Phosphido complexes derived from 1,1′-ferrocenediyl-bridged secondary diphosphines

Article abstract of DOI:10.1039/c7dt00941k

This paper focuses on ferrocene-based secondary diphosphines of the type [Fe{η⁵-C₅H₄(PHR)}₂] with P-substituents of distinctly different steric and electronic properties, namely methyl, neopentyl (Np), tert-butyl, phenyl and 3,5-bis(trifluoromethyl)phenyl (XyF). The reaction of [Fe{η⁵-C₅H₄(PHPh)}₂] (H₂1a) and [Fe{η⁵-C₅H₄(PHt-Bu)}₂] (H₂1b) with n-BuLi in the presence of TMEDA afforded lithium diphosphides of the type [Li₂(μ-1)(TMEDA)₂], which contain a cyclic non-planar Li₂P₂ core. The analogous reactions of [Fe{η⁵-C₅H₄(PHMe)}₂] (H₂1c) and [Fe{η⁵-C₅H₄(PHNp)}₂] (H₂1d) furnished dimeric aggregates exhibiting a ladder-type Li₄P₄ motif, viz. [Li₄(μ-1c)₂(TMEDA)₃] and [Li₂(μ-1d)(TMEDA)]₂. H₂1e (R = XyF) did not afford a stable lithium diphosphide. A Br?nsted metathesis with Zr(NMe₂)₄ was possible with the aryl-substituted compounds H₂1a and H₂1e, leading to products of the type [{Zr(NMe₂)₃}₂(μ-1)]. In contrast, the alkyl-substituted congeners H₂1b-H₂1d were inert towards Zr(NMe₂)₄. The reaction of [Fe{η⁵-C₅H₄(PHR)}₂] with nickelocene afforded intractable mixtures of numerous products in the case of H₂1c and H₂1e. In the other three cases, compounds of the type [(NiCp)₂(μ-1)] were isolated. For H₂1b and H₂1d a two-stepped reaction via a phosphino-phosphido intermediate of the type [NiCp(H1)] was observed, which could be isolated and fully characterised in the case of [NiCp(H1b)].

Full text of DOI:10.1039/c7dt00941k

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Phosphido complexes derived from 1,1’-
ferrocenediyl-bridged secondary diphosphines†‡
Cite this: DOI: 10.1039/c7dt00941k
Sandra Hitzel, Christian Färber,§ Clemens Bruhn and Ulrich Siemeling
*
This paper focuses on ferrocene-based secondary diphosphines of the type [Fe{η5-C5H4(PHR)}2] with
P-substituents of distinctly different steric and electronic properties, namely methyl, neopentyl (Np), tert-
butyl, phenyl and 3,5-bis(trifluoromethyl)phenyl (XyF). The reaction of [Fe{η5-C5H4(PHPh)}2] (H21a) and
[Fe{η5-C5H4(PHt-Bu)}2] (H21b) with n-BuLi in the presence of TMEDA afforded lithium diphosphides of
the type [Li2(μ-1)(TMEDA)2], which contain a cyclic non-planar Li2P2 core. The analogous reactions of
[Fe{η5-C5H4(PHMe)}2] (H21c) and [Fe{η5-C5H4(PHNp)}2] (H21d) furnished dimeric aggregates exhibiting a
ladder-type Li4P4 motif, viz. [Li4(μ-1c)2(TMEDA)3] and [Li2(μ-1d)(TMEDA)]2. H21e (R = XyF) did not afford a
stable lithium diphosphide. A Brønsted metathesis with Zr(NMe2)4 was possible with the aryl-substituted
compounds H21a and H21e, leading to products of the type [{Zr(NMe2)3}2(μ-1)]. In contrast, the alkyl-sub-
stituted congeners H21b–H21d were inert towards Zr(NMe2)4. The reaction of [Fe{η5-C5H4(PHR)}2] with
nickelocene afforded intractable mixtures of numerous products in the case of H21c and H21e. In the
other three cases, compounds of the type [(NiCp)2(μ-1)] were isolated. For H21b and H21d a two-stepped
reaction via a phosphino–phosphido intermediate of the type [NiCp(H1)] was observed, which could be
isolated and fully characterised in the case of [NiCp(H1b)].
Received 15th March 2017,
Accepted 25th April 2017
DOI: 10.1039/c7dt00941k
rsc.li/dalton
various compounds of this class and their reactions affording
corresponding phosphido complexes.
Introduction
We have a long-standing interest in ferrocene-based chelate
The phosphorus atom of a uninegative PR2 unit contains
ligands other than the iconic 1,1′-bis(diphenylphosphino) two lone pairs of electrons. The coordination chemistry of
ferrocene (dppf) and related standard diphosphines.1 A sub- these phosphido ligands is highly diverse, because both term-
stantial part of this work from our group has focused on inal and bridging coordination modes are possible. In the
diamido chelate complexes derived from secondary diamines bridging mode, both lone pairs are occupied in metal–phos-
of the type fc(NHR)2 (fc = 1,1′-ferrocenylene). First examples of phorus bonds. In the terminal mode, the bonding environ-
such compounds were reported in 2001 almost simultaneously ment of the phosphorus atom can be either trigonal pyramidal
by us1j and by the groups of Arnold2 and Gibson and Long.3 or trigonal planar.7 Only one lone pair on phosphorus is occu-
The chemistry of chelates containing the diamido ligand pied in the trigonal pyramidal case. In the trigonal planar
framework [fc(NR)2]2− has flourished enormously since then, case, the second lone pair is engaged in π bonding to the
in particular through contributions in the area of f-block metal centre, formally giving rise to a metal–phosphorus
elements by the groups of Arnold,4 Eppinger5 and, in particu- double bond. Terminal phosphido complexes are attracting
lar, Diaconescu.6 The heavier analogues of the ferrocene-based considerable attention due to their relevance in important
diamines mentioned above are secondary diphosphines of the catalytic reactions such as phosphine dehydrocoupling and
type fc(PHR)2. In this report we describe the synthesis of the hydrophosphination of alkenes and alkynes.8 The first
structurally authenticated example was published in 1975.9,10
Phosphido-bridged complexes have been known for more than
half a century11 and continue to be of widespread interest.12
Institute of Chemistry, University of Kassel, Heinrich-Plett-Str. 40, 34132 Kassel,
For example, μ-PR2 units are useful for the stabilisation of
Germany. E-mail: siemeling@uni-kassel.de
oligonuclear metal complexes and clusters,13 including even
†Dedicated to Prof. Evamarie Hey-Hawkins on the occasion of her 60th birthday.
nanosized metalloid ones.14 First examples of complexes
‡Electronic supplementary information (ESI) available: Plots of NMR spectra,
2−
crystal data and structure refinement details. CCDC 1536257–1536270. For ESI
and crystallographic data in CIF or other electronic format see DOI: 10.1039/
c7dt00941k
containing diphosphido ligands X(PR)2
were published
already in 1967.15 Surprisingly, just a single ferrocene-based
ligand of this type is known to date, namely fc(PPh)2 (1a2−),
2−
§Present address: Department of Chemistry and Pharmacy, Friedrich-Alexander-
Universität Erlangen-Nürnberg, Egerlandstr. 3, 91058 Erlangen, Germany.
which is present in the gold(I) complex [Au2(1a)]n reported in
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2010 by Glueck and co-workers as the only example so far of a ration of the Grignard reagent worked better in our hands with
complex containing this ligand.16 This diphosphido complex NpBr than with NpCl, and consequently PBr3 was used instead
was synthesised by dehydrochlorination of its diphosphine of PCl3 in order to avoid halide scrambling). The yield of ana-
precursor [(AuCl)2(μ-H21a)]. Interestingly, the parent secondary lytically pure product obtained over three steps was 29% for
diphosphine fc(PHPh)2 (H21a) is commercially available, H21a, 47% each for H21b and H21d and 44% for H21e.
although its synthesis has not been described so far. Very
The phosphorus atoms of 1,1′-ferrocenylene-bridged sec-
recently, Pietschnig and co-workers published the only other ondary diphosphines of the type fc(PHR)2 are chiral centres
1,1′-ferrocenylene-bridged secondary diphosphine, namely fc and rac and meso isomers are therefore expected for these
(PHt-Bu)2 (H21b).17 In a parallel study, this compound was compounds. In the case of the known compound H21b, the
investigated also in our group, together with several new hom- presence of two isomers is reflected by the observation of two
ologues described below.
doublets in the 31P NMR spectrum (δ −26.9 and −27.4 ppm in
C6D6 solution).17 Likewise, two closely spaced doublets are
present in the 31P NMR spectrum of the phenyl congener H21a
(δ −60.8 and −61.2 ppm in C6D6 solution) and the bis(trifluoro-
methyl)phenyl congener H21e (δ −61.2 and −61.5 ppm in
C6D6 solution). The diastereomeric ratio is 1 : 1 in each case.
In contrast, the new alkyl-substituted congeners H21c (R = Me)
and H21d (R = Np) each exhibit only a single doublet in the
31P NMR spectrum (C6D6), respectively located at −89.9 and
−86.8 ppm. We surmise that in these cases the chemical shift
difference of the rac and meso isomers is not sufficient for the
detection of resolved individual signals. We have been able to
determine the structures of rac-H21a, meso-H21b and meso-
H21e by single-crystal X-ray diffraction (XRD) studies (Fig. 1–3).
Pertinent metric parameters are collected in Table 1.
