The preparation and coordination chemistry of phosphorus(III) derivatives of dialkyl ureas and thioureas

Article abstract of DOI:10.1039/b104122n

The preparation of Ph₂PNEtC(O)NEtPPh₂ and Ph₂PNMeC(S)NMePPh₂ is reported. The coordination chemistry of Ph₂PNEtC(O)NEtPPh₂, Ph₂PNMeC(O)NMePPh₂ and Ph₂PNMeC(S)NMePPh₂ with Pt(II) and Pd(II) has been studied. The urea derivatives react with MCl₂(cod) (M = Pd, Pt) to give simple MCl₂L complexes. Demonstrative examples of simple chelate Mo(CO)₄L and bimetallic ClAu-L-AuCl complexes have also been prepared. However with Pd(OAc)₂ bimetallic compounds [PdOPh₂{N(Me)C(O)N(Me)PPh₂}]₂ containing hydrolysed ligands (P-N bond cleaved) are formed. Furthermore the thiourea compound reacts with PtCl₂(cod) to give [Pt{Ph₂PN(Me)- C(N(Me)HS)}Cl₂], a true heterocycle containing a PtSCNP ring. The new compounds have been characterised spectroscopically and the X-ray structures of six complexes are reported.

Full text of DOI:10.1039/b104122n

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The preparation and coordination chemistry of phosphorus(III)
derivatives of dialkyl ureas and thioureas
Alexandra M. Z. Slawin, Matthew Wainwright and J. Derek Woollins*
Department of Chemistry, University of St Andrews, St Andrews, Fife, UK KY16 9ST.
E-mail: jdw3@st-and.ac.uk
Received 10th May 2001, Accepted 2nd August 2001
First published as an Advance Article on the web 12th September 2001
The preparation of Ph2PNEtC(O)NEtPPh2 and Ph2PNMeC(S)NMePPh2 is reported. The coordination chemistry
of Ph2PNEtC(O)NEtPPh2, Ph2PNMeC(O)NMePPh2 and Ph2PNMeC(S)NMePPh2 with Pt() and Pd() has been
studied. The urea derivatives react with MCl2(cod) (M = Pd, Pt) to give simple MCl2L complexes. Demonstrative
examples of simple chelate Mo(CO)4L and bimetallic ClAu–L–AuCl complexes have also been prepared. However
with Pd(OAc)2 bimetallic compounds [PdOPh2{N(Me)C(O)N(Me)PPh2}]2 containing hydrolysed ligands (P–N
bond cleaved) are formed. Furthermore the thiourea compound reacts with PtCl2(cod) to give [Pt{Ph2PN(Me)-
C(N(Me)HS)}Cl2], a true heterocycle containing a PtSCNP ring. The new compounds have been characterised
spectroscopically and the X-ray structures of six complexes are reported.
After initial investigations in the 1960’s,1,2 research into diphos-
phines based on urea and thiourea backbones became dormant
until interest was recently rekindled.3–8 The mild reaction con-
ditions required in the synthesis of these ligands coupled with
the inexpensive nature of the starting materials ensures that
the products remain economically viable for applications in
catalysis, while the substituent groups on both the phosphorus
and the nitrogen atoms can be easily varied, offering excellent
control of the steric and electronic properties of the ligands.
[Ph2PN(Et)]2CO 2. A solution of N,NЈ-diethylurea (2.00 g,
17.2 mmol) and triethylamine (3.63 g, 5.0 cm3, 35.0 mmol) in
dichloromethane (20.0 cm3) was added dropwise over a period
of 4 h to a stirred solution of chlorodiphenylphosphine (7.57 g,
6.2 cm3, 35.0 mmol) in dichloromethane (10.0 cm3). Stirring
was continued for 48 h. The solvent was removed in vacuo and
diethyl ether (20.0 cm3) added. The white solid was collected by
suction filtration, washed with water to remove triethylamine
hydrochloride and dried over P4O10 in vacuo. Yield: 3.35 g, 40%.
The presence of the C᎐O and C᎐S functionalities also offers
᎐
᎐
sites which can be chemically modified to alter the properties of
the compounds. Here we report on the coordination properties
of the known compounds, as well as the synthesis and coordin-
ation chemistry of new diphosphine derivatives of dialkylureas
and thioureas. Some aspects of this work have appeared in a
preliminary communication.9
cis-[PtCl2{Ph2PN(Me)CON(Me)PPh2}] 3. To a solution of
[PtCl2(cod)] (0.033 g, 0.08 mmol) in dichloromethane (5.0 cm3)
was added solid [Ph2PN(Me)]2CO (0.040 g, 0.08 mmol) and the
colourless solution stirred for ca. 1 h. The solution was con-
centrated under reduced pressure to ca. 1.0 cm3 and diethyl
ether (10.0 cm3) added. The white product was collected by
suction filtration. Yield: 0.050 g, 79%.
Experimental
cis-[PtCl2{Ph2PN(Et)CON(Et)PPh2}] 4. To a solution of
[PtCl2(cod)] (0.038 g, 0.10 mmol) in dichloromethane (5.0 cm3)
was added solid [Ph2PN(Et)]2CO (0.050 g, 0.10 mmol) and the
colourless solution stirred for ca. 2 h. The solution was con-
centrated under reduced pressure to ca. 1.0 cm3 and diethyl
ether (10.0 cm3) added. The white product was collected by
suction filtration. Yield: 0.045 g, 58%.
General experimental conditions and instrumentation were as
previously reported.10,11 [AuCl(tht)] (tht = tetrahydrothio-
phene),12 [MCl2(cod)] (M = Pt or Pd; cod = cycloocta-1,5-
diene),13,14 [PtMeX(cod)] (X = Cl or Me),15 [Mo(CO)4(pip)2]
(pip = piperidine),16 and [{Rh(µ-Cl)(cod)}2],17 were prepared
using literature procedures. Chlorodiphenylphosphine and tri-
ethylamine were distilled prior to use. N,NЈ-Dimethylurea,
N,NЈ-diethylurea, N,NЈ-diethylthiourea, P2O5, AgClO4 and
reagent grade KBr were used without further purification.
