Effect of weak hydrogen bonding and included solvent on the crystal structure of the square-planar complex trans-Pt{PPh2(C16H15)}2Cl 2

Article abstract of DOI:10.1039/a807483f

Crystallisation of the square-planar complex trans-Pt{PPh₂(C₁₆H₁₅)}₂Cl ₂ from dichloromethane-diethyl ether (1:1) affords two different solvates; trans-Pt{PPh₂(C₁₆H₁₅)

Full text of DOI:10.1039/a807483f

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E†ect of weak hydrogen bonding and included solvent on the crystal
structure of the square-planar complex trans-Pt{PPh (C H )} Cl
2 16 15 2 2
Priya Suman,a Philip W. Dyer,b Paul J. Dyson,*,a Stuart L. Jamesa and Jonathan W. Steedc
a Centre for Chemical Synthesis, Department of Chemistry, Imperial College of Science,
T echnology and Medicine, South Kensington, L ondon, UK SW 7 2AY
b Department of Chemistry, T he University of L eicester, University Road, L eicester,
UK L E1 7RH
L e t t e r
c Department of Chemistry, KingÏs College L ondon, Strand, L ondon, UK W C2R 2L S
Crystallisation of the square-planar complex trans-PtMPPh (C
H
)N Cl from dichloromethaneÈdiethyl ether
2
16 15 2
2
(1 : 1) a†ords two di†erent solvates;trans-PtMPPh (C
H
)N Cl É CH Cl 1 andtrans-
2
16 15 2
2
2 2
PtMPPh (C
H
)N Cl É Et O 2; the CH Cl forms H-bonding interactions with the complex whereas the Et O
2
16 15 2
2
2
2
2
2
participates only in weak van der Waals interactions; these di†erences arise from the di†erent hydrogen-
bonding characteristics of each solvent.
Scrutinising apparently weak intra- and inter-molecular inter-
actions in solid-state structures can yield valuable information
concerning the gross molecular and crystal structures and
often provides an insight into unexpected structural motifs.1
Ultimately, such studies may provide the experimentalist with
adequate knowledge to design and engineer crystals with spe-
ciÐc physical properties.2 After the general steric demands
imposed by molecules, one of the most important factors dic-
tating structural motifs are hydrogen-bonding interactions.3
Some hydrogen bonds are relatively strong and many exam-
ples of this type are encountered in biological systems.4 Other
hydrogen-bonding interactions are much weaker but they can
still have a marked inÑuence on structure.5 The presence of
solvent molecules in crystals is clearly important in deÐning
the precise structure but we are only aware of one deliberate
study where a neutral inorganic complex has been crystallised
with di†erent solvent molecules giving rise to very di†erent
packing motifs.6 In this letter we report the molecular and
crystal structures of the inorganic complex trans-
analysed by single crystal X-ray di†raction.p
Both solvates contain two independent molecules of trans-
PtMPPh (C
H )N Cl , each molecule having essentially the
2
16 15 2 2
same conformation, and a representative structure (from 2) is
shown in Fig. 1. The similarity between the structures may be
illustrated by a comparison of the key parameters in Table 1.
The most notable features of trans-PtMPPh (C
H
)N Cl are
2
16 15 2
2
Ðrstly that it is a meso complex with one R and one S ligand.
Secondly, the [2.2]paracyclophane substituents orientate into
positions such that an outer-ring proton forms a long-range
interaction with axial sites on the Pt centre to give a pseudo-
octahedral geometry [the distance CwHÉ É ÉPt 2.78È2.90 Ó]
shown by the dotted lines in Fig. 1. Although this interaction
is weak it is clearly very important in square-planar complex-
es carrying this phosphine ligand since it is also present in
other examples,10 some yet to be published.
Other intra- and inter-molecular interactions are also
present and these are shown in Fig. 2 and 3 for solvates 1 and
PtMPPh (C
H )N Cl containing di†erent solvents. The
p Structural details for 1: C
H Cl P Pt, M 1220.74 g mol~1, tri-
2
16 15 2 2
58 54 6 2
unique aspect of this investigation is that the gross packing
motifs of the two solvates is very similar, but subtle di†erences
in the actual structures of the complexes are observed.
clinic, space group P1, a \ 12.2171(6), b \ 13.0694(8), c \ 16.6592(8)
Ó, a \ 79.094(2), b \ 82.943(2), c \ 80.139(2)¡. U \ 2562.1(2) Ó3,
Z \ 2, l \ 31.53 cm~1, T \ 123 K, reÑections measured: 21 873,
unique data: 9334 (R \ 0.043), parameters: 608, R [F2 [ 2r(F2)]
Reaction of two equivalents of diphenyl[2.2]para-
cyclophanylphosphine,
int
1
Cl OP Pt, M 1125.01 g
0.0494, wR (all data) 0.1390. 2: C
H
rac-PPh (C
H
),¤
with
cis-
2
60 60
2
2
2
16 15
mol~1, triclinic, space group P1, a \ 10.9266(7), b \ 13.3688(9),
c \ 17.8209(13) Ó, a \ 100.957(2), b \ 98.816(2), c \ 95.460(2)¡.
U \ 2504.7(3) Ó3, Z \ 2, l \ 30.13 cm~1, T \ 100 K, reÑections
Pt(NC H ) Cl in dichloromethane at room temperature for
5
5 2 2
24 h a†ords trans-PtMPPh (C
H )N Cl É CH Cl 1 in ca.
2
16 15 2
2
2 2
85% yield after recrystallisation from dichloromethaneÈ
measured: 15 464, unique data: 9167 (R \ 0.059), parameters: 599,
int
R
[F2 [ 2r(F2)] 0.0472, wR (all data) 0.1294. Crystals were
diethyl ether (1 : 1).” Crystals containing each solvate, CH Cl
