New building blocks in amide chemistry - N-lithiobis(trimethylstannyl)amine and N-lithiotrimethylstannyl(trimethylsilyl)amine

Article abstract of DOI:10.1002/1521-3773(20010917)40:18<3405::AID-ANIE3405>3.0.CO;2-S

Monomers as well as dimers have been established for the structures of N-lithiostannylamines in the solid state as well as in solution (the picture shows the crystal structure of the monomer [(Me₃Sn)₂-NLi{ (Me₂NCH₂CH₂)₂NMe}]). These compounds, which were synthesized for the first time from stannylamines with n-butyllithium, are remarkably reactive in solution despite having extremely short Li-N and Sn-N bonds. The selective and successive cleavage of the Li-N and Sn-N bonds under mild conditions holds great promise for their synthetic application.

Full text of DOI:10.1002/1521-3773(20010917)40:18<3405::AID-ANIE3405>3.0.CO;2-S

COMMUNICATIONS
tenberger, J. Organomet. Chem. 1992, 441, 457 ± 464; c) K. Onitsuka,
H. Katayama, K. Sonogashira, F. Ozawa, J. Chem. Soc. Chem.
Commun. 1995, 2267 ± 2268; d) K. Schlögl, W. Steyrer, Monatsh.
Chem. 1965, 96, 1520 ± 1535; e) G. Haller, Monatsh. Chem. 1967, 98,
82 ± 94; f) K. Schlögl, H. Soukup, Monatsh. Chem. 1968, 99, 927 ± 946;
g) K. Wurst, O. Elsner, H. Schottenberger, Synlett 1995, 8, 833 ± 834.
[5] A synthesis and oxidative coupling of 1,2-diethynylferrocene has been
described by Bunz et al.: a) U. H. F. Bunz, J. Organomet. Chem. 1995,
494, C8 ± C11; b) M. Altmann, J. Friedrich, F. Beer, R. Reuter, V.
Enkelmann, U. H. F. Bunz, J. Am. Chem. Soc. 1997, 119, 1472 ± 1473.
[6] G. Eglinton, W. McCrae, Adv. Org. Chem. 1963, 4, 222 ± 328.
[7] a) K. H. H. Fabian, Dissertation, Technische Universität Darmstadt,
2000; b) N. Nimmerfroh, Dissertation, Technische Hochschule Darm-
stadt, 1989.
[8] B. Stowasser, K. Hafner, Angew. Chem. 1986, 98, 477 ± 479; Angew.
Chem. Int. Ed. Engl. 1986, 25, 466 ± 468.
[9] The energy barrier of ring rotation for 1,1',3,3'-tetra-tert-butylferro-
cene 3b is somewhat lower at DG* ˆ 54.8 kJmol 1: W. Luke, A.
Streitwieser, Jr., J. Am. Chem. Soc. 1981, 103, 3241 ± 3243.
[10] After the addition of the chiral shift reagent europium(iii)-tris[3-
heptafluoropropylhydroxymethylene)-d-camphorate] [Eu(hfc)3] the
1H NMR spectrum of 3d shows no evidence of the presence of the
racemic anti-isomer.
[11] The cyclic voltammetric measurements were carried out in CH2Cl2 at
208C with Bu4NPF6 (0.1m) as supporting electrolyte and calibrated
New Building Blocks in Amide ChemistryÐ
N-Lithiobis(trimethylstannyl)amine and
N-Lithiotrimethylstannyl(trimethylsilyl)amine**
Christine Neumann, Thomas Seifert, Wolfgang Storch,*
Martina Vosteen, and Bernd Wrackmeyer*
The enormous synthetic utility of N-lithiosilylamines,
in particular of N-lithiobis(trimethylsilyl)amine, [LiN-
(SiMe3)2],[1] has been well documented.[2] In contrast, related
tin derivatives have remained unknown so far, and N-
lithiostannylamines in general have received scant attention,[3]
probably because of the greatly enhanced reactivity of the
Sn N bond[4] when compared with Si N bonds. However, this
enhanced reactivity is desirable in metal amides for further
transformations, and therefore, selective smooth syntheses of
such amides bearing one or two trimethylstannyl groups at
the nitrogen atom are an attractive goal. We have now
succeeded in obtaining pure N-lithiobis(trimethylstannyl)-
amine, [LiN(SnMe3)2] (2a), and N-lithiotrimethylsilyl(tri-
methylstannyl)amine, [LiN(SiMe3)SnMe3] (2b), for the first
time from the 1:1 reaction of tris(trimethylstannyl)amine,
(Me3Sn)3N (1a),[5] and trimethylsilylbis(trimethylstannyl)-
amine, (Me3Sn)2NSiMe3 (1b),[6] respectively, with butyllithi-
um (Scheme 1). The low solubility of 2a,b points to a mixture
of oligomers (x ꢀ1 in Scheme 1).
