Extending the range of stabilised, primary and secondary phosphanes containing ferrocenyl or ruthenocenyl groups

Article abstract of DOI:10.1016/j.ica.2014.01.049

Alkylation reactions of FcCH₂P(CH₂OH)₂ [Fc = (η⁵-C₅H₅)Fe(η⁵-C ₅H₄)] with MeI or p-BrCH₂C₆H ₄NO₂, or of CyP(CH

Full text of DOI:10.1016/j.ica.2014.01.049

Inorganica Chimica Acta 414 (2014) 181–190
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Inorganica Chimica Acta
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Extending the range of stabilised, primary and secondary phosphanes
containing ferrocenyl or ruthenocenyl groups
a
b
Toshie Asamizu a, William Henderson a, , Brian K. Nicholson , Evamarie Hey-Hawkins
⇑
a Department of Chemistry, University of Waikato, Private Bag 3105, Hamilton 3240, New Zealand
b Institut für Anorganische Chemie, University of Leipzig, Johannisallee 29, Leipzig D-04103, Germany
a r t i c l e i n f o
a b s t r a c t
Alkylation reactions of FcCH2P(CH2OH)2 [Fc = (g g
5-C5H5)Fe( 5-C5H4)] with MeI or p-BrCH2C6H4NO2, or of
Article history:
CyP(CH2OH)2 with [FcCH2NMe+3]Iꢀ gave hydroxymethylphosphanes FcCH2PR(CH2OH) (R = Me, Cy or p-O2-
NCH2C6H4) which were converted to the new secondary phosphanes FcCH2PHR on treatment with Na2-
S2O5. A series of longer-chain ferrocenylalkyl primary phosphanes Fc(CH2)nPH2 was also prepared by
reactions of the bromoalkylferrocenes Fc(CH2)nBr (n = 4, 6 or 11) with P(CH2OH)3 to give intermediate
hydroxymethylphosphanes Fc(CH2)nP(CH2OH)2, followed by reaction with Na2S2O5. Fc(CH2)6PH2 was
converted into its crystalline BH3 adduct, which was structurally characterised. The synthesis of the
new ruthenocene (Rc)-derived primary phosphane RcCH2PH2, the first example of a ruthenocene-derived
primary phosphane, is also reported.
Received 3 December 2013
Received in revised form 21 January 2014
Accepted 30 January 2014
Available online 7 February 2014
Keywords:
Primary phosphanes
Secondary phosphanes
Ferrocene compounds
Ruthenocene compounds
Crystal structure
Ó 2014 Elsevier B.V. All rights reserved.
1. Introduction
suggesting that the alkyl spacer may be a crucial factor in affording
stability. Such phosphanes, in particular FcCH2PH2 (due to its ease
Primary phosphanes RPH2 are valuable chemical precursors,
which are normally air-sensitive, are typically highly toxic, and
have noxious odours. In recent years, there has been interest in
the development of some remarkably air-stable primary phos-
phines, primarily to increase the ease of handling of these sub-
stances; [1–3] key developments in this field up to 2005 have
been reviewed by Brynda [4]. One of the principal strategies that
has been used for stabilising many reactive main group hydride
species is a simple steric approach [5,6]. Although frequently suc-
cessful, this approach runs the inherent risk that stabilisation will
occur at the expense of compromising the chemistry of the phos-
phane group, which would be undesirable. Primary phosphanes
and arsanes stabilised by non-steric means are relatively rare in
the literature, but good examples of non-sterically protected, air-
stable primary phosphanes are (H2PCH2)2CHCH2NHPh and (H2-
PCH2)2CHC(O)NHPh [7].
of synthesis from readily available precursors), have subsequently
attracted interest as precursors for further derivatisation or as li-
gands in their own right [12–27]. Bidentate ferrocene-derived li-
gands containing –CH2PH2 and other donor ligand groups have
also been studied [28]. Furthermore, a recent theoretical study by
Higham and co-workers [29] has proposed the electronic basis for
the ferrocene-imparted stabilisation, which suggests it could be
quite widely applicable.
PH2
EH2
Fe
Fe
2, E = P
3, E = As
1
We have previously reported that the ferrocenyl (Fc) group
incorporated via a (CH2)n spacer (n = 1 or 2) stabilises primary
phosphanes and an arsane in a series of crystalline compounds
including FcCH2PH2 1 [8] and FcCH2CH2EH2 (2, E = P; 3, E = As)
[9] with excellent air stability (>2 years for 1). An improved syn-
thesis of 1 was subsequently reported [10]. In contrast, it is known
that FcPH2 (with no CH2 groups) is rather air-sensitive, [9,11]
The ferrocenylmethyl group has been used to impart stability to
a range of other phosphanes, including the trialkylphosphanes
(FcCH2)3P [10,30] and FcCH2PtBu2 [31]. However, to date, there
have been relatively few secondary ferrocenylalkylphosphanes re-
ported; these include (FcCH2)2PH [10,14,18,13]. We wished to
investigate the extent of this ferrocene-based stabilisation by syn-
thesis of a series of new derivatives. In this contribution we de-
scribe some new secondary phosphane analogues FcCH2PHR,
together with syntheses of analogues containing a longer alkyl
⇑
Corresponding author. Tel.: +64 7 848 4656.
E-mail address: w.henderson@waikato.ac.nz (W. Henderson).
http://dx.doi.org/10.1016/j.ica.2014.01.049
0020-1693/Ó 2014 Elsevier B.V. All rights reserved.

182
T. Asamizu et al. / Inorganica Chimica Acta 414 (2014) 181–190
spacer between the ferrocene and phosphane Fc(CH2)nPH2 (n = 4, 6,
11), and the corresponding ruthenocene (Rc)-derived primary
phosphane RcCH2PH2.
in the electrospray capillary [34]. Phosphane 9 was also analysed
by an alternative technique previously used to aid ionisation of
phosphanes [35,36] and arsanes [37], by in situ formation of cat-
ionic silver(I)-phosphane adducts upon addition of a small quan-
tity of AgNO3. Applying this methodology for 9, the
corresponding silver adducts [M+Ag]+ and [2M+Ag]+ were easily
observed with much higher intensity than that of [M]+ observed
in the absence of added Ag+. Confirmation of the silver adduct ions
was readily achieved by comparison of experimental and calcu-
lated isotope patterns, which are highly distinctive from the pres-
ence of 107Ag and 109Ag isotopes.
2. Results and discussion
2.1. Secondary phosphanes
Synthesis of a series of new secondary phosphanes used the fac-
ile conversion of a P–CH2OH group into a P–H group by removal of
formaldehyde, HCHO, as summarised in Scheme 1. The known
hydroxymethylphosphane FcCH2P(CH2OH)2 was readily alkylated
with MeI or p-BrCH2C6H4NO2 followed by treatment with base to
give the intermediate hydroxymethylphosphanes 4 and 5 respec-
tively, while alkylation of CyP(CH2OH)2 with [FcCH2NMe3]I corre-
spondingly gave FcCH2PCy(CH2OH) 6. This route was chosen for
the cyclohexyl compound, because of the poorer alkylating proper-
ties of cyclohexyl halides, and also the commercial availability of
CyPH2, which is readily converted into [CyP(CH2OH)3]Cl. Treat-
ment of the reaction mixtures with Et3N ensured conversion to
the hydroxymethylphosphanes, which were obtained as red-or-
ange oils that were used directly in the preparation of the second-
ary phosphanes.
The hydroxymethylphosphanes 4, 5 and 6 were treated with
Na2S2O5 in a two phase water/petroleum spirits system at reflux
for 3 h under a nitrogen atmosphere, following conditions that
have been previously used to convert hydroxymethylphosphanes
into primary or secondary phosphanes [8,10]. After separating
and washing the organic phase with water, evaporation of the or-
ganic phase yielded the desired secondary phosphanes 7, 8, and 9
(Scheme 1) as orange-red oils in moderate to good yields. The dis-
tinctive phosphane odour was noted from all three secondary
phosphanes. The crude products were purified by preparative
TLC, giving pure secondary phosphanes which solidified at
ꢀ18 °C and were characterised by IR and NMR spectroscopies,
ESI MS and microelemental analysis.
The 31P NMR resonances for 7, 8 and 9 appeared at d ꢀ73.5,
1
ꢀ49.1 and ꢀ41.1 ppm respectively, as a doublet with a JPH cou-
pling constant in the expected range (192–199 Hz). The 31P NMR
signal for 7 was the furthest upfield (by ca. 30 ppm), consistent
with the methyl group being the most electron-donating and
hence the most shielding of the three organic substituents on
phosphorus. The PH proton signals of 7, 8 and 9 appeared in the
1H NMR spectra at ca. d 3.3 ppm as a doublet of multiplets with
3
1JPH and JHH coupling constants of ꢁ196 and ꢁ6 Hz, respectively;
these resonances are shifted further downfield (by ꢁ0.4 ppm) com-
pared to FcCH2PH2 1 (d 2.9 ppm) [8].
