Ligand dependence of binding to three-coordinate Fe(II) complexes.

A series of three- and four-coordinate iron(II) complexes with nitrogen, chlorine, oxygen, and sulfur ligands is presented. The electronic variation is explored by measuring the association constant of the neutral ligands and the reduction potential of the iron(II) complexes. Varying the neutral ligand gives large changes in K(eq), which decrease in the order CN(t)Bu > pyridine >2-picoline > DMF > MeCN > THF > PPh(3).

Quantitative geometric descriptions of the belt iron atoms of the iron-molybdenum cofactor of nitrogenase and synthetic iron(II) model complexes.

Six of the seven iron atoms in the iron-molybdenum cofactor of nitrogenase display an unusual geometry, which is distorted from the tetrahedral geometry that is most common in iron-sulfur clusters. This distortion pulls the iron along one C3 axis of the tetrahedron toward a trigonal pyramid. The trigonal pyramidal coordination geometry is rare in four-coordinate transition metal complexes.

Macrocyclic Binucleating β-Diketiminate Ligands and their Lithium, Aluminum, and Zinc Complexes.

The incorporation of rigid aromatic linkers into β-diketiminate ligands creates a binucleating scaffold that holds two metals near each other. This paper discloses the synthesis, characterization, and reactivity of mBin(2-), which has a meta-substituted xylylene spacer, and pBin(2-), which has a para-substituted xylylene spacer. Lithium, aluminum, and zinc complexes of each ligand are isolated, and in some cases are characterized by X-ray crystallography.

Studies of low-coordinate iron dinitrogen complexes.

Understanding the interaction of N2 with iron is relevant to the iron catalyst used in the Haber process and to possible roles of the FeMoco active site of nitrogenase. The work reported here uses synthetic compounds to evaluate the extent of NN weakening in low-coordinate iron complexes with an FeNNFe core. The steric effects, oxidation level, presence of alkali metals, and coordination number of the iron atoms are varied, to gain insight into the factors that weaken the NN bond.

Synthesis and reactivity of low-coordinate iron(II) fluoride complexes and their use in the catalytic hydrodefluorination of fluorocarbons.

Transition metal fluoride complexes are of interest because they are potentially useful in a multitude of catalytic applications, including C-F bond activation and fluorocarbon functionalization. We report the first crystallographically characterized examples of molecular iron(II) fluorides: [L(Me)Fe(mu-F)]2 (1(2)) and L(tBu)FeF (2) (L = bulky beta-diketiminate). These complexes react with donor molecules (L'), yielding trigonal-pyramidal complexes L(R)FeF(L').

Facile synthesis, structure, and luminescence properties of Pt(diimine)bis(arylacetylide) chromophore-donor dyads.

The luminescent complex Pt(dpphen)bis(arylacetylide) complex (1) (dpphen = 4,7-diphenylphenanthroline and arylacetylide = 4-ethynylbenzaldehyde) has been synthesized and characterized structurally and spectroscopically. Complex 1 has been employed in the synthesis of donor-chromophore (D-C) dyads through Schiff base condensations of different anilines to give imine-linked dyads 2-4 and through imine reduction with borohydride, to give the corresponding amine-linked dyads 2a-4a. Crystal structure determinations of 1-4 and 4a establish a distorted square-planar geometry around the Pt(II) ion in each system with cis arylacetylide ligands and a diimine-constrained N-Pt-N bond angle of ca.

Low-coordinate iron(II) amido complexes of beta-diketiminates: synthesis, structure, and reactivity.

The synthesis, structure, and reactivity of a series of low-coordinate Fe(II) diketiminate amido complexes are presented. Complexes L(R)FeNHAr (R = methyl, tert-butyl; Ar = para-tolyl, 2,6-xylyl, and 2,6-diisopropylphenyl) bind Lewis bases to give trigonal pyramidal and trigonal bipyramidal adducts. In the adducts, crystallographic and (1)H NMR evidence supports the existence of agostic interactions in solid and solution states.

N=N bond cleavage by a low-coordinate ironII hydride complex.

Reaction of the three-coordinate complex LFeCl (L = bulky beta-diketiminate) with KBEt3H gives a dark red iron(II) hydride complex. The complex is a dimer in the solid state, but spectroscopy and kinetics suggest that an orange three-coordinate monomer is in equilibrium with the dimer in solution. The double bond of azobenzene is completely cleaved by heating with the hydride complex, and a hydrazido intermediate can be isolated.

Synthesis and characterization of platinum diimine bis(acetylide) complexes containing easily derivatizable aryl acetylide ligands.

