Palladium(II) and Platinum(II) Complexes of the Heterodifunctional Ligand Ph2PNHP(O)Ph2

Article abstract of DOI:10.1021/ic951247d

The noncomplexed ligand Ph₂PNHP(O)Ph₂ (HL) has been prepared, for the first time, from Ph₂PNHPPh₂ (dppa) and H₂O₂ in moderate yield. On further treatment with H₂O₂ the

Full text of DOI:10.1021/ic951247d

Inorg. Chem. 1996, 35, 3675-3682
3675
Palladium(II) and Platinum(II) Complexes of the Heterodifunctional Ligand
Ph2PNHP(O)Ph2
Pravat Bhattacharyya, Alexandra M. Z. Slawin, Martin B. Smith, and J. Derek Woollins*
Department of Chemistry, Loughborough University, Loughborough, Leic. LE11 3TU, U.K.
ReceiVed September 26, 1995X
The noncomplexed ligand Ph2PNHP(O)Ph2 (HL) has been prepared, for the first time, from Ph2PNHPPh2 (dppa)
and H2O2 in moderate yield. On further treatment with H2O2 the phosphine oxide Ph2P(O)NHP(O)Ph2 (1) can
be formed. Reaction of [MCl2(COD)] (M ) Pt or Pd; COD ) cycloocta-1,5-diene) with 2 molar equiv of HL
affords [MCl2(HL)2] (4, 5) in which both ligands are monodentate P-bound. The analogous dibromo and diiodo
derivatives [MX2(HL)2] (6-9) were prepared from either [MX2(COD)] (M ) Pt or Pd; X ) Br or I) and HL or
treatment of [MCl2(HL)2] with an excess of NaI. Facile base deprotonation of the amine proton in 4 or 5 affords
a new class of metallacycles [M(L)2] [L- ) Ph2PNP(O)Ph2-] (10, 11) incorporating two five-membered M-P-
N-P-O rings. Compound 10 was independently made from [Pt(CH3)2(COD)] and 2 equiv of HL in toluene at
ambient temperature whereas the reaction of [Pt(CH3)Cl(COD)] with 2 equiv of HL affords solely trans-[Pt-
(CH3)Cl(HL)2] (13). Protonation of the neutral compound 10 with HCl in ethanol regenerates the ring-opened
cis complex 4. In contrast, addition of HBF4‚OEt2 to 10 (or 11) results in exclusive protonation at the nitrogen
atom of the chelating ligands to give cis-[M{Ph2PNHP(O)Ph2-P,O}2][BF4]2 (15, 16); both chelate rings remain
intact. The dicationic compounds 15, 16 can also be synthesized from 4, 5 in dichloromethane using Ag[BF4] as
a chloride abstractor. All new compounds described have been characterized by a combination of multinuclear
NMR spectroscopy, IR spectroscopy, and elemental analyses. The molecular structures of Ph2PNHP(O)Ph2, cis-
[PtBr2{Ph2PNHP(O)Ph2-P}2], cis-[Pt{Ph2PNP(O)Ph2-P,O}2], trans-[Pt(CH3)Cl{Ph2PNHP(O)Ph2-P}2] and cis-
[Pt{Ph2PNHP(O)Ph2-P,O}2][BF4]2 have been determined by single-crystal X-ray diffraction. Crystals of HL are
triclinic, space group P1h, with a ) 10.410(2) Å, b ) 12.083(2) Å, c ) 9.036(4) Å, R ) 103.05(2)°, â ) 99.09-
(2)°, γ ) 72.98(1)°, V ) 1054 Å3, and Z ) 2. The final R and Rw values were 0.061 and 0.047, respectively.
Crystals of 6 are triclinic, space group P1h, with a ) 13.113(4) Å, b ) 15.996(4) Å, c ) 13.011(4) Å, R )
102.65(3)°, â ) 117.39(2)°, γ ) 101.03(2)°, V ) 2225 Å3, and Z ) 2. The final R and Rw values were 0.039
and 0.031, respectively. Crystals of 10 are monoclinic, space group P21/a, with a ) 17.600(13) Å, b ) 13.498-
(10) Å, c ) 18.641(9) Å, â ) 105.13(1)°, V ) 4274 Å3, and Z ) 4. The final R and Rw values were 0.041 and
0.036, respectively. Crystals of 13 are triclinic, space group P1h, with a ) 14.686(2) Å, b ) 18.735(2) Å, c )
9.018(3) Å, R ) 91.71(2)°, â ) 102.27(2)°, γ ) 68.54(1)°, V ) 2253 Å3, and Z ) 2. The final R and Rw values
were 0.041 and 0.044, respectively. Crystals of 15 are orthorhombic, space group P21212, with a ) 14.100(2) Å,
b ) 19.002(1) Å, c ) 9.145(2) Å, V ) 2450 Å3, and Z ) 2. The final R and Rw values were 0.052 and 0.057,
respectively. The P-bound monodentate complexes contain ligands with similar bond lengths to the neutral
compound, while deprotonation/chelation results in lengthening of the P-O and shortening of the P-N bond
length as a result of electronic delocalization.
Introduction
chemistry of tetraorganoimidodiphosphinate ligands, [R2P(E)-
NP(E)R2]- (E ) O, S, Se; R ) alkyl, aryl, aryloxy), is
The transition metal chemistry of bis(diphenylphosphino)-
amine, NH(PPh2)2 (dppa), which is isoelectronic with bis-
(diphenylphosphino)methane, CH2(PPh2)2 (dppm), has received
widespread attention.1 In contrast, there are limited examples
of metal complexes2-4 of the neutral bis(chalcogenide) R2P-
(E)NHP(E)R2 (E ) O, S; R ) Me or Ph) whereas the metal
considerably better understood.4-22 Anionic ligands of this type
have found important uses as metal extractants23 but are also
(10) Silvestru, C.; Haiduc, I.; Cea-Olivares, R.; Zimbron, A. Polyhedron
1994, 13, 3159.
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D. J.; Woollins, J. D. J. Chem. Soc., Dalton Trans. 1995, 1607.
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Soc., Chem. Commun. 1994, 421.
X Abstract published in AdVance ACS Abstracts, May 1, 1996.
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S0020-1669(95)01247-X CCC: $12.00 © 1996 American Chemical Society

3676 Inorganic Chemistry, Vol. 35, No. 12, 1996
Bhattacharyya et al.
widely conceived as inorganic analogues of the more familar
â-diketonate ligands, most notably acetylacetonate (acac).
