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Transition Metals (Ligands)

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1 Transition Metals (Ligands)
Labs Dry Lab 5 Preface to Qualitative Analysis #34/35/36/37 Common Anions/Qualitiataive I/II/III #38 Transition Metal Chemistry Chemical Equations Chapter 5, 13

2 Characteristics of Transition Metals
Representative elements show similarities in groups, but changes occur within period as # valence electrons changes Chemical/physical properties of transition metal elements vary only slightly across period/ within given group Difference due to inner electrons being last electrons added Inner d/f electrons cannot participate as easily in bonding as valence s and p electrons Chemistry of transition elements not affected as greatly by gradual change in # electrons as representatives 3/25/2017

3 High density Hard, tough and strong (compared to IA)
Due to strong metallic atom-atom bonding Typical metallic characterisctics 1st row-in general, electrical conductivity increases Ag best conductor of heat/electric current Cu close 2nd High MP/BP Bonding between atoms very strong Only weakened at high Ts Mercury liquid at room T (very low MP) High density Due to strong bonding between atoms 1st row-shows steady increase with exception of zinc 3/25/2017

4 Oxidation states Variability due to similar energy in 4s/3d subshells
Atom form ions of roughly same stability by losing different numbers of electrons +3 oxidation states more stable at beginning of series, but +2 oxidation states more stable toward end Nickel, copper, zinc Only have s electrons available Requires too much energy to strip d electrons away Fewer oxidation states available Vanadium, chromium, manganese Many common oxidation states from availability of s/d electrons Some elements exhibit +4 state, and Mn even shows +5, +6, and +7 Transition metals usually exhibit their highest oxidation states in compounds with oxygen, fluorine, or chlorine KMnO4 and K2Cr2O7 examples 3/25/2017

5 Atomic Radius Ionization Energy
Representative elements decrease across period Transition metals decrease only slightly across period Consistent w/increase in effective nuclear charge as atomic number increases Greater the charge, smaller the atom All 1st row transition elements have 4s orbitals as outermost occupied orbitals Radius decreases, then increase after iron Ionization Energy 1st IE of 1st transition metal series remarkably similar, increasing very gradually from left to right Slight increase over 1st 5 elements then IE barely changes from Fe to Cu 3/25/2017

6 Effective nuclear charge experienced by outermost electrons depends on shielding provided by inner electrons Nuclear charge increases from scandium to copper (electrons added to inner 3d subshell) 3d electrons shield 4s electrons from increasing nuclear charge for most part Consequently 4s electrons of 1st row transition elements feel only slightly increasing effective nuclear charge as atomic number increases, and atomic radii makes only gradual decrease 3/25/2017

7 Less reactive than IA/IIA
Other properties, including chemical reactivity, show great differences Less reactive than IA/IIA Do not react as quickly w/water or oxygen so they do not corrode as quickly Iron forms oxides that scale off, constantly exposing new metal to corrosion Others do not readily form oxides (noble metals-Au, Ag, Pt, Pd) Greater strength than IA/IIA-used as alloys Some form oxides that adhere tightly to metallic surface (Cr, Ni, Co), protecting metal from further oxidation 3/25/2017

8 In forming ionic compounds w/nonmetals
More than one oxidation state is often found Cations are often complex ions (transition metal ion is surrounded by certain # of ligands-molecules or ions that behave as Lewis bases) Most compounds are colored, because transition metal ion in complex can absorb visible light of specific wavelengths Many compounds paramagnetic (contain unpaired electrons) 3/25/2017

9 Ti - titanium(III) chloride, TiCl3, is purple
Sc/Zn- scandium (ScCl3)/Zinc (ZnSO4) salts are colorless/ not typical of transition metals Ti - titanium(III) chloride, TiCl3, is purple Cr - chromium(III) sulfate, Cr2(SO4)3, is dark green (chromate(VI) salts are yellow, dichromate(VI) salts are orange) Mn – manganese -  potassium(VII) permanganate, KMnO4, is purple (manganese(II) salts-MnCl2-pale pink) Iron(II) compounds usually light green/Iron(III) compounds orange/brown Co - cobalt sulfate, CoSO4, is pinkish Ni - nickel chloride, NiCl2, is green Cu – most common copper compounds [copper(II) sulfate, CuSO4] are blue in crystals/solution and sometimes green V - vanadium(III) chloride, VCl3, is green 3/25/2017