against cobaltocenium/cobaltocene (Eox
ˆ
1.04 VSCE; SCE ˆ satu-
rated calomel electrode). The scan speed was 100 mVs 1; working
electrode: Pt button; reference electrode: Pt wire.
[12] A differential scanning calorimetry (DSC) measurement carried out
at up to 2508C gave no indication of topochemical solid-state
polymerization.
[13] The oligomeric mixture is readily soluble in n-pentane and shows
molecular masses of up to M ˆ 9200 (molecular mass of the icosomer
(20mer) of 3d) in the matrix-assisted laser desorption/ionization time-
of-flight (MALDI-TOF) mass spectrum.
1
[14] Broadened H NMR ring-proton signals have also been observed by
Watanabe et al. with ferroceno[1.1]ruthenophane. This finding was
attributed to a rapid equilibrium between the syn conformers (syn-A
and syn-B) in solution which proceeds through a twist form. A similar
equilibrium is also possibly present in the case of the ferrocenophane
6: a) M. Watanabe, A. Nagasawa, I. Motoyama, T. Takayama, Bull.
Chem. Soc. Jpn. 1998, 71, 2127 ± 2136; b) U. T. Mueller-Westerhoff,
Angew. Chem. 1986, 98, 700 ± 716; Angew. Chem. Int. Ed. Engl. 1986,
25, 702 ± 718.
[15] Crystal structure analysis: Nonius CAD4 four circle diffractometer,
MoKa (graphite monochromator, l ˆ 0.71093 Š), Tˆ 298 K; crystal
dimensions 0.6  0.25  0.1 mm3; C60H80Fe2; Mr ˆ 913.10; a ˆ
16.157(4), b ˆ 12.041(2), c ˆ 28.564(4) Š, a ˆ 90.0(0), b ˆ 105.85(1),
g ˆ 90.0(0)8, Vˆ 5346(2) Š3; monoclinic, space group P21/n, Z ˆ 4,
1calcd ˆ 1.135 gcm 3, m ˆ 0.58 mm 1, 6478 independent reflections with
1.32 ꢁ 2Vꢁ 20.988, 5674 observed with Fo ꢁ 4s(F); R(F) ˆ 0.0349,
Rw(F) ˆ 0.1017. Structure solution and refinement: SHELXS-86,
SHELXL-93, LSQ calculation, differential Fourier synthesis, H atoms
of tert-butyl groups positioned geometrically. Graphics: PLUTON-93.
Crystallographic data (excluding structure factors) for the structure
reported in this paper have been deposited with the Cambridge
Crystallographic Data Centre as supplementary publication
no. CCDC-162621. Copies of the data can be obtained free of charge
on application to CCDC, 12 Union Road, Cambridge CB21EZ, UK
(fax: (‡44)1223-336-033; e-mail: deposit@ccdc.cam.ac.uk).
[16] P. Seiler, J. D. Dunitz, Acta Crystallogr. Sect. B 1979, 35, 1068 ± 1074.
[17] M. Dröûmar-Wolf, Handbook of Inorganic and Organometallic
Chemistry, Iron-Organic Compounds, Part A, Vol. 11 (Ed.: A. Slaw-
ish), Springer, Berlin, 1995, pp. 9 ± 10.
Scheme 1. Synthesis of 2a,b, 3a,b, and 4a,b. x ˆ 1, 2.
