The preparation and coordination chemistry of phosphorus(III) derivatives of piperazine and homopiperazine

Article abstract of DOI:10.1016/S0277-5387(02)01007-0

Reaction of piperazine or homopiperazine with R₂PCl [R₂ = Ph₂, OC₂H₄O, OC₆H₄O] gives six new bidentate phosphines. Simple bis-chelate and bridging complexes with demonstrative Mo(0), Pd(II), Pt(II) and Ru(II) centres are reported. The crystal structures of Ph₂P(O)N(C₂H₄)₂P(O) Ph₂, cis-[PdCl₂{Ph₂PN(C₂ H₄)₂NPPh₂}] (7) and cis-[PtCl₂{Ph₂PN(C₅H₁₀) NPPh₂}][PtcodCl₂]₂ (15) are reported. In Ph₂P(O)N(C₂H₄)₂P(O)Ph₂ the central N₂C₄ ring has a chair conformation and the P=O groups are trans. In 7 the piperazine backbone results in P-Pd-P bite angle of approximately 95° whilst in 15 the homopiperazine backbone enlarges the bite angle to 97°.

Full text of DOI:10.1016/S0277-5387(02)01007-0

Polyhedron 21 (2002) 1729ꢁ1736
/
www.elsevier.com/locate/poly
The preparation and coordination chemistry of phosphorus(III)
derivatives of piperazine and homopiperazine
M. Rodriguez i Zubiri, Alexandra M.Z. Slawin, Matthew Wainwright,
J. Derek Woollins
Department of Chemistry, University of St. Andrews, St. Andrews, Fife KY16 9ST, UK
Received 8 January 2002; accepted 11 March 2002
Abstract
Reaction of piperazine or homopiperazine with R2PCl [R2ꢀ
bis-chelate and bridging complexes with demonstrative Mo(0), Pd(II), Pt(II) and Ru(II) centres are reported. The crystal structures
/
Ph2, OC2H4O, OC6H4O] gives six new bidentate phosphines. Simple
of Ph2P(O)N(C2H4)2P(O)Ph2, cis-[PdCl2{Ph2PN(C2H4)2NPPh2}] (7) and cis-[PtCl2{Ph2PN(C5H10)NPPh2}][PtcodCl2]2 (15) are
O groups are trans. In 7 the
reported. In Ph2P(O)N(C2H4)2P(O)Ph2 the central N2C4 ring has a chair conformation and the PÄ
/
piperazine backbone results in PÃ
/
PdÃ
/
P bite angle of approximately 958 whilst in 15 the homopiperazine backbone enlarges the bite
angle to 978. # 2002 Elsevier Science Ltd. All rights reserved.
Keywords: Coordination chemistry; Crystal structures; Piperazine; Homopiperazine
1. Introduction
and bite angle control by forming umbrella-like ligands
around a metal centre. Here we report on the synthesis
of diphosphine derivatives of piperazine and homopi-
perazine and their reactions with different metal com-
pounds.
We have recently reported a number of syntheses of
new monodentate and bidentate P(III) and P(V) ligands
via simple PÃ
/
N bond forming reactions [1ꢁ5]. Apart
/
from systems with totally non-carbon backbones we
have been able to synthesise the first six-membered true
heterocycles [6] and we have developed some very
2. Experimental
electron rich [7,8] hemilabile [9ꢁ11] and chiral ligands
/
[12,13] by this approach. One of the important roles
occupied by ligands in catalytic metal complexes is to
offer steric protection to the catalytically active site. In
polymerisation catalysts for example, this requirement
may be achieved by incorporating bulky substituent
groups into the ligand which hinder the approach of the
reactants and ‘steer’ them towards the reacting polymer
chain [14]. With this in mind, we have studied the
reactions of the cyclic amine compounds piperazine and
homopiperazine with different chlorophosphines to
ascertain the possibility of synthesising diphosphine
chelates, which would offer significant steric hindrance
General experimental conditions and instrumentation
were as set out in Section 2.28 and as described
previously [13]. [{RuCl(m-Cl)(h6-p-MeC6H4i Pr)}2][15]
was prepared using the literature procedure and piper-
azine, homopiperazine, 1,2-phenylenephosphoro-chlor-
idite and 2-chloro-1,3,2-dioxaphospholane were used
without further purification.
2.1. Ph2PN(C2H4)2NPPh2 (1)
A solution of chlorodiphenylphosphine (5.1 g, 4.2
cm3, 24.0 mmol) in thf (20.0 cm3) was added dropwise
over a period of 30 min to a stirred solution of
piperazine (1.00 g, 12.0 mmol) and triethylamine (2.40
g, 3.3 cm3, 24.0 mmol) in thf (30 cm3) at room
temperature (r.t.). Stirring was continued for 24 h,
* Corresponding author. Tel.: ꢂ
463384
E-mail address: jdw3@st-and.ac.uk (J.D. Woollins).
/
44-1334-463861; fax: ꢂ44-1334-
/
0277-5387/02/$ - see front matter # 2002 Elsevier Science Ltd. All rights reserved.