Pd(OAc)2 was kindly donated by BP Chemicals Ltd.
cis-[PtMe2{Ph2PN(Me)CON(Me)PPh2}] 5. To a solution of
[PtMe2(cod)] (0.044 g, 0.13 mmol) in dichloromethane (10.0
cm3) was added solid [Ph2PN(Me)]2CO (0.060 g, 0.13 mmol)
and the colourless solution stirred for ca. 3 h. The solution
was concentrated under reduced pressure to ca. 1.0 cm3 and
light petroleum (bp 60–80 ЊC) (10.0 cm3) added. The white
product was collected by suction filtration. Yield: 0.058 g, 65%.
Syntheses
[Ph2PN(Me)]2CO 1. A solution of N,NЈ-dimethylurea (2.00
g, 22.7 mmol) and triethylamine (4.59 g, 6.5 cm3, 45.4 mmol) in
dichloromethane (20.0 cm3) was added dropwise over a period
of 3 h to a stirred solution of chlorodiphenylphosphine (9.94 g,
8.2 cm3, 35 mmol) in dichloromethane (10.0 cm3). Stirring was
continued for 24 h. The solvent was removed in vacuo and
diethyl ether (20.0 cm3) added. The white solid was collected by
suction filtration, washed with water to remove triethylamine
hydrochloride and dried over P4O10 in vacuo. Yield: 5.76 g, 56%.
cis-[PtMe2{Ph2PN(Et)CON(Et)PPh2}] 6. To a solution of
[PtMe2(cod)] (0.034 g, 0.10 mmol) in dichloromethane (5.0 cm3)
was added solid [Ph2PN(Et)]2CO (0.050 g, 0.10 mmol) and the
colourless solution stirred for ca. 2 h. The solution was con-
centrated under reduced pressure to ca. 1.0 cm3 and light
petroleum (bp 60–80 ЊC) (10.0 cm3) added. The white product
was collected by suction filtration. Yield: 0.046 g, 63%.
2724
J. Chem. Soc., Dalton Trans., 2001, 2724–2730
This journal is © The Royal Society of Chemistry 2001
DOI: 10.1039/b104122n

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cis-[PtMe(Cl){Ph2PN(Me)CON(Me)PPh2}] 7. To a solution
of [PtMe(Cl)(cod)] (0.054 g, 0.15 mmol) in dichloromethane
(10.0 cm3) was added solid [Ph2PN(Me)]2CO (0.070 g, 0.15
mmol) and the colourless solution stirred for ca. 1 h. The solu-
tion was concentrated under reduced pressure to ca. 1.0 cm3
and diethyl ether (10.0 cm3) added. The white product was
collected by suction filtration. Yield: 0.075 g, 67%.
(5.0 cm3) added. The brown product was collected by suction
filtration. Yield: 0.092 g, 58%.
[{Ph2P(AuCl)N(Et)CON(Et)P(AuCl)Ph2}] 15. To a solution
of [AuCl(tht)] (0.032 g, 0.10 mmol) in dichloromethane (10.0
cm3) was added solid [Ph2PN(Et)]2CO (0.050 g, 0.10 mmol) and
the colourless solution stirred for ca. 15 min. The solution was
concentrated under reduced pressure to ca. 1.0 cm3 and diethyl
ether (5.0 cm3) added. The colourless product was collected by
suction filtration. Yield: 0.069 g, 72%.
cis-[PtMe(Cl){Ph2PN(Et)CON(Et)PPh2}] 8. To a solution of
[PtMe(Cl)(cod)] (0.036 g, 0.10 mmol) in dichloromethane (5.0
cm3) was added solid [Ph2PN(Et)]2CO (0.050 g, 0.10 mmol) and
the colourless solution stirred for ca. 2 h. The solution was
concentrated under reduced pressure to ca. 1.0 cm3 and diethyl
ether (10.0 cm3) added. The white product was collected by
suction filtration. Yield: 0.049 g, 63%.
[Ph2PN(Et)]2CS 16. A solution of chlorodiphenylphosphine
(5.0 g, 4.1 cm3, 22.7 mmol) in diethyl ether (20.0 cm3) was added
dropwise over a period of 45 min to a stirred solution of N,NЈ-
diethylthiourea (3.00 g, 22.7 mmol) and triethylamine (4.60 g,
6.3 cm3, 35.0 mmol) in diethyl ether (100.0 cm3) and thf (20.0
cm3) at Ϫ5 ЊC. The reaction mixture was then allowed to warm
to room temperature and stirring continued for 72 h during
which time triethylammonium hydrochloride separated from
the colourless solution. A second solution of chlorodiphenyl-
phosphine (5.0 g, 4.1 cm3, 22.7 mmol) in diethyl ether (20.0 cm3)
was added to the reaction mixture and stirring continued for a
further 48 h. Triethylammonium hydrochloride was removed by
suction filtration and reduction of the solvent volume in vacuo
resulted in precipitation of the product as a white solid. Yield:
2.94 g, 26%.
cis-[PdCl2{Ph2PN(Me)CON(Me)PPh2}] 9. To a yellow solu-
tion of PdCl2(cod) (0.033 g, 0.08 mmol) in dichloromethane
(10.0 cm3) was added solid [Ph2PN(Me)]2CO (0.040 g, 0.08
mmol) and the yellow solution stirred for ca. 3 h. The solution
was concentrated under reduced pressure to ca. 1.0 cm3 and
diethyl ether (10.0 cm3) added. The yellow product was col-
lected by suction filtration. Yield: 0.040 g, 73%.
cis-[PdCl2{Ph2PN(Et)CON(Et)PPh2}] 10. To a yellow solu-
tion of [PdCl2(cod)] (0.029 g, 0.10 mmol) in dichloromethane
(5.0 cm3) was added solid [Ph2PN(Et)]2CO (0.050 g, 0.10 mmol)
and the yellow solution stirred for ca. 1 h. The solution was
concentrated under reduced pressure to ca. 1.0 cm3 and diethyl
ether (10.0 cm3) added. The yellow product was collected by
suction filtration. Yield: 0.050 g, 73%.
[PtCl2{Ph2PN(Me)CSN(Me)H}] 17. To a solution of [PtCl2-
(cod)] (0.040 g, 0.10 mmol) in dichloromethane (5.0 cm3) was
added solid [Ph2PN(Me)]2CS (0.050 g, 0.10 mmol) and the pale
yellow solution stirred for ca. 1 h. The solution was concen-
trated under reduced pressure to ca. 1.0 cm3 and diethyl ether
(10 cm3) added. The pale yellow product was collected by
suction filtration. Yield: 0.050 g, 85%. IR (KBr disc, cmϪ1):
3222w, 3052w, 1577vs, 1482m, 1436vs, 1376s, 1325vs, 1218w,
1185w, 1142w, 1106vs, 1059m, 997m, 829s, 747s, 718m, 691s,
578s, 541m, 521m, 490s, 318w, 290m, 3235m, 221vs and 210vs.
