Balancing Adduct Formation and Ligand Coupling with the Bulky Allyl Complexes [1,3-(SiMe₃)₂C₃H₃]₂M (M = Fe, Co, Ni)

Passage of CO at atmospheric pressure through solutions of A′₂M (M = Fe, Co, Ni; A′ = [1,3-(SiMe₃)₂C₃H₃]⁻) in hexanes produces the corresponding allyl complexes A′₂Fe­(CO)₂, A′Co­(CO)₃, and A′₂Ni­(CO), respectively. Although the iron and nickel species can be isolated as pure liquids, the cobalt complex is accompanied by the coupling product 1,3,4,6-tetrakis­(trimethylsilyl)-1,5-hexadiene. A′Co­(CO)₃ was independently prepared from the reaction of Co₂(CO)₈, A′Br, and PhCH₂N­(C₂H₅)₃⁺Cl^– in aqueous base. The IR stretching frequencies of A′₂Fe­(CO)₂ and A′Co­(CO)₃ are lower than those in the unsubstituted analogues, indicating that the trimethylsilated allyl ligand is a better electron donor than the parent version. Density functional theory calculations were performed on various conformations of the complexes, which reproduced the frequency-lowering effect of the trimethylsilyl groups. They also indicate that the thermodynamics of the formation of A′₂Ni­(CO) and the unknown (C₃H₅)₂Ni­(CO) are similar, suggesting that the thermal stability of the former is of kinetic origin. Oxidative coupling of the allyl ligands in A′₂Fe and A′₂Co is induced with I₂; this is different from the case with A′₂Ni, which has previously been shown to produce the mixed allyl halide complex [A′Ni­(μ-I)₂]₂

Smoking prevalence and trends among a U.S. national sample of women of reproductive age in rural versus urban settings.

U.S. smoking prevalence is declining at a slower rate in rural than urban settings and contributing to regional health disparities. Cigarette smoking among women of reproductive age is particularly concerning due to the potential for serious maternal and infant adverse health effects should a smoker become pregnant. The aim of the present study was to examine whether this rural-urban disparity impacts women of reproductive age (ages 15-44) including pregnant women. Data came from the ten most recent years of the U.S. National Survey on Drug Use and Health (2007-2016). We estimated prevalence of current smoking and nicotine dependence among women categorized by rural-urban residence, pregnancy status, and trends using chi-square testing and multivariable modeling while adjusting for common risk factors for smoking. Despite overall decreasing trends in smoking prevalence, prevalence was higher among rural than urban women of reproductive age overall (χ2(1) = 579.33, p < .0001) and among non-pregnant (χ2(1) = 578.0, p < .0001) and pregnant (χ2(1) = 79.69, p < .0001) women examined separately. An interaction between residence and pregnancy status showed adjusted odds of smoking among urban pregnant compared to non-pregnant women (AOR = .58, [.53 -.63]) were lower than those among rural pregnant compared to non-pregnant women (AOR = 0.75, [.62 -.92]), consistent with greater pregnancy-related smoking cessation among urban pregnant women. Prevalence of nicotine dependence was also higher in rural than urban smokers overall (χ2(2) = 790.42, p < .0001) and among non-pregnant (χ2(2) = 790.58, p < .0001) and pregnant women examined separately (χ2(2) = 63.69, p < .0001), with no significant changes over time. Associations involving residence and pregnancy status remained significant in models adjusting for covariates (ps < 0.05). Results document greater prevalence of smoking and nicotine dependence and suggest less pregnancy-related quitting among rural compared to urban women, disparities that have potential for direct, multi-generational adverse health impacts