New cis- and trans-arylplatinum(II) acetylide compounds containing a bis(imino)aryl [NCN] ligand

Article abstract of DOI:10.1021/om010447w

The first platinum(II) halogenide compounds containing the (σ³-N,C,N)isophtalaldimine ligand, 2a and 2b, have been prepared via an oxidative addition of the bromoisophthalaldimine ligands 1a and 1b to a Pt(0) precursor. Depending on the imine s

Full text of DOI:10.1021/om010447w

Organometallics 2001, 20, 4437-4440
4437
New cis- a n d tr a n s-Ar ylp la tin u m (II) Acetylid e
Com p ou n d s Con ta in in g a Bis(im in o)a r yl [NCN] Liga n d
Wilhelmus J . Hoogervorst,† Cornelis J . Elsevier,*,† Martin Lutz,‡ and
Anthony L. Spek‡
Institute of Molecular Chemistry, Organometallic and Coordination Chemistry,
University of Amsterdam, Nieuwe Achtergracht 166, 1018 WV Amsterdam, The Netherlands,
and Bijvoet Center for Biomolecular Research, Department of Crystal and Structural
Chemistry, Utrecht University, Padualaan 8, 3584 CH Utrecht, The Netherlands
Received May 25, 2001
Ch a r t 1
Summary: The first platinum(II) halogenide compounds
containing the (σ3-N,C,N)isophtalaldimine ligand, 2a
and 2b, have been prepared via an oxidative addition
of the bromoisophthalaldimine ligands 1a and 1b to a
Pt(0) precursor. Depending on the imine substituents,
the reaction of these compounds with LiC≡CSiMe3 in
THF results in a monomeric trans-diorganoplatinum(II)
compound (3) or a dimeric cis-diorganoplatinum(II)
compound (4). Both 3 and 4 have been characterized by
means of an X-ray crystal structure determination.
In tr od u ction
Cis- as well as trans-diorganometallic compounds of
palladium and platinum are relevant to mechanistic
considerations concerning C-C bond formation and
C-C bond activation reactions.1,2 Recently, we have
worked on the organometallic chemistry of late transi-
tion metals involving bidentate nitrogen ligands. Apart
from the coordination chemistry of R-diimine ligands (A,
Chart 1) such as DAB and BIAN, the use of many Pd
and Pt complexes containing such ligands in carbon-
element bond forming reactions has been studied.3
Employing bidentate coordinating R-diimine ligands,
exclusively compounds with cis configuration can be
obtained in a square planar diorganometallic compound
B (Chart 1). In contrast, by using a meridional coordi-
nating ligand of type C (Chart 1) in principle a trans-
diorganoplatinum compound D (Chart 1, R′ ) a carbon
fragment) can be synthesized.
rapidly expanded. Apart from [P-C-P]- 1,5 also [N-C-
7
N]-,6 [S-C-S]-, and [O-C-O]- 8 ligands have been
investigated. Whereas the bis(amino) [N-C-N]- ligand
has extensively been investigated, to our knowledge the
tridentate coordination chemistry of the bis(imino)
[N-C-N]- ligand, C, has hardly been studied.9 Only
one publication by Vila et al. has appeared concerning
palladium(II) derivatives of C (E, Chart 1),10a which
have not been further investigated.10b Other examples
containing 1,3-bis(imino)aryl ligands are limited to
compounds F (Chart 1), where the ligand bridges two
metals after a double ortho-metalation reaction.11
As indicated above, we are particularly interested in
trans-diorganoplatinum compounds of type D (Chart 1),
which should be accessible by transmetalation of a
(5) (a) Rimml, H.; Venanzi, L. M. J . Organomet. Chem. 1983, 259,
C6-C7. (b) Gupta, M.; Hagen, C.; Kaska, W. C.; Cramer, R. E.; J ensen,
C. M. J . Am. Chem. Soc. 1997, 119, 840-841. (c) J ouaiti, A.; Geoffroy,
M.; Collin, J .-P. Inorg. Chim. Acta 1996, 245, 69-73.
