7
2
H.-F. Han et al. / Polyhedron 99 (2015) 71–76
symmetric amidinatoaluminum complex synthesized from DCC
20]. We herein report the synthesis and characterization of three
new asymmetric guanidinato metal complexes, [{(C N}
AlCl (2)
). Our
(s, 6H, PhCH
(m, 4H, C ), 6.81–7.03 (m, 12H, C
d (ppm): 13.57 (CH CH ), 20.20 (PhCH
124.98, 125.52, 128.60, 128.98, 129.40, 134.40, 136.52, 143.49,
146.39 (C ), 165.55 (NCN).
3
), 2.66 (t, 4H, CH
2
CH
3
), 2.87 (t, 4H, CH
2
CH
). C NMR (CDCl , 25 °C):
), 42.80 (CH CH ), 123.16,
3
), 6.27
1
3
[
6
H
5
6
H
5
3
2
H
5
)
2
2
3
3
2
3
C(NC
and [{(C
6
H
5
)(NAr)LiOEt
N}C(NC
2
]
2
(1), [{(C
2
H
5
)
2
N}C(NC
6
H
5
) (NAr)]
2
2
H
5
)
2
6
H
5
)(NAr)] AlCH
2
3
(3) (Ar = 2,6-Me
2
C
6
H
3
6 5
H
report also includes their application in the Meerwein–Ponndorf–
Verley (MPV) reduction.
2 5 2 6 5 2 3 2 6 3
2.4. Synthesis of 3, [{(C H ) N}C(NC H )(NAr)] AlCH (Ar = 2,6-Me C H )
2
. Experimental
2.4.1. Method 1
To a stirred solution of diethylamine (0.30 mL, 3.0 mmol) in
hexane (15 mL), trimethylaluminum (0.75 mL, 1.5 mmol) was
added dropwise. The mixture was heated to 60 °C for 12 h and then
2
.1. General remarks
0
All manipulations were performed under a nitrogen atmo-
cooled to 0 °C, N-(2,6-dimethyl)phenyl-N -phenyl carbodiimide
sphere with rigorous exclusion of oxygen and water using standard
Schlenk and cannula techniques. Solvents were dried with appro-
priate drying agents, degassed, and stored over a potassium mirror
or activated molecular sieves (4 Å) prior to use. Deuterated solvent
(0.666 g, 3.0 mmol) was added. The mixture was stirred for 8 h to
afford a cloudy solution, which was filtered. The filtrate was con-
centrated to ca. 10 mL in vacuo and stored at ꢀ10 °C, yielding col-
orless crystals of 3 (85.5%).
6 6 3
C D and CDCl were dried over activated molecular sieves (4 Å)
and vacuum transferred before use. MeLi (1.6 M solution in hex-
ane; Alfa Aesar), n-BuLi (2.0 M solution in hexane; Alfa Aesar)
2.4.2. Method 2
To a stirred solution of 2 (0.651 g, 1.0 mmol) in diethylether
(25 mL), MeLi (0.63 mL, 1.0 mmol) was added dropwise at
ꢀ78 °C. The mixture was allowed to warm to room temperature
and stirred for an additional 8 h. After removal of volatiles in vacuo,
the resultant white solid was extracted into dichloromethane. The
filtrate of dichloromethane was evaporated in vacuo and the resi-
due was recrystallized from hexane to give colorless crystals of
and AlMe
commercially and used as received. ArN@C@NC
Me ) was prepared according to the literature procedures
21]. Diethylamine, aromatic and aliphatic aldehydes were dried
over MgSO and redistilled before use. Elemental analyses were
performed on a Vario EL-III instrument. H NMR (300 MHz) and
3
(2.0 M solution in hexane; Alfa Aesar) were obtained
6
H
5
(Ar = 2,6-
2 6 3
C H
[
4
1
1
3
C NMR (75 MHz) spectra of the compounds were recorded on a
compound 3 (77.6%). Anal. Calc. for C39H51AlN : C, 74.25; H, 8.15;
N, 13.32. Found: C, 74.12; H, 8.04; N, 13.45%. H NMR (CDCl3,
6
1
Bruker DRX 300 instrument and referenced internally to the resid-
ual solvent resonances (chemical shift data in d).
25 °C): d (ppm): ꢀ0.92 (s, 3H,AlCH ), 0.75(t, 12H, CH CH ) 1.98
3
2
3
(
s, 6H, PhCH
3
), 2.41 (s, 6H, PhCH
3
), 2.60 (q, 4H, CH
2
CH
3
), 2.83 (q,
4
C
H, CH
), 7.00 (d, 2H, C
), 12.73 (CH CH
CH ), 122.14, 124.41, 124.91, 128.76, 128.96, 129.13, 134.58,
35.58, 144.76, 148.16 (C ), 164.43 (NCN).
