Reactivity of Phosphanylphosphinidene Complex of Tungsten(VI) toward Phosphines: A New Method of Synthesis of catena-Polyphosphorus Ligands

Article abstract of DOI:10.1021/acs.inorgchem.5b01063

The reactivity of an anionic phosphanylphosphinidene complex of tungsten(VI), [(2,6-i-Pr₂C₆H₃N)₂(Cl)W(η²-t-Bu₂P=P)]Li·3DME toward PMe₃, halogenophosphines, and iodine was investigated. Reaction of the starting complex with Me₃P led to formation of a new neutral phosphanylphosphinidene complex, [(2,6-i-Pr₂C₆H₃N)₂(Me₃P)W(η²-t-Bu₂P=P)]. Reactions with halogenophosphines yielded new catena-phosphorus complexes. From reaction with Ph₂PCl and Ph₂PBr, a complex with an anionic triphosphorus ligand t-Bu₂P-P^(-)-PPh₂ was isolated. The main product of reaction with PhPCl₂ was a tungsten(VI) complex with a pentaphosphorus ligand, t-Bu₂P-P^(-)-P(Ph)-P^(-)-P-t-Bu₂. Iodine reacted with the starting complex as an electrophile under splitting of the P-P bond in the t-Bu₂P=P unit to yield [(1,2-η-t-Bu₂P-P-P-t-Bu₂)W(2,6-i-Pr₂C₆H₃N)₂Cl], t-Bu₂PI, and phosphorus polymers. The molecular structures of the isolated products in the solid state and in solution were established by single crystal X-ray diffraction and NMR spectroscopy. (Chemical Equation Presented).

Full text of DOI:10.1021/acs.inorgchem.5b01063

Article
pubs.acs.org/IC
Reactivity of Phosphanylphosphinidene Complex of Tungsten(VI)
toward Phosphines: A New Method of Synthesis of catena-
Polyphosphorus Ligands
Rafał Grubba,*,† Anna Ordyszewska,† Kinga Kaniewska,† Łukasz Ponikiewski,† Jarosław Chojnacki,†
Dietrich Gudat,‡ and Jerzy Pikies†
†Chemical Faculty, Department of Inorganic Chemistry, Gdansk University of Technology, G. Narutowicza St. 11/12, Pl-80-233
Gdansk, Poland
‡Institut fur Anorganische Chemie, Universitat Stuttgart, Pfaffenwaldring 55, 70550 Stuttgart, Germany
̈
̈
S
* Supporting Information
ABSTRACT: The reactivity of an anionic phosphanylphos-
phinidene complex of tungsten(VI), [(2,6-i-Pr2C6H3N)2(Cl)-
W(η2-t-Bu2PP)]Li·3DME toward PMe3, halogenophos-
phines, and iodine was investigated. Reaction of the starting
complex with Me3P led to formation of a new neutral
p h o s p h a n y l p h o s p h i n i d e n e c o m p l e x , [ ( 2 , 6 - i -
Pr2C6H3N)2(Me3P)W(η2-t-Bu2PP)]. Reactions with halo-
genophosphines yielded new catena-phosphorus complexes.
From reaction with Ph2PCl and Ph2PBr, a complex with an
anionic triphosphorus ligand t-Bu2P−P(−)−PPh2 was isolated.
The main product of reaction with PhPCl2 was a tungsten(VI)
complex with a pentaphosphorus ligand, t-Bu2P−P(−)−P(Ph)−
P(−)−P-t-Bu2. Iodine reacted with the starting complex as an electrophile under splitting of the P−P bond in the t-Bu2PP unit
to yield [(1,2-η-t-Bu2P−P−P-t-Bu2)W(2,6-i-Pr2C6H3N)2Cl], t-Bu2PI, and phosphorus polymers. The molecular structures of the
isolated products in the solid state and in solution were established by single crystal X-ray diffraction and NMR spectroscopy.
three types of compounds containing phosphanylphosphini-
dene groups (R2P−P): (a) relatively stable neutral, side-on
complexes [L2Pt(η2-R2PP)] (L = tertiary phosphine; R = t-
Bu, i-Pr, i-Pr2N, Et2N)11 whose reactions with [(OC)5M·
INTRODUCTION
■
Phosphinidene complexes with RP ligands can be considered as
phosphorus analogues of carbene complexes with R2C ligands1
which can be classified as electrophilic (Fischer type)2 or
nucleophilic (Schrock type) ones.3 For phosphinidene
complexes, the donor properties of spectator ligands at the
transition metal center exert likewise an essential impact on the
“philicity” of the P atom.4 Complexes with strongly σ-donating
spectator ligands show nucleophilic properties of the RP unit
and are often sufficiently stable to be isolated,1,5 while
complexes with strongly π-accepting spectator ligands (i.e.,
CO) exhibit electrophilic phosphinidene units and are often
only generated as transient species.1,6 The electrophilic
phosphinidene complexes can be stabilized if the P-substituent
R is a strong π-donor.7 For example, introduction of
aminosubstituents enabled the isolation of thermally stable
and sterically unprotected molybdenum and tungsten com-
plexes with terminal aminophosphinidene ligands, which
display, however, weaker electrophilic reactivity8 than that of
closely related transient alkyl phosphinidene complexes of
molybdenum.9
13
THF]12 (M = Cr, W) and t-Bu2P−PP(Me)tBu2 suggest
nucleophilic character of the R2P−P unit, (b) very reactive
complexes [(Me2PhP)Zr(η1-P−P-t-Bu2)]14 and [Cp2Zr{μ2-
PP(NEt2)2}2ZrCp2]15 with terminal and bridging R2P−P
units, and (c) relatively stable anionic side-on complexes
[(ArN)2(Cl)Wη2-R2PP)] (Ar = 2,6-i-Pr2C6H3; M = Mo and
W; R = t-Bu and i-Pr).16,17 Complexes that are related to group
c were prepared by Cummins et al. using nucleophilic terminal
phosphide complexes of niobium Na[(P)Nb{N(3,5-Me2C6H3)-
Np}3]18 and tungsten [(P)W{N(3,5-Me2C6H3)iPr}3]19 as
platforms for electrophilic phosphenium synthons. However,
chemical properties of such complexes have not been
investigated at all. Recently, metal complexes bearing terminal
phosphido and phosphinidene ligands were introduced as
important tools for the preparation of phosphorus−element
bonds.20 Thus, we undertook an investigation of the reactivity
of [(2,6-i-Pr2C6H3N)2(Cl)M(η2-t-Bu2PP)]Li·3DME toward
tertiary phosphines and halogenophosphines, and report here
Our group develops the chemistry of phosphanylphosphini-
denes (heavier analogues of aminophosphinidenes) and
phosphanylphosphides,10 especially as ligands in transition
metal chemistry. Altogether, we elaborated the synthesis of
Received: May 12, 2015
© XXXX American Chemical Society
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our results leading to new complexes with catena-phosphorus
ligands.
