Lanthanum and alkali metal coordination chemistry of the bis(dimethylphenylsilyl)amide ligand

Article abstract of DOI:10.1021/ic052091c

The coordination chemistry of the bis(dimethylphenylsilyl)amide ligand, [N(SiMe₂Ph)₂]^1-, with sodium, potassium, and lanthanum has been investigated for comparison with the more commonly used [N(SiMe₃)₂]^1- and [N(SiHMe₂) ₂]^1- ligands. HN(SiMe₂Ph)₂ reacts with KH to produce KN(SiMe₂Ph)₂, 1, which crystallizes from toluene as the dimer [KN(SiMe₂Ph)₂(C ₇H₈)]₂, 2. The structure of 2 shows that the [N(SiMe₂Ph)₂]^1- ligand can function as a polyhapto ligand with coordination from each phenyl group as well as the normal nitrogen ligation and agostic methyl interactions common in methylsilylamides. Each potassium in 2 is ligated by an η⁴-toluene, two bridging nitrogen atoms, and an η²-phenyl, an η¹-phenyl, and an η¹-methyl group. KN(SiMe₂Ph)₂ crystallizes from toluene in the presence of 18-crown-6 to make the monometallic complex (18-crown-6)KN(SiMe₂Ph)₂, 3, in which [N(SiMe₂Ph)₂]^1- functions as a simple monodentate ligand through nitrogen. The reaction of HN(SiMe₂Ph) ₂ with NaH in THF at reflux for 2 days generates Na[N(SiMe ₂Ph)₂], 4, which crystallizes as the solvated dimer {(THF)Na[μ-η¹:η¹-N(SiMe₂Ph) ₂]}₂, 5. A lanthanide metallocene derivative of [N(SiMe₂Ph)₂]^1- was obtained by reaction of K[N(SiMe₂Ph)₂] with [(C₅Me₅) ₂La]-[(μ-Ph)₂BPh₂]. Crystals of (C ₅Me₅)₂La[N(SiMe₂Ph)₂], 6, show agostic interactions between lanthanum and methyl groups of each silyl substituent. The [N(SiMe₃)₂]^1- analogue of 3, (18-crown-6)KN(SiMe₃)₂, 7, was also structurally characterized for comparison.

Full text of DOI:10.1021/ic052091c

Inorg. Chem. 2006, 45, 3437−3443
Lanthanum and Alkali Metal Coordination Chemistry of the
Bis(dimethylphenylsilyl)amide Ligand
William J. Evans,* Daniel B. Rego, and Joseph W. Ziller
Department of Chemistry, UniVersity of California, IrVine, California 92697-2025
Received December 6, 2005
The coordination chemistry of the bis(dimethylphenylsilyl)amide ligand, [N(SiMe2Ph)2]1-, with sodium, potassium,
-
and lanthanum has been investigated for comparison with the more commonly used [N(SiMe3)2]1- and [N(SiHMe2)2]1
ligands. HN(SiMe2Ph)2 reacts with KH to produce KN(SiMe2Ph)2, 1, which crystallizes from toluene as the dimer
-
[KN(SiMe2Ph)2(C7H8)]2, 2. The structure of 2 shows that the [N(SiMe2Ph)2]1 ligand can function as a polyhapto
ligand with coordination from each phenyl group as well as the normal nitrogen ligation and agostic methyl interactions
common in methylsilylamides. Each potassium in 2 is ligated by an
η
4-toluene, two bridging nitrogen atoms, and
an
η
2-phenyl, an
η
1-phenyl, and an
η
1-methyl group. KN(SiMe2Ph)2 crystallizes from toluene in the presence of
18-crown-6 to make the monometallic complex (18-crown-6)KN(SiMe2Ph)2, 3, in which [N(SiMe2Ph)2]1 functions
-
as a simple monodentate ligand through nitrogen. The reaction of HN(SiMe2Ph)2 with NaH in THF at reflux for 2
days generates Na[N(SiMe2Ph)2], 4, which crystallizes as the solvated dimer
A lanthanide metallocene derivative of [N(SiMe2Ph)2]1- was obtained by reaction of K[N(SiMe2Ph)2] with [(C5Me5)2La]-
{(THF)Na[µ- :η }2, 5.
η1 1-N(SiMe2Ph)2]
[(
µ
-Ph)2BPh2]. Crystals of (C5Me5)2La[N(SiMe2Ph)2], 6, show agostic interactions between lanthanum and methyl
-
groups of each silyl substituent. The [N(SiMe3)2]1 analogue of 3, (18-crown-6)KN(SiMe3)2, 7, was also structurally
characterized for comparison.
Introduction
[N(SiHMe2)2]1- 10-15 has also proven to be useful as a
precursor and offers steric flexibility that can be used to
advantage.
While the [N(SiHMe2)2]1- ligand provides a sterically
smaller alternative to [N(SiMe3)2]1-, silylamide ligands with
greater steric bulk, such as [N(SiMe2Ph)2]1-,16-19 {N[SiMe2-
(OSiMe3)]2}1-,16 {N[SiMe2(OPh)]2}1-,16 [N(SiPh3)2]1-,17
Bulky silylamide ligands, [N(SiR3)2]1-, have played an
important role in the development of low coordinate chem-
istry for a variety of metals.1-3 In the f element area, the
most commonly used silylamide, [N(SiMe3)2]1-, has provided
rare examples of low coordinate complexes accessible for
all the metals, typically in good yield.3-6 [N(SiMe3)2]1-
complexes of the lanthanides are structurally interesting3-6
and have proven to be excellent precursors to a variety of
other f element compounds.3-9 The less sterically crowded
(9) Bradley, D. C.; Ghotra, J. S.; Hart, F. A.; Hursthouse, M. B.; Raithby,
P. R. J. Chem. Soc., Dalton Trans. 1977, 1166.
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Am. Chem. Soc. 2000, 122, 1544.
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E.; Spiegler, M. J. Chem. Soc., Dalton Trans. 1998, 847.
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(15) Estler, F.; Herdtweck, E.; Anwander, R. J. Chem. Soc., Dalton Trans.
2002, 3088.
* To whom correspondence should be addressed. E-mail: wevans@uci.edu.
(1) Bradley, D. C. Chem. Br. II 1975, 393.
(2) Lappert, M. F.; Power, P. P.; Sanger, A. R.; Srivastava, R. C. Metal
and Metalloid Amides. Synthesis, Structures, and Physical and
Chemical Properties; 1980.
(3) Bradley, D. C.; Ghotra, J. S.; Hart, F. A. J. Chem. Soc., Dalton Trans.
1973, 1021.
(4) Bradley, D. C.; Ahmed, M. Polyhedron 1983, 2, 87.
(5) Ghotra, J. S.; Hursthouse, M. D.; Welch, A. J. J. Chem. Soc., Chem.
Commun. 1973, 669.
(16) Veith, M.; Koban, A.; Fries, K.; Spaniol, P.; Elsa¨sser, R.; Rammo,
A.; Huch, V.; Kleinsteuber, U. Organometallics 1998, 17, 2612.
