272 Organometallics, Vol. 25, No. 1, 2006
Milione et al.
AVANCE 400 operating at 300 and 400 MHz for 1H, respectively.
2H, J ) 6.7 Hz, Al-CH2CH(CH3)2), 0.23 (m, 2H, Al-CH2CH-
(CH3)2), 0.86 (dd, 6H, J1 ) 6.7 Hz, J2 ) 3.8 Hz, Al-CH2CH(CH3)2),
1.14 (dd, 2H, J1 ) 10.0 Hz, J2 ) 6.7 Hz, Al-CH2CH(CH3)2), 1.30
(s, 9H, 5-tBu-Ph), 1.57 (s, 3H, 3-CH3-Pz), 1.60 (s, 9H, 3-tBu-Ph),
1.73 (m, 1H, Al-CH2CH(CH3)2), 1.98 (m, 1H, Al-CH2CH(CH3)2),
1.84 (s, 3H, 3-CH3-Pz), 2.08 (s, 3H, 5-CH3-Pz), 2.18 (s, 3H, 5-CH3-
Pz), 5.41 (s, 1H, Pz-H), 5.61 (s, 1H, Pz-H), 6.78 (brs, 1H, 6-H-
Ar), 7.05 (s, 1H, -CH-), 7.55 (d, 1H, J ) 2.6 Hz, 4-H-Ar).
13C{1H} NMR (75 MHz, C6D6, 25 °C): δ 12.09, 12.15, 14.14,
14.29, 23.30 (br), 25.08 (br), 26.82, 26.98 28.64, 28.84, 28.95,
29.41, 31.08, 32.22, 34.57, 36.17, 77.27, 107.49, 108.57, 108.77,
122.52, 126.61, 127.45, 139.97, 140.63, 146.84, 147.67, 151.69,
159.34. 27Al NMR (104.23 MHz, toluene-d8, 100 °C): δ 142.5(W1/2
) 4360 Hz).
1
The H and 13C chemical shifts are referenced to SiMe4 using the
residual protio impurities of the deuterated solvents as external
reference. 27Al chemical shifts are reported versus Al(acac)3, and
11B and 19F chemical shifts are reported versus BF3(OEt2) and
CFCl3, respectively. Elemental analyses were performed with a
Perkin-Elmer 240-C. Infrared spectra were recorded on a FT-IR
Bruker Vector 22. AlMe3, AlEt3, and Al(iBu)3 (Aldrich) were
1
checked for purity by H NMR and used as received. B(C6F5)3,
[Ph3C][B(C6F5)4], and [HNMe2Ph][B(C6F5)4] were purchased from
Boulder Scientific and used as received. Bpzmp-H ligand was
synthesized according to the literature procedure.34 ꢀ-Caprolactone
(Aldrich) was degassed and dried over CaH2 overnight and then
freshly vacuum distilled before use.
Synthesis of (bpzmp)AlMe2 (1). A solution of AlMe3 (1.72
mmol) in hexane (2.52 mL, 0.682 M) was added to a solution of
bpzmp-H (0.520 g, 1.72 mmol) in hexane (50 mL, 0.0344 M) at
room temperature. Evolution of methane was observed. The
resulting pale yellow solution was stirred for 1 h. All volatiles were
removed in vacuo, and the residue was extracted with toluene (40
mL). Filtration followed by concentrating the pale yellow filtrate
and cooling the concentrated toluene solution at -10 °C afforded
a white crystalline solid. Yield: 0.535 g (68%). Single crystals
suitable for X-ray analysis were grown from saturated toluene
solution at -20 °C. Anal. Calcd for C27H41N4OAl‚1/2C7H8: C,
71.73; H, 8.88; N, 10.97. Found: C, 72.08; H, 8.94; N, 10.82.
Spectroscopic data for (bpzmp)AlMe2 (1): 1H NMR (400 MHz,
toluene-d8, 25 °C): δ -0.54 (bs, 6H, Al-CH3), 1.32 (s, 9H, 5-tBu-
Ph), 1.60 (s, 9H, 3-tBu-Ph), 1.81 (s, 6H, 3-CH3-Pz), 2.05 (s, 6H,
5-CH3-Pz), 5.46 (s, 2H, Pz-H), 6.81 (d, 1H, J ) 2.4 Hz, 6-H-Ar),
7.06 (s, 1H, -CH-), 7.58 (d, 1H, J ) 2.4 Hz, 4-H-Ar). 13C{1H}
NMR (100 MHz, C6D6, 25 °C): δ -7.42 (br), 12.25, 14.18, 30.71,
32.29, 34.60, 36.03, 77.52, 108.76, 121.77, 126.50, 127.40, 139.71,
140.67, 158.39. 27Al NMR (104.23 MHz, toluene-d8, 100 °C): δ
145.7(W1/2 ) 2684 Hz).