New Pt(II) diimine bis(acetylide) complexes where the diimine is a substituted bipyridine or phenanthroline and the arylacetylide is 4-ethynylbenzaldehyde have been prepared in good to excellent yields. Spectroscopic characterization supports a square planar coordination geometry with cis-alkynyl ligands, and the crystal structure of one of the complexes, Pt(phen)(Ctbd1;CC(6)H(4)CHO)(2) (1), confirms the assignment. The new diimine bis(acetylide) complexes exhibit an absorption band ca.

Nickel complexes of a bulky beta-diketiminate ligand.

Nickel(II) chloride forms a complex with tetrahydrofuran, NiCl(2)(THF)(1.5), that can be used to prepare nickel chloride complexes of a bulky beta-diketiminate ligand L(Me). [L(Me)NiCl](2) and L(Me)NiCl(2)LiTHF(2), which have tetrahedral geometries in the solid state, are in equilibrium with three-coordinate L(Me)NiCl.

Alkyl isomerisation in three-coordinate iron(II) complexes.

The tertiary to iso-butyl isomerisation of three-coordinate iron(II) diketiminate complexes is reported and a hydride intermediate is proposed on the basis of exchange experiments.

Electronically unsaturated three-coordinate chloride and methyl complexes of iron, cobalt, and nickel.

Three-coordinate organometallic complexes are rare, especially with the prototypical methyl ligand. Using a hindered, rigid bidentate ligand (L), it is possible to create 12-electron methyliron(II) and 13-electron methylcobalt(II) complexes. These complexes are thermally stable, and (1)H NMR spectra suggest that the low coordination number is maintained in solution.

Multiple emissions and brilliant white luminescence from gold(I) O,O'-di(alkyl)dithiophosphate dimers.

The Au(I) dimers Au(2)[S(2)P(OR)(2)](2) for R = Me, Et are found to exhibit a structure in which aurophilic interactions yield one-dimensional Au...

A new tantalum dinitrogen complex and a parahydrogen-induced polarization study of its reaction with hydrogen.

Reduction of Cp*(2)TaCl(2) with sodium amalgam in THF under a nitrogen atmosphere results in the formation of the novel complex (Cp*(2)TaCl)(2)(micro-N(2)). This dinuclear complex containing a micro-eta(1):eta(1) dinitrogen bridge has been characterized by NMR and X-ray crystallography. The complex possesses a C(2)-symmetric structure with each Ta bound to diastereotopic Cp* rings and chloride in addition to the micro-N(2) bridge.

Rapid synthesis of the 7-deoxy zaragozic acid core.

[reaction: see text] We have developed an efficient synthesis of the 7-deoxy zaragozic acid core. The synthesis begins with a Feist-Bénary reaction that assembles all three carbons of the polycarboxylic acid portion of the core. This reaction is followed by highly diastereoselective aldol and dihydroxylation reactions that set the remaining stereocenters of the core.

Syntheses, Molecular Structures, and Spectroscopy of Gold(III) Dithiolate Complexes.

Two Au(III) dithiolate complexes, [Au(dbbpy)(tdt)]PF(6) and Au(eta(2)-C,N-ppy)(tdt), (dbbpy = 4,4'-di-tert-butyl-2,2'-bipyridine; tdt = 3,4-toluenedithiolate; ppy = C-deprotonated 2-phenylpyridine), have been prepared and structurally characterized by X-ray crystallography. The complexes have low-energy absorption bands that exhibit mild solvatochromism (lambda(max) = 444 nm (epsilon, 2310 M(-)(1) cm(-)(1)) in CH(2)Cl(2) and 406 nm (epsilon, 3170 M(-)(1) cm(-)(1)) in DMSO) and are tentatively assigned to a charge-transfer-to-diimine transition. This transition occurs at higher energy than the analogous charge-transfer transition in related Pt(II) complexes (e.

Multiiron Polyoxoanions. Synthesis, Characterization, X-ray Crystal Structure, and Catalytic H(2)O(2)-Based Alkene Oxidation by [(n-C(4)H(9))(4)N](6)[Fe(III)(4)(H(2)O)(2)(PW(9)O(34))(2)].

A tetranuclear ferric Keggin sandwich-type heteropolyanion has been synthesized by the reaction of the lacunary species Delta-Na(8)H[PW(9)O(34)] with FeCl(2) followed by O(2) oxidation in nonaqueous media. The structure of [(n-C(4)H(9))(4)N](6)[Fe(III)(4)(H(2)O)(2)(PW(9)O(34))(2)].4CH(3)CN.