(6) (a) van Koten, G. Pure Appl. Chem. 1989, 61, 1681-1694. (b)
Rietveld, M. H. P.; Grove, D. M.; van Koten, G. New. J . Chem. 1997,
21, 751-771. (c) Denmark, S. E.; Stavenger, R. A.; Faucher, A.-M.;
Edwards, J . P. J . Org. Chem. 1997, 62, 3375-3389. (d) Beley, M.;
Collin, J . P.; Louis, R.; Metz, B.; Sauvage, J . P. J . Am. Chem. Soc.
1991, 113, 8521-8522. (e) Canty, A. J .; Patel, J .; Skelton, B. W.; White,
A. H. J . Organomet. Chem. 2000, 599, 195-199.
(7) (a) Errington, J .; McDonald, W. S.; Shaw, B. L. J . Chem. Soc.,
Dalton Trans. 1980, 2312-2314. (b) Dupont, J .; Beydoun, N.; Pfeffer,
M. J . Chem. Soc., Dalton Trans. 1989, 1715-1720.
(8) (a) Markies, P. R.; Altink, R. M.; Villena, A.; Akkerman, O. S.;
Bickelhaupt, F.; Smeets, W. J . J .; Spek, A. L. J . Organomet. Chem.
1991, 402, 289-312.
Ligand C can be seen as a meridional coordinating
ligand of type [D-C-D]-, in which two imine moieties
are used as donor groups. Since the first publication by
Shaw4 concerning a [P-C-P]- ligand, the organome-
tallic chemistry of tridentate ligands of this type has
* Corresponding author. E-mail: else4@anorg.chem.uva.nl.
† University of Amsterdam.
‡ Utrecht University.
(1) Rybtchinski, B.; Milstein, D. Angew. Chem., Int. Ed. 1999, 38,
870-883.
(2) Hill, G. S.; Puddephatt, R. J . Organometallics 1998, 17, 1478-
1486.
(3) (a) Elsevier, C. J . Coord. Chem. Rev. 1999, 185-186, 809-822.
(b) van Laren, M. W.; Elsevier, C. J . Angew. Chem., Int. Ed. 1999, 38,
3715-3717. (c) Delis, J . G. P.; Groen, J . H.; Vrieze, K.; van Leeuwen,
P. W. N. M.; Veldman, N.; Spek, A. L. Organometallics 1997, 16, 551-
562.
(4) Moulton, C. J .; Shaw, B. L. J . Chem. Soc., Dalton Trans. 1976,
1020-1024.
(9) Nu¨ckel, S.; Burger, P. Organometallics 2000, 19, 3305-3311.
(10) (a) Vila, J . M.; Gayoso, M.; Pereira; Lo`pez Torres, M.; Ferna´n-
dez, J . J .; Ferna´ndez, A.; Ortigueira, J . M. J . Organomet. Chem. 1996,
506, 165-174. (b) Vila, J . M. Personal communication.
(11) (a) Philips, I. G.; Steel, P. J . J . Organomet. Chem. 1991, 410,
247-255. (b) Nanda, K. K.; Nag, K.; Venkatsubramanian, K.; Paul, P.
Inorg. Chim. Acta 1992, 196, 195-199.
