Hypercoordinate Aryltrialkyl Silanes and Stannanes
Organometallics, Vol. 16, No. 25, 1997 5497
primarily 8 and 9, was dissolved in a minimum amount of
hexane and separated using column chromatography (neutral
alumina). Elution with hexane:Et3N ) 97:3 gave a fraction
containing 9. Evaporation of this fraction in vacuo afforded
pure 9 as a white solid. Yield: 4.6 g (59%). 1H NMR (C6D6,
300 MHz): δ 3.74 (s, 8 H, CH2), 2.05 (s, 24 H, NMe2), 0.46 (s,
18 H, SiMe3). 13C NMR (C6D6, 75 MHz): δ 144.2, 143.7 (Ar),
61.9 (CH2), 44.7 (NMe2), 4.3 (SiMe3). 29Si NMR (C6D6, 59.6
MHz): δ -11.2 (SiMe3). Anal. Calcd for C24H50N4Si2: C,
63.93; H, 11.18; N, 12.43. Found: C, 63.77; H, 11.45; N, 12.33.
Further elution of the column with Et2O:Et3N ) 97:3 gave
a fraction containing 8, i.e., [Me3Si{C6(CH2NMe2)4-2,3,5,6}].
Concentration (in vacuo) of this fraction yielded a pale yellow
oil, which solidified at room temperature. Yield: 2.4 g (36%).
Mp: 38-41 °C. 1H NMR (CDCl3, 200 MHz): δ 7.12 (s, 1 H,
ArH), 3.61 and 3.45 (s, 4 H, NCH2), 2.16 and 2.02 (s, 12 H,
NMe2), 0.28 (s, 9 H, Me3Si). 13C NMR (CDCl3, 50 MHz): δ
144.9, 142.5, 135.5, 133.3 (Ar), 62.7, 60.4 (NCH2), 45.4, 44.8
(NMe2), 4.0 (Me3Si).
(a ) Gen er a l P r oced u r e for th e Rea ction s of Sila n es 5
a n d 9 a n d Sta n n a n es 6 a n d 10 w ith P d (OAc)2. A solution
of the silane or stannane in MeOH (∼1 M) was added to a
stirred solution of Pd(OAc)2 (1 molar equiv for 5 and 6, 2 molar
equiv for 9 and 10) in MeOH (∼1 M) at room temperature,
and the reaction mixture was stirred at this temperature until
all Pd(OAc)2 had been converted. A solution of excess LiCl in
MeOH (∼1 M) was then added at room temperature, and the
reaction mixture was stirred for 15 min at this temperature.
During this time a precipitate formed. The products in the
MeOH solution and in the precipitate that had formed were
1
analyzed by H and 13C NMR spectroscopy.
(b) Gen er a l P r oced u r e for th e Rea ction s of Sila n es 5
a n d 9 a n d Sta n n a n es 6 a n d 10 w ith [MCl2(COD)] (M )
P d , P t). A solution of the silanes or stannanes in CH2Cl2 (∼1
M) was added to a stirred solution of [MCl2(COD)] (M ) Pd,
Pt; 1 molar equiv for 5 and 6, 2 molar equiv for 9 and 10) in
CH2Cl2 (∼1 M) at room temperature, and the reaction mixture
was stirred at this temperature until all [MCl2(COD)] had been
converted. If during this time a white precipitate had formed,
this precipitate was filtered off, washed with CH2Cl2, and dried
in vacuo prior to analysis. The products in the CH2Cl2 solution
and in the precipitate (if formed) were analyzed by NMR
spectroscopy. The reaction of 10 with [PtCl2(COD)] in CH2Cl2
afforded [(Me2Sn)2-1,4-{C6(CH2NMe2)4-2,3,5,6}]2+(Cl-)2 (18a )
as a white solid. 1H NMR (D2O, 200 MHz): δ 3.88 (s, 8 H,
Syn th esis of [(Me3Sn )2-1,4-{C6(CH2NMe2)4-2,3,5,6}] (10).
