Hydrogen bonding and self-assembly in the crystal structures of ferrocenylmethanol derivatives having different phosphorus substituents on the ferrocene unit

Article abstract of DOI:10.1039/b204655p

Ferrocenylmethanol derivatives bearing a phosphorus substituent in position two of the ferrocene unit, rac-2-(diphenylphosphino)ferrocenylmethanol (3), rac-2-(diphenylphosphinoyl)ferrocenylmethanol (4), and rac-2-(diphenylthiophosphoryl)ferrocenylmethanol (5), have been synthesized and structurally characterized by single-crystal X-ray diffraction. While the overall molecular geometry does not differ significantly in the whole series, showing only differences in the arrangement at the phosphorus atom owing to a replacement of the lone electron pair (2, 3) with oxygen (4) and sulfur (5), and in the conformation of the hydroxylmethyl group, the compounds form different crystal packing patterns that result from a counterplay of hydrogen bonding of various types and non-polar interactions. Alcohol 3 associates into dimers by double O-H···O hydrogen bridges between disordered hydroxy groups of neighbouring molecules. The distribution of molecules in the crystal of 4 appears identical to that of 3. However, the structure of 4 comprises intermolecular O-H···O=P hydrogen bridges instead. The packing of phosphine sulfide 5 is different, featuring intramolecular O-H···S bridges. Although the molecular entities are involved in further interactions such as O-H···P and C-H···O hydrogen bonding, and π-π stacking interaction of the phenyl rings, which further propagate the molecular network, the principal force towards self-assembly always results in the formation of entropically favoured, closed cyclic systems. The solid state structure of the common precursor, rac-2-(diphenylphosphino)ferrocenylmethyl acetate (2) shows only C-H···O intermolecular interactions due to the lack of a better hydrogen bond donor.

Full text of DOI:10.1039/b204655p

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Hydrogen bonding and self-assembly in the crystal structures
of ferrocenylmethanol derivatives having different phosphorus
substituents on the ferrocene unit
ˇ
Petr Stepnicka* and Ivana Cısarova
ˇ
ˇ
ˇ
´
´
Department of Inorganic Chemistry, Charles University, Hlavova 2030, 128 40 Prague 2,
Czech Republic. E-mail: stepnic@mail.natur.cuni.cz
Received (in Strasbourg, France) 7th May 2002, Accepted 24th June 2002
First published as an Advance Article on the web 16th September 2002
Ferrocenylmethanol derivatives bearing a phosphorus substituent in position two of the ferrocene unit,
rac-2-(diphenylphosphino)ferrocenylmethanol (3), rac-2-(diphenylphosphinoyl)ferrocenylmethanol (4), and
rac-2-(diphenylthiophosphoryl)ferrocenylmethanol (5), have been synthesized and structurally characterized by
single-crystal X-ray diffraction. While the overall molecular geometry does not differ significantly in the whole
series, showing only differences in the arrangement at the phosphorus atom owing to a replacement of the
lone electron pair (2, 3) with oxygen (4) and sulfur (5), and in the conformation of the hydroxylmethyl group,
the compounds form different crystal packing patterns that result from a counterplay of hydrogen bonding of
various types and non-polar interactions. Alcohol 3 associates into dimers by double O–Hꢀ ꢀ ꢀO hydrogen
bridges between disordered hydroxy groups of neighbouring molecules. The distribution of molecules in the
crystal of 4 appears identical to that of 3. However, the structure of 4 comprises intermolecular O–Hꢀ ꢀ ꢀO=P
hydrogen bridges instead. The packing of phosphine sulfide 5 is different, featuring intramolecular O–Hꢀ ꢀ ꢀS
bridges. Although the molecular entities are involved in further interactions such as O–Hꢀ ꢀ ꢀP and C–Hꢀ ꢀ ꢀO
hydrogen bonding, and p-p stacking interaction of the phenyl rings, which further propagate the molecular
network, the principal force towards self-assembly always results in the formation of entropically
favoured, closed cyclic systems. The solid state structure of the common precursor, rac-2-
(diphenylphosphino)ferrocenylmethyl acetate (2) shows only C–Hꢀ ꢀ ꢀO intermolecular interactions due to the
lack of a better hydrogen bond donor.
During our studies with ferrocene phosphinocarboxylic
ligands1 and related systems,2 we have found that introduction
or modification of a polar group that can be involved in hydro-
gen bonding changes significantly the solid-state packing,
resulting in some cases in formation of supramolecular assem-
blies and adducts, and can also dramatically alter crystalliza-
tion abilities in a pair of compounds that differ only by the
presence of the group capable of hydrogen bonding. Consider-
ing these observations as well as the fact that the hydrogen
bonding in polar ferrocene compounds plays a crucial role in
the aggregation of biologically relevant, ferrocene-based mole-
cules3 and in crystal engineering,4 we decided to study the
factors governing the crystal assembly in a series of ferrocenyl-
methanol derivatives having different phosphorus substituents
in position two of the ferrocene unit.
2-(diphenylphosphinoyl)ferrocenylmethanol (4), and 2-(diphe-
nylthiophosphoryl)ferrocenylmethanol (5), and their precur-
sor, 2-(diphenylphosphino)ferrocenylmethyl acetate (2).