10.1021/om010447w CCC: $20.00 © 2001 American Chemical Society
Publication on Web 09/15/2001

4438 Organometallics, Vol. 20, No. 21, 2001
Notes
Sch em e 1
Pt(II) halogenide analogue of E. Trans-diorganometallic
compounds of the related bis(dimethylamine) [N-C-
N]- ligand have been synthesized and studied before,
e.g., by van Koten et al.12
Resu lts a n d Discu ssion
The synthesis of the platinum(II) bromide precursors
is shown in Scheme 1. Starting from 2-bromoiso-
phthalaldehyde,13 the novel bisimines 1a (R ) 2,6-(i-
Pr)2-C6H3) and 1b (R ) 4-MeO-C6H4) were synthesized
via a condensation reaction in good yields (76% and 94%,
respectively). The oxidative addition reactions of the
C-Br bond of 1a and 1b to a suitable Pt(0) precursor6c
(Pt(dipdba)2 14) in THF at 50 °C resulted in the forma-
tion of 2a and 2b. After separation from free dipdba by
washing, compounds 2a (63%, orange) and 2b (64%,
reddish brown) were isolated as air stable solids after
crystallization.
F igu r e 1. Displacement ellipsoid plot of 3 with ellipsoids
drawn at the 50% probability level. Hydrogens are omitted
for clarity. Selected bond lengths (Å) and angles (deg):
Pt(1)-N(1)2.050(2);Pt(1)-N(2)2.043(2);Pt(1)-C(1)1.945(2);
Pt(1)-C(33) 2.065(3); C(33)-C(34) 1.200(4); N(1)-C(7)
1.306(3); N(2)-C(8) 1.303(3). N(1)-Pt(1)-N(2) 157.21(9);
C(1)-Pt(1)-C(33) 178.41(9); C(1)-Pt(1)-N(1) 78.55(9);
C(1)-Pt(1)-N(2) 78.76(9); Pt(1)-C(33)-C(34) 174.5(2);
C(33)-C(34)-Si(1) 169.1(2).
Sch em e 2
1
From the H and 13C NMR spectra of 2a and 2b it
can be concluded that the imine groups are equivalent
and coordinating to the platinum atom, as appears from
the isochronicity and the large couplings between the
imine proton and the 195Pt isotope. For 2a and 2b the
3J (1H,195Pt) couplings are 144 and 139 Hz, respectively.
In the 13C NMR spectrum of 2a and 2b the ipso carbon
bound to platinum is found at high frequency, and the
expected large 1J (13C,195Pt) coupling is observed (δ )
179 ppm, J ) 927 Hz and δ ) 175 ppm, J ) 938 Hz,
respectively).12c
After the synthesis of these platinum(II) bromide
precursors, we reacted 2a and 2b with LiCtCSiMe3 to
investigate whether trans-arylplatinum(II) acetylides
compounds could be obtained. The reaction of 2a and
LiCtCSiMe3 in THF at -60 °C and warming up to 20
°C resulted in the complete conversion of 2a to 3
(Scheme 2), as evidenced by an additional resonance in
the 1H NMR spectrum at δ ) -0.42 ppm.12b,c It is
noteworthy that the 3J (1H,195Pt) of the imine proton
decreases to 133 Hz due to the cis influence of the
acetylide. In the 13C NMR spectrum the ipso phenyl
carbon bound to the platinum shifts to 199 ppm and the
1J (13C,195Pt) decreases from 927 Hz in 2a to 616 Hz in
3, as a result of the strong trans influence of the
acetylide. The molecular structure of 3 is depicted in
Figure 1, and selected bond lengths and angles are given
in the figure caption.
In the crystal structure the platinum has a distorted
square planar environment with a sum of cis angles of
359.9°. The N-Pt-C angles of the five-membered
chelate rings amount to 78.55(9)° and 78.76(9)°, which
is significantly smaller than the ideal values of 90° and
is caused by ring strain. This also leads to a distorted
trans N-Pt-N angle of 157.21(9)°, which is slightly
smaller compared to compounds derived from the bis-
(dimethylamine) [N-C-N]- ligand system, which is
probably due to the higher strain arising from the
shorter imine CdNR double bond as compared to the
amine C-NR2 single bond.15 The Pt-Caryl and Pt-N
bond lengths have expected values, 1.945(2) and
2.043(2)-2.050(2) Å, respectively. The acetylide group
is coordinated end-on with a Pt-Cacetylide bond length
of 2.065(2) Å, which is relatively long,16 probably caused
(12) (a) Terheijden, J .; van Koten, G.; Muller, F.; Grove, D. M.;