Results and discussion
Synthesis and characterisation of diphosphines
We have prepared three new 1,1′-ferrocenylene-bridged second-
ary diphosphines of the type fc(PHR)2, viz. H21c (R = methyl),
H21d [R = neopentyl (Np)] and H21e [R = 3,5-bis(trifluoro-
methyl)phenyl (XyF)]. The synthesis of these compounds is
outlined in Scheme 1. The phenyl congener H21a is also
included, because its preparation has not been reported to
date. In addition, this scheme shows our synthesis of H21b,
since this differs from the recently reported route.17
The methyl-substituted compound H21c was prepared in
analogy to the published synthesis of the tert-butyl congener
H21b.17 The reaction of fc[PCl(NEt2)]2 (available in a two-
stepped reaction starting from 1,1′-dilithioferrocene)18 and
methyllithium afforded fc[PMe(NEt2)]2 [(NEt2)21c], which was
subsequently transformed to fc(PMeCl)2 (Cl21c) with HCl in
diethyl ether. In the final step, Cl21c was reduced to H21c with
lithium aluminium hydride. The yield of analytically pure
H21c was 47% over three steps. All other diphosphines were
more conveniently prepared by following a different synthetic
approach for the intermediates of the type fc[PR(NEt2)]2, which
is based on the reaction of 1,1′-dilithioferrocene with com-
pounds of the type PX(NEt2)R (X = Cl, Br). The chloro com-
pounds are readily available by published procedures for R =
Crystalline meso-H21b and meso-H21e each exhibit crystallo-
graphically imposed inversion symmetry (molecular point
group Ci), which leads to a staggered arrangement of the cyclo-
pentadienyl rings with diametrically opposed phosphino sub-
stituents. Essentially the same structural motif is found for
rac-H21a, which exhibits an approximately Ci symmetric fcP2
core. The phosphorus bond lengths and angles compare well
with those reported for the only two other examples of structu-
rally characterised ferrocene-based secondary phosphines, viz.
Fc–PH–t-Bu23 and Fc–PH–Acn–Pi-Pr2 (Acn = acenaphthen-5,6-
diyl).24
Synthesis and characterisation of lithium diphosphides
Ph,19 t-Bu,20 and XyF.21 The neopentyl derivative PBr(NEt2)Np Secondary phosphines can be deprotonated with standard
was easily prepared from diethylamine and PBr2Np, which was alkyllithium reagents. The resulting lithium phosphides LiPR2
obtained in a routine way22 from PBr3 and NpMgBr (the prepa- frequently form higher-order aggregates, which are insoluble
Scheme 1 Synthesis of H21a–H21e. Reagents and conditions: (a) PCl(NEt2)R (for a, b, d and e), diethyl ether, 0 °C → room temperature; (b) HCl in
diethyl ether, room temperature; (c) MeLi, diethyl ether, −60 °C → room temperature; (d) LiAlH4, THF, room temperature, then H2O.
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Fig. 3 Molecular structure of meso-H21e in the crystal.
Fig. 1 Molecular structure of rac-H21a in the crystal. Only one enantio-
Table 1 Selected bond lengths (Å) and angles (°) in secondary diamines
mer is shown.
of the type fc(NHR)2
P–Cfc
P–CR
C–P–C
Torsion anglea
178.0
rac-H21a
1.804(3)
1.808(3)
1.816(3)
1.802(3)
1.834(3)
1.824(3)
1.878(3)
1.863(3)
102.9(1)
102.3(1)
103.3(1)
101.0(1)
meso-H21b
meso-H21eb
180
180
a Cfc–cg–cg–Cfc (cg = cyclopentadienyl ring centroid) torsion angle.
b The structure was refined with disordered P atoms (two split posi-
tions with 65 and 35% probability). The data refer to the most prob-
able atom positions.
Pietschnig and co-workers recently described the formation of
the lithium diphosphide Li21b by reaction of H21b with n-BuLi
in the presence of TMEDA (two equivalents each).17 31P and
7Li NMR data indicate that the two phosphorus atoms are
associated symmetrically with the two lithium atoms in hydro-
carbon solution. Interestingly, the phosphine-to-phosphide
transformation, which occurs by lithiation of H21b, has a neg-
ligible effect on the chemical shift of the 31P NMR signal.31 We
have isolated the TMEDA adduct [Li2(μ-1b)(TMEDA)2] from
this reaction in n-hexane as orange-red crystals in 79% yield
(Scheme 2).
Fig. 2 Molecular structure of meso-H21b in the crystal.
in common organic solvents and thus difficult to crystallise
and characterise.25 This may be avoided by adduct formation
with TMEDA, THF or similar Lewis basic donors. For example,
the crystal structures of [Li(PPh2)(Et2O)]n,26 [Li(PPh2)
Its molecular structure in the solid state reveals a symmetri-
cally bridging arrangement of the lithium and phosphorus
atoms, which form a non-planar Li2P2 ring (see below). This
compound exhibits a surprisingly high solubility in benzene.
26
28
(DME)]n,27 [Li(PPh2)(THF)2]n and [Li(PPh2)(TMEDA)]2 were
reported already decades ago, whereas that of pristine lithium
diphenylphosphide is still unknown. In the same vein, the
crystal structure of the adduct [Li2{o-C6H4(PPh)2}(TMEDA)2]
was published in 1987,29 whereas that of the donor-free
lithium diphosphide has not been reported to date.30
1
7
Consequently, good quality H, Li, 13C and 31P NMR spectra
7
could be obtained from C6D6 solutions. Our Li (δ 1.9 ppm; t,
1JPLi = 51 Hz) and 31P NMR spectroscopic data (δ −26.9 ppm;
1
sept, JPLi = 51 Hz) (Table 2) are similar to those reported by
Pietschnig and co-workers for Li21b in C6D6.
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that observed for [Li2(μ-1b)(TMEDA)2] (see below). In compari-
son to the tert-butyl congener, lithiation has a non-negligible
effect on the chemical shift of the 31P NMR signal in this case
1
(upfield shift, Δδ ≈ −6 ppm in C6D6; see Table 2). No JPLi
coupling is observed, since the respective 7Li and 31P NMR
signal is fairly broad both for C6D6 and for THF-d8 solutions.
The analogous reaction of the methyl congener H21c in
n-hexane furnished the product as an amorphous red solid.
Crystals suitable for an XRD study could not be obtained in
this case, despite many attempts with various solvents. The 1H
NMR spectrum indicates a 2 : 3 ratio of 1c and TMEDA in this
product, which therefore may be plausibly represented as
[Li4(1c)2(TMEDA)3] (76% yield). Unfortunately, the result of the
CHN analysis is not in satisfactory agreement with this compo-
sition, because the value determined for nitrogen is too low by
2.4%. We note, however, that we have observed an almost iden-
tical deviation from the calculated value for nitrogen in the
case of the structurally characterised compounds [Li2(μ-1a)
(TMEDA)2] and [Li2(μ-1b)(TMEDA)2]. This indicates that the
quantity of TMEDA was lower in the samples used for CHN
analysis than in the samples used for NMR spectroscopy and
XRD (very likely because the samples used for CHN analysis
were routinely subjected to oil pump vacuum for prolonged
periods of time, which removed some of the reasonably volatile
TMEDA). The solubility of [Li4(1c)2(TMEDA)3] was sufficient for
NMR spectroscopic purposes only in THF-d8. Two broad
Scheme 2 Lithiation of H21a–H21d with n-BuLi in the presence of
TMEDA afforded compounds of structure type A (R = Ph, t-Bu) or B (R =
Me, Np; in the latter case the Li atoms marked with a surrounding
square are tricoordinate, while in the former case these Li atoms are
probably bridged by a TMEDA ligand and are tetracoordinate). Attempts
to lithiate H21e afforded only intractable material. Reagents and con-
ditions: (a) n-BuLi, TMEDA, n-hexane, room temperature.
Table 2 31P NMR spectroscopic data of the diphosphines H21a–H21d
and the corresponding lithium diphosphide TMEDA adducts
C6D6
THF-d8
Δδa
H21a
[Li2(μ-1a)(TMEDA)2]
H21b
[Li2(μ-1b)(TMEDA)2]
H21c
[Li4(μ-1c)2(TMEDA)3]
H21d
−60.8, −61.2
−66.9 (br.)
−62.0 (br.)
−6
−26.9, −27.4
−26.9 (sept, 1JPLi = 51 Hz) −26.6 (br.)
0
−89.9
b
−125.7 (br.) −36
−86.8
b
[Li2(μ-1d)(TMEDA)]2
−118.9 (br.) −32
7
a
31P NMR signal shift caused by lithiation of H21. b Insufficient
signals are observed in the Li spectrum (δ 11.3 and 6.2 ppm)
and the 31P NMR spectrum exhibits a single, fairly broad
signal (δ −125.7 ppm). In comparison to the tert-butyl and
phenyl congeners, lithiation has a pronounced effect on the
solubility.
1
Note that a significantly larger JPLi value of 80 Hz was chemical shift of the 31P NMR signal in this case, causing an
reported by Lappert and co-workers for the donor-free lithium upfield shift of Δδ ≈ −36 ppm (see Table 2). A similarly pro-
phosphide dimer [LiP{CH(SiMe3)2}2]2 in C6D6.32 The use of the nounced upfield shift was observed upon lithiation of the neo-
donor solvent THF-d8 leads to the observation of a respective pentyl congener H21d (Δδ ≈ −32 ppm; see Table 2), which
broad signal in the 7Li (δ 4.0 ppm) and 31P NMR spectrum furnished [Li2(μ-1d)(TMEDA)]2 as orange-red crystals in 71%
(δ −26.6 ppm) instead of the well-resolved 7Li triplet and 31P yield under our standard conditions (two equivalents each of
septet detected for [Li2(μ-1b)(TMEDA)2] in C6D6 solution. The n-BuLi and TMEDA in n-hexane solution). In the solid state,
1
absence of JPLi coupling in solution NMR spectra of lithium two types of lithium atoms are present in the structure (see
phosphides has been ascribed to lithium exchange processes below). A broad 7Li NMR signal is observed for this compound
which are rapid on the NMR time scale and/or to the for- in THF-d8 solution (δ 3.4 ppm). This signal is not symmetrical
mation of solvated lithium cations and phosphide anions in and apparently exhibits a shoulder. Similar to the methyl con-
strong donor solvents like THF.33 For example, lithium diphe- gener [Li4(1c)2(TMEDA)3], the solubility of [Li2(μ-1d)(TMEDA)]2
nylphosphide forms a dimeric aggregate at low temperatures in C6D6 was not sufficient for NMR purposes and THF-d8 was
in Et2O solution,34 which exhibits a triplet in the 7Li and a used throughout. The 31P NMR spectrum contains a single,
septet in the 31P NMR spectrum at 202 K (1JPLi = 44 Hz) or fairly broad signal (δ −118.9 ppm). The 1H and 13C NMR
below,31b,34,35 but no such coupling is observed in THF solu- spectra are compatible with symmetrical structures in solution,
tion even at 155 K.33a The lithiation of the other ferrocene- which exhibit equivalent PR units in both cases (R = Me, Np).
based diphosphines was also investigated by us and revealed The lithiation of H21e afforded a product which unfortunately
the formation of two structure types, viz. monomer A and resisted characterisation. A pale orange precipitate resulted
dimeric aggregate B in Scheme 2, depending on the substitu- under our standard conditions, which immediately turned
ents R. Due to the only moderate solubility of the phenyl con- black upon contact with standard organic solvents, including
gener H21a in n-hexane, this compound was reacted with C6D6 and THF-d8. When the lithiation was performed in
n-BuLi and TMEDA (two equivalents each) in a mixture of toluene or THF solution at −90 °C, a colour change from
toluene and n-hexane (3 : 1), which afforded the TMEDA orange to red was observed, compatible with the formation of
adduct [Li2(μ-1a)(TMEDA)2] as orange-red crystals in 80% the target phosphide. However, upon warming to ca. −40 °C,
yield. The molecular structure in the solid state is similar to the colour rapidly turned brown and a dark precipitate
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formed. We surmise that this behaviour is due to the compara-
tively high CH acidity of the aryl groups caused by the CF3 sub-
stituents. Note, for example, that 1,3-bis(trifluoromethyl)
benzene is readily lithiated with n-BuLi in the presence36 or
absence of TMEDA.37
The structures of [Li2(μ-1a)(TMEDA)2], [Li2(μ-1b)(TMEDA)2]
and [Li2(μ-1d)(TMEDA)]2, were determined by single-crystal
XRD analyses (Fig. 4–6). Pertinent metric parameters are col-
lected in Table 3.