FAB mass spectrum: m/z 519, [M Ϫ Cl]ϩ.
[Pd{OPPh2}{N(Me)C(O)N(Me)PPh2}]2 11. To a yellow solu-
tion of [Pd(OAc)2] (0.150 g, 0.70 mmol) in dichloromethane
(10.0 cm3) was added solid [Ph2PN(Me)]2CO (0.320 g, 0.70
mmol) and the dark yellow solution stirred for ca. 2 h. The
solution was concentrated under reduced pressure to ca. 1.0 cm3
and diethyl ether (10.0 cm3) added. The dark yellow product
was collected by suction filtration. Yield: 0.251 g, 31%. IR (KBr
disc, cmϪ1): 3052w, 2915w, 1630vs, 1610vs, 1480w, 1434s, 1325s,
1208w, 1105vs, 1010vs, 995vs, 948w, 815w, 744s, 692vs, 595w,
552vs, 535s, 508vs, 492s and 345w.
Crystallography
Crystallography (Table 1) was performed using a Bruker
SMART diffractometer; full hemisphere of data with 0.3Њ
‘slices’, room temperature, Mo-Kα radiation and empirical
absorption corrections. All non-H atoms were refined aniso-
tropically, H atoms were idealised. All calculations employed
the SHELXTL program system.11 The poor quality of crystals
for 12 precluded any improvement in the quality of this
structure—several different crystals were examined with no
improvement. Details for 9, 11 and 17 have already been
reported.9
[Pd{OPPh2}{N(Et)C(O)N(Et)PPh2}]2 12. To
a
yellow
solution of [Pd(OAc)2] (0.045 g, 0.2 mmol) in dichloromethane
(5.0 cm3) was added solid [Ph2PN(Me)]2CO (0.100 g,
0.02 mmol) and the dark yellow solution stirred for ca. 2 h. The
solution was concentrated under reduced pressure to ca. 1 cm3
and diethyl ether (10 cm3) added. The dark yellow product was
collected by suction filtration. Yield: 0.127 g, 51%. IR (KBr
disc, cmϪ1): 3053w, 2927w, 1672w, 1620vs, 1481w, 1435s, 1369w,
1319s, 1281s, 1219w, 1181s, 1103s, 1034s, 1022s, 996s, 746s,
695vs, 593w, 553vs, 529s, 505s, 472w and 328w.
CCDC reference numbers 168899–168904.
See http://www.rsc.org/suppdata/dt/b1/b104122n/ for crystal-
lographic data in CIF or other electronic format.
cis-[Mo(CO)4{Ph2PN(Me)CON(Me)PPh2}] 13. To
a
partially dissolved solution of [Mo(CO)4(pip)2] (0.580 g, 1.50
mmol) in dichloromethane (20.0 cm3) was added solid [Ph2P-
N(Me)]2CO (0.700 g, 1.50 mmol). The solution was heated to
reflux for ca. 15 min and allowed to cool to room temperature.
The solution was concentrated under reduced pressure to ca.
2.0 cm3 and methanol (15.0 cm3) added. The yellow product
was collected by suction filtration. Yield: 0.725 g, 71%.
Results and discussion
Both ourselves18 and Schmutzler3–8 have reported the synthesis
of diphosphine derivatives of ureas from silylated starting
materials. We have now discovered that the synthesis of [Ph2P-
N(Me)]2CO 1 is also possible from the reaction of N,NЈ-
dimethylurea with two equivalents of Ph2PCl, in the presence
of NEt3, in dichloromethane [eqn. (1)].
cis-[Rh(cod){Ph2PN(Et)CON(Et)PPh2}]؉[ClO4]؊ 14. To a
stirred solution of [RhCl(cod)]2 (0.050 g, 0.10 mmol) in acetone
(20.0 cm3) was added AgClO4 and the solution stirred for 15
min. The colourless precipitate was removed by filtration and
washed with acetone (10.0 cm3). To the combined filtrates and
washings was added solid [Ph2PN(Et)]2CO (0.098 g, 0.20 mmol)
and the solution stirred for ca. 1 h. The solution was concen-
trated under reduced pressure to ca. 1.0 cm3 and diethyl ether
(1)
J. Chem. Soc., Dalton Trans., 2001, 2724–2730
2725

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Table 1 Details of X-ray data collection and refinements
Compound
3
4
11
12
13
15
Empirical formula
C27H26Cl2N2-
OP2Pt
722.4
Orthorhombic
P21cn
C29H30Cl2N2-
OP2Pt
750.5
Triclinic
P1
C37H42Cl4N2-
OP2Pd2
947.3
Monoclinic
P21/c
C59H62N4O4P4-
Pd2Cl2
1298.7
Monoclinic
P21/n
C31H26N2O5-
P2Mo
664.4
Monoclinic
P21/c
C30H31Cl5N2-
OP2Au2
1068.7
Monoclinic
P21/c
Formula weight
Crystal system
Space group
a/Å
b/Å
c/Å
α/Њ
10.0447(5)
14.4768(7)
18.5427(9)
90
90
90
9.8640(4)
10.8209(4)
15.1644(6)
78.430(1)
80.056(1)
66.664(1)
1448
14.2866(3)
27.6453(5)
9.7662(2)
90
92.632(1)
90
10.4350(2)
18.7436(3)
15.6919(1)
90
94.362(1)
90
12.0547(1)
17.0186(2)
14.662(1)
90
94.485(1)
90
14.5596(5)
15.4267(5)
16.1541(5)
90
98.36(1)
90
β/Њ
γ/Њ
V/Å3
2696
3853
3060
2999
3590
Z
4
1.78
2605
2
1.72
5727
4
1.63
4874
2
1.41
1785
4
1.47
3487
4
1.98
5380
Density (calc.)/Mg mϪ3
Observed ind. refl.
