Heterolytic addition of E-H bonds across Pt-P bonds in Pt N-heterocyclic phosphenium/phosphido complexes

Article abstract of DOI:10.1039/c2dt30455d

The reactivity of E-H bonds (E = S, O, Cl) with Pt(ii) complexes ligated by an N-heterocyclic phosphido-containing diphosphine ligand have been investigated. Addition of PhSH to [(PPP)Pt(PPh₃)][PF₆] (1) results in clean formation of

Full text of DOI:10.1039/c2dt30455d

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PAPER
Heterolytic addition of E–H bonds across Pt–P bonds in Pt N-heterocyclic
phosphenium/phosphido complexes†
Baofei Pan, Mark W. Bezpalko, Bruce M. Foxman and Christine M. Thomas*
Received 24th February 2012, Accepted 16th April 2012
DOI: 10.1039/c2dt30455d
The reactivity of E–H bonds (E = S, O, Cl) with Pt(II) complexes ligated by an N-heterocyclic phosphido-
containing diphosphine ligand have been investigated. Addition of PhSH to [(PPP)Pt(PPh3)][PF6] (1)
results in clean formation of [(PP(H)P)Pt(SPh)][PF6] (3), in which the substrate has added across the
Pt–PNHP bond. Similar reactivity occurs when 1 is treated with ROH (R = Ph, Me), but in this case the
O–H bond adds across the Pt–P bond in the opposite direction producing [(PP(OR)P)Pt(H)(PPh3)][PF6]
(R = Ph (4), Me (5)). HCl addition to 1 cleanly generates [(PP(H)P)PtCl][PF6] (6PF6). The neutral
Pt–NHP complex (PPP)PtCl (2) exhibits similar reactivity; however, in the presence of the nucleophilic
Cl− anion, the (PP(OR)P)Pt(H)Cl species presumably generated via addition of ROH (R = Me, Et)
undergoes an Arbuzov-like dealkylation reaction to exclusively form the N-heterocylic phosphinito
species (PP(O)P)Pt(H) (7).
Inspired by the success of both FLPs and metal–Lewis acid
Introduction
complexes, we chose to investigate a different type of Lewis acid
functionality, N-heterocyclic phosphenium cations (NHP+s).
The facile activation of σ bonds presents an ongoing challenge
to synthetic chemists in terms of both organic synthesis and
renewable energy applications. In response to this challenge, a
recent promising strategy has emerged based on the concept of
Frustrated Lewis Pairs (FLPs), allowing combinations of strong
Lewis acids and Lewis bases with the proper steric constraints to
perform unusual σ bond activation processes in the absence of
transition metals.1–4 An alternative approach that does make use
of transition metals is the linkage of a transition metal fragment
to a strong Lewis acid via a ligand scaffold to generate M → E
platforms in which an electron-rich transition metal donates elec-
tron density to a tethered main group Lewis acidic atom such as
B5–14 or Sb.15–19 Rather than steric “frustration”, the constraint
in these systems is electronic in nature, since even the most elec-
tron-rich transition metal fragments still maintain an electroposi-
tive character. While the interactions in metal–Lewis acid
complexes are still being explored at the very fundamental level,
there have been several reports of reactivity in which substrates
add oxidatively either across the M → E bond or directly to the
Lewis acidic main group functionality.9,11,13,17,19 In a sense, the
early/late heterobimetallic compounds recently reported in our
own group display similar electronic structure and reactivity.20
These cationic P-containing analogues of N-heterocyclic car-
benes are strongly Lewis acidic owing to their cationic charge
and the empty non-bonding orbital remaining on
phosphorus.21–23 Moreover, their electronic properties render
them excellent π-acceptors yet poor σ-donors, in stark contrast to
NHCs.24–26 Notably, attempts in our lab to utilize NHP+s as the
Lewis acidic half of a FLP system were unsuccessful, suggesting
that they are weaker acids than B(C6F5)3.27 Nonetheless, we did
choose to incorporate an NHP unit into the central position of a
chelating diphosphine pincer ligand to investigate M → P inter-
actions and reactivity of metal–NHP complexes.28 Interestingly,
we found that coordination of the NHP–diphosphine ligand to
electron rich fragments such as Co−1(CO)2, Pd0(PPh3), or
Pt0(PPh3) resulted in complexes with an unusual pyramidal geo-
metry about the central NHP unit.29,30 Structural and compu-
tational studies revealed that this geometry was indicative of a
stereochemically active lone pair on phosphorus, and thus an
NHP− phosphido description. Further experimental and theoreti-
cal investigations suggest that oxidation/reduction and ligand
coordination/dissociation can lead to interconversion of NHP+
and NHP− configurations, similar to the archetypal non-innocent
nitrosyl ligand NO+/NO− (Scheme 1).30
Brandeis University, Department of Chemistry, 415 South Street MS015,
Waltham, MA, USA. E-mail: thomasc@brandeis.edu; Fax: +1 (781)
736-2516; Tel: +1 (781)736-2576
†Electronic supplementary information (ESI) available: Additional com-
putational and spectral details and complete crystallographic data in CIF
format for 4, 6PF6, and 7. CCDC 869435–869437. For ESI and crystallo-
graphic data in CIF or other electronic format see DOI: 10.1039/
c2dt30455d
Scheme 1 Interconversion of NHP+ and NHP− coordination modes.
