Reactivity of diimido complexes of moybdenum and tungsten towards lithium derivatives of diphosphanes and triphosphanes

Article abstract of DOI:10.1002/ejic.201301302

The reaction of R₂P-P(SiMe₃)Li (R = tBu, iPr) with the diimido molybdenum complex [(ArN)₂MoCl₂·dme] (Ar = 2,6-iPr₂C₆H₃; dme = 1,2-dimethoxyethane) yielded the side-on-coordinated

Full text of DOI:10.1002/ejic.201301302

FULL PAPER
DOI:10.1002/ejic.201301302
Reactivity of Diimido Complexes of Molybdenum and
Tungsten towards Lithium Derivatives of Diphosphanes
and Triphosphanes
CLUSTER
ISSUE
Rafał Grubba,*[a] Aleksandra Wis´niewska,[a] Łukasz Ponikiewski,[a]
Maria Caporali,*[b] Maurizio Peruzzini,[b] and Jerzy Pikies[a]
Keywords: Phosphorus / Molybdenum / Tungsten / Lithium / Imides
The reaction of R2P–P(SiMe3)Li (R = tBu, iPr) with the diimido
molybdenum complex [(ArN)2MoCl2·dme] (Ar 2,6-
dme] (Ar = 2,6-iPr2C6H3; M = Mo, W) with tBu2P–P(Li)–PtBu2
gavemolybdenumandtungstencomplexes[(2,6-iPr2C6H3N)2-
M(Cl)(1,2-η-tBu2P=P–PtBu2)] (3Mo, 3W) bearing an unusual
triphosphorus ligand. The solid-state structures of [(2,6-
iPr2C6H3N)2Mo(Cl)(η2-P=PtBu2)]– (7Mo), [(2,6-iPr2C6H3N)2-
Mo(Cl)(η2-P=PiPr2)]– (8Mo), [(2,6-iPr2C6H3N)2Mo(Cl)(1,2-η-
tBu2P=P–PtBu2)] (3Mo) and [(2,6-iPr2C6H3N)2W(Cl)(1,2-η-
tBu2P=P–PtBu2)] (3W) were established by single-crystal X-
ray diffraction analysis.
=
iPr2C6H3; dme = 1,2-dimethoxyethane) yielded the side-on-
coordinated phosphanylphosphinidene anionic complexes
[(2,6-iPr2C6H3N)2Mo(Cl)(η2-P=PR2)]– (7Mo, 8Mo). The ther-
mal decomposition of [(2,6-iPr2C6H3N)2M(Cl)(η2-P=PR2)]–
[M = Mo (7Mo), W (8W)] to [(2,6-iPr2C6H3N)2M(Cl)(1,2-η-
tBu2P=P–PtBu2)] [M = Mo (3Mo), W (3W)] was investigated
by 31P{1H} NMR spectroscopy. The reactions of [(ArN)2MCl2·
type) in nature.[2,21–23] The nucleophilic properties of related
phosphanylphosphinidene complexes such as [(R3P)2Pt(η2-
P=PtBu2)] were demonstrated by the reaction with
Introduction
Phosphinidenes (R-P) are important species mainly be-
cause of their role as transient compounds and one-phos-
phorus synthons in the chemistry of low-valent phosphorus
species.[1–3] Free phosphinidenes are extremely unstable
compounds and have not been isolated until now. Theoreti-
cal investigations indicate a triplet ground state for the par-
ent compound P–H,[2,4] whereas a singlet ground state is
more favoured if R is a σ-acceptor and π-donor group.[5,6]
Our group has a special interest in the chemistry of phos-
phanylphosphinidene ligands (R2PP) which can be accessed
by at least three different pathways, namely 1) from phos-
pha-Wittig reagents tBu2PP=PR3,[7–11] 2) from lithium de-
rivatives of diphosphines R2P-P(SiMe3)Li[12–15,28] or 3) by
the reaction of the anionic niobium terminal phosphido
complex Na[(P)Nb{N(3,5-Me2C6H3)Np}3][16–18] and the
tungsten terminal phosphido complex [(P)W{N(3,5-
Me2C6H3)iPr}3][19] with electrophilic R2PCl.
[(OC)5Cr(thf)],[24] which afforded [η2-{(CO)5Cr
-
( P=PtBu2)}Pt(PR3)2], whereas the ene-like properties were
confirmed by their reactivity with the phospha-Wittig rea-
gent tBu2P–P=P(Me)tBu2.[25] Recently we have found that
R2P–P(SiMe3)Li (R = tBu or iPr) can act as precursors of
phosphanylphosphido
ligands,
introducing
the
R2PP(SiMe3) moiety at the Cp2W[26] or Cp2Mo[27] metal
centres followed by rearrangement to give a H4C5–P–PtBu2
ligand and the migration of H or SiMe3 onto a metal atom.
