Structural relationships in the homologous series of alkyltriphenylstannane compounds of formula Ph3Sn(CH2)n - 1CH 3, with n even and in the range 4-14 and 18

Article abstract of DOI:10.1016/j.poly.2005.07.024

The solid state structures of several compounds in the homologous series of alkyltriphenylstannanes of general formula Ph₃Sn(CH ₂)_{n - 1}CH₃ have been determined. For n in the range 4-10 the structures are monocli

Full text of DOI:10.1016/j.poly.2005.07.024

Polyhedron 25 (2006) 695–701
www.elsevier.com/locate/poly
Structural relationships in the homologous series of
alkyltriphenylstannane compounds of formula
Ph3Sn(CH2)n À 1CH3, with n even and in the range 4–14 and 18
a
a,
a
a
Gillian M. Allan , R. Alan Howie *, John N. Low , Janet M.S. Skakle ,
b
c
James L. Wardell , Solange M.S.V. Wardell
a
Department of Chemistry, University of Aberdeen, Meston Walk, Old Aberdeen AB24 3UE, Scotland, UK
ˆ
´
Departamento de Quı´mica Inorganica, Instituto de Quımica, Universidade Federal do Rio de Janeiro, CP 68563, 21945-970 Rio de Janeiro, RJ, Brazil
b
c
ˆ
Fundac¸ao Oswaldo Cruz, Far-Manguinhos, Rua Sizenando Nabuco 100, Manguinhos, 21041-250 Rio de Janeiro, RJ, Brazil
Received 14 June 2005; accepted 14 July 2005
Available online 29 August 2005
Abstract
The solid state structures of several compounds in the homologous series of alkyltriphenylstannanes of general formula
Ph3Sn(CH2)n À 1CH3 have been determined. For n in the range 4–10 the structures are monoclinic with space group P21/c. For n
ꢀ
greater than 10 they are, instead, triclinic with space group P1. The structural difference between the two classes is attributable
to a change in the degree of control over the packing of the molecules exerted by the triphenylstannyl entity on the one hand
and the alkyl chain on the other.
ꢀ 2005 Elsevier Ltd. All rights reserved.
Keywords: Alkyltriphenylstannane; Homologous series; X-ray structures
1. Introduction
1,2:5,6-di-O-isopropylidene-3-C-triphenylstannylmethyl-
a-D-allofuranose [4].
Tetraorganotin compounds, with few recognized
exceptions, have near tetrahedral geometries and four
coordinate tin centres, even for compounds having quite
distinct organic groups, an example being Ph3SnCH2-
CMe2Ph [1]. The exceptions arise when suitably posi-
tioned donor centres are located in the molecules, which
allow tin–donor intramolecular interactions. Examples
include (Z)-3,4,4-trimethylstannyl)-1-pentene-3-ol [2],
bis[3-pyridine-2-yl-thien-2-yl]bis(p-tolyl)stannane [3] and
As part of a study concerned with the properties and
structures of organotin compounds having long-chain
alkyl groups, we have prepared a number of compounds
of general formula Ph3Sn(CH2)n À 1CH3 (1: n = 4, 6, 8,
10, 12, 14, 18 and 22). While we understood that the geom-
etries about tin will be distorted tetrahedral in all cases, we
wished to investigate such matters as how the alkyl chains,
in particular the longer alkyl chains, will pack, the influ-
ence throughout the series of p-intermolecular interac-
tions involving the phenyl groups and whether disorder
would, in some cases, be an intractable problem. Compar-
atively few of the solid state structures of 1 have been
reported. Indeed, recourse to the Cambridge Structural
Database (version 5.26) [5], accessed by means of the
Chemical Database Service of the EPSRC [6] reveals only
*
Corresponding author. Tel.: +44 1224 272907; fax: +44 1224
272921.
E-mail address: r.a.howie@abdn.ac.uk (R.A. Howie).
0277-5387/$ - see front matter ꢀ 2005 Elsevier Ltd. All rights reserved.
doi:10.1016/j.poly.2005.07.024

696
G.M. Allan et al. / Polyhedron 25 (2006) 695–701
two relevant entries. These are the structures of ethyltri-
phenyltin, (1: n = 2), [7] and triphenyltetradecylstannane,
(1: n = 14), [8]. We now report the solid state structures of
(1: n = 4–12 and n = 18). In addition infrared and NMR
spectra are reported.
column chromatography (on silica gel with petroleum
ether as eluent) and recystallizations from EtOH.
