Low oxidation state s-block species

Question 1

First indications that Ae1+ compounds might be viable

Answer 1

From Zn chemistry
Possible to isolate formal Zn(I) compounds that contain Zn-Zn bonds using a bulky Cp* ligand
Compound can be isolated

Question 2

Synthesis of Zn(I) Cp* compound

Answer 2

2 routes:
From Et2Zn and CpZn
OR
CpZnCl + K —> CpZn-ZnCp + KCl

Question 3

First isolation of Mg(I) compound

Answer 3

Reduction of 2 equivalents of a beta-diketiminate Mg iodide using 2Na/K to give a Mg(I) compound with an Mg-Mg bond that can be isolated
Beta-diketiminate ligands provide kinetic stability so there is no disproportionation into Mg and M(gII)

Question 4

Reactivity of soluble Mg(I) compounds

Answer 4

Behave as ‘bespoke’ 2-electron reducing agents
(2 electron because each Mg wants to lose one electron to form Mg2+)
Can perform organic and inorganic reductions
See flashcard

Question 5

Electrides

Answer 5

Formed from the interaction of a crown ether/cryptand with an alkali metal at low temperature
‘Anion’ of the system is a free electron
The electron sits in voids/channels within the crystal in a ‘hydrogen-atom-like’ state i.e. the ground state of the trapped electrons is largely 1s in character

Question 6

Absorption spectra of electrides

Answer 6

All display intense near IR absorptions that are assigned to the 1s –> 2p transition of the free electron (this is independent of the metal)
All the metals also show metal-dependent transitions that can be assigned to alkali metal anions, M-
–> = ‘alkalides’

Question 7

Formation/synthesis of alkalides

Answer 7

Commonly formed by reduction of a less electropositive alkali metal by a more electropositive metal (i.e. a stronger reducing agent) in the presence of a crown ether or cryptand
e.g. Na + Rb + L —> [LRb]+Na-

OR
Disproportionation of the metal in the 0 oxidation state
2Na + L —> [LNa]+Na-

Question 8

Uses of inorganic electrides

Answer 8

The ‘disproportionation chemistry’ of Na doesn’t just happen in liquid NH3 - can also happen in zeolites/silica gel when impregnated with Na metal
Can be used as heterogenised sources of electrode materials for carrying out reduction reactions