Hydrido phosphanido bridged polynuclear complexes obtained by protonation of a phosphinito bridged Pt(I) complex with HBF4 and HF

Article abstract of DOI:10.1021/ic102475e

The protonation of the phosphinito-bridged Pt(I) complex [(PHCy ₂)Pt(μ-PCy₂){κ²P,O-μ-P(O)Cy ₂}Pt(PHCy₂)](Pt-Pt) (1) by aqueous HBF₄ or hydrofluoric acid leads selectively to the hydrido-bridged solvento species syn-[(PHCy₂)(H₂O)Pt(μ-PCy₂)(μ-H) Pt(PHCy₂){κP-P- (OH)Cy₂}](Y)₂(Pt-Pt) ([2-H₂O]Y₂) {Y = BF₄, F(HF)_n} when an excess of acid was used. On standing in halogenated solvents, complex [2-H₂O](BF₄)₂ undergoes a slow but complete isomerization to [(PHCy₂)₂Pt(μ-PCy₂)(μ- H)Pt{κP-P(OH)Cy₂}(H₂O)](BF₄) ₂(Pt-Pt) ([4-H₂O][BF₄]₂) having the P(OH)Cy₂ ligand trans to the hydride. The water molecule coordinated to platinum in [2-H₂O][BF₄]₂ is readily replaced by halides, nitriles, and triphenylphosphane, and the acetonitrile complex [2-CH₃CN][BF₄]₂ was characterized by XRD analysis. Solvento species other than aqua complexes, such as [2-acetone-d₆]²⁺ or [2-CD₂Cl₂] ²⁺ were obtained in solution by the reaction of excess etherate HBF4 with 1 in the relevant solvent. The complex [2-H₂O](Y)2 [Y = F(HF)_n] spontaneously isomerizes into the terminal hydrido complexes [(PHCy₂)Pt(μ-PCy₂){κ²P,O-μ- P(O)Cy₂}Pt(H)(PHCy₂)](Y)(Pt-Pt) ([6](Y)). In the presence of HF, complex [6](Y) transforms into the bis-phosphanidobridged Pt(II) dinuclear complex [(PHCy₂)(H)Pt(μ-PCy₂) ₂Pt{κP-P(OH)Cy₂}](Y)(Pt-Pt) ([7](Y)). When the reaction of 1 with HF was carried out with diluted hydrofluoric acid by allowing the HF to slowly diffuse into the dichloromethane solution, the main product was the linear 60e tetranuclear complex [(PHCy₂){κP-P(O)Cy ₂}Pt1(μ-PCy₂)(μ-H)Pt₂(μ-PCy ₂)]₂(Pt1-Pt₂) (8). Insoluble compound 8 is readily protonated by HBF₄ in dichloromethane, forming the more soluble species [(PHCy₂){κPP( OH)Cy₂}Pt1(μ- PCy₂)(μ-H)Pt₂(μ-PCy₂)] ₂(BF₄)₂(Pt1-Pt₂) {[9][BF ₄]₂}. XRD analysis of [9][BF₄]₂ · 2CH₂Cl₂ shows that [9]²⁺ is comprised of four coplanar Pt atoms held together by four phosphanido and two hydrido bridges. Both XRD and NMR analyses indicate alternate intermetal distances with peripheral Pt-Pt bonds and a longer central Pt · · · Pt separation. DFT calculations allow tracing of the mechanistic pathways for the protonation of 1 by HBF4 and HF and evaluation of their energetic aspects. Our results indicate that in both cases the protonation occurs through an initial proton transfer from the acid to the phosphinito oxygen, which then shuttles the incoming proton to the Pt-Pt bond. The different evolution of the reaction with HF, leading also to [6](Y) or 8, has been explained in terms of the peculiar behavior of the F(HF)_n- anions and their strong basicity for n = 0 or 1.

Full text of DOI:10.1021/ic102475e

ARTICLE
pubs.acs.org/IC
Hydrido Phosphanido Bridged Polynuclear Complexes Obtained by
Protonation of a Phosphinito Bridged Pt(I) Complex with HBF4 and HF
Mario Latronico,† Piero Mastrorilli,*,† Vito Gallo,† Maria Michela Dell’Anna,† Francesco Creati,‡
Nazzareno Re,‡ and Ulli Englert§
†Dipartimento di Ingegneria delle Acque e di Chimica del Politecnico di Bari, via Orabona 4, I-70125 Bari, Italy
‡Dipartimento di Scienze del Farmaco, Universitꢀa “G. d’Annunzio”, Via dei Vestini 31, 06100 Chieti, Italy
§Institut f€ur Anorganische Chemie der RWTH, Landoltweg 1, D-52074 Aachen, Germany
S Supporting Information
b
ABSTRACT: The protonation of the phosphinito-bridged Pt(I) complex
[(PHCy2)Pt(μ-PCy2){κ2P,O-μ-P(O)Cy2}Pt(PHCy2)](Pt-Pt) (1) by aqu-
eous HBF4 or hydrofluoric acid leads selectively to the hydrido-bridged
solvento species syn-[(PHCy2)(H2O)Pt(μ-PCy2)(μ-H)Pt(PHCy2){κP-P-
(OH)Cy2}](Y)2(Pt-Pt) ([2-H2O]Y2) {Y = BF4, F(HF)n} when an excess of
acid was used. On standing in halogenated solvents, complex [2-H2O](BF4)2
undergoes a slow but complete isomerization to [(PHCy2)2Pt(μ-PCy2)(μ-
H)Pt{κP-P(OH)Cy2}(H2O)](BF4)2(Pt-Pt) ([4-H2O][BF4]2) having the
P(OH)Cy2 ligand trans to the hydride. The water molecule coordinated to
platinum in [2-H2O][BF4]2 is readily replaced by halides, nitriles, and
triphenylphosphane, and the acetonitrile complex [2-CH3CN][BF4]2 was
characterized by XRD analysis. Solvento species other than aqua complexes,
such as [2-acetone-d6]2þ or [2-CD2Cl2]2þ were obtained in solution by the
reaction of excess etherate HBF4 with 1 in the relevant solvent. The complex
[2-H2O](Y)2 [Y = F(HF)n] spontaneously isomerizes into the terminal hydrido complexes [(PHCy2)Pt(μ-PCy2){κ2P,O-μ-
P(O)Cy2}Pt(H)(PHCy2)](Y)(Pt-Pt) ([6](Y)). In the presence of HF, complex [6](Y) transforms into the bis-phosphanido-
bridged Pt(II) dinuclear complex [(PHCy2)(H)Pt(μ-PCy2)2Pt{κP-P(OH)Cy2}](Y)(Pt-Pt) ([7](Y)). When the reaction of 1
with HF was carried out with diluted hydrofluoric acid by allowing the HF to slowly diffuse into the dichloromethane solution, the
main product was the linear 60e tetranuclear complex [(PHCy2){κP-P(O)Cy2}Pt1(μ-PCy2)(μ-H)Pt2(μ-PCy2)]2(Pt1-Pt2) (8).
Insoluble compound 8 is readily protonated by HBF4 in dichloromethane, forming the more soluble species [(PHCy2){κP-
P(OH)Cy2}Pt1(μ-PCy2)(μ-H)Pt2(μ-PCy2)]2(BF4)2(Pt1-Pt2) {[9][BF4]2}. XRD analysis of [9][BF4]2 2CH2Cl2 shows that
3
[9]2þ is comprised of four coplanar Pt atoms held together by four phosphanido and two hydrido bridges. Both XRD and NMR
analyses indicate alternate intermetal distances with peripheral Pt-Pt bonds and a longer central Pt Pt separation. DFT
3 3 3
calculations allow tracing of the mechanistic pathways for the protonation of 1 by HBF4 and HF and evaluation of their energetic
aspects. Our results indicate that in both cases the protonation occurs through an initial proton transfer from the acid to the
phosphinito oxygen, which then shuttles the incoming proton to the Pt-Pt bond. The different evolution of the reaction with HF,
leading also to [6](Y) or 8, has been explained in terms of the peculiar behavior of the F(HF)n- anions and their strong basicity for
n = 0 or 1.
’ INTRODUCTION
excess acid, [(PHCy2)(X)Pt(μ-PCy2)(μ-H)Pt(PHCy2){κP-P-
(OH)Cy2}]X (Pt-Pt) (X = Cl or Br). On the other hand,
the protonation of 1 by weaker acids such as dicyclohexylpho-
sphane oxide, phenol, or 1,1,1-trifluoroethanol stops at the
monoprotonated species [(PHCy2)(X0)Pt(μ-PCy2)(μ-H)Pt-
(PHCy2){κP-P(O)Cy2}](Pt-Pt) (X0 = P(O)Cy2, PhO, or
CF3CH2O) even when a strong excess of protonating agent is
used. Notably, both HI and PhSH give, as final products, the
anti-[(PHCy2)(X00)Pt(μ-PCy2)(μ-H)Pt(PHCy2)(X00)](Pt-Pt)
The phosphinito-bridged complex [(PHCy2)Pt(μ-PCy2)-
{κ2P,O-μ-P(O)Cy2}Pt(PHCy2)](Pt-Pt) (1)1 represents an
attractive molecule due to the presence of the Pt-O fragment,
which imparts a multifaceted reactivity comprising substitution,2
addition,3 and H2 activation.4 The protonation of 1 by Brønsted
acids such as HCl, HBr, HI, PhOH, P(OH)Cy2, CF3CH2OH,
and PhSH resulted in all cases in bridging hydrido diplatinum
complexes5 as shown in Scheme 1.
It is apparent from Scheme 1 that HCl and HBr give first the
monoprotonated compounds [(PHCy2)(X)Pt(μ-PCy2)(μ-H)-
Pt(PHCy2){κP-P(O)Cy2}](Pt-Pt) and then, in the presence of
Received: December 10, 2010
Published: March 17, 2011
r
2011 American Chemical Society
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Scheme 1. Reactivity of 1 with Brønsted Acids Having Coordinating Anions
Scheme 2. Mechanism of Protonation of 1 by HX (X = Cl, Br, I, SPh)
(X00 = I or PhS) complexes, featuring two X00 residues covalently
bound to the Pt atoms.
precipitation of the dicationic hydrido-bridged aqua complex
syn-[(PHCy2)(H2O)Pt(μ-PCy2)(μ-H)Pt(PHCy2){κP-P(OH)-
Cy2}](BF4)2 (Pt-Pt) ([2-H2O][BF4]2), which represents the
product of double protonation of 1 (Scheme 3). The structure of
[2-H2O]2þ is similar to that of the reaction products of 1 with
excess HCl or HBr ([2-Cl]þ or [2-Br]þ respectively, Scheme 1),
the only differences being the water ligand in place of the halide
bonded to Pt1 and, as a consequence, the charge of the cationic
complex.
These findings indicate that the product of the protonation of 1
depends on both the acid strength of the HX molecule and on the
affinity to platinum of the X residue. In fact, HI and PhSH, two
Brønsted acids endowed with very different acid strengths but having
in common a residue characterized by a strong affinity to platinum,
gave isostructural products (Scheme 1). A mechanistic study based
on NMR data and DFT calculations revealed that the kinetic
protonation site is the phosphinito oxygen which shuttles the
incoming proton to the Pt-Pt bond. The reaction was shown to
pass through the formation of a six-membered platinacycle complex
A detected in solution by NMR spectroscopy when less than 1 equiv
of HX (X = Cl, Br, I, SPh) was reacted with 13,6 (Scheme 2).
A common feature for all reactions shown in Scheme 1 is that the
X residues possess a fair to good coordinating ability toward Pt, thus
forming in all products a covalent bond with the electrophilic2 Pt1
atom (the one originally bearing the phosphinito oxygen).
In order to investigate the protonation of 1 with Brønsted acids
whose anion possesses poor coordinating ability toward Pt, we decided
to study the reaction of 1 with HBF4 and with HF, which led to new
dinuclear or tetranuclear hydrido phosphanido-bridged Pt complexes.
As expected, 31P and 195Pt NMR spectroscopic features of the
aqua complex [2-H2O]2þ (Table 1) resemble those of the
cationic complexes [(PHCy2)(X)Pt(μ-PCy2)(μ-H)Pt{κP-P-
(OH)Cy2}(PHCy2)]þ(Pt-Pt) (X = Cl, Br, I)3 and will be not
discussed here. The 1H NMR spectrum of [2-H2O]2þ recorded
at 295 K in CD2Cl2 showed, besides the cyclohexyl and the PH
protons, a multiplet centered at δ -5.48 attributable to the
bridging hydride, and a very broad signal at δ 5.8 (Figure 1). On
lowering the temperature down to 258 K, the latter signal splits
into two broad signals at δ 5.34 and δ 6.33 ascribable to the
protons of the coordinated water and of the POH moiety,
respectively. These attributions are corroborated by the disap-
pearance of the signal at δ 5.34 (but not of that at δ 6.33) upon
the addition of acetonitrile to a CD2Cl2 solution of [2-H2O]2þ
.