[I > 2.0σ(I )]
Final R, Rw
0.0209, 0.0389
0.0257, 0.0590
0.0470, 0.1041
0.1033, 0.2379
0.0251, 0.0609
0.0354, 0.0752
Table 2 Elemental analyses and selected spectroscopic data (calculated values in parentheses)
δP (ppm)/
1J (Hz)
ν(CO)/ ν(CN)/
ν(PN)/
Formula
m/z
456
484
722
715 [ϪCl]
681
710
cmϪ1
cmϪ1
cmϪ1
C (%)
H (%)
N (%)
1
2
3
4
5
6
7
[Ph2PN(Me)]2CO
[Ph2PN(Et)]2CO
[PtCl2 {{Ph2PN(Me)}2CO}]
[PtCl2{{Ph2PN(Et)}2CO}]
[PtMe2{{Ph2PN(Me)}2CO}]
[PtMe2{{Ph2PN(Et)}2CO}]
[PtCl(Me){{Ph2PN(Me)}2CO}]
54.6
56.1
1646
1649
1672
1669
1626
1652
1637
1432
1432
1435
1436
1434
1436
1433
961
992
973
997
983
994
984
70.6 (71.0) 5.3 (5.7) 5.8 (6.1)
70.8 (71.2) 6.2 (6.2) 5.3 (5.8)
44.8 (44.9) 3.4 (3.6) 3.6 (3.8)
46.2 (46.4) 4.2 (4.0) 3.9 (3.7)
49.3 (50.1) 4.9 (5.1) 4.0 (4.2)
52.7 (52.4) 5.8 (5.1) 4.0 (3.9)
47.5 (47.9) 4.0 (4.2) 3.7 (3.9)
53.4/3792
56.7/3910
74.9/1944
77.7/1997
74.1/1819;
61.4/4509a
77.1/1891;
64.2/4596a
76.2
701
8
[PtCl(Me){{Ph2PN(Et)}2CO}]
730
1658
1436
996
48.8 (49.3) 4.0 (4.5) 3.1 (3.8)
9
10
11
12
13
14
15
16
17
[PdCl2{Ph2PN(Me)}2CO]
[PdCl2{Ph2PN(Et)}2CO]
598 [ϪCl]
626 [ϪCl]
1158
1214
664
1648
1670
1630
1620
1643
1435
1436
1434/1325
1435/1319
1433
991
996
995
996
962
996
997
997
997
50.9 (51.2) 3.8 (4.1) 3.9 (4.4)
52.8 (52.6) 4.4 (4.5) 3.8 (4.2)
56.1 (55.5) 4.3 (4.5) 4.3 (4.8)
56.8 (57.4) 4.6 (5.0) 4.0 (4.6)
55.4 (56.0) 3.8 (3.9) 4.1 (4.2)
58.7 (58.9) 5.1 (5.3) 3.4 (3.5)
36.9 (36.6) 3.6 (3.2) 3.2 (2.9)
69.3 (69.6) 6.0 (6.0) 5.3 (5.6)
32.1 (32.4) 2.9 (3.1) 4.8 (5.1)
80.1
[Pd{OPPh2}{N(Me)C(O)N(Me)PPh2}]2
[Pd{OPPh2}{N(Et)C(O)N(Et)PPh2}]2
[Mo(CO)4{Ph2PN(Me)}2CO]
[Rh(cod){Ph2PN(Et)}2CO][ClO4]
[(AuCl)2{Ph2PN(Et)}2CO}]
[Ph2PN(Et)]2CS
71.2; 84.4
69.5; 84.4
101.9
90.3/167
75.7
67.8
78.3/3967
695 [ϪClO4] 1664
1437
949
468 [ϪS]
519 [ϪCl]
1655
1436
1435
1436
1174b
1059b
[Pt{Ph2PN(Me)C(N(Me)HS)}Cl2]
a 2J(PP) 31 Hz. b ν(CS).
Slow addition of a dichloromethane solution of {HN(Me)}2-
CO and NEt3 to a dichloromethane solution of Ph2PCl at room
temperature results in a viscous, pale yellow solution. 31P-{1H}
NMR studies conducted on the methylurea reaction immedi-
ately after completion of the addition of the urea show that the
reaction mixture contains three phosphorus-containing species,
the starting material Ph2PCl, at δP 82.9, the desired product 1, at
δP 54.6, and presumably the mono-substituted product {Ph2P-
N(Me)C(O)N(Me)H} at δP 46.4. We can be confident in this
assignment as the value of its chemical shift, δP 46.4, and its
position relative to the bis-substituted product are analogous to
the values for mono-substituted products of similar, related
thiourea systems.19 Stirring the reaction mixture overnight
results in the loss of the species at δP 82.9 and δP 46.4 and leaves
1 as the only phosphorus-containing species. Removal of the
solvent in vacuo, leaves an off white solid residue which is
washed with water to remove NEt3ؒHCl. Collection of the solid
by suction filtration and drying over P4O10 in vacuo results in the
product, 1, as a white solid in 56% yield. Air- and moisture-
tolerant, 1 is readily soluble in both dichloromethane and thf.
Elemental analysis is in good agreement with the calculated
values (Table 2) and FABϩ mass spectrometry shows the
expected parent-ion peak (m/z 456 [M]ϩ). The IR spectrum of 1
contains strong bands which can be assigned to ν(CO), ν(CN)
and ν(PN) (Table 2).
As mentioned above, Schmutzler and co-workers have
reported the synthesis of phosphine derivatives of N,NЈ-
dimethylurea.3–8 However, reports of metal complexes contain-
ing these ligands are rare, especially where the ligands act as
P,PЈ chelates. Therefore, using 1 and 2, we have investigated
their complexation chemistry more fully via reactions with
various metal compounds.