Vrieze, K. J . Organomet. Chem. 1986, 315, 401-417. (b) van Koten,
G.; van Beek, J . A. M.; Wehman-Ooyevaar, I. C. M.; Muller, F.; Stam,
C. H.; Terheijden, J . Organometallics 1990, 9, 903-912. (c) Back, S.;
Gossage, R. A.; Lutz, M.; del R´ıo, I.; Spek, A. L.; Lang, H.; van Koten,
G. Organometallics 2000, 19, 3296-3304.
(13) Gelling, O. J .; Feringa, B. L. Recl. Trav. Chim. Pays-Bas 1991,
110, 89-91.
(14) (a) Keasey, A.; Mann, B. E.; Yates, A.; Maitlis, P. M. J .
Organomet. Chem. 1978, 152, 117-123. (b) Dipdba ) 4,4′-diisopropyl-
dibenzylideneacetone.

Notes
Organometallics, Vol. 20, No. 21, 2001 4439
by the small N-Pt-N angle and the trans influence of
the aryl group.
The substituent on the imine group seems to have a
distinct effect on the structure of the compounds formed
in a reaction of 2a and 2b and LiCtCSiMe3. Whereas
the reaction of 2a (R ) 2,6-(i-Pr)2-C6H3) and LiCtCSiMe3
resulted in the formation of the trans diorgano-
platinum compound 3, in an analogous reaction of 2b
(R ) 4-MeO-C6H4), a different reaction product was
obtained.
1H NMR spectroscopic analysis of the reaction mix-
ture obtained by addition of LiCtCSiMe3 to 2b (R )
4-MeO-C6H4) in THF at -60 °C and warming up to 20
°C showed two inequivalent imine moieties (HCdN at
10.1 and 7.4 ppm). The 10.1 ppm resonance belongs to
an uncoordinated imine moiety, and for the coordinating
3
imine moiety at 7.4 ppm, the small J (1H,195Pt) of 73
Hz as compared to the starting material (139 Hz)
pointed at an acetylide group trans to this imine. We
suggested that the acetylide moiety was in a configu-
ration cis to the central aryl carbon and that the
compound had dimerized across the Pt-acetylide moiety
to furnish 4 (Scheme 2). This was supported by the
infrared spectrum of a solid sample in which the triple
bond resonated at a lower wavenumber (νCtC ) 1949
cm-1) compared to 3 (νCtC ) 2032 cm-1), indeed pointing
to a side-on coordination of the acetylide. FD-MS showed
the existence of a dimeric species. The molecular
structure of 4 was unambiguously proven by an X-ray
F igu r e 2. Displacement ellipsoid plot of 4 with ellipsoids
drawn at the 50% probability level. Hydrogens are omitted
for clarity. Selected bond lengths (Å) and angles (deg):
Pt(1)-N(1)2.087(3);Pt(2)-N(3)2.090(3);Pt(1)-C(1)2.018(3);
Pt(2)-C(28) 2.010(3); Pt(1)-C(23) 1.945(3); Pt(2)-C(50)
1.935(4); Pt(1)-C(50) 2.376(3); Pt(1)-C(51) 2.330(3); Pt(2)-
C(23) 2.397(3); Pt(2)-C(24) 2.335(3); C(23)-C(24) 1.228(5);
C(50)-C(51) 1.231(5). C(1)-Pt(1)-N(1) 81.01(12); C(28)-
Pt(2)-N(3) 80.54(13); N(1)-Pt(1)-C(23) 170.93(14); N(3)-
Pt(2)-C(50) 169.65(13); C(1)-Pt(1)-C(23) 102.20(13); C(28)-
Pt(2)-C(50) 99.69(14); Pt(1)-C(23)-C(24) 161.7(3); Pt(2)-
C(50)-C(51) 165.0(3); Pt(1)-C(23)-Pt(2) 92.63(12); Pt(1)-
C(50)-Pt(2) 93.57(14); C(23)-C(24)-Si(1) 158.1(3); C(50)-
C(51)-Si(2) 159.5(3).