The bridging hydride participates in exchange phenomena
involving the protons of the coordinated water and of the
coordinated P(OH)Cy2, as the addition of D2O to a CD2Cl2
solution of [2-H2O]2þ caused the complete disappearance of the
’ RESULTS AND DISCUSSION
Reaction with HBF4. The addition of excess (>2 equiv)
aqueous HBF4 to an n-hexane solution of 1 causes the immediate
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Scheme 3
Table 1. NMR Features of Solvento Species [2-L]2þ (δ’s are in ppm; coupling constants are in Hz)
complexa
L
δ P1
δ P2
δ P3
δ P4
δ H1
δ Pt1
δ Pt2
2J(P1,P3)
[2-H2O]2þ
[2-acetone-d6]2þb
[2-CD2Cl2]2þb
H2O
149.7
154.0
152.4
9.1
5.4
126.8
126.2
128.8
-1.7
-3.7
0.2
-5.48
-5.49
-5.50
-5302
-5296
-5292
-5589
-5580
-5576
289
292
297
acetone-d6
CD2Cl2
11.1
a As a tetrafluoroborate salt. A more complete NMR characterization is reported in the Supporting Information. b Obtained in an NMR tube starting
from 1 þ HBF4 Me2O (>2 equiv) at room temperature in the corresponding coordinating solvent.
3
an equilibrium between the monocationic complex [3-H2O]þ
and the dicationic species [2-H2O]2þ (Scheme 4), a result parallel-
ing that obtained with HCl.3
Differently from the cases of HCl, HBr, HI, and PhSH, when
less than 1 equiv of HBF4 was reacted with 1, no traces of
intermediates similar to A (Scheme 2) were detected in solution
by NMR spectroscopy, even at low T (200 K).
While the related chlorido or bromido complexes [2-X]þ (X =
Cl, Br) were found stable in solution (even in the presence of the
corresponding halohydric acid), [2-H2O]2þ spontaneously iso-
merizes to [(PHCy2)2Pt(μ-PCy2)(μ-H)Pt{κP-P(OH)Cy2}-
(H2O)]2þ(Pt-Pt) ([4-H2O]2þ, Scheme 5) when left in halo-
genated solvents. The conversion [2-H2O]2þ f [4-H2O]2þ is
slow but irreversible, being completed after 1 month in CD2Cl2
at room temperature (rt), indicating that such transformation is
thermodynamically favored. In the 31P{1H} NMR spectrum of
[4-H2O]2þ, the bridging phosphanide P1 is strongly coupled to
the coordinated P3HCy2 (2JP(1),P(3) = 229 Hz) while the
coordinated P4(OH)Cy2 is coupled only to the coordinated
P2HCy2 (3JP(2),P(4) = 38 Hz). The assignment of the structure
depicted in Scheme 5 to [4-H2O]2þ was possible by means of
1
1H-195Pt HMQC (Figure 2) and H-31P HMQC spectra,
which indicated, inter alia, that the two PHCy2 ligands are bon-
ded to the same Pt1 atom.
The complex [2-H2O]2þ could be selectively obtained from
Figure 1. NMR spectra of [2-H2O][BF4]2 in CD2Cl2: (a) 1H NMR at
the protonation of 1 only if fresh HBF4(aq) was used. The use of
“aged” HBF4(aq) (which is known to be slowly hydrolyzed to
HBF3OH)9 gave a mixture containing variable amounts of
[(PHCy2){B(OH)F3}Pt(μ-PCy2)(μ-H)Pt(PHCy2){κP-P(OH)-
Cy2}]BF4(Pt-Pt) ([2-B(OH)F3][BF4]).10
295 K; (b) 1H NMR at 258 K; (c) 1H{31P} NMR at 258 K.
1H signals attributed to the POH, coordinated H2O, and bridging
hydride.7 This is in accordance with the acidic character of
bridging hydrides bonded to (formally) Pt(II) centers.8
When the protonation of 1 in CH2Cl2 was carried out using
HBF4(aq) in amounts ranging from 1 to 2 equiv, only extremely
broad signals were found in the 1H and 31P{1H} NMR spectra
over a wide range of temperatures, indicating the occurrence of
The complex [2-H2O]2þ slowly decomposes in solution in the
presence of excess HBF4, giving rise to fragmentation of the
dinuclear core with the formation, after one week, of several
products, among which the mononuclear Pt(II) species cis-[Pt(H)-
{κP-P(OH)Cy2}(PHCy2)2][BF4] ([5][BF4]) was identified.11
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Scheme 4
Scheme 5
Figure 2. 1H-195Pt HMQC spectrum of [4-H2O]2þ (CD2Cl2, 295 K).
When the protonation of 1 by HBF4 was carried out using
etherate (instead of aqueous) HBF4 in coordinating solvents
such as acetone-d6 or CD2Cl2, different solvento species quanti-
tatively formed,12 whose main NMR features are listed in
Table 1.
the 195Pt NMR resonances of [2-CH3CN]2þ and [2-PhCN]2þ
are all slightly high-field shifted with respect to those of the
starting complex [2-H2O]2þ
.
The XRD structure of [2-CH3CN]2þ is shown in Figure 3 and
resembles those already reported for the related complexes [2-
X]þ (X = Cl, Br).3 In the dication [2-CH3CN]2þ, the two Pt
atoms are linked by a metal-metal bond of 2.8239(4) Å and
bridged by a phosphanide subtending a Pt-P-Pt angle of
77.03(6)°. The coordination planes around each platinum are
almost coplanar with a dihedral angle of 7.2(7)°. The H directly
bonded to P4 forms an intramolecular hydrogen bond with the
oxygen, as already found for [2-X]þ (X = Cl, Br).3 The hydroxyl
H of the P(OH)Cy2 ligand forms a hydrogen bond with one of
the BF4- anions with H F = 1.85 Å and O-H F = 158°.
The coordinated solvent molecule of complexes [2-L]2þ is
readily displaced by stronger ligands such as Cl-, Br-, organoni-
triles, or PPh3. The quantitative transformation of [2-H2O]2þ
into the corresponding chlorido or bromido complexes [2-X]þ
(X = Cl, Br)3 was observed when solid NaCl or KBr was added to
a CH2Cl2 solution of [2-H2O]2þ at rt.
The addition of acetonitrile or benzonitrile to [2-H2O]2þ in
chloroform at rt immediately caused a ligand exchange with the
formation of the RCN adducts shown in Scheme 6.
3 3 3
3 3 3
Differently from the solvento species listed in Table 1, which
gave quite broad NMR signals at rt, complexes [2-CH3CN]2þ
and [2-PhCN]2þ are characterized by sharp 195Pt, 31P (Figures
The Pt1-N distance of 2.083(6) Å is perfectly in line with that of
other acetonitrile Pt(II) complexes.13 After completion of the
structure model for [2-CH3CN]2þ with the exception of the
bridging hydride, a difference Fourier synthesis revealed a local
1
S5, S6, S8, and S9, Supporting Information), and H NMR
signals at rt, presumably as a consequence of the lesser lability of
electron density maximum of 1 e Å-3 at a distance of ca. 2 Å for
3
the ligand trans to μ-P bonded to Pt1. The 1H hydride as well as
Pt2 and 1.2 Å for Pt1. When a similarity restraint for equal Pt-H
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Scheme 6
doublet of doublets due to the trans couplings with the coordi-
nated PPh3 (2JP,P = 225 Hz) and P(OH)Cy2 (2JP,P = 270 Hz).
The signal attributed to the coordinated PPh3 was found at δ 4.5
as a broad doublet (2JP,P = 225 Hz), while the signals of the two
coordinated PHCy2 ligands fell at δ -1.7 (P2) and δ -3.1 (P4).
The two 195Pt NMR signals are almost isochronous, falling at δ
-5705 (Pt1) and δ -5684 (Pt2).
Reaction with HF. Hydrofluoric acid was chosen to investi-
gate the protonation of 1 with a weak acid having a poorly
coordinating anion.17
While no reaction occurred when an excess of HF(aq) was
added to a toluene solution of 1,18 carrying out the reaction in
dichloromethane led to dinuclear or tetranuclear Pt hydrides,
depending on the experimental conditions.
The addition of 2.5 equiv of concentrated hydrofluoric acid
(50%w) to a dichloromethane solution of 1 gave the bis proto-
nated complex [2-H2O]2þ, whose counteranions were presum-
ably the HF or H2O adducts of fluoride, {F(HF)n}- or
{F(H2O)n}-, respectively.19 For the sake of simplicity, in the
following formulas, such counteranions will be denoted simply as
Y-. The species [2-H2O](Y)2 showed slightly different 1H, 31P,
and 195Pt NMR features compared to those of [2-H2O][BF4]2
(see the Experimental Section) presumably as a result of different
interactions between the dication and the counteranions.20 The
formation of [2-H2O]2þ by the protonation of 1 by HF(aq)
indicates that when an excess of acid (HF or HBF4) is used, the
reaction course is irrespective of the protonating agent, the
counteranion of which serves only to neutralize the dicationic
complex formed.
Complex [2-H2O](Y)2 was difficult to purify, as it consists of a
mixture of several species differing for the counteranion (i.e.,
{F(HF)}-, {F(H2O)}-,{F(HF)2}-, etc.). In solution, [2-
H2O](Y)2 was found to transform spontaneously into the
complex [(PHCy2)Pt1(μ-PCy2){κ2P,O-μ-P(O)Cy2}Pt2(PHCy2)-
(H)](Y)(Pt-Pt) ([6](Y), Scheme 9), the structure of which was
inferred from its NMR features. The 1H NMR spectrum of [6]þ
showed a high-field signal at δ -1.61 which was assigned, by
means of 1H-195Pt HMQC experiments, to a terminal hydride
directly bonded to Pt2 (1JH,Pt(2) = 832 Hz). Such a signal appears
Figure 3. PLATON15 drawing of [2-CH3CN](BF4)2. Hydrogen atoms
bonded to C have been omitted for clarity. Interatomic distances (Å) and
angles (deg): Pt1-Pt2 = 2.8239(4), Pt1-P1 = 2.275(18), Pt1-P2 =
2.2617(19), Pt1-N1 = 2.083(7), Pt1-H3 = 1.66(2), Pt2-P1 =
2.3063(18), Pt2-P3 = 2.302(2), Pt2-P4 = 2.271(2), Pt2-H3 =
1.64(3), P3-O1 = 1.596(6), N(1)-C(25) = 1.143(9), Pt1-P1-Pt2 =
77.03(6), Pt1-H3-Pt2 = 118(3), P1-Pt1-H3 = 83.7(15), P1-Pt1-
P2 = 102.19(7), P1-Pt1-N1 = 166.84(15), P2-Pt1-H3 = 172.7(15),
P2-Pt1-N1 = 90.95(15), N1-Pt1-H3 = 83.3(15), Pt2-Pt1-P1 =
52.74(5), Pt2-Pt1-H3 = 30.9(15), Pt2-Pt1-P2 = 154.74(5), Pt2-
Pt1-N1 = 114.19(15), P1-Pt2-H3 = 81.5(13), P1-Pt2-P3 =
157.96(7), P1-Pt2-P4 = 106.50(7), P3-Pt2-H3 = 77.5(13), P3-
Pt2-P4 = 95.06(7), P4-Pt2-H3 = 170.5(12), Pt1-Pt2-P1 =
50.23(5), Pt1-Pt2-H3 = 31.2(12), Pt1-Pt2-P3 = 108.63(5), Pt1-
Pt2-P4 = 156.10(5), H4 O1 = 2.44, P4-H4 O1 = 133,
3 3 3
3 3 3
H1 F2i = 1.85, O1-H1 F2i = 2.647(7). Symmetry operator i =
3 3 3
3 3 3
-x, y - 0.5, 0.5 - z.
distances was introduced, refinement of this density maximum, as
the bridging H atom, converged with a physically meaningful
displacement parameter and reasonable bond distances and
angles.14
Complex [2-CH3CN]2þ can be directly synthesized by treat-
ing an n-hexane/acetonitrile solution of 1 with HBF4 (either
aqueous or etherate). The protonation to [2-CH3CN]2þ is
reversible: treating a CHCl3 solution of [2-CH3CN]2þ with
aqueous NaOH gives, first, the monocationic phosphinito com-
plex [3-CH3CN]þ16 and eventually the starting compound 1
(Scheme 7).
as a dddd because of scalar couplings with four P atoms (JH,P
=
105 Hz, 19 Hz, 16 Hz, 8 Hz). The 31P{1H} NMR spectrum of
[6]þ showed four signals centered at δ 182.0, δ 80.6, δ 9.4, and δ
-5.7. Of these, that at δ 182.0 splits into a doublet (JP,H = 105
Hz) in the proton coupled 31P NMR spectrum and was assigned
to the bridging phosphanide subtending a Pt-Pt bond having
the terminal hydride in the trans position. The signal at δ 80.6
was assigned to the bridging phosphinite bonded to Pt1 through
the O atom and bonded to Pt2 through the P atom having in the
trans position a dicyclohexylphosphane (δ -5.7, 2JP(3),P(4) = 157
The reaction of [2-H2O]2þ with PPh3 in CH2Cl2 gave quan-
titatively the substitution product [(PHCy2)(PPh3)Pt(μ-PCy2)-
(μ-H)Pt(PHCy2){κP-P(OH)Cy2}]2þ(Pt-Pt) ([2-PPh3]2þ
;
Scheme 8).
In the 31P{1H} NMR spectrum of [2-PPh3]2þ, the signal
attributed to the bridging phosphanide was found at δ 171.9 as a
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Scheme 7
Scheme 8
Scheme 9. Reaction of 1 with Concentrated Hydrofluoric Acid
Hz). The signal at δ 9.4 belongs to the P2 dicyclohexylphosphane
bonded to Pt1 in the trans position with respect to the Pt2. The
195Pt signals were found at δ -5147 (Pt1) and δ -5983 (Pt2).