The reactions of 1 and 2 with equimolar quantities of
[PtCl2(cod)] in dichloromethane proceed smoothly to yield
the P,PЈ-chelates cis-[PtCl2{{Ph2PN(Me)}2CO}], 3, and cis-
[PtCl2{{Ph2PN(Et)}2CO}], 4 as six-membered metallacycles,
spectroscopic properties are summarised in Table 2. The mag-
1
nitude of the J(195Pt–31P) couplings (3792 for 3 and 3910 Hz
for 4) are in agreement with reported values for similar diphos-
phine urea chelates containing a phosphorus trans to chloride
in Pt() systems.20 The IR spectra of 3 and 4 show bands which
can be assigned to ν(CO), ν(CN) and ν(PN) (Table 2); ν(CO) is
shifted slightly to higher frequency upon complexation. Single
crystal X-ray studies confirm the cis chelate geometry of the
ligands and that the molecules are square planar at the plat-
inum (Fig. 1, Table 3). The molecules have approximate C2
symmetry and the bite angles are close to 90Њ [90.7(2) for 3 and
88.8(3)Њ for 4] indicating that this size ring is very well suited to
square planar coordination. In 3 the six-membered PtP2N2C
ring is hinged about P(2)–N(1) by 45Њ while in 4 the same ring is
2726
J. Chem. Soc., Dalton Trans., 2001, 2724–2730

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Table 3 Selected bond lengths (Å) and angles (Њ) for compounds 3, 4, 9 and 10
3
4
9
10
P(1)–M(1)
P(2)–M(1)
M(1)–Cl(1)
M(1)–Cl(2)
N(1)–P(1)
2.207(4)
2.2054(13)
2.3567(13)
2.362(4)
1.716(6)
1.749(8)
1.413(10)
1.360(12)
1.499(8)
1.485(8)
1.222(11)
2.2141(8)
2.2157(8)
2.3414(9)
2.3595(9)
1.725(3)
1.714(3)
1.385(5)
1.411(5)
1.488(5)
1.500(5)
1.217(5)
2.2003(8)
2.2072(8)
2.3476(8)
2.3418(9)
1.697(2)
1.704(2)
1.380(4)
1.377(4)
1.494(4)
1.486(4)
1.224(3)
2.2165(13)
2.2135(13)
2.3545(13)
2.3577(13)
1.707(4)
1.712(4)
1.382(6)
1.397(6)
1.506(6)
1.504(6)
1.215(6)
N(2)–P(2)
N(1)–C(13)
N(2)–C(13)
N(1)–C(26)
N(2)–C(27)
C(13)–O(13)
P(1)–M(1)–P(2)
N(1)–P(1)–M(1)
N(2)–P(2)–M(1)
Cl(1)–M(1)–Cl(2)
Cl(1)–M(1)–P(1)
Cl(2)–M(1)–P(2)
P(1)–N(1)–C(13)
P(2)–N(2)–C(13)
N(1)–C(13)–N(2)
N(1)–C(13)–O(13)
N(2)–C(13)–O(13)
C(13)–N(2)–C(27)
C(13)–N(1)–C(26)
90.7(2)
88.8(3)
94.76(3)
91.47(5)
115.93(14)
116.05(14)
90.28(5)
89.26(5)
89.22(5)
126.2(3)
117.2(3)
120.2(4)
120.7(4)
119.1(4)
113.2(4)
112.9(4)
114.9(2)
112.0(3)
89.4(14)
86.9(14)
92.7(2)
125.1(6)
123.5(6)
119.8(8)
118.8(9)
121.1(9)
116.1(7)
111.7(6)
111.0(11)
114.8(11)
87.9(4)
95.5(3)
87.7(3)
122.5(2)
120.6(2)
117.8(3)
121.0(4)
121.1(4)
112.5(3)
115.1(3)
118.19(9)
118.41(9)
91.47(3)
86.84(3)
86.98(3)
132.6(2)
131.5(2)
122.9(3)
118.6(3)
118.5(3)
112.8(2)
112.4(4)
bond lengths within the PtP2N2C ring are significantly shorter
than N–Me/N–Et bond lengths, indicating some degree of
delocalisation across the N C᎐O groups. In both complexes the
᎐
2
P–N bond lengths [1.716(6) and 1.749(8) Å for 3 and 1.725(3)
and 1.714(3) Å for 4] are similar to those observed in related
compounds.18,20
Both {Ph2PN(Me)}2CO and {Ph2PN(Et)}2CO also react
successfully with [PtMe2(cod)] to produce P,PЈ chelates
[eqn. (2)] and with [PtCl(Me)(cod)] to give cis-[PtCl(Me)-
(2)
{{Ph2PN(Me)}2CO}], 7 and cis-[PtCl(Me){{Ph2PN(Et)}2CO}],
8 respectively.
Palladium complexes involving [Ph2PN(Me)]2CO and
[Ph2PN(Et)]2CO acting as bidentate P,PЈ chelates are also
successfully formed when the diphosphines 1 and 2 are
reacted with [PdCl2(cod)]. In the solid state structures of cis-
[PdCl2{{Ph2PN(Me)}2CO}] 9 and cis-[PdCl2{{Ph2PN(Et)}2-
CO}] 10 the molecules have approximate non-crystallographic
C2 symmetry and similar geometry about the metal to 3 and 4.
Perhaps the most surprising difference is an enlargement of the
P–N–C angles in 9 and 10 relative to those in 3 and 4, for which
there is no ready explanation. In 9 the PdP2N2C ring is effect-
ively planar and co-planar with the coordination sphere. The
same ring in 10 is puckered, though not hinged like the
examples in 3 and 4, with C(13) and O(13) in the same plane as
the coordination sphere and N(1) and N(2) lying 0.5 Å above
and below the plane respectively. As with compounds 3 and 4
the P–N bond lengths in 9 and 10 [1.697(2) and 1.704(2) Å for 9
and 1.707(4) and 1.712(4) Å for 10] are within the expected
range20 and, once again, the C–N bond lengths within the
PtP2N2C rings of both molecules are significantly shorter than
the N–Me/N–Et bond lengths, indicating some degree of
Fig. 1 (a) Solid state structure of cis-[PtCl2{{Ph2PN(Me)}2CO}] 3. (b)
Solid state structure of cis-[PtCl2{{Ph2PN(Et)}2CO}] 4.
hinged about P(1)–N(2) by 51Њ. In both molecules the exocyclic
urea oxygen atom is effectively in the plane of its substituents.
The internal angles of the rings in both 3 and 4 are all close to
trigonal and it is noticeable in both molecules that the C–N
delocalisation across the N C᎐O groups. The Pd–Cl and Pd–P
᎐
2
bond lengths in 9 and 10 are normal.