In contrast to cyclo-polyphosphorus compounds and
ligands,21,22 catenated polyphosphorus species are relatively
rare, and synthetic access to this class of phosphorus derivatives
is limitied.23 Acyclic polyphosphorus ligands with three or more
phosphorus atoms can be divided into two main classes, catena-
polyphosphane and catena-polyphosphanido ligands. Transition
metal complexes with acyclic polyphosphane ligands can be
obtained in reactions of the corresponding triphosphanes or
tetraphosphanes with iron or molybdenum carbonyl com-
plexes.24 A ruthenium complex with a P(OH)2PHPHPH(OH)
ligand was synthesized via a hydrolysis reaction of complexed
P4 molecules.25 As precursors of catena-polyphosphido ligands
in syntheses of the transition metal complexes, di-10b,26 and
triphosphanides17,27 or tetraphosphane-diides23b,28 were used.
Several catena-polyphosphido complexes were synthesized via
cleavage of a P−P bond in cyclophosphines,29 or the cyclo-P5
unit of the ferrocene analogue [Cp*FeP5]30 which occurs when
the phosphorus substrates react with transition metal frag-
ments. Additionally, chlorophosphines R2NPCl2 (R= Et, i-Pr)31
or the complex tetrakis(methydichlorophosphine)nickel(0)32
was used as a source of polyphosphido ligands in reactions with
Na2Fe(CO)4 and Re2(CO)10, respectively.
Figure 1. Ball-and-stick representation of the structure of the anion of
crystalline [Li+·3DME][Cl(ArN)2W(η2-t-Bu2PP)−] (1) showing the
atom-numbering scheme; H atoms have been omitted for clarity.
Important bond lengths (Å) and bond angles (deg): P1−P2
2.1065(17), P1−W1 2.4056(11), P2−W1 2.5713(11), W1−Cl
2.4150(10), W1−N1 1.793(4), W1−N2 1.785(4), P2−W1−P1
49.94(4), N1−W1−N2 108.89(16), W1−N1−C1 176.3(3), C25−
P2−C29 110.2(2).
shorter P1−W1 (2.4056(11) Å) and longer P2−W1 distances
(2.5713(11) Å) in 1 are similar to those reported by Cummins
et al. for [{(3,5-Me2C6H3)(i-Pr)N}3W(η2-Ph2PP)+].19 For-
mally, the tungsten atom is pentacoordinated, but the
coordination geometry can also be described as distorted
pseudotetrahedral (ligation by N1, N2, Cl1, and the P1−P2
bond).
In this Article, we present a simple new method for the
synthesis of acyclic polyphosphanido ligands starting from a
phosphanylphosphinidene complex of tungsten(VI).
In view of the strong σ- and π-donor properties of the imido
spectator ligands and the π-donor properties of the R2P moiety
within the R2P−P group,35 nucleophilic properties for the
phosphinidene phosphorus atom in 1 should be expected. As a
part of our studies of the reactivity of phosphanylphosphini-
dene complexes, we therefore studied reactions with
nucleophilic Me3P and electrophilic Ph2PCl, Ph2PBr, PhPCl2.
The outcome of the reaction of 1 with Me3P indicates that the
phosphinidene P atom in 1 does not exhibit any significant
Lewis acidity. Rather, the Me3P ligand substitutes the chlorido
ligand at tungsten to yield at ambient temperature the new
neutral phosphanylphosphinidene complex 2 (Scheme 2).
RESULTS AND DISCUSSION
■
Recently, we described the synthesis of a series of anionic
phosphanylphosphinidene complexes of molybdenum(VI) and
tungsten(VI)16,17 by reactions of diimido−dichlorido metal
complexes with appropriate lithium diphosphanides33 in DME
(Scheme 1).
Scheme 1. Synthesis of Phosphanylphosphinidene
Complexes [Li+·3DME][Cl(ArN)2M(η2-R2PP)−]
Scheme 2. Synthesis of the Phosphanylphosphinidene
Complex 2
For an investigation of the reactivity of these species, we
selected the tungsten(VI) complex with a t-Bu2P−P ligand (1).
This compound is the most stable species in the series and can
be easily isolated in high yield in crystalline form. Having
previously derived the constitution of 1 only from spectro-
scopic data in solution,16 we have now obtained X-ray quality
crystals of 1 which make it possible to discuss the geometry of
the complex also in the solid state. The red tetrasolvate [Li+·
3DME][Cl(ArN)2W(η2-tBu2PP)−]·DME16 (1·DME) crys-
tallized from toluene as a red trisolvate [Li+·3DME][Cl-
(ArN)2W(η2-tBu2PP)−] (1). The solid state structure of the
anion of 1 is shown in Figure 1.