Only recently have the monochalcogenides Ph2PNHP(E)Ph2
(E ) S, Se) been described24 although Cavell has reported25
the related ligands Ph2PN(Ph)P(E)Ph2 (E ) S, Se). To further
develop our understanding of these ligand systems, we sought
to prepare the ligand Ph2PNHP(O)Ph2 (hereafter abbreviated
HL) containing both a “soft” and a “hard” donor atom. Some
studies with the isoelectronic ligands Ph2PCH2P(O)Ph226-36 and
Ph2PCH2P(S)Ph237,38 have also been reported. We envisage five
different possible modes of coordination of metal ions toward
either neutral HL or anionic L- as shown in Chart 1. Uni-
dentate P-bonded coordination (type I) should be favored by
low valent transition metals (“soft” metal atom) while O-bonded
coordination (type II) should favor early transition metal ions
(“hard” metal atom). The ligand may adopt a P,O-chelating
mode in which the ligand is either neutral (type III) or anionic
(type IV), in both cases resulting in five membered metallacycle
formation. Alternatively bridging modes, types V and VI, are
possible with formation of homobimetallic and heterobimetallic
compounds. We have recently prepared a dimeric palladium-
(II) complex with two bridging anionic [Ph2PNP(O)Ph2-P,O]-
ligands (type V).39
Chart 1
Rossi and co-workers40 have reported rhenium complexes of
the neutral ligand HL and deprotonated L- (types III and IV
respectively). The bound ligands in both cases were prepared
from the rhenium(V)-oxo complex [AsPh4][ReOCl4] and NH-
(PPh2)2. More recently a Co(II) complex with both a chelating
dppa and a monodentate P-bound [Ph2PNP(O)Ph2]- ligand has
been reported from the nonoxidized ligand dppa with partial
oxidation of the initially formed monodentate dppa ligand and
then deprotonation.41 Here we describe a rational route to the
monochalcogenide Ph2PNHP(O)Ph2 and also the coordination
chemistry of this ligand toward palladium(II) and platinum(II).
The structures of the free ligand HL and of the complexes cis-
[PtBr2{Ph2PNHP(O)Ph2-P}2], cis-[Pt{Ph2PNP(O)Ph2-P,O}2],
trans-[Pt(CH3)Cl{Ph2PNHP(O)Ph2-P}2], and cis-[Pt{Ph2PNHP-
(O)Ph2-P,O}2][BF4]2 have been determined by single-crystal
X-ray diffraction.
(21) Laguna, A.; Laguna, M.; Rojo, A.; Nieves Fraile, M. J. Organomet.
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Acta 1980, 40, 199.
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Experimental Section
Materials. The ligand Ph2PNHPPh2 (dppa) was prepared according
to a literature method42a as were the metal complexes [MX2(COD)]
(M ) Pt, Pd; X ) Cl, Br, I, CH3),43-45 [PtCl2(SEt2)2],46 [PtCl2-
(PhCN)2],47 and [Pt(CH3)Cl(COD)].48 tBuOK (95% purity), NEt3, Ag-
[BF4], and HBF4‚OEt2 (85%) were purchased from Aldrich Chemical
Co. and used without further purification. Tetrahydrofuran, diethyl
ether, toluene, and dichloromethane were dried and deaerated by
standard methods prior to use. Potassium tetrachloroplatinate and
sodium tetrachloropalladate were provided on loan by Johnson-Mathey
Inc.
Instrumentation. Infrared spectra were recorded on KBr pellets
in the range 4000-220 cm-1 on a Perkin-Elmer System 2000 FT-IR
spectrometer. 1H NMR spectra (250 MHz) were recorded on a Bruker
AC250 FT NMR spectrometer with δ referenced to external TMS. The
31P{1H} NMR spectra (36.2 or 101.3 MHz) were recorded either on a
Jeol FX90Q or a Bruker AC250 FT NMR spectrometer with δ
referenced to external phosphoric acid. 195Pt{1H} NMR spectra (53.7
MHz) were recorded on a Bruker AC250 FT NMR spectrometer with
(24) Bhattacharyya, P.; Slawin, A. M. Z.; Williams, D. J.; Woollins, J. D.
J. Chem. Soc., Dalton Trans. 1995, 3189.
(25) Balakrishna, M. S.; Klein, R.; Uhlenbrock, S.; Pinkerton, A. A.; Cavell,
R. G. Inorg. Chem. 1993, 32, 5676.
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467, 85.
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Casellato, U.; Graziani, R. Inorg. Chim. Acta 1993, 204, 63.
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Thornton-Pett, M. J. Chem. Soc., Dalton Trans. 1991, 1519.
(30) Bondarenko, N. A.; Rudomino, M. V.; Tsvetkov, E. N. Synthesis 1991,
125.
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Inorg. Chim. Acta 1990, 178, 101.
(32) Darensbourg, D. J.; Zalewski, D. J.; Plepys, C.; Campana, C. Inorg.
Chem. 1987, 26, 3727.
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Chem. Commun. 1987, 1891.
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325, 285.
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B. Inorg. Chem. 1985, 24, 900.
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Chem. Soc., Chem. Commun. 1982, 198.
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Chem. Soc., Chem. Commun. 1995, 197.
(38) Wong, T. Y. H.; Barnabas, A. F.; Sallin, D.; James, B. R. Inorg. Chem.
1995, 34, 2278. Ph2PCH2P(S)Ph2 is an end product obtained from the
homogeneously catalyzed conversion of H2S to H2.
(39) Slawin, A. M. Z.; Smith, M. B.; Woollins, J. D. Polyhedron 1996,
15, 1579.
(42) (a) Wang, F. T.; Najdzionek, J.; Leneker, K. L.; Wasserman, H.;
Braitsch, D. M. Synth. React. Inorg. Met. Org. Chem. 1978, 8, 119.
For alternative synthetic routes to Ph2P(O)NHP(O)Ph2 see: (b) Fluck,
E.; Goldmann, F. L. Chem. Ber. 1963, 96, 3091. (c) Schmidpeter, A.;
Groeger, H. Chem. Ber. 1967, 100, 3979. (d) Williams, D. J. Inorg.
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60, 882.
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V. J. Chem. Soc., Dalton Trans. 1994, 339.
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Pd and Pt Complexes of Ph2PNHP(O)Ph2
Inorganic Chemistry, Vol. 35, No. 12, 1996 3677
δ referenced to external H2PtCl6 (in D2O/HCl). Elemental analyses
(Perkin-Elmer 2400 CHN Elemental Analyzer) were performed by the
Loughborough University Service within the Department of Chemistry.
Preparation of Ph2PNHP(O)Ph2 (HL). To a THF (50 cm3) solution
of Ph2PNHPPh2 (2.58 g, 6.69 mmol) at 0 °C was added dropwise
aqueous H2O2 (30% w/w, ca. 0.70 cm3) with vigorous stirring. Stirring
was continued for 10 min and the resulting solution left at ca. -20 °C
for 18 h. The white solid Ph2P(O)NHP(O)Ph2 was filtered off and the
volume of the THF filtrate reduced to 5-10 cm3. Addition of diethyl
ether (30 cm3) affords a white solid, HL, which was collected by suction
filtration and dried in vacuo. Crude yield: 1.32 g, 49%. Anal. Calcd
(found) for C24H21NOP2: C, 71.80 (71.20); H, 5.30 (5.10); N, 3.50
The solid was filtered, washed with MeOH, and dried. Yield: 0.109
g, 92%. Anal. Calcd (found) for C48H42N2O2P4PdI2: C, 49.55 (49.35);
H, 3.65 (3.20); N, 2.40 (3.25). Selected IR data (KBr): 3149 ν(NsH),
1221 ν(PdO) cm-1
.