Very recently we found that R2P–P(SiMe3)Li (R = tBu and
iPr) reacts with the tungsten(VI) complex [(2,6-iPr2C6H3N)2-
WCl2·dme] to yield the corresponding side-on-bonded an-
ionic tungsten phosphanylphosphinidene complex [(2,6-
iPr2C6H3N)2W(Cl)(η2-P–PtBu2)][Li(dme)3]·dme or [(2,6-
iPr2C6H3N)2W(Cl)(η2-P=PiPr2)][Li(dme)3]·0.5C6D6,
res-
pectively.[15] Continuing our research in this area, we report
herein on the reactivity of R2P–P(SiMe3)Li (R = tBu and
iPr) and tBu2P–P(Li)–PtBu2 towards the diimido molybd-
enum(VI) and tungsten(VI) complexes [(2,6-iPr2C6H3N)2-
MCl2·dme].
According to the influence[20] of electron-donating spec-
tator ligands, the monometallic complexes with R2PP li-
gands synthesized by our group are nucleophilic (Schrock
[a] Chemical Faculty, Department of Inorganic Chemistry, Gdan´sk
University of Technology,
G. Narutowicza St. 11/12, 80-233 Gdansk, Poland
E-mail: grubba@pg.gda.pl
Results
http://www.kchn.pg.gda.pl
[b] Consiglio Nazionale delle Ricerche (CNR), Istituto di Chimica
dei Composti OrganoMetallici - ICCOM, Area di Ricerca di
Firenze,
The reactivity of the lithium salts of diphosphanes R2P–
P(SiMe3)Li (R = tBu, iPr) towards the diimido molybd-
enum complex [(2,6-iPr2C6H3N)2MoCl2·dme] depends cru-
cially on the donor properties of the reaction medium.
Via Madonna del Piano 10, 50019 Sesto Fiorentino (Firenze),
Italy
E-mail: maria.caporali@iccom.cnr.it
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When the reaction was carried out in toluene with a 1:1
The 31P NMR spectrum of 7Mo displays two strongly
stoichiometry between the ligand and the metal complex, coupled doublets at δ = 106.3 (phosphinidene P) and
31P NMR analysis clearly indicated the formation of phos- 64.4 ppm (phosphanyl P), which corroborate the proposed
phanylphosphido complexes as the main products. In more formula of 7Mo with a side-on phosphanylphosphinidene
detail, the reaction involving tBu2P–P(SiMe3)Li performed ligand, tBu2P–P, dihapto-coordinated to the metal. The rel-
1
in toluene gave mainly (50%) the phosphanylphosphido atively large coupling of JP1-P2 = 488.3 Hz suggests a
complex [(2,6-iPr2C6H3N)2Mo(Cl)(Me3SiP–PtBu2)] (1Mo; double-bond character of the P–P bond within the tBu2P–
Scheme 1) together with a smaller amount (10%) of the de- P ligand; this feature is corroborated by the short P1–P2
silylated analogue [(2,6-iPr2C6H3N)2Mo(Cl)(HP–PtBu2)] distance [2.131(3) Å] in the molecular structure of 7Mo, as
(2Mo). The triphosphorus compound [(1,2-η-tBu2P=P– determined by a single-crystal X-ray diffraction study (Fig-
PtBu2)Mo({(2,6-iPr2C6H3N)2Cl})] (3Mo) was also formed ure 1). In addition, the 31P NMR spectrum shows signals
(10%) together with a tetraphosphorus species (spin system ascribable to the diphosphane tBu2P–P(SiMe3)2 together
AAЈXXЈ), very likely [(tBu2P=P–P=PtBu2){Mo(2,6- with other minor resonances due to tBu2P–P(SiMe3)H and
iPr2C6H3N)2Cl}2] (4Mo, 10%; see the Exp. Sect.).
tBu2P–P(SiMe3)Li.
Scheme 1. Synthesis of phosphanylphosphido complexes 1Mo and
5Mo.
The 31P{1H} NMR spectrum of the 1:1 reaction of [(2,6-
iPr2C6H3N)2MoCl2·dme] with iPr2P–P(SiMe3)Li in toluene
shows a strong AX pattern, which is attributed to the phos-
phanylphosphido
complex
[(2,6-iPr2C6H3N)2Mo(Cl)-
(Me3SiP–PiPr2)] (5Mo; 90.1%; Scheme 1). The desilylated
analogue of 5Mo, namely [(2,6-iPr2C6H3N)2Mo(Cl)(HP–
PiPr2)] (6Mo, 0.9%), and the free diphosphane iPr2P–
P(SiMe3)H (9%) were also observed as minor components
in the NMR spectrum.
