Demethylation of trimethylphosphite promoted by dichlorodiphosphineplatinum and palladium complexes. Structures of the metallophosphonate complexes [Pt(P∧P){P(O)(OMe)2}2] (P∧P=dppe, dppp)

Article abstract of DOI:10.1016/S0277-5387(98)00395-7

Platinum and palladium complexes of the type [MCl₂(P^∧P)] (P^∧P=dppm, dppe, dppp) react with P(OMe)₃ at low temperatures to generate the bis(phosphite) species [M(P^∧P){P(OMe)₃}₂]

Full text of DOI:10.1016/S0277-5387(98)00395-7

Polyhedron 18 (1999) 1067–1075
Demethylation of trimethylphosphite promoted by
dichlorodiphosphineplatinum and palladium complexes.
Structures of the metallophosphonate complexes
[Pt(P P)hP(O)(OMe)2j2] (P P5dppe, dppp)
*
Robert A. Stockland Jr., Diane L. Maher, Gordon K. Anderson , Nigam P. Rath
Department of Chemistry, University of Missouri–St. Louis, 8001 Natural Bridge Road, St. Louis, MO 63121, USA
Received 17 August 1998; accepted 5 October 1998
Abstract
Platinum and palladium complexes of the type [MCl2(P P)] (P P5dppm, dppe, dppp) react with P(OMe)3 at low temperatures to
generate the bis(phosphite) species [M(P P)hP(OMe)3j2]21, which have been characterized by 31P NMR spectroscopy at low
temperatures. On warming, the [M(P P)hP(OMe)3j2]Cl2 complexes undergo an Arbuzov-like reaction to generate the bis(phosphonate)
derivatives [M(P P)hP(O)(OMe)2j2], which have been characterized by elemental analysis and NMR spectroscopy. The platinum
complexes with P P5dppe and dppp have been characterized in the solid state by single crystal X-ray diffraction; each complex exhibits
square planar geometry about the metal center. [Pt(dppe)hP(OMe)3j2][PF6]2 was isolated by performing the reaction of [PtCl2(dppe)] with
P(OMe)3 in the presence of
2
mol equiv. of TlPF6, whereas the mixed phosphite–phosphonate complex
[Pt(dppe)hP(OMe)3jhP(O)(OMe)2j]PF6 was prepared by carrying out the reaction in the presence of only 1 mol equiv. of TlPF6.
Formation of the phosphite complexes is rapid and quantitative for both metals, as observed by low temperature 31P NMR spectroscopy.
At ambient temperature, an equilibrium exists between free and coordinated phosphite, the latter being favored for platinum but
apparently not for palladium. This results in formation of the phosphonate complexes being much faster for Pt than for Pd, unless a
considerable excess of P(OMe)3 is added. The demethylation reactions could be reversed by treating [Pt(dppe)hP(O)(OMe)2j2] or
[Pt(dppe)hP(OMe)3jhP(O)(OMe)2j]PF6 with Me3O1BF42, although the reactions were not quantitative. Protonation of
[Pt(dppe)hP(O)(OMe)2j2][PF6]2 with HBF4 gave first [Pt(dppe)hP(O)(OMe)2j2H]1 and, finally, [Pt(dppe)hP(OH)(OMe)2j2]21
.
1999
Elsevier Science Ltd. All rights reserved.
Keywords: Platinum; Palladium; Phosphonate; Phosphite; Arbusov; Demethylation
1. Introduction
eties in order to maintain electroneutrality [2–8]. Neutral
complexes, in contrast, do not typically contain such H1
ions. The protons may be abstracted by base, and the free
metallophosphonates may serve as ligands to another
transition metal center, including cobalt, nickel, copper and
zinc.
Metallophosphonate complexes have been known for a
number of years. Platinum complexes of the type
[PthP(O)(OR)2j4H2] have been prepared by reaction of
K2PtCl4 with HP(O)(OR)2 [1] and subsequent displace-
ment with dppe gave [Pt(dppe)hP(O)(OR)2j2] [2]. The
latter could be prepared alternatively by reaction of
[PtCl2(dppe)] with AgOP(OR)2. The palladium dimer
[Pd2(m-Cl)2hP(O)(OR)2j4H2] was produced from [Pd2(m-
Cl)2(h3-C3H4Me)2] and HP(O)(OR)2 [3]. A recurring
feature in complexes prepared from HP(O)(OR)2 is the
presence of a hydrogen bridging between two P–O moi-
There have been several reports of an alternative ap-
proach to metallophosphonates, namely reactions of transi-
tion metal halide complexes with tertiary phosphites
[9,10]. These reactions, metal-substituted versions of the
well-known Arbuzov reaction, have been observed for
complexes of metals including iron [11–14], cobalt
[15,16], ruthenium [17,18], rhenium [19] and platinum
[20], and an intramolecular example involving a cobalt
system has been reported recently [21]. The metal-me-
diated Arbuzov reaction has been shown to occur either by
*
Corresponding
ganderson@umsl.edu
author.