10 Electron Configuration Exceptions
Electrons are removed from 4s orbital before they are taken out of 3d Energies of 3d/4s orbitals are not as close together in ions of transition metals as in neutral atoms In ions of transition elements, 3d orbitals are lower in energy than 4s orbitals Therefore, electrons most easily lost are those in outermost principal energy level, the ns Additional electrons may then be lost from (n – 1)d orbital 3/25/2017

11 3/25/2017

12 Complex Ions Ligands

13 Definitions: Coordination compound Complex ion Counter ions
Complex ion and counter ions Are neutral Complex ion Central transition metal with attached ligands Has net charge (+/-) Complex is set off in brackets that isolate it from the rest of compound Ions outside brackets-free (uncomplexed) ions Metal cation-central atom Counter ions Anions/cations needed to balance charge so it has no net charge 3/25/2017

14 Ligand (complexing agent)
Neutral molecule or anion w/lone pair that can be used to form bond to central metal ion (Mono)Unidentate ligand Can form one bond to metal ion One donor atom present and can occupy only one site in coordination sphere Even if more than one pair of electrons available, if donation of one pair does not allow for proper positions to make additional bonds, other pairs don’t bond Halide ions, SCN- (thiocyanate ions), anions of weak acids 3/25/2017

15 (Multi)Polydentate ligand (tri/tetra/hexa)
Bidentate ligand 2 donor atoms present and can occupy 2 or more coordination sites (2 bonds to metal ion) Most common (diamines/anions of diprotic organic acids) (Multi)Polydentate ligand (tri/tetra/hexa) Can form more than two bonds to metal ion Appear to grasp metal between 2 or more donor atoms, called chelating agents (Greek “claw”) 3/25/2017

16 Bidentate/polydentate ligands-chelating ligands
Extra stable because two bonds must be broken to separate metal from ligand EDTA4 Excellent chelating ligand Ethylenediaminetetraacetic acid Has 6 pairs of electrons to donate Molecule flexible enough to allow each of 6 pairs to form bonds with metal ion Important for chemical analysis of metal ions using simple titration methods, found in many cosmetics, drugs, foods as preservative by forming complexes with metal ions, acts as catalysts to promote oxidation 3/25/2017

17 Ligands: Coordination sphere of metal-metal ions/ligands within brackets Normally either negative ion/polar molecule Must contain at least one lone pair of electrons that can serve as electron-pair donors or Lewis bases Metal ions (particularly transition metal ions) have vacant valence orbitals which can serve as electron-pair acceptors or Lewis acids 3/25/2017

18 Part of ligand that bonds directly with metal-donor atom
[Co(NH3)5Cl]2+-5 N atoms and 1 Cl atom serve as donor atoms for Co Number of donor atoms surrounding central metal atom-coordination number of the metal Above, there are 6 donor atoms, so Co has a coordination number of 6 Coordination number of a metal is equal to twice its charge-there are many exceptions to this rule, but this can be helpful in completing an equation in reaction question on AP exam 3/25/2017

19 Coordination number: Number of bonds formed by metal ions to ligands in complex ions varies from 2-8 depending on size, charge, electron configuration of transition metal ion Many metal ions have more than one 2 ligands give linear structure, 4-tetrahedral or square planar, 6-octahedral Typical Coordination #s for some common metal ions M+ Coor. #s M2+ Coor. #s M3+ Coor. #s Cu+ 2, 4 Mn2+ 4, 6 Sc3+ 6 Ag Fe Cr3+ 6 Au+ 2, 4 Co2+ 4, 6 Co3+ 6 Ni2+ 4, 6 Au3+ 4 Cu2+ 4, 6 Zn2+ 4, 6 3/25/2017

20 Examples [Ag(NH3)2]Cl and K3[Fe(CN)6]
Complex ion is shown enclosed in brackets In the silver compound, Cl– is a free chloride ion, and in the iron compound each K+ is a free potassium ion K+ and Cl– ions are examples of counter ions which serve to balance or neutralize the charge of the complex ion Coordination number of Pt2+ in [Pt(NH3)4] 2+ is 4, and that of Co2+ in [Co(NH3)6] 2+ is 6. 3/25/2017

21 Common ligands Polar molecules: Neutral Molecules: Anions: Aquo H2O
Ammine NH3 Carbonyl CO Nitrosyl NO Neutral Molecules: Methylamine CH3NH2 Ethylenediamine (en) H2NCH2CH2NH2 Anions: Fluoro-/chloro-/bromo-/iodo- F-/Cl–/Br–/l– Cyano CN– Hydroxo OH– Thiosulfato S2O32- Carbonato CO32- Oxalato C2O42- 3/25/2017

