Synthesis of chelate complexes and the dichalcogen derivatives of the unsymmetrical diphosphine ligand Ph2PNHC6H4PPh2. Molecular structure of [PtCl2(Ph2PNHC6H4PPh 2)]·0.75dmso·0.75CHCl3

Article abstract of DOI:10.1039/b101772l

[M(η³-C₃H₅)(L)][Cl] (M = Pt or Pd and L = Ph₂PNHC₆H₄PPh₂), [MX₂(L)] (where M = Pt, X = Me, Cl, Br or I and where M = Pd or Ni X = Cl), [PtMeCl(L)], [Mo(CO)₄(L)] and [(AuCl)₂(L)] have been synthesised. In all complexes except [(AuCl)₂(Ph₂PNHC₆H₄PPh ₂)] where the diphosphine acts as a bridging ligand between the two metal centres a chelating coordination mode is observed. We have also prepared and characterised the dichalcogen compounds Ph₂P(E)NHC₆H₄P(E)Ph₂ (where E = O, S or Se) and found that the disulfide reacts cleanly with [PdCl₂(PhCN)₂] in dichloromethane or Na₂[PdCl₄] in ethanol with elimination of HCl to give the unusual neutral N-metallated species [PdCl(Ph₂P(S)NC₆H₄P(S)Ph₂-S,N, S)], which contains both S-P-C-C-N-Pd six and N-P-S-Pd four-membered metallacycles. The cationic species [Pd(PPh₃)(Ph₂P(S)NC₆H₄P(S)Ph ₂-S,N,S)][ClO₄] was generated by the sequential addition of first Ag[ClO₄] followed by PPh₃ to the neutral chloride. The molecular structure of [PtCl₂(Ph₂PNHC₆H₄PPh ₂)]·0.75dmso·0.75CHCl₃, which reveals a puckered ring and displays hydrogen-bonding interactions between the ligand amine proton and the oxygen atom of the dmso molecule, has been determined by single crystal X-ray diffraction.

Full text of DOI:10.1039/b101772l

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Synthesis of chelate complexes and the dichalcogen derivatives
of the unsymmetrical diphosphine ligand Ph2PNHC6H4PPh2.
Molecular structure of [PtCl2(Ph2PNHC6H4PPh2)]ؒ0.75dmsoؒ
0.75CHCl3
Stephen M. Aucott, Alexandra M. Z. Slawin and J. Derek Woollins*
Department of Chemistry, University of St. Andrews, St. Andrews, Fife, UK KY16 9NB.
E-mail: j.d.woollins@st-andrews.ac.uk
Received 23rd February 2001, Accepted 31st May 2001
First published as an Advance Article on the web 16th July 2001
[M(η3-C3H5)(L)][Cl] (M = Pt or Pd and L = Ph2PNHC6H4PPh2), [MX2(L)] (where M = Pt, X = Me, Cl, Br or I and
where M = Pd or Ni X = Cl), [PtMeCl(L)], [Mo(CO)4(L)] and [(AuCl)2(L)] have been synthesised. In all complexes
except [(AuCl)2(Ph2PNHC6H4PPh2)] where the diphosphine acts as a bridging ligand between the two metal centres
a chelating coordination mode is observed. We have also prepared and characterised the dichalcogen compounds
Ph2P(E)NHC6H4P(E)Ph2 (where E = O, S or Se) and found that the disulfide reacts cleanly with [PdCl2(PhCN)2] in
dichloromethane or Na2[PdCl4] in ethanol with elimination of HCl to give the unusual neutral N-metallated species
[PdCl(Ph2P(S)NC6H4P(S)Ph2-S,N,S)], which contains both S–P–C–C–N–Pd six and N–P–S–Pd four-membered
metallacycles. The cationic species [Pd(PPh3)(Ph2P(S)NC6H4P(S)Ph2-S,N,S)][ClO4] was generated by the sequential
additionoffirstAg[ClO4]followedbyPPh3 totheneutralchloride.Themolecularstructureof[PtCl2(Ph2PNHC6H4PPh2)]ؒ
0.75dmsoؒ0.75CHCl3, which reveals a puckered ring and displays hydrogen-bonding interactions between the
ligand amine proton and the oxygen atom of the dmso molecule, has been determined by single crystal X-ray
diffraction.
chloride-bridged dimers in thf leads to monometallic species in
which the diphosphine ligand binds to the metal only via the
amino–phosphine moiety. Subsequent dissolution of these
complexes in other solvents e.g. chloroform or methanol/
Introduction
Throughout inorganic and organometallic chemistry few
ligands have been as extensively employed as symmetrical
tertiary diphosphines; well known examples being dppm
chloroform mixtures resulted in their conversion to the corre-
Ph2PCH2PPh2 bis(diphenylphosphino)methane, dppe Ph2-
sponding cationic chelate complexes.25 In this paper we report
P(CH2)2PPh2 bis(diphenylphosphino)ethane, dppp Ph2P(CH2)3-
the synthesis and characterisation of Ph2PNHC6H4PPh2 chelate
PPh2 bis(diphenylphosphino)propane and the aromatic
compounds of platinum group and other late transition metals
backboned Ph2PC6H4PPh2 1,2-phenylenebis(diphenylphos-
in addition to [Ph2P(AuCl)NHC6H4P(AuCl)Ph2] where the
phine). In comparison there are relatively few examples in the
ligand bridges the two (AuCl) groups.
chemical literature of unsymmetrical, potentially bidentate bis-
phosphines containing P–C–C–X–P backbones, where X = C,1,2
Si,3,4 O,5–11 or S,12 fewer still where X = N,13–15 and no examples,
to the best of our knowledge, where transition metal complexes
have been prepared using preformed P–C–C–N–P backboned
ligands. Six-membered P–C–C–O–P–M metallacycles (where
M = Pd16,17 and Pt17) and platinum() and palladium() P–C–
C–N–P–M metallacycles have previously been reported18 but
all were formed by intramolecular reactions brought on by
high temperature thermolysis. Further examples of P–C–C–O–
P–M metallacycles include the photochemical formation of
Experimental
General
Unless otherwise stated, manipulations were performed under
an oxygen-free nitrogen atmosphere using predried solvents and
standard Schlenk techniques. The compound Ph2PNHC6-
H4PPh2 was prepared as previously reported.25 The complexes
[Pt(µ-Cl)(µ-η2 : η1-C3H5)]4,26 [Pd(µ-Cl)(η3-C3H5)]2,27 [MX(Y)-
(cod)] (M = Pt or Pd; X, Y = Me, Cl, Br or I; cod = cycloocta-
1,5-diene),28–31 [PdCl2(NCPh)2],32 [Mo(CO)4(pip)2]33 (pip =
piperidine) or [AuCl(tht)]34 (tht = tetrahydrothiophene) were
prepared according to literature procedures. Aqueous H2O2
(30% w/w, Fluka), PPh3 (Aldrich 99% purity), NiCl2ؒ6H2O
(Aldrich) and Ag[ClO4] (Aldrich 99% purity) were obtained
commercially and used without further purification.