PII: S 0 2 7 7 - 5 3 8 7 ( 0 2 ) 0 1 0 0 7 - 0

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M. Rodriguez i Zubiri et al. / Polyhedron 21 (2002) 1729ꢁ1736
/
during which time triethylammonium hydrochloride
separated from the colourless solution. This precipitate
was removed by suction filtration and the filtrate
evaporated to dryness in vacuo to give a white solid
product. Yield: 3.92 g, 75%.
2.6. cis-[PtMe2{(C6H4O2)PN(C2H4)2NP(C6H4O2)}]
(6)
To a solution of [PtMe2(cod)] (0.080 g, 0.24 mmol) in
dichloromethane (10.0 cm3) was added solid
(C6H4O2)PN(C2H4)2NP(C6H4O2) (0.087 g, 0.24 mmol)
and the colourless solution stirred for approximately 2
h. The solution was concentrated under reduced pres-
sure to approximately 1.0 cm3 and diethyl ether (40.0
cm3) added. The white product was collected by suction
filtration. Yield: 0.089 g, 63%.
2.2. (C6H4O2)PN(C2H4)2NP(C6H4O2) (2)
A
solution of 1,2-phenylenephosphoro-chloridite
(4.65 g, 16.7 mmol) in thf (60.0 cm3) was added dropwise
over a period of 1 h to a stirred solution of piperazine
(0.72 g, 8.3 mmol) and triethylamine (1.69 g, 2.3 cm3,
16.7 mmol) in thf (70.0 cm3). Stirring was continued for
a further 2 h, during which time triethylammonium
hydrochloride separated from the colourless solution.
This precipitate was removed by suction filtration and
the filtrate evaporated to dryness in vacuo to give a
white solid product. Yield: 2.15 g, 71%.
2.7. cis-[PdCl2{Ph2PN(C2H4)2NPPh2}] (7)
To a solution of [PdCl2(cod)] (0.100 g, 0.35 mmol) in
dichloromethane (5.0 cm3) was added solid
Ph2PN(C2H4)2NPPh2 (0.160 g, 0.35 mmol) and the
yellow solution stirred for approximately 2 h. The
solution was concentrated under reduced pressure to
approximately 1.0 cm3 and diethyl ether (10.0 cm3)
added. The yellow product was collected by suction
filtration. Yield: 0.137 g, 62%.
2.3. (C2H4O2)PN(C2H4)2NP(C2H4O2) (3)
A solution of 2-chloro-1,3,2-dioxaphospholane (5.69
g, 4.0 cm3, 45.0 mmol) in thf (70.0 cm3) was added
dropwise over a period of 1 h to a stirred solution of
piperazine (1.93 g, 22.5 mmol) and triethylamine (4.54 g,
6.2 cm3, 45.0 mmol) in thf (80.0 cm3). Stirring was
continued for a further 2 h, during which time triethy-
lammonium hydrochloride separated from the colour-
less solution. This precipitate was removed by suction
filtration and the filtrate evaporated to dryness in vacuo
to give a white solid product. Yield: 4.31 g, 72%.
2.8. cis-[Mo(CO)4{Ph2PN(C2H4)2NPPh2}] (8)
To a partially dissolved solution of [Mo(CO)4(pip)2]
(0.500 g, 1.30 mmol) in dichloromethane (20.0 cm3) was
added solid Ph2PN(C2H4)2NPPh2 (0.590 g, 1.30 mmol).
The solution was heated to reflux for approximately 15
min and allowed to cool to r.t. The solution was
concentrated under reduced pressure to approximately
2.0 cm3 and methanol (15.0 cm3) added. The yellow
product was collected by suction filtration. Yield: 0.635
g, 72%.
2.4. cis-[PtCl2{Ph2PN(C2H4)2NPPh2}] (4)
To a solution of [PtCl2(cod)] (0.100 g, 0.26 mmol) in
dichloromethane (5.0 cm3) was added solid
Ph2PN(C2H4)2NPPh2 (0.120 g, 0.26 mmol) and the
colourless solution stirred for approximately 2 h. The
solution was concentrated under reduced pressure to
approximately 1.0 cm3 and diethyl ether (10.0 cm3)
added. The white product was collected by suction
filtration. Yield: 0.152 g, 79%.
2.9. [Ph2P(AuCl)N(C2H4)2NP(AuCl)Ph2] (9)
To a solution of [AuCl(tht)] (0.071 g, 0.22 mmol) in
dichloromethane (5.0 cm3) was added solid
Ph2PN(C2H4)2NPPh2 (0.050 g, 0.11 mmol) and the
colourless solution stirred for approximately 1 h. The
solution was concentrated under reduced pressure to
approximately 1.0 cm3 and diethyl ether (5.0 cm3)
added. The white product was collected by suction
filtration. Yield: 0.054 g, 53%.