M.p. (1: n = 4) 61–62 ꢁC, lit. 61–62 ꢁC [9]; (1: n = 6)
55–56 ꢁC, lit. 54 ꢁC [9]; (1: n = 8) 53–54 ꢁC, lit. 54–
55 ꢁC [9]; (1: n = 10) 49–50 ꢁC; (1: n = 12) 52–53 ꢁC;
(1: n = 14) 58–59 ꢁC; (1: n = 16) 63–64 ꢁC; (1: n = 18)
68–70 ꢁC; (1: n = 22) 75–77 ꢁC.
Selected spectral data.
2. Experimental
1H NMR (400 MHz, CDCl3) for (1: n > 4): d 1.2–1.8
[(2n + 1)H, ms], 7.3–7.4 [9H, p- + m-aryl-H], 7.5–7.6
[6H, o-aryl-H].
Infrared spectra were recorded in KBr or CsI disks on
a Nicolet-Magna IR 760 instrument. NMR spectra were
recorded on Bruker 250 MHz and Varian 400 MHz
instruments. Melting points were measured using a
Kofler hot-stage microscope.
13C NMR (100 MHz, CDCl3) for (1: n > 4): d: 11.1
[J(13C–119,117Sn) = 398/381 Hz, Ca], 14.0–32.0 [alkyl C,
(n À 2) carbon atoms], 34.2 [J(13C–119,117Sn) = 50 Hz],
128.4 [J(13C–119,117Sn) = 48 Hz, Cmeta], 128.7 [J(13C–
119,117Sn) = 10.7 Hz, Cpara], 137.0 [J(13C–119,117Sn) =
45.8 Hz, Cortho], 139.2 [J(13C–119,117Sn) = 478/458 Hz,
2.1. Preparation of compounds
C
ipso].
119Sn NMR (93 MHz, CDCl3) for (1: n > 4): d
To the Grignard reagent from alkyl bromide
(4.3 mmol) and Mg (4.5 mmol) in Et2O (30 ml) was
added a solution of Ph3SnCl (1.54 g, 4.0 mmol) in
Et2O (20 ml). The reaction mixture was refluxed for
30 min and water carefully added. The organic layer
was collected, dried over magnesium sulfate and evapo-
rated. The residues were purified by a combination of
À100 0.5.
IR: (KBr or CsI).
All compounds from n = 4 to n = 22 had common IR
bands at: 3060–2852, 1577, 1479, 1470, 1427, 1375, 1330,
1300, 1259, 1188, 1153, 1074, 1022, 996, 861, 729, 698,
658, 445, 447–444, 264–262, ca. 240 cmÀ1. The relative
Table 1
Crystal data and structure refinement for monoclinic 1
Compound
n = 4
n = 6
n = 8
n = 10
Empirical formula
Formula weight
Temperature (K)
Crystal system
Space group
Unit cell dimensions
C
22H24Sn
C24H28Sn
435.15
150(2)
monoclinic
P21/c
C26H32Sn
463.21
150(2)
monoclinic
P21/c
C28H36Sn
491.26
150(2)
monoclinic
P21/c
407.10
120(2)
monoclinic
P21/c
˚
a (A)
17.2815(10)
15.0892(7)
7.3345(4)
18.8103(6)
15.1779(4)
7.5151
20.5732(7)
15.1268(4)
7.5183(2)
21.9317(13)
14.8018(7)
7.6859(3)
˚
b (A)
˚
c (A)
b (ꢁ)
92.996(2)
1910.0(3)
4
1.416
1.336
824
99.1096(12)
2118.51(10)
4
1.364
1.209
97.7961(11)
2318.12(12)
4
1.327
1.109
92.936(2)
2491.8(2)
4
1.310
1.036
1016
3
˚
Volume (A )
Z
Dcalc (Mg mÀ3
Absorption coefficient (mmÀ1
F(000)
)
)
888
952
Crystal size (mm)
h Range for data collection (ꢁ)
Index ranges
0.20 · 0.20 · 0.15
2.95–27.58
À15 6 h 6 22;
À19 6 k 6 17;
À9 6 l 6 9
0.9750 and 0.5860
13912/4340/2735
0.1140
0.44 · 0.15 · 0.03
3.06–27.48
À21 6 h 6 24;
À19 6 k 6 19;
À9 6 l 6 9
0.9660 and 0.5780
16457/4815/3540
0.0886
0.28 · 0.10 · 0.03
3.00–26.37
À25 6 h 6 25;
À17 6 k 6 18;
À9 6 l 6 9
0.9670 and 0.8890
16182/4696/3443
0.0543
0.15 · 0.10 · 0.05
2.99–27.50
À23 6 h 6 26;
À17 6 k 6 19;
À9 6 l 6 9
0.9700 and 0.9010