The reaction of 1a or 1b, dissolved in hexane, with BuLi in
hexane (Scheme 1a) afforded colorless, extremely air- and
moisture-sensitive powders that could be isolated and stored
[*] Dr. W. Storch, C. Neumann, Dr. T. Seifert, Dr. M. Vosteen
Department Chemie der Universität München
Butenandt-Strasse 5 ± 13, Haus D, 81377 München (Germany)
Fax : (‡49)89-21807337
E-mail: wst@cup.uni-muenchen.de
Prof. Dr. B. Wrackmeyer
Laboratorium für Anorganische Chemie
Universität Bayreuth
[18] The separation is, however, almost identical to the Fe ± CCp separa-
tions found by Okuda et al. with 1,1',2,2',3,3'-hexakis(trimethylsilyl)-
ferrocene, which lie between 205.0 and 211.3 pm: J. Okuda, E.
Herdtweck, Chem. Ber. 1988, 121, 1899 ± 1905.
[19] C. LeVanda, K. Bechgaard, D. O. Cowan, J. Org. Chem. 1976, 41,
2700 ± 2704.
95440 Bayreuth (Germany)
Fax : (‡49)921-552157
E-mail: b.wrack@uni-bayreuth.de
[20] J. A. Kramer, D. N. Hendrickson, Inorg. Chem. 1980, 19, 3330 ± 3337.
[**] This work was supported by the Deutsche Forschungsgemeinschaft
and the Fonds der Chemischen Industrie.
Angew. Chem. Int. Ed. 2001, 40, No. 18
ꢀ WILEY-VCH Verlag GmbH, D-69451 Weinheim, 2001
1433-7851/01/4018-3405 $ 17.50+.50/0
3405

COMMUNICATIONS
for prolonged time under argon atmosphere. After addition of
(1.92(1) Š) in 3a is the shortest so far for a bond to a
tetracoordinate Li atom (e.g. d(Li N) ˆ 1.98(2) Š in
[(Me3Si)2NLi(pmdta)][9, 10]). The Sn1 N1 (1.994(5) Š) and
Sn2 N2 (1.995(5) Š) distances in 3a are the shortest Sn N
single bonds observed as yet (see e.g. 1a: d(Sn N) ˆ
2.037(6) Š (av)[11]). In spite of this, the Sn-N-Sn angle
(115.5(2)8) is smaller than in any known structure of
bis(trimethylstannyl)amine derivatives containing a three-
coordinate nitrogen atom. In contrast, the silicon analogue of
3a, [(Me3Si)2NLi(pmdta)], displays a wide Si-N-Si angle
(125.3(2)8).[9, 10] Although this wide angle may be caused by
repulsive interactions of the silyl groups, the different
electronic properties of the Si N and Sn N bonds need to
be taken into consideration when discussing the molecular
structures of these compounds. The nitrogen atom in 3a
resides in a trigonal-planar environment.
N,N',N''-pentamethyldiethylenetriamine
((Me2NCH2CH2)2-
NMe; pmdta) to a suspension of 2a in hexane at 408C,
crystalline [(Me3Sn)2NLi(pmdta)] (3a) was isolated (Sche-
me 1b). When 2a was dissolved in tBuOMe, in the absence of
pmdta, the dimer [{(Me3Sn)2NLi(tBuOMe)}2] (4a) was ob-
tained as a crystalline product (Scheme 1c). Compound 2b,
dissolved in tBuOMe (Scheme 1c), gave the analogous dimer
[{Me3Sn(Me3Si)NLi(tBuOMe)}2] (4b), and treatment of 4b,
dissolved in tBuOMe, with pmdta, afforded the mononuclear
species [Me3Sn(Me3Si)NLi(pmdta)] (3b) in good yield.