Complex 2 crystallizes as a red microcrystalline solid from
pentane. The molecular structure of 2 is shown in Figure 2. The
substitution of Cl by PMe3 exerts substantial impact on the
spatial alignment of the ligands around the tungsten atom and
on the NMR data of the t-Bu2PP group. The geometry around
the W1 atom can still be seen as distorted pseudotetrahedral,
but the PMe3 ligand is now adjacent to the unsubstituted P1
atom of the P1−P2 bond, whereas the Cl atom in 1 was
situated close to the P2 atom. Moreover, the distances P1−P2
of 2.066(3) Å and W1−P2 of 2.462(2) Å are shortened, and
the distance W1−P1 of 2.493(2) Å is lengthened compared to
The η2 binding mode of the t-Bu2PP group is clearly evident.
The short P1−P2 distance of 2.1065(17) Å is almost identical
with the P−P distance of 2.101(3) Å in [Cl(ArN)2W(η2-i-
Pr2PP)−],16 and resembles the values of 2.0973(12) Å in
[{(3,5-Me2C6H3)(i-Pr)N}3W(η2-Ph2PP) +]19 and 2.114 Å in
[μ-(1,2:2-η-t-Bu2P−P){Mo(CO)2CptBu}2].34 The values of the
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To our surprise, the reactivity of nucleophilic phosphinidene
complexes toward phosphorus electrophiles was almost unex-
plored. Stephan et al. studied reactions of [Cp2Zr(PMe3)-
PMes*] with Me2SiCl2, Me2GeCl2, and Me2SnCl2, and
observed a transfer of the PMes* moiety to Si, Ge, and Sn
with formation of four-membered E2P2 rings (E= Si, Ge, Sn).39
Protasiewicz et al. studied reactions of [Cp2Zr(PMe3)PDmp]
(Dmp =2,6-Mes2C6H3) with Ph2PCl and observed formation of
Ph2P-PDmp-PPh2.40 In contrast to these reports, reaction of 1
with Ph2PCl produced ([(2,6-i-Pr2C6H3N)2WCl2], a small
amount of the P1-substitution product [(1,2-η-t-Bu2P−P−
PPh2)W([(2,6-iPr2C6H3N)2Cl] (3-Cl), and a mixture of
products which do not contain tungsten atoms (Ph2P-PPh2,
t-Bu2P-PPh2,31 t-Bu2PCl, and t-Bu2PH, Scheme 4). We did not
Figure 2. Ball-and-stick representation of the molecular structure of 2
in the crystal showing the atom-numbering scheme. H atoms have
been omitted for clarity. Important bond lengths (Å) and bond angles
(deg): P1−P2 2.066(3), P1−W1 2.493(2), P2−W1 2.462(2), W1−P3
2.479(2), W1−N1 1.820(6), W1−N2 1.796(6), P2−W1−P1
49.27(7), N1−W1−N2 114.8(3), W1−N1−C1 164.7(6), W1−N2−
C13 169.9(6), C29−P2−C25 111.1(4).
Scheme 4. Reaction of Complex 1 with Ph2PCl
1. The ligand displacement also changes the chemical shift of
1
the phosphinidene-P atom and the value of JPP within the t-
Bu2P2−P1 moiety (62.8 ppm (P2), 17.6 ppm (P1), and 1JP1−P2
= 454 Hz in 1 compared to 53.3 ppm (P2), − 29.6 ppm (P1),
1
observe (in the 31P NMR spectrum of the reaction mixture)
any traces of the tetraphosphane (Ph2P)2P(P-t-Bu2),42 which
might be anticipated in view of the results of Protasiewicz.40
The observed product distribution strongly suggests a
participation of radical side processes. The absence of
(Ph2P)2P(P-t-Bu2) among the products suggests that 3-Cl
does not react with Ph2PCl. Indeed, reaction of 1 with an excess
of Ph2PCl does not produce (Ph2P)2P(P-t-Bu2).
and JP1−P2 = 529 Hz in 2). In contrast to 1, in 2 we observed
all P−W couplings, which nicely support the X-ray results. The
value of 1JPW to the PMe3 ligand (396 Hz) is typical for tertiary
phosphine complexes of tungsten.36 The JPW coupling to the
1
P(t-Bu)2 group is smaller (246 Hz) since the incorporation of
the P and W atoms into a 3-membered ring induces presumably
an increased p-character in the PW bond, and hence decreases
J
PW. The still smaller coupling to the naked P atom (1JPW = 48
According to 31P NMR studies, the reaction of Ph2PBr with 1
proceeded much more selectively and yielded a significant
amount of 3-Cl together with a moderate amount of [(1,2-η-t-
Bu2P−P−PPh2)W([(2,6-i-Pr2C6H3N)2Br] (3-Br) (Scheme 5).
In addition, a significant amount of Ph2P-PPh2 was formed.
Hz) is due to the fact that the P atom still carries a lone pair
(with high s-character), and the PW bond is thus formally a σ-
bond which exhibits a lower degree of s-character than a dative
bond.37 Small P−M couplings to the naked phosphorus atom
were also observed for phosphanylphosphinide Pt(0) com-
plexes.11 Altogether, the 31P NMR and X-ray data indicate that
the bonding situation in 2 resembles that in [L2Pt(η2-t-Bu2P
P] (L = tertiary phosphine).11a
Scheme 5. Reaction of Complex 1 with Ph2PBr
The electronic structure of the t-Bu2P−P group was
investigated by theoretical methods.11a The results obtained
suggest that the P−P bond in the phosphanylphosphinidine
group is short: depending on the computational method, the
bond length varies from 1.97 Å (RI-DFT) to 2.052 Å (ab initio
calculations),11a compared to 1.945 Å for singlet Me2P−P (ab
initio calculations).38 The lengthening of the P−P bonds in 1
and 2 (2.11 and 2.07 Å) is a result of the η2-coordination of the
singlet phosphinidene to the metal center. The calculations
indicate that the P−P bond in the phoshanylphosphinidene
ligand has a significant ionicity, with the positive charge being
located on the substituted and the negative charge on the naked
P atom.11a Taking into account the computational results and
the experimental data for complexes 1 and 2, the best
representation of phosphanylphosphinidene ligands in side-on
complexes is given by the Lewis structure shown in Scheme 3.