Overalkylated by-products (Scheme 2) were also isolated from
the syntheses of 8 and 9. Compound 10 was obtained as a yellow
solid in poor yield (3%) from the synthesis of 9, precipitating out
upon re-extraction of the crude product with diethyl ether or a
mixture of diethyl ether and petroleum spirits; the compound
was characterised by NMR spectroscopy and ESI MS. The 31P
NMR spectrum showed a singlet at d ꢀ7.6 ppm, shifted by
34 ppm further downfield compared to the corresponding second-
ary phosphane 9. In the 1H NMR spectrum, the CH2 proton signal
appeared as a singlet at d 2.5 ppm, while the cyclohexyl protons
gave unresolved multiplets at d 1.2–1.8. The integration of the sig-
nals agreed with the number of protons in the expected environ-
ments (CH2:C6H11:Fc = 4:11:18). [Scheme
3 shows the atom
numbering scheme for the secondary phosphanes]. The positive-
ion ESI mass spectrum with added AgNO3 gave silver adducts
[M+Ag]+ (m/z 620), and [2M+Ag]+ (m/z 1132). The compound ap-
peared to be unstable in CDCl3 solution, decomposing after
2 weeks at room temperature in a capped NMR tube in air; the
31P NMR signal disappeared and the solution turned from yellow
to dark brown. Crude 9 was also found to contain a trace amount
of CyPH2 by 31P NMR spectroscopy (a triplet at d ꢀ110.2 with a
The PH stretches of 7, 8 and 9 appeared in the range 2268–
2278 cmꢀ1, as a medium to strong band, consistent with values
of ca. 2280 10 cmꢀ1 typically observed for this class of compound
[32]. Compounds 8 and 9 were characterised by positive-ion ESI
MS in MeOH, giving the [M]+ parent ion at the expected m/z value.
The observation of an [M]+ ion for ferrocenyl compounds in ESI MS
analysis is common, [33] and arises from electrochemical oxidation
P(CH2OH)2
Fe
MeI
or
p-NO2C6H4CH2Br
R
1
R
P
P
Na2S2O5
CH2OH
Fe
H
Fe
P(CH2OH)3
CyP(CH2OH)2
4, R = Me
5, R = p-O2NC6H4CH2
6, R = Cy
7, R = Me
8, R = p-NO2C6H4CH2
9, R = Cy
NMe3+I-
Fe
Scheme 1. Synthesis of the ferrocenyl-substituted secondary phosphanes FcCH2PHR 7, 8 and 9 (R = Me, Cy or p-O2NCH2C6H4).

T. Asamizu et al. / Inorganica Chimica Acta 414 (2014) 181–190
183
2.2. Long chain ferrocenylalkylphosphanes Fc(CH2)nPH2
PR2
PR
To date, the longest alkylene spacer which has been incorpo-
rated into a ferrocene-substituted primary phosphane is the
CH2CH2 group in FcCH2CH2PH2 2 [9]. We wished to explore the
synthesis of compounds with longer chain spacers and accordingly
a series of new ferrocenylalkyl primary phosphanes were prepared
by extensions of the reported literature methods [8,39] with minor
modifications where needed; Scheme 4 summarises the syntheses.
Reaction of the bromoalkylferrocenes Fc(CH2)nBr (n = 4, 6 and
11) with excess P(CH2OH)3 [generated in situ from P(CH2OH)4Cl
with KOH], in refluxing methanol followed by workup with added
NEt3 gave the hydroxymethylphosphanes Fc(CH2)nP(CH2OH)2
(n = 4 13, 6 14 or 11 15) as red oils in good yields. Attempted crys-
tallisation of the crude phosphanes 13 and 14 [methanol/dichloro-
methane/petroleum spirits] was not successful, and the
compounds were used in the conversion to the primary phos-
phanes without further purification. However, recrystallisation of
Fc(CH2)11P(CH2OH)2 15 from the same solvent mixture gave a yel-
low solid which gave satisfactory microanalytical data. The 31P
NMR signals for 13, 14 and 15 appeared as singlets at ꢁd
ꢀ22 ppm, shifted further downfield by d 3 ppm compared to
FcCH2P(CH2OH)2 [36]. This is consistent with the extended length
of the alkylene spacer, which effectively isolates the deshielding
ferrocene group from the phosphorus. ESI MS analysis of 13, 14
and 15 in MeOH with added AgNO3 gave [M+Ag]+ and/or
[2M+Ag]+ ions; in the absence of AgNO3, the molecular ions [M]+
were observed.
Fe
Fe
2
12, R = p-O2NC6H4CH2
10, R = Cy
11, R = p-O2NC6H4CH2
Scheme 2. Overalkylated byproducts 10, 11 and 12.
R
2
5
3
4
P
1
2
3
H
Fe
4
4
4
Scheme 3. Atom labelling used in NMR assignments of ferrocenyl secondary
phosphanes; hydrogen atoms are numbered according to the carbon to which they
are bonded.
1JPH coupling constant of 194 Hz, consistent with the literature
chemical shift of ꢀ110.1 ppm) [38].
Compounds 11 and 12 were isolated from the synthesis of 8 by
chromatography of the crude product on a TLC plate, eluting with a
1:1 mixture of dichloromethane and petroleum spirits. Compound
11 was obtained as a red oil in very low yield (0.8 %) from the frac-
tion at Rf 0.33, and 12 as a red solid in moderate yield (24%) from
the fraction at Rf 0.66 after removal of the solvents under reduced
pressure. Compound 11 was only partially characterised by 31P
(singlet at d ꢀ12.3 ppm), 1H and 13C NMR spectroscopies as it
was obtained only in very low yield. Compound 12 was character-
ised by ESI MS, microelemental analysis, 31P, 1H and 13C NMR and
IR spectroscopies. Positive-ion ESI MS of 12 in MeOH with added
AgNO3 showed the molecular ion, [M]+ (m/z observed. 502.074;
calcd. 502.073) and the corresponding silver adduct, [M+Ag]+ (m/
z observed 608.978; calcd. 608.979). The IR spectrum of 12 showed
N–O stretches at 1513 and 1343 cmꢀ1 as very strong bands, very
similar to 8.
The hydroxymethylphosphanes 13, 14 and 15 were treated
with Na2S2O5 in a two-phase water-petroleum spirits mixture in
air or under an N2 atmosphere for 3 h, Scheme 4. After work-up, re-
moval of the solvent from the organic phase gave the desired pri-
mary phosphanes 16, 17 and 18 as yellow-red oils in moderate
to good yields (16 35%; 17 83%; 18 28%) with distinctive phos-
phane odours. The crude products were purified by chromatogra-
phy (preparative TLC), eluting with petroleum spirits or
a
mixture of petroleum spirits/diethyl ether or petroleum spirits/
dichloromethane. The desired bands were collected and extracted
with dichloromethane; evaporation gave the products as yellow-
red oils.
The primary phosphanes 16, 17 and 18 were characterised by
31P, 1H and 13C NMR and IR spectroscopies, and by ESI and GC mass
spectrometries. Phosphanes 17 and 18 could not be completely
purified by chromatography on a preparative TLC plate or by
recrystallisation, and gave unsatisfactory microanalytical data;
the characterisation of these compounds is therefore based on
spectroscopic data. However, phosphane 16 could be purified by
microdistillation [10ꢀ6 torr, 65 °C, 12 h] and was obtained as an
The oxidative stability of the phosphanes was qualitatively
investigated by 31P NMR monitoring of CDCl3 solutions (prepared
in air) in a capped NMR tube at room temperature. Secondary
phosphanes are generally readily oxidised in air to form the corre-
sponding oxides, R2P(O)H, which are also relatively unstable and
can be further oxidised to give the stable phosphinic acid, R2-
P(O)OH. The least stable secondary phosphane was FcCH2PH(CH2-
C6H4NO2) 8, which was completely oxidised in little over
2 weeks. By contrast, the cyclohexylphosphane 9 showed reason-
able air stability under the given conditions and the 31P NMR signal
was observed for more than 4 months. The methylphosphane 7 ap-
peared to show intermediate stability, being fully oxidised in
around 6 weeks.
oil which was analytically pure. The mP–H stretches in the IR spec-
tra of Fc(CH2)nPH2 (16, 17 and 18) were observed at 2289, 2283
and 2290 cmꢀ1, respectively, as a medium to strong intensity band,
consistent with literature values for other related compounds
Fc(CH2)nPH2 (n = 1 1; 2285s cmꢀ1 or n = 2 2; 2294 m cmꢀ1). ESI
MS showed the molecular ions [M]+ in positive-ion mode at a
P(CH2OH)2
P(CH2OH)3
Br
PH2
n
Na2S2O5
n
n
Fe
Fe
Fe
16, n = 4
13, n = 4
14, n = 6
15, n = 11
17, n = 6
18, n = 11
Scheme 4. Synthesis of longer-chain ferrocene-substituted primary phosphanes.

184
T. Asamizu et al. / Inorganica Chimica Acta 414 (2014) 181–190
capillary exit voltage of 150 V, while EI MS also showed a strong
molecular ion, together with the usual fragment ions [FcCH2]+,
[CpFe]+ and [Fe]+.
with the description in the literature for FcCH2PH2(BH3) [10]. The
1H NMR spectrum showed the phosphane protons at d 4.5 ppm
1
3
as a doublet of sextets with JPH and JHH coupling constants of
360 and 1 Hz, respectively. The borane proton signal was observed
at d 1.4 ppm as an unresolved multiplet. In the 13C NMR spectrum,
The 31P NMR resonances for 16, 17 and 18 appeared as a triplet
at ꢁd ꢀ136 ppm with a 1JPH coupling constant of ꢁ194 Hz. The sig-
nals are shifted upfield by ꢁ7 ppm compared to FcCH2PH2 1 [8] (cf.
d ꢀ129.1 ppm), but are the same as that for FcCH2CH2PH2 2 [9] (cf.
1
the JPC coupling constant for the PCH2 carbon (35.4 Hz) was con-
sistent with that for FcCH2PH2ꢂBH3 [10]. Resonances were assigned
according to 2D NMR data but definitive assignments could not be
made for the methylene proton signals of the alkyl chain due to
overlap. The adduct was stable in air at ambient temperature; nei-
ther decomposition nor oxidation of the compound was noted
upon handling or storing for at least 1 week in air at room
temperature.