[W(CO) (Ph POC(Ph)᎐CHPPh )] from [W(CO)4(Ph2PCH-
᎐
4
2
2
(C(O)Ph)PPh2)]19 a series of Group 10 metallacycles formed by
reaction of Ph2PCl or PhPCl2 with phosphino–enolate
complexes20–22 and the elimination/rearrangement reaction of a
palladium complex bearing a phosphino–hydroquinone ligand
in an acidic medium23
24
We recently described the synthesis of Ph2PNHC6H4PPh2
Infrared spectra were recorded as KBr pellets in the range
an unsymmetrical diphosphine derived from 2-(diphenylphos-
phino)aniline25 and have shown that the difference in basicity
or the steric properties of the two different phosphorus atoms
of Ph2PNHC6H4PPh2 can be exploited to obtain different
coordination modes i.e. bidentate versus monodentate. We have
previously shown that reaction of Ph2PNHC6H4PPh2 with η6-
aryl Ru(), Os() and Cp* (Cp* = η5-C5Me5) Rh(), Ir()
4000–220 cmϪ1 on a Perkin-Elmer system 2000 Fourier trans-
1
form spectrometer, H NMR spectra (250 MHz) on a Bruker
AC250 FT spectrometer with δ referenced to external SiMe4
and 31P-{1H} NMR spectra (36.2 or 101.3 MHz) either on
a JEOL FX90Q or a Bruker AC250 FT spectrometer with
δ referenced to external H3PO4. Microanalyses were performed
by the Loughborough University Service.
DOI: 10.1039/b101772l
J. Chem. Soc., Dalton Trans., 2001, 2279–2287
This journal is © The Royal Society of Chemistry 2001
2279

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Sodium tetrachloropalladate (Na[PdCl4]) along with other
precious metal salts were provided on loan by Johnson Matthey
plc.
mmol) in dichloromethane (4 cm3) and Ph2PNHC6H4PPh2
(0.116 g, 0.25 mmol) and stirred for 17 hours (overnight),
collected by suction filtration, washed with ice cold dichloro-
methane (2 × 2 cm3) then petroleum ether (2 × 10 cm3) followed
by diethyl ether (2 × 10 cm3) to give a pale yellow microcrystal-
line product. Yield: 0.173 g, 78%. Microanalysis: Found (Calcd.
for C30H25I2NP2Pt) C 39.73 (39.58), H 3.05 (2.77), N 1.48
(1.54)%. FABϩ MS: m/z 933/4 [M ϩ Na]ϩ, 910 [M]ϩ, 783/4
[M Ϫ I]ϩ and 656/7 [M Ϫ 2I]2ϩ. Selected IR data (KBr): 3199br
[ν(N–H)], 899br [ν(P–N)] and 353br cmϪ1 [ν(Pt–I)].
Syntheses
[Pt(ꢀ3-C3H5)(Ph2PNHC6H4PPh2)][Cl] 1. To a stirred thf
suspension (10 cm3) of [Pt(µ-Cl)(µ-η2 : η1-C3H5)]4 (0.109 g, 0.10
mmol) was added in one portion solid Ph2PNHC6H4PPh2
(0.185 g, 0.40 mmol). The mixture was stirred for 4 hours
to give a very pale yellow solution which was filtered through
a small plug of Celite to remove a small quantity of dark
insoluble material and concentrated under vacuum to half its
original volume. Diethyl ether (20 cm3) was slowly added to the
stirred filtrate and the resulting pale yellow precipitate was
collected by filtration washed with diethyl ether (2 × 10 cm3)
and dried in vacuo. Yield: 0.267 g, 91%. Microanalysis: Found
(Calcd. for C33H30ClNP2Pt) C 54.18 (54.09), H 3.87 (4.13),
[PtMe2(Ph2PNHC6H4PPh2)] 6. This was prepared in the
same way as the platinum complex 3 using [PtMe2(cod)] (0.072
g, 0.22 mmol) in dichloromethane (1.5 cm3) and Ph2PNHC6-
H4PPh2 (0.105 g, 0.23 mmol) and stirred for 2 hours to give a
clear yellow solution. Light petroleum (10 cm3) was added and
the dichloromethane was removed by slow evaporation to give
a cream coloured precipitate. The product was collected by
suction filtration and washed with light petroleum (2 × 10 cm3)
followed by diethyl ether (2 × 10 cm3) and dried in vacuo. Yield:
0.122 g, 82%. Microanalysis: Found (Calcd. for C32H31NP2Pt)
C 55.39 (55.98), H 4.63 (4.55), N 2.06 (2.04)%. 1H NMR
(CDCl3/d8-dmso): δ 8.17 (m, 1 H, NH), 7.56–7.49 (m, 4 H,
aromatics), 7.41–7.29 (m, 16 H, aromatics), 7.17 (m, 1 H,
aromatic), 6.95 (m, 1 H, aromatic), 6.79 (m, 1 H, aromatic),
1
N 1.85 (1.91)%. H NMR (CD2Cl2): δ 7.99 (br s, 1 H, NH),
7.72–7.20 (m, 22 H, aromatics), 6.92 (m, 1 H, aromatic), 6.72
(m, 1 H, aromatic), 5.26 (m, 1 H, allyl), 3.99 (v br s, 2 H, allyl),
3.01 (v br s, 2 H, allyl). FABϩ MS: m/z 697 [MϪCl]ϩ and 656/7
[MϪClϪ(C3H5)]2ϩ. Selected IR data (KBr): 2800w [ν(N–H)]
and 919br cmϪ1 [ν(P–N)].
[Pd(ꢀ3-C3H5)(Ph2PNHC6H4PPh2)][Cl] 2. To a stirred toluene
(10 cm3) suspension of [Pd(µ-Cl)(η3-C3H5)]2 (0.095 g, 0.26
mmol) was added in one portion solid Ph2PNHC6H4PPh2
(0.240 g, 0.52 mmol). The mixture was stirred for 4 hours to
give a pale yellow precipitate which was collected by filtration,
washed with toluene (5 cm3) and diethyl ether (2 × 10 cm3) and
dried in vacuo. Yield: 0.291 g, 87%. Microanalysis: Found
(Calcd. for C33H30ClNP2Pd) C 61.44 (61.51), H 4.69 (4.69),
2
6.69 (m, 1 H, aromatic) and 0.34 (m, 6 H, J(195Pt–1H) 69 Hz,
PtMe). FABϩ MS: m/z 709 [M ϩ Na]ϩ, 687 [M ϩ H]ϩ, 671
[M Ϫ CH3]ϩ and 656/7 [M Ϫ 2CH3]2ϩ. Selected IR data (KBr):
3314vs [ν(N–H)] and 883vs cmϪ1 [ν(P–N)].
Isomers of [PtMeCl(Ph2PNHC6H4PPh2)] 7. A dichloro-
methane (15 cm3) solution of Ph2PNHC6H4PPh2 (0.123 g,
0.27 mmol) was added drop-wise over a 10 minute period to a
rapidly stirred dichloromethane (15 cm3) solution of [PtMeCl-
(cod)] (0.094 g, 0.27 mmol) and the mixture was stirred for
1 hour. Light petroleum (10 cm3) was added and the volume
of the reaction solvent was reduced to ca. 15 cm3. The resulting
cream coloured precipitate was collected by suction filtration,
washed with light petroleum (2 × 10 cm3) followed by diethyl
ether (2 × 5 cm3) and dried in vacuo. Yield: 0.167 g, 89%.
