Multinuclear and dynamic NMR study of trans-[Pt(Cl)(PHCy2) 2(PCy2)], [Pt(Cl)(PHCy2)3][BF 4], [Pt(Cl)(PHCy2)3][Cl], trans-[Pt(Cl) (PHCy2)2{P(S)Cy2}], and trans-[Pt(Cl)(PHCy 2)2{P(O)Cy2

Article abstract of DOI:10.1021/ic051198x

Dynamic NMR experiments on trans-[Pt(Cl)(PHCy₂) ₂{P(X)Cy₂}]² where X is a lone pair (1, z = 0), H (2, z = +1), S (3, z = 0), or O (4, z = 0) show that the rotation around the P(X)-Pt bond is hindered for all molecules studied, with ΔG ^? ranging from 8.2 to 11.0 kcal/mol. The highest value of the series was calculated for trans-[Pt(Cl)-(PHCy₂)₂{P(O) Cy₂}] (4) where intramolecular P=O...H-P interactions act as a molecular brake at room temperature. Single-crystal X-ray diffraction confirms the presence of both intra and intermolecular P=O...H interactions in solid 4. In the case of [Pt(Cl)(PHCy₂)₃]Cl, multinuclear NMR analysis indicates the presence of a P-H...Cl^- interaction in aromatic or halogenated solvents which could have also a minor effect on the rotational barrier around the P(X)-Pt bond.

Full text of DOI:10.1021/ic051198x

Inorg. Chem. 2005, 44, 9097−9104
Multinuclear and Dynamic NMR Study of trans-[Pt(Cl)(PHCy2)2(PCy2)],
[Pt(Cl)(PHCy2)3][BF4], [Pt(Cl)(PHCy2)3][Cl],
trans-[Pt(Cl)(PHCy2)2 P(S)Cy2 ], and trans-[Pt(Cl)(PHCy2)2
Influence of Intramolecular P P and Cl‚‚‚ P Interactions on
Restricted Rotation about Pt P Bond. X-ray Structure of
trans-[Pt(Cl)(PHCy2)2 P(O)Cy2
{
}
{P(O)Cy2}].
d
O
‚‚‚
H−
H−
−
{
}]
Piero Mastrorilli,*,† Cosimo F. Nobile,† Mario Latronico,†,# Vito Gallo,† Ulli Englert,‡
Francesco P. Fanizzi,§ and Oronzo Sciacovelli|
Dipartimento di Ingegneria delle Acque e di Chimica del Politecnico di Bari, Via Orabona 4,
I-70125 Bari, Italy, Institut fu¨r Anorganische Chemie der RWTH, Landoltweg 1, D-52074 Aachen,
Germany, Dipartimento di Scienze e Tecnologie Biologiche e Ambientali, UniVersita` di Lecce, Via
Monteroni, I-73100, Lecce, Italy, Consortium C.A.R.S.O., Cancer Research Center I-70010,
Valenzano-Bari, Italy, and Dipartimento di Chimica dell’UniVersita` degli Studi di Bari, Via
Orabona 4, I-70125 Bari, Italy
Received July 18, 2005
Dynamic NMR experiments on trans-[Pt(Cl)(PHCy2)2
S (3, z 0), or O (4, z 0) show that the rotation around the P(X)
with
Gq ranging from 8.2 to 11.0 kcal/mol. The highest value of the series was calculated for trans-[Pt(Cl)-
(PHCy2)2 P(O)Cy2 ] (4) where intramolecular P P interactions act as a molecular brake at room temperature.
Single-crystal X-ray diffraction confirms the presence of both intra and intermolecular P ‚‚‚H interactions in
solid 4. In the case of [Pt(Cl)(PHCy2)3]Cl, multinuclear NMR analysis indicates the presence of a P
‚‚‚Cl- interaction
in aromatic or halogenated solvents which could have also a minor effect on the rotational barrier around the
{
P(X)Cy2
}
]z where X is a lone pair (1, z
Pt bond is hindered for all molecules studied,
) 0), H (2, z ) +1),
)
)
−
∆
{
}
dO‚‚‚H−
d
O
−H
P(X)−Pt bond.
Introduction
been found to participate to the aforementioned dynamic
processes, such as arene stacking3 or the presence of four
fairly small phosphanyl ligands in a coordination plane.4 The
preferred technique used in the study of molecular dynamics
is NMR, which requires the presence of an NMR active
nucleus acting as probe for the slow exchange resulting from
the molecular motion in the complex. Typical nuclei used
Since the extensive work of Bushweller on stereodynamics
of the ligand-metal bond,1 the interest in the dynamic
behaviors of transition metal complexes has been uninter-
rupted, with particular attention being devoted to the study
of rotational isomerism caused by restricted rotation around
a ligand-metal bond.2,3 Although the factor on which a
restricted rotation around a ligand-metal bond depends is
often the bulk of the ligand, nevertheless other causes have
1
as probes are H and 31P but also 19F and 13C have been
exploited, for example, in the dynamic study of Pt(dppe)-
* To whom correspondence should be addressed. E-mail: p.mastrorilli@
poliba.it.
(1) Bushweller, C. H.; Hoogasian, S.; English, A. D.; Miller, J. S.;
Lourandos, M. Z. Inorg. Chem. 1981, 20, 3448-3455. (b) Bushweller,
C. H.; Rithner, C. D.; Butcher, D. J. Inorg. Chem. 1984, 23, 1967-
1970. (c) Bushweller, C. H.; Rithner, C. D.; Butcher, D. J. Inorg.
Chem. 1986, 25, 1610-1616. (d) Rithner, C. D.; Bushweller, C. H. J.
Phys. Chem. 1986, 90, 5023-5028. (e) DiMeglio, C. M.; Luck, L.
A.; Rithner, C. D.; Rheingold, A. L.; Elcesser, W. L.; Hubbard, J. L.;
Bushweller, C. H. J. Phys. Chem. 1990, 94, 6255-6263. (f) DiMeglio,
C. M.; Ahmed, K. J.; Luck, L. A.; Weltin, E. E.; Rheingold, A. L.;
Bushweller, C. H. J. Phys. Chem. 1992, 96, 8765-8777.
† Dipartimento di Ingegneria delle Acque e di Chimica del Politecnico
di Bari.
‡ Institut fu¨r Anorganische Chemie der RWTH.
§ Universita` di Lecce and Consortium C.A.R.S.O.
| Dipartimento di Chimica dell’Universita` degli Studi di Bari.
# On a leave of absence from Dipartimento di Ingegneria e Fisica
dell’Ambiente, Universita` della Basilicata, viale dell’Ateneo Lucano 10,
I-85100 Potenza, Italy.
