A new polymorph, form C, of [1,2-bis(diphenylphosphino)ethane]-dichloronickel(II)

Article abstract of DOI:10.1107/S0108270101003961

The title compound, [NiCl₂(C₂₆H₂₄P₂)], has arisen as a result of the unexpected reduction (hydrogenation) of the trans-1.2-bis(diphenylphosphino)ethene ligand. The hydrothermal reaction conditions have produced a third polymorphic form of the compound which has twofold symmetry, crystallizes in an enantiomer-selective manner and contains an unexpectedly short C-C (ethane) bond. Contacts of the form C-H···Cl are present, one involving alkyl and the other aryl hydrogen, with C···Cl distance of 3.556 (4) and 3.664 (6) A, respectively.

Full text of DOI:10.1107/S0108270101003961

metal-organic compounds
Acta Crystallographica Section C
Crystal Structure
Communications
the asymmetric unit consists of one Cl and half of the ligand
comprising P, the ethane C1, and C2±C13 of the phenyl groups
attached to P. The latter are in the 4b general positions.
According to Busby et al. (1993), molecules of B possess
similar but non-crystallographic twofold axial symmetry, while
those of A do not due to the disposition of the phenyl groups.
In all of the polymorphs, the coordination of Ni remains
essentially similar, in the form of a slight tetrahedral distortion
from a square-planar arrangement.
ISSN 0108-2701
A new polymorph, form C, of
[
1,2-bis(diphenylphosphino)ethane]-
dichloronickel(II)
Solely on the basis of the mode of preparation of C (see
below), it was assumed initially that in forming the complex C
the original trans-substituted diphosphinoalkene had simply
undergone transformation to the cis form. However, the
length of the putative C C bond provoked investigation of a
model with two rather than one H atom attached to C1
resulting in a small but signi®cant improvement in the R
a
b
b
Jo C. Davison, Mark R. St J. Foreman, R. Alan Howie, *
b
a,b
M. John Plater and Janet M. S. Skakle
a
School of Physics, University of Aberdeen, Fraser Noble Building, Aberdeen
b
AB24 3UE, Scotland, and Department of Chemistry, University of Aberdeen,
Meston Walk, Aberdeen AB24 3UE, Scotland
Correspondence e-mail: r.a.howie@abdn.ac.uk
1
factor. The correctness of this model was con®rmed by H
NMR and supported by elemental analysis and the discovery
of crystals of A in admixture with C, one of which was used to
provide intensity data at 150 K [A(150)] whose analysis is
presented here merely for comparison purposes (Fig. 2 and
Table 1).
It follows that in the synthesis of C, accompanied by some
A, by the method described below, the initial phosphine
disubstituted alkene ligand has undergone hydrogenation.
This is comparable with the dihalobis(triphenylphosphine)-
nickel(II)-catalysed hydrogenation of methyl linoleate with
tetrahydrofuran as the hydrogen source (Itatani & Bailar,
Received 8 November 2000
Accepted 3 February 2001
The title compound, [NiCl (C H P )], has arisen as a result
2
26 24 2
of the unexpected reduction (hydrogenation) of the trans-1,2-
bis(diphenylphosphino)ethene ligand. The hydrothermal
reaction conditions have produced a third polymorphic form
of the compound which has twofold symmetry, crystallizes in
an enantiomer-selective manner and contains an unexpectedly
short CÐC (ethane) bond. Contacts of the form CÐHÁ Á ÁCl
are present, one involving alkyl and the other aryl hydrogen,
1
tion of H in a similar system as reported by Davies et al.
967) supported by the detailed investigation of the genera-
Ê
with CÁ Á ÁCl distances of 3.556 (4) and 3.664 (6) A, respec-
2
tively.
(1998).
In the scheme, molecules of A, B and C are handed because,
Comment
relative to the immediate coordination of Ni with Cl down
below the plane of the paper (small rectangles), the CÐC
ethane bond of the ligand may be either rotated clockwise, (i),
or anticlockwise, (ii). Centrosymmetric A and B are racemic in
this respect but C is not. By coincidence, the molecules of
C(293) correspond to (i) and those of C(150), with a second
crystal, to (ii).
