Sulfur-Assisted Phenyl Migration from Phosphorus to Platinum in PtW2 and PtMo2 Clusters Containing Thioether-Functionalized Short-Bite Ligands of the Bis(diphenylphosphanyl)amine-Type

Article abstract of DOI:10.1021/acs.inorgchem.5b00223

The reactivity of dichloroplatinum(II) complexes containing thioether-functionalized bis(diphenylphosphanyl)amines of formula (Ph₂P)₂N(CH₂)₂SR (R = (CH₂)₅CH₃, CH₂Ph) t

Full text of DOI:10.1021/acs.inorgchem.5b00223

Article
pubs.acs.org/IC
Sulfur-Assisted Phenyl Migration from Phosphorus to Platinum
in PtW2 and PtMo2 Clusters Containing Thioether-Functionalized
Short-Bite Ligands of the Bis(diphenylphosphanyl)amine-Type
Stefano Todisco,† Piero Mastrorilli,*,†,‡ Mario Latronico,†,‡ Vito Gallo,† Ulli Englert,§ Nazzareno Re,∥
Francesco Creati,∥ and Pierre Braunstein*,⊥
†Dipartimento di Ingegneria Civile, Ambientale, del Territorio, Edile e di Chimica (DICATECh), Politecnico di Bari, via Orabona 4,
I-70125 Bari, Italy
‡Istituto di Chimica dei Composti Organometallici (ICCOM-CNR), Consiglio Nazionale delle Ricerche, Via Orabona 4, 70125 Bari, Italy
§Institut fur Anorganische Chemie der RWTH, Landoltweg 1, D-52074 Aachen, Germany
̈
∥Dipartimento di Farmacia, Universita
̀
G. d’Annunzio, Via dei Vestini 31, 06100 Chieti, Italy
⊥Laboratoire de Chimie de Coordination, UMR 7177 CNRS, Universite
F-67081 Strasbourg, France
́
de Strasbourg, 4 rue Blaise Pascal, CS 90032,
S
* Supporting Information
ABSTRACT: The reactivity of dichloroplatinum(II) complexes
containing thioether-functionalized bis(diphenylphosphanyl)-
amines of formula (Ph2P)2N(CH2)2SR (R = (CH2)5CH3,
CH2Ph) toward group 6 carbonylmetalates Na[M(CO)3Cp]
(M = Mo or W, Cp = cyclopentadienyl) was explored. Reactions
with two or more equivalents of Na[M(CO)3Cp] (M = Mo or
W) afforded the trinuclear complexes of general formula
[PtPh{M(CO)3Cp}{μ-P(Ph)N(CH2CH2SR)(PPh2)-κ3P,P,S}M-
(CO)2Cp] (3 M = Mo, R = (CH2)5CH3; 4 M = Mo, R =
CH2Ph; 9 M = W, R = (CH2)5CH3; 10 M = W, R = CH2Ph),
the structure of which consists of a six-membered platinacycle
condensed with a four-membered M−P−N−P cycle, together
with small amounts of isomeric PtM2 clusters [PtM2(CO)5Cp2{(Ph2P)2N(CH2CH2SR)-κ2P,P}] (5 M = Mo, R = (CH2)5CH3;
6 M = Mo, R = CH2Ph; 11 M = W, R = (CH2)5CH3; 12 M = W, R = CH2Ph) in which the ligand (Ph2P)2NR solely chelates the Pt
atom or bridges an M−Pt bond as in [PtM2(CO)5Cp2{μ-(Ph2P)2N(CH2CH2SR)-κ2P,P}] (7 M = Mo, R = (CH2)5CH3; 8 M = Mo,
R = CH2Ph; 13 M = W, R = (CH2)5CH3; 14 M = W, R = CH2Ph). The synthesis of the trinuclear complexes 3, 4, 9, and 10 entails
an unexpected P-phenyl bond cleavage reaction and phenyl migration onto Pt. When only 1 equiv of Na[M(CO)3Cp] (M = Mo or
W) was used, the heterodinuclear products of monosubstitution [PtCl{M(CO)3Cp}{Ph2PN(R)PPh2-P,P}] (15 M = Mo, R =
(CH2)5CH3; 16 M = Mo, R = CH2Ph; 17 M = W, R = (CH2)5CH3; 18 M = W, R = CH2Ph) were obtained, which are the
precursors to the bicyclic products 3, 4, 9, and 10, respectively. Density functional calculations were performed to study the
thermodynamics of the formation of all the new complexes, to evaluate the relative stabilities of the isomeric chelated and bridged
forms, and to trace the mechanism of formation of the phosphanido-bridged products 3, 4, 9, and 10. It was concluded that Pt(II)
complexes containing a thioether-functionalized short-bite ligand, [PtCl2{Ph2PN(R)PPh2}], react with Na[M(CO)3Cp] to yield first
heterodinuclear Pt−M and then heterotrinuclear PtM2 complexes resulting from the activation of a P−C bond in one of the PPh2
groups and phenyl migration to Pt. The critical role of an intramolecular thioether group was demonstrated.
number of kinetic and thermodynamic parameters involved, their
subtlety and intricacy, the diversity of metals and ligands available
and, even for transition metals with similar valence shells, the
differences in reactivity of the metal centers and of their ligands in
the precursor molecules. In our laboratories, we have investigated
the synthesis of mixed-metal trinuclear clusters with PtCo2,
PtMo2, or PtW2 cores, stabilized by short-bite ligands1 such as
1. INTRODUCTION
Despite spectacular developments and achievements in cluster
chemistry since F. A. Cotton coined the term in 1962−1963, it
remains often difficult or even impossible to predict the
molecular formula and structure of a cluster resulting from a
chemical synthesis, even if the latter has been designed for this
purpose. It is also well-recognized that reactions aiming toward
the synthesis of specific cluster compounds may not be
successful, while most exciting and novel structures have often
resulted from serendipity. This situation results from the large
Received: January 29, 2015
© XXXX American Chemical Society
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Scheme 1. Trinuclear PtCo2, PtMo2, or PtW2 Clusters with dppa or N-Substituted dppa Ligands
bis(diphenylphosphanyl)methane [dppm], bis(diphenyl-
phosphanyl)amine [dppa], and N-substituted dppa of formula
(Ph2P)2N-R [R = (CH2)9CH3, (CH2)2S(CH2)5CH3, (CH2)2S-
CH2Ph, Ph]. The N-functionalization was introduced to examine
its stereoelectronic influence on the nature of the reaction
products and the possibility to deposit/anchor the correspond-
ing clusters on various surfaces.2,3 The synthetic methodology
consisted in the reaction of a P,P-chelated, dichloro Pt(II)
precursor complex with a carbonylmetalate reagent. This substi-
tution reaction can trigger the opening of the four-membered
led to the phosphanido-bridged trinuclear compounds [PtPh-
{Mo(CO)3Cp}{μ-P(Ph)N(CH2CH2SR)(PPh2)-κ3P,P,S}Mo-
(CO)2Cp] (3 R = (CH2)5CH3; 4 R = CH2Ph) in 55% and 71%
yield, respectively (Scheme 2). Small amounts of trinuclear
clusters containing a chelating diphosphane, [PtMo2(CO)5Cp2-
{(Ph2P)2N(CH2CH2SR)-κ2P,P}] (5 R = (CH2)5CH3; 6 R =
CH2Ph), or a bridged diphosphane, [PtMo2(CO)5Cp2{μ-
(Ph2P)2N(CH2CH2SR)-κ2P,P}] (7 R = (CH2)5CH3; 8 R =
CH2Ph, see Table 1), were also obtained. These clusters are
formula isomers; one phosphorus donor has migrated from Pt to
Mo, while a CO ligand has moved from Mo to Pt.
ring M−P−C (or N)−P and afford heterometallic complexes
containing a stabilizing, bridging diphosphine in a thermody-
namically more favorable five-membered ring.4 While the use of
unsubstituted dppm and dppa ligands has resulted in PtCo2,5,6
PtMo2, or PtW2 clusters3,7 in which the diphosphine ligand
exhibits exclusively a bridging coordination mode, that of
n-decyl-substituted dppa (Ph2P)2N(CH2)9CH3 led to triangular
clusters in which the diphosphine exhibits both bridging and
chelating coordination modes (Scheme 1).3,8 It is noteworthy
that the reaction of dppm with a preformed heterometallic chain
complex of the type trans-Pt[M(CO)3Cp]2(NCPh)2] resulted in
the formation of the first heterobimetallic complexes containing
bridging and chelating dppm ligands.9 The behavior of thioether-
functionalized ligands (Ph2P)2N-R in which R = (CH2)2S-
(CH2)5CH3, (CH2)2SCH2Ph has been reported for platinum−
cobalt clusters and parallels that observed with n-decyl-substituted
dppa, in that both bridged and chelated isomeric PtCo2 clusters
are formed.3
In the course of further studies on the reactivity of Pt(II)
complexes of the type [PtCl2{(Ph2P)2N(CH2)2SR-P,P}] (R =
(CH2)5CH3, CH2Ph), bearing a thioether-functionalized dppa
chelate, with the Mo- and W-based metalates Na[M(CO)3Cp]
(M = Mo or W throughout the paper), we unexpectedly isolated
trinuclear complexes resulting from the activation of a P−phenyl
bond and the migration of this phenyl ring to the platinum atom.
Such dramatic molecular rearrangements are relevant to co-
operativity effects in heterometallic-induced reactivity.10
The 31P{1H} NMR spectra of complexes 3 and 4 contain two
mutually coupled doublets (JP,P = 68 Hz for both 3 and 4) in the
region from 73 to 90 ppm. The formation of these phosphanido-
bridged compounds resulted from a P−C bond cleavage reac-
tion and phenyl migration from phosphorus to platinum. The
thermally induced migration of a phenyl group from a
coordinated phosphane ligand onto platinum has precedents in
homodi- and trinuclear platinum chemistry, with the formation
of, for example, the phosphanido-bridged diplatinum complex
[Pt(PPh3)2(μ-H)(μ-PPh2)Pt(PPh3)Ph],11,12 the phosphinito
complex [Pt{PhP(o-C6H4CH2O)}(Ph2PO)(Ph2POH)Ph]13 or
the cluster [Pt3(μ-PPh2)3Ph(PPh3)2].14
The reaction of 1 or 2 with excess [W(CO)3Cp]− at 323 K in
THF similarly afforded the phosphanido-bridged complexes
[PtPh{W(CO)3Cp}{μ-P(Ph)N(CH2CH2SR)(PPh2)-κ3P,P,S}-
W(CO)2Cp] (9 R = (CH2)5CH3; 10 R = CH2Ph) in 34−36%
yield, respectively (Scheme 2), along with the formula isomeric
trinuclear clusters [PtW2(CO)5Cp2{(Ph2P)2N(CH2CH2SR)-
κ2P,P}] (11 R = (CH2)5CH3; 12 R = CH2Ph) and
[PtW2(CO)5Cp2{μ-(Ph2P)2N(CH2CH2SR)-κ2P,P}] (13 R =
(CH2)5CH3; 14 R = CH2Ph), see Table 1). The 31P{1H} NMR
resonances for 9 and 10 appear as two mutually coupled doublets
(JP,P = 55 Hz for both 9 and 10) in the region of 40−60 ppm.
When the reaction of complex 1 (or 2) with 1 to 4 equiv of
[M(CO)3Cp]− at 323 K was performed in MeCN instead of
THF as solvent, it stopped at the monosubstitution products
[PtCl{M(CO)3Cp}{Ph2PN(R)PPh2-P,P}] (15 M = Mo, R =
(CH2)5CH3; 16 M = Mo, R = CH2Ph; 17 M = W, R =
(CH2)5CH3; 18 M = W, R = CH2Ph; Scheme 2 and Table 2).
These dinuclear Pt−M complexes, likely intermediates in the
synthesis of the trinuclear clusters, were detected when less than
2 equiv of [M(CO)3Cp]− was used at 323 K in THF. Their
2. RESULTS AND DISCUSSION
2.1. Reactivity of the Platinum Complexes 1 and 2 with
Na[M(CO)3Cp]. The reaction of [PtCl2{(Ph2P)2-
N(CH2CH2SR)-P,P}] (1 R = (CH2)5CH3; 2 R = CH2Ph)
with excess [Mo(CO)3Cp]− at 323 K in tetrahydrofuran (THF)
B
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Scheme 2. Reactivity of 1 and 2 with Na[M(CO)3Cp]
Table 1. 31P{1H} NMR Data for Compounds 5−8 and 11−14 (THF, 298 K)
R
M
δ P1, ppm
δ P2, ppm
2JP,P, Hz
1JP,Pt, Hz
1JP,W, Hz
5
(CH2)5CH3
CH2Ph
Mo
Mo
W
61.0
61.1
3168
3169
3038
3040
a
6
11
12
7
(CH2)5CH3
CH2Ph
45.5
W
47.3
(CH2)5CH3
CH2Ph
Mo
Mo
W
121.7
122.1
85.2
84.8
84.6
75.8
77.4
46
45
61
60
8
a
13
14
(CH2)5CH3
CH2Ph
4045
4050
350
349
W
87.1
a
Not determined due to the low intensity of the signals.
31P{1H} NMR data (Table 2) are very similar to those of the
corresponding (Ph2P)2N(CH2)9CH3 analogues 19 (M = Mo)
and 20 (M = W).3
To ascertain whether an external thioether ligand could
facilitate a P−C bond activation of the type observed during
the synthesis of 3, 4, 9, and 10, we performed the reaction
of [PtCl2{(Ph2P)2N(n-decyl)-P,P}] with 2 equiv of Na[Mo-
(CO)3Cp] in the presence of excess di-n-butylsulfide. The course
of the reaction was identical to that performed in the absence of
di-n-butylsulfide,15 indicating that the P−C bond activation
leading to 3, 4, 9, and 10, requires the presence of a sulfur atom
within the tail of the PNP ligand.
The structures of complexes 4 and 9 were determined by X-ray
diffraction analysis. Multinuclear NMR spectroscopy indicated
that the structures found in the solid state are maintained in
solution. The complete analogy of spectroscopic features found
As already noticed for the latter complexes,3 the 31P{1H}
NMR signal of phosphorus P2 trans to the [M(CO)3Cp] group
in 15−18 is very broad in THF at 298 K, a phenomenon that can
be explained by partial dissociation of the [M(CO)3Cp]− moiety
in THF where an equilibrium can occur between the coordinated
and the (tight) ion-pair forms. The different behavior of inter-
mediates 15−18 in acetonitrile and in THF can thus be explained
by assuming that reactivity with fresh [MCp(CO)3]− is possible
only for the ion pair present in THF.