(1) and Et O (2) were obtained and both have been
1
2
2
2
mounted using silicon grease on the end of a glass Ðbre and cooled on
the di†ractometer using an Oxford Cryostream. All crystallographic
measurements were carried out with a Nonius KappaCCD di†rac-
tometer equipped with graphite-monochromated Mo-Ka radiation
using z rotations with 2¡ frames and a detector-to-crystal distance of
25 mm. Unit cell determination and integration was carried out by the
program DENZO-SMN.7 Data sets were corrected for Lorentz and
polarization e†ects and for the e†ects of absorption using the program
Scalepack.7 Structures were solved using the direct methods option of
SHELXS-978 and developed using conventional alternating cycles of
least squares reÐnement and di†erence Fourier synthesis (SHELXL-
977) with the aid of RES2INS.9 All non-hydrogen atoms were reÐned
anisotropically, whilst hydrogen atoms were Ðxed in idealized posi-
tions and allowed to ride. Hydrogen atom thermal parameters were
tied to those of the atom to which they were attached. CCDC refer-
ence number 440/068.
2
* E-mail: p.dyson=ic.ac.uk
¤ rac-PPh (C
H
) is prepared from the dropwise addition of
2
16 15
PPh Cl (0.77 g, 3.48 mmol) to LiC
H
(0.74 g, 3.48 mmol) in diethyl
2
16 15
ether (40 ml) at 0 ¡C with PPh Cl (0.77 g, 3.48 mmol) over 10 min
2
followed by warming to room temperature for a further 3 h. The com-
pound is isolated in ca. 60% yield after recrystallisation from hot
ethanol.
” trans-PtMPPh (C
H
)N Cl . 1H NMR (CDCl ) phenyl rings: d 7.92
2
16 15
2
2
3
(m, 4H), 7.64 (m, 6H); paracyclophane: 6.84È6.41 (m, 7H, aromatic
protons), 3.48È2.87 (m, 8H, methylene protons). 31P-M1HN NMR
(CDCl ): d 19.56 (J
\ 2574 Hz). Mass spectrum (FAB`): m/z 1051
3
PthP
(M`).
New J. Chem., 1998, Pages 1311È1313
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Fig. 1 The structure of one of the two independent trans-
Fig. 2 The structure of 1 showing intra- and inter-molecular contacts
PtMPPh (C
H
)N Cl molecules from solvate 2
2
16 15
2
2
involved in this inter-molecular hydrogen bond. It is
likely that the di†erent types of weak interactions involving
the two Cl ions give rise to the subtle di†erences in the
actual structures of the four platinum complexes.
2, respectively. In the former structure there is no direct inter-
action between the two complexes although they are con-
nected indirectly via the dichloromethane solvate. Indeed, the
most dominant feature after the PtÉ É ÉH interaction appears to
be weak hydrogen bonding with the chlorides attached to the
metal centres since these interactions are always present in
square-planar complexes carrying diphenyl[2.2]paracyclo-
The presence of two independent molecules in square-
planar MP Cl (M \ Pd or Pt; P \ phosphine) complexes is
2
2
very rare and only three examples were found in the Cam-
bridge Crystallographic Database.11 This would suggest that
the steric demands of this unusual asymmetric phosphine are
responsible and appears to be a common trend for other
palladiumÈdiphenyl[2.2]paracyclophanylphosphine complex-
es. We are currently preparing related phosphines in which
the [2.2]paracyclohanyl substituent is replaced by groups of
similar size but with very di†erent electronic properties such
as metallocenes in an attempt to establish the extent to which
electronic factors play a role in the crystal architecture.
phanylphosphine. The Pt(1)Cl fragment interacts with the
2
dichloromethane solvate (see Fig. 2) [Cl(1)É É ÉH(1s2) 2.60 Ó]
and the Pt(2)Cl fragment interacts intra-molecularly with
2
protons on the CH linkers in the [2.2]paracyclophanyl group
2
[C1(2)É É ÉH(35a) 2.77 Ó]. The Cl atoms of the dichloro-
methane also form a hydrogen bond with a proton on the
[2.2]paracyclophane
ring
on
the
other
molecule
[Cl(3s)É É ÉH(41) 2.82 Ó] thereby indirectly connecting the two
platinum complexes. In contrast, 2, which contains diethyl
ether solvate, does not show any interactions between the
solvent and complexes, presumably because of the lower
acidity of the CwH protons of diethyl ether relative to
dichloromethane. Despite this, it can be seen from Fig. 3 that
a related scenario exists for the PtCl fragments with Pt(1)Cl
2
2
involved in intra-molecular interactions, albeit with phenyl
ring protons [Cl(1)É É ÉH(24) 2.80 Ó]. In Pt(2)Cl these inter-
2
actions are inter-molecular in nature. Two pseudo-geminal
protons from the face-to-face rings of the [2.2]paracyclo-
phanyl unit [Cl(2)É É ÉH(5) 2.91 and Cl(2)É É ÉH(10) 2.87 Ó] are
Table 1 A comparison of key bond lengths (Ó) and angles (¡) for the
four molecules trans-PtMPPh (C
H
)N Cl
2
16 15
2
2
1
Pt(1)wCl(1)
2.3150(13)
2.3355(14)
2.84
Pt(2)wCl(2)
2.3189(13)
2.3386(15)
2.79
Pt(1)wP(1)
Pt(2)wP(2)
Pt(1)É É ÉH(10)
Cl(1)wPt(1)wP(1)
Pt(2)É É ÉH(38)
Cl(2)wPt(2)wP(2)@
87.99(5)
88.27(5)
2
Pt(1)wCl(1)
Pt(1)wP(1)
Pt(1)É É ÉH(14)
Cl(1)wPt(1)wP(1)
2.3131(16)
2.3319(16)
2.78
Pt(2)wCl(2)
2.3104(16)
2.3303(16)
2.90
Pt(2)wP(2)
Pt(2)É É ÉH(42)
Cl(2)wPt(2)wP(2)
86.55(6)
87.33(6)
Fig. 3 The structure of 2 showing intra- and inter-molecular contacts
1312
New J. Chem., 1998, Pages 1311È1213

