Contakes et al.
Reaction of FeCl2 with Et4NCN under CO. Under a CO
atmosphere a solution of 0.127 g (1.00 mmol) of FeCl2 in 10 mL
of MeCN was treated with a solution of 0.624 g (4.00 mmol) of
Et4NCN in 10 mL of MeCN. After 8 h, the yellow solution was
evaporated to dryness, and the residue was redissolved in 10 mL
of H2O. The aqueous extract was then slowly added to a solution
of 0.75 g (2.0 mmol) of Ph4PCl in 10 mL of H2O. The white
precipitate of trans-(PPh4)2[Fe(CN)4(CO)2] (1) and cis-(PPh4)2[Fe-
(CN)4(CO)2] (2) was filtered off and then extracted into 5 mL of
MeCN. Addition of 50 mL of Et2O to the MeCN extract induced
precipitation of trans-(PPh4)2[Fe(CN)4(CO)2] (1). Yield: 0.345 g
(39%). The aqueous filtrate from above was added to a solution of
1.15 g (2.0 mmol) of PPNCl in 300 mL of H2O. The resulting
white precipitate (PPN)3[Fe(CN)5(CO)] (3) was collected by
filtration and washed with 10 mL of H2O and 25 mL of Et2O.
Colorless powders of 3 became yellow upon drying. Yield: 0.66 g
(36%).
and the disappearance of the reactant trans-[Fe(CN)4(CO)2]2- (1)
was monitored at 1999 cm-1. The reaction at 82 °C was complete
in 120 min.
Preparative Scale Reaction of trans-(PPh4)2[Fe(CN)4(CO)2]
(1) and CN-. A solution of 0.06 g (0.067 mmol) of trans-(PPh4)2-
[Fe(CN)4(CO)2] (1) and 0.025 g (0.068 mmol) of Ph4PCN in 10
mL of MeCN was warmed to reflux for 6 h. During this time the
reaction was monitored by IR spectroscopy. The IR spectrum
showed the formation of (PPN)3[Fe(CN)5(CO)] (3). The solution
was filtered to remove a small quantity of an insoluble impurity.
The filtrate was evaporated to dryness, and the residue was
redissolved in 5 mL of H2O. The aqueous solution was slowly added
to a solution of 0.75 g of PPNCl in 100 mL of H2O to precipitate
white 3. Yield: 0.098 g (79%).
Thermolysis of trans-(PPh4)2[Fe(CN)4(CO)2] (1). A solution
of 0.13 g of trans-(PPh4)2[Fe(CN)4(CO)2] (1) in 10 mL of MeCN
was warmed to reflux for 12 h to give a yellow precipitate and a
pale yellow solution. After removal of the yellow precipitate (0.01
g) by filtration, the colorless filtrate was evaporated to dryness.
The residue was washed with 10 mL of H2O to give a white
suspension of cis-(PPh4)2[Fe(CN)4(CO)2] (2) (0.004 g), which was
collected by filtration. The aqueous filtrate was added to a solution
of 0.5 g of PPNCl in 100 mL of H2O. The resulting white precipitate
was collected by filtration and washed with 6 mL of H2O and 25
mL of ether followed by drying in vacuo to produce a yellow solid
of (PPN)3[Fe(CN)5(CO)] (3). Yield: 0.112 g (42%).
trans-(PPh4)2[Fe(CN)4(CO)2] (1). IR (CH3CN): νCN ) 2103
(s); νCO ) 1999 (s) cm-1 13C NMR (126 MHz, CD3CN): δ 212.84
.
(s, Fe-CO), 140.58 (s, Fe-CN). Anal. Calcd for C54H44FeN4O4P2
(found): C, 69.68 (69.45); H, 4.76 (4.92); N, 6.02 (5.74).
(PPN)3[Fe(CN)5(CO)] (3). IR (CH3CN): νCN 2090 (w), 2075
(s); νCO 1932 (s) cm-1. IR (KBr): νCN ) 2090 (sh), 2075(s); νCO
) 1925 (s) cm-1. ESI-MS: m/z ) 1290.3 ([PPN]2[Fe(CO)(CN)5]),
724.5 ([PPN][Fe(CO)(CN)3]), 134.1 ([Fe(CN)3]). 13C NMR (126
MHz, CD3CN): 221.44 (s, Fe-CO), 157.77 (s, Fe-CN), 155.69
(s, Fe-CN). Anal. Calcd for C114H90FeN8OP6‚0.5H2O (found): C,
74.47 (73.96); H, 4.99 (4.67); N, 6.09 (6.39).
