Synthesis and structural characterisation of 1’-(diphenylphosphino)ferrocene-1-phosphonic acid, its ammonium salts and Pd(II) complexes

Article abstract of DOI:10.1016/j.jorganchem.2019.04.012

A new polar phosphinoferrocene ligand, viz. 1’-(diphenylphosphino)ferrocene-1-phosphonic acid (H₂L), was prepared by hydrolysis of the corresponding phosphonate ethyl ester. However, the compound is relatively unstable, gradually decomposing up

Full text of DOI:10.1016/j.jorganchem.2019.04.012

Accepted Manuscript
Synthesis and structural characterisation of 1’-(diphenylphosphino)ferrocene-1-
phosphonic acid, its ammonium salts and Pd(II) complexes
Filip Horký, Ivana Císařová, Jiří Schulz, Petr Štěpnička
PII:
S0022-328X(19)30146-9
DOI:
https://doi.org/10.1016/j.jorganchem.2019.04.012
JOM 20762
Reference:
To appear in: Journal of Organometallic Chemistry
Received Date: 1 March 2019
Revised Date: 28 March 2019
Accepted Date: 11 April 2019
Please cite this article as: F. Horký, I. Císařová, Jiří. Schulz, P. Štěpnička, Synthesis and structural
characterisation of 1’-(diphenylphosphino)ferrocene-1-phosphonic acid, its ammonium salts
and Pd(II) complexes, Journal of Organometallic Chemistry (2019), doi: https://doi.org/10.1016/
j.jorganchem.2019.04.012.
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ACCEPTED MANUSCRIPT
Synthesis and structural characterisation of 1’-(diphenylphosphino)ferrocene-1-phosphonic
acid, its ammonium salts and Pd(II) complexes
Filip Horký, Ivana Císařová, Jiří Schulz and Petr Štěpnička*
Department of Inorganic Chemistry, Faculty of Science, Charles University, Hlavova 2030, 128 40
Prague, Czech Republic
* Corresponding author. E-mail address: petr.stepnicka@natur.cuni.cz
Abstract. A new polar phosphinoferrocene ligand, viz. 1’-(diphenylphosphino)ferrocene-1-
phosphonic acid (H2L), was prepared by hydrolysis of the corresponding phosphonate ethyl ester.
However, the compound is relatively unstable, gradually decomposing upon prolonged storage,
ultimately affording phosphine oxide H2LO. When the phosphine moiety was protected (e.g., in
phosphine oxide H2LO and adduct H2L·BH3), no decomposition was observed. An alternative
approach to prepare more stable H2L surrogates by converting the phosphonic acid into ammonium
salts (dabcoH)(HL) and [(OHCH2CH2)2NH2](HL) (dabco = 1,4-diazabicyclo[2.2.2]octane) resulted in
no significant stabilisation. H2L reacted with [PdCl2(cod)] (cod = cycloocta-1,5-diene), producing the
bis(phosphine) complex, trans-[PdCl2(H2L-κP)2]. When mixed with Pd(II)-acetylacetonate (acac)
complexes with ortho-metallated auxiliary ligands, [(LCY)Pd(acac)] (LCY = 2-[(dimethylamino-
κN)methyl]phenyl-κC1 and 2-[(methylthio-κS)methyl]phenyl-κC1), H2L gave rise to bis-chelate
complexes of the [(LCY)Pd(HL-κ2O,P)] type. H2L, the ammonium salts featuring the HL− anion, and
all Pd(II) complexes were structurally characterised by single-crystal X-ray diffraction analysis.
Variations in phosphonate P-O bond lengths observed in the crystal structures were rationalised by
DFT computations.
Keywords: Ferrocene; Phosphine ligands; Phosphonates; Palladium complexes; Structure elucidation;
DFT computations
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1. Introduction
Introducing polar moieties into phosphine molecules is a time-tested and efficient approach for the
design of new hydrophilic ligands [1]. In this regard, acidic functional groups such as carboxylate,
phosphonate and especially sulfonate are among the most frequently used polar moieties. Their
incorporation into phosphine molecules results in structurally versatile hybrid phosphine ligands with
diverse coordination modes and pH-dependent behaviour [2]. However, this approach has been used
less often in the chemistry of otherwise ubiquitous phosphinoferrocene ligands [3]. Examples of
functional ferrocene phosphines structurally analogous to the widely studied 1,1’-
bis(diphenylphosphino)ferrocene (dppf, Scheme 1) [4], include 1’-(diphenylphosphino)-1-
ferrocenecarboxylic acid (Hdpf) [5] and the recently reported phosphinoferrocene sulfonate A [6]
(Scheme 1). The analogous 1-(diphenylphosphino)-1-ferrocenephosphonic acid (H2L) has not yet been
reported, although diethyl 1’-(diphenylphosphino)-1-ferrocenephosphonate, the obvious precursor of
H2L, has already been prepared, used as a synthetic intermediate [7] and studied as a ligand in Group
12 metal complexes [8]. To expand the series of dppf-like phosphinoferrocene ligands featuring polar
acidic functional groups, we prepared H2L, an organometallic analogue of the triphenylphosphine
derivative B (Scheme 1) [9]. The synthesis and characterisation of H2L, its ammonium salts and
palladium(II) complexes are reported in this paper.
Scheme 1. Polar phosphines relevant to this study
2. Results and discussion
2.1 Synthesis and characterisation of H2L, its derivatives and salts
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Acid H2L was obtained from a reaction of phosphonate ester 2 [8] with Me3SiBr followed by
hydrolysis [10] (Scheme 2). Even when carefully purified, the acid gradually decomposed at room
1
temperature and at 4°C. Decomposition is first manifested as sample darkening and broadening of H
NMR signals. Later, the 31P NMR spectra show resonances due to the corresponding phosphine oxide
(δP 16.5 and 31.7 in dmso-d6). Partly decomposed samples of H2L could be purified by column
chromatography (silica gel, chloroform-methanol 10:1), which removed a faster eluting brown band
containing unknown decomposition products, followed by an orange band due to H2L and, finally, a
slowly moving band containing phosphine oxide H2LO. H2L was also crystallised from ethyl acetate.
However, this crystallisation was associated with a substantial loss of crude material and produced
easily decomposing, orange crystals.
Scheme 2. Synthesis of H2L, its borane adduct H2L·BH3 and phosphine oxide H2LO
Attempts to stabilise the phosphino-phosphonate by converting it into crystalline ammonium salts
were only partly successful. H2L neutralisation with 1 or 2.5 equiv. of 1,4-diazabicyclo[2.2.2]octane
(dabco) and diethanolamine (i.e., 2,2’-iminodiethanol) uniformly led to salts containing the singly
deprotonated anion HL−, (dabcoH)(HL) (5) and ((OHCH2CH2)2NH2)(HL) (6), respectively. Only such
salts were obtained, irrespective of the amount of base added, in line with the large differences
between the first and second dissociation constants of phosphonic acids (cf. pKa1 2.3, pKa2 7.6 for
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PhCH2PO3H2 [11]). Salts 5 and 6 were spectroscopically and crystallographically characterised, but
they nevertheless decomposed upon prolonged storage.
Notably, spontaneous decomposition of ferrocenephosphonic acids, such as FcCH2PO3H2, most likely
a self-catalysed oxidation, has already been reported [12]. However, the spontaneous decomposition of
the phosphine-substituted derivative H2L may be further complicated by processes involving the
phosphine moiety in which the primary decomposition products are converted into the phosphine
oxide H2LO. To confirm this assumption, the phosphine oxide H2LO and the phosphine-borane adduct
H2L·BH3 were prepared via H2O2-oxidation of H2L and analogously to H2L from the P-protected
precursor 3, respectively (Scheme 2). Both H2LO and H2L·BH3 showed no signs of decomposition
when stored at room temperature for weeks.
In the 1H NMR spectra, H2L and its P-modified derivatives display four signals due to chemically non-
equivalent ferrocene CH groups. These signals broaden into unresolved signals in the spectra of H2L
and H2LO, which also show multiplets due to the PPh2 moieties. The presence of the phosphonate
moiety is manifested as 31P NMR resonances at δP ≈ 17 ppm (in dmso-d6). The signal of the phosphine
moiety in H2L is observed at δP −17.4, whereas this signal appears characteristically shifted to lower
field in H2LO and H2L·BH3 (δP 31.7 and 15.6 ppm, respectively). H2L, its phosphine oxide, and the
borane adduct display the corresponding pseudomolecular ions ([M + H]+) in their ESI mass spectra.
The molecular structure of H2L is depicted in Figure 1. The compound crystallises unsolvated, with
the symmetry of the monoclinic space group P21/n and with one formula unit in the asymmetric unit.
The individual molecules in the crystal structure assemble via O-H···O hydrogen bonds, forming one-
dimensional chains along the crystallographic b axis (Figure 2).
Parameters describing the molecular geometry of H2L match those of the respective monofunctional
ferrocene derivatives, FcPO3H2 [13] and FcPPh2 [14] (Fc = ferrocenyl). The cyclopentadienyl rings in
the H2L molecule are essentially parallel (tilt angle: 0.8(1)°), indicating only minor variations in
individual Fe-C distances (2.033(2)-2.062(2) Å), and adopt an intermediate conformation between
anticlinal eclipsed and antiperiplanar staggered [4b] that brings the substituents to approximately
opposite (anti) positions, as shown by the τ angle (−165.7(1)°; N.B. τ is the dihedral angle C1-Cg1-
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Cg2-C6, where Cg1 and Cg2 are the centroids of the cyclopentadienyl rings C(1-5) and C(6-10),
respectively).
Figure 1. PLATON plot of the molecular structure of H2L showing atom labelling and displacement
ellipsoids at the 50% probability level.
Figure 2. Section of the hydrogen-bonded assembly in the structure of H2L; for clarity, only OH
hydrogens are shown. H-bond parameters: O2···O1 = 2.572(2) Å, O3···O1 = 2.630(2) Å.
Table 1. Selected distances and angles for H2L, 5 and 6 (in Å and deg)
Parameter
P-O1
H2L
5a
6b
1.510(1)
1.550(1)
1.554(2)
111.35(7)
111.30(8)
1.505(3)
1.509(2)
1.578(3)
116.4(2)
106.5(2)
1.498(1)
1.519(1)
1.577(1)
115.48(6)
108.53(6)
P-O2
P-O3
O1-P1-O2
O1-P1-O3
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O2-P1-O3
P1-C1
108.08(8)
111.5(1)
1.800(3)
1.810(3)
1.837(3)
1.840(3)
−139.6(2)
109.01(6)
1.787(1)
1.820(2)
1.839(2)
1.835(2)
1.753(2)
1.818(2)
1.832(2)
1.840(2)
−165.7(1)
P2-C6
P2-C11
P2-C17
τ
85.4(1)
a
b
Further data: N-C distance range in (dabcoH)+ = 1.457(6)-1.499(5) Å. Further data: N-C23
1.492(2), N-C25 1.496(2), O4-C24 1.429(2), O5-C26 1.417(2), C23-N-C25 113.8(1).
In addition to free H2L, the crystal structures of salts 5 and 6 were also solved. The molecular
structures of the salts are depicted in Figure 3, and the selected geometric parameters are outlined in
Table 1.
Figure 3. PLATON plots of the molecules structures of 5 (top) and 6 (bottom); displacement
ellipsoids correspond to the 50% probability level.
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The ferrocene moieties in the structures of 5 and 6 adopt their regular geometries, showing only
insignificant tilting (2.8(2)° in 5, and 2.9(1)° in 9). However, they have different conformations. While
the ferrocene substituents in 5 adopt rather distant positions, those in 6 are rotated closer to each other
(cf. the τ angles in Table 1). Notably, the deprotonation of the phosphonate groups markedly
differentiates the P-O bonds, presumably due to charge delocalisation. In both salts, the bonds
formally attributable to P=O and P-O− units (P1-O1 and P1-O2) are substantially shorter than the
bonds towards the OH groups (P1-O3). On the contrary, the P-O bond lengths of the free acid H2L
suggest the presence of one P=O (1.51 Å) and two P-O bonds (1.55 Å). Similar features can be
observed when converting phenylphosphonic acid [15] into ammonium salts of the (R2NH2)(PhPO3H)
type [16]. In addition, deprotonation of the phosphonate moiety results in a shortening of the pivotal
C1-P1 bond so that the sum of the C1-P1 and P1-O2 bond lengths remains virtually constant.
The shortening of the P-O2 bond distance, which can be attributed to resonance stabilization of the
negative charge by delocalization over the O1-P-O2 moiety, is well reproduced by DFT computations
(Table 2). The Mayer bond indices (MBIs) calculated for ferrocenylphosphonic acid and the
corresponding monoanion as model compounds at the M06/def-TZVP:sdd(Fe) level of theory support
this explanation, revealing the significantly increased bond order of the P-O2 bond (1.863) and the
slightly decreased bond order of the P-O1 bond (1.818). Consequently, P-O1 and P-O2 bonds have
very similar lengths, shorter than the remaining P-OH bond. The calculated charges, which are very
similar at the three oxygen atoms in FcPO3H2, somewhat differentiate upon deprotonation. The largest
negative charge in FcPO3H− is found at the O2 oxygen atom, as expected.
Table 2. Calculated bond distances, Mayer bond indices (MBIs) and Merz-Kollman charges (MKs) at
the oxygen atoms
Compound
FcPO3H2
Bond
P-O1
P-O2
P-O3
Bond distance [Å] MBIs
MKs
–0.63
–0.62
–0.58
1.462
1.602
1.590
1.961
1.153
1.169
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P-O1
P-O2
P-O3
1.481
1.485
1.649
1.818
1.863
0.982
–0.73
–0.79
–0.69
FcPO3H−
Salts 5 and 6 incorporated molecules of halogenated solvents, used during the crystallisation, in their
structures. Unfortunately, the solvent molecules were severely disordered within the structural voids
and had to be eliminated from the structure model (see Experimental). Notably, the crystal assembly
of the ions that form the structure of salt 5 is relatively simple (Figure 4), reflecting the prevalence of
H-bond acceptors over conventional H-bond donors (OH, NH). Specifically, the anions HL− associate
into dimers around crystallographic inversion centres through charge-supported O-H···O− hydrogen
bonds (O2···O3 = 2.533(4) Å), while the phosphoryl oxygens O1 form additional hydrogen bonds
with the NH groups of the adjacent cations (dabcoH)+ (O1···N1 = 2.597(4) Å). Conversely, the
supramolecular assembly of 6 is relatively complex due to the presence of additional H-bond donors in
the structure (Figure 5). Similarly to 5, the phosphonate moieties form dimeric units via the O3-
H···O2 interactions, whose midpoints coincide with the crystallographic inversion centres (O2···O3 =
2.554(1) Å). Furthermore, each phosphonate moiety acts as a hydrogen bond acceptor for a proximal
ammonium cation, forming two O-H···O bonds (O4···O2 = 2.669(2) Å, O5···O1 = 2.696(1) Å) and
one relatively longer N-H···O hydrogen bond (N2···O1 = 3.054(2) Å). The resulting
{(OHCH2CH2)2NH2}2{HL}2 motifs are interlinked into a two-dimensional array by additional N-
H···O interactions towards the P=O oxygen (N···O1 = 2.853(2) Å) and by N-H···OH interactions
(N···O4 = 2.902(2) Å).
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Figure 4. Hydrogen-bonded dimers in the crystal structure of 5; only NH hydrogens are shown for
clarity.
Figure 5. Section of the hydrogen-bonded assembly in the crystal structure of 6; for clarity, the bulky
phosphinoferrocenyl moieties are replaced with black boxes, and only the NH and OH hydrogens are
shown. The arrows indicate lateral propagation of the columnar arrays.
2.2 Preparation and characterisation of Pd(II) complexes
A series of Pd(II) complexes [17] was prepared and structurally characterised to study the coordination
behaviour of H2L. Various Pd(II) precursors were used in the testing reactions, differing in supporting
ligands and in the number of accessible coordination sites at the central Pd(II) ion, including those that
may possibly assist in the H2L conversion into a phosphino-phosphonate anion. Thus, the reaction of
H2L with [PdCl2(cod)] (cod = cycloocta-1,5-diene) produced the bis(phosphine) complex 7 (Scheme
3). The compound is relatively unstable, readily decomposing in solution, which in turn complicates
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the characterisation of the compound and its purification. For instance, attempts to purify 7 by
crystallization typically resulted in massive losses of the material.
Scheme 3. Synthesis of the bis(phosphine) complex 7 (cod = cycloocta-1,5-diene)
1
The H NMR spectra of 7 display broad signals due to the ferrocene and PPh2 fragments at the
expected positions, and the coordination of the phosphine moiety is manifested as a shift of the 31P
NMR resonance to a lower field (δP 17.0 ppm; N.B. the signals due to the phosphonate moiety is
observed as a broad singlet at δP 18.0). Repeated attempts to obtain crystalline material suitable for X-
ray diffraction analysis eventually afforded crystals of the stoichiometric solvate 7·3EtOH from
ethanol/diethyl ether (Figure 6). The geometry of the coordination sphere around Pd(II) is similar to
that of the formally parent compound trans-[PdCl2(FcPPh2-κP)2] [6a], and the parameters of the
independent but chemically equivalent halves of the complex molecule differ only marginally. The
bulky phosphinoferrocene ligands occupy mutually opposite positions, highlighting the near
centrosymmetric arrangement of the complex (accordingly, the phosphonate units are directed away
from the ligated metal centre with τ(Fe1) and τ(Fe2) of −145.0(1)° and 139.7(1)°). In turn, this
suggests that the relatively lower symmetry of the complex molecule results from intermolecular
interactions and from the overall symmetry of the crystal array rather than from any intrinsic
asymmetry (e.g., in ligand coordination).
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Figure 6. View of the complex molecule in the structure of 7·3EtOH. Displacement ellipsoids at the
50% probability level. Selected distances and angles (in Å and deg): Pd-Cl1 2.2989(5), Pd-Cl2
2.2980(5), Pd-P2 2.3440(4), Pd-P4 2.3328(4), Cl1-Pd-P2 88.04(2), Cl1-Pd-P4 92.19(2), Cl2-Pd-P2
92.90(2), Cl2-Pd-P4 86.87(2), P1-O1 1.502(1), P1-O2 1.556(1), P1-O3 1.547(1), P1-C1 1.768(2), P2-
C6 1.802(1), P2-C11 1.830(1), P2-C17 1.818(1), P3-O4 1.501(1).
In the crystal, ferrocene ligands from different complex molecules pair into dimers through (O-
H···O=P)2 interactions involving their uncoordinated phosphonate groups. These fragments further
assemble into infinite chains via interactions between the remaining phosphonate OH moieties and the
solvating ethanol molecules (Figure 7). The phosphoryl oxygen atoms (P=O) serve as additional H-
bond acceptors for these interactions. When combined, hydrogen bond interactions give rise to layers
oriented parallel to the crystallographic (1 1 1) planes.
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Figure 7. Section of the hydrogen-bonded assembly in the structure of 7·3EtOH. Only the OH
hydrogens and the pivotal atoms from the phenyl rings are shown for clarity. Hydrogen bond
parameters (in Å): O2···O4 2.559(2) Å, O3···O1S 2.502(2), O5···O2S 2.488(2), O6···O1 2.616(2),
O1S···O1 2.669(2), O2S···O3S 2.622(2), O3S···O4 2.712(2).
When mixed with Pd(II) acetylacetonate (acac) complexes containing supporting ortho-palladated
ligands, viz. [(LCY)Pd(acac)], where LCY = 2-[(dimethylamino-κN)methyl]phenyl-κC1 and 2-
[(methylthio-κS)methyl]phenyl-κC1, H2L produced the neutral bis-chelate complexes 8 and 9 (Scheme
4), formed through proton transfer from H2L to the acetylacetonate ligand and through O,P-chelating
coordination of the formed anion HL−.
Scheme 4. Synthesis of Pd(II) complexes with supporting ortho-metallated ligands (Hacac =
acetylacetone).
1
Compounds 8 and 9 result as yellow solids and are stable under ambient conditions. Their H and 13C
NMR spectra display signals attributable to the ferrocene phosphino-phosphonate and to the respective
ortho-metallated ligand. The resonances due to the CH2SMe/CH2NMe2 arms are split into 31P-coupled
doublets, thus suggesting a trans-P,N/S relationship for both compounds. The 31P NMR signals
attributable to the Pd-bound phosphine moieties are identified (in CDCl3) as singlets at δP 29.1 and
26.2 ppm for 8 and 9, respectively, whereas the resonances of the O-coordinated PO3H− units are
found at δP 19.2 (8) and 19.9 ppm (9) (i.e., shifted to a higher field in relation to H2L itself; δP 26.7
ppm in CDCl3). ESI MS spectra further corroborate the formulation of 8 and 9, showing [M + H]+
ions.
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Complexes 8 and 9 crystallise relatively willingly but tend to incorporate disordered solvent molecules
in their crystals (see Experimental). In addition, compound 8 crystallizes with two structurally
independent but otherwise very similar molecules in the asymmetric unit (space group P−1; for an
overlap, see the Supporting Information, Figure S1). Views of the molecular structures of 8 (molecule
1) and 9 are presented in Figure 8, and the relevant structural parameters are outlined in Table 3. The
Pd-donor distances and the interligand angles determined for 8 and 9 are generally similar to those
found in analogous complexes featuring O,P-chelating phosphinoferrocene sulfonate ligand
−
Ph2PfcSO3 [6a]. Similarly to phosphinosulfonate complexes, the Pd-P bond length in 9 is
significantly longer than in 8, thus reflecting a stronger trans influence of the sulfur donor [18]. The
coordination environments of the palladium(II) ions in 8 and 9 are distorted due to variations in
individual Pd-donor distances and to steric demands of the chelate rings. However, the degree of
distortion differs between the complexes. In 9, which features the larger sulfur donor atom, the angle
associated with the LCY chelating ligand is larger (i.e., departs less from the ideal 90°) but the
coordination plane is more severely twisted than in 8, as shown by the dihedral angle of the {Pd,O,P}
and {Pd,C,S} “half-planes” associated with the two chelate rings (16.09(7)°). The analogous angles
subtended by the {Pd,O,P} and {Pd,C,N} planes in 8 are only 6.28(9)° (Pd1) and 8.60(9)° (Pd2).
O,P-chelating coordination requires that the donor moieties of the phosphinophosphonate anion HL–
be rotated into positions closer than those found in the crystal structures discussed above (H2L, its salts
and complex 7). Consequently, the conformations of the 1,1’-disubstituted ferrocene units in 8 and 9
are between synclinal staggered (ideal value: 36°) and synclinal eclipsed (ideal value: 72°),
characterised by τ angles of 53.2(2)° (8, molecule 1), 42.9(2)° (8, molecule 2), and 39.6(1)° (9). In
addition, the deprotonation and coordination of the phosphonate group results in the differentiation of
the P-O distances, as observed in salts 5 and 6. In particular, the P=O and P-O(Pd) bonds of 8 and 9
are shorter than the P-OH bond involved in hydrogen bonding interactions.
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Figure 8. PLATON plots of the molecular structures of 8 (molecule 1) and 9 (molecule 2);
displacement ellipsoids at the 50% probability level.
Table 3. Selected distances and angles for 8 and 9 (in Å and deg)
Parameter
Pd-P
8 (molecule 1, Z = N)
2.2644(6)
8 (molecule 2, Z = N)
2.2494(6)
9 (Z = S)
2.3126(6)
2.145(2)
2.007(2)
Pd-O
2.137(2)
2.132(2)
Pd-C
2.001(2)
1.988(2)
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Pd-Z
2.142(2)
2.144(2)
89.28(5)
96.88(7)
92.86(7)
81.25(8)
1.504(2)
1.511(2)
1.573(2)
2.3292(6)
93.34(4)
97.87(6)
85.67(4)
84.98(6)
1.504(2)
1.512(2)
1.579(2)
P-Pd-O
P-Pd-C
Z-Pd-O
Z-Pd-C
P=O
90.68(4)
97.05(6)
91.36(7)
81.18(8)
1.506(2)
1.510(2)
1.579(2)
P-O(Pd)
P-OH
In the crystals of 8 and 9, the complex associates through pairs of O-H···O=P hydrogen bonds into
dimers around the crystallographic inversion centres (in 8, the dimers are formed between molecules 1
or 2 separately). The intermolecular O···O distances are 2.588(2) Å (O13···O11), 2.522(2) Å
(O23···O21) for 8, and 2.584(2) Å (O3 ···O1) for 9. Notably, both the symmetry of the crystal lattice
(space group P21/c) and even the particular supramolecular interactions indicate that complex 9, which
contains a stereogenic sulfur atom, is obtained in racemic form.
Figure 9. Hydrogen-bonded dimeric motif in the structure of 8 (molecule 1 interacts with its inversion
image); only OH hydrogens are shown for clarity.
3. Conclusion
1’-(Diphenylphosphino)ferrocene-1-phosphonic acid (H2L), a new addition into the family of polar
phosphinoferrocene ligands, can be prepared in a conventional manner from the corresponding
phosphonate ester. Although the compound is relatively unstable and spontaneously decomposes upon
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storage, it can be converted into acidic ammonium salts containing the anion HL− and used to prepare
transition metal complexes. While in its native form compound H2L coordinates soft Pd(II) ions as a
P-monodentate donor, deprotonation to HL− (e.g., by proton transfer to a suitable Pd-bound ligand)
opens a convenient access to O,P-chelated complexes. The phosphonate moieties in the free acid H2L,
its salts and even the Pd(II) complexes participate in intermolecular (or interionic) hydrogen-bonding
interactions. In turn, these interactions give rise to discrete or polymeric solid-state assemblies, whose
complexity changes with the number of the available hydrogen bond donors and acceptors. Overall,
the coordination behaviour of H2L resembles that of phosphinoferrocene sulfonate A rather than the
behaviour of the analogous phosphinocarboxylic ligand Hdpf, except that anion HL− resulting by
monodeprotonation of H2L retains one of its OH groups and can thus enter into hydrogen bonding
interactions as a H-bond donor.
4. Experimental
4.1 Materials and methods
All preparations were performed under an argon atmosphere using standard Schlenk techniques.
Compounds 2 [8], 3 [19], [(LNC)Pd(acac)] [20], and [(LYC)Pd(acac)] [21] were prepared according to
literature procedures. Other chemicals were purchased from commercial suppliers (Sigma-Aldrich,
Alfa-Aesar) and used as received. Anhydrous dichloromethane and THF were obtained using a
PureSolv MD5 solvent purification system (Innovative Technology, Inc., Amesbury, MA, USA).
Solvents for chromatography and crystallisations were of reagent grade (Lach-Ner, Czech Republic)
and used without any additional purification step.
1H, 31P{1H}, and 13C{1H} NMR spectra were recorded at 25°C with a Varian Unity Inova 400
1
spectrometer operating at 400, 101 and 162 MHz for H, 13C and 31P, respectively. Chemical shifts (δ
in ppm) are given relative to internal tetramethylsilane (1H and 13C) and to external 85% aqueous
H3PO4 (31P). In addition to the standard notation of signal multiplicity (s = singlet, d = doublet, t =
triplet, etc.) [22], vt and vq are used to distinguish virtual triplet and quartets arising from the second-
order spin systems formed by cyclopentadienyl hydrogens. FTIR spectra were acquired on a Thermo
Nicolet 6700 instrument over the 400-4000 cm−1 range. Electrospray ionization (ESI) mass spectra
16

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were recorded on a Compact QTOF-MS spectrometer (Bruker Daltonics) using samples dissolved in
HPLC-grade methanol. Elemental analyses were performed with a PE 2400 Series II CHNS/O
Elemental Analyser (Perkin Elmer). The amount of clathrated solvent (if present) was confirmed by
NMR analysis.
4.2 Synthesis of [1’-(diphenylphosphino)ferrocenyl]phosphonic acid (H2L)
Neat bromo-trimethylsilane (1.3 mL, 10 mmol) was added dropwise to a solution of ester 2 (1.67 g,
3.3 mmol) in dichloromethane (60 mL). The resulting mixture was stirred for 4 h and then evaporated
under vacuum. The residue was dissolved in dichloromethane (10 mL) and treated with water (0.5
mL) under vigorous stirring for 30 min. The resulting mixture was dried over MgSO4, filtered and
evaporated under vacuum to afford an orange oily residue, which was purified by column
chromatography over silica gel using chloroform-methanol (10:1) as eluent. A single orange band was
collected and concentrated. The product was dissolved in chloroform (3 mL) and precipitated by
adding an excess of hexane. The separated solid was filtered off, washed with hexane and dried under
vacuum, yielding H2L·0.5H2O as a pale orange powder (1.02 g, 67%). Crystals of unsolvated H2L
suitable for X-ray diffraction analysis were obtained from ethyl acetate-hexane.
1H NMR (dmso-d6): δ 3.75 (very br s, 2 H, PO3H2), 4.02 (br s, 2 H, fc), 4.11 (br s, 2 H, fc), 4.24 (br s,
2 H, fc), 4.57 (br s, 2 H, fc) 7.25−7.38 (m, 10 H, PPh2). 13C{1H} NMR (dmso-d6): δ 71.13 (d, JPC = 11
Hz, CH of fc), 71.50 (d, JPC = 15 Hz, CH of fc), 73.25 (d, JPC = 3 Hz, CH of fc), 73.44 (d, JPC = 15 Hz,
CH of fc), 75.80 (br d, JPC = 6 Hz, C-PPh2 of fc), 128.25 (d, JPC = 7 Hz, CH of PPh2), 128.55 (s, CH of
PPh2), 133.00 (d, JPC = 20 Hz, CH of PPh2), 138.73 (d, JPC = 11 Hz, Cipso of PPh2). The signal due to
ferrocene C–PO3H2 was not observed. 31P{1H} NMR (dmso-d6): δ –17.4 (s, PPh2), 17.3 (br s, PO3H2).
31P{1H} NMR (CDCl3): δ –16.0 (s, PPh2), 26.7 (br s, PO3H2). IR (Nujol): νmax 1654 br m, 1586 m,
1437 m, 1309 m, 1195 s, 1161 m, 1122 w, 1070 w, 1034 s, 997s, 641 w, 573 s, 487 s, 455 m cm−1. EI+
MS: m/z 451 ([M + H]+). Anal. Calc. for C22H20O3FeP2·0.5H2O (459.2): C 57.54, H 4.61%. Found: C
57.60, H 4.55%.
4.3 Synthesis of diethyl [1’-(diphenylphosphino)ferrocenyl]phosphonate−borane (1/1) (4)
17

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A stirring solution of 1-(diphenylphosphino)-1’-bromferrocene–borane (3; 1.85 g, 4.0 mmol) in dry
THF (150 mL) was cooled in a dry ice/ethanol bath to −78°C and treated with n-butyllithium (1.6 mL
of 2.5 M in hexanes, 0.44 mmol). After stirring the reaction mixture for 15 min, neat diethyl
chlorophosphate (0.8 mL, 0.55 mmol) was introduced, and the mixture was stirred at −78 °C for
another 15 min and then at room temperature for 3 h. Then, it was evaporated under reduced pressure,
and the residue was purified by column chromatography over alumina. Chloroform-diethyl ether (2:3)
was used to remove non-polar byproducts (mostly FcPPh2·BH3). Subsequent elution with chloroform-
diethyl ether (3:2) eluted ester 4. Yield: 1.39 g (60%), an orange oil.
1H NMR (CDCl3): δ 1.20 (br s, 3 H, BH3), 1.30 (t, 3JHH= 7.1 Hz, 6 H, CH3), 4.06 (q, 3JHH= 7.0 Hz, 4 H,
CH2), 4.38 (br s, 4 H, fc), 4.52 (vq, Jʹ = 1.7 Hz, 2 H, fc), 4.74 (vq, Jʹ = 1.0 Hz, 2 H, fc), 7.39-7.44 (m,
4 H, PPh2), 7.45-7.51 (m, 2 H, PPh2), 7.54-7.61 (m, 4 H, PPh2). 31P{1H} NMR (CDCl3): δ 16.3 (br d,
JPH = 55 Hz, PPh2BH3), 24.8 (s, PO3Et2). 13C{1H}: δ 16.43 (d, 3JPC = 6 Hz, CH3), 61.82 (d, 2JPC = 6 Hz,
CH2), 70.54 (d, JPC = 67 Hz, C-PO3Et2), 72.78 (d, JPC = 15 Hz, CH of fc), 73.84 (d, JPC = 13 Hz, CH of
fc), 74.05 (d, JPC = 10 Hz, CH of fc), 74.74 (d, JPC = 7 Hz, CH of fc), 128.50 (d, JPC = 10 Hz, CH of
PPh2), 130.82 (d, 1JPC = 82 Hz, Cipso of PPh2), 131.04 (d, JPC = 2 Hz, CH of PPh2), 132.60 (d, JPC = 9
Hz, CH of PPh2). The signal due to ferrocene C-PPh2 was not observed. IR (Nujol): vmax 3460 br s,
3077 m, 3056 s, 2386 s, 2254 m, 1653 m, 1589 w, 1574 w, 1484 m, 1437 s, 1390 s, 1370 s, 1313 m,
1248 s, 1189 s, 1106 s, 1033 s, 962 s, 834 s, 795 m, 739 s, 700 s, 639 m, 623 m, 595 s, 527 s, 490 s
cm−1. ESI+ MS: m/z 519 ([M − H]+), 521 ([M + H]+). Anal. Calc. for C26H31BFeO3P2·2/3CH2Cl2
(576.6): C 55.53, H 5.65%. Found: C 55.34, 5.55%.
4.4 Synthesis of [1’-(diphenylphosphino)ferrocenyl]phosphonic acid−borane (1/1) (H2L·BH3)
Bromo-trimethylsilane (1.1 mL, 8.0 mmol) was added dropwise to a solution of adduct 4 (1.39 g,
2.7 mmol) in dichloromethane (60 mL), and the mixture was stirred for 4 h before evaporation under
vacuum. The residue was taken up with dichloromethane (10 mL), and the solution was treated with
water (0.5 mL) under stirring for 30 min. The resulting mixture was dried over MgSO4, filtered and
evaporated under vacuum to give an orange oily residue, which was purified by column
chromatography over silica gel using a dichloromethane-methanol (10:1) as eluent. A single orange
18

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band was collected and evaporated. The product was re-dissolved in chloroform (3 mL) and
precipitated by adding an excess of hexane. The separated solid was filtered off, washed with hexane
and dried under vacuum to give H2L·BH3 as an orange solid (0.91 g, 73%).
1H NMR (dmso-d6): δ 1.20 (very br s, 3 H, BH3), 4.04 (vq, Jʹ = 1.8 Hz, 2 H, fc), 4.20 (vq, Jʹ = 2.2 Hz,
2 H, fc), 4.25 (very br s, 2 H, OH), 4.49 (vq, Jʹ = 1.8 Hz, 2 H, fc), 4.72 (br d, Jʹ = 1.4 Hz, 2 H, fc),
7.47−7.58 (m, 10 H, PPh2). 13C{1H} NMR (dmso-d6): δ 68.80 (d, JPC = 68 Hz, C-PPh2 of fc), 71.93 (d,
JPC = 15 Hz, CH of fc), 72.19 (d, JPC = 13 Hz, CH of fc), 73.40 (d, JPC = 10 Hz, CH of fc), 74.55 (d,
JPC = 8 Hz, CH of fc), 74.89 (d, JPC = 202 Hz, C-PO3H2 of fc), 128.73 (d, JPC = 10 Hz, CH of PPh2),
130.64 (d, JPC = 60 Hz, Cipso of PPh2), 131.21 (d, JPC = 2 Hz, CH of PPh2), 132.10 (d, JPC = 10 Hz, CH
of PPh2). 31P{1H} NMR (dmso-d6): δ 15.6 (br s, PPh2), 17.8 (s, PO3H2). IR (Nujol): IR (Nujol): vmax
2725 w, 2383 s, 1683 w, 1588 w, 1467 s, 1377 s, 1312 w, 1256 w, 1197 s, 1174 s, 1107 s, 1059 s,
1036 s, 999 s, 943 m, 886 m, 837 s, 739 s, 698 s, 639 m, 624 m, 610 w, 576 m, 527 m, 475 s cm−1.
ESI+ MS: m/z 487 ([M + H]+). Anal. Calc. for C22H23BFeO3P2 (464.0): C 56.94, H 5.00%. Found: C
56.65, H 5.08%.
4.5 Synthesis of [1’-(diphenylphosphinoyl)ferrocenyl]phosphonic acid (H2LO)
Hydrogen peroxide in excess (0.2 mL, 30% in H2O) was added dropwise to a solution of H2L (90 mg,
0.20 mmol) in acetone (5 mL). The resulting mixture was stirred for 1 hour, dried over MgSO4,
filtered and evaporated under vacuum. The product was dissolved in dichloromethane (3 ml) and
precipitated by adding excess of hexane. The separated solid was filtered off, washed with hexane and
dried under vacuum, yielding H2LO·H2O as an orange solid (50 mg, 52%).
1H NMR (dmso-d6): δ 4.24 (br s, 2 H, fc), 4.37 (br s, 2 H, fc), 4.51 (br s, 2 H, fc), 4.73 (br s, 2 H, fc),
7.53−7.73 (m, 10 H, P(O)Ph2). 13C{1H} NMR (dmso-d6): δ 71. 52 (d, JPC = 13 Hz, CH of fc), 71.63 (d,
JPC = 115 Hz, C-PPh2 of fc), 72.53 (d, JPC = 15 Hz, CH of fc), 73.48 (d, JPC = 6 Hz, CH of fc), 73.60
(d, JPC = 9 Hz, CH of fc), 74.50 (d, JPC = 198 Hz, C-PO3H2 of fc), 128.71 (d, JPC = 12 Hz, CH of
PPh2), 130.77 (d, JPC = 10 Hz, CH of PPh2), 132.19 (d, JPC = 3 Hz, CH of PPh2), 132.58 (d, 1JPC = 107
Hz, Cipso of PPh2). 31P {1H} NMR (dmso-d6): δ 16.5 (s, PO3H2), 31.7 (s, P(O)Ph2). IR (Nujol): vmax
1706 m, 1591 w, 1310 w, 1152 s, 1122 s, 1098 m, 1072 m, 998 w, 941 w, 539 m, 752 m, 571 s, 534 m,
19

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497 m cm−1. ESI+ MS: m/z 467 ([M + H]+), 489 ([M + Na]+). Anal. Calc. for C22H20FeO4P2·H2O
(484.2): C 54.57, H 4.58%. Found: C 54.62, 4.17%.
4.6 Synthesis of (dabcoH)(HL) (5)
H2L (67.5 mg, 0.15 mmol) and dabco (16.8 mg, 0.15 mmol) were dissolved in a mixture of
dichloromethane (7 mL) and methanol (4 mL). After stirring for 30 min, the volatiles were removed
under vacuum to produce salt 5 as an orange solid in quantitative yield (84.3 mg). The crystals used
for structure determination were obtained by recrystallisation from chloroform/hexane.
1H NMR (CDCl3): δ 3.00 (s, 12 H, CH2), 4.03 (s, 2 H, fc), 4.18 (s, 2 H, fc), 4.42 (s, 2 H, fc), 4.63 (s, 2
H, fc), 5.79 (very br s, 1 H, OH), 7.26−7.37 (m, 10 H, PPh2). 13C{1H} NMR (dmso-d6): δ 44.83 (s,
CH2 dabco), 70.54 (d, JPC = 11 Hz, CH of fc), 71.56 (d, JPC = 14 Hz, CH of fc), 73.27 (d, JPC = 16 Hz,
CH of fc), 73.35 (br s, CH of fc), 75.16 (d, JPC = 7 Hz, C-PPh2 of fc), 78.46 (d, JPC = 199 Hz, C-PO3H
of fc), 128.19 (d, JPC = 7 Hz, CH of PPh2), 128.46 (s, CH of PPh2), 132.99 (d, JPC = 19 Hz, CH of
31
PPh2), 138.95 (d, JPC = 11 Hz, Cipso of PPh2). P{1H} NMR (dmso-d6): δ –17.1 (s, PPh2), 14.8 (br s,
PO3H). ESI+ MS: m/z 113 ([C6H13N2]+), 451 ([H2L + H]+). IR (Nujol): νmax 3393 br m, 3051 w, 2725
w, 1981 w, 1697 w, 1585 w, 1568 w, 1541 w, 1318 m, 1230 m, 1208 w, 1192 w, 1181 m, 1139 s,
1060 s, 1027 m, 995 m, 972 m, 917 s, 881 s, 830 m, 784 w, 746 s, 698 s, 669 w, 650 w, 607 m, 583 s,
529 w, 502 s, 483 m, 457 m, 441 m, 423 w cm−1. HR − MS: m/z 449 ([PPh2fcPO3H]−). Anal. Calc. for
C28H32O3N2FeP2·0.5CH2Cl2 (604.8): C 56.60, H 5.50, N 4.63%. Found: C 56.14, H 5.47, N 4.79%.
4.7 Synthesis of ((HOCH2CH2)2NH2)(HL) (6)
H2L (90.0 mg, 0.20 mmol) and bis(2-hydroxyethyl)amine (21.0 mg, 0.20 mmol) were dissolved in
acetone (5 mL), and the mixture was stirred for 15 min. Subsequent evaporation under vacuum left salt
6 as a yellow powder in quantitative yield (111 mg). Crystals suitable for X-ray diffraction analysis
were obtained after layering the solution of the salt in dichloromethane-THF (1:1) with hexane.
1H NMR (dmso-d6): δ 2.91 (br s, 4 H, NCH2), 3.64 (br s, 4 H, OCH2), 3.93 (vq, Jʹ = 1.8 Hz, 2 H, fc),
4.07 (vq, Jʹ = 1.8 Hz, fc), 4.17 (vq, Jʹ = 2.2 Hz, fc), 4.53 (vt, Jʹ = 1.8 Hz, fc), 4.86 (very br s, 2 H,
13
CH2OH), 7.25−7.36 (m, 10 H, PPh2). C{1H} NMR (dmso-d6): δ 49.91 (s, NCH2), 57.12 (s, OCH2),
20

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70.46 (d, JPC = 12 Hz, CH of fc), 71.39 (d, JPC = 14 Hz, CH of fc), 73.18 (d, JPC = 15 Hz, CH of fc),
73.23 (d, JPC = 5 Hz, CH of fc), 75.17 (d, JPC = 7 Hz, C-PPh2 of fc), 78.92 (d, JPC = 195 Hz, C-PO3H of
fc), 128.20 (d, JPC = 7 Hz, CH of PPh2), 128.46 (s, CH of PPh2), 132.99 (d, JPC = 19 Hz, CH of PPh2),
138.95 (d, JPC = 11 Hz, Cipso of PPh2). 31P{1H} NMR (dmso): δ −17.1 (s, PPh2), 15.0 (s, PO3H). IR
(Nujol): νmax 2041 m, 1932 m, 1683 w, 1653 w, 1558 w, 1540 w, 1307 m, 1169 m, 1073 m, 1035 m,
971 m, 833 m, 695 m, 608 m, 569 m, 483 m cm−1. ESI+ MS: m/z 451 ([H2L + H]+). Anal. Calc. for
C26H31O5NFeP2 (555.3): C 56.23, H 5.63, N 2.52%. Found: C 56.01, H 5.47, N 2.37%.
4.8 Synthesis of trans-[PdCl2(H2L-κP)2] (7)
H2L (90.0 mg, 0.20 mmol) and [PdCl2(cod)] (28.5 mg, 0.10 mmol) were dissolved in dichloromethane
(30 mL), and the resulting mixture was stirred for 1 h. Then, the solvent was evaporated under reduced
pressure, the residue was dissolved in methanol-dichloromethane (1:1, 10 mL), and the solution was
precipitated by adding an excess of pentane-diethyl ether (1:1, 40 mL). The separated solid was
filtered off, washed with pentane and dried under vacuum, affording 7·0.5CH2Cl2 as a brown powder
(88 mg, 79%). The crystals of 7·3EtOH used for structure determination were grown by liquid-phase
diffusion of diethyl ether into an ethanolic solution of the complex.
1H NMR (dmso-d6): δ 4.11 (very br s, 4 H, OH), 4.55 (br s, 8 H, fc), 4.70 (br s, 4 H, fc), 4.75 (br s, 4
31
H, fc), 7.38−7.60 (m, 20 H, PPh2). P{1H} NMR (dmso-d6): δ 17.0 (s, PPh2), 18.0 (br s, PO3H2). IR
(Nujol): νmax 2726 w, 1653 br w, 1481 w, 1437 s, 1196 s, 1166 s, 1099 s, 1061w, 1035 s, 1000 s, 932 s,
884 m, 872 w, 841 m, 814 w, 748 m, 708 w, 696 s, 669 w, 644 w, 627 w, 580 m, 541 m, 507 s, 465 m,
455 w cm−1. EIS+ MS: m/z 1049 ([PdL2Na2 + H]+). Anal. Calc. for C44H40O6Cl2Fe2P4Pd·0.5CH2Cl2
(1120.2): C 47.71, H 3.69%. Found: C 47.73, H 3.72%.
4.9 Synthesis of [(LNC)Pd(HL- 2O,P)] (8)
κ
H2L (36.0 mg, 0.08 mmol) and [(LNC)Pd(acac)] (27.2 mg, 0.08 mmol) were dissolved in
dichloromethane (5 mL), and the reaction mixture was stirred for 30 min. Subsequent solvent removal
produced 8·0.25CH2Cl2 as a yellow solid. Yield: 50.0 mg (88%). Crystals of 8·2CH2Cl2 suitable for
X-ray diffraction analysis were obtained from dichloromethane/ethyl acetate/hexane.
21

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1H NMR (CDCl3): δ 2.88 (s, 6 H, NMe2), 3.99 (br s, 2 H, NCH2), 4.02 (br s, 2 H, fc), 4.25 (br s, 2 H,
fc), 4.57 (br s, 2 H, fc), 4.74 (br s, 2 H, fc), 5.85 (t, J = 7.1 Hz, 1 H, C6H4), 6.17 (t, J = 7.3 Hz, 1 H,
C6H4), 6.66 (t, J = 7.32 Hz, 1 H, C6H4), 6.84 (t, J = 7.2 Hz, 1 H, C6H4), 7.22−7.29 (m, 4 H, PPh2),
7.30−7.37 (m, 2 H, PPh2), 7.55−7.64 (m, 4 H, PPh2). 13C{1H} NMR (CDCl3): 50.03 (br s, NMe2),
70.59 (br s, CH of fc), 71.76 (d, JPC = 53 Hz, C-PPh2 of fc), 72.44 (br s, NCH2), 72.52 (s, CH of fc),
74.23 (br d, J = 13 Hz, CH of fc), 76.53 (br s, partly overlapping with the solvent signal, CH of fc),
≈77.5 (d, C-PO3H of fc; overlapping with the solvent resonance), 122.06 (s, CH of C6H4), 123.27 (s,
CH of C6H4), 124.50 (d, JPC = 5 Hz, CH of C6H4), 127.88 (d, JPC = 11 Hz, PPh2), 130.12 (s, CH of
PPh2), 133.59 (d, JPC = 52 Hz, Cipso of PPh2), 134.62 (d, JPC = 12 Hz, CH of PPh2), 137.37 (d, JPC = 10
Hz, CH of C6H4), 146.21 (s, Cipso of C6H4), 148.38 (s, Cipso of C6H4).31P{1H} NMR (CDCl3): δ 19.2 (s,
PO3H), 29.1 (s, PPh2). IR (Nujol): νmax 1168 br m, 1073 m, 1032 m, 930 m, 887 m, 844 m, 743 m, 696
m, 584 m, 485 m cm−1. ESI+ MS: m/z 690 ([M + H]+). Anal. Calcd. for C31H31FeNO3P2Pd·0.25CH2Cl2
(711.0): C 52.79, H 4.47, N 1.97%. Found: C 52.79, H 4.56, 1.99%.
4.10 Synthesis of [(LSC)Pd(HL-κ2O,P)] (9)
H2L (36.0 mg, 0.08 mmol) and [(LSC)Pd(acac)] (27.5 mg, 0.08 mmol) were dissolved in
dichloromethane (5 mL), and the resulting mixture was stirred for 30 min. Subsequent solvent removal
afforded analytically pure 9 as a yellow solid. Yield 47.7 mg (86%). Recrystallization from
dichloromethane-hexane gave single-crystals suitable for X-ray diffraction analysis.
1H NMR (CDCl3): δ 2.64 (d, JPH = 3.6 Hz, 3 H, SMe), 4.05 (br s, 4 H, SCH2 and fc), 4.31 (br s, 2 H,
fc), 4.60 (br s, 2 H, fc), 4.79 (br s, 2 H, fc), 6.11 (br m, 2 H, C6H4), 6.59 (br t, J = 7.5 Hz, 1 H, C6H4),
6.84 (br d, J = 7.5 Hz, 1 H, C6H4), 7.20−7.28 (m, 4 H, PPh2), 7.29−7.35 (m, 2 H, PPh2), 7.51−7.60 (m,
13
4 H, PPh2). C{1H} NMR (CDCl3): δ 20.41 (s, SMe), 46.23 (s, SCH2), 70.61 (br s, CH of fc), 71.64
(d, JPC = 51 Hz, C-PPh2 of fc), 72.58 (d, JPC = 8 Hz, CH of fc), 74.25 (d, JPC = 13 Hz, CH of fc), 76.66
(d, overlapping with the solvent resonance, CH of fc), ≈78.5 (d, C-PO3H of fc, partly overlapped by
the solvent signal), 123.20 (s, CH of C6H4), 123.83 (s, CH of C6H4), 125.01 (d, JPC = 6 Hz, CH of
C6H4), 127.94 (d, JPC = 11 Hz, CH of PPh2), 130.15 (s, CH of PPh2), 133.00 (d, JPC = 50 Hz, Cipso of
22

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PPh2), 134.54 (d, JPC = 12 Hz, CH of PPh2), 139.46 (d, JPC = 13 Hz, CH of C6H4), 147.26 (s, Cipso of
31
C6H4), 149.80 (s, Cipso of C6H4). P{1H} NMR (CDCl3): δ 19.9 (s, PO3H), 26.2 (s, PPh2). IR (Nujol):
νmax 3056 m, 1717 br m, 1573 m, 1483 m, 1436 s, 1312 m, 1260 m, 1196 s, 1166 m, 1148 s, 1095 m,
1068 s, 1046 w, 1029 m, 998 w, 971 w, 924 s, 889 m, 826 m, 751 m, 735 m, 694 s, 653 w, 626 w, 584
s, 539 m, 519 m, 482 s, 470 s, 449 w cm−1. ESI+ MS: m/z 693 ([M + H]+). Anal. Calc. for
C30H28FeO3P2PdS (692.8): C 52.01, H 4.07%. Found: C 51.96, H 4.10%.
4.11 X-ray crystallography
Diffraction data (±h±k±l, θmax = 27.5°) were collected at 120(2) (for 5) or 150(2) K (for all other
compounds) using a Bruker D8 VENTURE Kappa Duo PHOTON100 instrument equipped with a IµS
micro-focus X-ray tube (Mo Kα radiation, λ = 0.71073 Å). The structures were solved using direct
methods (SHELXT [23]) and then refined using the full-matrix least-squares routine based on F2 using
SHELXL-2014 or SHELXL-2016 [24]. The non-hydrogen atoms were refined with anisotropic
displacement parameters. The OH and NH hydrogens were identified on difference density maps and
refined either freely (only for H2L) or as riding atoms with Uiso(H) set to a 1.2Ueq of their bonding
atom. Hydrogens at carbon atoms were included in their theoretical positions and refined analogously.
In some cases, the analysed crystals contained disordered molecules of halogenated solvents used
during the crystallisation (5: chloroform; 6, 8 and 9: dichloromethane). The contributions of these
molecules to the overall scattering were numerically eliminated by PLATON SQUEEZE [25]. A
recent version of the PLATON program [26] was used to perform all geometric calculations and to
prepare the structural diagrams.
Selected crystallographic data, data collection and structure refinement parameters are available in
Supporting Information. CCDC 1899917-1899922 contains supplementary crystallographic data on
this paper. These data are available, free of charge from The Cambridge Crystallographic Data Centre
via www.ccdc.cam.ac.uk/data_request/cif.
4.12 DFT computations
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DFT calculations have been performed using the M06 density functional [27] and SDD (Fe) [28] and
def2-TZVP (C, H, O and P) [29] basis sets together with Grimme’s D3 dispersion correction [30], as
implemented in the Gaussian 16 program package [31]. The solid-state structure of FcPO3H2
determined by X-ray diffraction analysis [13] was used as a starting point for geometry optimization.
Mayer bond indices [32] and Merz-Kollman charges [33] were obtained using the software package
Multiwfn [34].
Appendix A. Supplementary data
Supplementary
data
to
this
article
are
available
online
from
https://doi.org/10.1016/j.jorganchem.XXXX.
Acknowledgements
This work was supported by the Charles University Research Centre, program No. UNCE/SCI/014.
Computational resources were provided by the CESNET LM2015042 and by the CERIT Scientific
Cloud LM2015085, supported within the programme “Projects of Large Research, Development, and
Innovations Infrastructures”.
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[2] a) A. Bader, E. Lindner, Coord. Chem. Rev. 108 (1991) 27; b) C. S. Slone, D. A. Weinberger, C.
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Synthesis and structural characterisation of 1’-(diphenylphosphino)ferrocene-1-
phosphonic acid, its ammonium salts and Pd(II) complexes
Filip Horký, Ivana Císařová, Jiří Schulz and Petr Štěpnička*
Department of Inorganic Chemistry, Faculty of Science, Charles University, Hlavova 2030,
128 40 Prague, Czech Republic
* Corresponding author. E-mail address: petr.stepnicka@natur.cuni.cz
Highlights
•
•
•
•
A new polar phosphinoferrocene phosphonate ligand was prepared
The compound was converted to its ammonium salts
Pd(II) complexes with native and deprotonated ligand were synthesised
Crystal structures of the salts and Pd(II) complexes were determined