FULL PAPER
CHN analyzer. NMR spectra were recorded with a Varian FT-400
spectrometer using standard VARIAN-FT software for NOESY-
1D, COSY, g-HSQC and g-HMBC. FTIR spectra were recorded
with a Bruker Tensor 27 spectrophotometer. [MgBz2(thf)2] and
{[Nb(CH2SiMe3)3(CH3CN)]2(μ-1,4-NC6H4N)} were prepared ac-
cording to literature procedures.[8b,11] Amines, diisopropylcarbodi-
imide and 2,6-dimethylphenyl isocyanide were purchased from Ald-
rich.
[d, 3JHH = 6.2 Hz, 12 H, CH(CH3)2], 1.20 [d, 3JHH = 6.1 Hz, 12 H,
CH(CH3)2], 1.59, 1.61 (AB, 2JHH = 10.2 Hz, 8 H, CH2SiMe3), 3.17
3
[m, 2 H, CH(CH3)2], 3.24 [m, 2 H, CH(CH3)2], 3.63 (d, JHH
=
3
3
9.4 Hz, NH), 7.01 (d, JHH = 7.5 Hz, 4 H, C6H4), 7.32 (d, JHH
= 7.5 Hz, 4 H, C6H4), 7.44 (s, 4 H, C6H4) ppm. 13C{1H} NMR
(100.6 MHz, C6D6): δ = 2.96 (SiMe3), 22.90 [CH(CH3)2], 25.25
[CH(CH3)2], 44.97 [CH(CH3)2], 46.62 [CH(CH3)2], 64.76
(CH2SiMe3), 115.05, 125.40, 126.37, 132.30, 147.55, 153.17 (C6H4),
164.52 (CN3) ppm. C48H88Br2N8Nb2Si4 (1235.23): calcd. C 46.67,
H 7.18; found C 46.75, H 7.25.
General Procedure for the Synthesis of Guanidines: In a glovebox,
amine (12.00 mmol), carbodiimide (12.00 mmol), 1.5%mol of
[MgBz2(thf)2] and toluene (10 mL) were added to a Schlenk tube.
The Schlenk tube was taken outside the glovebox and the reaction
was carried out at room temperature for 1 h. The solvent was re-
moved under reduced pressure and the residue was extracted with
diethyl ether, filtered to give a clear solution and the solution was
cooled to –40 °C to provide the solid guanidines as crystalline prod-
ucts. Identification was carried out by comparison with the NMR
spectroscopic data previously reported in the literature. Yields close
to 95% were obtained in ppm.
[{Nb(Me3SiCH2C=Nxylyl)2[(4-tBuC6H4)N=C(NiPr)(NHiPr)]}2(μ-
1,4-NC6H4N)] (8): In a glovebox, xylylNC (0.13 g, 1.00 mmol) was
added to a solution of 5 (0.30 g, 0.25 mmol) in toluene (10 mL).
The reaction mixture was stirred for 30 min and the solvents evapo-
rated to dryness in vacuo. The yellow oily material was redissolved
in pentane and cooled to –20 °C to afford yellow crystals of 8, yield
0.34 g (80 %). 1H NMR (400 MHz, C6D6): δ = 0.14 (s, 36 H,
3
3
SiMe3), 0.69 [d, JHH = 6.1 Hz, 12 H, CH(CH3)2], 1.32 [d, JHH
=
6.0 Hz, 12 H, CH(CH3)2], 1.29 (s, 18 H, tBu), 2.10 (s, 12 H,
2
Me2C5H3), 2.47 (s, 12 H, Me2C5H3), 3.06, 3.11 (AB, JHH
=
[{Nb(CH2SiMe3)2[(4-tBuC6H4)N=C(NiPr)(NHiPr)]}2(μ-1,4-
NC6H4N)] (5): 2-(4-tert-Butylphenyl)-1,3-diisopropylguanidine
(0.18 g, 0.66 mmol) in toluene (10 mL) was added to a solution of
{[Nb(CH2SiMe3)3(CH3CN)]2(μ-1,4-NC6H4N)} (0.30 g, 0.33 mmol)
in toluene (10 mL). The reaction mixture was stirred for 1 h at
room temperature. The resulting dark yellow solution was evapo-
rated to dryness in vacuo. The yellow solid was redissolved in pent-
ane and cooled to –20 °C for crystallization, to afford yellow crys-
3
10.0 Hz, 8 H, CH2SiMe3), 3.38 [m, 2 H, CH(CH3)2], 3.47 (d, JHH
= 10.6 Hz, NH), 3.51 [m, 2 H, CH(CH3)2], 6.83–7.25 (m, 24 H,
C6H4) ppm. 13C{1H} NMR (100.6 MHz, C6D6): δ = 0.31 (SiMe3),
19.54 (Me2C5H3), 19.85 (Me2C5H3), 23.41 [CH(CH3)2], 25.15
[CH(CH3)2], 31.51 [C(CH3)3], 32.58 (CH2SiMe3), 33.77 [C(CH3)3],
44.83 [CH(CH3)2], 46.06 [CH(CH3)2], 115.50, 121.10, 123.50,
124.66, 125.11, 130.76, 130.99, 140.19, 145.63, 145.96, 151.52
(C6H4), 161.60 (CN3), 230.84 (xylylN=CCH2SiMe3) ppm.
