Coordination Chemistry I: Structures and Isomers 123

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Chapter 9 Coordination Chemistry I: Structures and Isomers 123

CHAPTER 9: COORDINATION CHEMISTRY I: STRUCTURES AND ISOMERS

9.1 Hexagonal: C2v C2v D2h

Hexagonal pyramidal: Cs Cs C2v

Trigonal prismatic: Cs C2v C2

Trigonal antiprismatic: Cs C2 C2h

The structures with C2 symmetry would be optically active.

9.2 a. dicyanotetrakis(methylisocyano)iron(II) or dicyanotetrakis(methylisocyano)iron(0)

b. rubidium tetrafluoroargentate(III) or rubidium tetrafluoroargentate(1–)

c. cis- and trans-carbonylchlorobis(triphenylphosphine)iridium(I) or cis- and trans- carbon ylchlorobis(triphenylphospine)iridium(0)

d. pentaammineazidocobalt(III) sulfate or pentaammineazidocobalt(2+) sulfate

e. diamminesilver(I) tetrafluoroborate(III) or diamminesilver(1+) tetrafluoroborate(1–) – (The BF4 ion is commonly called “tetrafluoroborate.”)

9.3 a. tris(oxalato)vanadate(III) or tris(oxalato)vanadate(3–)

b. sodium tetrachloroaluminate(III) or sodium tetrachloroaluminate(1–)

c. carbonatobis(ethylenediamine)cobalt(III) chloride or carbonatobis(ethy lenediamine)cobalt(1+) chloride

d. tris(2,2-bipyridine)nickel(II) nitrate or tris(2,2-bipyridine)nickel(2+) nitrate (The IUPAC name of the bidentate ligand, 2,2-bipyridyl may also be used; this ligand is most familiarly called “bipy.”)

e. hexacarbonylmolybdenum(0) (also commonly called “molybdenum hexacarbonyl”). The (0) is often omitted.

9.4 a. tetraamminecopper(II) or tetraamminecopper(2+)

b. tetrachloroplatinate(II) or tetrachloroplatinate(2–)

c. tris(dimethyldithiocarbamato)iron(III) or tris(dimethyldithiocarbamato)iron(0)

d. hexacyanomanganate(II) or hexacyanomanganate(4–)

e. nonahydridorhenate(VII) or nonahydridorhenate(2–) (This ion is commonly called “enneahydridorhenate.”)

9.5 a. triamminetrichloroplatinum(IV) or triamminetrichloroplatinum(1+)

b. diamminediaquadichlorocobalt(III) or diamminediaquadichlorocobalt(1+)

c. diamminediaquabromochlorocobalt(III) or diamminediaquabromochlorocobalt(1+)

d. triaquabromochloroiodochromium(III) or triaquabromochloroiodochromium(0)

e. dichlorobis(ethylenediamine)platinum(IV) or dichlorobis(ethylenediamine)platinum(2+) or dichlorobis(1,2-ethanediamine)platinum(IV) or dichlorobis(1,2- ethanediamine)platinum(2+)

f. diamminedichloro(o-phenanthroline)chromium(III) or diamminedichloro(o- phenanthroline)chro mium(1+) or diamminedichloro(1,10-phenanthroline)chromium(III) or diamminedichloro(1,10-phenanthroline)chromium(1+)

g. bis(2,2-bipyridine)bromochloroplatinum(IV) or bis(2,2- bypyridine)bromochloroplatinum(2+) or bis(2,2-bipyridyl)bromochloroplatinum(IV) or bis(2,2- bipyridyl)bromochloroplatinum(2+)

h. dibromo[o-phenylene(dimethylarsine)(dimethylphosphine)]rhenium(II) or dibrom o[o-phenylene(dimethylarsine)(dimethylphosphine)]rhenium(0) or dibrom o[1,2-phenylene(dimethylarsine)(dimethylphosphine)]rhenium(II) or dibrom o[1,2-phenylene(dimethylarsine)(dimethylphosphine)]rhenium(0)

i. dibromochlorodiethylenetriaminerhenium(III) or dibrom ochlorodiethylenetriaminerhenium(0) or dibromochloro(2,2- diam inodiethylamine)rhenium(III) or dibromochloro(2,2- diam inodiethylamine)rhenium(0)

