Richard S. Herrick

ORDERED CONFORMATIONS IN BIS(AMINO ACID) DERIVATIVES OF 1,1'-FERROCENEDICARBOXYLIC ACID

Abstract Two bis(amino acid) derivatives of 1,1′-ferrocenedicarboxylic acid were characterized by IR, 1 H NMR and 13 C NMR spectroscopy. Each was found to adopt an ordered, intramolecularly hydrogen bonded conformation in CHCl 3 .

Preparation and characterization of chromium, molybdenum and tungsten compounds containing amino acid ester derivatized diimine ligands. Crystal structure of Mo(CO)4(pyca-β-ala-OEt)

Abstract The title compounds were prepared by heating solutions of ester-protected amino acids (H-β-Ala-OEt, H- l -Ala-OEt, H- l -Val-OMe, H- l -Asp(OMe)-OMe, GABA-OMe) and pyridine-2-carboxaldehyde in the presence of M(CO)4(pip)2 (M=Mo,W) or [NEt4][Cr(CO)5I]. The resulting novel complexes, M(CO)4(pyca-xxx-OR) (pyca=pyridinecarbaldehyde imine), contain an η2-N,N′-diimine ligand and were characterized by 1H- and 13C-NMR, IR and UV–vis measurements. The lone band in the visible portion of the electronic spectrum is assigned to a MLCT transition and exhibits solvatochromism. The crystal structure of Mo(CO)4(pyca-β-ala-OEt) (1b), was determined and confirms the presence of the bidentate α-diimine ligand. The metal lies in a pseudo Cs symmetry environment.

Flash photolytic investigation of photoinduced carbon monoxide dissociation from dinuclear manganese carbonyl compounds

Etude de la photolyse eclair de Mn 2 (CO) 8 (PR 3 ) 2 avec R=n-Bu, i-Bu, iPr, O-i-Pr, Me ou (PR 3 ) 2 =Ph 2 PCH 2 CH 2 CH 2 PPh 2 . Observation du spectre de Mn 2 (CO) 7 L 2 . Etude cinetique de sa recombinaison avec CO. Effet du ligand L. Mecanisme propose

Synthesis of dimeric ReI amino acid conjugate complexes

The aqueous one-step reaction of Re(CO)(3)(H(2)O)(3)(+) with pyridine-2-carboxyaldehyde and glycine or alanine produces a new class of cyclic dimeric products. The ligands of the chiral C(2)-symmetric products are bound via the diimine at one rhenium centre and via the pendant carboxylate to a second rhenium center.

Reactions of the Re(CO)3(H2O)3+ Synthon with Monodentate Ligands under Aqueous Conditions

The reactions of ammonia, pyridine (py), N-methyl imidazole (N-MeIm), tetrahydrothiophene (tht), and piperidine (pip) with Re(CO) 3(H 2O) 3 (+), 1 ( + ), were investigated employing aqueous conditions under atmospheric dioxygen. The reaction of [ 1]Br in aqueous ammonia led to [Re(CO) 3(NH 3) 3]Br ([ 2]Br) as the only product isolated. For the aqueous reactions of [ 1]Br with py, N-MeIm, and tht, mixtures of products are formed because of competition between the bromide and added ligand, even when the ligand is present in excess. Substitution of the PF 6 (-) anion for Br (-) leads to the clean formation of [Re(CO) 3L 3][PF 6] ([ 3][PF 6]-[ 5][PF 6]) for py, N-MeIm, and tht, respectively, as the only products observed. Reaction of [ 1][PF 6] with pip produces the dimeric species, (pip)(CO) 3Re(micro-OH) 2Re(CO) 3(pip), 6. Reactions of [ 1]Br were also performed in methanol for comparison purposes. The reaction with pip in this solvent led to the analogous dimer, (pip)(CO) 3Re(micro-OMe) 2Re(CO) 3(pip), 7; however, reactions with py, N-MeIm, and tht gave Re(CO) 3L 2Br, 8- 10, respectively, as the only products. The crystal structures of compounds [ 2]Br- 10 are reported.

The synthesis and toxicity of tripodal tricarbonyl rhenium complexes as radiopharmaceutical models.

We report the synthesis and toxicity of a series of rhenium(I) tricarbonyl complexes incorporating the trisaminomethylethane (TAME) ligand. Compounds with the (TAME)Re(CO)(3)(+) cation were synthesized via several routes, including by use of Re(CO)(5)X precursors as well as the aqueous cation Re(CO)(3)(H(2)O)(3)(+). Salts of the formula [(TAME)Re(CO)(3)]X where X=Br(-), Cl(-), NO(3)(-), PF(6)(-) and ClO(4)(-) were evaluated using two cell lines: the monoclonal S3 HeLa line and a vascular smooth muscle cell line harvested from mice. All compounds have isostructural cations and differ only in the identity of the non-coordinating anion. None of the complexes exhibited any appreciable toxicity in the HeLa line up to the solubility limit. In the vascular smooth muscle cell line, the bromide salt exhibited some cytotoxicity, but this observation most likely results from the presence of bromide anion, which has been shown to have limited toxicity.

The synthesis and pH-dependent behaviour of Re(CO)3 conjugates with diimine phenolic ligands

In this report we present a study of a series of Re(CO)3 pyridine-imine complexes with pendant phenol groups. We investigated the effects of the position of the phenol hydroxyl group (para, meta or ortho to the imine) on the steric and electronic characteristics of a series of Re(CO)3X(pyca-C6H4OH) compounds, where X = Cl, Br and pyca = pyridine-2-carbaldehyde imine. These compounds can be generated either via ligand synthesis followed by metal chelation (compound 4) or via a one-pot method (compounds 2, 3, 5 and 6). All six compounds show striking differences in pH-dependent UV-visible absorption based on the position of the phenol hydroxyl group.

KINETIC STUDIES OF LEWIS BASE ADDITION TO CpFe(CO)(η3-CH2C6H4-p-X); X = OMe, Me, H,F, Cl, Br

Abstract Kinetic studies illuminate details of the reaction of photoproduced CpFe(CO)(η3-CH2C6H5) with two electron Lewis bases. Rate constants of 151(10)M−1s−1 for CO back reaction and between 440 and 3200 M−1s−1 for reaction with various phosphine nucleophiles were recorded. Linear free energy analysis quantifies the stereoelectronic effect of the nucleophile. Variation of the para-substituent on the benzyl group demonstrates that an electron rich benzyl group impedes reaction. The effect of ancillary ligands was seen by substitution of C5Me5 for C5H5. The large, electron rich C5Me5 speeds up CO substitution but slows down PPh3 substitution. Mechanistic clues were obtained from Eyring plots for reaction of CpFe(CO)(η3-CH2C6H5) with 4 different phosphines. Examination of the measured enthalpy and entropy barriers suggests a stepwise reaction mechanism.

Re(CO)3‑Templated Formation of Aza(dibenzo)dipyrromethenes

The Re(CO)3 unit was used to template the formation of aza(dibenzopyrro)methene (ADBM) in the presence of pyridine or N-methylimidazole. The products of these template reactions are six-coordinate complexes, with a facial arrangement of the carbonyls, a bidentate ADBM, and a sixth ligand (pyridine or N-methylimiadozle). Three types of ADBM ligands are produced from these reactions, depending on the degree of hydrolysis; bis(imine)-terminated, bis(oxo)-terminated, and mixed-imine/oxo chelates were formed.

Flash Photolysis Studies of Dinuclear Manganese Carbonyl Compounds

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