In a more polar solvent like dme, tBu2P–P(SiMe3)Li re-
acted with [(2,6-iPr2C6H3N)2MoCl2·dme] in a ratio 2:1 to
yield almost solely the anionic MoVI side-on-bonded phos-
Figure 1. X-ray structure of the anion of 7Mo showing the atomic
numbering scheme. Ellipsoids drawn at the 25% probability level;
hydrogen atoms have been omitted for clarity. Selected bond
lengths [Å] and angles [°]: P1–P2 2.131(3), P1–Mo1 2.424(2), P2–
Mo1 2.464(2), Mo1–Cl1 2.464(2), Mo1–N1 1.769(7), Mo1–N2
1.770(5), P2–C25 1.968(7), P2–C29 1.78(1), P1–Mo1–P2 51.69(7),
N1–Mo1–N2 110.7(2), C29–P2–C25 109.6(5).
phanylphosphinidene
complex
[(2,6-iPr2C6H3N)2-
Mo(Cl)(η2-P=PtBu2)]– (7Mo). Scheme 2 shows the forma-
Complex [(2,6-iPr2C6H3N)2Mo(Cl)(η2-P=PiPr2)]– (8Mo)
tion of 7Mo and its analogue 8Mo bearing the η2-iPr2P=P was isolated as a microcrystalline product, however, this
ligand.
compound is not stable in dme solution and we did not
The presence of dme or thf was necessary for the forma- observe any signals in the 31P NMR spectrum correspond-
tion of phosphanylphosphinidene complexes 7Mo and ing to 8Mo. We observed only iPr2P–P(SiMe3)2 as the major
8Mo. Only in donor solvents did lithiation of the P–SiMe3 product together with minor amounts of the protonated de-
bond of the primarily formed phosphanylphosphido com- rivatives iPr2P–P(SiMe3)H and iPr2P–PH–PiPr2. Dissolving
plexes 1Mo and 5Mo take place followed by rearrangement crystals of 8Mo in C6D6 (solvate with four molecules of
of the lithium derivative (Scheme 2).
dme) also caused rapid decomposition.
Scheme 2. Formation of the phosphanylphosphinidene complexes 7Mo and 8Mo.
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The solid-state structures of the anions of 7Mo and 8Mo Sect.) and traces of tBu2PH, as shown in Scheme 3. Al-
are shown in Figure 1 and Figure 2, respectively. Both com- though the formula of 9Mo could not be ascertained on the
plexes possess similar structural features and were isolated basis of 31P NMR spectroscopy alone, the presence of two
as solvate lithium salts with three dme molecules coordinat- diphosphorus ligands is unquestionable. The large coupling
1
ing to Li and one additional molecule of dme in the lattice. constant of J(P-P) = –666.2 Hz is impressive and suggests
The anions of both 7Mo and 8Mo are pentacoordinate a multiple P–P bond for the P-P unit.
around the molybdenum atom with the phosphanylphos-
The synthesis and some spectroscopic data for terminal
phinidene ligand, R2P=P (R = tBu or iPr), side-on-coordi- WVI phosphanylphosphido complex [(2,6-iPr2C6H3N)2-
nated to molybdenum with a short P–P distance of W(Cl)(Me3SiP–PtBu2)] (1W) and the related anionic phos-
2.131(3) Å in 7Mo and an even shorter distance in 8Mo phanylphosphinidene tungsten complex [(2,6-iPr2C6H3N)2-
equal to 2.089(2) Å. These values are very similar to the W(Cl)(η2-P–PtBu2)][Li(dme)3]·dme (7W) was published re-
recently published P–P distance of 2.101 Å in the complex cently by our group.[15] The tungsten compound 7W is
[(2,6-iPr2C6H3N)2W(Cl)(η2-P=PiPr2)]–[15] and are in agree- much more stable than 7Mo. Heating a solution of 7W in
ment with the literature data found for other phosphanyl- C6D6 at 50 °C overnight led to only partial decomposition
phosphinidene ligands η2-bonded to a W or Nb centre[16–18] with the formation of [(2,6-iPr2C6H3N)2W(Cl)(HP–PtBu2)]
but are slightly longer than those determined for related Pt0 (2W) and a small amount of [(η2-tBu2P=P–PtBu2)W(2,6-
complexes.[8,12] In the case of 7Mo, the P–P bond length is iPr2C6H3N)2Cl] (3W) together with an unknown com-
very similar to that found (2.114 Å) in [μ-(1,2:2- pound (10W) that displays an AX pattern (31P NMR, see
tBu2P=P){Mo(CO)2Cpt}2].[31]
the Exp. Sect.).
We have already shown that the skeleton R2P–P=PR2
may be obtained from R2P–P(SiMe3)Li by the reaction of
the lithium salt with transition-metal complexes.[32] Simi-
larly, we also reported that a small amount of (tBu2P)3P
may be generated during the reaction of tBu2P–P(Li)–PtBu2
with [(R3P)2MCl2] (M = Ni, Pd, Pt).[33] These previous
achievements give some credence to the formation of the
R2P–P=PR2 assembly from the R2P–P moiety as well as of
(tBu2P)3P from tBu2P–P(Li)–PtBu2 under the assistance of
transition-metal complexes.
In this study we have, however, obtained [(2,6-
iPr2C6H3N)2M(Cl)(1,2-η-tBu2P=P–PtBu2)] [M
=
Mo
(3Mo), W (3W)] from the reaction of [(2,6-iPr2C6H3N)2-
MCl2] (M = Mo, W) with tBu2P–P(Li)–PtBu2 (Scheme 4).