Microanalysis: Found (Calcd. for C31H28ClNP2Pt) C 52.39
(52.66), H 3.75 (3.99), N 1.93 (1.98)%. FABϩ MS: m/z 707 [M]ϩ,
1
2
N 2.04 (2.17)%. H NMR (CDCl3): δ 8.11 (m, 1 H, J(31P–1H)
7 Hz, NH), 7.60–7.22 (m, 22 H, aromatics), 6.86 (m, 1 H,
2
aromatic), 6.61 (m, 1 H, aromatic), 5.63 (pent, 1 H, J(1H–1H)
10.6 Hz, allyl), 3.62 (v br s, 4 H, allyl). FABϩ MS: m/z 608
[M Ϫ Cl]ϩ and 567/8 [M Ϫ Cl Ϫ (C3H5)]2ϩ. Selected IR data
(KBr): 2786w [ν(N–H)] and 914br cmϪ1 [ν(P–N)].
[PtCl2(Ph2PNHC6H4PPh2)] 3. To a stirred dichloromethane
(3 cm3) solution of [PtCl2(cod)] (0.092 g, 0.25 mmol) was added
in one portion solid Ph2PNHC6H4PPh2 (0.116 g, 0.25 mmol)
and stirred for 2 hours. The resulting cream coloured micro-
crystalline product was collected by suction filtration washed
with ice cold dichloromethane (2 × 2 cm 3) then petroleum ether
(2 × 20 cm3) followed by diethyl ether (2 × 20 cm3) and dried in
vacuo. Yield: 0.170 g, 95%. Microanalysis: Found (Calcd. for
C30H25Cl2NP2Pt) C 50.05 (49.53), H 3.86 (3.46), N 2.06 (1.93)%.
1H NMR (CDCl3/d6-dmso): δ 8.30 (m, 1 H, NH), 7.72 (m, 4 H,
aromatics), 7.60–7.29 (m, 17 H, aromatics), 7.12 (m, 1 H,
aromatic), 6.89 (m, 1 H, aromatic) and 6.55 (m, 1 H, aromatic).
FABϩ MS: m/z 692 [M Ϫ Cl]ϩ and 656/7 [M Ϫ 2Cl]2ϩ. Selected
IR data (KBr): 3191br [ν(N–H)], 919br [ν(P–N)] and 313w,
290w cmϪ1 [ν(Pt–Cl)].
672 [M Ϫ Cl]ϩ, 692 [M Ϫ CH3]ϩ and 656/7 [M Ϫ Cl Ϫ CH3]2ϩ
.
[PdCl2(Ph2PNHC6H4PPh2)] 8. This was prepared in the same
way as the platinum complex 3 using [PdCl2(cod)] (0.075 g, 0.26
mmol) in dichloromethane (2.5 cm3) and Ph2PNHC6H4PPh2
(0.125 g, 0.27 mmol). The pale yellow precipitate was collected
by suction filtration washed with ice cold dichloromethane
(2 × 1 cm3), then petroleum ether (20 cm3) followed by diethyl
ether (2 × 10 cm3) and dried in vacuo. Yield: 0.159 g, 95%. Micro-
analysis: Found (Calcd. for C30H25Cl2NP2Pd) C 56.58 (56.41),
H 3.96 (3.94), N 2.18 (2.19)%. 1H NMR (CDCl3/dmso): δ 8.34
(br t, 1 H, 2J(31P–1H) 6 Hz, NH), 7.71 (m, 4 H, aromatics), 7.61–
7.32 (m, 17 H, aromatics), 7.19 (m, 1 H, aromatic), 6.87 (m, 1 H,
aromatic) and 6.59 (m, 1 H, aromatic). FABϩ MS: m/z 662
[M ϩ Na]ϩ, 604 [M Ϫ Cl]ϩ and 568 [M Ϫ 2Cl]2ϩ. Selected IR
data (KBr): 3125m [ν(N–H)], 925br [ν(P–N)] and 312w, 290w
cmϪ1 [ν(Pd–Cl)].
[PtBr2(Ph2PNHC6H4PPh2)] 4. This was prepared in the same
way as the platinum complex 3 using [PtBr2(cod)] (0.129 g, 0.28
mmol) in dichloromethane (4 cm3) and Ph2PNHC6H4PPh2
(0.130 g, 0.28 mmol) and stirred for 17 hours (overnight),
collected by suction filtration, washed with ice cold dichloro-
methane (2 × 2 cm3) then petroleum ether (2 × 10 cm3) followed
by diethyl ether (15 cm3) to give a cream coloured microcrystal-
line product. Yield: 0.191 g, 84%. Microanalysis: Found (Calcd.
for C30H25Br2NP2Pt) C 44.97 (44.14), H 3.43 (3.09), N 1.78
(1.72)%. FABϩ MS: m/z 839 [M ϩ Na]ϩ, 816 [M]ϩ, 736
[M Ϫ Br]ϩ and 656/7 [M Ϫ 2Br]2ϩ. Selected IR data (KBr):
3199br [ν(N–H)], 906br [ν(P–N)] and 305br cmϪ1 [ν(Pt–Br)].
[NiCl2(Ph2PNHC6H4PPh2)] 9. Solid Ph2PNHC6H4PPh2
(0.167 g, 0.36 mmol) was added in one portion to a hot stirred
ethanol solution (5 cm3) of NiCl2ؒ6H2O (0.086 g, 0.36 mmol)
causing an immediate colour change from pale green to deep
red. The reaction mixture was heated and stirred for a further
10 minutes and then allowed to cool. The resulting bright red
crystalline material was collected by suction filtration washed
with ethanol (2 × 5 cm3) and dried in vacuo. Yield: 0.154 g, 72%.
Microanalysis: Found (Calcd. for C30H25Cl2NP2Ni) C 60.31
(60.96), H 4.01 (4.26), N 2.15 (2.37)%. FABϩ MS: m/z 591 [M]ϩ,
[PtI2(Ph2PNHC6H4PPh2)] 5. This was prepared in the same
way as the platinum complex 3 using [PtI2(cod)] (0.136 g, 0.24
2280
J. Chem. Soc., Dalton Trans., 2001, 2279–2287

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556 [M Ϫ Cl]ϩ and 520 [M Ϫ 2Cl]2ϩ. Selected IR data (KBr):
3201m [ν(N–H)], 917m [ν(P–N)] and 330br cmϪ1 [ν(Ni–Cl)].
and 548 [M ϩ Na]ϩ. Selected IR data (KBr): 3106m [ν(N–H)],
926s [ν(P–N)] and 642s, 632s cmϪ1 [ν(P᎐S)].
᎐
Ph2P(Se)NHC6H4P(Se)Ph2 14. Ph2PNHC6H4PPh2 (0.421 g,
0.91 mmol) and grey selenium (0.144 g, 1.82 mmol) were heated
to reflux in toluene (20 cm3) for 30 minutes. The solvent was
removedinvacuoandthecrudeproductwastakenupindichloro-
methane (10 cm3) and filtered through Celite to remove a trace
of unreacted selenium. The filtrate was evaporated to dryness
and the crude product was recrystallised from the minimum of
warm toluene. The colourless crystalline solid was collected by
suction filtration washed with ice cold toluene (5 cm3) and dried
overnight in vacuo. Yield: 0.463 g, 82%. Microanalysis: Found
(Calcd. for C30H25NP2Se2) C 57.95 (58.17), H 4.16 (4.07),
N 2.58 (2.26)%. 1H NMR (CDCl3): δ 8.19 (br d, 1 H, 2J(31P–1H)
7 Hz, NH), 7.75 (m, 4 H, aromatics), 7.63–7.27 (m, 18 H,
aromatics), 6.85 (m, 1 H, aromatic) and 6.67 (m, 1 H, aromatic).