2.5. cis-[PtCl2{(C6H4O2)PN(C2H4)2NP(C6H4O2)}]
(5)
2.10. [(C6H4O2)P(AuCl)N(C2H4)2-
NP(AuCl)(C6H4O2)] (10)
To a solution of [PtCl2(cod)] (0.100 g, 0.26 mmol) in
dichloromethane (15.0 cm3) was added solid
(C6H4O2)PN(C2H4)2NP(C6H4O2) (0.097 g, 0.26 mmol)
and the colourless solution stirred for approximately 2
h. The solution was concentrated under reduced pres-
sure to approximately 1.0 cm3 and diethyl ether (15.0
cm3) added. The white product was collected by suction
filtration. Yield: 0.150 g, 89%.
To a solution of [AuCl(tht)] (0.184 g, 0.58 mmol) in
dichloromethane (15.0 cm3) was added solid
(C6H4O2)PN(C2H4)2NP(C6H4O2) (0.104 g, 0.29 mmol)
and the colourless solution stirred for approximately 1
h. The solution was concentrated under reduced pres-
sure to approximately 1.0 cm3 and diethyl ether (30.0

M. Rodriguez i Zubiri et al. / Polyhedron 21 (2002) 1729ꢁ
/1736
1731
cm3) added. The white product was collected by suction
filtration. Yield: 0.205 g, 86%.
solution was concentrated under reduced pressure to
approximately 1.0 cm3 and diethyl ether (40.0 cm3)
added. The white product was collected by suction
filtration. Yield: 0.180 g, 92%.
2.11. [(C2H4O2)P(AuCl)N(C2H4)2-
NP(AuCl)(C2H4O2)] (11)
2.16. cis-[PtMe2{Ph2PN(C5H10)NPPh2}] (16)
To a solution of [AuCl(tht)] (0.160 g, 0.50 mmol) in
dichloromethane (15.0 cm3) was added solid
(C2H4O2)PN(C2H4)2NP(C2H4O2) (0.068 g, 0.25 mmol)
and the colourless solution stirred for approximately 2
h. The solution was concentrated under reduced pres-
sure to approximately 1.0 cm3 and diethyl ether (30.0
cm3) added. The white product was collected by suction
filtration. Yield: 0.140 g, 76%.
To a solution of [PtMe2(cod)] (0.100 g, 0.30 mmol) in
dichloromethane (10.0 cm3) was added solid
Ph2PN(C5H10)NPPh2 (0.140 g, 0.30 mmol) and the
colourless solution stirred for approximately 2 h. The
solution was concentrated under reduced pressure to
approximately 1.0 cm3 and diethyl ether (30.0 cm3)
added. The white product was collected by suction
filtration. Yield: 0.130 g, 64%.
2.12. [{RuCl2(h6-p-
MeC6Hi4Pr)}2{Ph2PN(C2H4)2NPPh2}] (12)
2.17. cis-[PdCl2{Ph2PN(C5H10)NPPh2}] (17)
To a solution of [{RuCl(m-Cl)(h6-p-MeC6H4i Pr)}2]
(0.250 g, 0.40 mmol) in thf (20.0 cm3) was added solid
Ph2PN(C2H4)2NPPh2 (0.185 g, 0.40 mmol) and the
brown solution stirred for approximately 12 h. The
solution was concentrated under reduced pressure to
approximately 2.0 cm3 and diethyl ether (10.0 cm3)
To a solution of [PdCl2(cod)] (0.152 g, 0.53 mmol) in
dichloromethane (20.0 cm3) was added solid
Ph2PN(C5H10)NPPh2 (0.250 g, 0.53 mmol) and the
yellow solution stirred for approximately 2 h. The
solution was concentrated under reduced pressure to
approximately 1.0 cm3 and diethyl ether (40.0 cm3)
added. The yellow product was collected by suction
filtration. Yield: 0.300 g, 87%.
added. The redꢁ
/
brown product was collected by suction
10.0 cm3).
filtration and washed with diethyl ether (2ꢃ
/
Yield: 0.299 g, 69%.
2.18. [Ph2P(AuCl)N(C5H10)NP(AuCl)Ph2] (18)
2.13. Ph2PN(C5H10)NPPh2 (13)
To a solution of [AuCl(tht)] (0.192 g, 0.60 mmol) in
dichloromethane (15.0 cm3) was added solid
Ph2PN(C5H10)NPPh2 (0.140 g, 0.30 mmol) and the
colourless solution stirred for approximately 1 h. The
solution was concentrated under reduced pressure to
approximately 1.0 cm3 and diethyl ether (35.0 cm3)
added. The white product was collected by suction
filtration. Yield: 0.214 g, 76%.
A solution of chlorodiphenylphosphine (6.87 g, 5.6
cm3, 31.2 mmol) in thf (50.0 cm3) was added dropwise
over a period of 1 h to a stirred solution of homopiper-
azine (1.56 g, 15.6 mmol) and triethylamine (3.13 g, 4.3
cm3, 31.3 mmol) in thf (75 cm3) at r.t. Stirring was
continued for 2 h, during which time triethylammonium
hydrochloride separated from the colourless solution.
This precipitate was removed by suction filtration and
the filtrate evaporated to dryness in vacuo to give a
white solid product. Yield: 4.92 g, 68%.