22 Naming complex ions Ligands named before central metal atom
Anionic ligands names end in “o” ide  o chloride  chloro ate  ato sulfate  sulfato Neutral ligands named as molecule except H2O  aquo/NH3  ammine/CO  carbonyl # ligands in complex use Greek prefixes di for 2/tri for 3/tetra for 4/penta for 5/hex for 6 Prefixes bis-, tris-, tetrakis-, etc. used when other are already used 3/25/2017

23 Name of anionic complex ion ends in “ate,” sometimes Latin name used
Name of cationic complex ion ends in name of central metal ion w/oxidation state shown as Roman numeral in () at end of metal’s name Name of anionic complex ion ends in “ate,” sometimes Latin name used chromium(II)  chromate(II) nickel(II)  nickelate(II) platinum(II)  platinate(II) Iron(II)  ferrate(II) Copper(I)  cuprate(I) Lead(II)  plumbate(II) silver=argentate Gold(I)  aurate(I) Tin(IV)  stannate(IV) 3/25/2017

24 Writing Formula of a Complex
Identify central metal ion Identify charge on central metal ion in () Identify ligands Identify # ligands Calculate total chare on ligands Calculate charge on complex ion Charge on metal ion + total charge on ligands Ligands written first, then central metal ion When more than one type of ligand present, name alphabetically (prefixes don’t affect order) 3/25/2017

25 Name complex ion w/formula Fe(CN)63-
Anionic ligands have names ending in 'o' CN- named as cyano # ligands in complex specified using Greek prefix 6 ligands = hexa → hexacyano Oxidation state of central metal atom shown w/Roman numeral in parantheses at end of metal's name Central metal ion is iron Charge on iron: 3- = x + (6 x 1-) 3- = x -6 x = 3+ Central metal ion: iron (III) Complex ion is anion, therefore name will end in ferrate (III) Ligands named before central metal ion: hexacyanoferrate (III) 3/25/2017

26 No. of Ligands and prefix Central Ion Name Complex Ion Name
Formula Ligand Name No. of Ligands and prefix Central Ion Name Complex Ion Name Ag(NH3)2+ ammine 2 → di silver (I) (+1= x + 2(0), x = +1) diamminesilver (I) ion (complex is a cation) Ag(CN)2- cyano silver (I) → argentate (I) (-1= x + 2(-1), x = +1) dicyanoargentate (I) ion (complex is an anion) Cu(H2O)62+ aquo 6 → hexa copper (II) (+2= x + 6(0), x = +2) hexaaquocopper (II) ion (complex is a cation) CuCl42- chloro 4 → tetra copper (II) → cuprate (II) (-2= x + 4(-1), x = +2) tetrachlorocuprate (II) ion (complex is an anion) 3/25/2017

27 Write formula for complex ion tetraamminecopper (II)
Identify central metal ion : copper, Cu Identify charge on central metal ion in (): 2+ Identify ligands: ammine = NH3 (neutral species) Identify # ligands: tetra = 4 Calculate total charge on ligands = 4 x 0 = 0 Calculate charge on complex ion = charge on metal ion + total charge on ligands = = 2+ Write formula giving central metal ion first followed by ligands : Cu(NH3)42+ 3/25/2017

28 hexaaquocobalt (II) ion Co2+ (charge in parentheses) H2O (aquo = H2O)
Name Central Ion Formula Ligand Formula No. of Ligands Complex Ion Formula hexaaquocobalt (II) ion Co2+ (charge in parentheses) H2O (aquo = H2O) hexa = 6 Co(H2O)62+ (4 x 0 +2 = +2) tetrachlorocobaltate (II) ion (ate = anion) Cl- (chloro = Cl-) tetra = 4 CoCl42- (4 x = -2) tetracarbonylnickel (II) ion Ni2+ (charge in parentheses) CO (carbonyl = CO) Ni(CO)42+ (4 x = +2) tetracyanonickelate (II) ion (ate = anion) CN- (cyano = CN-) Ni(CN)42- (4 x = -2) 3/25/2017

29 K2[Ni(CN)4] Name cation-potassium Name anion-potassium tetracyano
Oxidation state of central atom-potassium tetracyanonickelate(II) 3/25/2017

30 [Co(NH3)2(en)2]Cl2 Name ligands first in alphabetical order-diamminebis(ethylenediamine) Name central atom w/oxidation number-diamminebis(ethylenediamine)cobalt(II) Name anion- diamminebis(ethylenediamine)cobalt(II)chloride 3/25/2017