Results and discussion
Syntheses and characterization
Bright yellow, crystalline acetate 2 was obtained in 76% yield
from
rac-N,N-dimethyl-[2-(diphenylphosphino)ferrocenyl]-
methylamine (1) using the well-established direct acetylation
approach6 (Scheme 1). A subsequent hydrolysis with potas-
sium hydroxide in refluxing methanol–water mixture afforded
Compounds derived from ferrocenylmethanol and ferroce-
nylmethyl acetate represent excellent entries into the synthesis
of ferrocene derivatives since they are not only readily avail-
able from the corresponding (dimethylaminomethyl)ferrocenes
but the hydroxy and acetate groups, respectively, may be easily
replaced by many other functional substituents.5 The numer-
ous chiral compounds obtained by this approach bearing other
donor groups on the ferrocene unit in a position adjacent to
the methylene tether were tested as ligands in various transi-
tion metal mediated organic transformations.5a,b Hence, any
structural information is of practical relevance as it may
allow for a more rational design of new compounds. As a
contribution to this field, we report here the solid-state struc-
tures of three planarly chiral but racemic ferrocenylmethanol
derivatives: 2-(diphenylphosphino)ferrocenylmethanol (3),
Scheme 1
DOI: 10.1039/b204655p
New J. Chem., 2002, 26, 1389–1396
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This journal is # The Royal Society of Chemistry and the Centre National de la Recherche Scientifique 2002

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the yellow-orange phosphinoalcohol 3 (92%), which was con-
verted with hydrogen peroxide to the corresponding phosphine
oxide 4 (75% yield after recrystallization) or, with sulfur, to
phosphine sulfide 5 (quantitatively). All compounds were char-
acterized by high-resolution mass spectrometry and NMR
1
spectroscopy. The H and 31P NMR data for 2 and 3 corre-
spond very well to the data reported for the respective Sp enan-
tiomers.7 However, we present a different assignment for the
13C NMR signals based on a comparison with NMR spectra
of simple FcCH2Y derivatives (Fc ¼ ferrocenyl, Y ¼ OH,
NMe2 , CO2H), their 2-Ph2P-, 2-Ph2P(O)- and 2-Ph2P(S)-
ferrocenyl analogues, and on a comparison of the observed
JPC scalar coupling constants with the values reported for tri-
phenylphosphine and triphenylphosphine oxide.8
Solid-state structures
Molecular parameters. The molecular structures of com-
pounds 2–5 are shown in Figs. 1–4 and selected geometric
parameters are summarized in Table 1. The compounds are
all racemic, crystallizing in centrosymmetric space groups.
The unit cells accommodate equal numbers of molecules with
Rp and Sp configurations related by crystallographic inversion
centres. At first glance, the molecular structures of 2–5 show
no unexpected features. The ferrocene units uniformly exhibit
only negligible tilt [max. 1.4(1)ꢁ for 5] but their cyclopentadie-
nyl rings adopt different conformations. While the conforma-
tion of 2, 3, and 4 are similar with the cyclopentadienyl rings
rotated by about 10ꢁ from the ideal eclipsed conformation
(t ¼ 0ꢁ), the respective t(C1–Cg1–Cg2–C6) torsion angles
being ꢂ9.6(2)ꢁ, ꢂ10.9(2)ꢁ, and ꢂ12.4 (2)ꢁ, the conformation
of the phosphine sulfide 5 [t ¼ 23.5(2)ꢁ] also deviates by ca.
10ꢁ but from the other extreme, the fully staggered conforma-
tion with t ¼ 36ꢁ. In all the cases, the Fe–Cg1 distance is
slightly shorter than the Fe–Cg2 distance (see Table 1 for plane
definitions). Although the relative difference amounts to only
1%, it may well reflect the electron-withdrawing nature of
the substituents and, hence, a partial electron density transfer
in the direction Cp2Fe ! Cp1.
Fig. 2 View of the molecular structure of alcohol 3 with the atom
numbering scheme. Both positions of the disordered hydroxy group
are shown. The thermal motion ellipsoids are drawn at 50% probabil-
ity level.
substituent, the maximum deformation was observed for sul-
fide 5, where the torsion angle t(C11–C1–C2–P) amounts to
7.1(3)ꢁ. The arrangement of the (pseudo)tetrahedral Ph2P(E)
moiety reflects nicely the different steric requirements of the
lone electron pair (2, 3) or the heteroatom (4, 5). Introduction
of the heteroatom results in a shortening of the P–C bonds and
opening of the C–P–C angles. The P–C distances and C–P–C
angles in phosphines 2 and 3 are similar to those in 10-(diphe-
nylphosphino)ferrocenecarboxylic acid1a or [10-(diphenylpho-
sphino)ferrocenyl]methanol.2 Similar parameters for phosphine
oxide 4 compare well to the data reported for 10-(diphenylpho-
1a
sphinoyl)ferrocenecarboxylic acid [P=O 1.487(2) A] or 1,10-
˚
9
bis(diphenylphosphinoyl)ferrocene [P=O 1.493(2) A], while
˚
The sterically demanding Ph2P(E) substituent in position
two of the ferrocene framework seems to induce no significant
torsion at the C1–C2 bond of the cyclopentadienyl ring
but, in keeping with the increased bulkiness of the Ph2P(E)
the P=S bond length in 5 corresponds to the value reported
˚
for triphenylphosphine sulfide [1.9554(7) and 1.9548(7) A at
180 K].10
Fig. 1 View of the molecular structure of 2 showing the atom num-
bering scheme. As the rings are labelled consecutively, only pivotal
and their adjacent carbon atoms are labelled. The thermal motion
ellipsoids are drawn at 50% probability level.
Fig. 3 View of the molecular structure of 4 with the atom numbering
scheme. The thermal motion ellipsoids are drawn at 50% probability
level.