In contrast to the reaction involving the lithium derivatives
of diphosphanes, the outcomes of these reactions do not
depend on the donor properties of the solvent. Red crystals
Figure 2. X-ray structure of the anion of 8Mo showing the atomic
numbering scheme. Ellipsoids drawn at the 50% probability level;
hydrogen atoms have been omitted for clarity. Selected bond
lengths [Å] and angles [°]: P1–P2 2.089(2), P1–Mo1 2.383(1), P2–
Mo1 2.547(1), Mo1–Cl1 2.403(1), Mo1–N1 1.767(4), Mo1–N2
1.784(4), P2–C25 1.845(6), P2–C28 1.877(5), P1–Mo1–P2 49.99(4),
N1–Mo1–N2 109.6(2), C25–P2–C28 105.8(2).
Crystals of 7Mo are stable at room temperature under
an inert atmosphere, but decompose in C6D6 slowly to form
2Mo and the new complex [(2,6-iPr2C6H3N)2Mo(Cl)(1,2-η-
tBu2P=P–PtBu2)] (3Mo). Heating this solution at 50 °C for
3 h led to the almost total decomposition of 7Mo to 3Mo
together with around 61.7% of the tetraphosphorus com-
Scheme 4. Synthesis of [(2,6-iPr2C6H3N)2M(Cl)(1,2-η-tBu2P=P–
pound 9Mo (31P NMR, AAЈXXЈ spin pattern, see the Exp. PtBu2)] (3Mo and 3W).
Scheme 3. Thermal decomposition of 7Mo.
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of the phosphido complexes 3Mo and 3W suitable for X- is such that the cation can be described as a diphosphenium
ray crystallography were obtained by slow crystallization cation[35] (Scheme 5, structure A) with a significant contri-
from n-pentane.
bution from the second canonical structure B representing
Compounds 3Mo and 3W crystallize in the Pbca space the non-classical phosphido ligand.
group with eight molecules in the elementary cell. Their X-
ray structures reveal very similar structural features and are
shown in Figure 3 and Figure 4, respectively.
Scheme 5. Two possible canonical structures of [(1,2-η-tBu2P=P–
PtBu2)M(2,6-iPr2C6H3N)2Cl].
Similar structures are known for complexes of Ni group
metals with the η2-bonded tBu2–P–PtBu2 ligand.[33,34] Here,
for both 3Mo and 3W, the P1–P2 distances are short and
indicate multiple bond character, but the P1–P3 distances
are in the range of a P–P single bond. There are, however,
significant structural differences between 3Mo (3W) and re-
lated complexes of the late-transition metals that are also
reflected in the NMR parameters of the P atoms. For exam-
Figure 3. X-ray structure of the anion of 3Mo showing the atomic
numbering scheme. Ellipsoids drawn at the 25% probability level;
hydrogen atoms have been omitted for clarity. Selected bond ple, the bond lengths in 3W are as follows: P1–P2 2.158(2),
lengths [Å] and angles [°]: P1–P2 2.1517(12), P1–P3 2.2407(12), P1–
P1–P3 2.235(2), P1–W1 2.524(2), P2–W1 2.578(2) Å. In ad-
Mo1 2.5371(9), P2–Mo1 2.5789(9), Mo1–Cl1 2.3902(9), Mo1–N1
dition, the coupling constants JP-P and JP-W clearly support
1.783(3), Mo1–N2 1.773(3), P1–Mo1–P2 49.73(3), N1–Mo1–N2
1
1
1
the X-ray results: JP1-P2 = 417.3, JP1-P3 = 272.9, JP1-W1
114.54(12), C1–N1–Mo1 173.8(2), C13–N2–Mo1 161.5(2), P2–P1–
P3 112.31(5), P2–P1–Mo1 66.14(3), P3–P1–Mo1 127.45(4).
1
= 102.4, JP2-W1 = 28.3 Hz. These results indicate that the
phosphido P1 atom is more strongly bonded to the metal
than the P2 atom. An opposite trend was found for the
similar platinum complex [(1,2-η2-tBu2P2=P1–P3tBu2)-
Pt(Cl)(p-Tol3P)]: P1–P2 2.1450(2) Å, P1–P3 2.2180(3) Å,
1
P1–Pt1 2.408(2) Å, P2–Pt1 2.212(2) Å and JP1-P2 = 447.3,
1JP1-P3 = 254.7, 1JP1-Pt1 = 188.1, 1JP2-Pt1 = 2776.8 Hz. Thus,
in this case the phosphido P1 atom is very weakly bonded
to the Pt centre but the P2 atom is strongly bonded and
shows properties (1JP,Pt and P–Pt distance) typical of a terti-
ary phosphine in a [(R3P)4Pt] complex.
Conclusions
The lithium derivatives of both di- and triphosphanes are
effective precursors for the generation of polyphosphorus
ligands. By the reaction protocol described in this work, we
have obtained two phosphanylphosphinidene complexes of
molybdenum featuring a side-on η2-bonded R2P–P moiety.