FABϩ MS: m/z 621 [M]ϩ. Selected IR data (KBr): 3081m
[Mo(CO)4(Ph2PNHC6H4PPh2)] 10. [Mo(CO)4(pip)2] (0.403 g,
1.07 mmol) and Ph2PNHC6H4PPh2 (0.493 g, 1.07 mmol) were
refluxed in dichloromethane (20 cm3) under an N2 atmosphere
for 1.5 hours. The pale orange solution was cooled to room
temperature and methanol (ca. 20 cm3) was added then the
mixture was concentrated to ca. 30 cm3 and left to stand at
Ϫ4 ЊC overnight. The cream coloured solid was collected by
suction filtration washed with methanol (10 cm3) and diethyl
ether (10 cm3) and dried in vacuo. Yield: 0.623 g, 88%. Micro-
analysis: Found (Calcd. for C34H25MoNO4P2) C 60.58 (61.00),
H 3.50 (3.76), 1.82 (2.09)%. 1H NMR (CDCl3): δ 7.45–7.16 (m,
21 H, aromatics), 6.87 (m, H, aromatic), 6.61 (m, 1 H,
aromatic), 6.49 (m, 1 H, aromatic), 4.79 (br d, 1 H, 2J(31P–1H) 8
Hz, NH). FABϩ MS: m/z 669/670 [M]ϩ, 641 [M Ϫ CO]ϩ, 613
[M Ϫ 2CO]ϩ, 585 [M Ϫ 3CO]ϩ and 557 [M Ϫ 4CO]ϩ. Selected
IR data (KBr): 3331m [ν(N–H)], 893s [ν(P–N)] and 2017s,
1925vs, 1903vs, 1884vs cmϪ1 [ν(CO)].
[ν(N–H)], 921s [ν(P–N)] and 561vs, 543s cmϪ1 [ν(P᎐Se)].
᎐
[PdCl(Ph2P(S)NC6H4P(S)Ph2-S,N,S)] 15. Method (a). To an
ethanol solution (10 cm3) of Na2[PdCl4] (0.073 g, 0.248 mmol)
was added Ph2P(S)NHC6H4P(S)Ph2 13 (0.132 g, 0.251 mmol) as
a solid in one go. The reaction mixture was gently heated until
the Ph2P(S)NHC6H4P(S)Ph2 had completely dissolved, then
stirred for 17 hours. The resulting red solid was collected by
filtration, re-dissolved in dichloromethane (10 cm3) and filtered
through a small Celite pad. Slow addition of diethyl ether (50
cm3) to the stirred filtrate gave 15 as bright red microcrystals,
which were collected by suction filtration, washed with diethyl
ether (2 × 10 cm3) and dried in vacuo. Yield 0.129 g, 78%.
Microanalysis: Found (Calcd. for C30H24ClNP2PdS2) C 53.73
[(AuCl)2(Ph2PNHC6H4PPh2)] 11. [AuCl(tht)] (0.115 g, 0.36
mmol) was dissolved in dichloromethane (5 cm3) and solid
Ph2PNHC6H4PPh2 (0.082 g, 0.18 mmol) was added in one
portion. The mixture was stirred for 30 minutes giving a clear
brown coloured solution which was then filtered through Celite
to remove a small amount of insoluble material and reduced in
volume to ca. 2 cm3. Petroleum ether (bp 60–80 ЊC) was added
drop-wise (30 cm3) and the colourless microcrystalline product
was collected by suction filtration washed with petroleum ether
(2 × 10 cm3) and dried in vacuo. Yield: 0.150 g, 91%. Micro-
analysis: Found (Calcd. for C30H25Au2Cl2NP2) C 38.75 (38.90),
H 2.59 (2.72), N 1.50 (1.51)%. 1H NMR (CD2Cl2): δ 7.65–7.33
(m, 21 H, aromatics), 7.18 (m, 1 H, aromatic), 7.05 (m, 1 H,
1
(54.14), H 3.53 (3.64), N 2.00 (2.11)%. H NMR (CD2Cl2):
δ 7.84–7.53 (m, 20 H, aromatics), 7.13–7.06 (m, 1 H, aromatic)
and 6.79–6.60 (m, 3 H, aromatics). FABϩ MS: m/z, 666/7 [M]ϩ
and 630/1 [M Ϫ Cl]ϩ. Selected IR data (KBr): 809m [ν(P–N)]
2
aromatic), 6.70 (m, 1 H, aromatic) and 5.61 (br t, 1 H, J(31P–
1H) 3 Hz, NH). FABϩ MS: m/z 949 [M ϩ Na]ϩ, 926 [M]ϩ and
891 [M Ϫ Cl]ϩ. Selected IR data (KBr): 3238m [ν(N–H)], 922s
[ν(P–N)] and 339w cmϪ1 [ν(Au–Cl)].
634s, 622m [ν(P᎐S)] and 305w cmϪ1 [ν(Pd–Cl)].
᎐
Method (b). Solid Ph2P(S)NHC6H4P(S)Ph2 13 (0.141 g,
0.268 mmol) was added in one portion to a stirred dichloro-
methane (15 cm3) solution of [PdCl2(NCPh)] (0.102 g, 0.266
mmol). The resulting dark red solution was stirred for 17 hours
and then filtered through a Celite plug to remove a small
quantity of insoluble black material. The filtrate was concen-
trated in vacuo to ca. 5 cm3 and the addition of diethyl ether (30
cm3) caused the precipitation of a dark red microcrystalline
solid. Yield 0.133 g, 75%. The spectroscopic properties of this
material were identical to those described above.
Ph2P(O)NHC6H4P(O)Ph2 12. Aqueous hydrogen peroxide
(30% w/w, 0.2 cm3, 1.76 mmol) was added drop-wise to a solu-
tion of Ph2PNHC6H4PPh2 (0.360 g, 0.78 mmol) in thf (10 cm3)
and the mixture was stirred for 30 minutes. The solvent was
removed in vacuo to give a viscous oil which was dissolved in
dichloromethane (30 cm3) and dried over magnesium sulfate.
The drying agent was removed by filtration and the filtrate was
evaporated to dryness. The product was recrystallised from the
minimum of hot toluene and after storage overnight at Ϫ4 ЊC
the colourless crystalline product was collected by suction
filtration washed with ice cold toluene (5 cm3) and dried
in vacuo. Yield: 0.304 g, 79%. Microanalysis: Found (Calcd. for
C30H25NO2P2) C 72.78 (73.02), H 5.32 (5.11), N 2.74 (2.84)%.
[Pd(PPh3)(Ph2P(S)NC6H4P(S)Ph2-S,N,S)][ClO4] 16. To a
dichloromethane solution (10 cm3) of [PdCl(Ph2P(S)NC6H4-
P(S)Ph2-S,N,S)] 15 (0.125 g, 0.188 mmol) was added solid
Ag[ClO4] (0.040 g, 0.193 mmol). The reaction mixture was
stirred for 3 hours and the precipitated AgCl was removed by
filtration through a small Celite pad. To the red filtrate was
added solid PPh3 (0.050 g, 0.191 mmol) which caused an
immediate colour change from red to orange. The slow addition
of diethyl ether to the orange solution gave 16 as bright orange
microcrystals, which were collected by suction filtration,
washed with diethyl ether (2 × 10 cm3) and dried in vacuo. Yield
0.166 g, 89%. Microanalysis: Found (Calcd. for C48H39ClNO4-
2
1H NMR (CDCl3): δ 9.43 (br d, 1 H, J(31P–1H) 12 Hz, NH)
and 7.73–7.20 (m, 22 H, aromatics) and 6.97–6.79 (m, 2 H,
aromatics). FABϩ MS: m/z 493 [M]ϩ. Selected IR data (KBr):
3149br [ν(N–H)], 1188s, 1173s [ν(P᎐O)] and 952s cmϪ1 [ν(P–N)].
