988 Organometallics, Vol. 30, No. 5, 2011
Table 1. Crystallographic Dataa for Compounds 2-4
Torvisco and Ruhlandt-Senge
2
3
4
formula
fw
MgN8Si2O2P2C30H64
711.32
13.85(8)
16.67(9)
18.84(9)
90
109.20(10)
90
4111.1(4)
4
P21/n
MgN8Si2O2P2C36H76
MgN11Si2O3P3C48H106
795.48
11.69(8)
11.69(8)
34.79(3)
90
90
90
4748(6)
4
1058.84
11.41(2)
21.72(4)
12.80(3)
90
100.03(3)
90
3127.3(6)
2
P21
˚
a (A)
˚
b (A)
˚
c (A)
R (deg)
β (deg)
γ (deg)
V (deg)
Z
space group
dcalcd (Mg/m3)
P4122
1.113
0.193
1.149
0.215
99(2)
1.124
0.188
96(2)
μ (mm-1
T (K)
)
97(2)
2θ range (deg)
no. of indep rflns
no. of params
R1, wR2 (all data)b
R1, wR2 (>2σ)b
1.67-25.00
7242
412
0.0516, 0.1375
0.0434, 0.1308
P
1.74-25.00
4152
240
0.0893, 0.1303
0.0577, 0.1159
P
2.61-28.07
10 956
631
0.0653, 0.1354
0.0570, 0.1311
P
P
Mo KR radiation (λ = 0.710 73 A). b R1 = ||Fo| - |Fc||/ |Fo|; wR2 = [ w(Fo2 - Fc2)2/ w(Fo2)2]1/2
.
a
˚
affected groups and included the refinement of the respective
occupancies. Compound 1 was found to contain a high degree of
positional disorder and refined using split positions for both ligands
(60/40) and HMPA molecules (70/30); however, important struc-
tural features were able to be elucidated.
Typical Experiment. nBu2Mg (1 mL, 1 mmol) was addedslowly
via syringe to a solution of the secondary amine (2 mmol) in 40 mL
hexanes. This was refluxed overnight to afford a clear solution.
The solution was then reduced in volume. A slight excess of
HMPA (2.5 mmol, 0.44 mL) was added via syringe to create a
cloudy suspension. Suitable crystals (colorless blocks) deposited at
room temperature.
(o-CH*) 114.7 (m-CH*), 122.4 (p-CH), 123.7 (o-CH), 144.4
(m-CH), 145.6 (i-C), 146.67 (i-C*). IR (cm-1): ν 2965 s, 2732 m,
2542 s, 1569 m, 1446 s, 1364 s, 1323 s, 1248 m, 1210 w, 1173 w,
922w, 832 w, 738 w, 479 w, 345 w.
Results
Synthetic Aspects. All compounds were synthesized using
alkane elimination, a reaction route utilized to synthesize a
variety of magnesium compounds in both high yield and
purity.14,16,35-38 This route is attractive due to the commer-
cial availability of dibutylmagnesium (n-/sec-Bu2Mg), straight-
forward reaction conditions, and ease of workup (eq 1). These
reactions have been shown to be solvent dependent; perform-
ing these reactions in the presence of polar solvents frequently
led to incomplete reactions.14,16 To avoid these issues, all
reactions were conducted in hexane. Donor adducts were easily
obtained by the addition of a donor to the hexane solutions
after the reaction took place.14,16
Mg[N(SiMe3)2]2(hmpa)2 (1). (2 mmol, 0.32 g, 0.42 mL) Yield:
1
0.99 g, 73%. Mp: 131-135 ꢀC. H NMR (300 MHz, 25 ꢀC,
C6D6): δH 0.549 (s, 36H, -SiCH3), 2.32 (d, 36H, HMPA). 13
C
NMR (300 MHz, 25 ꢀC, C6D6): δC 7.743 (-SiCH3), 37.21 (CH3
HMPA). IR (cm-1): ν 2916 s, 2882 m, 2723 m, 1450 s, 1377 s,
1298 m, 1210 w, 1182 w, 988 w, 902 s, 823 w, 360 w.
Mg[N(SiMe3)(Ph)]2(hmpa)2 (2). (2 mmol, 0.33 g, 0.35 mL)
Yield: 0.96 g, 63%. Mp:160-169 ꢀC. 1H NMR(300 MHz, 25 ꢀC,
C6D6): δH 0.618 (s, 18H, -SiCH3), 2.21 (d, 36H, HMPA), 6.03
(m, 4H, o-CH), 6.76 (m, 4H, p-CH), 7.28 (m, 8H, m-CH). 13C
NMR (300 MHz, 25 ꢀC, C6D6): δC 4.10 (-SiCH3), 36.71 (CH3
HMPA), 118.3 (m-CH), 126.0 (p-CH), 129.9 (o-CH), 162.1 (i-C).