(17) Chen, H.; Bartlett, R. A.; Rasika Dias, H. V.; Olmstead, M. M.; Power,
P. P. J. Am. Chem. Soc. 1989, 111, 4338.
(6) Andersen, R. A.; Templeton, D. H.; Zalkin, A. Inorg. Chem. 1978,
17, 2317.
(7) Evans, W. J.; Lee, D. S.; Ziller, J. W. J. Am. Chem. Soc. 2003, 126,
454.
(8) Evans, W. J.; Lee, D. S.; Rego, D. B.; Perotti, J. M.; Kozimor, S. A.;
Moore, E. K.; Ziller, J. W. J. Am. Chem. Soc. 2004, 126, 14574.
(18) Carmalt, C. J.; Mileham, J. D.; White, A. J. P.; Williams, D. J.; Steed,
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10.1021/ic052091c CCC: $33.50
Published on Web 03/14/2006
© 2006 American Chemical Society
Inorganic Chemistry, Vol. 45, No. 8, 2006 3437

Evans et al.
[N(SiMePh2)2]1-,20,21 and [NR(SiMe3)]1- (R ) Ph,22 C6H3iPr2-
After 2 days, solvent was removed in vacuo, and the solids were
extracted with toluene. Recrystallization from toluene and subse-
quent removal of solvent in vacuo gave 1 as a white powder (16.086
t
2,6,22,23 SiMe2 Bu,24 mesityl24), are not so readily available.
None has been ligated to an f element to our knowledge.
This report addresses the use of the larger silylamide
ligand bis(dimethylphenylsilyl)amide, [N(SiMe2Ph)2]1-, in
f element chemistry. A lithium salt of this amide, Li2[µ-
N(SiMe2Ph)2]2,16 has been structurally characterized, and
iron,17 copper,19 gallium,18 and tin25 derivatives have been
made. Since in synthetic f element chemistry, lithium readily
forms “ate” salt adducts,26,27 sodium and potassium precursors
are often preferred. We report here the synthesis and
structural characterization of potassium and sodium salts of
the [N(SiMe2Ph)2]1- ligand as well as the first f element
complex of this silylamide. For the latter purpose, the
favorable coordination environment of a bis(pentamethyl-
cyclopentadienyl) system was used, and the tetraphenylborate
salt, [(C5Me5)2Ln][(µ-Ph)2BPh2],28 was employed as an
effective precursor.
1
g, 83%). H NMR (THF-d8) δ 0.09 (s, 12 H, N(SiMe2Ph)2), 7.08
(t, 2H, p-N(SiMe2Ph)2), 7.15 (t, 4H, m-N(SiMe2Ph)2), 7.66 (d, 4H,
o-N(SiMe2Ph)2). 13C NMR (THF-d8) δ 5.9 (N(SiMe2Ph)2), 127.0
(p-N(SiMe2Ph)2), 127.5 (m-N(SiMe2Ph)2), 134.5 (o-N(SiMe2Ph)2),
152.5 (i-N(SiMe2Ph)2). 1H NMR (C6D6) δ 0.29 (s, 12H, N(SiMe2-
Ph)2), 7.21 (m, 6H, N(SiMe2Ph)2), 7.52 (d, 4H, o-N(SiMe2Ph)2).
13C NMR (C6D6) δ 6.1 (N(SiMe2Ph)2), 128.7 (N(SiMe2Ph)2), 133.5
(o-N(SiMe2Ph)2), 149.9 (i-N(SiMe2Ph)2). Anal. Calcd for C16H22-
Si2NK: C, 59.37; H, 6.80; N, 4.33. Found: C, 59.47; H 7.17; N,
4.33. IR 3069m, 3049w, 2957m, 2362m, 2343w, 1957w, 1891w,
1814w, 1772w, 1749w, 1718w, 1698w, 1687w, 1671w, 1652w,
1556w, 1525m, 1428m, 1251s, 1181s, 1116s, 1000s, 930s, 830s,
830s, 799s, 768s, 726m, 699s cm-1. At -35 °C over 1-3 days, a
concentrated sample of 1 in toluene produced colorless X-ray quality
crystals of [KN(SiMe2Ph)2(C7H8)]2, 2, in the space group C2/c.
Colorless X-ray quality crystals of 2 in the space group P1h can be
obtained from a concentrated sample of crude 1 in THF. A solution
of 1 (110 mg, 0.34 mmol) and 18-crown-6 (91 mg, 0.34 mmol) in
ca. 2 mL toluene at -35 °C, over 1-2 days, produced colorless
crystals of (18-crown-6)KN(SiMe2Ph)2, 3‚1/2(C7H8).
Experimental Section
The manipulations described below were performed under
nitrogen with the rigorous exclusion of air and water using Schlenk,
vacuum line, and glovebox techniques. [(C5Me5)2La][(µ-Ph)2BPh2]28
Synthesis of NaN(SiMe2Ph)2, 4, and {(THF)Na[µ-η1:η1-
N(SiMe2Ph)2]}2, 5. HN(SiMe2Ph)2 (1.998 g, 7.00 mmol) was
sparged with nitrogen and cannulated onto a suspension of NaH
(0.207 g, 8.63 mmol) in ca. 30 mL of THF. The solution was heated
at reflux under nitrogen for 2 days. The solvent was removed in
vacuo and gummy off-white solids were extracted with toluene.
The mixture was filtered, and the toluene was removed to give an
off-white solid that was washed with a minimal amount of THF to
leave a white solid. This was recrystallized from toluene at -35
°C over 1-3 days to form {(THF)Na[µ-η1:η1-N(SiMe2Ph)2]}2, 5.
Crystals of 5 were crushed to a powder, dried under vacuum, and
recrystallized from methylcyclohexane to give 4 as a white powder
(1.739 g, 81%). 1H NMR (THF-d8) δ 0.09 (s, 12H, N(SiMe2Ph)2),
7.08 (t, 2H, p-N(SiMe2Ph)2), 7.15 (t, 4H, m-N(SiMe2Ph)2),
7.67 (d, 4H, o-N(SiMe2Ph)2). 13C NMR (THF-d8) δ 5.9 (N(SiMe2-
Ph)2), 127.1 (p-N(SiMe2Ph)2), 127.5 (m-N(SiMe2Ph)2), 134.6 (o-
N(SiMe2Ph)2), 152.2 (i-N(SiMe2Ph)2). 1H NMR (C6D6) δ 0.36 (s,
12H, N(SiMe2Ph)2), 7.22 (m, 6H, N(SiMe2Ph)2), 7.60 (d, 4H,
o-N(SiMe2Ph)2). 13C NMR (C6D6) δ 5.7 (N(SiMe2Ph)2), 128.7,
128.8 (N(SiMe2Ph)2), 133.5 (o-N(SiMe2Ph)2), 145.0 (i-N(SiMe2Ph)2).
Anal. Calcd for C16H22Si2NNa: C, 62.48; H, 7.21; N, 4.55.