10.1021/ic051198x CCC: $30.25
Published on Web 10/20/2005
© 2005 American Chemical Society
Inorganic Chemistry, Vol. 44, No. 24, 2005 9097

Mastrorilli et al.
Figure 1.
(COC3F7)(PPhAr) (19F),5 [Pt(η3-C3H5)(PCy3)2]+,6 Pt(C2H4)2-
(PR3),7 or [M(η6-arene)(CO)2(PPh3)] (M ) Cr, Mo) (13C).8
In this paper, we report on the dynamic behavior of four
dicyclohexylphosphanyl Pt(II) complexes which have the
trans-Pt(PHCy2)2Cl moiety in common. The complexes
studied are trans-[Pt(Cl)(PHCy2)2(PCy2)] (1), [Pt(Cl)(PHCy2)3]-
BF4 (2), [Pt(Cl)(PHCy2)3]Cl (2a), trans-[Pt(Cl)(PHCy2)2{κP-
P(S)Cy2}] (3), and trans-[Pt(Cl)(PHCy2)2{κP-P(O)Cy2}] (4)
(Figure 1). Multinuclear dynamic NMR spectroscopy gave
approximate free energies of activation for the dynamic
processes.9
syringe pump. All ESI/MS spectra were recorded with an Agilent
LC/MS SL series instrument adopting the following general
conditions: electrospray, positive ions, flow rate 0.200 mL min-1
,
drying gas flow 4.0 L min-1, nebulizer pressure 25 psi, drying gas
temperature 300 °C, capillary voltage 4000 V, mass range
400÷1400 m/z. The isotopic pattern was calculated by the Isotope
Pattern Viewer software available free of charge from the
www.surfacespectra.com website. NMR spectra were recorded on
BRUKER Avance DRX400 spectrometer; frequencies are refer-
enced to Me4Si (1H and 13C), 85% H3PO4 (31P), 1 M aqueous NaCl
(25Cl), and H2PtCl6
(
195Pt). The reported temperatures were
calibrated from the chemical shift difference of the signals in the
1H spectrum of a standard sample of methanol. The uncertainty in
the ∆GqTc values ((0.2 kcal/mol) was estimated on the basis of the
assumption that there is an error of 5 °C in the determination of
the coalescence temperature.
[Pt(Cl)(PCy2H)3]Cl11 (2a). A solution of dicyclohexylphosphane
(0.250 g, 1.263 mmol) in 10 mL of toluene was added to PtCl2
(0.112 g, 0.421 mmol) and the resulting suspension was stirred
overnight at room temperature. After the evaporation of the solvent
and the addition of CH3OH (15 mL), the resulting colorless solution
was filtered through a Celite pad; then it was concentrated, and
toluene was added, causing the precipitation of 2a as a white solid.
The solid was isolated by filtration and washed with n-hexane.
Yield: 0.263 g (73%).
Experimental Section
All manipulations of complex 1 (prepared as described in ref
10) were carried out under a pure argon atmosphere, using freshly
distilled and oxygen-free solvents. Dicyclohexylphosphane (Strem)
and PtCl2 (Acros) were used as received. C, H, and S elemental
analyses were carried out on a Eurovector CHNS-O Elemental
Analyzer. Cl elemental analysis was performed by potentiometric
titration using a Metrohm DMS Titrino. Melting points were
measured with a Gallenkamp apparatus and were not corrected.
Infrared spectra were recorded on a Bruker Vector 22 spectrometer.
Thf solutions of the complexes were infused with a Cole-Parmer
Alternatively, a toluene solution of dicyclohexylphosphane (0.17
g, 0.86 mmol in 5 mL) was added dropwise at room temperature
to a stirred toluene suspension of cis-[PtCl2(PHCy)2] (0.569 g, 0,86
mmol in 10 mL). After 6 h, the white solid formed was isolated by
filtration and washed with n-hexane (0.614 g, 71%).
(2) Bright, A.; Mann, B. E.; Masters, C.; Shaw, B. L.; Slade, R. M.;
Stainbank, R. E. J. Chem. Soc. A 1971, 1826-1831. (b) Mann, B. E.;
Masters, C.; Shaw, B. L.; Stainbank, R. E. J. Chem. Soc., Chem.
Commun. 1971, 1103-1104. (c) Attig, T. G.; Clark, H. C. J.
Organomet. Chem. 1975, 94, C49-C52. (d) Faller, J. W.; Johnson,
B. V. J. Organomet. Chem. 1975, 96, 99-113. (e) Empsall, H. D.;
Mentzer, E.; Pawson, D.; Shaw, B. L. J. Chem. Soc., Chem. Commun.
1977, 311-313. (f) Empsall, H. D.; Hyde, E. M.; Mentzer, E.; Shaw,
B. L. J. Chem. Soc., Dalton Trans. 1977, 2285-2291. (g) Hunter, G.;
Weakley, T. J. R.; Weissensteiner, W. J. Chem. Soc., Dalton Trans.
1987, 1545-1550. (h) Deeming, A. J.; Doherty, S.; Marshall, J. E.
Polyhedron 1991, 10, 1857-1864. (i) Daniel, T.; Werner, H. J. Chem.
Soc., Dalton Trans. 1994, 221-227. (j) Deeming, A. J.; Doherty, S.
Polyhedron 1996, 15, 1175-1190. (k) Deeming, A. J.; Cockerton, B.
R.; Doherty, S. Polyhedron 1997, 16, 1945-1956. (l) Bo¨ttcher, H.
C.; Graf, M.; Merzweiler, K. Polyhedron 1997, 16, 341-343. (m)
Pelczar, E. M.; Nytko, E. A.; Zhuravel, M. A.; Smith, J. M.; Glueck,
D. S.; Sommer, R.; Incarvito, C. D.; Rheingold, A. L. Polyhedron
2002, 21, 2409-2419. (n) Giannandrea, R.; Mastrorilli, P.; Palma,
M.; Fanizzi, F. P.; Englert, U.; Nobile, C. F. Eur. J. Inorg. Chem.
2000, 2573-2576.
The complex is air stable, soluble in halogenated solvents,
acetonitrile, alcohols, and thf, and insoluble in toluene.