n-BuLi (3.3 mL, 1.5 M solution in pentane, 5 mmol) was slowly
added over a period of 5 min to a stirred solution of 2 (0.92 g,
2 mmol) in THF (15 mL) at -78 °C. The reaction mixture
was allowed to warm to room temperature over a period of 30
min and stirred for an additional 30 min. Then a solution of
Me3SnCl (1.0 g, 5 mmol) in THF (10 mL) was added in one
portion, and the mixture was stirred for 2 h. The resulting
clear colorless solution was evaporated in vacuo to leave an
off-white oily residue which was extracted with hot hexane (4
× 25 mL). Concentration of the combined hexane extracts in
vacuo afforded 10 (0.67 g, 53%) as a white solid. Analytically
pure colorless crystals of 10 (mp 186-189 °C), suitable for an
X-ray analysis, were obtained by slowly cooling a saturated
solution of 10 either in warm benzene or in hot hexane. 1H
NMR (C6D6, 200 MHz): δ 3.52 (s, 8 H, NCH2), 1.98 (s, 24 H,
NMe2), 0.37 (s, 18 H, 2J SnH ) 50 Hz, Me3Sn). 13C NMR (C6D6,
50 MHz): δ 147.1 (1J SnC not observed, Cipso), 142.5 (2J SnC ) 49
2
NCH2), 2.50 (s, 24 H, NMe2), 0.81 (s, 12 H, J SnH ) 63 Hz,
Me2Sn). 13C NMR (D2O, 50 MHz): δ 143.2 (1J SnC not observed,
3
C
ipso), 141.2 (2J SnC ) 65 Hz, J SnC ) 40 Hz, Cortho), 63.2 (3J SnC
) 35 Hz, J SnC ) 11 Hz, NCH2), 48.1 (NMe2), -4.3 (1J SnC
)
4
453 and 434 Hz, SnMe2). Evaporation of the filtrate yielded
a pale yellow solid, identified as [PtClMe(COD)].
Syn t h esis of [Me2Sn {C6H 3(CH2NMe2)2-2,6}]+([Me3-
Sn Cl2]-) (14b). A stirred solution of Me3SnCl (270 mg, 1.35
mmol) and 6 (228 mg, 0.64 mmol) in CH2Cl2 (5 mL) was heated
at reflux temperature for 72 h. Then the reaction mixture was
evaporated in vacuo to ∼1 mL, and hexane (4 mL) was added,
which resulted in the precipitation of a white solid. This
precipitate was filtered off, washed with hexane (3 × 5 mL),
and dried in vacuo. Yield: 350 mg (95%) of a white solid,
identified as 14b. Colorless crystals (mp 154-157 °C) were
obtained by layering a solution of 14b in MeOH with Et2O.
1H NMR (D2O, 200 MHz): δ 7.41 (t, 1 H, 3J HH ) 7.5 Hz, ArH),
7.23 (d, 2 H, 3J HH ) 7.5 Hz, ArH), 3.82 (s, 4 H, NCH2), 2.44 (s,
12 H, NMe2), 0.82 (s, 6 H, 2J SnH ) 64 Hz, Me2Sn), 0.53 (s, 9 H,
2J SnH ) 68 Hz, Me3Sn). 13C NMR (D2O, 50 MHz): δ 145.3
(3J SnC ) 36 Hz, Ar), 138.4 (1J SnC not observed, Cipso), 133.8 (4J SnC
) 11 Hz, Ar), 128.5 (2J SnC ) 57 Hz, Ar), 66.3 (3J SnC ) 34 Hz,
CH2), 47.8 (NMe2), 1.5 (1J SnC ) 499 and 478 Hz, Me3Sn), -3.7
(1J SnC ) 454 and 434 Hz, Me2Sn). 119Sn NMR (CD3OD, 74.85
MHz): δ 72.0 (br s, cation), 34.1 (s, anion). Anal. Calcd for
14b corrected for 15 mol % loss of Me3SnCl: C, 36.48; H, 6.05;
N, 5.14. Found: C, 36.50; H, 6.20; N, 5.09.
3
Hz, J SnC ) 27 Hz, Cortho), 60.6 (3J SnC ) 26 Hz, CH2), 44.8
(NMe2), -1.9 (1J SnC ) 371 and 355 Hz, Me3Sn). 119Sn NMR
(C6D6, 75 MHz): δ -107.0 (s, 5J (119Sn,117Sn) ) 75 Hz, SnMe3).
Anal. Calcd for C24H50N4Sn2: C, 45.61; H, 7.97; N, 8.86.
Found: C, 45.65; H, 7.89; N, 8.81.
