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CM4212 – Main Group
CM4212 – TM OM
Main Group OM
1. Which reaction utilizes organoboron species?
2. What is the bond order of M-H-M bridges?
3. Bridged complexes form due to ...
both electronic and steric reasons.
change in concentration.
Bridges only form, when the complex fragments are electronically unsaturated. Electronically saturated complexes do not dimerize, etc. even if their ligands are small.
4. Which reaction utilizes Grignard\'s reagent?
5. What is the bond order of M-Br-M bridges?
6. Aggregation of organolithium compounds occurs preferably in ...
Non-polar, protic solvents
Polar, protic solvents
Polar, non-protic solvents
Non-polar, non-protic solvents
Protic solvents decompose organolithium species (acid-base reaction), and polar solvents tend to break higher aggregates apart through coordination to the electron-deficient Li-centers.
7. Main group organyls react primarily as ...
They are essentially "stabilized" carbanions which due to the negative charge react as strong nucleophiles or bases.
8. Which of the statements is true?
Hydrido bridges are favored over alkyl bridges due to electronic reasons.
Hydrido bridges are favored over alkyl bridges due to steric reasons.
Alkyl bridges are favored over hydrido bridges due to electronic reasons.
Alkyl bridges are favored over hydrido bridges due to steric reasons.
Alkyl- and hydrido-bridges are both electron-deficient (3c-2e). They only differ in their sterics, and bridges with smaller ligands (hydrido) are preferred.
9. Homoleptic carbonyl complexes exhibit only one CO band.
The number of carbonyl bands depends on the number of unique carbonyl ligands, which in turn is influenced by geometry and symmetry.
10. Carbonyl complexes are favorably formed with low valent metal centers.
Carbonyl ligands are good pi-acceptors. Low valent metal centers provide sufficient electron density for favorable pi-backbonding to bound carbonyl ligands.
11. Which reaction utilizes organozinc species?
12. Which ligands form the most stable bridges between metals?
Alkyl and hydrido bridges are electron-deficient, while alkoxido bridges are sterically less favorable.
13. Which are the most reactive main-group organyls?
Organolithium compounds are the most reactive in this series, because they have the highest bond polarity (most ionic bond-character).
14. Many main-group organyls are ...
Many main-group organyls are very strong bases which exothermically react with water (moisture sensitive). The heat released can ignite them (pyrophoric) and/or the organic solvent they are stored in.
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