9.6 a. dicarbonylbis(dimethyldithiocarbamato)ruthenium(III) or dicarbonylbis(dimethyldithiocarbamato)ruthenium(1+)

b. trisoxalatocobaltate(III) or trisoxalatocobaltate(3–)

c. tris(ethylenediamine)ruthenium(II) or tris(ethylenediamine)ruthenium(2+)

d. bis(2,2-bipyridine)dichloronickel(II) or bis(2,2-bipyridine)dichloronickel(2+)

9.7 a. Bis(en)Co(III)-µ-amido-µ-hydroxobis(en)Co(III)

4+ N N

H2 N N N Co Co N O N H N N

I H2O

ONO OH2 ONO I Pd Pd H2O ONO H2O ONO

I I

ONO OH2 ONO OH2 Pd Pd ONO OH2 H2O I

I ONO

I I

H2O I I OH2 Pd Pd ONO ONO ONO ONO

H2O OH2

enantiomers c. Fe(dtc)3 S S – S CH3 S S S S S Fe Fe = C N S S S S S S H S S

At low temperature, restricted rotation about the C—N bond can lead to additional isomers as a consequence of the different substituents on the nitrogen. These isomers can be observed by NMR.

9.8 a. triammineaquadichlorocobalt(III) chloride Isomers are of the cation:

+ + + H2O Cl NH3

H3N Cl H3N OH2 H2O NH3 Co Co Co H3N NH3 H3N NH3 Cl NH3

Cl Cl Cl cis trans

mer fac

b. -oxo-bis(pentammine-chromium(III)) ion 4+ H N NH 3 H3N H3N 3 O Cr Cr H3N NH3 NH NH H3N 3 3 NH3

c. potassium diaquabis(oxalato)manganate(III) Isomers are of the anion:

– – – O O H2O

O O O O O O Mn Mn Mn H2O O O OH2 O O

H2O OH2 H2O cis enantiomers trans Cl NH 3 9.9 a. cis-diamminebromochloroplatinum(II) Pt

Br NH3

b. diaquadiiododinitritopalladium(IV) H2O ONO Pt ONO OH2

I O O O C O C C C O c. tri--carbonylbis(tricarbonyliron(0)) C Fe Fe

9.10 O

CH2 C

– = N O H2N O

O O N N

N N N N O N N O M M M M O O O O N O O N

N N O O fac mer 9.11 M(AB)3 B B A A

A A A A B A A B M M M M B B B B A B B A

A A B B fac mer

9.12 a. [Pt(NH ) Cl ]+ 3 3 3 + + NH3 Cl

Cl NH3 H3N NH3 Pt Pt Cl NH3 Cl NH3

Cl Cl fac mer

+ b. [Co(NH3)2(H2O)2Cl2]

+ + + + NH3 Cl NH3 NH3

H2O NH3 H2O NH3 Cl OH2 Cl OH2 Co Co Co Co Cl OH2 H2O NH3 Cl OH2 H2O Cl

Cl Cl NH3 NH3

+ + OH2 H2O

H2O NH3 H3N OH2 Co Co Cl NH3 H3N Cl

Cl Cl enantiomers

+ c. [Co(NH3)2(H2O)2BrCl]

+ + + + OH2 Cl NH3 NH3

H3N Br H2O NH3 Br OH2 Cl OH2 Co Co Co Co H3N Cl H2O NH3 Cl OH2 H2O Br

OH2 Br NH3 NH3

+ + + + OH2 H2O OH2 H2O

H2O NH3 H3N OH2 H2O NH3 H3N OH2 Co Co Co Co Br Cl NH3 H3N Br NH3 H3N Cl

Cl Cl Br Br

enantiomers enantiomers

d. Cr(H2O)3BrClI

OH2 H2O

H2O OH2 H2O OH2 Cr Cr Cl I I Cl

Br Br enantiomers

OH2 OH2 OH2

Cl OH2 I OH2 Cl OH2 Cr Cr Cr H2O Br H2O Br H2O I

I Cl Br

2+ e. [Pt(en)2Cl2]

