John E. Sheats

Stabilization of negative charge by the cobalticinium nucleus

Abstract The acidity of alkylcobalticinium salts is greatly enhanced and the basicity of aminocobalticinium salts is greatly reduced in comparison to alkyl- and amine-benzenes and -ferrocenes. The methyl hydrogens of 1,1′-dimethylcobalticinium ion exchange in 0.91 M NaOD in D20 with a rate constant of 1.40 x 10−2 min−1 at 70°C and an activation energy of 25.4 ± 1 kcal mol−1. The pKa of benzhydrylcobalticinium ion is 15–16 at 25°C, approximately 1011 times more acidic than triphenylmethane. The following basicities (PKb) were observed: aminocobalticinium, 15.6 ± 0.1, 1,1′-diaminocobalticinium, 13.5 ± 0.1 and 18.1 ± 0.1, 1-amino-1′-carboxycobalticinium, 18.06 ± 0.05. These values are interpreted in terms of strong electron-withdrawing field, inductive and resonance effects exerted by the cobalticinium moiety.

The preparation, polymerization and copolymerization of (η5-vinylcyclopentadienyl)dicarbonylnitrosylchromium, (η5-C5H4CHCH2)Cr(CO)2NO

Abstract The first report on the preparation, polymerization, and copolymerization of a nitrosyl-containing vinylcyclopentadienylmetal monomer, (η5-C5H4CHCH2)-Cr(CO)2NO, is described. (η5-Vinylcyclopentadienyl)-dicarbonylnitrosylchromium (A) was prepared in good yield by the acylation of η5-cyclopentadienyl-carbonylnitrosylchromium followed by sodium borohydride reduction of the keto function and acid-catalyzed dehydration. Monomer A homopolymerizes and copolymerizes with styrene, N-vinylpyrrolidone, and vinyl cymantrene in the presence of azo initiators. Reactivity ratios in the copolymerization of A with styrene were r1 = 0.30 and r2 = 0.82 from which the value of e for A was found to be −1.98. Thus, A is an exceptionally electron-rich monomer.

Stabilization of negative charge by the cobalticinium nucleus : II. Acidity of hydroxy-2,3,4,5-tetraaryl and hydroxy-2,3,4,5-tetraalkyl cobalticinium and rhodicinium salts☆

Abstract Hydroxy-2,3,4,5-tetra-substituted cobalticinium and rhodicinium salts exist in proteolytic equilibrium with stable cyclopentadienone complexes. The changes in IR, UV and NMR spectra upon dissociation are described. Acidity constants, K a , have been determined spectrophotometrically for the following hydroxymetallocinium salts, C 5 R 4 OH M + C 5 H 5 : R = CH 3 , M = Co, 4.30 ± 0.07; R = C 6 H 5 , M = Co, 2.42 ± 0.05; R = C 6 F 5 , M = Co, −0.60 ± 0.10; R = C 6 H 5 , M = Rh, 2.54 ± 0.03; R = C 6 F 5 , M = Rh, −0.41 ± 0.10. The acidity increases with increasing electronegativity of the R group and decreases slightly when Co III is replaced by Rh III . The lower acidity of the Rh compounds reflects a slightly lower electronegativity of Rh as compared to Co.

Synthesis and Characterization of Antimony (V)-Polycobalticinium Esters

Abstract Antimony (V) polycobalticinium esters, where the anion was PF6 −, Cl−, Br− and NO3 −, were synthesized. A number of factors were found to be important in the synthesis, including anion exchange and pH. The products containing PF6 − are oligomeric (DP w = 7) whereas the other products are di-and trimeric. The products undergo oxidative degradation beginning about 100 to 225°C. They are near semiconductors with resistivities about 105 to 107 ohm-cm.

Stabilization of negative charge by the cobalticinium nucleus : III. The effect of substituents on the acidities of hydroxy-cobalticinium and -rhodicinium salts☆

The acidity constant, Ka, has been determined spectrophotometrically for 13 substituted hydroxycobalticinium and hydroxyrhodicinium salts. The acidity is increased with increasing electronegativity of the substituent but is decreased with rhodium(III) replacing cobalt(III) or with the addition of five methyl groups on the second cyclopentadienyl ring. An attempt has been made to relate acidities to Hammetts substituent constants. The pKa of the unsubstituted hydroxycobalticinium ion is estimated to be 3.38 ± 0.08. The pKas of 10 hydroxycobalticinium salts show a linear correlation with v(CO) of the deprotonated cyclopentadienone analogues. Values of pKa1 and pKa2 of cyclopentadienyl(tetraethyl-p-hydroquinone)cobalt have been found to be −2.42 ± 0.10 and 1.15 ± 0.06.