Diimido molybdenum complexes bearing an R2P–P ligand
are much less stable than their tungsten analogues. Heating
a C6D6 solution of [(2,6-iPr2C6H3N)2M(Cl)(η2-P=PtBu2)]-
[Li(dme)3]·dme (M = Mo, W) led to an intriguing transfor-
mation of the phosphanylphosphinidene ligand into the
Figure 4. X-ray structure of 3W anion showing the atom-number-
ing scheme. Ellipsoids drawn at the 25% probability level; hydrogen
atoms have been omitted for clarity. Selected bond lengths [Å] and
angles [°]: P1–P2 2.158(2), P1–P3 2.235(2), P1–W1 2.524(2), P2–
W1 2.578(2), W1–Cl1 2.376(2), W1–N1 1.778(3), W1–N2 1.775(6),
P1–W1–P2 50.01(6), N1–W1–N2 114.2(2), C1–N1–W1 173.3(4),
C13–N2–W1 163.3(5), P2–P1–P3 112.80(10), P2–P1–W1 63.71(6),
P3–P1–W1 128.13(9).
The most striking feature of both structures is the side- new triphosphorus ligand tBu2P=P–PtBu2 and the corre-
on bonding mode of the R2P2=P1 fragment belonging to sponding complexes [(2,6-iPr2C6H3N)2M(Cl)(1,2-η-
the ligand R2P=P–PR2, which was first observed for [(1,2- tBu2P=P–PtBu2)] (M = Mo, W). These complexes were in-
η2-R2P=P–PR2)M(Cl)L] (L = tertiary phosphine; M = Ni, dependently prepared by direct reaction of the lithium salt
Pd, Pt).[33,34] The bonding situation of these dihapto ligands tBu2P–P(Li)PtBu2 with the diimido precursors [(ArN)2-
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[Li·3dme]+·dme (7Mo): A solution of tBu2P–P(SiMe3)Li·1.6thf
(0.278 g, 0.751 mmol) in dme (2 mL) was added dropwise to a solu-
tion of [(ArN)2MoCl2·dme] (0.228 g, 0.376 mmol) in dme (2 mL)
cooled to –40 °C. The reaction mixture was stirred at room tem-
perature for 1 h and then the solvent was reduced to a half under
reduced pressure. The resulting solution was filtered and stored at
–20 °C. After 24 h, dark-violet crystals of 7Mo were separated
(180 mg), yield 46.7%. 31P{1H} NMR (161.9 MHz, C6D6, 25 °C):
MCl2·dme] (M = Mo, W) and were properly characterized
in solution (NMR) and in the solid state (X-ray diffraction).
Experimental Section
Toluene and dme were dried with K/benzophenone and distilled
under argon. Pentane and petroleum ether (boiling range 40–60 °C)
were dried with Na/benzophenone/diglyme and distilled under ar-
gon. All manipulations were performed in flame-dried Schlenk-
type glassware on a vacuum line and also in a glove-box (Ar).
31P{1H} NMR (external standard 85% H3PO4), 13C{1H} and 1H
(internal TMS) spectra were recorded with a Bruker AV 300 MHz,
Bruker AV 400 MHz and Varian Unity 500 MHz spectrometers at
room temperature. The SpinWorks 3.17[39] software and Simulation
Module Nummrit[40] were used for the simulation of the NMR
1
1
δ = 106.3 (d, JP1-P2 = 488.3 Hz, P1), 64.4 (d, JP1-P2 = 488.3 Hz,
1
3
P2) ppm. H NMR (400.1 MHz, C6D6, 25 °C): δ = 7.45 (d, JH,H
3
= 6.9 Hz, aromatic), 6.97 (t, JH,H = 6.8 Hz, aromatic), 4.54 (sept,
3JH,H = 6.8 Hz, CH), 3.06 (s, dme), 2.99 (s, dme), 1.75 (d, JH-P
=
=
3
3
3
14.1 Hz, tBu2P), 1.46 (d, JH,H = 6.9 Hz, CH3), 1.39 (d, JH,H
6.9 Hz, CH3) ppm. 13C{1H} NMR (100.6 MHz, C6D6, 25 °C): δ =
155.8 (s, C), 141.7 (s), 121.9 (s), 121.5 (s), 70.9 (s, CH3OCH2CH2-
OCH3), 58.5 (s, CH3OCH2CH2OCH3), 37.9 (CHMe2), 32.7 (d,
1JC,P = 5.4 Hz), 27.6 (CHMe2), 24.4 (d, JC,P = 18.4 Hz) ppm. In
2
spectra. Literature methods were used to prepare R2P–P(SiMe3)-
the 1H NMR spectrum, the integration of the doublet at δ =
1.75 ppm and the singlets at δ = 3.06 and 2.99 ppm shows a 4:1
molar ratio of dme and [(2,6-iPr2C6H3N)2Mo(Cl)(η2-P=PtBu2)]–.