Fax:
1314-516-5342;
e-mail:
0277-5387/99/$ – see front matter
PII: S0277-5387(98)00395-7
1999 Elsevier Science Ltd. All rights reserved.

1068
R.A. Stockland et al. / Polyhedron 18 (1999) 1067–1075
an ionic or a radical mechanism [10]. In the ionic
mechanism, a halide is displaced from the metal center to
generate a phosphite complex. Subsequent attack of halide
on the coordinated phosphite leads to expulsion of an alkyl
halide and generation of the metallophosphonate. There is
considerable evidence for the operation of this mechanism
in some cases, and the intermediate metal phosphite
complex may be detected or even isolated.
Trimethylphosphite complexes of platinum have been
shown to undergo single, double and even quadruple
demethylation reactions to give metallophosphonate com-
plexes [20]. Diphosphinepalladium and platinum phospho-
nate complexes have been prepared, but not by the
demethylation route. The chloride-bridged palladium com-
plex [Pd2(m-Cl)2hP(O)(OMe)2j4H2] reacts with dppe, for
example, in the presence of AgPF6 to produce the cationic
complex [Pd(dppe)hP(O)(OMe)2j2H]PF6, in which the
bridging hydrogen is retained [22]. The platinum complex
[Pt(dppm)hP(O)(OMe)2j2] has been generated by reaction
of [PthP(O)(OMe)2j4H2] with dppm, and has been em-
ployed as an O,O-donor towards a number of organometal-
lic fragments [23].
In this paper, we report the reactions of diphosphinepal-
ladium and platinum complexes of the type [MCl2(P P)]
with P(OMe)3, which result in demethylation of two
phosphite ligands to generate the neutral metallophospho-
nate species [M(P P)hP(O)(OMe)2j2] (M5Pd, Pt; P P5
dppm, dppe, dppp). The intermediate phosphite complexes
[M(P P)hP(OMe)3j2]21 have been characterized by 31P
NMR spectroscopy at low temperatures, and have been
isolated in one case. We also report the crystal structures of
the platinum phosphonate derivatives [Pt(P P)-
hP(O)(OMe)2j2] (P P5dppe, dppp).
(phosphonate)platinum
complexes
[PtCl(P P)-
hP(O)(OMe)2j], bis(phosphonate) complexes [Pt(P P)-
hP(O)(OMe)2j2] and unreacted starting material. 31P NMR
data for the mono(phosphonate) complexes are given in
Table 1. In each case, three resonances, with 195Pt satel-
lites, were observed. A large 2J(P,P) coupling constant
(over 600 Hz) was found between the trans P atoms P1 and
P3, and two smaller couplings were seen between the pairs
of P atoms cis to one another. The signal due to P2
exhibits a coupling to 195Pt of around 3500 Hz, as
expected for a P atom lying opposite a relatively low
trans-influence ligand such as chloride. Of the two mutual-
ly trans P atoms, the phosphonate displays a much larger
coupling than the tertiary phosphine, as observed previous-
ly [22].
With two or more equiv. of P(OMe)3, further reaction
occurs to generate the bis(phosphonate) complexes quan-
titatively. Each complex of the type [Pt(P P)-
hP(O)(OMe)2j2] gave rise to two sets of signals in its 31P
NMR spectrum, each of which exhibited coupling to
platinum (Table 2). Excluding the 195Pt satellites, the four
P atoms constituted an AA9XX9 spin system, giving rise to
two ten-line patterns [24], and the spectra have been
simulated as such in each case. Each ten-line pattern was
dominated by the large coupling, in excess of 500 Hz,
between mutually trans P atoms. Assuming this coupling
to be of positive sign [25], the cis coupling between the
diphosphine and phosphonate P atoms must be negative
(approx. 230 Hz) in all cases. The cis couplings between
the two P atoms of the diphosphine and between the two
phosphonate P atoms must be of the same sign (although
their absolute signs cannot be determined).
2. Results and discussion
Treatment of CH2Cl2 solutions of [PtCl2(P P)] with 1
mol equiv. of P(OMe)3 resulted in mixtures of the mono-
The analogous reactions of [PdCl2(P P)] with 1 mol
equiv. of P(OMe)3 also produced mixtures of [PdCl(P P)-
Table 1
31P NMR parameters for the complexes [MCl(P)P)hP(O)(OMe)2j]a
b
b
b
M, P P
dP1
dP2
dP3
2J(P1,P2)
2J(P1,P3)
2J(P2,P3)
Pd, dppm
Pd, dppe
Pd, dppp
Pt, dppm
259.6 dd
39.2 dd
25.1 dd
246.8 dd
(1364)
43.3 dd
(1772)
0.7 dd
(1613)
235.9 dd
57.3 t
16.7 dd
244.7 d
(3467)
41.3 dd
(3803)
21.9 dd
(3722)
66.3 dd
67.7 dd
64.8 dd
58.3 d
(4122)
68.2 dd
(3924)
61.4 dd
(3856)
99
25
54
50
766
678
679
650
21
25
40
15
Pt, dppe
Pt, dppp
7
600
598
22
21
28
a Spectra were recorded for CDCl3 solutions at ambient temperature.
b
1J(Pt,P) values are given in parentheses.

