Platinum(II) and palladium(II) complexes containing a mixed donor 'P 2N' multidentate ligand

Article abstract of DOI:10.1016/j.poly.2004.01.015

The 'P₂N' mixed donor ligand 2-(diphenylphosphino)-N-[2- (diphenylphosphino)benzylidene]benzeneamine (PNCHP) reacts with [MCl ₂(1,5-cyclooctadiene)] and [M(CH₃)Cl(1,5-cyclooctadiene)] to give the complexes [M(PNCHP-κ³P,N,P)Cl]Cl (M=Pt or Pd) and [Pd(PNCHP-κ³P,N,P)(CH₃)]Cl, respectively. The ionic chloride can be exchanged with BF₄^- by reaction with AgBF₄. Abstraction of the covalent chloride with AgBF₄ in the presence of acetonitrile yields [Pt(PNCHP-κ³P,N,P)(CH ₃CN)]²⁺. The acetonitrile ligand of this dication can be substituted with a variety of ligands to afford complexes of the type, [Pt(PNCHP-κ³P,N,P)L]²⁺ (L=the monodentate ligands: triphenylphosphine, 2-picoline, 3-picoline or the chelate ligands: 1,10-phenanthroline, 2,2^′-bipyridine, bis(diphenylphosphino) ethane, 2,2^′:6^′,2″-terpyridine). The latter ligands all bind in a bidentate fashion to give five-coordinate complexes. The compounds have been characterised by spectroscopic and analytical means. The single crystal structures of the four-coordinate complexes, [Pt(PNCHP-κ³P,N,P)Cl]Cl and [Pt(PNCHP-κ³P,N,P) (PPh₃)](BF₄)₂, and the five-coordinate complexes, [Pt(PNCHP-κ³P,N,P)L](BF₄)₂ (L=1,10-phenanthroline and 2,2^′:6^′,2″- terpyridine), have been determined.

Full text of DOI:10.1016/j.poly.2004.01.015

Polyhedron 23 (2004) 1159–1168
www.elsevier.com/locate/poly
Platinum(II) and palladium(II) complexes containing a mixed donor
‘P2N’ multidentate ligand
1
*
*
Eric W. Ainscough , Andrew M. Brodie , Anthony K. Burrell , Andreas Derwahl,
Geoffrey B. Jameson, Steven K. Taylor
Chemistry, Institute of Fundamental Sciences, Massey University, Private Bag 11 222, Palmerston North, New Zealand
Received 10 December 2003; accepted 22 January 2004
Abstract
The ‘P2N’ mixed donor ligand 2-(diphenylphosphino)-N-[2-(diphenylphosphino)benzylidene]benzeneamine (PNCHP) reacts
with [MCl2(1,5-cyclooctadiene)] and [M(CH3)Cl(1,5-cyclooctadiene)] to give the complexes [M(PNCHP-j3P; N; P)Cl]Cl (M ¼ Pt or
Pd) and [Pd(PNCHP-j3P; N; P)(CH3)]Cl, respectively. The ionic chloride can be exchanged with BF4ꢀ by reaction with AgBF4.
Abstraction of the covalent chloride with AgBF4 in the presence of acetonitrile yields [Pt(PNCHP-j3P; N; P)(CH3CN)]2þ. The
acetonitrile ligand of this dication can be substituted with a variety of ligands to afford complexes of the type, [Pt(PNCHP-
j3P; N; P)L]2þ (L ¼ the monodentate ligands: triphenylphosphine, 2-picoline, 3-picoline or the chelate ligands: 1,10-phenanthroline,
2,20-bipyridine, bis(diphenylphosphino)ethane, 2,20:60,200-terpyridine). The latter ligands all bind in a bidentate fashion to give five-
coordinate complexes. The compounds have been characterised by spectroscopic and analytical means. The single crystal structures
of the four-coordinate complexes, [Pt(PNCHP-j3P; N; P)Cl]Cl and [Pt(PNCHP-j3P; N; P)(PPh3)](BF4)2, and the five-coordinate
complexes, [Pt(PNCHP-j3P; N; P)L](BF4)2 (L ¼ 1,10-phenanthroline and 2,20:60,200-terpyridine), have been determined.
Ó 2004 Elsevier Ltd. All rights reserved.
Keywords: Crystal structure; Platinum; Palladium; Phosphorus–nitrogen donor
1. Introduction
1). Therefore, with respect to the Hard and Soft Acid
and Base (HSAB) principle, the ligand should be well
suited to binding to platinum(II) and palladium(II). The
favourable ‘soft’–‘soft’ interactions of the phosphorus
donor atoms of the PNCHP ligand with the low valent
metal atom of concern are expected to anchor the ligand
to the platinum(II) or palladium(II) metal centre. On
one hand, the ‘borderline’-‘soft’ nitrogen–metal atom
interaction will have the potential for facile dissociation,
and consequently the metal–PNCHP complex could
exhibit interesting reactivity patterns [5]. For example,
ring-opening, which is considered to be an important
step in the mechanism of successful CO insertions ‘into’
metal–methyl bonds involving other terdentate ligands,
allows an incoming CO ligand to bind to a coordination
site in the square plane cis to the methyl group [6]. On
the other hand, PNCHP has shown preference for
terdentate coordination, occupying three sites of a
square plane and has shown no previous signs of ring-
opening [7]. Therefore, in this study we have concen-
Interest in the chemistry of the platinum group metals
with mixed-donor, multidentate ligands [1] tends to be
driven by interest in these systems as potential catalysts
[1a,2]. To date, studies which involve ligands containing
mixed phosphorus and nitrogen donor atoms have
generally focussed on bidentate ligands [1,2c,3]. In
contrast, mixed donor terdentate ligands, such as
the ‘P2N’ ligand, 2-(diphenylphosphino)-N-[2-(diph-
enylphosphino)benzylidene]benzeneamine
(PNCHP),
have received considerably less attention. PNCHP con-
tains two inequivalent ‘soft’ phosphorus donor atoms
and a ‘borderline’ nitrogen donor atom [4] (see Scheme
* Corresponding authors. Tel.: +64-6-350-5102; fax: +64-6-350-5682.
E-mail address: a.brodie@massey.ac.nz (A.M. Brodie).
1
Present address: Actinide, Catalysis and Separations Chemistry, C-
SIC, Mail Stop J514, Los Alamos National Laboratory, Los Alamos,
NM 87545, USA.
0277-5387/$ - see front matter Ó 2004 Elsevier Ltd. All rights reserved.
doi:10.1016/j.poly.2004.01.015

1160
E.W. Ainscough et al. / Polyhedron 23 (2004) 1159–1168
displaces COD and the chloro group from [Pd(COD)(-
CH3)Cl] yielding the compound [Pd(PNCHP-
j3P; N; P)(CH3)]Cl (7).
