Bis[1,3-bis(diphenylmethylsilylamido)propane]zirconium: A spirocyclic complex containing a sterically demanding chelating amido ligand

Article abstract of DOI:10.1515/znb-1999-1007

Lithiation of the diamine CH₂(CH₂NHSiMePh₂)₂ using n-butyl lithium and subsequent reaction with zirconium tetrachloride yielded the bis(chelate)-amidozirconium complex [Zr{CH₂(CH₂NSiMePh₂)₂}₂]. The spirocyclic molecule has a distorted tetrahedral coordination at the zirconium centre with overall C₂ symmetry broken only by the relative orientation of four phenyl rings. The bulky diphenylmethylsilyl substituents at the amido-N functions as well as the ligand backbone sterically protect the metal centre and render it inert towards conproportionation with zirconium chloride.

Full text of DOI:10.1515/znb-1999-1007

Bis[l,3-bis(diphenylmethylsilylamido)propane]zirconium: A Spirocyclic
Complex Containing a Sterically Demanding Chelating Amido Ligand
Santiago Garcia-Yustea, Konrad W. Hellmanna, Lutz H. Gadeb’*, Ian J. Scowenc,
and Mary McPartlinc
a Institut für Anorganische Chemie der Universität Würzburg,
Am Hubland, 97074 Würzburg, Germany
b Laboratoire de Chimie Organometallique et de Catalyse, UMR 7513, Institut Le Bel,
Universite Louis Pasteur, 4, rue Blaise Pascal, 67070 Strasbourg Cedex, France
c School of Applied Chemistry, University of North London,
Holloway Road, London N7 8 DB, U.K.
* Reprint requests to Prof. L. H. Gade. E-mail: gade@chimie.u-strasbg.fr
Dedicated to Prof. R. Schmutzler on the occasion of his 65lh birthday
Z. Naturforsch. 54 b, 1260-1264 (1999); received July 2, 1999
Silylamides, Zirconium Amide, Chelate Ligands, Crystal Structure
Lithiation of the diamine CH2 (CH2 NHSiMePh2 ) 2 using »-butyl lithium and subsequent
reaction with zirconium tetrachloride yielded the bis(chelate)-amidozirconium complex
[Zr{CH2 (CH2 NSiMePli2 )2 }2 ]- The spirocyclic molecule has a distorted tetrahedral coordi-
nation at the zirconium centre with overall C2 symmetry broken only by the relative orientation
of four phenyl rings. The bulky diphenylmethylsilyl substituents at the amido-N functions
as well as the ligand backbone sterically protect the metal centre and render it inert towards
conproportionation with zirconium chloride.
Introduction
chelating amido ligand [CH2(CH2NSiMe3 )2 ]2~,
which was first reported by Bürger and cowork-
ers [10] has recently been studied by us, both in
connection with the synthesis of early-late heter-
obimetallic complexes [11 - 13] and the prepa-
ration of novel amido complexes of the heavy
group 13 elements [14, 15]. The effective steric
shielding of the metal atoms in the systems stud-
ied to date is due to the folded propylene chain
of the chelate ring as well as the peripheral silyl
groups. In order to enhance the stability of the
complexes we have increased the steric demand
of the N-bonded silyl functions. In this paper we
wish to report first results obtained with the new
/V-methyldiphenylsilyl substituted chelating amido
The chemistry of group 4 metal complexes con-
taining chelating amido ligands has recently at-
tracted considerable attention in the quest for early
transition metal complex fragments which may
replace the well established metallocene deriva-
tives. The development of several high activity
olefin polymerization catalysts containing diamido
chelates, in particular, has fuelled the research in this
area [1 - 8], It appears that the size of the chelate
ring as well as the nature of the peripheral N-bound
groups are crucial parameters determining the re-
activity of the systems. Other application-oriented
research focussing on spirocyclic volatile chelate-
amido complexes for use in MOCVD technology
has been reported by Herrmann and coworkers [9].
ligand [CH2(CH2NSiMePh2 )2 ]2_.