Anal. Calcd for C36H69Cl2P3Pt: C, 50.23; H, 8.08; Cl, 8.24; P,
10.79. Found: C, 50.28; H, 8.11; Cl, 8.18; P, 10.62. ESI-MS:
m/z 824.4 [M]+. mp: 300 °C (dec). IR (Nujol mull, cm-1): ν 2308
(w) ν(P-H), 2280 (s), 1344 (m), 1328 (w), 1296 (m), 1267 (s),
1201 (m), 1172 (s), 1126 (s), 1074 (m), 1044 (s), 1009 (vs), 918
(vs), 876 (s), 846 (s), 819 (m), 740 (m), 729 (s), 514 (s), 469 (s),
449 (m), 411 (w), 400 (m), 388 (m), 367 (m), 310 (s) ν(Pt-Cl).
1
1H NMR (CD2Cl2, 400 MHz): δ 4.96 (m, JP-H ) 395 Hz,
1
2
PX-H), 4.48 (m, JP-H ) 363 Hz, JPt-H ) 87 Hz, PA/B-H). 31P
1
1
NMR (CD2Cl2, 162 MHz): δ 5.8 (t, JP-Pt ) 3137 Hz, JP-H
)
)
395 Hz, 2JPP ) 15 Hz, PX), 14.8 (s, br, 1JP-Pt ) 2215 Hz, 2JP
APB
(3) Fanizzi, F. P.; Lanfranchi, M.; Natile, G.; Tiripicchio, A. Inorg. Chem.
1994, 33, 3331-3339.
349 Hz, 1JP-H ) 363 Hz, 3JP-H ) 1.6 Hz, PA/B). 195Pt NMR (CD2-
(4) Deeming, A. J.; Doherty, S.; Marshall, J. E.; Powell, N. I. J. Chem.
Soc., Chem. Commun. 1989, 1351-1353.
1
1
X
A/B
Cl2, 86 MHz): δ -4793 (dt, JP
) 3137 Hz, JP
) 2215
-Pt
-Pt
Hz).
(5) Wicht, D. K.; Glueck, D. S.; Liable-Sands, L. M.; Rheingold, A.
Organometallics 1999, 18, 5130-5140.
[Pt(Cl)(PCy2H)3]BF412 (2). AgBF4 (61.2 mg, 0.314 mmol) was
added at room temperature to a stirred CH2Cl2 solution of 2a (270
mg, 0.314 mmol, in 4 mL), causing the immediate precipitation of
AgCl. After 10 min, the suspension was filtrated through a Celite
(6) Mann, B. E.; Musco, A. J. Organomet. Chem. 1979, 181, 439-443.
(7) Harrison, N. C.; Murray, M.; Spencer, J. L.; Stone, F. G. A. J. Chem.
Soc., Dalton Trans. 1978, 1337-1342.
(8) Chudek, J. A.; Hunter, G.; MacKay, R. L.; Kremminger, P.; Schlo¨gl,
K.; Weissensteiner, W. J. Chem. Soc., Dalton Trans. 1990, 2001-
2005.
(11) Anand, S. P.; Goldwhite, H.; Spielman, J. R. Transition Met. Chem.
1977, 2, 158-160. (b) Moers, F. G.; Thewissen, D. H. M. W.;
Steggerda, J. J. J. Inorg. Nucl. Chem. 1977, 39, 1321-1322.
(12) Forder, R. J.; Mitchell, I. S.; Reid, G.; Simpson, R. H. Polyhedron
1994, 15, 2129-2133.
(9) Friebolin, H. Basic One- and Two-Dimensional NMR Spectroscopy,
2nd ed.; VCH: New York, 1993; p 287-314.
(10) Mastrorilli, P.; Nobile, C. F.; Fanizzi, F. P.; Latronico, M.; Hu, C.;
Englert, U. Eur. J. Inorg. Chem. 2002, 1210-1218.
9098 Inorganic Chemistry, Vol. 44, No. 24, 2005

Multinuclear and Dynamic NMR Study of {Pt(Cl)(PHCy2)2[P(X)Cy2]}
Table 1. Crystallographic Data and Structural Refinement Details for 4
empirical formula
formula mass
temp (K)
wavelength (Å)
cryst syst
space group
unit cell dimensions
a (Å)
C36H70ClO2P3Pt
858.37
110(2)
0.71073
triclinic
P1h
11.9262(8)
13.3376(10)
13.4580(9)
101.035(2)
111.432(2)
94.637(2)
1929.0(2)
2
b (Å)
c (Å)
R (deg)
â (deg)
γ (deg)
V (Å3)
Z
D
calcd (Mg m-3
)
1.478
3.860
abs coeff (mm-1
)
θ range (deg)
independent reflns
observed reflns
2.23-29.16
10259
8980
data/parameters
10259/388
1.067
0.0402
GOF on F2
R1a (I > 2σ(I))
wR2b (all data)
0.0890
largest diff. peak/hole [e‚ Å-3
]
2.753, -2.692 (<0.9 Å from Pt)
2
2
2
a R1 ) ∑||Fo| - |Fc||/∑|Fo|. b wR2 ) [∑w(Fo - Fc )2/∑w(Fo )2]1/2
.
pad, and the filtrate was evaporated in vacuo yielding pure 2 as a
white solid (265 mg, 92%).
Figure 2. 31P{1H} DNMR of 1 (thf-d8).
The complex is air stable, soluble in halogenated solvents,
acetonitrile, alcohols, and thf, and insoluble in toluene.
the solid obtained was washed with toluene and dried under vacuum.
Yield: 0.128 g (92%).
Anal. Calcd for C36H69BClF4P3Pt: C, 47.40; H, 7.62; Cl, 3.89;
P, 10.19. Found: C, 47.38; H, 7.65; Cl, 3.81; P, 10.12. mp: 265-
266 °C. IR (Nujol mull, cm-1): ν 2360 (w) ν(P-H), 1297 (w),
1269 (w), 1203 (w), 1180 (m), 1062 (s) ν(B-F from BF4), 919
(m), 842 (m), 819 (w), 727 (w), 518 (m), 465 (w), 311 (m) ν(Pt-
The complex is air stable, hygroscopic, soluble in halogenated
solvents, alcohols, and thf, and scarcely soluble in toluene and
n-hexane.