C
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Table 2. 31P{1H} NMR Data for the Heterodinuclear Complexes 15−18 (CD3CN, 298 K)
R
M
δ P1, ppm
δ P2, ppm
2JP,P, Hz
1JP1,Pt, Hz
1JP2,Pt, Hz
15
16
17
18
19
20
(CH2)2S(CH2)5CH3
(CH2)2SCH2Ph
(CH2)2S(CH2)5CH3
(CH2)2SCH2Ph
(CH2)9CH3
Mo
Mo
W
29.2
29.3
28.0
27.5
28.4
26.6
53.8
53.9
52.3
51.7
53.6
51.6
28
27
27
27
28
28
3557
3560
3584
3585
3549
3571
2648
2658
2571
2574
2648
2583
W
a
a
Mo
W
(CH2)9CH3
a
From ref 3.
distorted square planar coordination geometry to accommodate
the steric requirements of the six-membered ring.
The Pt−Mo bond distance of 2.9174(5) Å is comparable to
those reported for other complexes containing a platinum−
molybdenum bond.9,16−20 The values of the Pt1−C35 and Pt1−
C36 distances and of the O3−C35−Mo2 and O4−C36−Mo2
angles indicate a weak interaction between the Pt atom and the
carbonyl ligands (Figure 1). The coordination of the thioether
group to Pt results in a pyramidal geometry at sulfur with the sum
of the angles ∑θS = 322.1°. The four-membered ring is almost
planar since the plane defined by the atoms P1, N1, and P2
almost coincides with that defined by P1, Mo1, and P2 (∑θ =
358.80°).
Complex 9 crystallizes as a THF hemisolvate, and the co-
crystallized solvent molecule is disordered about a crystallographic
center of inversion. The structure of the complex (Figure 2) is
similar to that of 4 from which it differs by the nature of the
S-substituent (n-hexyl instead of benzyl) and of the group 6 metal
(W replacing Mo).
The Pt−W bond distance of 2.9158(4) Å in 9 is comparable to
those reported for other complexes containing a platinum−
tungsten bond.16,21−28 In this case too, there is a weak interaction
between the Pt and the W2-bound carbonyl ligands, as indicated
by the values of the Pt1−C34 and Pt1−C35 distances and of the
O5−C34−W2 and O3−C35−W2 angles. The sum of the angles
at the pyramidal sulfur is ∑θS = 320.1(3)°. The four-membered
ring P1, N1, P2, and W1 is almost planar, with a maximum
displacement of 0.012(5) Å for N1.
Figure 1. PLATON drawing of complex 4. Displacement ellipsoids are
scaled to 30% probability, and H atoms were omitted for clarity. Selected
interatomic distances (Å) and angles (deg): Pt1−C43 2.019(5), Pt1−P1
2.300(1), Pt1−S1 2.403(1), Pt1−C36 2.414(5), Pt1−C35 2.508(5),
Pt1−Mo2 2.9174(5), Mo2−C35 1.964(6), Mo2−C36 1.975(5), Mo1−
P2 2.452(1), Mo1−P1 2.567(1), P1−N1 1.737(4), P2−N1 1.670(4),
P1···P2 2.658(2); C43−Pt1−P1 92.7(1), C43−Pt1−S1 174.5(1), P1−
Pt1−S1 91.98(4), C43−Pt1−C36 91.75(17), C43−Pt1−C35 92.7(2),
P1−Pt1−C36 140.4(1), P1−Pt1−C35 136.4(1), S1−Pt1−C36
82.8(1), S1−Pt1−C35 85.9(1), C35−Pt1−C36 82.6(2), C43−Pt1−
Mo2 85.3(1), P1−Pt1−Mo2 176.96(3), S1−Pt1−Mo2 90.12(3), C36−
Pt1−Mo2 42.2(1), C35−Pt1−Mo2 41.6(1), P2−Mo1−P1 63.91(4),
C1−S1−C28 101.0(2), C28−S1−Pt1 108.7(2), C1−S1−Pt1 112.3(2),
Pt1−P1−Mo1 132.88(5), C12−N1−P2 124.0(3), C12−N1−P1
125.4(3), P2−N1−P1 102.5(2), N1−P2−Mo1 99.2(1), N1−P1−
Mo1 93.2(1).
The percentage of pyramidal character (P.P.C.%) at nitrogen,
calculated according to Farrar29 by the sum ∑θN of the angles
at nitrogen, can be used to compare the strain of the four-
membered P1−N1−P2−M1 ring in 4 and 9. With ∑θN values of
351.9(4) for 4 and 356.6(4) for 9, the corresponding P.P.C.% of
25.7% and 10.8%, respectively, indicate that the P1−N1−P2−
Mo ring is more strained than the corresponding P1−N1−P2-W
ring.
for 3/4 or 9/10 allows us to assign for 3 and 10 the structures
depicted in Scheme 2. The crystal structure of 4 is depicted in
Figure 1.
In the 31P{1H} NMR spectra of 9 (Figure 3) and 10, the
bridging P1 atoms gives rise to doublets at δ 59.0 (60.0) flanked
by 195Pt and 183W satellites from which the coupling constants
1JP,Pt = 2904 (2875) Hz and 1JP,W = 158 (156) Hz, respectively,
could be extracted. The tungsten-bound P2 gives rise to a doublet
at δ 39.9 (41.5) flanked by 195Pt and 183W satellites (2JP,Pt = 23
The unusual structure of complex 4 consists of a six-membered
platinacycle condensed with a four-membered M−P−N−P
cycle. The phosphanido group and the Mo-bound phosphane
form a four-membered ring, while the phosphanido and the
thioether groups chelate the platinum atom to give a six-
membered ring. The coordination around Pt is completed with a
phenyl group, which was originally attached to phosphorus, and
a [Mo(CO)3Cp] metalloligand. The platinum atom has a
1
(20) Hz, JP,W = 231 (230) Hz). For the corresponding Mo
complexes 3 and 4, the 31P signals are downfield-shifted with
respect to the W analogues, the phosphanide nucleus P1
resonates at δ 88.7 (1JP,Pt = 2849 Hz in 3, 1JP,Pt = 2819 Hz in 4),
D
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(δ 2.36) protons by combining the information obtained from
1H−195Pt HMQC and 1H COSY experiments at 298 K, whereas
the remaining signals (11 H) were ascribed to the C5H11 ligand
tail. The cyclopentadienyl protons gave rise to two singlets at δ
4.92 and δ 4.75, which were assigned on the basis of a 1H−31P
HMQC experiment at 298 K. The signal at δ 4.92 is scalar-
coupled to both P atoms and ascribed to the Cp bonded to W1,
while the signal at δ 4.75 showed no correlation to P and was
1
attributed to the Cp bonded to W2 (Chart 1). The H−31P
Chart 1
Figure 2. PLATON drawing of complex 9 in 9·0.5THF. Displacement
ellipsoids are scaled to 50% probability; the solvent molecule and H
atoms were omitted for clarity. Selected interatomic distances (Å) and
angles (deg): Pt1−P1 2.300(2), Pt1−S1 2.415(2), Pt1−W2 2.9157(4),
Pt1−C42 2.032(6), Pt1−C34 2.518(6), Pt1−C35 2.392(6), W2−C34
1.964(7), W2−C35 1.959(6), W2−C36 1.942(7), W1−P1 2.548(2),
W1−P2 2.462(2), W1−C15 1.968(7), W1−C16 1.962(7); P1−Pt1−S1
92.22(5); C42−Pt1−P1 93.8(2); C42−Pt1−W2 85.3(2); S1−Pt1−W2
88.99(4); O3−C34−W2 166.1(5); O4−C35−W2 167.6(5); Pt1−S1−
C1 112.6(2); Pt1−S1−C28 107.5(2); C1−S1−C28 100.0(3); C2−
N1−P1 126.1(4); C2−N1−P2 126.5(4); P1−N1−P2 104.0(3); N1−
P1−W1 93.00(2); N1−P2−W1 98.6(2); P1−W1−P2 64.45(5).
Figure 4. 1H−31P HMQC spectrum of 9 (phenyl region, 298 K,
THF-d8).
HMQC spectrum at 298 K (Figure 4) showed, in the phenyl
region, intense cross peaks between the ortho protons of PhB
(δ 8.41), PhC (δ 7.96), and PhD (δ 7.55) rings (Chart 1) and the
P atoms to which these rings are bonded. The ortho protons of
PhA were found at δ 7.41, in a spectral region crowded by
overlapping signals, by means of a 1H−195Pt HMQC experiment
performed at 330 K in THF-d8 (Figure 5).
Figure 3. 31P{1H} NMR spectrum of 9 (THF-d8, 298 K).
Once the ortho protons of the Pt-bound phenyl ring A were
identified, the corresponding meta (δ 6.77) and para (δ 6.62)
and the phosphane nucleus P2 resonates at δ 73.1 in 3 and at
73.2 in 4. In all cases, the 31P{1H} NMR spectra showed broad P1
signals (Δν1/2 ranging from 5 to 12 Hz) and relatively sharp P2
signals (Δν1/2 = 2 Hz), consistent with the existence, in
THF solution, of ion pairs of formula [M(CO)3Cp][PtPh-
{μP(Ph)N(CH2CH2SR)(PPh2)-κ3P,P,S}M(CO)2Cp]+ (M =
Mo or W; R = (CH2)5CH3 or CH2Ph).
1
protons of this ring were easily assigned by H COSY at
330 K. The fact that the 1H−195Pt correlation between
the ortho protons of the phenyl ring A and Pt was not
1
apparent in the H−195Pt HMQC spectrum recorded at
298 K must be ascribed to the very broad signals for the ortho
protons of the phenyl ring A at 298 K, presumably due to
hindered rotation of the phenyl ring about the Cipso−Pt
bond. On raising the temperature to 330 K, the phenyl
rotation is facilitated, and the very broad signal at 298 K
for the meta protons of phenyl ring A becomes a sharper,
pseudotriplet at 330 K.
The 195Pt NMR signal for the PtMo2 complexes is found at
δ −3508 (3) and δ −3517 (4) and for the PtW2 complexes at
δ −3591 (9) and δ −3605 (10). A detailed NMR study was
performed for the structurally characterized PtW2 complex 9.
1
The H NMR spectrum of 9 consists of three regions char-
acteristic for the aliphatic protons (3.6−0.5 ppm), the cyclo-
pentadienyl protons (5.1−4.5 ppm), and the phenyl protons
(8.5−6.5 ppm). In the aliphatic region, the most deshielded
signals were assigned to the −NCH2 (δ 3.22 and 3.01),
−CH2SCH2CH2N (δ 2.73 and 2.24), and −CH2SCH2CH2N
The Cipso signals of the four phenyl rings, attributed by means
of 13C{1H} APT and 1H−13C HMBC experiments at 298 K, were
found at δ 142.4 (JC,P = 7 Hz) for ring A, δ 143.7 (JC,P = 9 Hz) for
ring B, and δ 138.7 (JC,P = 43 Hz) and δ 133.5 (JC,P = 50 Hz) for
rings C and D, respectively. The para-C atom of ring A gave a
E
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about the Cipso−Pt bond is less important than for the PtW2
analogue 9. The IR spectra of complexes 3, 4, 9, and 10 in THF
showed three bands between 1786 and 1976 cm−1 (see
Experimental Section) for the terminal carbonyls bonded to
Mo or W.
The high-resolution mass spectrometry (HRMS(+)) spectro-
grams of complexes 3, 4, 9, and 10 recorded with a collision
energy of 10 eV, applied at the exit of the quadrupole,30 showed
in all cases intense peaks resulting from loss of [M(CO)3Cp]−.
On lowering the collision energy to 2.0 eV, complex 3 led also to
the peaks attributable to the [M + H]+ cation, while complexes 4
and 10 led to the peaks attributable to the [M]+ cation, and
complex 9 led to the peak for [M + Na]+. Figure 6 shows
the comparison between the experimental signals and the iso-
tope pattern calculated for [3+H]+ on the basis of the natural
abundances.
Figure 5. 1H−195Pt HMQC spectrum of 9 (phenyl region, 330 K, THF-d8).
2.2. Reactivity with Halide Ions. Complexes 3, 4, 9, and 10
are stable in the solid state and in THF or aromatic solvents but
promptly react with halide ions to give the substitution products
21−26 (Scheme 3 and Table 3) in which the Pt-bound metalate
[M(CO)3Cp]− is replaced by the incoming halide. All reactions
depicted in Scheme 3 were quantitative, as ascertained by solu-
tion NMR spectroscopy.
The reactions of 3, 4, 9, and 10 with solid [n-Bu4N]Cl in THF
afforded quantitatively the corresponding yellow chlorido
complexes 21−24, while reactions of 4 with [n-Bu4N]Br or
[n-Bu4N]I yielded the yellow bromido and iodido complexes 25
and 26, respectively (Scheme 3). To overcome the difficulty of
singlet at δ 122.7 at 298 K, while the corresponding ortho- and
meta-C signals were not detected at 298 K.
The main spectroscopic features of complexes 3, 4, and 10
were similarly extracted and are reported in the Experimental
Section. For the PtMo2 complex 3, the ortho protons of phenyl
ring A (bonded to Pt) appear in the 1H NMR spectrum recorded
in C6D6 at 298 K as a doublet centered at δ 7.91, as undoubtedly
1
1
indicated by the combination of the H−31P HMQC and H
COSY experiments, which is flanked by 195Pt satellites (3JH,Pt
=
50 Hz). The corresponding resonance for the meta protons (at δ
6.87) is quite sharp, indicating that, if present, hindered rotation
Figure 6. Experimental (black) and calculated (red) HRMS(+) spectrogram of the [M + H]+ ion of 3 (exact mass = 1188.0492 da,31 measured
1188.0368) in acetone. The error between calculated and observed isotope patterns is 0.5 ppm.
F
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Scheme 3. Reactivity of Complexes 3, 4, 9, 10 with Halides
Table 3. 31P{1H} NMR Data for the Halido-Complexes 21−29 (THF, 298 K)
compound
R
M
X
Y
δ P1, ppm
δ P2, ppm
2JP,P, Hz
1JP,Pt, Hz
21
22
(CH2)5CH3
CH2Ph
Mo
Mo
W
Cl
Cl
Cl
Cl
Br
I
PhA
PhA
PhA
PhA
PhA
PhA
I
72.8
75.0
43.8
45.2
75.5
73.6
65.1
62.0
71.9
74.6
43.2
42.8
74.7
74.9
77.8
80.4
74
75
62
62
74
71
74
85
3582
3576
3713
3634
3541
3393
2653
2969
a
23
(CH2)5CH3
CH2Ph
24
25
26
27
29
W
CH2Ph
Mo
Mo
Mo
Mo
CH2Ph
CH2Ph
I
CH2Ph
Cl
Cl
a
in CDCl3.
removing the anion [Mo(CO)3Cp]− liberated in the reaction, we
performed the reaction between 4 and [n-Bu4N]X in THF under
O2 bubbling. Under these conditions, [Mo(CO)3Cp]− is readily
oxidized in oxo species,9,32 which were easily separated from the
reaction mixture.