2.19. (C6H4O2)PN(C5H10)NP(C6H4O2) (19)
A
solution of 1,2-phenylenephosphoro-chloridite
2.14. [Ph2P{Se}N(C5H10)N{Se}PPh2}] (14)
(4.65 g, 16.7 mmol) in thf (55.0 cm3) was added dropwise
over a period of 1 h to a stirred solution of homopiper-
azine (0.84 g, 8.3 mmol) and triethylamine (1.69 g, 2.3
cm3, 16.7 mmol) in thf (85.0 cm3). Stirring was
continued for a further 2 h, during which time triethy-
lammonium hydrochloride separated from the colour-
less solution. This precipitate was removed by suction
filtration and the filtrate evaporated to dryness in vacuo
to give a white solid product. Yield: 2.58 g, 82%.
To a toluene (20 ml) solution of selenium (0.075 g,
0.904 mmol) was added Ph2P{Se}N(C5H10)N{Se}PPh2
(0.207 g, 0.281 mmol). The reaction was stirred and
heated to reflux for 2ꢁ3 h. The product was collected by
/
suction filtration under nitrogen atmosphere and an off-
white product was isolated. Yield: 0.123 g, 70%.
2.15. cis-[PtCl2{Ph2PN(C5H10)NPPh2}] (15)
2.20. cis-[PtCl2{(C6H4O2)PN(C5H10)NP(C6H4O2)}]
(20)
To a solution of [PtCl2(cod)] (0.100 g, 0.26 mmol) in
dichloromethane (10.0 cm3) was added solid
Ph2PN(C5H10)NPPh2 (0.125 g, 0.26 mmol) and the
colourless solution stirred for approximately 2 h. The
To a solution of [PtCl2(cod)] (0.179 g, 0.48 mmol) in
dichloromethane (15.0 cm3) was added solid

1732
M. Rodriguez i Zubiri et al. / Polyhedron 21 (2002) 1729ꢁ1736
/
i
(C6H4O2)PN(C2H4)2NP(C6H4O2) (0.180 g, 0.48 mmol)
and the colourless solution stirred for approximately 2
h. The solution was concentrated under reduced pres-
sure to approximately 1.0 cm3 and diethyl ether (30.0
cm3) added. The white product was collected by suction
filtration. Yield: 0.104 g, 84%.
2.25. Pr2PN(C5H10)NPiPr2 (25)
A solution of diisopropylphosphinechloride (1.61 ml,
0.01 g, 10.0 mmol) in thf (20 cm3) was added dropwise
to a stirred solution of homopiperazine (0.49 g, 4.89
mmol) and degassed Et3N (1.40 ml, 0.01 g, 10.0 mmol)
in thf (20 cm3) at r.t. The reaction mixture was stirred
for a further 2 h, during which time triethylammonium
hydrochloride separated from the colourless solution.
This precipitate was removed by suction filtration and
the filtrate evaporated to dryness in vacuo to give an oily
colourless product.
2.21. cis-[PtMe2{(C6H4O2)PN(C5H10)-
NP(C6H4O2)}] (21)
To a solution of [PtMe2(cod)] (0.100 g, 0.30 mmol) in
dichloromethane (10.0 cm3) was added solid (C6H4O2)-
PN(C2H4)2NP(C6H4O2) (0.114 g, 0.30 mmol) and the
colourless solution stirred for approximately 2 h. The
solution was concentrated under reduced pressure to
approximately 1.0 cm3 and diethyl ether (35.0 cm3)
added. The white product was collected by suction
filtration. Yield: 0.120 g, 66%.
2.26. [iPr2P{Se}N(C5H10)N{Se}PiPr2}] (26)
To a toluene (10 ml) solution of selenium (0.105 g,
1.330 mmol) was added solid ligand L3 (0.212 g, 0.638
mmol). The reaction was stirred and heated to reflux for
2ꢁ3 h under reflux. The product was collected by
suction filtration under nitrogen atmosphere and an
off-white product was isolated. Yield: 0.146 g, 47%.
/
2.22. cis-[PdCl2{(C6H4O2)PN(C5H10)-
NP(C6H4O2)}] (22)
To a solution of [PdCl2(cod)] (0.285 g, 1.00 mmol) in
dichloromethane (25.0 cm3) was added solid (C6H4O2)-
PN(C5H10)NP(C6H4O2) (0.378 g, 1.0 mmol) and the
yellow solution stirred for approximately 2 h. The
solution was concentrated under reduced pressure to
approximately 1.0 cm3 and diethyl ether (30.0 cm3)
added. The yellow product was collected by suction
filtration. Yield: 0.520 g, 94%.
2.27. cis-[PtCl2{iPr2PN(C5H10)NPiPr2}] (27)
To a solution of [PtCl2(cod)] (0.202 g, 0.541 mmol) in
dichloromethane (10 ml) was added solid ligand L3
(0.180 g, 0.541 mmol). The mixture reaction was stirred
for 2 h then diethyl ether (5 ml) was added to solubilise
the cod moiety whilst the complex is insoluble and was
precipitated as a white solid. After 15 min in the
ultrasonic bath, the sample was filtered, the white solid
was washed with diethyl ether. Yield: 0.324 g, 50%.