Anal. Calcd for C36H68ClOP3Pt: C, 51.45; H, 8.16; Cl, 4.22; P,
11.06. Found: C, 51.37; H, 8.20; Cl, 4.19; P, 11.00. mp: 206-
208 °C. ESI-MS: m/z 840.5 [M + H]+. IR (Nujol, cm-1): ν 2314
(w) ν(P-H), 1294 (m), 1175 (m) and 1075 (s) ν(PdO), 1003 (m),
916 (m), 880 (m), 850 (m), 814 (m), 543 (s), 513 (m), 390 (m),
275 (m) ν(Pt-Cl). 1H NMR (CD2Cl2, 400 MHz): δ 4.12 (m, 1JP-H
) 372 Hz, 2JPt-H ) 96 Hz). 31P NMR (CD2Cl2, 162 MHz): δ 25.1
1
1
Cl). H NMR (CD2Cl2, 400 MHz): δ 4.15 (m, JP-H ) 351 Hz,
1
2
2JPt-H ) 86 Hz, PA/B-H), 4.28 (m, JP-H ) 385 Hz, JPt-H ) 46
Hz, PX-H). 31P NMR (CD2Cl2, 162 MHz): δ 9.9 (t, 1JP-Pt ) 3159,
1JP-H ) 385 Hz, JP
) 15 Hz, PX), 16.8 (s, br, JP-Pt ) 2224
2
1
A/BPX
Hz, 2JP ) 339 Hz, 1JP-H ) 351 Hz, 3JP-H ) 1.0 Hz, PA/B). 195Pt
APB
NMR (CD2Cl2, 86 MHz): δ -4802 (dt, 1JP -Pt ) 3159 Hz,1JP
X
A/B-Pt
(s, br, 1JP-Pt ) 2842 Hz, 1JP-H ) 372 Hz, 2JP ) 357 Hz, PA/B),
APB
) 2224 Hz).
X
54.1 (t, 1JP -Pt ) 3111 Hz, 2JP ) 16 Hz, P ). 195Pt NMR (CD2-
X
XPA
trans-[Pt(Cl)(PHCy2)2{KP-P(S)Cy2}] (3). The addition of el-
emental sulfur (7.9 mg, 0.247 mequiv) to a stirred toluene solution
of 1 (0.204 g, 0.247 mmol in 6 mL) caused the precipitation of 3
as white solid, which was isolated by filtration, washed with toluene
(2 × 2 mL) and dried under vacuum. Yield: 0.176 g (83%).
1
1
X-Pt
A/B-Pt
) 2842
Cl2, 86 MHz): δ -4619 (dt, JP
) 3111 Hz, JP
Hz).
X-ray Crystallography.13Crystal data, parameters for intensity
data collection, and convergence results for 4 are compiled in Table
1. Data were collected with Mo KR radiation (graphite monochro-
mator, λ ) 0.71073 Å) on a Bruker D8 goniometer with SMART
CCD area detector at 110(2) K on a crystal with approximate
dimensions of 0.17 × 0.14 × 0.05 mm. An empirical absorption
correction14 (minimum trans. 0.56, maximum trans. 0.83) was
applied before averaging symmetry equivalent data (R(int) )
0.0577). The structure was solved by direct methods15 and refined
with full-matrix least-squares on F2.16
The complex is air stable, poorly soluble in thf, and scarcely
soluble in toluene.
Anal. Calcd for C36H68ClP3PtS: C, 50.49; H, 8.00; Cl, 4.14; P
10.85. Found: C, 50.55; H, 7.87; Cl, 4.04; P, 10.94. mp: 204 °C
(dec). ESI-MS: m/z 856.3 [M + H]+. IR (Nujol mull, cm-1): ν
2334 (w) ν(P-H), 1296 (w), 1264 (w), 1173 (m), 1117 (w), 1076
(w), 1005 (m), 916 (w), 888 (w), 855 (m), 814 (w), 738 (m), 579
(s) ν(PdS), 510 (m), 467 (w), 284 (m) ν(Pt-Cl). 1H NMR (C6D6,
1
2
400 MHz): δ 4.63 (m, JP-H ) 370 Hz, JPt-H ) 80 Hz, P-H).
(13) 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
277690. Copies of the data can be obtained free of charge by
application to CCDC, 12 Union Road, Cambridge CB2 1EZ, UK.
Fax: int. code + 44(1223)336-033. E-mail: deposit@ccdc.cam.ac.uk.
(14) Sheldrick, G. M. SADABS, Program for Empirical Absorption
Correction of Area Detector Data: University of Go¨ttingen: Go¨ttin-
gen, Germany, 1996.
31P NMR (thf-d8, 162 MHz, 325 K): δ 42.6 (s, 1JP-Pt ) 3043 Hz,
PX), 34.3 (s, br, JP-Pt ) 2816 Hz, JPAPB ) 354 Hz, JP-H ) 369
1
2
1
Hz, PA/B). 195Pt NMR (C6D6, 86 MHz): δ -4660 (dt, JP
)
1
X-Pt
1
A/B
3010 Hz, JP
) 2842 Hz).
-Pt
trans-[Pt(Cl)(PHCy2)2{KP-P(O)Cy2}] (4). Carefully deaerated
H2O2 (200 µL, 40% v/v) was added to a toluene solution of 1 (0.136
g, 0.165 mmol in 4 mL), and the resulting mixture was vigorously
stirred for 5 min. The resulting white suspension was filtered, and
(15) Sheldrick, G. M. SHELXS97, Program for Crystal Structure Solution;
University of Go¨ttingen: Go¨ttingen, Germany, 1997.
Inorganic Chemistry, Vol. 44, No. 24, 2005 9099

Mastrorilli et al.
Table 2. 31P Spectroscopic Features of trans-[Pt(Cl)(PHCy2)2{P(X)Cy2}] Species at Low Temperature
complex
X
δA
δB
δX
J(A-B)
Tc (K)
∆ν (Hz)a
kc (s-1
)
∆Gq (kcal mol-1
)
solvent
Thf-d8
CD2Cl2
CD2Cl2
CD2Cl2/CH3OH
Thf-d8
CD2Cl2/CH3OH
T (K)
1
2
2a
2a
3
-
H
H
H
S
39.17
22.58
21.00
22.61
45.99
25.49
24.66
10.71
11.40
11.10
18.12
22.00
18.05
8.12
6.10
8.40
40.84
64.49
413
342
343
342
360
345
202
235
240
230
225
248
2350
1923
1584
1864
4519
566
5680
4660
3980
4540
10200
2260
8.2
9.7
10.0
9.5
8.9
10.6
160
175
183
165
160
170
4
O
a At kc ) 0.
Table 3. 1H Spectroscopic Features of trans-[Pt(Cl)(PHCy2)2{P(X)Cy2}] Species at Low Temperature
complex
X
δA
δB
Tc (K)
∆ν (Hz)
kc (s-1
)
∆Gq (kcal mol-1
)
solvent
T (K)
1
2
3
4
4
-
H
S
O
O
3.95
4.03
5.01
4.28
4.06
3.89
3.85
4.17
3.70
3.74
165
203
200
235
225
24
75
334
231
127
53
167
743
513
283
8.2
9.7
8.9
11.0
10.5
Thf-d8
CD2Cl2
Thf-d8
CD2Cl2
160
165
160
170
170
CD2Cl2/CD3OD
Results and Discussion
bound to metals such as Re,18 Fe,19 Nb,20 Ir,21 W,22 Pd,23
and Pt,5,23,24 range between 10.9 and 18.0 kcal/mol.