The formation of 3-X as major product is in line with the
expected nucleophilic attack of the phosphinidene P atom on
the electrophile Ph2PBr. The successful isolation of the
complexes is attributable to a lower chlorophilicity of the W-
center which results in the low reactivity of 3-X toward Ph2PX
(X = Cl, Br), contrarily to Protasiewicz’ zirconium complexes.
Figure 3 shows the X-ray structure of 3-Cl which crystallizes as
orange solid.
The molecular structure of 3-Cl is similar to those of the
complexes [(1,2-η-t-Bu2P−P−P-t-Bu2)M(2,6-i-Pr2C6H3N)2Cl]
(M = Mo, W) recently published by us.17 Typical for this class
of compounds is the side-on bonding of the t-Bu2P−P fragment
of a t-Bu2P−P−PR2 unit (R = t-Bu or Ph) which can be seen as
η2-triphosphanido ligand. The geometry around the W1 atom is
Scheme 3. Lewis Structure of t-Bu2P−P Ligand in Complex 1
and 2
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ligand t-Bu2P−P(−)−P(Ph)−P(Ph)−P(−)−P-t-Bu2. The forma-
tion of 5-Cl indicates intermediate generation of t-Bu2PCl as a
product of a radical side reaction, and its subsequent trapping
by 1 according to Scheme 4.
Complex 4a was isolated as orange solid by crystallization
from pentane. Figure 4 shows the X-ray structure of 4a. The
Figure 3. Ball-and-stick representation of the molecular structure 3-Cl
in the crystal showing the atom-numbering scheme. H atoms have
been omitted for clarity. Important bond lengths (Å) and bond angles
(deg): P1−P2 2.2432(15), P2−P3 2.1801(15), P2−W1 2.5216(11),
P3−W1 2.6130(10), W1−Cl1 2.4154(9), W1−N1 1.787(3), W1−N2
1.775(3), P2−W1−P3 50.21(3), N1−W1−N2 111.85(15), C13−N1−
W1 170.7(3), C25−N2−W1 155.7(3), P1−P2−P3 112.22(6), P3−
P2−W1 67.07(4), P1−P2−W1 115.17(5), P2−P1−C1 98.43(14),
P2−P1−C7 95.75(19), C1−P1−C7 103.41(19), C37−P3−C41
114.01(19). C37−P3−P2 105.51(14), P2−P3−C41 120.44(14).
Figure 4. Ball-and-stick representation of the molecular structure 4a in
the crystal showing the atom-numbering scheme. H atoms have been
omitted for clarity. Important bond lengths (Å) and bond angles
(deg): P1−P2 2.176(5), P2−P3 2.247(5), P3−P4 2.238(5), P4−P5
2.168(5), P1−W1 2.556(4), P2−W1 2.552(4), P3−C33 1.850(14),
W1−Cl1 2.368(4), W1−N1 1.726(11), W1−N2 1.774(12), P1−W1−
P2 50.73(12), P1−P2−P3 112.7(2), P1−P2−W1 63.81(13), P3−P2−
W1 106.22(18), P3−P4−P5 112.9(2), N1−W1−N2 113.6(5), P2−
P3−P4 95.4(12), P2−P3−C33 92.7(5), P4−P3−C33 99.3(5), C21−
N2−W1 170.0(11), C9−N1−W1 164.6(10), C1−P1−C5 114.9(6),
P2−P1−C5 118.6(4), P2−P1−C1 106.1(7).
similar to that in 1 and can be described as pseudotetrahedral.
The P2−P3 distance of 2.1801(15) Å is somewhat longer than
the corresponding distance in [(1,2-η-t-Bu2P−P−P-t-Bu2)W-
(2,6-i-Pr2C6H3N)2Cl] (2.158 Å).17 Moreover, we observed P−
P bond lengthening in phosphanylphosphido complexes (t-
Bu2P−P−PR2) compared to the P−P bond in the appropriate
parent phosphanylphosphinidene complex 1. The P−P distance
in 3-Cl indicates partial multiple bond character when
compared to the pure uncoordinated single P−P bond distance
of 2.20−2.24 Å. The coordination geometry at P2 (sum of
angles ∑P2 = 294.97°) and P1 (∑P1 = 297.59°) is distinctly
pyramidal. The P3-atom exhibits a distorted tetrahedral
coordination in which the “intraligand” angles are somewhat
widened (∑P3 = 339.96° under neglect of the P3−W1 bond).