The molecular structure of Fc(CH2)6PH2(BH3) 19 is shown in
Fig. 2, and selected bond lengths and angles are given in Table 1.
The compound appears to be structurally very similar to
FcCH2PH2(BH3) [10] except the extended alkyl spacer was absent
in the latter compound. The hexyl chain adopts the classical stag-
gered structure, maximising the separation of the ferrocenyl and
PH2(BH3) groups. The B–H bond lengths and H–B–H bond angles
of 19 [1.074(18)–1.127(18) Å and 112.2(13)–114.8(14)° respec-
tively] are comparable to those for FcCH2PH2ꢂBH3 [1.08(2)–
1.10(2) Å and 111.1(15)–113.9(15)°]. The P-H bond lengths are also
very comparable. The P–B bond length and B–P–H and P–B–H
angles of 19 [1.9204(17) Å and 113.8(9)–115.0(8) and 102.9(10)–
106.2(10)° respectively] are also essentially the same as those
in FcCH2PH2(BH3) [1.9230(17) Å and 115.7(9)–115.8(9) and
102.6(10)–109.1(11)°] but the C–P–B bond angle of 117.18(7)° in
19 is significantly larger than that of FcCH2PH2(BH3) [113.01(7)°].
d ꢀ135.8 ppm), suggesting that the deshielding effect of ferrocene
1
becomes negligible beyond two
r
-bonds. The JPH coupling con-
stant was consistent with that for 1 and 2. The phosphane protons
of 16, 17 and 18 appeared in the 1H NMR spectra at d 2.7 ppm, the
same as that for 2 [9] but shifted slightly upfield by d 0.2 ppm com-
pared to 1, due to the lack of a deshielding effect from the ferro-
1
3
cene group. The JPH and JHH coupling constants of 194–195 and
7 Hz, respectively, also agree with the literature values for 1 and
2 [8,9].
The longer-chain primary phosphanes were found to have sig-
nificant stability towards air, such that the compounds could easily
be handled and stored in air for moderate periods (weeks) without
significant oxidation occurring. However, investigation of the air-
stability of CDCl3 solutions of the phosphanes by 31P NMR spec-
troscopy showed that over a period of several months, oxidation
with loss of the characteristic RPH2 signal occurred. The longest-
chain primary phosphane Fc(CH2)11PH2 18 was fully oxidised after
ꢁ3 months and was the least air stable of the series, while
Fc(CH2)4PH2 16 and Fc(CH2)6PH2 17 were stable for around
4 months.
Borane adducts of phosphanes are often formed in order to sta-
bilise, and to furnish more highly crystalline derivatives. The
chemistry of phosphane-boranes has been recently reviewed
[40]. Glueck et al. [10] have reported that the ferrocenyl primary
phosphane FcCH2PH2 1 forms a crystalline borane adduct on reac-
tion with BH3(SMe2). Since it was not possible to grow a single
crystal of any of the primary phosphanes prepared in this study,
Fc(CH2)6PH2 17 was derivatised by reaction with BH3(SMe2) to give
the borane adduct Fc(CH2)6PH2(BH3) 19 (Scheme 5) in order to ob-
tain X-ray crystallographic structural data on an adduct. Reaction
of 17 with BH3(SMe2) in dry hexane at ꢀ64 °C under an N2 atmo-
sphere followed by workup gave Fc(CH2)6PH2(BH3) 19 in moderate
yield (26%) as orange needles, which were analytically pure. The P–
H and B–H stretches were observed as overlapping strong broad
bands at around 2398 cmꢀ1. The increase in the P–H stretching fre-
quency from 2280 to 2398 cmꢀ1 upon the addition of BH3 is consis-
tent with that observed for FcCH2PH2(BH3) [10]. Positive-ion ESI
MS analysis at a capillary exit voltage of 100 V showed the [M]+
ion (m/z observed 316.119; calcd. 316.120 for C16H26BFeP) together
with the sodium and potassium adducts, [M+Na]+ (m/z observed
339.109; calcd. 339.111 for C16H26BFeNaP) and [M+K]+ (m/z ob-
served 355.058; calcd. 355.084 for C16H26BFeKP), respectively.
The presence of Fe and B provide a unique isotopic signature for
the ions, with good agreement observed between experimental
and calculated isotope patterns.
2.3. Synthesis and characterisation of the ruthenocene-derived
primary phosphane RcCH2PH2
To investigate whether the stabilisation effect was unique to
ferrocene or could be extended to other metallocenes, the rutheno-
cene compound RcCH2PH2 [Rc = (
pared. No ruthenocenylmethylphosphane compounds
C5H5)Ru(
5-C5H4CH2PR2) derived from mono-substituted ruthe-
g g
5-C5H5)Ru( 5-C5H4)] was pre-
(
g5
-
g
nocene have been previously reported, though there have been a
number of studies on the 1,3-di-substituted pincer precursors
(g g
5-C5H5)Ru{ 5-C5H3(CH2PR2)2} (R = tBu, iPr), [41] 1,2-disubsti-
The proton-coupled 31P NMR spectrum of 19 showed a broad
-45
-60
δ/ppm
-50
-55
1
triplet at d ꢀ52.3 ppm with a JPH coupling constant of 362 Hz,
Fig. 1. Proton-coupled 31P NMR spectrum of Fc(CH2)6PH2(BH3) 19.
Fig. 1. The broadening comes from coupling to boron, consistent
PH2 BH3
6
PH2
BH3(SMe2)
6
Fe
Fe
19
17
Scheme 5. Conversion of Fc(CH2)6PH2 17 to its borane adduct Fc(CH2)6PH2ꢂBH3 19.

T. Asamizu et al. / Inorganica Chimica Acta 414 (2014) 181–190
185
Fig. 2. Molecular structure of Fc(CH2)6PH2(BH3) 19 showing the atom numbering scheme.
Table 1
RcCH2PH2 21 was characterised by IR and NMR spectroscopies
and ESI MS. The PH stretch was observed at 2290 cmꢀ1 as a med-
ium intensity peak, consistent with the values observed for FcCH2-
PH2 1 (2285 cmꢀ1) and for the ferrocenyl analogues with extended
alkylene spacers e.g. Fc(CH2)nPH2 (vide supra). The proton-coupled
Selected bond lengths (Å) and angles (°) for Fc(CH2)6PH2(BH3) 19.
P(2)–C(6)
P(2)–H(4)
B(1)–H(1)
B(1)–H(3)
1.8164(13)
1.305(19)
1.074(18)
1.11(2)
P(2)–B(1)
P(2)–H(5)
B(1)–H(2)
1.9204(17)
1.29(2)
1.127(18)
1
31P NMR spectrum of 21 yielded a triplet at d ꢀ132.5 with a JPH
C(6)–P(2)–B(1)
B(1)–P(2)–H(4)
B(1)–P(2)–H(5)
P(2)–B(1)–H(1)
H(1)–B(1)–H(2)
H(1)–B(1)–H(3)
117.18(7)
115.0(8)
113.8(9)
106.1(10)
114.8(14)
113.4(14)
C(6)–P(2)–H(4)
C(6)–P(2)–H(5)
H(4)–P(2)–H(5)
P(2)–B(1)–H(2)
P(2)–B(1)–H(3)
H(2)–B(1)–H(3)
104.0(8)
103.0(8)
102.0(12)
102.9(10)
106.2(10)
112.2(13)
coupling constant of 193 Hz; this is shifted upfield by 3 ppm com-
pared to the corresponding ferrocenyl primary phosphane FcCH2-
PH2 1 [8]. In the 1H NMR spectrum, the phosphane proton signal
appeared at d 2.9 as a doublet of triplets with 1JPH and 3JHH coupling
constants of 194 and 7 Hz respectively. The cyclopentadienyl pro-
ton signals were shifted further downfield by an average of
0.5 ppm compared to the corresponding ferrocenyl analogue 1.
RcCH2PH2 21 was also characterised by EI and ESI MS. In the EI
mass spectrum, the fragmentation of the molecular ion [M]+ to
[RcCH2]+ and [CpRu]+ followed analogous pathways to those of
the ferrocenyl primary phosphane 1. ESI MS at a capillary exit volt-
age of 150 V did not yield the molecular ion [M]+ but instead
[MꢀPH2]+ (m/z observed 244.989; calcd. 244.989 for C11H11Ru)
was observed, with good agreement between observed and calcu-
lated isotope patterns. Addition of AgNO3 gave the silver adduct
[M+Ag]+ (m/z observed 384.885; calcd. 384.884 for C11H13AgPRu).
Attempted purification of the compound by chromatography or
crystallisation was unsuccessful; satisfactory microelemental data
and single crystals suitable for an X-ray diffraction study could not
be obtained, so the assignment of the compound as RcCH2PH2 is
based on spectroscopic evidence.
tuted compounds such as (g
5-C5Me5)Ru{C5H3(PPh2)(CHMePCy2)}
[42] and the 1,10-disubstituted Ru( 5-C5H4CHMePPh2)2 [43]. Sev-
g
eral phosphonium salts such as RcCHRPPh+3 (R = H, Me) are also
known [44].