J. Chem. Soc., Dalton Trans., 2001, 2724–2730
2727

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Table 5 Selected bond lengths (Å) and angles (Њ) for 12ؒCH2Cl2
Pd(1)–N(21)
Pd(1)–P(1)
Pd(1)–O(1A)
Pd(1)–P(2)
1.990(11) P(2)–N(22)
1.639(12)
1.43(2)
1.21(2)
1.28(2)
2.221(4)
2.051(9)
2.160(5)
N(22)–C(21)
C(21)–N(21)
C(21)–O(21)
P(2)–Pd(1)–N(21)
Pd(1)–P(2)–N(22)
P(2)–N(22)–C(21)
N(22)–C(21)–N(21)
80.6(4)
103.2(5)
114.0(12)
115.7(130)
C(21)–N(21)–Pd(1) 124.3(12)
Pd(1)–P(1)–O(1) 112.7(4)
N(21)–Pd(1)–O(1A) 92.9(5)
P(1)–Pd(1)–O(1A) 84.6(4)
spiro in the tricyclic system. The PdPN2C rings are close to
planar [maximum deviations for the two rings are 0.01 Å for
N(2) and Ϫ0.05 Å for N(31)] with the C᎐O and the NMe
᎐
groups being effectively co-planar with the PdPN2C rings. The
internal nitrogen angles in the PdPN2C ring are close to
trigonal, whilst the angle at the phosphorus is slightly reduced
from a perfect tetrahedral angle. The central Pd2P2O2 ring
adopts a chair geometry with the central Pd2P2O2 core having
two PdOP planes inclined by ca. 138Њ. Within this ring the P–O
bond lengths [P(2)–O(2) 1.536(4) and P(32)–O(32) 1.539(3) Å]
are appropriate for a coordinated [Ph2PO]Ϫ anion and similar to
those reported for a Pd2P2O2 ring21 but slightly shorter than
those reported for [(Ph3P)Pt(Ph2PO)2Pt(PPh3)].22
Using the same method employed in the preparation of 11,
[Pd{OPPh2}{N(Et)C(O)N(Et)PPh2}]2, 12 was isolated as a
yellow solid in 51% yield (Table 5 for bond lengths and angles).
The reaction of [Ph2PN(Me)]2CO, 1 with [Mo(CO)4(pip)2] in
dichloromethane results in the displacement of the piperidine
molecules and the formation of the P,PЈ chelate complex
cis-[Mo(CO)4{Ph2PN(Me)C(O)N(Me)PPh2}], 13 [eqn. (4)].
Fig. 2 Solid state structure of [Pd{OPPh2}{N(Et)C(O)N(Et)PPh2}]2ؒ
CH2Cl2 12; 11 has a very similar structure and is not reproduced.
Table 4 Selected bond lengths (Å) and angles (Њ) for 11
Pd(1)–N(2)
Pd(1)–P(1)
Pd(1)–O(32)
Pd(1)–P(2)
P(1)–N(1)
N(1)–C(13)
C(13)–N(2)
C(13)–O(13)
P(2)–O(2)
2.083(4)
2.2043(14) Pd(2)–P(31)
2.092(3) Pd(2)–O(2)
2.2764(14) Pd(2)–P(31)
Pd(2)–N(32)
2.059(4)
2.1985(14)
2.075(3)
2.2600(14)
1.676(5)
1.414(7)
1.328(7)
1.240(6)
1.539(3)
1.674(5)
1.424(7)
1.323(7)
1.235(6)
1.536(4)
P(31)–N(31)
N(31)–C(43)
C(43)–N(32)
C(43)–O(43)
P(32)–O(32)
P(1)–Pd(1)–N(2)
Pd(1)–P(1)–N(1)
P(1)–N(1)–C(13)
N(1)–C(13)–N(2)
C(13)–N(2)–Pd(1) 121.6(4)
Pd(1)–P(2)–O(2) 113.9(2)
Pd(1)–O(32)–P(32) 128.4(7)
81.81(13)
102.6(2)
119.4(3)
114.6(5)
P(31)–Pd(2)–N(32)
81.90(13)
Pd(2)–P(31)–N(31) 102.3(2)
C(43)–N(31)–P(31) 119.2(3)
N(31)–C(43)–N(32) 114.2(5)
C(43)–N(32)–Pd(2) 121.9(4)
Pd(2)–P(32)–O(32) 112.8(2)
(4)
Pd(2)–O(2)–P(2)
134.8(2)
Compounds 9 and 10 demonstrate that the ligands [Ph2P-
N(Me)]2CO 1 and [Ph2PN(Et)]2CO 2 can act as simple metal
chelates and form six-membered ring systems when reacted
with [PdCl2(cod)]. However, reaction of the two ligands with
palladium acetate fails to result in the expected chelate systems.
Instead P–N bond cleavage takes place and the reaction
involves the formation of a [Ph2PO]Ϫ ligand which is incorpor-
ated into a Pd2P2O2 heterocycle [eqn. (3)]. It seems likely that
The solid state structure of 13 (Table 6, Fig. 3) reveals
octahedral geometry at the molybdenum with some contraction
of the P(1)–Mo(1)–P(2) angle [80.7(2)Њ]. The Mo–C distances
differ as a consequence of the trans ligand, with Mo–C(31) and
Mo–C(34) (trans to P) being shorter (ca. 2.00 Å) than Mo–
C(32) and Mo–C(33) (trans to carbonyl) (ca. 2.03 Å). Unlike 9
the MoP2N2C ring is non-planar, being hinged by 55Њ along the
N(2)–P(1) vector. Within the MoP2N2C ring the P–N and C–N
bond lengths are close to those reported for similar systems.23
The reaction of two equivalents [Ph2PN(Et)]2CO, 2 with
[RhCl(cod)]2 in acetone proceeds according to eqn. (5) to yield
(3)
(5)
the P–N cleavage is acid catalysed by the acetate, with water
from the palladium acetate providing the source of oxygen for
the hydrolysis.
The 31P-{1H} NMR spectrum of 11 shows two broad singlet
peaks at δP 84.4 and δP 71.2. We assign the phosphorus in the
[Ph2PO]Ϫ ligand to the species further downfield at δP 84.4 due
to its proximity to the electronegative oxygen atom and con-
sequently the phosphorus in the PNCNPd ring is assigned
to the peak at δP 71.2. FABϩ mass spectrometry shows the
parent-ion peak (m/z 1158 [M]ϩ) and a peak corresponding to
[Pd{OPPh2}{N(Me)C(O)N(Me)PPh2}]ϩ (m/z 579) and the IR
spectrum shows peaks which can be assigned to ν(CO) (1630
cmϪ1), ν(CN) (1434 cmϪ1) and ν(PN) (995 cmϪ1). Elemental
analysis is in good agreement with calculated values. The
solid state structure of [Pd{OPPh2}{N(Me)C(O)N(Me)PPh2}]2
(Fig. 2, Table 4) reveals the square planar palladium centres as
the P,PЈ chelate product cis-[Rh(cod){Ph2PN(Et)CON(Et)-
PPh2}][ClO4], 14.