The ionic chloride of both 1a and 1b can be exchanged
for a BFꢀ4 ion to give [M(PNCHP-j3P; N; P)Cl]BF4
(M ¼ Pd 2a and M ¼ Pt 2b). In the presence of acetoni-
trile (MeCN) a second chloride of 1b can be abstracted
with AgBF4 to give [Pt(PNCHP-j3P; N; P)(MeCN)]-
(BF4)2 3. The chloride of 7 is easily exchanged for BF4ꢀ
by a metathetical reaction of 7 with AgBF4, affording the
compound [Pd(PNCHP-j3P; N; P)(CH3)]BF4 8. When
compound 8 was subjected to CO (7 atm) at room tem-
perature there was no evidence for the formation of a CO
adduct or for an insertion reaction. This is in contrast to
palladium complexes with terdentate nitrogen ligands
[6a], where insertion likely occurs via a mechanism in-
volving dissociation of one of the distal nitrogen atoms
to from a four-coordinate intermediate. In 8 the PNCHP
ligand cannot dissociate a distal phosphorus atom [6a].
The reaction of 3 with monodentate ligands, L (L ¼ 2-
picoline, 3-picoline or triphenylphosphine) results in the
substitution of the coordinated acetonitrile to give four-
coordinate, dicationic complexes of the type
[Pt(PNCHP-j3P; N; P)(L-j1)]2þ (4) (Scheme 3). Analo-
gous substitution reactions with the bidentate ligands
(L–L), 2,20-bipyridine (bipy), 1,10-phenanthroline
(phen) or bis(diphenylphosphino)ethane (diphos)] gave
complexes of the type [Pt(PNCHP-j3P; N; P)(L–L-
j2)]2þ (5), where the metal is now considered to be five-
coordinate. Reaction of 3 with the potentially terdentate
ligand 2,20:60,200-terpyridine (terpy) also gives rise to a
five-coordinate complex, [Pt(PNCHP-j3P; N; P)(terpy-
j2N; N)]2þ (6).
P
N
CH
P
PNCHP
Scheme 1.
trated on the replacement of the chloride group with
‘strong’ bidentate ligands, such as 1,10-phenanthroline
(phen), 2,20-bipyridine (bipy) and bis(diphenylphosph-
ino)ethane (diphos) as well as the terdentate, 2,20:60,200-
terpyridine (terpy) and report that these additional
ligands are forced to bind to the fifth coordination site
of the metal to give five-coordinate d8 metal complexes.
2. Results and discussion
2.1. Synthesisof[Pt(PNCHP-j3P; N; P)(MeCN)](BF4)2
(3) and related compounds
The syntheses of [M(PNCHP-j3P; N; P)Cl]Cl
(M ¼ Pd 1a or Pt 1b) and [Pd(PNCHP-j3P; N; P)-
(CH3)]Cl (7) are depicted in Scheme 2. PNCHP coor-
dinates to platinum(II) and palladium(II) in a terdentate
fashion by displacing 1,5-cyclooctadiene (COD) and one
chloride from [M(COD)Cl2] to yield complexes of the
type [M(PNCHP-j3P; N; P)Cl]Cl (M ¼ Pd 1a and
M ¼ Pt 1b). Attempts to isolate [M(PNCHP-j2P; P)Cl2]
were unsuccessful. However, several intermediates,
which were suggestive of mono- and bidentate PNCHP
species, were observed when monitoring the synthesis of
[M(PNCHP-j3P; N; P)Cl]Cl by 31P NMR. PNCHP
2.2. Single crystal X-ray diffraction studies
The X-ray determined crystal structures of 1b, 4a, 5a,
and 6 are shown as ORTEP plots of the cations in Figs.
1–4, respectively, and selected bond lengths and angles
are given in Table 2.
-
+
BF4
+ Cl-
AgBF4
PNCHP
toluene
Cl
Cl
N
P
P
M
M
N
P
P
2.2.1. Crystal structure of [Pt(PNCHP-j3P; N; P)Cl]-
Cl ꢁ 2CH2Cl2 (1b)
M
Cl
CH2Cl2
Cl
2a (M = Pd)
2b (M = Pt)
1a (M = Pd)
1b (M = Pt)
M = Pd or Pt
AgBF4
The structure of the cation [Pt(PNCHP-
j3P; N; P)Cl]þ of 1b (Fig. 1) contains a four-coordinate
platinum atom with the two phosphorus atoms [P(1)
and P(2)] and the imine nitrogen atom (N0 or N00) of
PNCHP and one chloride [Cl(1)] atom making up the
four donor atoms. A second chloride (ionic) and two
molecules of dichloromethane are also present but
omitted from Fig. 1 for clarity. The coordination ge-
ometry around the platinum atom is slightly distorted
square planar which can be attributed to the steric re-
quirements of the coordinated PNCHP ligand. The
CH3CN
-
2+
(BF4
)
2
N
P
P
Pt
NCCH3
3
+ Cl-
BF4
-
+
AgBF4
CH2Cl2
PNCHP
Cl
N
P
Pd
N
P
P
Pd
Pd
CH3
CH2Cl2 or
benzene
P
CH3
CH3
8
7
PNCHP = P N P
ꢀ
mean C(1)@N imine bond length at 1.272 A is similar to
ꢀ
the value found for the free ligand (1.266 A) [4] as well
Scheme 2.

E.W. Ainscough et al. / Polyhedron 23 (2004) 1159–1168
1161
-
2+
(BF4
)
2
-
2+
(BF4
)
2
N
P
P
Pt
NCCH3
L-L-L
N
P
P
L
Pt
L
3
CH2Cl2
L
L-L
L
CH2Cl2
CH2Cl2
6
-
2+
-
(BF4
)
2
2+ (BF4
)
2
N
P
P
N
P
P
L
Pt
Pt
L
L
4
5
PNCHP = P N P
N
N
or
L = PPh3 or
N
N
N
N
Ph2P
Ph2P
a
or
or
b
c
L-L =
N
N
N
L-L-L =
a
b
c
Scheme 3.
as for the related compounds, 4a, 5a and 6 [1.290(6)–
ꢀ
1.297(15) A] reported in this study.
As for 1b, the coordination geometry of the platinum is
slightly distorted square planar. Calculation of a plane
involving the platinum atom and the four donor atoms,
N, P(1), P(2) and P(3), shows a significant deviation from
2.2.2. Crystal structure of [Pt(PNCHP-j3P; N; P)-
(PPh3)](BF4)2 (4a)
ꢀ
coplanarity of 0.146 A, much greater than in the struc-
ꢀ
ture discussed above (0.095 for molecule A and 0.024 A
for molecule B). The Pt–P bond lengths to PNCHP [Pt–
The structure of the dication, [Pt(PNCHP-
j3P; N; P)(PPh3)]2þ 4a (Fig. 2), shows the two phos-
phorus atoms [P(1) and P(2)] and nitrogen atom (N) of
PNCHP and the phosphorus atom of a triphenylphos-
phine [P(3)] coordinated to a central platinum atom (Pt).