31 pentaammineiodocobalt(III) chloride [Cu(NH3)4]SO4
[CoI(NH3)5]Cl2 pentaammineiodocobalt(III) chloride [Cu(NH3)4]SO4 tetraamminecopper(II) sulfate [CrCl(en)2(H2O)]Cl2 aquachlorobis(ethylenediamine)chromium(III) chloride (NH4)2[CdCl4] ammonium tetrachlorocadmate(II) Na[Rh(EDTA)] sodium ethylenediaminetetraacetatorhodate(III) [Pd(en)2][CrCl4(NH3)2] bis(ethylenediamine)palladium(II)diamminetetrachlorochromate(III) K3[Fe(ox)(ONO)4] potassium tetranitritooxalatoferrate(III) 3/25/2017

32 aquapentachlororuthenate(III) [Fe(CN)6]4- hexacyanoferrate(II)
Ag(NH3)2]+ diamminesilver(I) [RuCl5(H2O)]2- aquapentachlororuthenate(III) [Fe(CN)6]4- hexacyanoferrate(II) Na4[Ni(C2O4)3] sodium tris(oxalato)nickelate(II) (NH4)2[CuBr4] ammonium tetrabromocuprate(II) [Co(NH3)5Cl](NO3)2 pentaamminechlorocobalt(III) nitrate [Co(H2O)6]I3 hexaaquacobalt(III) iodide K2[PtCl4] potassium tetrachloroplatinate(II) 3/25/2017

33 Potassium hexafluorocobaltate (III) K3[CoF6]
tetraamminechloronitrocobalt(III) chloride [CoClNO2(NH3)4]Cl tris(ethylenediamine)nickel(II) sulfate [Ni(en)3]SO4 tetramminedichloroplatinum(IV) tetrachloroplatinate(II) [PtCl2(NH3)4][PtCl4] tris(ethylenediamine)cobalt(II) nitrate [Co(en)3](NO3)2 cobalt(II) hexanitrocobaltate(III) Co3[Co(NO2)6]2 ammineaquadicarbonyldicyanoiron(III) [Fe(CN)2(NH3)(H2O)(CO)2]+ 3/25/2017

34 Sodium tetracyanoosmium(III) Na[Os(CN)4]
Tris(ethylenediamine)nickel(II) tetraoxomanganate(II) [Ni(en)3]3[MnO4] Hexaamminezinc(II) tris(oxalato)chromate(III) [Zn(NH3)6]3[Cr(ox)3]2 tris(oxalato)vanadate(II) [V(ox)3]4- sodium dihydroxodinitritomercurate(II) Na2[Hg(OH)2(ONO)2] ammonium tetrabromoaurate(II) (NH4)2[AuBr4] Potassium ethylenediaminetetraacetatoferrate(II) K2[Fe(EDTA)] diaquabis(ethylenediamine)iridium(III) chloride [Ir(H2O)2(en)2]Cl3 3/25/2017

35 In complexation reactions, Lewis bases have many names
Ligands, complexing agents, chelates, sequestering agents Most ligands have one pair of electrons to donate (ammonia) Some have two pairs of elections and some up to six pairs Ligands that provide more than one electron pair in forming a complex must be large, flexible molecules so that each pair of electrons can be oriented properly to form a bond 3/25/2017

36 Complexation reactions can be written generally as
Mn+ + xLm- ⇋ MLxn-mx where Mn+ is a metal ion with a charge of +n and Lm- is a liquid with a charge of –m Ag tends to accept two electron pairs Cu accepts four electron pairs Other metal ions tend to accept six electron pairs in complexes This information allows us to accurately write most complexation reactions once the number of electron pairs that a ligand can donate has been determined 3/25/2017

37 Shapes (Geometry) of Some Complex Ions
Coordination number = # ligands = 2 → linear Coordination number = # ligands = 4 → tetrahedral or square-planar Coordination number = # ligands = 6 → octahedral (octahedral geometry is most common for transition metal complexes) Complex Ion Formula No. of Ligands Coordination Number Shape Ag(NH3)2+ 2 linear CuCl2- Cr(NH3)63+ 6 octahedral Fe(CN)63- 3/25/2017

38 Homework: Read , pp Q pp , #21a, 22a, 24, 30, 32, 34, 46 Do 1 additional problem and 1 challenge problem Submit quizzes by to me-some you won’t be able to do, so skip them: 3/25/2017

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