shifted in comparison to the monomeric TlAr(Trip)2 (Trip = C(6)H(2)-2,4,6-Pr(i)(3)).     

The reactivity of gallium-(I), -(II) and -(III) heterocycles towards Group 15 substrates: attempts to prepare gallium-terminal pnictinidene complexes

The reactivity of a series of Ga(I), Ga(II) and Ga(III) heterocyclic compounds towards a number of Group 15 substrates has been investigated with a view to prepare examples of gallium-terminal pnictinidene complexes. Although no examples of such complexes were isolated, a number of novel complexes have been prepared. The reactions of the gallium(I) N-heterocyclic carbene analogue, [K(tmeda)][:Ga{[N(Ar)C(H)](2)}] (Ar = 2,6-diisopropylphenyl) with cyclo-(PPh)(5) and PhN[double bond, length as m-dash]NPh led to the unusual anionic spirocyclic complexes, [{kappa(2)P,P'-(PhP)(4)}Ga{[N(Ar)C(H)](2)}](-) and [{kappa(2)N,C-PhNN(H)(C(6)H(4))}Ga{[N(Ar)C(H)](2)}](-), via formal reductions of the Group 15 substrate. The reaction of the digallane(4), [Ga{[N(Ar)C(H)](2)}](2), with (Me(3)Si)N(3) afforded the paramagnetic, dimeric imido-gallane complex, [{[N(Ar)C(H) ](2)}Ga{mu-N(SiMe(3))}](2), via a Ga-Ga bond insertion process. In addition, the new gallium(III) phosphide, [GaI{P(H)Mes*}{[N(Ar)C(H)](2) }], Mes* = C(6)H(2)Bu(t)(3)-2,4,6; was prepared and treated with diazabicycloundecane (DBU) to give [Ga(DBU){P(H)Mes*}{[N(Ar)C(H)](2)}], presumably via a gallium-terminal phosphinidene intermediate, [Ga{[double bond, length as m-dash]PMes*}{[N(Ar)C(H)](2) }]. The possible mechanisms of all reactions are discussed, all new complexes have been crystallographically characterised and all paramagnetic complexes have been studied by ENDOR and/or EPR spectroscopy.     

Quantum chemical study on the configurations of encapsulated metal ions and the molecular vibration modes in endohedral dimetallofullerene La2@C80

The configuration of La ions of La(2)@C(80) in the [80]fullerene cage was investigated by use of quantum chemical calculations. We found that the D(3)(d)() configuration is the global minimum in total energy, being more stable by 1.9 kcal/mol than the D(2)(h)() configuration, which has been considered to be the most stable. The potential energy surface calculation clarified that La ions travel between 10 equivalent D(3)(d)() positions through D(2)(h)() positions and consequently form pentagonal dodecahedral trajectory, which is in good agreement with the previous synchrotron radiation structural study. The experimental and theoretical investigation of the Raman spectrum revealed that the symmetry of molecular vibration is dramatically reduced simply by encapsulation of two La ions, and resulting vibrational modes were successfully assigned. The Raman peak at 163 cm(-)(1) was interpreted as the in-phase synchronously coupled mode of the [80]fullerene cage elongation and the La-La stretching, rather than a conventional and naive assignment as a metal-to-cage vibration mode.     

Synthesis and characterization of aryl substituted bis(2-pyridyl)amines and their copper olefin complexes: investigation of remote steric control over olefin binding

The aryl-functionalized pyridylamine 2-(i)PrC(6)H(4)N(H)py (1) and bis(2-pyridyl)amines of the type ArN(py)(2) for Ar = Mes (2), 2,6-Et(2)C(6)H(3) (3), 2-(i)PrC(6)H(4) (4), 2,6-(i)Pr(2)C(6)H(3) (5), and 1-naph (6), have been prepared by the palladium-catalyzed cross-coupling of substituted anilines with 2-bromopyridine, and have been characterized by (1)H and (13)C NMR NMR, FTIR, MS, and TGA. Complexes of these new N-aryl bis(2-pyridyl)amines have been prepared for the acid salts [H{ArN(py)(2)}]BF(4) where Ar = Mes (7) and 2-(i)PrC(6)H(4) (8), and the dimeric bridged complexes [Cu{ArN(py)(2)}(μ-X)(Y)](2) where X/Y = Cl(-) and Ar = Ph (9), 2-(i)PrC(6)H(4) (10), and 1-naph (11), in addition to X = OH(-), Y = H(2)O and Ar = Mes (12). The olefin complexes [Cu(Ar-dpa)(styrene)]BF(4) for Ar = Ph (13), Mes (14), 2-(i)PrC(6)H(4) (15), and 1-naph (16), in addition to the norborylene complexes of Ar = Mes (17) and 2-(i)PrC(6)H(4) (18) have been prepared and characterized by (1)H and (13)C NMR, FTIR, and TGA. The crystal structures have been determined for compounds 1-17. Secondary amine 1 crystallizes in hydrogen-bonded head-to-tail dimers, while the N-aryl bis(2-pyridyl)amines 2-6 crystallize in a three-bladed propellar conformation, having nearly planar geometries about the amine nitrogen. The geometry about copper centers in the dimeric complexes 9-12 is distorted trigonal bypyramidal, with the axial positions occupied by one of the two pyridyl nitrogens and one of the bridging ligands (i.e., Cl or OH). The copper atoms in each of the olefin complexes 13-17 are coordinated to the two pyridine nitrogen atoms and the appropriate olefin; consistent with a pseudo three-coordinate Cu(I) cation. Distortion of pyridyl ring geometries about the copper centers, and concomitant bending of the aryl groups away from the CuN(amine) vectors were found to correlate with the steric bulk of the aryl group present in both dimeric and olefin complexes. Such distortion is also observed to a lesser extent in the acid salts as well. The (1)H and (13)C NMR spectra of [Cu(Ar-dpa)(olefin)]BF(4) exhibit an upfield shift in the olefin signal as compared to free olefin. A good correlation exists between the (1)H and (13)C NMR Δδ values and olefin dissociation temperatures, confirming that the shift of the olefin NMR resonances upon coordination is associated with the binding strength of the complex.     

Large endohedral fullerenes containing two metal ions, Sm2@D2(35)-C88, Sm2@C1(21)-C90, and Sm2@D3(85)-C92, and their relationship to endohedral fullerenes containing two gadolinium ions

The carbon soot obtained by electric arc vaporization of carbon rods doped with Sm(2)O(3) contains a series of monometallic endohedral fullerenes, Sm@C(2n), along with smaller quantities of the dimetallic endohedrals Sm(2)@C(2n) with n = 44, 45, 46, and the previously described Sm(2)@D(3d)(822)-C(104). The compounds Sm(2)@C(2n) with n = 44, 45, 46 were purified by high pressure liquid chromatography on several different columns. For endohedral fullerenes that contain two metal atoms, there are two structural possibilities: a normal dimetallofullerene, M(2)@C(2n), or a metal carbide, M(2)(μ-C(2))@C(2n-2). For structural analysis, the individual Sm(2)@C(2n) endohedral fullerenes were cocrystallized with Ni(octaethylporphyrin), and the products were examined by single-crystal X-ray diffraction. These data identified the three new endohedrals as normal dimetallofullerenes and not as carbides: Sm(2)@D(2)(35)-C(88), Sm(2)@C(1)(21)-C(90), and Sm(2)@D(3)(85)-C(92). All four of the known Sm(2)@C(2n) endohedral fullerenes have cages that obey the isolated pentagon rule (IPR). As the cage size expands in this series, so do the distances between the variously disordered samarium atoms. Since the UV/vis/NIR spectra of Sm(2)@D(2)(35)-C(88) and Sm(2)@C(1)(21)-C(90) are very similar to those of Gd(2)C(90) and Gd(2)C(92), we conclude that Gd(2)C(90) and Gd(2)C(92) are the carbides Gd(2)(μ-C(2))@D(2)(35)-C(88) and Gd(2)(μ-C(2))@C(1)(21)-C(90), respectively.     

