The preparation and coordination of 1,3-C6H4-{C(O) N(PPh2)CH2Ph}2 - A new multidentate ligand

Article abstract of DOI:10.1016/j.poly.2003.12.005

Reaction of isophthaloyl dichloride with two equivalents of benzylamine in the presence of Et₃N gives N,N′-dibenzyl-1,3-isophthaldiamide which reacts with two equivalents of Ph₂PCl, in the presence of n-BuLi at -78°C to give 1,3-C₆H₄-{C(O)N(PPh ₂)CH₂Ph}₂ (1). Reaction of 1 with [PtCl ₂(cod)] in dichloromethane gives the P,P′,C tridentate bis-chelate [Pt(Cl){1,3-C₆H₄-{C(O)N(PPh ₂)CH₂Ph}₂}] (2), whilst reaction of 1 with two equivalents of [(C₃H₅)PdCl]₂ in thf results in [{PdCl(C₃H₅)}₂ {1,3-C₆H ₄-{C(O)N(PPh₂)CH₂Ph}₂}] (3) in which the ligand bridges two palladium centres. The X-ray structures of 2 and 3 are reported.

Full text of DOI:10.1016/j.poly.2003.12.005

Polyhedron 23 (2004) 865–868
www.elsevier.com/locate/poly
The preparation and coordination of 1,3-C6H4-{C(O)N(PPh2)
CH2Ph}2 – a new multidentate ligand
*
M. Rodriguez i Zubiri, Heather L. Milton, Alexandra M.Z. Slawin, J. Derek Woollins
School of Chemistry, University of St. Andrews, St. Andrews, Fife KY16 9ST, UK
Received 7 October 2003; accepted 8 December 2003
Abstract
Reaction of isophthaloyl dichloride with two equivalents of benzylamine in the presence of Et3N gives N,N0-dibenzyl-1,3-is-
ophthaldiamide which reacts with two equivalents of Ph2PCl, in the presence of n-BuLi at )78 °C to give 1,3-C6H4-
{C(O)N(PPh2)CH2Ph}2 (1). Reaction of 1 with [PtCl2(cod)] in dichloromethane gives the P; P0; C tridentate bis-chelate [Pt(Cl){1,3-
C6H4-{C(O)N(PPh2)CH2Ph}2}] (2), whilst reaction of 1 with two equivalents of [(C3H5)PdCl]2 in thf results in [{PdCl(C3H5)}2
{1,3-C6H4-{C(O)N(PPh2)CH2Ph}2}] (3) in which the ligand bridges two palladium centres. The X-ray structures of 2 and 3 are
reported.
Ó 2003 Elsevier Ltd. All rights reserved.
1. Introduction
bered S; N chelate rings at platinum(II) [17] and are
comparable to [(EPPh2)2N]ꢀ (E ¼ S or Se), which
generates cis-[Pt{(EPPh2)2N-E; E0}(PR3)2]Cl [18,19]. As
part of our continuing studies on phosphine ligands
containing P–N bonds [19–23], here we report a new
ligand derived from isophthaloyl dichloride which was
designed to give six-membered chelate ring systems but
surprisingly forms a tridentate and bidentate bridged
complexes.
Imidodiphosphinate anions [R2P(E)NP(E0)R02]ꢀ (R,
R0 ¼ alkyl, aryl or alkoxy; E, E0 ¼ O, S or Se) have
received substantial attention in recent years, finding
use in applications such as metal extraction agents,
NMR shift reagents and in catalytic functions [1–8].
We are currently investigating the chemistry of struc-
turally similar phosphorus(V) derivatised guanidines
and amidines R2P(E)N@C(X)(NH2) (R ¼ alkyl or aryl;
E ¼ oxygen or sulfur; X ¼ NH2 or alkyl). These mole-
cules, readily available from [R2P(E)(NCN)]ꢀ [9–16],
possess an ionisable nitrogen-bound proton and
have the capacity for delocalisation of the resulting
uninegative charge through the p-system of the
[R2P(E)N@C(X)(NH)]ꢀ anion; hence they could func-
tion as E; N-bidentate ligands in a manner analogous
to imidodiphosphinates. We have previously prepared
cis-[Pt(Ln-S; N)(PR3)2]- Cl(PR3 ¼ PMe2Ph or 1/2 dppe)
from cis-[PtCl2(PR3)2] and the potassium salts of
2. Results and discussion
N,N0-Dibenzyl-1,3-isophthaldiamide was prepared by
reaction of isophthaloyl dichloride with two equivalents
of benzylamine in the presence of Et3N in dichlorome-
thane in the following equation:
ð1Þ
Me2P(S)N@C(NH2)2, or
Ph2P(S)N@C(NH2)2 in which (Ln)ꢀ form six-mem-
Ph2P(S)N@C(Me)(NH2)
Reaction of N,N0-dibenzyl-1,3-isophthaldiamide with
two equivalents of Ph2PCl, in the presence of n-BuLi at
)78 °C, proceeds in thf to give 1 as a pale yellow solid in
76% yield in the following equation:
* Corresponding author. Tel.: +44-1334-463861; fax: +44-1334-
463384.
E-mail address: jdw3@st-andrews.ac.uk (J. Derek Woollins).
0277-5387/$ - see front matter Ó 2003 Elsevier Ltd. All rights reserved.
doi:10.1016/j.poly.2003.12.005