IR (cm-1): ν 2953 s, 2723 m, 1574 m, 1458 s, 1372 s, 1303 s, 1258
m, 1210 w, 1172 w, 919 w, 823 w, 718 w, 489 w.
HMPA f
n-=sec-Bu2Mg þ 2HNðSiMe3ÞðRÞ
hexane; 65 ꢀC
Mg½NðSiMe3ÞðRÞꢀ2ðhmpaÞ2 þ 2BuH
ð1Þ
1 - 3
Mg[N(SiMe3)(Mes)]2(hmpa)2 (3). A white precipitate was
isolated and redissolved in toluene. The solution was filtered,
and crystals (colorless blocks) deposited at room temperature.
(2 mmol, 0.49 g, 0.45 mL) Yield: 0.94 g, 59%. Mp: 167-174 ꢀC.
1H NMR (300 MHz, 25 ꢀC, C6D6): δH 0.42 (s, 18H, -SiCH3),
2.12 (d, 6H, p-CH3), 2.17 (s, 12H, o-CH3), 2.44 (d, 36H, HMPA),
6.84 (s, 4H, m-CH). 13C NMR (300 MHz, 25 ꢀC, C6D6): δC 4.5
(-SiCH3), 36.71 (CH3 HMPA), 20.9 (p-CH3), 21.7 (o-CH3),
125.0 (p-CH), 129.1 (m-CH), 135.0 (o-CH), 153.6 (i-C). IR
(cm-1): ν 2957 s, 2723 m, 2552 s, 1569 m, 1446 s, 1372 s,
1303 s, 1268 m, 1210 w, 1172 w, 919 w, 823 w, 718 w, 489 w, 365 w.
[Mg{N(SiMe3)(Dipp)}(hmpa)3][N(SiMe3)(Dipp)] (4). (2 mmol,
0.49 g, 0.55 mL) Yield: 1.37 g, 65%. Mp: 180-185 ꢀC. 1H
NMR (300 MHz, 25 ꢀC, C6D6): δH 0.19 (s, 9H, -SiCH3*),
0.51 (s, 9H, -SiCH3), 1.08 (d, 12H, -CH(CH3)2*), 1.39 (d, 12H,
-CH(CH3)2), 2.20 (d, 54H, HMPA), 3.99 (m, 2H, -CH(CH3)2),
4.7 (m, 2H, -CH(CH3)2*), 6.77 (m, 4H, p-CH*), 6.99 (m, 4H, p-
CH), 7.09 (m, 8H, m-CH*), 7.12 (m, 8H, m-CH). 13C NMR (300
MHz, 25 ꢀC, C6D6): δC 4.3 (-SiCH3), 4.85 (-SiCH3*), 36.71
(CH3 HMPA), 25.52 (p-CH(CH3)2*), 26.48 (p-CH(CH3)2*),
27.57 (p-CH(CH3)2), 29.46 (p-CH(CH3)2), 106.4 (p-CH*), 111.4
R ¼ SiMe3 ð1Þ; Ph ð2Þ; Mes ð3Þ
Compounds 1-3 have been isolated using the above reaction
route (eq 1). For the bulkier HN(SiMe3)(Dipp), ligand d, addi-
tion of HMPA yielded a rare separated amido species 4 (eq 2).
HMPA f
n-=sec-Bu2Mg þ 2HNðSiMe3ÞðDippÞ
hexane; 65 ꢀC
½MgfNðSiMe3ÞðDippÞgðhmpaÞ3ꢀ½NðSiMe3ÞðDippÞꢀ
4
þ 2BuH
ð2Þ
(35) Wannagat, V. U.; Autzen, H.; Kuckertz, H.; Wismar, H.-J. Z.
Anorg. Allg. Chem. 1972, 394, 254.
(36) Engelhardt, L. M.; Jolly, B. S.; Junk, P. C.; Raston, C. L.;
Skelton, B. W.; White, A. H. Aust. J. Chem. 1986, 39, 1337.
(37) Bartlett, R. A.; Olmstead, M. M.; Power, P. P. Inorg. Chem.
1994, 33, 4800.
(38) Ruhlandt-Senge, K. Inorg. Chem. 1995, 34, 3499.