2.23. [(C6H4O2)P(AuCl)N(C5H10)-
NP(AuCl)(C6H4O2)] (23)
To a solution of [AuCl(tht)] (0.140 g, 0.44 mmol) in
dichloromethane (15.0 cm3) was added solid (C6H4O2)-
PN(C5H10)NP(C6H4O2) (0.083 g, 0.22 mmol) and the
colourless solution stirred for approximately 1 h. The
solution was concentrated under reduced pressure to
approximately 1.0 cm3 and diethyl ether (30.0 cm3)
added. The white product was collected by suction
filtration. Yield: 0.150 g, 81%.
2.28. Crystallography
Crystallography was performed using a Bruker
SMART diffractometer; full hemisphere of data with
0.38 ‘slices’, r.t., Mo Ka radiation and empirical
absorption corrections. All of the other non-H atoms
were refined anisotropically with the hydrogen atoms
being refined in idealised geometries. All calculations
employed the SHELXTL program system [16].
2.24. (C2H4O2)PN(C5H10)NP(C2H4O2) (24)
Compound 7: C28H28Cl2N2P2Pd Mꢀ
/
631.8, mono-
27.882(3),
5575 A , Zꢀ8 (two
1.51 g cmꢄ3, F(000)ꢀ
1.62 mmꢄ1. Of 24 012 measured
data, 7949 were unique and observed [I ꢀ2.0s(I)] to
give Rꢀ0.080 and wR2ꢀ0.1421.
Compound 15: C47H58Cl10N2P2Pt3 Mꢀ
orthorhombic, space group Pca2(1), aꢀ16.556(1), bꢀ
5383 A , Zꢀ4, Dcalc
3152, m(Mo Ka)ꢀ
8.37 mmꢄ1
Of 21 988 measured data 7523 were unique and observed
[I ꢀ2.0s(I)] to give Rꢀ0.0291 and wR2ꢀ0.0712. The
clinic, space group P21/n, aꢀ11.223(1), bꢀ
/
/
3
˚
˚
A solution of 2-chloro-1,3,2-dioxaphospholane (5.69
g, 4.0 cm3, 45.0 mmol) in thf (55.0 cm3) was added
dropwise over a period of 1 h to a stirred solution of
homopiperazine (2.25 g, 22.5 mmol) and triethylamine
(4.54 g, 6.2 cm3, 45.0 mmol) in thf (100.0 cm3). Stirring
was continued for a further 2 h, during which time
triethylammonium hydrochloride separated from the
colourless solution. This precipitate was removed by
suction filtration and the filtrate evaporated to dryness
in vacuo to give a white solid product. Yield: 4.91 g,
78%.
cꢀ
independent molecules), Dcalc
2560, m(Mo Ka)ꢀ
/
17.936(2) A. bꢀ
/
96.646(3)8 Uꢀ
/
/
ꢀ
/
/
/
/
/
/
/
1652.7,
/
/
3
˚
9.814(1), cꢀ
/
33.1291(1). Uꢀ
/
/
ꢀ
/
2.04 g cmꢄ3, F(000)ꢀ
/
/
.
/
/
/

M. Rodriguez i Zubiri et al. / Polyhedron 21 (2002) 1729ꢁ
/1736
1733
H atoms on one of the solvent molecules was not
included in the refinement.
Ph2(O)PNC4H8NP(O)Ph2×
504.5, monoclinic, space group P21/n, aꢀ
/
H2O: C28H30N2O3P2 Mꢀ
/
/
9.736(1), bꢀ
/
3
˚
˚
12.868(3), cꢀ
/
10.940(2) A. bꢀ
/
111.89(1)8 Uꢀ
/1272 A ,
Zꢀ2, Dcalc
/
ꢀ
/
1.32 g cmꢄ3, F(000)ꢀ
/
532, m(Mo Ka)ꢀ
/
0.204 mmꢄ1 (there was considerable decomposition
during data collection and no absorption correction
was applied). Of 2560 measured data 1414 were unique
and observed [I ꢀ
/
2.0s(I)] to give Rꢀ0.0376 and
/
wR2ꢀ0.0858.
/
Fig. 1. Solid state structure of Ph2P(O)N(C2H4)NP(O)Ph2.
3. Results and discussion
with selected bond lengths and angles in Table 2. The
piperazine ring adopts a chair conformation with the PÄ
O groups being on opposite sides of the molecule.
Reaction of 1 and 2 with equimolar quantities of
[PtCl2(cod)] in dichloromethane (Eq. (2)) to yield the
seven-membered, P,P? chelates 4 and 5.
/
Reaction of piperazine with 2 equiv. of the chloropho-
sphines Ph2PCl, R2ꢀPh2 (1), C6H4O2 (2) and OC2H4O
(3)
/
ð1Þ
(C6H4O2)PCl and (C2H4O2)PCl, in the presence of
NEt3, proceeds in thf to give 1, 2 and 3 respectively (Eq.
(1)).