866
M. Rodriguez i Zubiri et al. / Polyhedron 23 (2004) 865–868
ð2Þ
The 31P–{1H} NMR spectrum of 1 consists of a
singlet at d (P) 58.5 ppm, the large downfield shift when
compared to (1,3-bis(diphenylphosphinoacetyl)benzene,
d (P) 27.2 ppm) [24] reflecting the substitution of the
methylene carbon centres in 1,3-bis(diphenylphosphi-
noacetyl)benzene by nitrogen atoms in 1.
FABþ mass spectrometry of 1 shows the expected
parent-ion peaks whilst its IR spectrum contains bands
that can be assigned to m(P–N) and m(C@O) (916 and
1651 cmꢀ1, respectively). Although air- and moisture-
stable for short periods in the solid state, 1 is soluble in
both thf and dichloromethane and in these solutions it
oxidises readily in air.
Fig. 1. Solid state structure of P; P0; C[Pt(Cl){1,3-C6H4-
{C(O)N(PPh2)CH2Ph}2}] (2). Selected bond lengths (A) and angles (°).
ꢀ
Numbers in square brackets are the equivalent parameter for the
second independent molecule. Pt(1)–C(4) 2.02(1) [2.01(1)], Pt(1)–P(1)
2.259(4) [2.261(4)], Pt(1)–P(10) 2.280(4) [2.273(4)], Pt(1)–Cl(1) 2.357(4)
[2.360(4)], P(1)–N(1) 1.73(1) [1.71(1)], N(1)–C(2) 1.37(2) [1.444(18)],
N(10)–C(9) 1.397(16) [1.364(17)]; P(1)–Pt(1)–P(10) 168.52(14)
[168.68(14)], P(1)–Pt(1)–C(4) 84.5(4) [85.8(4)], P(10)–Pt(1)–C(4) 84.3(4)
[83.0(4)], P(1)–Pt(1)–Cl(1) 94.80(13) [94.68(14)], P(10)–Pt(1)–Cl(1)
96.24(14) [96.27(14)].
Reaction of
1
with equimolar quantities of
[PtCl2(cod)] in dichloromethane gives Eq. (3) the P; P0; C
chelate [Pt(Cl){1,3-C6H4-{C(O)N(PPh2)CH2Ph}2}] (2)
as a colourless solid in good yield (85%); apart from the
expected P; P coordination the central aryl group is
metalated by the platinum atom.
ð4Þ
The 31P–{1H} NMR spectrum of 3 shows a singlet at
d (P) 72.5 ppm, a downfield shift of approximately 14
ppm from the free ligand. FABþ mass spectrometry
does not show the expected parent-ion peaks and shows
instead the fragmentation patterns consistent with the
loss of one chloride ion (m=z 1043 [M–Clꢀ]). Elemental
analysis data are in agreement with calculated values
and, once again, the IR spectrum of 3 shows bands
which can be assigned to m(P–N) (915 cmꢀ1), m(C@O)
(1648 cmꢀ1) and m(Pd–Cl) (279 cmꢀ1).
The X-ray structure of 3 (Table 1, Fig. 2) shows that
the ligand bridges the palladium atoms, with the mole-
cule having a somewhat helical nature. The P–N and Pd–
Cl distances are typical of this type of compound. It is
somewhat surprising that the palladium system forms a
binuclear product rather than metallating since generally
palladium is more prone to metallation than platinum.
In a batch test of the rhodium complex (formed in
situ) of 1 as a hydroformylation catalyst for the con-
version of 1-hexene at 20 atm CO/H2 and 100 °C we
obtained poor selectivity to aldehyde (29%) with a linear
to branched ratio of 1.6:1 suggesting that 1 is only an
average ligand for this catalytic process.
ð3Þ
FABþ mass spectrometry shows the expected parent-
ion peak for 2 (m=z 942 [M]). The IR spectrum of 2
shows bands due to m(P–N) (915 cmꢀ1) and m(CO) (1651
cmꢀ1), and a single band characteristic of m(Pt–Cl) (306
cmꢀ1). The 31P–{1H} NMR spectrum of 2 consists of a
singlet (d (P) 67.9 ppm) with satellites from coupling to
195Pt and a [1J{195Pt–31P} 3080 Hz] which is in agree-
ment with the literature data on similar complexes were
the metal center is bound to two phosphorus atoms and
to a carbon atom from the ligand backbone ring [25].
The X-ray structure of 2 (Fig. 1) confirms that the
ligand is bound in a tridentate mode to the platinum.
The ligand contains two fused six-membered Pt–P–N–
C–C–C-C rings and the metal centre adopts square
planar geometry. The square planar geometry of the
platinum centre is distorted, the P–Pt–C angles are
narrower than the ideal 90° and P–Pt–Cl angles are
larger than 90°. The ligand is not planar and the Ph
groups on the phosphorus are on opposite faces of the
coordination plane. The P–N and Pt–Cl distances are
typical of a single bond.
The reaction of
1
with two equivalents of
3. Experimental
[(C3H5)PdCl]2 in thf gives [{PdCl(C3H5)}2{1,3-C6H4-
{C(O)N(PPh2)CH2Ph}2}] (3) in which the ligand
bridges two Pd centres in the following equation:
Unless otherwise stated, manipulations were per-
formed under an oxygen-free nitrogen atmosphere using