18801/5461/2371
0.1550
Maximum and minimum transmission
Reflections collected/unique/observationa
Rint
Data/restraints/parameters
Goodness-of-fit on F2
4340/0/209
1.213
4815/0/227
0.976
4696/0/245
0.996
5461/26/299
0.906
Final R indices [I > 2r(I)]
R1 = 0.0796;
wR2 = 0.1965
R1 = 0.1356;
wR2 = 0.2114
2.887 and À1.971
R1 = 0.0428;
wR2 = 0.0972
R1 = 0.0656;
wR2 = 0.1075
0.957 and À2.196
R1 = 0.0373;
wR2 = 0.0886
R1 = 0.0613;
wR2 = 0.0996
0.815 and À0.976
R1 = 0.0519;
wR2 = 0.0738
R1 = 0.1874;
wR2 = 0.0989
0.796 and À0.637
Final R indices (all data)
À3
˚
Largest difference peak and hole (e A
)
a
Condition for observed status I > 2r(I).

G.M. Allan et al. / Polyhedron 25 (2006) 695–701
697
intensities of the medium-strong bands at 1479 and
1470 cmÀ1 decreased as n increased, such that the
1470 cmÀ1 band was by far the weaker for n = 4 but be-
came the more intense for n = 14. The weak band at
863–850 cmÀ1 becomes progressively weaker as n in-
creases from n = 4.
2.2.2. Structure solution and refinement
All of the structures were solved by application of the
direct methods routine of SHELXS97 [14] and the initial
solutions completed and the structures fully refined on
F2 with SHELXL97 [15]. In all cases, in the final stages of
refinement, hydrogen atoms were introduced in calcu-
lated positions with C–H bond lengths set to 0.95, 0.98
˚
2.2. X-ray structure determinations
and 0.99 A for phenyl, methyl and methylene hydrogen
atoms, respectively, and refined with a riding model with
the isotropic displacement parameter of hydrogen set to
1.5 times for methyl, or 1.2 times otherwise, the equivalent
isotropic displacement parameter of the carbon atom to
which the hydrogen is attached. The rotational orienta-
tion of the methyl groups was also refined. The refinement
of the structure of (1: n = 10) was slightly complicated by
disorder over pairs of sites of equal occupancy of carbon
atoms C(4), C(6), C(8) and C(10). The disordered atoms
in each pair are distinguished by suffix D and E as
C(4D)/C(4E) and the disorder taken into account in the
placement of the hydrogen atoms. The program ORTEP-3
for Windows [16] was used in the preparation of Figs.
2–5 and PLATON [17] was used to generate the data for
2.2.1. Data collection
Intensity data for all of the structures presented here
were obtained with Mo Ka radiation (k = 0.71073 A)
˚
from colourless crystals, at 120 K for (1: n = 4), 100 K
for (1: n = 18) and 150 K for the remainder, by means
of the Enraf Nonius Kappa CCD area detector diffrac-
tometer of the National Crystallography Centre of the
EPSRC at Southampton. Data collection, cell refine-
ment and data reduction were all achieved by means
of the programs DENZO [10] and COLLECT [11]. Correction
for absorption by comparison of the intensities of equiv-
alent reflections was carried out by means of the pro-
gram SORTAV [12,13].
