Module 7

Question 1

what bonding is most prominent in Ln organometallic chemistry

Answer 1

ionic bonding

Question 2

why can oxidative addition now occur for Ln elements

Answer 2

cannot go up or down 2 oxidation states

Question 3

because organo Ln complexes contain vacant orbitals what reactions can they take part in

Answer 3

B-hydride elemination
B-alkyl elimination
agostic interaction
insertions

Question 4

what is the charge on an alkyl group

Answer 4

-1

Question 5

give an example of an organoLn ate complex

Answer 5

[Lu(tBu)4]

Question 6

give an example of an Lnorgano complex with an Li complex cation

Answer 6

[Li(tmeda)]3 [LuMe6]

Question 7

give an example of an organoLn with a chelating ligand

Answer 7

[Lu(C6H4(H2NMe2)3]

Question 8

what are available to form [Ln(C6H4(H2NMe2)3]

Answer 8

Er, Yb, Lu

Question 9

give an example of an organoLn with bulky ligands

Answer 9

[La(CH(SiMe3)2)3]

Question 10

give an example of a bulky ligand that fills the coordination sphere of an Ln2+ ion

Answer 10

Yb(C(SiMe3)3)2

Question 11

what is the reaction equation for salt metathesis

Answer 11

LnCl3 + n(XLi) —-> LnXn + nLiCl

Question 12

what happens if only 3 ligands are reacted with LnCl in salt metathesis, and how can it be avoided

Answer 12

Ln will form an adduct with LiCl

Can be avoided by using Ln(OAr)3 not LnCl3

Question 13

describe the reactivity of alkyl Lns

Answer 13

very reactive

Question 14

how can the reactivity of alkyl Lns be moderated

Answer 14

with spectator ligands

Question 15

what are some required properties of spectator ligands

Answer 15

must increase coordinative saturation
pKa of protonated ligand < pKa protonated alkyl
must be tunable
must stabilise against redistribution

Question 16

what is redistribution

Answer 16

3LnRL2-> LnR3 + 2LnL3

Question 17

how can Cp be tuned as a spectator ligands

Answer 17

solubility
bulk
can be linked to chelate

Question 18

what complexes do neutral ligands form

Answer 18

cationic complexes

Question 19

what are the properties of cationic complexes

Answer 19

highly electrophilic

enhanced reactivity

Question 20

what is a rough value for strength of Ln-C bond

Answer 20

200 kJmol-1

Question 21

for which Ln is activation energy of sigma bond metathesis highest

Answer 21

late (small) Ln

Question 22

describe the regioselectivity of alkene insertion to Ln complexes

Answer 22

least hindered end bonds to Ln

Question 23

what are the 2 types of degradation reaction

Answer 23

b alkyl elimination

b hydride elimination

Question 24

how can 1e- Ox. addition occur in organoactinides

Answer 24

bimetallic ox. addition

Question 25

how does the strength of An-C compare to Ln-C

Answer 25

stronger

Question 26

what are reactions of organoactinoids governed by

Answer 26

sterics

Question 27

how is LnCp3 made

Answer 27

LnCl3 + 3NaCp --THF--> 3NaCl + Cp3Ln(THF) --> Cp3Ln

Question 28

how is LnCp*2 made

Answer 28

LnI2 + 2NaCp* --THF-> LnCp*2(THF) + 2NaI ---> LnCp*

Question 29

what properties does a ligand need to stabilies Ln2+

Answer 29

bulky

Question 30

how can Cp complex with An

Answer 30

AnCp*3 - bulky | AnCp4 - for Th,U,Pa,Np

Question 31

how is UCp*3 made

Answer 31

UCl3 + 3KCp* -> 3KCl + Cp*3U

Question 32

how is ThCp4 made

Answer 32

ThCl4 + 4KCp -> ThCp4 + 4KCl

Question 33

what is the main bonding interaction in Cp complexes

Answer 33

interaction of of An-Cp is via 6d orbitals excluding 6dz^2

Question 34

how does isocyanide react with Cp3Ln/An

Answer 34

forms adduct - Cp complexes are lewis acidic

Question 35

which Cp complex does isocyanide back-bond with

Answer 35

U

Question 36

how is COT made negative

Answer 36

Addition of 2e-

Question 37

what can be said about the symmetry of the HOMO in COT

Answer 37

has the correct symmetry to interact with f orbitals

Question 38

how many COT ligands and be accommodated by Ln/An

Answer 38

2 Ligands

Question 39

what elements can form [An(COT)2]

Answer 39

Th, U, Np, Pu

Question 40

what elements can form K[Ln(COT)2]

Answer 40

all Ln

Question 41

how are the 2 COTs arranged in a Uranium complex

Answer 41

eclipsed -D8H

Question 42

how are the 2 COTs arranged in a cerium complex

Answer 42

staggered

Question 43

describe the bonding in uranocene

Answer 43

bonding orbitals in ligand can donate into U f-orbitals | Uf4+ f orbital can donate into pi* on COT

Question 44

what is the stability of uranocene

Answer 44

thermally stable

Question 45

compare the reactivity of K[Ln(COT)2] and [U(COT)2]

Answer 45

K[Ln(COT)2] is more reactive

Question 46

describe [Ce(COT)2]

Answer 46

Ce(III) with 2 cot ligands is less reactive than would be expected though

Question 47

what happens to a carbonyl when it is bonded to Ln

Answer 47

C atom is activated

Question 48

why are Ln good at activating carbonyls

Answer 48

``` high affinity for O labile Ln-L bond Large radii - can handle many substrates flexible coordination geometry contraction across series allows for tuning ```

Question 49

how does lewis acidity change across the group

Answer 49

increase with decreasing radius | Yb3+>Lu3+ due to partly filled shell

Question 50

which Ln ions favour enantiometeric selectivity

Answer 50

large ions

Question 51

what factors affect the rate of alkene insertion

Answer 51

accessibility of binding site preferible monomeric non-coordinating solvent

Question 52

what is the regioselectivity of alkene insertion

Answer 52

Ln usually goes to least hindered end

Question 53

what is the optimum Ln for insertion of butadiene

Answer 53

Nd

Question 54

which Ln ions cannot be used in butadiene insertion and why

Answer 54

Sm and Eu are reduced

Question 55

why is C-H activation in hydrocarbons so difficult

Answer 55

``` No lone pairs no low lying vacant orbitals C-H bonds are not acidic strong bonds hard to be selective ```

Question 56

what metal properties does sigma bond metathesis require

Answer 56

electrophilic metal centre

Question 57

why could Ox. addition be possible for U

Answer 57

can go up 2 oxidation state