R.A. Stockland et al. / Polyhedron 18 (1999) 1067–1075
1069
Table 2
31P NMR parameters for the complexes [M(P P)hP(O)(OMe)2j2]a
b
b
M, P
P
dP1,P2
dP3,P4
2J(P1,P2)
2J(P1,P3)5
2J(P2,P4)
2J(P1,P4)5
2J(P2,P3)
2J(P3,P4)
Pd, dppm
Pd, dppe
Pd, dppp
Pt, dppm
Pt, dppe
Pt, dppp
229.7
43.1
0.5
239.6 (1612)
47.6 (1866)
4.3 (1840)
75.0
73.9
70.5
70.7 (4358)
68.6 (4194)
67.9 (4172)
647
626
670
628
69
593
545
543
546
507
510
4
227
225
212
231
232
748
747
751
737
628
630
620
a Spectra were recorded for CDCl3 solutions at ambient temperature.
b
1J(Pt,P) values are given in parentheses.
hP(O)(OMe)2j], [Pd(P P)hP(O)(OMe)2j2] and unreacted
[PdCl2(P P)] and, again, with two or more equiv. of
P(OMe)3, the bis(phosphonate) complexes were the exclu-
sive products. The 31P NMR spectra of the palladium
complexes were qualitatively similar to those of their
platinum analogues (except for the absence of satellites). In
contrast to their platinum analogues, in the bis(phospho-
nate) palladium complexes, the two cis couplings between
the two P atoms of the diphosphine and between the two
phosphonate P atoms must be of opposite sign in order to
simulate the spectrum correctly (Table 2).
Curiously, the reactions of the platinum complexes to
generate the bis(phosphonate) derivatives were over within
a few minutes, whereas the reactions involving palladium
took several days to go to completion. This was un-
expected in view of the usually much greater reactivity of
palladium compounds. When a solution of [PtCl2(dppe)]
was treated with 25 mol equiv. of P(OMe)3, the rate of
reaction was unchanged, but when [PdCl2(dppe)] was
treated similarly, the bis(phosphonate)palladium complex
was formed as rapidly as its platinum analogue. These
results suggest the existence of an equilibrium involving
coordinated and free phosphite at ambient temperature (Eq.
1), with coordinated P(OMe)3 being favored in the
platinum case. For palladium, the equilibrium position
would favor the free phosphite in the presence of only 2
equiv. of P(OMe)3, but the addition of a large excess of
phosphite would drive the reaction to the right.
When CD2Cl2 or CDCl3 solutions of [PtCl2(P P)] were
treated with 4 mol equiv. of P(OMe)3 at low temperatures,
the bis(phosphite) complexes [Pt(P P)hP(OMe)3j2]21 were
formed rapidly, but warming to ambient temperature
caused conversion to the bis(phosphonate) derivatives and
MeCl (dH 3.0) (Eq. 2). The bis(phosphite)platinum cations
also exhibited AA9XX9 patterns in their 31Ph1Hj NMR
spectra, and the appropriate parameters are given in Table
3.
The dppe complex [Pt(dppe)hP(OMe)3j2]Cl2, in particular,
Table 3
a
31P NMR parameters for the complexes [M(P P)hP(OMe)3j2]Cl2
b
b
M, P
P
dP1,P2
dP3,P4
2J(P1,P2)
2J(P1,P3)5
2J(P2,P4)
2J(P1,P4)5
2J(P2,P3)
2J(P3,P4)
Pd, dppm
Pd, dppec
Pd, dppp
Pt, dppm
Pt, dppe
Pt, dppp
232.4
54.9
4.2
246.1 (2022)
39.7 (2327)
104.5
103.0
100.3
87.8 (4699)
85.0 (4551)
82.4 (4438)
621
64
620
642
610
639
585
523
536
536
500
492
19
212
24
213
231
229
659
633
735
656
648
645
219.8 (2247)
a Spectra were recorded for CDCl3 solutions at 2538C.
b
1J(Pt,P) values are given in parentheses.
c Recorded for a CD2Cl2 solution at 2938C.

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R.A. Stockland et al. / Polyhedron 18 (1999) 1067–1075
exhibited one set of resonances at 39.7 ppm [1J(Pt,P)5
2327 Hz] due to the dppe P atoms and another at 85.0 ppm
[1J(Pt,P)54551 Hz] due to the coordinated P(OMe)3. The
corresponding reactions of [PdCl2(P P)] with P(OMe)3 at
2788C also generated the bis(phosphite)palladium cations
quantitatively in situ. Their 31P NMR parameters are also
collected in Table 3.