We have further checked the reactivity of 1 toward PhPCl2
(molar ratio 2:1) and have observed the formation of
[Cl(ArN)2W(η2-t-Bu2P−P)−P(Ph)−(η2-P−P-t-Bu2)W-
(NAr)2(Cl)] (4a) together with small amounts of t-Bu2PCl, t-
Bu2PH, [(1,2-η-t-Bu2P−P−P-t-Bu2)W(2,6-i-Pr2C6H3N)2Cl] (5-
Cl),17 and two hexaphosphorus compounds which give rise to
higher order 31P NMR spectra of AA′MM′X2 type and will be
denoted as 4b, 4c (Scheme 6). Complex 4a was isolated from
molecule consists of two [(t-Bu2P−P)W(2,6-i-Pr2C6H3N)2Cl]
parts connected by a bridging PPh group. The spatial alignment
in the terminal fragments resembles the structure of 3-Cl. The
t-Bu2P−P distances of 2.176(5) and 2.168(5) Å indicate partial
double bond character of the P1−P2 and P4−P5 bonds. The
average P2/P4−P3(Ph) distance of 2.242 Å is longer and
suggests single bond character for the central P2−P3 and P3−
P4 bonds. The coordination geometries at the P1/P5 and P2/
P4 atoms are likewise similar as in 3-Cl. The geometry around
P3(PPh) (sum of angles ∑P3 = 282.7°) is even more
pyramidal than in 3-Cl (287.4°). Moreover, the planes of the
phenyl rings at P3 and the 2,6-isopropylphenyl ring at N3
deviate from coplanarity by only 3.8° and have a centroid−
centroid distance of 3.838 Å, suggesting a possible π−π stacking
interaction.
Isolated 4a was found to be unstable in solution and decayed
in C6D6 within a few weeks at ambient temperature to a
complicated product mixture which shows complex signal
patterns most of which exhibit higher order splittings.
Structural assignment is based on the analysis of 31P spectra
Scheme 6. Reaction of Complex 1 with PhPCl2
1
by spectral simulation, and on the analysis of H,31P HMQC
spectra which allowed us to distinguish between the P atoms of
P-t-Bu2, P(naked), and PPh moieties. NMR spectroscopic
monitoring revealed that the initial stage of the reaction was
dominated by formation of a new pentaphosphorus tungsten
complex 4d, which was identified by its first order 31P{1H}
spectrum and is a product of rearrangement of complex 4a
(Scheme 7). Moreover, the formation of small amounts of
complex 4b and a product assigned as a complex 4e with an
anionic tetraphosphorus ligand t-Bu2P−P(−)−P(−)−P-t-Bu2 was
observed.
the reaction mixture as orange crystals and its solid state
structure determined by X-ray diffraction. The remaining
compounds were only identified in solution by NMR
spectroscopy (see Experimental Section). Although 4b and 4c
could not be isolated and unmistakably identified, we assign
them, on the basis of an analysis of the observed coupling
patterns tentatively as complexes featuring a hexaphosphanido
NMR spectra recorded after complete conversion of 4a
indicate the presence of significant amounts of complexes 4d,
4b, and a further hexaphosphorus compound (4f) which
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Scheme 7. Rearrangement of Complex 4a
Scheme 9. Reaction of Complex 1 with Iodine
exhibits presumably a similar hexaphosphorus skeleton as 4b
and can possibly be regarded as a rearrangement product of this
species. In addition, a minor quantity of 4e was still present.
We suggest that reactions of the anionic phosphanylphos-
phinidine complex 1 with halogenophosphines proceed via a
nucleophilc substitution mechanism (Scheme 8). In the
similar to Scheme 5. The complex 5-Cl can also be
independently prepared by direct reaction of t-Bu2P−P(Li)−
P−t-Bu2 with [(2,6-i-Pr2C6H3N)2WCl2].17
EXPERIMENTAL SECTION
■
DME was dried over K/benzophenone and distilled under argon.
Toluene was dried over Na/benzophenone and distilled under argon.
Pentane was dried over Na/benzophenone/diglyme and distilled
under argon. All manipulations were performed in flame-dried Schlenk
Scheme 8. Suggested Mechanism of the Reaction of 1 with
(Di)halogenophosphines
1
type glassware on a vacuum line. Solution 31P, 13C, and H spectra
were recorded on Bruker AV300 MHz, Bruker AV400 MHz, and
1
Varian 500 MHz spectrometers (external standard TMS for H, 13C;
85% H3PO4 for 31P) at ambient temperature. We determined the
composition of reaction solutions by integration of the R2P signals in
the 31P{1H} NMR spectra. We compare the signals of similar groups.
Me3P, Ph2PCl, and PhPCl2 were purchased from Aldrich and used as
received. A literature method was used to prepare Ph2PBr.44 Coupling
constants and chemical shifts of species giving rise to higher order
splittings were determined by spectral simulation using the WIND-
AISY module as implemented in the TopSpin software.
Crystallization of 1·DME from Toluene. A literature method
was used to prepare complex 1·DME.16 Solid 1·DME (500 mg, 0.42
mmol) was then dissolved in ca. 5 mL of toluene. This solution was
stored at −20 °C, and red crystals of 1 suitable for X-ray analysis were
deposited within 1 week. The yield of crystallization was 110 mg, 0.100
mmol, 24%. For NMR data of 1 see ref 16.
Reaction of
1 with PMe3. Synthesis of [(2,6-i-
Pr2C6H3N)2(Me3P)W(η2-t-Bu2PP)] (2). PMe3 (0.076 g, 1 mmol)
was added dropwise to a solution of 1 (512 mg, 0.50 mmol) in 5 mL
of toluene at −30 to −40 °C. During the reaction the color of the
solution changed from red to purple. The mixture was then kept at
ambient temperature for 24 h. The volume of the mixture was reduced
to one-half under reduced pressure, and the remaining solution was
formation of 3-Cl, the nucleophilic phosphinidene phosphorus
atom attacks the more electrophilic diphenylhalogenophos-
phine to form a new P−P bond under halide displacement. The
reaction with dichlorophenylphosphine serves as a route to
pentaphosphorus compounds. Probably, the first step of this
synthesis proceeds via formation of a transient triphosphanido
complex with a t-Bu2P−P(−)−P(Cl)Ph ligand. Then, the
phosphinidene P atom of a second equivalent of 1 attacks
the P(Cl)Ph group to give the pentaphospha-diido ligand.
