Article
Inorganic Chemistry, Vol. 50, No. 1, 2011 127
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(9.55 g, 91%). H NMR (CDCl3): δ 2.32 (s, CH3, 12H), 2.51
(t, CH2, J = 6.5 Hz, 4H), 2.66 (t, CH2, J = 6.5 Hz, 4H), 3.85
(s, CH3, 6H), 7.00 (s, arom. H, 2H), 9.91 (s, NH, 2H). 13C NMR
(CDCl3): δ 33.84 (CH2), 44.87 (N-CH3), 55.19 (CH2), 56.17
(O-CH3), 108.59 (aryl-C), 123.73 (aryl-C), 146.72 (aryl-C),
171.15 (amide-C). MS (ESIþ): m/z = 367.13 (MHþ), 389.13
(MNaþ), 733.28 (M2Hþ), 755.26 (M2Naþ).
[N2N2cat]ZrCl2 (4). Dark red/brown amorphous solid (2.68 g,
91%). Anal. Calcd. (Found) for C18H32N4O2Cl2Zr (%): C,
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43.36 (43.79); H, 6.47 (6.23); N, 11.24 (11.04). H NMR (CD-
Cl3, 253 K): δ 1.84 (d, br, CH2, J = 11.5 Hz, 2H), 2.00 (q, br,
CH2, J = 13.5 Hz, 2H), 2.37 (s, CH2, 6H), 2.66 (d, br, CH2, J =
12.5 Hz, 2H), 2.86 (s, CH3, 6H), 3.68 (s, br, CH2, 2H), 3.80 (s,
CH3, 6H), 3.87 (d, br, CH2, J = 13.5 Hz, 2H), 4.48 (t, br, CH2,
J = 13.0 Hz, 2H), 6.13 (s, arom. H, 2H). 13C NMR (CDCl3): δ
25.97 (CH2), 49.19 (CH2), 57.25 (N-CH3), 65.68 (O-CH3),
94.36 (aryl-C), 141.10 (aryl-C), 142.25 (aryl-C). UV-vis
(toluene) λmax/nm (ε/M-1 cm-1): 304 (15,000), 356 (6,000).
General Procedure for Synthesis of [N2N2cat]Ti(NMe2)2 (5) and
[N2N2cat]Zr(NMe2)2 (6). A barely thawed solution of [N2N2cat]-
MCl2 [M = Ti (3), Zr (4)] (0.44-0.50 mmol, 1 equiv.) in 10 mL of
toluene was added to a barely thawed suspension of LiNMe2 (2
equiv) in 7 mL of Et2O and stirred at room temperature overnight.
The reaction mixture was filtered, and the solvent was removed
under vacuum and co-evaporated twice with pentane yielding the
[N2N2cat]M(NMe2)2 complexes.
Using Gaseous Me2NH. A suspension of 1 (10.0 g, 28.6 mmol)
was stirred in 150 mL of CH2Cl2 at room temperature, through
which gaseous Me2NH was slowly bubbled. When the resultant
exotherm brought the solution close to reflux the solution was
allowed to cool to room temperature. This process was repeated
until thin layer chromatography (TLC) analysis in EtOAc
showed only material with Rf = 0. The now homogeneous
CH2Cl2 solution was washed with 1 M NaOH in 20% saturated
NaCl (3 ꢀ 100 mL). The combined aqueous layers were ex-
tracted with 100 mL of CH2Cl2, the combined organics were
dried with MgSO4 and the solvent removed under reduced
pressure. The residue was co-evaporated twice with Et2O,
resulting in quantitative yield of the product as a beige/brown
solid of sufficient purity to be used in subsequent reactions.