The Cambridge Structural Database (CSD; Allen & Kennard,
993), accessed at the Chemical Database Service of the
1
EPSRC (Fletcher et al., 1996), provides three reports of
structures for the title compound. Spek et al. (1987) reported
the structure of the dichloromethane solvate (FUJXUD)
which was subsequently re-examined by Busby et al. (1993)
and designated form B along with a second unsolvated
structure (form A, PIFDUD). The structure of form A was
later determined with greater precision (PIFDUD01; Davies
et al., 1998). Following the notation of Busby et al. (1993), we
designate the polymorph described here as form C. In the
following discussion the various structures (polymorphs) are
designated simply by letter as A, B or C and in addition the 150
and 293 K structures presented here are further differentiated
as A(150), C(150) and C(293).
Table 1 shows that the molecules of A, B and C are very
similar, except that the ethane CÐC of the ligand is
Ê
approximately 0.1 A shorter in C than in A or B. The dihedral
angles around this bond, while of opposite sign for the enan-
tiomers C(293) and C(150), are smaller in magnitude than the
corresponding values in A or B.
Short CÐC bonds in ligands of this type are by no means
uncommon and extreme cases are, for example, values of
Ê
1
P,P -dichlorochromium(II) (DAJDUN; Girolami et al., 1985)
Ê
or 1.326 (10) A in dichlorobis[1,2-bis(dimethylphosphino)-
ethane]iron(II) (BAWSOH; di Vaira et al., 1981), and are
usually accounted for by disorder or extreme thermal displa-
.380 (10) A in trans-bis[1,2-bis(dimethylphosphino)ethane]-
0
The molecules of C (Fig. 1) contain a twofold crystal-
lographic symmetry axis passing through Ni and the midpoint
i
of the C1ÐC1 bond [symmetry code: (i) � x, y, � z]. Thus, in
addition to Ni in the 2a special positions of the space group I2,
ꢀ
690 # 2001 International Union of Crystallography
Printed in Great Britain ± all rights reserved
Acta Cryst. (2001). C57, 690±693

metal-organic compounds
electron density to the C atom to which it is attached, thus
imparting some double-bond character to the CÐC bond and
thus shortening it. If this is the case, the effect is surprisingly
large. There is also present in C an aryl H contact of the form
C12ÐH12Á Á ÁCl which serves to interconnect the columns of
molecules in sheets parallel to (101). Both of these contacts
were elucidated by means of PLATON (Spek, 1990).
Figure 1
A molecule of C showing the atom-labelling scheme. Selected symmetry-
related [symmetry code: (i) � x, y, � z] atoms are labelled. Non-H atoms
are shown as 50% probability ellipsoids and H atoms are shown as open
circles.
cement or a combination of both. However, in the case of C,
the complete success of the re®nement of the absolute struc-
ture in both instances with no evidence of twinning or any
other form of disorder leaves the shortness of the ethane CÐC
bond still to be accounted for by other means. Decrease in the
temperature of data collection from 293 to 150 K has no effect
on this CÐC bond length in A but causes an increase in length
by about 1% in C. This can be attributed to libration in the
case of C but the change is small compared with the overall
discrepancy between C and A or B. There is, however, one
feature in the structure of C which is totally absent in A or B.
This is the hydrogen-bond type contact of the form C1Ð
H1AÁ Á ÁCl present in Fig. 3 and Tables 2 and 3, which inter-
connects the molecules in columns propagated in the direction
of the polar b axis. In this arrangement, Cl donates electron
density to the alkyl H atom, which is then presumed to release
Figure 3
Part of a layer parallel to (101), which is also the plane of projection, of
CÐHÁ Á ÁCl-connected (dashed lines) molecules of C. The cell edge b runs
down the page and, aside from the omission of aryl H atoms not involved
in hydrogen-bond formation, the representation is the same as in the
other ®gures.
