Unprecedented behavior of 2,2′:6′,2″-Terpyridine: Dinuclear platinum(II) derivatives with a new N,?C,N bridging ligand

Article abstract of DOI:10.1021/om000884v

We report the synthesis and characterization of some dinuclear organoplatinum(II) species where 2,2′:6′,2″-terpyridine (terpy) behaves as a 2-fold-deprotonated N,?C,N ligand bridging two [Pt(CH₃)(L)] units (L = neutral ligand). Each platinum at

Full text of DOI:10.1021/om000884v

1148
Organometallics 2001, 20, 1148-1152
Un p r eced en ted Beh a vior of 2,2′:6′,2′′-Ter p yr id in e:
Din u clea r P la tin u m (II) Der iva tives w ith a New N,C∧C,N
Br id gin g Liga n d
Angelino Doppiu, Giovanni Minghetti,*,† Maria Agostina Cinellu,
Sergio Stoccoro, and Antonio Zucca
Dipartimento di Chimica, Universita` di Sassari, Via Vienna 2, I-07100 Sassari, Italy
Mario Manassero*,‡
Dipartimento di Chimica Strutturale e Stereochimica Inorganica, Universita` di Milano,
Centro CNR, I-20133 Milano, Italy
Received October 16, 2000
We report the synthesis and characterization of some dinuclear organoplatinum(II) species
where 2,2′:6′,2′′-terpyridine (terpy) behaves as a 2-fold-deprotonated N,C∧C,N ligand bridging
two [Pt(CH3)(L)] units (L ) neutral ligand). Each platinum atom is further bonded to a
nitrogen of a terminal pyridine and to a 3′ or 5′ carbon atom of the inner pyridine ring. As
far as we know, these are the first examples of cyclometalated terpy as well as of a 3,5-
dimetalated pyridine ring. The X-ray structure of one of these species (L ) CO) shows it to
be an organoplatinum polymer.
In tr od u ction
with biomolecules6a-d and their outstanding photophysi-
cal properties,6e-m which make them play a key role in
several fields of current interest.
Here we report the synthesis and characterization of
dinuclear cyclometalated platinum(II) derivatives where
terpy displays an unprecedented behavior acting as a
2-fold deprotonated N,C∧C,N ligand. This demonstrates
that, despite the great number of studies devoted to this
old ligand, its coordination behavior still has surprises
in store for us.
2,2′:6′,2′′-Terpyridine (terpy) has been studied for
many years as a strong chelating agent to metal ions.1
Its most common bonding mode is as an N,N′,N′′ neutral
ligand, either in octahedral or square-planar geometry.2
Examples of N,N′ endobidentate behavior are much less
common;3 at least one example where it acts as a
monodentate ligand is known.4 Metalated derivatives
have been reported only when a nitrogen of a terminal
pyridine ring has been protected by quaternization. In
the latter case, terpy coordinates either as a bidentate
N,N′ donor or as an anionic tridentate N,N′,C ligand.5
Platinum(II) derivatives of terpy and its analogues
have been widely studied, because of their interaction
Resu lts a n d Discu ssion
The reaction between terpy and cis-[Pt(CH3)2(DMSO)2]
(DMSO ) dimethyl sulfoxide), in toluene at 90 °C (molar
ratio Pt:terpy 2:1), affords, almost quantitatively, the
dinuclear species 1 (see Scheme 1), having C2v sym-
metry. Each platinum atom is bonded to a nitrogen of
an outer pyridine and to a meta-carbon of the inner
pyridine; the coordination spheres of the platinum
atoms are completed by DMSO and a methyl group.
† E-mail: mingh@ssmain.uniss.it.
‡ E-mail: m.manassero@csmtbo.mi.cnr.it.
(1) Constable, E. C. Adv. Inorg. Chem. Radiochem. 1986, 30, 69-
121.