The structural motif found for [Li2(μ-1a)(TMEDA)2] and
[Li2(μ-1b)(TMEDA)2] (structure type A in Scheme 2) closely
resembles that of the monomeric bis(diorganophosphide)
[Li2{o-C6H4(PPh)2}(TMEDA)2]29 as well as that of the dimeric
27
diorganophosphides
[LiPt-Bu2(DME)]2
and
[Li(PPh2)
(TMEDA)]2.28 The lithium and phosphorus atoms form a four-
membered ring, which is not planar. The dihedral angle
between the two Li2P planes is 45.9° in the case of [Li2(μ-1a)
(TMEDA)2] and 41.5° for the [Li2(μ-1b)(TMEDA)2] molecule
shown in Fig. 5. For comparison, this angle is 38.5° in the case
of [Li2{o-C6H4(PPh)2}(TMEDA)2].29 The Li–P distances are Fig. 5 Molecular structure of [Li2(μ-1b)(TMEDA)2] in the crystal. The
asymmetric unit contains two independent molecules, one of which
exhibits a disorder in a TMEDA unit. Only the non-disordered molecule
is shown. TMEDA carbon atoms are shown as smaller circles without
hydrogen atoms for clarity.
indistinguishable within experimental error in each case and
are typical for lithium diorganophosphides containing four-
coordinate lithium.25 The dimeric aggregate [Li2(μ-1d)
(TMEDA)]2 exhibits quite a different structural motif (structure
type B in Scheme 2). The lithium and phosphorus atoms form
a four-rung ladder, which is strongly reminiscent of the
arrangement found for [Li2(μ3-Pt-Bu2)(μ2-Pt-Bu2)(THF)]2.38 In
both structures two types of lithium and phosphorus atoms
Fig. 6 Molecular structure of [Li2(μ-1d)(TMEDA)]2 in the crystal. TMEDA
and neopentyl carbon atoms are shown as smaller circles without
hydrogen atoms for clarity. The Li⋯Fe contact of 2.610(6) Å is indicated
by a broken line.
are each present, which differ in their number of Li–P bonds
(either two or three). Each lithium atom bonded to only two
phosphorus atoms is additionally coordinated by a donor
molecule. In the case of [Li2(μ3-Pt-Bu2)(μ2-Pt-Bu2)(THF)]2, all
Fig. 4 Molecular structure of [Li2(μ-1a)(TMEDA)2] in the crystal. TMEDA
carbon atoms are shown as smaller circles without hydrogen atoms for
clarity.
lithium atoms are in a tricoordinate bonding environment
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Table 3 Selected bond lengths (Å) and angles (°) for the lithium
diphosphide TMEDA adducts derived from H21a, H21b and H21d
C6H4(PHPh)]2 (py = pyridine-2,6-diyl), which furnished the
PNP pincer complex [Zr{py[o-C6H4(PPh)]2-κ3N,P,P′}(NMe2)2].42
Indeed, the two aryl-substituted congeners H21a and H21e
each reacted smoothly and swiftly with Zr(NMe2)4 under mild
conditions (room temperature, 1 h), respectively affording
[{Zr(NMe2)3}2(μ-1a)] and [{Zr(NMe2)3}2(μ-1e)] (Scheme 3).
The yield was quantitative, when two equivalents of
Zr(NMe2)4 were used. In contrast, the alkyl-substituted com-
pounds H21b–H21d turned out to be inert even under rather
forcing conditions (toluene-d8, 100 °C, several days), which is
in line with an analogous observation reported by Hayes and
co-workers for the bis(dialkylphosphine) m-C6H4(CH2PHt-
Bu)2.30a Very likely, the acidity of the secondary phosphines is
not sufficient in the alkyl-substituted cases for a Brønsted
Average Li–P Li–P–Li
P–Li–P
C–P–C
[Li2(μ-1a)(TMEDA)2]
2.59
89.3(2)
88.8(2)
88.8(3)
88.8(3)
84.4(2)c
82.0(2)
82.1(2)
84.2(3)
83.5(3)
103.7(2)
101.7(2)
98.9(3)
99.8(3)
[Li2(μ-1b)(TMEDA)2] 2.57
[Li2(μ-1d)(TMEDA)]2 2.49a
99.0(2)a 103.5(2)
2.59b
80.3(2)d 117.8(2)a
62.2(2)d 125.8(2)a
98.3(2)
132.4(2)d
94.3(2)b
a Tricoordinate Li atoms. b Tetracoordinate Li atoms. c μ2-P. d μ3-P.
(either P3 or P2O), because THF is a monodentate donor. In
the case of [Li2(μ-1d)(TMEDA)]2, the bidentate donor TMEDA
causes a four-coordinate P2N2 environment for two of the
lithium atoms, while the other two are in a tricoordinate P3
environment. Due to crystallographically imposed inversion
symmetry (molecular point group Ci), the central Li2P2 ring of
[Li2(μ-1d)(TMEDA)]2 is exactly planar, whereas the outer Li2P2
rings each exhibit a dihedral angle between the two Li2P
planes of 14.1°. On average, the Li–P distances of the tricoordi-
nate lithium atoms are 0.1 Å shorter than those of the four-
coordinate ones, which is in accord with previous obser-
vations.25 Each tricoordinate lithium atom exhibits an
additional short contact to the iron atom of its fcP2 unit. The
Li–Fe distance of 2.610(6) Å is almost identical with the sum of
the covalent radii (Li 1.28 Å, low-spin Fe 1.32 Å).39 We have
observed a similarly short Li⋯Fe contact of 2.62 Å for the
closely related ferrocene-based lithium amide [Li2fc(NMes)2],
where we came to the conclusion that the proximity of the two
metal atoms very likely does not reflect intermetallic bonding,
but is primarily due to steric effects.40 In contrast to [Li2(μ-1a)
(TMEDA)2] and [Li2(μ-1b)(TMEDA)2], the N-substituents of
each fc(PR)2 moiety are in a cis orientation in the case of
[Li2(μ-1d)(TMEDA)]2. Steric repulsion between these neopentyl
groups is indicated by a cyclopentadienyl ring tilt angle of
11.1°, which is significantly larger than the corresponding
angles of 4.1° and 1.6° determined for [Li2(μ-1a)(TMEDA)2]
and [Li2(μ-1b)(TMEDA)2], respectively. We surmise that in the
case of [Li4(1c)2(TMEDA)3] the small methyl groups allow the
coordination of an additional TMEDA ligand, which probably
bridges the two lithium atoms that are in a P3 environment
(Scheme 2).
metathesis
with
Zr(NMe2)4.
[{Zr(NMe2)3}2(μ-1a)]
and
[{Zr(NMe2)3}2(μ-1e)] each exhibit a fairly broad singlet in the
31P NMR spectrum, respectively located at −32.8 and
−30.9 ppm. These values correspond to a low-field shift of
ca. 30 ppm in comparison to the corresponding diphosphine,
which is similar to the effect observed by Winston and Bercaw
upon going from py[o-C6H4(PHPh)]2 to [Zr{py[o-C6H4(PPh)]2-
κ3N,P,P′}(NMe2)2] (Δδ ≈ 44 ppm).42
Single-crystal
XRD
studies
were
performed
for
[{Zr(NMe2)3}2(μ-1a)] and [{Zr(NMe2)3}2(μ-1e)], which revealed
that, similar to [Zr{py[o-C6H4(PPh)]}(NMe2)2],42 the zirconium
atoms are in a five-coordinate P2N3 bonding environment in
these compounds (Fig. 7 and 8). Pertinent metric parameters
are collected in Table 4.
The zirconium and phosphorus atoms in [{Zr(NMe2)3}2(μ-1a)]
and [{Zr(NMe2)3}2(μ-1f)] form a four-membered ring, which is
not planar. The dihedral angle between the two Zr2P planes is
57.9° and 58.5° for the two independent molecules of the
former and 58.4° for the latter compound. The deviation from
planarity is more pronounced than in the case of the lithium
diphosphides, where a dihedral angle of at most 45.9° was
observed (see above). The zirconium coordination environ-
ment in [{Zr(NMe2)3}2(μ-1a)] and [{Zr(NMe2)3}2(μ-1f)] may be
described as distorted trigonal bipyramidal. In each case, the
axial positions are occupied by one amido and one phosphido
ligand and both zirconium atoms share the same phosphorus
atom in axial position. The corresponding Naxial–Zr–Paxial bond
angles deviate strongly from linearity (ca. 150°). The Zr–N and
Zr–P bond lengths each vary only marginally, and the same
holds true for the P–Zr–P and Zr–P–Zr bond angles. The differ-
ence between the average Zr–N and Zr–P bond lengths is
Reaction of the diphosphines with Zr(NMe2)4
In our work with the secondary diamines fc(NHPh)2 and fc
(NHTipp)2 (Tipp = 2,4,6-triisopropylphenyl) we found that
these compounds cleanly react with Zr(NMe2)4 at room temp-
erature, respectively affording [Zr{fc(NPh)2}(NMe2)2(NHMe2)]
and [Zr{fc(NTipp)2}(NMe2)2].1g,j Phosphines are generally more
acidic than the corresponding amines.41 We therefore expected
an analogous Brønsted metathesis reaction for the secondary
diphosphines of the type H21, similar to that reported by
Scheme 3 Reaction of H21a and H21e with Zr(NMe2)4. Reagents and
conditions: (a) Zr(NMe2)4, THF (for a) or toluene (for e), room
Winston and Bercaw for the bis(diarylphosphine) py[o- temperature.