᎐
Ph2P(S)NHC6H4P(S)Ph2 13. Ph2PNHC6H4PPh2 (0.410 g,
0.89 mmol) and elemental sulfur (0.057 g, 1.78 mmol) were
stirred in toluene (20 cm3) for 90 minutes. The solvent was
removedinvacuoandthecrudeproductwastakenupindichloro-
methane (10 cm3) and filtered through Celite. The filtrate was
evaporated to dryness and the crude product was recrystallised
from a minimum of warm toluene. The colourless solid was
collected by suction filtration washed with ice cold toluene (5
cm3) and dried overnight in vacuo. Yield: 0.402 g, 86%. Micro-
analysis: Found (Calcd. for C30H25NP2S2) C 68.45 (68.56), H
1
P3PdS2) C 57.97 (58.12), H 3.75 (3.97), N 1.38 (1.41)%. H
NMR (CD2Cl2): δ 7.78–7.49 (m, 20 H, aromatics), 7.10–7.02
(m, 1 H, aromatic) and 6.83–6.67 (m, 3 H, aromatics). FABϩ
MS: m/z, 893 [M Ϫ (ClO4)]ϩ. Selected IR data (KBr): 1094vs
[ν(ClO4)], 798m [ν(P–N)] and 639s, 622m cmϪ1 [ν(P᎐S)].
᎐
X-Ray crystallography
1
4.74 (4.79), N 2.63 (2.66)%. H NMR (CDCl3): δ 8.35 (br d,
X-Ray diffraction studies on crystals of 3 grown from
chloroform–dimethyl sulfoxide–diethyl ether were performed at
293 K using a Bruker SMART diffractometer with graphite-
1 H, 2J(31P–1H) 8 Hz, NH), 7.78–7.21 (m, 22 H, aromatics) and
6.85–6.71 (m, 2 H, aromatics). FABϩ MS: m/z 526 [M ϩ H]ϩ
J. Chem. Soc., Dalton Trans., 2001, 2279–2287
2281

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Scheme 1 (i) [Pt(µ-Cl)(η3-C3H5)]4, thf or [Pd(µ-Cl)(η3-C3H5)]2, C6H5Me; (ii) [PtXXЈ(cod)] (X = XЈ = Me, Cl, Br, I or X = Cl and XЈ = Me),
[PdCl2(cod)], CH2Cl2, or NiCl2ؒ6H2O, EtOH; (iii) [Mo(CO)4(pip)2], CH2Cl2; (iv) [AuCl(tht)], CH2Cl2; (v) H2O2(aq), thf or S8/Se8, C6H5Me; (vi)
[PdCl2(NCPh)2], CH2Cl2 or Na2PdCl4, EtOH, (vii) Ag[ClO4], CH2Cl2, PPh3.
monochromated Mo-Kα radiation (λ = 0.71073 Å). The struc-
ture was solved by direct methods, non-hydrogen atoms were
refined with anisotropic displacement parameters; hydrogen
atoms bound to carbon were idealised and fixed (C–H 0.95 Å),
the NH protons were located by a ∆F map and allowed to refine
anisotropically. Structural refinements were by the full-matrix
least-squares method on F 2 using the program SHELXTL.35
small 2J(31P–31P) couplings of 35 (1) and 71 Hz (2), with corre-
sponding platinum satellites for compound 1. The NHPPh2
(PX) high frequency resonance is observed at δ (P) 62.9 [1J(195Pt–
31PX) 4058 Hz], for 1 and δ (P) 74.3 for 2 while the low frequency
signal occurs at δ (P) 4.5 [1J(195Pt–31PA) 3529 Hz], and δ (P) 14.7
1
for 1 and 2 respectively. The H NMR spectra are consistent
with the proposed structures and include amine δ 7.99 (1),
δ 8.11 (2) and allyl δ 5.26 (m) and broad singlets at 3.99 and 3.01
C32.35H30.25Cl4.25NO0.75P2PtS0.75
,
M = 875.56, monoclinic,
2
space group P21/n, a = 12.2267(2) Å, b = 21.7198(3) Å,
c = 14.1548(2) Å, β = 98.8060(10)o, U = 3714.66(10) Å3, Z = 4,
Dc = 1.566 Mg mϪ3, µ = 4.236 mmϪ1, F(000) = 1716, crystal
size = 0.2 × 0.3 × 0.4 mm. Of 16141 measured data, 5310 were
unique (Rint 0.0217) to give R1[I > 2σ(I )] = 0.0330 and
wR2 = 0.0893.
for 1 and δ 5.63 [pent, J(1H–1H) 10.6 Hz] and a very broad
singlet at δ 3.62 for 2. Further supporting data includes IR
(KBr) bands at 2800 (1), 2786 (2) and a band at 919 (1), 914
cmϪ1 (2) assigned as ν(NH) and ν(PN) respectively. The reduc-
tion in the ν(NH) band energies in the IR spectra of complexes
1 and 2 compared to for example complex 3 [3191 cmϪ1] is
CCDC reference number 159100.
characteristic of a strong hydrogen-bonding interaction
See http://www.rsc.org/suppdata/dt/b1/b101772l/ for crystal-
lographic data in CIF or other electronic format.