2
CH
3
), 6.11 (s, 4H, C
6
H
5
), 6.72 (d, 2H, C
). C NMR (C , 25 °C): d (ppm): 2.00
), 20.10 (PhCH ), 20.45 (PhCH ), 42.71
6 5
H ), 6.85 (t, 8H,
2
Me
.2. Synthesis of 1, [{(C
C H )
2 6 3
2 5 2 6 5 2 2
H ) N}C(NC H )(NAr)LiOEt ] (Ar = 2,6-
1
3
6
H
5
6
H
5
6 6
D
(
(
AlCH
CH
3
2
3
3
3
To a stirred solution of diethylamine (0.20 mL, 2.0 mmol) in
2
3
1
6 5
H
diethylether (10 mL), n-BuLi (0.91 mL, 2.0 mmol) was added
dropwise at 0 °C. The resulting mixture was slowly warmed to room
temperature for 2 h and then cooled to 0 °C, N-(2,6-dimethyl)phe-
2.5. Typical procedure employed for the Meerwein–Ponndorf–Verley
(MPV) reduction
0
nyl-N -phenyl carbodiimide (0.444 g, 2.0 mmol) was added. The
mixture was allowed to warm to room temperature and stirred for
an additional 4 h. The volatiles were removed under reduced pres-
sure. The residue was washed with pentane (2 ꢁ 5 mL) and dried
invacuotogivetheproductasa whitesolid, whichwasrecrystallized
from hexane–diethylether (1:1) solution at ꢀ5 °C to give the color-
To a solution of catalyst (0.4 mmol) in toluene (10 mL) was
added 2-propanol (8.0 mmol), followed by the addition of the alde-
hyde (4.0 mmol). The reaction mixture was then refluxed for the
required reaction time under an atmosphere of nitrogen. The reac-
tion was then cooled to room temperature and the conversion
2 6 2
less crystals of compound 1 (89.5%). Anal. Calc. for C46H68Li N O :
1
1
C, 73.57; H, 9.13; N, 11.19. Found: C, 73.44; H, 9.01; N, 11.31%. H
NMR (C , 25 °C): d (ppm): 0.69 (b, 6H, NCH CH ), 0.92 (t, 6H,
OCH CH ), 1.95 (s, 6H, PhCH ), 3.05 (b, 4H, NCH CH ), 3.08 (q, 4H,
OCH CH ), 6.54–6.93 (m, 8H, C ). C NMR (C , 25 °C): d
CH ), 15.37 (OCH CH ), 18.76 (PhCH ), 42.82
), 65.76 (OCH ), 118.14, 121.06, 121.86, 122.29, 129.26,
29.59, 142.16, 147.45, 148.50, 149.51 (C ), 164.99 (NCN).
yield was determined by H NMR spectroscopic study based on
the integration in the methylene and the CHO region.
6
D
6
2
3
2
3
3
3
2
3
13
2
6
H
5
6 6
D
3
. Results and discussion
(
(
ppm): 12.92 (NCH
NCH
2
3
2
3
3
2
2
3.1. Synthesis and characterization
1
6 5
H
As shown in Scheme 1, preparation of the starting material
2
Me
.3. Synthesis of 2, [{(C
2
H
5
)
2
N}C(NC
6
H
5
)(NAr)]
2
AlCl (Ar = 2,6-
Et
NC
1). [{(C
prepared via the salt-elimination reaction of compound 1 and
AlCl N}-
at ꢀ78 °C. Reaction of 2 with MeLi produced [{(C
C(NC )(NAr)] AlCH (Ar = 2,6-Me ) (3) which was also syn-
thesized by the insertion reaction of carbodiimides into Al–N bond
via one-pot reaction of Et NH, Al(Me) and carbodiimine.
Compounds 1–3 were prepared in good yield and easily purified
by recrystallization from the appropriate solvents. The results of
the elemental analyses for 1–3 are well in accordance with the cor-
responding supposed compositions (as shown in the Section 2).
Each of the compounds 1, 2 and 3 was characterized by 1H and
2
NH with n-BuLi and unsymmetric carbodiimine ArN@C@
gave [{(C N}C(NC )(NAr)LiOEt (Ar = 2,6-Me
N}C(NC )(NAr)] AlCl (Ar = 2,6-Me ) (2) was
2
6
C H
3
)
6
H
5
2
5
H )
2
6
H
5
2
]
2
2 6 3
C H )
(
2 5
H )
2
6
H
5
2
2 6 3
C H
To a stirred solution of 1 (0.751 g, 1.0 mmol) in diethylether
25 mL), AlCl
(
3
(0.133 g, 1.0 mmol) was added at ꢀ78 °C. The mix-
3
2 5 2
H )
ture was allowed to warm to room temperature and stirred for
an additional 8 h. After removal of volatiles in vacuo, the resultant
white solid was extracted into dichloromethane. The filtrate of
dichloromethane was evaporated in vacuo and the residue was
recrystallized from diethylether to give colorless crystals of com-
6
H
5
2
3
2 6 3
C H
2
3
,
pound 2 (80.5%). Anal. Calc. for C38
N, 12.90. Found: C, 69.96; H, 7.29; N, 12.98%. H NMR (CDCl
5 °C): d (ppm): 0.79 (t, 12H, CH CH ), 2.07 (s, 6H, PhCH ), 2.44
6
H48AlClN : C, 70.08; H, 7.43;
1
3
,
2
2
3
3