The transformation of [2-H2O](Y)2 into [6](Y), never ob-
served with [2-H2O][BF4]2, points out a crucial role played by
the fluoride-based Y- counteranion, as confirmed by the almost
complete transformation of [2-H2O]2þ into [6]þ observed
when a [2-H2O][BF4]2 was treated with a saturated aqueous
solution of NaF at room temperature. Further details on the
reaction pathway from [2-H2O]2þ to [6]þ were obtained by
DFT calculations and are reported below.
bearing, besides the bridging phosphanides, a terminal PHCy2
(δP 1.7) and a terminal hydride (δH -2.84, 1JH,Pt(1) 833 Hz); the
other Pt atom is tricoordinated, the ligand other than bridging
phosphanides being a P-bound dicyclohexylphosphinic acid
(δP 134.8). The structure of [7]þ is similar to that of the cationic
complex [(PHtBu2)(H)Pt(μ-PtBu2)2Pt{PHtBu2}]þ(Pt-Pt)
obtained by the reaction of tetracyanoethylene with anti-[-
(PHtBu2)(H)Pt(μ-PtBu2)]2.22
The transformation of a μ-phosphanido/μ-phosphinito com-
plex into a bis μ-phosphanido species has been already observed
in the reaction of 1 with PHCy2.3 This suggests that, also in the
present case, free PHCy2 formed upon dissociation from [6]þ
may play a role in the isomerization [6]þ f [7]þ.
Finally, allowing a diluted (5%w) hydrofluoric acid solution to
slowly diffuse in a dichloromethane solution of 1 at rt resulted in
the formation, besides the species containing the Pt-Pt bond
discussed above, of a new compound showing a distinctive 31P
NMR multiplet centered at δ -111.5, typical for bridging phospha-
nides not subtending a Pt-Pt bond,21 a broad singlet at δ 6.0
Monitoring by 31P NMR spectroscopy the solutions contain-
ing complex [6](Y) (plus residual [2-H2O](Y)2 and HF)
showed the transformation of [6](Y) into the bis-phosphanido-
bridged Pt(II) dinuclear complex [(PHCy2)(H)Pt1(μ-PCy2)2-
Pt2{P(OH)Cy2}](Y)(Pt-Pt) ([7](Y), Scheme 9). The complex
[7]þ is a dinuclear species containing two bridging phosphanides
subtending a Pt-Pt bond according to their low field 31P NMR
resonances21 (δ299.6 and δ294.3). One Pt atom is tetracoordinated,
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Scheme 10. Reactions of 1 with Aqueous HF under Conditions of Slow Diffusion of the Acid
Figure 4. MS/MS spectrogram of 8 showing the fragmentation pattern of the ion at m/z 2395.1.
ascribable to a coordinated PHCy2, plus signals in the regions of
coordinated P(O)Cy2 (δ ca. 80) and of bridging phosphanides
subtending a Pt-Pt bond (δca.138). Workup of the reaction mixture
allowed us to isolate a white compound (8), which was found
insoluble in solvents such as halogenated hydrocarbons, aromatic
compounds, and dmso. Its IR spectrum in KBr showed a 1636 cm-1
band ascribable to a bridging hydride and a single PH band at
2327 cm-1, while no bands typical for the POH moiety were present.
The structure proposed for 8 is reported in Scheme 10 and was
confirmed by ESI-MS analysis and by its reactivity toward HBF4.
The ESI-MS spectrogram of a very diluted chloroform solution
of 8 showed the peaks at m/z 2395.1, whose isotope pattern is
perfectly superimposable on that calculated for the ion
[C96H181O2P8Pt4]þ (corresponding to [8þH]þ), and at m/z
1198.1 ascribable to the doubly charged ion [8þ2H]2þ. The
peak at m/z 2395.1 was isolated for a MS/MS analysis, which
showed a fragmentation pattern (Figure 4) consisting of the loss
of a PHCy2 (m/z = 2197.1), a P(OH)Cy2 (m/z = 2181.0), two
PHCy2’s (m/z = 1998.9), a PHCy2, and a P(OH)Cy2 (m/z =
1983.0). All ions deriving from the fragmentation of [8þH]þ
were also observed (with their characteristic isotope pattern) in
the ESI-MS spectrogram of 8.
The addition of HBF4 2Me2O to a suspension of 8 in CD2Cl2
3
resulted in a pale yellow homogeneous solution of the
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Figure 6. Skeleton of [9]2þ
.
Scheme 11
Figure 5. PLATON15 drawing of [9]2þ. Hydrogen atoms bonded to C
have been omitted for clarity. Interatomic distances (Å) and angles
(deg): Pt(1)-P(1) 2.2883(19), Pt(1)-P(4) 2.3114(17), Pt(1)-P(4)i
2.3448(19), Pt(1)-Pt(2) 2.8994(6), Pt(1)-Pt(1)i 3.6539(11), Pt-
(1)-H(1M) 1.81(7), Pt(2)-P(3) 2.2684(19), Pt(2)-P(1) 2.3047(17),
Pt(2)-P(2) 2.3079(18), Pt(2)-H(1M) 1.75(8), P(2)-O(1)
1.612(5), P(3)-H(3) 1.19(6), P(4)-Pt(1)i 2.3446(19); P(1)-Pt-
(1)-P(4) 108.04(6), P(1)-Pt(1)-P(4)i 167.07(6), P(4)-Pt(1)-
P(4)i 76.61(6), P(1)-Pt(1)-Pt(2) 51.11(4), P(4)-Pt(1)-Pt(2)
157.33(5), P(4)i-Pt(1)-Pt(2) 125.78(4), P(1)-Pt(1)-H(1M)
85(2), P(4)-Pt(1)-H(1M) 166(2), P(4)i-Pt(1)-H(1M), 91(2),
Pt(2)-Pt(1)-H(1M) 35(2), P(3)-Pt(2)-P(1) 94.71(6), P(3)-Pt-
(2)-P(2) 96.48(6), P(1)-Pt(2)-P(2) 167.02(6), P(3)-Pt(2)-Pt-
(1) 145.04(4), P(1)-Pt(2)-Pt(1) 50.61(5), P(2)-Pt(2)-Pt(1)
117.51(5), P(3)-Pt(2)-H(1M) 178(2), P(1)-Pt(2)-H(1M)
86(2), P(2)-Pt(2)-H(1M) 83(2), Pt(1)-Pt(2)-H(1M) 36(2), Pt-
(1)-P(1)-Pt(2) 78.29(5), O(1)-P(2)-Pt(2) 108.45(18), Pt(2)-
P(3)-H(3) 113(3), Pt(1)-P(4)-Pt(1)i 103.39(6). Symmetry opera-
tor i = 1 - x, -y, 2 - z.
Crystals of [9][BF4]2 suitable for X-ray analysis were obtained
as a dichloromethane solvate from the slow evaporation of a
CH2Cl2 solution. The XRD structure of [9][BF4]2 2CH2Cl2 is
3
shown in Figure 5. The compound consists of a divalent cationic
-
complex, two BF4 ions, and two clathrated molecules of
CH2Cl2.24 The cation is a centrosymmetric tetrametallic com-
plex in which the Pt atoms are bridged by four dicyclohexylpho-
sphanido and two hydrido ligands. The structure can be regarded
as two “(Cy2PH){κP-PCy2(OH)}Pt(μ-PCy2)(μ-H)Pt” sub-
units held together by two PCy2 groups to form a Pt2P2 rhombus.
The Pt1-Pt1i distance within this core is 3.6539(11) Å, indicat-
ing that there is no metal-metal bond. The intermetallic
distance between the two Pt atoms of each subunit (Pt1-Pt2)
is 2.8994(6) Å, in full agreement with the presence of a Pt-Pt
bond. The different interatomic separations observed passing
from Pt1-Pt1i to Pt1-Pt2 is reflected by the very different Pt-
μP-Pt angles which pass from 103.39(6)° (Pt1-P4-Pt1i) to
78.29(5)° (Pt1-P1-Pt2), a further confirmation of the re-
nowned flexibility of bridging phosphanides.21 The valence
electron count for [9]2þ is 60, so the entire cation requires
two metal-metal bonds to guarantee coordinative saturation to
all Pt atoms, as found in the crystal structure. The coordination
environments around the four Pt centers are essentially coplanar,
as shown in Figure 6. The coordination planes of Pt2 and Pt1
subtend a dihedral angle of 15.0(16)°, whereas the ligands
around Pt1 and Pt1i are coplanar for symmetry reasons. The
P(OH)Cy2 hydrogen forms a hydrogen bond with the tetra-
fluoroborate anion, analogously to what was found for [2-
tetranuclear complex [(PHCy2){κP-P(OH)Cy2}]Pt1(μ-PCy2)-
(μ-H)Pt2(μ-PCy2)]2(BF4)2(Pt1-Pt2) ([9][BF4]2).23
Also, the compound [9][BF4]2, once formed, tends to pre-
cipitate from dichloromethane but, differently from 8, is soluble
in dmso-d6. The 31P{1H} NMR of complex [9]2þ in dmso-d6
shows four signals at δ 138.1, 119.5, 0.6, and -111.1, all flanked
by 195Pt satellites, attributable to the four pairs of unequivalent P
nuclei. The P atoms of the bridging phosphanides are involved in
a second order spin system which was fully resolved by computer
simulation (Figure S15, Supporting Information). The multi-
plets at δ 138.1 and δ -111.1 are attributable to the bridging
phosphanides subtending (δ 138.1) or not subtending (δ
-111.1) a Pt-Pt bond. The signal at δ 119.5 is a doublet of
doublets due to couplings with the trans (2JP,P = 244 Hz) and the
cis (2JP,P = 25 Hz) P atoms, attributable to the coordinated
P(OH)Cy2; that at δ 0.6 is broad and falls in the region of the
coordinated PHCy2. The proton coupled 31P NMR spectrum
confirms these attributions, as the only signal that significantly
splits by passing from decoupled to coupled experiments is that
at δ 0.6 (1JP,H = 355 Hz). The 1H NMR spectrum shows, besides
the signals due to cyclohexyl protons, (i) a deshielded singlet at δ
10.04 flanked by 195Pt satellites (3JH,Pt = 57 Hz) attributable to
the POH protons, (ii) a broad doublet at δ 5.28 flanked by 195Pt
satellites (2JH,Pt = 65 Hz) attributable to the H directly bonded
to P (1JP,H = 355 Hz), and (iii) a broad multiplet flanked by
195Pt satellites (1JH,Pt(1) = 576 Hz, 1JH,Pt(2) = 440 Hz) centered at
δ -5.85, attributable to the bridging hydrides. The NMR
resonances of 195Pt1 and 195Pt2 were found at δ -5014 and δ
-5630, respectively.
CH3CN][BF4]2. In the case of [9]2þ, the distance F3BF
3 3 3
HOP is 2.02 Å and the O-H F angle is 157°.
3 3 3
Tetranuclear phosphanido complexes of Pt are rare. The
25
known examples comprise cyclic complexes (featuring Pt4P4
or Pt4P2I226 rings) as well as linear26,27 and bent27b,28 species.
The formation of 8 can be envisioned as deriving from the
dimerization of fragment B (Scheme 11), which, in turn, can be
supposed to form via deprotonation of the coordinated P2HCy2
by the fluoride bases present in the environment, under the
particular conditions employed for the synthesis.
DFT Studies. Density functional calculations were performed
to study the energetics and the mechanism of the protonation
reaction of 1 by HBF4 and HF. This study was carried out using
models with methyl groups in place of cyclohexyl groups. The
reliability of this model in reproducing the experimental geome-
trical parameters had already been proven for complexes 12 and its
protonation products with HX (X = Cl, Br)3 and was confirmed for
[2-CH3CN][BF4]2 and [9][BF4]2, the products of protonation
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Scheme 12. Energy Diagram for the Stable Products of the Protonation Reaction of 1 with H3OþBF4
-
structurally characterized by XRD analysis, for which the calculated
bond lengths and angles differ less than 0.06 Å and 5° from the
experimental data. For the sake of simplicity, in the following
discussion, we will not distinguish between the actual cyclohexyl-
substituted complexes and their methyl-substituted models. The
DFT calculations on [2-CH3CN][BF4]2 and [9][BF4]2 were
performed considering explicitly the complexes as ion pairs, made
up of a dinuclear or tetranuclear dicationic core and two BF4- anions,
as indicated by X-ray diffraction studies.
solutions,29 as confirmed by our DFT calculations, indicating that
the H3OþBF4- ion pair is more stable than H2O and HBF4 (by 8.8
kcal mol-1 in n-hexane and 7.6 kcal mol-1 in dichloromethane), we
considered the H3OþBF4- ion pair as the actual reacting species.
Scheme 12 shows an energy gain of 28 kcal mol-1 in n-hexane
(31 kcal mol-1 in dichloromethane) for the protonation of 1 by 1
equiv of H3OþBF4- leading to [3-H2O][BF4] and of a further
8 kcal mol-1 (13 kcal mol-1 in dichloromethane) for protonation
by a second equivalent of H3OþBF4-, leading to [2-H2O]-
[BF4]2, with an overall reaction energy of -36 kcal mol-1 (-44
kcal mol-1 in dichloromethane) for the double protonation of 1.
Slightly higher values were calculated for the formation energies
of [2-CD2Cl2][BF4]2 (-48 kcal mol-1), [2-acetone-d6][BF4]2
Reaction with HBF4
Thermodynamics of the Formation of [3-L][BF4], [2-L]-
[BF4]2, and [4-H2O][BF4]2. We first addressed the thermody-
namics of the protonation reaction of 1 with 1 or 2 equiv of
HBF4, trying to account for all of the considered experimental
conditions, i.e., the addition of aqueous HBF4 to an n-hexane or
dichloromethane solution of 1, and the addition of etherate
HBF4 to the solution of 1 in acetone-d6, CD2Cl2, and acetonitrile.