Table 2
Crystal data and structure refinement for triclinic 1
Compound
n = 12
n = 14a
n = 18
Empirical formula
Formula weight
Temperature (K)
Crystal system
Space group
Unit cell dimensions
C
30H40Sn
C32H44Sn
547.36
150(2)
C36H52Sn
603.47
100(2)
519.31
150(2)
triclinic
triclinic
triclinic
ꢀ
ꢀ
ꢀ
P1
P1
P1
˚
a (A)
7.5658(2)
7.5417(2)
7.5141(2)
˚
b (A)
9.8632(2)
9.8665(2)
20.3571(6)
95.2205(10)
91.5327(9)
110.1477(18)
1413.45(6)
9.9055(3)
˚
c (A)
19.1427(4)
83.1364(7)
85.0506(7)
69.6585(7)
1328.27(5)
2
1.298
0.976
540
23.0264(8)
80.6766(12)
83.6935(12)
70.127(2)
1587.75(8)
2
1.262
0.826
636
a (ꢁ)
b (ꢁ)
c (ꢁ)
3
˚
Volume (A )
Z
2
Dcalc (Mg mÀ3
Absorption coefficient (mmÀ1
F(000)
)
1.286
0.921
572
)
Crystal size (mm)
h Range for data collection (ꢁ)
0.20 · 0.10 · 0.10
1.07–27.48
À9 6 h 6 9; À11 6 k 6 12;
À24 6 l 6 24
0.9760 and 0.6830
17645/5914/5305
0.0585
0.20 · 0.07 · 0.002
1.01–27.52
À7 6 h 6 9; À12 6 k 6 12;
À26 6 l 6 26
0.8750 and 0.7820
14968/6317/4900
0.0903
0.20 · 0.06 · 0.01
2.97–27.50
À9 6 h 6 9; À12 6 k 6 12;
À29 6 l 6 29
0.3690 and 0.3690
24524/6933/5233
0.1505
Index ranges
Maximum and minimum transmission
Reflections collected/unique/observationb
Rint
Data/restraints/parameters
Goodness-of-fit on F2
5914/0/281
1.115
6317/0/299
1.034
6933/0/335
1.024
Final R indices [I > 2r(I)]
R1 = 0.0355;
wR2 = 0.0874
R1 = 0.0439;
wR2 = 0.1005
0.723 and À1.839
R1 = 0.0400;
wR2 = 0.0827
R1 = 0.0646;
wR2 = 0.1069
0.793 and À0.711
R1 = 0.0532;
wR2 = 0.1097
R1 = 0.0836;
wR2 = 0.1214
1.062 and À1.499
Final R indices (all data)
À3
˚
Largest difference peak and hole (e A
)
a
Replicates structure reported in [8].
Condition for observed status I > 2r(I).
b

698
G.M. Allan et al. / Polyhedron 25 (2006) 695–701
Tables 4 and 5 and Supplementary Tables S2–S7. Further
details of data collection and structure refinement are
given in Tables 1 and 2.
3. Results and discussion
3.1. Synthesis
The Grignard synthesis of compounds, 1, proceeded
readily. However, for the longer chain compounds, i.e.
(1: n > 12), separation from other long chain material,
such as any unreacted alkyl bromide or the alkane
formed on hydrolysis of the Grignard reagent, was more
troublesome and purification required repeated crystalli-
zations. As expected for members of a homologous
series, compounds 1 exhibited similar spectral proper-
ties, see Section 2. Particularly noteworthy, in this
respect, were the IR spectra, in general, and specifically
in the NMR spectra, the d 119Sn values (all ꢀ100 ppm),
the J(119,117Sn–13C) values for the ipso-aromatic and
a-aliphatic carbons, 478/458 and 398/381 Hz, respec-
tively. It is apparent from these data that the tin envi-
ronment is similar throughout the studied series.
Fig. 1. Melting points (ꢁC) for X(CH2)n À 1CH3 for n even and
X = Ph3Sn, OH, Br and H. See Supplementary Table S1 for numerical
values.
The slight U-shaped melting point dependence for the
organotin derivatives suggests opposing factors are at
play, e.g., as n increases, the significance of the Ph3Sn
moiety is initially reduced and later overtaken by an
increasing influence of the long chain alkyl groups. As
we now report below, the structure determinations re-
veal two distinct packing arrangements, with the space
group change occurring as n changes from 10 to 12.