Dalton Trans.
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Fig. 7 Molecular structure of [{Zr(NMe2)3}2(μ-1a)] in the crystal. Only
one of the two independent molecules present in the asymmetric unit is
shown. Methyl carbon atoms are shown as smaller circles without
hydrogen atoms for clarity.
Fig. 8 Molecular structure of [{Zr(NMe2)3}2(μ-1e)] in the crystal. Methyl
carbon atoms are shown as smaller circles without hydrogen atoms for
clarity.
0.78 Å, which is much larger than the covalent radii difference
of nitrogen and phosphorus (Δdcov 0.36 Å).39 In conjunction
with the trigonal planar bonding environment of the nitrogen
atoms, this indicates partial double bond character for the
zirconium–nitrogen bonds due to a significant degree of
π-bonding. Each phosphorus atom in [{Zr(NMe2)3}2(μ-1a)] and
[{Zr(NMe2)3}2(μ-1e)] bridges two zirconium atoms and is tetra-
coordinate. Consequently, the average Zr–P bond length of
2.83 Å is significantly longer than that of Bercaw’s pincer
complex [Zr{py[o-C6H4(PPh)]2-κ3N,P,P′}(NMe2)2] (2.69 Å), which
contains tricoordinate phosphorus atoms. In fact, the
Zr–Pphosphido bond lengths in our complexes are essentially
identical to the Zr–Pphosphine bond length of 2.824(1) Å
reported by Ballmann and co-workers for the trisamidopho-
sphine complex [Zr{P[o-C6H4(CH2NXyl)]3-κ4N,N′,N″,P}(NMe2)]
(Xyl = 3,5-dimethylphenyl).43
Interestingly, an analogous reaction was reported by Heinicke
and Jux for the secondary 2-phosphinophenol HPArOHEt
(ArOH = 2-OH-3-MeC6H3), leading to [NiCp(μ-PArOHEt)]2.46 The
Brønsted acidity of this secondary (alkyl)(aryl)phosphine is
certainly lower than that of the phenolic OH group present in
the ArOH group. Nevertheless, the reaction with nickelocene
leads to the phosphido, and not to the phenolato, complex.
We note in this context that phenolato complexes of the type
[NiCp(μ-OAr)]2 are not unprecedented even for bulky cyclopen-
tadienyl and aryl groups.47 The preference for the formation of
the phosphido complex may be rationalised in terms of
Pearson’s HSAB principle.48 Complexes of the type
[NiCp(μ-PR2)]2 are surprisingly scarce, and only two structurally
characterised example have been reported to date, namely
49
[NiCp(μ-PPh2)]2 (obtained from the reaction of Ph2P–PPh2
and [NiCp(μ-CO)]2 in boiling toluene)50 and [NiCp
Reaction of the diphosphines with nickelocene
According to sporadic reports in the literature, secondary (μ-PMeMes)]2 (prepared from [NiCp(μ-HPMes)]2 by a repetitive
phosphines may undergo Brønsted metathesis reactions with lithiation/methylation sequence using n-BuLi and MeI).51
nickelocene, which prompted us to investigate compounds
All five compounds H21a–H21e showed a reaction with nick-
H21a–H21e in this context. For example, Stone and co-workers elocene, which was monitored by 31P NMR spectroscopy. In
described the reaction between the rather acidic bis(trifluoro- the case of the methyl congener H21c and the 3,5-bis(trifluoro-
methyl)phosphine44 and nickelocene, which afforded the methyl)phenyl congener H21e, only intractable mixtures of
phosphide-bridged dimeric complex [NiCp{μ-P(CF3)2}]2.45 numerous products were obtained, which resisted further ana-
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Table 4 Selected bond lengths (Å) and angles (°) for the zirconium chelates of the type [{Zr(NMe2)3}2(μ-1)]
Average Zr–N
Average Zr–P
P–Zr–P
Zr–P–Zr
C–P–C
[{Zr(NMe2)3}2(μ-1a)]a
2.05
2.82
66.12(2)
65.92(2)
65.04(2)
65.28(2)
64.96(7)
64.50(7)
103.35(3)
102.68(3)
103.89(3)
103.67(3)
104.87(8)
103.81(8)
105.9(1)
103.5(1)
101.8(2)
100.8(1)
101.3(4)
103.7(4)
2.05
2.05
2.84
2.83
[{Zr(NMe2)3}2(μ-1e)]
a Two independent molecules.
lysis. The formation of insoluble material and the observation (H1d)] is revealed by a doublet located at −3.2 ppm (1JPH = 283
of increasingly broad 31P NMR signals during the course of Hz), which collapses to a singlet in the 31P{1H}NMR spectrum.
these reactions suggest the formation of oligomeric or poly- The phosphido P atom causes a singlet at −12.3 ppm. In con-
meric and/or paramagnetic species. In contrast, the tert-butyl trast to the tert-butyl congener [NiCp(H1b)], no coupling is
substituted congener H21b was particularly well-behaved in observed between the two inequivalent phosphorus atoms. The
this context (Scheme 4).
reaction of H21d with one equivalent of nickelocene was less
Its reaction with two equivalents of nickelocene in THF for specific than that of H21b and afforded mixtures of unreacted
two days cleanly afforded the expected bis(diorganophosphido) starting material, [(NiCp)2(μ-1d)] and [NiCp(H1d)], whose similar
chelate [(NiCp)2(μ-1b)] in 83% isolated yield. The phosphorus solubilities severely hampered purification of the latter com-
atoms in this compound are equivalent and give rise to a pound by recrystallization. Regrettably, therefore, [NiCp(H1d)]
singlet in the 31P NMR spectrum (δ −47.4 ppm in C6D6 solu- could not be obtained in pure form. The reaction of the phenyl
tion). 31P NMR spectroscopy revealed the presence of a single congener H21a with two equivalents of nickelocene in THF for
intermediate during this reaction, which was assumed to be two days afforded [(NiCp)2(μ-1a)] in 84% isolated yield. In this
the phosphino–phosphido chelate [NiCp(H1b)] due to the case, several intermediates are involved according to the results
presence of characteristic signals in the 31P NMR spectrum, of our 31P NMR spectroscopic monitoring of the reaction. It has
1
2
located at 69.8 (dd, JPH = 365 Hz, JPP = 89 Hz) and 63.0 ppm not been possible to elucidate their nature.
(d, 2JPP = 89 Hz) for the phosphino and the phosphido P atom,
The bis(diorganophosphido) chelates [(NiCp)2(μ-1a)] and
respectively.52 Our hypothesis could be verified by the prepa- [(NiCp)2(μ-1b)] were structurally characterised by XRD (Fig. 9
ration of [NiCp(H1b)] through a rational synthesis. This com- and 10). The structure of the phosphino–phosphido complex
pound was afforded in 76% isolated yield by the reaction of [NiCp(H1b)] was also determined (Fig. 11). We have not been
H21b with only one equivalent of nickelocene at room temp-
erature. According to a 31P NMR spectroscopic analysis, the
neopentyl congener H21d also reacts with nickelocene in a
two-stepped manner, leading to [(NiCp)2(μ-1d)] via [NiCp
(H1d)] in an almost quantitative process (90% isolated yield).
The 31P NMR spectroscopic signatures of these two complexes
are analogous to those of the respective tert-butyl congener.
A singlet is observed in the 31P NMR spectrum (δ −109.2 ppm
in C6D6 solution) of [(NiCp)2(μ-1d)] due to the equivalent phos-
phorus atoms. The presence of a phosphino P atom in [NiCp
Scheme 4 Reaction of H21a, H21b and H21d with nickelocene.
Reagents and conditions: (a) Nickelocene, THF, room temperature.
[NiCp(H1a)] is plausibly assumed as an intermediate in the reaction
affording [(NiCp)2(μ-1a)].
Fig. 9 Molecular structure of [(NiCp)2(μ-1a)] in the crystal.
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Fig. S2 in the ESI‡). From a formal point of view, this unusual
fulvalenide-bridged complex53 is the result of an oxidative
coupling of [(NiCp)2(μ-1b)]. In the same vein, our crystallisa-
tion experiments with [(NiCp)2(μ-1a)] and [NiCp(H1b)] respect-
ively afforded single crystals of [Ni{μ-[NiCp(μ-1a)]}2] and [Ni
(H1b)2] (see Fig. S3 and S4 in the ESI‡) by serendipity. We
refrain from speculating about the formation pathway of these
unexpected complexes. Table 5 contains pertinent metric para-
meters of the nickel complexes of this study which were
obtained by rational synthesis (see Table S2 in the ESI‡ for the
other nickel complexes).