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Harman, W. D. Organometallics 1999, 18, 573-581. (b) Abel, E. W.;
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Bauer, W. R.; Lippard, S. J . Biochemistry 1976, 15, 4339-4346. (c)
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10.1021/om000884v CCC: $20.00 © 2001 American Chemical Society
Publication on Web 02/22/2001

Unprecedented Behavior of 2,2′:6′,2′′-Terpyridine
Organometallics, Vol. 20, No. 6, 2001 1149
Sch em e 1
Metalation, which affords two C,N five-membered rings,
entails C(sp2)-H activation and elimination of methane.
Although examples of C(3)-metalated pyridine rings are
known,7 albeit not common, to the best of our knowledge
no C(3),C(5)-dimetalated species have been reported.
When the reaction is carried out in a 1:1 Pt:terpy
molar ratio, only the dimetalated species 1 is formed,
and the unreacted ligand can be recovered from the
reaction mixture.
It seems therefore that one platinum on the pyridine
ring activates it toward further substitution. It is worth
noting that the same behavior was reported several
years ago by Trofimenko in the cyclopalladation of some
di(aminomethyl)benzenes and taken as evidence for an
electrophilic reaction.8
Compound 1 is soluble in DMSO but sparingly soluble
in solvents such as dichloromethane and acetone. The
1H NMR spectrum of 1 ([D6]acetone) shows interesting
features: in the aromatic region only five signals in a
2:2:1:2:2 ratio are observed, two doublets, a singlet, and
two triplets. The singlet (H(4′), δ 8.38 ppm) unambigu-
ously shows coupling to two equivalent 195Pt nuclei
(main signal/inner satellites ratio ca. 1:2:1).9 On the
whole, signals in the aromatic region integrate to nine
protons, showing that two protons of the neutral terpy
are missing. In the aliphatic region, the signals of
DMSO and of the methyl group are coupled to one 195Pt
nucleus. The J (Pt,H) value of the protons of DMSO (18.1
Hz) suggests it is S-bonded and trans to a carbon atom.10
These features, in addition to the clear symmetry of the
spectrum pattern, are a first indication of the nature of
compound 1. The 13C{1H} NMR spectrum in [D6]DMSO
and an APT (attached proton test) experiment confirm
the structure proposed on the basis of 1H NMR. Further
support is provided by the microanalyses and the FAB
(positive ions) mass spectrum, which shows the molec-
ular ion at m/z 807+.
In compound 1, the DMSO can be easily replaced by
other ligands, like acetonitrile and carbon monoxide:
unfortunately, the obtained species, 2 and 3, respec-
tively, are too insoluble to allow their characterization
by NMR spectroscopy. However, the microanalyses are
in agreement and the IR spectra show a very weak
absorption peak at 2282 cm-1 (C-N stretching of the
coordinate acetonitrile) for 2 and two strong absorption
peaks at 2043 and 2030 cm-1 (C-O stretching for
terminal carbon monoxide) for 3, as expected for a
molecule with C2v symmetry.11 1 and 3 show an ex-
traordinary thermal stability: they decompose without
melting at a temperature higher than 250 °C.
Orange-red crystals of 3, suitable for an X-ray analy-
sis, were obtained by carbonylation of a very dilute
unstirred dichloromethane solution of 1. An ORTEP
view of the complex molecule is shown in Figure 1.
Principal bond parameters are listed in the Figure 1
caption. The molecule possesses an idealized C2v sym-
metry, with the 2-fold axis passing through atoms N2
and C8. Each of the two Pt atoms displays a square-
planar coordination with a slight square-pyramidal
distortion. The Pt1-C7 and Pt2-C9 distances, 2.050-
(6) and 2.051(5) Å, respectively, are slightly longer than
the Pt-C bond length, 1.990(5) Å, found in [PtCl(L)-
(S(CH3)2)] (HL ) 6-tert-butyl-2,2′-bipyridine),7a thus
suggesting that the trans-influence of CO is slightly
larger than that of Cl. The Pt1-C16 and Pt2-C18
distances, 2.061(6) and 2.066(8) Å, respectively, are in
(7) (a) Minghetti, G.; Doppiu, A.; Zucca, A.; Stoccoro, S.; Cinellu,
M. A.; Manassero, M.; Sansoni, M. Chem. Heterocycl. Compd. 1999,
35, 992-1000. (b) Isobe, K.; Kai, E.; Nakamura, Y.; Nishimoto, K.;
Miwa, T.; Kawaguchi, S.; Kinoshita, K.; Nakatsu, K. J . Am. Chem.