1
structure analysis. From the above-mentioned H NMR
1
data, H NOE experiments, and IR spectroscopy of a
benzene solution of 4 it was concluded that 4 is also
dimeric in solution.
The molecular structure of 4 is depicted in Figure 2,
and selected bond lengths and angles are given in the
figure caption. Compound 4 is a dimer with two acetyl-
ide units acting as bridging ligands. They are each coor-
dinated end-on to one and side-on to the other platinum,
respectively. The Pt1‚‚‚Pt2 distance is 3.15573(19) Å,
indicating that there is no bonding interaction. As
expected, the Pt-Cacetylide end-on distances of 1.945(3)
and 1.935(4) Å are much smaller than the Pt-Cacetylide
side-on distances of 2.330(3)-2.397(3) Å. The different
coordination mode of the acetylide unit in compounds
4 and 3 is not reflected in the CtC distances, which
are the same within standard deviations. The Pt-Caryl
distance is slightly smaller in 3 than in 4, which
probably is a consequence of the tridentate coor-
dination in 3 as compared to the bidentate coordination
in 4.
The core of compound 4 can be considered as a six-
membered Pt-C-C-Pt-C-C ring. This ring is not
planar, but severely puckered with a dihedral angle of
75.07(12)° between the two Pt-C-C-Pt units. This
means that the Pt2(CtC)2 core is much more puckered
than in a structure published by Fornie´s,17 in which the
analogous dihedral angle is 45°. We conclude that this
geometry is strongly dependent on the steric demands
of the ligand system.
Although organometallic compounds that are dimers
via π-coordination of a M-CtC moiety are known (M
) Ti,18 Zr,19 Rh, Ir,20 Re,21 and Pt17,22), such compounds
remain relatively rare. Moreover, most of these were
synthesized from dimeric precursors ([LxM-Cl]2, Ir, Rh,
Ti, Zr) or by exchange of the acetylide between the two
metal centers (Pt, Zr). Clearly in the case of 4 the
Pt2(CtC)2 core results from a dimerization of two
independently formed Pt-CtC-R units.
Con clu sion
It is shown that the coordination properties of the
imine moiety are strongly influenced by the electronic
and steric effects of its substituent. The difference in
lability of the imine moieties bearing 2,6-(i-Pr)2-C6H3
or 4-MeO-C6H4 groups directs the reaction pathway to
the formation of 3 or 4, respectively.
(17) Fornie´s, J .; Go´mez-Saso, M. A.; Lalinde, E.; Mart´ınez, F.;
Moreno, M. T. Organometallics 1992, 11, 2873-2883.
(18) Wood, G. L.; Knobler, C. B.; Frederick, M.; Hawthorne, M. F.
Inorg. Chem. 1989, 28, 382-384.
(19) Erker, G.; Fro¨mberg, W.; Benn, R.; Mynott, R.; Angermund,
K.; Kru¨ger, C. Organometallics 1989, 8, 911-920.
(15) (a) Smeets, W. J . J .; Spek, A. L.; Duisenberg, A. J . M.; van Beek,
J . A. M.; van Koten, G. Acta Crystallogr., Sect. C: Cryst. Struct.
Commun. 1987, C43, 463-465. (b) J ames, S. L.; Verspui, G.; Spek, A.
L.; van Koten, G. Chem. Commun. 1996, 1309-1310. (c) Davies, P. J .;
Veldman, N.; Grove, D. M.; Spek, A. L.; Lutz, B. T. G.; van Koten, G.
Angew. Chem., Int. Ed. Engl. 1996, 35, 1959-1961.
(20) (a) Mu¨ller, J .; Tschampel, M.; Pickardt, J . J . Organomet. Chem.