The nickel complexes which contain bridging bis(diorgano-
phosphido) ligands exhibit four-membered Ni2P2 rings, which
are not planar. The dihedral angles between the two Ni2P
planes range from 43.6° for [(NiCp)2(μ-1a)] to 56.6° for
[Ni{[NiCp(μ2-1a)]}2], which is in between the corresponding
Li2P (41.5 and 45.9°) and Zr2P dihedral angles (ca. 58°)
observed in this study (see above). We note that the Ni2P2 core
of [NiCp(μ-PPh2)]2 is perfectly planar (dihedral angle 0°),49
whereas that of [NiCp(μ-PMeMes)]2 exhibits a large dihedral
angle of 60.1° for the Ni2P planes.51 The structurally character-
ised nickel complexes of our study have rather similar Ni–P
bond lengths. These range from 2.1426(7) Å in [(NiCp)2(μ-1a)]
to 2.220(4) Å in [Ni{[NiCp(μ2-1a)]}2] and thus compare well
with values reported for closely related nickel(II) compounds
such as, for example, the bis(diorganophosphine) complexes
[NiX2(HPCy2)2] (X = Cl, Br, Cy = cyclohexyl),54 the phosphino–
Fig. 10 Molecular structure of [(NiCp)2(μ-1b)] in the co-crystal with
[Ni(μ2-OH){NiCp(μ2-1b)}]2.
phosphido complex [NiCp{HP(SiFTipp2)}(PPh3)]55 and the
49
bis(diorganophosphido) complexes [NiCp(μ-PPh2)]2
and
[NiCp(μ-PMeMes)]2.51 We note that the Ni–P bond lengths of
2.1446(6) Å determined for the homoleptic nickel(0) diorgano-
phosphine complex [Ni(HPPh2)4] also lie in this range.56 If the
Cp ligand is viewed as occupying one coordination site, all
complexes except [Ni(H1b)2] contain three-coordinate nickel
atoms. In addition, [Ni(μ2-OH){NiCp(μ2-1b)}]2 and [Ni{[NiCp
(μ2-1a)]}2] also contain four-coordinate ones, which are in a
distorted square-planar coordination environment. This is in
contrast to the tetrahedral coordination of the nickel atom in
[Ni(H1b)2], a structure associated with paramagnetic behaviour
for NiII.57 It is tempting to surmise that the broad 31P NMR
signals observed in the case of the reactions of H21c and H21e
with nickelocene are at least in part due to paramagnetic
species of this type.
Fig. 11 Molecular structure of [NiCp(H1b)] in the crystal.
Table 5 Selected bond lengths (Å) and angles (°) for the nickel com-
plexes of this study which were obtained by rational synthesis
able to grow suitable single crystals of [(NiCp)2(μ-1b)], despite
Average Ni–P
Ni–P–Ni
P–Ni–P
C–P–C
many attempts. Finally,
a
co-crystal composed of
a
1 : 1 mixture of [(NiCp)2(μ-1b)] and [Ni(μ2-OH){NiCp(μ2-1b)}]2
(see Fig. S1 in the ESI‡) was serendipitously obtained, which
was used for the structural study. The hydroxido complex was
probably formed from [(NiCp)2(μ-1b)] and adventitious moist-
ure during our numerous crystallisation experiments, which in
addition furnished a single crystal of a further unexpected
compound, namely [{Ni[NiCp(μ2-1b)]}2{μ2-η5:η5-(C5H4)2}] (see
[(NiCp)2(μ-1a)]
2.15
98.29(3)
98.20(3)
96.93(3)
75.03(2)
74.64(2)
74.58(3)
85.76(7)
107.2(1)
105.6(1)
101.3(1)
100.2(3)
100.6(3)
[(NiCp)2(μ-1b)]a
[NiCp(H1b)]b
2.17
2.19
a Molecular C2v symmetry. b Approximate Cs symmetry of the [Ni(H1b)]
fragment, because the phosphino and phosphido P atom could not be
distinguished from one another experimentally.
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ethylamine and PBr2Np, which was obtained from the reaction
of PBr3 with NpMgBr. NMR spectra were recorded with Varian
Summary and conclusion
We have investigated 1,1′-ferrocenylene-bridged secondary NMRS-500 and MR-400 spectrometers operating at 499.7 and
diphosphines of the type fc(PHR)2 (H21) with various 399.9 MHz, respectively, for 1H. Where necessary, signal
P-substituents, ranging from alkyl groups of distinctly different assignments were made with the help of 2D NMR experiments,
steric bulk (Me < Np < t-Bu) to comparatively electron-with- in particular HSQC, HMBC and HH-COSY. High-resolution ESI
drawing aryl groups (Ph < XyF). The reaction of these com- mass spectra were obtained with a micrOTOF time-of-flight
pounds with n-BuLi in the presence of TMEDA cleanly mass spectrometer (Bruker Daltonics, Bremen, Germany)
afforded the corresponding lithium diphosphide TMEDA using an Apollo™ “ion funnel” ESI source. Mass calibration
adducts, except in the case of R = XyF, where only intractable was performed immediately prior to the measurement with
material was obtained. Monomeric compounds of the type ESI Tune Mix Standard (Agilent, Waldbronn, Germany).
[Li2(μ-1)(TMEDA)2] with a cyclic non-planar P2Li2 core were iso- Elemental analyses were carried out with a HEKAtech Euro
lated in the case of R = Ph and t-Bu. In contrast, dimeric aggre- EA-CHNS elemental analyser at the Institute of Chemistry,
gates exhibiting a ladder-type Li4P4 motif were afforded with University of Kassel, Germany.
the primary alkyl substituents Me and Np, viz.
Preparative work
[Li4(μ-1c)2(TMEDA)3] and [Li2(μ-1d)(TMEDA)]2.
A Brønsted
metathesis with Zr(NMe2)4 was possible only with the aryl-
H21a
substituted compounds H21a (R = Ph) and H21e (R = XyF), leading
Synthesis of (NEt2)21a. A solution of PCl(NEt2)Ph (29.40 g,
to products of the type [{Zr(NMe2)3}2(μ-1)]. The inertness of the 136.3 mmol) in diethyl ether (60 mL) was added dropwise to a
alkyl-substituted congeners suggests that their acidity is not stirred suspension of [(fcLi2)3(TMEDA)2] (18.77 g, 22.7 mmol)
sufficient for this reaction. All secondary diphosphines of our in diethyl ether (140 mL) cooled with an ice bath. Stirring was
study underwent a reaction with nickelocene. Intractable mix- continued at room temperature for 2 d. Insoluble material was
tures of numerous products were obtained with the methyl removed by filtration through a Celite pad and washed with
congener H21c and the 3,5-bis(trifluoromethyl)phenyl conge- diethyl ether (2 × 40 mL). The filtrate and washings were com-
ner H21e. In the other cases, compounds of the type bined and volatile components removed in vacuo. The residue
[(NiCp)2(μ-1)] were isolated. For R = t-Bu and Np a two-stepped was triturated with n-hexane (150 mL). Insoluble material was
reaction via a phosphino–phosphido intermediate of the type removed by filtration through a Celite pad and washed with
[NiCp(H1)] was observed. The lithium, zirconium and nickel n-hexane (3 × 15 mL). The filtrate and washings were com-
compounds prepared in our study clearly demonstrate the pro- bined and volatile components removed in vacuo, leaving
pensity of the diphosphido system 12− to act as a “bridging (NEt2)21a as a yellow solid. Yield 37.07 g (100%). NMR spectro-
chelate ligand”, leading to cyclic non-planar M2P2 units. In scopic data are in agreement with those published by Mizuta
view of the rather diverse nature of the metals used so far, and co-workers, who obtained this compound via a different
namely an early and a late transition metal as well as an route as an orange liquid.18a
s-block metal, our results augur well for the development of a
Synthesis of Cl21a. A solution of HCl in diethyl ether
rich coordination chemistry with ferrocene-based diphosphido (27.2 mL, 5.0 M, 136 mmol) was added dropwise to a stirred
ligands of this type. Our future work will particularly address solution of (NEt2)21a (18.51 g, 34.0 mmol) in diethyl ether
the functionality of the redox-active ligand backbone, which (150 mL) cooled to −80 °C. The cooling bath was removed and
renders these ligands non-innocent. Note that the exploration stirring was continued for 2 h. Insoluble material was removed
of phosphorus-containing redox-active ligands has been by filtration through a Celite pad and washed with diethyl
mostly confined to metallocene-based phosphines akin to the ether (5 × 20 mL). The volume of the combined filtrate and
iconic dppf,58 with anionic phosphorus ligands being particu- washings was reduced to approximately one half in vacuo.
larly scarce in this context.58a,c The diphosphido system 12− Storing of the solution at −40 °C afforded Cl21a as an orange,
represents a promising platform for systematic studies in this microcrystalline solid, which was isolated by filtration and
direction.
dried in vacuo. Yield 7.21 g (45%). NMR spectroscopic data are
in agreement with those published by Mizuta and co-workers,
who obtained this compound by using PCl3 instead of HCl in
diethyl ether.18a
Synthesis of H21a (1 : 1 mixture of diastereomers). Finely pow-
dered lithium aluminium hydride (1.45 g, 38.2 mmol) was
Experimental
General considerations
All reactions were performed in an inert atmosphere (argon or added to a stirred solution of Cl21a (7.21 g, 15.3 mmol) in THF
dinitrogen) by using standard Schlenk techniques or a conven- (100 mL). After 14 h the mixture was cooled with an ice bath
tional glovebox. Starting materials were procured from stan- and water (2.76 mL, 153.2 mmol) was slowly added dropwise.
dard commercial sources and used as received. PCl(NEt2)Ph,19 The ice bath was removed and stirring was continued for 2 h.
PCl(NEt2)t-Bu,20 PCl(NEt2)XyF,21 [(fcLi2)3(TMEDA)2]59 and fc Insoluble material was removed by filtration through a Celite
18
[PCl(NEt2)]2 were synthesised by following adapted versions pad and washed with THF (4 × 20 mL). The filtrate and wash-
of published procedures. PBr(NEt2)Np was prepared from di- ings were combined and volatile components removed
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in vacuo. The residue was subjected to purification by column 385.0908 [M + Na]+, 385.0913 calc. for [C18H28FeNaP2]+. Calc.
chromatography (silica gel, toluene). Remaining minor impuri- for C18H28FeP2 (362.2): C, 59.7; H, 7.8. Found: C, 59.7; H, 8.2.
ties were subsequently removed by Soxhlet extraction of the
H21c
product adsorbed on silica gel with n-hexane. Yield 4.02 (65%;
Synthesis of (NEt2)21c. A solution of MeLi in diethyl ether
1
29% over all steps). H NMR (C6D6): δ 7.42 (m, 4H, Ph), 7.03 (33.1 mL, 1.60 M, 53.0 mmol) was added dropwise to a stirred
1
(m, 6H, Ph), 5.15 (d, 2H, PH, JPH = 219 Hz); 4.25, 4.21 (2 m, solution of fc[PCl(NEt2)]2 (12.21 g, 26.5 mmol) in diethyl ether
2 × 1H, C5H4); 4.17–4.01 (m, 6H, C5H4). 13C{1H} NMR (C6D6): (250 mL) cooled to −60 °C. Stirring was continued at room
δ 137.4, 133.0, 128.6, 128.2 (4 m, Ph); 76.8, 76.4, 75.9, 75.8, temperature for 14 h. Volatile components were removed
72.6, 72.4, 70.0, 69.4 (8 m, C5H4). 31P NMR (C6D6): δ −60.8, in vacuo. The residue was triturated with n-hexane (60 mL).