Tertiary phosphines react with iodine to give iodophospho-
nium compounds R3P−I+−I−.43 Taking into account the
nucleophilic properties of 1, we have also tested its reactivity
toward I2. 31P NMR investigations of the reaction solution
revealed formation of t-Bu2PI and a complex assigned as [(1,2-
η-t-Bu2P−P−P-t-Bu2)W(2,6-i-Pr2C6H3N)2Cl] (5-Cl) as main
products, together with small amounts of [(1,2-η-t-Bu2P−P−
Pt-Bu2)W(2,6-i-Pr2C6H3N)2I] (5-I), t-Bu2PCl, and [(η2-t-
Bu2P−PH)W(2,6-i-Pr2C6H3N)2Cl] (6) (Scheme 9).
analyzed by 31P{1H}, 31P, and H NMR. Solvent and excess of PMe3
1
were then evaporated under reduced pressure, and the residue was
extracted with pentane. After a few minutes, crystalline 2 precipitated
(320 mg, yield 81%). Results of the examination of the 31P{1H} NMR
of the reaction solution: 2 (88%); PMe3 (excess); t-Bu2PP(SiMe3)2
(6%, contamination of starting complex 1);16 t-Bu2PH (4%);16 t-
Bu2PP(SiMe3)H (2%, contamination of starting complex 1).16
Data for 2 follow. 31P{1H}: δ 54.9 (dd, 1JPP = 529 Hz, 2JPP = 22 Hz,
2
1JPW = 246 Hz, t-Bu2P); −4.3 (dd, JPP = 22, 2JPP = 47 Hz, 1JPW = 396
1
2
1
Hz, PMe3); −26.3 (dd, JPP = 529 Hz, JPP = 47 Hz, JPW = 48 Hz,
PW). 1H: δ 6.95−6.70 (m, overlapped, 6 H, C6H3), 3.73 (sept, 3JHH
=
=
6.8 Hz, 4 H, CH), 1.40 (d, 2JPH = 10.0 Hz, 9 H, Me3P), 1.22 (d, 3JPH
3
16.4 Hz, 18 H, t-Bu2P), 0.98 (d, JHH = 6.8 Hz, 6 H, CH3), 0.86 (d,
3JHH = 6.8 Hz, 6 H, CH3). 13C{1H}: δ 155.4 (s, Ci), 140.9 (s, Co),
124.0 (s, Cp), 123.3 (s, Cm), 38.1 (d, J = 18.1 Hz, H3CP), 33.1 (d, J =
4.2 Hz, H3CCP), 27.5 (s H3CCP), 25.5 (s, CHCH3), 24.9 (s,
CHCH3).
Reaction of 1 with Ph2PCl. Formation of 3-Cl. Ph2PCl (110
mg, 0.50 mmol) was added dropwise to a solution of 1 (512 mg, 0.50
mmol) in 3 mL of DME at −30 to −40 °C. During the reaction, the
color of the solution changed from red to orange. The solution was
then held at ambient temperature for 24 h. The volume was reduced to
one-half under reduced pressure and the resulting solution analyzed by
31P{1H}, 31P, and 1H NMR. Results of the examination of the 31P{1H}
NMR of the reaction mixture follow: 3-Cl (9%); Ph2P-PPh2 (41%);41
These results indicate that the electrophile I2 reacts with 1
predominantly under cleavage of the P−P bond of the t-
Bu2PP unit to yield t-Bu2PI and presumably insoluble
phosphorus compounds. To our surprise, we did not found any
traces of PI3. The formation of 5-I and t-Bu2PCl arises
obviously from halide metathesis between 5-Cl and t-Bu2PI
E
DOI: 10.1021/acs.inorgchem.5b01063
Inorg. Chem. XXXX, XXX, XXX−XXX

Inorganic Chemistry
Article
t-Bu2P-PPh2 (17%);41 t-Bu2PCl;45 (8%) Ph2PCl (8%);46 t-Bu2PH
Data for 4c follow. 31P{1H} (simulated as AA′MM′X2 spin system):
1
(8%).
δ 56.9 (A, t-Bu2P); −36.3 (M, P); −68.9 (X, PPh); JAM = −317.4,
1
1
Data for 3-Cl follow. 31P{1H}: δ 48.5 (d, JPP = 377 Hz, JPW = 26
3JAM′ = 26.7 Hz, 3JAX′ = 92.1 Hz, 1JMX = −118.7 Hz, 2JMM = 199.0 Hz,
4JMM = −5.0 Hz.
1
1
Hz, t-Bu2P); −12.0 (d, JPP = 204, Ph2P); −132.1 (dd, JPP = 204 Hz,
1JPP = 377 Hz, JPW = 74 Hz, P).
1
Data for 4d follow. 31P{1H} (AEHMX spin system): δ 47.7 (A, d,
1
1
1JAE = −438 Hz, JP−W ≈ 10 Hz, t-Bu2P); 47.6 (H, ddd, JHX = −256,
Reaction of 1 with Ph2PBr. Formation of 3-Cl and 3-Br.
Ph2PBr (132 mg, 0.50 mmol) was added dropwise to a solution of 1
(512 mg, 0.50 mmol) in 3 mL of DME at −30 to −40 °C. During the
reaction, the color of the solution changed from red to orange. The
solution was then held at ambient temperature for 24 h. The volume
was reduced to one-half under reduced pressure, and the resulting
solution was analyzed by 31P{1H}, 31P, and 1H NMR. The solvent was
then evaporated under reduced pressure and the residue extracted with
5 mL of pentane. The extract was filtrated, reduced to one-half under
reduced pressure, and stored at room temperature. Orange crystals of
3-Cl deposited within 24 h (250 mg, yield 54%). Results of the
examination of the 31P{1H} NMR of the reaction mixture: 3-Cl (48%),
3-Br (14%), Ph2P-PPh2 (19%), t-Bu2PH (19%).
