Organometallics
Article
yield). 1H NMR (400 MHz, C6D6) δ 19.96 (2H, Δv1/2 128 Hz, OR−
Ph), 18.95 (36H, Δv1/2 288 Hz, tBu), 16.93 (4H, Δv1/2 22 Hz, OR−
Ph), 9.84 (4H, Δv1/2 19 Hz, OR−Ph), 2.72 (6H, Δv1/2 58 Hz, OMe),
1.58 (8H, Δv1/2 23 Hz, CNR−Ph). IR (cm−1): 2955 (w), 2901 (w),
2168 (s), 1605 (w), 1505 (s), 1381 (w), 1303 (w), 1258 (s), 1065
(s), 1018 (m), 857 (s), 748 (m), 718 (m), 687 (w). λmax (εM) 731
(990), 550 (555). μeff = 3.6 0.4) μB (calcd 3.9). Anal. Calcd for
C46H60N2O4Co: C, 72.3; H, 7.9; N, 3.7. Found: C, 71.1; H, 7.5; N,
4.6.
2H, o-NC6H4), 7.12 (t, J = 8 Hz, 4H, p-Ph), 7.02 (t, J = 8 Hz, 1H, m-
NC6H3), 3.19 (s, 3H, Me).
1
Characterization of Ph2CCN(2-Cl-6-Me-C6H3) (8). H NMR
(400 MHz, C6D6) δ 7.40 (d, J = 8 Hz, 4H, o-Ph), 7.13 (t, J = 8 Hz,
4H, m-C6H3), 7.01 (t, J = 8 Hz, 2H, p-Ph), 6.99 (d, J = 8 Hz, 1H, m-
NC6H3Cl), 6.63 (d, 1H, m-NC6H3Me), 2.06 (s, 3H, Me).
Characterization of Ph2CCNAd (9). 1H NMR (400 MHz,
C6D6) δ 7.50 (d, J = 4 Hz, 4H, o-Ph), 7.19 (t, J = 4 Hz, 4H, m-C6H3),
7.03 (t, J = 4 Hz, 2H, p-Ph), 1.89 (s, 6H), 1.83 (s, 3H), 1.41 (t, J = 12
Hz, 6H).
Synthesis of Co(OR)2(CNAd)2 (5). A THF solution of adamantyl
isocyanide (74 mg, 0.46 mmol) was added to a stirred blue THF
solution of cobalt bis(alkoxide) 1 (74 mg, 0.12 mmol). There was an
immediate color change of the solution to dark red. The reaction was
stirred for 2 h, upon which the volatiles were removed in vacuo. The
resulting red residue was dissolved in ether, filtered, and placed in the
freezer overnight at −35°C to give a red powder (75 mg, 80% yield).
1H NMR (400 MHz, C6D6) δ 20.90 (2H, Δv1/2 39 Hz, OR−Ph),
General Procedure for Catalytic Formation of Ketenimines
in Table 1. A C6D6 solution of the isocyanide (12 equiv),
diazoalkane/diazoester (10 equiv), and TMB or hexamethylbenzene
(HMB) (1 equiv) was added to a stirred C6D6 solution of 2. A
notable color change occurred to either dark red (2,6-dimethylphenyl
isocyanide and adamantyl isocyanide) or dark brown (4-methox-
yphenyl isocyanide, cyclohexyl isocyanide, and benzyl isocyanide) for
methyl diazo(phenyl)acetate. A color change to orange occurred with
ethyl diazoacetate and all isocyanides except 4-methoxyphenyl
isocyanide and 2,6-dimethylphenyl isocyanide. Evolution of N2 was
observed in most cases. NMR of the reaction mixture was taken after
24 h, and yield was calculated with reference to internal standard.
Major byproducts were identified by NMR and GC-MS. All products
were confirmed by GC-MS analysis of silica plugs of each reaction.