between the amine proton of the ligand and the chloride
counter ion, causing a significant reduction in the NH stretch-
ing frequency. Treatment of [PtCl2(cod)] with Ph2PNH-
C6H4PPh2 in dichloromethane gives a cream coloured solid in
excellent yield (95%). The product was characterised as the
expected chelate species. The 31P-{1H} NMR spectrum (in
CDCl3/dmso) of [PtCl2(Ph2PNHC6H4PPh2)] 3 is an AX type
spectrum and contains two sharp doublets at δ (PA) Ϫ0.4
[1J(195Pt–31PA) 3508 Hz] and δ (PX) 53.8 [1J(195Pt–31PX) 3932 Hz],
assigned to the PPh3 and the NHPPh2 centres respectively, with
a small 2J(31PA–31PX) coupling of 21 Hz. The large 1J(195Pt–31PA)
and 1J(195Pt–31PX) coupling constants are in agreement with
values previously found for platinum() complexes where phos-
phorus is trans to chloride.37 The 1H NMR spectrum (in CDCl3/
d6-dmso) shows a multiplet at δ 8.30, which we have assigned to
the amine proton – as an exchange reaction with D2O causes
the resonance to disappear. Further evidence in support of the
cis chelate structure comes from the IR spectrum which shows
two distinct ν(Pt–Cl) stretches at 313 and 290 cmϪ1 which are
also consistent with a cis-PtCl2 geometry. The IR spectrum also
Results and discussion
Chelate complexes of Ph2PNHC6H4PPh2
Ph2PNHC6H4PPh2 reacts with [Pt(µ-Cl)(µ-η2 : η1-C3H5)]4 in thf
and [Pd(µ-Cl)(η3-C3H5)]2 in toluene at room temperature to give
the cationic chelate complexes [M(η3-C3H5)(Ph2PNHC6H4-
PPh2)][Cl] (where M = Pt 1 or Pd 2) in excellent yields (91% and
87% respectively) (Scheme 1). The attempted synthesis of 1 in
chloroform resulted in the isolation of a mixture of the desired
product and the dichloride complex [PtCl2(Ph2PNHC6H4PPh2)]
3 (31P-{1H} NMR evidence, Table 1) which we were unable to
separate. The decomposition of the platinum allyl complex 1 is
presumably a result of reaction with free HCl in the chloroform
resulting in the loss of propene and formation of the observed
dichloride species.36 The 31P-{1H} NMR spectra for complexes
1 and 2 are of the AX type and show two sharp doublets and
2282
J. Chem. Soc., Dalton Trans., 2001, 2279–2287

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Table 1 31P-{1H} NMRa data for complexes of Ph2PNHC6H4PPh2 (where PA = triarylphosphine {PPh3} and PX = diarylaminophosphine
{NHPPh2})
Chemical shifts (ppm)
Coupling constants/Hz
Complex
δ(PA)
δ(PX)
1J(Pt–PA)
1J(Pt–PX)
2J(PA–PX)
1
4.5
14.7
Ϫ0.4
—
62.9
74.3
53.8
—
3529
—
3508
—
4058
—
3932
—
35
71
21
—
—
26
23
28
5
—
35
—
n.o.e
n.o.e
n.o.e
3
2b
3c
4
5
—
—
—
—
6c
10.7
11.9
11.1
18.1
—
33.6
20.1
36.5
39.9
27.2 (691)
42.6
38.5
70.6
63.2
71.5
77.8
—
91.7
60.9
18.4
57.3
47.0 (787)
79.4
76.1
1808
1696
4126
—
—
—
—
—
—
—
2063
4615
1965
—
—
—
—
—
—
—
7(A)d
7(B)d
8c
9
10c
11
12b
13b
14b,f
15
—
—
—
—
16g
3
a Spectra (101.3 MHz) measured in CD2Cl2 unless otherwise stated. b Spectra (101.3 MHz) measured in CDCl3. c Spectra (36.2 MHz) measured in
CDCl3/dmso. d Spectra (101.3 MHz) measured in CDCl3/dmso. e n.o. = not observed. f Values in parentheses denote 1J(77Se–31P)/Hz. g Other 31P-{1H}
spectral parameters for 16 δ(PPh3) 34.3 3J(PPh3–PA) 6 Hz, 3J(PPh3–PX) 18 Hz.
Fig.
2
Core geometry in [PtCl2(Ph2PNHC6H4PPh2)]ؒ0.75dmsoؒ
0.75CHCl3 3.
Table 2 Selected bond lengths (Å) and angles (Њ) for [PtCl2(Ph2-
PNHC6H4PPh2)]ؒ0.75dmsoؒ0.75CHCl3
Fig.
1
Crystal structure of [PtCl2(Ph2PNHC6H4PPh2)]ؒ0.75dmsoؒ
0.75CHCl3 3.
P(1)–Pt(1)
Pt(1)–Cl(1)
P(1)–N(1)
C(1)–C(2)
2.2126(13) P(2)–Pt(1)
2.3664(14) Pt(1)–Cl(2)
2.2319(13)
2.358(2)
1.407(7)
1.821(5)
shows a broad band at 3191 cmϪ1 and a band at 919 cmϪ1
assigned as ν(NH) and ν(PN) respectively. Crystals of [PtCl2-
(Ph2PNHC6H4PPh2)]ؒ0.75dmsoؒ0.75CHCl3 suitable for X-ray
crystallography were grown in approximately 2 hours by layer-
ing a CDCl3/dmso solution of [PtCl2Ph2PNHC6H4PPh2] 3 with
diethyl ether. The crystal structure of the complex (Fig. 1) along
with its core geometry (Fig. 2) and selected bond lengths and
angles (Table 2) confirm the proposed cis chelate geometry. The
crystal structure shows that the [PtCl2(Ph2PNHC6H4PPh2)] 3
molecule is approximately square planar at platinum [maximum
deviations from Pt(1)–P(1)–P(2)–Cl(1)–Cl(2) mean plane 0.06
Å above for Pt(1)]. The bite angle of the chelating phosphine is
close to the ideal 90Њ [P(1)–Pt(1)–P(2) 91.03(5)]. The Pt(1)–
P(1)–N(1)–C(1)–C(2)–P(2) six-membered ring can be con-
sidered as two planes of four atoms with two atoms, N(1) and
P(2) in common. The N(1)–C(1)–C(2)–P(2) atoms are planar
whilst the Pt(1)–P(1)–P(2)–N(1) plane shows a mean deviation
1.689(4)
1.404(8)
N(1)–C(1)
P(2)–C(2)
P(1)–Pt(1)–P(2)
P(1)–Pt(1)–Cl(2)
P(1)–Pt(1)–Cl(1)
Pt(1)–P(1)–N(1)
P(1)–N(1)–C(1)
N(1)–C(1)–C(2)
91.03(5)
172.80(6)
87.38(5)
113.90(2)
120.70(4)
120.50(5)
Cl(1)–Pt(1)–Cl(2)
P(2)–Pt(1)–Cl(1)
P(2)–Pt(1)–Cl(2)
Pt(1)–P(2)–C(2)
P(2)–C(2)–C(1)
89.45(6)
178.36(5)
92.18(6)
114.10(2)
119.00(4)
of only 0.04 Å. The ‘hinge angle’ between the N(1)–C(1)–C(2)–
P(2) and Pt(1)–P(1)–P(2)–N(1) planes is approximately 46Њ.
The crystal structure also reveals that each molecule of
[PtCl2(Ph2PNHC6H4PPh2)] 3 crystallises with 0.75 molecules of
CDCl3 and 0.75 molecules of dimethyl sulfoxide, the oxygen
atom of which is hydrogen-bonded to the amine proton of
3 [H(1n) ؒ ؒ ؒ O(50) 1.93 Å, O(50) ؒ ؒ ؒ N(1) 2.86 Å, N(1)–
J. Chem. Soc., Dalton Trans., 2001, 2279–2287
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compared to those of the platinum complexes (3, 6 and 7 {A
and B}) (Table 1). The coupling is only slightly larger than the
4J(31PA–31PX) coupling of 4 Hz observed for the free ligand and
smaller than those found in complexes where the ligand is
acting as a monodentate phosphorus donor which have an
average 4J(31PA–31PX) coupling of 9 Hz.25 The positive-ion FAB
mass spectrum failed to give the anticipated parent-ion peak
but showed the expected [M Ϫ Cl]ϩ and [M Ϫ 2Cl]2ϩ fragments.