Results and Discussion
Apart from these applications in polymer synthe-
sis and materials chemistry, the stabilization of re-
active complex fragments which may be employed
in stoichiometric organometallic reactions or as
molecular building blocks has been an important as-
pect of research in this field. The coordination chem-
istry of the dianionic /V-trimethylsilyl substituted
The amino precursor CH2 (CH2NHSiMePh2 )2 (1)
of the difunctional ligand was synthesized by con-
densation of 1,3-diaminopropane with PfbMeSiCl
using Et}N as auxiliary base. Lithiation with butyl-
lithium in thf yielded the solvated lithiumamide
[CH2 {CH2 N(Li-thf)SiMePh2 }2 ] (2) which may be
K
0932-0776/99/1000-1260 $ 06.00 (c) 1999 Verlag der Zeitschrift für Naturforschung. Tübingen • www.znaturforsch.com
Brought to you by | New York University Bobst Library Technical Services
Authenticated
Download Date | 6/21/15 10:37 PM

S. Garcia-Yuste et al. ■Bis[l,3-bis(diphenylmethylsilylamido)propane]zirconium
1261
CI13A) CI18A)
CI18)
~ CI131
isolated as a colourless oil or, alternatively, gener-
ated in situ for further conversions (Scheme 1).
BuLi/thf
n
/
\
MePh,Si
SiPh2Me MePh,Si
/NWLi Li/NN
/
\
thf
thf
2
Scheme 1
Reaction of 2 with zirconium tetrachloride in a
2 :1 ratio in toluene gave the spirocyclic, homoleptic
zirconium complex [Zr{CH2(CH2NSiMePh2)2}2]
(3) which was obtained as a crystalline colourless
solid (70% yield) (Scheme 2).
n
ZrCL/toluene
N
N
n
MePh2Si
SiPh2Me
CM2AT~^cw7At
MePh2Si / \ SiPh2Me
SiPh,Me
MePh2Si
/\ i*' L i
\
thf
N N
thf
Fig. 1. A view of the disordered molecular structure
of [Zr{CH2 (CH2 NSiMePh2)2}2] (3) which has virtual
C2 symmetry in the crystal. Unfavourably short con-
tact distances between symmetry related components
of the disordered phenyl rings [C(41)- • C(41a) 3.221,
H(41)- • H(41a) 1.98 A] reduce the molecular symmetry
to Ci for individual molecules.
2
Scheme 2
In order to establish the molecular structure of
complex 3 and, in particular, to assess the influence
of the increased steric bulk of the diphenylmethylsi-
lyl groups, a single crystal X-ray structure analysis
was carried out. Two different views of the molec-
ular structure of 3 in the crystal are displayed in
Fig. 1 and 2, while the principal bond lengths and
interbond angles are listed in Table I.
Si(l) and Si(la) as shown in Fig. 1. However, exact
C2 symmetry for the individual molecules is ruled
out by unfavourably short contacts between sym-
metry related phenyl rings [C(41)- • C(41a) 3.221,
H(41)- • H(41a) 1.976 A, cf. respective sums of Van
der Waals radii 3.50 and 2.40 A] as a consequence of
the steric congestion in the co-ordination sphere. As
a result two orientations of disordered phenyl rings
C(40)/C(40A) reduce the molecular symmetry to
C i. The structural centre piece is the distorted tetra-
hedral tetraamidozirconium unit which links the two
chelate rings to form an overall spirocyclic arrange-
ment (Fig. 2).
The “intra-ring” N-Zr-N angles [N( 1)-Zr( 1)-N(2)
101.59(13)°] are markedly smaller than the “inter-
ring” N-Zr-N angles [N(l)-Zr(l)-N(l') 112.4(2),
N(l)-Zr(l)-N(2') 113.80(13)°] which is a conse-
quence of the steric constraints imposed by the lig-
and framework. In the only other structurally char-
acterized example of a spirocyclic tetraamidozirco-
nium complex reported by Bürger and coworkers,
l{Me2Si(N/Bu)2 }2Zr] [16], the distortion from a
tetrahedral arrangement of the donor functions is
Table I. Selected bond lengths and angles for
[Zr{CH2(CH2 NSiMePh2 )2 }2 ] (3).