The corresponding platinum(II) compound [PtI2{Ph2PNHP(O)Ph2-
P}2] 8 was synthesized as an isomeric mixture of cis- and trans-isomers
from [PtI2(COD)] and 2 equiv of HL or alternatively from compound
4 and an excess of NaI. Yield: 0.101 g, 90%. Anal. Calcd (found)
for C48H42N2O2P4PtI2: C, 46.05 (46.60); H, 3.40 (2.95); N, 2.25 (2.25).
Selected IR data (KBr): 3288, 3205, 3152 ν(NsH), 1220 ν(PdO)
cm-1
.
Preparation of cis-[Pt{Ph2PNP(O)Ph2-P,O}2] (10). Method A.
To a suspension of cis-[PtCl2{Ph2PNHP(O)Ph2-P}2] (0.073 g, 0.068
mmol) in MeOH (1 cm3) was added tBuOK (0.016 g, 0.143 mmol) as
a solid in one portion. The resulting suspension was stirred for ca. 5
min and the solid collected by suction filtration, washed with distilled
water (1 cm3) and MeOH (1 cm3), and dried in vacuo. Yield: 0.056
g, 82%. Anal. Calcd (found) for C48H40N2O2P4Pt: C, 57.90 (57.35);
H, 4.05 (3.85); N, 2.80 (2.85).
Method B. To [Pt(CH3)2(COD)] (0.046 g, 0.138 mmol) and Ph2-
PNHP(O)Ph2 (0.110 g, 0.274 mmol) was added toluene (3 cm3). After
28 h of stirring, the pale yellow solution was filtered and diethyl ether
(5 cm3) added to yield a white solid. The solid was collected by suction
filtration and dried in vacuo. Yield: 0.071 g, 52%.
Preparation of cis-[Pd{Ph2PNP(O)Ph2-P,O}2] (11). To a yellow
suspension of [PdCl2{Ph2PNHP(O)Ph2-P}2] (0.088 g, 0.090 mmol) in
MeOH (1 cm3) was added tBuOK (0.021 g, 0.187 mmol) as a solid in
one portion. The resulting deep yellow suspension was stirred for ca.
5 min and the solid collected by suction filtration, washed with distilled
water (1 cm3) and MeOH (1 cm3), and dried in vacuo. Yield: 0.059
g, 73%. The compound 11 could be recrystallized from CH2Cl2/Et2O.
Anal. Calcd (found) for C48H40N2O2P4Pd: C, 63.55 (63.25); H, 4.45
(4.25); N, 3.10 (3.05).
Preparation of trans-[Pt(CH3)Cl{Ph2PNHP(O)Ph2-P}2] (13). To
[Pt(CH3)Cl(COD)] (0.050 g, 0.141 mmol) and Ph2PNHP(O)Ph2 (0.120
g, 0.299 mmol) was added CH2Cl2 (3 cm3) and the solution stirred for
20 min. After filtering, addition of diethyl ether (30 cm3) afforded a
white solid which was collected by suction filtration and dried in vacuo.
Yield: 0.120 g, 81%. Anal. Calcd (found) for C49H45N2O2P4PtCl: C,
56.15 (55.55); H, 4.35 (4.05); N, 2.65 (3.00). Selected IR data (KBr):
3198, 3135 ν(NsH), 1232, 1222 ν(PdO), 298 ν(PtsCl) cm-1. Slow
diffusion of diethyl ether into a CH2Cl2 solution gave crystals of 13
suitable for X-ray crystallography.
(3.65). Selected IR data (KBr): 3049 ν(NsH), 1183 ν(PdO) cm-1
.
The purity of the product was routinely shown, by 31P{1H} NMR
spectroscopy, to be 90-95%, and this crude material was used without
further purification. The minor contaminant identified was Ph2P(O)-
NHP(O)Ph2. Slow diffusion of diethyl ether into a THF/H2O solution
of HL gave crystals suitable for X-ray crystallography.
Oxidation of Ph2PNHP(O)Ph2 to Ph2P(O)NHP(O)Ph2 (1). A THF
(ca. 0.3 cm3) solution of Ph2PNHP(O)Ph2 (0.020 g, 0.050 mmol) was
treated with aqueous H2O2 (30% w/w, 2 drops, ca. 0.020 g) and the
solution examined by 31P{1H} NMR spectroscopy. Quantitative
conversion to Ph2P(O)NHP(O)Ph2 (1) was observed as shown by a
single 31P resonance at 20.7 ppm. Compound 1 was collected by suction
filtration. Yield: 0.021 g, quantitative.
Preparation of cis-[PtCl2{Ph2PNHP(O)Ph2-P}2] (4). Method A.
[PtCl2(COD)] (0.096 g, 0.257 mmol) and Ph2PNHP(O)Ph2 (0.205 g,
0.548 mmol) were dissolved in CH2Cl2 (10 cm3) and stirred for 75
min. The volume of the solution was concentrated under reduced
pressure to ca. 1-2 cm3 whereupon a white solid 4 deposited. Further
precipitation was induced by additon of diethyl ether (30 cm3) and the
solid collected by filtration. Yield: 0.257 g, 94%. Anal. Calcd (found)
for C48H42N2O2P4PtCl2: C, 53.95 (53.25); H, 3.95 (3.85); N, 2.60 (2.85).
Selected IR data (KBr): 3293, 3172 ν(NsH), 1217 ν(PdO), 315, 283
ν(PtsCl) cm-1
.
Alternatively complex 4 can be prepared in excellent yield (>95%)
from either [PtCl2(SEt2)2] or [PtCl2(PhCN)2] under similar conditions.
Method B. A white suspension of cis-[Pt{Ph2PNP(O)Ph2-P,O}2]
(0.032 g, 0.032 mmol) in EtOH (2 cm3) was treated with concentrated
HCl (2 drops, ca. 0.092 g) and the mixture stirred for 10 min. The
solid was filtered and dried. Yield: 0.033 g, 97%. 31P{1H} NMR
spectroscopy showed the exclusive formation of cis-[PtCl2{Ph2PNHP-
(O)Ph2-P}2] 4.
Preparation of trans-[Pt(CH3)I{Ph2PNHP(O)Ph2-P}2] (14). To
a solution of trans-[Pt(CH3)Cl{Ph2PNHP(O)Ph2-P}2] (0.057 g, 0.054
mmol) in MeOH (10 cm3) was added NaI (0.079 g, 0.527 mmol) in
MeOH (1 cm3). The colorless solution was stirred for ca. 1 h and
evaporated to dryness under reduced pressure. To the residue was
added distilled water (5 cm3). The solid product was collected by
suction filtration and dried. Yield: 0.053 g, 85%. Anal. Calcd (found)
for C49H45N2O2P4PtI: C, 51.65 (51.25); H, 4.00 (3.95); N, 2.45 (2.45).