Synthetic methods analogous to those used to synthesise FcCH2-
PH2 were used to synthesise the ruthenocenylmethyl phosphane
RcCH2PH2, and are summarised in Scheme 6. Ruthenocene (RcH)
was converted to RcCH2NMe2 and subsequently [RcCH2NMe3]+Iꢀ
using literature methods (refer Section 4). [RcCH2NMe3]+Iꢀ was
then refluxed with excess P(CH2OH)3 in MeOH under a nitrogen
atmosphere for >20 h and treated with triethylamine. After work-
up, the desired hydroxymethylphosphane RcCH2P(CH2OH)2 20
was obtained as a pale-yellow oil in low yield (10%). The entire
yield of 20 was refluxed with Na2S2O5 in a two-phase system of
water and petroleum spirits for 3 h under nitrogen. Recovery of
the product from the organic phase gave the desired primary phos-
phane 21 as a pale-yellow oil in moderate yield (43%), which had a
distinctive phosphane odour; workup of the aqueous phase yielded
RcCH2P(O)(CH2OH)H 22 (vide infra).
A white solid, isolated in low yield (5%) by evaporation of the
aqueous phase separated from the reaction mixture in the synthe-
sis of 21, was tentatively characterised as the new secondary
hydroxymethylphosphane oxide RcCH2P(O)(CH2OH)H 22 by NMR
spectroscopy. The (proton-coupled) 31P NMR showed a pseudo
1
2
doublet of triplets at d 35.7 with JPH and JPH coupling constants
PH2
Ru
+
21
NMe3
P(CH2OH)2
P(CH2OH)3
+
Na2S2O5
Ru
Ru
O
H
P
CH2OH
Ru
20
22
Scheme 6. Reaction sequence for the synthesis of the ruthenocene-substituted primary phosphane RcCH2PH2 21.

186
T. Asamizu et al. / Inorganica Chimica Acta 414 (2014) 181–190
of 467 and 14 Hz, respectively. The chemical shift and coupling
constant are consistent with a secondary phosphane oxide. The
cyclopentadienyl and CH2 proton and carbon signals were ob-
served in the same region as RcCH2PH2 and are also comparable
to [RcCH2NMe3]I [45]. No further characterisation was done on this
compound.
RcCH2PH2 21 appears to have some air stability but much less
than the corresponding ferrocene analogue FcCH2PH2 1 which is
stable in air for as long as 2 years in the solid state [8]. Examination
of a CDCl3 solution of the compound by 31P NMR spectroscopy in a
capped NMR tube showed that nearly half of the phosphane had
oxidised after around 1 month.
(Retardol C) as an 80% w/w aqueous solution (Albright & Wilson
Ltd., Oldbury, UK), CH3I (May and Baker Ltd.), p-BrCH2C6H4NO2
(BDH), KOH (Ajax. Finechem. Pty Ltd.), NEt3 (Aldrich), Na2S2O5
(Ajax Finechem. Pty Ltd.) and BH3(SMe2) (2 M solution in THF,
Aldrich).
The following compounds were prepared via the literature pro-
cedures: [FcCH2NMe3]I, [47] FcCH2P(CH2OH)2, [39] Fc(CH2)4Br,
[48] Fc(CH2)6Br, [49] Fc(CH2)11Br, [50] [Ru(g
5-C5H5)2] [51] and
[RcCH2NMe3]+Iꢀ [45]. [CyP(CH2OH)3]+Clꢀ was prepared from
CyPH2 (Strem) by reaction with HCl/HCHO and recrystallisation
of the product from isopropanol [36].
Unless otherwise specified, reactions were carried out under
nitrogen using standard Schlenk line techniques and dry deoxy-
genated solvents (obtained from a PureSolv SP-SD-5 Solvent Puri-
fication System). The work-ups were performed at room
temperature in air unless otherwise stated. Petroleum spirits refers
to the fraction of boiling range 60–80 °C and diethyl ether was ob-
tained from a PureSolv SP-SD-5 solvent purification system. Hex-
ane refers throughout to n-hexane, which was of AR grade.
Water was singly distilled prior to use.
Thin layer chromatography was performed on 70 ꢃ 15 mm
Merck Kieselgel 60 F254 silica gel plates. Preparative thin layer
chromatography (TLC) plates were prepared from silica gel (Merck
Kieselgel 60 PF254) following established methods.
3. Conclusions
In summary, we have successfully extended the range of stabi-
lised ferrocenylalkylphosphanes. The compounds can be synthes-
ised from readily accessible precursors, using an extension of
previously developed methodologies. In addition, we have pre-
pared the first example of a ruthenocene-derived primary phos-
phane. Preliminary studies indicate that these new derivatives
also show appreciable air-stability.
4. Experimental
4.1. Instrumentation
4.2.1. Synthesis of FcCH2P(CH2OH)Cy 6
KOH (1.61 g, 28.70 mmol) was added to a solution of [CyP(CH2-
OH)3]Cl (7.12 g, 29.34 mmol) in methanol (40 mL). The mixture
was stirred for 1 h at room temperature before being added drop-
wise to a solution of [FcCH2NMe3]I (3.60 g, 9.35 mmol) in methanol
(40 mL). The reaction mixture was refluxed for 21 h. After cooling,
the solvent was reduced to about 8 mL and distilled water (30 mL),
diethyl ether (70 mL) and triethylamine (30 mL) were added. The
mixture was stirred for 1 h. The aqueous layer was removed and
re-extracted with diethyl ether (30 mL). The combined organic lay-
ers were washed with distilled water (3 ꢃ 20 mL) and then filtered.
Removal of the solvent under reduced pressure gave 6 as a red oil
(5.25 g), which was partly characterised and used directly for the
synthesis of FcCH2PHCy. ESI-MS (MeOH, cone voltage 20 V, with
added AgNO3) m/z 344 [M]+, 796 [2M+Ag]+. 31P{1H} NMR: d
ꢀ11.3 (s).
ESI mass spectra were recorded either on a VG Platform II
instrument (low resolution), or on a Bruker Daltonics MicrOTOF
instrument (high resolution), as methanol solutions (unless other-
wise stated); the extent of fragmentation was controlled by varia-
tion of the cone voltage (Platform) or capillary exit voltage
(MicrOTOF). Identification of ions was facilitated by comparison
of m/z values and isotope patterns of observed and calculated ions,
the latter obtained using either an internet-based program (for low
resolution matching), [46] or proprietary instrument-based
software.
Elemental analyses were performed at the Campbell Microana-
lytical Laboratory, University of Otago, New Zealand. FTIR spectra
were recorded as KBr disks on a Digilab Scimitar FTS 2000 series
spectrometer using Varian Resolution software version 4.1.0.101
or Perkin Elmer Spectrum 100 FT-IR spectrometer using Spectrum
software. GC–mass spectra were recorded on a Hewlett–Packard
5890 Series 1 gas chromatograph coupled to a Hewlett–Packard
5973 Series Mass Selective Detector, operating at 70 eV, using a
HP1 column containing cross-linked methylsilicone gum,
4.2.2. Synthesis of FcCH2PHMe 7
MeI (0.13 mL, 2.08 mmol) was added dropwise to a solution of
FcCH2P(CH2OH)2 (0.63 g, 2.16 mmol) in methanol (15 mL). The
mixture was stirred for 15 min. at 50 °C. The solvent was removed
under vacuum and distilled water (60 mL), petroleum spirits
(60 mL), triethylamine (2 drops) and Na2S2O5 (0.47 g, 2.47 mmol)
were added sequentially. The mixture was refluxed for 3 h in air.
After cooling, the aqueous layer was removed and re-extracted
with petroleum spirits (30 mL). The combined organic extracts
were washed with distilled water (4 ꢃ 20 mL). The solvent was re-
duced to 8 mL and cooled at ꢀ18 °C for 16 h. An unidentified yel-
low precipitate was removed by filtration. The filtrate was
concentrated to about 2 mL and subjected to chromatography with
a preparative TLC plate, eluting with diethyl ether/petroleum spir-
its (1:10). The yellow band at Rf 0.86 gave 7 as a yellow oil (0.17 g,
24 m ꢃ 0.2 mm ꢃ 0.33
lm film thickness. The sample was injected
using a HP 7683A Autosampler as a CH2Cl2 or MeOH solution and
eluted using
a 50–295 °C temperature ramp, at a rate of
50 °C minꢀ1 from 100–150 °C and 10 °C minꢀ1 from 150–295 °C
with a 2.25 min solvent delay. The samples were freshly prepared
prior to analysis either in MeOH or CH2Cl2.
NMR spectra were recorded in CDCl3 solution on a Bruker
Avance DRX 300 or a Bruker Avance DRX 400 spectrometer using
TOPSPIN software version 1.3 or a Bruker300AVR or a Bruker400AVR
using TOPSPIN software version 3.0. Chemical shifts are referenced to
residual solvent lines for 1H and 13C NMR spectra, and external
aqueous 85% H3PO4 for 31P NMR spectra, and are reported in
ppm. Scheme 3 shows the atom numbering scheme used for the
ferrocenyl phosphanes, illustrated for the secondary derivatives.
33%). C12H15FeP requires: C, 58.57; H, 6.14. Found: C, 59.00; H,
1
6.19%. IR:
m
P–H 2276s cmꢀ1
.
31P NMR d ꢀ73.5 (PH, d, JPH 199).
1H NMR d 1.7 (CH3, unresolved m, 3H), 2.7 (CH2, d of m, 2H), 3.1
1
3
3
4.2. Materials
(PH, d of q, JPH 194, JHH 4, 1H), 4.06 (H3, t, JHH 2, 2H), 4.08 (H2,
t, JHH 2, 2H), 4.11 (H4, s, 5H). 13C{1H} NMR: d 19.8 (CH2, d, JPC
3
1
1
3
The following chemicals were obtained from commercial
sources and used as supplied: ferrocene (Aldrich), [P(CH2OH)4]Cl
14), 31.2 (CH3, d, JPC 8), 67.3 (C3, s, CH), 68.3 (C2, d, JPC 4, CH),
2
68.8 (C4, s, CH), 87.0 (C1, d, JPC 6, C).