The solid-state molecular structures of 3a[7] and 4a[8] are
shown in Figures 1 and 2, respectively. The sterically demand-
ing stannyl group has a special influence on the bonding
properties in these metal amides. The bond length Li1 N1
In the dimer 4a, the lithium atoms are three-coordinate,
and the N2Li2 ring is planar. The Li N distances are longer
than those in 3a, but slightly shorter than those in the dimer
[{(Me3Si)2NLi(Et2O)}2].[12] The planes around the lithium and
the oxygen atoms in 4a form an angle of about 408. The N-Li-
N angle of 103.9(2)8 as well as the Li-N-Li angle of 76.1(2)8
are similar to that in the corresponding bis(silyl) derivative.
However, the small Sn-N-Sn angle (111.0(1)8) in 4a (which is
even smaller than in 3a) is again remarkably different from
the Si-N-Si angle (121.9(4)8).
The relationship between solid-state structures of lithium
amides[13] and their state of association in solution[14] can be
assessed best by studying 6Li- and 15N-labeled material.
Therefore, the reactions of 15N-labeled (ca. 12%) 1a and 1b
Figure 1. Molecular structure of [(Me3Sn)2NLi(pmdta)] (3a; ORTEP,
thermal ellipsoids represent a 25% probability). Selected bond lengths [Š]
and angles [8]: Li1-N1 1.92(1), Sn1-N1 1.994(5), Sn2-N1 1.995(5), Li1-N2
2.15(1), Li-N3 2.18(1), Li1-N4 2.22(1), Sn1-C1 2.179(7), Sn1-C2 2.145(8),
Sn1-C3 2.145(9), Sn2-C4 2.148(7), Sn2-C5 2.162(8), Sn2-C6 2.157(8); Sn1-
N1-Sn2 115.5(2), Sn1-N1-Li1 123.8(4), Sn2-N1-Li1 120.6(4), N1-Li1- N2
116.1(5), N1-Li1-N3 129.4(6), N1-Li1-N4 120.2(6),C2-Sn1-C3 108.2(4), C1-
Sn1-C2 103.7(3), N1-Sn1-C1 115.8(3).
6
with Li-labeled (99%) MeLi in tBuOMe were carried out
6
and studied by Li, 15N, and 119Sn NMR spectroscopy. After
complete reaction of 1a with MeLi in tBuOMe, 4a was
formed as a single species together with Me4Sn. The dimer 4a
was identified by the typical pattern in the 15N NMR spectrum
6
(coupling of 15N nucleus with two equivalent Li nuclei) and
by the intensities of the 15N satellites in the 6Li NMR spectrum
(according to the degree of 15N labeling). Furthermore, the
119Sn NMR spectrum of 4a shows a single resonance,
accompanied by 15N satellites and 117Sn satellites with correct
intensities. Therefore, the structure of the dimer 4a at low
temperature is retained in solution. When pmdta was added to
the solution of 4a in tBuOMe, the presence of mainly two
species, 3a and 4a, and a minor unidentified compound,
became apparent.
The monomeric structure of 3a ( 408C) follows from the
1:1:1 triplet (1J(15N,6Li) ˆ 7.5 Hz) in the 15N NMR spectrum.
6
This confirms that only one Li atom is linked to the central
6
nitrogen atom. The Li NMR spectrum ( 408C) displays a
singlet, which is accompanied by satellite signals with coupling
constants of 1J(15N,6Li) ꢀ 7.5 Hz and 2J(119/117Sn,6Li) ꢀ
7.5 Hz. The monomer 3a exhibits a broad 119Sn NMR signal
at room temperature which splits below 208C into two
broadened signals of equal intensity. Again there are 15N
satellites, as well as 119Sn (AB spin system) and 117Sn satellites
(AX spin system), indicating that the two 119Sn NMR signals
belong to tin atoms in the same molecule. Apparently there is
restricted rotation about the Li N(SnMe3)2 bond (DG=ˆ
Figure 2. Molecular structure of [{(Me3Sn)2NLi(tBuOMe)}2] (4a; ORTEP,
thermal ellipsoids represent a 25% probability). Selected bond lengths [Š]
and angles [8]: Li1-N1 2.001(5), Li1A-N1 2.022(5), Sn1-N1 2.032(2), Sn2-N1
2.032(2), Li1-O1 1.987(6), O1-C8 1.437(5), Sn1-C1 2.153(3), Sn1-C2
2.164(3), Sn1-C3 2.160(3), Sn2-C6 2.167(3); Sn1-N1-Sn2 111.0(1), Sn1-
N1-Li1 115.4(2), Sn2-N1-Li1 120.2(2), N1-Li1-N1A 103.9(2), Li1-N1-Li1A
76.1(2), N1-Sn1-C1 107.4(1), N1-Sn2-C6 114.4(1).
