Mary L. Good

A Mössbauer study of automotive emission control catalysts

Abstract Mossbauer data have been obtained for a series of barium oxide stabilized ruthenium automotive emission control catalysts. The data indicate that the chemical form of the ruthenium in the stabilized catalysts is a mixture of RuO 2 and BaRuO 3 . All of the ruthenium is reduced to the metallic state in the presence of a reducing gas atmosphere at high temperatures. The catalysts are destabilized as the oxidation-reduction cycle is repeated as indicated in the continually decreasing BaRuO 3 to RuO 2 ratio. Thus the destabilization appears to be caused by a physical separation of the ruthenium metal (metal atom clustering) from the stabilizing BaO phase.

BIOASSAYS AND ENVIRONMENTAL EFFECTS OF ORGANOTIN MARINE ANTIFOULANTS

Coatings containing various organotins as marine antifoulants have been proven to provide effective, long-lived protection of marine vessels and marine installation. Their efficacy as compared to other antifoulants and other antifouling methodologies has been the focus of a number of both fundamental studies and technological investigation. In addition, the relative environmental impact of their widespread use as compared to alternate antifouling procedures has become an urgent question. This paper reports our initial studies of the effects of tributyltin acetate on both invertebrates and vertebrates from a local, south Louisiana estuary. Summary results are: (1) at concentrations of organotin of 0.15 ppm and above, all vertebrates (fishes) died within three hours (most died within twenty minutes of exposure); (2) at an organotin concentration of 0.10 ppm all vertebrates died within twenty-four hours; (3) at an organotin concentration of 0.15 ppm all invertebrates (mollusc) died between five and eight days; (4) all controls remained healthy and active throughout the experiments; and (5) some habitat substrates were found to detoxify organotin solutions by absorbing (or adsorbing) the toxicant.

Syntheses, characterization, and Mossbauer study of Sn(II and Sn(IV) complexes of the cyclopentadienedithiocarboxylate ligand

The preparation and physical characterization of the tetraethylammonium salts of bis(cyclopentadienedithiocarboxylate)stannate(II) and tris(cyclopentadienedithiocarboxylate)stannate(IV) are reported. The coupling constants for the ring protons of the coordinated and uncoordinated ligand indicate that the oxidation state variation of the metal has little effect on the electronic structure of the ligand. The Mossbauer parameters for the Sn(IV) complex (δ = 1.05 ± 0.02 mm/sec with respect to SnO2, Line width = 1.05 mm/sec) are normal for a pseudo-octahedral complex. The values for the Sn(II) complex are somewhat abnormal for a Sn(II) complex (δ = 0.29 mm/sec, Line width = 1.65 mm/sec) and are interpreted as indicative of metalmetal bonding in the molecular structure.

INFRARED AND NUCLEAR MAGNETIC RESONANCE ANALYSIS OF ORGANOTIN TOXICANTS FOR MARINE ANTIFOULING COATINGS

Infrared and nuclear magnetic resonance spectroscopies have been employed to elucidate the chemical and structural properties of triorganotin compounds incorporated into marine antifoulant coating formulations. It is necessary to determine the molecular species of the toxicant in order to be able to predict the mechanism of toxicant release and to design new, more effective coatings. In two conventional vinyl antifoulant coatings, the toxicant was found to react with one component in the coating formulation to yield different triorganotin compounds. A change in the v asym(SnC) vibration was found to correlate with a change in the coordination geometry of tin. These results indicate that infrared spectroscopy is a powerful technique that can provide insights into the chemical processes occurring in the antifouling coatings.

DETERMINATION OF ORGANOTIN STRUCTURES IN ANTIFOULING COATINGS BY MOSSBAUER SPECTROSCOPIC TECHNIQUES

In characterizing the leaching properties of antifouling coatings containing organotin compounds, it has become necessary to determine the structure of the tin species in the coating. An extensive investigation of the Mossbauer parameters of numerous tin compounds of the type R 3 SnX (R = n-butyl, n-propyl, phenyl; X = I, Br, C1, OH, OAc, F) has shown that the quadrupole splitting parameter and ρ (ratio of isomer shift to quadrupole splitting) are related to the molecular geometry. The Mossbauer parameters for organotin polymers used in antifouling coatings and conventional coating formulations containing organotin compounds have been obtained. The quadrupole splitting and ρ value in these cases are sensitive to structural changes which occur in the organotin compounds upon incorporation into these coating matrixes. Mossbauer studies have been performed on the compounds [(C 4 H 9 ) 3 Sn] 2 O, (C 4 H 9 ) 3 SnOAc, (C 4 H 9 ) 3 SnF in various matrices and solvent systems, and the results are discussed in the context of the behavior of these compounds in the coating systems.