Transition metal chemistry

[earlier transition metals] +3 = more common than +2 = strongly reducing [later transition metals] +2 = more common than +3 +3 oxn state = strongly oxidising

increasing 3rd and higher I.E. across series d-orbitals become more core-like (closer to nucleus)

decreases in order of F- > Cl- > Br- > I-

high covalent character high charge density on metal (v. polarising) TiCl4 = covalently bonded liquid + soluble in benzene TiCl2 = ionic solid

[intermediate = below line] can still be observed (disproportionation reaction may be slow) = kinetically stable

Sc3+ (d0) colourless strong Lewis acid

+4 (d0) - TiO3 2-, TiO 2+ not Ti4+ -> charge = so high (would pull hydrogens from water ligand - TiO2+) strong Lewi acid Ti3+ = strong reducing agent No Ti2+ aq chem - TiCl2 reacts violently with water, reducing it to H2

VO4 3- at pH 14 VO2 + at pH 0 reduced to VO2+ (blue), V3+ (green) and V2+ (violet) - all stable rwt disproportionation VO2+ = square planar V2+ = strongly reducing and oxidised by air (needs to be kept in inert atmosphere)

Cr(IV) = powerful oxidising agent Cr2O7 2- (orange) in acidic solutions CrO4 2- (green) in alkaline solutions Cr2O7 2- + 3H2O -> CrO4 2- + 2H3O+ Cr(III) d3 - high CFSE; kinetically inert Cr(II) = strongly reducing

Mn(VII) = powerful oxidising agent MnO4- = tetrahedral anion intense colour due to M->L transfer band Mn(III) = distorted octahedral due to J-T distortion Mn(II) = v. pale (d->d = forbidden by all selection rules)

Fe3+ + e- -> Fe2+ position of equilibrium + stability of oxn state determined by ligands Fe3+ = acidic solutions - high charge on metal equilibrium affects by pH -Fe3+ stable at pH <2 Fe2+ + O2 + 4H3O+ -> 4Fe3+ + 6H2O (stable but slowly oxidises due to presence of dissolved oxygen) strongly coloured - M->M transfer bands

Co(III) = strong oxidising agent LS complex - kinetically inert despite thermodynamic driving force N-donor ligands (e.g. NH3) greatly stabilise Co3+ rwt reduction Co(II) - colour depends on geometry octahedral = pink tetrahedral = intense blue

no longer have centre of symmetry

Δoct = smaller for tetrahedral compared to octahedral

Ni(II) = stable to oxidation + reduction range of geometries (depends on counter ion)

Cu2+ (cupric) and Cu+ (cuprous) octahedral = distorted due to J-T effect

Zn2+ colourless (no d-d e- transition possible) wide range of geometries not really a transition metal - neither metal nor compound has partially filled d orbitals

CrO3 + [CrO4]2- = strong oxidising agents WO and [WO4]2- = not readily reduced high oxn states: 1st row < 2nd row < 3rd row Mo(IV) and W(IV) = common Mo(III) and W(III) = sparse high coordination numbers possible for larger metals (1st row - ions not big enough)

Ni and Pd = +2 Pt = +4 Pd + Pt = square planar (high Δoct) M-M bonds and low oxn states (+1,0) = more important down group

don’t have correct symmetry directed between axis

pairing energies have been shown to be lower in metal complexes than in gaseous Mn+ ions indicates inter-electronic repulsion is less in complexes so effective size of metal orbitals has increased = nephelauxetic effect

in absence of any magnetic moment (i.e. unpaired e-) = induced magnetic field that opposes main field =diamagnetism (MD) *repelled by magnetic field

if there’s a magnetic moment (unpaired e-) and moments don’t interact with each other, they align to give overall magnetic moment (MP) *attracted to magnetic field

as charge on M increases, Δ increases [reason] ionic radius decreases ∴ M-L decreases greater interaction between M and L orbitals increases energy of antibonding eg orbitals ∴ t2g-eg gap increases