a) Lengths (A)
Zr(l)-N(l)
Si(l)-N(l)
Si(l)-C(4)
Si(l)-C(10)
Si(l)-C(20)
N(l)-Cl)
2.065(3) Zr(l)-N(2)
2.059(3)
1.732(4)
1.860(5)
1.884(4)
1.896(4)
1.728(4)
1.865(5)
1.903(3)
Si(2)-N(2)
Si(2)-C(5)
Si(2)-C(30)
1.875(6) Si(2)-C(40)
N(2)-C(2)
C(2)-C(3)
1.493(6)
1.478(7)
1.489(6)
1.484(7)
C(l)-C(3)
b) Angles (°)
N(l)-Zr(l)-N(2)
N(l)-Zr(l)-N(la)
113.9(2)
114.1(2)
101.5(2) N(l)-Zr(l)-N(2a)
112.4(2) N(2)-Zr( 1)-N(2a)
Zr( 1)-N( 1)-Si( 1) 128.0(2) Zr( 1)-N(2)-Si(2) 129.4(2)
Zr(l)-N(l)-C(l) 117.3(3) Zr(l)-N(2)-C(2) 115.5(3)
Si(l)-N(l)-C(l) 114.7(3) Si(2)-N(2)-C(2) 115.0(3)
N(l)-C(l)-C(3)
C(l)-C(3)-C(2)
116.7(4)
116.9(4) N(2)-C(2)-C(3)
119.1(5)
In the crystal there is a crystallographic C2 axis even more pronounced due to the small bite angle
through the metal atom and the midpoint between
defined by the chelating diamidosilane ligands.
Brought to you by | New York University Bobst Library Technical Services
Authenticated
Download Date | 6/21/15 10:37 PM

1262
S. Garcia-Yuste et al. ■Bis[l,3-bis(diphenylmethylsilylamido)propane]zirconium
bond distance in these two chelate compounds
is longer that of 2.025(3) Ä in the complex
[ZrCl(/i-Cl){N(SiHMe2 )2 }2]2 which has monoden-
tate amido ligands and an effectively six-coordinate
geometry at zirconium [2 0 ]; in the latter compound
the presence of two electronegative chloro ligands
apparently enhances the 7r-donation from the nitro-
gen donors. In [ZrCl{N(SiMe3 )2}3 ] [2.070(3) A]
[2 1 ], where there are only one chloro ligand and
three monodentate amido ligands, the Zr-N bond is
longer than in the dichloride, and is not significantly
different from that in the present study.
The molecular structure of 3 shows, that the
metal centre is very efficiently shielded by the lig-
and backbone as well as the peripheral substituents.
This renders the compound inert towards conpro-
portionation reactions with ZrCU carried out in
toluene at 90°C in order to obtain the amidochloro
mixed-ligand complex. This contrasts the facile
convertability of the trimethylsilyl-substituted ana-
Fig. 2. The spirocyclic structure of
[Zr{CH2(CH2NSiMePh2)2}2] (3) showing the distorted
tetrahedral co-ordination at the zirconium centre.
logue which we reported previously [1 1 ].
The geometry at the nitrogen-N atoms in 3
is trigonal planar (sum of the interbond angles,
N(l): 360.0, N(2): 359.9°) as has been observed
in nearly all the established crystal structures of
transition metal amides [17]. A structural conse-
quence of the planarity of the nitrogen donor func-
tions is the “half-twist” conformation [18] of the
two six-membered chelate rings. The four diphenyl-
methylsilyl substituents of the amido functions in
the complex adopt a very similar orientation with
respect to the central structural unit. Wheras the Si-
bonded methyl groups point in the direction of the
amido functions the phenyl groups are oriented to-
wards the propylene ligand backbone (Fig. 2). The
pairs of phenyl groups on each silyl substituent are
approximately orthogonal to each other (dihedral
angles range from 73.8 to 85.0°) with the exception
of one component of the disorder; the ring [C(40)-
C(45)] is at an angle of 55.4° to [C(30)-C(35)].
Mutually perpendicular relative orientations for the
phenyl rings are observed in many diphenylphos-
phido and diphenylphosphinomethane compounds
[19]. The zirconium-nitrogen distances are equal
within experimental error and although the mean
Zr-N bond length of 2.062(3) Ä is slightly longer
than the mean value of 2.053(2) A in the bis-
chelate complex [{Me2Si(NrBu)2 }2Zr] the dif-
ference is of low significance. The mean Zr-N
Experimental Part
All manipulations were performed under dry argon
in standard (Schlenk) glassware which was flame dried
with a Bunsen burner prior to use. Solvents were dried
according to standard procedures and saturated with Ar.
The deuterated solvents used for the NMR spectroscopic
measurements were degassed by three successive “freeze-
pump-thaw” cycles and dried over 4-A molecular sieves.
The 1H, l3 C, and2ySi NMR spectra were recorded on a
Bruker AC 200 spectrometer equipped with a B-VT-2000
variable temperature unit (at 200.13, 50.32, and 39.76
MHz, respectively) with tetramethylsilane as reference.