The resulting platinum complex exhibited a first order
31Ph1Hj NMR spectrum, each of the four resonances
appearing as a doublet of doublets of doublets (dP1 103.5,
1
2J(P,P) 509, 41, 33 Hz, J(Pt,P) 4480 Hz, P(OMe)3; dP2
61.4, 2J(P,P) 470, 41, 23 Hz, 1J(Pt,P) 3685 Hz,
2
1
P(O)(OMe)2; dP3 50.3, J(P,P) 470, 33, 10 Hz, J(Pt,P)
2
1762 Hz, dppe P cis to P(OMe)3; dP4 49.6, J(P,P) 509,
23, 10 Hz, 1J(Pt,P) 2413 Hz, dppe P trans to P(OMe)3), as
expected for the [Pt(dppe)hP(OMe)3jhP(O)(OMe)2j]1 cat-
ion. The spectrum remained essentially unchanged be-
tween 250 and 1508C, indicating that this species is
static between these temperatures. In the presence of
excess P(OMe)3, the signals due to the complex and free
phosphite were sharp at 2508C, but as the temperature
was raised, the resonances at 143.7 and 103.5 ppm, due to
free and coordinated P(OMe)3, respectively became broad,
indicating that phosphite exchange was occurring. A 31P–
31P 2D-EXSY experiment performed at 08C exhibited cross
peaks for the free and coordinated P(OMe)3, but not for
the phosphonate P atom, indicating that exchange occurs
between free and coordinated phosphite, but that methyl
transfer does not occur between the phosphite and phos-
phonate moieties.
Treatment of [PtCl2(dppe)] with 2 mol equiv. of
P(OMe)3 at 2788C, followed by 2 mol equiv. of TlPF6,
allowed isolation of the bis(phosphite)platinum cation as
its PF26 salt. Interestingly, the 31P NMR parameters for
[Pt(dppe)hP(OMe)3j2][PF6]2 [dP 51.6, 1J(Pt,P)52138 Hz;
dP 96.8, 1J(Pt,P)54056 Hz] are significantly different
from those of its chloride salt. This suggested to us that
there might be some association of the chloride ions with
the metal complex at low temperature in that case. To test
this, we treated [PtI2(dppe)] with 2 mol equiv. of P(OMe)3
at 2788C to generate the bis(phosphite) complex as its
iodide salt, which exhibited a further different set of 31P
1
NMR parameters [dP 29.8, J(Pt,P)52290 Hz; dP 77.4,
1J(Pt,P)54592 Hz]. We have previously observed similar
variations in dP and 1J(Pt,P) that we attributed to ion-
pairing, iodide interacting more strongly than chloride with
the complex [26]. A stronger interaction with iodide is
apparent here also, based on the magnitudes of the
chemical shift changes.
We investigated whether the demethylation reactions
might be reversible. As indicated above, when a solution
of [M(P P)hP(OMe)3j2]Cl2 is allowed to stand at 258C,
demethylation occurs quantitatively to yield [M(P P)-
hP(O)(OMe)2j2] and MeCl. When we treated
[Pt(dppe)hP(O)(OMe)2j2] with 2–3 mol equiv. of MeI or
C5H11Cl, no reaction occurred, although MeP(O)(OMe)2
(dP 32.0) was formed after prolonged reaction with excess
MeI. Reaction did occur with the more potent methylating
When a CDCl3 solution of [PtCl2(dppe)] and 4 mol
equiv. of P(OMe)3 was allowed to warm gradually, the
signals due to [Pt(dppe)hP(OMe)3j2]21 and free P(OMe)3
became broad and, at 258C, the signals due to the complex
were so broad that they disappeared into the baseline. This
suggests that there is rapid exchange of free and coordi-
nated phosphite at this temperature. On standing at am-
bient temperature, the resonances due to the bis(phospho-
nate) complex gradually grew in and increased in intensity.
The palladium system behaved similarly, except that the
signals due to [Pd(dppe)hP(O)(OMe)2j2] grew in much
more slowly.
Conversion of the bis(phosphite) complex to its bis-
(phosphonate) counterpart should occur by stepwise de-
methylation of the two phosphite ligands. Thus, a species
of the form [Pt(dppe)hP(OMe)3jhP(O)(OMe)2j]1 should be
an intermediate in this process. We generated this complex
by reacting [PtCl2(dppe)] with 2 equiv. of P(OMe)3 in
CH2Cl2 solution at 2788C in the presence of 1 equiv. of
TlPF6, followed by warming to ambient temperature, as
shown in Eq. 3. This resulted in precipitation of TlCl,
thereby leaving only one chloride ion to react with the
bis(phosphite) complex so that only one demethylation
step could occur.
agent
Me3O1BF24 ,
however.
When
[Pt(dppe)-
hP(O)(OMe)2j2]wastreatedwith1molequiv.ofMe3O1BF42
in CDCl3 /acetone solution at 258C (the complex is
insoluble in acetone, and Me3O1BF42 is insoluble in
CDCl3), the major product was [Pt(dppe)hP(OMe)3j-
hP(O)(OMe)2j]1, identified by its 31P NMR spectrum,
although other minor products were formed also. The
reaction was also slow, taking approximately 24 h to go to
completion. With excess Me3O1BF42, the major product
was the bis(phosphite)platinum cation, but again the
reaction was slow and a number of other species were
formed. Treatment of the mixed phosphite–phosphonate
complex [Pt(dppe)hP(OMe)3jhP(O)(OMe)2j]PF6 with 1
mol equiv. of Me3O1BF24 for 12 h at 258C gave
[Pt(dppe)hP(OMe)3j2]21 as the major product. Thus, it is
possible to reverse the demethylation reactions, although a
fairly strong methylating agent is required, and this does
not represent an efficient way to prepare bis(tertiary
phosphite)platinum complexes.