ð2Þ
The 31P {1H} NMR spectra of both compounds are
singlets with satellites from coupling to 195Pt, the nature
of the substituent groups on the phosphorus being
reflected in the positions of the chemical shifts (d(P)
53.5 and 99.6 ppm, respectively) and the magnitude of
Addition of the chlorophosphine in thf to a solution
of piperazine in thf, at r.t., results in the immediate
precipitation of [Et3NH]Cl as the reaction proceeds.
Removal of the ammonium salt by filtration, reduction
of the volume of thf in vacuo and addition of diethyl
the 1J(195PtÃ
/
31P) coupling constants (3972 and 5480 Hz,
ether gives the new species in 70ꢁ
80% yield. The 31P
/
respectively) which are in accord with values previously
reported for similarly substituted phosphines when trans
to a chloride in a Pt(II) complex 2 [5,17,18] also reacts
with [PtMe2(cod)], in dichloromethane, to produce the
{1H} NMR spectrum of 1 comprises a singlet at d(P)
62.9. The possibility of this peak representing the mono-
substituted amine was rejected after performing in situ
31P NMR studies. Monitoring of the reaction mixture at
regular intervals, immediately after completion of the
chlorodiphenylphosphine addition, shows a phospho-
rus-containing species, with a chemical shift of d(P)
35.1, to be the initial reaction product. This is assumed
to be the mono-substituted amine and gradually de-
creases in intensity as the reaction proceeds, to leave 1 as
the only phosphorus containing compound. The 31P
{1H} NMR spectrum of 2 and 3 are singlets at d(P)
144.2 and 137.9 ppm respectively; the large downfield
shift when compared with 1 reflecting the close proxi-
mity of the phosphorus centre to the strongly electro-
negative oxygen atoms. Although stable for short
P,P? chelate
(C6H4O2)}] (6).
cis-[PtMe2{(C6H4O2)PN(C2H4)2NP-
periods in the solid state in solution 1ꢁ3 oxidise readily
/
in solution in air. Crystals of 1O2 were obtained from a
CH2Cl2 solution of 1 and the structure is shown in Fig. 1
Fig. 2. Solid state structure of cis-[PdCl2{Ph2PN(C2H4)2NPPh2}] (7).

1734
M. Rodriguez i Zubiri et al. / Polyhedron 21 (2002) 1729ꢁ1736
/
Table 1
Elemental analysis and selected spectroscopic data
Formula
d
31P (ppm)/1J(PtÃP)
m/e
n(CN) n(PN)
C
H
N
(Hz)
1
2
3
4
5
6
7
8
9
Ph2PN(C2H4)2NPPh2
62.9
144.2
137.9
455
1478
1479
1438
1435
1477
1480
1435
1435
1434
1445
1445
1432
930
918
952
960
966
966
959
959
966
966
967
953
73.8(74.0) 6.2(6.2)
53.2(53.0) 4.3(4.4)
35.6(36.1) 6.2(6.0)
46.9(46.7) 3.7(3.9)
30.4(30.6) 2.8(2.6)
36.3(36.8) 3.9(3.8)
52.9(53.3) 4.5(4.5)
57.6(58.0) 3.9(4.3)
36.4(36.6) 2.8(3.1)
23.2(23.2) 1.9(1.9)
13.3(13.1) 2.2(2.2)
54.1(54.0) 5.3(5.3)
5.5(6.2)
(C6H4O2)PN(C2H4)2NP(C6H4O2)
(C2H4O2)PN(C2H4)2NP(C2H4O2)
cis-[PtCl2{Ph2PN(C2H4)2NPPh2]
cis-[PtCl2{(C6H4O2)2PN(C2H4)2NP(C6H4O2)2}]
cis-[PtMe2{(C6H4O2)2PN(C2H4)2NP(C6H4O2)2}]
cis-[PdCl2{Ph2PN(C2H4)2NPPh2}]
362
266
7.3(7.7)
9.9(10.5)
3.2(3.9)
4.3(4.5)
4.6(4.8)
4.3(4.4)
3.8(4.2)
2.4(3.1)
3.3(3.4)
3.8(3.8)
2.2(2.6)
53.5/3972
99.6/5480
154.9/2977
101.7
720
597[-Cl]
587
632
a
cis-[Mo(CO)4{Ph2PN(C2H4)2NPPh2}]
[Ph2P{AuCl}N(C2H4)2NP{AuCl}Ph2]
97.2
80.7
634
883[ÃCl]
827
10 [(C6H4O2)2P{AuCl}N(C2H4)2NP{AuCl}(C6H4O2)2] 136.4
11 [(C2H4O2)2P{AuCl}N(C2H4)2NP{AuCl}(C2H4O2)2] 131.7
695[ÃCl]
1066
12 [{RuCl2(h6-p-Me-
69.8