To this purpose, we considered the formation of the initial
monoprotonated products, the [(PHCy2)(L)Pt(μ-PCy2)(μ-
H)Pt{κP-P(O)Cy2}(PHCy2)](BF4) ion pairs, [3-L][BF4], and
the final [(PHCy2)(L)Pt(μ-PCy2)(μ-H)Pt{κP-P(OH)Cy2}-
(PHCy2)](BF4)2 products [2-L][BF4]2, with L = H2O, acet-
one-d6, CD2Cl2, and acetonitrile. According to the experimental
procedure, the solvation effects were calculated for the solvent L
itself when L = acetone-d6, CD2Cl2, and acetonitrile, and for both
n-hexane and dichloromethane when L = H2O.
(-59 kcal mol-1), and [2-CH3CN][BF4]2 (- 65 kcal mol-1
)
from 1 and two HBF4’s plus one L solvent molecule. The cor-
responding energies for the formation of the corresponding [3-
L][BF4] monoprotonated species are -27 kcal mol-1 (L =
CD2Cl2), -35 kcal mol-1 (L = acetone), and -41 kcal mol-1
(L = CH3CN).
Finally, we addressed the thermodynamics of the isomeriza-
tion product [4-H2O][BF4]2, obtained when [2-H2O][BF4]2
was left in a solution of halogenated solvents. Calculations
indicated that the isomerization of [2-H2O]2þ into [4-H2O]2þ
is an energetically favored process, even though by only 4
kcal mol-1 (9 kcal mol-1 in dichloromethane).
Special care was paid to consider the formation of [3-H2O]-
[BF4] and [2- H2O][BF4]2 from the addition of aqueous HBF4
to an n-hexane or dichloromethane solution of 1. Taking into
account that HBF4 is known to be completely ionized in aqueous
Mechanism of Protonation. Theoretical calculations were
carried out to shed light on the mechanism of the protonation
reaction of 1 with aqueous HBF4, calculating the energies of
possible intermediates and the energy barriers of the main steps.
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Scheme 13. Possible Ion Pairs for the Reaction of 1 with H3OþBF4
-a
a Reaction energies are referred to 1 and the H3OþBF4- pair infinitely apart in n-hexane.
In principle, several potential protonation sites are available in
complex 1, that is, the two platinum atoms, the phosphinito
oxygen, the metal-metal bond, and the Pt-P bonds. We first
addressed the preliminary approach of the H3OþBF4- ion pair
to 1 and investigated the formation of a hydrogen bond between
the H3Oþ ion and each of these sites. Several geometry
optimizations starting from various orientations of H3Oþ al-
lowed us to locate five stable adducts corresponding to the
formation of a hydrogen bond between H3Oþ and either the Pt1
or Pt2 atom (one of the three H-O bonds lying perpendicular to
the platinum coordination plane), with two Pt-P bonds (one of
the H-O bonds lying in the Pt1 (Pt2) coordination plane and
interacting with both the bridging μP1 and the P2 (P4) terminal
phosphorus ligands), and with the Pt1-P2 bond (the H3Oþ unit
lying in the Pt1 coordination plane trans to the bridging
phosphanido ligand). The hydrogen bond adduct of the
-
H3OþBF4 ion pair with the phosphinito oxygen undergoes a
barrierless proton transfer leading to the dinuclear cationic
species C (Scheme 13) in which a water molecule bridges the
BF4- counteranion and the POH moiety. The species C, with a
binding energy of 16 kcal mol-1 with respect to 1 and
H3OþBF4 infinitely apart, is by far more stable than the five
-
calculated hydrogen bond adducts. Indeed, the adducts with a
hydrogen bond between the H3OþBF4- pair and the Pt atoms
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Scheme 14. Overall Energy Profile for the Reaction of 1 and the H3Oþ BF4- Ion Pair Leading to [2-H2O][BF4]2
a
a Reaction energies are reported with respect to 1 þ H3OþBF4- or 1 þ2H3OþBF4- in n-hexane.
showed bonding energies of 6-7 kcal mol-1, while the adducts
where the interaction occurs with the Pt-P bonds showed
Pt atoms), the high contribution of the p(O) orbital to the HOMO
of 1, and the formation of the complexes with the smallest structural
bonding energies of 4-5 kcal mol-1
.
changes relative to the parent species 1.3
We then studied the proton transfer process within each of the
five calculated hydrogen-bonded adducts, performing geometry
optimizations on the resulting H2O bridged ion pairs between
We then addressed the mechanism leading from the initially
formed ion pair C to the final product [2-H2O][BF4]2, trying to
identify the main intermediates and transition states. As shown in
Scheme 2, the protonation of 1 with strong hydrohalic acids HX
(X = Cl, Br, I) passes through intermediates A, endowed with a
-
the protonated dinuclear species and the BF4 anion, and
evaluating their energies with respect to 1 and H3OþBF4
-
six-membered Pt—X H-O-P-Pt ring that evolves first
infinitely apart. All geometry optimizations led to five further
3 3 3
minima on the potential energy surface for 1 plus H3OþBF4
-
into the monoprotonated compounds [(PHCy2)(X)Pt(μ-
PCy2)(μ-H)Pt(Cy2PH){κP-P(O)Cy2}](Pt-Pt) and then, in
the presence of excess acid, into the diprotonated compounds,
[(PHCy2)(X)Pt(μ-PCy2)(μ-H)Pt(Cy2PH){κP-P(OH)Cy2}]X
(Pt-Pt). Although monitoring the protonation of 1 by VT-NMR
with aqueous HBF4 in n-hexane did not reveal any signal
attributable to a six-membered platinacycle intermediate I similar
to A (with H2O in place of the Cl ligand), we have nonetheless
assumed for the protonation by HBF4(aq) a path similar to that
found for HCl, i.e., the sequence 1 f C f I f [3-H2O]þ
(Scheme 14). Indeed, a geometry optimization led to a stable
minimum for the putative intermediate I (see Figure 7), 5 kcal
corresponding to the protonation of one platinum atom (D, E, F,
and G) and to the metal-metal bond (H) (Scheme 13). The
calculated energy gains for the corresponding ion pairs range
from 7 to 14 kcal mol-1, showing bonding energies lower than
that found for C (16 kcal mol-1).
These results indicate the oxygen protonated structure C as the
most stable species formed by proton transfer from H3OþBF4- to 1.
This behavior parallels what was found for the protonation of 1 with
HCl and had already been rationalized in terms of the high negative
charge on the O atom, the easier proton approach to O (less
hampered by steric hindrance of the large cyclohexyl groups than the
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Figure 7. Structures of some intermediates and transition states of the protonation of 1 with aqueous HBF4 or HF, see text.
mol-1 more stable than C and 21 kcal mol-1 than 1 and H3Oþ-
imaginary frequency of 1228 cm-1 corresponding to the ex-
pected normal mode. Thisþtransition state is actually connected
BF4- infinitely apart.
0
Moreover, the significant elongation of the Pt1-O bond upon
oxygen protonation, from 2.18 Å in 1 to 2.32 Å in C, indicates a
high degree of bond weakening and suggests a low-energy
pathway for the migration of the H2O hydrogen bonded to the
phosphinic acid in the initially formed ion pair C to the Pt1 left
coordinatively unsaturated by the detachment of the oxygen and
leading to the six-membered intermediate I.
to a conformer [3-H2O] , having the phosphinito oxygen
directed toward the bridging hydride, slightly less stable (by 3
kcal mol-1) than the global minimum [3-H2O]þ, where the
oxygen atom is directed away from the bridging hydride, and to
which it is expected to easily relax. These results show that the
proton transfer from the phosphinito oxygen to the Pt-Pt bond
is an exothermic process (by 7 kcal mol-1) with a relatively low
energy barrier, 18 kcal mol-1, indicating that the intramolecular
conversion of I into [3-H2O]þ is a quite facile process. The
difference between the energy barrier found for the analogous
process operative during the protonation of 1 by HCl (29 vs 18
This point was further investigated by calculating the energy
profile for this pathway, taking the Pt-O(water) distance as a
reaction coordinate. This distance was varied from 4.19 Å, the
value in C, to 2.32 Å, the value in I, optimizing all of the
remaining geometrical parameters at each fixed value of the
reaction coordinate. The calculated energy profile (Scheme 14)
indicates that this is a facile exothermic process, with a reaction
kcal mol-1) may be held responsible for the fact that the
3
intermediate I was undetectable by NMR spectroscopy even at
low T.
energy of -5 kcal mol-1 and a maximum of only 6 kcal mol-1
,
The lower energy barrier for the proton transfer from the
oxygen to the Pt-Pt bond observed for the I f [3-H2O]þ
transformation with respect to the A f [3-Cl] one could be due
to the slightly higher electron charge on the Pt-Pt bond present
in the former case.
We also addressed the second protonation step of 1, i.e., the
protonation of [3-H2O][BF4] by H3OþBF4- to give [2-H2O]-
[BF4]2. In principle, the protonation sites in [3-H2O]þ are
represented by the platinum atoms, the bridging hydride, the
Pt-P bonds, the aqua ligand, and the phosphinito oxygen. By
considering the interaction of [3-H2O]þ with a H3OþBF4- ion
pair, we looked for the possible hydrogen-bonded adducts by
energy optimization of several starting geometries with all
possible orientations of the attacking H3Oþ unit. Stable hydro-
gen-bound adducts were found for the H3Oþ moiety interacting
3
3
suggesting that C is a highly unstable species which evolves
immediately to I.
We then considered also the energy profile of the intramole-
cular rearrangement from I to the monoprotonated species [3-
H2O]þ (Scheme 14). In this case, the distance between the
hydrogen bridging the oxygen atoms and the midpoint of the
Pt-Pt bond was taken as the reaction coordinate, which was
varied from 3.35 Å, the value in I, to 1.07 Å, the final value in [3-
H2O]þ, obtaining a maximum in the energy profile ca. 21 kcal
mol-1 above I. Since the chosen reaction coordinate is only
approximate, and the corresponding maximum is quite high, we
performed a transition state search starting from the structure of
the maximum. This procedure gave a structure for the TS 18 kcal
mol-1 above that for I (Figure 7). The frequency analysis gave an
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-
with the Pt atoms, the Pt-P bonds, and the aqua ligand, with
bonding energies in the range of 2-10 kcal mol-1. However, the
and initially placed in the same positions occupied by the BF4
ion in the X-ray structure of [2-CH3CN][BF4]2, i.e., close to and
interacting with the hydrogen atoms of the phosphinic acid and
of the P2HCy2 ligands (see Figure 3), a barrierless proton
transfer occurred from the phosphinito oxygen and even from
the phosphane P atom to the F- ion, leading to one or two HF
molecules and a neutral [(PCy2)(H2O)Pt(μ-PCy2)(μ-H)Pt-
(PHCy2){κP-P(O)Cy2}](Pt-Pt) species, J (corresponding to
B, Scheme 11, but with Pt1 bonded to H2O), featuring a terminal
PCy2- ligand (Figure 7). The proton transfer occurs even if the
geometry optimization is carried out in a CH2Cl2 solution,
indicating that this is not an artifact of the gas-phase calculations.
The same result was obtained when a [F(HF)]- ion was
employed to simulate the Y- counteranion in the calculations,
the proton transfer leading to the same neutral Pt-Pt species and
to one or two (HF)2 dimers. Only when a larger [F(HF)n]- (n =
2-4) counteranion was employed, with two to four HF mole-
cules stabilizing the F- ion, did the geometry optimization lead
to the expected [3-H2O](Y) ion pair and [2-H2O](Y)2 ion triple
complexes. Unfortunately, the large size of these anions, their
floppiness, and the flatness of the potential energy surface for
their interaction with the dinuclear [3-H2O]þ or [2-H2O]2þ
cations led to convergence difficulties and exponentially in-
creased the computational load, making extensive calculations
on the thermodynamics and kinetics of the protonation of 1 by
HF an extremely difficult task, out of the scope of this study.
Nonetheless, our calculations gave important indications on
the protonation of 1 by HF:
hydrogen bond adduct of H3OþBF4 with the phosphinito
-
oxygen undergoes a barrierless proton transfer leading to the
final product [2-H2O][BF4]2 where the transferred proton on
-
the oxygen atom interacts with the BF4 anion through two
hydrogen bonds with a bridging H2O molecule. Therefore, our
calculations indicate that [3-H2O][BF4] is spontaneously pro-
-
tonated by a H3OþBF4 ion pair at the phosphinito oxygen,
leading to [2-H2O][BF4]2 with an energy gain of 8 kcal mol-1
(Scheme 14).
Reaction with HF
Thermodynamics and Mechanism of Protonation of 1 by
HF. We also considered the protonation reaction of 1 with HF,
trying to shed light on the reasons for the different behavior
shown by this acid compared to the other halohydric acids (HCl,
HBr, and HI), on one hand, and on the analogies with the
behavior of HBF4, on the other hand. We thus addressed the
thermodynamics of the protonation reaction of 1 with one HF
molecule in dichloromethane and compared it with the thermo-
dynamics, already investigated by us,3 for the analogous reaction
with HCl, HBr, and HI. The comparison indicates that while the
protonation of 1 by 1 equiv of HX (X = Cl, Br, I) to [3-X] leads to
an energy gain of 34-44 kcal mol-1, the protonation by HF to
give the hypothetical product [3-F] leads to an energy gain of
only 19 kcal mol-1. The reason for such a low formation energy
calculated for [3-F] can be attributed to the well-known low
affinity of Pt(II) for the F- ligand,30 and ultimately to the low
Pt-F bond energy. To further investigate this point, we calcu-
lated the energy required to detach the X- ion from the [3-X]
species in a CH2Cl2 solution, estimating Pt-X bond energies of
43-48 kcal mol-1 for X = Cl, Br, and I and only 33 kcal mol-1
for X = F. An analogous calculation on the detachment of the
H2O molecule from [3-H2O]þ leads to a Pt-OH2 bond energy
of 35 kcal mol-1, a value slightly higher than that of the Pt-F
bond, but still much lower than those of the Pt-Cl, Pt-Br, and
Pt-I bonds.