Isolation of the ketenimines was done by removing all volatiles,
dissolving in a minimal amount of hexane, and passing through a
Pasteur pipet full of silica. HOR and standard were eluted via addition
of 50 mL of hexane to solvent. Product was obtained by passing a 40
mL solution 5−10% ether/hexane solution through the pipet. Low
isolated yields were obtained due to the high co-elution with HOR,
standard, and byproducts.
t
19.26 (36H, Δv1/2 204 Hz, Bu), 16.78 (4H, Δv1/2 16 Hz, OR−Ph),
10.02 (4H, Δv1/2 14 Hz, OR−Ph), 0.63 (2H, Δv1/2 33 Hz, Ad), −0.63
(6H, Δv1/2 23 Hz, Ad), −1.25 (6H, Δv1/2 20 Hz, Ad), −2.11 (6H,
Δv1/2 3 Hz, Ad), −4.50 (10H, Δv1/2 83 Hz, Ad). IR (cm−1): 2956
(w), 2902 (w), 2855 (w), 2122 (s),1450 (m), 1350 (w), 1312 (w),
1072 (3), 887(w), 710 (w). λmax (εM) 751 (240), 550 (340), 464
(160). μeff = 3.9 0.4 μB (calcd 3.9). Anal. Calcd for C52H76N2O2Co:
C, 76.2; H, 9.3; N, 3.4. Found: C, 75.9; H, 9.2; N, 3.4.
Reaction of 3 and Diphenyldiazomethane. A C6D6 solution of
diphenyldiazomethane (0.74 mL, 0.173 M) was added to a stirring
dark red C6D6 solution of 3 (49 mg, 0.064 mmol). The reaction was
stirred at room temperature for 5 h; no color change was observed. 1H
NMR showed unreacted diphenyldiazomethane and peaks character-
istic of 3.
Synthesis and characterization of ketenimines Ph2CCN(2,6-
Me2C6H3), Ph2CCN(4-OMe-C6H4), and Ph2CCNCy have
been previously described.19−21 Other ketenimines Ph2CCN(2-
Cl-6-Me-C6H3), Ph2CCNAd, (Ph)(COOMe)CCNAd,
(Ph)(COOMe)CCN(4-OMe-C6H4), (Ph)(COOMe)CC
NCy, (Ph)(COOMe)CCNBn, (H)(COOEt)CCNAd,
(H)(COOEt)CCNCy, and (H)(COOEt)CCNBn have
not been previously reported. All ketenimines reported in this work
Reaction of 5 and Ethyl Diazoacetate. A toluene solution of
ethyl diazoacetate (0.2 mL, 1.1 M) was added to a stirring dark red
C6D6 solution of 5 (90 mg, 0.11 mmol). A color change to dark
brown with vigorous gas formation was observed. Reaction was stirred
for 1 h at room temperature. NMR of the crude reaction mixture
shows formation of ketenimine, although peaks were broadened. The
1
reaction was filtered through a plug of silica. H NMR of the filtered
reaction mixture showed formation of ketenimine.
1
were identified by H NMR and GC-MS. The ketenimines which
Reaction of 1 and Methyl Diazo(phenyl)acetate. A hexane
solution of methyl diazo(phenyl)acetate (0.13 mL, 0.6 M) was added
to a stirring blue hexane solution of 1 (50 mg, 0.078 mmol). The
reaction turns teal immediately and dark brown within a minute. The
reaction was stirred at room temperature for 1 h. Volatiles were
removed in vacuo. NMR of the crude reaction mixture was taken in
C6D6 showing a hypothesized carbene (peaks assigned below) along
with unreacted diazoester. Volatiles were removed in vacuo and the
dark residue was dissolved in ether. Recrystallization at −35 °C gave
were obtained in high yields in catalytic reactions (Ph)(COOMe)C
CNCy and (H)(COOEt)CCNAd were further purified,
isolated as yellow oils, and characterized by 1H NMR and 13C
NMR. NMR signals for the observed ketenimines in entries 1 and 2
are reported above (for the stoichiometric reactions); they were also
observed in the catalytic NMR reactions. However, some of the peaks
were found to be hidden under starting material, due to the poor
catalytic performance with 2,6-dimethylphenyl isocyanide. For entry
3, Ph2CCNCy, the shifts were confirmed by comparing to
literature reports:21 1H NMR (400 MHz, C6D6) δ 7.46 (d, 4H, o-Ph),
7.18 (t, 4H, m-Ph), 7.08 (t, 2H, p-Ph), 3.29 (m, 1H, N−αCy), 1.87
(m, 2H, equatorial NCy), 1.51 (m, 2H, NCy), 1.3 (m, 3H, N−Cy),
0.96 (m, 3H, NCy).