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4 D. H. Williams and M. S. Westwell, Chem. Soc. Rev., 1998, 27, 57.
5 (a) G. R. Desiraju, Acc. Chem. Res., 1996, 29, 441; (b) T. Steiner,
Cryst. Rev., 1996, 6, 1.
Acknowledgements
We thank the Royal Society for a University Research Fellow-
ship (P.J.D.) and the EPSRC (P.S.) for Ðnancial support. We
also thank Johnson Matthey PLC for the loan of platinum
chlorides. The EPSRC and KingÏs College London are also
thanked for the provision of the X-ray di†ractometer and the
Nuffield Foundation for the provision of computing
equipment.
6 M. T. Ashby, Inorg. Chem., 1995, 34, 5429.
7 Z. Otwinowski and W. Minor, in Methods in Enzymology, ed.
C. W. Carter and R. M. Sweet, Academic Press, London, 1996.
8 G. M. Sheldrick, SHELX-97, University of Gottingen, Gottingen,
1997.
9 L. J. Barbour, RES2INS, University of MissouriÈColumbia,
1995È1998.
10 P. W. Dyer, P. J. Dyson, S. L. James, P. Suman, J. E. Davies and
C. M. Martin, Chem. Commun., 1998, 1375.
11 (a) W. Tumas, J. C. Huang, P. E. Fanwick and C. P. Kubiak,
Organometallics, 1992, 11, 2944; (b) C. M. DiMeglio, K. J. Ahmed,
L. A. Luck, E. E. Weltin, A. L. Rheingold and C. H. Bushweller, J.
Phys. Chem., 1992, 96, 8765.
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Received 24th July, 1998;
L etter 8/07483F
New J. Chem., 1998, Pages 1311È1313
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