1988, 355, 513-524.
(21) Mihan, S.; Weidmann, T.; Weinrich, V.; Fenske, D.; Beck, W.
J . Organomet. Chem. 1997, 541, 423-439.
(22) (a) Berenguer, J . R.; Fornie´s, J .; Mart´ınez, F.; Cubero, J . C.;
Lalinde, E.; Moreno, M. T.; Welch, A. J . Polyhedron 1993, 12, 1797-
1804. (b) Falvello, L. R.; Fornie´s, J .; Mart´ın, A.; Go´mez, J .; Lalinde,
E.; Moreno, M. T.; Sacrista´n, J . Inorg. Chem. 1999, 38, 3116-3125.
(16) Abel, E. W. Comprehensive Organometallic Chemistry II:
A
Review of the Literature 1982-1994; Stone, F. G. A., Wilkinson, G.,
Eds.; 1995; Vol. 9, p 431.

4440 Organometallics, Vol. 20, No. 21, 2001
Notes
123.5 (CH) 114.6 (CH) 114.1 (CH) 111 (PtCCSi) (PtCCSi not
observed) 55.1 (OCH3) 54.8 (OCH3) 0.6 (Si(CH3)3). MS(FD): m/z
calcd ([M]+ C54H56N4O2Pt2Si2) 1271. Found: 1271. Anal. Calcd
for C54H56N4O2Pt2Si2: C, 51.01; H, 4.44; N, 4.41. Found: C,
51.02; H, 4.51; N, 4.45. Single crystals suitable for X-ray
structure determination were obtained by slow diffusion of
pentane into a diluted CH2Cl2 solution.
Exp er im en ta l Section
Gen er a l Com m en ts. All reactions were carried out under
a dinitrogen atmosphere using standard Schlenk techniques.
Solvents were dried and distilled prior to use, according to
standard methods. In NMR spectra positive chemical shifts
(δ) are denoted downfield from an external TMS reference.
HRMS measurements were performed on a J EOL J MS SX/
SX102A four-sector mass spectrometer, coupled to a J EOL MS-
MP7000 data system. IR spectra were measured on a Biorad
FTS-7 spectrophotometer of a KBr pellet, unless stated
otherwise. Elemental analyses were carried out at H. Kolbe
Mikroanalytisches Laboratorium, Mu¨lheim an der Ruhr. Melt-
ing points are uncorrected.
Cr ysta l Str u ctu r e Deter m in a tion s. X-ray intensities
were measured on a Nonius KappaCCD diffractometer with
rotating anode (λ ) 0.71073 Å) at a temperature of 150 K. The
structures were solved with Patterson methods (DIRDIF9723
)
and refined with SHELXL9724 against F2 of all reflections.
Non-hydrogen atoms were refined freely with anisotropic
displacement parameters. Hydrogen atoms were refined freely
with isotropic displacement parameters in compound 3 and
as rigid groups in 4. Molecular illustrations, structure check-
ing, and calculations were performed with the PLATON
package.25
14
Ma t er ia ls. 2-Bromoisopthalaldehyde13 and Pt(dipdba)2
were synthesized according to literature procedures,
LiCtCSiMe3 was prepared from HCtCSiMe3 in THF and
n-BuLi in hexane, and all other starting materials were
obtained from commercial sources and used as received. The
synthesis and characterization of compounds 1a ,b and
2a ,b is described in the Supporting Information.