C6Hi4Pr)}2{Ph2PN(C2H4)2NPPh2}]
13 Ph2PN(C5H10)NPPh2
14 Ph2P(Se)N(C5H10)NP(Se)Ph2
65.7
468
629
734
1431
1455
1436
921
912
936
925
953
903
916
951
919
916
908
931
919
912
900
74.4(74.3) 6.1(6.4)
55.9(55.6) 4.7(4.8)
47.4(47.5) 3.9(4.1)
53.1(53.6) 4.9(5.2)
54.3(54.0) 4.8(4.7)
37.6(37.4) 3.2(3.2)
53.8(54.3) 4.3(4.8)
31.5(31.8) 2.9(2.8)
37.6(37.9) 3.9(4.0)
36.9(36.8) 3.6(3.3)
23.8(24.3) 2.1(2.1)
5.8(5.9)
4.3(4.5)
3.4(3.8)
3.8(4.0)
4.2(4.4)
2.7(3.0)
6.9(7.4)
3.9(4.4)
4.5(4.7)
4.6(5.0)
3.2(3.3)
71.9/753
64.1/4092
89.1/2231
92.6
15 [PtCl2{Ph2PN(C5H10)NPPh2}]
16 [PtMe2{Ph2PN(C5H10)NPPh2}]
17 [PdCl2{Ph2PN(C5H10)NPPh2}]
18 [Ph2P{AuCl}N(C5H10)NP{AuCl}Ph2]
19 (C6H4O2)PN(C5H10)NP(C6H4O2)
20 [PtCl2{(C6H4O2)PN(C5H10)NP(C6H4O2)}]
21 [PtMe2{(C6H4O2)PN(C5H10)NP(C6H4O2)}]
22 [PdCl2{(C6H4O2)PN(C5H10)NP(C6H4O2)}]
23 [(C6H4O2)P{AuCl}N(C5H10)NP{AuCl}(C6H4O2)]
24 (C2H4O2)PN(C5H10)NP(C2H4O2)
25 iPr2PN(C5H10)NiPPr2
678[ÃCH3] 1435
646
1432
1433
1459
1478
78.7
148.3
897[ÃCl]
376
606[-Cl]
102.3/5466
156.9/2937
125.6
586[ÃCH3] 1480
553
805[ÃCl]
280
1459
1441
1450
139.9
143.8
38.8(38.6) 6.8(6.4) 10.4(10.0)
60.3(61.4) 12.7(11.6) 8.6(8.4)
55.9(55.6) 4.71(4.8) 4.3(4.5)
96.0
101.5/753
87.6/4020
215[ÃPr2P] 1463
629
597
26 iPr2P(Se)N(C5H10)NiP(Se)Pr2
27 cis-PtCl2[(iPr2PN(C5H10)NiPPr2)]
1455
1459
34.7(34.1) 6.9(6.4)
4.6(4.7)
NMR in CDCl3. Microanalyses, calculated values in brackets. FAB MS data; values are for parent ions except where indicated otherwise.
a
n(CO) 2021, 1917, 1901, 1888 cmꢄ1
.
Similarly, the reaction of 1 with an equimolar
quantity of [PdCl2(cod)] in thf results in the bidentate,
P,P? chelate complex cis-[PdCl2{Ph2PN(C2H4)2NPPh2]
(7). The X-ray structure of 7 contains two crystal-
lographically independent molecules and shows the
product to have the expected square-planar geometry
about the Pd centre (Table 2, Fig. 2). The bidentate
nature of the co-ordination to the metal results in the
adopts a boat conformation and forms an ‘umbrella-
like’ structure around the Pd centre. The structure also
reveals that the square-planar palladium centre is some-
Table 3
Selected comparative bond lengths (A) and angles (o) in
˚
{[Pt(cod)Cl2]2×[PtCl2{Ph2PN(C5H10)NPPh2}]},
(C2H4)2NPPh2}] (7) and cis-[PtCl2{Ph2PN(C5H10)NPPh2}] (15)
[PdCl2{Ph2PN-
formation of two seven-membered PdÃ
/
PÃ
/
NÃ
/
CÃ
/
CÃ
/
NÃ
/
Bond
[PdCl2{Ph2PN-
(C2H4)2NPPh2}] (7)
cis-[PtCl2{Ph2PN-
(C5H10)NPPh2}] (15)
P ring systems The N(C2H4)2N backbone of the ligand
Bond lengths
M(1)ÃP(1)
M(1)ÃP(4)
M(1)ÃCl(1)
M(1)ÃCl(2)
P(1)ÃN(1)
P(4)ÃN(4)
Table 2
Selected comparative bond lengths (A) and angles (o) in
2.246(5) [2.265(5)]
2.256 (5) [2.246(5)]
2.391 (4) [2.363(4)]
2.381 (5) [2.388(5)]
1.697 (13) [1.680(12)]
1.666 (13) [1.704(14)]
2.255(6)
2.215(6)
2.358(7)
2.388(5)
1.70(2)
˚
Ph2P(O)N(C2H4N)P(O)Ph2 and Pr2P(Se)N(C5H10)NP(Se)iPr2
i
Ph2P(O)N-
(C2H4N)P(O)Ph2
iPr2P(Se)N-
(C5H10)NP(Se)iPr2
1.64(2)
Bond lengths
P(1)ÃE(1)
P(4)ÃE(4)
P(1)ÃN(1)
P(4)ÃN(4)
Bond angles
1.475(2)
1.646(3)
2.115(5)
2.118(5)
1.655(13)
1.688(14)
P(1)ÃM(1)ÃP(4)
Cl(1)ÃM(1)ÃCl(2)
M(1)ÃP(1)ÃN(1)
M(1)ÃP(4)ÃN(2)
93.9(2) [94.7(2)]
92.1(2) [91.9(2)]
120.1(5) [121.8(6)]
123.3(5) [121.2(6)]
97.3(1)
89.1(1)
119.0(8)
125.0(8)
Bond angles
N.B. The values in parentheses are for the second crystallographi-
cally independent molecule.