In
contrast
to
the
above,
treatment
of
[Pt(dppe)hP(O)(OMe)2j2] with 1 mol equiv. of HBF4
resulted in quantitative conversion to a new species that
exhibited the familiar AA9XX9 pattern in its 31P NMR
spectrum (dP 83.3, 1J(Pt,P)53880 Hz; dP 48.9, 1J(Pt,P)5

R.A. Stockland et al. / Polyhedron 18 (1999) 1067–1075
1071
2000 Hz). Treatment with excess HBF4 produced yet
another AA9XX9 pattern (dP 92.6, 1J(Pt,P)54046 Hz; dP
51.8, 1J(Pt,P)52103 Hz), the couplings being very remin-
iscent of those observed for [Pt(dppe)hP(OMe)3j2][PF6]2.
In contrast to the methylations described above, these
reactions were complete within a few minutes at ambient
temperature. We propose that the latter is the bis-
(dimethylphosphite)platinum complex [Pt(dppe)hP(OH)-
(OMe)2j2][BF4]2, in which the phosphite is stabilized in
its phosphorus(III) form by coordination to the metal. The
intermediate complex exhibits a resonance at 7.9 ppm in its
1H NMR spectrum, which is at a chemical shift similar to
that found in other bis(phosphonate) complexes in which a
hydrogen bridges between the two P5O moieties [2–8].
Thus, we propose the reaction sequence shown in Eq. 4 to
account for these observations.
Fig. 1. Molecular structure of [Pt(dppe)hP(O)(OMe)2j2] showing the atom
labeling scheme.
ters exhibit the largest angles between platinum and the
P5O bond (117.3 and 117.48) and the smallest between
the two methoxy groups (101.1 and 102.28). This is to be
expected if the P5O double bond is considered to occupy
more space than a P–O single bond.
The dppp analogue crystallizes in the space group
P21 /n, with two molecules per unit cell. Its molecular
structure is shown in Fig. 2, with selected bond distances
and angles being presented in Table 5. The sum of the four
cis P–Pt–P angles in this case is 360.428, again indicating
that the PtP4 unit is nearly planar. Here, the angles are all
2.1. Molecular structures of [Pt(P P)hP(O)(OMe)2 j2 ]
(P P5dppe, dppp)
Table 4
The dppe complex [Pt(dppe)hP(O)(OMe)2j2] crystallizes
˚
Selected bond distances (A) and angles (8) for [Pt(dppe)hP(O)(OMe)2j2]
¯
in the space group P1 with two molecules per unit cell.
Bond distances
The molecular structure is shown in Fig. 1, and selected
bond distances and angles are given in Table 4. The sum of
the four cis P–Pt–P angles is 360.048, indicating that the
PtP4 unit is almost exactly planar. The smallest angle of
85.058 is that between the two P atoms of the dppe ligand,
and the largest (93.998) is between the two phosphonate
groups. The Pt–P2 distance is very slightly longer than the
other three Pt–P distances, which are all identical within
Pt–P1
Pt–P3
P3–O1
P3–O3
P4–O5
2.3136(8)
2.3114(8)
1.486(2)
1.595(2)
1.597(2)
Pt–P2
Pt–P4
P3–O2
P4–O4
P4–O6
2.3251(8)
2.3111(8)
1.602(2)
1.486(2)
1.587(2)
Bond angles
P1–Pt–P2
P1–Pt–P4
P2–Pt–P4
Pt–P1–C1
Pt–P1–C9
C1–P1–C9
Pt–P2–C2
Pt–P2–C21
C2–P2–C21
Pt–P3–O1
Pt–P3–O3
O1–P3–O3
Pt–P4–O4
Pt–P4–O6
O4–P4–O6
85.05(3)
89.18(3)
P1–Pt–P3
P2–Pt–P3
P3–Pt–P4
176.55(2)
91.82(3)
93.99(3)
174.01(2)
107.08(10)
116.42(10)
102.14(13)
105.13(9)
117.63(9)
103.45(13)
117.38(10)
107.40(9)
110.16(13)
117.29(9)
106.94(9)
110.66(13)
˚
experimental error. The P5O bonds of 1.486 A are
Pt–P1–C3
C1–P1–C3
C3–P1–C9
Pt–P2–C15
C2–P2–C15
C15–P2–C21
Pt–P3–O2
O1–P3–O2
O2–P3–O3
Pt–P4–O5
O4–P4–O5
O5–P4–O6
115.96(9)
104.12(14)
109.39(13)
115.51(9)
103.35(14)
109.82(12)
109.74(10)
109.78(13)
101.13(14)
108.55(9)
110.06(12)
102.23(13)
considerably shorter than the four P–O single bonds
˚
(average 1.595 A), as expected. Each phosphorus atom
shows some distortion from tetrahedral geometry, but
probably for different reasons. The dppe P atoms exhibit
smaller angles where the ligand backbone carbons are
involved, presumably due to the conformational inflexibili-
ty of the five-membered chelate ring. In contrast, the
Pt–P–Ph angles are in the range 115.5–117.68, and the
Ph–P–Ph is close to the perfect tetrahedral angle. In the
case of the phosphonate ligands, the phosphorus(V) cen-

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R.A. Stockland et al. / Polyhedron 18 (1999) 1067–1075
groups. The angles around the dppp P atoms also show
some variation, ranging from 98.8 to 118.58.