Cr yst a l Da t a a n d Det a ils on Da t a Collect ion a n d
Refin em en t: Com p ou n d 3. C37H48N2PtSi, fw ) 743.95,
orange needle, 0.38 × 0.22 × 0.21 mm3, triclinic, P1h (No. 2), a
) 9.9706(3) Å, b ) 11.1440(3) Å, c ) 17.3043(5) Å, R ) 82.8786-
(10)°, â ) 79.7901(13)°, γ ) 65.0548(10)°, V ) 1713.14(9) Å3,
Z ) 2, F ) 1.442 g/cm3; 31 975 reflections were measured; 7825
reflections were unique (Rint ) 0.056). The θ range was 1.20-
27.49° with indices hkl -12/12, -14/14, -22/22. An analytical
absorption correction was applied (program PLATON,3 routine
ABST, µ ) 4.16 mm-1, 0.24-0.49 transmission); 562 refined
parameters, no restraints. R-values [I > 2σ(I)]: R1 ) 0.0198,
wR2 ) 0.0505. R-values [all reflns]: R1 ) 0.0228, wR2 )
0.0540. GoF ) 1.119. The residual electron density is between
-1.10 and 1.14 e/Å3.
σ-Tr im eth ylsilyleth yn yl-N,N′-bis(2,6-d iisop r op ylp h en -
yl)isop h th a la ld im in e-2-ylp la tin a (II) (3). To a solution of
2a (100 mg, 0.138 mmol) in THF (20 mL) at -60 °C was added
a solution of LiCtCSiMe3 0.068 M in THF (2.2 mL, 0.152
mmol, 1.1 equiv). After slow warming up to 20 °C the solvent
was evaporated in vacuo and the residue was extracted with
10 mL of pentane. After evaporation of the solvent in vacuo
the residue was crystallized from MeOH. After standing at
-20 °C for 4 days, the orange crystals were isolated by the
removal of the mother liquor. Washing with a little cold MeOH
and drying in vacuo yielded 81.8 mg (0.11 mmol, 80%) of
orange crystals. Mp: 160 °C decomp. 1H NMR (300 MHz,
3
CDCl3): δ 8.45 (s, J (1H195Pt) ) 133 Hz, 2H; HCdN) 7.77 (d,
Com p ou n d 4. C54H56N4O4Pt2Si2, fw ) 1271.39, red plate,
0.21 × 0.17 × 0.09 mm3, triclinic, P1h (No. 2), a ) 11.5121(2)
Å, b ) 13.4158(3) Å, c ) 16.3824(2) A, R ) 88.2974(11)°, â )
82.1793(11)°, γ ) 84.6873(7)°, V ) 2495.49(8) Å3, Z ) 2, F )
1.692 g/cm3; 34 245 reflections were measured; 11 344 reflec-
tions were unique (Rint ) 0.063). The θ range was 1.25-27.51°
with indices hkl -14/14, -17/17, -21/21. The applied absorp-
tion correction was based on multiple measured reflections
(program PLATON,3 routine MULABS, µ ) 5.70 mm-1, 0.47-
0.61 transmission); 605 refined parameters, no restraints.
R-values [I > 2σ(I)]: R1 ) 0.0280, wR2 ) 0.0663. R-values
[all reflns]: R1 ) 0.0366, wR2 ) 0.0699. GoF ) 1.042. The
residual electron density is between -1.82 and 1.48 e/Å3.
J ) 7.8 Hz, 2H) 7.35 (t, J ) 7.8 Hz, 1H) 7.17 (m, 6H) 3.16
(septet, J ) 7 Hz, 4H; CH3CHCH3) 1.26 (d, J ) 7 Hz, 24H;
CH3CHCH3) 1.16 (d, J ) 6.5 Hz, 24H; CH3CHCH3) -0.42 (s,
9H, Si(CH3)3); 13C NMR (126 MHz, CDCl3): δ 198.9 (1J (13C195Pt)
) 616 Hz, C-Pt) 179.8 (2J (13C195Pt) ) 73 Hz, CdN-C) 154.8
(1J (13C195Pt) ) 1048 Hz, Pt-CCSi) 147.3 (CdN-C) 144.5
(2J (13C195Pt) ) 95 Hz, C) 141.5 (C) 127.4 (CH) 127.2 (CH) 123.0
(CH) 123.0 (CH) 115.5 (2J (13C195Pt) ) 211 Hz, Pt-CCSi) 27.9
(CH3CHCH3) 24.4 (CH3CHCH3) 23.0 (CH3CHCH3) 1.24 (Si-
(CH3)3). HRMS(FAB): m/z calcd ([M - H]+ C37H49N2SiPt)
744.3315. Found: 744.3331. Anal. Calcd for C37H48N2PtSi: C,
59.73; H, 6.50; N, 3.77. Found: C, 59.80; H, 6.55; N, 3.82.