Experimental
trans-1,2-Bis(diphenylphosphino)ethene (114 mg, 0.288 mmol), nickel
chloride hexahydrate (68 mg, 0.286 mmol) and ethanol (10 ml) were
placed in a 23 ml Parr bomb. After sealing, the bomb was heated at
�
1
1
00 K h to 423 K and maintained at this temperature for 48 h.
�
1
Thereafter the bomb was cooled to 293 K at a rate of 5 K h . After
opening, the brown±yellow crystals were collected by ®ltration,
washed with ethanol and air dried to afford C as an analytically pure
solid. Found: C 59.1, H 4.5% (C26
H
24Cl
.6%). IR (KBr): 1638 (m), 1618 (m), 1476 (w), 1433 (s), 1406 (w),
2
NiP
2
requires C 59.2, H
4
1
1
7
385 (w), 1306 (w), 1274 (w), 1186 (w), 1160 (w), 1129 (w), 1102 )s),
069 (sh), 1025 (w), 997 (w), 875 (w), 847 (w), 813 (m), 782 (w),
�
1
1
48 (s), 717 (s), 704 (m), 689 (s), and 652 (w) (cm ). H NMR
250 MHz, CDCl ): ꢀH 8.0 (m) and 7.5 (m, 20H), and 2.1 (m, 4H); cf.
footnote a in Table 1 of Davies et al. (1998).
(
3
Compound C(150)
Crystal data
�
3
[
M
NiCl
= 528.0
Monoclinic, I2
2
(C26
H
24
P
2
)]
D
x
= 1.406 Mg m
r
Mo Kꢂ radiation
Cell parameters from 5686
re¯ections
Ê
a = 12.4551 (14) A
Ê
b = 7.9901 (8) A
Ê
c = 13.0350 (19) A
ꢁ
ꢃ = 3.0±27.5
ꢄ = 1.13 mm
T = 150 (2) K
� 1
ꢁ
ꢁ
= 105.983 (5)
Ê
3
V = 1247.1 (3) A
Z = 2
Needle, brown±yellow
0.20 Â 0.03 Â 0.03 mm
Data collection
KappaCCD diffractometer
1946 re¯ections with I > 2ꢅ(I)
'
and ! scans
Absorption correction: multi-scan
SORTAV; Blessing, 1995, 1997)
min = 0.887, Tmax = 0.999
5686 measured re¯ections
686 independent re¯ections
Rint = 0.064
ꢁ
ꢃ
max = 27.5
(
T
h = � 15 ! 12
Figure 2
A molecule of A(150) showing the atom-labelling scheme. The
representation is the same as that of Fig. 1.
k = � 8 ! 10
l = � 13 ! 16
2
Intensity decay: none
ꢀ
Acta Cryst. (2001). C57, 690±693
Davison et al.
[NiCl
2
(C26
24 2
H P )] 691

metal-organic compounds
Table 1
Selected bond lengths and angles (A, ) for A, B and C.
Ê
ꢁ
0
A
A
A(150)
B
C(293)
C(150)
NiÐCl
NiÐP
PÐC1
PÐC2
PÐC8
C1ÐC1
2.199 (2)
2.154 (2)
1.837 (5)
1.814 (4)
1.818 (4)
1.516 (11)
2.1990 (6)
2.1524 (6)
1.832 (2)
1.820 (2)
1.816 (2)
1.508 (3)
2.2002 (4)
2.1493 (5)
1.8340 (14)
1.8200 (14)
1.8150 (14)
1.515 (3)
2.2003 (11)
2.1507 (11)
1.834 (4)
1.808 (3)
1.811 (3)
1.523 (7)
2.1999 (14)
2.1340 (15)
1.833 (4)
1.800 (4)
1.792 (6)
1.400 (11)
2.0254 (13)
2.1346 (13)
1.836 (4)
1.800 (4)
1.804 (4)
1.413 (10)
i
NiÐPÐC1
NiÐPÐC2
NiÐPÐC8
ClÐNiÐCl
ClÐNiÐP
ClÐNiÐP
i
PÐNiÐP
C1ÐPÐC2
C1ÐPÐC8
C2ÐPÐC8
PÐC1ÐC1