The 31P-{1H} NMR spectrum of 14 contains a single
1
phosphorus-containing species at δP 90.3 with a J(103Rh–31P)
coupling of 167 Hz and the FABϩ mass spectrum shows a peak
corresponding to [Rh(cod){Ph2PN(Et)CON(Et)PPh2-P,PЈ}]ϩ
(m/z 695).
Compounds 3–10, 13 and 14 demonstrate the ability of
the ligands [Ph2PN(Me)]2CO and [Ph2PN(Et)]2CO to act as
2728
J. Chem. Soc., Dalton Trans., 2001, 2724–2730

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Fig. 4 Solid state structure of [Ph2P{AuCl}N(Et)C(O)N(Et)P{AuCl}-
Ph2]ؒCHCl3 15.
Table 7 Selected bond lengths (Å) and angles (Њ) for 15ؒCHCl3
Au(1)–Cl(1)
P(1)–Au(1)
P(1)–N(1)
N(1)–C(26)
N(1)–C(13)
C(13)–O(13)
C(13)–N(2)
N(2)–C(27)
N(2)–P(2)
2.316(2)
2.239(2)
1.709(5)
1.475(7)
1.415(7)
1.213(6)
1.389(7)
1.492(7)
1.706(5)
2.243(2)
2.298(2)
P(1)–Au(1)–Cl(1)
N(1)–P(1)–Au(1)
C(26)–N(1)–P(1)
C(13)–N(1)–P(1)
N(1)–C(13)–O(13)
N(1)–C(13)–N(2)
N(2)–C(13)–O(13)
C(13)–N(2)–P(2)
C(27)–N(2)–P(2)
N(2)–P(2)–Au(2)
P(2)–Au(2)–Cl(2)
171.29(6)
114.1(2)
120.6(4)
117.3(4)
121.5(5)
116.3(5)
122.2(5)
118.3 (4)
118.9(4)
110.1(2)
174.48(7)
Fig. 3 Solid state structure of cis-[Mo(CO)4{Ph2PN(Me)C(O)N(Me)-
PPh2}] 13.
P(2)–Au(2)
Au(2)–Cl(2)
Table 6 Selected bond lengths (Å) and bond angles (Њ) for cis-
[Mo(CO)4{Ph2PN(Me)C(O)N(Me)PPh2}] 13
Mo(1)–P(1)
Mo(1)–P(2)
P(1)–N(1)
2.4849(7)
2.4808(6)
1.743(2)
1.731(2)
1.379(3)
1.411(3)
2.003(3)
2.024(3)
2.037(3)
2.001(3)
P(1)–Mo(1)–P(2)
Mo(1)–P(1)–N(1)
Mo(1)–P(2)–N(2)
P(1)–N(1)–C(13)
P(2)–N(2)–C(13)
N(2)–C(13)–N(1)
C(31)–Mo(1)–P(1)
C(31)–Mo(1)–P(2)
C(34)–Mo(1)–P(1)
C(34)–Mo(1)–P(2)
80.72(2)
107.69(7)
116.23(7)
123.0(2)
124.4(2)
118.6(2)
170.25(8)
90.70(8)
97.54(9)
176.29(8)
reported the synthesis of diphosphine derivatives of thioureas,
the latter showing that {Ph2PN(Me)}2CS can be formed from
the reaction of N,NЈ-dimethylthiourea and two equivalents of
chlorodiphenylphosphine. We have found that the analogous
reaction involving N,NЈ-diethylthiourea results in the ligand
[Ph2PN(Et)]2CS 16. Reports of metal complexes containing
ligands of the type [Ph2PN(R)]2CE (E = O, S) are rare.
Schmutzler and Gruber reported the synthesis of [Ph2P-
N(Me)]2CS but did not describe any complexation chemistry
for the ligand.25
P(2)–N(2)
N(1)–C(13)
N(2)–C(13)
Mo(1)–C(31)
Mo(1)–C(32)
Mo(1)–C(33)
Mo(1)–C(34)
bidentate P,PЈ chelates and form six-membered metallacycles.
Schmutzler and co-workers have also previously reported that
[(Ph)(tBu)PN(Me)]2CO can act as a bidentate bridging ligand
between two metal centres when reacted with [Fe2(CO)9].8
We have also demonstrated that [Ph2PN(Et)]2CO can act as a
bidentate bridging ligand when reacted with [AuCl(tht)] to form
the complex [Ph2P{AuCl}N(Et)C(O)N(Et)P{AuCl}Ph2], 15
[eqn. (6)].
We have found that reaction of [Ph2PN(Me)]2CS with equi-
molar quantities of [PtCl2(cod)] in thf fails to give the expected
P,PЈ chelate system and instead proceeds according to eqn. (7)
(7)
(6)
with P–N bond cleavage, to give the novel five-membered
heterocycle 17. The sulfur containing system probably behaves
differently to 1 or 2 because of the tendency of the S atom to
coordinate the metal centre. We envisage an intermediate
containing a five-membered PtPNCS ring with the pendant
N(Me)PPh2 group undergoing P–N bond cleavage after the
coordination is complete though we have no clear evidence
supporting this mechanism. Clearly, hydrolytic P–N cleavage at
this stage would give rise to Ph2P(O)H/[Ph2PO]Ϫ which has the
opportunity to coordinate in a similar fashion to 11 and 12. The
fact that this is not observed may suggest that the cleavage in
the formation of 11 and 12 may be ‘associative’ with the
opportunity for the ligand to coordinate through two phos-
phorus and one nitrogen atom in that case.