Some lability of the Pt-bound [M(CO)3Cp] group in 3, 4, 9,
and 10 may be anticipated from the ion pair structure present in
solutions as suggested by 31P NMR. Furthermore, the easy loss of
[M(CO)3Cp]− during the electrospray ionization mass spectro-
metry(+) analysis of 3, 4, 9, and 10 is consistent with the lability
of this group. The ease of replacement of [M(CO)3Cp]− with a
halide explains why a quantitative transformation into 21−24
was observed when the trinuclear complexes 3, 4, 9, and 10 were
percolated through a silica chromatographic column using
CHCl3 as eluent.
The HRMS(+) spectrogram of 22, 25, and 26 recorded in
MeOH/HCOOH showed the peaks due to [M−X]+ (X = Cl, Br,
or I) and those attributable to [M+K]+ (1022.9945 Da for 22,
1050.9716 Da for 25, and 1098.9589 Da for 26). The solid-state
IR spectra of 22, 25, and 26 were almost superimposable,
showing two very strong carbonyl stretching bands around 1966
and 1893 cm−1. The ν(Pt−Cl) IR absorption band of the
chlorido complex 22 was observed at 280 cm−1. The structure of
complexes 21, 23, and 24 was inferred from their spectroscopic
features by comparison with those of 22. For 21−26, the P2
NMR signal remained nearly unchanged, while that of P1 was
upfield-shifted by 15−20 ppm. As expected from the different
trans influences of M(CO)3Cp and X (X = Cl, Br, I), the direct
31P−195Pt coupling constants of P1 increases by ca. 600 Hz on
going from 3, 4, 9, and 10 to 21−26. The 195Pt NMR signal is
shifted to higher fields on going from 22 (Cl, δ −4034), 25 (Br, δ
−4110) to 26 (I, δ −4297). The coordination to Pt of the phenyl
group PhA and of the thioether S atom was confirmed by
1H−195Pt HMQC experiments, which showed the correlations
between the 195Pt and both the ortho protons of PhA and the two
methylene protons bonded to S.
2.3. Reverse Migration of the Phenyl Group. Metal-
mediated P−C bond cleavage reactions are well-documented
(especially for PPh3 and dppm) and are not only relevant to
possible catalyst deactivation mechanisms33 but often give rise
to new stable organometallic species resulting from molecular
rearrangements.34−43 However, only few systems have been
reported in which the original P−C bond can be reformed. The
first example of this kind was reported in 1976 and deals with the
reversible oxidative addition of PPh3 to zerovalent nickel and
palladium complexes.44 Subsequently, the reversible phenyl
migration between iron and phosphorus on a phosphoranide
complex,45 the reversible thermal phenyl migration from PPh3 on
a triruthenium carbonyl cluster,46 and the reversible phenyl
migration from Ru to P in a BINAP complex, without loss of
stereogenicity at the metal atom,47 have been described. As far as
platinum chemistry is concerned, a 1H EXSY analysis has demon-
strated the exchange between rings A and B in the dinuclear
diphenylphosphanido-bridged benzoquinolinate complex
[NBu4][(RF)2Pt(μ-PPh2)2Pt(C13H8N-κ2N,C)] (RF = C6F5;
C13H8N = benzoquinolinate), as a result from a reversible P−C
bond breaking reaction (Scheme 4).48
In the same study, it was shown that treating [NBu4][(RF)2Pt-
(μ-PPh2)2Pt(C13H8N-κ2N,C)] (RF = C6F5; C13H8N = benzo-
quinolinate) with I2 resulted in P−C bond formation between a
G
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Scheme 4. Reversible P−C Bond Breaking Occurring in a Dinuclear Diphenylphosphanido-Bridged Benzoquinolinate Pt
Complex48
Scheme 5. Reactivity of 4 with Iodine and Migration of the Phenyl Group from Pt to P
Scheme 6. Reactivity of 4 with HCl
bridging PPh2 and the coordinated benzoquinoline. This type of
I2-induced P−C bond formation was not unprecedented: it has
been reported for the cluster [Pt3(μ-PPh2)3Ph(PPh3)2] when its
Pt-bound phenyl group migrates to phosphorus to give [Pt3(μ-
PPh2)3(μ-I)(PPh3)3]I49 and for several polynuclear diphenyl-
phosphanido-bridged platinum and palladium complexes
bearing pentafluorophenyl groups, which give coordinated
PPh2(C6F5) as the result of reductive coupling.50−52
To test whether molecular iodine could induce phenyl migra-
tion from platinum back to P1 in our trinuclear species, we
treated 4 with I2 in THF under 1 atm of CO at room tempera-
ture for 4 h. The reaction led to a mixture of [PtI2{μ-P(Ph)-
N(CH2)2SCH2Ph)(PPh2)-κ3P,P,S}M(CO)2Cp] (27) (80%) and
cis-[PtI2{(Ph2P)2N(CH2)2SCH2Ph-P,P}] (28, 20%, Scheme 5).
The formation of 28 requires that phenyl migration has occurred
from platinum to phosphorus, and this demonstrates that in our
system, P−C and Pt−C bond activation can be thermally and
chemically triggered, respectively. Depending on the conditions,
phenyl migration can thus occur from P to Pt or from Pt to P.
The structure of the reaction products 27 and 28 was con-
firmed by comparison of their spectroscopic features with those
of authentic samples: 27 was prepared by reaction of 26
with I2 and 28 by reaction of [PtI2(cod)] with the ligand
(Ph2P)2N(CH2)2SCH2Ph. Monitoring of the reaction of Scheme 5
by 31P NMR revealed that after 20 min the starting material 4 was
consumed and that the THF solution contained 20% of 28 and
80% of 26. After 1 h of reaction, the amount of 28 was unchanged
(20%), but 26 progressively transformed into 27, giving a
solution containing 32% of 26 and 48% of 27. After 4 h, the
continuing transformation of 26 into 27 afforded a solution
containing only 27 (80%) and 28 (20%). These data indicate that
4 reacts with 2 equiv of iodine to give first 26 and 28, complex 27
resulting from further iodination of 26. That 26 is the precursor
to 27 and not to 28 was confirmed by the reaction of 26 with an
equimolar amount of I2 in THF at 298 K, which afforded
quantitatively 27 and PhI,53 without any formation of 28.54
The synthesis of 28 entails the loss of the Mo1(CO)2Cp
fragment as [MoI(CO)3Cp], which was actually detected by IR
spectroscopy (diagnostic band at 2040 cm−1)55,56 as the only
mononuclear molybdenum carbonyl species present in solution
after the reaction mixture was stirred for 4 h. The formation of
this complex requires the presence of external CO. To examine
H
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Scheme 7. Proposed Steps in the Reaction of 4 with I2 under CO Atmosphere
the effect of CO on the selectivity of the reaction between 4 and
I2 in THF at 298 K, an experiment was performed in the absence
of external CO. This afforded, after 1 h of reaction, complex 26 in
>95% spectroscopic yield and only traces (<5%) of 28,57
indicating a beneficial effect of CO for directing the iodination of
4 toward the product of phenyl transfer 28.
of 4 with I2 or HCl are depicted in Scheme 7 and in Supporting
Information, Scheme S1, respectively.
To substantiate the mechanism proposed for explaining the
similar reactivity exhibited by 4 with I2 or HCl, we investigated
the reaction of CO alone with complex 4. Placing a THF solution
of 4 under CO at 298 K caused the formation of a new species,
whose spectroscopic features are compatible with the formula
proposed for 4-CO. The 31P{1H} spectrum of the solution
showed, beside signals ascribed to 4, two mutually coupled
doublets (2JP,P = 67 Hz) at δ 81.6 and δ 118.7, the latter flanked
by 195Pt satellites (1JP,Pt = 2403 Hz), in a 4-CO/4 integral ratio of
20:80, and ascribable to P2 and P1 of 4-CO, respectively (see
Scheme 7 for numbering). Moreover, by performing the
The phenyl transfer back from Pt to P1 was also observed when
4 was reacted with gaseous HCl. The reaction, performed in
THF under 1 atm of CO led, after 20 h, to a mixture containing
20% of 2, the product of phenyl migration from platinum to
phosphorus, analogous to 28, and ca. 80% of 29 (Scheme 6).
When performed in the absence of external CO, the same
reaction led quantitatively to 29, with formation of benzene (gas
chromatography-mass spectrometry). Monitoring the reaction
between 4 and HCl/CO revealed that 2 forms at an early stage of
the reaction, and as soon as 4 is consumed (less than 20 min), the
amount of 2 in solution remains steady, while the monochlorido
species 22 is converted into 29 by the excess of HCl. The
intermediacy of 22 also shows that the Mo−Pt bond in 4 is more
reactive toward HCl(g) than the more covalent Pt−Ph bond.
The identical yield of the phenyl migration product (20%) and
the nonphenyl-migrated product (80%) for both the I2/CO
(Scheme 5) and the HCl/CO reactions (Scheme 6) suggests a
common mechanism, in which the presence of CO plays a crucial
role. Thus, it is conceivable that 4 could give rise to the equili-
brium depicted in Scheme 7 where CO reversibly coordinates to
the Pt center of the ion pair, displacing the sulfur atom. The
outcome of the reactions with I2 (or HCl) can be rationalized by
assuming that the carbonylated product 4-CO is present in the
equilibrium mixture in a ca. 20% amount and that complex 4-CO
is the precursor to the migration products 28 (or 2), while the
remaining 80% of 4 is the precursor to the dinuclear species 26
and 27 (or 22 and 29). The pathways proposed for the reaction
carbonylation of 4 with 13CO, it was possible to detect the 13
C
NMR signal of the Pt-bound carbonyl of 4-CO as a doublet
(2JC,P = 3 Hz) at δ 183.9 flanked by 195Pt satellites (1JC,Pt = 1014 Hz).
The appearance of the signal at δ 118.7 as a doublet (and
not as a doublet of doublets) also when 13CO was used, along
with the small value found for the geminal 13C−31P coupling
constant (3 Hz, not resolved in the 31P NMR spectrum owing to
the broadness of the P1 signal) indicates that the carbonyl ligand
replaces the sulfur atom rather than the Mo(CO)3Cp anion, thus
substantiating the formula proposed for 4-CO.
According to Scheme 7, the carbonylated species 4-CO could
react with iodine to give intermediate A, which, in turn, can give
28 by loss of the Mo1(CO)2Cp fragment (in the form of
[MoI(CO)3Cp]), phenyl transfer back to P1, and coordination of
P2 and of an external iodide (not necessarily in this sequence).
Although the collected data are insufficient to determine with
certainty the reaction profile for the transformation from 4-CO
to 28, we propose that the phenyl transfer occurs after loss of the
Mo1(CO)2Cp fragment that leaves the Pt-bound P1 atom with a
phosphenium character favorable to accept aryl migration.58,59
I
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Scheme 8. Proposed Mechanism for the Formation of the Bridged and Chelated Trinuclear PtM2 Clusters
2.4. Density Functional Theory Studies. Density func-
tional theory (DFT) calculations at the M06/LACV3P+
+**//M06/LACVP* level were performed to study the
thermodynamics of the transformations and trace a possible
mechanism for the formation of the condensed six-membered
platinacycle and four-membered M′−P−N−P-cycle complexes
3−4 and 9−10, explaining the role of the sulfur on the
N-substituted dppa ligand.
In a recent DFT study on the reactivity of mononuclear Pt
complexes analogous to 1 and 2, but containing a n-decyl-
substituted dppa, with Na[M(CO)3Cp], which led only to the
formation of dinuclear PtM (analogous to 15−18) and trinuclear
PtM2 (analogous to 5−8 and 11−14) complexes, we found
geometries and relative stabilities of the chelated and bridged
isomers of the PtM2 clusters in good agreement with all the
experimental data available, thus showing that the M06/
LACV3P++**//M06/LACVP* level of theory employed
was sufficiently adequate to deal with this class of trinuclear
complexes.3
The reliability of this level of theory in reproducing also the
geometrical parameters of the new six-membered platinacycle
complexes was confirmed by a geometry optimization of the
structurally characterized complexes 4 and 9, which gave bond
lengths and angles within 0.06 Å and 4°, respectively, of the
experimental data.
On the basis of experimental data and DFT calculations, we
also proposed a reaction mechanism for the formation of the
dinuclear PtM and the triangular PtM2 species, the only products
isolated when an n-decyl-substituted dppa ligand was employed.3
An analogous mechanism, see Scheme 8, is suggested for the
reaction of 1,2 with Na[M(CO)3Cp], which leads to the
monosubstitution products 15−18 and to the chelated 5,6 and
11,12 and bridged 7,8 and 13,14 trinuclear clusters, while the
formation of the final complexes 3,4 and 9,10 allegedly occurs
from one of the intermediates in this mechanism through the
intervention of the sulfur atom of the thioether dppa substituent.
Accordingly, the first step would consist of the nucleophilic
substitution of the [M(CO)3Cp]− anion for a Cl− ligand of 1 or
2, leading to the corresponding monosubstitution dinuclear
products 15−18: two possible isomers can be formed for each
of these dinuclear species, 15−18 and B, corresponding to the
chelate or bridged coordination of the diphosphanylamine.
These monosubstituted complexes undergo a second nucleo-
philic substitution step whereby the remaining chloride ligand on
Pt is replaced by the second [M(CO)3Cp]− anion. The second
substitution on the bridged isomer B is expected to lead to a
trinuclear chain complex C, observed only for R = H,5 which then
loses a carbonyl group and forms a M−M bond to give the
bridged clusters 7,8 or 13,14. The second substitution on the
chelate isomer 15 is instead expected to lead to a trinuclear PtM2
species D whose evolution may follow two different pathways:
(i) formation of a M−M bond between the two cis M(CO)3Cp
groups with loss of a carbonyl ligand and migration of a carbonyl
to a bridging position, resulting in the chelate clusters: 5,6 or
11,12 (path 1); (ii) shift of one of the phosphorus atoms from Pt
to the adjacent M atom with simultaneous migration of a CO
from the P-bonded M to the Pt centerthat is, change in the
coordination of the N-substituted dppa from chelated to
bridgedleading to the linear chain complexes C, which
would then evolve to the bridged clusters 7,8 or 13,14 (path 2).