Synthesis and properties of substituted rhodicinium salts

Abstract Rhodicinium salts with the following substituents; H, CH3, 1,1′-(CH3)2, CO2H, 1,1′-(CO2H)2, 1,1′-(COCl)2, 1,1′-(CO2CH3)2 and 1,1′-(NH2)2 have been prepared as their hexafluorophosphate salts by the procedure previously employed for synthesis of the corresponding cobalticinium salts. The rhodicinium salts are paler in color but similar in stability and physical and chemical properties to the corresponding cobalticinium salts. IR, UV and 1H and 13C NMR spectra of the rhodicinium salts and their cobalticinium and ferrocene analogs are discussed. The basicity of 1,1′-diaminorhodicinium in aqueous acid, pk1 = 13.36 ± 0.06, pk2 = 17.04 ± 0.06, was determined spectrophotometrically. The values for the corresponding 1,1′-diaminocobalticinium salt are pk1 = 13.5 ± 0.1 and pk2 = 18.1 ± 0.1. The slightly greater basicity of the 1,1′-diaminorhodicinium is attributed to the greater separation of the cyclopentadienyl rings which moves the amino groups farther from the positively charged metal atom and from each other.

The stability and electronic structure of diphenylcobalticiniummethyl carbonium ion

Abstract The cobalticinium group, because of its strongly electron-withdrawing inductive, field and resonance effects greatly decreases the stability of a carbonium ion in the α-position of a side chain. The stability constant of C5H5Co+C5H4(C6H5)2C+, (I) has been determined spectrophotometrically in 80–96% sulfuric acid: pKR−15.3 ± 0.3. The relative stabilities for R(C6H5)2C+ are: cobalticinium, 1; H, 102; phenyl, 5 × 108; ferrocenyl 1016. Compound I, however, shows a lower sensitivity to changes in solvent acidity than would be predicted by the HR scale. Proton and 13C NMR spectra of I in ClSO3H/D2SO4 indicate delocalization of the positive charge onto the phenyl groups comparable to that of (C6H5)2CH+ and C6H5)3C+ and delocalization to a much lesser extent onto the cobalticinium group.

Production of Organometallic Polymers by the Interfacial Technique. XXXII. Reaction Variables in the Synthesis of Oligomeric Tin Poly(cobalticinium Esters) and Thermal Properties of the Products

Abstract The synthesis of oligomeric tin poly(cobalticinium esters) is presented as a function of the particular reaction variables stirring rate, pH and amount of added base, mole ratio of reactants, concentration of reactants, and volume of organic phase. Factors which decrease the solubility of the stannane apparently act to increase the yield of polyester. The thermal characterization of I was carried out via DSC and TGA. The products generally exhibit endotherms below 150 to 200[ddot]C which may be related to Tg. Above 200[ddot]C, degradation occurs in air by an oxidative mode.

History of Organometallic Polymers

Abstract In the last 20 years a wide variety of new types of polymers has been prepared containing metals as an integral part of the polymer backbone. This paper summarizes deveopments in the following major areas: vinylic polymers, including vinyl metal-locene derivatives and vinylic tin monomers; condensation polymers; polyorganophosphazenes; coordination polymers; mixed valence polymers with electrical conductivity such as (SN)x, polyacetylene and polyphenylene; stacked polymers such as platinum blue, polyphthalocyanines, and TTF-TCNQ. The methods of synthesis and potential applications of these materials in areas such as catalysis, elastomers with low and high temperature stability, metallic conductors, semiconductors, bacteriacides, fungicides, and cancer chemotherapeutic agents are discussed.

Synthesis of Organometallic Polymers for Inertial Fusion Applications

Nuclear fusion, the energy process operating in the sun, offers promise of production of almost unlimited energy without the toxic and radioactive wastes associated with nuclear fission. Harnessing nuclear fusion, however, has proven to be a challenging task that may not be completed for another thirty years. Because of the strong repulsive forces to be overcome in order for nuclei to fuse, the process will take place only at temperatures above 50,000,000°. No known materials can contain matter at this temperature. Thus the fusion reaction must be confined without its touching the walls of its container. Two approaches have been taken — Magnetic Confinement, which is currently being investigated at the Forrestal Laboratories in Princeton, and Inertial Confinement2 which is being investigated at KMS Fusion, Inc. in Ann Arbor, Michigan, at the University of Rochester, at the National Laboratories at Los Alamos, New Mexico, and Livermore, California and elsewhere.