The platinum–phosphonate Pt–P distances in the two
˚
complexes described here (2.304–2.318 A) were almost
identical to those reported for [PthP(O)(OMe)2j-
hP(OMe)3j3]1 [2.322(3) A] and cis-[PthP(O)(OMe)2j2-
˚
˚
hP(OMe)3j2] [2.329(10) A] [20]. These complexes are also
almost planar, the sums of the P–Pt–P angles being 362.0
and 361.98, respectively. In these complexes, all of the
P–Pt–P angles lie within the range 88–928. The large
1J(Pt,P) values found for the phosphonate P atoms, along
with the insensitivity of the Pt–P distances to the nature of
the trans ligands, suggests that these bonds are strong and
that the Pt–P distances are close to optimal.
3. Summary
Platinum and palladium complexes of the type
[MCl2(P P)] (P P5dppm, dppe, dppp) react with
P(OMe)3 at low temperatures to give first the bis(phos-
phite) species [M(P P)hP(OMe)3j2]21, which, on warming,
undergo an Arbuzov-like reaction with the liberated chlo-
ride to generate the bis(phosphonate) derivatives
[M(P P)hP(O)(OMe)2j2]. The products have been char-
acterized by NMR spectroscopy, and the platinum com-
plexes with P P5dppe and dppp have been subjected to
single crystal X-ray diffraction studies. Formation of the
phosphite complexes is rapid and quantitative for both
metals at low temperatures. At ambient temperature, an
equilibrium exists between free and coordinated phosphite,
the latter being favored for platinum but apparently not for
palladium. This results in the formation of the phosphonate
complexes being much faster for Pt than for Pd, unless a
considerable excess of P(OMe)3 is added. The demethyla-
tion reactions could be reversed by treating the phospho-
nate complexes with Me3O1BF24 . Studies of the reactions
of the metallophosphonate complexes are continuing.
Fig. 2. Molecular structure of [Pt(dppp)hP(O)(OMe)2j2] showing the atom
labeling scheme.
closer to 908, suggesting that there is less strain in the
six-membered chelate ring. There is a significant differ-
ence between the Pt–P bond lengths in this complex, those
˚
to the phosphonate ligands being approximately 0.03 A
shorter. The angles around the phosphonate P atoms range
from 97.5 to 120.28, the largest value corresponding to one
of the angles between platinum and a P5O bond. The
smallest angles are again between the pairs of methoxy
Table 5
˚
Selected bond distances (A) and angles (8) for [Pt(dppp)hP(O)(OMe)2j2]
Bond distances
Pt–P1
Pt–P3
P3–O1
P3–O3
P4–O5
2.3392(9)
2.3181(9)
1.484(3)
1.606(3)
1.614(3)
Pt–P2
Pt–P4
P3–O2
P4–O4
P4–O6
2.3459(8)
2.3039(8)
1.604(3)
1.479(2)
1.609(3)
4. Experimental
Bond angles
P1–Pt–P2
P1–Pt–P4
P2–Pt–P4
Pt–P1–C1
Pt–P1–C10
C1–P1–C10
Pt–P2–C3
Pt–P2–C22
C2–P2–C22
Pt–P3–O1
Pt–P3–O3
O1–P3–O3
Pt–P4–O4
Pt–P4–O6
O4–P4–O6
88.59(3)
92.75(3)
175.01(3)
111.77(12)
114.22(12)
104.9(2)
111.55(12)
117.12(10)
99.7(2)
114.76(12)
116.75(12)
109.2(2)
P1–Pt–P3
P2–Pt–P3
P3–Pt–P4
174.08(3)
88.38(3)
90.70(3)
118.46(11)
98.8(2)
106.8(2)
114.83(11)
104.3(2)
107.6(2)
104.11(10)
113.1(2)
97.54(14)
106.48(10)
110.7(2)
99.8(2)
All reactions were carried out under an atmosphere of
argon. Solvents were dried and distilled immediately prior
to use. The diphosphines were purchased from Strem and
were used as received. The complexes [MCl2(P P)] (M5
Pd, Pt; P P5dppm, dppe, dppp) were prepared by dis-
placement of cyclooctadiene from [MCl2(cod)] by the
appropriate diphosphine [27,28]. NMR spectra were re-
Pt–P1–C4
C1–P1–C4
C4–P1–C10
Pt–P2–C16
C3–P2–C16
C16–P2–C22
Pt–P3–O2
O1–P3–O2
O2–P3–O3
Pt–P4–O5
O4–P4–O5
O5–P4–O6
1
corded on a Bruker ARX-500 spectrometer. H and 31P
chemical shifts were measured relative to the residual
solvent signal and external H3PO4, respectively, with
positive shifts representing deshielding; coupling constants
are given in Hertz. Microanalyses were performed by
Atlantic Microlab Inc. (Norcross, GA, USA).