We first calculated the thermodynamics of the formation of the
monosubstitution products 15−18, the chelated triangular
J
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a
Table 4. Relative Enthalpies and Free Energies in THF
15−18
B
D
C
7,8 and 13,14
5,6 and 11,12
3,4 and 9,10
Enthalpy
M = Mo, R = (CH2)5CH3
M = Mo, R = CH2Ph
M = W, R = (CH2)5CH3
M = W, R = CH2Ph
−35.7
−40.1
−36.1
−38.1
−28.7
−33.4
−27.9
−31.5
−66.7
−70.0
−54.2
−69.8
−73.2
−72.6
−70.1
−72.8
−49.3
−50.0
−45.1
−46.7
−55.5
−54.9
−54.2
−54.1
−61.3
−63.2
−62.0
−63.7
Free Energy
M = Mo, R = (CH2)5CH3
M = Mo, R = CH2Ph
M = W, R = (CH2)5CH3
M = W, R = CH2Ph
−23.6
−28.0
−24.0
−25.5
−14.6
−19.1
−15.2
−17.0
−38.3
−44.3
−34.0
−43.6
−41.9
−30.9
−34.1
−26.2
−30.9
−40.0
−39.9
−34.0
39.0
−43.5
−49.7
−43.7
−50.1
−47.4
−41.1
−45.4
a
The tabulated values correspond to the formation of the dinuclear PtM species 15−18, the triangular PtM2 clusters 7,8, 13,14 (chelated) and 5,6,
11,12 (bridged), the intermediates B−D, and to the six-membered platinacycle complexes 3, 4, 9, and 10 obtained from the mononuclear Pt
complexes 1, 2, and 1 or 2 equiv of Na[M(CO)3Cp], according to the mechanism reported in Scheme 8.
Figure 7. Enthalpy profile for the formation in THF of the dinuclear PtMo species 15, the triangular PtMo2 clusters 7 (chelated) and 5 (bridged), the
foreseen intermediates B−D, and the six-membered platinacycle complex 3 from the mononuclear Pt complex 1 and 1 or 2 equiv of Na[Mo(CO)3Cp],
according to the mechanism reported in Scheme 8 (data for M = Mo and R′ = CH2CH2S(CH2)5CH3).
clusters 5,6 and 11,12, the bridged clusters 7,8 and 13,14, and
also of the six-membered platinacycle complexes 3,4 and 9,10,
resulting from the reaction of the mononuclear Pt complexes 1,2
with 1 or 2 equiv of Na[M(CO)3Cp].
formation being the entropic gain due to the loss of a CO
molecule.
To gain more insight into the mechanism of formation of the
six-membered platinacycle complexes 3,4 and 9,10 from the
mononuclear Pt complexes 1,2, we performed DFT calculations
on several plausible mechanisms envisaged on the basis of the
experimental data. It is important to remember that the skeletal
rearrangement observed in the formation of these six-membered
platinacycle complexes did not occur with the analogous
complexes where the dppa ligand is substituted with the
n-decyl chain, which points to a key role of the sulfur donor in
triggering this reaction. Moreover, the failure of an external
thioether ligand to facilitate P−C bond activation in a manner
similar to that observed for the synthesis of 3,4 and 9,10,
indicates the importance of the chelate effect of the potentially
tridentate (PSP) ligand which, from a theoretical point of view,
The relative enthalpies and free energies of the species
involved in this mechanism are reported in Table 4, and shown
for M = Mo and R = (CH2)5CH3 in Figures 7 and Supporting
Information, Figure S18. It is apparent that both chloride sub-
stitution steps are exothermic and exoergonic and that the six-
membered platinacycle complexes are 10−20 kcal mol−1 more
stable in free energy than the bridged or chelated trinuclear
clusters. Moreover, as already found for the analogous complexes
with a simple n-decyl chain on the dppa ligand, the linear chain
intermediate C is significantly more stable than both isomers of
the trinuclear clusters, and to a lesser extent than the six-
membered platinacycle complexes, the driving force for their
K
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Scheme 9. A Possible Mechanism for the Formation of the Six-Membered Platinacycle Complexes 3, 4, 9, and 10 Starting from
a
Species C
a
Two different pathways can be considered, a or a′, see text.
underlines the key role played by entropy in the limiting step of
the reaction.
sulfur atom of the N-substituted dppa ligand, indicated a large
energy increase, above 40 kcal/mol, thus ruling out this
possibility.
Even with this limitation, several possible reaction mechanisms
can be envisaged for the sulfur-triggered phenyl migration
leading to the formation of 3−4, 9−10. In principle, the
migration could occur starting from (i) the initial reactants 1,2;
(ii) the monosubstitution products 15−18; (iii) the chelated
trinuclear clusters 5,6, 11,12; (iv) the bridged trinuclear clusters
7,8, 13,14; (v) any of the stable intermediates B−D in Scheme 8;
upon intramolecular sulfur attack followed by phenyl migration
and further steps and/or rearrangements depending on the
starting molecule.
A closer look at the structure of the six-membered platinacycle
points out that the two M metals are far apart from each other
and that the PNP ligand is bonded to the Pt and to one of the M
centers, suggesting as plausible starting species for the phenyl
migration a bridged PtM2 species in which the two M metals are
not bound to each other, as in intermediate C. The mono-
substitution intermediate B should also be taken into account as
starting species for the phenyl migration, provided that the
second metalate substitution occurs after phenyl migration.
Intermediate C is probably the most plausible candidate for the
initial phenyl migration as it is the most stable species identified
(see Table 4), and only two additional steps, a Pt−M bond
breaking and a CO decoordination, are required for the
formation of the six-membered platinacycle. A simple mecha-
nism can be devised starting from C that consists of the following
steps: the breaking of the Pt−MP bond, stabilized by a CO bridge
between Pt and the P-bound M center, which is assisted (a) or
followed (a′) by the intramolecular coordination of the sulfur
atom to Pt with CO migration from Pt to M; (b) the subsequent
phenyl migration from P to the unsatured Pt center; (c) the final
coordination of the P atom already bound to Pt to the Mo center
with loss of the M-bound CO, see Scheme 9.
Another candidate for the phenyl migration is the bridged
isomer B of the monosubstitution products 15−18, see
Scheme 8, with the second metalate substitution occurring
after phenyl migration. This possibility is supported by the
following experimental evidence: (i) the isolation of the
dinuclear PtM species 15−18 upon reaction of 1,2 with only 1
equiv of Na[M(CO)3Cp]; (ii) the reaction of 3,4, 9,10 with
halide sources gives the dinuclear products 21−26, maintaining
the same six-membered platinacycle but with the Pt-bound
[M(CO)3Cp] moiety replaced by Cl. After several attempts, we
found a plausible inner redox mechanism whereby an initial
heterolytic breaking of the Pt−M bond occurs from the bridged
isomer B leading to the unstable species E and changing the
initial metal formal oxidation states, Pt(II) and M(0),
respectively, to Pt(0) and M(II). The shift of the Mo−Pt bond
electron pair to the Pt atom upon breaking is testified by the
changes of Mulliken charges on the metal atoms (from +0.120 on
Pt and +0.040 on Mo in B to −0.070 on Pt and +0.247 on Mo
in E), see Supporting Information, Table S1. This process is
assisted by the approach of a second sodium metalate with the
substitution of the chloride on Pt. The mechanism proceeds with
(i) the intramolecular coordination of the sulfur atom of the
N-substituted dppa ligand to the coordinatively unsaturated
Pt(0) center and (ii) the P to Pt phenyl migration, and is
completed (iii) by the coordination of the P atom previously
bound to Pt to the M center (Scheme 10). The key step for the P
to Pt phenyl migration can be viewed as a P−Ph oxidative
addition to the metal center, which is favored by a transiently
formed Pt(0) species and by the lenghtening of one of the
carbonyl−MoII bond.
A careful scrutiny by DFT calculations for M = Mo confirmed
the feasibility of such a mechanism. Calculations were performed
on the intermediate B and on all the species involved in each of
However, preliminary calculations on the breaking of the bond
between Pt and the P-substituted M atom, with or without
simultaneous intramolecular coordination of the Pt center by the
L
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a
Scheme 10. Proposed Mechanism for the Formation of the Six-Membered Platinacycles Products
a
Enthalpies and free energies (in kcal mol−1) are reported for the compounds with M = Mo and R = (CH2)5CH3 in THF.
the above steps, including the identification of possible transition
states for the key steps, and the evaluation of all their energies.
The calculated enthalpies and free energies of all the
intermediates and main transition states involved in this mecha-
nism are reported in Scheme 10 and Figure 8 for M = Mo and
R = (CH2)5CH3 and show that the highest barrier corresponds to
the breaking of the Pt−Mo bond with a value of 22 kcal·mol−1 in
enthalpy (26 kcal·mol−1 in free energy). The height of these
barriers indicates a very slow kinetics at room temperature, which
is consistent with the occurrence of this reaction at 323 K but not
M
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Article
Figure 8. Free energy profile (in kcal·mol−1), in THF, for the formation of the six-membered platinacycles product 3 from intermediate B, according to
the mechanism of Scheme 10.
at 273 K. In fact, performing the reactions of 1 or 2 with
Na[M(CO)3Cp] at 273 K in THF afforded, after 24 h, only the
monosubstituted species 15−18.
It is worth noting that the highest minimum in the potential
energy surface from which the phenyl migration is triggered, H, is
a rather unstable species with platinum already coordinated by
the sulfur atom and a carbonyl group of the P-bound Mo unit
loosely bonded to M (calculated C−Mo distance = 2.283 Å). Its
structure is quite close to the corresponding transition state as is
its energy, only 5 kcal·mol−1 below in enthalpy (5 kcal·mol−1 in
free energy). The driving force for the migration of the phenyl
cation can be therefore the increased negative charge borne by
the Pt(0) metal center upon S coordination (−0.08 e). The
phenyl migration also leads to a significant increase of the metal
charge (+0.12 e) in line with the proposed increase of the Pt
formal oxidation number from 0 in H to +2 in I (see Mulliken
charges in Supporting Information, Table S1).
To substantiate the mechanism proposed by DFT calculations,
we monitored by 31P{1H} NMR THF solutions of 1 or 2 to
which Na[Mo(CO)3Cp] or Na[W(CO)3Cp] were successively
Figure 9. Course of the reaction between 2 and Na[Mo(CO)3Cp].
added at 323 K. Figure 9 shows the course of the reaction
between 2 and Na[Mo(CO)3Cp]. It is apparent that in the early
stage of the reaction (1 equiv of Na[Mo(CO)3Cp] added), the
starting material is converted into the monochlorido species 16,
which, as soon as it accumulates in solution, evolves toward the
phosphanido-bridged complex 4, which constitutes the major
reaction product, along with the chelate species 6 and the bridged
cluster 8. After 2.2 equiv of Na[Mo(CO)3Cp] were added, the
reaction solution contained ∼70% of 4, along with 13% of 6 and
10% of 8, plus other unidentified decomposition compounds.
Prolonged reaction times resulted only in extensive decom-
position of 6 and 8. The monitoring of the reaction between 1
and Na[Mo(CO)3Cp] gave comparable results (Supporting
Information, Figure S19). In the case of the tungsten species,
the reaction is less selective toward the formation of the
N
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corresponding phosphanido-bridged complexes, and the decom-
position of the chelate and bridged species at long reaction times
is more pronounced. The solution obtained after addition of
2.2 equiv of Na[W(CO)3Cp] to 1 (Figure 10) contained ∼34%
in the 31P{1H} NMR spectrum and by a doublet centered at δ
−3599 in the 195Pt{1H} NMR spectrum. The absence of 183W
satellites for the 31P{1H} NMR signals, together with the simi-
larity of 195Pt{1H} NMR chemical shift with that of the PtW2
complex 10 (δ −3605), indicate that the new species is
the phosphanido bridged complex 31 in which a Mo atom is
chelated by the two P atoms, and a W atom is bonded to Pt
(Scheme 11).61
The formation of 31 indicates that of the 2 equiv of metalate
necessary to form the phosphanido-bridged species 3, 4, 9, and
10, the first one contains the metal atom to become chelated by
the two P atoms (M1 in Scheme 2), and the second one contains
the metal atom bonded to platinum (i.e., M2 in Scheme 2) in the
final products. This is in accord with the mechanism outlined in
Scheme 10, where the Mo chelated by the two P atoms arises
from the Mo present in the monochlorido species 15, while the
Mo atom bound to Pt in the final products originates from the
second equivalent of metalate. The formation of the
phosphanido-bridged complex 30 in which a W atom is chelated
by the two P atoms, and a Mo atom is bonded to Pt (see headings
of Table 4), was detected by performing the sequential reaction
of 2 with first Na[W(CO)3Cp] and then Na[Mo(CO)3Cp].
However, the addition of Na[Mo(CO)3Cp] to a solution
containing mostly the monochlorido complex 17 led to a partial
substitution of the Mo for the W yielding 16. The reaction of 16
and 17, contemporarily present in solution together with
Na[Mo(CO)3Cp] and Na[W(CO)3Cp], afforded 31 (18%), 4
(14%), and 10 (14%), besides 30 (17%)62 (see Table 5 for the
associated NMR features).
Figure 10. Course of the reaction between 1 and Na[W(CO)3Cp].
of the phosphanido-bridged complex 9, along with 32% of 13 and
12% of 11, plus other unidentified decomposition compounds.
The monitoring of the reaction between 2 and Na[W(CO)3Cp]
gave comparable results (Supporting Information, Figure S20).
The contemporary formation of chelate, bridged, and
phosphanido-bridged species observed during reaction monitor-
ing suggests that the chelate and bridged species are not pre-
cursors to the phosphanido-bridged complexes, in accord with
the DFT mechanism.
Another clue to the mechanism proposed by DFT methods
stemmed from the sequential reaction of 2 with first Na[Mo-
(CO)3Cp] and then Na[W(CO)3Cp]. For this experiment, to
a THF solution of 2 kept at 323 K was added 1.0 equiv of
Na[Mo(CO)3Cp], causing the formation of the monochlorido
complex 16 (90%) plus minor amounts of 4, 6, and 8. The
subsequent addition of 1.0 equiv of Na[W(CO)3Cp] resulted in
the formation of a new species, in ca. 60% spectroscopic yield,60
characterized by two doublets at δ 90.1 and δ 73.0 (JP,P = 68 Hz)
3. CONCLUSIONS
A major result from this work has been the demonstration that
the presence of a thioether function in the N-substituent of dppa-
type ligands chelated to Pt(II) complexes dramatically influences
the nature of the reaction products with carbonylmetalates
such as [Mo(CO)3Cp]− or [W(CO)3Cp]−. This unexpected
influence was clearly demonstrated by comparison with similar
reactions performed with dppa-type ligands having a
N-substituent alkyl chain of similar length than the thioether
group. Whereas in both cases formation of the expected Pt−M
bonds was observed, only when the thioether function was
present did we observe a thermally induced transfer of a phenyl
group from a PPh2 group to platinum. Furthermore, it was shown
that the corresponding P−C bond activation reaction could be
Scheme 11. Sequential Reaction of 2 with First Na[W(CO)3Cp] and Then Na[Mo(CO)3Cp]
O
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Table 5. 31P{1H} NMR Features of the Trinuclear Complexes
4, 10, 30, and 31 (THF, 298 K)
Multinuclear NMR spectra were recorded with a Bruker Avance 400
spectrometer (400 MHz for 1H) at 298 K; chemical shifts are reported in
parts per million referenced to SiMe4 for 1H and 13C, to H3PO4 for 31P,
and to H2PtCl6 for 195Pt. The signal attributions and coupling constant
assessment was made on the basis of a multinuclear NMR analysis
including, beside one-dimensional spectra, 31P{1H} COSY, 1H COSY,
1H NOESY, 1H−13C HMQC, 1H−13C HMBC, 1H−31P HMQC,
1H−195Pt HMQC. The IR spectra were recorded with Bruker Vector 22
or Jasco FT-IR-4200 spectrometers. High-resolution mass spectrometry
(HRMS) and MS/MS analyses were performed using a time-of-flight
mass spectrometer equipped with an electrospray ion source (Bruker
micrOTOF-Q II). The analyses were performed in a positive ion mode.
The sample solutions were introduced by continuous infusion with the
aid of a syringe pump at a flow rate of 180 μL/h. The instrument was
operated at end plate offset −500 V and capillary −4500 V. Nebulizer
pressure was 0.3 bar (N2), and the drying gas (N2) flow was 4 L/min.
Drying gas temperature was set at 453 K. The software used for the
simulations is Bruker Daltonics DataAnalysis (version 4.0). C, H, and N
elemental analyses were performed with a Eurovector CHNS-O EA3000
Elemental Analyzer. Cl elemental analysis was performed by poten-
tiometric titration using a Metrohm DMS Titrino. The complexes
[PtCl2{(Ph2P)2N(CH2CH2SR)-PP}] [R = CH2C6H5, (CH2)5CH3],8
[PtI2(cod)],63 Na[M(CO)3Cp] (M = Mo, W, as 1,2-dimethoxyhethane
solvates),64 and the diphosphanylamine (Ph2P)2N(CH2)2SCH2Ph8
were prepared by literature methods. Gaseous HCl was prepared by
action of concentrated sulfuric acid on solid NaCl.
δ P1,
ppm
δ P2,
ppm
2JP,P
Hz
,
1JP,Pt
Hz
,
δ Pt,
ppm
compound M1
M2
4
Mo
W
Mo
W
88.7
60.0
58.1
90.1
73.1
41.5
41.5
73.0
68
55
57
68
2819
2875
2811
2798
−3517
−3605
−3514
−3599
10
30
31
W
Mo
W
Mo
made reversible upon oxidation with iodine or protonation. Such
thermally or chemically triggered transformations in hetero-
metallic complexes are relevant not only to the synthesis of novel
architectures but also to elementary steps that may occur under
catalytic conditions. Furthermore, they provide direct evidence
for the occurrence of synergistic effects in polynuclear com-
plexes, in particular, in heterometallic systems. Spectroscopic
and/or structural investigations by X-ray diffraction have
established the nature of the complexes described in this work
and a theoretical study by DFT methods has allowed us to
suggest mechanistic pathways for the transformations observed
experimentally.
X-ray Crystallography.65 Crystal data, parameters for intensity
data collection, and convergence results for 9 and 4 are compiled in
Table 6. Diffraction-quality crystals were obtained by slow diffusion of
n-hexane into THF solutions of the compounds. Data were collected
with Mo Kα radiation (λ = 0.710 73 Å) on a Bruker D8 goniometer with
SMART CCD area detector; radiation sources were a sealed tube for the
intensity data of 4 and an INCOATEC microsource with multilayer
optics in the case of 9. Multiscan-based absorption corrections were
performed with the help of the program SADABS.66 The structures were
4. EXPERIMENTAL SECTION
All manipulations were conducted under an inert gas (argon) using
standard Schlenk techniques. Solvents were dried and distilled under
argon according to standard procedures.
Table 6. Crystallographic Data and Structural Refinement Details for 9 and 4
9
4
empirical formula
formula mass
temperature [K]
approx. crystal dimensions [mm]
wavelength [Å]
crystal system
space group
unit cell dimensions
a [Å]
C49H51NO5.5P2PtSW2
1398.70
C48H41Mo2NO5P2PtS
1192.79
100(2)
193(2)
0.17 × 0.03 × 0.03
0.710 73
0.3 × 0.3 × 0.2
0.710 73
triclinic
triclinic
P1
P1
̅
̅
11.5033(8)
13.1859(9)
16.4015(11)
68.7160(10)
77.7450(10)
78.5260(10)
2244.9(3)
2
8.9112(9)
12.4727(13)
20.138(2)
87.646(2)
87.333(2)
80.118(2)
2201.4(4)
2
b [Å]
c [Å]
α [deg]
β [deg]
γ [deg]
V [Å3]
Z
D
calcd. [Mg m−3
]
2.069
1.799
absorption coeff. [mm−1
]
8.387
3.899
θ range for data coll. [deg]
collected reflections
1.67 to 28.60
40 879
2.32 to 27.04
27 717
independent reflections (Rint)
data/parameters
11 373 (0.0883)
11 373/549
0.995
9563 (0.0575)
9563/541
1.005
GOF on F2
a
R
(I > 2σ(I))
0.0395
0.0398
b
wR2 (all data)
0.0792
0.0644
largest diff. peak/hole [e·Å−3
]
2.840−2.512
1.243−0.668
a
b
2
2
R = ∑||F0| − |Fc||/∑|F0|. wR2 = [∑w(F0 − Fc2)2/∑w(F0 )2]1/2
.
P
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solved by direct methods and refined with full-matrix least-squares on
F2.67 A total of 77 rigid-bond restraints68 were employed in the re-
finement of 9 to ensure physically acceptable displacement parameters.
Synthesis of the Monosubstituted Complexes 15−18. An
acetonitrile solution (7 mL) of Na[Mo(CO)3Cp]·2DME (69 mg,
0.155 mmol; DME = 1,2-dimethoxyethane) was added dropwise to a
stirred solution of 1 (95 mg, 0.146 mmol) in acetonitrile (3.0 mL) and
kept at 323 K. The pale yellow solution turned immediately orange, and
after it was stirred for 1 h, the mixture was cooled; analysis by NMR and
HRMS revealed the quantitative transformation into 15 (spectroscopic
yield >95%). Removal of the solvent and treatment with toluene to
purify the product resulted in partial conversion of 15 into 5+7 due to
the slight excess of metalate used. The same procedure was followed for
the synthesis of 16−18. The atom numbering of the sketch in Chart 1
was used for the NMR characterization.
νCO (THF)/cm−1: 1792 (vs), 1894 (vs), 1976 (vs). 1H NMR (THF-d8,
298 K): δ 8.49 (ddd, 3JH,P = 11 Hz, 3JH,H = 8 Hz, 4JH,H = 1 Hz, 2H, ortho
HringB), 7.96 (ddd, 3JH,P = 11 Hz, 3JH,H = 8 Hz, 4JH,H = 1 Hz, 2H, ortho
HringC), 7.56 (overlapped, 6H, ortho HringD + ortho Hri3ngA + meta HringC),
7.50 (overlapped, 1H, para HringC), 7.43 (pseudo t, JH,H = 8 Hz, 2H,
meta-HringB), 7.33 (overlapped, 3H, meta HringD + para-HringB), 7.17 (m,
1H, para HringD), 7.06 (m, 3H, meta + para- Hbenzyl ring), 6.91 (m, 2H,
ortho- Hbenzyl ring), 6.83 (broad, 2H, meta-HringA), 6.67 (td, 3JH,H = 7 Hz,
4JH,H = 1 Hz, 1H, para-HringA), 4.79 (d, 4JH,P = 0.6 Hz, 5 H, Cp-Mo1), 4.73
(s, 5 H, Cp-Mo2), 4.03 (d, 2JH,H = 14 Hz, 1 H, C6H5HCH-S), 3.28 (d,
2JH,H = 14 Hz, C6H5HCH-S), 3.20 (m, 1H, HCH-N), 3.03 (m, 1H,
HCH-N), 1.93 (m, 1H, S-HCHCH2N), 1.81 (m, 2H, S-HCHCH2N).
13C{1H} APT (THF-d8, 298 K): δ 240.2 (d, JC,P = 26 Hz, CO), 238.4 (d,
JC,P = 26 Hz, CO), 237.7 (br, CO), 235.2 (br, CO), 235.0 (br, CO),
144.1 (br, Cipso), 142.4 (d, br, JC,P = 7 Hz, Cipso), 136.9 (d, JC,P = 38 Hz,
Cipso), 135.2 (s, Cipso), 133.3 (d, JC,P = 14 Hz, CPh), 132.5 (d, JC,P = 47 Hz,
Cipso), 131.6 (d, JC,P = 11 Hz, CPh), 131.0 (d, JC,P = 2 Hz, CPh), 130.8 (d,
JC,P = 10 Hz, CPh), 130.7 (d, JC,P = 3 Hz, CPh), 129.3 (s, CPh), 129.2 (d,
JC,P = 2 Hz, CPh), 129.0 (d, JC,P = 10 Hz, CPh), 128.7 (d, JC,P = 10 Hz,
CPh), 128.3 (s, CPh), 128.1 (s, CPh), 127.8 (s, CPh), 127.7 (s, CPh), 127.4
(s, CPh), 121.4 (s, CPh), 92.4 (s, CCp‑Mo2), 90.6 (s, CCp‑Mo1), 46.3 (s,
CH2N), 38.3 (s, PhCH2S), 25.5 (s, SCH2CH2N). 31P{1H} NMR (THF-
Synthesis of 3. A THF solution (25 mL) of Na[Mo(CO)3Cp]·
2DME (148 mg, 0.33 mmol) was added dropwise within 40 min to a
stirred solution of 1 (150 mg, 0.15 mmol) in THF (3.0 mL) kept at
323 K. The pale yellow solution darkened, and after it was stirred for 4 h,
the mixture was cooled to room temperature and the solvent was
removed under reduced pressure. Toluene (30 mL) was added to the
residue, and the resulting suspension was filtered. The filtrate was
evaporated, and the residue was washed with methanol (2 × 5 mL). Pure
3 was obtained as a dark yellow solid by crystallization from THF/n-
hexane. Yield: 55%. Anal. Calcd for C47H47Mo2NO5P2PtS (3): C 47.56,
H 3.99, N 1.18; Found C 47.61, H 3.94, N 1.12%. HRMS(+) in MeCN/
MeOH (collision energy = 10 eV), exact mass for the cation
[C39H40MoNO2P2PtS]+: 942.1110; measured: m/z: 942.1143 [M−
{Mo(CO)3Cp}]+. HRMS(+) in acetone (collision energy = 2 eV), exact
mass for the cation [C51H56NO6P2PtSMo2]+: 1188.0492 da; measured
m/z: 1188.0368 [M + H]+. IR νCO (KBr)/cm−1: 1779 (vs), 1798 (vs),
1898 (sh), 1889 (vs), 1977 (sh), 1970 (vs) ; νCO (THF)/cm−1: 1788 (vs),
1894 (vs), 1975 (vs).
d8, 298 K): δ 88.7 (d, 2JP,P = 68 Hz, 1JP,Pt = 2819 Hz, P1), 73.1 (d, 2JP,P
68 Hz, P2). 195Pt{1H} NMR (THF-d8, 298 K): δ −3517 (broad d, 1JP,Pt
2819 Hz)
=
=
Synthesis of 9. Complex 9 was prepared using the same procedure
as for 3, starting from Na[W(CO)3Cp]·2DME (177 mg, 0.33 mmol)
and 1 (121 mg, 0.15 mmol). Yield: 36%. Anal. Calcd for
C51H55NO6P2PtSW2 (9·0.5 THF) C 42.08, H 3.68, N 1.00; Found C
42.55, H 3.92, N 0.95%. HRMS(+) in THF/MeOH (collision energy =
10 eV), exact mass for the cation [C40H36NO2P2PtSW]+: 1028.1499;
measured: m/z: 1028.1600 [M−{W(CO)3Cp}]+. HRMS(+) in THF/
MeOH (collision energy = 2 eV), exact mass for the cation
[C47H47NNaO5P2PtSW2]+: 1386.1229 da; measured m/z: 1386.1279
[M + Na]+. IR νCO (KBr)/cm−1: 1773 (vs), 1796 (vs), 1879 (vs), 1889
(vs), 1961 (vs, broad); νCO (THF)/cm−1: 1786 (vs), 1885 (vs), 1967
(vs). 1H NMR (THF-d8, 298 K): δ 8.41 (ddd, 3JH,P = 11 Hz, 3JH,H = 7 Hz,
1H NMR (C6D6, 298 K): δ 8.80 (dd, 3JH,P = 10 Hz, 3JH,H = 8 Hz, 2H,
ortho HringB), 7.99 (ddd, 3JH,P = 11 Hz, 3JH,H = 8 Hz, 4JH,H = 1 Hz, 2H,
ortho HringC), 7.91 (d, 3JH,H = 7 Hz, 3JH,Pt = 50 Hz, 2H, ortho HringA), 7.42
(overlapped, 2H, meta HringC), 7.41 (overlapped, 2H, ortho HringD), 7.39
3
4
(overlapped, 2H, meta HringB), 7.26 (pseudo td, JH,H = 7 Hz, JH,P
=
3
3
4JH,H = 1, 2H, ortho HringB), δ 7.96 (ddd, JH,P = 11 Hz, JH,H = 7 Hz,
4JH,H = 1, 2H, ortho HringC), 7.58 (overlapped, 2H, meta HringC), 7.55
(overlapped, 2H, ortho HringD), 7.51 (overlapped, 2H, meta HringD), 7.49
(overlapped, 1H, para HringC), 7.44 (overlapped, 3H, ortho HringA + para
2 Hz, 2H, meta-HringD), 7.16 (overlapped, 1H, para HringD), 7.14
(overlapped, 1H, para HringC), 7.07 (t, 1H, para-HringB), 6.87 (t, 3JH,H
=
7 Hz, 2H, meta-HringA), 6.71 (t, 3JH,H = 7 Hz, 1H, para-HringA), 4.87 (s,
2
5 H, Cp-Mo1), 4.50 (s, 5 H, Cp-Mo2), 3.09 (ddd, 1H, JH,H = 16 Hz,
3
4
HringD), 7.35 (pseudo td, JH,H = 7 Hz, JH,P = 1 Hz, 2H, meta-HringB),
7.23 (td, 3JH,H = 7, 5JH,P = 1 Hz, 1 H, para-HringB), 6.77 (broad, 2H, meta-
HringA), 6.62 (td, 3JH,H = 7 Hz, 4JH,P = 1 Hz, 1H, para-HringA), 4.92 (s, 5 H,
Cp-W1), 4.75 (s, 5 H, Cp-W2), 3.22 (m, 1H, HCH-N), 3.01 (m, 1H,
3JH,H = 9 Hz, 3JH,H = 6 Hz, C5H11HCH-S), 2.86 (m, 1H, HCH-N), 2.67
(m, 1H, HCH-N), 2.35 (ddd, 1H, 2JH,H = 14 Hz, 3JH,H = 10 Hz, 3JH,H
=
=
4 Hz, C5H11HCH-S, 1.87 (ddd, 1H, 2JH,H = 14 Hz, 3JH,H = 8 Hz, 3JH,H
2
3
2 Hz, S-HCHCH2N), 1.77 (ddd, 1H, JH,H = 14 Hz, JH,H = 7 Hz,
3JH,H = 2 Hz, S-HCHCH2N),1.37−0.99 (8 H, alkyl protons), 0.82 (t,
3JH,H = 7 Hz, 3H, CH3). 13C{1H} APT (THF-d8, 298 K): δ 240.5 (d,
2
3
3
HCH-N), 2.73 (ddd, 1H, JH,H = 16 Hz, JH,H = 10 Hz, JH,H = 6 Hz,
C5H11HCHS), 2.37 (m, 2H, HCHCH2N), 2.24 (ddd, 1H, 2JH,H = 16 Hz,
3JH,H = 10 Hz, JH,H = 6 Hz, C5H11HCHS), 1.43−1.05 (8 H, alkyl
3
J
C,P = 25 Hz, CO), 238.6 (d, JC,P = 26 Hz, CO), 237.0 (br, CO), 235.3
protons), 0.79 (t, JH,H = 7 Hz, 3 H, CH3). 13C{1H} APT (THF-d8,
3
(br, CO), 235.2 (br, CO), 143.7 (br, Cipso), 142.1 (d, br, JC,P = 7 Hz,
Cipso), 137.5 (d, JC,P = 37 Hz, Cipso), 133.5 (d, JC,P = 13 Hz, CPh), 132.9
(d, JC,P = 47 Hz, Cipso), 131.7 (d, JC,P = 12 Hz, CPh), 131.2 (d, JC,P = 2 Hz,
CPh), 131.0 (d, JC,P = 12 Hz, CPh), 130.8 (d, JC,P = 2 Hz, CPh), 129.3 (s,
CPh), 129.2 (s, CPh), 129.1 (s, CPh), 128.8 (d, JC,P = 11 Hz, CPh), 127.9 (s,
CPh), 127.8 (s, CPh), 121.3 (s, CPh), 92.7 (s, CCp‑Mo2), 90.6 (s, CCp‑Mo1),
46.4 (br, CH2N), 33.4 (s, C5H11CH2S), 31.7 (s, CAlk), 31.3 (s, CAlk), 29.9
(s, CAlk), 27.2 (s, CH2CH2N), 22.6 (s, CAlk), 13.6 (s, CH3). 31P{1H}
NMR (THF-d8, 298 K): δ 88.7 (d, 2JP,P = 68 Hz, 1JP,Pt = 2849 Hz, P1),
73.2 (d, 2JP,P = 68 Hz, P2). 195Pt{1H} NMR (THF-d8, 298 K): δ −3508
(broad d, 1JP,Pt = 2849).
Synthesis of 4. Complex 4 was prepared by following the same
procedure used for 3, starting from Na[Mo(CO)3Cp]·2DME (147 mg,
0.33 mmol) and 2 (119 mg, 0.15 mmol). Yield: 71%. Anal. Calcd for
C48H41Mo2NO5P2PtS: C 48.33, H 3.46, N 1.17; found C 48.28, H 3.49,
N 1.11%. HRMS(+) in MeCN/MeOH (collision energy = 10 eV), exact
mass for the cation [C40H36MoNO2P2PtS]+: 948.0641; measured: m/z:
948.0653 [M−{Mo(CO)3Cp}]+. HRMS(+) in acetone (collision
energy = 2 eV), exact mass for the cation [C48H41Mo2NO5P2PtS]+:
1192.9944 da; measured m/z: 1192.9973 [M]+. IR νCO (KBr)/cm−1:
1785 (vs), 1801 (vs), 1873 (vs), 1896 (vs), 1965 (vs), 1974 (vs);
298 K): δ 232.0 (d, JC,P = 20 Hz, CO), δ 230.7 (d, JC,P = 20 Hz, CO), δ
230.3 (br, CO), 229.4 (br, CO), 227.1 (br, CO), 143.7 (d, br, JC,P = 9 Hz,
Cipso), 142.4 (d, br, JC,P = 7 Hz, Cipso), 138.7 (d, JC,P = 43 Hz, Cipso), 135.5
(d, JC,P = 15 Hz, CPh), 133.5 (d, JC,P = 50 Hz, Cipso), 133.0 (d, JC,P = 13
Hz, CPh), 132.8 (d, JC,P = 12 Hz, CPh), 132.5 (s, CPh), 132.3 (s, CPh),
130.7 (s, CPh), 130.5 (s, CPh), 130.4 (s, CPh), 130.0 (d, JC,P = 10 Hz, CPh),
129.1 (s, CPh), 129.0 (s, CPh), 122.7 (s, CPh), 93.0 (s, CCp‑W2), 90.7 (s,
CCp‑W1), 48.4 (br, CH2N), 34.9 (s, C5H11CH2S), 32.8 (s, CAlk), 31.2 (s,
CAlk), 29.9 (s, CAlk), 27.4 (br, CH2CH2N), 23.9 (s, CAlk), 14.9 (s, CH3).
2
1
31P{1H} NMR (THF-d8, 298 K): δ 59.0 (d, JP,P = 55 Hz, JP,Pt
=
2904 Hz, JP,W = 158 Hz, P1), 39.9 (d, JP,P = 55 Hz, JP,W = 231 Hz,
3JP,Pt = 23 Hz, P2). 195Pt{1H} NMR (THF-d8, 298 K): δ −3591 (broad d,
1JP,Pt = 2904 Hz).
1
2
1
Synthesis of 10. Complex 10 was prepared using the same
procedure as for 3, starting from Na[W(CO)3Cp]·2DME (166 mg,
0.31 mmol) and 2 (110 mg, 0.14 mmol). Yield: 34%. Anal. Calcd for
C48H41NO5P2PtSW2: C 42.12, H 3.02, N 1.02; Found: C 42.24, H
3.08, N 0.99%. HRMS(+) in DME/MeOH (collision energy = 10 eV),
exact mass for the cation [C40H36NO2P2PtSW]+ 1034.1080; measured:
m/z: 1034.1094 [M−{W(CO)3Cp}]+. HRMS(+) in DME/MeOH
Q
DOI: 10.1021/acs.inorgchem.5b00223
Inorg. Chem. XXXX, XXX, XXX−XXX

Inorganic Chemistry
Article
(collision energy = 2 eV), exact mass for the cation
[C48H41NO5P2PtSW2]+: 1369.0862 da; measured m/z: 1369.0816
[M]+. IR νCO (KBr)/cm−1: 1781 (vs), 1796 (vs), 1863 (vs), 1893
(vs), 1955 (vs), 1964 (vs); νCO (THF)/cm−1: 1787 (vs), 1885 (vs),
In all cases, 31P NMR analyses (Table 3) showed, after 20 min, the
quantitative formation of the complexes 21, 23, and 24.
Synthesis of 25. Complex 25 was prepared using the same
procedure followed for 22, starting from 4 (22 mg, 0.019 mmol) and
solid [n-Bu4N]Br (6.26 mg, 0.019 mmol). Yield: 60%. Anal. Calcd for
C40H36BrMoNO2P2PtS: C, 46.75; H, 3.53; N, 1.36; Found: C 46.28, H
3.40, N 1.34%. HRMS(+) in MeOH/HCOOH, exact mass for the
cation [C40H36BrKMoNO2P2PtS]+ 1049.9712; measured: m/z:
1049.9718 [M+K]+. The spectrogram showed also an intense peak
due to [M−Br]+ (exp. 948.0636 Da, calculated 948.0641 Da). IR νCO
1966 (vs). 1H NMR (THF-d8, 298 K): δ 8.47 (dd, 3JH,P = 11 Hz, 3JH,H
=
8 Hz, 2H, ortho HringB), 7.92 (dd, 3JH,P = 11 Hz, 3JH,H = 7 Hz, 2H, ortho
HringC), 7.56 (overlapped, 2H, meta HringC), 7.55 (overlapped, 2H, ortho
HringD), 7.47 (overlapped, 5H, para HringC + ortho HringA + meta HringD),
7.41 (overlapped, 3H, para HringD+ meta-HringB), 7.29 (t, 3JH,H = 7, 1 H,
para-HringB), 7.08 (m, 3H, meta + para-Hbenzyl ring), 6.97 (m, 2H, ortho-
Hbenzyl ring), 6.81 (very broad, 2H, meta-HringA), 6.65 (t, 3JH,H = 7 Hz, 1H,
1
(KBr)/cm−1: 1967 (vs), 1894 (vs). H NMR (C6D6, 298 K): δ 8.72
para-HringA), 4.91 (s, 5 H, Cp-W1), 4.79 (s, 5 H, Cp-W2), 4.05 (d, 2JH,H
=
(ddd, 3JH,P = 11 Hz, 3JH,H = 8 Hz, 4JH,H = 1 Hz, 2 H, ortho-HringB), 8.24
(d, 3JH,H = 7 Hz, 4JH,H = 1 Hz, 4JH,Pt = 58 Hz, 2 H, ortho-HringA), 7.64 (m,
ortho-HringC), 7.40 (dd, 3JH,P = 11 Hz, 3JH,H = 8 Hz, 2 H, ortho-HringD),
14 Hz, 1 H, C6H5HCH-S), 3.34 (d, 2JH,H = 14 Hz, C6H5HCH-S), 3.15
(m, 1H, HCH-N), 2.90 (m, 1H, HCH-N), 1.99 (m, 1H, S-HCHCH2N),
1.83 (m, 2H, S-HCHCH2N). 13C{1H} APT (THF-d8, 298 K): δ 231.6
(d, JC,P = 21 Hz, CO), 230.8 (d, JC,P = 21 Hz, CO), 229.1 (br, CO), 227.9
(br, CO), 226.9 (br, CO), 144.2 (d, br, JC,P = 8 Hz, Cipso), 142.7 (d, br,
JC,P = 6 Hz, Cipso), 138.2 (d, JC,P = 44 Hz, Cipso), 137.0 (s, Cipso), 135.3 (d,
JC,P = 14 Hz, CPh), 133.3 (d, JC,P = 51 Hz, Cipso), 133.0 (d, JC,P = 11 Hz,
CPh), 132.6 (d, JC,P = 11 Hz, CPh), 132.5 (d, JC,P = 2 Hz, CPh), 132.3 (d,
JC,P = 2 Hz, CPh), 130.9 (s, CPh), 130.8 (d, JC,P = 2 Hz, CPh), 130.4 (d,
JC,P = 10 Hz, CPh), 130.0 (d, JC,P = 10 Hz, CPh), 129.8 (m, CPh), 129.2 (s,
CPh), 129.1 (s, CPh), 128.9 (s, CPh), 122.8 (s, C, benzyl ring), 92.8
(s, CCp‑W2), 90.8 (s, CCp‑W1), 48.4 (s, CH2N), 39.9 (s, PhCH2S), 26.9 (s,
SCH2CH2N). 31P{1H} NMR (THF-d8, 298 K): δ 60.0 (d, 2JP,P = 55 Hz,
from 7.26 to 7.05 (m, 12 H, meta-HringD + meta-HringA + meta-HringB
para-HringB + para-HringD + para-HringC + ortho-Hbenzyl ring + para-
Hbenzyl ring), from 7.04 to 6.94 (m, 5 H, meta-HringC + meta-Hbenzyl ring
+
+
2
para-HringA), 4.90 (d, JH,H = 14 Hz, 1 H, C6H5HCH-S), 4.55 (s, 5 H,
Cp−Mo1), 4.20 (d, JH,H = 14 Hz, 1 H, C6H5HCH-S), 2.47 (m, 1 H,
2
HCH-N), 2.40 (m, 1 H, HCH-N), 1.58 (m, 1 H, S-HCHCH2N), 1.46
(m, 1 H, S-HCHCH2N). 13C{1H} APT (C6D6, 298 K): δ 244.1 (d, JC,P
=
26 Hz, CO), 239.9 (d, JC,P = 27 Hz, CO), 142.8 (d, JC,P = 9 Hz, Cipso),
140.8 (d, JC,P = 14 Hz, Cipso), 140.1 (d, JC,P = 4 Hz, CPh), 137.9 (d, JC,P
38 Hz, Cipso), 136.0 (s, Cipso), 135.7 (d, JC,P = 12 Hz, CPh), 131.7 (d, JC,P
=
=
44 Hz, Cipso), 131.6 (d, JC,P = 10 Hz CPh), 130.9 (d, JC,P = 14 Hz, CPh),
130.7 (d, JC,P = 12 Hz, CPh), 130.1 (s, CPh), 129.9 (s, CPh), 128.9 (d,
JC,P = 10 Hz, CPh), 128.6 (s, CPh), 128.5 (s, CPh),128.4 (d, JC,P = 9 Hz,
CPh), 128.0 (s, CPh), 127.6 (s, CPh), 126.9 (s, CPh), 122.9 (s, CPh) 94.3 (s,
CCp‑Mo), 46.4 (s, CH2N), 41.3 (s, PhCH2S), 23.9 (s, SCH2CH2N).