Soc. 1980, 102, 2475-2476. (c) Fanizzi, F. P.; Sunley, G. J .; Wheeler,
J . A.; Adams, H.; Bailey, N. A.; Maitlis, P. M. Organometallics 1990,
9, 131-136.
(8) Trofimenko, S. Inorg. Chem. 1972, 12, 1215-1221.
(9) In a symmetric dinuclear species the ratio among the three
isotopomers, Pt-Pt (43.8%), 195Pt-Pt (44.8%), 195Pt-195Pt (11.4%)
(where 195Pt is the isotope with I ) 1/2 in 33.8% abundance and Pt
represents all the other isotopes with I ) 0), is ca. 4:4:1. A hydrogen
coupled to both platinum nuclei should display a five-line pattern with
a 1:8:18:8:1 ratio.
(10) (a) Price, J . H.; Williamson, A. N.; Schramm, R. F.; Wayland,
B. B. Inorg. Chem. 1972, 11, 1280-1284. (b) Romeo, R.; Monsu` Scolaro,
L.; Nastasi, N.; Mann, B. E.; Bruno, G.; Nicolo`, F. Inorg. Chem., 1996,
35, 7691-7698.
(11) Kettle, S. F. A.; Diana, E.; Rossetti, R.; Stanghellini, P. L. J .
Chem. Educ. 1998, 75, 1333-1338.

1150 Organometallics, Vol. 20, No. 6, 2001
Doppiu et al.
weakly bonding,6f,15 so that the packing in the present
compound can be described as based on infinite mono-
dimensional organoplatinum chains. Neighboring chains
are kept together partly by graphitic interactions (in-
terplanar distance 3.52(2) Å) and partly by normal van
der Waals contacts.
Displacement of DMSO in complex 1 by triphenylphos-
phine (PPh3) and tricyclohexylphosphine (PCy3) affords
almost quantitatively compounds 4 and 5, respectively
(see Scheme 1). These compounds are much more
soluble than 1-3 in organic solvents and allow a better
characterization in solution by 1H, 13C{1H}, and 31P{1H}
NMR spectroscopy. In particular, for compound 5, the
lack of aromatic rings besides those of terpy, makes
assignment of 13C resonances much easier.
The unusual coordination of terpy as a tetradentate
bridging ligand yields species still having a noncoordi-
nated nitrogen. This suggests their potential either to
act as N ligands or to give cyclometalated C,N,C species,
similar to those arising from 2,6-diphenylpyridine.16
These features open up possibilities for new interesting
homo- or heteropolynuclear assemblies.
F igu r e 1. ORTEP view of a molecule of 3. Thermal
ellipsoids are drawn at the 30% probability level. Selected
bond distances (Å) and angles (deg): Pt1-N1 2.137(5),
Pt1-C7 2.050(6), Pt1-C16 2.061(6), Pt1-C17 1.914(7),
C17-O1 1.103(10), Pt2-N3 2.124(5), Pt2-C9 2.051(5),
Pt2-C18 2.066(8), Pt2-C19 1.866(6), C19-O2 1.148(7),
N1-Pt1-C7 79.4(2), N1-Pt1-C16 170.7(3), N1-Pt1-C17
101.4(2), C7-Pt1-C16 91.4(3), C7-Pt1-C17 178.5(3),
C16-Pt1-C17 87.8(3), N3-Pt2-C9 79.7(2), N3-Pt2-C18
170.2(3), N3-Pt2-C19 100.2(3), C9-Pt2-C18 91.4(3), C9-
Pt2-C19 179.4(3), C18-Pt2-C19 88.7(3).
Exp er im en ta l Section
The platinum complex cis-[Pt(CH3)2(DMSO)2] was prepared
according to literature methods.17 All the solvents were puri-
fied and dried before use according to standard procedures.
