RESUMO
Adducts of bismuth trihalides BiX3 (X = Cl, Br, I) and the PS3 ligand (PS3 = P(C6H4-o-CH2SCH3)3) react with HCl to form inorganic/organic hybrids with the general formula [HPS3BiX4]2. On the basis of their solid-state structures determined by single-crystal X-ray diffraction, these compounds exhibit discrete bis-zwitterionic assemblies consisting of two phosphonium units [HPS3]+ linked to a central dibismuthate core [Bi2X8]2- via SâBi dative interactions. Remarkably, the phosphorus center of the PS3 ligand undergoes protonation with hydrochloric acid. This is in stark contrast to the protonation of phosphines commonly observed with hydrogen halides resulting in equilibrium. To understand the important factors in this protonation reaction, 31P NMR experiments and DFT computations have been performed. Furthermore, the dibismuthate linker was utilized to obtain the coordination polymer {[AgPS3BiCl3(OTf)]2(CH3CN)2}∞, in which dicationic [Ag(PS3)]22+ macrocycles containing five-coordinate silver centers connect the dianionic [Bi2Cl6(OTf)2]2- dibismuthate fragments. The bonding situation in these dibismuthates has been investigated by single-crystal X-ray diffraction and DFT calculations (NBO analysis, AIM analysis, charge distribution).
RESUMO
To account for the charge transfer and covalent character in bonding between P and Bi centers, the electronic structures of [P(C6H4-o-CH2SCH3)3BiCln](3-n)+ (n = 0-3) model species have been investigated computationally. On the basis of this survey a synthetic target compound with a dative PâBi bond has been selected. Consecutively, the highly reactive bismuth cage [P(C6H4-o-CH2SCH3)3Bi]3+ has been accessed experimentally and characterized. Importantly, our experiments (single-crystal X-ray diffraction and solid-state NMR spectroscopy) and computations (NBO and AIM analysis) reveal that the P···Bi bonding in this trication can be described as a dative bond. Here we have shown that our accordion-like molecular framework allows for tuning of the interaction between P and Bi centers.
RESUMO
To study pnictogen bonding involving bismuth, flexible accordion-like molecular complexes of the composition [P(C6 H4 -o-CH2 SCH3 )3 BiX3 ], (X=Cl, Br, I) have been synthesised and characterised. The strength of the weak and mainly electrostatic interaction between the Bi and P centres strongly depends on the character of the halogen substituent on bismuth, which is confirmed by single-crystal X-ray diffraction analyses, DFT and ab initio computations. Significantly, 209 Bi-31 P through-space coupling (J=2560â Hz) is observed in solid-state 31 Pâ NMR spectra, which is so far unprecedented in the literature, delivering direct information on the magnitude of this pnictogen interaction.
RESUMO
The scientific study of teamwork in the context of spaceflight has uncovered a considerable amount of knowledge over the past 20 years. Although much is known about the underlying factors and processes of teamwork, much is left to be discovered for teams who will be operating in extreme isolation and confinement during a future Mars mission. Special considerations must be made to enhance teamwork and team well-being for multi-year missions during which the small team will live and work together. We discuss the unique challenges of effective teamwork in a Mars mission scenario, and the difficulties of studying teamwork using analogs of the space environment. We then describe the National Aeronautics and Space Administration's current practices and research on teamwork, which includes team selection and composition, teamwork training, countermeasures to mitigate risks to effective team performance, and the measurement and monitoring of team functioning. We end with a discussion of the teamwork research areas that are most critical for a successful journey to Mars. (PsycINFO Database Record