Found: C, 62.44; H 7.55; N, 4.05. IR 3366w, 3015m, 2953s,
2895m, 2358w, 2328w, 1957w, 1884w, 1818w, 1772w, 1749w,
1718w, 1648w, 1590m, 1556m, 1525m, 1428s, 1320m, 1301m,
1251s, 1177s, 1108s, 1050s, 1050s, 1000m, 925s, 845s, 799s, 741s,
29
and Y[N(SiMe3)2]3 were made according to the literature. KH
and NaH were purchased from Aldrich and washed with hexanes
before use. 18-Crown-6 was purchased from Aldrich and placed
under vacuum overnight before use. Diphenyltetramethyldisilazane
was purchased from Gelest and used as received. Solvents were
sparged with argon and dried using GlassContour columns.30 NMR
solvents were dried over sodium potassium alloy, degassed, and
vacuum transferred before use. 1H NMR and 13C NMR spectra were
recorded with Bruker 500 MHz and DRX 400 MHz spectrometers.
Infrared spectra were recorded as thin-films obtained from benzene
using an ASI ReactIR 1000 spectrometer.31 Elemental analyses were
performed by Desert Analytics (Tucson, AZ) or by complexometric
titration.32
Synthesis of KN(SiMe2Ph)2, 1, [KN(SiMe2Ph)2(C7H8)]2, 2,
and (18-Crown-6)KN(SiMe2Ph)2, 3. HN(SiMe2Ph)2 (17.056 g,
59.73 mmol) was sparged with nitrogen and cannulated into a
suspension of KH (2.706 g, 67.47 mmol) in ca. 200 mL of THF.
Gas evolution was observed as the solution stirred under nitrogen.
(20) Power, P. P.; Ruhlandt-Senge, K.; Shoner, S. C. Inorg. Chem. 1991,
30, 5013.
(21) Bartlett, R. A.; Olmstead, M. M.; Power, P. P. Inorg. Chem. 1994,
33, 4800.
(22) Schumann, H.; Gottfriedsen, J.; Dechert, S.; Girgsdies, F. Z. Anorg.
Allg. Chem. 2000, 626, 747.
699s cm-1
.
(23) Tang, Y.; Zakharov, L. N.; Rheingold, A. L.; Kemp, R. A. Organo-
metallics 2005, 24, 836.
(24) Schumann, H.; Winterfeld, J.; Rosenthal, E. C. E.; Hemling, H.; Esser,
L. Z. Anorg. Allg. Chem. 1995, 621, 122.
(25) Babcock, J. R.; Liable-Sands, L.; Rheingold, A. L.; Sita, L. R.
Organometallics 1999, 18, 4437.
(26) Evans, W. J.; Boyle, T. J.; Ziller, J. W. Inorg. Chem. 1992, 31, 1120.
(27) Tang, Y.; Zakharov, L. N.; Rheingold, A. L.; Kemp, R. A. Polyhedron
2005, 23, 1739.
(28) Evans, W. J.; Seibel, C. A.; Ziller, W. J. J. Am. Chem. Soc. 1998,
120, 6745.
(29) Herrmann, W. A.; Anwander, R.; Kleine, M.; Scherer, W. Chem. Ber.
1992, 125, 1971.
(30) For more information, see http://www.glasscontour.com.
(31) Evans, W. J.; Johnston, M. A.; Ziller, J. W. Inorg. Chem. 2000, 39,
3421.
(32) Evans, W. J.; Engerer, S. C.; Coleson, K. M. J. Am. Chem. Soc. 1981,
103, 6672.
Synthesis of (C5Me5)2La[N(SiMe2Ph)2], 6. [(C5Me5)2La][(µ-
Ph)2BPh2] (53 mg, 0.07 mmol) and 1 (21 mg, 0.07 mmol) were
combined in ca. 20 mL of toluene and allowed to stir overnight.
The solution was filtered, and the solvent was removed in vacuo
leaving a white powder. A concentrated solution of the solid in
toluene produced colorless X-ray quality crystals over 1-3 days
at -35 °C (42 mg, 93%). 1H NMR (THF-d8) δ 0.33 (s, 12H,
N(SiMe2Ph)2), 1.97 (s, 30H C5Me5), 7.23 (m, 6H, N(SiMe2Ph)2),
7.26 (d, 4H, o-N(SiMe2Ph)2). 13C NMR (THF-d8) δ 3.0 (N(SiMe2-
Ph)2), 12.2 (C5Me5), 122.1 (C5Me5), 128.5, 129.3 (N(SiMe2Ph)2),
1
134.6 (o-N(SiMe2Ph)2), 144.6 (i-N(SiMe2Ph)2). H NMR (C6D6)
δ 0.44 (s, 12H, N(SiMe2Ph)2), 2.00 (s, 30H C5Me5), 7.24 (m, 6H,
N(SiMe2Ph)2), 7.62 (d, 4H, o-N(SiMe2Ph)2). 13C NMR (C6D6) δ
3.0 (N(SiMe2Ph)2), 12.2 (C5Me5), 121.8 (C5Me5), 129.2, 129.7
3438 Inorganic Chemistry, Vol. 45, No. 8, 2006

Bis(dimethylphenylsilyl)amide Coordination Chemistry
Table 1. X-ray Data Collection Parameters for [KN(SiMe2Ph)2(C7H8)]2
(2), {(THF)Na[µ-η1:η1-N(SiMe2Ph)2]}2 (5), (C5Me5)2La[N(SiMe2Ph)2]
(6), and (18-Crown-6)KN(SiMe3)2 (7)
were included using a riding model. There were two independent
molecules of the formula unit present. One molecule was located
in a general position, and the other was located about an inversion
center (Z ) 3). Least-squares analysis yielded wR2 ) 0.2386 and
GOF ) 1.031 for 731 variables refined against 12488 data (0.80
Å). As a comparison for refinement on F, R1 ) 0.0900 for those
7009 data with I > 2.0σ(I).
2
5
6
7
fw
T (K)
831.52
163(2)
759.24
163(2)
693.88
163(2)
463.81
163(2)
cryst syst
space group
a (Å)
b (Å)
c (Å)
monoclinic monoclinic monoclinic triclinic
C2/c
P21/c
P21/c
P1h
{(THF)Na[µ-η1:η1-N(SiMe2Ph)2]}2, 5. A colorless crystal of
approximate dimensions 0.27 × 0.28 × 0.29 mm3 was handled as
described above. The diffraction symmetry was 2/m, and the
systematic absences were consistent with the centrosymmetric
monoclinic space group P21/c which was later determined to be
correct. Hydrogen atoms were included using a riding model. Least-
squares analysis yielded wR2 ) 0.1994 and GOF ) 1.028 for 451
variables refined against 8985 data (0.80 Å). As a comparison for
refinement on F, R1 ) 0.0634 for those 5134 data with I > 2.0σ(I).
(C5Me5)2La[N(SiMe2Ph)2], 6. A colorless crystal of approximate
dimensions 0.29 × 0.30 × 0.32 mm3 was handled as described
above. The diffraction symmetry was 2/m, and the systematic
absences were consistent with the centrosymmetric monoclinic
space group P21/c which was later determined to be correct.
