Notes and references
z [SiF3(Me3tacn)][SiF5]: SiF4 gas was slowly bubbled into a solution of
Me3tacn (173 mg, 1.0 mmol) in 15 mL toluene with stirring for 2 h,
resulting in slow formation of a white precipitate. The volatiles were
removed under vacuum to leave a white solid, which was then washed
with hexane and dried. Yield: 4 90%. The NMR spectra show small
amounts of [SiF6]2ꢀ and Fꢀ (a common problem in fluorosilicate
systems);7 hence, satisfactory microanalytical data were not obtained.
ES+ mass spectrum (MeCN): m/z = 256 [SiF3(Me3tacn)]+; ESꢀ mass
spectrum (MeCN): m/z = 123 [SiF5]ꢀ. 1H NMR (300 MHz, 295 K,
CD2Cl2): 3.37 (m) [6H], 3.09 (m) [6H], 2.80 (s) [9H]. 19F{1H} NMR
(376.5 MHz, 295 K, CD2Cl2): ꢀ137.0 (br) [SiF5]ꢀ, ꢀ147.6 (s) 1JSiF
=
208 Hz. IR (Nujol/cmꢀ1): 882(s), 798(s), 770(sh), 751(m).
The preparation was also carried out in CH2Cl2, producing a
spectroscopically identical product. Mixing equivalent amounts of
[SiF3(Me3tacn)][SiF5] and Na[B{3,5-(CF3)2C6H3}4] in CH2Cl2,
followed by removal of NaF by filtration, gave [SiF3(Me3tacn)]-
[B{3,5-(CF3)2C6H3}4]. 19F{1H} NMR (376.5 MHz, 295 K,
Fig. 2 View of the structure of the cation in [SiF4{Me2N(CH2)2N-
(Me)(CH2)2NMe2(CH2Cl)}][SiF5] with atom numbering scheme.
Ellipsoids are drawn at the 50% probability level and H atoms are
omitted for clarity. Selected bond lengths (A) and angles (1): Si1–F1 =
1.634(3), Si1–F2 = 1.656(3), Si1–F3 = 1.645(3), Si1–F4 = 1.655(3),
Si1–N1 = 2.026(4), Si1–N2 = 2.069(4); N1–Si1–N2 = 86.02(17),
F–Si1–F (cis) = 91.05(15)–95.87(16).
1
CD2Cl2): ꢀ63.2 (s), ꢀ147.0 (s) JSiF = 205 Hz. ES+ mass spectrum
(MeCN): m/z = 256 [SiF3(Me3tacn)]+, ESꢀ mass spectrum (MeCN):
m/z = 863 [B{3,5-(CF3)2C6H3}4]ꢀ.
[SiF4{j2-Me2N(CH2)2N(Me)(CH2)2NMe2(CH2Cl)}][SiF5]: SiF4 was
bubbled slowly into a solution of pmdta (173 mg, 1.0 mmol) in 15 mL
CH2Cl2 with stirring for 1 h. The solvent was removed in vacuo, to
leave a white solid, which was washed with hexane and dried in vacuo.
1H NMR (295 K, CD2Cl2): 2.70 (br,s) [2H] CH2Cl, 2.43 (m) [4H] CH2,
2.34 (m) [4H] CH2, 2.21 (s) [3H], MeN, 2.18 (br,s) [12H] Me2N.
19F{1H} NMR (CD2Cl2): ꢀ125.4 (t), ꢀ126.2 (t), ꢀ137.0 (s), ꢀ153.7
(Fig. 2)z shows an octahedral silicon centre coordinated to
four fluorines with similar d(Si–F) to those in [SiF4(tmeda)]
(below), and with the triamine bound in a k2-mode. The ‘‘free’’
amine function is quaternised by a CH2Cl group resulting
from reaction with the solvent. An [SiF5]ꢀ anion pro-
vides electroneutrality. The spectroscopic data are also con-
sistent with this formulation, and there was no evidence
for formation of an SiF3N3 cation analogous to the Me3tacn
complex.
2
(t) JFF = 18 Hz. Colourless crystals of [SiF4{k2-Me2N(CH2)2-
N(Me)(CH2)2NMe2(CH2Cl)}][SiF5] were obtained by cooling
dichloromethane solution of the complex in a freezer.