Li·nL (R = tBu,[41] iPr;[29] L = thf), tBu2P–P(Li)–PtBu2
and
[42]
[(ArN)2MoCl2·dme] (Ar = 2,6-iPr2C6H3).[30] We compared the mo-
lar composition of reaction solutions by integration of the R2P
signals in the 31P NMR spectra.
Reaction of iPr2P–P(SiMe3)Li with [(2,6-iPr2C6H3N)2MoCl2] in
dme.
Synthesis
of
[(2,6-iPr2C6H3N)2Mo(Cl)(η2-P=PiPr2)]–
Reaction of tBu2P–P(SiMe3)Li with [(2,6-iPr2C6H3N)2MoCl2] in
[Li·3dme]+ (8Mo·3dme). A solution of iPr2P–P(SiMe3)Li·1.5thf
(0.252 g, 0.751 mmol) in dme (2 mL) was added dropwise to a solu-
tion of [(ArN)2MoCl2·dme] (0.228 g, 0.376 mmol) in dme (2 mL)
cooled to –40 °C. The reaction mixture was stirred at room tem-
perature for 1 h. The solvent was then reduced to a half under
reduced pressure. The violet solution was filtered and stored at
–20 °C. After 24 h, dark-violet crystals of 8Mo were formed
(95 mg, 25.3%). We were unable to record the NMR spectra of this
compound because of its instability in solution. In addition, we did
not observe any resonances that can be attributed to 8Mo even in
the reaction mixture. NMR analysis of the reaction mixture gave
Toluene:
A
solution of tBu2P–P(SiMe3)Li·1.6thf (0.139 g,
0.376 mmol) in toluene (2 mL) was added dropwise to a suspension
of [(ArN)2MoCl2·dme] (0.228 g, 0.376 mmol) in toluene (2 mL) co-
oled to –40 °C. The solution was heated to room temperature and
kept at this temperature for 1 h. The solvent was then evaporated
under reduced pressure and a dark-violet oily residue was obtained.
This residue was very soluble in n-pentane. Attempts at crystalli-
zation at both room and low temperatures were unsuccessful. The
yields were estimated by integration of the 31P{1H} NMR signals.
31P{1H} NMR (161.9 MHz, C6D6, 25 °C): 1Mo: δ = 41.9 (d, 1JP1-P2
= 456.9 Hz, tBu2P2), –174.8 (d, 1JP1-P2 = 456.9 Hz, P1) ppm (main
the following data. 31P{1H} NMR (161.9 MHz, C6D6, 25 °C):
1
product; 50%); 2Mo: δ = 53.5 (d, JP1-P2 = 312.2 Hz, tBu2P2),
1
–231.2 (d, JP1-P2 = 312.2 Hz, P1) ppm; 31P NMR: δ = –231.2 (dd,
1
iPr2P2–P1(SiMe3)H:
δ
=
–9.0 (d, JP1-P2
=
188.7 Hz, P2),
–202.3 ppm (d, 1JP1-P2 = 188.6 Hz, P1) ppm; 31P NMR: –202.3 ppm
(dd, JP1-P2 = 188.6, JP1-H = 186 Hz, P1) ppm; iPr2P2–P1-
1JP1-P2 = 312.2, 1JP1-H = 157.8 Hz, P1) ppm (10%); 3Mo: see below
(10%); 4Mo: AAЈXXЈ spin pattern: δ = 58.4 (AAЈ), –94.5
1
1
1
3
1
(SiMe3)2: δ = 8.9 (d, JP1-P2 = 315.8 Hz, P2), –216.2 ppm (d,
(XXЈ) ppm, simulated coupling constants: JA-AЈ = –9.0, JA-X
=
1JP1-P2 = 315.8 Hz, P1) ppm; iPr2P2–P1H–PiPr2: δ = –2.6 (d,
2
1
–425.0, JA-XЈ = 1.0, JX-XЈ = –239.5 Hz (10%).
1JP1-P2
=
199.0 Hz, P2), –140.2 ppm (t, JP1-P2
=
199.0 Hz,
1
tBu2P–P(SiMe3)H and tBu2P–P(SiMe3)2 were also formed in yields
of 12 and 8%, and their resonances are in agreement with literature
data.[41]
1
1
P1) ppm; 31P NMR: –140.2 ppm (dt, JP1-P2 = 199.0, JP1-H
=
190 Hz, P1) ppm.
Thermal Behaviour of [(2,6-iPr2C6H3N)2Mo(Cl)(η2-P=PtBu2)]–
[Li·3dme]+·dme (7Mo): A solution of 7Mo (0.050 g, 0.049 mmol) in
C6D6 (0.7 mL) was heated at 50 °C for 3 h in a sealed NMR tube.
The composition of the reaction mixture was studied by 31P{1H}
NMR spectroscopy, which confirmed the presence of 33.3% 3Mo,
61.7% 9Mo and 5% tBu2PH in the ratio.