Hydrogen atoms were located from a difference Fourier map and
refined (x, y, z and Uiso). At convergence, wR2 ) 0.0494 and GOF
) 1.044 for 569 variables refined against 8534 data. As a
comparison for refinement on F, R1 ) 0.0183 for those 7909 data
with I > 2.0σ(I).
(18-Crown-6)KN(SiMe3)2, 7. Y[N(SiMe3)2]3 (73 mg, 0.13
mmol) in ca. 5 mL THF was added to 18-crown-6 (34 mg, 0.13
mmol) in ca. 5 mL THF with K (5 mg, 0.13 mmol) dropwise, and
this mixture was allowed to stir overnight.38 The solvent was then
removed in vacuo. At -35 °C, over 1-3 days, a concentrated
sample in diethyl ether produced colorless X-ray quality crystals.
A colorless crystal of approximate dimensions 0.08 × 0.11 × 0.15
mm3 was handled as described above. There were no systematic
absences nor any diffraction symmetry other than the Friedel
condition. The centrosymmetric triclinic space group P1h was
assigned and later determined to be correct. Hydrogen atoms were
included using a riding model. At convergence, wR2 ) 0.0792 and
GOF ) 1.029 for 253 variables refined against 6291 data. As a
comparison for refinement on F, R1 ) 0.0287 for those 5614 data
with I > 2.0σ(I).
18.300(5)
13.331(4)
20.992(6)
90
111.917(4) 103.521(3) 97.307(2)
90
11.143(20 10.7007(11) 9.3271(8)
22.300(4)
18.258(3)
90
14.9335(15) 10.6844(9)
21.830(2)
90
14.9957(12)
104.7620(10)
98.9240(10)
110.5980(10)
1302.30(19)
2
R (deg)
â (deg)
γ (deg)
V (Å3)
Z
90
90
4751(2)
4
4411.1(14) 3460.1(6)
4
4
F
calcd (Mg/m3)
1.162
0.332
1.143
0.188
0.0634
0.1994
1.332
1.328
0.0183
0.0494
1.183
0.325
0.0287
0.0792
µ (mm-1
)
R1 [I > 2.0σ(I)] 0.0316
wR2 (all data) 0.0853
(N(SiMe2Ph)2), 134.4 (o-N(SiMe2Ph)2), 144.3 (i-N(SiMe2Ph)2).
Calcd for C36H52Si2NLa: La, 20.02. Found: La, 19.8. IR 3367w,
3654w, 3632w, 3370w, 2957m, 2907m, 2856m, 2729w, 2366w,
2343w, 1993w, 1883w, 1816w, 1776w, 1552w, 1428s, 1378m,
1320w, 1247s, 1177s, 1015s, 930s, 834s, 811s, 772s, 718s, 699s
cm-1
.
X-ray Data Collection, Structure Determination, and Refine-
ment for 2, 5, 6, and 7. X-ray crystallographic data were obtained
by mounting a crystal on a glass fiber and transferring it to a Bruker
CCD platform diffractometer. The SMART33 program package was
used to determine the unit cell parameters and for data collection
(25 s/frame scan time for a sphere of diffraction data). The raw
frame data were processed using SAINT34 and SADABS35 to yield
the reflection data file. Subsequent calculations were carried out
using the SHELXTL36 program. The structures were solved by
direct methods and refined on F2 by full-matrix least-squares
techniques. The analytical scattering factors37 for neutral atoms were
used throughout the analysis. Crystallographic data appear in Table
1.
[KN(SiMe2Ph)2(C7H8)]2, 2. A colorless crystal obtained from
toluene of approximate dimensions 0.10 × 0.37 × 0.45 mm3 was
handled as described above. The diffraction symmetry was 2/m,
and the systematic absences were consistent with the monoclinic
space groups Cc and C2/c. It was later determined that the
centrosymmetric space group C2/c was correct. Hydrogen atoms
were located from a difference Fourier map and refined (x, y, z
and Uiso). The molecule was located about an inversion center (Z
) 4). At convergence, wR2 ) 0.0853 and GOF ) 1.035 for 364
variables refined against 5748 data. As a comparison for refinement
on F, R1 ) 0.0316 for those 4674 data with I > 2.0σ(I).
A colorless crystal obtained from THF of approximate dimen-
sions 0.22 × 0.25 × 0.30 mm3 was mounted on a glass fiber and
transferred to a Bruker CCD platform diffractometer. There were
no systematic absences nor any diffraction symmetry other than
the Friedel condition. The centrosymmetric triclinic space group
P1h was assigned and later determined to be correct. Hydrogen atoms
Results and Discussion
Synthesis. KN(SiMe2Ph)2, 1, was readily synthesized on
the gram scale by the addition of HN(SiMe2Ph)2 to excess
KH in THF. A slight excess of KH was used to avoid the
need to remove unreacted HN(SiMe2Ph)2, eq 1. Removal of
THF, extraction with toluene, and filtration to separate excess
KH gave a toluene solution that provided KN(SiMe2Ph)2, 1,
as an off white powder after removal of solvent.
HN(SiMe2Ph)2 + 1.1KH f KN(SiMe2Ph)2 + H2 (1)
Compound 1 is soluble in THF and toluene, but it is only
sparingly soluble in n-hexane.
Recrystallization of 1 from toluene gives the toluene
complex [KN(SiMe2Ph)2(C7H8)]2, 2, Figure 1. Crystals of 2
were also obtained from crystallization of 1 from THF in
(33) SMART Software Users Guide, version 5.1; Bruker Analytical X-ray
Systems, Inc.: Madison, WI, 1999.
(34) SAINT Software Users Guide, version 6.0; Bruker Analytical X-ray
Systems, Inc.: Madison, WI, 1999.
(35) Sheldrick, G. M. SADABS, version 2.05; Bruker Analytical X-ray
Systems, Inc.: Madison, WI, 2001.
(36) Sheldrick, G. M. SHELXTL, version 6.12; Bruker Analytical X-ray
Systems, Inc.: Madison, WI, 2001.
(37) International Tables for X-ray Crystallography; Kluwer Academic
Publishers: Dordrecht, 1992; Vol. C.
(38) For a more thorough review of alkali metal/LnZ3 reduction systems,
see: Evans, W. J.; Lee, D. S. Can. J. Chem. 2005, 83, 375.
Inorganic Chemistry, Vol. 45, No. 8, 2006 3439

Evans et al.
Figure 3. Thermal ellipsoid plot of (18-crown-6)KN(SiMe3)2, 7, with
ellipsoids drawn at the 50% probability level.
Figure 1. Thermal ellipsoid plot of [KN(SiMe2Ph)2(C7H8)]2, 2, with
ellipsoids drawn at the 50% probability level.
Figure 4. Thermal ellipsoid plot of {(THF)Na[µ-η1:η1-N(SiMe2Ph)2]}2,
5, with ellipsoids drawn at the 50% probability level.