Infrared spectra were recorded on Perkin Elmer 1420
and Bruker IRS 25 FT-spectrometers. Elemental analyses
were carried out in the microanalytical laboratory of the
chemistry dept, at Würzburg.
1,3-Bis(diphenylmethylsilylamino)propane (\)
Diphenylmethylchlorosilane (7.63 g, 32.8 mmol) dis-
solved in 50 ml of diethyl ether was added dropwise to
a stirred solution of 1.3-diaminopropane (1.22 g, 16.4
mmol) and triethylamine (3.32 g, 32.8 mmol) in diethyl
ether (200 ml)which was cooled to 0°C. The reaction mix-
ture was stirred at r.t. for 15 h, the solid triethylammonium
chloride formed in the reaction subsequently removed by
filtration. The solvent of the filtrate was removed in vacuo
at r.t. and the oil remaining in the reaction vessel kept
under vacuum (10- 3 mbar) for 3h after which time no
Brought to you by | New York University Bobst Library Technical Services
Authenticated
Download Date | 6/21/15 10:37 PM

S. Garcia-Yuste et al. ■Bis[l,3-bis(diphenylmethylsilylamido)propane]zirconium
1263
Table II. Crystal data and structure refinement for com-
plex 3.
residual solvent could be detected by NMR spectroscopy.
Yield 6 .12 g (80 % ).).-1H NMR (C6 D6): 6 = 0.88 (s, 6 H,
SiCH3), 1.62 (m, 2H, C//2 CH2 N), 2.91 (vt, 4H, CH2 N),
7.43 (m, 20H, SiPh2).- I3 C{'H} NMR (C6 D6): 6 = -2.6
(SiCH3), 38.8 (CH2CH2 N), 39.7 (CH2 N), 127.7 (C3,5,
Ph), 129.5 (C4, Ph), 134.4 (C2’6, Ph), 137.8 (C1, Ph).-
7 Li{1H} NMR(C6 D6): 6 =0.24.- 2 9 Si{1H} NMR (C6 D6):
6 = -19.3.
C58H64N4Si4Zr
1020.71
monoclinic
Empirical formula
fw
Crystal system
Space group
Unit cell dimensions
a [A]
b [A]
c[ A]
a[°]
/2/a (No. 15)
17.564(2)
18.4050(14)
18.510(3)
-
C29 H34 N2 Si2 (466.77)
Calcd C 74.62 H 7.34 N 6.00 %,
Found C 74.50 H7.19 N5.91% .
114.942(8)
ß [°]
-v r°i
Dilithium [1,3-bis(diphenylmethylsilylamido)propane]
tris(tetrahydrofuran) (2)
V [A3, Z]
Z
5425.7(10)
4
1.250
Mo-Ä^q (0.71073)
0.331
Dcaic / Mg m- 3
Radiation (A/A)
p [mm-1]
Butyllithium (5.00 mmol, 2.5 ml of a 2M solu-
tion in hexane) was added to a stirred solution of
CH2 (CH2NHSiMePh2 ) 2 (1.17 g, 2.50 mmol) in tetrahy-
drofuran which was cooled to -78°C. The reaction mixture
was warmed to r.t. and stirred for another 30 min. After
removal of the solvent the solvated lithium amide was
isolated as an analytically pure viscous oil in quantitative
yield (1,55g).-1H NMR (C6 D6): 6 = 0.68 (s, 6 H, SiCH3),
1.18 (m, 8 H, C //2 CH20), 1. 8 6 (m, 2H, C//2CH2 N), 3.27
(m, 8 H, CH2C //2 0), 3.86 (vt, 4H, CH2 N), 7.16 (m,
20H, SiPh2).- i3 C{'H} NMR (C6 D6): 6 = -0.6 (SiCH3),
25.2 (CH2CH2 0), 41.5 (CH2CH2 N), 50.5 (CH2 N), 68.5
(CH2 CH20), 128.0(C3-5, Ph), 128.2(C4, Ph), 134.9(C26,
Ph), 145.2 (C1, Ph).- 7 Li{1H} NMR (C6 D6): 6 = 0.24.-
29Si{1H} NMR (C6 D6): 6 = -19.3.