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2, 4, and 5 but leaves other parameters intact. The ester part
in 2 can be compared to chiral 1-[10,2-bis(diphenylphosphino)-
ferrocenyl]ethyl acetate,12 which shows a very similar C=O
˚
bond length [1.19(2) A] but slightly shorter C(Cp)–CO
˚
˚
[1.49(1) A] and longer O–C(:O) [1.37(1) A] and C(Cp)C–O
˚
[1.48(1) A] distances.
Solid-state packing. With the exception of acetate 2, which
lacks a suitable hydrogen bond donor in the structure, the
O–Hꢀ ꢀ ꢀY (Y ¼ O or S) hydrogen bonding is the principal
force towards intermolecular aggregation in all the studied
cases (hydrogen bond parameters are summarized in Table 2).
The packing of 2 features only weak intermolecular C–Hꢀ ꢀ ꢀO
hydrogen bonds between the acyl oxygen atom O2 and two
aromatic CH and one methylene groups from three different
neighbouring molecules, which link the molecules into a com-
plicated three dimensional net.
As mentioned above, the structure of phosphinoalcohol 3
consists of molecules with two different orientations of the
hydroxymethyl substituent in a 1 : 1 ratio. The basic repeating
unit in the solid state is a dimer consisting of two neighbouring
molecules with different configuration of the hydroxymethyl
group that are linked by hydrogen bonds at an Oꢀ ꢀ ꢀO distance
Fig. 4 View of the molecular structure of 5 with the atom numbering
scheme. The thermal motion ellipsoids are drawn at 50% probability
level.
˚
of 2.751(3) A (see Table 2). However, due to the disorder, a
symmetrically related, complementary hydrogen bond system
arises within each dimer (Fig. 5, top). Thus, on average, the
solid-state packing emulates higher symmetry by forming a
system of centrosymmetric double hydrogen bridges with
0.50 occupancy for both components. Such an arrangement
results very likely from steric properties of the molecule: the
bulky, non-polar (diphenylphosphino)ferrocenyl moieties are
packed at the normal van der Waals distances so as to fill effi-
ciently the space, leaving enough space for the peripheral
hydroxymethyl group so that the latter can adopt two confor-
mations so as not to violate the higher symmetry already
imposed by the 2-(diphenylphosphino)ferrocenyl moieties
(Fig. 5, bottom). Notably, the Oꢀ ꢀ ꢀO hydrogen bonding is
not the sole stabilizing interaction in the structure of 3. The
O1–H91 group is further involved in weaker hydrogen bond-
ing to the phosphorus atom of an adjacent molecule, O1–
Albeit the geometry of the hydroxymethyl substituent in 3,
4, and 5 is very similar, as judged from the respective bond dis-
tances and bond angles that themselves do not deviate in any
significant way from those in 1,10-bis(hydroxymethyl)ferro-
cene11 or 10-(diphenylphosphino)ferrocenylmethanol,2 for
example, the CH2OH groups have different orientations
towards the parent ferrocene unit. The changes in conforma-
tion at the C1–C11 bond can be accounted for by differences
in crystal packing in which the groups participate. In phos-
phine 3, the hydroxymethyl group is statistically disordered,
having the oxygen atom distributed equally over two positions,
or in other words, with the hydroxymethyl group adopting two
different orientations towards the ferrocene unit. The disorder,
which likely arises from the crystal packing (see below), ren-
ders the C–O bond significantly shorter compared to those in
H91ꢀ ꢀ ꢀPv [O1ꢀ ꢀ ꢀPv 3.394 A; symmetry codes are given in
˚
˚
Table 1 Selected geometric parameters for compounds 2–5 (A, deg)
Parametera
2b
3
4
5
E
Void
Void
O
S
Fe–Cg1
1.6446(7)
1.6572(9)
0.5(1)
1.6445(8)
1.6565(9)
0.5(1)
1.6443(9)
1.6580(9)
0.4(1)
1.6375(8)
1.656(1)
1.4(1)
Fe–Cg2
cCp,Cp2
P=E
P–C2
–
–
1.810(2)
1.488(1)
1.782(2)
1.9567(6)
1.790(2)
1.816(2)
1.840(2), 1.839(2)
–
P–C(Ph)c
cCPEd
cCPCe
cCp1,Ph1
cCp1,Ph2
cPh1,Ph2
C1–C2–P–E
C11–C1–C2–P
C1–C11
1.834(2), 1.838(2)
–
1.806(2), 1.806(2)
111.11(8)–115.58(8)
105.33(8)–106.84(8)
89.3(1)
1.818(2), 1.810(2)
111.77(6)–115.72(5)
105.21(7)–106.09(7)
82.63(9)
101.19(7)–103.31(7)
89.74(9)
76.19(9)
73.13(9)
–
101.66(7)–102.15(7)
89.7(1)
75.11(9)
75.0(1)
81.1(1)
62.72(9)
77.32(8)
87.84(9)
–
39.6(2)
ꢂ0.6(2)
28.2(2)
7.1(3)
ꢂ3.1(2)
1.485(2)
1.461(2)
106.0(1)
ꢂ81.2(2)
ꢂ3.8(2)
1.498(3)
1.500(2)
1.410(2)
1.498(2)
1.425(2)
C11–O
cC1C11O
C2–C1–C11–O
1.295(3), 1.291(3)f
124.0(2), 115.9(2)f
153.1(2),ꢂ74.7(2)f
113.1(1)
161.7(2)
112.7(2)
67.9(2)
a
Plane definitions: Cp1, C(1–5); Cp2, C(6–10); Cg1 and Cg2 are the respective cyclopentadienyl ring centroids. 2: Ph1, C(14–19); Ph2, C(20–25); 3–5:
Ph1, C(12–17); Ph2, C(18–23). Further data for 2: C12–O1 1.334(2), C12=O2 1.199(2), C12–C13 1.489(3) A; O1–C12–O2 123.4(2), cCp , Ac
b
1
˚
c
d
e
87.4(1)ꢁ [Ac ¼ plane of the acetyl group {C12,O1,O2,C13}]. 3–5: P–C(12,18), 2: P–C(14,20). 2: C(2,14,20)–P–E; 3–5: C(2,12,18)–P–E. 2:
f
C(2)–P–C(14,20) and C(14)–P–C(20); 3–5: C(2)–P–C(12,18) and C(12)–P–C(18). Two entries due to the disorder of the hydroxymethyl group
(see Experimental). Parameters involving O1 and O2 are given, respectively [O(1)–C(11)–O(2) 104.9(2)ꢁ].
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Table 2 Hydrogen bond parameters for 2–5a
b
ꢁ
˚
Compd
Type
H-bond D–Hꢀ ꢀ ꢀA
Dꢀ ꢀ ꢀA [D–H] (A), D–Hꢀ ꢀ ꢀA ( )
2
Inter
Inter
Inter
Interc
Inter
Interc
Inter
Intra
Inter
Inter
Intrac
Inter
C(11)–H(11B)ꢀ ꢀ ꢀO(2)i
C(16)–H(16)ꢀ ꢀ ꢀO(2)ii
C(22)–H(22)ꢀ ꢀ ꢀO(2)iii
O(2)–H(92)ꢀ ꢀ ꢀ O(1)iv
O(1)–H(91)ꢀ ꢀ ꢀPv
3.339(2) [0.97], 151
3.431(2) [0.93], 172
3.424(2) [0.93], 170
2.751(3) [0.92], 161
3.394(3) [1.09], 157
2.687(2) [1.02(3)], 173(2)
3.205(2) [0.97], 126
3.297(2) [0.97], 129
3.361(2) [0.93], 166
3.376(2) [0.93], 149
3.414(2) [0.82(3)], 147(2)
3.389(2) [0.93], 158
3
4
O(1)–H(90)ꢀ ꢀ ꢀO(2)vi
C(11)–H(11A)ꢀ ꢀ ꢀO(1)vii
C(11)–H(11B)ꢀ ꢀ ꢀO(2)
C(6)–H(6)ꢀ ꢀ ꢀO(2)vi
C(14)–H(14)ꢀ ꢀ ꢀO(1)viii
O–H(90)ꢀ ꢀ ꢀS
5
C(16)–H(16)ꢀ ꢀ ꢀOix
a
Symmetry operators: i (1 ꢂ x, 1 ꢂ y, 1 ꢂ z), ii (ꢂx, 1 ꢂ y, 1 ꢂ z), iii (1 ꢂ x, 1 ꢂ y, ꢂz), iv (1 ꢂ x, 2 ꢂ y, ꢂz), v (ꢂx, 2 ꢂ y, ꢂz), vi (1 ꢂ x, 1 ꢂ y,
b
c
1 ꢂ z), vii (2 ꢂ x, 1 ꢂ y, 1 ꢂ z), viii (x, 1 + y, z), ix (2 ꢂ x, ꢂy, ꢂz). Parameters including fixed hydrogen atoms are given without esd. The
principal component.
Table 2]. Thus, the alcohol function containing O1 acts as both
the hydrogen donor (towards P) and acceptor (towards O2).
Furthermore, the molecular entity is connected to its centro-
symmetric counterpart by an offset p-p stacking interaction
involving two by-symmetry perfectly parallel phenyl rings at a
1
1
˚
ring centroid distance Ph ꢀ ꢀ ꢀPh &(1 ꢂx, 1ꢂy, ꢂz) of 4.21 A
(Fig. 5, bottom). This distance is about 25% longer than the
˚
interlamellar separation in a-graphite (3.35 A).
According to a search in the Cambridge Structural Database
(version 522, release of November 2001), O–Hꢀ ꢀ ꢀP hydrogen
bonds are not unprecedented but still rather scarce; the known
examples are restricted only to hydroxyphosphines. For six
˚
entries with Hꢀ ꢀ ꢀP distances not exceeding 3.0 A, the Oꢀ ꢀ ꢀP
13
distances in inter- and intramolecular O–Hꢀ ꢀ ꢀP bonds span a
˚
range of 3.03–3.50 A. As examples may serve structures of
2-[tert-butyl(phenyl)phosphinol]-4-methylphenol [intermole-
cular, Oꢀ ꢀ ꢀP 3.190(1) A, O–Hꢀ ꢀ ꢀP 152 at 143 K],13a rac-1,
ꢁ
˚
10-bis[diphenylphosphino)-2-[1-(2-hydroxyphenylamino)ethyl]-
13b
ꢁ
˚
ferrocene [intermolecular, Oꢀ ꢀ ꢀP 3.504 A, O–Hꢀ ꢀ ꢀP 146 ],
diphenyl-[2-(2-hydroxyphenyliminomethyl)phenyl]phosphine
13c
[intramolecular, Oꢀ ꢀ ꢀP 3.483 A, O–Hꢀ ꢀ ꢀP 154 ] or 2-[20-(tert-
butylphenylphosphino)phenyl]phenol ꢀ methanol (1 : 1) solvate
which features a combined system of hydrogen bonds very
similar to that in 3, O–Hꢀ ꢀ ꢀO(Me)–Hꢀ ꢀ ꢀP, with Oꢀ ꢀ ꢀP
ꢁ
˚
ꢁ
˚
˚
3.327(2) A, O–Hꢀ ꢀ ꢀP 171 , and Oꢀ ꢀ ꢀO 2.703(2) A, O–Hꢀ ꢀ ꢀO
174ꢁ (at 143 K).13d
Rather surprisingly, the arrangement of molecules in the
crystal of phosphine oxide 4 is almost the same as in the parent
phosphine 3. This is best revealed after a transformation of the
original unit cell of 4 into a cell similar to 3 and a comparison
of the atomic coordinates. Indeed, the structures show an iden-
tical distribution and orientation of the molecules in the crystal
(Fig. 6), suggesting that even the nature of intermolecular inter-
actions may be similar as well. However, unlike phosphine 3,
the phosphine oxide forms centrosymmetric, hydrogen bonded
macrocyclic dimers with O1ꢀ ꢀ ꢀO2vi distances of 2.687(2) A
˚
(Fig. 7). The observed Oꢀ ꢀ ꢀO distance is similar to that
reported for the structure of 1,10-bis(hydroxymethyl)ferrocene
11
[Oꢀ ꢀ ꢀO 2.71 and 2.69 A] and the adduct of 1,10-bis(diphenyl-
˚
hydoxymethyl)ferrocene ꢀ N,N-dimethylformamide (1
: 1)
[fc(CPh2OH) ꢀ Me2NCHO: CPh2O–Hꢀ ꢀ ꢀOCHNMe2 2.721(3)
4e
0
˚
A (fc ¼ ferrocene-1,1 -diyl) ] but significantly longer than
the hydrogen bonds observed in phosphinoyl carboxylic
acids, C(=O)O–Hꢀ ꢀ ꢀO=P:10-(diphenylphosphinoyl)ferrocene-
Fig. 5 A perspective view of the dimeric motif in the structure of 3
(top) and a view of the unit cell of 3 along the crystallographic c axis
(bottom). All the important intermolecular interactions, the O–Hꢀ ꢀ ꢀO
hydrogen bonds (dashed lines), the p-p stacking interactions (dotted
line), and the O–Hꢀ ꢀ ꢀP hydrogen bonds (arrow), are shown. For
clarity, only hydroxyl hydrogen atoms are displayed in the bottom dia-
gram.
carboxylic acid [Oꢀ ꢀ ꢀO 2.588(3) A]1a and (Sp)-2-(diphenylphos-
˚
1h
˚
phinoyl)ferrocenecarboxylic acid [Oꢀ ꢀ ꢀO 2.556(4) A].
Besides the strong, double O–Hꢀ ꢀ ꢀO hydrogen bond, the pack-
ing of 4 is further stabilized by a system of weaker inter- and
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Fig. 6 The unit cell of 3 (left) and the transformed unit cell of 4 (right) as viewed along the crystallographic a axis. Hydrogen atoms at C11 in 3
were omitted due to disorder.
intramolecular C–Hꢀ ꢀ ꢀO hydrogen bonds (Table 2) and,
similarly to 3, by a face-to-face stacking interaction between
the Ph1 phenyl ring and its symmetry-related counterpart
Ph1ꢀ ꢀ ꢀPh1&(2ꢂx, 2 ꢂ y, 1 ꢂ z) with a ring centroid distance
interaction in the O ! P direction but with a better acceptor,
O–Hꢀ ꢀ ꢀO=P, dominates the structure of 4. The replacement
of the (weak) O–Hꢀ ꢀ ꢀP with the (rather strong) O–Hꢀ ꢀ ꢀO=P
hydrogen bond, which leaves the crystal packing virtually
unchanged, indicates that O–Hꢀ ꢀ ꢀP hydrogen bonds affect
the crystal packing far more than generally acknowledged.
Finally, the hydroxyl group in sulfide 5 participates in intra-
molecular hydrogen O–Hꢀ ꢀ ꢀS bonding to form a cycle of six
˚
of 4.15 A.
The changes of the intermolecular interactions on going
from 3 to 4 can be ascribed to a competition of potential
hydrogen bond acceptors for the hydroxymethyl group. While
the structure of 3 is dominated by O–Hꢀ ꢀ ꢀO interactions
between the disordered hydroxymethyl groups with coopera-
tive contribution of weaker O–Hꢀ ꢀ ꢀP bonds (a hydroxy group
groups wins over the phosphine as a better acceptor), the
˚
non-hydrogen atoms with an Oꢀ ꢀ ꢀS edge of 3.414(2) A. Simi-
larly to 3, the hydroxyl function is further involved in intermo-
lecular C–Hꢀ ꢀ ꢀOix hydrogen bonding as an acceptor. This
interaction binds the molecules into cyclic dimers that are
packed at the normal van der Waals distances (Fig. 8).
Conclusions
Ferrocenylmethanol derivatives having (c-)tetrahedral
P(E)Ph2 (E ¼ void, O, S) substituents on the same or the
other1,2 cyclopentadienyl ring represent well-defined supramo-
lecular building blocks that, in the absence of other molecules
capable of hydrogen bond formation, tend to associate primar-
ily through intermolecular O–Hꢀ ꢀ ꢀO hydrogen bonds to either
neighbouring hydroxy groups or, as shown for 4, to a better
acceptor when available. When another hydroxy group acts
as an acceptor, it may become involved in further interactions
with other proximal polar groups as the hydrogen bond donor.
Furthermore, the variation of the E element allows for differ-
ent packing patterns due to changed steric demands of the
Ph2P(E) substituent and, more importantly, due to its changed
hydrogen bond acceptor power. Further intramolecular inter-
actions influencing the solid-state packing are p-p stacking
interactions of the phenyl substituents and also much less pre-
dictable C–Hꢀ ꢀ ꢀO hydrogen bonds, which represent the only
interactions observed for compound 2 where the hydroxy
group cannot enter hydrogen bonding as the donor. Regard-
less of the other interactions accounting for propagation
of the molecular network, the principal force towards self-
assembly in alcohols 3–5 results in the formation of entropi-
cally favoured, closed cyclic systems [3: 6, 4: 12, and 5: 6 (intra)
non-hydrogen atoms]. Solid-state packing seems to be in the
case of 2–5 dictated by the steric requirements of the bulky
phosphinylated ferrocene framework (non-polar interactions),
which, however, leaves enough space for the attached polar
groups and assembles into a crystal so as to force the polar
Fig. 7 View of the dimeric, hydrogen-bonded motif in the structure
of phosphine oxide 4.
New J. Chem., 2002, 26, 1389–1396
1393

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2
J ꢃ 2.6, 1.5 Hz, 1 H, C5H3), 4.97 (d, JHH ¼ 12.0 Hz, 1 H,
2
4
CH2), 5.16 (dd, JHH ¼ 12.0, JPH ¼ 2.4 Hz, 1 H, CH2),
7.14–7.56 (m, 10 H, PPh2). 13C{1H} NMR (CDCl3): d 20.39
3
(Me), 61.79 (d, JPC ¼ 10 Hz, CH2), 69.64 (C5H5), 70.02
(CH of C5H3), 72.30 (d, JPC ¼ 4 Hz, CH of C5H3), 73.04
1
(d, JPC ¼ 4 Hz, CH of C5H3), 77.70 (d, JPC ¼ 9 Hz, C–P of
2
C5H3), 86.28 (d, JPC ¼ 25 Hz, C–CH2 of C5H3), 127.82
3
(CHp of PPh2), 127.89 (d, JPC ¼ 6 Hz, CHm of PPh2),
3
128.18 (d, JPC ¼ 8 Hz, CHm of PPh2), 129.17 (CHp of
2
PPh2), 132.49 (d, JPC ¼ 18 Hz, CHo of PPh2), 134.92 (d,
1
2JPC ¼ 21 Hz, CHo of PPh2), 136.99 (d, JPC ¼ 8 Hz, Cipso
1
of PPh2), 139.65 (d, JPC ¼ 10 Hz, Cipso of PPh2), 170.62
(MeCO). 31P{1H} NMR (CDCl3): d ꢂ22.7 (s). HR MS: calcd.
for C25H23FeO2P: 442.0785, found 442.0816.
rac-2-(Diphenylphosphino)ferrocenylmethanol (3). A suspen-
sion of acetate 2 (0.320 g, 0.72 mmol) in a mixture of methanol
(24 ml) and 3 M aqueous potassium hydroxide (12 ml, 36
mmol) was refluxed under argon for 6 h. The reaction mixture
was diluted with water (50 ml) and cooled in an ice bath. The
separated solid was filtered off, washed well with water, dried
in air, and purified by chromatography on silica gel using
dichloromethane–methanol (10 : 1, n/n) as the eluent to afford
3 as a yellow-orange solid (0.266 g, 92%).
1H NMR (CDCl3): d 1.48 (br s, 1 H, OH), 3.75 (m, 1 H,
C5H3), 4.09 (s, 5 H, C5H5), 4.30 (t, J ꢃ 2.5 Hz, 1 H, C5H3),
2
4.42 (d, JHH ¼ 12.4 Hz, 1 H, CH2), 4.51–4.57 (m, 2 H, CH2
and C5H3), 7.16–7.58 (m, 10 H, PPh2). 13C{1H} NMR
3
(CDCl3): d 59.88 (d, JPC ¼ 9 Hz, CH2), 69.44 (C5H5), 69.57
Fig. 8 View of the weakly bonded dimeric arrays in the structure of 5
showing the intramolecular O–Hꢀ ꢀ ꢀS and intermolecular C–Hꢀ ꢀ ꢀO
hydrogen bonds as dashed lines.
(CH of C5H3), 71.52 (d, JPC ¼ 4 Hz, CH of C5H3), 71.64 (d,
1
JPC ¼ 4 Hz, CH of C5H3), 76.03 (d, JPC ¼ 7 Hz, C–P of
2
C5H3), 92.59 (d, JPC ¼ 23 Hz, C–CH2 of C5H3), 128.20 (d,
3JPC ¼ 7 Hz, CHm of PPh2), 128.22 (CHp of PPh2), 128.35
3
groups into mutual proximity. As documented by the virtually
isostructural compounds 3 and 4, any far-reaching conclusions
drawn from incomplete structural data for a series of closely
related entities with changed peripheral parts or modified only
marginally without influencing the overall molecular geometry
should be taken with utmost care.
(d, JPC ¼ 6 Hz, CHm of PPh2), 129.19 (CHp of PPh2),
2
2
132.33 (d, JPC ¼ 18 Hz, CHo of PPh2), 134.75 (d, JPC ¼ 21
1
Hz, CHo of PPh2), 136.81 (d, JPC ¼ 9 Hz, Cipso of PPh2),
139.60 (d, JPC ¼ 11 Hz, Cipso of PPh2). 31P{1H} NMR
1
(CDCl3): d ꢂ22.6 (s). HR MS: calcd. for C23H21FeOP:
400.0679, found 400.0689.
rac-2-(Diphenylphosphinoyl)ferrocenylmethanol (4). In air, a
solution of 3 (0.080 g, 0.20 mmol) in acetone (10 ml) was
cooled in an ice bath and treated with 30% aqueous hydrogen
peroxide (5 drops). A yellow precipitate separated from the
mixture. After stirring for 1 h at 0 ꢁC, the mixture was diluted
with water (10 ml), the precipitate was filtered off, and dried
under vacuum. The crude product was dissolved in a little
ethyl acetate and crystallized by hexane diffusion to give 4 as
a fine yellow-orange microcrystalline solid (0.062 g, 75%).
1H NMR (CDCl3): d 3.93 (m, 1 H, C5H3), 4.16 (d,
2JHH ¼ 13.1 Hz, 1 H, CH2), 4.26 (s, 5 H, C5H5), 4.33 (d,
2JHH ¼ 13.2 Hz, 1 H, CH2), 4.34 (t, J ꢃ 2.4 Hz, C5H3), 4.54
(m, 1 H, C5H3), 5.46 (very br s, 1 H, OH), 7.36–7.86 (m, 10
H, PPh2). 13C{1H} NMR (CDCl3): d 58.63 (CH2), ca. 69.57
Experimental
General comments
Toluene was dried by storing with potassium and distilled
under argon. Acetic anhydride and methanol were distilled
under argon. rac-N,N-Dimethyl[2-(diphenylphosphino)ferro-
cenyl]methylamine (1) was synthesized by a literature proce-
dure.14 All other chemicals were used as received from
commercial suppliers.
NMR spectra were recorded on a Varian UNITY Inova 400
spectrometer (1H, 399.95; 13C, 100.58; 31P, 161.90 MHz) at
298 K. Chemical shifts (d/ppm) are given relative to internal
tetramethylsilane (1H and 13C) or external 85% aqueous
H3PO4 (31P). High resolution mass spectra were measured on
a VG 7070E spectrometer at 70 eV using perfluorokerosene
as an internal mass scale calibrant.
1
(d, JPC ꢃ 115 Hz, C–P of C5H3), 69.66 (d, JPC ¼ 11 Hz, CH
of C5H3), 70.17 (C5H5), 73.03 (d, JPC ¼ 15 Hz, CH of
C5H3), 74.09 (d, JPC ¼ 10 Hz, CH of C5H3), 95.48 (d,
2JPC ¼ 11 Hz, C–CH2 of C5H3), 128.27, 128.44 (2 ꢄ d,
2
3JPC ¼ 12 Hz, CHm of PPh2), 131.39, 131.53 (2 ꢄ d, JPC
¼
Syntheses
4
10 Hz, CHo of PPh2), 131.81, 131.97 (d, JPC ¼ 3 Hz, CHp
1
rac-[2-(Diphenylphosphino)ferrocenyl]methyl acetate (2).
Amine 1 (0.427 g, 1.0 mmol) and freshly distilled acetic anhy-
dride (1 ml) were charged into a small reaction flask, the flask
was flushed with argon and stoppered. The mixture was heated
to 100 ꢁC for 2 h with stirring and then allowed to stand at
ꢂ18 ꢁC overnight. The solidified mixture was transferred to a
glass frit, thoroughly washed with methanol and dried in air
to yield 2 as a bright yellow crystalline solid (0.334 g, 76%).
1H NMR (CDCl3): d 1.60 (s, 3 H, Me), 3.77 (m, 1 H, C5H3),
4.07 (s, 5 H, C5H5), 4.32 (t, J ꢃ 2.5 Hz, 1 H, C5H3), 4.53 (dt,
of PPh2), 132.37 (d, JPC ¼ 108 Hz, Cipso of PPh2), 134.23
(d, JPC ¼ 106 Hz, Cipso of PPh2). 31P{1H} NMR (CDCl3): d
1
34.1 (s). HR MS: calcd. for C23H21FeO2P: 416.0629, found
416.0673.
rac-2-(Diphenylthiophosphoryl)ferrocenylmethanol (5). Alco-
hol 3 (0.040 g, 0.10 mmol) and sulfur (6.5 mg, 0.2 mmol) were
dissolved in dry toluene (3 ml) under argon and the solution
was heated to 100 ꢁC for 1 h. Then, the solvent was removed
under reduced pressure and the residue purified by column
1394
New J. Chem., 2002, 26, 1389–1396

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Table 3 Crystallographic data, data collection and structure refinement for 2–5
Compound
2
3
4
5
Formula
C25H23FeO2P
442.25
Triclinic
C23H21FeOP
400.22
Triclinic
C23H21FeO2P
416.22
Triclinic
C23H21FeOPS
432.28
Monoclinic
P21/C (No. 14)
8.6792(1)
17.6265(3)
13.2883(2)
90
M/g molꢂ1
Crystal system
Space group
¯
P1(No. 2)
¯
P1(No. 2)
¯
P1(No. 2)
˚
a/A
10.2946(2)
10.9414(2)
10.9792(2)
87.570(1)
66.034(1)
71.624(1)
1067.18(3)
2
7.8638(1)
10.1888(2)
12.0270(2)
89.292(1)
81.086(1)
80.009(1)
937.46(3)
2
7.8574(2)
10.1678(2)
12.1411(3)
90.566(2)
100.600(2)
97.935(2)
943.68(4)
2
˚
b/A
˚
c/A
a/ꢁ
b/ꢁ
g/ꢁ
105.749(1)
90
3
˚
U/A
1956.58(5)
4
0.969
Z
m(Mo Ka)/mmꢂ1
Unique reflect.
Obsd reflect.a
R (obsd reflect)b /%
R (all data)b /%
wR(all data)b /%
Rintc /%
0.800
4849
0.898
4272
0.899
4334
4488
4135
4399
2.90
3841
3.07
3867
3.14
2.94
3.28
3.30
7.60
3.57
8.34
3.73
8.19
7.12
3.3
3.0
2.7
3.0
a
b
2
c
2
2
Diffractions with Io > 2s(Io). R(F) ¼ S||FoꢂFc||/S|Fo|, wR(F2) ¼ {S[w(Fo ꢂFc2)2]/[Sw(Fo2)2]}1/2
.
Rint ¼ S|Fo ꢂFo,mean2|/SFo
.
chromatography (silica gel, dichloromethane–methanol 10 : 1,
n/n) to give 5 as an orange solid in quantitative yield (0.043 g).
1H NMR (CDCl3): d 3.37 (br s, 1 H, OH), 3.78 (m, 1 H,
C5H3), 4.29–4.33 (m, 1 H, C5H3), 4.31 (s, 5 H, C5H5), 4.31
The structures were solved by direct methods (SIR9216) and
refined by weighted full-matrix least-squares on F2
(SHELXL9717). Final geometric calculations were carried
out with a recent version of the Platon program.18 All non-
hydrogen atoms were refined with anisotropic thermal motion
parameters. With the exception of the hydroxy hydrogens, the
hydrogen atoms were included in calculated positions [C–H
bond lengths: 0.93 (aromatic), 0.97 (methylene) and 0.96
2
(d, JHH ¼ 12.8 Hz, 1 H, CH2), 4.58 (m, 1 H, C5H3), 4.68
2
(d, JHH ¼ 12.8 Hz, 1 H, CH2), 7.34–7.89 (m, 10 H, PPh2).
13C{1H} NMR (CDCl3): d 58.57 (CH2), 68.96 (d, JPC ¼ 10
1
Hz, CH of C5H3), 70.46 (C5H5), 73.87 (d, JPC ¼ 95 Hz, C–
˚
P of C5H3), 74.50 (d, JPC ¼ 12 Hz, CH of C5H3), 74.86 (d,
(methyl) A] and assigned Uiso(H) ¼ 1.2 Ueq(C) (aromatic and
2
JPC ¼ 10 Hz, CH of C5H3), 93.48 (d, JPC ¼ 12 Hz, C–CH2
methylene) or 1.5 Ueq(C) (methyl). Hydroxyl hydrogen atoms
in 2, 4, and 5 were clearly identified on the electron density
maps and isotropically refined. The disordered hydroxylmethyl
group in 3 was modelled considering two positions for the oxy-
gen atom with 0.50 occupancies but only one position for the
C11 atom as revealed by difference electron density maps.
After these non-hydrogen atoms had been refined with aniso-
tropic thermal motion parameters, the two respective hydroxyl
hydrogen atoms H91 and H92 could be located on the differ-
ence electron density map but they were fixed in the positions
identified and assigned Uiso(H) ¼ 1.2 Ueq(O).
3
of C5H3), 128.12 (d, JPC ¼ 13 Hz, CHm of PPh2), 128.42 (d,
4
3JPC ¼ 12 Hz, CHm of PPh2), 131.38 (d, JPC ¼ 3 Hz, CHp
4
of PPh2), 131.57 (d, JPC ¼ 4 Hz, CHp of PPh2), 131.64,
2
132.12 (2 ꢄ d, JPC ¼ 11 Hz, CHo of PPh2); 132.72 (d,
1
1JPC ¼ 87 Hz, Cipso of PPh2), 134.96 (d, JPC ¼ 88 Hz, Cipso
of PPh2). 31P{1H} NMR (CDCl3): d +42.3 (s). HR MS: calcd.
for C23H21FeOPS: 432.0400, found 432.0386.
CCDC reference numbers 185007–185010. See http://
www.rsc.org/suppdata/nj/b2/b204655p/ for crystallographic
data in CIF or other electronic format.
X-Ray crystallography
X-ray quality crystals were obtained by recrystallization from
methanol (3: orange prism, 0.20 ꢄ 0.30 ꢄ 0.35 mm3), and ethyl
acetate–hexane (4: orange prism 0.20 ꢄ 0.30 ꢄ 0.60 mm3; 5:
orange prism, 0.25 ꢄ 0.43 ꢄ 0.45 mm3), or selected directly
from the reaction batch (2: orange plate, 0.15 ꢄ 0.40 ꢄ 0.50
mm3). Diffraction data (Table 3) for all compounds were col-
lected on a Nonius Kappa CCD diffractometer equipped with
Cryostream Cooler (Oxford Crysoystems) at 150 K using gra-
Acknowledgements
This work was supported by Grant Agency of the Czech
Republic (grant Nos. 203/01/P002, 203/99/M037, 203/02/
0436) and is a part of a long-term Research plan of the Faculty
of Sciences, Charles University.
˚
phite monochromated MoKa radiation (l ¼ 0.71073 A) and
analyzed with the HKL program package.15 Absorption was
neglected.
3: 327 frames were collected (2.0ꢁ o rotation, 40 s counting
time), 18 524 integrated diffractions. The cell parameters were
determined by least-squares fitting from 10 607 diffractions
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New J. Chem., 2002, 26, 1389–1396