Figure 2. Ball and stick diagram of the structure of (18-crown-
6)KN(SiMe2Ph)2, 3.
the presence of toluene. In this case, 2 crystallized in a
different space group containing two crystallographically
independent molecules similar to that obtained from toluene.
Crystallization of 1 in the presence of 18-crown-6 yielded
(18-crown-6)KN(SiMe2Ph)2, 3, Figure 2, which has a
structure similar to that of the [N(SiMe3)2]1- analogue, (18-
crown-6)KN(SiMe3)2, 7, Figure 3.
In contrast to the synthesis of 1, the analogous reaction
of HN(SiMe2Ph)2 with NaH gave poor yields of the sodium
salt. It was necessary to heat a THF slurry of NaH and
HN(SiMe2Ph)2 at reflux for 2 days in order to get a
significant yield, eq 2.
Figure 5. Thermal ellipsoid plot of (C5Me5)2La[N(SiMe2Ph)2], 6, with
ellipsoids drawn at the 50% probability level.
HN(SiMe2Ph)2 + 1.1NaH f NaN(SiMe2Ph)2 + H2 (2)
To examine the ligation of [N(SiMe2Ph)2]1- to a lanthanide
in a typical coordination environment, 1 was added to
[(C5Me5)2La][(µ-Ph)2BPh2]28 to generate the metallocene
complex, (C5Me5)2La[N(SiMe2Ph)2], 6, eq 3, Figure 5.
Although 6 could also be made from the reaction of 1 and
(C5Me5)2LaCl2K(THF)2,39 a precursor to [(C5Me5)2La][(µ-
Ph)2BPh2], the reaction product failed to yield a product as
Upon workup, an off-white gummy powder was obtained
that could be purified by washing with THF and recrystal-
lizing from toluene. This gave the solvated dimer {(THF)-
Na[µ-η1:η1-N(SiMe2Ph)2]}2, 5, Figure 4. Unsolvated NaN-
(SiMe2Ph)2, 4, could be obtained by crushing crystals of 5,
drying under vacuum, and crystallizing from methylcyclo-
hexane.
3440 Inorganic Chemistry, Vol. 45, No. 8, 2006

Bis(dimethylphenylsilyl)amide Coordination Chemistry
Table 2. Summary of Selected Bond Lengths (Å) and Angles (deg) for
Compounds 2, 5, 6, and 7
[KN(SiMe2Ph)2(C7H8)]2 (2)
K(1)-N(1)
K(1)-N(1A)
K(1)-C(19)
K(1)-C(7)
K(1)-C(10)
K(1)-C(1A)
K(1)-C(20)
K(1)-C(6A)
K(1)-C(18)
K(1)-C(21)
2.660(1)
2.874(1)
3.241(2)
3.245(2)
3.248(2)
3.265(2)
3.265(2)
3.343(2)
3.497(2)
3.532(2)
N(1)-K(1)-N(1A)
K(1)-N(1)-K(1A)
Si(1)-N(1)-Si(2)
Si(1)-N(1)-K(1)
Si(2)-N(1)-K(1)
Si(1)-N(1)-K(1A)
Si(2)-N(1)-K(1A)
93.28(4)
86.72(4)
132.06(7)
105.87(5)
116.79(6)
94.48(5)
108.23(6)
Si(1)-N(1)
Si(2)-N(1)
1.672(1)
1.672(1)
{(THF)Na[µ-η1:η1-N(SiMe2Ph)2]}2 (5)
Na(1)-O(1)
Na(1)-N(2)
Na(1)-N(1)
Na(2)-O(2)
Na(2)-N(1)
Na(2)-N(2)
Si(1)-N(1)
Si(2)-N(1)
Si(3)-N(2)
Si(4)-N(2)
Na(1)-C(22)
Na(2)-C(14)
2.298(3)
2.399(4)
2.481(4)
2.302(3)
2.397(4)
2.483(3)
1.685(3)
1.682(3)
1.679(3)
1.686(3)
3.196
N(1)-Na(1)-N(2)
N(1)-Na(2)-N(2)
O(1)-Na(1)-N(1)
O(1)-Na(1)-N(2)
O(2)-Na(2)-N(1)
O(2)-Na(2)-N(2)
Si(1)-N(1)-Si(2)
Si(3)-N(2)-Si(4)
Si(2)-N(1)-Na(2)
Si(1)-N(1)-Na(2)
Si(2)-N(1)-Na(1)
Si(1)-N(1)-Na(1)
Si(3)-N(2)-Na(1)
Si(4)-N(2)-Na(1)
Si(3)-N(2)-Na(2)
Si(4)-N(2)-Na(2)
99.91(12)
99.92(12)
135.17(13)
117.54(12)
119.94(13)
134.03(13)
128.4(2)
pure as that in eq 3. This emphasizes the utility of the
[(C5Me5)2Ln][(µ-Ph)2BPh2] complexes as synthetic precur-
sors.28,40, 41
Structure. The crystal structures of 2, 3, 5, and 6 show
that the [N(SiMe2Ph)2]1- ligand can ligate metals in several
ways. The most conventional structure obtained from this
study is that of the crown ether complex, (18-crown-
6)KN(SiMe2Ph)2,42 3, Figure 2. Unfortunately, the crystal-
lographic data were good enough only to determine con-
nectivity for this complex. Its overall structure is analogous
to that of the bis(trimethylsilyl) analogue, (18-crown-
6)KN(SiMe3)2, 7, Figure 3, a complex that did give crystals
suitable for a detailed metrical analysis (Table 2).
The next most conventional structure arising from this
study was the THF solvate of 4 which crystallizes as the
dimer, {(THF)Na[µ-η1:η1-N(SiMe2Ph)2]}2, 5, Figure 4.
This compound has known [N(SiMe3)2]1- analogues:
{(THF)Na[µ-η1:η1-N(SiMe3)2]}2,43 8, and (THF)Na-
[µ-η1: η 1-N(SiMe3)2]2K(THF)2,44 9. However, in contrast to
the similarity of complexes 3 and 7, there are some inter-
esting differences between the structure of 5 and those of 8
and 9 that highlight differences in [N(SiMe3)2]1- versus
[N(SiMe2Ph)2]1- ligation.