M. Rodriguez i Zubiri et al. / Polyhedron 23 (2004) 865–868
867
Table 1
Crystal data and structure refinement details
solution of benzylamine (6.3 ml, 6.20 g, 58.00 mmol)
dropwise over a period of 30 min. The reaction mixture
was stirring for 2 h 30 min, during which time triethy-
lammonium hydrochloride separated from the solution.
This precipitate was removed by suction filtration and
the filtrate was evaporated to dryness in vacuo to give a
white solid product. Recrystallisation from ethanol–
water–acetone gave white crystals. Yield: 8.789 g, 88%;
Microanalysis: Found (Calc.): C, 76.9 (76.7); H, 5.8
2
3
Empirical formula
Formula weight
Crystal system
Space group
C46H37ClN2O2P2Pt C53H50Cl4N2O2P2Pd2
1163.49
triclinic
942.26
triclinic
ꢁ
ꢁ
P1
P1
ꢀ
a (A)
14.854(2)
15.754(2)
18.469(2)
111.581(2)
102.825(2)
94.704(2)
3854.3(8)
4
11.816(2)
12.769(2)
17.579(3)
70.114(3)
83.496(3)
82.846(3)
2467.4(7)
2
ꢀ
b (A)
ꢀ
c (A)
1
a (°)
b (°)
c (°)
(5.9); N, 8.2 (8.1)%; H NMR: d 8.19 ppm (t, 1 H, ar-
omatic, J ¼ 2:74 Hz), 7.91 ppm (dd, 2H, aromatic,
J ¼ 2:74 and 8.22 Hz), 7.47 ppm (t, 1H, aromatic,
J ¼ 8:22 Hz), 7.34-7.22 ppm (m, 10 H, aromatic), 6.60
ppm (t, 2 H, NH, J ¼ 5:48 Hz); Selected IR data (KBr):
m(NH) 3290 cmꢀ1, m(CO) 1635 cmꢀ1; FABþ MS: m=z
344 [M].
3
ꢀ
V (A )
Z
qcalc (Mg/m3)
1.624
3.835
1.561
1.053
M (mmꢀ1
Reflections collected 19 093
)
12 272
6885 (0.0496)
Individual reflection 10 749 (0.0301)
(Rint
)
3.2. 1,3-C6H4-{C(O)N(PPh2)CH2Ph}2 (1)
Final R indices
[I > 2rðIÞ]
R1 ¼ 0:0351,
wR2 ¼ 0:0881
R1 ¼ 0:0485,
wR2 ¼ 0:1014
A dry and degassed thf (30 ml) solution of 1,3-C6H4-
{CONHCH2Ph}2 (0.482 g, 1.4 mmol) was cooled to )78
°C in an acetone-dry ice bath. To the cooled solution
was added dropwise a hexane solution of n-BuLi (1.2 ml,
2.5 mol dmꢀ3, 2.94 mmol) over 30 min. After the ad-
dition the mixture was stirred at )78 °C for 1 h and
another 30 additional min at room temperature. The
reaction solution was cooled to )78 °C again and to it
was added dropwise a solution of diphenylchlorophos-
phine (0.53 ml, 0.649 g, 2.94 mmol) in thf (10 ml) over 30
min. Stirring was continued for another 1 h at )78 °C.
Then the cooling bath was removed and the mixture was
stirred overnight at room temperature. The solution was
evaporated to dryness in vacuo and dichloromethane
(30 ml) was added. Lithium chloride, which precipitated,
was removed by filtration under nitrogen and then the
volatiles were evaporated in vacuo to leave a white solid.
Yield: 0.758 g, 76%; Microanalysis: Found (Calc.): C,
77.5 (77.4); H, 5.2 (5.4); N, 4.5 (3.9)%; 31P–{1H} NMR
(CDCl3): 58.5 (s) ppm; Selected IR data KBr (CH2Cl2):
m(PN) 916 cmꢀ1, m(C@O) 1651 cmꢀ1; FABþ MS: m=z
712 [M], 735 [M + Na]þ.
Fig. 2. Solid state structure of [{PdCl(C3H5)}2{1,3-C6H4-
ꢀ
{C(O)N(PPh2)CH2Ph}2}] (3). Selected bond lengths (A) and angles (°):
Pd(1)–P(1) 2.302(2), Pd(1)–Cl(1) 2.386(2), P(1)–N(1) 1.735(5), P(10)–
N(10) 1.728(5), N(1)–C(2) 1.380(8), C(2)–C(3) 1.485(9), C(3)–C(4)
1.380(9), C(4)–C(5) 1.385(9), C(5)–C(9) 1.520(9), C(9)–N(10) 1.390(8),
Pd(2)–Cl(2) 2.370(2), Pd(2)–P(10) 2.291(2); Pd(1)–P(1)–N(1)
113.23(19), P(1)–N(1)–C(2) 122.7(4), N(1)–C(2)–C(3) 120.5(6), C(3)–
C(4)–C(5) 121.5(6), C(4)–C(5)–C(9) 120.5(6), C(9)–N(10)–P(10)
124.4(4), N(10)–P(10)–Pd(2) 111.38(19), Cl(1)–Pd(1)–P(1) 97.32(6),
Cl(2)–Pd(2)–P(10) 93.79(7).
predried solvents and standard Schlenk techniques.
31P{1H} and H NMR spectra (109.4 and 270.0 MHz,
3.3. P,P0,C-[Pt(Cl){1,3-C6H4-{C(O)N(PPh2)CH2Ph}2}]
(2)
1
CDCl3) were recorded on a JEOL Delta GSX 270
spectrometer, IR spectra (pressed KBr disks) on a Per-
kin–Elmer System 2000 FTIR/Raman instrument, ele-
mental analyses were performed by the University of St.
Andrews Microanalytical Service. Mass spectroscopy
were performed by the National Service in Swansea.
To a dichloromethane (5 ml) solution of [PtCl2(cod)]
(0.035 g, 0.094 mmol) was added a solution of 1,3-C6H4-
{CON(PPh2)HCH2Ph}2 (0.071 g, 0.10 mmol) in di-
chloromethane (5 ml) and the colourless solution stirred
for ca. 3 days. The solution was concentrated under
reduced pressure to ca. 2 ml and diethyl ether (20 ml)
added. The white product was collected by suction fil-
tration and washed with diethyl ether (2 ꢁ 10 ml). Yield:
75 mg, 85%; Microanalysis: Found (Calc.): C, 58.6
(58.6); H, 3.3 (4.0); N, 2.8 (3.0)%; 31P–{1H} NMR
3.1. N,N0-Dibenzyl-1,3-isophthalamide
To a dry and degassed dichloromethane (100 ml)
solution of isophthaloyl dichloride (5.890 g, 29.00
mmol) and triethylamine (8.5 ml, 6.160 g, 60.90 mmol)
was added a dry and degassed dichloromethane (10 ml)
1
(CDCl3): 67.9 (s) ppm, J(195Pt–31P) 3080 Hz; Selected