T. Asamizu et al. / Inorganica Chimica Acta 414 (2014) 181–190
187
4.2.3. Synthesis of FcCH2PH(CH2C6H4NO2) 8
ꢀ18 °C. C17H23FeP requires: C, 64.99; H, 7.38. Found: C, 65.18; H,
1
A mixture of FcCH2P(CH2OH)2 (2.04 g, 6.98 mmol) and p-BrCH2-
C6H4NO2 (1.82 g, 8.44 mmol) in methanol (60 mL) was refluxed for
22 h. After cooling, the solvent was removed under vacuum. Dis-
tilled water (30 mL), toluene (30 mL), triethylamine (1 mL) and
Na2S2O5 (1.33 g, 7.01 mmol) were added and the mixture was re-
fluxed for 5 h. After cooling, the aqueous phase was removed and
re-extracted with toluene (60 mL). The combined organic layer
was washed with distilled water (5 ꢃ 20 mL) and then filtered. Re-
moval of the solvent under reduced pressure gave a red solid
(2.43 g), which was chromatographed with a preparative TLC plate,
eluting with dichloromethane/light petroleum (1:1), giving orange
and yellow bands. Removal of the solvent of the orange band at Rf
0.57 gave FcCH2PH(CH2C6H4NO2) 8 as a red oil (0.46 g, 18%) which
solidified at ꢀ18 °C. C18H18FeNO2P requires: C, 58.88; H, 4.94; N,
7.56%. IR:
m
PH 2268s cmꢀ1
.
31P NMR d ꢀ41.1 (PH, d, JPH 199). 1H
2
NMR d 1.3–1.7 (C6H11, unresolved m, 11H), 2.7 (CH2, d of m, JPH
37, 2H), 3.1 (PH, d, 1JPH 198), 4.06 (H3, t, 3JHH 2, 2H), 4.09 (H2, unre-
solved m, 2H), 4.1 (H4, s, 5H). 13C{1H} NMR d 19.8 (CH2, d, 1JPC 13),
2
1
27.0 (CH2, d, JPC 8), 31.2 (CH2, d, JPC 7), 32.0 (br), 67.3 (C3, s, CH),
68.3 (C2, br s, CH), 68.8 (C4, s, CH), 87.0 (C1, d, 2JPC 5, C). ESI MS (cone
voltage 20 V, AgNO3 added): m/z 314 [M]+, 422 [M+Ag]+, 736
[2M+Ag]+.
4.2.4.1. Characterisation data for 10. 31P{1H} NMR d ꢀ7.6 (s); 1H
NMR d 1.2–1.8 (C6H11, unresolved m, 11H), 2.5 (CH2, s, 4H), 4.1
(CH, s, 18H). ESI MS (cone voltage 20 V, AgNO3 added): m/z 620
[M+Ag]+, 1132 [2M+Ag]+). Decomposition of 10 occurred over a
period of 2 weeks in CDCl3 solution at room temperature in a
capped NMR tube.
3.81. Found: C, 59.63; H, 4.92; N, 3.95%. IR:
mPH 2278 m mNO
1515vs, 1342vs cmꢀ1
d 2.6 (CH2, m, 2H), 3.0 (CH2, m, 2H), 3.4 (PH, d of p, JPH 198, JHH
7, 1H), 4.08 (H3, unresolved m, 2H), 4.10 (H2, unresolved m, 2H),
.
31P NMR d ꢀ49.1 (PH, d, JPH 192). 1H NMR
1
1
3
3
3
4.11 (H4, s, 5H), 7.3 (CH, d, JHH 8, 2H), 8.1 (CH, d, JHH 8,
4.2.5. Synthesis of Fc(CH2)4P(CH2OH)2 13
2H).13C{1H} NMR d 21.6 (CH2, d, JPC 14), 28.8 (CH2, d, JPC 17),
KOH (1.85 g, 32.97 mmol) was added to a solution of [P(CH2-
OH)4]Cl (8.29 g, 34.80 mmol) in methanol (19 mL). The mixture
was stirred for 1 h before being added dropwise to a solution of
Fc(CH2)4Br (3.63 g, 11.31 mmol) in methanol (20 mL). The reaction
mixture was refluxed for 21 h. After cooling, the solvent was re-
moved under reduced pressure. Distilled water (25 mL), diethyl
ether (60 mL) and triethylamine (25 mL) were added and the mix-
ture stirred for 1 h. The aqueous layer was removed and re-ex-
tracted with diethyl ether (30 mL). The combined organic layers
were washed with distilled water (3 ꢃ 20 mL) and filtered. Re-
moval of the solvent under reduced pressure gave 13 as a red oil
(3.36 g, 89%). C16H23FePO2 requires: C, 57.49; H, 6.94; N, 0.00.
Found: C, 58.84; H, 6.73; N, <0.2%. 31P{1H} NMR d ꢀ22.7 (s). 1H
NMR d 1.6 (CH2, m, 2H), 1.7 (CH2, m, 2H), 1.8 (CH2, m, 2H), 2.4
(CH2, m, 2H), 4.05 (CH, m, 4H), 4.10 (CH, s, 5H), 4.2 (CH2, d of m,
1
1
3
2
68.1 (C3, s), 68.6 (C2, d, JPC 4), 68.9 (C4, s), 85.6 (C1, d, JPC 7),
3
2
123.9 (CH, s), 129.3 (CH, d, JPC 4), 129.5 (C, s), 148.7 (C, d, JPC 3).
ESI MS (MeOH): m/z 367.043 [M]+ observed; 367.042 calcd. for
C18H18FeNO2P.
The yellow band at Rf 0.33 gave (FcCH2)2PCH2C6H4NO2 11 as a
red oil (0.02 g, 0.8%). 31P{1H} NMR d ꢀ12.3 (s). 1H NMR d 2.5
4
3
(CH2, q of d, JHH 8, 6H), 4.03 (CH, unresolved m, JHH 2, 4H), 4.06
3
(CH, unresolved m, JHH 2, 4H), 4.08 (H4, s, 10H), 7.3 (CH, d of d,
3,4
3
J
8, 1, 2H), 8.1 (CH, d, JHH 9, 2H). 13C{1H} NMR d 27.9 (CH2,
HH
1
1
3
d, JPC 19), 34.4 (CH2, d, JPC 21), 67.7 (CH, d, JPC 4), 68.9 (CH, d,
4JPC 3), 68.9 (C5, s, CH), 83.6 (C1, d, JPC 10), 123.6 (CH, s), 129.9
2
3
2
(CH, d, JPC 6), 146.2 (C, s), 147.0 (C, d, JPC 7).
Another by-product FcCH2P(CH2C6H4NO2)2 12 was obtained as
a red solid (0.84 g, 24%) from the orange fraction at Rf 0.66. C25H23-
FeN2O4P requires: C, 59.76; H, 4.62; N, 5.58. Found: C, 59.79; H,
1
2
2JPH 85, 4H). 13C{1H} NMR d 16.7 (d, JPC 9, CH2), 25.8 (d, JPC 15,
3
1
4.78; N, 5.71%. IR:
m
NO 1513vs, 1343vs cmꢀ1
.
31P{1H} NMR d
CH2), 29.3 (s, CH2), 32.7 (d, JPC 12, CH2), 61.9 (d, JPC 21, CH2),
67.1 (s, CH), 68.1 (s, CH), 68.5 (s, CH), 89.1 (C, s). ESI MS (MeOH
with AgNO3 added): m/z 334.078 [M]+ observed; 334.078 calcd.
for C16H23FeO2P; 440.984 [M+Ag]+ observed; 440.983 calcd. for
C16H23AgFeO2P; 775.061 [2M+Ag]+ observed; 775.061 calcd. for
ꢀ8.7 (s). 1H NMR d 2.6 (CH2, s, 2H), 2.9 (CH2, q, JHH 19, 4H), 4.03
(CH, unresolved m, 2H), 4.08 (H5, s, 5H), 4.11 (CH, unresolved m,
4
3
3
2H), 7.3 (CH, d, JHH 8, 4H), 8.1 (CH, d, JHH 8, 4H). 13C{1H} NMR d
1
1
27.7 (CH2, d, JPC 19), 34.1 (CH2, d, JPC 19), 68.0 (CH, s), 68.9 (CH,
3
2
d, JPC 3), 69.0 (CH, s), 82.2 (C, d, JPC 8), 123.9 (CH, s), 129.9 (CH,
d, 3JPC 6), 145.5 (C, t, 2JPC 4), 146.5 (C, s). ESI MS (MeOH with AgNO3
added): m/z 502.074 [M]+ observed; 502.073 calcd. for C25H23FeN2-
O4P; 608.978 [M+Ag]+ observed; 608.979 calcd. for
C32H46AgFe2O4P2.
4.2.6. Synthesis of Fc(CH2)6P(CH2OH)2 14
C
25H23AgFeN2O4P.