3.2. Crystallography
The melting points of Ph3Sn(CH2)n À 1CH3 cover a
relatively short range, from 49–50 to 75–77 ꢁC. Interest-
ingly, the melting points of 1 show a slight U-shaped
dependence on n (Fig. 1), with the lowest melting point
obtained for (1: n = 10). In contrast, the similar shaped
graphs for compounds of the series X(CH2)n À 1CH3
(X = H, Br or OH) show overall larger ranges of m.p.
and a general increase in m.p. with, however, reducing
increments as n is increased (see Fig. 1). For each of
the four series, X(CH2)n À 1CH3 ( X = H, Br, OH and
SnPh3), there appears to be a convergence of melting
point values. Of interest, the m.p.s show little differences
for n = 22 between the values for each series. It is clear
that as n increases, the specific effects of the Ph3Sn group
have diminishing influences on the m.p.s.
3.2.1. Atom labelling scheme
Fig. 2 shows, as an example of the molecular confor-
mation and atom labelling scheme of the molecules of all
of the compounds whose structures are described in this
paper, the molecule of (1: n = 8). In all cases, the carbon
atoms of the alkyl group are numbered from 1 to n with
C(1) bonded to tin. The sole exception to this is the use
of suffices D and E to distinguish between individual
atoms in the disordered pairs which, as noted above, oc-
cur in the structure of (1: n = 10). In all cases, the carbon
atoms of the phenyl groups are numbered cyclically with
C(1) bonded to tin. The phenyl groups are then distin-
guished by suffix a, b and c. No attempt has been made,
Fig. 2. The labelling scheme exemplified by the molecule of (1: n = 8). Ellipsoids are drawn at the 30% probability level and hydrogen atoms are
shown as small spheres of arbitrary radii.

G.M. Allan et al. / Polyhedron 25 (2006) 695–701
699
however, to ensure the use of completely consistent
clockwise or anticlockwise cyclical order nor have the
suffices been applied with strict regard to subtle varia-
tions in the functionality of the phenyl groups.
within the normal ranges and do not merit detailed dis-
cussion although the Sn(1)–C(1)–C(2) angles in the
range 113.7(2)–115.6(7)ꢁ are of some interest.
3.2.3. Molecular packing and intermolecular contacts
For convenience, in what follows the structures of (1:
n = 4–10) are designated type M (for monoclinic, with
space group P21/c) and those of (1: n = 12, 14 and 18)
3.2.2. Molecular geometry
Selected bond lengths and bond angles for the com-
pounds are given in Table 3. In all cases tin is in a
slightly distorted tetrahedral environment with, in all
but two cases, the Sn–Calkyl bond the longest bond to
tin. The C–Sn–C angles are in the range 106.6(2)–
113.9(3)ꢁ, where these limiting values are found in the
data for (1: n = 2) [7]. The bond lengths and bond angles
in the phenyl groups and the alkyl chains are generally
ꢀ
type T (for triclinic, with space group P1).
In the type M structures, as shown for (1: n = 6) in
Fig. 3 in which two adjacent layers are seen edge on,
the molecules form layers parallel to (1 0 0) with the al-
kyl groups directed towards the centre of the layer and
the phenyl groups on the layer surfaces. Similar layers
Table 3
˚
Selected bond lengths and bond angles (A, ꢁ) for various 1
n = 2a
n = 4
2.145(11)
n = 6
2.150(3)
n = 8
2.154(3)
n = 10
2.137(5)
n = 12
2.153(3)