Single crystals suitable for X-ray structure determination were
obtained by slow cooling of a methanolic solution from 20 to
-20 °C.
σ,µ2-Tr im eth ylsilyleth yn yl-N,N′-bis(4-m eth oxyp h en yl)-
isop h th a la ld im in e-2-ylp la tin a (II) Dim er (4). To a solution
of 2b (101.6 mg, 0.164 mmol) in THF (25 mL) at -60 °C was
added a solution of LiCtCSiMe3 0.068 M in THF (2.7 mL, 0.18
mmol, 1.1 equiv). After stirring at -60 °C for 30 min, the
mixture was allowed to warm to 20 °C. After stirring at 20 °C
for 16 h, the solvent was evaporated. The residue was
extracted with 15 mL of a 1:1 pentane/CH2Cl2 mixture. After
evaporation of the solvent in vacuo the residue was washed
twice with pentane (10 mL) and crystallized by a slow diffusion
of pentane into a concentrated CH2Cl2 solution. Washing of
the product with 10 mL of pentane and drying in vacuo yielded
58 mg (0.91 mmol, 55%) of the dimeric product as a dark brown
Ack n ow led gm en t. This work was supported in part
(W.J .H., M.L., A.L.S.) by the Council for Chemical
Sciences of the Netherlands Organization for Scientific
Research (CW-NWO).
Su p p or tin g In for m a tion Ava ila ble: Experimental de-
tails for the synthesis and characterization of 1a ,b and 2a ,b,
X-ray CIF files, and tables giving atomic coordinates, displace-
ment parameters, and bond distances and angles for 3 and 4.
This material is available free of charge via the Internet at
http://pubs.acs.org.
1
OM010447W
solid. Mp: 220 °C decomp. H NMR (500 MHz, C6D6): δ 10.1
(s, 2H; HCdN) 8.96 (d, J ) 8 Hz, 2H) 7.42 (s, 3J (1H195Pt) ) 73
Hz, 2H; HCdN) 7.41 (d, J ) 9 Hz, 4H) 7.11 (dd, J ) 8 Hz, J
) 7 Hz, 2H) 7.08 (d, J ) 9 Hz, 4H) 6.99 (d, J ) 7 Hz, 2H) 6.82
(d, J ) 9 Hz, 4H) 6.77 (d, J ) 9 Hz, 4H) 3.37 (s, 3H; OCH3)
3.26 (s, 3H; OCH3). 13C NMR (126 MHz, C6D6): δ 176.9 (Cd
N-Pt) 164.8 (CdN) 159.2 (COCH3) 158.4 (COCH3) 153.7 (C-
Pt) 148.9 (C-CdN-Pt) 146.0 (C-NdC) 142.2 (C-N-Pt) 141.3
(C-CdN-C) 132.5 (CH) 130.8 (CH) 124.6 (CH) 125.9 (CH)
(23) Beurskens, P. T.; Admiraal, G.; Beurskens, G.; Bosman, W. P.;
Garcia-Granda, S.; Gould, R. O.; Smits, J . M. M.; Smykalla, C. The
DIRDIF97 program system, Technical Report of the Crystallography
Laboratory; University of Nijmegen: The Netherlands. 1997.
(24) Sheldrick, G. M. SHELXL-97, Program for crystal structure
refinement; 1997.
(25) Spek, A. L. PLATON, A multipurpose crystallographic tool;
Utrecht University: The Netherlands, 2000.