1
tals of 5, yield 0.31 g (80%). H NMR (400 MHz, C6D6): δ = 0.29
C
92H142N12Nb2Si4 (1714.35): calcd. C 64.46, H 8.35; found C
3
(s, 36 H, SiMe3), 0.67 [d, JHH = 6.2 Hz, 12 H, CH(CH3)2], 1.26
64.66, H 8.50.
[d, 3JHH = 5.7 Hz, 12 H, CH(CH3)2], 1.29 (s, 18 H, tBu), 1.60, 1.67
2
(AB, JHH = 10.0 Hz, 8 H, CH2SiMe3), 3.27 [m, 2 H, CH(CH3)2],
[{Nb(Me3SiCH2C=Nxylyl)2[(4-MeOC6H4)N=C(NiPr)(NHiPr)]}2
(μ-1,4-NC6H4N)] (9): The same procedure described for 8 was fol-
lowed, using 6 (0.30 g, 0.26 mmol) and 2,6-Me2C6H3NC (0.13 g,
1.05 mmol), yield 0.38 g (88%). 1H NMR (400 MHz, C6D6): δ =
3
3.49 [m, 2 H, CH(CH3)2], 3.74 (d, JHH = 9.0 Hz, NH), 7.28–7.32
(m, 8 H, C6H4), 7.35 (s, 4 H, C6H4) ppm. 13C{1H} NMR
(100.6 MHz, C6D6): δ = 2.96 (SiMe3), 23.12 [CH(CH3)2], 25.10
[CH(CH3)2], 31.60 [C(CH3)3], 34.26 [C(CH3)3], 44.58 [CH(CH3)2],
47.40 [CH(CH3)2], 63.60 (CH2SiMe3), 123.38, 125.78, 125.87,
1 4 4 . 9 6 , 1 4 5 . 4 7 , 1 5 2 . 7 5 ( C 6 H 4 ) , 1 6 4 . 1 1 ( C N 3 ) p p m .
C56H106N8Nb2Si4 (1189.65): calcd. C 56.54, H 8.98; found C 56.66,
H 9.01.
3
0.14 (s, 36 H, SiMe3), 0.71 [d, JHH = 5.8 Hz, 12 H, CH(CH3)2],
1.33 [d, 3JHH = 6.2 Hz, 12 H, CH(CH3)2], 2.09 (s, 12 H, Me2C5H3),
2
2.47 (s, 12 H, Me2C5H3), 3.02, 3.09 (AB, JHH = 10.3 Hz, 8 H,
CH2SiMe3), 3.36 [m, 2 H, CH(CH3)2], 3.44 (s, 6 H, OMe), 3.53 [m,
2 H, CH(CH3)2], 3.55 (m, NH), 6.58–7.06 (m, 24 H, C6H4) ppm.
13C{1H} NMR (100.6 MHz, C6D6): δ = –0.09 (SiMe3), 19.75
(Me2C5H3), 20.15 (Me2C5H3), 23.56 [CH(CH3)2], 25.41 [CH-
(CH3)2], 32.83 (CH2SiMe3), 45.03 [CH(CH3)2], 46.21 [CH(CH3)2],
55.19 (OMe), 113.78, 115.05, 122.29, 123.71, 124.15, 125.31,
131.16, 142.05, 146.13, 151.61, 153.11 (C6H4), 161.80 (CN3), 231.07
(xylylN=CCH2SiMe3) ppm. C86H130N12Nb2O2Si4 (1662.19): calcd.
C 62.14, H 7.88; found C 62.25, H 7.95.