Synthesis, reactivity, and DFT studies of tantalum complexes incorporating diamido-N-heterocyclic carbene ligands. Facile endocyclic C-H bond activation

The syntheses of tantalum derivatives with the potentially tridentate diamido-N-heterocyclic carbene (NHC) ligand are described. Aminolysis and alkane elimination reactions with the diamine-NHC ligands, (Ar)[NCN]H(2) (where (Ar)[NCN]H(2) = (ArNHCH(2)CH(2))(2)(C(3)N(2)); Ar = Mes, p-Tol), provided complexes with a bidentate amide-amine donor configuration. Attempts to promote coordination of the remaining pendent amine donor were unsuccessful. Metathesis reactions with the dilithiated diamido-NHC ligand ((Ar)[NCN]Li(2)) and various Cl(x)Ta(NR'(2))(5-)(x) precursors were successful and generated the desired octahedral (Ar)[NCN]TaCl(x)(NR'(2))(3-)(x) complexes. Attempts to prepare trialkyl tantalum complexes by this methodology resulted in the formation of an unusual metallaaziridine derivative. DFT calculations on model complexes show that the strained metallaaziridine ring forms because it allows the remaining substituents to adopt preferable bonding positions. The calculations predict that the lowest energy pathway involves a tantalum alkylidene intermediate, which undergoes C-H bond activation alpha to the amido to form the metallaaziridine moiety. This mechanism was confirmed by examining the distribution of deuterium atoms in an experiment between (Mes)[NCN]Li(2) and Cl(2)Ta(CD(2)Ph)(3). The single-crystal X-ray structures of (p)(-Tol)[NCNH]Ta(NMe(2))(4) (3), (Mes)[NCNH]Ta=CHPh(CH(2)Ph)(2) (4), (p)(-Tol)[NCN]Ta(NMe(2))(3) (7), (Mes)[NCCN]Ta(CH(2)(t)Bu)(2) (11), and (Mes)[NCCN]TaCl(CH(2)(t)Bu) (14) are included.     

Positional control of encapsulated atoms inside a fullerene cage by exohedral addition

The exohedrally functionalized derivative of endohedral metallofullerene, Ce2@C80(Mes2SiCH2SiMes2), was successfully synthesized and fully characterized. X-ray crystallographic and NMR spectroscopic analyses reveal that the free random motion of two metal atoms in Ce2@C80 is controlled inside the cage by exohedral chemical functionalization.     

Stoichiometric Reduction of CO(2) to CO by Aluminum-Based Frustrated Lewis Pairs

Reducing frustration: The reaction of Mes(3) P(CO(2) )(AlI(3) )(2) in the presence of a CO(2) atmosphere results in the formation of Mes(3) P(CO(2) )(O(AlI(2) )(2) )(AlI(3) ) and [Mes(3) PI][AlI(4) ] (Mes=2,4,6-Me(3) C(6) H(2) ) with the evolution of CO.     

Synthesis and characterisation of the first carbene and diazabutadiene-indium(II) complexes

The reactions of IMes [:CN(Mes)C2H2N(Mes), Mes = mesityl] and DAB [(ArN=CH)2, Ar = C6H3Pri2-2,6] with indium(I) halides have afforded the first carbene and diazabutadiene indium(II) complexes, [In2Br4(IMes)2] and [In2Cl2(DAB.)2], both of which have been crystallographically characterised.     

Oxidative cleavage of tetraaryltetraphosphane-1,4-diides by nickel(II) and palladium(II): formation of unusual Ni(0) and Pd(0) diaryldiphosphene complexes

[Na(2)(thf)(4)(P(4)Mes(4))] (1) (Mes = 2,4,6-Me(3)C(6)H(2)) reacts with one equivalent of [NiCl(2)(PEt(3))(2)], [NiCl(2)(PMe(2)Ph)(2)], [PdCl(2)(PBu(n)(3))(2)] or [PdCl(2)(PMe(2)Ph)(2)] to give the corresponding nickel(0) and palladium(0) dimesityldiphosphene complexes [Ni(eta(2)-P(2)Mes(2))(PEt(3))(2)] (2), [Ni(eta(2)-P(2)Mes(2))(PMe(2)Ph)(2)] (3), [Pd(eta(2)-P(2)Mes(2))(PBu(n)(3))(2)] (4) and [Pd(eta(2)-P(2)Mes(2))(PMe(2)Ph)(2)] (5), respectively, via a redox reaction. The molecular structures of the diphosphene complexes 2-5 are described.     