Dynamic Behavior of 1. Dynamic 31P{1H} NMR spec-
trum of trans-[Pt(Cl)(PHCy2)2(PCy2)] (1) in thf-d8 is reported
in Figure 2. The 31P{1H} NMR signal at 295 K of the
coordinated trans-phosphanes consists of a doublet with ∆ν1/2
) 25 Hz, which broadens when the temperature is lowered
until 202 K, the coalescence temperature. Further lowering
of the temperature causes decoalescence, with the appearance
of an ABX spin system (X ) terminal phosphide P) the
details of which are summarized in Table 2. The coalescence
temperature (Tc ) 202 K) together with the ∆ν between the
resonances of PA and PB allowed us to calculate the exchange
constant, kc (5680 s-1), and the activation free energy, ∆Gq,
for the dynamic process (8.2 kcal/mol).
In the case of complex 1, both steric and electronic factors
should further increase the inversion barrier. In fact, although
bulky cyclohexyl substituents should lower the P inversion
barrier,25 the latter is increased because the clear PX
pyramidal geometry found in the X-ray crystal structure of
1 (sum of the angles at P of 320.5°,10 compared to 328.5°
for a tetrahedral atom and 360° for a planar atom) increases
the energy difference between the planar transition state for
the inversion and the pyramidal ground state.
As for the electronic effects that affect the inversion
barrier, our crystallographic and 31P NMR results10 point out
a low s character of the PX-Pt bond in 1 which should lead
to a high inversion barrier because of the rehybridization
energy necessary to reach the sp2 transition state.26 Taking
the 31PX-195Pt coupling constant as a probe of the s character
of the PX-Pt bond (the lower the constant, the lower the s
In the dynamic 1H spectrum, the coalescence temperature
was found to be around 165 K, and at 160 K (the lowest T
obtainable in thf-d8),17 the P-H signal separated into two
character)5 and the 1102-1112 Hz 1J
31PX-195
Pt value found for
1
A
B
broad doublets (δP -H ) 3.95, JP-H ) 380 Hz; δP -H
)
cyclometalated dimesityl phosphide Pt(II) complexes (for
which pure inversion barriers of ca. 13 kcal/mol have been
calculated),23 an inversion barrier higher than 13 kcal/mol
1
3.89, JP-H ) 360 Hz). These features indicate an ap-
proximate ∆Gq value identical to that calculated from 31P-
{1H} DNMR analysis (Table 3).
The dynamic behavior observed for 1 can be, in principle,
the result of two determinants: (i) a slow phosphorus
inversion in the pyramidal phosphide ligand and (ii) the
presence of several slowly interconverting rotamers because
of hindered rotation around the Pt-PX bond.
(18) Simpson, R. D.; Bergman, R. G. Organometallics 1992, 11, 1980-
1993. (b) Zwick, B. D.; Dewey, M. A.; Knight, D. A.; Buhro, W. E.;
Arif, A. M.; Gladysz, J. A. Organometallics 1992, 11, 2673-2685.
(c) Buhro, W. E.; Zwick, B. D.; Georgiou, S.; Hutchinson, J. P.;
Gladysz, J. A. J. Am. Chem. Soc. 1988, 110, 2427-2439. (d) Buhro,
W. E.; Gladysz, J. A. Inorg. Chem. 1985, 24, 3505-3507.
(19) Malisch, W.; Gunzelmann, N.; Thirase, K.; Neumayer, M. J. Orga-
nomet. Chem. 1998, 571, 215-222. (b) Crisp, G. T.; Salem, G.; Wild,
S. B.; Stephens, F. S. Organometallics 1989, 8, 2360-2367.
(20) Bonnet, G.; Kubicki, M. M.; Moise, C.; Lazzaroni, R.; Salvadori, P.;
Vitulli, G. Organometallics 1992, 11, 964-967.
These two hypotheses cannot be easily distinguished since,
in our system, their effect on the NMR features is the same.
In fact, the observed appearance of an ABX spin system
indicates only that, on lowering the temperature, both the
PX inversion and the rotation about the PX-Pt bond become
slow. However, the value of ∆Gq of 8.2 kcal/mol found for
1 is sensibly lower than those usually found for inversions
in related terminal phosphide complexes. Typical values for
∆Gq for dynamic processes involving terminal phosphides
(21) Fryzuk, M. D.; Joshi, K.; Chadha, K.; Rettig, S. J. J. Am. Chem. Soc.
1991, 113, 8724-8736.
(22) Malisch, W.; Maisch, R.; Meyer, A.; Greissinger, D.; Gross, E.;
Colquhoun, I. J.; McFarlane, W. Phosphorus, Sulfur Silicon Relat.
Elem. 1983, 18, 2299-2302.
(23) Zhuravel, M. A.; Glueck, D. S.; Zakharov, L. N.; Rheingold, A. L.
Organometallics 2002, 21, 3208-3214.
(24) Wicht, D. K.; Kovacik, I.; Glueck, D. S.; Liable-Sands, L. M.;
Incarvito, C. D.; Rheingold, A. L. Organometallics 1999, 18, 5141-
5151.
(25) Rauk, A.; Allen, L. C.; Mislow, K. Angew. Chem., Int. Ed. Engl. 1970,
9, 400-414.
(26) Wicht, D. K.; Paisner, S. N.; Lew, B. N.; Glueck, D. S.; Yap, G. P.
A.; Liable-Sands, L. M.; Rheingold, A.; Haar, C. M.; Nolan, S. P.
Organometallics 1998, 17, 652-660.
(16) Sheldrick, G. M. SHELXL97, Program for Crystal Structure Refine-
ment; University of Go¨ttingen: Go¨ttingen, Germany, 1997.
(17) Complex 1, as well as 3, reacts in halogenated solvents that therefore
could not be used in the low-temperature NMR experiments.
9100 Inorganic Chemistry, Vol. 44, No. 24, 2005

Multinuclear and Dynamic NMR Study of {Pt(Cl)(PHCy2)2[P(X)Cy2]}
Figure 3. PLUTON28 view of the rotamer found in the crystal of 1.