1
43.1 Æ 1.0 kJmol ), a feature observed here for the first time.
3406
ꢀ WILEY-VCH Verlag GmbH, D-69451 Weinheim, 2001
1433-7851/01/4018-3406 $ 17.50+.50/0
Angew. Chem. Int. Ed. 2001, 40, No. 18

COMMUNICATIONS
Ghotra, Inorg. Chim. Acta 1975, 13, 11 ± 16; d) T. D. Tilley, R. A.
Andersen, A. Zalkin, Inorg. Chem. 1984, 23, 2271 ± 2276; e) H. Cheng,
R. A. Bartlett, H. V. Rasika Dias, M. M. Olmstead, P. P. Power, J. Am.
Chem. Soc. 1989, 111, 4338 ± 4345.
Thus, the molecular structure in solution must be very similar
to that ªfrozenº in the solid state. Similar findings can be
deduced fom the NMR data available for 3b and 4b; in this
case additional data arises from the presence of the 29Si
isotope. The low-temperature NMR spectra are further
complicated by the presence of two isomers in the case of
4b and two rotamers in the case of 3b.[15]
The application of the new building blocks has been
documented with two extreme examples. The reactions of
the bulky substituted silicon and aluminum halides with 2a
[Eq. (1)] proceed under mild conditions ( 258C) providing
[3] T. Seifert, W. Storch, M. Vosteen, Eur. J. Inorg. Chem. 1998, 1343 ±
1349.
[4] Yu. I. Dergunov, V. F. Gerega, O. S. Dꢁyachkovskaya, Usp. Khim.
1977, 46, 2139; Russ. Chem. Rev. 1977, 46, 1132.
[5] K. Sisido, S. Kozima, J. Org. Chem. 1964, 29, 907 ± 909.
[6] H. W. Roesky, H. Wietzer, Chem. Ber. 1974, 107, 3186 ± 3190.
[7] a) Crystal structure analysis: Siemens/Bruker P4 diffractometer, CCD
area detector with Siemens LT
2
device; MoKa radiation, l ˆ
0.71063 Š, graphite monochromator; single crystals, coated with
perfluoroether oil, were mounted on a glass fiber. Crystal data were
determined and intensity data recorded at 193 K. The data reduction
was carried out by using the program SAINT, the structure solution by
the Patterson method, and the refinement by using the SHELXTL
system;[16] final refinement was performed by using the SHELX-97
programs.[17] All atoms except the hydrogen atoms are described with
anisotropic temperature factors, all hydrogen positions were geo-
metrically placed (d(C H) ˆ 0.96 Š) and refined by using the riding
model and fixed Uij. b) Crystal structure data of 3a: Mr ˆ 521.84;
colorless rhombs; size 0.20 Â 0.20 Â 0.30 mm, monoclinic; space group
P2(1)/n, Z ˆ 4, a ˆ 9.671(1), b ˆ 15.367(3), c ˆ 17.007 Š, b ˆ
1
101.73(1)8, Vˆ 2474.82(5) Š3, 1calcd ˆ 1.401 Mgm 3, m ˆ 2.020 mm
,
the products in good yield. These reactions can be carried out
with crude 2a, isolated as a powdery substrate, redissolved in
Et2O. The reaction of the halides with 1a instead of 2a was
unsuccessful even at elevated temperatures. To our knowl-
edge there is no other convenient route for the introduction of
the distannylamine moiety.[15]
F(000) ˆ 1048. Data collection: 10248 reflections in 10 ꢁ h ꢁ 10,
17 ꢁ k ꢁ 12, 18 ꢁ l ꢁ 18, 2q range 13.64 ± 46.508; 3078 independent
reflections; Rint ˆ 0.0366, 2331 reflections with Fo > 4s(Fo), semiem-
pirical absorption correction, max/min transmission: 1.000/0.787;
GOOF ˆ 1.117; 210 variables, R ˆ 0.040, wR2 ˆ 0.0919, largest differ-
ence peak: 0.921 eŠ 3. c) Crystallographic data (excluding structure
factors) for the structures reported in this paper have been deposited
with the Cambridge Crystallographic Data Centre as supplementary
publication no. CCDC-159571 (3a) and CCDC-159570 (4a). Copies of
the data can be obtained free of charge on application to CCDC, 12
Union Road, Cambridge CB21EZ, UK (fax: (‡44)1223-336-033;
e-mail: deposit@ccdc.cam.ac.uk).