120.20(11)
106.03(11)
111.6(2)

R.A. Stockland et al. / Polyhedron 18 (1999) 1067–1075
1073
4.1. Preparation of [Pt(dppm)hP(O)(OMe)2 j2 ]
colorless solid (0.102 g, 81%). Anal. Calc. for
C29H34O6P4Pd: C, 49.12; H, 4.80. Found: C: 49.03, H:
1
3
To a CH2Cl2 solution (27 ml) of [PtCl2(dppm)] (0.10 g,
0.15 mmol) was added P(OMe)3 (0.07 ml, 0.60 mmol).
The solution was stirred for 55 min, and it changed color
from colorless to yellow. The solvent and excess phosphite
were removed at ambient temperature. The resulting solid
was allowed to dry in vacuo overnight, leaving the product
as a white solid (0.11 g, 87%). Anal. Calc. for
C29H34O6P4Pt: C, 43.67; H, 4.30. Found: C, 42.92; H,
4.79. H NMR (CDCl3): dH 3.45 d, J(P,H)511.8 Hz,
12H, OCH3; 4.06 t, 2J(P,H)57.7 Hz, 2H CH2; 7.30–7.66
m, 20H, C6H5.
4.5. Preparation of [Pd(dppe)hP(O)(OMe)2 j2 ]
To a CH2Cl2 solution (5 mL) of [PdCl2(dppe)] (0.10 g,
0.17 mmol) was added P(OMe)3 (0.082 mL, 0.695 mmol)
by syringe. The solution was stirred for 96 h at ambient
temperature, then passed down a Florosil column and
eluted with CH2Cl2 –MeOH (1:1, v/v; 50 mL). The
solvents were removed and the resulting colorless powder
was washed with ether (50 mL). The solid was dried in
vacuo, leaving the desired product as a colorless solid
(0.116 g, 93%). Anal. Calc. for C30H36O6P4Pd: C, 49.83;
H, 4.98. Found: C, 50.03; H, 5.04. 1H NMR (CDCl3): dH
2.17 m, 4H, PCH2; 3.27 d, 3J(P,H)511.8 Hz, 12H OCH3;
7.43–7.73 m, 20H, C6H5.
The dppp complex was prepared similarly and isolated
as a colorless solid at a yield of 87%. Anal. Calc. for
C31H38O6P4Pd: C, 50.52; H, 5.20. Found: C, 50.32; H,
5.17. 1H NMR (CDCl3): dH 1.83 m, 2H, PCH2CH2; 2.18
m, 4H, PCH2; 3.18 d, 3J(P,H)511.2 Hz, 12H, OCH3;
7.36–7.67 m, 20H, C6H5.
1
3
4.31. H NMR (CDCl3): dH 3.50 d, J(P,H)511.8 Hz,
12H, OCH3; 4.53 t, 2J(P,H)59.4 Hz, 2H, CH2; 7.5 m, 7.8
m, 20H, C6H5.
4.2. Preparation of [Pt(dppe)hP(O)(OMe)2 j2 ]
To a CH2Cl2 solution (25 mL) of [PtCl2(dppe)] (0.10 g,
0.15 mmol) was added P(OMe)3 (0.07 mL, 0.60 mmol).
The solution was stirred for 15 min. The solvent and
unreacted phosphite were removed at 08C. The resulting
solid was allowed to dry in vacuo overnight, leaving the
product as a white solid (0.10 g, 84%). Anal. Calc. for
C30H36O6P4Pt: C, 44.40; H, 4.47. Found: C, 44.28; H,
1
4.56. H NMR (CDCl3): dH 2.28 m, 4H PCH2; 3.18 d,
3J(P,H)511.5 Hz, 12H, OCH3; 7.46–7.80 m, 20H, C6H5.
Crystals suitable for an X-ray diffraction study were
obtained by slow evaporation of a CH2Cl2 –hexane–ether
solution.
4.6. Preparation of
[Pt(dppe)hP(O)(OMe)2 jhP(OMe)3 j]PF6
4.3. Preparation of [Pt(dppp)hP(O)(OMe)2 j2 ]
A CH2Cl2 solution of [PtCl2(dppe)] (0.10 g, 0.15 mmol)
was cooled to 2788C in an acetone–dry ice bath and
P(OMe)3 (0.039 mL, 0.33 mmol) was added by syringe.
TlPF6 (0.053 g, 0.15 mmol) was added, followed by
distilled methanol (2.0 mL). The acetone–dry ice bath was
removed and the flask was allowed to warm gradually to
ambient temperature and stirred for a further 6 h. The
solvents were removed and the remaining solid was
washed with benzene and ether, and dried in vacuo to
leave the product as a colorless powder (0.14 g, 93%).
Even after pumping under high vacuum for several days,
Trimethylphosphite (0.035 mL, 0.30 mmol) was added
to a solution of [PtCl2(dppp)] (0.10 g, mmol) in CH2Cl2
(25 mL). The solution was stirred for 30 min, then the
solvent was removed at 08C. The resulting solid was
allowed to dry in vacuo overnight, leaving the product as a
white solid (0.095 g, 78%). Anal. Calc. for C31H38O6P4Pt:
1
C, 45.10; H, 4.64. Found: C, 45.04; H, 4.62. H NMR
(CDCl3): dH 1.80 m, 2H, PCH2CH2; 2.25 m, 4H, PCH2;
3.17 d, 3J(P,H)511.8 Hz, 12H, OCH3; 7.43–7.73 m, 20H,
C6H5. Crystals suitable for an X-ray diffraction study were
obtained by slow evaporation of a CH2Cl2 –hexane solu-
tion.