Elemental analyses were performed with a Perkin-Elmer
elemental analyzer 240B by Mr. A. Canu (Dipartimento di
Chimica, Universita` di Sassari). Infrared spectra were re-
corded with a Perkin-Elmer 983 using Nujol mulls. 1H, 13C-
{1H}, and 31P{1H} NMR spectra were recorded with a Varian
VXR 300 spectrometer operating at 299.9, 75.4, and 121.4
MHz, respectively. Chemical shifts are given in ppm relative
to internal TMS (1H, 13C) and external 85% H3PO4 (31P). The
mass spectrometric measurements were performed on a VG
7070EQ instrument, equipped with a PDP 11-250J data
system and operating under positive ion fast atom bombard-
ment (FAB) conditions with 3-nitrobenzyl alcohol as support-
ing matrix.
F igu r e 2. View of the crystal packing of compound 3,
showing the short Pt‚‚‚Pt intermolecular contacts (see text).
agreement with the Pt-CH3 bond lengths observed in
other trans CH3-Pt-N systems.12 The Pt1-N1 and
Pt2-N3 bond lengths, 2.137(5) and 2.124(5) Å, respec-
tively, are typical of Pt-N interactions trans to alkyl
groups.13 The two Pt-CO bond lengths, 1.914(7) and
1.866(6) Å, average 1.890 Å, are in good agreement with
the Pt(II)-CO distance, 1.897(7) Å, found in [Pt(COPh)-
(CH3)(CO)(PPh3)].14
Com p ou n d 1. To a solution of 2,2′:6′,2′′-terpyridine (0.312
g, 1.31 mmol) in anhydrous toluene (10 mL) was added cis-
[Pt(CH3)2(DMSO)2] (1.000 g, 2.62 mmol), and a red color
rapidly appeared. The stirred suspension, kept under an
atmosphere of argon, was heated to 90 °C. During the heating,
the solution became yellow and a yellow precipitate began to
form. After 3 h, the mixture was cooled to room temperature
and diethyl ether (20 mL) was added. The product was filtered
and washed with diethyl ether (3 × 5 mL). Yield: 1.03 g (97%,
The strain imposed on the terpyridine molecule by its
bridging behavior is apparent in the deviation from the
ideal value of 120° in the intra-ring angles of the N2-
C6-C7-C8-C9-C10 ring, which range from 115.3(5)°
to 126.6(6)°. However, no loss of aromaticity is present,
and the three pyridinic rings are all strictly planar.
1
1.28 mmol) Mp > 270 °C. H NMR (299.9 MHz, [D6]acetone,
25 °C): δ 9.78 (dd, 2H, 3J (H,H) ) 5.6 Hz, 4J (H,H) ≈ 1 Hz,
3J (Pt,H) ≈ 21 Hz), 8.47 (d, 2H, 3J (H,H) ) 8.1 Hz), 8.38 (s, 1H,
3
4
3J (Pt,H) ) 53.7 Hz), 8.10 (td, 2H, J (H,H) ) 7.8 Hz, J (H,H)
≈ 2 Hz), 7.45 (td, 2H, 3J (H,H) ) 5.6 Hz, 4J (H,H) ≈ 2 Hz), 3.24
A view of the crystal packing of the molecules of 3 is
shown in Figure 2. The packing is dictated by a short
Pt‚‚‚Pt contact of 3.283(1) Å between the Pt1 and Pt2
atoms of two neighboring, parallel molecules, translated
with respect to each other by one unit cell length along
the a axis, 6.869(1) Å. Pt(II)‚‚‚Pt(II) contacts below 3.50
Å are not unusual and are generally considered as
3
2
(s, 12H, J (Pt,H) ) 18.1 Hz), 0.76 (s, 6H, J (Pt,H) ) 84.0 Hz).
13C{1H} NMR (75.4 MHz, [D6]DMSO): δ 162.27 (s, J (Pt,C) )
55.0 Hz; C), 159.83 (s; C), 149.70 (s; CH), 147.85 (s, J (Pt,C) )
52.0 Hz; C), 143.71 (s, J (Pt,C) ) 89.0 Hz; CH), 139.01 (s; CH),
124.19 (s; CH), 120.38 (s; CH), -13.40 (s, J (Pt,C) ) 782.1 Hz;
(15) (a) Connick, W. B.; Marsh, R. E.; Schaefer, W. P.; Gray, H. B.
