Compounds of Interest Flashcards

Question

What is the synthesis of Na β-alumina?

Answer 1

Na₂CO₃ + Al₂O₃ -> NaAl₁₁O₇ Within a sealed vessel to avoid loss of Na₂O

Answer 2

Al³⁺ occupies Td and Oh holes in close-packed layers (similar to spinels) Every 5th layer has 3/4 of oxide ions missing Layered structure with Na within layers

Answer 3

Na+ mobility Mobile in oxide-deficient layers as smaller than O^2- and many states to occupy Only in 2 dimensions

Answer 4

As radii increases they are less mobile as cannot move as freely within oxide layers BUT Li+ has v low conductivity as so small it occupies smaller sites so higher activation energy for motion

Answer 5

Superconductor at temperatures as high as 40K

Answer 6

Intercatalation of K vapour into C₆₀ N-style doping

Answer 7

C₆₀ by itself are fcc With K+ cations in all Oh and Td with C₆₀^3- ccp

Answer 8

BCS theory - movement of pairs of e- (cooper pairs) coupled by lattice vibrations Tc = ωe^1/λ λ = VN(E_f) Tc also depends on lattice parameter a0 (as separation increases then bandwith increases)

Answer 9

Fast-ion conductor

Answer 10

KI + AgNO₃ -> α-AgI RbAg₄I₅ can be made by inserting some RbI only α-AgI at higher temp

Answer 11

Body-centered array of I^- Ag^{+ ions distributed across different sties and this mobility leads to being a conudctor?}

Answer 12

Rb+ and I- form a rigid lattice Ag+ randomly distributed between Td Sites Has higher ionic cond at low T but comprises overall response

Answer 13

Fast-ion conductor

Answer 14

Partial oxn of Rb @ low T gives Rb₆I which then decomposes to Rb₉O₂ and Rb

Answer 15

2x ORb₆ face-sharing octahedra e- delocalisation between Rb ions, so good ion conductor (and coloured) Short Rb-Rb distance

Answer 16

Melts to form Rb₂O & Rb Reacts with water to produce fully oxidised RbOH

Answer 17

Due to fluxonality of protons in NMR

Answer 18

TiCl₄ and 4NaCp

Answer 19

2x η5 CP and 2x η1 Cp to avoid exceeding 18VE rule 16 VE - poor overlap of 3d orbitals so only small stabilisation of bodning orbitals. Means doesnt follow 18 e- rule (like 4/5d) Makes sense as Ti(IV) is majority of Ti chemistry

Answer 20

16VE so can form suitable TS

Answer 21

Abnormal structure | they didnt even give a reason

Answer 22

Abnormal structure | they didnt even give a reason

Answer 23

TiO₂ and Ti at 1500C

Answer 24

when x=0, 15% of cation and anion sites vacant, means ordered monoclinic structure Change in stochiometry changes vacancy conc, but total conc same Vacancies reduce Ti-Ti distances and max M-M bonding, which is good for early TM as more extended d-orbitals

Answer 25

Reacts with acid to form Ti³⁺ and H₂ Because stable oxn states are 3/4, as early in period and compensated by electrostatic interactions with anions

Answer 26

NbO - 25% vacancies, more M-M as better 4d overlap so wider bands and more metallic NiO - cation vacancies, Ni_1-xO gives mixed valence (2/3). Mott-hubbard insulator to metallic conductor

Answer 27

Perovskite structure

Answer 28

React TiO₂ and BaCO₃ at high T

Answer 29

Cubic perovskite with corner-sharing TiO₆ octahedra Large Ba expands lattice along with the 2nd order JT, displaces Ti(IV) from centres of octahedra Leads to ferroelectric polarisation - charge accumlates in material while thermally stable

Answer 30

Structure comparison with 3d MOs and VO₂

Answer 31

V₂O₃ and V(s)