Synthesis of (bpzmp)AlEt2 (2). A solution of AlEt3 (1.22 mmol)
in hexane (5.00 mL, 0.244 M) was added to a solution of bpzmp-H
(0.500 g, 1.22 mmol) in hexane (50 mL, 0.0244 M) at room
temperature. Evolution of ethane was observed. The resulting pale
yellow solution was stirred for 1 h. The hexane solution was
concentrated and cooled at -10 °C, affording 0.324 g of a
crystalline white solid (54%). Single crystals suitable for X-ray
analysis were grown by recrystallization from hexane at -20 °C.
Anal. Calcd for C29H45N4OAl: C, 70.70; H, 9.21; N, 11.37.
Found: C, 70.88; H, 9.30; N, 11.25. Spectroscopic data for (bpzmp)-
AlEt2 (2): 1H NMR (400 MHz, toluene-d8, 25 °C): δ -0.10 (bs,
2H, Al-CH2CH3), 0.27 (bs, 2H, Al-CH2CH3), 1.23 (bs, 6H, Al-
CH2CH3), 1.32 (s, 9H, 5-tBu-Ph), 1.66 (s, 9H, 3-tBu-Ph), 1.77 (bs,
6H, 3-CH3-Pz), 2.10 (s, 6H, 5-CH3-Pz), 5.46 (bs, 2H, Pz-H), 6.73
(s, 1H, -CH-), 6.97 (d, 1H, J ) 2.4 Hz, 6-H-Ar), 7.53 (d, 1H, J
) 2.4 Hz, 4-H-Ar). Selected 13C{1H} NMR data (100 MHz, C6D6,
25 °C): δ 0.21 (vbr), 2.86 (vbr) 9.92, 12.20, 13.96, 30.61, 32.24,
34.56, 36.09, 77.56, 108.66 (br), 121.65, 126.55, 127.44, 139.66,
140.59, 158.94.
Synthesis of [(bpzmp)AlMe][MeB(C6F5)3] (4). In a 100 mL
round-bottom flask, (bpzmp)AlMe2 (1) (100 mg, 0.215 mmol) and
B(C6F5)3 (110 mg, 0.215 mmol) were added and dissolved in 20
mL of CH2Cl2. The resulting pale yellow solution was stirred for
30 min at room temperature and then evaporated to dryness to yield
a pale yellow foam. Trituration with cold hexane provoked the
precipitation of a colorless solid. The solvent was filtered off by
cannula and the solid residue dried under vacuum to afford
[(bpzmp)AlMe][MeB(C6F5)3] (4) as a colorless solid (150 mg, 70%).
Anal. Calcd for C45H41AlBF15N4O: C, 55,34; H, 4,23; N, 5,74.
Found: C, 55.97; H, 4.86; N, 5.42 Spectroscopic data for [(bpzmp)-
AlMe]+: 1H NMR (400 MHz, C6D6, 25 °C): δ -0.12 (s, 3H, Al-
CH3), 1.30 (s, 9H, 5-tBu-Ph), 1.43 (s, 9H, 3-tBu-Ph), 1.69 (s, 6H,
3-CH3-Pz), 1.77 (s, 6H, 5-CH3-Pz), 5.04 (s, 2H, Pz-H), 6.69 (s,
1H, -CH-), 6.94 (d, 1H, J ) 2.2 Hz, 6-H-Ar), 7.56 (d, 1H, J )
2.2 Hz, 4-H-Ar). Selected 13C{1H} NMR data (100 MHz, C6D6,
25 °C): δ -14.1 (Al-CH3), 10.6 (5-CH3-Pz), 12.1 (3-CH3-Pz), 29.9
(3-tBu-Ph), 31.8 (5-tBu-Ph), 72.7 (CH-), 109.4 (4-C-Pz), 125.1
(6-C-Ar), 129.1 (6-C-Ar). Spectroscopic data for [MeB(C6F5)3]-:
1H NMR (400 MHz, C6D6, 25 °C): δ 0.96 (BCH3). 13C{1H} NMR
(100 MHz, C6D6, 25 °C): δ 11.8 (BCH3). 19F NMR (376 MHz,
3
C6D6, 25 °C): δ -132.5 (d, JFF ) 19.4 Hz, 2F, o-C6F5), -164.9
3
3
(t, JFF ) 19.4 Hz, 2F, m-C6F5), -167.6 (t, JFF ) 19.4 Hz, 1F,
p-C6F5).
Generation of [(bpzmp)AlEt][EtB(C6F5)3] (5). In a glovebox,
equimolar amounts of (bpzmp)AlEt2 (2) (6 mg, 0.012 mmol) and
B(C6F5)3 (7 mg, 0.012 mmol) were added in a sample vial and
dissolved in 0.7 mL of C6D6. The resulting pale yellow solution
was transferred in a NMR tube (10 mm o.d.) and analyzed at 25
°C. Spectroscopic data for [(bpzmp)AlEt]+: 1H NMR (400 MHz,
C6D6, 25 °C): δ 0.47 (q, 2H, J ) 8.3 Hz, Al-CH2CH3), 1.31 (s,
9H, 5-tBu-Ph), 1.36 (t, 3H, J ) 8.3 Hz, Al-CH2CH3), 1.43 (s, 9H,
3-tBu-Ph), 1.74 (s, 6H, 3-CH3-Pz), 1.79 (s, 6H, 5-CH3-Pz), 5.07
(s, 2H, Pz-H), 6.71 (s, 1H, -CH-), 6.96 (d, 1H, J ) 2.4 Hz, 6-H-
Ar), 7.56 (d, 1H, J ) 2.4 Hz, 4-H-Ar). Selected 13C{1H} NMR
data (100 MHz, C6D6, 25 °C): δ -3.3 (Al-CH2CH3), 7.9 (Al-
CH2CH3), 10.9 (5-CH3-Pz), 12.2 (3-CH3-Pz), 29.9 (3-tBu-Ph), 31.8
(5-tBu-Ph), 72.8 (-CH-), 109.5 (4-C-Pz), 125.0 (6-C-Ar), 129.1
(4-C-Ar). Spectroscopic data for [EtB(C6F5)3]-: 1H NMR (400
MHz, C6D6, 25 °C): δ 1.08 (t, 2H, J ) 7.3 Hz, BCH2CH3), 1.72
(bq, 3H BCH2CH3). 13C{1H} NMR (100 MHz, C6D6, 25 °C): δ
13.2 (BCH2CH3), 15.4 (BCH2CH3). 19F NMR (376 MHz, C6D6,
25 °C): δ -131.9 (d, 3JFF ) 22.2 Hz, 2F, o-C6F5), -165.0 (t, 3JFF
Synthesis of (bpzmp)AliBu2 (3). A solution of AliBu3 (1.22
mmol) in hexane (5.00 mL, 0.244 M) was added to a solution of
bpzmp-H (0.500 g, 1.22 mmol) in hexane (50 mL, 0.0244 M) at
room temperature. Evolution of isobutane was observed. The
resulting pale yellow solution was stirred for 1 h and concentrated.
The resulting pale yellow solution was cooled at -10 °C, affording
0.467 g of a crystalline white solid (70%). Single crystals suitable
for X-ray analysis were grown by recrystallization from hexane at
-20 °C. Anal. Calcd for C33H53N4OAl: C, 72.22; H, 9.73; N, 10.21.
Found: C, 72.43; H, 9.81; N, 10.13. Spectroscopic data for (bpzmp)-
AliBu2 (3): 1H NMR (400 MHz, toluene-d8, 25 °C): δ 0.13 (q,
3
) 22.2 Hz, 2F, m-C6F5), -167.6 (t, JFF ) 22.2 Hz, 1F, p-C6F5).
Synthesis of [(bpzmp)AliBu][HB(C6F5)3] (6). In a 100 mL
round-bottom flask, (bpzmp)AliBu2 (3) (130 mg, 0.237 mmol) and
B(C6F5)3 (121 mg, 0.237 mmol) were added and dissolved in 20
mL of CH2Cl2. The resulting pale yellow solution was stirred for
30 min at room temperature and then evaporated to dryness to yield
a pale yellow foam. Trituration with cold hexane provoked the
precipitation of a colorless solid. The solvent was filtered off by
cannula and the solid residue dried under vacuum to afford
[(bpzmp)AliBu][HB(C6F5)3] (6) as a colorless solid (133 mg, 55%).
(34) (a) The, K. I.; Peterson, L. K. Can. J. Chem., 1973, 51, 422. (c)
Hammes, B. S.; Carrano, C. J. Inorg. Chem. 1999, 38, 3562.