ꢀ
P(1), 2.3151(12) A and Pt–P(2), 2.3247(12) A] are similar
ꢀ
Fig. 1. ORTEP diagram of the cation of complex 1b (major disorder
part) showing the numbering system used. Thermal ellipsoids are at the
50% probability level. Hydrogen atoms have been omitted for clarity.
Fig. 2. ORTEP diagram of the cation of complex 4a showing the
numbering system used. Thermal ellipsoids are at the 50% probability
level. Hydrogen atoms have been omitted for clarity.

1162
E.W. Ainscough et al. / Polyhedron 23 (2004) 1159–1168
2.2.3. Crystal structure of [Pt(PNCHP-j3P; N; P)-
(phen–j2N; N)](BF4)2 ꢁ CH2Cl2 (5a)
For the dication, [Pt(PNCHP-j3P; N; P)(phen–
j2N; N)]2þ of 5a (Fig. 3), the platinum atom is five-co-
ordinate with a slightly distorted square-pyramidal
geometry. The PNCHP ligand occupies three sites of the
basal plane, coordinating through the two phosphorus
atoms [P(1) and P(2)] and the nitrogen atom (N). The
remaining coordination site of the basal plane is filled by
one of the nitrogen atoms [N(1)] of the 1,10-phenan-
throline (phen) ligand. The second nitrogen atom [N(2)]
of the 1,10-phenanthroline is located at the apex of the
square pyramid. There is no significant difference be-
ꢀ
tween the Pt–N(imine) [2.038(2) A] and Pt–N(1)(phen)
ꢀ
[2.043(2) A] bond lengths, which are trans to one an-
other in the basal plane. The axial phen–N(2)–Pt dis-
ꢀ
tance of 2.526(2) A is considerably greater than the
ꢀ
equatorial N(1)–Pt distance of 2.043(2) A, the latter
being typical for platinum(II)-1,10-phenanthroline spe-
cies [10]. Due to the rigid structure of 1,10-phenan-
throline, the second nitrogen atom is forced to be in the
vicinity of the metal, making it difficult to decide whe-
ther or not the axial nitrogen atom-to-metal distance
N(2)–Pt corresponds to a weak bond. However, in 5a
the phen is considered to be bidentate for the following
reasons: (i) The platinum atom is displaced from the
Fig. 3. ORTEP diagram of the cation of complex 5a showing the
numbering system used. Thermal ellipsoids are at the 50% probability
level. Hydrogen atoms have been omitted for clarity.
ꢀ
basal plane by 0.1052(8) A towards the N(2) atom. (ii)
The ratio of the axial/equatorial phen–N–Pt bond
lengths at 1.24 is close to values for accepted five coor-
dinate species [11]. For example, ratios of 1.17 are found
for the five coordinate species [Ni(CN)5]2- and 1.14 for
the five coordinate [PtI2(CO)(dmphen)] (dmphen ¼ 2,9-
dimethyl-1,10-phenanthroline), where the phenanthro-
line ligand is bound in an axial-to-equatorial bidentate
mode. By contrast, in [PtCl(phen)(PEt3)2]þ, where the
phen ligand is considered monodentate, the ratio is 1.33
[12]. (iii) The N(1)–Pt–N(2) angle of 74.54(8)° lies close
to the average phen N–M–N angle of 79.5° when the
ligand is clearly bidentate [11]. For comparison, the
equivalent angles in [Pt(CN)(phen)2]þ and [PtCl-
(phen)(PEt3)2]þ, where the phen ligand is monodentate,
are 69.7(2)° and 68.2°, respectively [13,14]. (iv) The
difference between the Pt–N(1)–C(105) and Pt–N(1)–
C(101) angles of only )2.7°, is indicative of a phenan-
throline ligand bound to both the basal plane and the
apical site of the metal atom [15]. (v) Lastly, the axial
Fig. 4. ORTEP diagram of the cation of complex 6 showing the
numbering system used. Thermal ellipsoids are at the 50% probability
level. Hydrogen atoms have been omitted for clarity.
8
ꢀ
[2.332(2)–2.347(2) A] to other square planar d com-
plexes of platinum for compounds with two phosphines
trans to each other [8] Pt–P and Pt–N bond lengths are
similar to those found in the complexes cis-[Pt(PNH2)]2þ
and trans-[Pt(PNH2)]2þ (PNH2 ¼ o-aminophenyldiphe-
nylphosphine) [9]. However, the bond lengths Pt–P(1)
and Pt–P(2) are significantly longer (by 0.0215 and
ꢀ
phen–N–Pt distance [2.526(2) A] in 5a is considerably
shorter than the analogous distances in [Pt(CN)-
(phen)2]þ and [PtCl(phen)(PEt3)2]þ [2.761(5) and
ꢀ
2.843(20) A, respectively], which are considered to be
too long for a bonding interaction.
ꢀ
0.0390 A, respectively) than those found for [Pt(PNCHP-
j3P; N; P)Cl]þ (1b), which is consistent with the greater
steric requirement of the mutually cis coordinated tri-
phenylphosphine ligand – effectively there are three
bulky triphenylphosphino moieties in close proximity.