Answer 32

Distorted rocksalt with weak V-V varies between VO_0.8-1.3

Answer 33

Broad band (W>U) as early 3d TM Metallic conductor as partially filled t_2g

Answer 34

Later MOs - more contracted 3d, U>W, mott-hubbard insulators Early MOs - more extended 3d, M-M leads to more defective structure

Answer 35

Undergoes Pierl's distortion where it changes from metallic to insulating

Answer 36

V₂O₅ + CO -> CO₂ + VO₂

Answer 37

V(IV) is t_2g¹ Would expect metallic behaviour

Answer 38

>340K is undistorted metallic `<340K ` undergoes Pierls distortion, by which V-V dimers formed and e- localised in V-V bonds

Answer 39

1D chain of equally spaced ions with 1 e- is unstable Leads to distortion

Answer 40

Early in 3d, orbital overlap good and V-V bonds outweighs loss of lengthening V-O bonds

Answer 41

TiO₂ - rutile band gap insulator, d0 CrO₂ - 3d overlap not sufficient, undistrorted rutile NbO₂ - distortion occurs to higher temp as better overlap, insulating

Answer 42

Thermal decomp of CrO₃

Answer 43

Rutile structure - dyz and dxz able to mix with O 2p Leads to delocalisation in this band

Answer 44

Quintuple Cr-Cr

Answer 45

Trans-bent with quintuple bond 1xσ - d_z2 2xπ - d_yz, d_xz 2xδ - d_xy, d_x2-y2 Confirmed by X-ray, IR, and NMR (no Cr-H bonding)

Answer 46

Bulky ones- Limit intermolecular reactions which yields Also want few ligands as too many reduces VE available to form M-M

Answer 47

Quadruple bonds

Answer 48

CrCl₃ + Zn/HCl -> CrCl₂ CrCl₂ + NaOAc -> Cr(OAc)₂ All under N₂

Answer 49

Quadruple bonding All e- paired in dimer, so diamagnetism (Cr 2+ is JT distorted) Red due to δ-δ`*` transitions

Answer 50

Dimer with eclipsed config - as allows for quadruple bonds even if bad sterics C4V point group

Answer 51

Strong reducing agent Cr(II) - Cr(III) Reduces atmospheric O₂ so can used as scrubber for oxygen

Answer 52

Mo - shorter quadruple bonds as better overlap of 4d, and stronger bonding so δ-δ`*` gap larger so lesser thermal δ`*` population Re - same number of VE and eclipsed Os - not eclipsed as δ`*` fully occupied so sterics outweighs

Answer 53

Fischer carbene

Answer 54

Reacts with nulceophiles as C in carbene electrophilic

Answer 55

d-orbitals rel low energy due to π-acceptor co-ligands (CO) CR₂ has O/R sub which destabilises C 2p, leading to singlet carbene formation But C 2p empty, so C is electrophlic HOMO metal d-bsaed, LUMO is C-based

Answer 56

Schrock: no π-acceptor co-ligands, d-orbitals rel high in energy, no π-donors on C Triplet carbene

Answer 57

Interest due to fluxionality

Answer 58

Reaction between Fe(CO)₅ and cyclopentadiene dimer C₁₀H₁₂

Answer 59

React with Na/Hg amalgam to form v nucleophilic [CpFe(CO)₂]- anion Reacts with Br₂ or I₂ by OX -> CpFe(CO)₂X

Answer 60

Fluxional - between cis and trans via a non-bridged intermediate NMR: 1 CO in fast exchange, 2 in slow exchange (bridged & terminal)

Answer 61

Due to structure, elec conductivity, and magnetic properties

Answer 62

6Fe₂O₃ + high heat -> 4Fe₃O₄ + O₂ Heat is 1400C Also produced in the body but can be poisonous

Answer 63

Fe(II)Fe(III)₂O₄ has the inverse spinel structure ccp arrangement of O^2- with Fe(III) in 1/8 Td holes and 1/4 Td Oh, and Fe(II) in 1/4 Oh holes Fe(III) - hs d5, LFSE is 0 (no preference for Oh or Td) Fe(II) - hs d6, favours an Oh coord as 0.4Δ_Oh > 0.6Δ_Td

