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I Chem I - 11th Problem Assignment - Answers
Problems from R.-C.
Chapt. 19:
3. The higher oxidation states become increasing more stable as we go from the 4th
period to the 5th and the 6th, in each Group. However, within the 4th period, the most
stable/common oxidation states start out at the Group no. (4) for Ti and then go down
again to +3 for Cr, and then +2 for Mn. This oxidation state (+2) then remains the
most common one (at least in aqueous solution it is the most stable) through the
remainder of the 3d transition series through Cu, although +3 is also commonly found
for Fe and Co compounds (see Table 19.2 in Rayner-Canham)
Chapt. 18:
7.
N
N
N
N
N
Cl
Cl
N
N
Cl
Cl
cis (optical isomers)
10.
(a) [Cr(NH3)6]Br3
(b) [Co(NCS)(H2O)(en)2](NO3)2
(c) K2[Ni(CN)4]
(d) [Co(en)3]I3
11.
(a) [Mn(H2O)6](NO3)2
(b) Pd[PdF6]
(c) [CrCl2(H2O)4]Cl.2H2O
(d) K3[Mo(CN)8]
N
Co
Co
Co
N
Cl
N
N
N
Cl
trans
13.
N
N
N
N
N
ONO ONO
N
N
ONO
N
N
N
trans
N
NO2
ONO
(a)
N
Co
N
ONO
cis (optical isomers)
NO2
Co
Co
Co
N
ONO
N
N
(b) trans
19.
(a)
high spin
low spin
(b)
high spin
low spin
20. [FeCl4]2- is likely to be high spin because t is smaller than o and Cl- is relatively
low in the spectrochemical series (i.e., is a weak field ligand) (very few, if any,
tetrahedral complexes are low spin). On the other hand, [Fe(CN)6]3+, is quite likely to
be low spin, as CN- is high in the spectrochemical series (is a strong field ligand) and
Fe is in a +3 oxidation state (increases with increasing M oxidation state). Finally,
we are dealing with an octahedral complex (t = ca. 4/9 o).
22. The order of these ligands in the spectrochemical series is, F- < H2O < CN-; also
Cr4+ (in [CrF6]2-) would have a larger  than Cr3+.
24.
M2+
Sc2+ (unkn.)
Ti2+
V2+
Cr2+
Mn 2+
Fe2+
Co2+
Ni2+
dn
d1
d2
d3
d4
d5
d6
d7
d8
e m t2 n
e 1 t2 0
e 2 t2 0
e 2 t2 1
e 2 t2 2
e 2 t2 3
e 3 t2 3
e 4 t2 3
e 4 t2 4
-t
0.6
1.2
0.8
0.4
0
0.6
1.2
0.8
Cu2+
Zn2+
d9
d10
e 4 t2 5
e 4 t2 6
0.4
0
25. Ni2+(Fe3+)2O4; it should be inverse, since Fe3+ has no LFSE and Ni2+ has 1.2 o.
27. Ir(+I)
28. Fe2+ = d6; phen is a stronger field ligand than H2O and 3 phen are apparently
enough to overcome the spin pairing energy and produce low spin d6 Fe2+.
Additional problems:
1. (a) Give the highest known oxidation state for the following transition elements and
(b) choose the best ligand from the list (ii) in order to form a stable complex or
compound with it (do not use the same ligand more than once):
(i) Ti, Cr, Mn
(ii) O2-, S2-, F-, I-, Cl-, CO
Ti4+, Cl-; Cr6+, F- or O2-; Mn7+, O2- or F-
(c) For the following metal ions (or atoms), choose the best ligand from (ii) in order
to
form a stable complex or compound with it (again, do not use the same ligand more
than once):
(iii) Fe0, Cu+, W4+
Fe0, CO; Cu+, I- or S2-; W4+, I- or S2-
2. (a) Classify each of the following oxidation state situations into one of these three
groups: (i) common; (ii) possible under certain circumstances; or,
(iii) extremely unlikely or impossible:
Sc(IV), Cr(III), Cr(VI), Mn(0), Mn(II), Mn(VII), La(III), W(VI)
(i)
(ii)
(iii)
Likely: Cr(III), Mn(II),La(III), W(VI)
Possible: Cr(VI), Mn(0), Mn(VII)
Impossible: Sc(IV)
(b) For the oxidation states that you have placed in group (ii), possible under certain
circumstances, choose a ligand from the following list that would be most likely to
stabilize such an oxidation state:
Cl-, F-, O2-, S2-, or CO
Cr(VI), F- or O2-; Mn(0), CO; Mn(VII), F- or O23. Glycine has the structure NH2CH2COOH. It can lose a proton from the carboxyl group
and chelate through both the N and one of the O atoms. Draw structures for all possible
isomers of tris(glycinato)cobalt(III).
N
N
O
O
O
N
N
N
O
O
O
N
meridonal (optical isomers)
O
N
N
N
Co
Co
Co
Co
O
O
N
O
O
O
N
N
facial (optical isomers)
4. Give formulas for (a) pentaamminechlorocobalt(III) chloride; (b) hexaaquairon(3+)
nitrate; (c) cis-dichlorobis(ethylenediamine)ruthenium(II); (d) -hydroxobis[pentaammnechromium(III)] chloride.
(a) [CoCl(NH3)5]Cl2 ; (b) [Fe (H2O)6](NO3) 3 ; (c) [RuCl2(en)2] ;
(d) [(-OH){Cr(NH3)5}2]
5. (a) Give the formulas and draw the structures for the following complexes:
(i) cis-dichlorobis(ethylenediamine)cobalt(III)
(ii) fac-tricarbonyltris(triphenylphosphine)tungsten(0)
(iii) triaquatrithiocyanatomanganese(III) [thiocyanato = SCN-]
(i) see the first part of problem 18:7 above (from R.-C.)
(ii) [W(CO)3(PPh3)3];
P
(ii)
P
CO
O
C
S
S
C
N
OH2
(iii)
P
OC
(iii) [Mn(SCN)3(H2O)3]
OH2
OH2
C N
NC
N
C
S
facial, N-bonded SCN
OH2
OH2
H2O
OH2
OH2
S H2O
N
N C
CS
N
C
S
meridonal, N-bonded SCN
S
S
C
N
S C
N
facial, S-bonded SCN
other possible combinations of these isomers also exist
(b) Which, if any, of the above complexes are chiral (i.e., are optically active)?
Only the cis-[CoCl2(en)2]+
6. (a) Determine (i) the configuration [in the form (t2g)m(eg)n], (ii) the number of
unpaired electrons, and (iii) the Ligand Field Stabilization Energy (as a multiple of
) for each of the following octahedral complexes:
[Cr(NH3)6]3+, [Fe(CN)6]3-, [Ru(NH3)6]2+, [Cu(H2O)6]2+ , [Ni(H2O)6]2+
(i) (t2g)3(eg)0
(t2g)5(eg)0
(ii) 3
(iii) 1.2
(t2g)6(eg)0
1
2.0
(t2g)6(eg)3
0
2.4
(t2g)6(eg)2
1

0.6
2
1.2