1
−61.2 (2 d, JPH = 218 Hz). HRMS/ESI(+): m/z 508.9423 [M + Ag]+, Insoluble material was removed by filtration through a Celite
508.9441 calc. for [C22H20AgFeP2]+. Calc. for C22H20FeP2 pad and washed with n-hexane (4 × 15 mL). The filtrate and
(402.2): C, 65.7; H, 5.0. Found: C, 66.1; H, 5.4.
washings were combined and volatile components removed
H21b
in vacuo, leaving (NEt2)21c as an orange oil that was sufficiently
1
Synthesis of (NEt2)21b. A solution of PCl(NEt2)t-Bu (10.91 g, pure for the next step. Yield 11.13 g (100%). H NMR (C6D6):
55.8 mmol) in diethyl ether (20 mL) was added dropwise to a δ 4.28, 4.16, 4.13, 4.05 (4 br., 4 × 2H, C5H4); 2.81 (m, 8H,
3
stirred suspension of [(fcLi2)3(TMEDA)2] (7.68 g, 9.3 mmol) in CH2CH3), 1.39 (m, 6H, PMe), 0.87 (t, JHH = 7.0 Hz, 12H,
diethyl ether (150 mL) cooled with an ice bath. Stirring was CH2CH3). 13C{1H} NMR (C6D6): δ 81.2, 75.4, 75.1, 72.1, 70.7,
continued at room temperature for 2 d. Insoluble material was 68.9 (6 m, C5H4); 43.5 (m, CH2CH3), 15.4 (m, PCH3), 12.9 (m,
removed by filtration through a Celite pad and washed with CH2CH3). 31P NMR (C6D6): δ 34.2.
diethyl ether (4 × 15 mL). The filtrate and washings were com-
Synthesis of Cl21c. A solution of HCl in diethyl ether
bined and volatile components removed in vacuo, leaving (21.2 mL, 5.0 M, 106 mmol) was added dropwise to a stirred
(NEt2)21b as an amorphous orange solid that was sufficiently solution of (NEt2)21c (11.13 g, 26.5 mmol) in diethyl ether
pure for the next step. Yield 14.07 g (100%). NMR spectro- (200 mL) cooled to −60 °C. The cooling bath was removed and
scopic data are in agreement with those published by Mizuta stirring was continued for 2 h. Insoluble material was removed
and co-workers, who obtained this compound via a different by filtration through a Celite pad and washed with diethyl
route as a dark orange liquid.18a
ether (3 × 15 mL). The filtrate and washings were combined
Synthesis of Cl21b. A solution of HCl in diethyl ether and volatile components removed in vacuo, affording Cl21c as
(22.2 mL, 5.0 M, 111 mmol) was added dropwise to a stirred an orange oil that was sufficiently pure for the next step. Yield
1
solution of (NEt2)21b (14.07 g, 27.9 mmol) in diethyl ether 5.65 g (62%). H NMR (C6D6): δ 4.28 (br., 1H, C5H4), 4.16 (br.,
(150 mL) cooled to −80 °C. The cooling bath was removed and 2H, C5H4), 4.04 (br., 1H, C5H4), 3.96 (br., 4H, C5H4), 1.54 (m,
stirring was continued for 2 h. Insoluble material was removed 6H, Me). 13C{1H} NMR (C6D6): δ 74.8, 73.5, 72.5, 71.9, 70.0,
by filtration through a Celite pad and washed with diethyl 69.6 (6 m, C5H4); 19.4 (m, Me). 31P NMR (C6D6): δ 82.0.
ether (5 × 20 mL). The filtrate and washings were combined
Synthesis of H21c. Finely powdered lithium aluminium
and volatile components removed in vacuo, affording Cl21b as hydride (1.53 g, 40.3 mmol) was added to a stirred solution of
an orange, microcrystalline solid that was sufficiently pure for Cl21c (5.65 g, 26.0 mmol) in THF (100 mL). After 14 h the
the next step. Yield 11.21 g (93%). NMR spectroscopic data are mixture was cooled with an ice bath and water (2.91 mL,
in agreement with those published by Mizuta and co-workers, 161.5 mmol) was slowly added dropwise. The ice bath was
who obtained this compound by using PCl3 instead of HCl in removed and stirring was continued for 2 h. Insoluble material
diethyl ether.18a
was removed by filtration through a Celite pad and washed
Synthesis of H21b. Finely powdered lithium aluminium with THF (3 × 20 mL). The filtrate and washings were com-
hydride (2.47 g, 65.1 mmol) was added to a stirred solution of bined and volatile components removed in vacuo. The residue
Cl21b (11.21 g, 26.0 mmol) in THF (250 mL). After 14 h the was triturated with n-hexane (50 mL). Insoluble material was
mixture was cooled with an ice bath and water (4.68 mL, removed by filtration and washed with n-hexane (2 × 10 mL).
259.8 mmol) was slowly added dropwise. The ice bath was The filtrate and washings were combined and volatile com-
removed and stirring was continued for 2 h. Insoluble material ponents removed in vacuo, affording the product as an orange
was removed by filtration through a Celite pad and washed oil. Yield 3.47 g (77%; 47% over all steps). 1H NMR (C6D6):
1
with THF (4 × 25 mL). The filtrate and washings were com- δ 4.10 (d, JPH = 204 Hz, 2H, PH), 4.09 (m, 8H, C5H4), 1.08 (m,
bined and volatile components removed in vacuo. The residue 6H, Me). 13C{1H} NMR (C6D6): δ 75.2, 75.1, 74.1, 74.0, 71.9,
was subjected to purification by column chromatography 71.5 (6 m, C5H4); 7.1 (m, Me). 31P NMR (C6D6): δ −89.9 (d,
(silica gel, n-hexane). Remaining minor impurities were sub- 1JPH = 204 Hz). Calc. for C12H16FeP2 (278.0): C, 51.8; H, 5.8.
sequently removed by triturating the product with cold Found: C, 52.4; H, 5.7.
n-hexane (100 mL) and removing insoluble material by fil-
tration. The filtrate was reduced to dryness in vacuo, affording
H21d
Synthesis of (NEt2)21d (1 : 1 mixture of diastereomers). A solu-
the product as orange crystals. Yield 4.71 g (50%; 47% over all tion of PBr(NEt2)Np (13.50 g, 53.1 mmol) in diethyl ether
steps). NMR spectroscopic data are in agreement with those (50 mL) was added dropwise to a stirred suspension of
published by Pietschnig and co-workers.17 HRMS/ESI(+): m/z [(fcLi2)3(TMEDA)2] (7.31 g, 8.8 mmol) in diethyl ether (50 mL)
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cooled with an ice bath. Stirring was continued at room temp- 12H, Me). 13C{1H} NMR (C6D6): δ 147.1, 146.7, 131.5, 131.3,
erature for 1 d. Volatile components were removed in vacuo. 130.8, 124.3, 121.4 (7 m, XyF); 79.0, 78.8, 74.5, 73.7, 72.9, 72.7,
The residue was triturated with n-hexane (30 mL). Insoluble 72.2, 71.6, 71.1, 70.2, 69.5 (11 m, C5H4) 44.6 (m, CH2), 14.5 (m,
material was removed by filtration through a Celite pad and Me). 31P NMR (C6D6): δ 53.2, 51.7.
washed with n-hexane (2 × 10 mL). The filtrate and washings
were combined and volatile components removed in vacuo, of HCl in diethyl ether (17.2 mL, 5.0 M, 86 mmol) was added
leaving (NEt2)21d as a brownish-orange oil that was sufficiently dropwise to stirred solution of (NEt2)212 (17.96 g,
pure for the next step. Yield 14.09 g (100%). 31P NMR (C6D6): 22.0 mmol) in diethyl ether (200 mL) cooled to −70 °C. The
δ 38.3, 37.0. cooling bath was removed and stirring was continued for 14 h.
Synthesis of Cl21e (1 : 1 mixture of diastereomers). A solution
a
Synthesis of Cl21d (1 : 1 mixture of diastereomers). A solution Insoluble material was removed by filtration through a Celite
of HCl in diethyl ether (32.0 mL, 5.0 M, 160 mmol) was added pad and washed with diethyl ether (4 × 25 mL). The filtrate
dropwise to a stirred solution of (NEt2)21c (14.09 g, 26.5 mmol) and washings were combined and volatile components
in diethyl ether (100 mL) cooled to −80 °C. The cooling bath removed in vacuo, affording Cl21e as an orange solid that was
1
was removed and stirring was continued for 14 h. Insoluble sufficiently pure for the next step. Yield 13.82 (84%). H NMR
material was removed by filtration through a Celite pad and (C6D6): δ 8.00 (m, 4H, XyF), 7.68 (s, 2H, XyF); 4.23, 4.08, 4.00
washed with diethyl ether (3 × 15 mL). The filtrate and wash- (3 m, 3 × 2H, C5H4); 3.85, 3.80 (2 m, 2 × 1H, C5H4). 13C{1H}
ings were combined and volatile components removed NMR (C6D6): δ 143.6, 143.2, 132.1, 131.3, 124.1 (5 m, XyF);
1
in vacuo, affording Cl21d as a yellow solid that was sufficiently 123.5 (q, JCF = 273 Hz, CF3); 78.8, 78.5, 74.0, 72.3 (4 m, C5H4).
pure for the next step. Yield 10.03 g (83%). 31P NMR (C6D6): 31P NMR (C6D6): δ 72.8, 72.7.
δ 89.6, 88.1.