1
31PX-195Pt
has to be expected for 1, the J
929 Hz (thf-d8, 295 K).
value of which is
Moreover, theoretical calculations show that, contrary to
the case of early transition metal phosphides, in Fe(II)-PR2
complexes, the rotational barrier is always much lower than
the inversion barrier.27
In light of these considerations, we favor the rotational
process as the predominant process in determining the
activation barrier for 1, that is ∆Gqinv . ∆Grqot so that, at
room temperature, rotation is fast and inversion is slow.
Lowering the temperature would gradually lock the inversion
and slow the rotation. If this interpretation is correct, the
coalescence temperature would refer to a situation in which
the inversion is already locked and the rotation rate is on
the order of the NMR time scale.
We believe that the rotamer stable at low temperatures is
the sterically least hindered conformer depicted in Figure 3
and found in the crystal.10
Dynamic Behavior of 2, 3, and 4. To confirm our
assignment of ∆Gq predominantly to the rotational process,
we decided to compare the dynamic behavior of 1 with that
of complexes [Pt(PHCy2)3Cl]BF4 (2), trans-[Pt(Cl)(PHCy2)2-
{κP-P(S)Cy2}] (3), and trans-[Pt(Cl)(PHCy2)2{κP-P(O)Cy2}]
(4), which have the same trans-Pt(PHCy2)2Cl moiety and
differ from 1 in the substituent on PX (Figure 1).
All three complexes are characterized by a broad 31P{1H}
NMR signal for the PA/BHCy2 at 295 K [∆ν1/2 ) 100 Hz
(CD2Cl2), 190 Hz (thf-d8), and 76 Hz (CD2Cl2), for 2, 3,
and 4, respectively]. For complexes 2-4, the dissociation
equilibrium of a coordinated PHCy2 was also considered as
a possible factor responsible for the observed broadness of
the PA/B signals. However, since no trace of free PHCy2 was
observed by 31P{1H} NMR in the range of temperatures
(160-325 K) used for this study, the only dynamic process
held responsible for signal broadening was restricted rotation
about the Pt-PX bond.29
Figure 4. 1H{31P} DNMR spectrum of 3 (thf-d8).
AgBF4, and it had a behavior similar to that found for 1 for
the dynamic 31P{1H} NMR. The coalescence temperature
was 235 K and the calculated ∆Gq for the rotation around
PX-Pt bond was 9.7 kcal/mol (Tables 2-3).
Phosphanylsulfide complex 3 was obtained by reaction of
1 with 1 equiv of sulfur in toluene. Variable-temperature
31P{1H} NMR spectra were recorded in the temperature range
of 160-325 K. The proton-coupled 31P NMR spectrum at
325 K gave sufficiently sharp lines for the [AXY2]2M30 spin
system (A is PA/B, X is the proton bound to PA/B, Y represents
the methyne protons of the cyclohexyl rings bound to PA/B
,
and M is PX) to be analyzed for spectroscopic features (see
Experimental Section). Low-temperature 31P{1H} NMR
spectra showed the expected broadening of the PCy2H signal
which gave coalescence at 225 K and separated in the AB
system (with 195Pt satellites) at 160 K. The values calculated
for the kc and ∆Gq are 10200 s-1 and 8.9 kcal/mol,
respectively (Tables 2-3). A 200 K coalescence temperature
1
was found by dynamic H{31P} NMR analysis (Figure 4)
which again gave a ∆Gq value of 8.9 kcal/mol.
Phosphanyloxide complex 4, a side product of the aerobic
oxidation of 1,31 was selectively obtained by reaction of 1
with hydrogen peroxide. Variable-temperature 31P{1H} NMR
spectra and its dynamic 31P{1H} NMR behavior in CD2Cl2
are reported in Figure 5. When the temperature is lowered
to 235 K, the expected broadening and separation of PCy2H
signals is observed.
However, the separation of the PCy2H signals was
markedly less pronounced than in previous cases (less than
1.5 ppm in 4 vs 27 ppm in 3).
Cationic complex 2 was obtained as the tetrafluoroborate
salt by reaction of cis-[PtCl2(PHCy2)2] with PCy2H and
Interestingly, a further decrease of the temperature to 160
K in the case of compound 4, resulted in an unexpected
reapproaching of the PA/B signals, concomitant with their
(27) Rogers, J. R.; Wagner, T. P. S.; Marynick, D. S. Inorg. Chem. 1994,
33, 3104-3110.
(28) Spek, A. L. PLATON-98; University of Utrecht: Utrecht,The Neth-
erlands, 1998.
(29) Little PHCy2 dissociation was observed at room temperature when 2
was dissolved in 1,2-dichloroethane or when 3 was dissolved in
halogenated solvents.
(30) Palmer, R. A.; Whitcomb, D. R. J. Magn. Res. 1980, 39, 371-379.
(31) Mastrorilli, P.; Latronico, M.; Nobile, C. F.; Suranna, G. P.; Fanizzi,
F. P.; Englert, U.; Ciccarella, G. Dalton Trans. 2004, 1117-1119.
Inorganic Chemistry, Vol. 44, No. 24, 2005 9101

Mastrorilli et al.
Figure 7. PLATON28 drawing of 4; displacement ellipsoid are scaled to
50% probability, and the hydrogen atoms bonded to C have been omitted
for clarity. Selected interatomic distances (Å) and angles (deg): Pt-P(1)
) 2.2688(10), Pt-P(2) ) 2.2997(11), Pt-P(3) ) 2.3104(11), Pt-Cl )
2.4131(10), P-O ) 1.516(3), P(1)-Pt-P(2) ) 91.29(4), P(1)-Pt-P(3)
) 93.74(4), P(2)-Pt-P(3) ) 174.45(4), P(1)-Pt-Cl ) 176.23(4), P(2)-
Pt-Cl ) 88.51(4), P(3)-Pt-Cl ) 86.61(4).
tion. The molecular structure is depicted in Figure 7. The
distorted square planar geometry at the platinum center in 4
is similar to that in complex 1. The Pt-P distances of the
coordinated dicyclohexylphosphanes [2.2997(11) and 2.3104-
(11) Å] are slightly longer than that of Pt-P(O)Cy2 [2.2688-
(10) Å] as a consequence of the greater trans influence of P
with respect to Cl. The two P-H bonds of the PHCy2 ligands
are both oriented toward the PX (P1) ligand, one of them
being directed toward the oxygen bound to PX. In comparison
to related P-bound P(O)R2-Pt complexes [Pt(Ph){κP-P(O)-
Ph2}(RCN)(PPh3)] {R ) 9-anthracenyl or 3,5-dichloro-2,4,6-
trimethylphenyl, P-O distance ) 1.51(1) Å},32 anti-[Pt-
(PMePh2){κP-P(O)Ph2}(µ-NH2)]2 {P-O distance ) 1.526(11)
Å},33 [PtL{κP-P(O)Ph2}Cl] {L ) (+)-(1S,2R)-2-(dimethyl-
amino)-1-phenyl-1-diphenyl-phosphinoxypropane, P-O dis-
tance ) 1.501(4) Å},34 and [(PMe2Ph){κP-P(O)Me2}Pt(µ-
NPh)]2 {P-O distance ) 1.509(2) Å},35 the P-O bond
distance of 4 [1.516(3) Å] is typical for a double P-O bond.