KOH (1.91 g, 34.04 mmol) was added to a solution of [P(CH2-
OH)4]Cl (7.71 g, 32.37 mmol) in methanol (20 mL). The mixture
was stirred for 1 h before being added dropwise to a solution of
Fc(CH2)6Br (2.06 g, 5.89 mmol) in 95% ethanol (20 mL) and the
reaction mixture was refluxed for 20.5 h. After cooling, the solvent
was removed under reduced pressure. Water (25 mL), diethyl ether
(40 mL) and triethylamine (12 mL) were added and the mixture
was stirred for 2 h. The aqueous layer was removed and re-ex-
tracted with diethyl ether (30 mL). The combined organic layers
were washed with water (3 ꢃ 20 mL). Removal of the solvent un-
der reduced pressure gave 14 as a red oil (2.02 g, 95%). 31P{1H}
NMR d ꢀ22.9 (s). 1H NMR d 1.4–1.5 (CH2, m, 8H), 1.8 (CH2, m,
4.2.4. Synthesis of FcCH2PHCy 9
Na2S2O5 (2.44 g, 12.83 mmol) was added to a solution of FcCH2-
P(CH2OH)Cy 6 (5.25 g, 15.26 mmol) in a two-phase mixture of
water (60 mL) and petroleum spirits (60 mL). The mixture was re-
fluxed for 3 h in air. After cooling, the aqueous layer was removed
and the organic layer was washed with distilled water (3 ꢃ 20 mL).
Removal of the solvent from the organic layer under reduced pres-
sure gave a red oil (2.21 g; a trace of CyPH2 was observed by 31P
1
NMR of the crude product at d ꢀ110.2, t, JPH 194 Hz). The red oil
was extracted with a solvent mixture of diethyl ether (30 mL)
and petroleum spirits (30 mL) which resulted in an immediate pre-
cipitation of a yellow solid which was collected by filtration,
washed with cold diethyl ether (2 mL) and identified by 1H and
31P NMR spectroscopy and ESI MS as 10 (0.15 g, 3%). The organic
filtrates were combined and the solvents were removed under re-
duced pressure. The residue was subjected to chromatography
with a preparative TLC plate, eluting with diethyl ether/n-hexane
(1:10). The orange band at Rf 0.91 gave the pure 9 as a red oil
(0.55 g, 19% based on [FcCH2NMe3]I used) which solidified at
3
2H), 2.3 (CH2, t, JHH 8, 2H), 4.04 (H2,3, unresolved m, 4H), 4.09
2
(H4, s, 5H), 4.2 (CH2, d of m, JPH 92, 4H). 13C{1H} NMR d 16.8 (d,
2
1JPC 8, CH2), 25.8 (d, JPC 15, CH2), 29.3 (s, CH2), 29.5 (s, CH2), 31.0
3
1
(s, CH2), 31.2 (d, JPC 12, CH2), 61.9 (d, JPC 20, CH2), 67.0 (s, CH),
68.1 (s, CH), 68.5 (s, CH), 89.4 (C, s). ESI MS (MeOH with AgNO3
added): m/z 362.108 [M]+ observed; 362.109 calcd. for C18H27FeO2-
P; 385.099 [M+Na]+ observed; 385.099 calcd. for C18H27FeNaO2P;
469.014 [M+Ag]+ observed; 469.014 calcd. for C18H27AgFeO2P;
831.123 [2M+Ag]+ observed; 831.124 calcd. for C36H54AgFe2O4P2.

188
T. Asamizu et al. / Inorganica Chimica Acta 414 (2014) 181–190
4.2.7. Synthesis of Fc(CH2)11P(CH2OH)2 15
56 [Fe]+, 121 [CpFe]+, 199 [FcCH2]+, 302 [M]+. ESI MS (CH2Cl2/
KOH (3.40 g, 60.6 mmol) was added to a solution of [P(CH2-
OH)4]Cl (15.28 g, 64.15 mmol) in methanol (20 mL). The mixture
was stirred for 1 h before adding dropwise to a solution of
Fc(CH2)11Br (8.68 g, 20.69 mmol) in methanol (20 mL) and the
reaction mixture refluxed for 20.5 h. After cooling, the solvent
was reduced to ꢁ13 mL under reduced pressure. Water (12 mL),
diethyl ether (34 mL) and triethylamine (14 mL) were added and
the solution stirred for 2 h. The aqueous layer was removed and
re-extracted with diethyl ether (10 mL). The combined organic
layer was washed with water (6 ꢃ 10 mL). Removal of the solvent
under reduced pressure gave a red oil (8.29 g, 93%). Recrystallisa-
tion of the crude product by addition of petroleum spirits (b.p.
40–60 °C) to a dichloromethane-methanol solution followed by
cooling to ꢀ18 °C gave 15 as a yellow solid. C23H37FeO2P requires:
C, 63.87; H, 8.63; N, 0.00. Found: C, 63.95; H, 8.76; N, 0.47%. ESI MS
(MeOH with added AgNO3): m/z 432.186 [M]+ observed; 432.187
calcd. for C23H37FeO2P; 539.093 [M+Ag]+ observed; 539.092 calcd.
for C23H37AgFeO2P. 31P{1H} NMR d ꢀ22.7 (s). 1H NMR d 1.4–1.5
MeOH): m/z 302.088 [M]+ observed; 302.088 calcd. for C16H23FeP.
4.2.10. Synthesis of Fc(CH2)11PH2 18
Na2S2O5 (0.11 g, 0.57 mmol) was added to
a solution of
Fc(CH2)11P(CH2OH)2 15 (0.25 g, 0.64 mmol) in a two-phase mix-
ture of water (10 mL) and petroleum spirits (10 mL) and the mix-
ture was refluxed for 3 h. After cooling, the solvents were
removed with a syringe. The yellow precipitate was washed with
water (4 ꢃ 10 mL). After drying under vacuum, the residue
(0.26 g) was extracted with dichloromethane and filtered. The fil-
trate was subjected to chromatography with a preparative TLC
plate, eluting with dichloromethane/petroleum spirits (5:6). Re-
moval of the solvent from the yellow fraction at Rf 0.93 gave 18
as a yellow oil (0.06 g, 28%). C21H33FeP requires: C, 67.73; H,
8.94; N, 0.00. Found: C, 71.08; H, 9.36; N, <0.2%. IR:
mPH
1
2
2290 m cmꢀ1
.
31P NMR d ꢀ136.7 (PH2, t of t, JPH 195, JPH 6).1H
3
NMR d 1.3–1.5 (CH2, m, 22H), 2.3 (CH2, t, JHH 8, 2H), 2.7 (PH2, d
1
3
of t, JPH 195, JHH 7, 2H), 4.04 (CH, unresolved m, 4H), 4.09 (CH,
3
1
(CH2, m, 18H), 1.8 (CH2, m, 2H), 2.3 (CH2, t, JHH 8, 2H), 4.04 (CH,
s, 5H). 13C{1H} NMR d 13.7 (CH2, d, JPC 7), 29.2 (CH2, s), 29.6
m, 4H), 4.09 (CH, s, 5H), 4.2 (CH2, d of m, JPH 89, 4H).13C{1H}
(CH2, s), 30.6 (CH2, d, JPC 6), 31.1 (CH2, s), 32.9 (CH2, d, JPC 3),
67.0 (CH, s), 68.1 (CH, s), 68.5 (CH, s), 89.6 (C, s). GC–MS: m/z 121
[CpFe]+, 199 [FcCH2]+, 372 [M]+. ESI MS (CH2Cl2/MeOH): m/z
372.165 [M]+ observed; 372.166 calcd. for C21H33FeP.
2
2
3
1
2
NMR d 16.9 (d, JPC 8, CH2), 25.9 (d, JPC 15, CH2), 28.2–31.1 (s,
3
1
CH2), 31.3 (d, JPC 12, CH2), 61.8 (d, JPC 20, CH2), 67.0 (s, CH),
68.1 (s, CH), 68.5 (s, CH), 89.6 (C, s).
4.2.11. Synthesis of Fc(CH2)6PH2(BH3) 19
4.2.8. Synthesis of Fc(CH2)4PH2 16
Under a nitrogen atmosphere a solution of Fc(CH2)6PH2 17
(0.05 g, 0.17 mmol) in dry hexane (10 mL) was cooled to ꢀ63 °C.
BH3(SMe2) in THF (0.5 mL, 5.63 mmol) was added and the mixture
stirred at ꢀ63 °C for 15 min. Volatiles were removed under vac-
uum, and the residue recrystallised from dry n-hexane at ꢀ20 °C.
Orange needles of 19 (13.8 mg, 26%) were collected and washed
with cold hexane (2 ꢃ 1 mL). C16H26BFeP requires: C, 60.75; H,
8.29. Found: C, 60.84; H, 8.19%. ESI MS (CH2Cl2/MeOH): m/z
316.1195 [M]+ (calcd. for C16H26BFeP m/z 316.1209); 339.1096
[M+Na]+ observed; 339.1110 calcd. for C16H26BFeNaP; 355.0588
[M+K]+ observed; 355.0846 calcd. for C16H26BFeKP. 31P NMR
Na2S2O5 (0.03 g, 0.16 mmol) was added to
a solution of
Fc(CH2)4P(CH2OH)2 13 (0.07 g, 0.21 mmol) in a two-phase solvent
system of water (5 mL) and petroleum spirits (5 mL) and the mix-
ture was refluxed for 2 h. After cooling, the aqueous layer was re-
moved and re-extracted with petroleum spirits (10 mL). The
combined organic layer was washed with water (3 ꢃ 10 mL). Re-
moval of the solvent under reduced pressure gave a red oil which
was chromatographed with a preparative TLC plate, eluting with
petroleum spirits. Removal of the solvent from the yellow band
at Rf 1.0 gave 16 as a yellow oil (0.02 g, 35%). IR: m .