a
[SiF4(tmeda)]: SiF4 gas was slowly bubbled into a solution of tmeda
(116 mg, 1.0 mmol) in 15 mL of CH2Cl2 for 30 min with stirring. The
solvent was removed under vacuum to leave a white solid, which was
recrystallised from CH2Cl2 solution. Yield: 495%. Anal. calc. for
C6H16F4N2Siꢂ1/4CH2Cl2: C, 31.1; H, 6.7; N, 11.6. Found: C, 31.4; H,
7.5; N, 11.9%. 1H NMR (300 MHz, CD2Cl2): 2.72 (s) [4H], 2.50 (s)
[SiF4(tmeda)]8 contains a distorted six-coordinate silicon centre
(Fig. 3) with chelating tmeda, and the 19F{1H} NMR spectrum
(CD2Cl2) shows two triplets, d = ꢀ132.6 (2JFF = 20 Hz,
1
1JSiF = 188 Hz), ꢀ150.9 (2JFF = 20 Hz, JSiF = 150 Hz), the
2
[12H]. 19F{1H} NMR (295 K, CD2Cl2): ꢀ132.6 (t) JFF = 20 Hz,
2
1
1JSiF = 188 Hz), ꢀ150.9 (t) JFF = 20 Hz, JSiF = 150 Hz). IR
(Nujol/cmꢀ1): 843(s), 801(s), 725(m). Colourless crystals of [SiF4(tmeda)]
were obtained from CH2Cl2 solution by cooling in a freezer for
several days.
higher frequency resonance being due to Si–FtransN
.
y Crystal data for [SiF3(Me3tacn)]Cl: a few air-stable crystals of
[SiF3(Me3tacn)]Cl were obtained by slow evaporation of the solvent
from an MeCN solution of the product obtained from a reaction in
CH2Cl2. C9H21ClF3N3Si, M = 291.83, trigonal, space group R3c
(no. 161), a = 8.779(2), c = 29.255(2) A, U = 1952.7(6) A3, Z = 6,
m(Mo-Ka) = 0.405 mmꢀ1, T = 120 K, 2633 reflections measured,
911 unique reflections, Rint = 0.053, 53 parameters refined, R1
(all data) = 0.065, R1 [I 4 2s(I)] = 0.059, wR2 (all data) = 0.156,
wR2 [I 4 2s(I)] = 0.151. Structure solution and refinement were
routine.9,10
z Crystal
NMe2(CH2Cl)}][SiF5]: C10H25ClF9N3Si2, M = 449.96, triclinic, space
data
for
[SiF4{j2-Me2N(CH2)2N(Me)(CH2)2-
ꢀ
group P1 (no. 2), a = 6.9707(15), b = 11.533(2), c = 12.264(2) A, a =
107.672(10), b = 95.625(10), g = 98.336(10)1, U = 918.9(3) A3, Z = 2,
m(Mo-Ka) = 0.425 mmꢀ1, T = 120 K, 17 682 reflections measured,
4177 unique reflections, Rint = 0.081, 231 parameters refined, R1
(all data) = 0.125, R1 [I 4 2s(I)] = 0.082, wR2 (all data) = 0.237,
wR2 [I 4 2s(I)] = 0.201. Structure solution and refinement were
routine.9,10
Fig. 3 View of the structure of [SiF4(tmeda)] with atom numbering
scheme. Ellipsoids are drawn at the 40% probability level and H atoms
are omitted for clarity. Selected bond lengths (A) and angles (1):
Si1–F1 = 1.6541(12), Si1–F2 = 1.6477(11), Si1–F3 = 1.6432(10),
Si1–F4 = 1.6448(12), Si1–N1 = 2.0409(17), Si1–N2 = 2.0463(14);
N1–Si1–N2 = 85.10(7), F–Si1–F (cis) = 92.68(5)–96.42(6).
8 Crystal data for [SiF4(tmeda)]: C6H16F4N2Si, M = 220.30, monoclinic,
space group P21 (no. 4), a = 6.3146(15), b = 10.648(2), c = 7.6840(15) A,
b = 112.180(10)1, U = 478.40(17) A3, Z = 2, m(Mo-Ka) = 0.265 mmꢀ1
T = 120 K, 5735 reflections measured, 2049 unique reflections, Rint =
,
Thus, the formation of a [SiF3(ligand)]+ cation appears to
be unique to Me3tacn, reflecting the very strong tendency of
this macrocycle to coordinate as a tridentate ligand, and
leading to a remarkably stable complex. In contrast to the
results2 with GeF4, attempts to obtain thioether complexes of
Si(IV), including with [9]aneS3, did not lead to complexation.
We thank RCUK for support (EP/C006763/1).
0.027, 122 parameters refined, R1 (all data) = 0.030, R1 [I 4 2s(I)] =
0.028, wR2 (all data) = 0.071, wR2 [I 4 2s(I)] = 0.069. Structure solution
and refinement were routine.9,10
1 Comprehensive Coordination Chemistry II, ed. J. A. McCleverty
and T. J. Meyer, Elsevier, Oxford, UK, 2004, vol. 9 and references
therein.
2 F. Cheng, A. L. Hector, W. Levason, G. Reid, M. Webster and
W. Zhang, Chem. Commun., 2008, 5508; M. F. Davis, W. Levason,
ꢁc
This journal is The Royal Society of Chemistry 2009
Chem. Commun., 2009, 1334–1336 | 1335