The potential H donor O1 lies only 0.12 Å above the plane
defined by Pt1, P1, and P2; this close coplanarity allows for
an, albeit quite weak, hydrogen bond between O1 and H2.
A more complete picture of the hydrogen bonds in 4 must
take the intermolecular interactions into account. The asym-
metric unit in space group P1h contains one molecule of water
per complex. Two pairs of water and complex molecules,
related by crystallographic inversion, form an overall hydrogen-
bond pattern which can be described by the graph set symbol
Figure 5. 31P{1H} DNMR of 4 (CD2Cl2).
Figure 6. Alleged molecular motions of 4.
sharpening. This behavior prevented the calculation of the
∆Gq from the 31P NMR data. On the other hand, the dynamic
1H{31P} NMR analysis for 4 showed coalescence of the PH
signal at 235 K and splitting of the PH signal (δ 4.12 at 295
K) into two peaks centered at δ 4.3 and 3.7 (T < 225 K).
From these data, a 11.0 kcal/mol ∆Gqrot could be calculated
(Table 3). This relatively high ∆Gqrot value suggested the
presence of P-H‚‚‚OdP intramolecular interactions in the
case of compound 4 (Figure 6).
The reapproaching of the 31P signals observed upon
lowering the temperature from 235 to 180 K may be caused
by the occurrence of two dynamic processes with different
activation energies. Of these, the one at higher energy is
presumably the hindered rotation about the PX-Pt bond,
analogous to that observed for compounds 1-3, while the
one at lower energy could be the rotation about the PA-Pt
bond (Figure 6). The latter could be slowed only in the case
of 4 because of the aforementioned P-H‚‚‚OdP interaction
and could be responsible for the broadening of the 31PX NMR
signal at 160 K (Figure 5).
2
R4 (8).36 Figure 8 provides a graphical description of this
arrangement and gives important interatomic distances.
(32) Beck, W.; Keubler, M.; Leidl, E.; Nagel, U.; Schaal, M.; Cenini, S.;
Del Buttero, P.; Licandro, E.; Maiorana, S.; Chiesi-Villa, A. J. Chem.
Soc., Chem. Commun. 1981, 446-448.
(33) Alcock, N. W.; Bergamini, P.; Kemp, T. J.; Pringle, P. G. J. Chem.
Soc., Chem. Commun. 1987, 235-236.
(34) Francio`, G.; Arena, C. G.; Panzalorto, M.; Bruno, G.; Faraone, F. Inorg.
Chim. Acta 1998, 277, 119-126.
To confirm the existence of the P-H‚‚‚OdP interaction
in the solid state, a crystallographic analysis was performed.
X-ray diffraction studies were carried out on a single crystal
obtained by slow evaporation of a 1,2-dichloroethane solu-
(35) Li, J. J.; Li, W.; James, A. J.; Holbert, T.; Sharp, T. P.; Sharp, P. R.
Inorg. Chim. 1999, 38, 1563-1572.
(36) Etter, M. C.; MacDonald, J. C.; Bernstein, J. Acta Crystallogr. 1990,
B46, 256-262. (b) Grell, J.; Bernstein, J.; Tinhofer, G. Acta Crys-
tallogr. 1999, B55, 1030-1043.
9102 Inorganic Chemistry, Vol. 44, No. 24, 2005

Multinuclear and Dynamic NMR Study of {Pt(Cl)(PHCy2)2[P(X)Cy2]}
Table 4. Effect of the Solvent on the Chemical Shifts of
[Pt(Cl)(PHCy2)3]Cl (2a)a
dielectric constant
X
A/B
δP
solvent
δP
at 20 °C
CD2Cl2
CH3OH
CH3CN
5.4 (9.9)
9.8 (9.9)
9.6 (10.4) 15.1 (15.6)
10.1 (10.7) 17.1 (17.1)
14.3 (16.8)
14.7 (15.8)
9.1
33.6
36.6
CD2Cl2 with
two drops of CD3OD
a Values in parentheses refer to [Pt(Cl)(PHCy2)3]BF4 (2).
ments were 248 and 225 K, respectively. The corresponding
∆Grqot values were 10.6 (from 31P{1H} DNMR) and 10.5
1
kcal/mol (from H{31P} DNMR).
Interactions Involving the Cationic Fragment [Pt(Cl)-
(PHCy2)3]+ and the Counteranion. Finally, we have
considered the influence on the dynamic behavior of [Pt-
(Cl)(PHCy2)3]+ of a counteranion, such as chloride, capable
of interacting with the coordinated P-H more strongly than
Figure 8. PLUTON28 representation of the hydrogen-bond pattern in 4.
Selected interatomic distances (Å) and angles (deg): P(2)-H(2) ) 1.12,
P(2)‚‚‚O(1) ) 3.188(4), O(1)‚‚‚H(2) ) 2.492, P(2)-H(2)‚‚‚O(1) ) 119,
O(2)-H(2C) ) 0.93, O(2)‚‚‚O(1) ) 2.806(5), O(2)-H(2C)‚‚‚O(1) ) 167,
O(2)-H(2D) ) 0.94, O(2)‚‚‚O(1)′ ) 2.846(5), O(2)-H(2D)‚‚‚O(1)′ ) 173.
Primed atoms are related to unprimed ones by inversion.
-
BF4 .
From the DNMR experiments, a ∆Gqrot of 10.0 kcal/mol
was calculated for the complex [Pt(Cl)(PHCy2)3]Cl (2a), a
value slightly higher than that obtained for 2. This can be
interpreted by admitting that in the case of 2a there is a small
contribution to ∆Gqrot resulting from a PH‚‚‚Cl- interac-
tion,37 but the small difference between the ∆Gqrot values
does not permit conclusive statements. However, other
circumstantial NMR features reinforce this hypothesis.
Data collected in Table 4 show that, in contrast to what is
observed for 2, the 31PX chemical shift of 2a depends on the
solvent. A upfield shift with respect to 2 is observed in CD2-
Cl2, a solvent with a low dielectric constant (and therefore
poor solvating ability for Cl-).