n = 14b
2.151(3)
n = 18
2.149(4)
Sn(1)–C(alkyl)
Sn(1)–C(aryl)
2.172(9)
2.131(6)9
2.133(5)15
2.137(6)3
2.124(11)c
2.137(10)b
2.148(11)a
2.138(3)b
2.142(3)a
2.144(3)c
2.137(3)a
2.138(3)c
2.141(4)b
2.123(5)a
2.133(5)b
2.133(5)c
2.140(3)c
2.142(3)b
2.145(3)a
2.134(3)b
2.140(4)a
2.144(3)c
2.143(4)b
2.148(3)c
2.149(4)a
C(aryl)-Sn(1)–C(alkyl)
C(aryl)-Sn(1)–C(aryl)
109.8(3)9
110.3(3)15
113.9(3)3
111.9(4)c
107.7(4)b
109.1(4)a
110.05(13)b
108.64(12)a
111.48(13)c
111.28(13)a
108.75(12)c
110.98(14)b
107.0(2)a
112.8(2)b
111.5(2)c
112.98(10)c
108.60(10)b
107.20(10)a
108.57(13)b
112.85(14)a
107.14(13)c
108.49(15)b
107.35(14)c
113.02(15)a
108.99(17)9,15 108.1(4)bc
107.1(2)3,9
106.6(2)3,15
110.22(12)ab 109.56(12)ac 109.4(2)ab
107.74(12)bc 107.83(12)ab 108.7(2)ac
108.70(14)ac 108.39(14)bc 107.4(2)bc
108.20(10)bc 108.59(13)ab 108.78(15)bc
110.56(10)ac 109.33(13)bc 108.57(14)ab
109.23(10)ab 110.30(13)ac 110.53(13)ac
110.3(4)ac
109.7(4)ab
C(alkyl)–C(alkyl)-Sn(1) 115.6(7)
115.0(7)
113.7(2)
113.9(3)
114.1(4)
113.96(17)
114.1(2)
114.1(3)
The bond and angle designations are those of (1: n = 8) as in Fig. 1. The Sn–Cphenyl bonds are arranged in increasing order of length and the suffices,
as used in the refinements of the structures, are appended to the table entries, where appropriate, in order to identify which Cphenyl atoms, and
therefore phenyl groups, are involved in each case.
a
Calculated from previously published [7] data.
From a replicate of a previously reported [8] structure.
b
Fig. 3. The packing of the molecules in a type M structure. The example shown is (1: n = 6). Ellipsoids are shown at the 20% probability level and
hydrogen atoms have been omitted for clarity.

700
G.M. Allan et al. / Polyhedron 25 (2006) 695–701
Fig. 4. A section, one unit cell thick in the direction of a, through a
layer of molecules in a type T structure. The example shown is (1:
n = 18). Ellipsoids are shown at the 20% probability level and
hydrogen atoms have been omitted for clarity.
Fig. 5. Molecules in (1: n = 2) in columns propagated in the direction
of b. Ellipsoids are shown at the 20% probability level and hydrogen
atoms have been omitted for clarity.
of the HÁ Á ÁCg distances but this does not preclude their
use as an estimate, allbeit crude, of the degree of associa-
tion of the phenyl groups.
(Fig. 4) are found in the type T structures but the layers
are much thicker and the alkyl chains oriented in a dif-
ferent manner with respect to the thickness of the layer.
The molecules in the type T structures are packed in
layers parallel to (0 0 1). In this case crystallographic
centres of symmetry are the only factor, other than
unit cell translations, relating the molecules throughout
the structure. In the layers of the type M structures, the
centrosymmetric relationship between the molecules
within the layers is augmented by the operations of a
crystallographic c-glide plane (extending the layers in
the direction of c) and a crystallographic twofold screw
axis extending the layers in the direction of b. The
compound (1: n = 2) [7] is a very different case from
the type M and type T structures. Here, although the
unit cell is monoclinic the space group is C2/c and
the molecules, related to one another by the operation
of a crystallographic twofold screw axis, are found in
columns (Fig. 5).