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Scheme 2 Addition of E–H bonds to 1.
We now turn our attention to the addition of substrates to
metal–NHP complexes, with specific attention to addition of
substrates across the metal–PNHP bond. Several examples of 1,2-
addition of substrates across the Pd–amide bond in (PNP)Pd
complexes were recently reported by Ozerov and coworkers.31
To the best of our knowledge, there are no reported examples of
E–H (E = S, O) bond activation by FLPs, however, Stephan and
coworkers did show that disulfides RSSR are heterolytically
cleaved by mixture of B(C6F5)3 and PtBu3 to give [tBu3PSR]+-
[(C6F5)3BSR]−.32 There are also no reported examples of E–H
addition to metal–NHP complexes. While the ability of our
Pt–NHP complexes to interconvert between NHP− phosphide
and NHP+ phosphenium configurations leads to some ambiguity
in predicting reaction pathways, several reported examples of
the addition of ROH and RSH across M–P bonds in MvPR2
phosphido complexes provide good examples for comparative
purposes.33–37
Fig. 1 Displacement ellipsoid representation (50%) of 4. For clarity,
hydrogen atoms, the PF6 counteranion, and solvate molecules have
−
been omitted. Relevant bond distances (Å) and angles (°): Pt–P2, 2.2445
(9); Pt–P3, 2.3240(9); Pt–P4, 2.3573(9); Pt–P5, 2.3018(9); P2–O1,
1.625(3); P2–Pt1–P3, 90.29(3); P2–Pt–P4, 101.62(3); P3–Pt–P4,
111.77(3); P2–Pt–P5, 89.89(3); P3–Pt–P5, 126.32(3); P4–Pt–P5,
120.68(3); Pt–P2–O1, 112.38(11).
NMR signal at 7.8 ppm is indicative of bound PPh3. The most
diagnostic spectroscopic feature and the most pronounced differ-
ence from 3, however, is the clear presence of a Pt-hydride, indi-
cated by a multiplet at −10.27 ppm in the 1H NMR of the
phenol addition product. Thus, the O–H bond also oxidatively
adds across the Pt–P bond of 1, but in a different manner result-
ing in formation of [(PP(OPh)P)Pt(H)(PPh3)][PF6] (4), as shown
in Scheme 2. Alkyl-substituted alcohols such as methanol react
similarly with 1 to generate similar products such as [(PP(OMe)-
P)Pt(H)(PPh3)][PF6] (5).
Results and discussion
Heterolytic cleavage of E–H bonds by [(PPP)Pt(PPh3)]+ (1)
The solid-state structure of 4 was determined crystallographi-
cally and is shown in Fig. 1. The geometry about Pt is approxi-
mately trigonal bipyramidal (τ = 0.7),38 with the NHP-derived
heterocycle and the hydride occupying axial positions. The
Pt–PNHP distance of 2.2445(9) Å is similar to that in starting
material 1 (2.2600(7) Å),30 in stark contrast to literature
examples.39,40 For instance, in (CO)4Mo(NHPMe)(NHPMeOMe)
the Mo–P distance associated with the MeO-substituted NHP is
∼0.2 Å longer than the Mo–P distance associated with the NHP
unit.39 This case differs from the comparison of 4 with 1,
however, in that the NHP in the Mo system adopts a planar geo-
metry and is formally an NHP+ phosphenium with a double
bond to Mo, while the NHP in 4 is a pyramidal phosphite frag-
ment with a single bond to Pt. Addition of a phenoxy group to
the NHP fragment in 1 changes the nature of the M–P bond, but
in this case it does not serve to disrupt multiple bonding.