Experimental Section
N-lithiobis(trimethylstannyl)amine 2a, [(Me3Sn)2NLi(pmdta)] (3a), and
[(Me3Sn)2NLi(MeOtBu]2 (4a): A solution of 1a (2.53 g, 5 mmol) in hexane
(20 mL) was cooled at 508C, and BuLi (3.1 mL, 1.6m in hexane) was
added dropwise over 15 min under vigorous stirring. After the reaction
mixture had been allowed to slowly attain ambient temperature (15 h), the
white precipitate was filtered off, and volatile material was removed in
vacuo (10 3 Torr, 4 h). The colorless, extremely air- and moisture-sensitive
powder 2a was suspended in hexane (20 mL), cooled at 408C, and pmdta
(1.0 mL, 0.87 g, 5.0 mmol) was added. The colorless liquid was cooled in a
freezer at 788C for 30 days, from which 3a (1.80 g, 69%; m.p. >1288C
(decomp)) crystallized as colorless prisms. Dissolution of 2a in tBuOMe
(15 mL), followed by storage of the solution at 208C for 10 days gave
crystals of the dimer 4a (1.66 g, 76%; m.p. >2608C (decomp)). The
compounds 2b, 3b, and 4b could be obtained in the same way.[15]
[8] Crystal structure data of 4a: General data see ref. [7a]. Crystal data:
Mr ˆ 436.68; colorless prism; size 0.20  0.20  0.20 mm, monoclinic;
space group P2(1)/n, Z ˆ 4, a ˆ 9.912(2), b ˆ 17.966(4), c ˆ
3
10.925(3) Š, b ˆ 112.12(1)8, Vˆ 1802.4(7) Š3, 1calcd ˆ 1.609 Mgm
,
m ˆ 2.756 mm 1, F(000) ˆ 856. Data collection: 8637 reflections in
10 ꢁ h ꢁ 11, 21 ꢁ k ꢁ 21, 12 ꢁ l ꢁ 12, 2q range ˆ 13.64 ± 49.428;
2709 independent reflections; Rint ˆ 0.0271, 2412 reflections with Fo >
4s(Fo), semiempirical absorption correction, max/min transmission:
0.6087/0.6087; GOOF ˆ 1.109, 196 variables, R ˆ 0.0262, wR2 ˆ 0.0580,
3
[7c]
largest difference peak: 0.605 eŠ
.
[9] H. Zhang, I. L. Atwood, R. S. Rove, M. F. Lappert, University of
Sussex, Brighton, 1987, unpublished results.
[10] X-Ray structural analysis of [(Me3Si)2NLi([12]crown-4)]: P. P. Power,
X. Xiaojie, J. Chem. Soc. Chem. Commun. 1984, 358 ± 361.
[11] A. Appel, C. Kober, C. Neumann, H. Nöth, M. Schmidt, W. Storch,
Chem. Ber. 1996, 129, 175 ± 189.
[12] a) M. F. Lappert, M. J. Slade, A. Singh, J. L. Atwood, R. D. Rogers, R.
Shakir, J. Am. Chem. Soc. 1983, 105, 302 ± 304; b) L. M. Engelhardt,
A. S. May, C. L. Raston, A. H. White, J. Chem. Soc. 1983, 1671 ± 1673.
[13] a) R. E. Mulvey, Chem. Soc. Rev. 1991, 20, 167 ± 209; b) R. E. Mulvey,
Chem. Soc. Rev. 1998, 27, 339 ± 345; c) K. Gregory, P. von R. Schleyer,
R. Snaith, Adv. Inorg. Chem. 1991, 37, 47 ± 142.
[14] a) J. L. Rutherford, D. B. Collum, J. Am. Chem. Soc. 2001, 123, 199 ±
202; b) P. C. Andrews, P. J. Duggan, G. D. Fallon, T. D. McCarthy,
A. C. Peatt, J. Chem. Soc. Dalton Trans. 2000, 1937 ± 1945; c) K. B.
Aubrecht, B. J. Licht, D. B. Collum, Organometallics 1999, 18, 2981 ±
2987; d) M. A. Nichols, D. Waldmüller, P. G. Williard, J. Am. Chem.
Soc. 1994, 116, 1153 ± 1154.
3a: 1H, 13C, 6Li, 15N, and 119Sn NMR (C6D6 or [D8]toluene): d(1H) ˆ 0.37 (s,
2J(119Sn,1H) ˆ 48.8 Hz, 18H; SnMe3), 1.68 ± 1.72 (brs, 15H; NMe and
NMe2), 2.01 ± 2.18 (brs, 8H; CH2); d(13C) ˆ 0.2 (1J(119Sn,13C) ˆ 297.3 Hz,
SnMe3), 46.2 (NMe2), 53.7 (NMe), 57.1, 58.4 (CH2); at 408C: d(6Li) ˆ
2.7 (1J(15N,6Li) ˆ 7.5, 2J(119Sn,6Li) ˆ 7.5 Hz); d(15N) ˆ 359.6 (1:1:1 t,
1J(15N,6Li) ˆ 7.5 Hz);
d(119Sn) ˆ 49.3
(brs,
1J(119Sn,15N) ˆ 148,
2J(119Sn,117Sn) ˆ 470 Hz), 54.4 (brs, 1J(119Sn,15N) ˆ 146, 2J(119Sn,117Sn) ˆ
470 Hz).
4a: 1H, 13C, 6Li, 15N, and 119Sn NMR ([D8]toluene): d(1H) ˆ 0.69 (s,
2J(119Sn,1H) ˆ 49.2 Hz, 36H; SnMe3), 1.02 (s, 18H; tBu), 3.05 (s, 6H; Me);
d(13C) ˆ 1.83 (1J(119Sn,13C) ˆ 320.6 Hz, SnMe3), 27.2 ((CH3)3), 50.2
(OMe), 75.0 (OC); at
408C: d(6Li) ˆ 3.1 (1J(15N,6Li) ˆ 4.5 Hz);
d15N ˆ 366.2 (1:2:3:2:1 q, 1J(15N,6Li) ˆ 4.5 Hz), d(119Sn) ˆ 63.0 (brs,
2
1J(119Sn,15N) ˆ 143.5, J(119Sn,117Sn) ˆ 467 Hz).
Received: March 26, 2001 [Z16847]
[15] A full account of these data and of the synthesis and structure of 3b
and 4b will be given elsewhere.
[16] SHELXTL Plus, PC version, Siemens Analytical X-ray Instruments,
Inc., Madison, WI, 1980.
[17] G. M. Sheldrick, SHELXL-97, Program for the Refinement of Crystal
Structures, University of Göttingen, 1997.
[1] U. Wannagat, H. Niederprüm, Chem. Ber. 1961, 94, 1540 ± 1547.
[2] a) M. F. Lappert, P. P. Power, A. R. Sanger, R. C. Srivastava, Metal
and Metalloid Amides, Ellis Horwood/Wiley, Chichester, 1980,
pp. 689 ± 691; b) P. G. Eller, D. C. Bradley, M. B. Hursthouse, D. W.
Meek, Coord. Chem. Rev. 1977, 24, 1 ± 95; c) D. C. Bradley, J. S.
Angew. Chem. Int. Ed. 2001, 40, No. 18
ꢀ WILEY-VCH Verlag GmbH, D-69451 Weinheim, 2001
1433-7851/01/4018-3407 $ 17.50+.50/0
3407