31P{1H} NMR (C6D6, 298 K): δ 76.6 (d, 2JP,P = 74 Hz, 1JP,Pt = 3560 Hz,
P1), 74.8 (d, 2JP,P = 74 Hz, P2). 195Pt{1H} NMR (C6D6, 298 K): δ −4110
(d, 1JP,Pt = 3560 Hz).
1
2
1
1JP,Pt = 2875 Hz, JP,W = 156 Hz, P1), 41.5 (d, JP,P = 55 Hz, JP,W
=
230 Hz, 3JP,Pt = 20 Hz, P2). 195Pt{1H} NMR (THF, 298 K): δ −3605 (d,
1JP,Pt = 2875 Hz).
Synthesis of Complexes 21−24. Solid [n-Bu4N]Cl (11 mg,
0.041 mmol) was added at room temperature to a stirred solution of 4
(46 mg, 0.041 mmol) in THF (3.0 mL). After it was stirred for 30 min,
the brown solution turned dark red. To oxidize [n-Bu4N][Mo-
(CO)3Cp], pure dioxygen (10 mL, 298 K, 1 atm) was bubbled into
the solution through a gas-tight syringe causing, after further 30 min of
stirring, the formation of a red suspension. The solvent was removed
under reduced pressure, and the residue was treated with a 1:1 mixture
of toluene and n-hexane (2.0 mL + 2.0 mL) five times; these fractions
were collected. The yellow toluene/n-hexane solution was evaporated to
dryness, and crystallization from THF/hexane yielded pure 22 as a
yellow solid. Yield 57%. Anal. Calcd for C40H36ClMoNO2P2PtS C 48.86,
H 3.69, Cl 3.61, N 1.42; Found: C 48.78, H 3.60, Cl 3.54, N 1.36%.
HRMS(+) in MeOH/HCOOH, exact mass for the cation
[C40H36ClKMoNO2P2PtS]+ 1021.9959; measured: m/z: 1021.9950
[M+K]+. The spectrogram showed also an intense peak due to [M−Cl]+
(experimental 948.0622 Da, calculated 948.0641 Da) and a peak due to
the [2M−Cl]+ (exp. 1931.0962 Da, calculated 1931.0979 Da). IR νCO
(Nujol)/cm−1: 1965 (vs), 1893 (vs); νPt−Cl (Nujol)/cm−1: 280 (m). 1H
Synthesis of 26. Complex 26 was prepared using the same
procedure as followed for 22, starting from 4 (22 mg, 0.019 mmol) and
solid [n-Bu4N]I (7 mg, 0.019 mmol). Yield: 63%. Anal. Calcd for
C40H36IMoNO2P2PtS: C, 44.70; H, 3.38; N, 1.30; Found: C 44.38, H
3.20, N 1.33%. HRMS(+) in MeOH/HCOOH, exact mass for the
cation [C40H36IKMoNO2P2PtS]+ 1097.9583; measured: m/z:
1097.9584 [M+K]+. The spectrogram showed also an intense peak
due to [M−I]+ (exp. 948.0640 Da, calculated 948.0641 Da). IR νCO
1
(Nujol)/cm−1: 1966 (vs), 1892 (vs). H NMR (C6D6, 298 K): δ 8.76
(ddd, 3JH,P = 11 Hz, 3JH,H = 7 Hz, 4JH,H = 1 Hz, 2 H, ortho-HringB), 8.29
(d, 3JH,H = 7 Hz, 4JH,H = 1 Hz, 4JH,Pt = 67 Hz, 2 H, ortho-HringA), δ 7.70
(m, ortho-HringC), 7.36 (ddd, 3JH,P = 12 Hz, 3JH,H = 7 Hz, 4JH,H = 1 Hz,
2 H, ortho-HringD), from 7.26 to 7.04 (m, 10 H, meta-HringD + meta-
HringA + meta-HringB + para-HringB + para-HringD + ortho-Hbenzyl ring), 6.99
(m, 4 H, meta-HringC + para-HringC + para-Hbenzyl ring), 6.94 (m, 3 H,
meta-Hbenzyl ring + para-HringA), 5.02 (d, 2JH,H = 14 Hz, 1 H, C6H5HCH-S),
NMR (CDCl3, 298 K): δ 8.55 (ddd, 3JH,P = 11 Hz, 3JH,H = 8 Hz, 4JH,H
1 Hz, 2H, ortho-HringB), 7.76 (ddd, 3JH,P = 11 Hz, 3JH,H = 8 Hz, 4JH,H
1 Hz, 2H, ortho-HringC), from 7.64 to 7.47 (m, 10 H, ortho-HringD
=
=
+
2
4.56 (s, 5 H, Cp−Mo1), 3.96 (d, JH,H = 14 Hz, 1 H, C6H5HCH-S),
2.63 (m, 1 H, HCH-N), 2.55 (m, 1 H, HCH-N), 1.40 (m, 2 H,
S−CH2CH2N). 13C{1H} APT (C6D6, 298 K): δ 243.4 (m, CO), 239.7
(m, CO), 141.9 (d, JC,P = 7 Hz, Cipso), 141.8 (d, br, JC,P = 7 Hz, Cipso),
137.6 (d, JC,P = 38 Hz, Cipso), 136.2 (s, Cipso), 135.5 (m, CPh), 131.6 (m,
Cipso), 131.3 (d, JC,P = 11 Hz, CPh), 131.2 (broad, CPh), 131.0 (d, JC,P = 10
Hz, CPh), 130.9 (d, JC,P = 2 Hz, CPh), 130.8 (s, CPh), 130.1 (s, CPh), 129.7
(s, CPh), 128.9 (m, CPh), 128.6 (d, JC,P = 6 Hz, CPh), 128.5 (s, CPh), 128.0
(s, CPh), 127.6 (s, CPh), 126.9 (s, CPh), 122.7 (s, CPh), 93.9 (s, CCp‑Mo),
45.8 (s, CH2N), 41.9 (s, PhCH2S), 20.9 (s, SCH2CH2N). 31P{1H} NMR
(C6D6, 298 K): δ 75.0 (d, 2JP,P = 72 Hz, 1JP,Pt = 3392 Hz, P1), 75.0 (d,
meta-HringC + meta-HringD + para-HringC + para-HringD + meta-HringA),
7.44 (m, 3H, meta-HringB + para-HringB), 7.22 (m, 5 Hbenzyl ring), 6.96 (m,
3H, ortho-HringA + para-HringA), 4.74 (s, 5 H, Cp-Mo1), 4.57 (d, 2JH,H
=
14 Hz, 1 H, C6H5HCH-S), 4.10 (d, 2JH,H = 14 Hz, C6H5HCH-S), 3.04
(m, 1H, HCH-N), 2.79 (m, 1H, HCH-N), 1.94 (m, 2H, S−CH2CH2N).
13C{1H} APT (CDCl3, 298 K): δ 243.4 (d, JC,P = 28 Hz, CO), 239.6 (d,
JC,P = 31 Hz, CO), 142.6 (d, JC,P = 9 Hz, Cipso), 141.1 (d, JC,P = 3 Hz,
Cipso), 139.7 (dd, JC,P = 12 Hz, JC,P = 8 Hz, Cipso), 138.6 (s, CPh), 137.7 (d,
JC,P = 40 Hz, Cipso), 135.9 (d, JC,P = 12 Hz, CPh), 135.3 (s, Cipso), 131.7 (d,
JC,P = 11 Hz, Cipso) 131.4 (d, JC,P = 5 Hz CPh), 131.0 (d, JC,P = 12 Hz,
CPh), 130.4 (s, CPh), 129.9 (s, CPh), 129.3 (d, JC,P = 10 Hz, CPh), 128.7 (s,
CPh), 128.6 (d, JC,P = 25 Hz, CPh), 128.1 (m, CPh), 127.9 (s, CPh), 127.6
(s, CPh), 127.0 (s, CPh), 123.1 (s, CPh) 94.4 (s, CCp‑Mo), 46.5 (s, CH2N),
39.9 (s, PhCH2S), 24.1 (s, SCH2CH2N). 31P{1H} NMR (CDCl3, 298
K): δ 75.8 (d, 2JP,P = 75 Hz, 1JP,Pt = 3642 Hz, P1), 75.5 (d, 2JP,P = 75 Hz,
P2). 195Pt{1H} NMR (CDCl3, 298 K): δ −4034 (d, 1JP,Pt = 3642 Hz).
Reactions of 3, 9, and 10 with [n-Bu4N]Cl. The reactions between 3,
9, 10 and [n-Bu4N]Cl were performed in an NMR tube by mixing ca.
20 mg of trinuclear starting material with equimolar amounts of solid
[n-Bu4N]Cl in 0.5 mL THF, using a D2O capillary for lock, at 298 K.
2JP,P = 72 Hz, P2). 195Pt{1H} NMR (C6D6, 298 K): δ −4297 (d, 1JP,Pt
3392 Hz).
=
Reaction of 4 with I2. A round flask equipped with a dropping
funnel containing a THF (1.0 mL) solution of I2 (22 mg, 0.088 mmol)
was charged with a brown THF solution of 4 (50 mg, 0.044 mmol in
2.0 mL) and placed under 1 atm of CO by means of a manifold. The I2
solution was then dropped into the solution, and the mixture was stirred
for 4 h at 298 K. The IR analysis of the resulting mixture showed, in the
carbonyl region, very strong bands at 2040, 1974, 1963, and 1903 cm−1,
the first three ones being ascribed to [MoI(CO)3Cp].69 The reaction
solution was evaporated to dryness, and the residue was extracted with
R
DOI: 10.1021/acs.inorgchem.5b00223
Inorg. Chem. XXXX, XXX, XXX−XXX

Inorganic Chemistry
Article
C6D6 to give a dark solution submitted to multinuclear NMR analysis,
revealing the formation of a 27/28 mixture in a 4/1 molar ratio.
Monitoring of the Reaction between 4 and Iodine. A J-valve
NMR tube capped with a rubber septum containing a D2O capillary was
charged with a THF solution (0.3 mL) of 4 (22 mg, 0.017 mmol). The
solution was placed under a CO atmosphere by using a CO/vacuum
manifold, immerging the tube in an ice bath, and the dinitrogen
atmosphere was replaced with pure CO. Thus, a THF solution (0.2 mL)
of I2 (9 mg, 0.034 mmol) was added with the aid of a syringe, and the
tube was vigorously shaken. The resulting solution was submitted to
31P{1H} NMR analysis, at 298 K, after 20 min, 1 h, and 2 h.
mixture in a 4/1 molar ratio. The reaction of 4 with HCl(g) was
monitored using a J-valve NMR tube capped with a rubber septum
containing a D2O capillary. The tube was charged with a THF solution
(0.5 mL) of 4 (22 mg, 0.017 mmol), put under 1 atm of CO, and gaseous
HCl was added (5.0 mL, 298 K, 1 atm), which was bubbled into the
solution with the aid of a gas-tight syringe. The resulting solution was
analyzed by 31P{1H} NMR after 20 min, 6 h, 8 h, and 20 h, giving the
following percentage ratios (n/a indicates not applicable):
time
2
22 29
20 min 20 80 n/a
6 h
8 h
20 h
20 53 27
20 45 35
20 n/a 80
Synthesis of 27. To a THF solution (2 mL) of 26 (24 mg,
0.021 mmol), solid I2 was added (5.0 mg, 0.021 mmol) with stirring at
298 K. After 1 h, the solvent was removed under reduced pressure, and 27
was obtained as a yellow solid by crystallization from THF/n-hexane. Anal.
Calcd for C34H31I2MoNO2P2PtS: C, 36.32; H, 2.78; N, 1.25; Found: C
36.25, H 2.70, N 1.21%. HRMS(+) in MeOH/HCOOH, exact mass for
the cation [C34H31I2KMoNO2P2PtS]+ 1163.7973; measured: m/z:
1163.7962; [M+K]+. The spectrogram showed also an intense peak due
to [M−I]+ (exp. 997.9291 Da, calculated 997.9292 Da). IR νCO
Synthesis of 29. Gaseous HCl (5.0 mL, 298 K, 1 atm) was bubbled
into a vigorously stirred THF solution (2 mL) of 22 (26 mg,
0.022 mmol) at 298 K causing a color change of the solution from brown
to orange. After 20 min the solution was concentrated to 0.5 mL, and the
product was obtained as a yellow solid by precipitation with n-hexane.
The solid was washed with n-hexane (3 × 5 mL) and dried under
vacuum. Yield: 83%. Anal. Calcd for C34H31Cl2MoNO2P2PtS: C, 43.37;
H, 3.32; Cl, 7.53, N, 1.49; Found: C, 43.10; H, 3.28, Cl, 7.41; N, 1.46%.