PH 2289s cmꢀ1
31P NMR d ꢀ136.9 (PH2, t, 1JPH 194). 1H NMR d 1.5–1.6 (CH2, m, 6H),
2.3 (CH2, t, 3JHH 7, 2H), 2.7 (PH2, d of t, 1JPH 194, 3JHH 7, 2H), 4.05 (CH,
two unresolved singlets, 4H), 4.1 (H4, s, 5H). 13C{1H} NMR d 13.7
1
(CDCl3) d ꢀ52.32 (broad t, JPH 362). 1H NMR (400 MHz, CDCl3) d
1.26–1.53 (CH2 and BH3, m, 13H), 1.76–1.86 (CH2, m, 2H), 2.33
(CpCH2, t, 3JHH 7.8, 2H), 4.05–4.10 (CpH, s, 11H), 4.50 (PH2, d of sex-
1
2
3
(CH2, d, JPC 7), 29.2 (CH2, s), 32.0 (d, JPC 6), 32.8 (CH2, d, JPC 3),
67.1 (C3, s, CH), 68.1 (C2, s, CH), 68.5 (C4, s, CH), 89.1 (C1, s). GC–
MS: m/z 56 [Fe]+, 121 [CpFe]+, 199 [FcCH2]+, 274 [M]+. ESI MS (CH2-
Cl2/MeOH): m/z 274.056 [M]+ observed; 274.056 calcd. for C14H19-
FeP. A sample for elemental analysis was obtained by distillation
under 10ꢀ6 torr at 65 °C for 12 h. C14H19FeP requires: C, 61.34; H,
6.99. Found: C, 61.64; H, 6.61%.
1
3
1
tets, JPH 360, JHH 1.32). 13C{1H} NMR (CDCl3) d 16.5 (CH2PH2, JPC
3
35.4), 28.9 (CpCH2CH2CH2, s), 28.9 (CH2CH2CH2PH2, d, JPC 5.75),
29.5 (CpCH2, s), 30.2 (CH2CH2PH2, d, JPC 10.5), 31.0 (CpCH2CH2,
2
s), 67.2 (C3, s, CH), 68.2 (C2, s, CH), 68.7 (C5H5, s, CH), 89.5 (C1, s).
4.2.12. Synthesis of RcCH2P(CH2OH)2 20
KOH (1.30 g, 23.13 mmol) was added to a solution of [P(CH2-
OH)4]Cl (5.37 g, 22.54 mmol) in methanol (15 mL). The mixture
was stirred for 1 h before being added dropwise to a solution of
[RcCH2NMe3]I (1.95 g, 4.53 mmol) in methanol (15 mL) and the
reaction mixture was refluxed for 20 h. After cooling, the solvent
was removed under reduced pressure. Water (10 mL), diethyl ether
(25 mL) and triethylamine (5 mL) were added and the solution was
stirred for 1 h. The aqueous layer was removed and re-extracted
with diethyl ether (20 mL). The combined organic layers were
washed with water (5 ꢃ 10 mL). Removal of the solvent under re-
duced pressure gave 20 as a pale-yellow oil with some white solids
(0.95 g, 62%) which was used in the synthesis of RcCH2PH2 21
without further purification or characterisation.
4.2.9. Synthesis of Fc(CH2)6PH2 17
Na2S2O5 (1.08 g, 5.66 mmol) was added to
a solution of
Fc(CH2)6P(CH2OH)2 14 (2.04 g, 5.64 mmol) in a two-phase solvent
system of water (30 mL) and petroleum spirits (30 mL) and the
mixture was refluxed for 4 h in air. After cooling, the aqueous layer
was removed. The organic layer was washed with water
(3 ꢃ 10 mL) and filtered. Removal of the solvent under reduced
pressure gave a red oil (1.42 g, 83%). A sample for microelemental
analysis was obtained by chromatography on a preparative TLC
plate, eluting with ether/petroleum spirits (1:1). Removal of the
solvent of the fraction at Rf 0.70 gave 17 as a yellow oil. C16H23FeP
requires: C, 63.58; H, 7.68. Found: C, 62.04; H, 7.99%. IR:
mPH
1
2
2283 m cmꢀ1
.
31P NMR d ꢀ136.5 (PH2, t of t, JPH 195, JPH 6). 1H
4.2.13. Synthesis of RcCH2PH2 21
3
NMR d 1.3–1.6 (CH2, m, 10H), 2.3 (CH2, t, JHH 8, 2H), 2.7 (PH2, d
Na2S2O5 (0.54 g, 2.83 mmol) was added to a solution of crude
RcCH2P(CH2OH)2 20 (0.95 g, 2.83 mmol) in a two-phase mixture
of water (20 mL) and petroleum spirits (25 mL) and the mixture
was refluxed for 3 h. After cooling, the aqueous layer was removed.
The organic layer was washed with water (5 ꢃ 10 mL). Removal of
1
3
3
of t, JPH 195, JHH 7, 2H), 4.05 (CH, unresolved m, JHH 2, 4H),
4.09 (H4, s, 5H). 13C{1H} NMR d 13.7 (CH2, d, JPC 7), 29.2 (CH2, s),
1
2
3
29.6 (CH2, s), 30.5 (CH2, d, JPC 6), 31.0 (CH2, s), 32.9 (CH2, d, JPC
4), 67.0 (CH, s), 68.1 (CH, s), 68.5 (CH, s), 89.4 (C, s). GC–MS: m/z

T. Asamizu et al. / Inorganica Chimica Acta 414 (2014) 181–190
189
the solvent from the organic layer under reduced pressure gave a
References
pale yellow oil with some white solids (0.34 g, 43%). The crude
product was partially purified by chromatography with a prepara-
tive TLC plate, eluting with dichloromethane/petroleum spirits
(1:1). Removal of the solvent of the pale yellow fraction at Rf
0.76 gave 21 as a pale-yellow oil (0.08 g, 10%). Satisfactory micro-
analytical data could not be obtained: C11H13PRu requires: C,
[1] M. Brynda, M. Geoffroy, G. Bernardinelli, Chem. Commun. (1999) 961.
[2] R.M. Hiney, L.J. Higham, H. Müller-Bunz, D.G. Gilheany, Angew. Chem., Int. Ed.
Engl. 45 (2006) 7248.
[3] K.R. Prabhu, N. Pillarsetty, H. Gali, K.V. Katti, J. Am. Chem. Soc. 122 (2000) 1554.
[4] M. Brynda, Coord. Chem. Rev. 249 (2005) 2013.
[5] R.J. Baker, M. Brym, C. Jones, M. Waugh, J. Organomet. Chem. 689 (2004) 781.
[6] M. Brynda, G. Bernardinelli, C. Dutan, M. Geoffroy, Inorg. Chem. 42 (2003)
6586.
[7] N. Pillarsetty, K. Raghuraman, C.L. Barnes, K.V. Katti, J. Am. Chem. Soc. 127
(2005) 331.
[8] N.J. Goodwin, W. Henderson, B.K. Nicholson, J. Fawcett, D.R. Russell, J. Chem.
Soc., Dalton Trans. (1999) 1785.
[9] W. Henderson, S.R. Alley, J. Organomet. Chem. 656 (2002) 120.
[10] M.A. Pet, M.F. Cain, R.P. Hughes, D.S. Glueck, J.A. Golen, A.L. Rheingold, J.
Organomet. Chem. 694 (2009) 2279.
[11] C. Spang, F.T. Edelmann, M. Noltemeyer, H.W. Roesky, Chem. Ber. 122 (1989)
1247.
[12] R. Kalio, P. Lönnecke, J. Reinhold, E. Hey-Hawkins, Organometallics 26 (2007)
3884.
[13] S.I.M. Paris, F.R. Lemke, R. Sommer, P. Lönnecke, E. Hey-Hawkins, J. Organomet.
Chem. 690 (2005) 1807.
[14] R. Kalio, P. Lönnecke, A. Cinquantini, P. Zanello, E. Hey-Hawkins, Z. Anorg. Allg.
Chem. 633 (2007) 2470.
[15] S.I.M. Paris, J.L. Petersen, E. Hey-Hawkins, M.P. Jensen, Inorg. Chem. 45 (2006)
5561.
[16] S.I.M. Paris, U.A. Laskay, S. Liang, O. Pavlyuk, S. Tschirschwitz, P. Lönnecke, M.C.
McMills, G.P. Jackson, J.L. Petersen, E. Hey-Hawkins, M.P. Jensen, Inorg. Chim.
Acta 363 (2010) 3390.
[17] R. Sommer, P. Lönnecke, J. Reinhold, P.K. Baker, E. Hey-Hawkins,
Organometallics 24 (2005) 5256.
47.65; H, 4.73. Found: C, 45.03; H, 4.44%. IR:
m
PH 2290 m cmꢀ1
.
1
3
31P NMR d ꢀ132.5 (PH2, t, JPH 193). 1H NMR d 2.5 (CH2, m, JHH
1
3
3
4, 2H), 2.9 (PH2, d of t, JPH 194, JHH 7, 2H), 4.5 (CH, t, JHH 2,
2H), 4.56 (CH, s, 5H), 4.57 (CH, t, JHH 2, 2H). 13C{1H} NMR d 14.0
3
1
3
(CH2, d, JPC 8), 69.5 (CH, s), 70.7 (CH, s), 70.9 (CH, d, JPC 3), 92.6
(C1, unresolved m). GC–MS: m/z 167 [CpRu]+, 245 [RcCH2]+, 278
[M]+. ESI MS (MeOH): m/z 244.989 [MꢀPH2]+ observed; 244.989
calcd. for C11H11Ru; (MeOH with added AgNO3): m/z 384.885
[M+Ag]+ observed; 384.884 calcd. for C11H13AgPRu.