2.2.4. Crystal structure of [Pt(PNCHP-j3P; N; P)(ter-
py-j2N; N)](BF4)2 (6)
The geometry around the metal in [Pt(PNCHP-
j3P; N; P)(terpy-j2N; N)]2þ 6 (Fig. 4) is similar to that

E.W. Ainscough et al. / Polyhedron 23 (2004) 1159–1168
1163
Table 1
Crystal data and structure refinement for the complexes 1b, 4a, 5a, and 6
Compound
1b
4a
5a
6
Empirical formula
M
T (K)
Crystal system
C
39H33Cl6NP2Pt
C57H48B2Cl4F8NP3Pt
1350.38
203(2)
C50H39B2Cl2F8N3P2Pt
1183.39
203(2)
C52H40B2F8N4P2Pt
1151.53
200(2)
985.39
203(2)
triclinic
monoclinic
P2ð1Þ=c
13.1722(1)
21.81280(10)
19.7670(2)
90
triclinic
ꢁ
monoclinic
P2ð1Þ=m
11.289(2)
16.021(3)
13.684(3)
90
ꢁ
Space group
ꢀ
P1
P1
a (A)
10.7207(1)
13.8244(2)
14.5320(2)
114.840(2)
91.402(1)
96.559(1)
1935.45(4)
2
10.3338(1)
12.9595(2)
18.5480(2)
87.012(1)
88.389(1)
76.211(1)
2408.78(5)
2
ꢀ
b (A)
ꢀ
c (A)
a (°)
b (°)
c (°)
91.942(1)
90
107.97(3)
90
3
ꢀ
U (A )
5676.24(8)
4
2.810
2354.3(8)
2
3.122
Z
Absorption
4.152
3.160
coefficient (mmꢀ1
)
Reflections measured
Independent reflections
18848
8348 (Rint ¼ 0:0244)
31955
20996
19782
12425 (Rint ¼ 0:0285)
R1 ¼ 0:0449;
wR22 ¼ 0:0996
R1 ¼ 0:0603;
wR2 ¼ 0:1095
9682 (Rint ¼ 0:0130)
R1 ¼ 0:0207;
wR2 ¼ 0:0547
R1 ¼ 0:0220;
wR2 ¼ 0:0559
4368 (Rint ¼ 0:0992)
R1 ¼ 0:0458;
wR2 ¼ 0:1047
R1 ¼ 0:0627;
wR2 ¼ 0:1119
Final R indices [I > 2rðIÞ] R1 ¼ 0:0268;
wR2 ¼ 0:0654
R indices (all data)
R1 ¼ 0:0301;
wR2 ¼ 0:0673
Table 2
Selected bond lengths (A) and angles (°) for the complexes 1b, 4a, 5a, and 6 with estimated standard deviations in parentheses
ꢀ
1b
4a
5a
6
Bond lengths
Pt–P(1)
Pt–P(2)
Pt–N
2.2936(8)
2.2857(8)
2.038(4)–N0, 2.106(7)-N00
2.2875(9)
2.3151(12)
2.3247(12)
2.107(4)
2.2997(6)
2.2947(6)
2.038(2)
2.3058(16)
2.3058(16)
2.044(10)
Pt–Cl(1)
Pt–N(1)
Pt–N(2)
Pt–P(3)
N–C(1)
2.043(2)
2.526(2)
2.061(7)
2.625(7)
2.2688(13)
1.290(6)
1.301(6)-A, 1.242(8)-B
1.295(3)
1.297(15)
Bond angles
P(1)–Pt–P(2)
N–Pt–Cl(1)
N–Pt–P(3)
174.84(3)
169.83(10)-A, 168.20(14)-B
160.96(5)
161.34(2)
175.30(8)
175.68(12)
N–Pt–N(1)
P(1)–Pt–N
P(2)–Pt–N
172.52(8)
84.66(6)
86.84(6)
170.3(2)
80.3(2)
99.4(2)
80.85(10)-A, 98.08(16)-B
95.13(10)-A, 77.34(16)-B
93.14(3)
82.23(11)
83.37(11)
P(1)–Pt–Cl(1)
P(2)–Pt–Cl(1)
P(1)–Pt–P(3)
P(2)–Pt–P(3)
P(1)–Pt–N(1)
P(2)–Pt–N(1)
P(1)–Pt–N(2)
P(2)–Pt–N(2)
N(1)–Pt–N(2)
N–Pt–N(2)
91.29(3)
98.80(5)
96.49(5)
91.98(6)
98.25(6)
94.69(5)
103.04(5)
74.54(8)
99.03(8)
90.07(4)
90.07(4)
92.26(4)
92.26(4)
72.6(3)
109.1(3)
found in [Pt(PNCHP-j3P; N; P)(phen)]2þ. Again, the
platinum atom is square pyramidal with the two phos-
phorus atoms [P(1) and P(2)] and one nitrogen atom (N)
of PNCHP occupying three equatorial sites, with the
fourth site occupied by one of the terminal nitrogen
atoms [N(1)] of the 2,20,60200-terpyridine ligand. The
central nitrogen atom [N(2)] of the terpy occupies the
ꢀ
axial site with the axial Pt–N(2) distance at 2.625(7) A
being longer than the equatorial Pt–N(1) distance of
ꢀ
2.061(7) A. The Pt–N(2) distance is considered to cor-

1164
E.W. Ainscough et al. / Polyhedron 23 (2004) 1159–1168
respond to a bonding interaction since the same argu-
ments put forth to describe the nature of the axial Pt–
N(2) bond in [Pt(PNCHP)(phen–j2N; N)]2þ (5a) also
hold for 6, although the interaction is weaker: the
platinum atom is displaced from the basal donor atom
phosphorus atoms gives rise to a high frequency reso-
nance (d 45.9–28.7) and the other to a low frequency
resonance (d 19.5–12.3). The former resonances can
reasonably assigned to the phosphorus atoms involved
in the five-membered ring, due to the ring contribution
2
ꢀ
plane by only 0.0349(8) A towards the N(2) atom, the
(DR) effect [16,17]. The J(P,P) coupling constants ran-
axial/equatorial ratio is slightly larger at 1.27 and dif-
ference between the M–N(1)–C(105) and M–N(1)–
C(101) angles is also slightly larger at +5.0°. In addition,
unlike the phen ligand in 5a, the pyridyl ring containing
the axial bound nitrogen atom is free to rotate around
the C(105)–C(106) axis and therefore is not required to
orientate itself for bonding with the metal, as it does.
The two rings containing the N(1) and N(2) atoms lie in
one plane. In contrast, the mean plane of the pyridyl
ring containing the non-bonding nitrogen atom N(3) is
tilted 47.7° relative to the mean plane of the middle
pyridyl ring.
ged from 306 to 422 Hz which is indicative of a trans
arrangement of inequivalent phosphorus atoms [18].
Coupling constants of larger magnitude were exhibited
by the monocationic complexes, whilst those of smaller
magnitude were displayed by the dicationic complexes.
1J(P,Pt) coupling constants ranged from 2353 to 2789
Hz and were typical of trans-platinum(II) complexes
[18]. The 1J(P,Pt) coupling constants associated with the
higher frequency resonances, i.e. those from d 45.9–28.7,
were on average 30 Hz higher than their lower frequency
counterparts at d 19.5–12.3, further supporting the as-
signment of the signals at high frequency to the phos-
phorus atoms involved in the five-membered ring, again
due to the ring contribution (DR) effect [18].