2JHM = 37, JEH = 20 Hz, t-Bu2P); − 41.0 (M, ddd, JMX = −156 Hz,
2
1
2JEM = 42 Hz, 2JHM = 37 Hz, 1JPW ≈ 11 Hz, PPh); −30.2 (X, ddd, 1JEX
1
1
1
= −378 Hz, JHX = −256 Hz, JMX = −156 Hz, JPW ≈ 19 Hz, P); −
96.4 (E, dddd, 1JAE = −438 Hz, 1JEX = −378 Hz, 2JEM = 42 Hz, 2JEH
=
1
20 Hz, JPW ≈ 10 Hz, P).
1
1
Data for 3-Cl follow. 31P{1H}: δ 48.9 (d, JPP = 377 Hz, JPW = 25
1
1
Hz, t-Bu2P); −10.4 (d, JPP = 206 Hz, Ph2P); −130.2 (dd, JPP = 206
Hz, 1JPP = 377 Hz, 1JPW = 74 Hz, P). 1H: δ 7.55−7.45 (m, 5 H, C6H5),
δ 7.15−6.90 (m, 6 H, C6H3), 3.95 (sept, 3JHH = 6.8 Hz, 4 H, CH), 1.51
(d, 3JPH = 16.4 Hz, 18 H, tBu2P), 1.19 (d, 3JHH = 7.0 Hz, 12 H, CH3).
1
1
Data for 3-Br follow. 31P{1H}: δ 46.2 (d, JPP = 382 Hz, JPW = 26
Data for 4e follow. 31P{1H} (simulated as AA′XX′ spin system): δ
1
1
Hz, t-Bu2P); −12.3 (d, JPP = 204 Hz, Ph2P); −139.4 (dd, JPP = 204
1
3
1
1
1
56.7 (A, t-Bu2P); −121.3 (X, P); JAX = −383, JAA = 9 Hz, JXX
−220 Hz.
=
Hz, JPP = 382 Hz, JPW = 72 Hz, P).
Reaction of 1 with PhPCl2. Synthesis of 4a. PhPCl2 (45 mg,
0.25 mmol) was added dropwise to a solution of 1 (512 mg, 0.5
mmol) in 3 mL of DME at −30 to −40 °C. During the reaction, the
color of the solution changed from red to orange. The solution was
then held at ambient temperature for 24 h. The volume was reduced to
one-half under reduced pressure, and the resulting solution was
analyzed by 31P{1H}, 31P, and 1H NMR. The solvent was then
evaporated under reduced pressure, and the residue was extracted with
5 mL of pentane. Orange crystals of 4a deposited within 24 h (95 mg,
yield 24%). Results of the 31P{1H} NMR examination of the reaction
solution after a few weeks at room temperature: 4a (47%), t-Bu2PH
(22%), 4b (12%), 4c (12%), t-Bu2PCl (5%), [(1,2-η-t-Bu2PP−P-t-
Bu2)W(2,6-i-Pr2C6H3N)2Cl] (5-Cl)17 (2%).
Data for 4f follow. 31P{1H} (simulated as AA′MM′XX′ spin
system): δ 54.9 (A, t-Bu2P); −16.4 (M, PPh); −146.5 (X, P); 5JAA = 0
Hz, 1JMM = −270 Hz, 3JXX = 5 Hz, 1JAX = −374 Hz, 4JAX′ = 0 Hz, 2JAM
=
3
1
2
0 Hz, JAM′ = 0 Hz, JMX = −383 Hz, JMX′ = 0 Hz.
Reaction of 1 with I2. Synthesis of 5-Cl. I2 (64 mg, 0.25 mmol)
was added to a solution of 1 (512 mg, 0.50 mmol) in 3 mL of DME at
−30 to −40 °C. During the reaction, the color of the solution changed
from red to dark brown. The solution was then held at ambient
temperature for 24 h. The volume was reduced to one-half under
reduced pressure and the resulting solution analyzed by 31P{1H}, 31P,
1
and H NMR. Results of the examination of the 31P NMR of the
reaction solution: t-Bu2PI (59%);40 5-Cl (35%);17 [(η2-t-Bu2P−
PH)W(2,6-iPr2C6H3N)2Cl] (6) (6%);16 [(1,2-η2-tBu2P−P−PtBu2)W-
(2,6-iPr2C6H3N)2I] (5-I) (W).
The decay of 4a in C6D6 solution was monitored by NMR
spectroscopy within a few weeks. A 30 mg portion of crystalline 4a was
dissolved in 0.7 mL of C6D6 and stored in a flame-sealed NMR tube.
1
2
Data for 5-I follow. 31P{1H}: δ 44.3 (dd, JPP = 276 Hz, JPP = 13
Hz, tBu2P); 16.9 (dd, 1JPP1 = 428, 2JPP = 13 Hz, 1JPW = 45 Hz, tBu2PW),
1
This solution was analyzed by 31P and H,31P HMQC NMR. The
1
−163.9 (dd, JPP = 428, JPP = 276 Hz, P).
analysis of signal patterns with high order splittings was accomplished
by spectral simulation, and the results were used to propose a
constitution for the phosphorus ligands in 4b, 4c, 4e, and 4f. Results of
the examination of the 31P{1H} NMR of a freshly prepared C6D6
solution of crystalline 4a: 4a (54%), 4d (29%), 4b (14%), 4e (3%).
Results of the examination of the 31P{1H} NMR of a C6D6 solution of
4a after a few weeks at room temperature: 4d (44%), 4b (40%), 4f
(14%), 4e (2%).
Crystal Structure Determinations for 1, 2, 3-Cl, and 4a.
Good-quality single crystal specimens of 1, 2, 3-Cl, and 4a were
selected for X-ray diffraction experiments carried out at 120 K. The
diffraction data for 1, 3-Cl, and 4a were collected with a KM4CCD
kappa geometry diffractometer equipped with a Sapphire2 CCD
detector. An enhanced X-ray Mo Kα radiation source with a graphite
monochromator was used. Diffraction data of 2 was collected on a
STOE diffractometer equipped with an imaging plate detector system
IPDS 2 using the same radiation and monochromatization. The
structures were solved by direct methods and refined against F2 by
least-squares techniques using the SHELXS-97 and SHELXL-97
programs.47 Non-hydrogen atoms were refined with anisotropic
displacement parameters; hydrogen atoms were usually refined using
the isotropic model with Uiso(H) values fixed to be 1.5 times Ueq of C
atoms for CH3 or 1.2 times Ueq for CH groups and aromatic H. Voids
found in the structure of 1 were examined by the PLATON/
SQUEEZE program.48 Empty space of volume 204 Å3 was found at
position (0 1/2 1) with residual electron density of 6.0 electrons inside
the cave.
Data for 4a follow. 31P{1H} (simulated as AMM′XX′ spin system):
1
δ 41.8 (XX′, t-Bu2P); −1.3 (A, PhP); −104.5 (m, MM′, P); JAM
=
−254 Hz, 2JAX = 9 Hz, 2JMM = 252 Hz, 4JXX = 0.0 Hz, 1JMX = −399 Hz,
1
1
3JMX = −1 Hz, JMW = 25 Hz, JXW = 73 Hz.
Crystallographic data for the structures of 1, 2, 3-Cl and 4a reported
in this paper have been deposited with the Cambridge Crystallo-
graphic Data Centre as supplementary publication No. CCDC
1054762, CCDC 1054763, CCDC 1054764 and CCDC 1054765.
Copies of the data can be obtained free of charge on application to
CCDC, 12 Union Road, Cambridge CB2 1EZ, UK (fax: (+44) 1223−
336−033; e-mail: deposit@ccdc.cam.ac.uk).
Data for 4b follow. 31P{1H} (simulated as AA′MM′XX′ spin
1
system): δ 54.8 (A, t-Bu2P); −44.9 (M, P); −61.6 (X, PPh); JAM
=
−210 Hz, 2JAX = 50 Hz, 3JAX′ = −7 Hz, 4JAM′ = −36 Hz, 5JAA = 14 Hz,
2
3
1
1JMX = −112 Hz, JMX′ = 7. Hz, JMM = −26 Hz, JXX = −141 Hz.
F
DOI: 10.1021/acs.inorgchem.5b01063
Inorg. Chem. XXXX, XXX, XXX−XXX

Inorganic Chemistry
Article
(8) Sterenberg, B. T.; Sanli Senturk, O.; Udachin, K. A.; Carty, A. J.
Organometallics 2007, 26, 925−937.
SUMMARY
■
A comprehensive reactivity study of the stable anionic
phosphanylphosphinidene complex [(2,6-i-Pr2C6H3N)2(Cl)W-
(η2-t-Bu2PP)]Li·3DME (1) was carried out. The nucleo-
philic properties of this complex were demonstrated by
reactions with halogenophosphines Ph2PCl, Ph2PBr, or
PhPCl2 to give compounds with new anionic catena-
polyphosphorus ligands t-Bu2P−P(−)−PPh2 or t-Bu2P−P(−)−
P(Ph)−P(−)−P-t-Bu2, respectively, as main products. The
formation of these products is readily explained as resulting
from nucleophilic attack of the phosphinidene P atom on the
electrophilic phosphorus atom of the halogenophosphine. The
complex with the pentaphosphane-diido ligand t-Bu2P−P(−)−
P(Ph)−P(−)−P-t-Bu2 was found to be unstable in solution and
decayed into a product mixture containing, among other
products, complexes with tetra- and hexaphosphane-diido
ligands. Moreover, in the reaction of 1 with nucleophilic
Me3P, we observed substitution of the chlorido ligand by the
PMe3 ligand to give a new neutral phosphanylphosphinidene
complex.
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ASSOCIATED CONTENT
* Supporting Information
The Supporting Information is available free of charge on the
ACS Publications website at DOI: 10.1021/acs.inorg-
chem.5b01063.
■
Peruzzini, M.; Pikies, J. Eur. J. Inorg. Chem. 2014, 2014, 1811−1817.
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(b) Waterman, R. Dalton Trans. 2009, 18−26. (c) Slootweg, J. C.;
Lammertsma, K. In Science of Synthesis: Organophosphorus Compounds
v.42; Thieme Chemistry: Stuttgart, 2008.
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Crystallographic data (CIF)
List of compounds, crystallographic details, and spectro-
scopic data (PDF)
AUTHOR INFORMATION
Corresponding Author
*E-mail: grubba@pg.gda.pl.
Notes
■
(22) Butovskiy, M. V.; Balazs, G.; Bodensteiner, M.; Peresypkina, E.
V.; Virovets, A. V.; Sutter, J.; Scheer, M. Angew. Chem., Int. Ed. 2013,
52, 2972−2976.
The authors declare no competing financial interest.
ACKNOWLEDGMENTS
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(23) (a) Gom
255, 1360−1386. (b) Gom
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ez-Ruiz, S.; Hey-Hawkins, E. Coord. Chem. Rev. 2011,
ez-Ruiz, S.; Frank, R.; Gallego, B.; Zahn, S.;
R. G., A. O., and K. K. thank the Polish Ministry of Science and
Higher Education (Grant Iuventus Plus no. IP2012 037772) for
financial support. The authors thank KNMF (Karlsruhe Nano
Micro Facility) KIT Karlsruhe for X-ray single crystal
measurements.
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DOI: 10.1021/acs.inorgchem.5b01063
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