(i) For Y- = [F(HF)n]- (n = 2-4), the calculated geometries
for [3-H2O](Y) and [2-H2O](Y)2 are very close to those
calculated for [3-H2O][BF4] and [2-H2O][BF4]2, in
agreement with the NMR indications. This result also
suggests that stable [3-H2O](Y) and [2-H2O](Y)2 form
only with oligomeric counteranions Y- where the F- ion
is stabilized by tight hydrogen bonds with at least two HF
molecules.
(ii) For the [F(HF)2]- or [F(HF)3]- counteranions, pre-
sumably close to the actual ones, we could also calculate
the formation energies of [3-H2O](Y) and [2-H2O](Y)2
from 1 and one or two H3OþY- ion pairs in a dichlor-
omethane solution, obtaining values of 24 and 43 kcal
mol-1 (for Y- = [F(HF)2]-) and 25 and 41 kcal mol-1
(for Y- = [F(HF)3]-), respectively. Such values are
similar to those obtained for the formation of [3-H2O]-
[BF4] and [2-H2O][BF4]2 from 1 and one or two H3Oþ-
(BF4)- ion pairs in the same solvent, see Scheme 12.
Interestingly, if the formation energies of [3-H2O](Y)
and [2-H2O](Y)2 are calculated in toluene, much lower
The relatively low value calculated for the formation energy of
[3-F] (19 kcal mol-1) and the comparable bond energies found
for the Pt-F and Pt-OH2 bonds (33-35 kcal mol-1) give a
rationale for the fact that neither [3-F] nor the corresponding
doubly protonated [2-F]þ species could be isolated from reac-
tions of 1 with hydrofluoric acid.
Unfortunately, an accurate calculation of the thermodynamics
for the protonation of 1 by 1 and 2 equiv of HF leading to [3-
H2O](Y) and [2-H2O](Y)2, respectively, was prevented by the
subtle nature of the Y- counteranion, which is related to the
complicated behavior of HF in aqueous solution. Indeed, several
experimental and theoretical studies in recent decades have
shown that an aqueous solution of hydrofluoric acids are made
up of a complex mixture of hydrogen bonded HF/H2O clusters
in equilibrium with tightly bound [H2O Hþ F-] ion pairs
values are obtained (15 and 34 kcal mol-1 for Y-
[F(HF)2]- and 16 and 33 kcal mol-1 for Y-
=
=
[F(HF)3]-, respectively) which could partly account
for the lack of reactivity of 1 with HF in this solvent.
(iii) The results of the geometry optimization for [3-H2O]-
(Y) and [2-H2O](Y)2 when using, as a counteranion, F-
bare or solvated by only one HF molecule indicate that
these anions are sufficiently basic to abstract a proton
from the phosphinito O and phosphane P atoms. These
kinds of anions are expected to be present in diluted HF
solutions or to form upon the addition of an excess of
fluoride anions, conditions in which there are not enough
HF molecules to form [F(HF)n]- (n = 2-4) species.
When the protonation of 1 is carried out in diluted HF,
3 3 3
3 3 3
stabilized by hydrogen bonding with neighboring H2O and HF
molecules; while at low concentrations these ion pairs are quite
stable, at high HF concentrations they dissociate into H3Oþ,
stabilized by hydrogen bonding with HF and H2O, and a variety
of polyfluoride [F(HF)n]- and [F(HF)n(H2O)m]- anions with
n þ m varying from one to four.19
The results of geometry optimization for [3-H2O](Y) and [2-
H2O](Y)2 strongly depend on the kind of species which is
actually employed to simulate the Y- counteranion in the
calculations. In particular, when a bare F- ion was employed
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Scheme 15. Reaction Scheme for the Formation of [6](Y) from [2-H2O](Y)(F) (Y- = [F(HF)3]-)
the initially formed [3-H2O]þ can be deprotonated to J,
which is expected to easily dimerize to the tetranuclear
species 8, in good agreement with the experimental
findings.
Scheme 16. Energy profile for the formation of [6](Y) from
[2-H2O](Y)(F) (Y- = [F(HF)3]-)
Only the formation of [6]þ and of 8 was addressed in detail.
We first faced the formation of [6](Y) from [2-H2O](Y)(F)
considering an F- anion approaching the phosphinito hydroxyl
and a stable Y- = [F(HF)3]- anion hydrogen-bonded to a
terminal phosphane hydrogen. The initial step, i.e., the proton
abstraction from the phosphinito oxygen in [2-H2O](Y)(F) by
the F- counteranion leading to [3-H2O](Y) and a HF moiety, is
an exoenergetic and barrierless process, for which we calculated
an energy gain of 9 kcal mol-1. The subsequent coordination of
the phosphinito oxygen in [3-H2O](Y) to the Pt1 atom leading
to the formation of the final [6](Y) species is also exoenergetic by
5 kcal mol-1 so that for the overall formation of [6](Y) from [2-
H2O](Y)(F) we calculated a reaction energy of 14 kcal mol-1
.
In order to study the kinetics of the isomerization of [3-
H2O](Y) to [6](Y) and to shed light on its mechanism, we
calculated the energy profile for the binding of the phosphinito
oxygen to the Pt1 atom in [3-H2O](Y) as the initial step for the
formation of [6](Y). As the reaction coordinate was taken, the
Pt-O distance was varied from 4.19 Å, the value in [3-H2O](Y),
to 2.32 Å, the value in the final product [6](Y), optimizing all of
the remaining geometrical parameters at each fixed value of this
reaction coordinate. The calculated energy profile (Scheme 16)
shows that the oxygen coordination to Pt1 causes the detachment
of the water molecule but not of the bridging hydrogen atom
from Pt1 and leads to the formation of a [(PHCy2)Pt(μ-PCy2)-
(μ-H){κ2P,O-μ-P(O)Cy2}Pt(PHCy2)](Y)(Pt-Pt) species, K
(Scheme 15), characterized by the simultaneous presence of a
hydrogen and phosphinito bridges and indicates a relatively facile
process, with a maximum—an upper limit to the energy barrier—
of 17 kcal mol-1. A second energy profile was then calculated for
3
the rupture of the Pt1-H bond and formation of a terminal Pt2-
H species, taking the Pt1-H distance as a reaction coordinate
and varying it from 1.71 Å, the value in K, to 3.84 Å, the value in
[6](Y). The results indicate the formation of the isomer [60](Y)
rather than [6](Y) and a barrier of only 4 kcal mol-1, indicating
3
that this is a very easy process. The isomer [60](Y) is slightly less
stable than [6](Y), by 2 kcal mol-1, to which it is expected to
easily isomerize and which is therefore the final product of the
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reaction. The overall process can therefore be considered to
occur through the mechanism reported in Scheme 15.
H2PtCl6 (195Pt), CFCl3 (19F), and BF3 Et2O (11B). The signal attribu-
3
tions and coupling constant assessment were made on the basis of a
multinuclear NMR analysis of each compound including, besides 1D
spectra, 1H-31PHMQC, 1H-195Pt HMQC, 31P{1H} COSY, and 31P{1H}
long-range COSY. The coupling constants not directly extractable from
the monodimensional spectra were obtained and attributed by the tilts of
the multiplets due to the “passive” nuclei32 in the aforementioned 2D
spectra. High resolution mass spectrometry (HR-MS) analyses were
performed using a time-of-flight mass spectrometer equipped with an
electrospray ion source (Bruker micrOTOF). All analyses were carried
out in 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/min. The instrument was operated at end plate offset -500 V and
capillary -4500 V. Nebulizer pressure was 1.5 bar (N2), and the drying
gas (N2) flow was 10 L/min. Capillary exit and skimmer 1 were 120 and
40 V, respectively. The drying gas temperature was set at 220 °C. The
software used for the simulations is Bruker Daltonics DataAnalysis
(version 3.3). The ESI-MS and MS/MS analyses were carried out on a
triple quadrupole PE Sciex instrument (mod. API 365), equipped with a
Turbospray source.
Intrigued by this result, we have carried out the reaction of 1
with an 8-fold excess of hydrofluoric acid at 258 K in CD2Cl2, and
we were pleased to find that, at this temperature and after 1 h,
distinctive signals attributable to the isomer [60](Y)31 together
with those attributed to [2-H2O](Y)2 appeared in 31P{1H}, 1H,
and 195Pt{1H} NMR spectra of the reaction mixture. As ex-
pected, warming the reaction mixture up to 298 K triggered the
quantitative [60](Y)f[6](Y) isomerization, as evidenced by
NMR spectroscopy.
We finally evaluated the reaction energies for the steps
involved in the formation of 8 from [3-H2O](Y), for Y- = F-
interacting with the hydrogen atom on the phosphane coordi-
nated to Pt1. The first step, corresponding to a proton abstraction
from the P2 phosphorus (i.e., the P cis to H2O) in [3-H2O](F) by
the F- counteranion leading to J and a HF moieties, is an
exoenergetic and barrierless process, for which energy gains of
3 kcal mol-1 were calculated. The subsequent dimerization of two
J units, leading to the tetramer species 8, is a thermodynamically
favored process with a reaction energy of 15 kcal mol-1 and is also
expected to show a small energy barrier (not evaluated) corre-
sponding to the detachment of the water molecule in J.
For the complexes [2-L]2þ (L = H2O, CH3CN, PhCN), the HR-
MS(þ) spectrogram showed a very intense peak at m/z = 1197.53
corresponding to [M - L - H]þ, accompanied, when the analysis was
carried out in chloroform, by a peak at 1233.51 Da corresponding to
[M - L þ Cl]þ. Both peaks gave isotopic patterns superimposable on
those calculated on the basis of the proposed formulas. In the case of
[2-H2O]2þ a weak peak at m/z 1214.53 was present, attributable to the
[M - H]þ ion. For [2-PPh3]2þ, the spectrogram showed an intense
peak at m/z 1459.21, corresponding to the monocharged ion [2-PPh3]þ
together with a weak peak at m/z 730.32 corresponding to the doubly
charged ion [2-PPh3]2þ, as indicated by the isotope pattern (see the
Supporting Information).
’ CONCLUSIONS
Experimental and DFT data allowed us to outline the course of
the protonation of the phosphinito-bridged Pt(I) complex 1 with
HBF4 or HF, which, in general, parallels that already described
for halohydric acids such as HCl and HBr. In fact, hydrido-
bridged dicyclohexylphosphinic acid Pt(II) dinuclear complexes
[(PHCy2)(X)Pt(μ-PCy2)(μ-H)Pt(PHCy2){κP-P(OH)Cy2}]nþ
-
(Pt-Pt) ([2-X]nþ, X = Cl, Br, n = 1; X = H2O, acetone,
dichloromethane, CH3CN, n = 2) are formed in all cases with
excess acid. However, in the case of HBF4 or HF, the poorly
coordinating anions of these Brønsted acids are not incorporated
in the protonation products, which bear solvent molecules (H2O,
acetone, dichloromethane, acetonitrile) in order to fulfill the
coordination requirements of the platinum. Moreover, differ-
ently from the protonation products obtained with HCl or HBr,
which are indefinitely stable in solution, the hydrido-bridged
dicyclohexylphosphinic acid Pt(II) dinuclear complexes ob-
tained with HBF4 or HF spontaneously isomerize into new
species. Interestingly, the protonation of 1 by HF carried out with
diluted hydrofluoric acid resulted in the formation of the tetra-
nuclear complex 8. This has been explained admitting that,
under the described experimental conditions, a significant
amount of the species {F(HF)}-, or {F(H2O)n}-, able to
deprotonate one of the PHCy2 ligands, may be present in the
reaction medium.
Computational Details. DFT calculations have been performed
using the Amsterdam density-functional (ADF) package.33 The 1s
orbital for C, O, and F; 1s-2p orbitals for P; and 1s-4f orbitals for
Pt are kept frozen. For all main group atoms, the valence orbitals were
expanded in an uncontracted triple-ζ Slater-type orbital (STO) basis set
augmented with a polarization function. For platinum orbitals, we used a
double-ζ STO basis set for 5s and 5p and a triple-ζ STO basis set for 5d
and 6s. As polarization functions, we used one 6p function for Pt; one 4d
for P; one 3d for C, O, and F; and one 2p for H.
The LDA exchange correlation potential and energy were used,
together with the Vosko-Wilk-Nusair parametrization34 for homo-
geneous electron gas correlation, including Becke’s nonlocal correc-
tion35 to the local exchange expression and Perdew’s nonlocal correc-
tion36 to the local expression of correlation energy. Since the relativistic
effect is important in these Pt-containing dimers, the zero-order regular
approximation formalism (ZORA) without the spin-orbit coupling has
been included.37 Previous calculations indicate that gradient-corrected
functionals together with the ZORA approximation can predict reliable
properties of metal dimers in comparison with the Dirac four-component-
MP2 calculations.38 Molecular structures of all considered complexes
were optimized at this gradient-corrected relativistic level with the above
basis set. Single point calculations were subsequently performed on the
optimized geometries with a larger basis set obtained from the above one
through the addition of a second polarization function, a 5f for Pt; a 4f for
P, C, O and F; and one 3d for H. Solvent effects were taken into account
employing the COSMO continuum solvent model,39 in the standard
parametrization implemented in the ADF program.40 Free energies of
’ EXPERIMENTAL SECTION
Complex 1 was prepared as described in ref 2. Other reagents were
from commercial suppliers and were used without further purification.