Preparation of cis- and trans-[PdCl2{Ph2PNHP(O)Ph2-P}2] (5a,
5b). To a CH2Cl2 (20 cm3) solution of [PdCl2(COD)] (0.149 g, 0.522
mmol) was added Ph2PNHP(O)Ph2 (0.430 g, 1.07 mmol) as a solid in
one portion to give a yellow solution. After ca. 10-15 min, a yellow
precipitate formed and the mixture was stirred for a further 90 min.
The solid was collected by suction filtration and dried. Yield: 0.441
g, 86%. Anal. Calcd (found) for C48H42N2O2P4PdCl2: C, 58.80
(57.50); H, 4.35 (4.10); N, 2.85 (2.85). Selected IR data (KBr): 3176
Selected IR data (KBr): 3166 ν(NsH), 1220 ν(PdO) cm-1
.
ν(N-H), 1219 ν(PdO), 332, 293 ν(PdsCl) cm-1
.
Preparation of cis-[PtBr2{Ph2PNHP(O)Ph2-P}2] (6). To a CH2-
Cl2 (10 cm3) solution of [PtBr2(COD)] (0.079 g, 0.171 mmol) was added
Ph2PNHP(O)Ph2 (0.144 g, 0.359 mmol) as a solid in one portion. The
pale yellow solution was stirred for ca. 1 h and filtered and the volume
concentrated in vacuo to ca. 1-2 cm3. Addition of diethyl ether (10
cm3) gave the solid product. Yield: 0.170 g, 86%. Anal. Calcd
(found) for C48H42N2O2P4PtBr2: C, 49.80 (50.10); H, 3.65 (3.70); N,
2.40 (2.80). Selected IR data (KBr): 3293, 3166 ν(NsH), 1217 ν-
(PdO) cm-1. Slow diffusion of diethyl ether into a CH2Cl2 solution
of [PtBr2(COD)] and 2 equiv of HL gave crystals of 6 suitable for
X-ray crystallography.
Preparation of cis-[Pt{Ph2PNHP(O)Ph2-P,O}2][BF4]2 (15). Method
A. To a CDCl3 (0.6 cm3) solution of cis-[Pt{Ph2PNP(O)Ph2-P,O}2]
(0.054 g, 0.054 mmol) was added HBF4‚OEt2 (6 drops). The colorless
solution was stirred for 10 min. Addition of diethyl ether (2 cm3)
afforded a white solid, which was collected by suction filtration and
dried, in quantitative yield. Anal. Calcd (found) for C48H42N2O2P4-
PtB2F8: C, 49.20 (48.85); H, 3.60 (3.10); N, 2.40 (2.40). Selected IR
data (KBr): 3168 ν(NsH) cm-1
.
Method B. To a solution of [PtCl2{Ph2PNHP(O)Ph2-P}2] (0.103
g, 0.096 mmol) in dichloromethane (50 cm3) was added solid Ag[BF4]
(0.040 g, 0.206 mmol). After stirring for ca. 4h, the AgCl was filtered
through a small pad of Celite and the filtrate reduced in volume under
reduced pressure to ca. 1-2 cm3. Addition of diethyl ether (15 cm3)
gave a white solid, 15. Yield: 0.085 g, 75%. Slow diffusion of diethyl
ether into a MeOH solution gave crystals of 15 suitable for X-ray
crystallography.
The corresponding palladium(II) compound [PdBr2{Ph2PNHP(O)-
Ph2-P}2], 7, was prepared as the trans-isomer. Yield: 0.067 g, 91%.
Anal. Calcd (found) for C48H42N2O2P4PdBr2: C, 53.95 (53.30); H,
3.95 (3.90); N, 2.60 (2.70). Selected IR data (KBr): 3177 ν(NsH),
1220 ν(PdO) cm-1
.
Preparation of trans-[PdI2{Ph2PNHP(O)Ph2-P}2] (9). [PdCl2{Ph2-
PNHP(O)Ph2-P}2] (0.100 g, 0.102 mmol) and NaI (0.160 g, 1.067
mmol) in acetone (15 cm3) were stirred for ca. 3 h. The solvent was
evaporated to dryness in vacuo and distilled water (25 cm3) added.
The complex cis-[Pd{Ph2PNHP(O)Ph2-P,O}2][BF4]2 16 was syn-
thesized either from cis-[Pd{Ph2PNP(O)Ph2-P,O}2] and HBF4‚Et2O
(Yield: 0.063 g, 98%) or chloride abstraction from complex 5 using
Ag[BF4] in dichloromethane (Yield: 0.047 g, 42%). Anal. Calcd

3678 Inorganic Chemistry, Vol. 35, No. 12, 1996
Bhattacharyya et al.
Table 1. Crystallographic Data for Ph2PNHP(O)Ph2 (HL) cis-[PtBr2{Ph2PNHP(O)Ph2-P}2] (6), cis-[Pt{Ph2PNP(O)Ph2-P,O}2] (10),
trans-[Pt(CH3)Cl{Ph2PNHP(O)Ph2-P}2] (13) and cis-[Pt{Ph2PNHP(O)Ph2-P,O}2][BF4]2 (15)
HL
6
10
13
15
chem formula
fw
cryst syst
space group
a (Å)
b (Å)
c (Å)
C24H21NOP2
401.38
triclinic
P1h (No. 2)
10.410(2)
12.083(2)
9.036(4)
103.05(2)
99.09(2)
72.98(1)
1054
C48H42N2O2P4PtBr2
1157.67
triclinic
P1h (No. 2)
13.113(4)
15.996(4)
13.011(4)
102.65(3)
117.39(2)
101.03(2)
2225
C48H40N2O2P4Pt
995.84
monoclinic
P21/a (No. 14)
17.600(13)
13.498(10)
18.641(9)
C49H45N2O2P4PtCl
1048.34
triclinic
P1h (No. 2)
14.686(2)
18.735(2)
9.018(3)
91.71(2)
102.27(2)
68.54(1)
2253
C48H42N2O2P4PtB2F8
1171.46
orthorhombic
P21212 (No. 18)
14.100(2)
19.002(1)
9.145(2)
R (deg)
â (deg)
γ (deg)
V (Å3)
Z
105.13(1)
4274
4
1.55
76.5
0.041
0.036
2450
2
1.59
70.0
0.052
0.057
2
1.27
19.8
0.061
2
1.73
98.0
0.039
2
1.55
78.2
0.041
F
calcd (g cm-3
)
µ (cm-1
)
Ra
Rw
b
0.047
0.031
0.044
2
a R ) ∑||Fo| - |Fc||/∑|Fo|. b Rw ) [∑w(|Fo| - |Fc|)2/∑wFo ]1/2
.
(found) for C48H42N2O2P4PdB2F8: C, 53.25 (53.10); H, 3.90 (3.65);
N, 2.60 (2.60). Selected IR data (KBr): 3165 ν(NsH) cm-1
Scheme 1a
.