Zwitterionic stabilization of a reactive cobalt tris-isocyanide monoanion by cation coordination

A break with tradition: The cation, [Ph(3) P?N?PPh(3) ](+) ([PPN](+) ), was found to provide a stabilizing η(2) -arene interaction to the coordinatively unsaturated, tris-isocyanide monoanion, [Co(CNAr(Mes2) )(3) ](-) (Ar(Mes2) =2,6-(2,4,6-Me(3) C(6) H(2) )C(6) H(3) ); Co=purple, N=light purple, and P=orange). The resulting zwitterion is a source of [Co(CNAr(Mes2) )(3) ](-) anions, performing nucleophilic additions, carbon-element bond activations, and multistep decarbonylations.     

Isolation, characterization, and theoretical study of La2@C78

A new metallofullerene, La2@C78, has been synthesized by DC arc discharge method, isolated by high-performance liquid chromatography, and characterized by laser desorption time-of-flight mass spectrometry, UV-vis-NIR absorption, differential pulse voltammetry, 13C NMR spectroscopy, and theoretical calculations. The La2@C78/CS2 solution is dark violet and presents several characteristic absorption features at 647, 561, 533, and 386 nm, with an onset around 1000 nm. With respect to empty D3-C78, the capability of La2@C78 as an electron acceptor or donor is stronger. Addition of 1,1,2,2-tetrakis(2,4,6-trimethylphenyl)-1,2-disirane to La2@C78 photochemically, as well as thermally, affords bis- and mono-adducts. Theoretical studies and 13C NMR spectroscopic analysis of La2@C78 indicate that it possesses a D3h-C78 cage (78:5).     

Synthesis and charge-transfer chemistry of La2@I(h)-C80/Sc3N@I(h)-C80-zinc porphyrin conjugates: impact of endohedral cluster

Two stable electron donor-acceptor conjugates, that is, 3 and 5b, employing La(2)@I(h)-C(80) and Sc(3)N@I(h)-C(80), on one hand, and zinc tetraphenylporphyrin, on the other hand, have been prepared via [1+2] cycloaddition reactions of a diazo precursor. Combined studies of crystallography and NMR suggest a common (6,6)-open addition pattern of 3 and 5b. Still, subtly different conformations, that is, a restricted and a comparatively more flexible topography, emerge for 3 and 5b, respectively. In line with this aforementioned difference are the electrochemical assays, which imply appreciably stronger I(h)-C(80)/ZnP interactions in 3 when compared to those in 5b. Density functional calculations reveal significant attractions between the two entities of these conjugates, as well as their separately localized HOMOs and LUMOs. The geometrical conformations and LUMO distributions of 3 and 5b, at our applied computational level, are slightly varied with their different endohedral clusters. The clusters also exert different impact on the excited state reactivity of the conjugates. For example, 3 undergoes, upon photoexcitation, a fast charge separation process and yields a radical ion pair, whose nature, namely, (La(2)@C(80))(?-)-(ZnP)(?+)) versus (La(2)@C(80))(?+)-(ZnP)(?-)), varies with solvent polarity. 5b, on the other hand, afforded the same (Sc(3)N@C(80))(?-)-(ZnP)(?+)) radical ion pair regardless of the solvent.     

A digermyne with a Ge-Ge single bond that activates dihydrogen in the solid state

The reduction of the bulky amido-germanium(II) chloride complex, LGeCl (L = N(SiMe(3))(Ar*); Ar* = C(6)H(2)Me{C(H)Ph(2)}(2)-4,2,6), with the magnesium(I) dimer, [{((Mes)Nacnac)Mg}(2)] ((Mes)Nacnac = [(MesNCMe)(2)CH](-); Mes = mesityl), afforded LGeGeL, which represents the first example of a digermyne with a Ge-Ge single bond. Computational studies of the compound have highlighted significant electronic differences between it and multiply bonded digermynes. LGeGeL was shown to cleanly activate H(2) in solution or the solid state, at temperatures as low as -10 °C, to give the mixed valence compound, LGeGe(H)(2)L.