Although the starting complex 1 as well as all of the hydrido-bridged
products were found to be air stable, all manipulations were carried out
under a pure dinitrogen atmosphere, using freshly distilled and oxygen-
free solvents. C, H, N elemental analyses were carried out on a VARIO
MICRO-CHNSO elemental analyzer. Infrared spectra were recorded
on a Bruker Vector 22 spectrometer.
solvation in n-hexane (ε = 1.88, Rprobe = 3.74), acetone (ε = 20.7, Rprobe
=
3.08), and dichloromethane (ε = 8.9, Rprobe = 2.94) were calculated with
the largest basis set on the optimized geometries of all considered
molecules.
NMR spectra were recorded on BRUKER Avance 400 spectrometer;
frequencies are referenced to Me4Si (1H and 13C), 85% H3PO4 (31P),
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Table 2. Crystallographic Data and Structural Refinement
1H NMR (CD2Cl2, 258 K, δ): 6.33 (broad, H1), 5.34 (broad, H5),
4.58 (m, H2, 1JH(2),P(2) = 371 Hz, 2JH(2),Pt(1) = 193 Hz), 4.96 (m, H4,
Details for [9][BF4]2 2CH2Cl2and [2-CH3CN][BF4]2
3
1JH(4),P(4) = 362 Hz, 2JH(4),Pt(2) = 43 Hz), -5.48 (m, H3, 2JH(3),P(4)
=
2
2
2
[9][BF4]2
[2-CH3CN][BF4]2
71 Hz, JH(3),P(2) = 63 Hz, JH(3),P(1) = 18 Hz, JH(3),P(3) = 16 Hz,
1JH(3),Pt(2) = 541 Hz, 1JH(3),Pt(1) = 397 Hz) ppm.
empirical formula
formula mass
temp [K]
wavelength [Å]
cryst syst
space group
unit cell dimensions
a [Å]
C100H190B2Cl8F8O2P8Pt4 C50H95B2F8NOP4Pt2
31P{1H} NMR (CD2Cl2, 295 K, δ): 149.7 (dd, P1, 1JP(1),Pt(1) = 2940
Hz, 1JP(1),Pt(2) = 1498 Hz, 2JP(1),P(3) = 289 Hz, 2JP(1),P(4) = 13 Hz), 126.8
(dd, P3, 1JP(3),Pt(2) = 2770 Hz, 2JP(3),P(1) = 289 Hz, 2JP(3),P(4) = 23 Hz),
9.1 (d, P2, 1JP(2),Pt(1) = 4047 Hz, 2JP(2),Pt(2) = 206 Hz, 3JP(2),P(4) = 45 Hz),
2909.86
130(2)
1413.95
110(2)
0.71073
monoclinic
P21/c
0.71073
monoclinic
P21/c
-1.7 (broad, P4, 1JP(4),Pt(2) = 3414 Hz, 2JP(4),Pt(1) = 206 Hz, 2JP(4),P(1)
13 Hz, 2JP(4),P(3) = 23 Hz, 3JP(4),P(2) = 45 Hz) ppm.
=
195Pt{1H} NMR (CD2Cl2, 258 K δ): -5589 (m, Pt1, JPt(1),P(2)
=
1
4047 Hz, 1JPt(1),P(1) = 2940 Hz, 2JPt(1),P(4) = 206 Hz, 1JPt(1),Pt(2) = 714 Hz),
14.108(4)
26.736(7)
18.009(4)
121.086(17)
5817(3)
2
12.9836(6)
22.6964(11)
19.8898(10)
91.215(2)
5859.8(5)
4
-5302 (m, Pt2, 1JPt(2),P(4) = 3414 Hz,1JPt(2),P(3) = 2770 Hz, 1JPt(2),P(1)
1498 Hz, 2JPt(2),P(2) = 206 Hz 1JPt(2),Pt(1) = 714 Hz) ppm.
11B{1H} NMR (CDCl3, 298 K δ): -0.95 ppm.
=
b [Å]
c [Å]
β [deg]
V [Å3]
19F NMR (CD2Cl2, 298 K δ): -158.3 ppm.
Z
Dcalcd. [Mg m-3
abs coeff [mm-1
]
1.661
1.603
]
5.145
4.939
θ range for data coll.
[deg]
2.28-26.70
2.05-28.00
independent reflns
12097 (0.0750)
14137 (0.1211)
(Rint
)
observed reflns
36788
97869
[(PHCy2)2Pt(μ-PCy2)(μ-H)Pt{P(OH)Cy2}(H2O)][BF4]2(Pt-
Pt) ([4-H2O][BF4]2). An NMR tube charged with 60 mg of [2-
H2O][BF4]2 in 0.5 mL of CD2Cl2 was sealed under nitrogen and
allowed to stand at room temperature. Periodically recording 31P-
{1H} NMR spectra revealed the quantitative transformation into [4-
H2O][BF4]2 after 1 month. The recovered solution was concen-
trated to ca. 0.2 mL, and cold n-hexane was added, causing the
precipitation of pure [4-H2O][BF4]2 (50 mg, 83%).
data/params
goodness-of-fit on F2 1.008
Ra (I > 2σ(I))
wR2b (all data)
12097/603
14137/618
1.019
0.0452
0.0998
0.0529
0.0890
largest diff. peak/hole 1.498-1.600
[e Å-3
1.605-2.156
]
a R = ∑||Fo| - |Fc||/∑|Fo|. b wR2 = [∑w(Fo2 - Fc2)2/∑w(Fo ) ]
.
2 2 1/2
IR (KBr, cm-1): 3222 (br, s) ν(O-H); 2926 (s), 2926 (s); 2350 (w),
2343 (br w) ν(P-H); 2261 (vw) ν(P-O-H); 1634 (w) ν(μH-Pt); 1448
(s); 1346 (w); 1327 (w), 1295 (w); 1270 (m); 1058 (br vs), ν(BF4 þ PO);
917 (s) ; 886 (m); 848 (s); 818 (m);736 (m); 533 (m); 522 (s); 473 (m).
1H NMR (CD2Cl2, 295 K, δ): 5.9 (broad, POH þ Pt-OH2), 4.99 (d,
H1, 1JH,P = 368 Hz, 2JH,Pt = 63 Hz), 4.52 (m, H2, 1JH,P = 343 Hz, 2JH,Pt = 53
Hz), -6.29 (m, H3, 2JH(3),P(2) = 76 Hz, 2JH(3),P(4) = 65 Hz, 2JH(3),P(1) = 14
Hz, 2JH(3),P(3) = 14 Hz, 1JH(3),Pt(1) = 524 Hz, 1JH(3),Pt(2) = 386 Hz) ppm.
X-Ray Crystallography41. Crystal data, parameters for intensity
data collection, and convergence results for [2-CH3CN][BF4]2 and
[9][BF4]2 are compiled in Table 2. Diffraction quality crystals were
obtained from a chilled acetonitrile solution ([2-CH3CN][BF4]2) or by
slow evaporation of the solvent from a CH2Cl2 solution ([9][BF4]2).
Data were collected with Mo KR radiation (graphite monochromator,
λ = 0.71073 Å) on a Bruker D8 goniometer with a SMART CCD area
detector on crystals of approximate dimensions 0.17 ꢀ 0.13 ꢀ 0.04 mm
([9](BF4)2) and 0.16 ꢀ 0.03 ꢀ 0.03 mm ([2-CH3CN][BF4]2). Multi-
scan based absorption corrections were performed with the help of the
program SADABS.42 The structures were solved by direct methods and
refined with full-matrix least squares on F 2.43
[(PHCy2)(H2O)Pt(μ-PCy2)(μ-H)Pt(PHCy2){P(OH)Cy2}][BF4]2-
(Pt-Pt) ([2-H2O][BF4]2). A total of 45 μL of HBF4(aq) (50%w, 0.35
mmol) was added to an n-hexane solution of 1 (0.140 g, 0.12 mmol in
10 mL), and the resulting mixture was stirred for 2 h at room
temperature, causing the precipitation of a pale yellow powder. Then,
the solid was filtered off, washed with n-hexane (3 ꢀ 5 mL), and dried
under vacuum conditions for 12 h. Yield: 0.14 g (95%).
31P{1H} NMR (CD2Cl2, 295 K, δ): 141.6 (dt, P1, 1JP(1),Pt(1) = 1607
2
Hz, 1JP(1),Pt(2) = 3202 Hz, 2JP(1),P(3) = 229 Hz, 2JP(1),P2() ≈ JP(1),P(4)
11 Hz), 118.5 (dd, P4, 1JP(4),Pt(2) = 3871 Hz, 2JP(4),Pt(1) = 212 Hz, 3JP(4),P(2)
38 Hz, 2JP(4),P(1) = 11 Hz), 5.3 (dd, P3, 1JP(3),Pt(1) = 2125 Hz, 2JP(3),Pt(2)
=
=
=
69 Hz, JP(3),P(1) = 229 Hz, JP(3),P(2) = 24 Hz), -6.1 (broad, P2,
2
2
1JP(2),Pt(1) = 3356 Hz, 2JP(2),Pt(2) = 118 Hz) ppm.
195Pt{1H} NMR (CD2Cl2, 295 K, δ): -5728 (dddd, Pt1, 1JPt(1),P(2)
=
=
1
1
2
3356 Hz, JPt(1),P(3) = 2125 Hz, JPt(1),P(1) = 1607 Hz, JPt(1),P(4)
212 Hz), -5291 (dddd, Pt2, 1JPt(2),P(4) = 3871 Hz, 1JPt(2),P(1) = 3202 Hz,
2JPt(2),P(2) = 118 Hz, 2JPt(2),P(3) = 69 Hz) ppm.
The complex is very soluble in halogenated solvents and acetonitrile
and insoluble in Et2O, n-hexane, and aromatic solvents.
Anal. Calcd for C48H93B2F8O2P4Pt2: C, 41.48; H, 6.74. Found: C, 41.35;
H, 6.81. ESI-MS, exact mass for the dication C48H93O2P4Pt2: 1215.5421.
Measured: m/z 1197.5333 (M - H2O - H)þ; 1214.5272 (M - H)þ.
IR (KBr, cm-1): 3364 (br, m), ν(O-H þ P-O-H); 2929 (vs),
2852 (vs), 2335 (br w), ν(P-H); 2261 (w); 1635 (w) ν(μ H-Pt);1448
(s); 1344 (w); 1327 (w), 1295 (w); 1269 (m); 1074 (br vs), ν(BF4 þ PO);
917 (s); 884 (s); 848 (s); 817 (m); 764 (w); 737 (m); 521 (s); 475 (m).
[(PHCy2)(CH3CN)Pt(μ-PCy2)(μ-H)Pt(PHCy2){P(OH)Cy2}]-
[BF4]2(Pt-Pt) ([2-CH3CN][BF4]2). A total of 44 μL of HBF4Me2O
(0.43 mmol) was added to an n-hexane solution of 1 (0.20 g, 0.17 mmol
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in 10 mL), causing the immediate precipitation of a yellow-orange solid.
The resulting supension was stirred for 20 min at room temperature.
Then, the solid was filtered off, washed with Et2O (3 ꢀ 5 mL), and dried
under vacuum conditions. The solid was dissolvend in 5 mL of CH3CN,
and the resulting yellow solution was stirred for 10 min. The solvent was
then removed, and the compound [2-CH3CN][BF4]2 was isolated as a
pale yellow powder.
(br vs), ν(BF4 þ PO); 1003 (s), 916 (s); 884 (s); 848 (s); 817 (m); 760
(m); 735 (m); 684 (m), 520 (s); 473 (s).
1H NMR (CDCl3, 295 K, δ): 7.94-7.66 (m, arom), 5.10 (m, H2,
1JH(2),P(2) = 388 Hz, 2JH(2),Pt(1) = 166 Hz), 4.99 (m, H4, 1JH(4),P(4) = 373
Hz, 2JH(4),Pt(2) = 41 Hz), -6.370 (m, H3, 2JH(3),P(4) = 64 Hz, 2JH(3),P(2)
=
2
2
1
62 Hz, JH(3),P(1) = 17 Hz, JH(3),P(3) = 11 Hz, JH(3),Pt(2) = 510 Hz,
1JH(3),Pt(1) = 402 Hz), 7.5 (broad, H1) ppm.
Yield: 0.18 g (75%).
31P{1H} NMR (CDCl3, 295 K, δ): 155.8 (m, P1, 1JP(1),Pt(1) = 2656
Hz, 1JP(1),Pt(2) = 1477 Hz, 2JP(1),P(3) = 289 Hz, 2JP(1),P(4) = 2JP(1),P(2) 12
Hz), 126.0 (d, P3, 1JP(3),Pt(2) = 2772 Hz, 2JP(3),P(1) = 289 Hz), 1.4 (d, P2,
The complex is hygroscopic; soluble in halogenated solvents and
acetonitrile; and insoluble in Et2O, n-hexane, and aromatic solvents.
Anal. Calcd for C50H95B2F8NOP4Pt2: C, 42.47; H, 6.77; N, 0.99.
Found: C, 42.65; H, 6.81; N, 1.03. ESI-MS, exact mass for the dication
C50H95NOP4Pt2: 1239.5659. Measured: m/z 1197.5333 (M - CH3CN -
H)þ, 1233.5105 (M - CH3CN þ Cl)þ.
2
3
1JP(2),Pt(1) = 3799 Hz, JP(2),Pt(2) = 171 Hz, JP(2),P(4) = 40 Hz), 0.5
(broad, P4, 1JP(4),Pt(2) = 3508 Hz, 2JP(4),Pt(1) = 172 Hz) ppm.
195Pt{1H} NMR (CDCl3, 295 K, δ): -5651 (ddd, Pt1, 1JPt(1),P(2)
=
3799 Hz, 1JPt(1),P(1) = 26564 Hz, 2JPt(1),P(4) = 172 Hz, 1JPt(1),Pt(2) = 929
IR (KBr, cm-1): 3290 (broad w), ν(PO-H); 2931 (vs) 2852 (vs);
2324 (m), 2295 (m), ν(P-H þ CN); 1651 (br m) ν(μ H-Pt); 1450
(s); 1411 (w); 1373 (w); 1346 (w); 1327 (w), 1296 (m); 1271 (m);
1203 (w); 1174 (m); 1073 (br vs), ν(BF4 þ PO); 918 (s); 884 (s); 849
(m); 818 (m); 762 (w); 737 (m); 521 (s); 474 (m).
Hz), -5484 (dddd, Pt2, JPt(2),P(4) = 3508 Hz,1JPt(2),P(3) = 2772 Hz,
1
1JPt(2),P(1) = 1477 Hz, 2JPt(2),P(2) = 171 Hz 1JPt(2),Pt(1) = 929 Hz) ppm.
1H NMR (CD3CN, δ): 4.98 (m, H2, 1JH(2),P(2) = 391 Hz, 2JH(2),Pt(1)
=
167 Hz), 5.22 (m, H4, 1JH(4),P(4) = 379 Hz, 2JH(4),Pt(2) = 44 Hz), -6.50
(m,H3,2JH(3),P(4) =66Hz,2JH(3),P(2) =63Hz,2JH(3),P(1) =17Hz,2JH(3),P(3)
13 Hz, 1JH(3),Pt(2) = 514 Hz, 1JH(3),Pt(1) = 392 Hz), 6.6 (dd,44 H1,2JH(1),P(3)
12 Hz, 2JH(1),P(1) = 6 Hz, 3JH(1),Pt(2) = 64 Hz) ppm.
=
=
1H NMR (CDCl3, δ): 2.72 (CH3CN) ppm.
[(PHCy2)(PPh3)Pt(μ-PCy2)(μ-H)Pt(PHCy2){P(OH)Cy2}]-
[BF4]2(Pt-Pt) ([2-PPh3][BF4]2). A total of 15 mg of PPh3 (0.057
mmol) was added to a CH2Cl2 solution of [2-H2O][BF4]2 (0.069 g,
0.050 mmol in 1.0 mL), and the resulting mixture was stirred for 10 min
at room temperature. After concentration of the solution to ca. 0.5 mL
and the addition of n-hexane (2.0 mL), the resulting yellow solid was
separated, washed with n-hexane (3 ꢀ 1 mL), and dried under vacuum
conditions.
13C{1H} NMR (CDCl3, δ): 3.7 (CH3CN), 127 (CH3CN) ppm.
1
31P{1H} NMR (CD3CN, δ): 155.3 (dd, P1, JP(1),Pt(1) = 2674 Hz,
2
2
1JP(1),Pt(2) = 1485 Hz, JP(1),P(3) = 290 Hz, JP(1),P(4) = 13 Hz), 126.8
(dd, P3, 1JP(3),Pt(2) = 2764 Hz, 2JP(13),Pt(1) = 50 Hz, 2JP(3),P(1) = 290 Hz,
2JP(3),P(4) = 26 Hz), 0.6 (d, P2, JP(2),Pt(1) = 3820 Hz, JP(2),Pt(2)
=
2
176 Hz, JP(2),P(4) = 42 Hz), -2.2 (broad, P4, JP(4),Pt(2) = 3437 Hz,
3
1
2JP(4),Pt(1) = 176 Hz, 2JP(4),P(1) = 13 Hz, 2JP(4),P(3) = 26 Hz, 3JP(4),P(2)
=
42 Hz) ppm.
Yield: 0.053 g (70%).
The complex is hygroscopic; soluble in halogenated solvents; and
insoluble in Et2O, n-hexane, and aromatic solvents.
1
195Pt{1H} NMR (CD3CN, δ): -5653 (dddd, Pt1, JPt(1),P(2)
=
=
=
=
1
2
2
3820 Hz, JPt(1),P(1) = 2674 Hz, JPt(1),P(3) = 50 Hz, JPt(1),P(4)
1
1
176 Hz, JPt(1),Pt(2) = 929 Hz), -5512 (dddd, Pt2, JPt(2),P(4)
Anal. Calcd for C66H106B2F8OP5Pt2: C, 48.51; H, 6.54. Found: C,
48.27; H, 6.24. ESI-MS, exact mass for the dication C66H106OP5Pt2:
1459.6227. Measured: m/z 1459.2128 (M)þ.
3437 Hz,1JPt(2),P(3) = 2764 Hz, JPt(2),P(1) = 1485 Hz, JPt(2),P(2)
1
2
176 Hz 1JPt(2),Pt(1) = 929 Hz) ppm.
IR (KBr, cm-1): 3215 (br m), ν(PO-H); 2929 (vs), 2852 (s); 2350
(w) 2261 (w); 1634 (w) ν(μ H-Pt); 1588 (w); 1483 (m); 1442 (s);
1294 (w); 1270 (m); 1203 (w); 1180 (s); 1096 (br vs), ν(BF4 þ PO);
1001 (s); 918 (s); 884 (s); 848 (m); 816 (s); 747 (s); 697 (s); 512 (s);
490 (m).
1H NMR (CDCl3, 295 K δ): 7.81-7.35 (m, arom), 5.04 (m, H2,
1JH(2),P(2) = 365 Hz), 5.13 (m, H4, JH2(4),P(4) = 367 Hz, JH(4),Pt(2)
=
1
2
57 Hz), -5.97 (m, H3, JH(3),P(2) ≈ JH(3),P(4) = 62 Hz, JH(3),P(1)
2
2
2
2
≈ JH(3),P(3) ≈ JH(3),P(5) = 13 Hz, 1JH(3),Pt(1) = 470 Hz, 1JH(3),Pt(2)
=
[(PHCy2)(PhCN)Pt(μ-PCy2)(μ-H)Pt(PHCy2){P(OH)Cy2}]-
[BF4]2(Pt-Pt) ([2-PhCN][BF4]2). A total of 8 μL of benzonitrile was
added to a CH2Cl2 solution of [2-H2O][BF4]2 (0.080 g, 0.058 mmol in
1.0 mL), and the resulting solution was stirred for 30 min at room
temperature. After concentration of the solution to ca. 0.5 mL and the
addition of n-hexane (2.0 mL), the resulting yellow solid was separated,
washed with n-hexane (3 ꢀ 1 mL), and dried under vacuum conditions.
Yield: 0.068 g (79%).
The complex is hygroscopic; soluble in halogenated solvents; and
insoluble in Et2O, n-hexane, and aromatic solvents.
Anal. Calcd for C55H96B2F8NOP4Pt2: C, 44.79; H, 6.56; N, 0.95.
Found: C, 44.65; H, 6.81; N, 1.03.
484 Hz), 6.1 (broad, H1) ppm.
31P{1H} NMR (CDCl3, 295 K, δ): 171.9 (dd, P1, 1JP(1),Pt(2) = 1635
1
2
2
Hz, JP(1),Pt(1) = 1442 Hz, JP(1),P(5) = 225 Hz, JP(1),P(3) = 270 Hz),
123.7 (d, P3, JP(3),Pt(2) = 2898 Hz, JP(3),P(1) = 270 Hz), 4.5 (d, P5,
1
2
1JP(5),Pt(1) = 2420 Hz, 2JP(5),P(1) = 225 Hz,), -1.7 (broad, P2, 1JP(2),Pt(1)
=
3555 Hz, JP(2),Pt(2) = 170 Hz), -3.1 (broad, P4, JP(5),Pt(2) = 3494
2
1
Hz) ppm.
195Pt{1H} NMR (CDCl3, 295 K, δ): -5705 (m, Pt1, JPt(1),P(1)
=
1
1635 Hz, 1JPt(1),P(2) = 3555 Hz, 1JPt(1),P(5) = 2420 Hz), -5684 (m, Pt2,
1JPt(2),P(1) = 1442 Hz,1JPt(2),P(3) = 2898 Hz, 1JPt(2),P(4) = 3494 Hz) ppm.
ESI-MS, exact mass for the dication C55H96NOP4Pt2: 1300.5738.
Measured: m/z 1197.5445 (M - PhCN - H)þ and 1311.5338 (M -
PhCN þ Cl)þ.
IR (KBr, cm-1): 3222 (br w), ν(PO-H); 2927 (vs) 2851 (vs); 2260
(m), ν(P-HþCN); 1630 (w) ν(μ H-Pt); 1594 (w); 1488 (w); 1449
(s) 1345 (w); 1327 (w), 1295 (w); 1271 (m); 1201 (m); 1180 (s); 1059
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Inorganic Chemistry
ARTICLE
(ddd, P4, 1JP(4),Pt(2) = 5396 Hz, 2JP(4),P(1) = 57 Hz, 2JP(4),P(2) = 36 Hz,
3JP(4),P(3) = 69 Hz), 1.7 (dd, P2, 1JP(2),Pt(1) = 2920 Hz, 2JP(2),P(1) = 12 Hz,
2JP(2),P(3) = 170 Hz, 3JP(2),P(4) = 36 Hz) ppm.
Reactions of 1 with HF. In a PTFE NMR tube, a CD2Cl2 solution
of 1 (0.040 g, 0.033 mmol in 0.5 mL) was added to 60 μL of HF (50%w,
d = 1.155 g/mL) and vigorously shaken for 5 min. Multinuclear NMR
analysis revealed the quantitative transformation into [2-H2O](Y)2
(spectroscopic yield > 90%). On standing in solution, part of [2-
H2O](Y)2 transformed into [6](Y) (1 h), which, in turn, evolved, in
the presence of excess HF, into [7](Y) (ca. 24 h).
195Pt{1H} NMR (CD2Cl2, 298 K, δ): -6152 (ddd, Pt1, 1JPt(1),P(1)
=
1150 Hz, 1JPt(1),P(2) = 2920 Hz, 1JPt(1),P(3) = 1138 Hz), -5354 (ddd, Pt2,
1JPt(2),P(1) = 2378 Hz,1JPt(2),P(3) = 2552 Hz, 1JPt(2),P(4) = 5396 Hz) ppm.
NMR Features of [(PHCy2)(H2O)Pt(μ-PCy2)(μ-H)Pt(PHCy2){P(OH)-
Cy2}](Y)2(Pt-Pt) ([2-H2O](Y)2). 1H NMR (CD2Cl2, 298 K, δ): 4.65 (m,
H2, 1JH(2),P(2) = 365 Hz, 2JH(2),Pt(1) = 200 Hz), 5.05 (m, H4, 1JH(4),P(4)
=
2
2
366 Hz, JH(4),Pt(2) = 41 Hz), -5.37 (m, H3, JH(3),P(4) = 68 Hz,
2JH(3),P(2) = 73 Hz, 2JH(3),P(1) = 15 Hz, 2JH(3),P(3) = 16 Hz, 1JH(3),Pt(2)
566 Hz, 1JH(3),Pt(1) = 402 Hz) ppm.
=
31P{1H} NMR (CD2Cl2, 298 K, δ): 140.8 (broad d, P1, 1JP(1),Pt(1)
=
1
2
2886 Hz, JP(1),Pt(2) = 1461 Hz, JP(1),P(3) = 294 Hz), 117.8 (d, P3,
1JP(3),Pt(2) = 2712 Hz, 2JP(3),P(1) = 294 Hz), 12.8 (d, P2, 1JP(2),Pt(1) = 4158
Hz, 2JP(2),Pt(2) = 211 Hz, 3JP(2),P(4) = 45 Hz), 3.4 (broad, P4, 1JP(4),Pt(2)
3496 Hz, 2JP(4),Pt(1) = 165 Hz) ppm.
=
=
Reactions of [2-H2O][BF4]2 with NaF. A mixture of NaF (5 mg,
0.12 mmol) and [2-H2O][BF4]2 (0.035 g, 0.025 mmol) in 2.0 mL water
was sonicated at 298 K for 1 h. Extraction with 0.5 mL of CD2Cl2 gave a
yellow-orange solution which showed at the multinuclear NMR analysis
the presence of [6]þ as the main species.
195Pt{1H} NMR (CD2Cl2, 298 K δ): -5540 (m, Pt1, JPt(1),P(2)
1
4043 Hz, 1JPt(1),P(1) = 2886 Hz, 2JPt(1),P(4) = 165 Hz), -5147 (m, Pt2,
1JPt(2),P(4) = 3496 Hz,1JPt(2),P(3) = 2712 Hz, JPt(2),P(1) = 1461 Hz,
1
2JPt(2),P(2) = 221 Hz) ppm.
Formation of Tetranuclear Compounds. Synthesis of
[(PHCy2){KP-P(O)Cy2}Pt1(μ-PCy2)(μ-H)Pt2(μ-PCy2)]2(Pt1-Pt2) (8). A
PTFE NMR tube filled with a dichloromethane solution of 1 (80 mg,
0.067 mmol in 0.5 mL) was added to 40 μL of hydrofluoric acid (5%w),
without stirring, and the resulting biphasic system was left at 298 K for 24
h. Then, the supernatant aqueous phase was sucked up by a cannula, and
the organic phase was concentrated to ca. 0.2 mL. The addition of n-
hexane caused the formation of a white solid (8), which was filtered off,
washed with n-hexane, and dried under vacuum conditions. Yield: 32 mg
(40%).
1
NMR Features of [6](Y). H NMR (CD2Cl2, 298 K δ): 4.90 (m, H2,
1JH(2),P(2) = 369 Hz, 1JH(2),Pt(1) = 140 Hz), 5.40 (m, H3, 1JH(3),P(4) = 360
Anal. Calcd for C96H180O2P8Pt4: C, 48.15; H, 7.58. Found: C, 47.95;
H, 7.51. ESI-MS, exact mass for the cation [C96H181O2P8Pt4]þ:
2395.04. Measured: m/z 2395.1 (M þ H)þ.
Hz), -1.61 (dddd, H1, 2JH(1),P(1) = 105 Hz, 2JH(1),P(4) = 19 Hz, 2JH(1),P(4)
=
16 Hz, 2JH(1),P(2) = 8 Hz,1JH(1),Pt(2) = 832 Hz, 2JH(1)Pt(1) = 50 Hz) ppm.
31P{1H} NMR (CD2Cl2, 298 K, δ): 182.0 (dd, P1, 1JP(1),Pt(1) = 3529
Hz, 1JP(1),Pt(2) = 1483 Hz, 2JP2(1),P(2) = 44 Hz, 2JP(1),P(4) = 16 Hz), 80.6 (dd,
IR (KBr, cm-1): 2926 (vs), 2850 (vs); 2327 (br w) ν(P-H); 1636
(br w) ν(μ H-Pt); 1447 (s); 1343 (w); 1328 (w); 1292 (m); 1266 (m);
1192 (m) 1178 (s); 1104 (s) ; 1046 (m); 1002 (s) 919 (m); 886 (s); 849
(s); 817 (m); 734 (vs); 574 (m); 539 (m); 522 (m); 482 (s); 462 (s).
P3, JP(3),Pt(2) = 1425 Hz, JP(3),Pt(1) = 250 Hz, JP(3),P(4) = 157 Hz,
1
2
3JP(3),P(2) = 56 Hz), 9.4 (m, P2, JP(2),Pt(1) = 4868 Hz, JP(2),Pt(2)
=
1
2
[(PHCy2){P(OH)Cy2}Pt1(μ-PCy2)(μ-H)Pt2(μ-PCy2)]2[BF4]2(Pt1-Pt2)
40 Hz, 2JP(2),P(1) = 44 Hz, 2JP(2),P(3) = 56 Hz, 3JP(2),P(4) = 40 Hz), -5.7
3
(m, P4, JP(4),Pt(2) = 2451 Hz, JP(4),P(1) = 16 Hz, JP(4),P(2) = 40 Hz,
1
2
3
2CH2Cl2 ([9][BF4]2). A CH2Cl2 suspension of 8 (30 mg, 0.013 mmol in
1.0 mL) was added to 4 μL of HBF4Me2O and stirred for 5 min. The
addition of n-hexane to the mixture caused the precipitation of a white
solid ([9][BF4]2), which was filtered off, washed with n-hexane, and
dried under vacuum conditions. Yield: 28 mg (87%).
2JP(4),P(3) = 157 Hz).
195Pt{1H} NMR (CD2Cl2, 298 K, δ): -5147 (ddd, Pt1, 1JPt(1),P(1)
=
3529 Hz, 1JPt(1),P(2) = 4868 Hz, 2JPt(1),P(3) = 250 Hz), -5983 (dddd, Pt2,
1JPt(2),P(1) = 1483 Hz,1JPt(2),P(3) = 1425 Hz, JPt(2),P(4) = 2451 Hz,
1
IR (KBr, cm-1): 3180 (br w) ν(POH); 2928 (vs), 2852 (vs); 2264
(w); 1628 (w) ν(μ H-Pt); 1292 (m); 1266 (m); 1178 (m); 1101 (br
vs) ν(BF4 þ PO); 1001 (s); 914 (s); 884 (s); 848 (m); 815 (m); 724
(s); 520 (s); 489 (s); 461 (s); 403 (m); 379 (s).
2JPt(2),P(2) = 40 Hz) ppm.
1H NMR (dmso-d6, 315 K, δ): 10.04 (s, H1, 1JH(21),Pt(2) = 57 Hz), 5.73
1
(s, CH2Cl2), 5.28 (m, H3, JH(3),P(3) = 355 Hz, JH(3),Pt(2) = 65 Hz),
-5.85 (m, H2, 2JH(2),P(1) = 21 Hz, 2JH(2),P(2) = 17 Hz, 2JH(2),P(3) = 83 Hz,
2JH(2),P(4) = 38 Hz, 1JH(2),Pt(1) = 576 Hz, 1JH(2),Pt(2) = 440 Hz) ppm.
31P{1H} NMR (CD2Cl2, 298 K, δ): 136.4 (m, P1, 1JP(1),Pt(1) = 1700
1
2
2
0
Hz, JP(1),Pt(2) = 1380 Hz, JP(1),P(4 ) = 260 Hz, JP(1),P(2) = 246 Hz,
2JP(1),P(4) = 8 Hz, 2JP(1),P(3) = 7 Hz), 121.5 (dd, P2, 1JP(2),Pt(2) = 2828 Hz,
2JP(2),Pt(1) = 40 Hz, 2JP(2),P(1) = 246 Hz, 2JP(2),P(3) = 15 Hz), 4.3 (broad,
1
NMR Features of [7](Y). H NMR (CD2Cl2, 298 K δ): 6.1 (broad,
P3, 1JP(3),Pt(2) = 3387 Hz, 2JP(3),Pt(1) =70Hz, 2JP(3),P(2) =15Hz, 3JP(3),P(4)
=
H3) 5.57 (m, H2, 1JH(2),P(2) = 352 Hz, 1JH(2),Pt(1) = 23 Hz), -2.84 (m,
10 Hz, JP(3),P(1) = 7 Hz), -110.5 (broad, P4, JP(4),Pt(1) = 2550 Hz,
2
1
H1, 2JH(1),P(1) = 106 Hz, 3JH(1),P(4) =29Hz, 2JH(1),P(2) =23Hz, 2JH(1),P(3)
10 Hz,1JH(1),Pt(1) = 833 Hz) ppm.
=
JP(4),Pt(2) = 91 Hz, 1JP(4 ),Pt(1) = 1850 Hz, 2JP(4 ),Pt(2) = 22 Hz, 2JP(4),P(4 )
=
=
2
0
0
0
170 Hz, 3JP(4),P(3) = 10 Hz, 3JP(4),P(1) = 8 Hz, 2JP(4 ),P(1) = 260 Hz, 3JP(4 ),P(2)
0
0
31P{1H} NMR (CD2Cl2, 298 K, δ): 299.6 (ddd, P1, 1JP(1),Pt(1) = 1150
35 Hz) ppm.
Hz, 1JP(1),Pt(2) = 2378 Hz, 2JP(1),P(2) =12Hz, 2JP(1),P(3) =198Hz,2JP(1),P(4)
=
195Pt{1H} NMR (CD2Cl2, 298 K, δ): -5019 (broad, Pt1, 1JPt(1),P(4)
=
57 Hz), 294.3 (ddd, P3, JP(3),Pt(1) = 1138 Hz, JP(3),Pt(2) = 2552 Hz,
2434 Hz, 2JPt(1),P(4 ) = 2002 Hz), -5630 (broad, Pt2, 1JPt(2),P(1) = 1816
Hz, 1JPt(2),P(2) = 2828 Hz, 1JPt(2),P(3) = 3363 Hz) ppm.
1
1
0
2JP(3),P(2) = 170 Hz, JP(3),P(1) = 198 Hz, JP(3),P(4) = 69 Hz), 134.8
2
2
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Inorganic Chemistry
ARTICLE
(13) Ara, I.; Chaouche, N.; Forniꢁes, J.; Fortu~no, C.; Kribii, A.;
Martín, A. Eur. J. Inorg. Chem. 2005, 3894–3901.
(14) Albinati, A.; Bracher, G.; Carmona, D.; Jans, J. H. P.; Klooster,
W. T.; Koetzle, T. F.; Macchioni, A.; Ricci, J. S.; Thouvenot, R.; Venanzi,
L. M. Inorg. Chim. Acta 1997, 265, 255–265.
(15) Spek, A. L. J. Appl. Crystallogr. 2003, 36, 7–13.
(16) NMR data for [3-CH3CN]þ are given as Supporting Information.
(17) Due to the low affinity of F for Pt, only a few fluorido or
bifluorido Pt complexes are known: (a) Hintermann, L. H.; L€ang, F.;
Maire, P.; Togni, A. Eur. J. Inorg. Chem. 2006, 1397–1412. (b) Yahav, A.;
Goldberg, I.; Vigalok, A. Inorg. Chem. 2005, 44, 1547–1553 and refs
therein. (c) Yahav, A.; Goldberg, I.; Vigalok, A. J. Am. Chem. Soc. 2003,
125, 13634–13635. (d) Jasim, N. A.; Perutz, R. N. J. Am. Chem. Soc.
2000, 122, 8685–8693. (e) Hintermann, S.; Pregosin, P. S.; R€uegger, H.;
Clark, H. C. J. Organomet. Chem. 1992, 435, 225–234.
(18) Only broadening of the 31P{1H} NMR signals was observed, as
reported in ref 2.
(19) It is known that fluoride ions exist in solution solvated by
hydrogen bond donors: (a) Giguꢀere, P. A. Chem. Phys. Lett. 1976,
41, 598–600. (b) Giguꢀere, P. A.; Turrell, S. Can. J. Chem. 1976,
54, 3477–3482. (c) Braddy, R.; McTigue, P. T.; Verity, B. J. Fluor.
Chem. 1994, 66, 63–67. (d) Shenderovich, I. G.; Smirnov, S. N.;
Denisov, G. B.; Gindin, V. A.; Golubev, N. S.; Dunger, A.; Reibke, R.;
Kirpekar, S.; Malkina, O. L.; Limbach, H.-H. Ber. Bunsenges. Phys. Chem.
1998, 102, 422–428.
(20) Such a behavior has been already observed passing from
[(Cy2PH)(Cl)Pt(μ-PCy2)(μ-H)Pt(Cy2PH){κP-P(OH)Cy2}]Cl
(Pt-Pt) ([2-Cl]Cl) to [(Cy2PH)(Cl)Pt(μ-PCy2)(μ-H)Pt(Cy2PH)-
{κP-P(OH)Cy2}][BF4] (Pt-Pt) ([2-Cl][BF4]). See ref 2.
(21) Mastrorilli, P. Eur. J. Inorg. Chem. 2008, 4835–4850 and refs
therein.
(22) Leoni, P.; Pasquali, M.; Fortunelli, A.; Germano, G.; Albinati, A.
J. Am. Chem. Soc. 1998, 120, 9564–9573.
(23) The same reactivity was observed reacting 8 with HCl, which
led to the soluble species [9]Cl2.
’ ASSOCIATED CONTENT
Supporting Information. 31P{1H} NMR spectra of [2-
S
b
H2O][BF4]2, [2-CH3CN][BF4]2, [2-PhCN][BF4]2, [2-PPh3]-
1
[BF4]2, and [9][BF4]2; H{31P} NMR spectrum of [9][BF4]2;
1H-195Pt HMQC spectra of [2-H2O][BF4]2, [2-CH3CN][BF4]2,
[2-PhCN][BF4]2, [2-PPh3][BF4]2, and [9][BF4]2; 1H EXSY spec-
trum of [2-H2O][BF4]2; MS data of [2-H2O][BF4]2, [2-CH3CN]-
[BF4]2, [2-PPh3][BF4]2, and8;NMRfeaturesof[2-BF3OH][BF4],
[5]þ, [2-acetone-d6][BF4]2, [2-CD2Cl2][BF4]2, [3-CH3CN]-
[BF4], and [60](Y); crystallographic data in CIF format for the
structural analyses of [2-CH3CN][BF4]2 and [9][BF4]2 2CH2Cl2.
This material is available free of charge via the Internet at http://
pubs.acs.org.
3
’ AUTHOR INFORMATION
Corresponding Author
*E-mail: p.mastrorilli@poliba.it.
’ ACKNOWLEDGMENT
Dr. A. Sibaouih and Prof. T. Repo (University of Helsinki, FI,
HRMS) and Dr. Andrea Raffaelli (CNR ICCOM, UOS of Pisa, IT,
MS/MS) are gratefully acknowledged for the mass spectrometry
analyses. COST Phosphorus Science Network (PhoSciNet, project
CM0802) is gratefully acknowledged for financial support.
(24) The clathrated dichloromethane is held responsible for the
signal at δ 5.73 in the 1H NMR spectrum recorded in dmso-d6.
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Mastrorilli, P.; Giardina Papa, D.; Nobile, C. F.; Peruzzini, M. Inorg.
Chem. 2006, 45, 6892–6900.
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Inorganic Chemistry
ARTICLE
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3
the Cambridge Crystallographic Data Centre as supplementary publica-
tion nos. CCDC 803464 ([9][BF4]2 2CH2Cl2) and CCDC 803463
3
([2-CH3CN][BF4]2). Copies of the data can be obtained free of charge
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