Rea ction of [Me3Sn {C6H(CH2NMe2)4-2,3,5,6}] w ith n -
Bu Li. To a stirred solution of C6H2(CH2NMe2)4-2,3,5,6 (0.10
g, 0.3 mmol) in hexane (3 mL) was added n-BuLi (0.2 mL, 1.6
M solution in hexanes, 0.32 mmol) in one portion. The reaction
mixture was stirred for 17 h at room temperature, and all
volatiles were evaporated in vacuo to afford a yellow oily
residue. This residue was dissolved in THF (4 mL), and to
this solution at room temperature was added solid Me3SnCl
(60 mg, 0.3 mmol) in one portion; the resultant reaction
mixture was stirred for 15 min at room temperature. After
this time, the volatiles were removed in vacuo and the
resulting oily residue was extracted with hexane (5 mL). The
hexane solution obtained from this procedure, which contains
mostly the monostannane [Me3Sn{C6H(CH2NMe2)4-2,3,5,6}],
was treated with n-BuLi (0.2 mL, 1.6 M solution in hexanes,
0.32 mmol) as described above and the mixture stirred for 17
h at room temperature. To this solution was added H2O (3
drops), and the reaction mixture was filtered through Celite.
Evaporation of the filtrate in vacuo yielded a yellow oily
residue, which was identified by 1H NMR spectroscopy (CDCl3
solution) as C6H2(CH2NMe2)4-1,2,4,5.
Rea ction s of Sila n es 5 a n d 9 a n d Sta n n a n es 6 a n d 10
w ith P d (OAc)2 a n d [M′Cl2(COD)] (M′ ) P d , P t). Reactions
were performed using typically 2 mmol of silane or stannane
and 2 (for 5 and 6) or 4 mmol (for 9 and 10) of palladium(II)
or platinum(II) substrate. Products were identified based on
reported NMR data: [M′Cl{C6H3(CH2NMe2)2-2,6}] (M′ ) Pd
(11),13 Pt (12)13,17), [(M′Cl)2-1,4-{C6(CH2NMe2)4-2,3,5,6}] (M′ )
Pd (15), Pt (16)),8b,c [M′ClMe(COD)] (M′ ) Pd15, Pt18), and
[Me2Sn{C6H3(CH2NMe2)2-2,6}]+Cl- (14a ).16
Syn th esis of [(Me2Sn )2-1,4-{C6(CH2NMe2)4-2,3,5,6}]2+
-
([Me3Sn Cl2]-)2 (18b). A stirred solution of Me3SnCl (250 mg,
1.26 mmol) and 10 (196 mg, 0.31 mmol) in CH2Cl2 (10 mL)
was heated at reflux temperature (∼40 °C) for 72 h, and this
resulted in the formation of a white precipitate. This precipi-
tate was filtered off, washed with CH2Cl2 (3 × 5 mL), and dried
in vacuo. Yield: 195 mg (59%) of 18b as a white solid, mp
>200 °C. Analytically pure colorless crystals, suitable for an
X-ray analysis, were obtained by slow evaporation in air of a
solution of 18b in a 1:1 mixture of MeOH and dibutyl ether.
1H NMR (D2O, 200 MHz): δ 3.62 (s, 8 H, NCH2), 2.45 (s, 24
2
H, NMe2), 0.76 (s, 12 H, J SnH ) 62 and 65 Hz, Me2Sn), 0.52
2
(s, 12 H, J SnH ) 66 and 69 Hz, Me3Sn). 13C NMR (D2O, 50
MHz): δ 143.2 (1J SnC not observed, Cipso), 141.2 (2J SnC ) 65
3
4
Hz, J SnC ) 40 Hz, Ar), 63.2 (3J SnC ) 35 Hz, J SnC ) 11 Hz,
CH2), 48.1 (NMe2), 1.5 (1J SnC ) 501 and 479 Hz, Me3Sn), -4.2
(1J SnC ) 453 and 433 Hz, Me2Sn). 119Sn NMR (CD3OD, 75
MHz): δ 53.6 (br s, 5J (119Sn,117Sn) ) 75 Hz, J SnC(Me) ) 453
1
1
1
Hz, J SnC(Ar) ) 730 Hz, dication), 35.2 (s, J SnC(Me) ) 489 Hz,