[{Nb(CH2SiMe3)2[(4-MeOC6H4)N=C(NiPr)(NHiPr)]}2(μ-1,4-
NC6H4N)] (6): The same procedure described for 5 was followed,
using 2-(4-methoxyphenyl)-1,3-diisopropylguanidine (0.16 g,
0.66 mmol) and {[Nb(CH2SiMe3)3(CH3CN)]2(μ-1,4-NC6H4N)}
(0.30 g, 0.33 mmol) to afford yellow crystals of 6, yield 0.33 g
(89%). 1H NMR (400 MHz, C6D6): δ = 0.31 (s, 36 H, SiMe3), 0.70
[d, 3JHH = 6.3 Hz, 12 H, CH(CH3)2], 1.27 [d, 3JHH = 5.8 Hz, 12 H,
2
CH(CH3)2], 1.60, 1.68 (AB, JHH = 9.8 Hz, 8 H, CH2SiMe3), 3.27
[{Nb(Me3SiCH2C=Nxylyl)2[(4-BrC6H4)N=C(NiPr)(NHiPr)]}2(μ-
1,4-NC6H4N)] (10): The same procedure described for 8 was fol-
lowed, using 7 (0.30 g, 0.24 mmol) and 2,6-Me2C6H3NC (0.12 g,
0.97 mmol), yield 0.37 g (89%). 1H NMR (400 MHz, C6D6): δ =
[m, 2 H, CH(CH3)2], 3.37 (s, 6 H, OMe), 3.40 [m, 2 H, CH-
3
3
(CH3)2], 3.69 (d, JHH = 10.0 Hz, NH), 6.82 (d, JHH = 7.8 Hz, 4
3
H, C6H4), 7.21 (d, JHH = 7.8 Hz, 4 H, C6H4), 7.41 (s, 4 H,
C6H4) ppm. 13C{1H} NMR (100.6 MHz, C6D6): δ = 3.11 (SiMe3),
23.21 [CH(CH3)2], 25.23 [CH(CH3)2], 44.58 [CH(CH3)2], 47.48
[CH(CH3)2], 55.01 (OMe), 65.85 (CH2SiMe3), 114.73, 125.07,
126.34, 141.44, 153.16, 156.09 (C6H4), 164.50 (CN3) ppm.
C50H94N8Nb2O2Si4 (1137.49): calcd. C 52.79, H 8.33; found C
52.84, H 8.40.
3
0.09 (s, 36 H, SiMe3), 0.61 [d, JHH = 5.6 Hz, 12 H, CH(CH3)2],
1.25 [d, 3JHH = 5.7 Hz, 12 H, CH(CH3)2], 1.95 (s, 12 H, Me2C5H3),
2
2.43 (s, 12 H, Me2C5H3), 2.96, 3.02 (AB, JHH = 10.5 Hz, 8 H,
3
CH2SiMe3), 3.17 [m, 2 H, CH(CH3)2], 3.28 (d, JHH = 10.8 Hz,
NH), 3.39 [m, 2 H, CH(CH3)2], 6.60–7.24 (m, 24 H, C6H4) ppm.
13C{1H} NMR (100.6 MHz, C6D6): δ = 0.00 (SiMe3), 19.60
[{Nb(CH2SiMe3)2[(4-BrC6H4)N=C(NiPr)(NHiPr)]}2(μ-1,4- (Me2C5H3), 20.14 (Me2C5H3), 23.65 [CH(CH3)2], 25.20 [CH-
NC6H4N)] (7): The same procedure described for 5 was followed,
using 2-(4-bromophenyl)-1,3-diisopropylguanidine (0.19 g,
0.66 mmol) and {[Nb(CH2SiMe3)3(CH3CN)]2(μ-1,4-NC6H4N)}
(0.30 g, 0.33 mmol) to afford yellow crystals of 7, yield 0.37 g
(CH3)2], 32.92 (CH2SiMe3), 45.36 [CH(CH3)2], 46.30 [CH(CH3)2],
110.04, 123.21, 123.83, 125.59, 128.77, 131.03, 131.11, 145.98,
147.80, 151.77 (C6 H4 ), 161.80 (CN3 ), 230.73 (xylylN=
CCH2SiMe3) ppm. C84H124Br2N12Nb2Si4 (1759.93): calcd. C 57.33,
(90%). 1H NMR (400 MHz, C6D6): δ = 0.25 (s, 36 H, SiMe3), 0.61 H 7.10; found C 57.50, H 7.20.
Eur. J. Inorg. Chem. 2013, 2940–2946
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© 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim