Selective borane reduction of phosphinoferrocene carbaldehydes to phosphinoalcohol-borane adducts. the coordination behaviour of 1-(diphenylphosphino)- 1′-(methoxymethyl)ferrocene, a new ferrocene O,P-hybrid donor prepared from such an adduct

Article abstract of DOI:10.1039/c2dt32511j

The reduction of ferrocene phosphino-aldehydes, R₂PfcCHO (R = Ph, 2; Cy, 3; fc = ferrocene-1,1′-diyl, Cy = cyclohexyl) and (S _p)-[Fe(η⁵-C₅H₃-1-CHO-2-PPh ₂)(η⁵-C₅H₅)] ((S _p)-4), with BH₃·THF or BH₃· SMe₂ in THF at 0 °C selectively afforded the corresponding phosphinoalcohol-borane adducts, R₂PfcCH₂OH·BH ₃ (R = Ph, 5; Cy, 6) and (S_p)-[Fe(η⁵-C ₅H₃-1-CH₂OH-2-PPh₂) (η⁵-C₅H₅)]·BH₃ ((S _p)-7), in quantitative yields. In contrast, the reactions performed at elevated temperatures favoured the formation of methyl derivatives (e.g., Ph₂PfcCH₃·BH₃ (8)) resulting from overreduction (deoxygenation). The crystal structures of 3, 5, (S _p)-7, 8 and Cy₂PfcBr (9) have been determined by single-crystal X-ray diffraction analysis. The crystal assemblies of adducts 5 and (S_p)-7 are built up by means of C-H...O contacts, O-H...HB dihydrogen bonds and other soft interactions but, surprisingly, not via the conventional O-H...O hydrogen bonds. Adduct 5 was smoothly deprotected to give the corresponding free phosphine, Ph₂PfcCH ₂OH (1), and was further used for the preparation of a hybrid phosphinoether ligand, Ph₂PfcCH₂OMe (11). The latter compound was studied as a donor for Group 8-10 metal ions and for Cu(i), whereupon the following complexes were isolated and structurally characterised: [(η⁶-p-cymene)RuCl₂(11-κP)] (12*), [(η⁶-p-cymene)RuCl(11-κP)(MeCN)][SbF₆] (13*), [RhCl(cod)(11-κP)] (cod = η²: η²-cycloocta-1,5-diene; 14), trans-[PdCl₂(11-κP) ₂] (trans-15*), [PdCl(μ-Cl)(11-κP)]₂ (16*), cis- and trans-[PtCl₂(11-κP)₂] (cis-17 and trans-17*), and [Cu(CF₃SO₃-κO)(11- κP)(H₂O)] (18) (the asterisk indicates that the crystal structure was determined). In all these compounds, ligand 11 behaves as a P-monodentate donor while its ether group remains uncoordinated. This probably reflects structural flexibility of 11 resulting from the presence of the methylene linker and also distinguishes 11 from its known, non-spaced analogue Ph₂PfcOMe.

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PAPER
Selective borane reduction of phosphinoferrocene
carbaldehydes to phosphinoalcohol–borane adducts.
The coordination behaviour of 1-(diphenylphosphino)-
1’-(methoxymethyl)ferrocene, a new ferrocene
O,P-hybrid donor prepared from such an adduct†
Cite this: Dalton Trans., 2013, 42, 3373
Petr Štěpnička* and Ivana Císařová
The reduction of ferrocene phosphino-aldehydes, R2PfcCHO (R = Ph, 2; Cy, 3; fc = ferrocene-1,1’-diyl, Cy =
cyclohexyl) and (Sp)-[Fe(η5-C5H3-1-CHO-2-PPh2)(η5-C5H5)] ((Sp)-4), with BH3·THF or BH3·SMe2 in THF at
0 °C selectively afforded the corresponding phosphinoalcohol–borane adducts, R2PfcCH2OH·BH3 (R = Ph,
5; Cy, 6) and (Sp)-[Fe(η5-C5H3-1-CH2OH-2-PPh2)(η5-C5H5)]·BH3 ((Sp)-7), in quantitative yields. In contrast,
the reactions performed at elevated temperatures favoured the formation of methyl derivatives (e.g.,
Ph2PfcCH3·BH3 (8)) resulting from overreduction (deoxygenation). The crystal structures of 3, 5, (Sp)-7, 8
and Cy2PfcBr (9) have been determined by single-crystal X-ray diffraction analysis. The crystal assemblies
of adducts 5 and (Sp)-7 are built up by means of C–H⋯O contacts, O–H⋯HB dihydrogen bonds and
other soft interactions but, surprisingly, not via the conventional O–H⋯O hydrogen bonds. Adduct 5 was
smoothly deprotected to give the corresponding free phosphine, Ph2PfcCH2OH (1), and was further used
for the preparation of a hybrid phosphinoether ligand, Ph2PfcCH2OMe (11). The latter compound was
studied as a donor for Group 8–10 metal ions and for Cu(I), whereupon the following complexes were
isolated and structurally characterised: [(η6-p-cymene)RuCl2(11-κP)] (12*), [(η6-p-cymene)RuCl(11-κP)-
(MeCN)][SbF6] (13*), [RhCl(cod)(11-κP)] (cod = η2:η2-cycloocta-1,5-diene; 14), trans-[PdCl2(11-κP)2] (trans-
15*), [PdCl(μ-Cl)(11-κP)]2 (16*), cis- and trans-[PtCl2(11-κP)2] (cis-17 and trans-17*), and [Cu(CF3SO3-κO)-
(11-κP)(H2O)] (18) (the asterisk indicates that the crystal structure was determined). In all these com-
pounds, ligand 11 behaves as a P-monodentate donor while its ether group remains uncoordinated. This
probably reflects structural flexibility of 11 resulting from the presence of the methylene linker and also
distinguishes 11 from its known, non-spaced analogue Ph2PfcOMe.
Received 21st October 2012,
Accepted 27th November 2012
DOI: 10.1039/c2dt32511j
www.rsc.org/dalton
ligands, among which dppf and related compounds still play
an important role.3,4
Introduction
Investigations into phosphinoferrocene ligands started rather
Numerous practical applications of dppf in coordination
unobtrusively with the syntheses of (diphenylphosphino)ferro- chemistry and catalysis obviously prompted the preparation of
cene1 and 1,1′-bis(diphenylphosphino)ferrocene (dppf)2 in the its congeners. Several approaches towards the modification of
mid-1960s. These studies continue with unremitting vigour the parent dppf molecule are now established in the literature,
and have resulted in a vast family of structurally versatile one particular method being the replacement of one phos-
phine group with another functional moiety (FG in Scheme 1).
Department of Inorganic Chemistry, Faculty of Science, Charles University in Prague,
Hlavova 2030, 12840 Prague 2, Czech Republic. E-mail: stepnic@natur.cuni.cz;
Fax: +420 221 951 253
†Electronic supplementary information (ESI) available: The synthesis and crystal
structures of 3 and 9, description of the crystal packing of 5, view of the crystal
structure of trans-17, a view of the coordination sphere and the crystal packing
diagram for 18, and a summary of the crystallographic data in a tabular form.
CCDC 906406–906418. For ESI and crystallographic data in CIF or other elec-
Scheme 1 One of possible approaches towards modifications of the parent
dppf structure (FG denotes a functional substituent).
tronic format see DOI: 10.1039/c2dt32511j
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Scheme 2 Structural drawings of alcohol 1, Hdpf and aldehydes used in this
study (Cy = cyclohexyl).
The application of this approach resulted in a number of inter-
esting donor-asymmetric ligands of the type Ph2PfcY,5 where
fc is ferrocene-1,1′-diyl and Y is a (non-phosphine) donor
group or a functional moiety.5,6
Scheme 3 Borane-reduction of phosphinoaldehydes 2, 3 and (Sp)-4.
In the search for alternative phosphinoferrocene synthetic
building blocks, we prepared [1′-(diphenylphosphino)ferrocen-
1-yl]methanol (1, Scheme 2)7 via hydride reduction of
1′-(diphenylphosphino)ferrocene-1-carbaldehyde (2)7,8 and the
corresponding carboxylic acid (Hdpf).9–11 This alcohol was
recently shown to be a good starting material for the prep-
similarly deoxygenate ferrocenecarboxylic acid and the related
alcohols FcCH(OH)R.17 An analogous reaction was reported
even for phosphine-aldehyde (Sp)-4, which was converted
to (Sp)-2-(diphenylphosphino)-1-methylferrocene–borane (1/1)
upon reacting with BH3·SMe2 (3 equiv.) at room temperature
for 16 h.18
We found that when the reduction is performed with the
simple aldehyde 2 and an excess of borane dissolved in THF
(i.e., with commercially available BH3·THF in THF) at 0 °C, it
takes a different course, affording rapidly and selectively phos-
phinoalcohol–borane adduct 5 (Scheme 3). Adduct FcPPh2·BH3,
detected as the only minor side product in the crude reaction
mixture,23 resulted from the direct borylation of (diphenylpho-
sphino)ferrocene, which is notoriously present in 2 as a trace
impurity.24 This compound was efficiently removed by column
chromatography on silica gel, which then furnished analyti-
cally pure 5 in practically quantitative yield.
The selective formation of 5, a product type different from
what was previously detected, led us to elucidate a possible
influence of the reaction conditions on the reaction course.
When the reaction mixture was heated at reflux in THF over-
night, it afforded a mixture of alcohol 5 and 1-(diphenylphos-
phino)-1′-methylferrocene–borane (8), resulting from exhaustive
reduction. The latter, deoxygenated compound was isolated
in quantitative yield upon replacing BH3·THF with BH3·SMe2
(1 M in THF; refluxing in THF overnight), which is indeed
in line with the previous observations.18 The difference in
the reactivity of BH3·THF and BH3·SMe2 (i.e., partial vs. exhaus-
tive reduction) can be accounted for by the greater thermal
stability of the latter borane adduct. This assumption, based
on empirical observations,25 is supported by theoretical com-
putations, showing that the hypothetical reaction of BH3
with H2S to form an adduct is more exothermic than that
with H2O.26
aration
of
a
semi-homologous
dppf
congener,
Ph2PfcCH2PPh2,6i which led us to search for similar building
blocks and their synthetic applications, mainly in the prep-
aration of phosphinoferrocene ligands. It is notable that
similar phosphino–alcohol synthons have been used only scar-
cely in ferrocene chemistry12 and had to be protected during
some parts of the reaction sequence owing to the presence of
the oxidation-sensitive phosphine moiety.13
With an aim of further developing the synthetic appli-
cations of phosphinoferrocene alcohols, we decided to study
the reduction of phosphinoferrocene carbaldehydes with
borane as a classical though ‘non-innocent’ reducing agent,14
which itself can serve as a phosphine protecting group.15 In
this contribution, we describe our study on borane reduction
of the representative phosphinoferrocene aldehydes 2, 3 and
(Sp)-4 (Scheme 2) and a detailed characterisation of the result-
ing phosphinoalcohol–borane adducts. Furthermore, we
demonstrate the synthetic potential of these adducts by a two-
step conversion of [1′-(diphenylphosphino)ferrocene-1-yl]-
methanol–borane (1/1) (i.e., 1·BH3) as a representative to
1′-(diphenylphosphino)-1-(methoxymethyl)ferrocene and report
our investigations into the coordination behaviour of this
novel O,P-hybrid16 ferrocene ligand towards Group 8–10 metal
cations and copper(I).
Results and discussion
Borane reduction of phosphinoferrocene aldehydes
In order to verify whether the discovered selective partial
reduction represents a generally applicable transformation,
similar reactions were carried out with aldehyde 3 bearing a
different phosphino group and with the isomeric, planar-
chiral aldehyde (Sp)-4.11b Aldehyde 3 was prepared analogously
to 27 from 1,1′-dibromoferrocene (Scheme 4). The dibromide
was first converted27 to phosphine-bromide 9 by lithiation and
The reduction of ferrocenecarbonyl compounds FcC(O)R,
where Fc is ferrocenyl and R is H or an organyl group, with
various hydridoboron agents (e.g., BH3·SMe2,17,18 NaBH4–
CF3CO2H,19 BF3·OEt2–NaBH3(CN),20 TiCl4–NaBH3(CN),21 Zn-
(BH4)2–ZnCl2 22) was previously demonstrated to proceed in an
exhaustive manner to afford the respective alkylferrocenes,
FcCH2R. Borane-dimethylsulphide was further shown to
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Scheme 4 Preparation of aldehyde 3 (DMF = N,N-dimethylformamide).
Scheme 5 Preparation of phosphine-ether 11 (dabco
=
1,4-diazabicyclo-
[2.2.2]octane).
reaction with ClPCy2. In a similar manner, intermediate 9 was
lithiated and carbonylated with N,N-dimethylformamide to
give aldehyde 3. Compounds 3 and 9 were fully characterised
by spectroscopic methods and their molecular structures were
determined by X-ray diffraction analysis (see ESI†).
The reduction of 3 with BH3–THF proceeded similarly to 2,
producing the corresponding adduct 6 (Scheme 3; 97% iso-
lated yield). Likewise, the borane reduction of (Sp)-4 cleanly
produced adduct (Sp)-7 (Scheme 3) as a viscous oil. According
to the analytical data, the product isolated by simple flash
column chromatography was essentially pure. Any further
‘purification’ of (Sp)-7 proved rather difficult due to a tendency
to retain traces of the solvents and a reluctance to crystallise.
Nonetheless, crystals of (Sp)-7 suitable for X-ray diffraction
BH3 group with dabco. This procedure provided 11 as an
orange-yellow solid in an 85% yield.
Compounds 10 and 11 were characterised by the usual
spectroscopic methods and their crystal structures have been
determined by X-ray diffraction analysis. Successful methy-
lation of 5 was manifested by the signals of the methoxymethyl
group (10: CH2, δH 3.88, δC 69.88; OMe, δH 3.22, δC 57.79; 11:
CH2, δH 3.96, δC 70.31; OMe, δH 3.24, δC 57.68), whereas de-
borylation was clearly demonstrated in the 31P NMR spectra
(cf. δP: 16.4 for 10, and −16.3 for 11).
The crystal structures of 5, (Sp)-7, 8, 10 and 11
analysis were obtained by crystallisation from hot heptane The molecular structures of 5, 8 and (Sp)-7 are depicted in
(vide infra). Fig. 1–3. Compounds 5 and 8 are virtually isostructural, crystal-
The reduction of phosphinoferrocene aldehydes 2, 3 and lising with the symmetry of the monoclinic space group P21/c
1
(Sp)-4 was clearly manifested in the H and 13C NMR spectra and four structurally independent molecules (for geometric
by a disappearance of the characteristic resonances due to the data, see Tables 1 and 2). Compound (Sp)-7 crystallises in the
formyl substituents, which were replaced by the signals of the orthorhombic space group P212121 and one molecule per
hydroxymethyl groups. The resulting adducts displayed typical asymmetric unit.
1
broad signals of the BH3 protons in their H NMR spectra and
Structural parameters determined for 8, 5 and (Sp)-7 lie
broad doublet-like resonances in the 31P NMR spectra. within the common ranges and compare well with the data
Besides, the progress of the reduction reaction was nicely indi- reported for FcCH2OH,28 1,7 [2-(diphenylphosphino)ferrocen-
cated by a colour change from the initial red-orange to orange- 1-yl]methanol,29
and various
phosphinoferrocene–BH3
yellow reflecting a loss of conjugation.
adducts.18,30 The ferrocene units in the independent mo-
lecules of 5 exert similar Fe-ring centroid (Cg) distances and
negligible tilting (Table 1) while their substituents assume
conformations close to synclinal eclipsed as indicated by the
torsion angles Cn01–Cg(P,n)–Cg(C,n)–Cn06 of 77–78° (n = 1–4;
Preparation of phosphinoether ligand 11
Aiming at synthetic utilisation of the obtained phosphinoalco- cf. the theoretical value 72°).
hol–borane adducts, we first studied the possibility of depro-
Similarly, the parameters determined for the structurally
tecting the phosphine moiety. Gratifyingly, the BH3 group was independent albeit practically undistinguishable molecules of
smoothly removed upon reacting the representative adduct 5 8 (Table 2) do not depart from the values reported for 1,1′-
with 1,4-diazabicyclo[2.2.2]octane (dabco) in C6D6 (60 °C/3 h) dimethylferrocene31 and the BH3 adducts mentioned
to afford alcohol 1.15 This encouraged us to use adduct 5 above.18,30 The ferrocene moieties are regular showing tilt
further in the preparation of new phosphinoferrocene ligands.
angles below 2° and synclinal eclipsed conformations with τ =
Thus, a mixed-donor phosphinoether ligand 11 was syn- 79–80°. The fact that the Fe–Cg(P) distances are slightly
thesised (Scheme 5) by alkylation of alcohol 5 with NaOH– but statistically significantly shorter (0.010–0.016 Å) than
CH3I in dry dimethylsulphoxide, affording intermediate their matched Fe–Cp(C) distances in all the four molecules
adduct 10, and by the subsequent removal of the protecting probably reflects strengthening of the Fe–C bonds upon the
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Fig. 3 View of the molecular structure of (Sp)-7 showing displacement ellip-
soids at the 30% probability level. Selected data: Fe–Cg1 1.633(1), Fe–Cg2
1.652(2), P–B 1.930(3), P–C2 1.789(3), P–C12 1.825(3), P–C18 1.817(3), C1–C11
1.498(4), C11–O 1.437(3) Å; ∠Cp1,Cp2 3.2(2), C1–C11–O 111.0(2)°. The ring
planes are defined as follows: Cp1 = C(1–5), Cp2 = C(6–10); Cg1 and Cg2 are
the respective ring centroids.
Fig. 1 View of the molecule 1 in the structure of alcohol 5. Displacement ellip-
soids correspond to the 30% probability level. The labelling scheme is analogous
in all four crystallographically independent molecules.
Table 1 Selected geometric data for alcohol 5 (in Å and °)a
Parameter
Molecule 1 Molecule 2 Molecule 3 Molecule 4
Fe–Cg(P)
Fe–Cg(C)
∠Cp(P),Cp(C)
P–B
P–C(Cp)
P–C(Ph)
1.640(1)
1.651(1)
1.8(2)
1.913(3)
1.791(3)
1.813(3)/
1.824(3)b
1.436(3)
1.642(1)
1.645(2)
1.6(2)
1.924(3)
1.790(3)
1.812(3)/
1.823(3)b
1.466(7)/
1.39(1)c
1.646(1)
1.652(1)
2.4(2)
1.916(3)
1.785(3)
1.807(3)/
1.817(3)b
1.426(8)/
1.430(8)c
1.642(1)
1.653(1)
2.2(2)
1.927(4)
1.786(3)
1.817(3)/
1.815(3)b
1.436(3)
C–O
a Cp(P) and Cp(C) stand for the PPh2- and CH2OH-substituted
cyclopentadienyl rings, respectively. Cg(P) and Cg(C) are the respective
ring centroids. b Values for two phenyl rings: Pn–Cn12/Pn–Cn18
(n indicates the molecule). c Two values due to disorder (two
orientations of the CH2OH moiety).
Table 2 Selected geometric data for compound 8 (in Å and °)a
Parameter
Molecule 1 Molecule 2 Molecule 3 Molecule 4
Fig. 2 View of molecule 1 in the crystal structure of adduct 8. Displacement
ellipsoids correspond to the 30% probability level. The labelling of the other
three independent molecules is strictly analogous.
Fe–Cg(P)
Fe–Cg(C)
∠Cp(P),Cp(C)
τb
1.642(1)
1.652(1)
1.3(2)
1.640(1)
1.651(1)
1.6(2)
1.641(1)
1.653(1)
2.1(2)
1.637(1)
1.653(1)
1.3(2)
79.0(2)
79.9(2)
78.6(2)
80.3(2)
P–B
1.916(3)
1.782(3)
1.810(2)/
1.817(3)
1.495(4)
1.921(3)
1.783(3)
1.811(2)/
1.822(3)
1.494(4)
1.917(3)
1.790(3)
1.815(2)/
1.822(3)
1.494(4)
1.918(3)
1.788(3)
1.812(2)/
1.825(3)
1.507(4)
introduction of an electron-withdrawing substituent
(PPh2·BH3) to the cyclopentadienyl ring.32 Similar features
were observed for (Sp)-7, where the Fe–Cg distances differ by
ca. 0.02 Å. However, the presence of two substituents in adja-
cent positions results in a twisting at the C1–C2 bond (torsion
angle C11–C1–C2–P = 9.3(4)°) and in a slight increase of the
tilt angle to 3.2(2)°.
P–C(Cp)
P–C(Ph)c
C–CH3
a Cp(P) and Cp(C) denote the phosphine- and methyl-substituted
cyclopentadienyl rings, respectively. Cg(P) and Cg(C) are their
centroids. b Torsion angle C(n01)–Cp(P,n)–Cp(C,n)–C(n06). c Values for
two phenyl rings: Pn–Cn12/Pn–Cn18 (n indicates the molecule).
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Fig. 4 Intermolecular interactions in the structure of (Sp)-7. The arrows indicate
where the molecule enters into C–H⋯O hydrogen bonding interactions as the
donor. Hydrogen bond parameters: C8–H8⋯Oi: C8⋯Oi = 3.367(4) Å, angle at
H8 = 169°; C15–H15⋯Oii: C15⋯Oii = 3.363(4) Å, angle at H15 = 168°; (i) 1 + x,
y, z; (ii) 1 − x, −1/2 + y, 3/2 − z.
Fig. 5 View of molecule 1 in the structure of 10 with 30% probability displace-
ment ellipsoids. Selected data (Å and °), molecule 1: Fe–Cg(P1) and Fe–Cg(C1)
1.649(1), ∠Cp(P1),Cp(C1) 1.0(2); P1–C101 1.788(3), P1–C112 1.818(3), P1–C118
1.811(3), P1–B1 1.919(4), O1–C111 1.418(3), O1–C124 1.428(4); C101–P1–B1
115.4(1), C111–O1–C124 109.7(2); molecule 2: Fe–Cg(P2) 1.649(1), Fe–Cg(C2)
1.651(1), ∠Cp(P2),Cp(C2) 1.6(2); P2–C201 1.787(3), P2–C212 1.808(3), P2–C218
Rather unexpectedly, the crystal assemblies of 5 and (Sp)-7
do not involve the conventional O–H⋯O hydrogen bonds that
operate, e.g., in the crystal structures of FcCH2OH,28 1,7 and
rac-[2-(diphenylphosphino)ferrocen-1-yl]methanol.29 The mole-
cules of (Sp)-7 associate only via soft C–H⋯O hydrogen bonds, 1.817(3), P2–B2 1.915(3), O2–C211 1.417(3), O2–C224 1.429(4); C201–P2–B2
113.6(1), C211–O2–C224 110.0(2). The ring planes are defined as follows:
such that each molecule acts as a double H-bond donor and a
double H-bond acceptor (Fig. 4). When combined, these inter-
actions give rise to layers oriented parallel to the ab plane.
Cp(Pn) = C(n01–n05), Cp(Cn) = C(n06–n10); Cg(Pn) and Cg(Cn) are the respect-
ive centroids.
In addition, the molecules of (Sp)-7 form intramolecular
C–H⋯Cp-ring π-contacts (C13–H13⋯Cg1: C13⋯Cg1 = 3.618(3)
Å, angle at H13 = 136°; not indicated in Fig. 4) and intramole-
cular O1–H91⋯H3B–B1 dihydrogen bonds. In the latter inter-
5 further corroborates that the strong O–H⋯O hydrogen
bonds, a typical structure-directing force, play a negligible role
in the crystal packing of the latter adduct.37
action, the negatively charged boron-bound hydrogen (B–Hδ−
)
The molecular structures of 10 and 11 are depicted in Fig. 5
ˉ
behaves as a hydrogen bond acceptor for the hydroxyl group
within the same molecule (O⋯H3B = 2.77 Å, O–H91⋯H3B =
139°). The observed H91⋯H3B separation (2.00 Å) falls well
below a distance corresponding to twice the van der Waals
radii of the hydrogen atom (ca. 2.2 Å).
and 6. Adduct 10 crystallises with triclinic space group P1 and
two virtually identical molecules per asymmetric unit. The cor-
responding free phosphine 11 crystallises in the common
monoclinic space group P21/n. The compounds share the
overall structure: Their cyclopentadienyl rings assume a syn-
clinal eclipsed conformation (τ = 75.1(2)° and 77.1(2)° for mo-
lecules 1 and 2 of 10, and 75.9(1)° for 11) and exert negligible
tilting (below 2°). In both cases, the CH2OMe arms point to
the side of the ‘lateral’ phenyl group in the phosphine substi-
tuent and below the ferrocene unit.
It should be noted that dihydrogen bonds33 involving the
BH3 units as acceptors have been previously studied, predomi-
nantly in B–N compounds. However, a survey of the Cambridge
Structural Database revealed that even the BH⋯H–O contacts
are relatively common.34 Most often, they are encountered in
−
the crystal structures of adducts formed from salts with BH4
(BH3CN−) anions and aminoalcohols.35 Structures featuring
favourable P–BH3⋯HO contacts are also quite abundant.36
The individual molecules in the structure of 5 also associate
into a complicated three-dimensional assembly via the rela-
tively weak interactions such as C–H⋯O and O–H⋯HB hydro-
gen bonds, C–H⋯HB contacts and π–π stacking interactions
(see ESI†). The structure thus lacks a principal (e.g., O–H⋯O)
intermolecular interaction favouring a particular orientation of
the individual molecules, which in turn results in an increase
of the number of structurally independent molecules and dis-
order of the hydroxymethyl moieties. The crystal packing of 8
is essentially molecular and its isostructural relationship with
Preparation and characterisation of complexes with ligand 11
Compound 11 is a hybrid and potentially a hemilabile ligand16
that is closely related to the archetypical phosphinoether
donors such as diphenyl(2-methoxymethyl)phosphine38 or
diphenyl[2-(methoxymethyl)phenyl]phosphine39 and, mainly,
to its ‘non-spaced’ counterpart, Ph2PfcOMe.40,41 Considering
the particular combination of the donor atoms in 11, the
coordination properties of this ligand have been studied
towards divalent Group 10 metal ions, ruthenium(II), rhodium(I)
and copper(I).
Ru(II) and Rh(I) complexes with auxiliary π-ligands. For
screening experiments we chose Ru(II) and Rh(I) precursors
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1
The H NMR spectra of 12 and 13 confirm the formulation
of these complexes by showing signals due to 11 and the Ru-
bound arene. The signal of the coordinated acetonitrile in 13
5
seen at δH 2.13 is split into a doublet with JPH of 1.4 Hz.42
Because of the presence of the stereogenic Ru atom in 13, the
ferrocene protons are diastereotopic and give rise to eight
1
signals in the H NMR spectrum. Analogously, the signals due
to CH protons at the η6-arene ligand and the methyl groups of
the CHMe2 substituent in 13 are seen as four and two distinct
signals, respectively. In contrast, the methylene protons in the
remote CH2OMe pendant are degenerate. The P-coordination
of 11 is indicated by a shift of the 31P NMR resonance to a
lower field (coordination shift, ΔP(12) = 35.7 ppm). A further
shift is seen upon removal of the chloride ligand (ΔP(13) =
46.0 ppm), presumably due to an increased donation to the
formed electron-poor Ru+ centre. Both complexes have been
structurally characterised. Their structures are shown in Fig. 7
and 8. Geometric data are given in Table 3.
Both compounds possess the expected three-legged piano
stool structure. The interatomic distances as well as the overall
geometry of 12 and 13 are similar to those determined earlier
for [(η6-p-cymene)RuCl2(Hdpf-κP)]43 and complexes of the type
[(η6-arene)RuCl(PR3)(MeCN)][PF6],42 respectively. In both struc-
tures, the pseudo-octahedral environments of the Ru(II)
centres are distorted, showing dissimilar interligand angles
(Cg3–Ru–basal donor >> basal donor–Ru–basal donor). Yet,
the dihedral angle subtended by the plane of the η6-arene ring
and the base of the piano stool structure is 3.4(2)° for 12
(basal plane: Cl1, Cl2, P) and 7.2(1)° for 13 (basal plane: Cl, N,
P), departing only marginally from 0° expected for an ideal
octahedron.
Fig. 6 View of the molecular structure of 11 showing displacement ellipsoids
at the 30% probability level. Selected distances and angles (in Å and °): Fe–
Cg(P) 1.6433(7), Fe–Cg(C) 1.6482(7), ∠Cp(C),Cp(C) 1.44(9); P–C1 1.814(2), P–C12
1.844(2), P–C18 1.834(2), O–C11 1.430(2), O–C24 1.415(2); O–C11–C6 110.1(1),
C11–O–C24 110.7(1). Note: The ring planes are defined as for 10.
bearing auxiliary π-ligands. Thus, the dimer [(η6-p-cymene)-
RuCl2]2 reacted readily with two molar equivalents of com-
pound 11, affording the expected bridge-cleavage product 12
in virtually quantitative yield (Scheme 6).
Repeated attempts to prepare an analogous O,P-chelating
complex via the removal of Ru-bound halide failed. The reac-
tion of 12 with Ag[SbF6] (in CH2Cl2–THF) or with Na[PF6] (in
CH2Cl2–methanol) produced only intractable complicated mix-
tures. Finally, when acetonitrile was employed as the solvent
for Ag[SbF6], the reaction proceeded cleanly to afford the cat-
ionic (arene)Ru(II) solvento complex 13 (Scheme 6).
Compound 11 reacted smoothly with dimer [RhCl(cod)]2
(cod = η2:η2-cycloocta-1,5-diene) to give phosphine complex 14
(Scheme 7). This complex shows a single 31P NMR resonance
Fig. 7 View of the molecular structure of complex 12. Displacement ellipsoids
Scheme 6 Preparation of (η6-p-cymene)Ru(II) complexes with ligand 11.
3378 | Dalton Trans., 2013, 42, 3373–3389
correspond to the 30% probability level.
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Fig. 8 View of the complex cation in the structure of 13·1/2CHCl3 showing dis-
placement ellipsoids at the 30% probability level.
Scheme 8 Preparation of Pd(II) complexes trans-15 and 16.
Table 3 Selected distances and angles for 12 and 13·1/2CHCl3 (in Å and °)
Group 10 metal complexes
Parametera
12
13b
The attempted reaction of 11 with [NiCl2(dme)] (dme = 1,2-
dimethoxyethane) did not afford any defined product, very
likely due to a low (solvolytic) stability of ‘complexes’ arising in
this system. On the other hand, reactions of phosphine 11
with [PdCl2(cod)] as a precursor of the softer ‘MCl2’ fragment
(Scheme 8) proceeded cleanly and produced two different
phosphine complexes depending on the reaction stoichio-
metry: the diphosphine complex trans-15 at a 2 : 1 ligand-to-
metal ratio, and the symmetric, chloride-bridged dimer 16
when the starting materials were mixed in equimolar
amounts.
The removal of chloride ligand(s) from complex trans-15 by
one or two equivalents of AgClO4 led to poorly defined, non-
crystallising violet materials. As an alternative approach to the
elusive O,P-chelate complex, ligand 11 was reacted with [Pd-
(MeCN)4][BF4]2 as a stable and defined Pd(II) source devoid of
firmly bound auxiliary donors.45 Treatment of [Pd(MeCN)4]-
[BF4]2 with 11 (2 equiv.) in CDCl3 proceeded under the liber-
ation of MeCN (δH 1.99) to afford a deep blue-violet product,
showing extremely broad NMR signals.46 Evaporation of the
reaction mixture afforded a violet glassy solid, which unfortu-
nately defied all attempts at purification by crystallisation.
When [Ph4As]Cl in excess was added to the reaction
mixture, a marked colour change from deep violet to red-
orange occurred immediately, reflecting the formation of the
dichloride complex trans-15, which was evidenced by the 1H
and 31P NMR spectra.47
X/Y
Ru–P
Ru–X
Ru–Y
Ru–Cg3
P–Ru–X/Y
X–Ru–Y
Cg–Ru–P
Cg–Ru–X/Y
Fe–Cg(P)
Fe–Cp(C)
∠Cp(P),Cp(C)
τ
Cl1/Cl2
2.364(1)
2.407(1)
2.409(1)
1.714(2)
88.48(5)/87.62(5)
88.41(5)
128.16(9)
122.3(1)/128.1(1)
1.642(3)
Cl/N
2.3543(7)
2.3889(8)
2.043(2)
1.710(1)
86.61(3)/87.55(7)
85.48(7)
130.96(4)
127.04(5)/124.80(7)
1.642(1)
1.649(2)
4.6(2)
1.647(3)
2.8(3)
96.3(4)
137.9(2)
a Definitions: Cg(P) and Cg(C) are defined as for 10 (see Fig. 5); τ is the
torsion angle C1–Cg(P)–Cg(C)–C6. Cg3 is the centroid of benzene ring
C(25–30). b Further data: C35–N = 1.132(4), C36–C35–N = 178.8(3).
Scheme 7 Preparation of complex 14.
at δP 23.6 (ΔP(14) = 39.9 ppm) split into a doublet due to an
interaction with the monoisotopic 103Rh (1JRh,P = 151 Hz). The
1H NMR spectrum confirms the presence of a coordinated
diene (in an asymmetric environment) and ligand 11. Attempts
to convert 14 into an O,P-chelate or a bridging complex either
via abstraction of the chloride ligand (with AgClO4) from 14 or
directly by the reaction of 11 with [(cod)Rh(Me2CO)2][SbF6]44
produced only ill-defined materials.
Although no defined product could be isolated from the
reaction between 11 and [Pd(MeCN)4][BF4]2, the overall reac-
tion course can be rationalised as shown in Scheme 9. In the
first step, phosphine 11 replaces the acetonitrile ligands to
give a fluxional cationic species of the type {Pd(11)2}2+ or its
analogue stabilised through a weak coordination of the solvent
or the counter anion. This intermediate readily takes up free
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Scheme 9 Stepwise formation of trans-15 from [Pd(MeCN)4][BF4]2, 11 and
[Ph4As]Cl.
chloride ions to afford the stable diphosphine complex trans-
15 via replacement of the ligand’s oxygen or weakly bound
supporting ligands.
Analogous reactions with [PtCl2(cod)] proceeded in
a
different manner. The reaction of [PtCl2(cod)] with 11 at a Pt–P
molar ratio of 1 : 1 in CDCl3 produced a mixture containing
unreacted [PtCl2(cod)], diphosphine complex cis-[PtCl2(11-κP)2]
1
(cis-17; δP 9.8, JPt,P = 3759 Hz) and liberated cod in equal
molar ratios, according to the NMR analysis. In addition to
Fig. 9 View of the molecular structure of trans-15 showing displacement ellip-
soids at the 30% probability level and only one position of the disordered Cl
atom. Prime-labelled atoms are generated by crystallographic inversion. Selected
distances and angles (in Å and °; parameters for trans-17 are given in square
brackets): M–P 2.3408(5) [2.3220(5)], M–Cl(a/b) 2.254(3)/2.313(2) [2.261(4)/
2.317(2)], P–M–Cl(a/b) 94.6(1)/90.53(6) [90.2(1)/94.51(5)].
these rather expected products, another Pt(II)–11 species was
1
also seen, albeit in tiny amounts (δP 11.5, JPt,P = 2622 Hz).
When the amount of the ligand was increased to two equiva-
lents (Pt–P = 1 : 2), the reaction gave rise to a mixture of cis-17
and liberated cod. Even in this case, however, the mentioned
side product was detected in the reaction mixture, correspond-
ing to ca. 3 mol% of the total Pt(II). Notably, the amount of the
side product increased slowly after the addition of excess 11
either directly during mixing of the starting materials or later
to the reaction mixture. Crystallisation of the reaction solution
by diffusion of diethyl ether afforded a mixture of small plate-
like crystals of cis-1748 and bar-like crystals of the other
(minor) product, which was unambiguously identified as trans-
17 by X-ray crystallography.
The observed behaviour corresponds with kinetic inertness
of Pt(II), which prevents the formation of the thermodynami-
cally favoured trans-isomer from [PtCl2(cod)]. Conversion of
cis-17 (the kinetic product) to trans-17 proceeds via an associat-
ive pathway and is therefore facilitated in the presence of free
11.49
70 : 30). This feature may well reflect the mobility of the
monoatomic ligands (though limited) within the empty space
defined by the bulky phosphinoferrocene ligands. The ferro-
cene moieties in trans-15 and trans-17 show tilt angles of ca. 3°
and adopt intermediate conformations close to synclinal
eclipsed (τ ≈ 82°).
The crystal structure of the dipalladium complex 16 is pres-
ented in Fig. 10. Even this complex crystallises with an
imposed crystallographic symmetry, such that the centre of the
Pd2Cl2 core coincides with the crystallographic inversion
centre. Palladium and its four ligating atoms (P, Cl1, Cl2 and
Cl2′) in 16 are coplanar within ca. 0.06 Å. The Pd–Cl distance
involving Cl1 as a terminal donor is expectedly shorter than
for the bridging chlorides Cl2/2′, which are bonded somewhat
asymmetrically. The relative bulkiness of the phosphine donor
as compared to the monoatomic chloride donors is nicely
reflected by the interligand angles, decreasing in the order
P–Pd–Cl2 > P–Pd–Cl1 > Cl2–Pd–Cl2′ > Cl1–Pd–Cl2′. Similar
structural features are observed for [PdCl(μ-Cl)(Ph2PfcPO3Et2-
κP)]2.51c
Complexes trans-15, 16 and trans-17 were structurally
characterised by X-ray diffraction analysis. Compounds trans-
15 and trans-17 are isostructural and, hence, only the structure
of the former complex is shown in Fig. 9 along with data for
both compounds. A view of the molecular structure of trans-17
is available as ESI (Fig. S3†).
Complexes trans-15 and trans-17 crystallise with an imposed
symmetry (the central atoms reside on crystallographic inver-
sion centres), which renders only the half of their molecules
structurally independent and the coordination spheres exactly
planar. Their structures are similar to those of trans-
[MCl2(Hdpf-κP)2]·2AcOH (M = Pd, Pt)50 and Pd(II) complexes
featuring P-monodentate, 1′-substituted (diphenylphosphino)-
ferrocene donors, trans-[MCl2(Ph2PfcY-κP)2].51 Unlike these
compounds, however, the chloride ligands in trans-15 and
trans-17 are disordered over two positions related by rotation
of the Pt–Cl bonds along the P–P′ axis (relative populations: ca.
The reaction of 11 with copper(I) triflate
In addition to the Group 8–10 metals, the coordination study
with 11 was extended to Cu(I), which has a significant hard-
soft borderline character.52 Mixing ligand 11 (2 equiv.) with
copper(I) triflate (as a toluene adduct) in dry CDCl3 afforded a
yellow solution, containing a single Cu-11 product according
to 31P NMR analysis (δP −7.7). Unfortunately, the 1H NMR
spectra were rather inconclusive as they displayed extremely
broad signals for the ferrocene CH and methylene protons.
Signals of the methoxy (δH 3.03) and the PPh2 groups were also
3380 | Dalton Trans., 2013, 42, 3373–3389
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Fig. 11 View of the molecular structure of complex 18 showing atom labelling
and displacement ellipsoids at the 30% probability level. For clarity, only one
orientation of the disordered methoxymethyl group in ligand 2 (Fe2) is shown.
The intramolecular hydrogen bond O1W–H2W⋯O5 is indicated by a dotted line
(O1W⋯O5 = 2.807(1) Å).
Fig. 10 View of the molecular structure of 16 showing 30% probability displa-
cement ellipsoids. For clarity, only one orientation of the disordered rings
C(6–10) and C(12–17) is shown. Primed atoms are generated by the crystallo-
graphic inversion. Selected distances and angles (in Å and °): Pd–Cl1 2.2621(10),
Pd–Cl2 2.3281(8), Pd–Cl2’ 2.4300(9), Pd–P 2.2294(8); P–Pd–Cl1 91.64(3), P–Pd–
Cl2 93.69(3), Cl1–Pd–Cl2 89.25(3), Cl2–Pd–Cl2’ 85.30(3).
Table 4 Selected distances and angles for complex 18 (in Å and °)a
Distances
Angles
Cu–P1
Cu–P2
Cu–O4
Cu–O1W
S–O (range)
S–C1
Fe1–Cp(P1)
Fe1–Cp(C1)
Fe2–Cp(P2)
Fe2–Cp(C2)
2.2527(9)
2.247(1)
2.2616(9)
2.149(1)
1.422(1)–1.439(1)
1.818(1)
1.644(2)
1.643(2)
1.643(2)
1.643(2)
P1–Cu–P2
P1–Cu–O4
P1–Cu–O1W
P2–Cu–O4
P2–Cu–O1W
O4–Cu–O1W
∠Cp(P1), Cp(C1)
∠Cp(P2), Cp(P2)
τ1
129.27(4)
104.92(4)
111.53(4)
103.68(4)
110.64(4)
87.65(4)
2.4(2)
2.2(3)
145.9(3)
140.8(4)
τ2
a Definitions of the ring planes: Cp(Pn) = C(n01–n05), Cp(Cn) = C(n06–
n10). CgP/C are the respective centroids. τn is the torsion angle C(n01)–
Cg(Pn)–Cg(Cn)–C(n06).
Scheme 10 Formation of 18 from [Cu(O3SCF3)]·1/2PhMe and 11.
Nonetheless, there is only a handful of such Cu(I) complexes
bearing phosphine and ether or aqua ligands that have been
structurally characterized,54 namely [Cu(PPh3)2(THF-κO)-
(O3SCF3-κO)]55 and a dicopper(I) complex with an extended,
calixarene-type ligand.56 The Cu–P bond lengths in 18 are
similar to each other and also to the Cu–PPh3 distances in
[Cu(PPh3)2(THF-κO)(O3SCF3-κO)]. In contrast, the individual
Cu–O distances differ significantly from each other (Cu–O1W
< Cu–O4), reflecting very likely the different donor abilities of
the triflate ion and water present as O-donors in 18 (cf. Cu–O-
(triflate) 2.168(2), Cu–O(THF) 2.125(2) Å in the reference com-
pound). The donor atoms in 18 constitute a distorted tetra-
hedral environment in which the P–Cu–P angle is the most open
and the O–Cu–O angle is the most acute (Fig. S4†). This distor-
tion seems to result not only from different steric demands of
the ligands, but also from an intramolecular hydrogen-
bonding interaction O1W–H12W⋯O5, which results in incli-
nation of O1W towards the coordinated triflate. The other
hydrogen atom (H1W) in the Cu-bound water molecule forms
a hydrogen bridge to ether oxygen (O1) in a neighbouring
broadened, but to a lesser extent. Evaporation of the reaction
mixture followed by the addition of commercial (wet) diethyl
ether and storing overnight at 4 °C afforded aqua complex 18
as a yellow crystalline solid (Scheme 10).
The 1H NMR spectrum of 18 showed the expected signals
due to coordinated 11; the 31P NMR signal (δP −7.8) was
observed close to that of the presumed intermediate [Cu(11)2]-
(O3SCF3). In its ESI mass spectrum, compound 18 displayed a
signal at m/z 891, corresponding to [Cu(11)2]+ as the heaviest
fragment species, whereas the IR spectra confirmed the pres-
ence of the triflate anion (1290, 1229 and 1026 cm−1 53
water.
Similar to the complexes mentioned above, the methoxy-
methyl group in complex 18 behaves as an innocent dangling
substituent. This was indeed corroborated by X-ray diffraction
analysis (Fig. 11 and Table 4).
)
and
The Cu(I) ion in complex 18 possesses a relatively common
P2O2 donor set (for a detailed view, see ESI, Fig. S4†).
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molecule, which in turn results in the formation of molecular relative to internal SiMe4 (13C and 1H) or to external 85%
pairs lying around crystallographic inversion centres (see ESI, aqueous H3PO4 (31P). In addition to the usual notation of
Fig. S5†).
signal multiplicity, vt and vq were used to distinguish virtual
triplets and quartets due to AA′BB′ and AA′BB′X spin systems
arising from the ferrocene cyclopentadienyls (A, B = 1H, X =
31P). IR spectra were recorded on an FT IR Nicolet Magna 650
spectrometer. Electron impact ionisation (EI) mass spectra
Conclusions
The reduction of ferrocenecarbaldehydes bearing phosphine including high-resolution measurements (HR) were obtained
substituents at position 1′ or 2 with an excess of BH3·L (L = with a GCT Premier spectrometer (Waters). Electrospray ioni-
THF or SMe2) in THF at 0 °C proceeds selectively to afford sation (ESI) mass spectra were recorded with a LCQ Fleet
stable phosphinoalcohol–borane adducts in quantitative (Thermo Fisher Scientific; HR) or an Esquire 3000 (Bruker; low
yields. In contrast, a similar reduction performed at elevated resolution) spectrometer.
temperatures (refluxing in THF) produces methylferrocene
derivatives resulting from the exhaustive reduction (deoxygena-
Syntheses
tion) of the starting phosphino-aldehydes. The observed differ-
Reaction tests with aldehyde 2. Aldehyde 2 (100 mg,
ence in the reaction course emphasises the need for careful 0.25 mmol) was dissolved in dry THF (5 mL) and the solution
optimisation of the reaction conditions in reductions with was cooled if required. The appropriate BH3 source (1 mmol)
borane which, on the other hand, may pay off by the highly was added and the resulting mixture was treated as specified
selective preparation of chemically different compounds.
below. In all cases, the addition of BH3 resulted in a swift
Importantly, the resulting phosphinoalcohol–borane colour change from the original reddish-orange to orange-
adducts represent stable, protected-at-phosphorus synthetic yellow. Upon completion of the reaction, the mixture was
building blocks suitable for the preparation of other phosphino- cooled to room temperature when necessary, treated with
ferrocenyl derivatives. With this study, we have demon- methanol (1 mL, stirring for 30 min) to destroy any unreacted
strated their synthetic potential by the smooth, two-step borane and then evaporated under vacuum. The product(s)
preparation of phosphinoether donor 11 from 5. Compound were isolated by column chromatography over silica gel using
11 extends the still narrow family of donors formally homo- ethyl acetate–hexane (2 : 1) as the eluent.
logous to the known functional phosphinoferrocene ligands
(Ph2PfcY → Ph2PfcCH2Y, ref. 6e–j).
The reduction of 2 with BH3·THF (1 M in THF, 1.0 mL,
1.0 mmol) at 0 °C (ice bath) for 90 min afforded pure 5 (97 mg,
The coordination study with 11 clearly demonstrated flexi- 93%). A tiny amount of FcPPh2·BH3 (ca. 5 mg) was easily
bility as well as the hybrid and potentially hemilabile nature of removed during chromatography as the first band. The reac-
this donor. The presence of a methylene spacer in 11 renders tion was performed several times with different lots of the
the ligand structure more flexible and requires the formation borane solution (1 M BH3 in THF stabilised with 0.005 M
of large chelate rings, which both lower the tendency towards NaBH4, all from Sigma-Aldrich) without any noticeable
the formation of stable chelates. If formed, the chelate rings change. Increasing the reaction temperature to ca. 23 °C did
seem to readily open in the presence of suitable donors such not change the reaction course (isolated yield of 5: 95 mg,
as Cl− and adventitious H2O. The behaviour of 11 thus con- 92%). The reduction with BH3·SMe2 (1 M in THF, 1.0 mL,
trasts with that of Ph2PfcOMe, in which chelate coordination 1.0 mmol) at 0 °C gave the same product (isolated yield of 5:
is facilitated by a more rigid pre-disposition of the donor 94 mg, 91%).
moieties.
In another series of experiments, the reducing agent was
added at room temperature and the mixture was immediately
transferred to a preheated oil bath and refluxed overnight
(16 h). The reaction with BH3·THF (1 M in THF, 1.0 mL,
1.0 mmol) under reflux furnished a mixture of two products
that were easily separated by column chromatography. The
Experimental
Materials and methods
The syntheses were carried out under an argon atmosphere first (faster eluting) band contained 8 (57 mg, 57%; contami-
and with the exclusion of direct sunlight. Tetrahydrofuran nated with FcPPh2·BH3), while the second was found to
(THF) was distilled from potassium/benzophenone ketyl. Sol- contain pure phosphinoalcohol–borane adduct 5 (41 mg,
vents used for work-up and chromatography (Lachner) were 39%). When the reaction was repeated, the products were iso-
used without any further purification. 1,1′-Dibromoferro- lated in different amounts (67 mg of crude 8, 27 mg (26%) of
cene,57 2,7 (Sp)-4,11b [(η6-p-cymene)RuCl2]2,58 and [MCl2(cod)] 5). A similar reduction with BH3·SMe2 (1 M in THF, 1.0 mL,
(M = Pd, Pt)59 were prepared as described in the literature. 1.0 mmol; refluxing/16 h) afforded a yellow solid, which gave
Other chemicals (including anhydrous acetonitrile, dimethyl- only one band during the chromatographic purification. Sub-
sulphoxide and dichloromethane) were used as received from sequent evaporation afforded 8 in quantitative yield (100 mg).
commercial sources (Sigma-Aldrich).
According to NMR analysis, the product was contaminated
NMR spectra were recorded with a Varian Unity Inova 400 with traces of FcPPh2·BH3. The compound was crystallised
spectrometer at 25 °C. Chemical shifts (δ/ppm) are given from hot heptane.
3382 | Dalton Trans., 2013, 42, 3373–3389
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Analytical data for 5. 1H NMR (CDCl3): δ ca. 0.75–1.80 (very vacuum to afford analytically pure adduct 5 as an orange
br m, 3 H, BH3), 1.45 (t, 3JHH = 6.0 Hz, 1 H, CH2OH), 4.07 (vt, J′ microcrystalline solid. Yield: 1.838 g (89%). If appropriate, the
3
= 1.9 Hz, 2 H, C5H4CH2OH), 4.12 (d, JHH = 6.0 Hz, 2 H, compound can be crystallised from hot heptane or warm ethyl
CH2OH), 4.22 (vt, J′ = 1.9 Hz, 2 H, C5H4CH2OH), 4.42 (vq, J′ = acetate–hexane.
1.9 Hz, 2 H, C5H4PPh2), 4.53 (m, 2 H, C5H4PPh2), 7.38–7.50 (m,
1′-(Dicyclohexylphosphino)-1-hydroxymethylferrocene–borane
8 H, PPh2), 7.54–7.62 (m, 2 H, PPh2). Note: the signals due to (1/1) (6). Compound 6 was obtained from aldehyde 3 (1.240 g,
CH2OH collapse into unresolved broad signals when the solu- 3.0 mmol in 30 mL of THF) and BH3·THF (7.5 mL of 1.0 M in
tion is allowed to stand for some time. 13C{1H} NMR (CDCl3): δ THF, 7.5 mmol) as described above for 5. The resulting crude
60.18 (CH2OH), 69.36 (d, 1JPC = 68 Hz, C–P of C5H4PPh2), 69.52 material was purified by chromatography on silica (packed in
and 70.01 (2 × s, 2 C, CH of C5H4CH2OH); 72.16 (d, JPC = 7 Hz, hexane–diethyl ether, 1 : 1). Hexane was used first to elute non-
2 C, CH of C5H4PPh2), 73.13 (d, JPC = 10 Hz, 2 C, CH of polar impurities and then replaced with hexane–diethyl ether
C5H4PPh2), 89.47 (s, C-CH2OH of C5H4CH2OH), 128.46 (d, JPC (1 : 1) to elute the major band due to the product. Subsequent
= 10 Hz, 4 C, CH of PPh2), 130.97 (d, JPC = 2 Hz, 2 C, CH of evaporation and drying under vacuum afforded pure 6 as an
1
PPh2), 131.07 (d, JPC = 59 Hz, 2 C, Cipso of PPh2), 132.60 (d, orange microcrystalline solid. Yield: 1.238 g (97%).
JPC = 10 Hz, 4 C, CH of PPh2). 31P{1H} NMR (CDCl3): δ 16.6 (br
1H NMR (CDCl3): δ ca. 0.15–1.10 (very br m, 3 H, BH3),
d). IR (Nujol): ν/cm−1 3576 w, 3539 m, 2403 s, 2366 s, 2341 m, 1.08–2.03 (m, 23 H, Cy and OH), 4.25 (vt, J′ ≈ 1.8 Hz, 2 H,
1308 m, 1230 m, 1181 m, 1172 s, 1109 s, 1056 vs, 1026 s, 997 C5H4CH2OH), 4.31 (vq, J′ ≈ 1.8 Hz, 2 H, C5H4PCy2), 4.35 (vt,
3
vs, 920 w, 846 m, 840 s, 821 s, 745 vs, 704 vs, 642 s, 623 w, J′ ≈ 1.9 Hz, 2 H, C5H4CH2OH), 4.41 (d, JHH = 5.6 Hz, 2 H,
611 m, 529 m, 519 m, 499 vs, 479 s, 466 m, 442 m. ESI+ MS: CH2OH), 4.43 (d of vt, J ≈ 1.0, 1.9 Hz, 2 H, C5H4PCy2). 13C{1H}
m/z 439 (probably [M + K − BH3]+), 437 (dominant; [M + Na]+), NMR (CDCl3): δ 25.91 (d, JPC = 2 Hz, CH2 of Cy), 26.81 (s, CH2
400 ([M − BH3]+). MS (EI): m/z (relative abundance): 414 of Cy), 26.83 (d, JPC ≈ 3 Hz, CH2 of Cy), 26.93 (d, JPC = 5 Hz,
(2, M+˙), 401 (5), 400 (20, [M − BH3]+˙), 385 (11), 384 (46, [M − CH2 of Cy), 27.09 (d, JPC = 3 Hz, CH2 of Cy), 32.27 (d, JPC
=
1
BH3 − O]+˙), 307 (11), 226 (8), 169 (5), 170 (5), 167 (100), 165 35 Hz, α-CH of Cy), 60.41 (CH2OH), 68.58 (d, 1JPC = 56 Hz, C–P
(22), 152 (5), 121 (3, [C5H5Fe]+), 56 (5, Fe+). HR MS (EI) calc. for of C5H4PPh2), 69.27 and 70.04 (2 × s, 2 C, CH of C5H4CH2OH);
C23H2411B56FeOP (M+˙) 414.1007; found 414.1018. Anal. calc. 70.81 and 72.30 (2 × d, JPC = 7 Hz, 2 C, CH of C5H4PPh2); 89.76
for C23H24BFeOP (414.1): C 66.71, H 5.84%. Found: C 66.41, (s, C-CH2OH of C5H4CH2OH). 31P{1H} NMR (CDCl3): δ 24.0 (br
H 5.92%.
d). IR (Nujol): ν/cm−1 3579 s, ca. 3200–3535 s (maximum at
Analytical data for 8. 1H NMR (CDCl3): δ ca. 0.75–1.80 (very 3431), 2370 vs, 2340/2333 s, 2250 m, 1311 w, 1296 w, 1275 w,
br m, 3 H, BH3), 1.73 (s, 3 H, CH3), 3.94 (vt, J′ = 1.9 Hz, 2 H, 1253 w, 1202 m, 1168 s, 1062 vs, 1049/1043 s, 1030/1024 m,
C5H4), 4.04 (vt, J′ = 1.8 Hz, 2 H, C5H4), 4.31 (vq, J′ = 1.9 Hz, 2 H, 1007 w, 981 m, 920 m, 890 m, 850 s, 838 s, 819 s, 763/758 s,
C5H4), 4.44 (m, 2 H, C5H4), 7.37–7.49 (m, 8 H, PPh2), 7.55–7.62 633 s, 605 s, 528 s, 507 s, 497 m, 464 m. MS (EI): m/z (relative
(m, 2 H, PPh2). 13C{1H} NMR (CDCl3): δ 14.15 (s, CH3), 68.56 abundance) 426 (4, M+˙), 413 (12), 412 (68, [M − BH3]+˙), 410
(d, 1JPC = 70 Hz, C–P of C5H4PPh2), 69.15 and 70.90 (2 × s, 2 C, (8), 397 (35), 396 (100, [M − BH3 − O]+˙), 394 (10), 330 (7), 329
CH of C5H4CH3); 72.72 (d, JPC = 7 Hz, 2 C, CH of C5H4PPh2), (27), 314 (14), 313 (43), 312 (5), 311 (6), 232 (31), 231 (100), 230
73.41 (d, JPC = 10 Hz, 2 C, CH of C5H4PPh2), 85.61 (s, C-CH3 of (9), 229 (25), 201 (5), 200 (32), 199 (28), 198 (8), 186 (23), 167
C5H4CH3), 128.35 (d, JPC = 10 Hz, 4 C, CH of PPh2), 130.77 (d, (5), 153 (5), 152 (18), 151 (13), 135 (34), 134 (20), 133 (5), 121
1
JPC = 2 Hz, 2 C, CH of PPh2), 131.51 (d, JPC = 59 Hz, 2 C, Cipso (36, [C5H5Fe]+), 79 (10, Fe+), 67 (5), 56 (13). HR MS (EI) calc. for
of PPh2), 132.65 (d, JPC = 9 Hz, 4 C, CH of PPh2). 31P{1H} NMR C23H3611B56FeOP (M+˙) 426.1946; found 426.1933. Anal. calc.
(CDCl3): δ 16.6 (br d). Anal. calc. for C23H24BFeOP (398.1): for C23H36BFeOP (426.1): C 64.82, H 8.52%. Found: C 65.01, H
C 69.40, H 6.08%. Found: C 69.54, H 5.93%.
Preparation of 1′-(diphenylphosphino)-1-hydroxymethylfer-
8.55%.
(Sp)-2-(Diphenylphosphino)-1-hydroxymethylferrocene–borane
rocene–borane (1/1) (5). A solution of BH3·THF (12 mL of (1/1) [(Sp)-7]. An ice-cooled solution of (Sp)-4 in dry THF
1.0 M in THF, 12 mmol; Sigma-Aldrich, stabilised with 0.005 (100 mg, 0.25 mmol in 5 mL) was treated with a solution of
M NaBH4) was added to a solution of 1 (1.995 g, 5.0 mmol) in BH3 in the same solvent (1.0 mL, 1.0 M, 1.0 mmol). The
dry THF (25 mL) with stirring and cooling in an ice bath. mixture immediately turned from orange to yellow. After stir-
Upon mixing, the colour of the reaction mixture quickly ring at 0 °C for 90 min, the reaction mixture was quenched
turned from the original red-orange to deep orange-yellow. with methanol (0.5 mL), diluted with diethyl ether and
After stirring at 0 °C for 90 min, the reaction mixture was evaporated under vacuum. The orange-yellow glassy residue
diluted with wet diethyl ether (5 mL of ether + 0.5 mL of H2O) was purified by column chromatography on silica gel with
to decompose an excess of borane, stirred for another 30 min diethyl ether. Evaporation of a single yellow band followed by
and evaporated. The orange residue was dissolved in a small drying under vacuum afforded pure (Sp)-7 as a yellow-orange
volume of warm ethyl acetate and introduced to the top of a glassy solid. Yield: 104 mg (quant.). When appropriate, the
silica gel column. Elution with ethyl acetate–hexane (2 : 1) led adduct can be re-crystallised from hot heptane. However, such
to the development of two bands. The first minor band con- crystallisation is accompanied by a significant loss of the
taining predominantly FcPPh2·BH3 was discarded. The second material and the compound often separates as an amorphous
orange-yellow band was collected and evaporated under solid.
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1H NMR (CDCl3): δ ca. 0.95–2.00 (very br m, 3 H, BH3), 1.94 2 H, C5H4CH2OH), 4.21 (vt, J′ = 1.9 Hz, 2 H, C5H4CH2OH), 4.38
3
(t, JHH = 6.9 Hz, 1 H, CH2OH), 3.92 (m, 1 H, C5H3), 4.20 (s, 5 (vq, J′ = 1.9 Hz, 2 H, C5H4PPh2), 4.49 (m, 2 H, C5H4PPh2),
2
3
H, C5H5), 4.31 (dd, JHH = 12.8, JHH ≈ 6.5 Hz, 1 H, CH2OH), 7.38–7.50 (m, 8 H, PPh2), 7.55–7.62 (m, 2 H, PPh2). 13C{1H}
1
4.41 (t, J = 2.9 Hz, 1 H, C5H3), 4.61 (m, 1 H, C5H3), 4.71 (dd, NMR (CDCl3): δ 57.79 (CH2OCH3), 69.16 (d, JPC = 69 Hz, C–P
3
2JHH = 12.8, JHH ≈ 6.8 Hz, 1 H, CH2OH), 7.32–7.58 (m, 8 H, of C5H4PPh2), 69.88 (CH2OCH3), 70.34, 71.05 (2 × s, 2 C, CH of
PPh2), 7.66–7.74 (m, 2 H, PPh2). 13C{1H} NMR (CDCl3): δ 59.28 C5H4CH2OH); 72.32 (d, JPC = 8 Hz, 2 C, CH of C5H4PPh2), 73.24
1
(CH2OH), 68.45 (d, JPC = 64 Hz, C–P of C5H3), 70.17 (s, C5H5), (d, JPC = 10 Hz, 2 C, CH of C5H4PPh2), 84.77 (s, C-CH2OH of
70.43 (d, JPC = 6 Hz, CH of C5H3), 73.88 (d, JPC = 4 Hz, CH of C5H4CH2OH), 128.43 (d, JPC = 10 Hz, 4 C, CH of PPh2), 130.90
1
C5H3), 74.09 (d, JPC = 7 Hz, CH of C5H3), 92.22 (d, 2JPC = 15 Hz, (d, JPC = 2 Hz, 2 C, CH of PPh2), 131.28 (d, JPC = 59 Hz, 2 C,
C-CH2OH of C5H3), 128.39 and 128.53 (2 × d, 2 C, JPC = 10 Hz,
C
ipso of PPh2), 132.64 (d, JPC = 10 Hz, 4 C, CH of PPh2). 31P{1H}
CH of PPh2); 130.23 (d, 1JPC = 61 Hz, Cipso of PPh2), 130.91 and NMR (CDCl3): δ 16.4 (br d). IR (Nujol): ν/cm−1 2411 s, 2386 vs,
1
131.23 (2 × d, JPC = 2 Hz, CH of PPh2); 131.31 (d, JPC = 59 Hz, 2354 s, 2249 w, 1310 m, 1241 m, 1196 m, 1181 m, 1172 m,
Cipso of PPh2), 132.37 and 133.25 (2 × d, JPC = 9 Hz, 2 C, CH of 1157 w, 1131 w, 1108 s, 1087 vs, 1058 vs, 1027 s, 952 s, 851 w,
PPh2). 31P{1H} NMR (CDCl3): δ 15.4 (br d). IR (neat): ν/cm−1 ca. 834 m, 818 w, 811 m, 762 m, 746 vs, 705 vs, 640 s, 623 w,
3430 very br m, 3077 w, 3057 w, 3006 w, 2392 s, 2352 sh, 2261 w, 611 m, 592 m, 518 w, 499 vs, 479 m, 467 m, 441 m. EI MS: m/z
1484 m, 1436 s, 1411 w, 1315 composite br, 1249 m, 1186 m, (relative abundance) 428 (4, M+˙), 414 (23, [M − BH3]+˙), 399
11 621 m, 1107 s, 1061 s, 1000 m, 825 s, 742 s, 699 s, 649 m, (12, [M − Me]+), 384 (100, [M − C2H4O]+˙, isobaric with
636 m, 611 m, 495 s, 478 s. MS (EI): m/z (relative abundance) 414 FcPPh2·BH3), 307 (26), 276 (5), 229 (10), 199 (4), 183 (7), 171
(6, M+˙), 400 (100, [M − BH3]+˙), 384 (37), 279 (11), 199 (8), 173 (9), 170 (10). HR MS (EI) calc. for C24H2611B56FeOP (M+˙)
(42, [PPh2 − 2H]+), 171 (7), 170 (6), 153 (7), 152 (9), 138 (9), 121 428.1164; found 428.1176. Anal. calc. for C24H26BFeOP (428.1):
(51, [C5H5Fe]+), 108 (14). HR MS (EI) calc. for C23H2411B56FeOP C 67.33, H 6.12%. Found: C 67.25, H 6.14%.
(M+˙) 414.1007; found 414.0997. Anal. calc. for C23H24BFeOP
1′-(Diphenylphosphino)-1-(methoxymethyl)ferrocene
(11).
(414.1): C 66.71, H 5.84%. Found: C 66.66, H 6.00%.
1,4-Diazabicyclo[2.2.2]octane (225 mg, 2.0 mmol) and 10
Deborylation of 5. Adduct 5 (10.5 mg, 0.025 mmol) and 1,4- (750 mg, 1.75 mmol) were dissolved in dry toluene (25 mL).
diazabicyclo[2.2.2]octane (3.5 mg, 0.03 mmol) were dissolved The reaction vessel was flushed with argon and sealed with a
in C6D6 (ca. 0.7 mL) and the solution was warmed to 60 °C for rubber septum. The mixture was stirred at room temperature
3 h. After cooling to room temperature, the mixture was ana- overnight and evaporated under vacuum. The residue was
lysed by 1H and 31P{1H} NMR spectroscopy. The spectra taken up with a small amount of THF and transferred to the
showed the presence of alcohol 1, dabco·BH3 [δH 2.12 and 2.35 top of a silica gel column. Elution with hexane–diethyl ether
(2 × m, 6 H, CH2); the signal of BH3 is very broad] and dabco (1 : 1) afforded a single orange band, which was collected and
[δH 2.44 (s, CH2)] (N.B. tentative assignment for dabco and evaporated to give 11 as an orange microcrystalline solid.
dabco·BH3 is given).
Yield: 694 mg (96%).
Data for 1: 1H NMR (C6D6): δ 1.51* (td, 3JHH = 6.2, J(H-bond)
1H NMR (CDCl3): δ 3.24 (s, 3 H, CH2OCH3), 3.96 (s, 2 H,
= 2.4 Hz, 1 H, OH), 3.90 (vt, J′ = 1.9 Hz, 2 H), 4.01 (vq, J′ = CH2OCH3), 4.07 (m, 4 H, C5H4), 4.16 (vt, J′ = 1.8 Hz, 2 H, C5H4),
3
1.9 Hz, 2 H) and 4.07 (br vt, 4 H) (CH of fc); 4.12* (d, JHH
=
4.34 (vt, J′ = 1.8 Hz, 2 H, C5H4), 7.28–7.39 (m, 10 H, PPh2). 13C
6.2 Hz, 2 H, CH2), 7.01–7.09 (m, 6 H) and 7.43–7.51 (m, 4 H) {1H} NMR (CDCl3): δ 57.68 (CH2OCH3), 69.77 (s, 2 C, CH of
(PPh2). 31P{1H} NMR: δ −16.2 (s). In the reaction mixture, the C5H4CH2OH), 70.31 (s, CH2OCH3), 70.51 (s, 2 C, CH of
signals are slightly shifted and those marked with an asterisk C5H4CH2OH), 71.23 (d, JPC = 4 Hz, 2 C, CH of C5H4PPh2), 73.29
collapse into singlets due to a rapid proton exchange.
(d, JPC = 15 Hz, 2 C, CH of C5H4PPh2), 76.25 (d, 1JPC = 6 Hz, C–
1′-(Diphenylphosphino)-1-(methoxymethyl)ferrocene–borane P of C5H4PPh2), 83.75 (s, C-CH2OH of C5H4CH2OH), 128.14 (d,
(1/1) (10). Alkylation of alcohol 5 was performed similarly to a JPC = 7 Hz, 4 C, CH of PPh2), 128.51 (s, 2 C, CH of PPh2),
1
method found in the literature.60 Thus, a solution of 7 130.51 (d, JPC = 20 Hz, 4 C, CH of PPh2), 139.06 (d, JPC
=
(830 mg, 2.0 mmol) in dimethylsulphoxide (10 mL) and neat 10 Hz, 2 C, Cipso of PPh2). 31P{1H} NMR (CDCl3): δ −16.3 (s). IR
iodomethane (0.85 g, 6 mmol) was introduced successively to a (Nujol): ν/cm−1 1238 m, 1189 s, 1161 s, 1089 vs, 1028 s, 946 s,
stirred suspension of finely ground KOH (225 mg, 4.0 mmol) 829 w, 842 m, 827 m, 749 s, 740 vs, 700 vs, 694 vs, 635 m,
in dry dimethylsulphoxide (5 mL). The resultant mixture was 569 m, 529 w, 519 m, 501 vs, 490 s, 462 m, 434 m. EI MS: m/z
stirred overnight, diluted with water (50 mL) and extracted (relative abundance) 414 (100, M+˙), 399 (6, [M − Me]+), 384
with diethyl ether (3 × 15 mL). The organic extracts were (7), 305 (13), 281 (7), 228 (15), 226 (47), 178 (12), 171 (6), 170
washed with water and brine, dried over MgSO4 and evapor- (7), 149 (93), 86 (48). HR MS (EI) calc. for C24H2356FeOP (M+˙)
ated under vacuum. The resulting orange residue was dis- 414.0836; found 414.0834. ESI MS: m/z 415 ([M + H]+), 437
solved in a small amount of THF and purified by flash ([M + Na]+), 453 ([M + K]+). Anal. calc. for C24H23FeOP (414.2):
chromatography (silica gel, diethyl ether). A single yellow band C 69.58, H 5.60%. Found: C 69.82, H 5.47%.
was collected and evaporated to afford analytically pure 10 as
an orange solid. Yield: 762 mg (89%).
Dichlorido(η6-p-cymene)[1′-(diphenylphosphino-κP)-1-(meth-
oxymethyl)ferrocene]ruthenium(II) (12). Di-μ-chloridobis[(η6-p-
1H NMR (CDCl3): δ ca. 0.75–1.80 (very br m, 3 H, BH3), 3.22 cymene)chloridoruthenium(II)] (18.5 mg, 0.03 mmol) and 11
(s, 3 H, CH2OCH3), 3.88 (s, 2 H, CH2OCH3), 4.07 (vt, J′ = 1.9 Hz, (25 mg, 0.06 mmol) were dissolved in dichloromethane (2 mL),
3384 | Dalton Trans., 2013, 42, 3373–3389
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yielding a dark orange-red solution. The solution was stirred 2 H, C5H4), 4.40 and 4.45 (2 × vt, J′ ≈ 1.8 Hz, 2 H, C5H4); 4.69
for 60 min, filtered through a PTFE syringe filter (0.45 μm) and (vq, J′ ≈ 1.9 Hz, 2 H, C5H4), 5.57 (m, 2 H, CH = of cod),
the filtrate was evaporated under vacuum. The residue was 7.32–7.43 (m, 6 H, PPh2), 7.56–7.73 (m, 4 H, PPh2). 31P{1H}
1
stirred with pentane and diethyl ether (5 mL each) overnight, NMR (CDCl3): δ 23.6 (d, JRhP = 151 Hz). ESI+ MS: m/z 683
leaving a solid, which was filtered off and dried under vacuum ([M + Na]+), 625 ([M − Cl]+; dominant). Anal. calc. for
to afford pure 12. Yield: 40.5 mg, 94% (red-brown microcrystal- C32H35ClFeOPRh (660.8): C 58.16, H 5.34%. Found: C 57.92, H
line solid).
1H NMR (CDCl3): δ 0.93 (d, 3JHH = 7.0 Hz, 6 H, CHMe2), 1.82
5.56%.
Attempted reaction of 11 with [NiCl2(dme)]. A solution of 11
3
(s, 3 H, C6H4Me), 2.56 (sept, JHH = 7.0 Hz, 1 H, CHMe2), 3.20 (41.5 mg, 0.10 mmol) in dry dichloromethane (2 mL) was
(s, 3 H, CH2OMe), 3.60 and 3.87 (2 × vt, J′ ≈ 1.9 Hz, 2 H, C5H4); added to a suspension of [NiCl2(dme)] (22 mg, 0.10 mmol;
3.96 (s, 2 H, CH2OMe), 4.31 (m, 2 H, C5H4), 4.49 (vq, J′ ≈ dme = 1,2-dimethoxyethane) suspended in absolute ethanol
1.7 Hz, 2 H, C5H4), 5.09 (d, J = 6.2 Hz, 2 H, C6H4), 5.16 (dd, J = (2 mL). The mixture was stirred for 1 h and evaporated.
6.2, ca. 1.3 Hz, 2 H, C6H4), 7.39–7.47 (m, 6 H, PPh2), 7.84–7.91 Attempted extraction of the evaporation residue led to an
(m, 4 H, PPh2). 31P{1H} NMR (CDCl3): δ 19.4 (s). ESI+ MS: m/z extensive decomposition.
685 ([M − Cl]+), 649 ([M − Cl − HCl]+). Anal. calc. for
C34H37Cl2FeOPRu (720.4): C 56.68, H 5.18%. Found: C 56.51, methyl)ferrocene]palladium(II)
H 5.27%. (14.5 mg, 0.05 mmol) and 11 (41.5 mg, 0.10 mmol) were dis-
trans-Dichloridobis[1′-(diphenylphosphino-κP)-1-(methoxy-
(trans-15). [PdCl2(cod)]
Reaction of 12 with Ag[SbF6]. Isolation of 13. Di-μ-chlorido- solved in dry dichloromethane (2.5 mL) to give a clear red-
bis[(η6-p-cymene)chloridoruthenium(II)] (15.5 mg, 25 μmol) orange solution. The reaction mixture was stirred for 30 min
and 11 (21 mg, 51 μmol) were dissolved in dichloromethane and filtered through a PTFE syringe filter (0.45 μm pore size).
(2 mL) and the solution was stirred for 30 min. To the result- The filtrate was layered with absolute ethanol (5 mL) and the
ing solution of complex 12 was added Ag[SbF6] (17 mg, mixture was allowed to crystallise by liquid-phase diffusion for
50 μmol) dissolved in dry MeCN (2 mL) and stirring was con- several days. The crystals that formed were filtered off, washed
tinued for another 30 min. The mixture was filtered through a with pentane and dried under vacuum. Yield of trans-15:
PTFE syringe filter and evaporated. The residue was triturated 47 mg (93%), red crystals.
with diethyl ether and pentane, and dried under vacuum to
1H NMR (CDCl3): δ 3.28 (s, 3 H, CH2OMe), 4.15 (s, 2 H,
give essentially pure 13 in practically quantitative yield. An CH2OMe), 4.36 (m, 2 H, C5H4), 4.43 (vt, J′ ≈ 1.8 Hz, 2 H, C5H4),
attempted crystallisation from chloroform–hexane afforded 4.53 (m, 2 H, C5H4), 4.57 (vt, J′ ≈ 1.8 Hz, 2 H, C5H4), 7.34–7.45
several single crystals of 13·1/2CHCl3 suitable for X-ray diffrac- (m, 6 H, PPh2), 7.60–7.67 (m, 4 H, PPh2). 31P{1H} NMR
tion analysis (red irregular block, 0.30 × 0.36 × 0.41 mm3).
(CDCl3): δ 15.4 (s). ESI+ MS: m/z 1029 ([M + Na]+), 1004 ([M −
3
1H NMR (CDCl3): δ 1.16 and 1.19 (2 × d, JHH = 6.9 Hz, 2H]+). Anal. calc. for C48H46Cl2Fe2O2P2Pd (1005.8): C 57.32,
3 H, CHMe2); 1.88 (s, 3 H, C6H4Me), 2.13 (d, 5JPH = 1.4 Hz, 3 H, H 4.61%. Found: C 57.03, H 4.47%.
3
MeCN), 2.71 (sept, JHH = 6.9 Hz, 1 H, CHMe2), 3.29 (s, 3 H,
Di-μ-chlorido-bis[chlorido{1′-(diphenylphosphino-κP)-1-(meth-
OMe), 3.84 (td, J = 2.5, 1.3 Hz, 1 H), 3.86 (td, J = 2.5, 1.3 Hz, 1 oxymethyl)ferrocene}palladium(II)] (16). [PdCl2(cod)] (28.5 mg,
H), 3.90 (m, 1 H), 4.07 (dt, J = 2.5, 1.3 Hz, 1 H), 4.19 (dt, J = 2.5, 0.10 mmol) and 11 (41.5 mg, 0.10 mmol) were dissolved in dry
1.3 Hz, 1 H), 4.44 (m, 1 H), 4.63 (m, 2 H) and 4.80 (m, 2 H) (8 × dichloromethane (2.5 mL) to give a dark red-brown solution.
CH of C5H4); 5.13 and 5.24 (2 × d of unresolved t, J = 6.2 Hz, 1 After stirring for 30 min, the solution was filtered through a
H, C6H4); 5.48 and 5.58 (2 × dd, J = 6.2, 1.5 Hz, 1 H, C6H4); PTFE syringe filter (0.45 μm pore size). The filtrate was diluted
7.51–7.90 (m, 10 H, PPh2). 31P{1H} NMR (CDCl3): δ 29.7 (s). with absolute ethanol (5 mL) and the mixture was allowed to
Anal. calc. for
C 42.92, H 4.00, N 1.37%. Found: C 42.66, H 4.32, N 1.24%.
C
36H40ClF6FeNOPRuSb·1/2CHCl3 (1021.5): crystallise at 4 °C overnight. The separated solid was filtered
off, washed with pentane and dried under vacuum. Yield of
Similar reactions of in situ generated 12 with a THF solution 16: 41 mg (69%), reddish-brown microcrystalline solid.
of Ag[SbF6] or, alternatively, with Na[PF6] in methanol pro-
duced only intractable mixtures.
1H NMR (CDCl3): δ 3.36 (s, 3 H, CH2OMe), 4.39 (s, 2 H,
CH2OMe), 4.51 (m, 2 H, C5H4), 4.56 (br vq, J′ ≈ 1.8 Hz, 2 H,
Chlorido(η2:η2-cycloocta-1,5-diene)[1′-(diphenylphosphino-κP)- C5H4), 4.71 (br vt, 2 H, C5H4), 4.79 (br s, 2 H, C5H4), 7.32–7.65
1-(methoxymethyl)ferrocene]rhodium(I) (14). Di-μ-chloridobis (m, 10 H, PPh2). 31P{1H} NMR (CDCl3): δ 31.7 (s). ESI+ MS: m/z
[(η2:η2-cycloocta-1,5-diene)rhodium(I)] (12.5 mg, 0.025 mmol) 1207 ([M
+
Na]+), 555/557 ([Pd(11)Cl]+). Anal. calc. for
46.41, 3.82%.
(2 mL). The solution was stirred for 1 h, filtered through a Found: C 46.46, H 3.77% (crystallised from CH2Cl2–ethanol).
PTFE syringe filter (0.45 μmm) and evaporated under vacuum. In situ NMR study of the reaction of [Pd(MeCN)4][BF4]2 with
and 11 (21 mg, 0.05 mmol) were dissolved in dichloromethane C48H46Cl2Fe2O2P2Pd·CH2Cl2 (1268.0):
C
H
The residue was washed with pentane (5 mL) and dried under 11. [Pd(MeCN)4][BF4]2 (4.5 mg, 0.010 mmol) and 11 (8.5 mg,
vacuum to give analytically pure 14 as a yellow-orange amor- 0.021 mmol) were mixed in dry CDCl3 (ca. 0.7 mL; dried over
phous solid. Yield: 33 mg (quant.).
CaH2). The solid precursors quickly dissolved to afford a deep
1H NMR (CDCl3): δ 1.87–2.13 and 2.35–2.53 (2 × m, 4 H, blue-violet solution. After stirring for 30 min, the reaction
CH2 of cod); 3.13 (m, 2 H, CHv of cod), 3.34 (s, 3 H, mixture was filtered (PTFE syringe filter) and analysed by 1H
CH2OMe), 4.31 (s, 2 H, CH2OMe), 4.38 (d of vt, J = 0.9, 1.9 Hz, and 31P NMR spectroscopy. The spectra revealed only very
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Dalton Transactions
broad, multiple resonances, which prevented any detailed 420 m cm−1. Anal. calc. for C49H48CuF3Fe2O6P2S (1059.1): C
interpretation.
55.56, H 4.57%. Found: C 55.72, H 4.52%.
As a next step, the solution was poured onto solid [Ph4As]Cl
(13.5 mg, ca. 0.03 mmol). The arsonium salt dissolved,
causing an immediate colour change from the initial deep
blue-violet to red-orange and separation of a fine precipitate.
After the addition, the mixture was stirred for another 30 min,
filtered as above and analysed again by NMR spectroscopy.
X-Ray crystallography
Single crystals suitable for X-ray diffraction analysis were
grown as described in ESI.† The full-set diffraction data ( h
k
1
l; θmax = 26.0–27.5°, data completeness ≥99%) were collected
with Nonius Kappa CCD or Bruker Apex II CCD diffractometers
equipped with a Cryostream Cooler (Oxford Cryosystems) at
150(2) K using graphite monochromated MoKα radiation (λ =
0.71073 Å). If appropriate, the data were corrected for absorp-
tion by methods incorporated in the diffractometer software.
The structures were solved by the direct methods (SIR9761)
and refined by full-matrix least squares on F2 (SHELXL9762).
Unless noted otherwise, the non-hydrogen atoms were refined
with anisotropic displacement parameters. The OH and BH
hydrogens were identified on difference density maps and
were refined as riding atoms with Uiso assigned to 1.2Ueq of
their bonding atoms (O and B). Other hydrogen atoms were
included at their calculated positions and refined as riding
atoms. Relevant crystallographic data and structure refinement
parameters are available as ESI (Tables S1 and S2†). Particular
details on structure refinement are as follows.
Comparison of the H and 31P{1H} NMR spectra with those of
an authentic sample confirmed the presence of trans-15 as the
major product (>90%). Two additional complexes (δP 15.3 and
15.9) and free 11 (δP −16.3) were also detected in the reaction
mixture.
Reaction of [PtCl2(cod)] with 11. Ligand 11 (21 mg,
0.05 mmol) and [PtCl2(cod)] (9.5 mg, 0.025 mmol) were dis-
solved in dry CDCl3 (1 mL; dried over CaH2). The solution was
stirred for 30 min and analysed by 1H and 31P NMR spec-
troscopy. The spectra suggest that cis-17 was formed along
with a tiny amount of the corresponding trans isomer and lib-
erated cod. The course of the reaction did not change when
dichloromethane was used as the solvent and the mixture was
evaporated prior to the NMR analysis. Attempts to isolate the
isomers in pure form failed.
NMR data for cis-17. 1H NMR (CDCl3): δ 3.23 (s, 3 H,
CH2OMe), 3.81 (vt, J′ = 1.9 Hz, 2 H, C5H4), 3.97 (s, 2 H,
CH2OMe), 4.02 (vt, J′ = 1.9 Hz, 2 H, C5H4), 4.17 (br vq, 2 H,
Two of four CH2OH independent moieties in the structure
of 5 are disordered and their C and O atoms were refined with
isotropic displacement parameters. The selected crystal of 10
suffered from non-merohedral twinning. The data were cor-
rected by PLATON63 and the contribution of the minor com-
ponent was refined to ca. 7.4%.
C5H4), 4.24 (br m, 2 H, C5H4), 7.14–7.67 (m, 10 H, PPh2). 31P
1
{1H} NMR (CDCl3): δ 9.8 (s flanked with 195Pt satellites, JPtP
=
3759 Hz). NMR data for trans-17. 31P{1H} NMR (CDCl3): δ 11.5
(s with 195Pt satellites, 1JPtP = 2622 Hz).
A similar reaction was also performed with equimolar
amounts of the starting materials. In this case, ligand 11
(41.5 mg, 0.10 mmol) and [PtCl2(cod)] (37.5 mg, 0.10 mmol)
were reacted in dichloromethane (2 mL) for 30 min and the
resulting solution was evaporated under vacuum. NMR analy-
sis of the residue revealed signals attributable to cis-17,
unreacted [PtCl2(cod)], residual cod and traces of trans-17.
Aqua-bis[1′-(diphenylphosphino-κP)-1-(methoxymethyl)ferro-
cene](trifluoromethanesulphonato-κO)copper(I) (10). A solu-
tion of ligand 11 (42 mg, 0.10 mmol) in dry CDCl3 (3 mL;
distilled from CaH2) was added to solid [Cu(CF3SO3)]·1/2PhMe
(13 mg, 0.050 mmol). The resulting mixture was stirred for
90 min and evaporated under vacuum leaving an oily residue,
which was mixed with diethyl ether (ca. 8 mL; not dried). The
yellow crystalline material which separated after standing at
4 °C overnight was filtered off, washed thoroughly with
pentane and dried under vacuum to give 18 as a yellow micro-
crystalline solid. Yield: 44 mg (83%).
The refinement of the structure model for complex
16·CH2Cl2 was complicated by disorder. First, one of the cyclo-
pentadienyl rings bearing the CH2OMe pendant was rotation-
ally disordered and was modelled over two equally populated
positions. Second, the solvent molecules were clearly detected
in structural voids but could not be refined. A new data set was
therefore generated using the SQUEEZE64 algorithm as incor-
porated in the PLATON program. A total of 172 electrons were
found in the 476 Å3 void space per unit cell (N.B. four mole-
cules of dichloromethane represent 168 electrons).
All geometric data and structural drawings were obtained
with a recent version of the PLATON program. The numerical
values are rounded with respect to their estimated deviations
(ESDs) given to one decimal place. Parameters relating to
atoms in constrained positions are given without ESDs.
1H NMR (CDCl3): δ 3.20 (br s, 3 H, CH2OMe), 3.8 (br s, 2 H,
CH2OMe), 3.98, 4.07, 4.15 and 4.35 (4 × br vt, 2 H, C5H4);
7.32–7.48 (br m, 10 H, PPh2). 31P{1H} NMR (CDCl3): δ −7.8 (s).
Acknowledgements
ESI+ MS: m/z 891 ([Cu(11)2]+), 535, 477 ([Cu(11)]+), 415 ([11 + This work was supported by the Czech Science Foundation
H]+). IR (Nujol): νmax 3365 and 3285 br m (νOH), 1765 compo- (project no. P207/10/0176) and is a part of a long-term
site m, 1587 w, 1571 w, 1304 w, 1290 vs, 1229 vs, 1193 m, 1186 research plan supported by the Ministry of Education, Youth
w, 1167 s, 1156 s, 1095 s, 1069 s, 1026 vs, 999 m, 928 m, 837 s, and Sports of the Czech Republic (project no.
748 s, 698 s, 632 s, 570 m, 537 m, 513 s, 499 s, 493 s, 466 s, MSM0021620857).
3386 | Dalton Trans., 2013, 42, 3373–3389
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Paper
CONH(CH2)nSO3[HNEt3] (n = 1–3): (t) J. Schulz, I. Císařová
and P. Štěpnička, Organometallics, 2012, 31, 729.
7 P. Štěpnička and T. Baše, Inorg. Chem. Commun., 2001, 4,
682.
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P. Štěpnička, Wiley, Chichester, 2008.
8 (a) M. D. Wright, Organometallics, 1990, 9, 853;
(b) I. R. Butler and R. L. Davies, Synthesis, 1996, 1350.
9 J. Podlaha, P. Štěpnička, J. Ludvík and I. Císařová, Organo-
metallics, 1996, 15, 543.
10 P. Štěpnička, Eur. J. Inorg. Chem., 2005, 3787.
4 Selected reviews: (a) R. C. J. Atkinson, V. Gibson and 11 The planar-chiral isomer, (Sp)-[Fe(η5-C5H3-1-CH2OH-2-
N. J. Long, Chem. Soc. Rev., 2004, 33, 313; (b) P. Barbaro,
C. Bianchini, G. Giambastiani and S. L. Parisel, Coord.
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5 P. Štěpnička, 1′-Functionalised ferrocene phosphines: syn-
thesis, coordination chemistry and catalytic applications,
PPh2)(η5-C5H5)], has been prepared from (a) (Sp)-2-(diphe-
nylphosphino)-1-{(S)-[(2-methoxymethyl)pyrrolidin-1-yl]-
methyl}ferrocene: C. Ganter and T. Wagner, Chem. Ber.,
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in Ferrocenes: Ligands, Materials and Biomolecules, ed. 12 (a) G. Argouarch, O. Samuel and H. B. Kagan, Eur. J. Org.
P. Štěpnička, Wiley, Chichester, 2008, ch. 5, pp. 177–204.
6 For recent examples, see: Y = OH: (a) R. C. J. Atkinson,
V. C. Gibson, N. J. Long and A. J. P. White, Dalton Trans.,
Chem., 2000, 2885; (b) I. R. Butler, P. K. Baker,
G. R. Eastham, K. M. Fortune, P. N. Horton and
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2010,
39,
7540;
Y
=
B(2,4,6-Me3C6H2)2:
(b) M. W. P. Bebbington, S. Bontemps, G. Bouhadir,
M. J. Hanton, R. P. Tooze, H. van Rensburg and
D. Bourissou, New J. Chem., 2010, 34, 1556; Y = CH2(benz- 13 Phosphine substituents have been typically protected as
imidazolium): (c) S. Gülcemal, A. Labande, J.-C. Daran,
B. Çetinkaya and R. Poli, Eur. J. Inorg. Chem., 2009, 1806;
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S. Krausse, D. Schaarschmidt, T. Rüffer and H. Lang, Orga-
nometallics, 2012, 31, 2310; Y = 2-Py, 3-Py and CH2(2-Py)
(Py = pyridyl): (e) P. Štěpnička, J. Schulz, T. Klemann,
U. Siemeling and I. Císařová, Organometallics, 2010, 29,
3187; (f) U. Siemeling, T. Klemann, C. Bruhn, J. Schulz and
the corresponding P-sulphides: (a) L. Routaboul,
S. Vincendeau, J.-C. Daran and E. Manoury, Tetrahedron:
Asymmetry, 2005, 16, 2685; (b) L. Routaboul, S. Vincendeau,
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E. Deydier, E. Manoury and R. Poli, C. R. Chim., 2010, 13,
890.
P.
Štěpnička,
Dalton
Trans.,
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40,
4722;
(g) U. Siemeling, T. Klemann, C. Bruhn, J. Schulz and 14 E. R. Burkhardt and K. Matos, Chem. Rev., 2006, 106, 2617
P. Štěpnička, Z. Anorg. Allg. Chem., 2011, 637, 1824; Y = and references therein.
CH2NMe2: (h) P. Štěpnička, M. Zábranský and I. Císařová, 15 (a) J. M. Brunel, B. Faure and M. Maffei, Coord. Chem. Rev.,
ChemistryOpen, 2012, 1, 71; Y = CH2PPh2: (i) P. Štěpnička,
I. Císařová and J. Schulz, Organometallics, 2011, 30, 4393;
1998, 178–180, 665; (b) M. Ohff, J. Holz, M. Quirmbach and
A. Boerner, Synthesis, 1998, 1391.
( j) P. Štěpnička and I. Císařová, J. Organomet. Chem., 2012, 16 (a) A. Bader and E. Lindner, Coord. Chem. Rev., 1991, 108,
716, 110; Y = CO2SnR3: (k) P. Štěpnička, I. Císařová and
A. Růžička, J. Organomet. Chem., 2010, 695, 271; Y =
CONHR (R = H, Cy, Ph, NH2): (l) P. Štěpnička, H. Solařová,
27; (b) C. S. Slone, D. A. Weinberger and C. A. Mirkin, Prog.
Inorg. Chem., 1999, 48, 243; (c) P. Braunstein and F. Naud,
Angew. Chem., Int. Ed., 2001, 40, 680.
M. Lamač and I. Císařová, J. Organomet. Chem., 2010, 695, 17 D.-H. Kim, E.-S. Ryu, C. S. Cho, S. C. Shim, H.-S. Kim and
2423; (m) P. Štěpnička, H. Solařová and I. Císařová, J. Orga- T.-J. Kim, Organometallics, 2000, 19, 5748.
nomet. Chem., 2011, 696, 3727; Y = CONHCH2(2-C6H4PPh2): 18 L. Routaboul, J. Chiffre, G. G. A. Balavoine, J.-C. Daran and
(n) P. Štěpnička, M. Krupa, M. Lamač and I. Císařová, E. Manoury, J. Organomet. Chem., 2001, 637–639, 364.
J. Organomet. Chem., 2009, 694, 2987; Y = CONHCH(R)- 19 S. Bhattacharyya, J. Chem. Soc., Perkin Trans. 1, 1996,
CO2Me and related compounds: (o) J. Tauchman, 1381.
I. Císařová and P. Štepnička, Organometallics, 2009, 28, 20 S. Bhattacharyya, J. Chem. Soc., Dalton Trans., 1996, 4617.
3288; (p) J. Tauchman, I. Císařová and P. Štěpnička, 21 S. Bhattacharyya, Synlett, 1996, 971.
Eur. J. Org. Chem., 2010, 4276; (q) J. Tauchman, I. Císařová 22 S. Bhattacharyya, Organometallics, 1996, 15, 1065.
and P. Štěpnička, Dalton Trans., 2011, 40, 11748; 23 The compound was identified by its NMR spectra. 1H NMR
(r) J. Tauchman, B. Therrien, G. Süss-Fink and
P. Štěpnička, Organometallics, 2012, 31, 3985;
CONH(2−n)(CH2CH2OH)n (n = 1, 2): (s) J. Schulz, I. Císařová
and P. Štěpnička, J. Organomet. Chem., 2009, 694, 2519; Y =
(CDCl3): δ ca. 0.80–1.70 (very br m, 3 H, BH3), 4.09 (s, 5 H,
C5H5), 4.42 (vq, J′ ≈ 2 Hz, 2 H, C5H4PPh2), 4.51 (m, 2 H,
C5H4PPh2), 7.37–7.62 (m, 10 H, PPh2). 31P{1H} NMR
(CDCl3): δ ca. 16.6 (broad signal).
Y
=
This journal is © The Royal Society of Chemistry 2013
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Dalton Transactions
24 FcPPh2 results from accidental protonolysis of 1′-(diphenyl- 38 (a) E. A. Cookson and P. C. Crofts, J. Chem. Soc. C, 1966,
phosphino)-1-lithioferrocene, which is generated in situ
and treated with N,N-dimethylformamide to afford 2. The
phosphine typically remains present (albeit in tiny
amounts) even after flash chromatography and crystallisa-
tion of the aldehyde. For examples of the synthetic use of
1′-(diphenylphosphino)-1-lithioferrocene, see ref. 5 and 8b.
25 See, for instance: http://www.organic-chemistry.org/chemi-
2003; (b) T. B. Rauchfuss, F. T. Pation and D. M. Roundhill,
Inorg. Chem., 1975, 14, 652; (c) W. E. McEwen,
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nometallics, 1999, 18, 2198.
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nomet. Chem., 1993, 458, 229; (h) E. Lindner, M. Haustein,
H. A. Mayer, H. Kühbauch, K. Vrieze and B. de Klerk-
26 H. Anane, A. Boutalib and F. Tomás, J. Phys. Chem. A, 1997,
101, 7879.
27 I. R. Butler and R. L. Davies, Synthesis, 1996, 1350 and
references cited therein.
28 G. Gasser, A. J. Fischmann, C. M. Forsyth and L. Spiccia,
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29 P. Štěpnička and I. Císařová, New J. Chem., 2002, 26,
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30 (a) K. J. Donaghy, P. J. Caroll and L. G. Sneddon, Inorg.
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F. Spindler, Helv. Chim. Acta, 2006, 89, 1772.
31 A. M. Makal, D. Plazuk, J. Zakrzewski, B. Misterkiewicz and
K. Wozniak, Inorg. Chem., 2010, 49, 4046.
32 D. W. Slocum and C. R. Ernst, Adv. Organomet. Chem.,
1972, 10, 79.
33 (a) M. P. Brown and R. W. Heseltine, J. Chem. Soc., Chem.
Commun., 1968, 1551; (b) M. P. Brown, R. W. Heseltine,
P. A. Smith and P. J. Walker, J. Chem. Soc. A, 1970, 410;
Engels,
Inorg.
Chim.
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215,
165;
(i) W. A. Herrmann, C. Brossmera, K. Öfele, M. Beller and
H. Fischer, J. Mol. Catal. A: Chem., 1995, 103, 133;
( j) E. Lindner, S. Pautz, R. Fawzi and M. Steimann, Organo-
metallics, 1998, 17, 3006; (k) C. W. Rogers, B. O. Patrick,
S. J. Rettig and M. O. Wolf, J. Chem. Soc., Dalton Trans.,
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(c) R. H. Crabtree, P. E. M. Siegbahn, O. Eisenstein, 40 R. C. J. Atkinson, V. C. Gibson, N. J. Long, A. J. P. White
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348; (d) R. Custelcean and J. E. Jackson, Chem. Rev., 2001, 41 The related planar-chiral ligand, [Fe{η5-C5H3(PPh2-1)(OMe-
101, 1963.
2)}2], has been reported by Zhang et al.: F. Xie, D. Liu and
34 A search in CSD (version 5.33 from November 2011 with
W. Zhang, Tetrahedron Lett., 2008, 49, 1012.
updates up to August 2012) for intermolecular BH3⋯OH 42 K. D. Redwine, H. D. Hansen, S. Bowley, J. Isbell, D. Vodak
contacts with H⋯H distance 1.0–2.5 Å and H-bond angle
and J. H. Nelson, Synth. React. Inorg. Met.-Org. Chem., 2000,
>120° resulted in 23 hits: (refcodes) ABUKAJ, ADIMOP,
30, 409.
ADINAC, ADINEG, AGEYUH, AVOCAQ, CENJIP, DAZPIE, 43 P. Štěpnička, J. Demel and J. Čejka, J. Mol. Catal. A: Chem.,
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IQEYAF, LICTIA, OLEVEH, REFCUB, SIQZEY, VADNIZ, 44 For a recent example of the use of these two complemen-
WAGBAH, XAFNAT, WANTAI.
35 These compounds have been prepared and studied inten-
tionally; see ref. 33d.
tary synthetic approaches, see: M. V. Jiménez, J. J. Pérez-
Torrente, M. I. Bartolomé, E. Vispe, F. J. Lahoz and
L. A. Oro, Macromolecules, 2009, 42, 8146.
36 Significant intermolecular BH⋯H–O contacts were 45 The
reaction
of
[Pd(MeCN)4](CF3SO3)2
with
2-
detected in ten of 23 structurally characterised borane
adducts of (amino)phosphino-alcohols and phenols
(refcodes AVOCAQ, IBATUC, IQEXUY, IQEAF, LICTIA,
OLEVEH, REFCUB, SIQZEY, VADNIZ, WAGBAH) for which
Ph2PC6H4CH2OMe (L) was shown to produce the stable bis-
chelate complex cis-[Pd(L-κ2O,P)](TfO)2: C. Andersson,
J. Friedrich, M. H. Johansson and Å. Oskarsson, J. Mol.
Struct., 1999, 479, 1.
the coordinates are available (H⋯H distances = 1.57–2.44 Å, 46 The 31P{1H} NMR spectrum of the reaction mixture
H⋯H–O angles = ca. 125–170°).
contains several broad signals (δP ca. 26.0, 32.5 and
37 The flexibility of the crystal assembly of 8 is further mani-
33.3).
fested by the crystal structure at room temperature, which 47 The presence of two additional minor Pd-11 species (δP
is totally disordered, not allowing even for a reliable deter-
mination of the lattice parameters, but becomes gradually
ordered during cooling.
15.3 and 15.9) and free 11 in the crude reaction mixture
may well reflect a departure from the ideal stoichiometry at
the small reaction scale.
3388 | Dalton Trans., 2013, 42, 3373–3389
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48 The crystal structure of cis-17 was determined but could
2802; ( j) Y = CONHCH2CONH2: ref. 6o; (k) Y = COCH2NH-
SO3(HNEt3): ref. 6t.
not be satisfactorily refined due to a poor quality of the
data (crystal) available. Nevertheless, the connectivity esta- 52 For a representative example from the chemistry of ferrocene
blished by X-ray analysis is unequivocal and confirms the
ligands, see: G. Pilloni, B. Corain, M. Degano, B. Longato
cis geometry of the complex.
and G. Zanotti, J. Chem. Soc., Dalton Trans., 1993, 1777.
49 Free 11 (2 mg) was added to a pre-formed solution of cis-17 53 G. A. Lawrance, Chem. Rev., 1986, 86, 17.
(0.025 mmol in ca. 0.7 mL CDCl3) and the composition of 54 According to a search in the Cambridge Structural Data-
the mixture was regularly monitored by the 1H and
base, version 5.33 of November 2011 with updates in
November 2011, and in February, May and August 2012.
31P NMR spectra. After the addition, the amount of trans-
17 gradually increased from the initial ca. 3 mol% to 55 D. A. Knight and S. W. Keller, J. Chem. Crystallogr., 2006,
20 mol% after 14 days. The isomerisation then stopped. 36, 531.
A similar cis–trans ratio of ca. 80 : 20 was determined for 56 [L2Cu2(H2O)2]X2, where L = bis[5-tert-butyl-2-(diphenylphos-
the product resulting from the reaction between
[PtCl2(cod)] and an excess of 11 (Pt–P ≈ 1 : 2.1) in
dichloromethane.
phino)-methyl-1-methoxyphenyl]methane, and X = ClO4
and BF4: X.-T. Meng, Q.-S. Li, F.-B. Xu, H.-B. Song,
C. E. Anson and Z.-Z. Zhang, Inorg. Chem., 2006, 45, 7986.
50 P. Štěpnička, J. Podlaha, R. Gyepes and M. Polášek, J. Orga- 57 T.-Y. Dong and L.-L. Lai, J. Organomet. Chem., 1996, 509,
nomet. Chem., 1998, 552, 293. 131.
51 Selected achiral compounds. (a) Y = P(O)Ph2: R. J. Coyle, 58 R. A. Zelonka and M. C. Baird, Can. J. Chem., 1972, 50,
Y. L. Slovokhotov, M. Y. Antipin and V. V. Grushin, Poly- 3063.
hedron, 1998, 17, 3059; (b) Y = SMe: V. C. Gibson, N. J. Long, 59 D. Drew and J. R. Doyle, Inorg. Synth., 1972, 13, 47.
A. J. P. White, C. K. Williams, D. J. Williams, M. Fontani 60 H. Plenio, J. Hermann and A. Sehring, Chem.–Eur. J., 2000,
and P. Zanello, J. Chem. Soc., Dalton Trans., 2002, 3280;
6, 1820.
(c) Y = PO3Et2: P. Štěpnička, I. Císařová and R. Gyepes, 61 A. Altomare, M. C. Burla, M. Camalli, G. L. Cascarano,
Eur. J. Inorg. Chem., 2006, 926; (d) Y = Py and CH2Py (Py =
2-pyridyl): ref. 6e; (e) Y = CHvCH2: P. Štěpnička and
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