2+ 2+ N N Cl 2+

N N N N N N Pt Pt Pt Cl N N Cl N N

Cl Cl Cl

cis enantiomers trans

+ f. [Cr(o-phen)(NH3)2Cl2]

+ + + +

N N N N N Cl N NH N N 3 NH3 H3N Cr Cr Cr Cr Cl NH3 H3N Cl Cl NH3 H3N Cl NH Cl Cl Cl 3 enantiomers trans Cl ligands trans NH3 ligands

g. [Pt(bipy) BrCl]2+ 2 2+ 2+

2+ Br N N

N N N Br Br N Pt Pt Pt Cl Cl N N N N Cl N N enantiomers

h. Re(arphos)2Br2 Abbreviating the bidentate ligands As P:

Br Br P P

P P P As Br As As Br Re Re Re Re As As As P Br As As Br Br Br P P  

As As As As

Br P P Br Br P P Br Re Re Re Re Br P P Br Br As As Br As As P P    

i. Re(dien)Br2Cl

Cl Cl Br

N Br Br N N Cl Re Re Re N Br Br N N Br

N N N

Br Cl

N Cl N Br Re Re N N N N

Br Br

9.13 a. M(ABA)(CDC)

C A B B

A D C B C A A C M M M M B A D A D A A D C C C C

b. M(ABA)(CDE)

C A A

A D C B B C M M M B A D A A D E E E

B B

C A A C M M D A A D E E

A A

C A A C M M D B B D

E E

9.14 A A A

C B A B B A M M M B C B C C B A C C

A A C C

A B B A A A A A M M M M B C C B B B B B C C C C

B B B B

A C C A A A A A M M M M B A B B B C C B C C C C

9.15 a. The “softer” phosphorus atom bonds preferentially to the soft metal Pd (see Section 6.6.1). b, c. Abbreviating the bidentate ligands NP:

Cl Cl P P

P P P N Cl N N Cl Ni Ni Ni Ni N N N P Cl N N Cl

Cl Cl P P  

N N N N

Cl P P Cl Cl P P Cl Ni Ni Ni Ni Cl P P Cl Cl N N Cl N N P P    

9.16 a, b. Abbreviating the bidentate ligands N P and O S:

Cl Cl

S P S N M M O N O P Cl Cl

N N P P

Cl P P Cl Cl N N Cl M M M M Cl O O Cl Cl O O Cl S S S S  

N N P P

Cl P P Cl Cl N N Cl M M M M Cl S S Cl Cl S S Cl O O O O    

N –

9.17 The single C–N stretching frequency indicates a trans structure for the cyanides (the symmetric stretch of the C C—N bonds is not IR active), while the two C–O bonds O O C C indicate a cis structure for the carbonyls (both the Co symmetric and antisymmetric C–O stretches are IR Br Br

active). As a result, the bromo ligands are also cis. C

9.18 There are 18 isomers overall, six with the chelating ligand in a mer geometry and 12 with the chelating ligand in a fac geometry. All are enantiomers. They are all shown below, with dashed lines separating the enantiomers.

N N N N N N

P Br Br P P Br Br P P NH3 H3N P M M M M M M As OH2 H2O As As NH H3N As As OH H O As 3 2 2 NH NH OH 3 3 OH2 2 Br Br

N N N N N N

P OH2 H2O P P NH3 H3N P P OH2 H2O P M M M M M M As Br Br As Br As Br As As NH3 H3N As NH NH OH 3 3 OH2 2 Br Br

NH3 NH3 OH OH NH NH 2 2 3 3 P N N P P N N P P N N P M M M M M M As OH2 H2O As As NH3 H3N As As Br Br As

Br Br Br Br OH2 OH2

9.19 a.  b.  c.  d. 

