A Library of Bridging Modes
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0.140 mol) in water (150 mL). The reaction mixture was stirred
for 1 h at -10 °C and concentrated in vacuo to remove the
dimethoxyethane. The pale yellow solution was diluted with water
(150 mL) and treated with 50% aqueous citric acid (60 mL). A
voluminous solid was collected and washed with petroleum ether
giving the product as 0.86 g (72%). H NMR (CDCl3): δ 2.58 (t,
2H, CH2), 2.68 (q, 2H, CH2), 2.84 (q, 2H, CH2), 3.47 (q, 2H, CH2),
3.97 (d, 2H, CH2-Gly), 6.58 (br, 1H, NH), 6.76 (br, 1H, NH). Mass
spectrum: m/z 223.0574 ({M + H}+, calcd 223.0575). Elemental
analysis gave the atom ratio S/N ) 0.994; percentages indicated
an water/ether solvate. Anal. Calcd for C7H14N2O2S2‚1/2H2O
(example): C, 36.34; H, 6.54; N, 12.11; S, 27.72. Found: C, 37.04;
H, 5.95; N, 11.84; S, 26.94.
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to give 26 g of product (92%). H NMR (d6-DMSO): δ 2.20 (t,
2H, CH2), 2.40 (t, 2H, CH2), 3.60 (d, 2H, CH2 Gly), 7.33 (m, 15H,
aryl), 13.2 (br, 1H, CO2H). Mass spectrum: m/z 303 ({Ph3CSHEt}+,
100%).
(Et4N)2[{Ni(L-655)}2Ni] ((Et4N)2[23]). To a solution of 22g
(1.30 g, 5.85 mmol) in 20 mL of methanol was added a solution of
NaOMe (1.33 g, 24.6 mmol) in 30 mL of methanol. To the clear
yellow solution was added a methanolic solution (5 mL) of Et4-
NCl (1.94 g, 11.7 mmol), resulting in the appearance of a turbid
yellow solution. This solution was stirred for 20 min, and to it was
added dropwise a solution of Ni(OAc)2‚4H2O (1.46 g, 5.85 mmol)
in 60 mL of methanol. The initial pale yellow color of the solution
changed to red and then to dark green as the addition was
completed. This mixture was allowed to stir for 2 h, and solvent
was removed in vacuo. The residue was extracted with acetonitrile.
The extract was filtered and layered with ether to cause the
[3-(Triphenylmethylthio)propionyl]glycine, N-hydroxysuc-
cinimide ester (22d). To a cooled solution of 22c (20.0 g, 0.049
mol) and N-hydroxysuccinimide (5.63 g, 0.049 mol) in 200 mL of
dimethoxyethane was added dropwise a solution of dicyclohexy-
lcarbodiimide (12.7 g, 0.56 mol) in 40 mL of dimethoxyethane such
that the temperature remained below 0 °C. The yellowish suspension
was stirred overnight at 4 °C. It was filtered to give a colorless
filtrate and a white precipitate that was thoroughly washed with
dichloromethane (150 mL). The filtrate and washings were com-
bined, and solvent was removed in vacuo to give a yellowish solid,
which was washed with ethyl acetate and ether and dried in vacuo.
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The product was obtained as 16 g of solid (65%). H NMR (d6-
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precipitation of the product as 1.10 g (44%) of a green solid. H
DMSO): δ 2.20 (m, 4H, CH2), 2.70 (m, 4H, CH2 Su), 4.20 (d,
2H, CH2 Gly), 7.30 (m, 15H, aryl), 8.7 (t, 1H, NH). Mass
spectrum: m/z 303 ({Ph3CSHEt}+, 100%), 502 ({Ph3CSCH2CH2-
CO2Su + H}+, 25%).
NMR (DMSO-d6, anion): δ 1.72-2.50 (m, 16), 3.42 (t, 4), Mass
spectrum: m/z 615 ({M + H}+, 75%), 308 ({(M + 2H+)/2}2+
,
100%).
(Et4N)2[Ni(L-655)] ((Et4N)2[24]). To a solution of 22g (0.244
g, 1.1 mmol) in 20 mL of methanol was added a solution of NaOMe
(0.238, 4.40 mmol) in 5 mL of methanol. This mixture was added
slowly to a green solution of (Et4N)2[{Ni(L-655)}2Ni] (0.873 g,
1.00 mmol) in 75 mL of acetonitrile. The green color changed to
red. The reaction mixture was stirred for 10 min, and a solution of
Et4NCl (0.729 g, 4.00 mmol) in acetonitrile (10 mL) was added,
causing a precipitate of NaCl. The mixture was stirred for 30 min,
and solvent was evaporated to dryness. The pale pink solid was
extracted with acetonitrile and the extract was filtered. Ether was
layered on top of the filtrate. The solid that separated was washed
twice with ether and dried to give the product as 1.27 g (79%) of
pink solid. 1H NMR (CD3CN, anion): δ 1.65 (t, 2H), 1.80 (t, 2H),
2.03 (t, 2H), 2.69 (t, 2H), 3.37 (s, 2H). Mass spectrum: m/z 538
({M + H}+, 100%).