2.3. NMR spectroscopy
The spectra of the two complexes, [Pt(PNCHP-
j3P; N; P)(PPh3)](BF4)2 (4a) and [Pt(PNCHP-j3P; N; P)-
(diphos)](BF4)2 (5c) contain additional phosphorus
signals due to their phosphine co-ligands. For 4a, where
the ancillary ligand is triphenylphosphine, an additional
resonance at d 5.1, with 2J(P,P) coupling constants of 18
and 21 Hz and a 1J(P,Pt) of 3397 Hz, was observed. The
relatively large 1J(P,Pt) coupling constant for the tri-
phenylphosphine ligand, relative to those observed for
PNCHP, is due to the poorer trans influence of the ni-
The 31P NMR data for selected compounds are col-
lected in Table 3. All the platinum(II) compounds dis-
played similar spectra, showing two doublets with
platinum-195 satellites which are assigned to the two
2
phosphorus atoms of the PNCHP ligand with J(P,P)
coupling between the two inequivalent phosphorus nu-
1
clei and J(Pt,P) coupling due to the spin 1/2 nucleus
195Pt, found in 33% abundance. In general, for all the
platinum(II) compounds discussed here, one of the
Table 3
NMR data for selected compounds
31P {1H}NMRa
Compound
1H NMRb
d
2J(PP)/Hz
1J(PPt)/Hz
d (CH@N)c
3J(HPt)/Hz
[Pd(PNCHP)Cl]Cl (1a)
[Pt(PNCHP)Cl]Cl (1b)
37.3, 22.6
32.0, 18.8
478
421
10.61
10.87
8.62(dd)d
9.48f
2542, 2495
2496, 2367, 3397
2493, 2490
2499, 2505
2789, 2757
2731, 2722
2435, 2353
106.5
63.9 [4J(HP) 11.6, 1.1]
92.2
90.3
91.6
90.9
[Pt(PNCHP)(PPh3)](BF4)2 (4a)
[Pt(PNCHP)(2-pico)](BF4)2 (4b)
[Pt(PNCHP)(3-pico)](BF4)2 (4c)
[Pt(PNCHP)(phen)](BF4)2 (5a)
[Pt(PNCHP)(bipy)](BF4)2 (5b)
[Pt(PNCHP)(diphos)](BF4)2 (5c)
38.5, 19.5, 5.1e
337, 21, 18
363
366
g
33.4, 18.5
34.4, 19.3g
29.9, 14.4
29.7, 15.2
45.9, 12.3
42.6j , 38.3j
28.7, 13.6
33.6, 27.5
9.46f
354
363
9.42h
8.95
i
396
k
k
3088
2698, 2669
[Pt(PNCHP)(terpy)](BF4)2 (6)
[Pd(PNCHP)Me]Cl (7)
306
392
9.04h
10.29
95.7
a Recorded at 109 MHz, chemical shifts are in ppm relative to 85% H3PO4, solvent CDCl3 unless stated otherwise.
b Recorded at 270 MHz, chemical shifts are in ppm relative to Si(CH3)4, solvent CDCl3 unless stated otherwise.
c In addition, compounds 4b, 4c and 7 show CH3-resonances at d 2.24, 1.97 and 0.56, respectively. 5c shows Ph2PCH2CH2PPh2resonances at d
3.02.
d In CD3CN.
e Ph3P resonance.
f In (CD3)2CO
g In CH3CN.
h In CD2Cl2.
i Obscured by aromatic CH resonances in the range d 7.95 – 5.94.
j Ph2PCH2CH2PPh 2resonance.
k Not resolved.

E.W. Ainscough et al. / Polyhedron 23 (2004) 1159–1168
1165
trogen when compared to the phosphorus atom. The
chemical shift is similar to other triphenylphosphine
platinum(II) compounds [19] with the J(P,P) coupling
1,10-phenanthroline and bis(diphenylphosphino)ethane,
does not result in any observable competition with the
PNCHP ligand for coordination sites. Instead, these li-
gands act in a bidentate fashion, with one of their donor
atoms occupying the fourth site of the square-plane, and
the second donor atom the apical site of a square pyr-
amid to give five-coordinate dicationic complexes. The
potentially tridentate ligand, 2,20,60,200-terpyridine, also
behaves as a bidentate, forming the five-coordinate
complex [Pt(PNCHP-j3P; N; P)(terpy-j2N; N)]2þ (6).
2
constant being typical of phosphorus atoms in a cis ar-
rangement [18]. Free diphos contains equivalent phos-
phorus atoms but on coordination in 5c, these become
inequivalent, exhibiting one resonance at 42.6 and the
other at d 38.3, values which support both diphos
phosphorus atoms being coordinated to the platinum
atom. The 1J(P,Pt) coupling constant of 3088 Hz is
typical of diphos coordinated in square planar plati-
num(II) complexes [20,21] and consistent with P trans to
N. The expected second 1J(P,Pt) coupling constant could
not be resolved.
4. Experimental
The phosphorus-31 NMR spectra of the palladium
complexes are similar to those of the platinum com-
pounds, but with the expected absence of phosphorus-
to-metal coupling. All spectra displayed two doublet
signals, which are assigned to the inequivalent phos-
phorus atoms of PNCHP. As for the platinum
compounds, chemical shifts are indicative of phospho-
4.1. Materials and instrumentation
Spectral measurements were performed as previously
described [7]. Microanalyses were performed by the
Campbell Microanalytical Laboratory, University of
Otago. Many of the compounds contained solvated
CH2Cl2 which was readily lost and the analytical data
reflect this. The PNCHP ligand [4], [Pt(COD)Cl2],
[Pd(COD)Cl2] and [Pd(COD)(Me)Cl] [22] were prepared
according to literature preparations. All reactions were
carried out under an inert atmosphere. Solvents were
dried by standard procedures [23].
2
rus-transition metal coordination. The J(P,P) coupling
constants were typical of the PNCHP ligand bound to
palladium(II) with its two phosphorus atoms trans to
one another. As previously reported [18], chemical shifts
and coupling constants for the palladium complexes
were significantly larger than those for their platinum
analogues.
4.2. Preparation of the complexes
All the compounds listed in Table 3 displayed a signal
in the range d 10.9–8.6 which can be assigned to the
imine proton of coordinated PNCHP with coupling to
195Pt (60 – 110 Hz) being observed for the platinum
complexes. As the ancillary ligand is changed from a
halogen to a nitrogen to a phosphorus donor ligand, the
chemical shift of the imine proton moves to lower fre-
4.2.1. [Pd(PNCHP-j3P; N; P)Cl]Cl (1a)
A mixture of [Pd(COD)Cl2] (0.100 g, 0.350 mmol)
and PNCHP (0.193 g, 0.351 mmol) in benzene (12 mL)
was heated to reflux for 1 h. The resulting yellow pre-
cipitate was isolated by filtration, washed with N-pen-
tane and air dried to yield 1a (0.235 g, 86.9%) as a yellow
powder. Anal. Calc. for C37H29Cl2NP2Pd ꢁ 0.5 CH2Cl2:
C, 58.54; H, 3.93; N, 1.82. Found: C, 58.41; H, 3.99; N,
1.78%.
3
quency and the J(H,Pt) coupling constant decreases.
The shift to lower frequency can be explained using the
relative trans influence of the donor atom of the ancil-
lary ligand. For example, when the ancillary donor atom
is phosphorus (high in the trans influence series), as it is
in [Pt(PNCHP-j3P; N; P)(PPh3)](BF4)2 (4a) and
[Pt(PNCHP-j3P; N; P)(diphos)](BF4)2 (5c), the imine
proton exhibits its lowest frequency shifts.