Synthesis of H21e (1 : 1 mixture of diastereomers). Finely pow-
Synthesis of H21d. Finely powdered lithium aluminium dered lithium aluminium hydride (1.76 g, 46.5 mmol) was
hydride (2.07 g, 54.5 mmol) was added to a stirred solution of added to a stirred solution of Cl21e (13.82 g, 19.6 mmol) in
Cl21d (10.03 g, 21.8 mmol) in THF (100 mL). After 14 h the THF (250 mL). After 14 h the mixture was cooled with an ice
mixture was cooled with an ice bath and water (3.93 mL, bath and water (3.35 mL, 186.0 mmol) was slowly added drop-
218.2 mmol) was slowly added dropwise. The ice bath was wise. The ice bath was removed and stirring was continued for
removed and stirring was continued for 2 h. Insoluble material 2 h. Insoluble material was removed by filtration through a
was removed by filtration through a Celite pad and washed Celite pad and washed with THF (3 × 25 mL). The filtrate and
with THF (4 × 20 mL). The filtrate and washings were com- washings were combined and volatile components removed
bined and volatile components removed in vacuo. The residue in vacuo. The residue was subjected to purification by column
was triturated with n-hexane (50 mL). Insoluble material was chromatography (silica gel, n-hexane), which afforded the
removed by filtration and washed with n-hexane (2 × 10 mL). product as an orange, microcrystalline solid. Yield 6.50 g
The filtrate and washings were combined and volatile com- (52%; 44% over all steps). 1H NMR (C6D6): δ 7.68 (m, 4H, XyF),
1
ponents removed in vacuo, affording the product as an orange 7.59 (s, 2H, XyF), 4.84 (d, JPH = 223 Hz, 2H, PH); 4.08, 4.05
oil, which crystallised upon standing. Yield 4.82 g (57%; 47% (2 m, 2 × 1H, C5H4); 4.00 (m, 4H, C5H4); 3.87, 3.84 (2 m, 2 ×
1
over all steps). H NMR (C6D6): δ 4.23 (m, 2H, C5H4), 4.14 (m, 1H, C5H4). 13C{1H} NMR (C6D6): δ 141.8, 141.6, 132.0, 131.7
1
1
6H, C5H4), 4.07 (d, JPH = 208 Hz, 2H, PH); 1.99, 1.48 (2 m, 2 × (4 m, XyF); 123.8 (q, JCF = 273 Hz, CF3), 121.9 (m, XyF); 77.1,
2H, CH2); 0.99 (m, 18H, Me). 13C{1H} NMR (C6D6): δ 75.9, 75.6, 76.8, 75.5, 75.4, 73.3, 73.1 (6 m, C5H4). 31P NMR (C6D6):
1
75.4, 75.3, 72.0, 71.7 (6 m, C5H4), 40.5 (m, CH2), 31.2 (m, δ −61.2, −61.5 (2 d, JPH = 223 Hz). HRMS/ESI(+): m/z 674.9958
CMe3), 30.6 (m, Me). 31P NMR (C6D6): δ −86.8 (d, JPH
=
[M + H]+, 674.9963 calc. for [C26H17F12FeP2]+. Calc. for
1
208 Hz). HRMS/ESI(+): m/z 413.1232 [M + Na]+, 413.1226 calc. C26H16F12FeP2 (674.2): C, 46.3; H, 2.4. Found: C, 46.5; H, 3.0.
for [C20H32FeNaP2]+. Calc. for C20H32FeP2 (390.3): C, 61.55; H,
[Li2(μ-1a)(TMEDA)2]. A solution of n-BuLi in n-hexane
8.3. Found: C, 61.4; H, 8.6.
(0.69 mL, 1.60 M, 1.10 mmol) was added with shaking to a
H21e
solution of H21a (201 mg, 0.50 mmol) and TMEDA (128 mg,
Synthesis of (NEt2)21e (1 : 1 mixture of diastereomers). A solu- 1.10 mmol) in a mixture of toluene (21 mL) and n-hexane
tion of PCl(NEt2)XyF (15.53 g, 44.2 mmol) in diethyl ether (7 mL). The volume of the mixture was reduced to ca. 5 mL
(40 mL) was added dropwise to a stirred suspension of in vacuo, affording the product as orange-red crystals, which
[(fcLi2)3(TMEDA)2] (6.08 g, 7.4 mmol) in diethyl ether (50 mL) were isolated by filtration and dried in vacuo. Yield 259 mg
1
cooled with an ice bath. Stirring was continued at room temp- (80%). H NMR (THF-d8): δ 6.96, 6.59 (2 br., 2 × 4H, P); 6.23
erature for 14 h. Insoluble material was removed by filtration (br., 2H, Ph); 4.01, 3.84 (2 br., 2 × 4H, C5H4), 2.30 (br., 8H,
1
through a Celite pad and washed with diethyl ether (2 × CH2), 2.15 (br., 24H, Me). H NMR (C6D6): δ 7.33 (br., 4H, Ph),
15 mL). The filtrate and washings were combined and volatile 7.10 (m, 4H, Ph), 6.77 (m, 2H, Ph), 4.45 (s, 4H, C5H4), 4.27 (s,
components removed in vacuo, leaving (NEt2)21e as an orange- 4H, C5H4), 2.12 (s, 24H, Me), 1.75 (br., 8H, CH2). 13C{1H} NMR
brown solid that was sufficiently pure for the next step. Yield (THF-d8): δ 163.2, 127.6, 126.8, 116.4 (4 br., Ph); 85.0, 78.9,
17.96 g (100%). 1H NMR (C6D6): δ 8.33, 8.18, 7.75 (3 m, 3 × 2H, 68.6 (3 br., C5H4); 58.9 (CH2), 46.3 (Me). 13C{1H} NMR (C6D6):
XyF); 4.49 (m, 1H, C5H4); 4.39, 4.29 (2 m, 2 × 2H, C5H4); 4.17, δ 127.6, 127.3 (2 m, Ph); 118.7 (Ph), 79.7 (br., C5H4), 78.7 (m,
3.88, 3.83 (3 m, 3 × 1H, C5H4); 2.78 (m, 8H, CH2), 0.81 (m, C5H4), 69.9 (C5H4), 57.0 (br., CH2), 46.8 (Me). 31P NMR
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7
(THF-d8): δ −62.0 (br.). 31P NMR (C6D6): δ −66.9 (br.). Li NMR (THF-d8): δ 3.78, 3.74 (2 s, 2 × 4H, C5H4), 2.32 (s, 4H,
(THF-d8): δ 2.9 (br.). 7Li NMR (C6D6): δ 2.4 (br.). Calc. for CH2NMe2), 2.17 (s, 12H, NMe2), 1.82 (s, 4H, CH2CMe3), 0.86 (s,
C34H50N4FeLi2P2 (646.5): C, 63.2; H, 7.8; N, 8.7. Found: C, 63.7; 18H, CMe3). 13C{1H} NMR (THF-d8): δ 75.9 (br., C5H4), 69.7 (m,
H, 8.2; N, 6.4. Although the result for nitrogen is outside the C5H4), 66.8 (C5H4), 58.8 (CH2NMe2), 46.3 (s, NMe2), 43.5 (m,
range viewed as establishing analytical purity, these data are CH2CMe3), 33.5 (br., CMe3), 31.3 (CMe3). 31P NMR (THF-d8):
provided to illustrate the best values obtained to date. The δ −118.9 (br.). 7Li NMR (THF-d8): δ 3.4 (br., sh.). Calc. for
data suggest partial loss of TMEDA and agree more with C52H92N4Fe2Li4P4 (1036.7): C, 60.25; H, 8.95; N, 5.4. Found: C,
[Li2(μ-1a)(TMEDA)1.5
]
[calc. for C31H42N3FeLi2P2 (588.4): 60.3; H, 9.3; N, 5.5.
C, 63.3; H, 7.2; N, 7.1].
[{Zr(NMe2)3}2(μ-1a)]. THF (20 mL) was added to H21a
[Li2(μ-1b)(TMEDA)2]. A solution of n-BuLi in n-hexane (302 mg, 0.75 mmol) and Zr(NMe2)4 (399 mg, 1.49 mmol). The
(0.39 mL, 1.60 M, 0.62 mmol) was added with shaking to a mixture was stirred for 1 h. Volatile components were removed
solution of H21b (101 mg, 0.28 mmol) and TMEDA (73 mg, in vacuo, leaving the product as a yellow, microcrystalline solid.
1
0.63 mmol) in n-hexane (10 mL). Orange-red crystals of the Yield 632 mg (100%). H NMR (C6D6): δ 7.40, 7.12, 6.96 (3 m,
product formed almost immediately, which were isolated by 10H, Ph); 4.42, 4.31 (2 s, 2 × 4H, C5H4): 3.00 (s, 36H, Me). 13C
filtration and dried in vacuo. Yield 131 mg (79%). 1H NMR {1H} NMR (C6D6): δ 145.1, 133.0, 130.7 (3 m, Ph); 125.1 (Ph);
(THF-d8): δ 3.90, 3.78 (2 m, 2 × 4H, C5H4); 2.31 (m, 8H, CH2), 78.5, 73.0, 68.0 (3 m, C5H4); 43.1 (m, Me). 31P NMR (C6D6):
2.16 (m, 24H, NMe2), 1.02 (m, 18H, CMe3). 1H NMR (C6D6): δ −32.8 (br.). C34H54N6FeP2Zr2 (847.1): C, 48.2; H, 6.4; N, 9.9.
δ 4.36, 4.17 (2 s, 2 × 4H, C5H4), 2.27 (s, 24H, NMe2), 1.95 (s, Found: C, 48.0; H, 6.7; N, 9.0.
8H, CH2), 1.44 (s, 18H, CMe3). 13C{1H} NMR (THF-d8): δ 83.1,
[{Zr(NMe2)3}2(μ-1e)]. Toluene (15 mL) was added to H21e
80.8 (2 m, C5H4); 68.2 (C5H4), 58.9 (CH2), 46.3 (NMe2), 35.5 (t, (297 mg, 0.44 mmol) and Zr(NMe2)4 (235 mg, 0.88 mmol). The
2JPC = 7 Hz, CMe3), 28.7 (m, CMe3). 13C{1H} NMR (C6D6): δ 82.3 mixture was stirred for 1 h. Volatile components were removed
(m, C5H4); 80.6, 68.7 (2 s, C5H4); 57.4 (CH2), 47.7 (NMe2), 35.8 in vacuo, leaving the product as a yellow, microcrystalline solid.