In each of these compounds, 5, 8, and 9, the sodium ion
is three coordinate due to two bridging nitrogen atoms and
a terminal THF. In 8 and 9, the sodium adopts the expected
trigonal planar geometry. However, in 5, Na(1), N(1), N(2),
and O(1) are not coplanar. In fact, O(1) is 0.942 Å (24.2°)
out of the NaN2 plane. The THF is oriented away from the
phenyl substituents of the silyl groups as shown in Figure
6. This arrangement puts the ortho carbon atoms C(22) and
C(14) within 3.2 Å of Na(1) and Na(2), respectively. This
is on the long end of Na-C(arene) distances in the
129.0(2)
112.47(17)
112.71(17)
106.04(16)
104.95(15)
114.13(17)
111.71(17)
108.28(16)
100.300(15)
3.190
Na(1)-N(1)-Na(2)
Na(1)-N(2)-Na(2)
80.12(11)
80.05(11)
(C5Me5)2La[N(SiMe2 Ph)2] (6)
La(1)-Cnt(1)a
La(1)-Cnt(2)a
La(1)-N(1)
2.589
2.549
Cnt(1)-La(1)-Cnt(2)
Cnt(1)-La(1)-N(1)
Cnt(2)-La(1)-N(1)
Si(1)-N(1)-Si(2)
Si(1)-N(1)-La(1)
Si(2)-N(1)-La(1)
N(1)-Si(1)-C(21)
N(1)-Si(1)-C(22)
N(1)-Si(2)-C(29)
N(1)-Si(2)-C(30)
130.9
116.9
112.1
132.49(7)
110.13(6)
116.07(6)
106.80(6)
116.55(7)
106.42(7)
113.39(7)
2.446(1)
3.121(2)
3.388(2)
3.01(2)
2.86(2)
2.95(2)
3.46(2)
1.692(1)
1.703(1)
La(1)-C(21)
La(1)-C(29)
La(1)-H(21A)
La(1)-H(21B)
La(1)-H(29A)
La(1)-H(29B)
Si(1)-N(1)
Si(2)-N(1)
(18-Crown-6)KN(SiMe3)2 (7)
K(1)-N(1)
K(1)-O(1)
K(1)-O(2)
K(1)-O(3)
K(1)-O(4)
K(1)-O(5)
K(1)-O(6)
2.760(1)
2.849(1)
2.961(1)
2.747(1)
2.820(1)
2.978(1)
2.895(1)
Si(1)-N(1)-Si(2)
Si(1)-N(1)-K(1)
Si(1)-N(1)-K(2)
130.47(6)
110.54(4)
116.85(5)
Si(1)-N(1)
Si(2)-N(1)
1.670(1)
1.665(1)
a Cnt(1) is the centroid of the C(1)-C(5) ring, and Cnt(2) is the centroid
of the C(11)-C(15) ring.
literature.45,46 The closest analogues of 5 with a Na-C(arene)
interaction are Na[C(SiMe3)2(SiMe2Ph)](TMEDA),47 which
has its shortest contacts at 2.934(3) and 2.965(3) Å, and
Na[C(SiMe3)(SiMe2Ph)2](TMEDA),47 which has 2.885(6)
and 3.026(5) Å Na-C(arene) lengths. The long Na-C(arene)
distance in 5 is notably longer than the shortest Na-C(arene)
distance of the similar trans-[Na{µ-N(SiMe3)(SiMe2Ph)]},48
which has a Na-C(arene) distance of 2.686(1) Å. In contrast,
the Na-C(arene) distance is comparable to the Yb-C(arene)
distance in Yb(OC6H3Ph2-2,6)3(THF)2,49 2.978(6) Å, which
is 3.130 Å when normalized to the radial size of Na.50
The Na2N2 unit in 5 is planar as it is in 8, but it is a
rectangle in 5 instead of the square found in 8. The parallel
Na(1)-N(1) and Na(2)-N(2) lengths in 5, 2.481(4) and
2.483(3) Å, respectively, are longer than the Na(1)-N(2)
and Na(2)-N(1) distances, 2.399(4) and 2.397(4) Å. In
(39) Jeske, G.; Lauke, H.; Mauermann, H.; Swepston, P. N.; Schumann,
H.; Marks, T. J. J. Am. Chem. Soc. 1985, 107, 8091.
(40) (a) Evans, W. J.; Lee, D. S.; Lie, C.; Ziller, J. W. Angew. Chem., Int.
Ed. 2004, 43, 5517. (b) Evans, W. J.; Perotti, J. M.; Brady, J. C.;
Ziller, J. W. J. Am. Chem. Soc. 2003, 125, 5204. (c) Evans, W. J.;
Perotti, J. M.; Ziller, J. W. J. Am. Chem. Soc. 2005, 127, 3894.
(41) Evans, W. J.; Nyce, G. W.; Forrestal, K. J.; Ziller, W. J. Organo-
metallics 2002, 20, 1050.
(42) X-ray unit cell parameters for 3 follow: cryst syst, triclinic; space
group, P1h; a ) 11.6717(14) Å; b ) 11.7444(14) Å; c ) 13.7456(17)
Å; R ) 87.787(2)°; â ) 76.661(2)°; γ ) 72.868(2)°; V, 1751.2(4)
Å3; Z ) 2; F ) 1.202 Mg/m3; final R indices [I > 2σ(I) ) 3548
data], R1 ) 0.1480, wR2 ) 0.4101.
(43) Karl, M.; Seybert, G.; Harms, K.; Agarwal, S.; Maleika, R.; Stelter,
W.; Greiner, A.; Heitz, W.; Neumu¨ller, B.; Dehnicke, K. Z. Anorg.
Allg. Chem. 1999, 625, 1301.
(44) Williard, P. G.; Nichols, M. A. J. Am. Chem. Soc. 1991, 113, 9671.
Inorganic Chemistry, Vol. 45, No. 8, 2006 3441

Evans et al.
such a pattern existed in 5, it was not discernible within the
error limits of the data. Both 5 and 10 suggest that the phenyl
group of the [N(SiMe2Ph)2]1- ligand can alter the structure
compared to [N(SiMe3)2]1- complexes.
The structure of (C5Me5)2La[N(SiMe2Ph)2], 6, Figure 5,
can also be compared with that of [N(SiMe3)2]1- analogues,
the (C5Me5)2Ln[N(SiMe3)2] complexes (Ln ) Sm,51 11;
Y,52,53 12; and U,41 13). This provides a good estimate of
the differences between [N(SiMe2Ph)2]1- and [N(SiMe3)2]1-
in an f element coordination environment.
In each of the four structures, the nitrogen donor atom is
located symmetrically in the metallocene wedge in the
(C5Me5 ring centroid)-metal-(C5Me5 ring centroid) plane.
The (C5Me5 ring centroid)-M-(C5Me5 ring centroid) angles
for 6 and 11-13 are similar: 130.0°, 132.8°, 132.2°, and
132.4°, respectively. The metal-(C5Me5 ring centroid)
distances for 6 are 2.589 and 2.549 Å. When values for 11
(2.479 and 2.470 Å), 12 (2.391 and 2.400 Å), and 13 (2.532
and 2.523 Å) are adjusted for the difference in ionic radius50
and normalized to La, they are numerically smaller: 2.553
and 2.544 Å for 11, 2.523 and 2.532 Å for 12, and 2.539
and 2.519 Å for 13, respectively. The M-N distance in 5,
2.446(1) Å, is also longer than the values found in 11, 12,
and 13 (2.301(3), 2.274(5), and 2.352(2) Å, respectively)
when these are normalized to La: 2.375, 2.406, and 2.359
Å, respectively. These data are consistent with the larger size
of [N(SiMe2Ph)2]1- versus [N(SiMe3)2]1-. Another difference
between 6 and 11-13 is that the arrangement of the two
silicon atoms and lanthanum around nitrogen is not planar
in 6. Lanthanum is 0.563 Å (13.3°) out of the plane and
oriented away from the phenyl groups. In contrast, in 11,
12, and 13, each metal is coplanar with the NSi2 plane. The
planar structure had been attributed to interaction of the
nitrogen lone pair with the lanthanide to give a shorter than
expected Ln-N bond length. The longer La-N in 6 is
consistent with the absence of this LaNSi2 coplanarity.