Treatment of cationic complex 1 with PhSH at room temperature
results in a new set of 31P NMR resonances at 74.6 ppm and
6.8 ppm corresponding to the central NHP phosphorus and an
equivalent set of phosphine sidearms, respectively. The upfield
shift in the central NHP resonance by comparison to starting
material 1 (δ 198.8 ppm) suggests oxidative addition of the S–H
bond across the Pt–PNHP bond to generate [(PP(H)P)Pt(SPh)]-
[PF6] (3), as shown in Scheme 2. The formulation of complex 3
1
is confirmed by the absence of a H NMR resonance indicative
of a Pt-hydride and an upfield-shifted doublet at 7.63 ppm
(1JP–H = 438 Hz) corresponding to a phosphorus-bound proton.
1
Likewise, the JP–H obtained from the proton-coupled 31P NMR
spectrum of 3 is identical.
In contrast, PhOH does not react with 1 at room temperature.
Upon heating, however, a new product gradually forms over the
course of several days. Similar to 3, this new product has a dra-
matically upfield-shifted 31P NMR resonance at 89.9 ppm for the
central NHP phosphorus and a single resonance at −15.7 ppm
corresponding to the phosphine sidearms. An additional 31P
Since 1,2-addition of S–H and O–H bonds led to different
products, complex 1 was also treated with one equivalent of HCl
to probe the preference for product formation as a function of
acidity. The product of this reaction, [(PP(H)P)PtCl][PF6] (6PF6),
Dalton Trans.
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Scheme 3 Calculated energies of several possible products of MeOH
addition to 1.
the NHP phosphorus atom may be the key step in the preferential
formation of 3 and 6PF6. However, the outcomes of these E–H
addition reactions could also be a consequence of preferences
dictated by hard–soft acid–base theory; i.e., the oxophilic nature
of phosphorus. Upon examination of literature examples of clea-
vage of E–H bonds across MvPR2 bonds, one can observe that
in cases of O–H bond heterolysis OR− always ends up on P,33–35
while two reported examples of S–H cleavage result in M–SR
species.36,37 Moreover, in a few control experiments with more
acidic phenol derivatives (pentafluorophenol and 2,4,6-trichloro-
phenol) products similar to 4 were observed as the exclusive pro-
ducts by NMR spectroscopy. Thus, acidity does not seem to
exclusively dictate the selectivity of 1,2-addition, and hard–soft
preferences clearly play an important role.
Fig. 2 Displacement ellipsoid representation (50%) of 6PF6
. For
−
clarity, hydrogen atoms and the PF6 counteranion have been omitted
and only one of the two molecules in the asymmetric unit is shown. In
addition only one of the two disordered position of the central NHP
phosphorus is shown. Relevant bond distances (Å): (molecule 1): Pt1–
P2/P3, 2.162(2)/2.18(3); Pt–P4, 2.298(2); Pt–P1, 2.2906(19); Pt–Cl1,
2.354(2); (molecule 2): Pt11–P102/103, 2.212(4)/2.142(5); Pt11–P101,
2.308(2); Pt11–P104, 2.300(2).
A computational investigation on the selectivity of these reac-
tions was carried out using density functional theory (DFT).
Upon first examining the possible products of the reaction of 1
with MeOH, we find that 5 is the lowest energy product (ΔG =
−5.3 kcal mol−1). Attempts to optimize the geometry of the Pt-
methoxide product [(PP(H)P)Pt(OMe)(PPh3)]+ were unsuccess-
ful and resulted in in silico dissociation of PPh3 to give [(PP(H)-
P)Pt(OMe)]+. As shown in Scheme 3, the product of oxidative
addition of MeOH directly to Pt without involvement from the
NHP moiety is too high in energy (ΔG = 56.4 kcal mol−1) to
contribute to the reaction pathway. Since it is also possible that
the PPh3 dissociates prior to oxidative addition to generate an
NHP+ phosphenium intermediate, we also examined the reaction
of the three-coordinate [(PPP)Pt]+ species with PhOH
(Scheme 4). In this case, not only is the (PP(OPh)P)PtH product
lower in energy than the (PP(H)P)PtOPh product (ΔG = −6.4
and 14.8 kcal mol−1, respectively), the computed activation
energy for formation of the Pt-hydride product is also signifi-
cantly lower (ΔG‡ = 37.2 kcal mol−1 compared to 50.0 kcal
mol−1). In the case of PhSH, where the isolated product is a Pt-
thiolate with apparent protonation of the central NHP unit, the
computed energies differences cannot be interpreted in such a
straightforward manner. As shown in Scheme 5, in the reaction
of [(PPP)Pt]+ with PhSH, the Pt-hydride species is predicted to
is similar to that of PhSH, with proton addition to the central
NHP phosphorus atom and coordination of the chloride anion to
Pt. The absence of coordinated PPh3 in 3 and 6PF6 is likely
attributed to the greater steric demand of the thiolate and chloride
ligands compared to the hydride ligand in 4 and 5.