X-ray Crystallographic Analyses of Ph2PNHP(O)Ph2 (HL), cis-
[PtBr2{Ph2PNHP(O)Ph2-P}2] (6), cis-[Pt{Ph2PNP(O)Ph2-P,O}2] (10),
trans-[Pt(CH3)Cl{Ph2PNHP(O)Ph2-P}2] (13), and cis-[Pt{Ph2PNHP-
(O)Ph2-P,O}2][BF4]2 (15). Details of crystal data collection and
refinements are given in Table 1. Data were collected on a Rigaku
AFC7S diffractometer [Cu KR radiation (λ ) 1.541 78 Å), ω-scans]
at 20.0 °C. Unit cell parameters were determined by centering 20
reflections and in every case three standard reflections were monitored
every 150 reflections. The data sets were corrected for absorption
(DIFABS).49a Structure solution49b (heavy atom method) and refinement
employed the TEXSAN software package.49c The non-hydrogen atoms
were refined anisotropically except for 6 where the phenyl carbon atoms
were refined isotropically. In 15 the phenyl rings and the [BF4]-
counterion were refined as rigid bodies. All N-H protons were located
from ∆F maps. In 6 the N-H protons were idealized, in all other
cases the N-H protons were allowed to refine isotropically. All
remaining hydrogen atoms were idealized (C-H ) 0.95 Å). The
polarity of 15 was tested by a Flack parameter refinement which refined
to 0.08(3) indicating the correct absolute stereochemistry.
Results and Discussion
Reaction of dppa with 2 equiv of aqueous H2O2 has been
shown to proceed with formation of Ph2P(O)NHP(O)Ph2 (1).42a
We have found that controlled oxidation of Ph2PNHPPh2 with
aqueous H2O2 (30% w/w) in THF at 0 °C affords the
heterodifunctional ligand Ph2PNHP(O)Ph2 HL (Scheme 1).
Although we were unable to prevent the formation of 1, the
low solubility of this species in THF at 0 °C enabled removal
by simple filtration from the HL which remained in solution.
In addition, we also noted the presence of residual dppa which
was also readily separated from HL. The mixed P, O ligand
was isolated as a white air stable solid in moderate yield (49%)
and had a purity by 31P{1H} NMR spectroscopy which routinely
exceeded 90%. The ligand HL is soluble in toluene, chlorinated
solvents, acetone, THF, low molecular weight alcohols (e.g.
MeOH), and dmso. In THF/C6D6 solution, the 31P{1H} NMR
spectrum of HL showed two sharp doublets at 28.0 ppm and
21.4 ppm, assigned to the phosphorus(III) and phosphorus(V)
centers respectively, with a 2J(PAPX) coupling of 61.6 Hz (Table
2).
a Key: (i) H2O2, 0 °C, THF; (ii) CDCl3, H2O2; (iii) E, THF (E ) S
or Se).
In the X-ray structure of HL the molecule (Figure 1) has
typical bond lengths and angles with the most notable feature
being the almost perfect syn arrangement of the NsH proton
and the PdO oxygen atom. This arrangement is a consequence
of a hydrogen-bonded dimer pair formation [N‚‚‚O 2.83 Å,
H‚‚‚O 1.72 Å, N-H‚‚‚O 167(1)°]. In HL the P(2)‚‚‚O(1)
distance is 4.21 Å which suggested to us that all of the
coordination modes in Chart 1 could be possible.
(49) (a) DIFABS: Walker, N. G.; Stuart, D. Acta Crystallogr., Sect. A
1983, 39, 158. (b) DIRDIF 92-PATTY: Beurskens, P. T.; Admiraal,
G.; Beurskens, G.; Bosman, W. P.; Garcia-Granda, S.; Gould, R. O.;
Smits, J. M. M.; Smykalla, C. The DIRDIF program system. Technical
Report of the Crystallography Laboratory, University of Nijmegen,
The Netherlands, 1992. (c) TEXSAN: Crystal Structure Analysis
Package; Molecular Structure Corporation: The Woodlands, TX, 1985
and 1992.
Solutions of HL are relatively stable toward aerial oxidation.
However, treatment with aqueous H2O2 in THF results in rapid
oxidation and formation [shown by 31P{1H}] of bis(diphe-
nylphosphinoyl)amine, 1, which has previously been reported.42
Reaction with other chalcogenides affords the mixed phospho-
rus(V) ligands Ph2P(E)NHP(O)Ph2 [E ) S (2), Se (3)].50

Pd and Pt Complexes of Ph2PNHP(O)Ph2
Inorganic Chemistry, Vol. 35, No. 12, 1996 3679
1
Table 2. Selected 31P{1H}, 195Pt{1H}, and H NMR dataa
compound δ(PA)b 1J(PtPA) δ(PX)b J(PtPX)c
Nd
δ(Pt)e
dppa
HLf
1
43.1
28.0g
21.4
20.7
21.6
21.1
20.9
22.1
22.7
21.2
22.8
24.1
62.3
63.4
22.7
22.6
23.9
62.8
68.1
61.6h
4
35.7i
58.3j
46.7
3955
3933
114
104
22
-4351
-4592
5a
5b
6
36.0
24.8
24
22
29
21
23
37.6i
48.5k
36.8l
35.4
7
8a
8b
9
10
11
12
13
14
15
16
3821
2544
108
83
45.4k
31.9
3880
167
4.3m -4184
54.1
6.3m
58.7n,o
56.0p
55.6q
37.4r
56.3r
2050
3202
3154
3924
23
17.6
10.1
84
88
88
-4638
-4906
2.9m -4239s
6.3m
a 31P{1H} NMR spectra (36.2 MHz) measured in CDCl3 unless
otherwise stated. Chemical shifts (δ) in ppm ((0.1) to high frequency
of 85% H3PO4. Coupling constants (J) in Hz ((3). 195Pt{1H} NMR
spectra (53.7 MHz) measured in CDCl3 unless otherwise stated. 1H
NMR spectra (250 MHz) measured in CDCl3. Chemical shifts (δ) in
ppm ((0.01) to high frequency of SiMe4 and coupling constants (J) in
Hz ((0.1). b PA ) phosphorus(III) center, PX ) phosphorus(V) center.
3
c In the monodentate complexes this is J(PtPX), while in the chelate
2
3
complexes there are contributions from J(PtPX) and J(PtPX). d N )
| J(PAPX) + 4J(PAPX′)|. e Triplet of triplets. f In CDCl3 δ(PA) 27.8 ppm,
2
δ(PX) 25.2 ppm, 2J(PAPX) 59.0 Hz. Additional uncharacterized species
at δ(P) +18.8 ppm and δ(P) -0.3 ppm observed. g Spectrum measured
in THF/C6D6. h 2J(PAPX) value. i The cis-isomer exclusively. j Mixture
of cis and trans-isomers observed in a 1:3.7 ratio respectively. k The
trans-isomer exclusively. l Mixture of cis and trans-isomers observed
in a 1:1.2 ratio respectively. m Value taken from spectrum measured at
101.3 MHz. n In addition to other uncharacterized species. o Comparitive
data for the complex cis-[Pt(CH3)2{Ph2PNHPPh2-P}2]: δ(PA) 63.1 ppm,
1J(PtP) 2058 Hz, δ(PX) 30.6 ppm, N 11 Hz (measured in CDCl3).