Inorg. Chem. 1997, 36, 913-921. (b) Houlding, V. H.; Miskowski, V.
M. Coord. Chem. Rev. 1991, 111, 145-161.
(12) Doppiu, A.; Cinellu, M. A.; Minghetti, G.; Stoccoro, S.; Zucca,
A.; Manassero, M.; Sansoni, M. Eur. J . Inorg. Chem. 2000, 2555-2563.
(13) Minghetti, G.; Cinellu, M. A.; Stoccoro, S.; Zucca, A.; Manassero,
M. J . Chem. Soc., Dalton Trans. 1995, 777-781.
(14) Chen, J .-T.; Huang, T.-M.; Cheng, M.-C.; Wang, Y. Organome-
tallics 1990, 9, 539-541.
(16) (a) Cornioley-Deuschel, C.; Ward, T.; von Zelewsky, A. Helv.
Chim. Acta 1988, 71, 130-133. (b) Cave, G. W. V.; Fanizzi, F. P.; Deeth,
R. J .; Errington, W.; Rourke, J . P. Organometallics 2000, 19, 1355-
1364.
(17) Eaborn, C.; Kundu, K.; Pidcock, A. J . Chem. Soc., Dalton Trans.
1981, 933.

Unprecedented Behavior of 2,2′:6′,2′′-Terpyridine
Organometallics, Vol. 20, No. 6, 2001 1151
CH3). IR (Nujol, cm-1): νmax 1607(s), 1564(s), 1106(m), 1093-
(s), 1013(s). FAB+-MS (3-nitrobenzyl alcohol matrix): m/z (%)
807(20) [M+], 792(15) [M+ - CH3], 729(30) [M+ - DMSO], 714-
(70) [M+ - CH3 - DMSO], 699(15) [M+ - 2CH3 - DMSO], 651-
(40) [M+ - 2DMSO], 636(100) [M+ - CH3 - 2DMSO], 621(65)
[M+ - 2CH3 - 2DMSO]. Anal. Calcd for C21H27N3O2S2Pt2 (Mr
) 807.81): C 31.22, H 3.38, N 5.20. Found: C 31.39, H 3.40,
N 5.31.
Ta ble 1. Cr ysta llogr a p h ic Da ta
3
formula
C19H15N3O2Pt2
707.53
M
color
orange-red
triclinic
P1h (no. 2)
6.869(1)
10.007(1)
14.821(2)
98.36(1)
103.31(1)
108.39(1)
914.2(2)
2
cryst syst
space group
a/Å
b/Å
c/Å
Compounds 2 and 3 were obtained in almost quantitative
yields by reaction, at room temperature, of a suspension of 1
(ca. 0.1 g) in CH2Cl2 (10 mL) with excess acetonitrile (5 mL),
2, and with CO (1 bar), 3, respectively. Compounds 4 and 5
were obtained in almost quantitative yields by reaction of 1
(ca. 0.1 g) in CH2Cl2 (5 mL) under argon, with the stoichio-
metric amount of phosphine.
R/deg
â/deg
γ/deg
U/Å3
Z
F(000)
644
Dc/g cm-3
2.57
293
T/K
Com p ou n d 2. Mp: 198 °C (decomposition without melting).
IR (Nujol, cm-1) νmax: 2281(vw), 1602(s), 1562(s). FAB+-MS
cryst dimens (mm)
µ(Mo KR)/cm-1
min. and max. transmn
factors
scan mode
frame width/deg
time per frame/s
no. of frames
detector-sample
distance/cm
θ-range/deg
reciprocal space explored
no. of reflns (total; ind)
Rint
0.04 × 0.10 × 0.45
154.6
m/z (%): 733(10) [M+], 692(10) [M+ - CH3CN], 677(15) [M+
-
CH3 - CH3CN], 662(10) [M+ - 2CH3 - CH3CN], 651(15) [M+
0.51-1.00
ω
0.30
25
2450
5.00
- 2CH3CN], 636(20) [M+ - CH3 - 2CH3CN], 621(20) [M+
2CH3 - 2CH3CN]. Anal. Calcd for C21H21N5Pt2 (Mr ) 733.71):
C 34.38, H 2.89, N 9.55. Found: C 34.20, H 2.75, N 9.45.