1
the H NMR spectrum revealed the presence of 0.2 equiv.
of C6H6. Anal. Calc. for C32.2H40.2F6O6P5Pt: C, 39.12; H,
1
4.02. Found: C, 39.10; H, 3.95. H NMR (CDCl3): dH
2.39 m, 4H, PCH2; 3.16 d, 3J(P,H)511.6 Hz, 6H,
4.4. Preparation of [Pd(dppm)hP(O)(OMe)2 j2 ]
3
P(O)(OCH3)2; 3.57 d, J(P,H)512.4 Hz, 9H, P(OCH3)3;
7.55–7.72 m, 20H, C6H5.
[PdCl2(dppm)] (0.10 g, 0.18 mmol) was dissolved in
CH2Cl2 (5 mL) and P(OMe)3 (0.084 mL, 0.71 mmol) was
added by syringe. The solution changed from pale yellow
to bright yellow upon addition of the phosphite, and it was
stirred for 96 h at 258C. The solution was then passed
down a Florosil column that was eluted with CH2Cl2 –
MeOH (1:1, v/v; 50 mL). The solvents were removed and
the remaining colorless powder was washed with ether (50
mL), then dried in vacuo to leave the desired product as a
4.7. Preparation of [Pt(dppe)hP(OMe)3 j2 ][PF6 ]2
[PtCl2(dppe)] (0.10 g, 0.15 mmol) was dissolved in
CH2Cl2 (50 mL) and the solution was cooled to 2788C.
Trimethylphosphite (35.4 mL, 0.30 mmol) was added by
syringe, followed by TlPF6 (0.12 g, 0.33 mmol). The
reaction mixture was allowed to warm gradually to am-

1074
R.A. Stockland et al. / Polyhedron 18 (1999) 1067–1075
Table 6
Data collection, structure solution and refinement parameters for [Pt(dppe)hP(O)(OMe)2j2] and [Pt(dppp)hP(O)(OMe)2j2]
[Pt(dppe)hP(O)(OMe)2j2]
[Pt(dppp)hP(O)(OMe)2j2]
Crystal system
Triclinic
P(21), 2
9.987(2)
11.254(3)
15.475(2)
105.771(11)
101.70(2)
99.825(14)
1591.3(5)
1.731
Monoclinic
P21 /n, 4
11.58410(1)
17.7003(2)
16.3389(2)
90
105.2120(1)
90
3232.78(6)
1.696
Space group, Z
˚
a (A)
˚
b (A)
˚
c (A)
a (8)
b (8)
g (8)
3
˚
V (A )
Density (g/cm23) (calculated)
Temperature (K)
298(2)
4.655
1.42–29.88
29 897
223(2)
4.580
1.73–29.95
37 040
Absorption coefficient (mm21
Range (deg)
)
Reflections collected
Independent reflections (Rint
)
7595 (0.04)
379
0.0235, 0.0528
0.0300, 0.0553
1.025
8534 (0.041)
379
0.0334, 0.0648
0.0450, 0.0745
1.096
Least squares parameters
R(F), Rw(F2) (F2.2.0 s(F2))
R(F), Rw(F2) (all data)
S(F2)
bient temperature and was stirred for 1 h. The mixture was
filtered and the residue was washed with benzene and
ether. The resulting solid was dried in vacuo, leaving the
product as a colorless powder (0.16 g, 95%). Anal. Calc.
for C32H42F12O6P6Pt: C, 33.95; H, 3.71. Found: C, 32.98;
H, 3.20. 1H NMR (CDCl3): dH 2.41 m, 4H, PCH2; 3.51 d,
18H, 3J(P,H)512.2 Hz, OCH3; 7.58–7.78 m, 20H, C6H5.
Acknowledgements
Thanks are expressed to the National Science Founda-
tion (grant number CHE-9508228) for support of this
work, to Mallinckrodt Inc. for a graduate student fellow-
ship (to RASJ), to the National Science Foundation (grant
number CHE-9318696) and the University of Missouri
Research Board for funds to purchase the X-ray diffrac-
tometer, and to the U.S. Department of Energy (grant
number DE-FG02-92CH10499) for funds to purchase the
NMR spectrometer.
4.8. Detection of other [M(P P)hP(OMe)3 j2 ]21
complexes
In a typical experiment, [MCl2(P P)] (0.010 g) was
dissolved in CDCl3 (0.5 mL) at 258C. The sample was
frozen in an acetone–dry ice bath, then, P(OMe)3 (4
equiv.) was added to the NMR tube by syringe. The tube
was transferred to the probe of the NMR spectrometer,
which had previously been cooled to 2508C. The 31Ph1Hj
NMR spectrum was recorded at this temperature. Reso-
nances due to the AA9XX9 system of the expected product
(Table 3) and free P(OMe)3 were observed.
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