2-(Triphenylmethylthio)ethylamine (22e). A mixture of 2-mer-
captoethylamine hydrochloride (11.5 g, 0.10 mol) and triphenyl-
methanol (26.3 g, 0.10 mol) in trifluoroacetic acid (100 mL) was
stirred at room temperature for 30 min and evaporated to a dark
brown oil. Addition of ether (500 mL) resulted in immediate
discharge of color and formation of a white precipitate that was
filtered off, washed with ether, and dried. The ether washings gave
a further crop, with a combined yield of 29.5 g (67%). The
trifluoroacetate salt (14.0 g, 32.0 mmol) obtained in this manner
was partitioned between 1 M aqueous NaOH and ether. Evaporation
of the ether phase and recrystallization from ether/hexanes gave
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the product as 9.0 g (87%) of a white crystalline compound. H
NMR (d6-DMSO): δ 1.05 (s, 2H, NH2), 2.45 (m, 4H, CH2), 7.23
(m, 15H, aryl). Mass spectrum: m/z 320 ({Ph3CS(CH2)2NH3}+,
30%), 243 ({CPh3}+, 100%).
[{Ni(L-655)}Ni(depe)] (25). To a solution of (Et4N)2[Ni(L-655)]
(0.027 g, 0.05 mmol) in 4 mL of acetonitrile was added dropwise
an orange-yellow solution of [Ni(depe)Cl2] (0.021 g, 0.05 mmol)
in 2 mL of acetonitrile. The resulting dark red solution was stirred
for 1 h, the reaction mixture was filtered, and ether was introduced
into the filtrate. The product was obtained as 0.025 g (62%) of red
crystals. Mass spectrum: m/z 543 ({M + H}+, 100%).
[{Ni(L-655)}Ni(dppe)] (26). To a solution of (Et4N)2[Ni(L-655)]
(0.054 g, 0.10 mmol) in 10 mL of acetonitrile was added a
suspension of [Ni(dppe)Cl2] (0.053 g, 0.10 mmol) in 5 mL of
acetonitrile. The dark brown reaction mixture was stirred for 10 h
and filtered, and the filtrate was evaporated to dryness. The residue
was washed with acetonitrile and ether and was dried. The solid
was extracted with dichloromethane and filtered. Ether was
introduced into the filtrate, causing separation of the product as
0.042 g (58%) of red-brown crystals.
N-[3-(Triphenylmethylthio)propionyl]-N′-[2-(triphenylmeth-
ylthio)ethyl]glycinamide (22f). A solution of ester 22d (3.65 g,
7.3 mmol) and amine 22e (2.33 g, 7.3 mmol) were combined in
dichloromethane (100 mL); the yellowish solution was stirred at 0
°C for 3 h and stored at -20 °C overnight. The white precipitate
was filtered off, washed copiously with dichloromethane (100 mL),
and dried. The filtrate, washed with 5% NaHCO3 solution (3 × 50
mL), dried overnight over Na2SO4, evaporated in vacuo, and
recrystallized from dichloromethane gave a further batch for a total
yield of 5.0 g (97%). 1H NMR (d6-DMSO): δ 2.10-2.20 (m, 6H,
CH2), 2.96 (q, 2H, CH2), 3.56 (d, 2H, CH2 Gly), 7.33 (m, 10H,
aryl), 7.90 (t, 1H, NH), 8.10 (t, 1H, NH). Mass spectrum: m/z 708
({M + H}+, 70%), 243 ({CPh3}+, 50%).
[N-(2-Mercaptopropyl)-N′-(2′-mercaptoethyl)]glycinamide (22g).
To a solution of 22f (3.80 g, 5.38 mmol) was added trifluoroacetic
acid (20 mL); the mixture was cooled in an ice-bath at 0 °C. To it
was added dropwise triethylsilane (2.0 mL, 12.5 mmol), causing
the appearance of a white precipitate. The mixture was diluted with
hexanes (35 mL) and water (35 mL), and the aqueous layer was
separated and washed with hexanes (3 × 30 mL). The combined
aqueous extract was filtered and evaporated in vacuo to yield a
colorless oil. The oil was triturated with ether to yield an off-white
solid that was collected, washed with ether, and dried in vacuo,
(Et4N)2[{Ni(L-655)}2Cu] ((Et4N)2[27]). To a solution of (Et4N)2-
[Ni(L-655)] (0.050 g, 0.093 mmol) in 10 mL of acetonitrile was
added dropwise a solution of Cu(OTf)2 (0.017 g, 0.046 mmol) in
5 mL of acetonitrile. The dark green solution was stirred for 10 h
and filtered, and ether was layered onto the filtrate. The product
was obtained as 0.034 g (85%) of green microcrystals. Mass
spectrum: m/z 339 ({M - (Et4N)2[Ni(L-655)] + H}+, 85%).
Inorganic Chemistry, Vol. 43, No. 19, 2004 5837