1
colorless crystals of the respective olefin (13% yield). H NMR (400
MHz, C6D6) δ 37.73 (3 H, Δv1/2 384 Hz, PhCCO2Me), 21.95 (6H,
Δv1/2 180 Hz, PhCCO2Me), 16.67 (2H, Δv1/2 28 Hz, Ph−OR), 12.77
t
(2H, Δv1/2 36 Hz, Ph−OR), 9.49 (36H, Δv1/2 220 Hz, Bu−OR),
9.30 (4H, Ph−OR), 5.26 (2H, Δv1/2 36 Hz, Ph−OR).
Characterization of (Ph)(COOMe)CCN(4-OMe-C6H4) (entry
5). 1H NMR (400 MHz, C6D6) δ 7.91 (d, J = 8 Hz, 2H, o-Ph), 7.19 (t,
J = 8 Hz, 2H, m-Ph), 7.07 (d, J = 8 Hz, 2H, p-Ph−CNR), 7.03 (t, J =
8 Hz, 1H, p-Ph), 6.51 (d, J = 8 Hz, 2H, m-Ph−CNR), 3.44 (3H, s,
CO2Me), 3.13 (s, 3H, Ar−OMe).
General Procedure for Stoichiometric Formation of
Ketenimines 6−9. A C6D6 solution of the isocyanide (3 equiv)
and TMB (1 equiv) was added to a stirring C6D6 solution of 2 (1
equiv). A notable color change occurred to either dark red (2,6-
dimethylphenyl isocyanide and adamantyl isocyanide) or dark brown
(4-methoxyphenyl isocyanide and 2-chloro-6-methylphenyl isocya-
nide). NMR of the reaction mixture was taken after 1 h and yield was
calculated with reference to 1,3,5-trimethoxybenzene (TMB).
Products 619 and 720 have been previously reported. The formation
of ketenimines was also confirmed by GC-MS in all cases.
Characterization of Ph2CCN(2,6-Me2C6H3) (6). 1H NMR
(400 MHz, C6D6) δ 7.36 (d, J = 4 Hz, 4H, o-Ph), 7.13 (t, J = 4 Hz,
4H, m-Ph), 7.01 (t, J = 4 Hz, 2H, p-Ph), 6.83 (bs, 3H, NC6H3), 2.22
(s, 6H, Me).
Characterization of (Ph)(COOMe)CCNAd (entry 6). 1H
NMR (400 MHz, C6D6) δ 7.95 (d, J = 8 Hz, 2H, o-Ph), 7.27 (t, J
= 8 Hz, 2H, m-Ph), 7.02 (t, J = 8 Hz, 1H, p-Ph), 3.52 (s, 3H, Me),
1.84 (s, 6H, Ad), 1.77 (s, 3H, Ad), 1.35 (s, 6H, Ad).
Characterization of (Ph)(COOMe)CCNCy (entry 7). 1H NMR
(400 MHz, C6D6) δ 7.91 (d, J = 8 Hz, 2H, o-Ph), 7.24 (t, J = 8 Hz,
2H, m-Ph), 7.02 (t, J = 8 Hz, 1H, p-Ph), 3.33 (sept, J = 4 Hz, 1H,
CNH), 1.69 (m, 2H, Cy), 1.43 (m, 2H, Cy), 1.32 (m, 3H), 1.19 (m,
1H), 0.92 (m, 3H). 13C NMR (100 MHz, C6D6) δ 172.13 (−CC
N−), 168.92 (COOMe), 132.65 (ipso-Ph), 129.20 (o-Ph), 127.5 (m-
Ph), 126.2 (p-Ph), 61.40 (COOMe), 51.36 (Cy), 34.05 (Cy), 25.58
(Cy), 24.55 (Cy).
Characterization of Ph2CCN(4-OMe-C6H4) (7). 1H NMR
(400 MHz, C6D6) δ 7.44 (d, J = 8 Hz, 4H, o-Ph), 7.28 (d, J = 8 Hz,
C
Organometallics XXXX, XXX, XXX−XXX