Figure 2. 31P{1H} NMR spectrum (36.2 MHz) of cis-[PtCl2{Ph2PNHP-
(O)Ph2-P}2] (4).
of cis- (5a) and trans-[PdCl2{Ph2PNHP(O)Ph2-P}2] (5b).
p Selected H NMR data: δ(H) -0.13 ppm, J(PtH) 81.2 Hz, J(PH)
1
2
3
7.4 Hz (PtCH3 resonance). q Selected 1H NMR data: δ(H) -0.11 ppm,
2J(PtH) 77.0 Hz, J(PH) 7.7 Hz (PtCH3 resonance). r Spectrum mea-
3
sured in MeOH/C6D6. s Spectrum measured in CDCl3/MeOH.
The 31P{1H} NMR spectrum of 4 (Figure 2) shows two sets
of resonances corresponding to the coordinated phosphorus-
(III) center and the “dangling” phosphorus(V) moiety. A large
1J(PtPA) coupling constant of 3955 Hz is in good agreement
with a cis disposition of ligands (i.e. phosphorus trans to
chloride). In addition 195Pt satellites are also observed for the
uncoordinated phosphorus(V) group [3J(PtPX) 114 Hz]. Since
the chemical shift for the pendant PdO group is comparable to
that in HL we infer that in compound 4 (and 5) there is no
chelating interaction with the metal center, and hence a
dicationic species such as [Pt{Ph2PNHP(O)Ph2-P,O}2]Cl2 is not
formed under these experimental conditions (see below for
further discussion). Further support comes from the IR spectrum
(KBr pellet) which shows two distinct ν(Pt-Cl) stretches at
315 and 283 cm-1 consistent with a cis-PtCl2 geometry. In
contrast, we observe that the neutral palladium complex 5 is
present as a mixture of cis-5a and trans-5b isomers; the trans
isomer is the predominant species observed in CDCl3 solutions
(1:3.7 ratio as determined by 31P{1H} NMR).
Figure 1. Line drawing of the crystal structure of Ph2PNHP(O)Ph2
(HL) showing a hydrogen-bonded dimer pair. Selected bond lengths
(Å) and angles (deg): P(1)-O(1) 1.508(2), P(1)-N(1) 1.651(3), P(2)-
N(1) 1.707(3); O(1)-P(1)-N(1) 111.0(1), P(1)-N(1)-P(2) 125.6(2).
The 2:1 molar ratio reaction of HL with [MCl2(COD)] [M
) Pt, Pd] in dichloromethane at room temperature affords
exclusively cis-[PtCl2{Ph2PNHP(O)Ph2-P}2] (4) and a mixture
(50) Slawin, A. M. Z.; Smith, M. B.; Woollins, J. D. Unpublished work.

3680 Inorganic Chemistry, Vol. 35, No. 12, 1996
Bhattacharyya et al.
Scheme 2a
t
a Key: (i) BuOK, MeOH; (ii) 2 HL, toluene.
oxygen atoms. H(1n) is involved in an intramolecular H-bond
to Br(2) (2.34 Å) which results in H(1n) being almost perfectly
anti with respect to O(1). H(3n) is also very close to anti. From
the IR spectrum, the observation of two ν(N-H) absorptions
at 3293 and 3166 cm-1 is consistent with only one of the NH
groups being involved in an intramolecular hydrogen bond to
Br.
Figure 3. Crystal structure of cis-[PtBr2{Ph2PNHP(O)Ph2-P}2] (6).
Selected bond lengths (Å) and angles (deg): Pt(1)-Br(1) 2.472(2),
Pt(1)-Br(2) 2.480(2), Pt(1)-P(2) 2.241(5) Pt(1)-P(4) 2.248(4), P(1)-
O(1) 1.47(1), P(1)-N(1) 1.67(1), P(2)-N(1) 1.68(1), P(3)-O(3) 1.492-
(9), P(3)-N(3) 1.71(1), P(4)-N(3) 1.68(1); Br(1)-Pt(1)-Br(2) 86.34-
(7), Br(1)-Pt(1)-P(2) 173.6(1), Br(1)-Pt(1)-P(4) 85.8(1), Br(2)-
Pt(1)-P(2) 91.2(1), Br(2)-Pt(1)-P(4) 171.6(1), P(2)-Pt(1)-P(4)
97.0(2), O(1)-P(1)-N(1) 113.3(6), Pt(1)-P(2)-N(1) 111.3(4), O(3)-
P(3)-N(3) 115.5(6), Pt(1)-P(4)-N(3) 115.3(4), P(1)-N(1)-P(2)
132.6(7), P(3)-N(3)-P(4) 130.3(7).
Previous work has demonstrated that â-ketophosphine metal
complexes can be deprotonated to afford coordinated phosphino
enolate ligands.51-56 Using a suitable base (e.g. the metal
t
alkoxide BuOK) we find that the acidic proton of the bound
HL ligand in the complexes 4 and 5 are readily removed,
affording the bischelate complexes [M{Ph2PNP(O)Ph2-P,O}2]
[M ) Pt (10); M ) Pd (11)] (Scheme 2). An alternative route
to 10, albeit in lower yield (52% vs 82%), is the reaction of
[Pt(CH3)2(COD)] with 2 equiv of HL in toluene at ambient
temperature.
The reaction of [PtCl2(COD)] with 1 equiv of HL did not
lead to the formation of the neutral chelate complex [PtCl2{Ph2-
PNHP(O)Ph2-P,O}] (A) but instead gave a mixture of 4,
unreacted starting material, and free COD as revealed by a
combination of 1H and 31P{1H} NMR spectroscopy. In contrast,
Cavell and co-workers25 were able to prepare analogous
compounds to A using the related ligands Ph2PN(Ph)P(E)Ph2
(E ) S or Se).