108.3 (2)
113.34 (13)
116.66 (13)
94.60 (9)
89.29 (6)
173.18 (8)
87.24 (10)
103.8 (2)
104.5 (2)
109.0 (2)
106.8 (3)
108.33 (6)
113.50 (6)
116.81 (6)
94.59 (3)
89.32 (2)
173.13 (3)
87.18 (3)
104.00 (9)
104.71 (8)
108.30 (8)
107.08 (14)
108.54 (6)
113.19 (6)
116.61 (6)
94.69 (3)
89.36 (2)
172.98 (2)
86.99 (2)
104.03 (8)
104.30 (8)
108.98 (8)
106.56 (11)
109.27 (12)
110.98 (12)
119.43 (12)
95.47 (4)
88.84 (4)
175.12 (5)
86.93 (4)
104.85 (14)
104.80 (14)
106.35 (14)
107.0 (2)
108.68 (15)
112.12 (19)
116.12 (16)
96.51 (8)
88.13 (4)
174.60 (7)
87.38 (8)
105.5 (3)
105.7 (3)
108.0 (2)
110.7 (3)
108.77 (16)
111.42 (17)
116.05 (15)
97.45 (7)
87.78 (4)
173.87 (6)
87.18 (7)
105.9 (2)
106.0 (2)
108.1 (2)
109.9 (3)
i
i
i
i
i
PÐC1ÐC1 ÐP
49.6 (6)
49.3 (2)
49.90 (18)
47.8 (4)
40.6 (8)
� 42.7 (6)
0
Notes: the bond and angle designations are those appropriate for the symmetric molecules of C [symmetry code: (i) � x, y, � z] and therefore data for A (PIFDUD; Busby et al., 1993), A
PIFDUD01; Davies et al., 1998), A(150) (this work) and B (FUJXUD; Spek et al., 1987) are for the most part given as pairwise mean values with s.u.'s adjusted accordingly. For all except
A(150), C(293) and C(150), PLATON (Spek, 1990) was used to compute distances and angles from CIF data from the CSD.
(
Re®nement
Re®nement
2
2
2
2
2
2
2
o
2
Re®nement on F
2
w = 1/[ꢅ (F
o
) + (0.0296P)
Re®nement on F
2
w = 1/[ꢅ (F
where P = (F
(Á/ꢅ)max < 0.001
) + (0.0223P) ]
2
2
2 2
R[F > 2ꢅ(F )] = 0.050
wR(F ) = 0.105
S = 1.04
+ 0.0327P]
where P = (F
(Á/ꢅ)max < 0.001
R[F > 2ꢅ(F )] = 0.049
wR(F ) = 0.100
o c
+ 2F )/3
2
2
2
c
2
o
+ 2F
)/3
Ê
� 3
Áꢆmax = 0.27 e A
S = 0.95
2861 re¯ections
Ê
� 3
Ê
� 3
2
1
686 re¯ections
41 parameters
Áꢆmax = 0.54 e A
Áꢆmin = � 0.34 e A
Ê
� 3
Áꢆmin = � 0.58 e A
141 parameters
H-atom parameters constrained
Absolute structure: Flack (1983)
Flack parameter = 0.01 (2)
H-atom parameters constrained
Absolute structure: Flack (1983)
Flack parameter = 0.01 (2)
Table 3
Table 2
Hydrogen-bonding geometry (A, ) for C(150).
Ê
ꢁ
Hydrogen-bonding geometry (A, ) for C(293).
Ê
ꢁ
DÐHÁ Á ÁA
DÐH
HÁ Á ÁA
DÁ Á ÁA
DÐHÁ Á ÁA
DÐHÁ Á ÁA
DÐH
HÁ Á ÁA
DÁ Á ÁA
DÐHÁ Á ÁA
i
i
C1ÐH1AÁ Á ÁCl
0.97
0.93
2.73
2.80
3.570 (4)
3.714 (8)
145
168
C1ÐH1AÁ Á ÁCl
0.99
0.95
2.69
2.74
3.556 (4)
3.664 (6)
147
166
ii
ii
C12ÐH12Á Á ÁCl
C12ÐH12Á Á ÁCl
1
2
1
2
1
2
1
1
2
1
2
Symmetry codes: (i) x; 1 ‡ y; z; (ii) � � x; ‡ y; � � z.
Symmetry codes: (i) x; y � 1; z; (ii) � 2 � x; y � ; � � z.