N,N0-Bis-(3-dimethylamino-propyl)-4,5-dimethoxy-benzene-1,
2-diamine, [N2N2cat]H2. Asolutionof2(6.96 g, 19.0 mmol) dissolved
in dry THF was added via cannula to a suspension of LiAlH4
(2.16 g, 57.0 mmol) in 20 mL of dry tetrahydrofuran (THF) cooled
in a dry ice/iPrOH bath under argon. After bubbling ceased, the
mixture was warmed to room temperature and then maintained at
reflux for 9 h to yield a yellow suspension. The mixture was cooled
in a dry ice bath, and water (20.0 mL, 1.11 mol) was slowly added to
quench the LiAlH4. The mixture was held at reflux overnight and
cooled to room temperature. The mixture was filtered through
Celite in an argon-filled glovebag, and the solvent was removed
from the filtrate using a rotary evaporator. The residue was distilled
(0.4 mtor, T > 140 °C) using a kugelrohr to yield a yellow oil (5.80
g, 90%). Anal. Calcd. (Found) for C18H34N4O2 (%): C, 63.87
(63.73); H, 10.12 (10.56); N, 16.55 (16.30). 1H NMR (C6D6): δ1.58
(quin., CH2, J = 6.5 Hz, 4H), 2.06 (s, CH3, 12H), 2.18 (t, CH2, J =
6.5 Hz, 4H), 3.02 (t, CH2, J = 6.5 Hz, 4H), 3.70 (s, CH3, 6H), 3.83
(s, br, NH, 2H), 6.55 (s, arom. H, 2H). 13C NMR (C6D6): δ
27.60 (CH2), 44.22 (CH2), 45.59 (N-CH3), 58.08 (CH2), 58.49
(O-CH3), 102.82 (aryl-C), 133.13 (aryl-C), 143.96 (aryl-C). MS
(ESIþ): m/z = 339.17 (MHþ), 377.19 (MKþ). UV-vis (C6H6)
[N2N2cat]Ti(NMe2)2 (5). Tacky, dark purple semi-solid, 88%.
1H NMR (C6D6): δ 1.74 (quin., CH2, J = 6.5 Hz, 4H), 1.95 (s,
CH3, 12H), 2.19 (t, CH3, J = 6.5 Hz, 4H), 2.97 (s, CH3, 12H),
3.81 (t, CH3, J = 6.5 Hz, 4H), 3.91 (s, CH3, 6H), 6.48 (s, arom.
H, 2H). 13C NMR (C6D6): δ 28.80 (CH2), 45.30 (N-CH3), 47.53
(N-CH3), 51.61 (CH2), 59.12 (CH2), 60.89 (O-CH3), 95.93
(aryl-C), 128.31 (aryl-C), 143.18 (aryl-C). UV-vis (toluene)
λ
max/nm (ε/M-1 cm-1): 322 (11,100), 382 (9,000), 538 (3,500).
[N2N2cat]Zr(NMe2)2 (6). Yellow solid, 86%. 1HNMR(C6D6):δ
1.54 (s, br, CH2, 4H), 1.88 (s, CH3, 12H), 2.19 (t, CH3, J = 5.5 Hz,
4H), 3.92-3.94 (m, CH3 þ CH2, 10H), 6.52 (s, arom. H, 2H). 13
C
NMR (C6D6): δ 25.88 (CH2), 44.08 (N-CH3), 47.67 (N-CH3),
47.77 (CH2), 59.46 (CH2), 65.53 (O-CH3), 96.01 (aryl-C), 128.31
(aryl-C), 145.04 (aryl-C). UV-vis (toluene) λmax/nm (ε/M-1
cm-1): 370 (11,400).
{[N2N2cat]Ti(μ-p-NC6H4Me)}2 (7). p-Toluidine (118 mg, 1.10
mmol) and KH (44.1 mg, 1.10 mmol) were combined in cold
THF and stirred at room temperature until the mixture was
homogeneous and no more bubbling was observed. This THF
solution was cooled in a cold well until nearly frozen, then
KH (44.1 mg, 1.10 mmol) and a cold solution of 3 (500 mg,
1.10 mmol) in THF were added, with a final solution volume of
50 mL. This mixture was warmed to room temperature and then
refluxed overnight under argon, during which time an inky-
brown color developed. Upon cooling to room temperature, the
THF was removed under vacuum, and the residue was extracted
into 50 mL of toluene and filtered. The solvent was removed
from the filtrate, and the residue was co-evaporated twice with
pentane to yield a brown/black, amorphous solid. This solid was
dissolved in a minimum amount of THF, then diluted with
pentane and held at -35 °C overnight. The resultant brown/
black powder was filtered and dried, yielding the clean product
(349 mg, 65%). 1H NMR (C6D6): δ 1.54 (s, br, CH2, 2H),
2.01-2.20 (m, br, CH2 þ CH3, 21H), 3.84 (s, CH3, 6H), 4.69 (s,
br, CH2, 4H), 6.19 (s, arom. H, 1H), 6.56 (s, arom. H, 1H), 6.78
(d, arom. H, J = 8.5 Hz, 2H), 6.97 (d, arom. H, J = 6.5 Hz, 2H).