F(000)
2144
Crystal size [mm]
0-Range [°]
Limiting hkl indices
0.52 x 0.32 x 0.30
2.21 to 23.00
-19 to 19,-20 to 20,
- 2 0 to 2 0
Reflections collected
Independent reflections (Rmi)
Max / min transmission
Data / restraints / parameters
5 on F2
Final R indices'
[I > 2cr(I)] (all data)
7820
3790 (0.0422)
0.9464/0.4817
3790 / 27 / 273
1.055
/?, =0.0550,
wRi = 0.1245
/?, = 0.0843,
wR-> = 0.1336
0.0602, 9.4998
0.509 and -0.426
C3 7 H4 8N2 Si2 L i.O (622.85)
Weights a, b1
Max and min Ap [eA-3]
Calcd C 71.35 H 7.77 N 4.50 %,
Found C 71.24 H 7.45 N 4.45 %.
1 S = [I w(F0 2 - Fc2)2/(n - p) ] l / 2 where n = number of
reflections and p = total number of Parameters, R\ = X|IFJ
- IFCI|/X IFol, w/ ? 2 = I [w(F0 2 - Fc2)2]/! [w(F02)2]i/Z,
w- 1 = [cr(F„ ) 2 + (aP) 2 + bP], P = [max(Fo2 ,0) + 2(Fc2 )]/3.
Bis[ 1,3-bis(diphenylmethylsilylamido)propane]zir-
conium (3)
Butyllithium (39.84 mmol, 99.6 ml of a 2.5 M solu-
tion in hexane) was slowly added to a stirred solution of
CH2 (CH2 NHSiMePh2 ) 2 (9.3 g, 19.92 mmol) in toluene
(30 ml), which was cooled to -40°C. The reaction mix-
ture was warmed to r.t. and, after the evolution of butane
had subsided, heated briefly under reflux. After stirring
at r.t. for another 30 min, the solution was cooled to
-50°C. Solid ZrCU (4.39 g, 19 mmol) was added, the
reaction mixture warmed to roomtemperature and the so-
lution stirred for another 4 d. After evaporation of the
solvent in vacuo the residue was extracted with pentane
(C6 D6): 6 = 0.2 (SiCH3), 39.0 (CH2CH2 N), 52.6 (CH2 N),
127.9 (C3-5, Ph), 129.3 (C4, Ph), 135.5 (C2 6, Ph), 138.2
(C1, Ph).- 2 9 Si{1H} NMR (C6 D6): 6 = -14.5.
C58H64N4Si4Zr (1020.74)
Calcd C 68.25 H 6.32 N 5.49 %,
Found C 68.09 H 6 .ll N 5.06 %.
Crystal structure determination of 3
Data collection for 3. A crystal was mounted in
(50ml) and the volume of the filtered extract reduced to ca. a Lindemann capillary under argon and in an inert
10 ml. Storage at -35°C yielded the zirconium complex
[Zr{CH2 (CH2 NSiMePh2 )2 }2 ] as a colourless crystalline
oil. X-ray intensity data were collected, with graphite-
monochromated radiation, on a Siemens P4 four-circle
solid. Yield 70%. M.p. 106°C (dec.).- 'H NMR (C6 D6): 6 diffractometer. Details of data collection, refinement and
= 0.90 (s, 6 H, SiCH3), 1.77 (m, 2H, C//2 CH2 N), 3.37 (m, crystal data are listed in Table II. Lorentz-polarisation and
4H, CH2 N), 7.00 - 7.60 (m, 20H, SiPh2).- I3 C{’H} NMR absorption corrections were applied to the data.
Brought to you by | New York University Bobst Library Technical Services
Authenticated
Download Date | 6/21/15 10:37 PM

1264
S. Garcia-Yuste et al. • Bis[l,3-bis(diphenylmethylsilylamido)propane]zirconium
Structure solution and refinementfor 3. The positions assigned anisotropic displacement parameters in the final
cycles of full-matrix least-squares refinement.
of the metal atom and most of the non-hydrogen atoms
were located by direct methods [22]. The positions of the
Crystallographic data for the structure of 3 reported
remaining non-hydrogen atoms were found from subse- in this paper have been deposited with the Cambridge
quent difference-Fourier sytheses. Two phenyl rings in
the asymmetric unit were disordered corresponding to tion no. CCDC-33563. Copies of the data can be obtained
Crystallographic Data Centre as supplementary publica-
a rotation about the corresponding Si-C bond, and for
both rings the ortho- and meta-carbon atoms were each
free of charge on application to The Director, CCDC, 12
Union Road, Cambridge CB2 1EZ, UK (fax.: int code
resolved into two components of 50:50 occupancy. Re- +(1223) 336033: e-mail: deposit@chemcrys.cam.ac.uk).