Another difference in the structure of 6 is that a methyl
carbon on each SiMe2Ph group is oriented toward lanthanum.
The La-C distances are 3.121(2) Å for C(21) and 3.388(2)
Å for C(29). Refinement of hydrogens attached to these
methyl groups gave distances to La of 2.86(2), 2.95(2),
3.01(2), and 3.46(2) Å for H(21B), H(29A), H(21A), and
H(29B), respectively. These distances are comparable to the
closest M-C(SiMe3) distances in 11-13 (3.216, 2.970(6),
and 3.197(4) Å, respectively) when normalized to La: 3.296,
3.110, and 3.197 Å, respectively. Metal-hydrogen distances
were obtained in the structures of 11 and 12 (2.97 and 2.45
Å, respectively) with distances normalized to La of 3.05 and
2.59 Å, respectively. In 11-13, however, only one methyl
group per [N(SiMe3)2]1- ligand is oriented toward the metal.
In 6, both methyl groups are within the distances common
for agostic interactions.
Figure 6. Ball and stick diagram of the structure of {(THF)Na[µ-η1:η1-
N(SiMe2Ph)2]}2, 5, as seen down the N(1)‚‚‚N(2) axis.
comparison, the Na-N distances in 8 are 2.398(2) and
2.399(2) Å. Complex 9 is not square due to its mixed metal
composition and has a Na(1)-N(1) distance of 2.365(3) Å.
Hence, 5 has two Na-N linkages that are significantly longer
than usual. The 2.298(3) and 2.302(3) Å Na-O(THF)
distances in 5 are comparable to those in 8 and 9, 2.267(2)
and 2.292(3) Å, respectively.
The structure of 5 can also be compared to its dimeric
unsolvated lithium analogue, Li2[µ-N(SiMe2Ph)2]2,16 10. This
complex has a square M2N2 unit with Li-N(SiMe2Ph)
distances in the narrow range 2.011(4)-2.035(4) Å. Addition
of the 0.40 Å difference in ionic radii between four
coordinate lithium and sodium50 gives expected values for
Na-N distances close to the short lengths observed in 5.
The structural description of 10 also includes a discussion
of Li-C(phenyl) distances that range from 2.53 to 2.77 Å.
Again, addition of 0.40 Å puts these in the range of the
closest Na-C(phenyl) distances in 5. In 10, the C-C phenyl
distances for carbons closest to lithium were found to be
numerically longer than those distant from the metal, but if
(45) Smith, J. D. AdV. Organomet. Chem. 1998, 43, 267.
(46) For example, the following Na-C(arene) distances have been
reported: 2.887 Å for Na(SiPhtBu2) (Lerner, H.-W.; Scholz, S.; Bolte,
M. Z. Anorg. Allg. Chem. 2001, 627, 1638); 2.950 Å for Na4(HBEt3)4-
(mesitylene)2 (Koster, R.; Schussler, W.; Boese, R.; Blaser, D. Chem.
Ber. 1991, 124, 2259); 2.996 Å for Na[Ln(3,5-di-tert-butylpyrazolato)4]-
(C7H8) (Ln ) Tb, Ho) (Deacon, G. B.; Delbridge, E. E.; Evans, D. J.;
Harika, R.; Junk, P. C.; Skelton, B. W.; White, A. H. Chem. Eur. J.
2004, 10, 1193); 2.970 Å for NaC(SiMe3)2(SiMe2PPh2) (Avent, A.
G.; Bonafoux, D.; Eaborn, C.; Hill, M. S.; Hitchcock, P. B.; Smith, J.
D. J. Chem. Soc., Dalton Trans. 2000, 2183); 3.037 Å for Na-
(C6H5Me)[Me3GaSi(SiMe3)] (Wochele, R.; Schwarz, W.; Klinkham-
mer, K. W.; Locke, K.; Weidlein, J. Z. Anorg. Allg. Chem. 2000, 626,
1963); 3.100 Å for (THF)2Na(Ph2N)2Sm[N(SiMe3)2]2 (Karl, M.;
Dashti-Mommertz, A.; Neumu¨ller, B.; Dehnicke, K. Z. Anorg. Allg.
Chem. 1998, 624, 355); 3.120 Å for Na(SiPhtBu2)(THF) (Lerner, H.-
W.; Scholz, S.; Bolte, M.; Wagner, M. Z. Anorg. Allg. Chem. 2004,
630, 443); and 3.259 Å for Na[tBuCuSi(SiMe3)3](C7H8) (Klinkhammer,
K. W.; Klett, J.; Xiong, Y.; Yao, S. Eur. J. Inorg. Chem. 2003, 3417).
(47) Eaborn, C.; Clegg, W.; Hitchcock, P. B.; Hopman, M.; Izod, K.;
O’Shaughnessy, P. N.; Smith, J. D. Organometallics 1997, 16, 4728.
(48) Antolini, F.; Hitchcock, P. B.; Lappert, M. F.; Merle, P. Chem.
Commun. 2000, 1301.
(51) Evans, W. J.; Keyer, R. A.; Ziller, J. W. Organometallics 1993, 12,
2618.
(52) den Haan, K. H.; de Boer, J. L.; Teuben, J. H. Organometallics 1986,
5, 1726. Two crystallographically independent molecules of 12; all
distances and angles, unless otherwise noted, refer to “molecule 1.”
(53) Klimper, M. G.; Go¨rlitzer, H. W.; Tafipolsky, M.; Spiegler, M.;
Scherer, W.; Anwander, R. J. Organomet. Chem. 2002, 647, 236.
(49) Deacon, G. B.; Nickel, S.; MacKinnon, P.; Tiekink, E. R. T. Aus. J.
Chem. 1990, 43, 1245.
(50) Shannon, R. D. Acta Crystallogr. 1976, A32, 751.
3442 Inorganic Chemistry, Vol. 45, No. 8, 2006

Bis(dimethylphenylsilyl)amide Coordination Chemistry
Another measure of agostic interactions in silylamides is
the distortion of N-Si-C angles. In 6, the angles involving
C(21) and C(29) are 106.80(6)° and 106.42(7)° compared
to the values of 116.55(7)° and 113.39(7)° for the methyl
carbons pointing away from the metal, C(22) and C(30),
respectively.
The most unusual structure in this study was obtained
when 1 was crystallized from toluene. This generated a
dimer, [KN(SiMe2Ph)2(C7H8)]2, 2, Figure 1, in which toluene
functions as a ligand. Complex 2 incorporates all of the
interactions seen in the previous structures; i.e., phenyl and
methyl carbons atoms of the [N(SiMe2Ph)2]1- ligand are
oriented toward the metal as well as the main donor atom,
the nitrogen. As in 5 and 10, the M2N2 unit is planar, but in
2, the M-N distances are even more disparate than in 5.