9.20 All are chiral if the ring in b does not switch conformations.

9.21 20b  20c top ring: , bottom ring: 

O Mo S Mo 9.22 a, b. 1. Mo O Mo O Mo S Mo O O W OW Cs C3v

O Mo S Mo 2. Mo O Mo S Mo S Mo O SW OW Cs Cs

S Mo Mo S O Mo Mo O 3. Mo O O Mo Mo S S Mo Cr O O Cr Cr O O Cr Se W W Se Se W W Se

C1 C1 C1 C1

Se Mo Mo Se O Mo Mo O Mo O O Mo Mo Se Se Mo

Cr O O Cr Cr O O Cr SW SW SW SW C1 C1 C1 C1

S Mo S Mo Mo Se Mo Se

Cr O WO OW O Cr Cs Cs

c. Yes, provided the structure has no symmetry or only Cn axes. Examples are the structures with C1 symmetry in part a.

19 + 9.23 The F doublet is from the two axial fluorines (split by the equatorial fluorine). F

19 The F triplet is from the equatorial fluorine (split by the two axial fluorines). O Os F The two doubly bonded oxygens are equatorial, as expected from VSEPR O considerations. Point group: C2v F

9.24 Examples include both cations and anions:

– – – – – [Cu(CN)2] , [Cu2(CN)3] , [Cu3(CN)4] , [Cu4(CN)5] , [Cu5(CN)6]

+ + + + + [Cu2(CN)] , [Cu3(CN)2] , [Cu4(CN)3] , [Cu5(CN)4] , [Cu6(CN)5]

Based primarily on calculations (rather than experimental data), Dance et al. proposed linear structures such as the following:

– [Cu(CN)2] : NC—Cu—CN

– [Cu2(CN)3] : NC—Cu—CN—Cu—CN

– [Cu3(CN)4] : NC—Cu—CN—Cu—CN—Cu—CN

+ [Cu2(CN)] : Cu—CN—Cu

+ [Cu3(CN)2] : Cu—CN—Cu—CN—Cu

+ [Cu4(CN)3] : Cu—CN—Cu—NC—Cu—CN—Cu

Where 2-coordinate copper appears in these ions, the geometry around the Cu is linear, as expected from VSEPR.

9.25 The bulky mesityl groups cause sufficient crowding that the phosphine ligands can show H C chirality (C3 symmetry) and can be considered as similar to left-handed (PL) and 3 right-handed (PR) propellers. If two P(mesityl)3 phosphines are attached in a CH3 linear arrangement to a gold atom, three isomers are possible:

H3C PL—Au—PL PR—Au—PR PL—Au—PR mesityl

(PR—Au—PL is equivalent to PL—Au—PR, as can best be seen with models.) NMR data at low temperature support the presence of these isomers, which interconvert at higher temperatures.

 9.26 The point group is D3h. A representation based on the nine 1s orbitals  of the hydride ligands is:    D3h E 2C3 3C2  2S3 3 h v  Re  9 0 1 3 0 3 2  A1 1 1 1 1 1 0 z  E 2 –1 0 2 –1 0 (x, y), (x2–y2, xy)  A2 1 1 –1 –1 –1 1 z  E 2 –1 0 –2 1 0 (xz, yz) = H

The representation  reduces to 2 A1 + 2 E + A2 + ECollectively these representations match all the functions for s (totally symmetric, matching A1), p, and d orbitals of Re, so all the s, p, and d orbitals of the metal have suitable symmetry for interaction. (The strength of these interactions will also depend on the match in energies between the rhenium orbitals and the 1s orbital of hydrogen.)