13C NMR (C6D6): δ 20.76 (CH3), 26.30 (CH2), 28.73 (CH2),
46.09 (N-CH3), 48.98 (CH2), 49.00 (CH2), 55.98 (CH2), 56.00
(N-CH3), 58.37 (CH2), 58.54 (CH2), 65.06 (O-CH3), 67.80
(O-CH3), 96.85 (aryl-C), 97.17 (aryl-C), 121.28 (aryl-C), 128.84
(aryl-C), 129.54 (aryl-C), 141.80 (aryl-C), 141.84 (aryl-C),
141.98 (aryl-C), 144.517 (aryl-C), 144.90 (aryl-C), 159.56 (aryl-
C). UV-vis (C6H6) λmax/nm (ε/M-1 cm-1): 322 (22,000), 404
(16,800), 444 (15,800).
λ
max/nm (ε/M-1 cm-1): 316 (6,100).
General Procedure for Synthesis of [N2N2cat]TiCl2 (3) and
[N2N2cat]ZrCl2 (4). A solution of [N2N2cat]H2 (2.00 g, 5.91
mmol) in 60 mL of Et2O was frozen in a cold well. Immediately
upon thawing, a solution of nBuLi in hexanes (3.01 M, 3.93 mL,
11.8 mmol) was added, and the resultant suspension was stirred
at room temperature for 2 h, during which time the color
changed from pale purple to yellow. The solvent volume was
reduced to 2 mL under vacuum, and the residue was suspended
in 100 mL of toluene and frozen. To this slurry was added
MCl4(THF)2 (1.97 g for M = Ti and 2.23 g for M = Zr, 5.91
mmol), and the mixture was allowed to stir at room temperature
for 4 days. The deeply colored suspension was filtered, the
toluene removed under vacuum, and the residue was co-evapo-
rated once with pentane yielding clean [N2N2]MCl2 complexes.
Samples for crystallographic analysis were grown by cooling of
a toluene/cyclopentane solution at -35 °C.
[N2N2cat]TiCl2 (3). Dark purple, microcrystalline solid (2.26
g, 84%). H NMR (CDCl3): δ 2.22 (d, br, CH2, J = 14.0 Hz,
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2H), 2.36 (q, br, CH2, J = 14.5 Hz, 2H), 2.83 (s, CH3, 6H), 2.94
(s, CH3, 6H), 3.02 (d, br, CH2, 12.5 Hz, 2H), 3.57 (d, br, CH2,
J=12.5 Hz, 2H), 3.71 (s, CH3, 6H), 4.29 (t, br, CH2, J=12.5 Hz,
2H), 5.48-5.54 (m, br, arom. H þ CH2, 4H). 13C NMR
(CDCl3): δ 27.71 (CH2), 52.94 (CH2), 56.12 (N-CH3), 65.77
(O-CH3), 91.81 (aryl-C), 139.27 (aryl-C), 147.08 (aryl-C).
UV-vis (toluene) λmax/nm (ε/M-1 cm-1): 332 (5,400), 412
(10,400), 554 (1,700).
[N2N2cat]Ti(N3)2, (8). A mixture of 3 (200 mg, 0.439 mmol)
and NaN3 (62.8 mg, 0.966 mmol) was stirred in 15 mL of THF at
room temperature for 5 days. The solution was filtered, and
solvent was removed under vacuum. The residue was stirred in
10 mL of toluene, filtered, and the solvent was removed from the
filtrate under vacuum to yield a purple, microcrystalline solid