HRMS(+) in MeOH/HCOOH, exact mass for the cation
[C34H31Cl2KMoNO2P2PtS]+ 979.9246; measured: m/z: 979.9251
[M+K]+. The spectrogram showed also an intense peak due to [M−Cl]+
1
(CHCl3)/cm−1: 1982 (vs), 1911 (vs). H NMR (C6D6, 298 K): δ
8.31 (ddd, 3JH,P = 11 Hz, 3JH,H = 8 Hz, 4JH,H = 1 Hz, 2 H, ortho-HringB),
7.56 (dd, 3JH,P = 11 Hz, 3JH,H = 8 Hz, ortho-HringC), 7.45 (d, 3JH,H = 7 Hz,
3
3
4
2 H, ortho-Hbenzyl ring), 7.35 (ddd, JH,P = 11 Hz, JH,H = 8 Hz, JH,H
1 Hz, 2 H, ortho-HringD), 7.24 (pseudo t, 3JH,H = 8 Hz, 2 H, meta-HringC),
7.11 (m, 2 H, meta-HringB) from 7.20 to 6.91 (m, 5 H, meta-HringD
para-HringB + para-HringC + para-HringD) 6.86 (t, 3JH,H = 7 Hz, 1 H, para-
=
(exp. 905.9957 Da, calculated 905.9930 Da). IR νCO (Nujol)/cm−1
:
+
1970 (vs), 1899 (vs); νPt−Cl (Nujol)/cm−1: 331 (s) 269 (m). 1H NMR
(CDCl3, 298 K): δ 7.87 (ddd, 3JH,P = 11 Hz, 3JH,H = 8 Hz, 4JH,H = 1 Hz,
2 H, ortho-HringB), from 7.67 to 7.50 (m, 10 H, ortho-HringC, ortho-
HringD, meta-HringC, meta-HringD, para-HringC, para-HringD from 7.34 to
7.19 (m, 3 H, meta-HringB, para-HringB), 5.45 (s, 5 H, Cp-Mo), 4.98 (d,
Hbenzyl ring), 6.61 (t, 3JH,H = 7 Hz, 2 H, meta-Hbenzyl ring), 4.49 (d, 2JH,H
=
14 Hz, 1 H, C6H5HCH-S), 5.15 (s, 5 H, Cp-Mo1), 4.03 (d, 2JH,H = 14 Hz,
1 H, C6H5HCH-S), 2.59 (m, 1 H, HCH-N), 2.46 (m, 1 H, HCH-N),
1.60 (m, 2 H, S−CH2CH2N). 13C{1H} APT (C6D6, 298 K): δ 243.8 (d,
JC,P = 25 Hz, CO), 239.8 (d, JC,P = 28 Hz, CO), from 139.0 to 124.0 (m,
16 CPh), 96.8 (s, CCp‑Mo), 46.8 (s, CH2N), 34.1 (s, PhCH2S), 30.8 (s,
2
2JH,H = 13 Hz, 1 H, C6H5HCH-S), 4.16 (d, JH,H = 13 Hz, 1 H,
C6H5HCH-S), 2.99 (m, 1 H, HCH-N), 2.48 (m, 1 H, HCH-N), 1.95 (m,
1 H, S-HCHCH2N), 1.59 (m, 1 H, S-HCHCH2N). 13C{1H} APT
(CDCl3, 298 K): δ 241.8 (d, JC,P = 30 Hz, CO), 235.3 (d, JC,P = 28 Hz,
CO), 139.0 (m, Cipso), 137.6 (d, JC,P = 4 Hz, CPh), 137.5 (d, JC,P = 35 Hz,
Cipso), 137.0 (s, Cipso), 135.7 (d, JC,P = 41 Hz, Cipso), 130.8 (m,
overlapped, CPh), 130.7 (m, overlapped, CPh), 129.6 (s, CPh), 129.0 (s,
CPh), 128.3 (d, JC,P = 11 Hz, CPh), 128.2 (s, CPh), 127.8 (s, CPh), 127.5 (s,
CPh), 127.4 (d, JC,P = 12 Hz, CPh), 127.0 (s, CPh), 124.5 (s, CPh), 94.5 (s,
CCp‑Mo), 46.7 (s, CH2N), 31.2 (broad, PhCH2S), 28.9 (broad,
SCH2CH2N). 31P{1H} NMR (CDCl3, 298 K): δ 63.8 (d, 2JP,P = 82 Hz,
1JP,Pt = 2971 Hz, P1), 81.6 (d, 2JP,P = 82 Hz, P2). 195Pt{1H} NMR (CDCl3,
SCH2CH2N). 31P{1H} NMR (THF, 298 K): δ 65.1 (d, JP,P = 74 Hz,
2
1JP,Pt = 2650 Hz, P1), 77.8 (d, 2JP,P = 74 Hz, P2). 195Pt{1H} NMR (THF,
298 K): δ −3343 (d, 1JP,Pt = 2650 Hz).
Synthesis of 28. A THF solution (2 mL) of (Ph2P)2N-
(CH2)2SCH2Ph (20 mg, 0.036 mmol) was added dropwise with stirring
at 298 K within 30 min to a THF solution (2 mL) of [PtI2(cod)] (20 mg,
0.036 mmol). After 30 min, the solution was concentrated (to ca.
0.5 mL), and the product was obtained by precipitation with n-hexane
(10 mL). The pale yellow solid was washed with n-hexane (3 × 5 mL)
and dried under vacuum. Yield: 92%. Anal. Calcd for C33H31Cl2NP2PtS:
C, 49.44; H, 3.90; Cl, 8.85; N, 1.75; Found: C 49.37, H 3.83, Cl 8.79, N
1.72%. HRMS(+) in MeOH/HCOOH, exact mass for the cation
[C33H31I2NNaP2PtS]+ 1006.9288; measured: m/z: 1006.9285 [M +
Na]+. IR (nujol), ν/cm−1: 3046 (m), 2932 (m), 1433 (s), 1313 (w),
1300 (w), 1159 (m), 1102 (vs), 1070 (m), 1026 (m), 1018 (m), 999
(m), 877 (s), 848 (s), 747 (s), 722 (s), 708 (w), 693 (vs), 664 (s), 576
(s), 518 (vs), 508 (vs), 491 (m), 473 (m), 438 (w), 407 (w), 381 (w),
298 K): δ −3793 (d, 1JP,Pt = 2971 Hz).
Monitoring of the Reaction between 1 and Na[Mo(CO)3Cp]·
2DME. To a Schlenk tube containing a stirred THF solution (2.0 mL)
of 1 (60 mg, 0.053 mmol) at 323 K was added a solution of
Na[Mo(CO)3Cp]·2DME (52 mg, 0.117 mmol) in THF (22 mL) in
successive portions of 10 mL (t = 0), 5 mL (after 1 h), and 7 mL (after
two more hours), by means of a dropping funnel. Thirty minutes after
each addition, an aliquot of the mixture (0.3 mL) was transferred into an
NMR tube containing a D2O capillary and used for recording 31P{1H}
NMR spectra at 298 K. The course of the reaction between 1
and Na[W(CO)3Cp], or 2 and Na[Mo(CO)3Cp], or 2 and Na[W-
(CO)3Cp] was monitored in an analogous manner.
296 (w). 1H NMR (CDCl3, 298 K): δ 7.76 (ddd, 3JH,P = 12 Hz, 3JH,H
=
7 Hz, 4JH,H = 2 Hz, 8 H, ortho-HPh), 7.65 (t, 3JH,H = 7 Hz, 4 H, para-HPh),
7.52 (pseudo t, 8 H, meta-HPh) from 7.21 to 7.10 (m, 3 H, orthoBzyl
+
paraBzyl), 6.93 (td, 3JH,H = 7 Hz, 4JH,H = 1 Hz, 2 H metaBzyl), 3.38 (s, 2 H,
C6H5CH2-S) 2.83 (m, 2 H, CH2-N), 1.97 (m, 2 H, S−CH2CH2N).
13C{1H} APT (CDCl3, 298 K): δ 137.7 (s, C6H5CH2S−, Cipso), 133.8 (s,
Monitoring of the Reaction Performed by Sequential
Addition of Na[Mo(CO)3Cp] and Na[W(CO)3Cp] to 2. To a Schlenk
tube containing a stirred THF solution (2.0 mL) of 2 (42 mg,
0.053 mmol) at 323 K was added first a solution of Na[Mo(CO)3Cp]·
2DME (24 mg, 0.053 mmol in THF (1.0 mL) and then a solution of
Na[W(CO)3Cp]·2DME (28 mg, 0.053 mmol) in THF (1.0 mL) by
means of dropping funnels kept under argon atmosphere.
C
para‑Ph), 133.5 (m, Cortho‑Ph) 129.8 (d, 3JC,P = 13 Hz, Cmeta‑Ph) 128.9 (s,
Cortho‑Bzyl) 128.8 (s, Cmeta‑Bzyl), 127.7 (m, Cipso), 127.6 (s, Cpara‑Bzyl) 49.5
2
(s, JC,P = 9 Hz, CH2N), 36.5 (s, PhCH2S), 29.0 (s, SCH2CH2N).
31P{1H} NMR (C6D6, 298 K): δ 13.9 (d, 1JP,Pt = 3039 Hz). 195Pt{1H}
NMR (THF, 298 K): δ −3457 (d, 1JP,Pt = 3010 Hz).
Reaction of 4 with Gaseous HCl. A Schlenk tube capped with a
rubber septum was charged at 298 K with a THF solution (2.0 mL) of 4
(26 mg, 0.022 mmol) and placed under CO atmosphere by using a CO/
vacuum manifold. Then, gaseous HCl (5.0 mL, 298 K, 1 atm) was
bubbled into the THF solution by means of a gas-tight syringe. After a
few minutes, the color of the solution turned from brown to orange. The
reaction mixture was further stirred for 15 h, then submitted to
multinuclear NMR analysis, which revealed the formation of a 2/29
In an analogous manner, to a THF solution (2.0 mL) of 1 (60 mg,
0.053 mmol) kept under stirring at 323 K, was added first a solution of
Na[W(CO)3Cp]·2DME (28 mg, 0.053 mmol) in THF (1.0 mL) and
then a solution of Na[Mo(CO)3Cp]·2DME (24 mg, 0.053 mmol) in
THF (1.0 mL).
After each addition, an aliquot of the mixture (0.3 mL) was trans-
ferred into an NMR tube containing a D2O capillary and used for record-
ing 31P{1H} and 195Pt{1H} NMR spectra at 298 K. Main spectroscopic
S
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Inorganic Chemistry
Article
features of the mixed Pt−Mo−W species 30 and 31 are reported in
Table 4
ΔH°(lattice, exp), and absolute standard entropies, S°(exp), of the crystal,
according to
Reaction in the Presence of Di-n-butylsulfide. Neat di-n-
butylsulfide (0.10 mL) was added to a vigorously stirred THF solution
(2.0 mL) of complex [PtCl2{(Ph2P)2N(n-decyl)}] (60 mg,
0.076 mmol) kept at 323 K. Then, solid Na[Mo(CO)3Cp] (69 mg,
0.152 mmol) was added to the solution and immediately the solution
turned from colorless to brown. The multinuclear NMR analysis of the
reaction solution revealed the formation of an 88/22 (mol/mol) mixture
of the complexes 32 and 33.3
H°(NaCl) = H°(Na+) + H°(Cl−) + ΔH°(lattice,exp)
G°(NaCl) = H°(NaCl) − TS°(exp)
Although the B3LYP exchange correlation functional has been
increasingly and successfully employed in DFT calculations in the last
two decades, it does not adequately treat dispersion interactions, and it is
has recently emerged that it may give inaccurate geometries and energies
when large molecules with significant steric and hydrophobic intra-
molecular interaction are considered. Recent benchmark studies have
shown that a newly developed exchange-correlation functional explicitly
built to take into account these effects, such as ML06, may give much
better results.73 In a previous study we performed benchmark calcu-
lations at both B3LYP and M06 levels on a series of PtCo2 trinuclear
cluster similar to those considered in this study,3 namely, [PtCo2(CO)7-
{(Ph2P)2NR}] with R = (CH2)9CH3, (CH2)2S(CH2)5CH3,
(CH2)2SCH2C6H5, C6H5, for which a large amount of experimental
structural and thermodynamic data (on the equilibrium between the
bridged and chelate isomers) are available, and found that only the M06
results were in reasonable agreement with the experimental data for the
isomerization enthalpies and free energies.8 Moreover, this level of
theory has been already successfully employed in theoretical studies of
the PtMo2 and PtW2 cluster, giving results in good agreement with all
experimental findings.3
Computational Details. All calculations were performed at DFT
level by using Jaguar 7.5 program.70 Geometry optimizations were
performed by using the B3LYP and M06 exchange-correlation
functionals.71−73
For all considered complexes, an exhaustive search of the most stable
structuresincluding possible isomers and conformerswas per-
formed in gas phase using the B3LYP functional and an LACVP*
basis set, consisting of the 6-31G(d) set for the main-group elements,74
and the Hay and Wadt core valence ECP basis set of double-ζ quality
plus one polarization f functions for the metal atoms.75−77 For the most
stable structures of each complex, vibrational frequency calculations
based on analytical second derivatives at the same level of theory were
performed to confirm the nature of the local minima and transition state
and to compute the zero-point-energy (ZPE) and vibrational entropy
corrections at 298.15 K. These structures were then reoptimized in gas
phase at the M06/LACVP* level of theory.
Solvation energies were evaluated by using the Poisson−Boltzmann
continuum solvent method implemented in Jaguar to simulate the THF
environment (ε = 24.3 and σ = 2.262 Å).78,79 Solvation energies were
only evaluated on the gas-phase stationary points. The electronic
and solvation energies of all the most stable stationary points
were reevalutated with single-point calculation using the larger
LACV3P++**, consisting of the 6-311++G(d,p) set for the main-
group elements80 and the Hay and Wadt core valence ECP basis set of
triple-ζ quality plus one diffuse d function and two polarization sp
functions for all metal atoms.75−77 The reaction enthalpies in solution
were estimated by adding the solvation free energy to the corresponding
gas-phase enthalpy.
ASSOCIATED CONTENT
* Supporting Information
■
S
HRMS(+) spectrogram and NMR spectra of 3, 4, 9, 10;
calculated geometries of 4, 11, and 12; free energy profile for the
formation of 15, 7, and 5, B−D, and 3; reaction courses of the
reactions between 1 and Na[Mo(CO)3Cp] or Na[W(CO)3Cp];
proposed mechanism for the reaction of 4 with HCl; Mulliken
charges on selected atoms of the intermediates B, E, F, G, H, I,
and of TSH−I. Cartesian coordinates of 3, B, E, F, G, H, I, TSF‑G
,
and TSH−I calculated at M06/LACVP* level. The Supporting
Information is available free of charge on the ACS Publications
website at DOI: 10.1021/acs.inorgchem.5b00223.
AUTHOR INFORMATION
Corresponding Authors
*E-mail: braunstein@unistra.fr. (P.B.)
*E-mail: pietro.mastrorilli@poliba.it. (P.M.)
■
Notes
Although our approachgeometry optimizations in gas phase
followed by single-point calculations in solvent and with a larger basis
setis standard in theoretical chemistry, optimization in solution that
may give better results for systems involving ion pairs. However, the
large size of the considered systems, up to almost 100 atoms and more
than 1000 basis set functions, make optimization and especially
frequency calculations in solution computationally far too demanding
and practically unfeasible. To better investigate the possible errors due
to this approximate approach, we considered the simplest prototype ion
pair model involved in the considered systems, that is, Na[Mo-
(CO)3Cp], by performing (i) a geometry optimization in gas phase
followed by single-point calculations in solvent and with a larger basis
set; (ii) a geometry optimization in solution followed by a single-point
calculation with a larger basis set. The results show negligible geometry
changes (except 0.7 Å for the Na+···O distances) and a moderate energy
relaxation of ∼6 kcal·mol−1, which is, however, expected to affect much
less the energy differences involved in reaction and activation energies
due to error compensation.
The authors declare no competing financial interest.
ACKNOWLEDGMENTS
We wish to thank the reviewers for their valuable suggestions.
The Politecnico di Bari (FRA funds to M.L.), the CNRS, the
■
́
MESR (Paris), and the Universite de Strasbourg are gratefully
acknowledged for financial support.
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