Group-12 metal complexes with isomeric 1-(diphenylphosphino)-1′-[N- (pyridylmethyl)carbamoyl]ferrocenes: Coordination polymers vs. finite multinuclear coordination assemblies

Article abstract of DOI:10.1039/b719334c

The isomeric ferrocene phosphine-carboxamides, 1-(diphenylphosphino)- 1′-{[N-(2-pyridyl)-methyl]carbamoyl}ferrocene (1) and 1- (diphenylphosphino)-1′-{[N-(4-pyridyl)methyl]carbamoyl}ferrocene (2) have been studied as ligands in group-12 metal bromide complexes. The reactions of 1 with CdBr₂?4H₂O and HgBr₂ at 1:1 mole ratio gave the discrete tetracadmium complex [Cd₂(μ-Br) ₂(1-1κ²O,N²)₂{μ- 1κ²O,N²:2κP-(C₅H ₄N)CH₂NHC(O)fcPPh₂-CdBr₃} ₂] (7; fc = ferrocene-1,1′-diyl) and the halogeno-bridged dimer [{Hg(μ-Br)Br(1-κP)}₂] (8), respectively. In the presence of acetic acid, the CdBr₂-1 system furnished a zwitterionic complex featuring protonated 1 as the P-monodentate donor, [CdBr₃{Ph ₂PfcC(O)NHCH₂(C₅H₄NH)-κP}] ?H₂O (6?H₂O). Under neutral conditions, compound 2, whose terminal donor groups are better arranged for the formation of extended assemblies, gave rise to one-dimensional coordination polymers [MBr₂{μ(P,N)-2}]_n (M = Cd, 4; M = Hg, 5). The crystal structures of 2?H₂O, its corresponding phosphine oxide (3?H₂O), and complexes 4, 5, 6?H₂O, 7 and 8 have been determined, revealing extensive hydrogen bonding interactions in the solid state. The Royal Society of Chemistry.

Full text of DOI:10.1039/b719334c

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An international journal of inorganic chemistry
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Number 18 | 14 May 2008 | Pages 2357–2504
PPh
2
Fe
O
N
C
N
H
CdBr · 4H O
2
2
Ph P
2
Fe
O
N
C
N
H
ISSN 1477-9226
PAPER
Stepnicka et al.
Group-12 metal complexes with
isomeric 1-(diphenylphosphino)-1’
[N-(pyridylmethyl)carbamoyl]
ferrocenes
PERSPECTIVE
Chung et al.
Cobalt–rhodium heterobimetallic
nanoparticle-catalyzed reactions
1477-9226(2008)18;1-2

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PAPER
www.rsc.org/dalton | Dalton Transactions
Group-12 metal complexes with isomeric 1-(diphenylphosphino)-1ꢀ-[N-
(pyridylmethyl)carbamoyl]ferrocenes: coordination polymers vs. finite
multinuclear coordination assemblies†
a
a
a
Janett Ku¨hnert,a,b Ivana C´ısarˇova´, Martin Lamacˇ and Petr Steˇpnicˇka*
ˇ
Received 14th December 2007, Accepted 14th February 2008
First published as an Advance Article on the web 11th March 2008
DOI: 10.1039/b719334c
The isomeric ferrocene phosphine-carboxamides, 1-(diphenylphosphino)-1ꢀ-{[N-(2-pyridyl)-methyl]-
carbamoyl}ferrocene (1) and 1-(diphenylphosphino)-1ꢀ-{[N-(4-pyridyl)methyl]carbamoyl}ferrocene (2)
have been studied as ligands in group-12 metal bromide complexes. The reactions of 1 with
CdBr2·4H2O and HgBr2 at 1:1 mole ratio gave the discrete tetracadmium complex [Cd2(l-Br)2(1-1j2O,
N2)2{l-1j2O,N2:2jP-(C5H4N)CH2NHC(O)fcPPh2-CdBr3}2] (7; fc = ferrocene-1,1ꢀ-diyl) and the
halogeno-bridged dimer [{Hg(l-Br)Br(1-jP)}2] (8), respectively. In the presence of acetic acid, the
CdBr2–1 system furnished a zwitterionic complex featuring protonated 1 as the P-monodentate donor,
[CdBr3{Ph2PfcC(O)NHCH2(C5H4NH)-jP}]·H2O (6·H2O). Under neutral conditions, compound 2,
whose terminal donor groups are better arranged for the formation of extended assemblies, gave rise to
one-dimensional coordination polymers [MBr2{l(P,N)-2}]n (M = Cd, 4; M = Hg, 5). The crystal
structures of 2·H2O, its corresponding phosphine oxide (3·H2O), and complexes 4, 5, 6·H2O, 7 and 8
have been determined, revealing extensive hydrogen bonding interactions in the solid state.
Introduction
Donors combining hard and soft ligating sites,1 the so-called hy-
brid ligands,2 have received considerable attention because of their
unique coordination and catalytic properties.3 The most frequently
encountered hybrid ligands are undoubtedly phosphines bearing
additional polar group(s) among which the phosphine-amides can
be regarded as typical representatives.
The majority of phosphine-carboxamides reported to date
Scheme 1
has been derived from 2-(diphenylphosphino)benzoic or x-
(diphenylphosphino)alkanoic acids4 and the compounds were
typically studied as ligands in discrete, polymeric and dendrimeric
coordination assemblies,4c–4h,5 used in models for radiopharma-
ceuticals,6 and tested as catalyst components.7,8
While studying ferrocene phosphinocarboxylic acids,9 we
turned also to their amide derivatives. So far, we have
demonstrated that phosphine-amides resulting from sim-
ple amines and 1ꢀ-(diphenylphosphino)ferrocenecarboxylic acid
(Hdpf, Scheme 1)9,10 or its planar-chiral, 1,2-isomer9,11 may serve
as versatile organometallic synthons12 and efficient ligands for
metal-catalysed organic reactions.13,14
multidentate donors, we decided to explore also the possibility
of constructing defined multinuclear coordination assemblies
thereof.16 For testing, we chose group-12 metals, the hardness of
which gradually changes from typically soft (Hg) to hard (Zn). In
this paper, we report the synthesis and crystal structures of discrete
multinuclear and polymeric coordination compounds obtained
from the isomeric phosphine-amides 1 and 2 (Scheme 1) and
group-12 metal bromides.