-
Com p ou n d 3. Mp: 250 °C (decomposition without melting).
IR (Nujol, cm-1) νmax: 2043(vs), 2030(vs), 1608(m), 1563(m).
Anal. Calcd for C19H15N3O2Pt2 (Mr ) 707.53): C 32.25, H 2.14,
N 5.94. Found: C 32.02, H 2.15, N 5.77.
3-26
( h, ( k, ( l
11 723; 4575
0.048
Com p ou n d 4. Mp: 250 °C (decomposition without melting).
final R2 and R2w indicesa
(F2, all reflns)
conventional R1 index
(I>2σ(I))
reflns with I>2σ(I)
no. of variables
goodness of fitb
0.058, 0.069
4
3
1H NMR (CDCl3): δ 8.84 (t, 1H, J (H,P) ) 5.4 Hz, J (Pt,H) )
3
48.1 Hz), 8.43 (d, 2H, J (H,H) ) 7.3 Hz), 7.85-7.62 (m, 16H),
0.032
3
7.45-7.30 (m, 18H), 6.58 (m, 2H), 0.86 (d, 6H, J (H,P) ) 7.8
Hz, 2J (Pt,H) ) 84.0 Hz). 31P{1H} NMR (121.4 MHz, CDCl3):
2915
235
0.98
δ 33.67 (s, 1J (Pt,P) ) 2133 Hz). 13C{1H} NMR (CDCl3):
δ
165.94 (s), 161.10 (d, J (C,P) ≈ 120 Hz), 161.04 (s), 150.27 (s),
144.08 (t, J (H,P) ≈ 40 Hz), 136.88 (s), 135.12 (d, J (C,P) ) 12.1
Hz), 132.82 (d, J (C,P) ) 42.3 Hz), 129.97 (s), 128.14 (d, J (C,P)
) 9.7 Hz), 122.41 (s), 120.73 (s), -12.18 (d, J (C,P) ) 5.0 Hz).
R2 ) [∑(|Fo2 - kFc |)/∑Fo2], R2w ) [∑w(Fo2 - kFc2)2/∑w(Fo2)2]1/2
.
a
2
[∑w(Fo - kFc2)2/(No - Nv)]1/2, where w ) 4Fo2/σ(Fo2)2, σ(Fo2) )
b
2
[σ2(Fo2) + (0.04Fo2)2]1/2, No is the number of observations and Nv
IR (Nujol, cm-1) νmax
:
1603(s), 1560(m), 694(s). FAB+-MS
the number of variables.
m/z(%): 898(10) [M+ - CH3 - PPh3], 636(10) [M+ - CH3
-
2PPh3], 621(10) [M+ - 2CH3-2PPh3]. Anal. Calcd for C53H45N3P2-
Pt2 (Mr ) 1176.17): C 54.12, H 3.86, N 3.57. Found: C 53.97,
H 3.70, N 3.40.
with the software SAINT,18 and an empirical absorption
correction was applied (SADABS19) to the 11 723 collected
reflections, 4575 of which are unique with Rint ) 0.048 (Rint
)
Com p ou n d 5: Mp: 220 °C (decomposition). 1H NMR (CD2-
2
∑|Fo2 - Fmean |/∑Fo2). Scattering factors and anomalous disper-
sion corrections were taken from ref 20. The calculations were
performed on an AST Power Premium 486/33 computer using
the Personal Structure Determination Package21 and the
physical constants tabulated therein. The structure was solved
by Patterson and Fourier methods and refined by full-matrix
least-squares, using all reflections and minimizing the function
3
4
Cl2): δ 8.74 (d, 2H, J (H,H) ) 5.6 Hz), 8.61 (t, 1H, J (H,P) )
3
3
5.1 Hz, J (Pt,H) ) 42.0 Hz), 8.47 (dd, 2H, J (H,H) ) 7.8 Hz,
4J (H,H) ≈ 1 Hz), 7.92 (td, 2H, J (H,H) ) 7.3 Hz, J (H,H) ≈ 1
3
4
3
4
Hz), 7.21 (td, 2H, J (H,H) ) 5.6 Hz, J (H,H) ≈ 1 Hz), 2.42-
0.82 (m, 72H). 31P{1H} NMR (CD2Cl2) δ: 24.52 (s, J (Pt,P) )
1
1993 Hz). 13C{1H} NMR (CD2Cl2): δ 166.33 (m, J (Pt,C) ) 45.2
Hz; C), 162.05 (dd, J (C,P) ) 113.5 Hz, J (C,P) ) 3.7 Hz; C),
160.43 (s, J (Pt,C) ≈ 19 Hz; C), 152.06 (s; CH), 142.57 (t, J (C,P)
) 39.1 Hz; CH), 137.25 (s; CH), 122.86 (s; CH), 121.10 (s,
J (Pt,C) ) 18.9 Hz; CH), 32.77 (d, J (C,P) ) 20.1 Hz; CH), 30.23
(s; CH2), 28.32 (d, J (C,P) ) 9.8 Hz; CH2), 27.01 (s; CH2), -16.11
2
2
∑w(Fo - k|Fc| )2 (refinement on F2). Anisotropic thermal
factors were refined for all the non-hydrogen atoms. The
hydrogen atoms of the methyl groups were detected in the final
Fourier maps and not refined. All the other hydrogen atoms
were placed in their ideal positions (C-H ) 0.97 Å, B 1.10
times that of the carbon atom to which they are attached) and
not refined. The final Fourier map shows a maximum residual
of 2.1(5) e/Å3 at 0.96 Å from Pt(1). The atomic coordinates of
the structure model have been deposited with the Cambridge
Crystallographic Data Centre.
(d, J (C,P) ) 7.3 Hz, J (Pt,C) ) 762.4 Hz; CH3). IR (Nujol, cm-1
)
ν
max: 1602(s), 1560(m). Anal. Calcd for C53H81N3P2Pt2 (Mr )
1212.47): C 52.50, H 6.75, N 3.47. Found: C 52.70, H 6.61, N
3.31.
X-r a y Da ta Collection s a n d Str u ctu r e Deter m in a tion s.
Crystal data and other experimental details are summarized
in Table 1. The diffraction experiment was carried out on a
Bruker SMART CCD area-detector diffractometer at room
temperature using Mo KR radiation (λ ) 0.71073 Å) with a
graphite crystal monochromator in the incident beam. Cell
parameters and orientation matrix were obtained from the
least-squares refinement of 55 reflections measured in three
different sets of 15 frames each, in the range 3° < θ < 23°. At
the end of data collections the first 50 frames, containing 89
reflections, were recollected to have a monitoring of crystal
decay, which was not observed, so that no time-decay correc-
tion was needed. The 2450 collected frames were processed
Ack n ow led gm en t. Financial support from the Uni-
versita` di Sassari is gratefully acknowledged. A.D.
(18) SAINT, Reference manual; Siemens Energy and Automation:
Madison, WI, 1994-1996.
(19) Sheldrick, G. M. SADABS, Empirical Absorption Correction
Program; University of Gottingen, 1997.
(20) International Tables for X-ray Crystallography, Vol. 4; Kynoch
Press: Birmingham, 1974.
(21) Frenz, B. A. Comput. Phys. 1988, 2, 42. Crystallographic
Computing 5; Oxford University Press: Oxford, 1991; Chapter 11, p
126.

1152 Organometallics, Vol. 20, No. 6, 2001
Doppiu et al.
coordinates for non-hydrogen atoms of 3, and a full list of bond
lengths and angles for 3. This material is available free of
charge via the Internet at http://pubs.acs.org.
thanks the Regione Autonoma della Sardegna for a
postgraduate research fellowship.
Su p p or tin g In for m a tion Ava ila ble: Positional and ther-
mal parameters (U’s) for the refined atoms of 3, atomic
OM000884V