Search results for "organometallic"

Co(II) chemistry of 2,6-bis(2-pyridylcarbonyl)pyridine: an icosanuclear Co cluster exhibiting superparamagnetic relaxation.

2006

High-nuclearity transition-metal complexes (clusters) are of special interest in chemistry and physics because, both in terms of size and physical properties, they bridge the gap between the microscopic and macroscopic world, and between quantum and classical systems. In terms of size, the smallest classical nanoparticles fabricated today are the same size as the largest metal clusters that are synthesized by bottom-up methods. In terms of physical properties, certain transition-metal clusters exhibit single-molecule magnetism at low temperatures, that is, they retain their magnetization in zero field in a manner analogous to that of classical macroscopic magnets, but at the same time they …

Synthesis and reactivity of the novel hydride derivative RhHCl(TIMP3) (HTIMP3 = tris[1-(diphenylphosphino)-3-methyl-1H-indol-2-yl]methane)

2009

The reaction of HTIMP(3) (HTIMP(3) = tris[1-(diphenylphosphino)-3-methyl-1H-indol-2-yl]methane) with [RhCl(COD)](2) and Rh(acac)(CO)(2) produces RhHCl(TIMP(3)) (1H) and Rh(TIMP(3))(CO) (2), respectively, both exhibiting tetradentate kappaC,kappa(3)P-coordination of the TIMP(3) moiety. The reaction of RhHCl(TIMP(3)) with nucleophiles (L) in the presence of AgBF(4) or AgPF(6) produces different compounds depending on the nature of L. Indeed, cationic Lewis adducts of formula [RhH(L)(TIMP(3))](+) ((2H+)-(5H+)) are obtained when L is CO, CNCH(2)Ph, pyridine or CH(2)CHCN. On the other hand, when the incoming nucleophile is CH(3)COOH the hydride-free complex [Rh(CH(3)COO)(TIMP(3))](+) ((6+)) is o…

Azine-bridged octanuclear copper(II) complexes assembled with a one-stranded ditopic thiocarbohydrazone ligand.

2005

Easy preparation of Cp*-functionalized N-heterocyclic carbenes and their coordination to rhodium and iridium

2010

A simple high-yielding method for the preparation of a tetramethylcyclopentadienyl-NHC ligand is described. This ligand has been successfully coordinated to Rh and Ir. A related Cp*-NHC ligand with a -CH(2)CMePh- linker between the Cp* and the NHC is also described, together with its coordination to Rh and Ir. This latter ligand, affords the orthocyclometallation of the phenyl ring yielding a constrained structure in which the ligand is tridentate. All the complexes have been fully characterized and their crystal structures are described. Preliminary catalytic results on the beta-alkylation of secondary alcohols and N-alkylation of aniline with primary alcohols are also reported.

Synthesis, structure and magnetic properties of oligometallic systems derived from di- and trinuclear copper(ii) amido-oximate complexes

2008

Three heterometallic complexes [M(H(2)O)(n)][Cu(3)L(2)(H(2)O)] (M = Mn(2+), Co(2+) or Ba(2+)) and one dinuclear compound (CuDien)(CuL{H(2)O}) were prepared by interaction of anionic compounds Cu(3)L(2)(2-) or CuL(2-) with the corresponding cations (H(4)L = 1,9-dicyano-1,9-bis(hydroximino)-3,7-diazanonane-2,8-dione; Dien = 1,5-diamino-3-azapentane). The complexes [M(H(2)O)(n)][Cu(3)L(2)(H(2)O)] have a polymeric structure, formed via oligomerization of Cu(3)L(2)(2-) units and additionally, in the case of the Ba-salt, by binding of Cu(3)L(2)(2-) units through Ba(2+). Antiferromagnetic interactions occur in all the complexes, while for [Co(H(2)O)(6)][Cu(3)L(2)(H(2)O)] there is evidence of some …

Tungsten(VI) complexes with aminobis(phenolato) [O,N,O] donor ligands.