Reaction of iPr2P–P(SiMe3)Li with [(2,6-iPr2C6H3N)2MoCl2] in
Toluene (5Mo, 6Mo):
A solution of iPr2P–P(SiMe3)Li·1.5thf
(0.126 g, 0.375 mmol) in toluene (2 mL) was added dropwise to a
suspension of [(ArN)2MoCl2·dme] (0.228 g, 0.376 mmol) in toluene
(2 mL) cooled to –40 °C. Then the solution was heated to room
temperature and kept at this temperature for 1 h. The solvent was
then evaporated under reduced pressure and a dark-violet oily resi-
due was obtained. This residue was highly soluble in n-pentane.
Attempts at crystallization at both room and low temperatures
were unsuccessful. The yields were estimated by integration of
31P{1H} NMR resonances. 31P{1H} NMR (161.9 MHz, C6D6,
31P{1H} NMR (161.9 MHz, C6D6, 25 °C): for 3Mo, see below;
9Mo AAЈXXЈ spin system: δ = 110.3 (AAЈ), –154.0 ppm (XXЈ);
JA-AЈ = 16, 1JA-X = –666, JA-XЈ = 65, JX-XЈ = –26 Hz. The multiplets
of 9Mo were simulated but coupling constants are only estimated
because of very broad signals.
1
25 °C): 5Mo: δ = 21.9 (d, JP1-P2 = 410.6 Hz, iPr2P2), –199.2 (d,
Thermal Behaviour of [(2,6-iPr2C6H3N)2W(Cl)(η2-P=PtBu2)]–
[Li·3dme]+·dme (7W): A solution of 7W (0.050 g, 0.045 mmol) in
C6D6 (0.7 mL) was heated at 50 °C overnight in a sealed NMR
tube. The composition of the reaction mixture was studied by
31P{1H} NMR spectroscopy, which confirmed the presence of
64.1% 7W, 12.8% 2W, 7.1% 3W, 2% 10W and 14% tBu2PH.
31P{1H} NMR (161.9 MHz, C6D6, 25 °C): 7W: δ = 64.9 (br. d, P2),
1JP1-P2 = 410.6 Hz, P1) ppm (main product; 90.1%); 6Mo: δ = 33.9
(d, 1JP1-P2 = 301.7 Hz, P2), –241.4 (d, 1JP1-P2 = 301.7 Hz, P1) ppm;
1
1
31P NMR: δ = –241.4 (dd, JP1-P2 = 301.7, JP1-H = 156.1 Hz,
1
P1) ppm (0.9%); iPr2P2–P1(SiMe3)H:
δ
=
9.0 (d, JP1-P2
=
188.6 Hz, P2), –202.3 (d, JP1-P2 = 188.6 Hz, P1) ppm; 31P NMR:
1
1
1
δ = –202.3 (dd, JP1-P2 = 188.6, JP1-H = 190.0 Hz, P1) ppm (9%).
1
1
Reaction of tBu2P–P(SiMe3)Li with [(2,6-iPr2C6H3N)2MoCl2] in
10.2 (br. d, JP1-P2 = 450.6 Hz, P1) ppm; 2W: δ = 52.2 (d, JP2-W
≈
1
dme.
Synthesis of
[(2,6-iPr2C6H3N)2Mo(Cl)(η2-P=PtBu2)]–
20 Hz, P2), –250.4 (d, JP1-P2 = –280.1 Hz, P1) ppm; 31P NMR:
Eur. J. Inorg. Chem. 2014, 1811–1817
1815
© 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

www.eurjic.org
FULL PAPER
1JP1-H = 160.1 Hz; for 3W, see below; 10W: δ = 81.1 (d, P1), –10.3
tural resolution was performed by using the SHELXS-97 package
solving the structures by direct methods and carrying out refine-
ments by full-matrix least-squares on F2 using the SHELXL-97[37]
program. All hydrogen atoms were positioned geometrically and
refined by using a riding model with C–H = 0.96 Å (CH3) with
Uiso(H) = 1.5Ueq(C), 0.97 Å (CH2), 0.98/0.99 Å (CH) and 0.94/
0.93 Å (aromatic) with Uiso(H) = 1.2Ueq(C).
1
(d, JP1–P2 = 566.0 Hz, P2) ppm; tBu2PH: δ = 19.5 (s) ppm; 31P
1
NMR: δ = 19.5 (d, JP-H = 199.0 Hz) ppm.
Reaction of tBu2P–PLi-PtBu2 with [(2,6-iPr2C6H3N)2MoCl2] in Tol-
uene Ϫ Synthesis of [(1,2-η-tBu2P=P–PtBu2)Mo(2,6-iPr2C6H3N)2-
(Cl)] (3Mo): A solution of [(2,6-iPr2C6H3N)2MoCl2]·dme (0.455 g,
0.75 mmol) in toluene (2 mL) was added at room temperature to a
suspension of tBu2P–PLi–PtBu2·0.5thf (0.273 g, 0.75 mmol) in tol-
uene (2 mL). The reaction mixture was stirred for 1 d; the suspen-
sion dissolved completely and turned red. The solvent was then
evaporated to dryness at 2ϫ10–3 Torr for 2 h. The reddish solid
residue was dissolved in n-pentane (4 mL), filtered and the volume
of the filtrate concentrated to 1 mL. After cooling for 2 d at 4 °C,
dark-red crystals of 3Mo were formed (0.373 g), yield 62%.