9.27

N N N N N N O Cr O O Cr O O Cr O O O O O O O O O O O O O O O O Mn O O Mn O Mn O O Mn O O O O O O O O O O O O O O O O O Cr O O Cr O O Cr O N N N N N N

9.28 N

N N O O N Co N N N N O O N N N O O O Co O O Co O O N O N N N N

N N N N

N N N N O N O O O Co Co O O O O N N N O O N N N N Co N O O N N

9.29 a. Cu(acacCN)2: D2h tpt: C2v

b. C6

9.30 All four metal-organic frameworks studied (MOF-177, Co(BDP), Cu-BTTri, Mg2(dobdc) ) are significantly more effective at adsorbing carbon dioxide relative to adsorbing hydrogen. This is

attributed, in part, to the higher polarizability of CO2 relative to that of H2. The formation of an induced dipole in these gases by exposed cations within MOFs is an important prerequisite for

adsorption. The two MOF properties that most strongly correlate with CO2 adsorption capacity are MOF surface area and MOF accessible pore volume. As these values (tabulated below)

increase, the CO2 adsorption capacity increases.

MOF Surface Area ( m2 g ) Accessible Pore Volume ( cm3 g ) MOF-177 4690 1.59 Co(BDP) 2030 0.93 Cu-BTTri 1750 0.713

Mg2(dobdc) 1800 0.573

The graphs in Figure 1 of the reference clearly indicate that Mg2(dobdc) adsorbs the most CO2 2+ at 5 bar. The arrangement and concentration of open Mg cation sites on the Mg2(dobdc)

surface is hypothesized to render this MOF more susceptible to CO2 adsorption. This MOF, along with Cu-BTTri, which also features exposed metal sites, are identified as the best prospects

for CO2 H2 separation.

9.31 The synthesis and application of amine-functionalized MOFs for CO2 adsorption is the general

topic of the reference. While the M2(dobdc) series of MOFs were proposed as excellent candidates for this functionalization (on the basis of their relatively large concentration of exposed metal cation sites), their amine-functionalization proved difficult. This was attributed to

the relatively narrow MOF channels that may hinder amine diffusion into M2(dobdc) .

One hypothesized solution was to prepare a MOF with the M2(dobdc) structure-type, but with larger pores. The wider linker dobpdc (below, along with dobdc for comparison) was used in the hope of obtaining MOFs with larger pores.

O O

O O O

dobdc O O

dobpdc

Amine-functionalized Mg2(dobpdc)was prepared by mixing H4(dobpdc), magnesium bromide, and a small solvent volume (a mixture of N,N’-diethylformamide and ethanol) in a Pyrex

container. The mixture was heated in a microwave reactor, and the M2(dobpdc) collected by

filtration after cooling. Dried samples of Mg2(dobpdc)were then heated for roughly one hour at

420 °C under dynamic vacuum. After this “activation” step, Mg2(dobpdc)was stirred with an excess of N,N’-dimethylethylenediamine (mmen) in hexanes for one day. Subsequent heating under vacuum resulted in removal of residual solvents to afford mmen-functionalized

Mg2(dobpdc). The “activation” step was found necessary to completely remove residual N,N’- diethylformamide from the Mg2+ coordination sites.

9.32 This reference discusses application of porphyrin-containing MOFs where the porphyrin provides a binding site for Fe(III) and Cu(II). The precursor to the porphyrin linker (TCPP) is provided below; the resulting carboxylates of this linker permit its incorporation into the MOF.

HOOC COOH

N H

N N

H N

HOOC COOH

The metallation options include premetallation and postmetallation. In premetallation,

H4-TCPP-Cu and H4-TCPP-FeCl , respectively, are used as reactants for the MOF synthesis. In this case, the porphyrin linker and its bound metal ion are installed simultaneously into the MOF. This general approach afforded MOF-525-Cu, MOF-545-Fe, and MOF-545-Cu. MOF-525-Fe could not be obtained via this strategy. For this MOF, postmetallation was employed, via the reaction of MOF-525 with Fe(III) chloride; Fe(III) ions were introduced into the MOF-525 porphyrin linkers via this method.

In terms of similarities and differences, MOF-545 can be metallated with both Fe(III) and Cu(II) via a premetallation strategy, while MOF-525 requires alternate procedures for incorporation of Cu(II) (premetallation) and Fe(III) (postmetallation), respectively.