The 2.660(1) and 2.874(1) Å distances for K(1)-N(1) and
K(1)-N(1′), respectively, can be compared to the values of
2.778 and 2.862 Å obtained by adding the 0.38 Å difference
in ionic radii between potassium and sodium50 to the values
in 5.
in 2. The shortest Na-C distance in 5, 3.190 Å, when
adjusted for the difference in ionic radius50 and normalized
to K, is 3.57 Å, which is much longer then the eight
previously noted K-C bonds in 2. The Na-N bond lengths
in 5, when adjusted for the difference in ionic radius50 and
normalized to K, are 2.777, 2.779, 2.861, and 2.863 Å, and
they are intermediate between the K-N distances of 2.660(1)
and 2.874(1) Å.
Unexpectedly, the crude product from a reaction forming
1 also crystallized from THF as a toluene adduct. Hence,
even in the presence of a good donor solvent like THF, this
toluene ligation is still obtainable. The crystals of 2 that were
obtained from THF differed from those obtained from toluene
in space group and in the fact that there were two indepen-
dent molecules in the unit cell with one molecule located in
a general position and the other located about an inversion
center.59 The molecule around the inversion center is
isomorphous with the dimer obtained from the toluene
solution. The other independent molecule is also analogous,
but it has more variations in bond distances. The largest one
involves the potassium-ipso phenyl carbon distance that was
found to be 3.192(6) Å.
The next closest approach of a ligand atom to potassium
in 2 involves the 3.231(2) Å K(1)-C(19) length of one of
the carbon atoms of the toluene. Three other arene carbon
atoms are located within 3.6 Å (C(20) 3.265(2) Å; C(18)
3.497(2) Å; C(21) 3.532(2) Å), and the other two ring
carbons are found at longer distances, 3.764, and 3.755 Å.
Hence, the coordination can be considered to be tetrahapto.
The coordination of arenes to potassium cations is not
unknown,54-57 although the coordination of a free arene, such
as toluene, is less common.55 The K-C(arene) distances in
2 are within the range of K-C(arene) distances noted in the
literature.45,58 The K-C(arene) distance is shorter than the
2.978(6) Å Yb-C(arene) distance of Yb(OC6H3Ph2-2,6)3-
Conclusion
The potassium salt of the [N(SiMe2Ph)2]1- ligand can be
readily obtained and is a good precursor for introducing this
ligand into the coordination sphere of a lanthanide. The
[N(SiMe2Ph)2]1- ligand appears to be sterically bulkier than
the commonly used [N(SiMe3)2]1- amide. In a lanthanide
metallocene environment, it coordinates with a slightly longer
Ln-N bond and with two agostic methyl interactions rather
than one. The [N(SiMe2Ph)2]1- ligand can coordinate to
metals in a variety of ways. It can function as a simple
monohapto ligand as in (18-crown-6)KN(SiMe2Ph)2, 3.
However, it can also engage in agostic interactions with its
methyl ligands as well as the phenyl ligands. In (C5Me5)2-
La[N(SiMe2Ph)2], 6, it is trihapto with one nitrogen and two
49
(THF)2 which is 3.570 Å when normalized to the radial
size of K.50
Both the methyl and phenyl substituents of the [N(SiMe2-
Ph)2]1- ligand have K-C distances similar to those in the
coordinated toluene. Hence, ipso carbon C(1) and ring carbon
C(6) of the phenyl ring are at distances from K(1′) of
3.265(2) Å and 3.343(2) Å, and the methyl carbon, C(7), is
oriented toward K(1) at a distance of 3.245(2) Å. Phenyl
carbon C(10) in the other phenyl substituent is oriented
toward K(1) at a distance of 3.248(2) Å. With the four
described K-C(phenyl) contacts, these four carbons combine
to have a total of eight carbons oriented toward potassium
1
methyl carbons, in {(THF)Na[µ-η1:η -N(SiMe2Ph)2]}2, 5,
and {Li[µ-η1:η1-N(SiMe2Ph)2]}2, 10, it is trihapto with one
nitrogen and two phenyl carbons, and in [KN(SiMe2Ph)2-
(C7H8)]2, 2, it is pentahapto with one nitrogen, three phenyl
carbons, and one methyl carbon. The coordinative versatility
of this ligand should make it an excellent choice when the
normal modes of bonding of [N(SiMe3)2]1- are inadequate
to give isolable fully characterizable complexes.
Acknowledgment. We thank the Chemical Sciences,
Geosciences, and Biosciences Division of the Office of Basic
Energy Sciences of the Department of Energy for support.
(54) Evans, W. J.; Ansari, M. A.; Khan, S. I. Organometallics 1995, 14,
558.
(55) Clark, D. L.; Watkin, J. G.; Huffman, J. C. Inorg. Chem. 1992, 31,
1556.
(56) Schaverien, C. J.; van Mechelen, J. B. Organometallics 1991, 10, 1704.
(57) Weiss, E. Angew. Chem., Int. Ed. Engl. 1993, 32, 1501.
(58) Typical K-C(arene) average distances in these complexes are 2.986
Å for KBPh4;57 3.512 Å for {K[(C5H5)2Nd(OC6H3Me2-2,6)2]}n;54
Supporting Information Available: X-ray diffraction details
(CIF) and X-ray data collection, structure solution, and refinement
of compounds 2, 3, 5, 6, and 7 (PDF). This material is available
free of charge via the Internet at http://pubs.acs.org.
i
3.300 Å for K[Nd(OC6H3 Pr2-2,6)4];55 3.196 Å for Ph3CK(THF)-
(PMDTA) (Hoffmann, D.; Bauer, W.; von R. Schleyer, P.; Pieper,
U.; Stalke, D. Organometallics 1993, 12, 1193); 3.275 Å for
[(C6H6)KOSiMe2Ph]4 (Fuentes, G. R.; Coan, P. S.; Streib, W. E.;
Caulton, K. G. Polyhedron 1991, 10, 2371); 3.369 Å for Lu[CH-
(SiMe3)2]3(µ-Cl)K(C7H8)2;56 and 3.28 and 3.193 Å for the C6H6 and
phenyl rings, respectively, in [K(C6H6)]{K[C(SiMe3)2(SiMe2Ph)]}
(Eaborn, C.; Hitchcock, P. B.; Izod, K.; Smith, J. D. Angew. Chem.,
Int. Ed. Engl. 1995, 34, 2679).
IC052091C
(59) X-ray unit cell parameters for 2 crystallized from THF follow: cryst
syst, triclinic; space group, P1h; a ) 11.334(5) Å; b ) 11.469(5) Å; c
) 28.841(12) Å; R ) 88.759(7)°; â ) 87.665(7)°; γ ) 72.764(6)°;
V, 3557(2) Å3; Z ) 3; F ) 1.164 Mg/m3; final R indices [I > 2σ(I)
) 3548 data], R1 ) 0.0900, wR2 ) 0.2386.
Inorganic Chemistry, Vol. 45, No. 8, 2006 3443