Compound C(293)
Compound A(150)
Crystal data
Crystal data
�
3
� 3
[
M
NiCl
= 528.0
Monoclinic, I2
2
(C26
H
24
P
2
)]
D
x
= 1.379 Mg m
[NiCl
= 528.0
Monoclinic, P2
a = 11.2779 (3) A
b = 13.3386 (4) A
c = 15.8739 (5) A
ꢁ = 98.7953 (16)
V = 2359.85 (12) A
Z = 4
2
(C26
H
24
P
2
)]
D
x
= 1.486 Mg m
r
Mo Kꢂ radiation
Cell parameters from 4976
re¯ections
M
r
Mo Kꢂ radiation
Cell parameters from 20644
re¯ections
1
/c
Ê
Ê
Ê
Ê
a = 12.5688 (15) A
Ê
b = 8.0208 (8) A
Ê
c = 13.0871 (9) A
ꢁ
ꢁ
ꢃ = 3.0±30.1
ꢄ = 1.11 mm
T = 293 (2) K
ꢃ = 2.9±27.5
ꢄ = 1.20 mm
T = 150 (2) K
� 1
� 1
ꢁ
ꢁ
ꢁ
= 105.531 (4)
Ê
3
Ê
3
V = 1271.2 (2) A
Z = 2
Needle, brown±yellow
0.35 Â 0.07 Â 0.05 mm
Block, brown±yellow
0.20 Â 0.15 Â 0.10 mm
Data collection
Data collection
KappaCCD diffractometer
1576 re¯ections with I > 2ꢅ(I)
KappaCCD diffractometer
4070 re¯ections with I > 2ꢅ(I)
'
and ! scans
Absorption correction: multi-scan
SORTAV; Blessing, 1995, 1997)
min = 0.896, Tmax = 0.955
R
int = 0.050
' and ! scans
Absorption correction: multi-scan
(SORTAV; Blessing, 1995, 1997)
Rint = 0.042
ꢃmax = 27.5
ꢁ
ꢁ
ꢃ
max = 30.1
(
T
h = � 16 ! 13
h = � 14 ! 14
k = � 10 ! 8
T
min = 0.659, Tmax = 0.887
9650 measured re¯ections
k = � 16 ! 17
4
2
976 measured re¯ections
861 independent re¯ections
l = � 15 ! 16
l = � 17 ! 20
Intensity decay: none
5198 independent re¯ections
Intensity decay: none
ꢀ
692 Davison et al.
[NiCl
2
(C26H P
24 2
)]
Acta Cryst. (2001). C57, 690±693

metal-organic compounds
Re®nement
We wish to acknowledge the use of the EPSRC's Chemical
Database Service at Daresbury together with the use of the
EPSRC X-ray crystallographic service at Southampton and
the valuable assistance of the staff there.
2
2
2
2
Re®nement on F
2
o
w = 1/[ꢅ (F ) + (0.0671P)
2
R[F > 2ꢅ(F )] = 0.042
wR(F ) = 0.117
S = 1.06
+ 0.0545P]
where P = (F
(Á/ꢅ)max < 0.001
Áꢆmax = 0.71 e A
Áꢆmin = � 0.54 e AÊ
2
2
2
c
o
+ 2F
)/3
Ê
� 3
5
2
198 re¯ections
80 parameters
� 3
Supplementary data for this paper are available from the IUCr electronic
archives (Reference: GG1036). Services for accessing these data are
described at the back of the journal.
H-atom parameters constrained
The room-temperature structure of C was solved initially by simply
extracting feasible positions for non-H atoms from a difference map
phased by placing Ni at the origin of the space group I2/m. This
readily produced an image of a pair of superimposed molecules and it
was comparatively easy to select one of these and continue re®ne-
ment in the true space group (I2). The coordinates thus derived were
used along with appropriately modi®ed cell dimensions as starting
parameters for the re®nement of the 150 K structure of C. Starting
parameters for the re®nement of A(150) were likewise taken from the
literature data (PIFDUD; Busby et al., 1993). In all three re®nements,
H atoms were placed in calculated positions and re®ned riding with
References
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Sci. 36, 746±749.
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absolute structures of C(150) and C(293) are based on 1170 and 1187
Friedel pairs, respectively.
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Hursthouse, M. B. (1985). J. Chem. Soc. Dalton Trans. pp. 1339±1348.
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and COLLECT; data reduction: DENZO and COLLECT;
program(s) used to solve structure: SHELXS86 (Sheldrick, 1990);
program(s) used to re®ne structure: SHELXL97 (Sheldrick, 1997);
molecular graphics: ORTEP-3 (Farrugia, 1997); software used to
prepare material for publication: SHELXL97.
ꢀ
Acta Cryst. (2001). C57, 690±693
Davison et al.
[NiCl
2
(C26
24 2
H P )] 693