2004

The reaction between trisdiolatotungsten(VI) complex [W(eg)(3)] (1) (eg = 1,2-ethanediolato dianion) and phenolic ligand precursor methylamino-N,N-bis(2-methylene-4,6-dimethylphenol) (H(2)L(Me)) or methylamino-N,N-bis(2-methylene-4-methyl-6-tert-butylphenol) (H(2)L(tBu)) affords monomeric oxotungsten complex [WO(eg)(L(Me))] (2) or [WO(eg)(L(tBu))] (3), respectively. These complexes react further with chlorinating reagents, which leads to the displacement of ethanediolato ligands from the complex units and formation of cis and trans isomers of the corresponding dichloro complexes [WOCl(2)(L(Me))] (4) and [WOCl(2)(L(tBu))] (5), respectively. Identical dichloro complexes were also prepared by …

Single-molecule magnetic behavior in a neutral terbium(III) complex of a picolinate-based nitronyl nitroxide free radical

2011

The terdentate anionic picolinate-based nitronyl nitroxide (picNN) free radical forms neutral and robust homoleptic complexes with rare earth-metal ions. The nonacoordinated Tb3+ complex Tb(picNN)3• 6H2O is a single-molecule magnet with an activation energy barrier Δ = 22.8 ± 0.5 K and preexponential factor τ0 = (5.5 ± 1.1) × 10-9 s. It shows magnetic hysteresis below 1 K. © 2011 American Chemical Society.

Cubane-Type Mo3FeS44+,5+ Complexes Containing Outer Diphosphane Ligands: Ligand Substitution Reactions, Spectroscopic Studies, and Electronic Structu…

2012

A general protocol to access Mo(3)FeS(4)(4+) clusters selectively modified at the Fe coordination site is presented starting from the all-chlorine Mo(3)(FeCl)S(4)(dmpe)(3)Cl(3) (1) [dmpe = 1,2-bis(dimethylphosphane-ethane)] cluster and tetrabutylammonium salts (n-Bu(4)NX) (X = CN(-), N(3)(-), and PhS(-)). Clusters Mo(3)(FeX)S(4)(dmpe)(3)Cl(3) [X = CN(-) (2), N(3)(-) (3), and PhS(-) (4)] are prepared in high yield, and comparison of geometric and redox features upon modification of the coordination environment at the Fe site at parity of ligands at the Mo sites is also presented. The existence of the cubane-type Mo(3)FeS(4)(4+,5+) redox couple is demonstrated by cyclic voltammetry and for co…

Stepwise sequential redox potential modulation possible on a single platform.

2011

Step by step: The cluster [3,3'-Co(1,2-C(2)B(9)H(11))(2)](-) is an excellent platform for making a stepwise tunable redox potential system by dehydroiodination. With the addition of up to eight iodine substituents (purple; see picture), there is a fall in the E(1/2)(Co(III)/Co(II)) value from -1.80 V to -0.68 V (vs. Fc(+)/Fc; Fc = ferrocene). A practical application of this tunability has been observed in the growth of polypyrrole.

Expanding the 2, 2’-bipyrimidine bridged 1D homonuclear coordination polymers family: [MIIbpymCl2] (M=Fe, Co) magnetic and structural characterization

2013

One pot reaction of hydrated chloride salts of Fe(II) and Co(II) with stoichiometric amounts of 2, 2’-bipyrimidine (bpym) in a methanol/ acetonitrile mixture afforded the corresponding 1D homonuclear coordination polymers, [μ-(bpym)MCl2]n. Crystal structures of both complexes are isomorphous in the highly symmetric orthorhombic space group Fddd. The 1D coordination polymers are composed of almost orthogonal alternating bipyrimidine bridges linking the {MCl2} units. The magnetic behaviour of the Fe(II)compound can be well understood as a uniform S=2 chain with antiferromagnetic exchange interaction between metal ion sites. In the case of the Co(II) ion, also an antiferromagnetic interaction …