(PPN)2[Fe(CN)4(1,10-phenanthroline)]. A solution of 0.127 g
(1.0 mmol) of FeCl2 in 10 mL of MeCN was treated with 0.624 g
(4.00 mmol) of Et4NCN in 10 mL of MeCN, and a red solution
formed. After 1 h of stirring, 0.18 g (1.0 mmol) of 1,10-
phenanthroline in 5 mL of MeCN was added to the red solution
and the solution turned blue. The blue solution was stirred overnight
and then evaporated to dryness, and the residue was redissolved in
10 mL of H2O to get a red aqueous solution. The aqueous solution
was added to a solution of 1.5 g (2.6 mmol) of PPNCl in 300 mL
of H2O to give a blue precipitate, which was collected by filtration
and washed with 10 mL of H2O and 25 mL of ether followed by
drying in vacuo to give blue (PPN)2[Fe(CN)4(C12H8N2)]. Yield:
1.12 g (79%). IR (CH3CN): νCN ) 2062 (s), 2079 (m), 2102 (w)
cm-1. ESI-MS: m/z ) 878.4 ([PPN][Fe(CN)4(C12H8N2)]), 341 ([Fe-
Reaction of FeCl2 with Et4NCN under CO in Refluxing
MeCN. Under a CO atmosphere a solution of 0.127 g (1.00 mmol)
of FeCl2 in 10 mL of MeCN was treated with 0.624 g (4.00 mmol)
of Et4NCN in 10 mL of MeCN. After 8 h, the yellow solution was
warmed to reflux for 18 h, producing a yellow suspension. The
yellow solid (80 mg) (4) was collected by filtration. The colorless
filtrate was evaporated to dryness, and the residue was extracted
into 10 mL of H2O. The aqueous extract was then slowly added to
a solution of 0.38 g of Ph4PCl in 10 mL of H2O to give white
cis-(PPh4)2[Fe(CN)4(CO)2] (2). Yield: 0.082 g (9%). The aqueous
filtrate was added to a solution of 1.15 g (2.0 mmol) of PPNCl in
300 mL of H2O to give a white precipitate, which was collected
by filtration and washed with 10 mL of H2O and 25 mL of ether.
Yield: 0.98 g (54%). Note that (PPN)3[Fe(CN)5(CO)] (3) changes
(reversibly) from colorless to yellow upon dehydration.
1
(CN)4(C12H8N2)]), 134.1 ([Fe(CN)3]). H NMR (500 MHz, CD3-
CN): δ 7.60 (dd), 7.88 (s), 8.17 (dd), 9.75 (br).
Methylation of (PPN)3[Fe(CN)5(CO)] (3). Synthesis of cis-
(PPN)2[Fe(CN)4(CNMe)(CO)]. A solution of 0.125 g (0.068 mmol)
of (PPN)3[Fe(CN)5(CO)] (3) in 5 mL of MeCN was treated with 8
µL (0.068 mmol) of MeOTf at -20 °C. After 0.5 h, the yellow
solution was evaporated to dryness, and the residue was washed
with 20 mL of H2O. The solid was recrystallized from MeCN using
Et2O to give pale yellow microcrystals of cis-(PPN)2[Fe(CN)4-
(CNMe)(CO)] (5). Yield: 0.05 g (56%). IR (CH3CN): νCN ) 2189
(m), 2111 (w), 2102 (m), 2090(s); νCO ) 1972 (s) cm-1. ESI-MS:
m/z ) 767.3 ([PPN][Fe(CN)4(CNMe)(CO)]), 698.3 ([PPN][Fe-
(CN)4]), 134.1 ([Fe(CN)3]). 1H NMR (500 MHz, CD3CN): δ 3.30
(s, MeNC). 13C NMR (126 MHz, CD3CN): δ 217.13 (s, Fe-CO),
149.93 (s, Fe-CN), 148.31 (s, Fe-CN), 147.86 (s, Fe-CN), 147.63
(s, Fe-CN). Anal. Calcd for C79H63FeN7OP2 MeCN (found): C,
71.97 (72.43); H, 4.82 (4.90); N, 7.71 (7.92).
cis-(PPh4)2[Fe(CN)4(CO)2] (2). IR (CH3CN): νCN ) 2119 (w),
2108 (m); νCO ) 2042 (s), 1994 (s) cm-1. ESI-MS: m/z ) 555.4
([PPh4][Fe(CN)4(CO)2]), 499.4 ([PPh4][Fe(CN)4]), 134.1 ([Fe-
(CN)3]). 13C NMR (126 MHz, CD3CN): δ 211.85 (s, Fe-CO),
141.83 (s, Fe-CN), 139.68 (s, Fe-CN). Anal. Calcd for C54H40-
FeN4O2P2 (found): C, 72.49 (72.60); H, 4.51 (4.35); N, 6.26 (6.60).
Yellow Solid (4). IR (KBr): 2995 (w), 2954 (w), 2215 (w), 2094
(s), 1995 (s), 1484 (m), 1456 (m), 1396 (m), 1307 (w), 1261 (w),
1184 (m), 1174 (m), 1035 (w), 1004 (m), 788 (m), 630 (m), 586
(m), 530 (w), 495 (m).
Reaction of 4 with Et4NCN. A solution of 0.05 g of Et4NCN
in 8 mL of MeCN was treated with 0.03 g of polymer 4. After 30
min, the polymer was completely dissolved and checked by IR
spectroscopy, which showed the formation of [Fe(CN)5(CO)]3-
.
Dimethylation of (PPN)3[Fe(CN)5(CO)] (3). A solution of 0.125
g of (PPN)3[Fe(CN)5(CO)] (3) in 5 mL of MeCN was treated with
16 µL (0.137 mmol) of MeOTf at -20 °C. After 0.5 h, the yellow
solution was evaporated to dryness, and the residue was washed
with 20 mL of H2O. The solid was recrystallized from MeCN using
Et2O to give white microcrystals of fac-(PPN)[Fe(CN)3(CNMe)2-
Kinetics Study of the Reaction of trans-(PPh4)2[Fe(CN)4(CO)2]
(1) and CN-. A solution of 0.07 g (0.078 mmol) of trans-(PPh4)2-
[Fe(CN)4(CO)2] (1) in 5 mL of MeCN (or EtCN) was treated with
0.122 g (0.78 mmol) of Et4NCN at 51, 63, 82, and 96 °C. The
buildup of product [Fe(CN)5(CO)]3- (3) was observed at 1932 cm-1
,
1676 Inorganic Chemistry, Vol. 41, No. 6, 2002