868
M. Rodriguez i Zubiri et al. / Polyhedron 23 (2004) 865–868
IR data (KBr): m(CO) 1651 cmꢀ1, m(PN) 915 cmꢀ1
m(PtCl) 306; FABþ MS: m=z 942 [M].
,
1EZ UK (fax +44-1223-336-033 or e-mail: de-
posit@ccdc.cam.ac.uk or www: http://www.ccdc.cam.
ac.uk).
3.4. [{Pd(C3H5)Cl}2{1,3-C6H4-{(CO)N(PPh2)CH2-
Ph}2}] (3)
Acknowledgements
To
a
dichloromethane (5 ml) solution of
[(C3H5)PdCl]2 (0.035 g, 0.09 mmol) was added a solu-
tion of 1,3-C6H4-{CON(PPh2)HCH2Ph}2 (0.072 g, 0.10
mmol) in dichloromethane (5 ml) and the colourless
solution stirred for ca. 3 days. The solution was con-
centrated under reduced pressure to ca. 2 ml and diethyl
ether (20 ml) added. The white product was collected by
suction filtration and washed with diethyl ether (2 ꢁ 10
ml). Yield: 86 mg, 80%; Microanalysis: Found (Calc.):
C, 54.4 (54.7); H, 4.2 (4.3); N, 2.3 (2.3)%; 31P–{1H}
NMR (CDCl3): 72.5 (s) ppm; Selected IR data (KBr): m
We are grateful to the EPSRC for support, to John-
son Matthey for loans of precious metals and to the
JREI for an equipment grant.
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