Results and discussion
Recently, we set out to study Hdpf-based amides bearing pyridyl
groups in the amide part as an additional donor site. These
amides have been studied as ligands for palladium complexes and
Suzuki reaction.15 In view of the coordination flexibility of these
The ligands
The synthesis of phosphinoamide 1 has been reported previously.15
Its isomeric compound 2 was prepared in an analogous manner,
i.e. by amidation of Hdpf with 4-(aminomethyl)pyridine in the
presence of peptide coupling agents.12,13,17 It was isolated by col-
umn chromatography in a good yield as an air stable, rusty orange
solid. A subsequent recrystallisation from ethyl acetate-hexane
(commercial) furnished a better defined, crystalline hydrate 2·H2O
(N.B. 1 can be crystallised in a similar manner; however, it results
in the unsolvated form). For the purpose of a structural study,
compound 2 was converted further to its corresponding phosphine
aCharles University in Prague, Faculty of Science, Department of Inorganic
Chemistry, Hlavova 2030, 128 40, Prague, Czech Republic. E-mail:
stepnic@natur.cuni.cz; Fax: +420 221 951 253
bChemnitz University of Technology, Institute of Chemistry, Department of
Inorganic Chemistry, 09111, Chemnitz, Germany
† Electronic supplementary information (ESI) available: A structural
drawing for 5 (Fig. S1). CCDC reference numbers 670833–670839.
For crystallographic data in CIF or other electronic format see DOI:
10.1039/b719334c
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oxide 3 by reacting with hydrogen peroxide. Crystallisation as
above afforded the hydrated product, 3·H2O.
Compounds 2 and 3 have been characterised by standard
1
spectral methods and by combustion analysis. In 1H and 13C{ H}
NMR spectra, they show characteristic signals attributable to
1ꢀ-(diphenylphoshino)ferrocenyl and pyridyl-amide groups. The
nature of the phosphorus substituents is best manifested in the
1
31P{ H} NMR spectra showing singlets at dP −16.9 and 32.6 for 2
and 3, respectively (cf . dP −17.6 for Hdpf and +32.9 for HdpfO).10
The IR spectra of 2 and 3 are dominated by the strong mC=O (amide
I) bands at 1643 and 1634 cm−1. The different positions of the
bands apparently reflect the differences in crystal packing (see
below).
In order to clarify the role of the solvent of crystallisation
and the phosphorus groups in the crystal assembly, the solid-
state structures of 2·H2O and 3·H2O have been established by
single-crystal X-ray diffraction. Views of the molecular structures
of 2·H2O and 3·H2O are shown in Fig. 1 and 2. The relevant
structural data are summarised in Table 1.
Fig. 2 PLATON plot of 3·H2O. The water molecule has been omitted
for clarity. Displacement ellipsoids enclose the 30% probability level. For
a comment on atom labelling, see note in Fig. 1.
In both cases, the geometry of the ferrocene moiety is regular,
showing practically equal Fe–Cg distances and negligible tilting
(Cg denotes cyclopentadienyl ring centroids). A notable difference
is found in the conformation of the ferrocene unit: Whereas
the ferrocene moiety in 2·H2O is close to syn-eclipsed, that in
3·H2O adopts a conformation near to anti-eclipsed (see s angles
in Table 1).
The geometry of the amide parts is regular as well, comparing
favourably to that in 1.15 The amide groups are syn-arranged (cf .
u angles in Table 1) but take different orientation towards their
parent cyclopentadienyl ring (Cp2). In 3·H2O, the {C11ON1}
plane is rotated from the Cp2 plane by only 3.5(3)◦, whilst that
in 2·H2O deviates from coplanarity with the Cp2 ring by as much
as 29.5(2)◦. These conformational changes can be attributed to
crystal packing, which is markedly different for both amides.
In the crystals of 2·H2O, the individual molecules associate into
infinite, hydrogen-bonded columnar stacks along the crystallo-
graphic a axis (Fig. 3). In this assembly, which is built up from
pairs of inversion related molecules, each amide molecule behaves
as a hydrogen bond donor via its amide NH group and a two-
fold hydrogen bond acceptor via the carbonyl oxygen and the
pyridyl nitrogen (Table 2). The water molecules are fully involved
in hydrogen bonding interactions, acting as ‘clamps’ between the
proximal amide molecules. The presence and properties of the
solvent molecules bring the number of hydrogen bond donors
Fig. 1 PLATON plot of 2·H2O. The water molecule has been omitted
for clarity. Displacement ellipsoids are scaled to 30% probability. Note:
the aromatic rings are numbered consecutively and, hence, only labels
of pivotal and their adjacent carbon atoms are shown. Similar labelling
scheme has been adopted also for the complexes.
◦
a
˚
Table 1 Selected geometric data for 2·H2O and 3·H2O (in A and
)
=
(NH, H2O) and acceptors (C O, pyridyl, H2O) to a perfect
Parameter
2·H2O
1.645(1)
3·H2O
1.646(1)
1.650(1)
1.786(2)
1.492(2)
1.481(3)
1.243(3)
1.333(3)
1.6(1)
match. This, together with the proper spatial distribution of
the H-bonding groups, which is aided by the flexibility of the
ferrocene-1,1ꢀ-diyl moiety, allows for an exploitation of all the
available (classical) hydrogen bonding groups which, in turn, leads
to the formation of a compact crystal assembly and to preferential
crystallisation of the hydrate.
Fe–Cg1
Fe–Cg2
C1–P
P–O1P
C6–C11
C11–O
C11–N1
∠Cp1,Cp2
sb
1.643(1)
1.821(2)
—
1.485(2)
1.233(2)
1.337(2)
3.8(1)
The H-bonded molecular array in 2·H2O is stabilised by offset
p · · · p stacking interactions within the pairs of inversion-related
(i.e. exactly parallel) pyridyl rings. The distance of the ring
centroids is 4.174(2) A and the rings are slipped by 1.92 A. In
addition, the neighbouring stacks are cross-linked by the relatively
77
159
O–C11–N1
C11–N1–C24
uc
122.8(2)
121.2(2)
6.3(3)
121.5(2)
120.5(2)
7.1(3)
˚
˚
a Definition of the ring planes: Cp1 = C(1–5), Cp2 = C(6–10). Cg1 and
Cg2 are the respective ring centroids. b Torsion angle C1–Cg1–Cg2–C6.
c Torsion angle O–C11–N1–C24.
=
weaker C–H(Ph) · · · O C interactions (Table 2).
Oxidation converts the phosphorus group into a strong hydro-
gen bond acceptor, which is naturally reflected in the packing
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◦
a
˚
Table 2 Hydrogen bond parameters for 2·H2O and 3·H2O (in A and
)
D–H · · · A
D · · · A
Angle at H
Compound 2·H2O
N1–H1N · · · O1Wi
O1W–H1W · · · O
O1W–H2W · · · N2ii
C16–H16 · · · Oiii
2.821(2)
168
175
167
134
2.863(2)
2.803(2)
3.299(3)
Compound 3·H2O
N1–H1N · · · O1Piv
O1W–H1W · · · O
O1W–H2W · · · N2v
C10–H10 · · · O1Piv
C20–H20 · · · Ovi
2.779(2)
161
174
176
145
146
141
2.775(2)
2.878(3)
3.306(3)
3.329(3)
C23–H23 · · · O1Wvii
3.230(3)
a D = donor, A = acceptor. Symmetry codes: i. x + 1, y, z; ii. −x, −y, −z +
1; iii. x, y + 1, z; iv. x, y−1, z; v. −x + 1, y + 1/2, −z + 1; vi. −x + 1, y +
1/2, −z; vii. x + 1, y, z.
Fig. 4 Section of the molecular assembly in the crystal of 3·H2O. For
clarity, only pivotal carbon atoms from the phenyl rings and the hydro-
gen-bonded H-atoms are shown. Hydrogen bonds are indicated by dashed
lines. Symmetry operations: A (x, y, z), B (x, y + 1, z), C (x, y − 1, z), D
(−x + 1, y + 1/2, −z + 1), E (−x + 1, y + 3/2, −z + 1), F (−x + 1, y −
1/2, −z + 1).
groups (Scheme 2). They have been studied as ligands in bromide
complexes of group-12 metals, whose coordination preferences
change broadly along with the metal radius and softness.1
Fig. 3 Section of the infinite columnar stack in crystalline 2·H2O. For clar-
ity, only pivotal carbon atoms from the phenyl rings and hydrogen-bonded
H-atoms are shown. Dashed lines indicate the hydrogen bonds and p · · · p
stacking interactions. Symmetry operations: A (x, y, z), B (x−1, y, z), C
(x + 1, y, z), D (−x, −y, −z + 1), E (−x−1, −y, −z + 1), F (−x + 1, −y,
−z + 1).
patterns (Fig. 4). In the crystal, the phosphoryl oxygen of 3·H2O
forms a hydrogen bond with the NH group located in adjacent
molecule related by elemental translation along the b axis. This
results into the formation of infinite chains that pair further
into twisted ribbons via hydrogen bonds from their embedded
water molecules to the (in-chain) pyridine nitrogen and carbonyl
oxygen atoms (Table 2). The formed helical assembly is chiral, the
compound crystallising in the space group P21. Similarly to the
previous case, the hydrogen-bonded arrays are interconnected by
C–H · · · O contacts (Table 2).
Scheme 2 Topology of the phosphinoamide ligands.
In order to avoid undesired formation of simple discrete com-
plexes (e.g., of bis-phosphane type), the complexation reactions
were performed at the 1:1 MBr2-to-ligand molar ratio (M = Zn,
Cd, Hg). However, defined solid products were obtained only for
cadmium and mercury; the zinc compounds were reluctant to
crystallise presumably due to their higher solubility. Although all
solid products have been characterised by X-ray crystallography,
it should be emphasised that the products posses strong tendency
to separate as amorphous or fine microcrystalline solids. Hence,
a careful optimisation of the synthetic conditions including the
Complexation study
Phosphinoamides 1 and 2 appear as good candidates for the
preparation of defined coordination assemblies, possessing chem-
ically different ligating sites and groups capable of hydrogen
bonding connected with flexible but spatially defined linking
2456 | Dalton Trans., 2008, 2454–2464
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◦
a
˚
proper choice of the reaction solvent, concentration and the
mode of mixing of the educts are essential for obtaining defined
crystalline materials.
Table 3 Selected geometric data for 4 and 5 (in A and
)
Parameter
4 (M = Cd)
5 (M = Hg)
It is also worth noting that characterisation of the products
by the conventional solution methods can be misleading since
the formed complexes are soluble only in polar solvents, in
which they, however, are prone to dissociation and solvolysis.
This can be demonstrated by solution 31P NMR data (DMSO
solvent) indicating the presence of free phosphine groups for all
cadmium complexes whilst the softer mercury(II) cation remains
P-coordinated. Likewise, the ESI+ MS spectra show ions resulting
typically by fragmentation of the molecular aggregates and a loss
of the Br− ion.
M–Br1
M–Br2
2.5308(4)
2.5474(4)
2.576(1)
2.301(3)
121.24(2)
121.08(2)
99.97(7)
106.10(2)
105.21(8)
99.20(8)
1.644(2)
1.652(2)
1.224(5)
1.350(5)
4.8(2)
2.5427(5)
2.5991(5)
2.438(1)
2.438(4)
114.60(2)
130.22(2)
94.5(1)
M–P
M–N2i
Br1–M–Br2
Br1–M–P
Br1–M–N2i
Br2–M–P
Br2–M–N2i
P–M–N2i
Fe–Cg1
Fe–Cg2
C11–O
C11–N1
∠Cp1,Cp2
sb
O–C11–N1
C11–N1–C24
uc
109.06(2)
99.1(1)
101.21(9)
1.644(2)
1.652(2)
1.231(5)
1.355(5)
5.2(2)
Complexes prepared from ligand 2
157
157
Despite the intrinsic flexibility of the ferrocene unit, the terminal
donor groups (phosphine and the pyridyl ring) in 2 are apparently
better set up for the formation of extended arrays than in 1. Indeed,
reactions involving ligand 2 afforded linear coordination polymers
for both cadmium and mercury: [MBr2{l(P,N)-2}]n (M = Cd,
4; M = Hg, 5; Scheme 3).
121.7(3)
120.1(3)
2.7(5)
121.2(4)
120.5(3)
2.9(6)
a The ring planes are defined as for 2 (see Table 1). Symmetry codes: i. x +
1,−y + 1/2, z − 1/2. b Torsion angle C1–Cg1–Cg2–C6. c Torsion angle
O–C11–N1–C24.
can be attributed to the larger radius of the mercury atom
(though it does not cause an expansion of the unit cell) and to
conformational changes in the ferrocene ligand.
The view of the polymeric chain in 4 is shown in Fig. 5 (for a
similar drawing of 5 see ESI, Fig. S1).† Geometric parameters for
both complexes are listed in Table 3. Quite expectedly, the metals
are coordinated by the phosphorus and pyridine nitrogen atoms
from two ligand molecules with two terminal bromides completing
the tetrahedral donor set. The metal-donor distances compare
favourably with those in complexes featuring these metals and
other 1ꢀ-functionalised ferrocene phosphines.18 However, probably
because of different steric demands of the ligating groups, the
coordination tetrahedrons in 4 and 5 are markedly distorted. The
extreme interligand angles differ by as much as ca. 22◦ in the
cadmium and by ca. 36◦ in the mercury complex.
The ferrocene substituents in 4 and 5 adopt an intermedi-
ate conformation between anti-eclipsed and anticlinal-staggered
(s = 157◦) and the pyridyl groups are directed away from the
ferrocene unit and almost perpendicular to it. In combination,
this brings the donor groups into distant positions (P · · · N2 =
Scheme 3
X-Ray diffraction analysis revealed compounds 4 and 5 to
be isostructural, showing very similar lattice parameters and
distribution of the atoms within the unit cell. The minor differences
˚
˚
11.799(3) A in 4 and 12.804(4) A in 5), that allow an efficient yet
spatially compact propagation of the polymeric chain.
Fig. 5 PLATON plot of the infinite linear polymeric chain in 4. Displacement ellipsoids enclose the 30% probability level.
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◦
a
˚
the only structurally characterised complex of this kind with a
Br3P donor set.
Table 4 Selected distances and angles for 6·H2O (in A and
)
Cd–Br1
Cd–Br2
Cd–Br3
Cd–P
Fe–Cg1
Fe–Cg2
C1–P
C6–C11
C11–O
C11–N1
N1–C24
2.5976(4)
2.5683(3)
2.5642(4)
2.5897(7)
1.648(1)
1.653(1)
1.797(3)
1.478(4)
1.233(3)
1.344(4)
1.449(4)
Br1–Cd–Br2
Br1–Cd–Br3
Br2–Cd–Br3
P–Cd–Br1
P–Cd–Br2
P–Cd–Br3
∠Cp1,Cp2
sb
109.46(1)
105.44(1)
112.60(1)
110.51(2)
112.44(2)
106.15(2)
7.2(2)
The ferrocene substituents in 6·H2O adopt a conformation
near to syn-eclipsed with the CdBr3 unit directed towards the
side accommodating the amide pendant group. When viewed
along the Cd–P bond, the CdBr3 and PC3 units appear mutually
staggered, which apparently minimises their steric repulsion. The
orientation of the amide and CdBr3 group allows the formation
of the conformation-stabilising intramolecular hydrogen bond
N1–H1N · · · Br1 (Table 5). Consequently, the Cd–Br1 bond is
noticeably longer than the remaining Cd–Br bonds. The hydrogen
bonding is further facilitated by the rotation of the amide moiety
along the pivotal C6–C11 bond, which brings the NH group into
the vicinity of its H-bonding partner (the dihedral angle of the
{C11ON1} and Cp2 planes is 18.9(3)◦).
86
O–C11–N1
C11–N1–C24
uc
121.0(3)
121.2(2)
−13.8(4)
a The ring planes are defined as for the free ligand (see Table 1). b Torsion
angle C1–Cg1–Cg2–C6. c Torsion angle O–C11–N1–C24.
In the crystal, the chains form layers oriented parallel to the
The crystal assembly of 6·H2O fully exploits the hydrogen-
bonding ability of the solvating molecules (Fig. 7). Its key feature
are squares formed from inversion related pairs of the water and
ac plane via inter-chain N1-H1N · · · Br1i (N1 · · · Br1i 3.544(3)
ii
˚
[3.499(3)] A for 4 [5]; i. x, −y + 1/2, z + 1/2) and C–H(Ph) · · · O
ii
˚
hydrogen bonds (C · · · O 3.286(4) [3.276(5)] A; ii. x + 1, y, z).
=
complex molecules connected via four O–H · · · O C hydrogen
An entirely different, ‘mononuclear’ product 6 (Scheme 3) re-
sulted when the equimolar CdBr2·4H2O–2 mixture was crystallised
from a solvent mixture containing acetic acid. The compound is a
zwitterion, combining the positively charged protonated pyridine
bonds (Table 5). The squares further act as H-bond acceptors
through the water oxygen atoms for two pyridyl rings located in
complex molecules resulting by translation in the y direction.
The assembly is supported by C–H · · · Br contacts and p · · · p
stacking of the pyridyl rings (Table 5).
−
ring with the negatively charged CdBr3 unit, and crystallises
in the form of the monohydrate 6·H2O. Although the product
composition corresponds with the initial reaction stoichiometry,
only the half of the educts could be efficiently utilised in its
formation as the latter requires three bromide atoms per cadmium.
The view of the molecular structure of 6·H2O is shown in Fig. 6.
Selected geometric data are given in Table 4. The cadmium atom
is surrounded by four ligating atoms in a tetrahedral array at
distances similar to those in 4. However, unlike 4, the coordination
polyhedron is quite symmetric in both the Cd–donor distances and
the interligand angles. According to a search of the Cambridge
Crystallographic Database,19 zwitterionic complexes of the type
[Cd(II)Br3(L+)] are not unprecedented. However, the only two
entries to CSD include complexes possessing protonated N-
heterocycles in place of L+.20 Compound 6·H2O thus represents
Fig. 7 View of the crystal packing in 6·H2O, showing the hydrogen bonds
as dashed lines. The arrows indicate where the propagation of the sheet-like
assembly occurs. Symmetry operations: A (x, y, z), B (−x + 1, −y + 1,
−z), C (x, y + 1, z), and D (−x + 1, −y + 2, −z).
Complexes prepared from ligand 1
The reactions of 1 with CdBr2·4H2O and HgBr2 at 1:1 molar ratio
afforded defined crystalline adducts, the composition of which,
“MBr2(1)”, corresponds to the reaction stoichiometry. However,
the real structures as established by X-ray crystallography are
Fig. 6 PLATON plot of 6·H2O showing the labelling scheme. The solvent
molecule has been omitted for clarity. Displacement ellipsoids enclose the
30% probability level.
2458 | Dalton Trans., 2008, 2454–2464
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˚
Table 5 Hydrogen bond and p-stacking parameters for 6·H2O (in A
and ◦
)
a
Hydrogen bonding
interactions
D · · · A
D–H · · · A
Angle at H
152
168
154
170
N1–H1N · · · Br1
O1W–H1W · · · Oi
O2W–H2W · · · O
O1W–H2W · · · N2ii
C8–H9 · · · Br3iii
3.435(3)
2.817(3)
2.767(3)
2.651(3))
3.491(3)
132
p-Stacking of the parallel
aromatic rings
Cg · · · Cgꢀ
Ring
Pyridyl
Phenyl C(12–17)
Slippage
2.81
2.26
4.389(2)iv
4.317(2)v
a D = donor, A = acceptor. Symmetry codes: i. −x+1, −y + 1, −z; ii. x,
y − 1, z; iii. x, y + 1, z; iv. −x + 1, −y, −z; v. −x + 2, −y, −z + 1.
rather complicated owing to the formation of higher coordination
assemblies.
Thus, the cadmium(II) complex 7 is formally a tetramer
involving two types of cadmium centres with different coordi-
nation geometries and donor sets (Scheme 4). Nonetheless, the
compound is rather symmetric, crystallising with an imposed
crystallographic symmetry (inversion centre). Its central part is
constituted by a Cd2(l-Br)2 core. The octahedral coordination
Fig. 8 PLATON plot of the molecular structure of 7. The prime-labelled
atoms are generated by the symmetry operation (−x + 2, −y, −z). The
labelling scheme is analogous to that of the free ligand (labels of the
C-atoms in the bridging ligand are obtained by adding 50). For clarity, all
hydrogens and phenyl ring carbons except the pivotal ones are omitted.
The displacement ellipsoids enclose 20% probability.
=
around the cadmium atoms is completed by the C O oxygen
and pyridine nitrogen atoms from two ligands. One of the ligand
moieties further forms a bridge towards the terminal CdBr3 unit,
coordinating it trough its phosphine group. The other phosphine
group remains uncoordinated.
around the Cd1 atoms is slightly asymmetric in both the Cd–donor
distances (Cd–Br > Cd–O/N) and interligand angles (81.7(1)–
98.90(7)◦). The most significant deformation occurring at the
O2–N12 edge can be attributed to steric repulsion of the bulky
phosphinoferrocenyl moieties.
The CdBr3 end-group in 7 is structurally similar to that in 6·H2O,
showing uniform Cd–Br bond lengths and slightly more opened
Br–Cd–Br angles. Similarly to 6·H2O, the charged CdBr3 group
in 7 takes part in intermolecular interactions, forming hydrogen
The tetrameric complex 7 is formed reproducibly but apparently
persists only in the solid state. Dissolution leads to disintegration
of the assembly as evidenced by the signals of free phosphine group
in the 31P NMR spectrum and fragment peaks [CdBr(1)]+ as the
highest mass in ESI+ mass spectra.
The overall structure of 7 is depicted in Fig. 8 and a detailed view
of the dicadmium core is presented in Fig. 9. Selected geometric
data are summarised in Table 6. Starting from the centre of the
bonds with the amide NH groups in proximal molecules: N11–
◦
i
i
˚
H1N · · · Br3 (N11 · · · Br3 = 3.312(4) A, angle at H1N = 148 ;
i. x−1, y−1, z−1) and N21–H2N · · · Br4ii (N2 · · · Br4ii = 3.363(4)
◦
˚
molecule, the geometry of the Cd2Br2 unit is rather regular: The
A, angle at H2N = 151 ; ii. −x + 2, −y + 1,−z + 1). The amide
and pyridyl groups are either coordinated or deeply buried within
the complex structure and, hence, do not enter intermolecular
interactions.
ꢀ
˚
Cd–Br/Br bond lengths differ by as low as ca. 0.03 A, while
the in-square angles deviate by only ca. 9◦ with the Cd1–Br1–
Cd1ꢀ angle being the less acute. The coordination environment
Scheme 4
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◦
a
˚
Table 6 Selected geometric data for 7 (in A and
)
Internal part
2.7510(6)
2.323(3)
2.385(3)
85.61(2)
94.90(8)
98.90(7)
93.8(1)
Cd1–Br1
Cd1–O1
Cd1–N12
Cd1–Br1i
Cd1–O2
Cd1–N22
O1–Cd1–O2
Br1ꢀ–Cd1–O2
Br1ꢀ–Cd1–N12
Br1ꢀ–Cd1–N22
O2–Cd1–N12
O2–Cd1–N22
2.7796(6)
2.328(3)
2.358(3)
94.6(1)
84.87(8)
93.71(8)
93.6(1)
Br1–Cd1–Br1i
Br1–Cd1–O1
Br1–Cd1–N12
Br1–Cd1–N22
O1–Cd1–N12
O1–Cd1–N22
86.2(1)
86.4(1)
81.7(1)
86.8(1)
Peripheral parts
2.5689(8)
2.5637(6)
119.77(2)
111.66(3)
107.76(2)
Ligand moieties
Terminal
1.641(2)
1.643(2)
2.0(3)
Cd2–Br2
Cd2–Br3
Br2–Cd2–Br3
Br2–Cd2–Br4
Br3–Cd2–Br4
Cd2–Br4
Cd2–P2
P2–Cd2–Br2
P2–Cd2–Br3
P2–Cd2–Br4
2.5685(8)
2.589(1)
103.82(4)
100.90(3)
112.42(3)
Parameter
Bridging
1.642(2)
1.654(3)
2.2(3)
Fe1 or Fe2–Cg1
Fe1 or Fe2–Cg2
∠Cp1,Cp2
sb
131
164
C11–O1 or C61–O2
C11–N11 or C61–N21
O1–C11–N11 or O2–C61–N21
1.243(6)
1.336(5)
122.4(4)
1.253(5)
1.334(6)
122.4(4)
a The ring planes are defined as for the free ligand (see Table 1). Symmetry operations: i. −x + 2, −y, −z. b Torsion angle C1–Cg1–Cg2–C6.
Fig. 9 View of the dinuclear core in 7. The bulky phosphinoferrocenyl
groups and their coordinated CdBr3 units are omitted.
Fig. 10 PLATON plot of the molecular structure of 8. The prime labelled
atoms are generated by the symmetry operation (−x + 2, −y, −z + 1). The
hydrogen atoms have been omitted for clarity. The displacement ellipsoids
In the case of mercury, the molecular aggregation is less
correspond to the 30% probability level.
pronounced. The structure determination for 8 (Fig. 10 and
Table 7) revealed a centrosymmetric, doubly halide-bridged dimer
as commonly encountered among 1:1 phosphine–mercury(II)
◦
a
˚
halide complexes. Because of the unlike Hg–donor bonds lengths
and, particularly, steric demands of the ligands, the coordination
polyhedra around the mercury atoms are severely distorted. This
can be best demonstrated by the interligand angles among which
the P–Hg–Br1 angle (ca. 138◦) is markedly more opened than
the remaining ones (ca. 91–107◦). As expected, the Hg–Br bonds
involving the terminal bromides (Br1) are shorter than those
to bridging ones (by ca. 12%). In many respects, the dinuclear
core resembles those in the analogous complexes [{HgBr(l-Br)(L-
jP)}2], where L = Hdpf,18a and Ph2PfcPO3Et2.18b
Table 7 Selected geometric data for 8 (in A and
)
Hg–Br1
Hg–Br2
Hg–Br2ꢀ
Hg–P
2.4928(5)
2.7858(4)
2.8077(4)
2.429(1)
3.9298(2)
1.642(2)
1.649(2)
1.240(5)
1.346(5)
Br1–Hg–Br2
Br1–Hg–Br2ꢀ
Br2–Hg–Br2ꢀ
P–Hg–Br1
P–Hg–Br2
P–Hg − Br2ꢀ
∠Cp1,Cp2
sb
106.85(2)
104.38(1)
90.73(1)
137.91(2)
103.80(2)
103.36(2)
2.8(2)
Hg · · · Hgꢀ
Fe–Cg1
Fe–Cg2
C11–O
72
122.2(4)
C11–N1
O–C11–N1
a The ring planes are defined as for the free ligand (see Table 1). Symmetry
The ferrocene unit in 8 adopts an almost ideal syn-eclipsed
conformation and is oriented so that the PC3 and HgBr3 moieties
codes: i. −x + 2, −y, −z + 1. b Torsion angle C1–Cg1–Cg2–C6.
2460 | Dalton Trans., 2008, 2454–2464
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are eclipsed. The amide pendant, not involved in coordination,
extends away from the dimer centre unit while its pyridyl group
is forced below the ferrocene framework. Even so, the amide
plane is rotated from the Cp2 ring by 35.3(4)◦. This is the likely
consequence of intermolecular aggregation, as the amide moiety is
involved in N1-H1N · · · Oi hydrogen bonds (N1 · · · Oi = 2.896(4)
ice-cooled solution of Hpdf (2.070 g, 5.00 mmol) and 1-
hydroxybenzotriazole (HOBt; 0.811 g, 6.00 mmol) in dry
dichloromethane (50 mL). After stirring for 30 min at 0 ◦C, neat
4-(aminomethyl)pyridine (0.62 mL, 6.00 mmol) was added. The
cooling bath was removed and the stirring was continued at room
temperature overnight. Then, the reaction mixture was extracted
successively with 1% aqueous citric acid, saturated aqueous
NaHCO3, and brine. The organic layer was dried over MgSO4
and evaporated. The orange residue was purified by column
chromatography on silica gel eluting first with dichloromethane to
remove a small amount of unreacted active benzotriazolyl ester13a
and then with dichloromethane/methanol (40:1) to elute the major
band of the product. Evaporation of the second fraction gave pure
2 as an orange solid. Yield: 1.992 g (79%). The compound can be
recrystallised from wet ethyl acetate-hexane to afford the hydrate
◦
˚
A, angle at H1N = 162 , i. x,−y + 1/2, z−1/2), resulting into the
formation of columnar stacks from the dimeric complex units.
The pyridyl nitrogens show no significant intermolecular contacts.
Conclusions
Phosphinoamides 1 and 2 are versatile ligands, whose donor
properties can be fine-tuned through changing the substitution
patterns at the pyridyl ring. Their coordination variability is
further enhanced by the flexibility of the linking groups (ferrocene-
1,1ꢀ-diyl and methylene) that help in pre-arranging the donor
moieties into proper and spatially defined positions.
With mercury(II) and cadmium(II) bromides, the 4-pyridyl
isomer 2 forms one-dimensional coordination polymers while
its 2-pyridyl counterpart 1 gives rise to discrete oligonuclear
assemblies. As exemplified by the structure of 6·H2O, protonation
at the pyridyl nitrogen provides another means for modification
of the ligating ability of these ligands by blocking one of the
donor sites. The series of the structurally characterised compounds
clearly corroborates the preference of cadmium for higher (and
variable) coordination numbers and ability to accommodate
hard donors. It also demonstrates the tendency of the prepared
coordination compounds to form well defined supramolecular
(crystal) assemblies by means of hydrogen bonds, the nature of
which changes with the number and spatial distribution of the
moieties capable of hydrogen-bonding interactions.
◦
1
2·H2O. M.p. 76–77 C (ethyl acetate-hexane, 2·H2O). H NMR
(CDCl3): d 4.01 (vq, J = 1.9 Hz, 2 H, fc), 4.25 (vt, J = 2.0 Hz,
2 H, fc), 4.41 (vt, J = 1.8 Hz, 2 H, fc), 4.48 (d, 3JHH = 6.2 Hz, 2 H,
CH2), 4.63 (vt, J = 2.0 Hz, 2 H, fc), 6.39 (t, 3JHH = 5.8 Hz, 1 H,
NH), 7.24 (m, 2 H, C5H4N), 7.28–7.38 (m, 10 H, PPh2), 8.49 (m,
1
2 H, C5H4N). 13C{ H} NMR (CDCl3): d42.43 (CH2), 69.76 (d, J =
1 Hz), 71.64 (2 × CH of fc); 72.62 (d, JPC = 4 Hz), 74.29 (d, JPC
=
1
13 Hz) (2 × CH of fc); 76.12 (Cipso of fc), 77.20 (d, JPC = 7 Hz,
Cipso of fc), 122.55 (CH of C5H4N), 128.34 (d, JPC = 7 Hz), 128.86,
133.43 (d, JPC = 20 Hz) (3 × CH of PPh2); 138.11 (d, 1JPC = 9 Hz,
Cipso of PPh2), 147.92 (Cipso of C5H4N), 149.96 (CH of C5H4N),
1
1
170.30 (C O). 31P{ H} NMR (CDCl3): d −16.9. 31P{ H} NMR
=
−1
=
(DMSO): d−18.3. IR (Nujol, m/cm ): 1643 (vs) (C O), 1603 (w),
1563 (w), 1539 (s), 1298 (vs), 1159 (s), 1092 (w), 1066 (w), 1027 (s),
1005 (w), 993 (w), 904 (w), 813 (s), 744 (s), 696 (s), 568 (w), 535
(w), 493 (s), 480 (s), 443 (s). Anal. calc. for C29H25FeN2OP·H2O
(522.3): C 66.68, H 5.21, N 5.36%. Found: C 66.51, H 5.18, N
4.97%.
Experimental
Preparation of 1-(diphenylphosphinoyl)-1ꢀ-{N-[(4-pyridyl)meth-
yl]carbamoyl}ferrocene (3). Aqueous hydrogen peroxide (2 mL
of 30% solution) was added to a stirred solution of 2 (150 mg,
0.297 mmol) in acetone (9 mL). Stirring was continued for 3.5 h
at room temperature, followed by addition of water (20 mL).
Acetone was removed under vacuum and the aqueous residue
was extracted with chloroform. The organic phase was dried
(MgSO4) and evaporated. The crude product purified by column
chromatography (silica gel, dichloromethane/methanol 20:1) and
crystallised from wet ethyl acetate-hexane to afford analytically
3·H2O as an orange crystalline solid. Yield: 101 mg (65%). M.p.:
109–111 ◦C. 1H NMR (CDCl3): d 3.91 (vq, J = 1.9 Hz, 2 H, fc),
4.17 (vt, J = 1.9 Hz, 2 H, fc), 4.51 (vq, J = 1.8 Hz, 2 H, fc), 4.52 (d,
3JHH = 6.2 Hz, 2 H, CH2), 5.09 (vt, J = 1.9 Hz, 2 H, fc), 7.38 (m,
2 H, C5H4N), 7.45–7.71 (m, 10 H, PPh2), 8.27 (m, 2 H, C5H4N),
The synthesis of 2 was performed under an argon atmosphere.
All other experiments were carried out in the air. Hdpf10 and 115
were prepared by the literature procedures (for 1: 31P{ H} NMR
1
(DMSO): d −18.2). Dichloromethane and chloroform were dried
over anhydrous potassium carbonate and distilled. Acetonitrile
and methanol were freshly distilled. Other chemicals and solvents
for crystallisations and chromatography were used as purchased.
Melting points were determined on a Kofler apparatus. NMR
spectra were measured on a Varian UNITY Inova 400 spec-
trometer at 298 K. Chemical shifts (d/ppm) are given relative
to internal SiMe4 (1H and 13C) or external 85% H3PO4 (31P). In
addition to standard notation, vt and vq are used to distinguish
virtual multiplets due to magnetically non-equivalent AAꢀBBꢀ
and AAꢀBBꢀX spin systems of the amide- and phosphorus-
substituted cyclopentadienyl rings, respectively (fc = ferrocene-
1,1ꢀ-diyl). IR spectra were recorded with an FT IR Nicolet Magna
760 instrument. Electrospray (ESI) mass spectra were recorded on
a Bruker Esquire 3000 spectrometer on methanol solutions.
1
9.62 (t, 3JHH = 6.5 Hz, 1 H, NH). 13C{ H} NMR (CDCl3): d 42.59
(CH2), 70.67, 70.87 (2 × CH of fc); 72.57 (d, JPC = 10 Hz, CH of
fc), 73.57 (d, 1JPC = 114 Hz, Cipso of fc), 74.87 (d, JPC = 13 Hz, CH
of fc), 78.29 (Cipso of fc), 123.39 (CH of C5H4N), 128.55 (d, JPC
=
13 Hz), 131.46 (d, JPC = 10 Hz), 132.12 (d, JPC = 3 Hz) (3 × CH
of PPh2); 132.60 (d, 1JPC = 108 Hz, Cipso of PPh2), 148.62 (Cipso of
Syntheses
1
C5H4N), 149.66 (CH of C5H4N), 170.21 (C O). 31P{ H} NMR
=
Preparation of 1-(diphenylphosphino)-1ꢀ-{N-[(4-pyridyl)methyl]-
carbamoyl}ferrocene (2). N-(3-dimethylaminopropyl)-Nꢀ-ethyl-
carbodiimide (EDC; 0.931 g, 6.00 mmol) was added to an
(CDCl3): d32.6. IR (Nujol, m/cm−1): 3446 (w), 3391 (w), 3248 (m),
1677 (m), 1634 (vs), 1602 (s), 1552 (vs), 1305 (vs), 11198 (s), 1186
(vs), 1166 (vs), 1123 (s), 1101 (s), 1074 (m), 1058 (m), 1036 (s), 1028
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(m), 996 (m), 901 (m), 840 (s), 784 (m), 767 (s), 755 (s), 706 (s),
637 (m), 668 (s), 526 (s), 607 (m), 481 (s), 466 (m). Anal. calc. for
C29H25FeN2O2P·H2O (538.3): C 64.70, H 5.06, N 5.20%. Found:
C 64.46, H 4.99, N 5.04%.
m/cm−1): 3430 (w), 3310 (m), 1622 (vs), 1537 (s), 1497 (m), 1280
(m), 1237 (s), 1168 (s), 1068 (w), 1034 (m), 1026 (m), 998 (m),
984 (m), 855 (m), 843 (m), 778 (m), 749 (s), 693 (s), 535 (w),
511 (m), 483 (m). ESI+ MS: m/z 697 ([6–2Br–H]+). Anal. calc.
for C29H26Br3CdFeN2OP·H2O (875.5): C 39.78, H 3.22, N 3.20%.
Found: C 39.84, H 3.11, N 3.20%.
Preparation of [CdBr2(l-Ph2PfcC(O)NHCH2(4-C5H4N))]n (4).
A solution of amide 2 (25 mg, 0.05 mmol) in chloroform (3 mL)
was carefully layered with methanol (1.5 ml) and then with a
methanol solution of CdBr2 · 4H2O (17 mg, 0.05 mmol in 5 mL).
After standing for two weeks, the resulting orange solution was
filtered and the filtrate was evaporated under vacuum. The solid
residue was redissolved in chloroform and layered with hexane.
Crystallization by diffusion over several weeks afforded 4 as an
orange microcrystalline solid. Yield: 29 mg (75%). 1H NMR
(DMSO): d 4.05 (vq, J = 1.8 Hz, 2 H, fc), 4.17 (vt, J = 1.9 Hz,
2 H, fc), 4.36 (vt, J = 1.8 Hz, 2 H, fc), 4.39 (d, 3JHH = 6.0 Hz, 2 H,
CH2), 4.77 (vt, J = 1.9 Hz, 2 H, fc), 7.28–7.42 (m, 12 H, PPh2 and
Preparation of 7. A solution of amide 1 (25 mg, 0.05 mmol) in
chloroform (1 mL) was layered with methanol (0.5 mL) and then
with a methanol solution of CdBr2 · 4H2O (17 mg, 0.05 mmol in
5 mL). Orange crystals of 7 that formed after several days were
filtered off, washed with methanol and diethyl ether, and dried
under reduced pressure. Yield: 27 mg (70%). 1H NMR (DMSO):
4.07 (vq, J = 1.9 Hz, 2 H, fc), 4.15 (vt, J = 1.9 Hz, 2 H, fc), 4.40
(vt, J = 1.8 Hz, 2 H, fc), 4.46 (d, 3JHH = 6.1 Hz, 2 H, CH2), 4.77
(vt, J = 2.0 Hz, 2 H, fc), 7.25 (ddd, JHH = 7.4, 4.9, 1.1 Hz, 1 H,
C5H4N), 7.28–7.40 (m, 11 H, PPh2 and C5H4N), 7.73 (ddd, JHH,1
≈
JHH,2 ≈ 7.6, JHH,3 = 1.9 Hz, 1 H, C5H4N), 8.44 (t, 3JHH = 6.1 Hz, 1
3
C5H4N), 8.49 (m, 2 H, C5H4N), 8.64 (t, J = 6.0 Hz, 1 H, NH).
1
H, NH), 8.49 (ddd, JHH = 4.8, 1.8, 1.0 Hz, 1 H, C5H4N). 31P{ H}
1
31P{ H} NMR (DMSO): d −18.2. IR (Nujol, m/cm−1): 3309 (m),
NMR (DMSO): d−18.1. IR (Nujol, m/cm−1): 1589 (vs), 1549 (vs),
1193 (m), 1165 (m), 1157 (m), 1105 (w), 838 (s), 827 (m), 772 (m),
743 (m), 730 (s), 695 (s), 622 (m), 539 (m), 512 (m), 500 (m), 488
(s), 458 (m), 447 (m). ESI+ MS: m/z 697 ([CdBr(1)]+). Anal. calc.
for C29H25Br2CdFeN2OP·0.3CHCl3 (812.3): C 43.32, H 3.14, N
3.45%. Found: C 43.40, H 3.07, N 3.23%.
1628 (vs), 1615 (s), 1545 (vs), 1225 (m), 1171 (m), 1102 (m), 1067
(m), 1021 (m), 840 (m), 748 (s), 698 (m), 693 (s), 499 (m), 471 (s).
ESI+ MS: m/z 505 ([2 + H]+), 527 ([2 + Na]+), 543 ([2 + K]+).
Anal. calc. for C29H25Br2CdFeN2OP (776.5): C 44.85, H 3.25, N
3.61%. Found: C 44.58, H 3.19, N 3.39%.
Preparation of [HgBr2{l-Ph2PfcC(O)NHCH2(4-C5H4N)}]n (5).
A solution of the amide (25 mg, 0.05 mmol) in chloroform (1 mL)
was carefully layered with methanol (0.5 mL) and then with a
methanol solution of HgBr2 (18 mg, 0.05 mmol in 5 mL). Orange
crystals formed during several days. Filtration of these crystals,
washing with methanol, diethyl ether, and drying under vacuum
Preparation of [{Hg(l-Br)Br(Ph2PfcC(O)NHCH2(2-C5H4N)-
jP)}2] (8). A solution of amide 1 (25 mg, 0.05 mmol) in
chloroform (2 mL) was layered with methanol (1.5 mL) and
then with a methanol solution of HgBr2 (18 mg, 0.05 mmol in
3 mL). A microcrystalline yellow-orange solid was obtained after
two days. It was isolated, washed with methanol and diethyl ether,
1
gave pure 5. Yield: 35 mg (81%). H NMR (DMSO): d 4.34 (d,
1
3JHH = 6.1 Hz, 2 H, CH2), 4.38 (m, 2 H, fc), 4.58 (m, 2 H, fc), 4.67
(m, 2 H, fc), 4.81 (vt, J = 1.9 Hz, 2 H, fc), 7.29 (m, 2 H, C5H4N),
and dried under reduced pressure. Yield of 8: 32 mg (74%). H
NMR (DMSO): d 4.36 (m, 2 H, fc), 4.43 (d, 3JHH = 6.2 Hz, 2 H,
CH2), 4.65 (m, 4 H, fc), 4.81 (vt, J = 1.9 Hz, 2 H, fc), 7.29 (m, 2 H,
C5H4N), 7.52–7.70 (m, 10 H, PPh2), 7.77 (ddd, JHH,1 ≈ JHH,1 ≈ 7.7,
JHH,3 = 1.8 Hz, 1 H, C5H4N), 8.46–8.53 (m, 2 H, C5H4N and NH).
7.57–7.69 (m, 10 H, PPh2), 8.51 (m, 2 H, C5H4N), 8.55 (t, 3JHH
=
6.1 Hz, 1 H, NH) 31P{ H} NMR (DMSO): d 26.8 (bs). IR (Nujol,
m/cm−1): 1628 (vs), 1548 (vs), 1223 (m), 1173 (m), 1102 (m), 1068
(m), 1029 (m), 841 (m), 749 (s), 716 (m), 700 (m), 692 (m), 521 (m),
507 (m), 500 (m), 472 (s). ESI+ MS: m/z 785 ([HgBr(2)]+). Anal.
calc. for C29H25Br2HgFeN2OP·CHCl3 (984.1): C 36.61, H 2.66, N
2.85%. Found: C 36.61, H 2.58, N 2.75%.
1
1
31P{ H} NMR (DMSO): d 26.3 (br s). IR (Nujol, m/cm−1): 1638
(vs), 1586 (m), 1569 (m), 1545 (vs), 1435 (s), 1411 (s), 1303 (vs),
1183 (s), 1172 (w), 1099 (m), 1063 (m), 1036 (m), 999 (m), 988 (m),
851 (s), 822 (s), 761 (s), 746 (m), 740 (s), 689 (s), 651 (m), 622 (m),
548 (m), 536 (m), 516 (s), 504 (vs), 492 (s), 476 (s), 461 (m). ESI+
MS: m/z 785 ([HgBr(1)]+). Anal. calc. for C58H50Br4Hg2Fe2N4O2P2
(1729.5): C 40.28, H 2.91, N 3.24%. Found: C 39.78, H 2.79, N
3.05%.
Preparation of [CdBr3(Ph2PfcC(O)NHCH2(4-C5H4NH)-jP)]·
H2O (6·H2O). CdBr2·4H2O (17 mg, 0.05 mmol) was dissolved
in a mixture of acetic acid/water (0.25/0.10 mL) and diluted with
acetic acid (1.5 mL). This solution was layered with acetonitrile
(1 mL) and then with an acetonitrile solution of amide 2 (25 mg,
0.05 mmol in 5 mL). The clear orange solution, which resulted in
three days, was filtered and layered with hexane. Orange crystals
grew within few days at the boundary layer of the biphasic system
and fell down to the bottom of the reaction vessel. This process
of “crystal growing” requires several days (typically slightly more
than one week). The separated crystals were isolated by suction,
washed with methanol, diethyl ether, and dried under reduced
X-Ray crystallography†
Single-crystals of the ligands were grown by crystallisation
from ethyl acetate-hexane (2·H2O: orange block, 0.09 × 0.13 ×
0.21 mm3) and from CDCl3-hexane (3·H2O: orange prism, 0.15 ×
0.20 × 0.57 mm3). Crystals of the complexes were selected directly
from the reaction batches (4: orange plate, 0.08 × 0.15 × 0.18 mm3;
5: orange block, 0.08 × 0.23 × 0.25 mm3; 6·H2O: orange plate,
0.10 × 0.18 × 0.25 mm3; 7: orange plate, 0.08 × 0.20 × 0.25 mm3;
and 8: orange plate, 0.03 × 0.17 × 0.25 mm3).
1
pressure to afford pure 6·H2O. Yield: 18 mg (82%). H NMR
(DMSO): d 4.08 (vq, J = 1.9 Hz, 2 H, fc), 4.20 (vt, J = 1.9 Hz,
2 H, fc), 4.41 (vt, J = 1.8 Hz, 2 H, fc), 4.58 (d, JHH = 6.0 Hz,
Full-set diffraction data (
h
k
l, 2h ≤ 53–56◦) were col-
3
2 H, CH2), 4.77 (vt, J = 1.9 Hz, 2 H, fc), 7.27–7.41 (m, 10 H,
PPh2), 7.82 (m, 2 H, C5H4N), 8.64 (t, 3J = 6.0 Hz, 1 H, NH), 7.78
lected either on an Oxford Diffraction XCalibur 2 diffractometer
equipped with CCD detector Sapphire 2 (2·H2O) or on a Nonius
KappaCCD diffractometer (all other). All measurements were
1
(m, 2 H, C5H4N). 31P{ H} NMR (DMSO): d −18.1. IR (Nujol,
2462 | Dalton Trans., 2008, 2454–2464
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performed at 150(2) K and with graphite-monochromatised Mo
˚
Ka radiation (k = 0.71073 A). When appropriate, the data were
corrected for absorption using the methods incorporated in the
diffractometer software. Details on the data collection, structure
solution and refinement are given in Table 8.
The structures were solved by direct methods (SIR-9721) and
refined by full-matrix least-squares routine on F2 (SHELXL9722).
The non-hydrogen atoms were refined with anisotropic displace-
ment parameters. The amide (NH) and water hydrogens were
located on the difference electron density maps and refined as
riding atoms. All other hydrogen atoms were included in calculated
positions and refined as riding atoms.
Final geometric calculations were performed with a recent
version of Platon program.23,24 CCDC reference numbers are given
in Table 8.
Acknowledgements
This work is as a part of the long-term research projects
supported by the Ministry of Education of the Czech Republic
(no. MSM0021620857 and LC06070).
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2464 | Dalton Trans., 2008, 2454–2464
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The Royal Society of Chemistry 2008
©