A
by-product which was tentatively identified as RcCH2-
P(O)H(CH2OH) 22 was obtained as a white solid (0.05 g, 5%) from
the aqueous phase of the reaction mixture. 31P NMR d 35.7 (PH, d
1
2
3
4
of t, JPH 467, JPH 14). 1H NMR d 3.0 (CH2, d of t, JHH 13, JHH 4,
3
2H), 4.0 (CH2, m, 2H), 4.5 (CH, d, JHH 1, 2H), 4.6 (CH, s, 5H), 4.7
(CH, unresolved m, 2H), 6.8 (PH, broad d, JPH 467, 1H). 13C{1H}
1
1
NMR d 26.7 (CH2), 58.7 (CH2, d, JPC 74), 70.6 (CH), 71.2 (CH),
71.9 (CH), 80.0 (C).
[18] R. Kalio, P. Lönnecke, E. Hey-Hawkins, J. Organomet. Chem. 693 (2008) 590.
[19] M.M. Dell’Anna, U. Englert, M. Latronico, P. Lorenzo Luis, P. Mastorilli, D.
Giardina Papa, C.F. Nobile, M. Peruzzini, Inorg. Chem. 45 (2006) 6892.
[20] M. Peruzzini, P. Barbaro, V. Bertolasi, C. Bianchini, I. DelosRios, N. Mantovani, L.
Marvelli, R. Rossi, Dalton Trans. (2003) 4121.
4.3. X-ray structure determination on Fc(CH2)6PH2(BH3) 19
Crystals of 19 were obtained by recrystallisation from n-hexane,
slowly cooling at ꢀ18 °C. Intensity data were obtained on a Bruker
[21] M.M. Dell’Anna, P. Mastrorilli, C.F. Nobile, B. Calmuschi-Cula, U. Englert, M.
Peruzzini, Dalton Trans. (2008) 6005.
SMART diffractometer with Mo K
a X-rays and corrected for
[22] M.M. Dell’Anna, D. Giardina-Papa, S. Ibáñez, A. Martin, P. Mastrorilli, C.F.
Nobile, M. Peruzzini, Eur. J. Inorg. Chem. (2009) 4454.
[23] B.J. Anderson, M.A. Guino-o, D.S. Glueck, J.A. Golen, A.G. DiPasquale, L.M.
Liable-Sands, A.L. Rheingold, Org. Lett. 10 (2008) 4425.
[24] M.F. Cain, R.P. Hughes, D.S. Glueck, J.A. Golen, C.E. Moore, A.L. Rheingold, Inorg.
Chem. 49 (2010) 7650.
absorption using a multi-scan procedure [52]. The structure was
solved by direct methods and developed and refined on F2o. All cal-
culations were with the SHELX97 programs [53,54] run under WINGX
[55]. Figures were generated with ORTEP-3 [56].
[25] R. Sommer, P. Lönnecke, P.K. Baker, E. Hey-Hawkins, Inorg. Chem. Commun. 5
(2002) 115.
[26] A.A. Karasik, R.N. Naumov, R. Sommer, O.G. Sinyashin, E. Hey-Hawkins,
Polyhedron 21 (2002) 2251.
4.3.1. Crystal data for Fc(CH2)6PH2(BH3) 19
C16H26BFeP;
P21/n; a = 14.9861(4) Å;
b = 110.711(1)°; V = 1609.17(7) Å3; Z = 4; T = 89(2) K; k(Mo
) = 0.71073 Å; (Mo
) = 1.021 mmꢀ1 Dcalc = 1.304 g cmꢀ3
Mr = 316.00;
monoclinic;
space
c = 19.7607(5) Å;
group
[27] A.A. Karasik, Y.S. Spiridonova, D.G. Yakhvarov, O.G. Sinyashin, P. Lönnecke, R.
Sommer, E. Hey-Hawkins, Mendeleev Commun. 15 (2005) 89.
[28] F. Labrue, B. Pons, L. Ricard, A. Marinetti, J. Organomet. Chem. 690 (2005) 2285.
[29] B. Stewart, A. Harriman, L.J. Higham, Organometallics 30 (2011) 5338.
[30] A.R. Seibert, M.F. Cain, D.S. Glueck, C. Nataro, J. Organomet. Chem. 696 (2011)
2259.
[31] M.D. Sliger, G.A. Broker, S.T. Griffin, R.D. Rogers, K.H. Shaughnessy, J.
Organomet. Chem. 690 (2005) 1478.
[32] G.M. Kosolapoff, L. Maier, Organic Phosphorus Compounds, vol. 1, Wiley-
Interscience, New York, 1972.
b = 5.8093(1) Å;
Ka
l
Ka
;
;
20240 reflections collected; 3871 unique (Rint = 0.0300). H atoms
on the (CH2)6 chain and the cyclopentadienyl rings were in calcu-
lated positions; the PH2 and BH3 hydrogen atoms were located and
refined with isotropic temperature factors. Final refinement gave
R1 = 0.0243, wR2 = 0.0616 for data with [I > 2r(I)] and R1 = 0.0289,
[33] See for example W. Henderson, A.G. Oliver, A.J. Downard, Polyhedron 15
(1996) 1165.
[34] W. Henderson, J.S. McIndoe, Mass Spectrometry of Inorganic, Coordination and
wR2 = 0.0645 for all data. Residual electron density (eꢀ Åꢀ3) maxi-
mum/minimum: 0.440/ꢀ0.211.
Organometallic Compounds
2005.
– Tools-Techniques-Tips, John Wiley & Sons,
[35] W. Henderson, G.M. Olsen, Polyhedron 17 (1998) 577.
[36] W. Henderson, G.M. Olsen, Polyhedron 15 (1996) 2105.
Acknowledgements
[37] M.G. Fitzpatrick, L.R. Hanton, W. Henderson, P.E. Kneebone, E.G. Levy, L.J.
McCaffrey, D.A. McMorran, Inorg. Chim. Acta 281 (1998) 101.
[38] G.C. Welch, T. Holtrichter-Roessmann, D.W. Stephan, Inorg. Chem. 47 (2008)
1904.
[39] N.J. Goodwin, W. Henderson, B.K. Nicholson, J.K. Sarfo, J. Fawcett, D.R. Russell,
J. Chem. Soc., Dalton Trans. (1997) 4377.
We thank the Marsden Fund of the Royal Society of New Zea-
land for financial support of this work, and Michelle Clark and Ant-
ony Parnell for technical support. Dr. Tania Groutso (University of
Auckland) is thanked for collection of the X-ray data set.
[40] A. Staubitz, A.P.M. Robertson, M.E. Sloan, I. Manners, Chem. Rev. 110 (2010)
4023.
[41] A.V. Polukeev, S.A. Kuklin, P.V. Petrovskii, S.M. Peregudova, A.F. Smol’yakov,
F.M. Dolgushin, A.A. Koridze, Dalton Trans. 40 (2011) 7201;
A.A. Koridze, A.V. Polezhaev, S.V. Safronov, A.M. Sheloumov, F.M. Dolgushin,
M.G. Ezernitskaya, B.V. Lokshin, P.V. Petrovskii, A.S. Peregudov,
Organometallics 29 (2010) 4360;
S.A. Kuklin, A.M. Sheloumov, F.M. Dolgushin, M.G. Ezernitskaya, A.S.
Peregudov, P.V. Petrovskii, A.A. Koridze, Organometallics 25 (2006) 5466.
[42] H.C.L. Abbenhuis, U. Burckhardt, V. Gramlich, A. Martelletti, J. Spencer, I.
Steiner, A. Togni, Organometallics 15 (1996) 1614.
Appendix A. Supplementary material
CCDC 971461 contains the supplementary crystallographic data
for Fc(CH2)6PH2(BH3). These data can be obtained free of charge
from The Cambridge Crystallographic Data Centre via
www.ccdc.cam.ac.uk/data_request/cif. Supplementary data associ-
ated with this article can be found, in the online version, at http://
dx.doi.org/10.1016/j.ica.2014.01.049.
[43] M. Watanabe, Tetrahedron Lett. 36 (1995) 8991.

190
T. Asamizu et al. / Inorganica Chimica Acta 414 (2014) 181–190
[44] See for example S. Barlow, A. Cowley, J.C. Green, T.J. Brunker, T. Hascall,
Organometallics 20 (2001) 5351.
[50] M. Tazaki, K. Okada, K. Yakata, K. Nakano, M. Sakai, T. Yonemitsu, Phosphorus,
Sulfur, Silicon Relat. Elem. 167 (2000) 239.
[45] M.C. Grossel, D.G. Hamilton, J.I. Fuller, E. Millan-Barios, J. Chem. Soc., Dalton
Trans. (1997) 3471.
[46] http://fluorine.ch.man.ac.uk/research/tools.php.
[47] D. Lednicer, C.R. Hauser, Org. Synth. Coll. 5 (1973) 434.
[48] C.J. Yu, H. Wang, Y. Wan, H. Yowanto, J.C. Kim, L.H. Donilon, C. Tao, M. Strong,
Y. Chong, J. Org. Chem. 66 (2001) 2937.
[51] E.P. Kündig, F.R. Monnier, Adv. Synth. Catal. 346 (2004) 901.
[52] R.H. Blessing, Acta Crystallogr., Sect. A 51 (1995) 33.
[53] G.M. Sheldrick, SHELX-97 Programs for the Solution and Refinement of Crystal
Structures (Release 97-2), University of Göttingen, Germany, 1997.
[54] G.M. Sheldrick, Acta Crystallogr., Sect. A 64 (2008) 112.
[55] L.J. Farrugia, J. Appl. Crystallogr. 32 (1999) 837.
[49] G. Zotti, S. Zecchin, G. Schiavon, A. Berlin, G. Pagani, A. Canavesi, Chem. Mater.
7 (1995) 2309.
[56] L.J. Farrugia, J. Appl. Crystallogr. 30 (1997) 565.