4.2.2. [Pt(PNCHP-j3P; N; P)Cl]Cl (1b)
A mixture of [Pt(COD)Cl2] (0.100 g, 0.267 mmol) and
PNCHP (0.147g, 0.267 mmol) in benzene (12 mL) was
stirred at room temperature for 40 min, giving a yellow
precipitate. The mixture was heated to reflux for 30 min
and allowed to cool. The resulting yellow precipitate was
isolated by filtration, washed with diethylether and air
dried to yield 1b (0.146 g, 60.7%) as a yellow powder.
The compound can be crystallised from dichlorome-
3. Conclusions
For the d8 metals, platinum(II) and palladium(II), the
PNCHP ligand coordinates to three sites of the
square-plane, using the two phosphorus atoms and the
imino-nitrogen atom. In the compound [Pt(PNCHP-
j3P; N; P)(MeCN)](BF4)2 (3), the acetonitrile ancillary
ligand, which occupies the fourth site of the square-
plane, can be substituted with monodentate ligands,
such as 2- and 3-picoline and triphenylphosphine. Re-
action of 3 with the bidentate ligands 2,20-bipyridine,
o
thane/N-hexane. M.p: 294-296 C (dec). Anal. Calc. for
C37H29Cl2NP2Pt ꢁ 1.5CH2Cl2: C, 49.04; H, 3.42; N, 1.49.
Found: C, 48.78; H, 2.75; N, 1.52%.
4.2.3. [Pd(PNCHP-j3P; N; P)Cl]BF4 (2a)
A mixture of 1a (0.202 g, 0.263 mmol) and AgBF4
(0.054 g, 0.277 mmol) in dichloromethane (12 mL) was

1166
E.W. Ainscough et al. / Polyhedron 23 (2004) 1159–1168
exposed to ultrasound for 1 h resulting in yellow and
white precipitates. This mixture was filtered through
kieselguhr and the trapped yellow precipitate dissolved
and washed through into the filtrate with acetonitrile,
leaving the insoluble white precipitate behind. The fil-
trate was taken to dryness in vacuo and the resulting
yellow residue crystallised from dichloromethane/n-
hexane. Compound 2a (0.169 g, 82.6%) was isolated as
large yellow crystals, washed with a dichloromethane/N-
pentane mixture and air-dried. Anal. Calc. for
C37H29BClF4NP2Pd: C, 57.10; H, 3.76; N, 1.80. Found:
C, 56.68; H, 3.70; N, 1.90%.
Anal. Calc. for C55H44B2F8NP3Pt ꢁ CH2Cl2: C, 53.15; H,
3.66; N, 1.11. Found: C, 53.36; H, 3.80; N, 1.18%.
4.2.7. [Pt(PNCHP-j3P; N; P)(2-pico)](BF4)2 (4b)
A mixture of 2b (0.162 g, 0.174 mmol) and AgBF4
(0.0360 g, 0.185 mmol) in acetonitrile (12 mL) was he-
ated to reflux for 30 min, giving a white precipitate. 2-
Picoline (2-pico) (0.0183 mL, 0.185 mmol) was added to
the reaction mixture and refluxing continued for a fur-
ther 30 min. The white precipitate was removed by fil-
tration through kieselguhr and the filtrate taken to
dryness in vacuo. The resulting yellow residue converted
to a white and brown mixture over two days. The white
product was separated from the insoluble brown prod-
uct by dissolving in dichloromethane, followed by fil-
tration. Crystallisation was initiated by addition of N-
hexane to the filtrate. Compound 4b (0.1354 g, 72.4%)
was isolated as white microcrystals, washed with dieth-
ylether and dried in vacuo. Anal. Calc. for
C43H36B2F8N2P2Pt: C, 51.06; H, 3.59; N, 2.78. Found:
C, 51.04; H, 3.48; N, 2.79%.
4.2.4. [Pt(PNCHP-j3P; N; P)Cl]BF4 (2b)
A mixture of 1b (0.300 g, 0.333 mmol) and AgBF4
(0.071 g, 365 mmol) in dichloromethane (12 mL) was
exposed to ultrasound for 1 h, resulting in yellow and
white precipitates. The mixture was filtered through
kieselguhr and the trapped yellow precipitate dissolved
and washed through into the filtrate using acetonitrile,
leaving the insoluble white precipitate behind. The filtrate
was taken to dryness in vacuo and the resulting yellow
residue crystallised from dichloromethane/N-hexane
overnight. Compound 2b (0.248 g, 79.9%) was isolated as
orange crystals, washed with a dichloromethane/N-pen-
tane mixture and air-dried. M.p. 198–200 oC. Anal. Calc.
for C37H29BClF4NP2Pt ꢁ 0.75CH2Cl2: C, 48.72; H, 3.30;
N, 1.51. Found: C, 48.55; H, 3.29; N, 1.56%.
4.2.8. [Pt(PNCHP-j3P; N; P)(3-pico)](BF4)2 (4c)
A mixture of 2b (0.154 g, 0.165 mmol) and AgBF4
(0.0343 g, 0.176 mmol) in acetonitrile (12 mL) was heated
to reflux for ca. 25 min, giving a white precipitate. 3-
Picoline (3-pico) (0.016 mL, 0.18 mmol) was added to the
reaction mixture and refluxing continued for a further 30
min. The white precipitate was removed by filtration
through kieselguhr and the filtrate taken to dryness in
vacuo. The resulting yellow residue was taken into so-
lution with acetonitrile, followed by addition of diethy-
lether to precipitate out the desired product. Compound
4c (0.101 g, 56.5%) was isolated as a very pale yellow
powder, washed with diethylether and air-dried. Anal.
Calc. for C43H36B2F8N2P2Pt ꢁ CH2Cl2: C, 48.20; H, 3.49;
N, 2.56. Found: C, 47.88; H, 3.31; N, 3.05%.
4.2.5. [Pt(PNCHP-j3P; N; P)(MeCN)](BF4)2 (3)
A mixture of 2b (0.401 g, 0.431 mmol) and AgBF4
(0.0899 g, 401 mmol) in acetonitrile (c.a. 15 mL) was
heated to reflux for 27 h, giving a dark-orange solution.
The solvent was removed in vacuo and the resulting
orange residue crystallised from dichloromethane/N-
hexane to yield 3 (0.369 g, 96.0%). Anal. Calc. for
C39H32B2F8N2P2Pt ꢁ 0.5CH2Cl2: C, 47.36; H, 3.32; N,
2.80. Found: C, 47.89; H, 3.45; N, 2.81%.
4.2.9. [Pt(PNCHP-j3P; N; P)(phen)](BF4)2 (5a)
A mixture of 3 (0.114 g, 0.119 mmol) and 1,10-phe-
nanthroline (phen) (0.024 g, 0.133 mmol) in benzene (15
mL) was heated to reflux for 1 h, giving an orange toffee-
like solid. The solvent was removed in vacuo and the
resulting orange residue taken up into dichloromethane
and heated to reflux overnight. The orange solution was
subject to vapour diffusion using N-hexane giving 5a
(0.126 g, 96.4%) as chunky orange crystals. Anal. Calc.
for C49H37B2F8N3P2Pt ꢁ CH2Cl2: C, 50.75; H, 3.32; N,
3.55. Found: C, 51.05; H, 2.95; N, 3.52%.
4.2.6. [Pt(PNCHP-j3P; N; P)(PPh3)](BF4)2 (4a)
A mixture 2b (0.101 g, 0.108 mmol) and AgBF4
(0.0226 g, 0.116 mmol) in acetonitrile (12 mL) was he-
ated to reflux for ca. 25 min, giving a white precipitate.