E(1)ÃP(1)ÃN(1)
E(4)ÃP(4)ÃN(4)
117.4(1)
114.8(5)
111.9(5)

M. Rodriguez i Zubiri et al. / Polyhedron 21 (2002) 1729ꢁ
/1736
1735
what distorted and in both of the two independent
molecules the bite angle of the piperazine is larger than
form seven-membered metallacycles. Reactions with
compounds containing Au(I) and Ru(II) show that 1ꢁ
3 can also act as a bridging ligands between two metal
/
the ideal 908 [94.0 (28) and 94.7 (28)] and the ClÃ
/
PdÃ/Cl
angles are also greater than 908 [92.1 (28) and 92.0 (28)].
The mean deviations of PdP2Cl2 from the plane are 0.14
centres (Eq. (4)).
˚
A for one of the molecules and 0.02 A for the second. In
˚
both molecules the PÃ
/
N, PdÃ
/
P and PÃ/Cl bond lengths
are all typical of single bonds.
ð4Þ
ð3Þ
Analogous ligands to 1ꢁ3 can be synthesised by
reacting the same chlorophosphines with homopiper-
/
The reaction of 1 with [Mo(CO)4(pip)2] in dichlor-
omethane proceeds, with displacement of the piperi-
dines, to give 8 (Eq. (3)). The 31P {1H} NMR spectrum
of 8 displays a singlet at d(P) 97.2, a downfield shift of
around 35 ppm upon complexation whilst its IR
spectrum contains four strong bands due to n(CO)
(2021, 1917, 1901 and 1888 cmꢄ1), confirming the cis
azine which differs from piperazine by containing an
extra CH2 group, therefore, forming a seven-membered
nitrogenꢁcarbon ring system. Reaction of homopiper-
/
azine with 2 equiv. of Ph2PCl, (C6H4O2)PCl and
(C2H4O2)PCl, in the presence of NEt3, proceeds in thf
to give 13, 19 and 24. Reaction of iPr2PCl with
i
homopiperazine yields the analogous Pr derivative 25.
The dP values of all three aryl ligands are slightly
downfield from the values observed for the analogous
structure. Compounds 4ꢁ/8 demonstrate the ability of
Ph2PN(C2H4)2NPPh2 and (C6H4O2)PN(C2H4)2NP-
(C6H4O2) to act as bidentate chelating ligands and
piperazine derivatives, 1ꢁ3, suggesting that the addition
/
Fig. 3. Different ring sizes in complexes containing the homopiperazine based ligands.

1736
M. Rodriguez i Zubiri et al. / Polyhedron 21 (2002) 1729ꢁ1736
/
data centre, CCDC Nos. 176413ꢁ176415. Copies of this
/
information may be obtained free of charge from The
Director CCDC, 12 Union Road, Cambridge, CB2 1EZ,
UK. (fax: ꢂ44-1223-336-033; email: deposit@ccdc.cam.
/
ac.uk or www: http://www.ccdc.cam.ac.uk.
Acknowledgements
We are grateful to the EPSRC for support, to
Johnson Matthey for loans of precious metals and to
the JREI for an equipment grant.
Fig. 4. The structure of [PtCl2{Ph2PN(C5H10)NPPh2}] in the crystal
structure of [Pt(cod)Cl2]2×[PtCl2{Ph2PN(C5H10)NPPh2}].
/
References
of an extra CH2 group into the ligand backbone causes a
slight deshielding of the phosphorus centres. The
homopiperazine derivatives form complexes in an ana-
logous fashion to their piperazine analogues. Spectro-
scopic data for the new compounds are summarised in
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[7] M.L. Clarke, D.J. Cole-Hamilton, A.M.Z. Slawin, J.D. Woollins,
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[10] S.M. Aucott, A.M.Z. Slawin, J.D. Woollins, J. Chem. Soc.,
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PÃ
/
PtÃ
/
P bite angle is expanded to 978 as a consequence
of the homopiperazine backbone.
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1761.
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This work clearly demonstrates the usefulness of
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Trans. (2001) 621.
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Ed. Engl. 38 (1999) 428.
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Synth. 21 (1982) 74.
4. Supplementary material
[16] SHELXTL, Bruker AXS, Madison, WI, 1999.
[17] A. Sen, Acc. Chem. Res. 26 (1993) 303.
[18] V.S. Reddy, K.V. Katti, C.L. Barnes, Chem. Ber. 127 (1994) 1355.
Crystallographic data for the structural analyses has
been deposited with the Cambridge Crystallographic