finement was based on F~ [22], and the disordered phenyl
rings were constrained to idealised geometry (C-C 1.39
A). All hydrogen atoms were placed in calculated posi-
tions with displacement parameters set equal to 1.2 Ueq
of the parent carbon atoms for the methylene and phenyl
groups, and 1.5Ueqfor the methyl groups. Semi-empirical
absorption corrections [2 2 ] using i/’-scans were applied
to the data. All full-occupancy non-hydrogen atoms were
Acknowledgements
This work was supported by the Deutsche Forschungs-
gemeinschaft (SFB 347), the European Union (TMR net-
work MECATSYN) and the Engineering and Physical
Science research Council (UK).
[14] K. W. Hellmann, L. H. Gade, R. Fleischer, D. Stalke,
Chem. Commun. 527 (1997).
[1] G. J. P. Britovsek, V. C. Gibson, D. F. Wass, Angew.
Chem., Int. Ed. Engl. 38, 429 (1999).
[15] K. W. Hellmann, A. Bergner, L. H. Gade, I. J.
Scowen, M. McPartlin, J. Organomet. Chem. 573,
156(1999).
[16] D. J. Brauer, H. Bürger, E. Essig, W. Gschwandtner,
J. Organomet. Chem. 190, 343 (1980).
[17] M. H. Chisholm, I. P. Rothwell, in G. Wilkinson, R.
D. Gillard, J. A. McCleverty (eds.): Comprehensive
Coordination Chemistry, Vol. 2, Pergamon Press,
Oxford p. 161 (1987).
[18] F. A. Carey, R. J. Sundberg: Advanced Organic
Chemistry - Part A, 2nd Ed., p. 113, Plenum Press,
New York (1984).
[2] T. W. Warren, R. R. Schröck, W. M. Davis,
Organometallics 15, 562 (1996).
[3] F. G. N. Cloke, T. J. Geldbach, P. B. Hitchcock,
J. Organomet. Chem. 506, 343 (1996).
[4] J. D. Scollard, D. H. McConville, J. Am. Chem. Soc.
118, 10008(1996).
[5] N. A. H. Male, M. Thornton-Pett, M. Bochmann,
J. Chem. Soc., Dalton Trans. 2487 (1996).
[6 ] J. D. Scollard, D. H. McConville, J. J. Vittal,
Organometallics 16, 4415 (1997).
[7] A. D. Horton, J. de With, Chem. Commun. 1375
(1996).
[19] See for example K.A. Azam, M.B. Hursthouse,
M.R. Islam, S.E. Kabir, K.M.A. Malik, R. Miah,
C. Sudbrake, H. Vahrenkamp. J. Chem. Soc., Dal-
ton Trans. 1097 (1998).
[20] W. A. Herrmann. N. W. Nuber, J. Behm, Chem. Ber.
125, 1405 (1992).
[8 ] F. Jäger, H. W. Roesky, H. Dorn, S. Shah, M. Nolte-
meyer, H.-G. Schmidt, Chem. Ber. 130, 399 (1997).
[9] W. A. Herrmann, M. Denk, R. W. Albach, J. Behm,
E. Herdtweck, Chem. Ber. 124, 683 (1991).
[10] H. Bürger, D. Beiersdorf, Z. Anorg. Allg. Chem. 459,
111 (1979).
[21] C. Airoldi, D. C. Bradley, H. Chudzynska, M. B.
Hursthouse, K. M. A. Malik, P. R. Raithby, J. Chem.
Soc., Dalton Trans. 2010 (1980).
[22] G. M. Sheldrick, SHELTXL (PC version 5.03)
Siemens Analytical Instruments Inc., Madison, W1
(1994).
[11] S. Friedrich, L. H. Gade, I. J. Scowen, M. McPartlin,
Organometallics 14, 5344 (1995).
[12] S. Friedrich. L. H. Gade, I. J. Scowen. M. McPartlin,
Angew. Chem., Int. Ed. Engl. 35, 1338 (1996).
[13] S. Friedrich, D. J. M. Trösch, L. H. Gade, I. J.
Scowen. M. McPartlin, Inorg. Chem., in press.
Brought to you by | New York University Bobst Library Technical Services
Authenticated
Download Date | 6/21/15 10:37 PM