PPh3 (0.0306 g, 0.117 mmol) was added to the reaction
mixture and refluxing continued for a further 30 min.
This mixture was filtered through kieselguhr and the
trapped yellow precipitate dissolved and washed through
into the filtrate with dichloromethane, leaving the ori-
ginal white precipitate behind. The filtrate solvent was
evaporated in vacuo and the resulting yellow residue
precipitated from dichloromethane/N-hexane overnight.
Compound 4a (0.103 g, 80.8%) was isolated as a very
pale yellow powder, washed with N-pentane and air-
dried. The powder can be recrystallised from a CH2Cl2/
N-hexane vapour diffusion to yield colourless crystals.
4.2.10. [Pt(PNCHP-j3P; N; P)(bipy)](BF4)2 (5b)
A yellow solution of 2b (0.194 g, 0.209 mmol) and
AgBF4 (0.0436 g, 0.224 mmol) in acetonitrile (12 mL)
was heated to reflux for 20 h. The resulting orange so-
lution was filtered through kieselguhr. 2,20-Bipyridine

E.W. Ainscough et al. / Polyhedron 23 (2004) 1159–1168
1167
(bipy) (0.033 g, 0.21 mmol), dissolved in acetonitrile,
was added to the filtrate and refluxing continued for a
further 1 h, giving an intense orange solution. The so-
lution was allowed to cool, followed by solvent removal
in vacuo. Additional white precipitate was removed by
filtration through kieselguhr and washed with acetoni-
trile, and the filtrate plus washings were taken to dryness
in vacuo. The resulting yellow residue was recrystallised
from dichloromethane/N-hexane. Compound 5b (0.141
g, 62.7%) was isolated as orange crystals, washed with
12 mL) and heated to reflux for 1 h. The reaction mixture
was filtered through kieselguhr. N-Pentane was vapour
diffused into the filtrate over a weekend. Compound 8
(0.114 g, 61.9%) was isolated as pale yellow microcrys-
tals, washed with N-pentane and dried in vacuo. Anal.
Calc. for C38H32BF4NP2Pd ꢁ 0.5CH2Cl2: C, 57.78; H,
4.16; N, 1.75. Found: C, 58.15; H, 4.18; N, 1.83%.
4.3. Crystallography
o
N-pentane and air-dried. M.p: 259-260 C. Anal. Calc.
Single crystals of the compounds, 1b, 4a, 5a and 6,
were grown as described under their respective syn-
theses and attached to the ends of glass fibres with
cyanoacrylate glue. Data collection and refinement
were performed as previously described [24]. Table 1
lists the crystal data for the compounds. For 1b, the
imine bond of the PNCHP ligand and contiguous
phenyl rings are disordered over two sites, A and B,
and were refined with a free variable giving the oc-
cupancy of these as 0.67 and 0.33, respectively. In the
case of 6, the platinum atom and the two pyridyl rings
of the terpy ligand lie on a mirror plane and were
refined with special position constraints. The PNCHP
ligand is disordered about this mirror plane and the
two single phenyl rings and the phosphorus are as-
signed with occupancies of 1. When the imine link
between the two phosphorus atoms was refined with
an occupancy of 0.5 (as this was indicated by the
large temperature factors in this part of the molecule
in the initial refinement) with the N constrained to lie
on the mirror plane, unreasonable C@N bond dis-
tances resulted. Removing the special position con-
straint allowed the imine nitrogen, N, and carbon,
C(1), to take their respective disordered positions
slightly above and below the mirror plane, hence
giving bond distances in the usual range.
for C47H37B2F8N3P2Pt ꢁ 0.5CH2Cl2: C, 51.08; H, 3.43;
N, 3.76. Found: C, 51.22; H, 3.26; N, 3.85%.
4.2.11. [Pt(PNCHP-j3P; N; P)(diphos)](BF4)2 (5c)
Compound 3 (0.100 g, 0.104 mmol) and bis(diph-
enylphosphino)ethane (diphos) (0.0420 g, 0.105 mmol)
were dissolved together in dichloromethane (12 mL) and
heated to reflux for 3 h. A small amount of the by-
product [Pt(diphos)2](BF4)2 (0.015 g, 24.5%), as a yellow
precipitate, was removed by filtration and the filtrate set
up for vapour diffusion with N-hexane. Compound 5c
was isolated as a yellow powder which on exposure to
air,
slowly
turns
green.
Anal.
Calc.
for
C63H53B2F8NP4Pt ꢁ 2CH2Cl2: C, 52.52; H, 3.86; N, 0.94.
Found: C, 52.60; H, 3.79; N, 0.58%.
4.2.12. [Pt(PNCHP-j3P; N; P)(terpy)](BF4)2 (6)
Compound 3 (0.100 g, 0.105 mmol) and 2,20,60,200-
terpyridine (terpy) (0.0244 g, 0.105 mmol) were dis-
solved together in dichloromethane (c.a. 12 mL) and
heated to reflux for ca. 3 h. The reaction mixture was
filtered and set up for vapour diffusion in N-hexane.
Compound 6 (0.0919 g, 76.9%) was isolated as orange
crystals, washed with N-pentane and air dried. Anal.
Calc. for C52H40B2F8N3P2Pt: C, 54.24; H, 3.50; N, 4.87.
Found: C, 53.97; H, 3.50; N, 4.85%
5. Supplementary material
4.2.13. [Pd(PNCHP-j3P; N; P)(CH3)]Cl (7)
CCDC 213469 (1b), 213470 (5a), 213471 (4a) and
213472 (6) contain the supplementary crystallographic
data for this paper. These data can be obtained free of
charge via www.ccdc.cam.ac.uk/conts/retrieving.html
(or from the Cambridge Crystallographic Data Centre,
12, Union Road, Cambridge CB2 1EZ, UK; fax: +44-
1223-336033; or data_request@ccdc.cam.ac.uk).
A mixture of [Pd(COD)(CH3)Cl] (0.101 g, 0.381
mmol) and PNCHP (0.208 g, 0.378 mmol) in dichlo-
romethane (12 mL) was stirred at room temperature for
1 h, giving a yellow solution. N-Hexane was added until
a slight cloudiness was observed. Very pale yellow mi-
crocrystals resulted after standing overnight. These were
isolated by filtration, washed with N-pentane and air
dried to yield 7 (0.239 g, 89.4%). Anal. Calc. for
C38H32ClNP2Pd: C, 64.60; H, 4.57; N, 1.98. Found: C,
64.30; H, 4.64; N, 2.01%.