The IR spectrum of the complex shows two distinct ν(Pd–Cl)
stretches at 313 and 290 cmϪ1 which are consistent with a cis-
PdCl2 geometry. The IR spectrum also shows a band at 3125
cmϪ1 and a band at 925 cmϪ1 assigned as ν(NH) and ν(PN)
respectively. The addition of solid Ph2PNHC6H4PPh2 to a hot
ethanol solution of NiCl2ؒ6H2O after cooling gives [NiCl2-
(Ph2PNHC6H4PPh2)] 9 as a bright-red crystalline solid. No 31P-
{1H} or 1H NMR spectra for this complex were observed,
indicating that in solution [NiCl2(Ph2PNHC6H4PPh2)] 9 is
paramagnetic. Since square planar Ni() complexes are
expected to be diamagnetic, this observation indicates that 9
exhibits distortions from idealised square-planar geometry. As
measurement of NMR parameters was not possible, complex
9 was characterised by IR spectroscopy, mass spectrometry and
microanalysis only. The IR spectrum showed bands at 3201, 917
and 330 cmϪ1 assigned as ν(NH), ν(PN) and ν(NiCl) respect-
ively. The positive-ion FAB mass spectrum gave the correct
parent-ion peak, m/z 591 [M]ϩ and the appropriate [M Ϫ Cl]ϩ
and [M Ϫ 2Cl]2ϩ fragments and microanalytical data were in
good agreement with the proposed [NiCl2(Ph2PNHC6H4PPh2)]
9 formulation (Experimental section).
Fig. 3 Products obtained by reaction of Ph2PNHC6H4PPh2 with
[PtClMe(cod)].
H(1n) ؒ ؒ ؒ O(50) 159Њ]. The dibromo- 4 and diiodo- 5 derivatives
of [PtCl2(Ph2PNHC6H4PPh2)] can be prepared by reaction of
Ph2PNHC6H4PPh2 with [PtBr2(cod)] and [PtI2(cod)] or by
metathesis of the dichloride with an excess of the appropriate
halide ion in refluxing acetone. Microanalytical data obtained
for the dibromo and diiodo complexes are in good agreement
with calculated values. Also in agreement were the positive-ion
FAB mass spectra which displayed the expected parent-ion
peaks and fragmentation patterns. {For 4 m/z 839 [M ϩ Na]ϩ,
816 [M]ϩ, 736 [M Ϫ Br]ϩ and 656/7 [M Ϫ 2Br]2ϩ}, {for 5 m/z
933/4 [M ϩ Na]ϩ, 910 [M]ϩ, 783/4 [M Ϫ I]ϩ and 656/7
[M Ϫ 2I]2ϩ}, with appropriate isotope distributions. Satis-
factory 31P-{1H} NMR data could not be collected due to the
insolubility, even in neat d6-dmso, of the diiodo complex and
the rapid halide exchange reaction of the dibromide which
takes place in CDCl3/dmso, resulting in multiplets around the
mean δ (P) values observed for the dichloride 3. A CDCl3/dmso
solution of [PtBr2(Ph2PNHC6H4PPh2)] reverts back to the
dichloride if left to stand for approximately one week. Reaction
of Ph2PNHC6H4PPh2 with [PtMe2(cod)] in dichloromethane
produces an off-white powder, characterised as the dimethyl
complex [PtMe2(Ph2PNHC6H4PPh2)] 6, as is evidenced by the
31P-{1H} NMR spectrum (in CDCl3/dmso). The much smaller
1J(195Pt–31PA) couplings associated with doublet resonances at
δ (PA) 10.7 [1J(195Pt–31P) 1808 Hz] (PPh3) and δ (PX) 70.6
[1J(195Pt–31PX) 2063 Hz] (NHPPh3) are consistent with those
found in complexes where phosphorus is trans to a methyl
group.38–40 The two inequivalent methyl group proton reson-
Ph2PNHC6H4PPh2 reacts with [Mo(CO)4(pip)2] in refluxing
dichloromethane by displacement of the piperidine molecules
to give the anticipated six-membered ring molybdenum com-
plex as shown in Scheme 1. The 31P-{1H} NMR spectrum of
[Mo(CO)4(Ph2PNHC6H4PPh2)] 10 showed two sharp doublets
2
at δ (PA) 33.6 and δ (PX) 91.7 with a J(31PA–31PX) coupling of
35 Hz which is consistent with that of other molybdenum
unsymmerical chelating bis-phosphine tetracarbonyl com-
plexes.41 Microanalytical data were in good agreement with
calculated values (Experimental section) as was the positive-ion
FAB mass spectrum which gave the anticipated parent-ion peak
at m/z 669/670 and showed successive loss of one, two, three
and four CO groups. IR data (KBr pellet) gave further support
to the proposed structure showing four distinct ν(CO) absorp-
tions in the range 2017–1884 cmϪ1 which are characteristic of
molybdenum cis-tetracarbonyl derivatives.42,43
1
ances in the H NMR spectrum of complex 6 (in CDCl3/d6-
dmso) appear as overlapping multiplets at approximately δ 0.30
flanked by platinum satellites [2J(195Pt–1H) 69 Hz]. Due to the
3
complexity of the splitting pattern the cis and trans J(31P–1H)
coupling constants could not be confidently assigned. The NH
signal appears as a multiplet at δ 8.17, confirmed by an
exchange reaction with D2O. A dilute dichloromethane solution
of Ph2PNHC6H4PPh2 added drop-wise over 10 minutes, (exten-
sion of the addition time to 2 hours gave the same products in
the same ratio), to a dilute solution of [PtClMe(cod)] in the
same solvent gives two products (Fig. 3). Structural assignment
is based on comparison of the 31P-{1H} NMR spectrum (in
CDCl3/dmso) of the isolated material, shown in (Fig. 4), to
those of the dichloro 3 and the dimethyl 6 analogues. The 31P-
{1H} NMR spectrum (CDCl3/dmso) (Fig. 4) showed that
isomer B constituted approximately 80–85% of the isolated
material (89% yield overall). The same NMR sample stored at
room temperature was run two and four weeks after the initial
31P-{1H} NMR experiment. Comparison of the spectra showed
that the isomer ratio had not changed. A sample of the same
material heated to approximately 60 ЊC in toluene failed to alter
the ratio of products, but, instead, gave rise to several new ones.
Isolation and characterisation of these products was not
attempted.
Bidentate bridging coordination chemistry of Ph2PNHC6H4PPh2
As well as the chelating mode of coordination, resulting in
the formation of six-membered metallacycles Ph2PNHC6H4-
PPh2 can act as a bridging ligand between two metal centres.
The reaction of two equivalents of [AuCl(tht)] (tht =
tetrahydrothiophene) with Ph2PNHC6H4PPh2 in dichloro-
methane gave [(AuCl)2(Ph2PNHC6H4PPh2)] 11 as a colourless
solid in excellent yield (91%). The complex displays two single
resonances in its 31P-{1H} NMR spectrum [δ (PX) 60.9 and
δ (PA) 20.1 for the NHPPh2 and PPh3 coordinating centres
respectively] and the 1H NMR spectrum showed the amine
proton as a broad triplet at δ 5.61 [2J(31P–1H) 3 Hz]. Micro-
analytical data were in good agreement with calculated values
(Experimental section) and the positive-ion FAB mass
spectrum gave the correct, though very weak, parent-ion peak
at m/z 926 along with a strong peak corresponding to
[M Ϫ Cl]ϩ. Assignment of the IR spectrum is difficult, but we
[PdCl2(Ph2PNHC6H4PPh2)] 8 was prepared and isolated in
the same manner as its platinum analogue 3. The expected AX
type 31P-{1H} NMR spectrum was obtained, δ (PA) 18.1 for the
Ph2P group and δ (PX) 77.8 for the NHPPh2 moiety, where both
of the phosphorus centres have been shifted significantly down
field (∆δ = 37.6 and 48.2 ppm respectively), indicating that
both phosphorus atoms have coordinated. However, the
2J(31PA–31PX) coupling constant of 5 Hz is very small when
can identify ν(NH) at 3238 cmϪ1 and ν(PN) at 922 cmϪ1
.