The 31P{1H} NMR spectrum of the platinum complex 10
shows a large 1J(PtPA) coupling constant of 3880 Hz (of similar
magnitude to 4) and a small J(PtPX) coupling constant [con-
2
3
tributions from J(PtPX) and J(PtPX)] of 167 Hz. The large
shift of the δ(31P) for the PdO group upon chelation is probably
due to the chelate ring effect, a feature that has been well studied
with other phosphorus-based ligands forming five-membered
rings.57
In the X-ray structure of 10 (Figure 4) the square planar
platinum is cis coordinated by the two deprotonated [Ph2-
PNP(O)Ph2]- ligands [maximum deviation from the PtP2O2
mean plane 0.12 Å for O(1)]. The two PtP2NO five-membered
rings are slightly puckered [Pt(1)-O(1)-P(1)-N(1)-P(2) mean
plane, with maximum deviation of N(1) 0.23 Å below the plane,
and Pt(1)-O(3)-P(3)-N(3)-P(4) with maximum deviation of
N(3) 0.28 Å above the plane]. Within the rings the phosphorus
centers are slightly distorted from tetrahedral while the Pt-
O-P and P-N-P angles are all ca. 115°. The PdO bonds
are lengthened and the P-N bonds are shortened with respect
to the free ligand as a consequence of the delocalization
associated with deprotonation. The P-Pt-P angle [103.2(1)°]
Treatment of [MX2(COD)] (M ) Pt, Pd; X ) Br, I) with 2
equiv of HL (or metathesis of 4 or 5 with NaI) gave the
following compounds: cis-[PtBr2{Ph2PNHP(O)Ph2-P}2] (6),
trans-[PdBr2{Ph2PNHP(O)Ph2-P}2] (7), cis- and trans-[PtI2{Ph2-
PNHP(O)Ph2-P}2] (8a, 8b), and trans-[PdI2{Ph2PNHP(O)Ph2-
P}2] (9). Characterizing data for 4-9 are given in Table 2 and
the Experimental Section. Suitable crystals of 6 were grown
by layering a dichloromethane solution of [PtBr2(COD)] / HL
with diethyl ether. From X-ray studies, the molecule (Figure
3) adopts a square planar geometry at platinum with cis
bromides and phosphorus coordination of the neutral ligands.
There is a slight twist about the coordination plane with P(2)
and P(4) lying -0.16 and +0.10 Å with respect to the PtBr2P2
mean plane. Within the ligand, the P-N bond lengths are similar
to those in the free ligand while the PdO bond length (which
is no longer involved in a strong hydrogen bond) is slightly
shorter in 6 than in HL [1.47(1) and 1.492(9) Å; cf. 1.508(2)
Å]. Interestingly the NsH protons in the ligand (which were
located by ∆F maps) are no longer syn with respect to the PdO
(51) Braunstein, P.; Chauvin, Y.; Na¨hring, J.; Dusausoy, Y.; Bayeul, D.;
Tiripicchio, A.; Ugozzoli, F. J. Chem. Soc., Dalton Trans. 1995, 851.
(52) Braunstein, P.; Chauvin, Y.; Na¨hring, J.; DeCain, A.; Fischer, J. J.
Chem. Soc. Dalton Trans. 1995, 863.
(53) Braunstein, P.; Kelly, D. G.; Tiripicchio, A.; Ugozzoli, F. Inorg. Chem.
1993, 32, 4845.
(54) Matt, D.; Huhn, M.; Fischer, J.; De Cian, A.; Kla¨ui, W.; Tkatchenko,
I.; Bonnet, M. C. J. Chem. Soc., Dalton Trans. 1993, 1173.
(55) Braunstein, P.; Matt, D.; Nobel, D.; Balegroune, F.; Bouaoud, S.-E.;
Grandjean, D. J. Chem. Soc., Dalton Trans. 1988, 353.
(56) Bouaoud, S.-E.; Braunstein, P.; Grandjean, D.; Matt, D.; Nobel, D.
Inorg. Chem. 1986, 25, 3765.
(57) Garrou, P. E. Chem. ReV. 1981, 81, 229.

Pd and Pt Complexes of Ph2PNHP(O)Ph2
Inorganic Chemistry, Vol. 35, No. 12, 1996 3681
Scheme 3. Proposed Mechanism for Formation of 10.
Scheme 4a
Figure 4. Crystal structure of cis-[Pt{Ph2PNP(O)Ph2-P,O}2] (10).
Selected bond lengths (Å) and angles (deg): Pt(1)-P(2) 2.235(3), Pt-
(1)-P(4) 2.235(3), Pt(1)-O(1) 2.110(6), Pt(1)-O(3) 2.103(6), P(1)-
O(1) 1.535(7), P(1)-N(1) 1.604(8), P(2)-N(1) 1.618(9), P(3)-O(3)
1.527(7), P(3)-N(3) 1.577(8), P(4)-N(3) 1.641(8); P(2)-Pt(1)-P(4)
103.2(1), P(2)-Pt(1)-O(1) 86.1(2), P(2)-Pt(1)-O(3) 170.7(2), P(4)-
Pt(1)-O(1) 169.9(2), P(4)-Pt(1)-O(3) 86.0(2), O(1)-Pt(1)-O(3)
84.9(3), O(1)-P(1)-N(1) 114.7(4), Pt(1)-P(2)-N(1) 106.9(3), O(3)-
P(3)-N(3) 114.4(4), Pt(1)-P(4)-N(3) 105.4(3), Pt(1)-O(1)-P(1)
114.3(4), Pt(1)-O(3)-P(3) 114.7(4), P(1)-N(1)-P(2) 115.3(5), P(3)-
N(3)-P(4) 115.4(5).
is enlarged, presumably as a consequence of the steric bulk of
the ligand; there are weak face-face phenyl-phenyl interactions
between the phenyl rings on the coordinated phosphorus atoms.
We have recently reported that the monochalcogenide ligands
Ph2PNHP(E)Ph2 (E ) S, Se) can either coordinate as a neutral
chelating ligand or undergo deprotonation in the absence of
base.24 This contrasts with our findings presented here.
A possible mechanism to account for the formation of the
platinum bischelate complex 10 from [Pt(CH3)2(COD)] is shown
in Scheme 3. We tentatively suggest that the complex cis-[Pt-
(CH3)2{PPh2NHP(O)Ph2-P}2] (12) is initially formed which can
exist in a resonance stabilized form (tautomeric) suitably
disposed for intramolecular protonolysis with concomittant
evolution of CH4. Although no attempts to test for CH4
formation or isolate any intermediates in this reaction were
pursued, we have observed the formation of 12 in solution (31P-
{1H} NMR evidence).
In view of the above observations we were intrigued as to
the reactivity of the organoplatinum compound [Pt(CH3)Cl(COD)]
with HL. Instead of the anticipated [PtCl{Ph2PNP(O)Ph2-
P,O}{Ph2PNHP(O)Ph2-P}] complex we obtained trans-
[Pt(CH3)Cl{Ph2PNHP(O)Ph2-P}2] (13) which could be met-
athesised to the (methyl)iodo compound trans-[Pt(CH3)-
I{Ph2PNHP(O)Ph2-P}2] (14) (Scheme 4). The characterizing
data are given in Table 2. In the X-ray structure of 13 (Figure
5) the molecule adopts a trans square planar conformation with
the P-N-P backbone of the ligands lying approximately in
the coordination plane [maximum deviation from the PtP2CCl
mean plane of C(49) 0.20 Å below the plane]. Interestingly,
the potential for N-H‚‚‚Cl hydrogen bonding appears to favor
the P-NH-P(O) ligands pointing in the same direction as each
other [i.e. the molecule has an approximate mirror plane running
through the C(49)-Pt-Cl vector]. The H‚‚‚Cl distances are
a Key: (i) 2 HL, CH2Cl2; (ii) NaI, MeOH.