Acknowledgements
We thank Associate Professor C.F. Rickard, Uni-
versity of Auckland, for X-ray data collection, Dr.
P.J.B. Edwards for assistance with NMR spectra and
the Massey University Research Fund for financial
support.
4.2.14. [Pd(PNCHP-j3P; N; P)(CH3)]BF4 (8)
Compound 7 (164 g, 0.232 mmol) and AgBF4 (0.0447
g, 0.230 mmol) were combined in dichloromethane (ca.

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€
(b) P. Wehman, R.E. Rulke, V.E. Kaasjager, P.C.J. Kamer, H.
Kooijman, A.L. Spek, C.J. Elsevier, K. Vrieze, P.W.N.M. van
Leeuwen, J. Chem. Soc., Chem. Commun. (1995) 331.
[7] E.W. Ainscough, A.M. Brodie, P.D. Buckley, A.K. Burrell,
S.M.F. Kennedy, J.M. Waters, J. Chem. Soc., Dalton Trans.
(2000) 2663.
References
ꢂ
[1] (a) G. Sanchez, J. Vives, J.L. Serrano, J. Pe’rez, G. Lo’pez, Inorg.
Chim. Acta 328 (2002) 74, and references therein;
(b) A.D. Getty, K.I. Goldberg, Organometallics 20 (2001) 2545;
(c) K.R. Reddy, K. Surekha, G.-H. Lee, S.-M. Peng, J.-T. Chen,
S.-T. Liu, Organometallics 20 (2001) 1292;
[8] L.M. Engelhardt, J.M. Patrick, C.L. Raston, P. Twiss, A.H.
White, Aust. J. Chem. 37 (1984) 2193.
(d) M.A. Jalil, S. Fujinami, H. Nishikawa, J. Chem. Soc., Dalton
Trans. (2001) 1091;
[9] M.K. Cooper, J.M. Downes, H.J. Goodwin, M. McPartlin, Inorg.
Chim. Acta 76 (1983) L157.
(e) M. Konrad, S. Wuthe, F. Meyer, E. Kaifer, Eur. J. Inorg.
Chem. (2001) 2233;
[10] A. Hazell, A. Mukhopadhyay, Acta Crystrallogr. B 36 (1980)
1647.
(f) S.M. Aucott, A.M.Z. Slawin, J.D. Woollins, J. Chem. Soc.,
Dalton Trans. (2000) 2559;
[11] G.W. Bushnell, K.R. Dixon, M.A. Khan, Can. J. Chem. 52 (1974)
1367, and references therein.
(g) A. Habtemariam, B. Watchman, B.S. Potter, R. Palmer, S.
Parsons, A. Parkin, P.J. Sadler, J. Chem. Soc., Dalton Trans.
(2001) 1306.
[12] K.N. Raymond, T.G. Spiro, A. Terzis, Inorg. Chem. 9 (1970) 2415.
[13] O. Wernberg, A. Hazell, J. Chem. Soc., Dalton Trans. (1980) 973.
[14] G.W. Bushnell, K.R. Dixon, M.A. Khan, Can. J. Chem. 56 (1978)
450.
[2] (a) P.-Y. Shi, Y.-H. Liu, S.-M. Peng, S.-T. Liu, Organometallics
21 (2002) 3203;
[15] L. Cavallo, R. Cini, J. Kobe, L.G. Marzilli, G. Natile, J. Chem.
Soc., Dalton Trans. (1991) 1867.
(b) Y.-C. Chen, C.-L. Chen, J.-T. Chen, S.-T. Liu, Organomet-
allics 20 (2001) 1285;
[16] S. Berger, S. Braun, H.-O. Kalinowski, NMR Spectroscopy of the
Non-metallic Elements, Wiley, Chichester, 1997, p. 837.
[17] G. Dyer, J. Roscoe, Inorg. Chem. 35 (1996) 4098, and references
therein.
(c) H. Yoshida, Y. Honda, E. Shirakawa, T. Hiyama, Chem.
Commun. (2001) 1880.
€
[3] (a) F. Stohr, D. Sturmayr, G. Kickelbick, U. Schubert, Eur. J.
Inorg. Chem. (2002) 2305;
[18] J. Mason (Ed.), Multinuclear NMR, Plenum Press, New York,
1987.
€
(b) C. Muller, C.N. Iverson, R.J. Lachicotte, W.D. Jones, J. Am.
Chem. Soc. 123 (2001) 9718.
[19] D.V. Khasnis, M. Lattman, U. Siriwardane, Inorg. Chem. 28
(1989) 681.
[4] E.W. Ainscough, A.M. Brodie, A.K. Burrell, X. Fan, M.J.R.
Halstead, S.M.F. Kennedy, J.M. Waters, Polyhedron 19 (2000)
2585.
[20] H.E. Bryndza, J.C. Calabrese, M. Marsi, D.C. Roe, W. Tam, J.E.
Bercaw, J. Am. Chem. Soc. 108 (1986) 4805.
[5] (a)
Kennedy, J. Am. Chem. Soc. 123 (2001) 10391;
(b) E.W. Ainscough, A.M. Brodie, A.K. Burrell, S.M.F.
E.W. Ainscough, A.M. Brodie, A.K. Burrell, S.M.F.
[21] G. Banditelli, A.L. Bandini, B. Bovio, Inorg. Chim. Acta 96
(1985) 213.
[22] A. Buijs, G.P.C.M. Dekker, C.J. Elsevier, W.J.J. Smeets, A.L.
Spek, C.H. Stam, P.W.N.M. van Leeuwen, K. Vrieze, Y.F. Wang,
Organometallics 11 (1992) 1937, and references therein.
[23] D.D. Perrin, W.L.F. Armarego, Purification of Laboratory
Chemicals, 3rd ed., Pergamon, Oxford, 1988.
Kennedy, J. Organomet. Chem. 609 (2000) 2;
(c) E.W. Ainscough, A.M. Brodie, A.K. Burrell, A. Derwahl,
S.K. Taylor, Inorg. Chim. Acta (2004) in press.
[6] (a) J.H. Groen, A. de Zwart, M.J.M. Vlaar, J.M. Ernsting,
P.W.N.M. van Leeuwen, K. Vrieze, H. Kooijman, W.J.J. Sma-
ates, A.L. Spek, P.H.M. Budzelaar, Q. Xiang, R.P. Thummel,
Eur. J. Inorg. Chem. (1998) 1129;
[24] S.E. Page, K.C. Gordon, A.K. Burrell, Inorg. Chem. 37 (1998)
4452.