Metal-ligand bond enthalpy data can afford invaluable insights into important reaction patterns in organometallic chemistry and catalysis. In this paper, the Fe-O and Fe-S homolytic bond dissociation energies [ΔH homo (Fe-O)'s and ΔH homo (Fe-S)'s] of two series of para-substituted phenoxydicarbonyl(h 5 -cyclopentadienyl) iron [p-G-C 6 H 4 OFp (1)] and (para-substituted benzenethiolato)dicarbonyl(h 5 -cyclopentadienyl) iron [p-G-C 6 H 4 SFp (2)] were studied using Hartree-Fock and density functional theory (DFT) methods with large basis sets. In this study, Fp is (h 5 -C 5 H 5 )Fe(CO) 2 , and G are NO 2 , CN, COMe, CO 2 Me, CF 3 , Br, Cl, F, H, Me, MeO, and NMe 2 . The results show that DFT methods can provide the best price/performance ratio and accurate predictions of ΔH homo (Fe-O)'s and ΔH homo (Fe-S)'s. The remote substituent effects on ΔH homo (Fe-O)'s and ΔH homo (Fe-S)'s [ΔΔH homo (Fe-O)'s and ΔΔH homo (Fe-S)'s] can also be satisfactorily predicted. The good correlations [r = 0.98 (g, 1), 0.98 (g, 2)] of ΔΔH homo (Fe-O)'s and ΔΔH homo (Fe-S)'s in series 1 and 2 with the substituent s p + constants imply that the para-substituent effects on ΔH homo (Fe-O)'s and ΔH homo (Fe-S)'s originate mainly from polar effects, but those on radical stability originate from both spin delocalization and polar effects. ΔΔH homo (Fe-O)'s (1) and ΔΔH homo (Fe-S)'s (2) conform to the captodative principle. Insight from this work may help the design of more effective catalytic processes.

Fagaceae is one of the largest and economically important taxa within Fagales. Considering the incongruence among inferences from plastid and nuclear genes in the previous Fagaceae phylogeny studies, we assess the performance of plastid phylogenomics in this complex family. We sequenced and assembled four complete plastid genomes (Fagus engleriana, Quercus spinosa, Quercus aquifolioides, and Quercus glauca) using reference-guided assembly approach. All of the other 12 published plastid genomes in Fagaceae were retrieved for genomic analyses (including repeats, sequence divergence and codon usage) and phylogenetic inference. The genomic analyses reveal that plastid genomes in Fagaceae are conserved. Comparing the phylogenetic relationships of the key genera in Fagaceae inferred from different codon positions and gene function datasets, we found that the first two codon sites dataset recovered nearly all relationships and received high support. Thus, the result suggested that codon composition bias had great influence on Fagaceae phylogenetic inference. Our study not only provides basic understanding of Fagaceae plastid genomes, but also illuminates the effectiveness of plastid phylogenomics in resolving relationships of this intractable family.

Fagopyrum dibotrys, belongs to Polygonaceae family, is one of national key conserved wild plants of China with important medicinal and economic values. Here, the complete chloroplast (cp) genome sequence of F. dibotrys is reported. The cp genome size is 159,919 bp with a typical quadripartite structure and consisting of a pair of inverted repeat regions (30,738 bp) separated by large single copy region (85,134 bp) and small single copy region (13,309 bp). Sequencing analyses indicated that the cp genome encodes 131 genes, including 80 protein-coding genes, 28 tRNA genes and 4 rRNA genes. The genome structure, gene order and codon usage are typical of angiosperm cp genomes. We also identified 48 simple sequence repeats (SSR) loci, fewer of them are distributed in the protein-coding sequences compared to the noncoding regions. Comparison of F. dibotrys cp genome to other Polygonaceae cp genomes indicated the inverted repeats (IRs) and coding regions were more conserved than single copy and noncoding regions, and several variation hotspots were detected. Coding gene sequence divergence analyses indicated that five genes (ndhK, petL rpoC2, ycf1, ycf2) were subject to positive selection. Phylogenetic analysis among 42 species based on cp genomes and 50 protein-coding genes indicated a close relationship between F. dibotrys and F. tataricum. In summary, the complete cp genome sequence of F. dibotrys reported in this study will provide useful plastid genomic resources for population genetics and pave the way for resolving phylogenetic relationships of order Caryophyllales.

The knowledge of accurate bond strengths is a fundamental basis for a proper analysis of chemical reaction mechanisms. Quantum chemical calculations at different levels of theory have been used to investigate heterolytic Fe–O and Fe–S bond energies of para‐substituted phenoxydicarbonyl(η5‐cyclopentadienyl) iron [p‐G‐C6H4O(η5‐C5H5)Fe(CO)2, abbreviated as p‐G‐C6H4OFp (1), where G = NO2, CN, COMe, CO2Me, CF3, Br, Cl, F, H, Me, MeO, and NMe2] and para‐substituted benzenethiolatodicarbonyl(η5‐cyclopentadienyl) iron [p‐G‐C6H4S(η5‐C5H5)Fe(CO)2, abbreviated as p‐G‐C6H4SFp (2)] complexes. The results show that BP86 and TPSSTPSS can provide the best price/performance ratio and more accurate predictions in the study of ΔHhet(Fe–O)'s and ΔHhet(Fe–S)'s. The excellent linear free‐energy relations [r = 0.99 (g, 1a), 1.00 (g, 2b)] among the ΔΔHhet (Fe–O)'s and Δpka's of O–H bonds of p‐G‐C6H4OH or ΔΔHhet(Fe‐S)'s and Δpka's of S–H bonds of p‐G‐C6H4SH imply that the governing structural factors for these bond scissions are similar. And the linear correlations [r = −0.99 (g, 1g), −0.98 (g, 2h)] among the ΔΔHhet (Fe‐O)'s or ΔΔHhet(Fe‐S)'s and the substituent σp− constants show that these correlations are in accordance with Hammett linear free‐energy relationships. The polar effects of these substituents and the basis set effects influence the accuracy of ΔHhet(Fe–O)'s or ΔHhet(Fe–S)'s. ΔΔHhet(Fe–O)'s(g) (1) and ΔΔHhet(Fe–S)'s(g)(2) follow the Capto‐dative principle. The substituent effects on the Fe–O bonds are much stronger than those on the less polar Fe–S bonds. Insight from this work may help the design of more effective catalytic processes. Copyright © 2013 John Wiley & Sons, Ltd.