The addition of few drops of methanol to a CD2Cl2
solution of 2a caused ion-pair breaking and resulted in 31PX
chemical shift (δ ) 10.1) and ∆Gq (9.5 kcal/mol) values
rot
very similar to those found for 2.
An analogous effect was observed in the 1H NMR spectra
where the chemical shift of PXHCy2 passed from δ 4.96 to
4.38 upon addition of methanol, the corresponding value for
2 in CD2Cl2 being δ 4.28.
The interaction between the Pt(II) cation and Cl- coun-
teranion could also be evidenced by 35Cl NMR spectroscopy.
The relaxation rate is related to the line width according
to
Figure 9. 31P{1H} DNMR of 4 (CD2Cl2/CH3OH).
To gain insight into the possible intramolecular H‚‚‚O
interaction in solution for 4, we have added few drops of
CH3OH to a CD2Cl2 solution of 4 and carried out multi-
nuclear dynamic NMR experiments on the resulting mixture.
The 31P{1H} spectra at variable temperatures (Figure 9)
showed a much less-marked reapproaching of signals which
could be related to the slowed lower-energy dynamic process
(i.e., rotation about the PA-Pt bond). This reapproaching
started at 200 K but did not prevent the calculation of the
higher ∆Gqrot from 31P NMR data. Moreover, in these
conditions, no broadening of the 31PX NMR signal was
observed at very low temperature.
1
πT2
∆ν1/2
)
In the liquid state, extreme narrowing conditions apply, and
the relaxation rates for 35Cl (I ) 3/2) are given by
1
1
2π2
5h2
η2
3
)
)
1 +
(eQq)2τ
c
(
)
T1 T2
where η is the asymmetry parameter, Q is the nuclear
quadruple moment, τc is the correlation time for molecular
(37) A hydrogen bond between a P-H and the Cl- has been reported in
ref 18b for [Re(Cp)(NO)(PPh3)(PPhH2)] both in solution and in the
solid state.
In the CD2Cl2/CH3OH mixture, the coalescence temper-
1
atures found for 4 by 31P{1H} and H{31P} DNMR experi-
Inorganic Chemistry, Vol. 44, No. 24, 2005 9103

Mastrorilli et al.
responsible for the different ∆Gqrot values found for 2 and
2a.
reorientation, and q is the electric field gradient at the
nucleus. This field results from the charge distribution around
the nucleus (i.e., the surrounding electrons and nearby
nuclei). Because of the spherical symmetry of the electron
Conclusions
cloud, the field gradient at the 35Cl nucleus in free Cl-
The comparison of the activation free energies collected
in Table 2 permits the following considerations. The least
value found for 1 is what one would expect for the hindered
rotation around the Pt-PX bond (at locked inversion) on the
basis of steric reasons. In fact, the terminal phosphido
complex 1 is characterized by the longest expected Pt-PX
bond [1J(P-Pt) ) 929 Hz for 1 vs 3159 (2), 3034 (3), and
3245 Hz (4)] and the least hindered substituent among the
series X ) lone pair, H, S, O. The highest value found for
4 (11.0 kcal/mol) can be the result of the presence of a P-H‚
‚‚OdP intramolecular interaction that, below 235 K, might
result in a slowing of the rotation about the PA-Pt bond.
The addition of a hydrogen bond breaker, such as CH3OH,
lowered the energy barrier for the rotation about the PX-Pt
bond (which became 10.5 kcal/mol) and increased the energy
gap of the two dynamic processes (i.e., rotation about the
PX-Pt and PA-Pt bonds). Single-crystal X-ray diffraction
confirmed the presence of both intra and intermolecular Pd
O‚‚‚H interactions in solid 4. For complex 2a, the presence
of ion pairing between PXHCy2 and the Cl- counteranion
has been proven by multinuclear NMR.
(g)
should be zero. When the chloride ion is in solution, its
solvation shell generates a fluctuating field gradient at the
nucleus. This gradient will not be large because solvent
molecules are disposed about the ion in an approximately
symmetrical way, and in solution, the free Cl- should give
a
35Cl NMR signal only a few Hz wide. The approach of a
counterion destroys the symmetry of the solvation shell and
increases the field gradient at the 35Cl nucleus.38 The
magnitude of the field gradient caused by the counterion is
strongly dependent on interionic distance. In the point charge
model, the 35Cl NMR line width is proportional to the sixth
power of the Cl-‚‚‚counterion distance:39 therefore, in a
contact ion pair a large field gradient will be generated at
the 35Cl nucleus, with a consequently great enhancement of
the relaxation, also the result of the relatively high value of
Q (-0.082‚10-28 m2). The result is a very broad 35Cl NMR
signal which could disappear in the rolling of the spectrum
baseline. Given that contact-ion pairing can be detected by
examining the 35Cl NMR line width as a function of
concentration,40 we have recorded 35Cl NMR spectra of CD2-
Cl2 solutions of 2a in the 8.2 × 10-3-6.2 × 10-2 range of
concentration, but in any case, no 35Cl signal was detected.
More diluted solutions were not considered because of the
low 35Cl NMR sensitivity (3.55 × 10-3 vs 1H). As expected,
the addition of one drop of methanol caused the appearance
of an intense 35Cl NMR signal centered at δ -21, thus
supporting the existence of a PH‚‚‚Cl- interaction being
Acknowledgment. Dr. G. Ciccarella is gratefully ac-
knowledged for the ESI-MS analyses. A grant from Italian
MIUR (PON Project 2000-2006 No. 3043/45) for the
purchase of the 400 MHz NMR spectrometer is acknowl-
edged. Italian MIUR (PRIN 2004, Project 2004030719_005)
is gratefully acknowledged for financial support.
Supporting Information Available: ESI-MS spectra of [Pt-
(Cl)(PHCy2)3]+ for 3 and 4, 31P{1H} NMR spectra of 2, 2a, and 3,
atomic coordinates, equivalent isotropic displacement parameters,
and bond lengths and angles for 4. This material is available free
of charge via the Internet at http://pubs.acs.org.
(38) Berman, H. A.; Stengle, T. R. J. Phys. Chem. 1975, 79, 1001-
1005.
(39) Barnes, R. G.; Smith, W. V. Phys. ReV. 1954, 93, 95-98. (b) Townes,
C. H.; Dailey, B. P. J. Chem. Phys. 1952, 20, 35-40.
(40) Avent, A. G.; Chalouer, P. A.; Day, M. P.; Seddon, K. R.; Welton, T.
J. Chem. Soc., Dalton Trans. 1994, 3405-3413.
IC051198X
9104 Inorganic Chemistry, Vol. 44, No. 24, 2005