Synthesis of Ph2P(E)NHC6H4P(E)Ph2
The generation of Ph2P(E)NHC6H4P(E)Ph2 (where E = O 12, S
13 and Se 14) from Ph2PNHC6H4PPh2 is straightforward.
Reaction of Ph2PNHC6H4PPh2 with a small excess of H2O2
2284
J. Chem. Soc., Dalton Trans., 2001, 2279–2287

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Fig. 4 31P-{1H} NMR spectum (101.3 MHz) of isolated material from reaction of Ph2PNHC6H4PPh2 with [PtClMe(cod)]. Peaks denoted with the
letters A and B respectively.
Table 3 Selected IR [KBr pellet] (cmϪ1) spectroscopic data for Ph2-
PNHC6H4PPh2 and compounds 12–14
phosphorus chalcogen bonds. Assignment is based upon
comparison of the IR spectra of the oxide ν(P᎐O) 1173 cmϪ1
,
᎐
sulfide ν(P᎐S) 632 cmϪ1 and selenide ν(P᎐Se) 545 cmϪ1 of 2-
᎐
᎐
Compound
ν(NH)
ν(PN)
ν(P᎐E)
᎐
(diphenylphosphino)aniline to the IR spectra of the dioxidised
bis-phosphines Ph2P(E)NHC6H4P(E)Ph2 12–14.
Ph2PNHC6H4PPh2
3300s
891s
952s,
926s,
921s,
—
12
13
14
3149br
3106m
3081m
1188s, 1173s*
642s, 632s*
561vs, 543s*
Coordination chemistry of Ph2P(S)NHC6H4P(S)Ph2
Ph2P(S)NHC6H4P(S)Ph2 13 reacts with [PdCl2(PhCN)2] in
dichloromethane and Na2[PdCl4] in ethanol by elimination of
HCl to give the same N-metallated species, [PdCl(Ph2P(S)-
NC6H4P(S)Ph2-S,N,S)] 15, which was isolated as a bright-red
crystalline solid in 75 and 78% respectively (Scheme 1). The
material is soluble in dichloromethane and chloroform but
insoluble in methanol, ethanol, diethyl ether and petroleum
ether. The 31P-{1H} NMR spectrum (in CD2Cl2) is, like that of
the free ligand 13, an AX type but, unlike 13, displays a small
4J(31PA–31PX) coupling of 3 Hz. The low frequency resonance
Bands highlighted * are assigned to E᎐PPh2(C6H4).
᎐
(aq) in thf, or stoichiometric quantities of S8 in toluene, or Se8
in refluxing toluene, lead to good yields (79%, 86% and 82%
respectively) of the dioxidised species (Scheme 1). Compounds
12, 13 and 14 were all isolated as colourless solids, soluble in
thf, acetonitrile, dichloromethane and chloroform, less so in
toluene, methanol and ethanol and slightly in petrol. The
4J(31PA–31PX) coupling constants were not observed in the 31P-
{1H} NMR spectra (in CDCl3) for any of the dioxidised ligand
species, displaying instead two single phosphorus resonances
(Table 1). The chalcogens of Ph2PC6H4NH2 2-(diphenylphos-
phino)aniline were prepared and characterised by 31P-{1H}
NMR (CDCl3). The following 31P-{1H} NMR data were
generated for the oxide [δ (P) 35.1], sulfide [δ (P) 39.7] and selen-
ide [δ (P) 26.9, 1J(31P–77Se) 695 Hz], allowing unambiguous
assignment of the two phosphorus environments of the dichal-
cogen species. The 1H NMR spectra (in CDCl3) of compounds
12 [δ 9.43 J(PX–H) 12 Hz], 13 [δ 8.35 J(PX–H) 8 Hz] and 14
[δ 8.19 J(PX–H) 7 Hz] all display the anticipated doublets for
the amine protons. Assignment of the IR spectra of 12–14 is
difficult but those bands we can identify along with those of
Ph2PNHC6H4PPh2 for comparative purposes are collected in
Table 3. Oxidation of Ph2PNHC6H4PPh2 causes significant
increases in ν(PN) band energies, which accompanies a large
decrease in ν(NH) energy, which may be an indication of inter-
at δ (P ) 42.6 assigned to the Ph P᎐S phosphorus centre is
᎐
A
3
comparable to that of the free ligand value δ (P) 39.9 but the
NHPh P᎐S resonance at δ (P) 79.4 has been significantly shifted
᎐
2
to higher frequency when compared to the NHPh P᎐S reson-
᎐
2
ance of 13 δ (P) 57.3. This shift to higher frequency occurs as
a result of ring strain and is observed in other complexes
containing Pd–S–P–N rings. A similar coordination mode to
13, (i.e. four- and six-membered ring formation), is observed
when the symmetrically substituted urea ligand N,N Ј-
bis(diphenylphosphino)urea disulfide [{Ph2P(S)NH}2CO] is
reacted with [PdCl2(PhCN)2] in dichloromethane.44 The 31P-
{1H} NMR value (in CDCl3) of the free ligand is δ (P) 52.2,45
the chemical shift of the phosphorus atoms within the six-
membered Pd–S–P–N–C–N metallacycle is δ (PA) 56.1 whilst
that of the phosphorus centre contained in the four-membered
ring is δ (P) 91.6, although no 4J(31PA–31PX) coupling was
observed. Further examples of four-membered metallacycles
containing anionic P–S–N moieties (where M = Al,46 Ni,47–50
Pd,51 Pt52 and Ti53) rings have been reported along with [Ph2P-
molecular hydrogen bonding. The ν(P᎐E) bands highlighted
᎐
with an asterisk* have been assigned to the PPh2(C6H4)
J. Chem. Soc., Dalton Trans., 2001, 2279–2287
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Fig. 5 31P-{1H} NMR spectrum (101.3 MHz) of [Pd(PPh3)(Ph2P(S)NC6H4P(S)Ph2-S,N,S)][ClO4] 16.
(S)NH2]Mn(CO)3Br54 which contains the neutral bidentate PN
donor Ph2P(S)NH2. Further evidence for the proposed anionic
tridentate S,N,S coordination mode is given by the IR and H
in [PdCl(Ph2P(S)NC6H4P(S)Ph2-S,N,S)] 15, the related com-
pounds Ph2P(O)NHC6H4P(O)Ph2 12 and Ph2P(Se)NHC6H4P-
(Se)Ph2 14 remain, as yet, unexplored. Further investigations
into the coordination chemistry of Ph2PNHC6H4PPh2 and
1
NMR spectra which indicate the absence of the amine proton.
Positive-ion FAB mass spectral and microanalytical data
were in excellent agreement with the proposed structure. We
also found that treatment of [PdCl(Ph2P(S)NC6H4P(S)Ph2-
S,N,S)] 15 in dichloromethane with Ag[ClO4], followed by PPh3
gave the cationic species [Pd(PPh3)(Ph2P(S)NC6H4P(S)Ph2-
S,N,S)][ClO4] 16 as a bright-orange crystalline solid in 89%
yield (Scheme 1). The 31P-{1H} spectrum (in CD2Cl2) of 16
(AMX spin system) (Fig. 5) clearly reveals three unique phos-
phorus environments. The lowest frequency resonance at δ (PA)
34.4 is assigned to the coordinated PPh3 group and displays two
Ph2P(E)NHC6H4P(E)Ph2 (E = O,
S or Se) are currently
underway.
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