1
(m, CMe3), 29.1 (br., CMe3). 31P NMR (THF-d8): δ −26.6 (br.). Yield 492 mg (100%). H NMR (C6D6): δ 7.87 (br. s, 4H, XyF),
1
31P NMR (C6D6): δ −26.9 (sept, JPLi = 51 Hz). 7Li NMR 7.58 (s, 2H, XyF); 4.25, 4.17 (2 s, 2 × 4H, C5H4); 2.84 (s, 36H,
1
(THF-d8): δ 4.0 (br.). 7Li NMR (C6D6): δ 1.9 (t, JPLi = 51 Hz). Me). 13C{1H} NMR (C6D6): δ 150.3, 131.0, 130.1 (3 m, XyF);
1
Calc. for C30H58N4FeLi2P2 (606.5): C, 59.4; H, 9.6; N, 9.2. 124.3 (q, JCF = 273 Hz, CF3), 118.7 (m, XyF); 78.2, 74.0, 65.4
Found: C, 59.5; H, 9.5; N, 6.8. Although the result for nitrogen (3 m, C5H4); 42.5 (br., Me). 31P NMR (C6D6): δ −30.9 (br.).
is outside the range viewed as establishing analytical purity, C38H50N6F12FeP2Zr2 (1119.1): C, 40.8; H, 4.5; N, 7.5. Found: C,
these data are provided to illustrate the best values obtained to 39.9; H, 4.8; N, 6.7.
date. The data suggest partial loss of TMEDA and agree more
with [Li2(μ-1b)(TMEDA)1.5] [calc. for C27H50N3FeLi2P2 (548.4): 0.75 mmol) and nickelocene (282 mg, 1.49 mmol). The
C, 59.1; H, 9.2; N, 7.7]. mixture was stirred for 2 d. Volatile components were removed
[(NiCp)2(μ-1a)]. THF (10 mL) was added to H21a (302 mg,
[Li4(μ-1c)2(TMEDA)3]. A solution of n-BuLi in n-hexane in vacuo. The residue was triturated with toluene (10 mL).
(0.74 mL, 1.60 M, 1.18 mmol) was added with shaking to a A small amount of insoluble material was removed by filtration
solution of H21c (150 mg, 0.54 mmol) and TMEDA (137 mg, through a Celite pad and washed with toluene (2 × 5 mL). The
1.18 mmol) in n-hexane (10 mL). The product precipitated filtrate and washings were combined and reduced to dryness
almost immediately as an amorphous red solid, which was iso- in vacuo, affording the product as a black, microcrystalline
1
1
lated by filtration and dried in vacuo. Yield 190 mg (76%). H solid. Yield 410 mg (84%). H NMR (C6D6): δ 7.59 (m, 4H, Ph),
NMR (THF-d8): δ 3.69, 3.50 (2 s, 2 × 8H, C5H4); 2.29 (s, 12H, 7.00 (m, 6H, Ph), 5.09 (m, 4H, C5H4), 4.95 (s, 10H, Cp), 4.28
CH2), 2.15 (s, 36H, NMe2), 1.35 (s, 12H, PMe). 13C{1H} NMR (m, 4H, C5H4). 13C{1H} NMR (C6D6): δ 143.3 (br., Ph); 131.1,
(THF-d8): δ 69.7, 68.2, 64.8 (3 m, C5H4); 58.9 (CH2), 46.3 127.9 (2 m, Ph); 127.4 (Ph), 89.8 (Cp); 84.4, 80.7 (2 m, C5H4);
(NMe2), 6.6 (m, CH3). 31P NMR (THF-d8): δ −125.7 (br.). 7Li 70.5 (br., C5H4). 31P NMR (C6D6): δ −96.9. HRMS/ESI(+): m/z
NMR (THF-d8): δ 11.3, 6.2 (2 × br.). Calc. for C42H76N6Fe2Li4P4 645.9708 [M]+, 645.9723 calc. for [C32H28FeNi2P2]+. Calc. for
(928.4): C, 54.3; H, 8.25; N, 9.05. Found: C, 53.7; H, 8.7; N, C32H28FeNi2P2 (647.7): C, 59.3; H, 4.4. Found: C, 59.3; H, 5.15.
6.65. Although the result for nitrogen is outside the range
[(NiCp)2(μ-1b)]. THF (10 mL) was added to H21b (311 mg,
viewed as establishing analytical purity, these data are pro- 0.86 mmol) and nickelocene (325 mg, 1.72 mmol). The
vided to illustrate the best values obtained to date. The data mixture was stirred for 2 d. Volatile components were removed
suggest partial loss of TMEDA and agree more with [Li2(μ-1c) in vacuo. The residue was triturated with n-hexane (10 mL).
(TMEDA)] [calc. for C18H30N2FeLi2P2 (406.1): C, 53.2; H, 7.4; A small amount of insoluble material was removed by filtration
N, 6.9].
through a Celite pad and washed with n-hexane (2 × 5 mL).
[Li2(μ-1d)(TMEDA)]2. A solution of n-BuLi in n-hexane The filtrate and washings were combined and reduced to
(0.80 mL, 1.60 M, 1.28 mmol) was added with shaking to a dryness in vacuo, affording the product as a brown, microcrys-
solution of H21d (200 mg, 0.51 mmol) and TMEDA (149 mg, talline solid. Yield 432 mg (83%). 1H NMR (C6D6): δ 5.31 (s,
1.28 mmol) in n-hexane (10 mL). Orange-red crystals of the 10H, Cp); 4.89, 4.14 (2 s, 2 × 4H, C5H4), 0.87 (m, 18H, Me). 13
C
product formed almost immediately, which were isolated by {1H} NMR (C6D6): δ 88.9 (Cp); 84.0, 80.1 (2 m, C5H4); 70.2
filtration and dried in vacuo. Yield 187 mg (71%). 1H NMR (C5H4), 30.1 (CMe3), 28.8 (m, CMe3). 31P NMR (C6D6): δ −47.4.
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HRMS/ESI(+): m/z 606.0323 [M]+, 606.0349 calc. for bonding partner. Experimental details for each diffraction
[C28H36FeNi2P2]+. Calc. for C28H36FeNi2P2 (607.8): C, 55.3; H, experiment are given in Table S1 (ESI‡). Data for all com-
6.0. Found: C, 55.45; H, 6.1.
pounds have been deposited with the Cambridge
[(NiCp)2(μ-1d)]. THF (10 mL) was added to H21d (301 mg, Crystallographic Database.
0.77 mmol) and nickelocene (291 mg, 1.54 mmol). The
mixture was stirred for 2 d. Volatile components were removed
in vacuo. The residue was triturated with n-hexane (10 mL).
A small amount of insoluble material was removed by filtration
References
through a Celite pad and washed with n-hexane (2 × 5 mL).
The filtrate and washings were combined and reduced to
dryness in vacuo, affording the product as a brown, amorphous
solid. Yield 436 mg (90%). 1H NMR (C6D6): δ 5.26 (s, 10H, Cp),
5.04 (br., 4H, C5H4), 4.10 (m, 4H, C5H4), 1.73 (m, 4H, CH2),
0.85 (s, 18H, Me). 13C{1H} NMR (C6D6): δ 90.0 (Cp); 80.2, 69.7,
69.2 (3 m, C5H4); 49.9 (m, CH2), 33.0 (CMe3), 31.3 (m, CMe3).
31P NMR (C6D6): δ −109.2. HRMS/ESI(+): m/z 634.0645 [M]+,
634.0662 calc. for [C30H40FeNi2P2]+. The compound was
reasonably pure according to 1H NMR spectroscopy (see
Fig. S53 in the ESI;‡ the spectrum shows a number of minor
impurities in addition to silicon grease, which was contained
already in the NMR solvent due to its storage in a stoppered
Schlenk flask). Satisfactory microanalytical data could not be
obtained.
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[NiCp(H1b)]. H21b (340 mg, 0.94 mmol) and nickelocene
(177 mg, 0.94 mmol) were dissolved in diethyl ether (20 mL).
Storing of the solution for14 h afforded the product as black
needles, which were isolated by filtration and dried in vacuo.
1
Yield 346 mg (76%). H NMR (C6D6): δ 5.49 (s, 5H, Cp), 4.83
(dd, 1H, PH, 1JPH = 365 Hz, 3JPH = 18 Hz); 4.52, 4.29, 4.21, 4.17,
3
3.90, 3.86 (6 m, 8H, C5H4); 1.27, 0.81 (2 d, JPH = 14.1 Hz, 2 ×
9H, Me). 13C{1H} NMR (C6D6): δ 87.8 (Cp); 77.8, 77.5, 77.3
(3 m, C5H4); 74.6, 73.6, 73.5 (3 s, C5H4); 71.4, 71.2, 67.6, 66.6
(4 m, C5H4); 30.6 (m, CMe3), 29.5 (m, CMe3), 27.0 (m, CMe3),
26.7 (m, CMe3). 31P NMR (C6D6): δ 69.8 (dd, PHt-Bu, 1JPH = 365
2
2
Hz, JPP = 89 Hz), 63.0 (d, Pt-Bu, JPP = 89 Hz). HRMS/ESI(+):
m/z 485.0734 [M + H]+, 485.0760 calc. for [C23H33FeNiP2]+.
Calc. for C23H32FeNiP2 (485.0): C, 57.0; H, 6.65. Found: C, 57.8;
H, 7.6.
2 A. Shafir, M. P. Power, G. D. Whitener and J. Arnold,
Organometallics, 2001, 20, 1365–1369.
X-ray crystal structure determinations
For each data collection a single crystal was mounted on a
glass fibre and all geometric and intensity data were taken
from this sample. Data collections were carried out using
Mo-Kα radiation (λ = 0.71073 Å) on a Stoe IPDS2 diffractometer
equipped with a 2-circle goniometer and an area detector
except for [{Zr(NMe2)3}2(μ-1e)], for which the diffraction experi-
ment was done using a Stoe StadiVari diffractometer equipped
with a 200 K Dectris Pilatus detector. The data sets were cor-
rected for absorption (by integration), Lorentz and polarisation
effects. The structures were solved by direct methods (SIR
2008)60 and refined using alternating cycles of least-squares
refinements against F2 (SHELXL2014/7).61 For [Li2(μ-1a)
(TMEDA)2] a disordered solvent molecule was removed from
the dataset using the SQUEEZE routine from PLATON.62
H atoms were included to the models in calculated positions
with the 1.2 fold isotropic displacement parameter of their
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Dalton Trans.
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Dalton Transactions
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