2.3 and 2.4 Å. The Pt-(P-N-P)2 unit thus lies close to
coplanar with the coordination plane [maximum deviations from
the PtClCP4N2 plane are 0.3 Å above the plane for both nitrogen
atoms with both oxygen atoms being 0.7 Å from this plane;
the noncoordinated phosphorus atoms are 0.04 Å from this
plane]. In common with 6 the N-H protons are anti with
respect to the respective oxygen atoms. Two N-H stretches
at 3198 and 3135 cm-1 are also observed in the IR spectrum of
13.
In order to ascertain the stability of the chelate rings we tested
the reactivity of 10 and 11 toward protonation (Scheme 5). The
M-P-N-P-O chelate rings are readily cleaved to regenerate
4 by addition of concentrated HCl to an ethanolic suspension
of 10 at ambient temperature; the retention of the cis geometry
was confirmed by 31P{1H} NMR. When compound 10 was
treated with the noncoordinating acid HBF4‚OEt2, the cationic
complex cis-[Pt{Ph2PNHP(O)Ph2}2][BF4]2 (15) could be iso-
lated in excellent yield. Compound 15 can also be made by
chloride abstraction from compound 4 in dichloromethane. The
analogous palladium(II) complex (16) could be prepared in a
similar way. The 31P{1H} NMR spectrum of 15 reveals that
1
upon protonation the J(PtPA) coupling constant is marginally

3682 Inorganic Chemistry, Vol. 35, No. 12, 1996
Bhattacharyya et al.
Figure 6. Crystal structure of the dication in cis-[Pt{Ph2PNHP(O)-
Ph2-P,O}2][BF4]2 (15). Selected bond lengths (Å) and angles (deg):
Pt(1)-P(2) 2.213(4), Pt(1)-P(2) 2.213(4), Pt(1)-O(1) 2.108(10), Pt-
(1)-O(1) 2.108(10), P(1)-O(1) 1.502(9), P(1)-N(1) 1.640(12), P(2)-
N(1) 1.700(11); P(2)-Pt(1)-P(2*) 98.5(2), P(2)-Pt(1)-O(1) 87.3(3),
P(2)-Pt(1)-O(1*) 174.2(3), O(1)-Pt(1)-O(1*) 86.9(5), O(1)-P(1)-
N(1) 107.2(6), Pt(1)-P(2)-N(1) 101.4(4), Pt(1)-O(1)-P(1) 118.6-
(6), P(1)-N(1)-P(2) 118.1(7).
Figure 5. Crystal structure of trans-[Pt(CH3)Cl{Ph2PNHP(O)Ph2-P}2]
(13). Selected bond lengths (Å) and angles (deg): Pt(1)-Cl(1) 2.423-
(2), Pt(1)-P(2) 2.298(2), Pt(1)-P(4) 2.292(2), Pt(1)-C(49) 2.070(6),
P(1)-O(1) 1.465(5), P(1)-N(1) 1.667(5), P(2)-N(1) 1.679(4), P(3)-
O(3) 1.478(4), P(3)-N(3) 1.669(5), P(4)-N(3) 1.695(5); Cl(1)-Pt-
(1)-P(2) 91.71(5), Cl(1)-Pt(1)-P(4) 91.95(5), Cl(1)-Pt(1)-C(49)
174.8(2), P(2)-Pt(1)-P(4) 173.39(5), P(2)-Pt(1)-C(49) 88.4(2),
P(4)-Pt(1)-C(49) 88.5(2), O(1)-P(1)-N(1) 113.9(3), Pt(1)-P(2)-
N(1) 110.7(2), O(3)-P(3)-N(3) 114.3(2), Pt(1)-P(4)-N(3) 108.4-
(2), P(1)-N(1)-P(2) 131.6(3), P(3)-N(3)-P(4) 131.3(3).
comparison with the deprotonated complex 10, reveals that the
P-N bond lengths [1.640(12) Å, P(1)-N(1), and 1.700(11) Å,
P(2)-N(1)] are longer and the PdO bond distance (1.502 Å)
is shorter in 15, i.e. there is less delocalization in the complex
containing the neutral ligand. The PtP2NO ring in 15 is slightly
puckered in a manner similar to those in 10 [N(1) lies 0.37 Å
below the PtP2NO plane]. The BF4- counterions are involved
in bifircated H-bonds to the N-H proton [H(25)-F(1) 2.21 Å,
H(25)-F(2) 1.94 Å, N‚‚‚B 3.73 Å]. Deprotonation of the amine
proton in 15 with NEt3 regenerates the bis chelate 10 while
treatment of 15 with an excess of LiCl in MeOH regenerates
compound 4.
Scheme 5a
Concluding Remarks
We have shown that the mixed P(III)-N-P(V) ligand Ph2-
PNHP(O)Ph2 can be prepared by oxidation of Ph2PNHPPh2 and
that this ligand has the potential to ligate in a variety of bonding
modes. Apart from behaving as a classical unidentate P-bonded
ligand, participation of the functional PdO group can be induced
by facile deprotonation of the amine proton on the ligand to
generate bis(chelate)metal complexes. Acid treatment either
regenerates the starting dichloro complex (with HCl) or proto-
nates the nitrogen of the M-P-N-P-O ring (with HBF4‚OEt2).
The compounds described represent to our knowledge relatively
rare examples of Pd and Pt coordinated by neutral phosphine
oxides or by anionic oxygen donor centers. Further studies are
currently in progress into the synthesis of heterobimetallic
complexes incorporating both early and late transition metal
moieties.
a Key: (i) Ag[BF4], CH2Cl2; (ii) LiCl; (iii) HBF4‚OEt2; (iv) NEt3;
t
(v) BuOK, MeOH; (vi) HCl, EtOH. M ) Pt, Pd.
increased to 3924 Hz and the J(PtPX) coupling constant is
reduced to 88 Hz. Interestingly, Shaw and co-workers34 suggest
that, in the related dications [Pt{PPh2CH2P(O)Ph2-P,O}2]2+2X-
(X ) NO3 or PF6), the coupling between Pt and P(O) (typically
70 Hz) is mainly a three-bond coupling. A single-crystal X-ray
diffraction study of one of these complexes, 15, confirms that
protonation has occured at the nitrogen atom of both chelate
rings. The structure of the complex is shown in Figure 6. The
structure of 15 has crystallographic C2 symmetry. The neutral
ligands are cis coordinated to the square planar center. A
Acknowledgment. We should like to thank the EPSRC for
support and Johnson-Matthey Inc. for loans of precious metals.
Supporting Information Available: Tables giving experimental
crystallographic details, bond lengths, bond angles, and anisotropic
displacement parameters for non-hydrogen atoms and atomic coordi-
nates for hydrogen atoms of HL, 6, 10, 13, and 15 (33 pages). Ordering
information is given on any current masthead page.
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