D And F Block 2

Front 1

What is 'syn gas' ?

Back 1

A mixture of CO and H2 and is manufactured from coal.

CO2 also produced as a by-product

Front 2

What are Fischer Tropsch reactions?

Back 2

A series of reactions using CO2 and H2 with the required pressure, head and catalyst to produce a range of products and is a critical way of making fuel

Front 3

What are the catalysts used for the Monsanto BP acetic acid process: MeOH + CO --> MeCOOH

Back 3

Iridium, cobalt or rhodium

Front 4

Why is spectrometry useful for characterisation of CO complexes?

Back 4

Can see fragmentation where CO ligands fall off

Front 5

Why is the CO IR stretch easy to identify?

Back 5

Not many other stretches in same range

Front 6

If there is only one environment, what must you NOT assume?

Back 6

There is only one stretch.

Group theory shows there will e multiple stretches but some will not result in a dipole change and therefore be absent from the IR spectra

Front 7

Give the hybridisation for the sigma bonds in the following complexes:

Ni(CO)4

Fe(CO)5

Cr(CO)6

Back 7

Sp3

Dsp3

D2sp3

Front 8

Draw an energy level for an octahedral ML6 complex

Back 8

See book

Front 9

What is the acid behaviour of a CO ligand?

Back 9

Weak base, electron pair donor for forward bonding

C-O empty pi* orbitals act as Lewis acid

Front 10

Show why there is a triple bond between C and O using a molecular energy diagram

Back 10

See pic

Front 11

Why does CO tend not to form complexes with elements with a high oxidation state?

What else can we deduce is unlikely to form a complex with CO ligands?

Back 11

Because the CO - metal backbonding requires a lot of electron density on the metal.

CO therefore unlikely to bid to non-metals such as BF3

Front 12

Explain why CO ligand bonding is an exams of synergic bonding

Back 12

CO forward bonding pushes electrons onto the metal increasing its electron density. This increases the backbonding which in turn helps the forward bonding again

Front 13

Will a stronger bond have a higher or lower IR frequency?

Back 13

Higher

Front 14

Why is the bond order going to be less than 3 for the CO bond when C is also acting as a ligand?

Back 14

Because electron density from metal will go into CO pi* orbital lengthening the bond and making it weaker

Front 15

What is the IR range for vCO for carbonyl compounds ?

Back 15

2150 - 1850

Front 16

What is the effect of charge on a complex on a CO stretch?

Back 16

Negative charge increases electron density on metal increasing backbonding, decreasing the strength of the CO bond so causing a lower frequency or vCO.

A positive charge opposite

Front 17

There cannot be more IR active bands than the number of carbonyl groups. What eventuality can cause this?

Back 17

Impurities

Isotopes

Front 18

For an Mn(CO)4 3- complex, explain why Mn(-3) can exist

Back 18

The negative charge is spread Into the backbonding

Electroneutrality principle, in reality the Mn is only slightly negative

Front 19

What is a homoeleptic compound ?

Back 19

One specific metal with one specific ligand

E.g. Cr(CO)6

Front 20

Why is V(CO)6 possible and V(CO)7 not?

Back 20

V is D5 meaning that the complex is going to have an odd number electrons.

With 6 ligands it can exist with a total of 17 electrons, but with 7 ligands there are 19 electrons and the extra electron goes into antibondig

Front 21

What are the consequences of a 17 electron complex e.g. Nb(CO)6

Back 21

Paramagnetic so liable to jahn teller and easily reduce to Nb(CO)6 -

Front 22

Why is V(CO)6 possible and V(CO)7 not?

Back 22

V is D5 meaning that the complex is going to have an odd number electrons.

With 6 ligands it can exist with a total of 17 electrons, but with 7 ligands there are 19 electrons and the extra electron goes into antibondig

Front 23

What are the consequences of a 17 electron complex e.g. Nb(CO)6

Back 23

Paramagnetic so liable to jahn teller and easily reduce to Nb(CO)6 -

Front 24

Why can group 4 metals not form carbonyl complexes

Back 24

To satisfy the 18 electron rule would have to be; M(CO)7

4 d electrons not enough to backbond to 7 CO

Front 25

What two complexes are known for group 7 metals with carbonyl ligands?

Back 25

M(CO)5- but very air sensitive

M(CO)6+

Front 26

Why is tc unknown in nature

Back 26

It's radioactive

Front 27

How can Mn exist with CO ligands without a charge?

Back 27

Forms

Mn2(CO)10 the extra electron comes from each Mn

Front 28

What is the hybridisation of Mn in Mn2(CO)10

Back 28

Octahedral so d2sp3

Front 29

How can Fe(CO)5 be identified ?

Back 29

Toxic and smelly but not everyone can smell it

Front 30

What evidence is there for Fe(CO)5 being trigonal pyramidal?

Back 30

2 stretches can be seen in the IR spectrum, one axial stretch one Equatorial

Front 31

Why is there only one CNMR peak for Fe(CO)5?

Back 31

Berry pseudo rotation, spins too fast for CNMR

Front 32

What happens to [Ru(CO)5] at room temp

Back 32

Decomposes to [Ru3(CO)12]

Front 33

What can be doe with Fe metal

Back 33

Heated to make magnets and metal films

Front 34

What does [Os(CO)5] look like

Back 34

Pale yellow solid

Front 35

What happens when hv and MeCO2H are added to [Fe(CO)5]? What can be seen grime HRS spectrum

Back 35

Fe - Fe hind formed with 2 bridging carbonyl groups.

Will show three CO stretches

Front 36

What evidence is there for an Fe-Fe bond and the existence of a [Fe2(CO)9] complex

Back 36

CO stretch on IR

Completes 18 electron rule

Molecule is diamagnetic

Front 37

What is a carbene?

Back 37

A molecule containing a neutral carbon atom with a valence of two and two unshared valence electrons

R=C:

Front 38

Give some examples of how to create carbonylate anions

Back 38

Add Li/Hg

Add Na/Hg (highly toxic)

Hv

Front 39

What occurs when [Mn(CO)10] is added to Br2?

Back 39

2[BrMn(CO)5]

Front 40

Distinguiish between the bonding in [Fe3(CO)12] and Ru(CO)12]

Back 40

The Fe comple has 3 Fe bonds and semibriding CO. Gives a very distorted shape with different bond lengths.

The Ru complex has no briding carbonyls. It is more or less a slightly disorted octahedral environment. Has CO in the plane and 6 CO out of the plane

Front 41

What is a metal cluster? Give an example

Back 41

[Ru3(CO)12]. It is a metal solubilised by internal ligands

Front 42

What is the only form group 9 CO complexes can exist?

Back 42

As anions, otherwise will not satisfy the 18 electron rule. E.g. [Co(CO)4]- and [Co(CO)5]+

Front 43

What is the result of adding MeC(=O)Cl to [Mn(CO)5]-?

Back 43

M-C bond formation

Front 44

What is required for a thermal substitution? Give an example uaing MeCN. In what positions do subsituted go in octahedral complex? What can be noted about CN- ligands?

Back 44

Heat and reflux with solvent containing ligand.

E.g. MeCN solvent with [Cr(CO)6]. CN- adds axial first, then cis equitorial then fac. The CN- ligands can then themselves be removed and substituted by other ligands.

Front 45

What are typical reagents for a photochemical substitution and their roles?

Back 45

THF, hv and ligand. hv causes dissociation of CO ligands, THF stabilises 16e- intermediate before being displaced by incoming ligand.

Front 46

What reagents are typically used for a chemically assisted CO substitution and how do they bring about the substitution?

Back 46

CH2Cl2 and Me3NO. One of the CO groups binds to the Me3NO via the O group. It leaves as CO2 being replaced by NMe3. This is a poor back-bonder and easily replaced by the desired ligand.

Front 47

What reagents are used for an electron transfer catalysed substitution?

Back 47

[Ph2CO]'

Front 48

What happens if M-Li is added to a carbonyl metal complex followed by [Me3O]+?

Back 48

It will act as a nucleophile attacking the CO to form a complex with a negative charge. The addition of MeO3 produces a Fisher carbene

Front 49

What is the effect of RO groups attacking complexes?

Back 49

Can attack ligands and form carbenes