It is of interest to consider the increment in the vol-
ume occupied by a single molecule as the alkyl chain in-
creases in length. In the transition from (1: n = 2) to (1:
3
˚
n = 4) it is of the order of only 25 A which is very small
for the addition of two methylene groups when the
volume commonly associated with one carbon atom is
3
˚
20 A . In this case the lengthening of the alkyl chain
Table 4
˚
Geometry (A, ꢁ) of intermolecular C–HÁ Á Áp interactions in (1: n = 8)
(type M structure)
C–HÁ Á ÁCg
HÁ Á ÁCg Hperp
c
C–HÁ Á ÁCg CÁ Á ÁCg
C(3A)–H(3D)Á Á ÁCg(1i)
3.038
2.868 19 138
2.847 17 140
3.209 12 122
3.000 23 116
2.955 15 138
2.994 27 113
3.802
3.781
3.873
3.774
3.810
3.825
C(4)–H(4A)Á Á ÁCg(2ii)
2.973
C(5A)–H(5D)Á Á ÁCg(3iii) 3.279
C(5C)–H(5F)Á Á ÁCg(1ii)
3.256
C(6B)–H(6E)Á Á ÁCg(3iv) 3.056
C(6C)–H(6F)Á Á ÁCg(1ii)
3.356
Another difference between the type M and type T
structures is to be found in the lists of intermolecular
C–HÁ Á Áp interactions exemplified in Tables 4 and 5
for (1: n = 8) and (1: n = 18), respectively, and available
in Supplementary Tables S3–S7 for the other 1 noted
in Tables 1 and 2. In the type M structures (Table 4),
there are six intermolecular contacts which satisfy the
PLATON [17] criteria but only four are found for the type
T structures (Table 5). The implication of this is that the
presence of the longer alkyl chains in the type T struc-
tures creates greater separation between the triphenyl
groups at the surface of the layers of molecules. Supple-
mentary Table S2 shows the presence of five C–HÁ Á Áp
contacts in the case of (1: n = 2). Casas et al. [7] have
discounted the significance of the C–HÁ Á Áp contacts in
the structure of (1: n = 2) on the grounds of the length
Notes. Ring (1) C(1A)–C(6A), ring (2) C(1B)–C(6B), ring (3) C(1C)–
C(6C). Hperp is the perpendicular distance of the hydrogen atom from
the plane of phenyl group n with centroid Cg(n) and c is the angle at
hydrogen between Hperp and HÁ Á ÁCg. Symmetry codes: (i) x, 3/2 À y,
1/2 + z; (ii) x, y, À1 + z; (iii) 1 À x, 1 À y, 1 À z; (iv) x, y, 1 + z.
Table 5
˚
Geometry (A, ꢁ) of intermolecular C–HÁ Á Áp interactions in (1: n = 18)
(type T structure)
C–HÁ Á ÁCg
HÁ Á ÁCg Hperp
3.012 2.926 14 158
3.211 141
c
C–HÁ Á ÁCg CÁ Á ÁCg
C(4)–H(4B)Á Á ÁCg(1i)
3.950
4.020
3.615
3.733
C(4A)–H(4D)Á Á ÁCg(2ii) 3.235
7
C(5C)–H(5F)Á Á ÁCg(2i)
3.085
2.964 16 117
2.897 12 139
C(6A)–H(6D)Á Á ÁCg(3iii) 2.960
Notes. As Table 4 but symmetry codes now (i) À1 + x, y, z; (ii) x,
1 + y, z; (iii) 1 + x, y, z.

G.M. Allan et al. / Polyhedron 25 (2006) 695–701
701
is, however, accompanied by a dramatic change of struc-
ture and of the way in which the molecules pack to-
gether. As n increases from 4 to 10 the volume
Southampton and the Chemical Database Service at
Daresbury and to Norma Thomson for her skill and
endeavour in preparing some of the compounds.
3
˚
changes start at 52 A and reduce progressively to
3
˚
49 A . On further increase of chain length from 10 to
18 the volume changes remain comparatively constant
in the range 41–44 A , now much as would be expected
Appendix A. Supplementary data
3
˚
for a two carbon increment in chain length. These
changes in the volume of individual molecules suggest
that in (1: n = 12–18) increase in alkyl chain length
has no more effect than to increase the thickness of the
layers of molecules. The small volume increase as n
changes from 2 to 4 is accounted for, in general terms,
by the change in molecular packing which occurs at this
point. The comparatively large, but decreasing, volume
changes accompanying the change of n from 4 to 10 is
taken to imply optimum packing of the phenyl groups
accompanied by comparatively inefficient packing of
the alkyl chains, culminating in the disorder in the alkyl
chain for (1: n = 10) noted above.
Supplementary cif format structural data is available
from the Cambridge Crystallographic Data Centre, 12
Union Road, Cambridge CB2 IEZ, UK (fax: +44
1223 336033; e-mail: deposit@ccdc.cam.ac.uk or
http://www.ccdc.cam.ac.uk), quoting the deposition
numbers CCDC 274515–274521. Supplementary Tables
S1–S7 are available electronically along with the Web
version of this paper. Supplementary data associated
with this article can be found, in the online version, at
doi:10.1016/j.poly.2005.07.024.
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Acknowledgements
The authors are grateful to the EPSRC, UK for ac-
cess to both the National Crystallography Centre at