The solid-state structure of 6PF6 was determined via X-ray
crystallography and is shown in Fig. 2. In both independent mol-
ecules in the asymmetric unit, the central NHP phosphorus atom
is disordered over two positions. This disorder was modelled
adequately, but prevented the detection of the hydrogen atom
1
bound to P. Its presence, however, is unequivocal based on H
NMR data and based on the balancing of charge in this diamag-
netic molecule. The structure reveals a square planar geometry
about Pt with a Pt–PNHP distance significantly shorter than in 4
or in the starting material 1. Rather than invoking an argument
about the NHP–H’s donor ability, this phenomenon can be
explained by the poorer trans influence of Cl− by comparison to
PR3 or H−.
be the thermodynamically favored product by ca. 8 kcal mol−1
.
From the above results, it appears that more acidic E–H bonds
(HCl, thiols) lead to the protonation of the central NHP phos-
phorus atom, while less acidic E–H bonds (phenol and alcohols)
lead to the opposite selectivity. The phosphido character of the
central NHP phosphorus atom suggests that initial protonation of
However, both products are shown to be energetically uphill
from the three coordinate Pt starting material. Thus, in this case,
we propose that it is important that PPh3 remain coordinated
(keeping the NHP unit in an NHP− phosphido configuration)
upon PhSH addition.
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Scheme 4 Calculated reaction pathway of the addition of PhOH to
[(PPP)Pt]+.
Fig. 3 Displacement ellipsoid representation (50%) of 7. For clarity,
hydrogen atoms have been omitted and only one of two disordered pos-
itions is shown. Relevant bond distances (Å) and angles (°): Pt–P1,
2.2586(7); Pt–P2, 2.2242(14); P2–O1, 1.485(4); P2–N2, 1.709(5);
P2–N1, 1.725(5); P1–Pt–P1, 177.86(4); Pt–P2–O1, 119.64(18).
Scheme 5 Calculated energetics of the reaction of [(PPP)Pt]+ with
PhSH.
reacts readily with MeOH but yields a product vastly different
from 5: While a Pt-hydride signal is still observed in the 1H
NMR of the product at −1.80 ppm and the 31P resonance for the
central phosphorus is shifted downfield to 86.7 ppm, no signal
attributable to a methyl group could be identified. Moreover,
EtOH addition to 2 resulted in a spectroscopically identical
product. The product was, therefore, tentatively assigned as
(PP(O)P)Pt(H) (7, Scheme 6). Notably, the RCl byproduct was
observed via both GC-MS and 1H NMR spectroscopy upon
completion of the reaction.
The solid-state structure of 7 confirms its formulation as an N-
heterocyclic phosphinito Pt-hydride complex (Fig. 3). While the
hydride could not be located in the difference Fourier map, its
location can be geometrically inferred. The geometry around the
Pt center is essentially square planar once the hydride’s supposed
position is taken into account. The Pt–PNHP distance (2.2242(14)
Å) is nearly identical to that in the unoxidized (PPP)PtBr
complex,30 and similar to the Pd–P distance in Bourissou’s
similar pincer complex {[o-iPr2P(C6H4)]2P(vO)Ph}Pd(Ph).41
This trend is in stark contrast to the previously observed
∼0.07 Å contraction of the Co–PNHP distance upon oxidation of
the central phosphorus in (PPP)Co(CO)2 to (PP(O)P)Co(CO)2;29
however, chloride-to-hydride substitution at the position trans to
the central phosphorus atom likely contributes to the PNHP–Pt
bond distance in this case as well.
Scheme 6 Addition of E–H bonds to 2.
Heterolytic cleavage of E–H bonds by (PPP)PtCl (2)
Element–hydrogen bond addition was also investigated starting
with the neutral NHP complex 2. Addition of HCl proceeded
similarly, affording a similar product [(PP(H)P)PtCl][Cl] (6Cl,
Scheme 6). PhSH addition to 2 also afforded a product spectro-
scopically identical to 3, although presumably with a Cl− coun-
−
teranion in place of PF6
.
In contrast, treatment of 2 with PhOH resulted in no reaction,
even in refluxing benzene for extended periods of time. Presum-
ably complex 2 is less reactive than 1 owing to the stronger
coordination of Cl− to Pt. Unlike the reaction with phenol, 2
The mechanism by which the unusual product 7 is formed
deserves consideration. There are a number of literature
examples of transition metal phosphites undergoing dealkylation
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unless otherwise noted. Benzene, n-pentane, tetrahydrofuran,
toluene, diethyl ether, and dichloromethane were degassed and
dried by sparging with ultra high purity argon gas followed by
passage through a series of drying columns using a Seca Solvent
System by Glass Contours. All solvents were stored over 3 Å
molecular sieves. Deuterated solvents were purchased from Cam-
bridge Isotope Laboratories, Inc., degassed via repeated freeze-
pump-thaw cycles, and dried over 3 Å molecular sieves. Sol-
vents were frequently tested using a standard solution of sodium
benzophenone ketyl in tetrahydrofuran to confirm the absence of
oxygen and moisture. Complexes 1 and 2 were synthesized
using literature procedures.30 Thiophenol, phenol, methanol,
ethanol and 1.0 M HCl solution in diethyl ether were purchased
from commercial vendors and used without further purification.
NMR spectra were recorded at ambient temperature unless other-
1
wise stated on Varian Inova 400 MHz instrument. H and 13C
NMR chemical shifts were referenced to residual solvent and
are reported in ppm. 31P NMR chemical shifts (in ppm) were
referenced to 85% H3PO4 (0 ppm). Elemental microanalyses
were performed by Complete Analysis Laboratories, Inc., Parsip-
pany, NJ.
Scheme 7 Proposed mechanism for formation of 7 from 2 and MeOH.
reactions via an Arbuzov-type reaction,42 although to our knowl-
edge this type of reactivity is unprecedented in N-heterocyclic
phosphite systems. Transition metal phosphite dealkylation
usually proceeds via either an ionic or radical mechanism, with
the former being more common in the presence of nucleophiles
such as halides. Thus, we propose that a plausible pathway
involves initial oxidative addition of MeOH to 2 to form an
intermediate Pt-hydride species similar to 4, followed by an
intramolecular SN2 reaction between the Pt-bound Cl− and the
methoxy carbon (Scheme 7). Notably, the Pt–Br and Pt–I ana-
logues of 2 also lead to 7 upon ROH addition.
Synthesis of [(PP(H)P)Pt(SPh)][PF6] (3)
Complex 1 (74.5 mg, 0.0615 mmol) was dissolved in THF
(10 mL). To this orange solution was added thiophenol (6.3 μL,
0.062 mol). The reaction mixture became a yellow solution in
15 minutes. Removal of the volatiles in vacuo afforded a yellow
solid as crude product. Crystallization of the crude product via
vapor diffusion of diethyl ether into a concentrated THF solution
yielded analytically pure product as yellow crystals. Yield:
1
75.6 mg, 93.0%. H NMR (400 MHz, CD2Cl2): δ 7.65 (t, 2H,
1
2
Ar-H), 7.63 (dd, 1H, P-H, JP–H = 438 Hz, JPt–H = 160 Hz),
7.55 (m, 2H, Ar-H), 7.49 (m, 9H, Ar-H), 7.32 (t, 4H, Ar-H),
7.27 (t, 4H, Ar-H), 7.22 (m, 2H, Ar-H), 7.09 (t, 2H, Ar-H), 6.97
(m, 2H, Ar-H), 6.71 (t, 2H, Ar-H), 6.66 (m, 2H, Ar-H), 6.57 (t,
2H, Ar-H), 3.91 (m, 2H, CH2), 3.77 (m, 2H, CH2). 31P NMR
Conclusions
In summary, we have shown that the E–H bonds of alcohols,
thiols, and hydrochloric acid add to Pt–NHP complexes via oxi-
dative addition across the Pt–PNHP bond. In all cases, the oxi-
dation state of Pt remains the same. Based on hard–soft acid/
base preferences, the products of 1,2-addition of O–H and S–H
bonds vary: Pt–H/P–OR products form preferentially in the O–H
bond cleavage case, while Pt–SR/P–H products form from S–H
addition reactions. Addition of HCl to Pt–NHP complexes also
exclusively form Pt–Cl/P–H products, but based on control reac-
tions with more acidic phenols we have established that product
preferences are not pH-controlled. Interestingly, in the presence
of nucleophilic halides, the P–OR phosphite products generated
via addition of alcohols undergo an Arbuzov-like dealkylation
reaction to release RX and generate an oxidized PvO phosphi-
nito product. The participation of the NHP moiety in reactions of
this type are further proof of the non-innocent nature of these
ligands.
(161.8 MHz, CD2Cl2): δ 74.6 (ddt, 1P, 1JPt–P = 2716 Hz, 1JP–H
=
=
2
1
2
438 Hz, JP–P = 36 Hz), 6.8 (dd, 2P, JPt–P = 2295 Hz, JP–P
36 Hz), −143.9 (sept, 1P, JP–F = 710 Hz). 13C NMR
(100.5 MHz, CD2Cl2): δ 145.9, 135.9, 134.8, 134.5, 134.2,
132.7, 132.4, 132.3, 129.4, 128.8, 127.6, 123.7, 123.0, 118.6,
48.3. Anal. Calcd for C44H38N2F6P4PtS: C, 49.86; H, 3.61; N,
2.64. Found: C, 49.81; H, 3.73; N, 2.69%.
1
Synthesis of [(PP(OPh)P)Pt(H)(PPh3)][PF6] (4)
Complex 1 (47.5 mg, 0.0392 mmol) was dissolved in dichloro-
methane (10 mL) and to this orange solution was added phenol
(3.7 mg, 0.039 mmol). The mixture was heated in a sealed
vessel in an oil bath at 60 °C for two days to ensure complete
reaction. After completion, removal of the volatiles from the col-
orless solution in vacuo afforded white solid as analytically pure
product. Yield: 48.7 mg, 95.1%. Colorless crystals suitable for
X-ray crystallography were grown via vapor diffusion of n-
Experimental
General considerations
1
pentane into a concentrated dichloromethane solution of 4. H
All syntheses reported were carried out using standard glovebox
and Schlenk techniques in the absence of water and dioxygen,
NMR (400 MHz, CD2Cl2): δ 7.67 (t, 2H, Ar-H), 7.31 (m, 6H,
Ar-H), 7.26–7.19 (m, 8H, Ar-H), 7.18–7.03 (m, 30H, Ar-H),
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6.23 (d, 2H, Ar-H), 3.43 (m, 2H, CH2), 3.14 (m, 2H, CH2),
(90 μL, 1.0 M solution in diethyl ether, 0.090 mmol). The reac-
tion mixture became a lighter yellow color within ten seconds of
addition. Removal of the volatiles from the colorless solution in
vacuo afforded yellow solid as analytically pure product. Yield:
1
2
−10.27 (dd, 1H, Pt-H, JPt–H = 670 Hz, JP–H = 280 Hz). 31P
1
NMR (161.8 MHz, CD2Cl2): δ 89.9 (dd, 1P, JPt–P = 2576 Hz,
1
2JP–H = 280 Hz), 7.8 (br, 1P, PPh3), −15.7 (d, 2P, JPt–P = 2747
1
1
Hz), −143.9 (sept, 1P, JP–F = 710 Hz). 13C NMR (100.5 MHz,
70.0 mg, 97.2%. H NMR (400 MHz, CD2Cl2): δ 7.87 (dd, 1H,
1
2
CD2Cl2): δ 146.1, 135.4, 134.3, 133.8, 133.7, 133.6, 133.2,
133.1, 131.8, 131.4, 130.1, 129.1, 128.6, 128.5, 126.2, 124.3,
122.3, 121.3, 48.1. Anal. Calcd for C62H53N2F6OP5Pt: C, 57.02;
H, 4.09; N, 2.14. Found: C, 56.91; H, 4.06; N, 2.23%.
P-H, JP–H = 472 Hz, JPt–H = 239 Hz), 7.69 (t, 2H, Ar-H), 7.60
(m, 2H, Ar-H), 7.54–7.40 (m, 20H, Ar-H), 7.09 (t, 2H, Ar-H),
6.97 (m, 2H, Ar-H), 4.38 (m, 2H, CH2), 3.85 (m, 2H, CH2). 31
P
1
NMR (161.8 MHz, CD2Cl2): δ 64.1 (ddt, 1P, JPt–P = 3560 Hz,
2
1
1JP–H = 472 Hz, JP–P = 29 Hz), 6.9 (dd, 2P, JPt–P = 2194 Hz,
2JP–P = 29 Hz), −143.9 (sept, 1P, JP–F = 710 Hz). 13C NMR
1
Synthesis of [(PP(OMe)P)Pt(H)(PPh3)][PF6] (5)
(100.5 MHz, CD2Cl2): δ 146.1, 134.9, 134.8, 134.4, 132.8,
132.4, 129.6, 129.2, 123.2, 119.7, 48.3. Anal. Calcd for
C38H33N2Cl2P3Pt: C, 52.07; H, 3.79; N, 3.20. Found: C, 52.81;
H, 3.98; N, 2.96%.
Complex 1 (44.3 mg, 0.0366 mmol) was dissolved in dichloro-
methane (10 mL) and to this orange solution was added MeOH
(1.6 μL, 0.040 mmol). The mixture was allowed to stir at rt for
12 hours to ensure complete reaction. Upon completion, removal
of volatiles from the resulting colorless solution afforded white
Synthesis of (PP(O)P)Pt(H) (7)
1
solid as analytically pure 5. Yield: 39.5 mg, 86.9%. H NMR
(400 MHz, CD2Cl2): δ 7.63 (t, 2H, Ar-H), 7.42 (m, 2H, Ar-H),
7.31 (m, 8H, Ar-H), 7.17 (t, 2H, Ar-H), 7.08 (m, 27H, Ar-H),
6.98 (m, 2H, Ar-H), 4.48 (m, 2H, CH2), 3.32 (m, 2H, CH2),
Complex 2 (22 mg, 0.026 mmol) was stirred in benzene (10 mL)
and to this yellow suspension was added MeOH (1.2 μL,
0.030 mmol). The mixture was allowed to stir at rt for 12 hours
to ensure complete reaction. Upon completion, removal of vola-
tiles from the resulting yellow solution afforded yellow solid as
crude product. Yield: 18.5 mg, 86.0%. Purification of the crude
product via vapor diffusion of n-pentane into a concentrated
dichloromethane solution of the crude product afforded yellow
2
3.02 (d, 3H, OCH3, JP–H = 12 Hz), −10.32 (dd, 1H, Pt-H,
2
1JPt–H = 664 Hz, JP–H = 275 Hz). 31P NMR (161.8 MHz,
1
2
CD2Cl2): δ 94.6 (dd, 1P, JPt–P = 2530 Hz, JP–H = 275 Hz),
9.8 (br, 1P, PPh3), −14.4 (d, 2P, 1JPt–P = 2830 Hz), −143.9 (sept,
1
1P, JP–F = 710 Hz). 13C NMR (100.5 MHz, CD2Cl2): δ 145.3,
1
134.9, 133.7, 133.6, 133.0, 132.7, 131.0, 130.3, 130.1, 128.8,
128.5, 128.4, 125.2, 124.5, 54.1, 49.3. Anal. Calcd for
C57H51N2F6OP5Pt: C, 55.03; H, 4.13; N, 2.25. Found: C, 55.08;
H, 4.25; N, 2.21%.
crystals suitable for X-ray crystallography. H NMR (400 MHz,
CD2Cl2): δ 7.71 (m, 2H, Ar-H), 7.63 (m, 2H, Ar-H), 7.49–7.36
(m, 18H, Ar-H), 7.04–6.96 (m, 4H, Ar-H), 6.82 (m, 2H, Ar-H),
4.17 (m, 2H, CH2), 3.46 (m, 2H, CH2), −1.80 (ddt, 1H, 1JPt–H
=
2
2
950 Hz, JNHP–H = 184 Hz, JP(Ar)–H = 16 Hz). 31P NMR
(161.8 MHz, CD2Cl2): δ 86.7 (ddt, 1P, 1JPt–P = 2260 Hz, 1JP–H
=
=
Synthesis of [(PP(H)P)PtCl][PF6] (6PF6
)
2
1
2
184 Hz, JP–P = 43 Hz), 5.1 (dd, 2P, JPt–P = 2607 Hz, JP–P
43 Hz). 13C NMR (100.5 MHz, CD2Cl2): δ 150.7, 136.3, 134.4,
134.0, 133.0, 131.0, 130.7, 128.6, 119.4, 118.0, 45.9. Anal.
Calcd for C38H33N2OP3Pt: C, 55.55; H, 4.05; N, 3.41. Found:
C, 55.49; H, 4.07; N, 3.33%.
Complex 1 (60.6 mg, 0.0500 mmol) was dissolved in dichloro-
methane (10 mL) and to this orange solution was added HCl
(55 μL, 1.0 M HCl in diethyl ether, 0.0550 mmol). The mixture
became colorless within ten seconds of addition. Removal of the
volatiles from the colorless solution in vacuo afforded light
yellow solid as analytically pure product 6PF6. Yield: 38.1 mg,
77.3%. Light yellow crystals suitable for X-ray crystallography
were grown via vapor diffusion of n-pentane into a concentrated
dichloromethane solution of complex 6PF6. 1H NMR (400 MHz,
CD2Cl2): δ 7.70 (t, 2H, Ar-H), 7.62 (m, 2H, Ar-H), 7.58 (m, 6H,
X-ray crystallography procedures
All operations were performed on a Bruker-Nonius Kappa
Apex2 diffractometer, using graphite-monochromated MoKα
radiation. All diffractometer manipulations, including data col-
lection, integration, scaling, and absorption corrections were
carried out using the Bruker Apex2 software.43 Preliminary cell
constants were obtained from three sets of 12 frames. Crystallo-
graphic parameters are summarized in Table 1, and further exper-
imental crystallographic details are described for each compound
in the ESI.† Data in CIF format are also provided in a separate
file.†
1
2
Ar-H), 7.57 (dd, 1H, P-H, JP–H = 465 Hz, JPt–H = 235 Hz),
7.49 (m, 8H, Ar-H), 7.42 (m, 4H, Ar-H), 7.31 (m, 2H, Ar-H),
7.12 (t, 2H, Ar-H), 6.98 (m, 2H, Ar-H), 4.10 (m, 2H, CH2),
3.83 (m, 2H, CH2). 31P NMR (161.8 MHz, CD2Cl2): δ 64.1
1
1
2
(ddt, 1P, JPt–P = 3596 Hz, JP–H = 465 Hz, JP–P = 29 Hz), 6.4
1
2
(dd, 2P, JPt–P = 2200 Hz, JP–P = 29 Hz), −143.9 (sept, 1P,
1JP–F = 710 Hz). 13C NMR (100.5 MHz, CD2Cl2): δ 145.8,
134.9, 134.7, 134.5, 132.9, 132.6, 129.7, 129.2, 123.5, 119.1,
47.8. Anal. Calcd for C38H33N2ClF6P4Pt: C, 46.28; H, 3.37; N,
2.84. Found: C, 46.22; H, 3.42; N, 2.76%.
Computational methods
All calculations were performed using Gaussian0944 for the
Linux operating system. Density functional theory calculations
were carried out using the B3LYP hybrid functional; Becke’s
three parameter exchange functional (B3)45 and the correlation
functional of Lee, Yang, and Parr (LYP).46 A mixed-basis set
Synthesis of [(PP(H)P)PtCl][Cl] (6Cl
)
Complex 2 (69.0 mg, 0.0821 mmol) was dissolved in dichloro-
methane (10 mL). To this yellow solution was added HCl
Dalton Trans.
This journal is © The Royal Society of Chemistry 2012

View Online
Table 1 Crystallographic data and refinement parameters for 4, 6PF6, and 7
4·2CH2Cl2
6PF6
7
Chemical formula
Fw
T (K)
C
64H57Cl4F6N2O1P5Pt1
C38H32Cl1F6NP4Pt1
985.11
120
C38H32N2O1P3Pt1
820.70
120
1475.93
120
λ (Å)
a (Å)
b (Å)
c (Å)
0.71073
14.8742(10)
35.625(3)
11.9635(9)
107.599(4)
6042.7(8)
P21/c
4, 1
1.622
26.95
0.71073
0.71073
12.1189(4)
13.4744(5)
22.8621(9)
98.743(2)
3689.9(2)
P21
4, 2
1.773
41.1
25.0443(7)
15.9342(5)
9.6935(3)
110.393(1)
3625.85(19)
C2/c
4, 0.5
1.503
40.33
β (°)
V (Å3)
Space group
Z, Z′
D
calc (g cm−3
)
μ (cm−1
)
Rint
0.048
17 579, 14 355
0.0418, 0.1067
0.044
21 159, 17 543
0.0419, 0.0835
0.032
5303, 4020
0.0242, 0.0605
Nref (all), Nref (I > 2σ(I))
R1 (I > 2σ(I)), wR2 a (all)
2
2 2
a R1 = ∑kFo| − |Fok/∑|Fo|; wR2 = {∑[w(Fo2 − Fc )2]/∑[w(Fo ) ]}1/2
.
14 A. Amgoune and D. Bourissou, Chem. Commun., 2011, 47, 859–871.
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was employed, using the LANL2DZ(p,d) double zeta basis set
with effective core potentials for phosphorus, iodine, and
platinum47–49 and Gaussian09’s internal LANL2DZ basis set
(equivalent to D95V50) for carbon, nitrogen, and hydrogen.
Using crystallographically determined geometries as a starting
point, the geometries were optimized to a minimum, followed by
analytical frequency calculations to confirm that no imaginary
frequencies were present. XYZ coordinates of the optimized geo-
metries of all calculated complexes are provided in the ESI.†
20 C. M. Thomas, Comments Inorg. Chem., 2011, 32, 14–38.
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