The FABϩ mass spectrum shows a parent-ion peak and a
peak corresponding to the loss of a chloride ion (m/z 949 [M]ϩ
and 913 [M Ϫ Cl]ϩ) and the IR spectrum shows peaks which
can be assigned to ν(CO), ν(CN) and ν(PN). The solid state
structure of 15 (Fig. 4, Table 7) confirms that the molecule
contains two gold centres. The overall W-shaped molecule has
approximately non-crystallographic symmetry with a two-fold
axis about the C(13)–O(13) bond, though the backbone is non-
planar; N(1) and N(2) lie Ϫ0.45 and ϩ0.21 Å from the N(1)–
C(13)–O(13)–N(2) mean plane. The P–Au–Cl angles are close
to linear, as expected, and there is no evidence of any delocal-
isation in the P2N2C chain. P–N, P–Au and Au–Cl bond lengths
are all comparable to those observed in similar compounds.24
Both ourselves18 and Schmutzler and Gruber19,25 have
The 31P-{1H} NMR spectrum of 17 shows a singlet with
satellites from coupling to 195Pt. The product has a chemical
shift of δP 78.3 and the magnitude of the coupling [1J(195Pt–31P)
3967 Hz] suggests a platinum() complex where phosphorus is
trans to chloride.25 FABϩ mass spectrometry failed to show the
J. Chem. Soc., Dalton Trans., 2001, 2724–2730
2729

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P,PЈ chelates and formation of six-membered ring systems,
while [Ph PN(Et)] C᎐O acts as a bridging ligand when reacted
᎐
2
2
with Au(). Different substituents on the nitrogen atoms appear
to have little influence on bond lengths and angles within
the metal complexes. The coordination chemistry of [Ph2PN-
(Me)] C᎐S is less predictable and results in P–N bond cleavage
᎐
2
and the formation of a five-membered heterocycle when reacted
with Pd(). Studies of the chemistry of these types of ligands
are still far from extensive.
Acknowledgements
We are grateful to BP Chemicals for support and to the JREI
for an equipment grant.
References
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171, Phosphorus Chemistry, ed. L. D. Quin and J. G. Verkade, ACS,
New York, 1981, p. 425.
Fig. 5 Solid state structure of [PtCl2{(Ph2)PN(Me)CSN(Me)H-P,S}]ؒ
dmsoؒCHCl3 17.
Table 8 Selected bond lengths (Å) and bond angles (Њ) for 17ؒdmsoؒ
CHCl3
4 N. Weferling, R. Schmutzler and W. S. Sheldrick, Liebigs. Ann.
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5 G. Bettermann, R. Schmutzler, S. Pohl and U. Thewalt, Polyhedron,
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8 R. Vogt, P. G. Jones, A. Kolbe and R. Schmutzler, Chem. Ber., 1991,
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Pt(1)–Cl(1)
Pt(1)–Cl(2)
Pt(1)–P(1)
Pt(1)–S(13)
P(1)–N(1)
N(1)–C(14)
N(1)–C(13)
C(13)–S(13)
C(13)–N(2)
N(2)–C(15)
2.324(4)
2.387(3)
2.188(3)
2.256(4)
1.739(10)
1.49(2)
1.34(2)
1.737(13)
1.34(2)
Cl(1)–Pt(1)–Cl(2)
P(1)–Pt(1)–S(13)
Pt(1)–P(1)–N(1)
P(1)–N(1)–C(13)
P(1)–N(1)–C(14)
N(1)–C(13)–S(13)
C(13)–S(13)–Pt(1)
C(13)–N(1)–C(14)
N(2)–C(13)–S(13)
C(15)–N(2)–C(13)
91.10(14)
88.02(13)
106.8(4)
118.7(8)
120.7(9)
121.7(10)
104.0(5)
120.2(11)
119.3(10)
123.4(14)
9 A. M. Z. Slawin, M. Wainwright and J. D. Woollins, New J. Chem.,
2000, 24, 69.
1.49(2)
10 A. M. Z. Slawin, J. D. Woollins and Q. Zhang, J. Chem. Soc., Dalton
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11 SHELXTL, Bruker AXS, Madison, WI, 1999.
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expected parent-ion peak but did show a peak corresponding to
17 with the loss of a chloride ion (m/z 519 [M Ϫ Cl]ϩ). The solid
state structure of 17ؒdmsoؒCHCl3 (Fig. 5, Table 8) is a rare
example of a fully characterised five-membered ‘true’ hetero-
cycle (i.e. a heterocycle in which every ring atom is different),
though there is a report of a related PtSNCP heterocycle.26,27
The X-ray structure of 17 reveals square planar coordination
of the platinum with the five-membered PtPNCS ring
being almost perfectly planar [maximum deviation from the
PtPNCSCl2 plane is 0.11 Å for S(13), with N(2), C(14) and
C(15) lying 0.05, 0.18 and Ϫ0.06 Å from this plane]. The bond
lengths and angles within 17 are in the expected range. The
Pt–Cl distances vary as a function of the trans element, within
the five-membered PtPNCS heterocycle the P–N and C–N
bonds are effectively single bonds whilst C(13)–S(13) is slightly
22 N. W. Alcock, P. Bergamini, T. M. Gomes-Carniero, R. D. Jackson,
J. Nicholls, A. G. Orpen, P. G. Pringle, S. Sostero and O. Traverso,
J. Chem. Soc., Chem. Commun., 1990, 980.
longer than a formal C᎐S double bond.
᎐
23 T. Q. Ly, A. M. Z. Slawin and J. D. Woollins, J. Chem. Soc., Dalton
Trans., 1997, 1611.
Conclusion
24 S. M. Aucott, PhD Thesis, Loughborough University, 1999.
25 M. Gruber and R. Schmutzler, Phosphorus, Sulfur Silicon Relat.
Elem., 1993, 80, 195.
26 N. Burford, S. Mason, R. E. Spence, J. M. Whelan, J. F. Richardson
and R. Rogers, Organometallics, 1992, 11, 2241.
27 S. Okaya, H. Shimomura and Y. Kushi, Chem. Lett., 1992, 2019.
Ligands of the type {Ph PN(R)} C᎐E (where R = Me or Et and
E = O or S) can be readily synthesised via reactions of dialkyl-
ureas or thioureas with chlorodiphenylphosphine. Reactions of
᎐
2
2
the compounds [Ph PN(Me)] C᎐O and [Ph PN(Et)] C᎐O with
᎐
᎐
2
2
2
2
Pt(), Pd(), Mo(0) and Rh(), results in the ligands acting as
2730
J. Chem. Soc., Dalton Trans., 2001, 2724–2730