Answer 64

Co₃O₄ adopts normal instead of inverse Co(III) in 1/2 Oh holes and Co(II) in 1/8 Td holes

Answer 65

Above 120K: e- transfer between Oh Fe(II) and Oh Fe(III) which are in edge-sharing octahedra. This is good as transition is t2g -> t2g, so no change in σ`*` and small franck-condon barrier to e- transfer Below 120K: Verwey distortion occurs which reduces conductivity

Answer 66

Ferro - can form a naturally occuring magnet

Answer 67

Decomposes with CO in blast furnace to Fe + CO₂ Binds to impurities in water and sediments, for purification

Answer 68

They are spin crossover compounds Which are compounds within which high-spin-to-low-spin transition at a TM centre, in response to a change in temperature or pressure

Answer 69

ls at low T, hs at high T Due to maximising vib entropy in higher T As in hs - weaker bonding, so vib energy levels closer together so more populated, more vib entropy

Answer 70

Both bipy/NCS- have intermediate field strengths Means hs/ls spin states are similar energies

Answer 71

Intense blue colour This arises from intravalent charge transfer (IVCT)

Answer 72

K₄[Fe^II(CN)₆] + Fe^III(H₂O)₆ ^{3+ -> KFe₂(CN)₆ + 6H₂O}

Answer 73

FCC of Fe^II(CN)₆ with Fe^III in Oh holes and K+ in 1/2 Td holes CN- linear between Fe ions, aligned so softer C adjacent to Fe^II and N next to Fe^III

Answer 74

Eqm between bridged and non-bridged structures Also used in org synthesis

Answer 75

Co^III(OAc)₃ + H₂ + CO @ high T and p H₂ reduces Co

Answer 76

Major isomer has 2xbridging CO and eclipsed terminal CO (C_2v) Unbridged has staggered CO (D_3d) Distinguished by IR

Answer 77

Reacts with alkyne Also reacts with Na then acidification to give a pre-catalyst used in hydroformylation reactions (HCo(CO)₄)

Answer 78

Superconducting material

Answer 79

Sol-gel precursor - dry and heat to form product High T ceramic synthesis with heating and grinding cycles

Answer 80

CuO₄ square-planes separated by layers of CuO₃ which insert or remove e-, which partially oxidises Cu(II) to Cu(III) This gives a superconducting metal If just Cu(II) then would be Mott-Hubbard insulator

Answer 81

Low T - BCS theory Higher T - not clearly explained but involves stronger e-/phonon coupling

Answer 82

Reaction with Y₂O₃ to give fast-ion conductor This is called yttria stabilised zirconia

Answer 83

Exists naturally Or heat Zr(OH)₄

Answer 84

Low T: 7-coord in monoclinic High T: 8-coord in dist fluorite Show in x-ray

Answer 85

Band gap insulator - O 2p valence filled and conduction 4d band empty

Answer 86

High T is sig more conductive As low T (monoclinic) has 2 distinct anion sites whereas fluorite has 1 anion sites More randomly distributed in high symm structure, so easier hoppijng between sites and faster conductivity

Answer 87

ZrO₂ + (x/2) Y₂O₃ -> Zr_1-xY_xO_2-2/x Y stabilises fluorite as Y(3+) larger than Zn(4+) which leads to O^{2- vacancies to maintain charge neutrality
Gives good ionic conduction at high T}

Answer 88

Solid electrolyte in oxygen sensors in internal combustion energies

Answer 89

TiO₂ - rutile at all T, Ti(IV) 6-coord as smaller SiO₂, GeO₂ - 4 coord system

Answer 90

Precursor to an alkene polymerisation catalyst

Answer 91

ZrCl₄ + 2NaCp -> Cp₂ZrCl₂ + 2NaCl Zr(II) to Zr(IV)