31P{1H} NMR (161.9 MHz, [D8]thf, 25 °C, for the labelling of P
atoms, see Figure 3): δ = 46.3 (dd, P3), 33.5 (dd, P2), –120.5 (dd,
The free dme solvent molecule in 8Mo was refined by suppressing
the symmetry restriction with a “PART –1” instruction. Owing to
its uncertain nature and the unresolvable disorder in 7Mo, the data
were processed with the SQUEEZE option in PLATON to remove
the cation [(dme)3Li]+ and the solvent dme contribution to the scat-
tering.[38] This was not included in the calculations of overall for-
mula weight, density and absorption coefficient.
CCDC-956894 (for 8Mo), -957205 (for 7Mo), -957997 (for 3Mo)
and -957998 (for 3W) contain the supplementary crystallographic
data for this paper. These data can be obtained free of charge
from The Cambridge Crystallographic Data Centre via
www.ccdc.cam.ac.uk/data_request/cif.
1
2
1
1JP1-P2 = 459.5 Hz, JP1-P3 = 269.7, JP2-P3 = 11.1 Hz, P1) ppm. H
NMR (400.1 MHz, [D8]thf, 25 °C): δ = 7.10–6.94 (m, overlapped,
3
3
6 H, C6H3), 3.90 (sept, JHH = 6.8 Hz, 4 H, CH), 1.71 (d, JPH
=
3
16.4 Hz, 18 H, tBu2P), 1.30 (d, JPH = 11.2 Hz, 18 H, tBu2P), 1.14
3
3
(d, JHH = 6.8 Hz, 12 H, CH3), 0.99 (d, JHH = 6.9 Hz, 12 H,
CH3) ppm. 13C{1H} NMR (100.6 MHz, [D8]thf, 25 °C): δ = 151.3
(s, Ci), 143.5 (s, Co), 124.6 (s, Cp), 120.2 (s, Cm), 37.7 (dd, J = 2.2,
3.6 Hz, H3CCP3), 33.0 (ddd, J = 2.1, 8.6, 34.9 Hz, H3CCP2), 28.4
(dd, J = 6.0, 13.9 Hz, H3CCP2) 29.2 (td, J = 4.1, 4.1, 3.2 Hz,
H3CCP3), 26.2 (d, J = 3.7 Hz, CHCH3), 21.4 (s, CHCH3) ppm.
Acknowledgments
R. G. thanks the Polish Ministry of Science and Higher Education
(Grant Iuventus Plus no. IP2012 037772) for financial support and
EU COST Action CM0802 for financing his stay at ICCOM CNR,
Florence, Italy. J. P. thanks the National Centre of Science NCN
(Grant Harmonia, no. 2012/06/M/ST5/00472) for financial sup-
port. M. C. and M. P. thank PRIN 2009, a project funded by the
Italian Ministry of Research, Education and Universities.
Reaction of tBu2P–PLi-PtBu2 with [(2,6-iPr2C6H3N)2WCl2] in
Toluene
Ϫ
Synthesis of [(1,2-η-tBu2P=P–PtBu2)W(Cl)(2,6-
iPr2C6H3N)2] (3W): A suspension of [(2,6-iPr2C6H3N)2WCl2·dme]
(0.521 g, 0.75 mmol) in toluene (2 mL) was added at room tempera-
ture to
a suspension of tBu2P–PLi–PtBu2·0.5thf (0.273 g,
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suspension dissolved and turned red. The solvent was then vacuum
dried at 2ϫ10–3 Torr for 2 h. The residue was dissolved in n-pent-
ane (4 mL) and filtered. The volume was concentrated to 1 mL.
After refrigeration for 2 d at 4 °C, dark-red crystals of 3W were
formed (0.451 g), yield 67%. 31P{1H} NMR (161.9 MHz, [D8]thf,
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29.8 (dd, P2), –145.5 (dd, 1JP1-P2 = 417.3, 1JP1-P3 = 272.9, 2JP2-P3
=
1
1
2
1
13.1, JP1-W = 102.0, JP2-W = 28.3, JP3-W = 8.6 Hz, P1) ppm. H
3
NMR (400.1 MHz, [D8]thf, 25 °C): δ = 7.23 (d, JHH = 7.5 Hz, 4
H, C6H3); 7.13 (t, JHH = 7.5 Hz, 2 H, C6H3), 4.02 (sept, JHH
3
3
=
3
6.7 Hz, 4 H, CH), 1.86 (d, JPH = 16.6 Hz, 18 H, tBu2P), 1.44 (d,
3JPH = 11.4 Hz, 18 H, tBu2P), 1.28 (d, 3JHH = 6.7 Hz, 12 H, CH3),
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=
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© 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

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Received: October 31, 2013
Published Online: November 29, 2013
Eur. J. Inorg. Chem. 2014, 1811–1817
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© 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim