Gas-phase studies on the reactivity of the azido(diethylenetriamine)platinum(II) cation and derived species

Article abstract of DOI:10.1071/CH03101

The recent report of the gas-phase loss of nitrogen from [Pt(dien)N₃]⁺ (dien = diethylenetriamine = N-(2-aminoethyl)ethane-1,2-diamine) under collision-induced dissociation (CID) conditions has prompted us to investigate the intriguing structure(s) of [Pt(dien)N]⁺. This was carried out via CID and ion-molecule reactions (IMR) of [Pt(dien)N]⁺ in the gas phase. Labelling studies (¹⁵N and ²H labelling of the dien ligand) were also employed. As a result, some of the previously proposed structures were ruled out and three other potential structures of [Pt(dien)N]⁺ are considered. Labelling studies also indicate that the hydrogen atoms of both the amino groups and the carbon backbone of the dien ligand are involved in loss of NH₃ from [Pt(dien)N]⁺. The gas-phase chemistry of [Pt(dien)N-NH₃]⁺, the fragmentation product of [Pt(dien)N]⁺, was also probed using IMR and CID. The crystal structure of the [Pt(dien)N₃]⁺ cation has also been determined.

Full text of DOI:10.1071/CH03101

CSIRO PUBLISHING
www.publish.csiro.au/journals/ajc
Aust. J. Chem. 2003, 56, 1201–1207
Gas-Phase Studies on the Reactivity of the
Azido(diethylenetriamine)platinum(ii) Cation and Derived Species
Sheena Wee,A Jonathan M. White,A W. David McFadyenA,B and Richard A. J. O’HairA,B
A
School of Chemistry, University of Melbourne, Parkville 3010, Australia.
B Authors to whom correspondence should be addressed (e-mail: d.mcfadyen@unimelb.edu.au;
rohair@unimelb.edu.au).
The recent report of the gas-phase loss of nitrogen from [Pt(dien)N3]+ (dien = diethylenetriamine = N-(2-amino-
ethyl)ethane-1,2-diamine) under collision-induced dissociation (CID) conditions has prompted us to investigate
the intriguing structure(s) of [Pt(dien)N]+. This was carried out via CID and ion–molecule reactions (IMR) of
[Pt(dien)N]+ in the gas phase. Labelling studies (15N and 2H labelling of the dien ligand) were also employed. As a
result, some of the previously proposed structures were ruled out and three other potential structures of [Pt(dien)N]+
are considered. Labelling studies also indicate that the hydrogen atoms of both the amino groups and the carbon
backbone of the dien ligand are involved in loss of NH3 from [Pt(dien)N]+. The gas-phase chemistry of [Pt(dien)N-
NH3]+, the fragmentation product of [Pt(dien)N]+, was also probed using IMR and CID. The crystal structure of
the [Pt(dien)N3]+ cation has also been determined.
Manuscript received: 23 April 2003.
Final version: 4 June 2003.
Introduction
the dien complex readily undergoes CID with the loss
of NH3.
While the development of the electrospray ionization (ESI)
techniquebyJohnFennhasresultedinaNobelprizefor‘mass
spectrometric analyses of biological macromolecules’,[1] this
technique has also opened up new horizons in the analy-
sis and fundamental gas-phase ion studies of inorganic and
organometallic systems.[2] ESI has provided opportunities to
examine the following properties of inorganic complexes:
(a) their fragmentation reactions including the use of colli-
sionalactivationtoformnovelgas-phasespecies;[3,4] (b)their
ion–molecule reactions, including the ‘gas-phase titration’
of vacant coordination sites;[5] (c) the photoelectron spec-
troscopy of anions;[6] (d) their gas-phase spectroscopy;[7]
(e) their ‘gas-phase’ solvation.[8]
To better understand the gas-phase chemistry of these sys-
tems and the structural nature of the [PtL3N]+ complexes, we
were motivated to more extensively examine the gas-phase
chemistry of [Pt(dien)N3]+. To assist in the elucidation of
mechanistic details, we have prepared the labelled analogues
of this complex—[Pt(15N2dien)N3]+ (where 15N2dien =
N-(2-[15N1]aminoethyl)ethane-1,2-(2-[15N1]diamine) and
[Pt(D5dien)N3]+ (whereD5dien = N-[2-([2H2]amino)ethyl]
ethane-1,2-(2-[2H3]diamine). Inaddition, wehavecarriedout
a single crystal X-ray diffraction study of the [Pt(dien)N3]+
cation to furnish structural information for potential use in
our ongoing study of this azido complex and related systems.
In this report, we describe the results of these investigations.
We have been examining the fundamental gas-phase ion
chemistry of Pt(ii) complexes ligated to tridentate ligands,
such as terpy (2,2ꢀ:6ꢀ2ꢀꢀ-terpyridine), dien, and Me5dien.
As part of this work, we have shown that [Pt(L3)N3]+
systems (where L3 = terpy, dien, and Me5dien) fragment
in the gas phase via loss of N2 to form [Pt(L3)N]+.[9–11]
The ion [Pt(terpy)N]+ readily undergoes IMR in the pres-
ence of the neutral reagents MeOH, MeCN, and Me2CO,
to yield adducts of composition [Pt(terpy)N + L]+ (where
L = MeOH, MeCN, and Me2CO). In the case of the
analogous dien complex, however, adduct formation with
the above mentioned neutral reagents does not occur.
[Pt(dien)N]+ undergoes a very slow substitution reac-
tion instead to form [Pt(dien)N − NH3 + L]+. We have
recently also observed that, unlike its terpy counterpart,[10]
Results and Discussion
Synthesis
The ligand 15N2dien was prepared as shown in Scheme 1.
The tosylated diethanolamine (2) was converted to its
bisphthalimido derivative (3) by reaction with potassium
[15N]phthalimide in dimethylformamide (DMF). Compound
(3) was deprotected to yield the labelled dien ligand by
prolonged reflux in HBr/AcOH.
Gas-Phase Reactions of [Pt(dien)N3]+, [Pt(dien)N]+, and
[Pt(dien)N − NH3]+
The gas-phase CID reactions, as well as ion–molecule reac-
tions, of [Pt(dien)N3]+,[Pt(dien)N]+, and[Pt(dien)N − NH3]+
© CSIRO 2003
10.1071/CH03101
0004-9425/03/121201

1202
R. A. J. O’Hair et al.
were studied using a modified quadrupole ion-trap mass
spectrometer.[12,13]
(a)
340.1 (1)
10 sec
340.1
∗
Gas-phase reactions of [Pt(dien)N3]+ and derived species
are shown in Scheme 2. The four-coordinated [Pt(dien)N3]+
does not react with MeOH, MeCN, or Me2CO (Fig. 1a and
Reaction (1) in Scheme 2) via either ligand addition or lig-
and substitution. Ligand addition is not expected for this
fully coordinated platinum(ii) complex. Unlike [Pt(dien)X]+
(where X = bromide, iodide, thiocynate, cyanate, or pyri-
dine) which lose HX upon CID,[9] no loss of HN3 occurred
from [Pt(dien)N3]+, contrary to our previous report[9] in
which traces of possibly HN3 loss were observed. Upon
CID, [Pt(dien)N3]+ fragments via the loss of N2 to form
[Pt(dien)N]+ (Fig. 2a and Reaction (3) in Scheme 2).
[Pt(dien)N]+ could correspond to a platinum(ii) nitrene (5),
a platinum(iv) nitride (6), or a platinum(iv) species which
has undergone rearrangement to form either (7) or (8)
(Scheme 3). To probe the structure of [Pt(dien)N]+, the com-
plex was isolated and subjected to CID and IMR. Isolation
of [Pt(dien)N]+, however, could not be achieved using a
narrow isolation window as this results in abundant loss of
signal with concomitant formation of very minor amounts
of a fragment at m/z 295 (due to NH3 loss). Thus, a large
100
80
60
40
20
0
260
280
300
320
340
360
380
400
(b)
312.1
∗
340.1 (1)
100
80
60
40
20
0
312.5 (8)
10 sec
[Pt(dien)N Ϫ NH3 ϩ MeOH]ϩ
327.0
260
280
300
320
340
360
380
400
(c)
# 326.9
340.1 (1)
312.5 (8)
100
80
60
40
20
0
TsCl, Et3N
N
H
N
OH
HO
OTs
TsO
295.2 (1)
30 ms
Ts
(2)
(1)
∗
295.2
O
K15
N
O
260
280
300
320
m/z
340
360
380
400
O
15N
O
O
1. HBr/HOAc
2. NaOH
15NH2
H215N
N
H
15N
O
N
Fig. 1. IMR of (a) [195Pt(dien)N3]+, (b) [195Pt(dien)N]+, and (c)
Ts
[
195Pt(dien)N − NH3]+ in the presence of MeOH. ∗ Denotes the pre-
cursor ion; # denotes the MeOH adduct. The number in bracket denotes
the width of the isolation window (in Thomson units; 1 Th = 1 amu per
positive charge) used in the mass-selection process.
(4)
(3)
Scheme 1. Preparation of labelled ligands.
Reaction (2)
Reaction (3)
Reaction (5)
CID
CID
[Pt(dien)N3]ϩ
[Pt(dien)N Ϫ NH3]ϩ
[Pt(dien)N]ϩ
ϪN2
ϪNH3
ϩL
ϩL
Reaction (1)
ϩL
Reaction (6)
Reaction (4)
(minor or slow)
[Pt(dien)N Ϫ NH3 ϩ L]ϩ
L ϭ RЈOH,
MeCN,
Me2CO
Scheme 2. Gas-phase reactions of [Pt(dien)N3]+ and derived species.

Gas-Phase Reactivity of the Azido(diethylenetriamine)platinum(ii) Cation
1203
be very reactive towards the neutral reagents MeOH, MeCN,
and Me2CO. In a similar fashion, the lack of adduct formation
indicates that structure (6) can be excluded as this structure is
analogous to the proposed structure of [Pt(terpy)N]+ which
forms adducts with neutral reagents.[10] The observation of
slow ligand subsitution is more consistent with either of the
structures (7) or (8). We note that ligand substitution reac-
tions have been observed for other metal complexes in the
gas-phase.[15]
340.1 (1)
(a)
ϪN2 ϪNH3 295.1
100
80
ϪN2
312.0
60
∗
40
20
0
340.1
†
‡
ϪN2 ϪCN2H4
312.9
296.0
268.1
Upon CID, [Pt(dien)N]+ loses NH3 to form [Pt(dien)N −
NH3]+ (Fig. 2b and Reaction (5) in Scheme 2) which sub-
sequently forms adducts readily with the neutral reagents
(Fig. 1c and Reaction (6) in Scheme 2). Figure 1c shows
that abundant adducts were formed with only 30 ms reaction
time, implying that [Pt(dien)N − NH3]+ is coordinatively
unsaturated (i.e. a three-coordinate complex, which would be
expected to readily add ligands in the gas-phase).[5,12] Once
again, these CID results are consistent with structures such
as (7) or (8) being precursors to [Pt(dien)N − NH3]+.
250 260 270 280 290 300 310 320 330 340 350
340.1 (1)
(b)
ϪNH3 295.2
100
312.5 (8)
80
60
40
∗
312.2
†
ϪCN2H4
268.2
‡
‡
20
0
313.0
295.9
322.9
2
Gas-Phase Reactions of [Pt(Me5dien)N3]+
250 260 270 280 290 300 310 320 330 340 350
The complex [Pt(Me5dien)N3]+, which is the fully methy-
lated analogue of [Pt(dien)N3]+, also undergoes CID to yield
the species [Pt(Me5dien)N]+.[11] In view of this observa-
tion, it was envisaged that CID studies of [Pt(Me5dien)N]+
could provide further insights into the possible structure(s)
of [Pt(dien)N]+ and the mechanistic basis of Reaction (5).
For instance, if [Pt(Me5dien)N]+ were to adopt structure (9)
(Scheme 4, an analogue of (6)), NMe2H loss would be
expected upon CID. However, if (9) were to isomerize to
(10) or (11) (analogues of (7) and (8) respectively), CID of
[Pt(Me5dien)N]+ may lead to the loss of NMe3.
m/z
Fig. 2. CID of (a) [195Pt(dien)N3]+ and (b) [195Pt(dien)N]+.
∗ Denotes the precursor ion; † denotes the water adduct; ‡ denotes the
CO adduct; # denotes the MeOH adduct. The number in bracket denotes
the width of the isolation window (in Th) used in the mass-selection
process.
ϩ
ϩ
H
N
H
N
N
PtII
N
N
PtIV
N
N
H
H
H
H
However, upon CID, [Pt(Me5dien)N]+ did not parallel the
behaviour of [Pt(dien)N]+, instead undergoing consecutive
losses of HCN and NH2 and complex dehydrogenation reac-
tions as illustrated in Scheme 5 (data not shown). Despite
the apparent similarities of these two compounds, the com-
plex fragmentation behaviour of [Pt(Me5dien)N]+ does not
provide insights into the possible structures of [Pt(dien)N]+.
H
H
H
H
N
(5)
(6)
ϩ
ϩ
H
N
N
N
N
PtIV
N
PtIV
N
Gas-Phase Studies of [Pt(15N2dien)N3]+ and
[Pt(D5dien)N3]+
H
H
H
H
H
N
H
N
H
H
H
In an attempt to enhance our understanding of the structure of
[Pt(dien)N]+, experiments were carried out using the labelled
systems [Pt(15N2dien)N3]+ and [Pt(D5dien)N3]+.
(7)
(8)
Scheme 3. Potential structures of [Pt(dien)N]+.
CID of [Pt(15N2dien)N]+ (Fig. 3a) shows that the NH3
loss from [Pt(15N2dien)N]+ does not involve the labelled
nitrogen from the 15N2dien ligand. This indicates that the
nitrogen of the NH3 lost in Reaction (5) is the residual nitro-
gen of the azido ligand and does not originate from the amino
group of the dien ligand. Thus, structure (6) can be ruled out
as a potential structure for [Pt(dien)N]+.
isolation window, as wide as 8 amu, was required to isolate
[Pt(dien)N]+ in decent abundance. This observation implies
that [Pt(dien)N]+ is fragile.[14] IMR of [Pt(dien)N]+ shows
that [Pt(dien)N]+ does not form adducts with MeOH, MeCN,
and Me2CO. Instead, it undergoes a very slow ligand sub-
stitution reaction with these neutral reagents (Fig. 1b and
Reaction (4) in Scheme 2). Figure 1b shows that only traces
of [Pt(dien)N − NH3 + MeOH]+ were formed even with a
10 s reaction time. This implies that structure (5) can be
excluded since one might expect the ligand N atom in (5) to
To establish the origin of the hydrogen of the evolved NH3,
CID was carried out upon [Pt(D5dien)N]+, the precursor of
which was generated in the condensed phase by exchange
with D2O. The solution was further diluted with D2O and
subjected to ESI-MS (see Experimental for details).The N–H

1204
R. A. J. O’Hair et al.
ϩ
ϩ
ϩ
Me
N
Me
N
N
PtIV
N
N
PtIV
N
N
N
PtIV
N
N
N
Me
Me
Me
Me
Me
Me
Me
Me
Me
N
Me
Me
Me
Me
(10)
Scheme 4. Potential structures of [Pt(Me5dien)N]+.
(9)
(11)
[Pt(Me5dien)N3]ϩ
ϪN2
(Fig. 3b). The small peak at m/z 299.1 corresponds to
[Pt(D5dien)N − NDH2]+ although it could also be ascribed
to a CO adduct of [Pt(D5dien)N − CN2D2H2]+ (m/z 271).
As a result, the loss of NDH2 from [Pt(D5dien)N]+cannot be
established with certainty. These observations establish that
at some stage both N–H and C–H bond scission has occurred
and indicate (12), (13), and (14) (Scheme 6) as further poten-
tial structures for [Pt(dien)N]+. These structures are not
without precedent, as platinum(ii) imine complexes derived
from non-aromatic ligands are well known.[17] More impor-
tantly, there is an example of a platinum(iv)-coordinated dien
ligand undergoing a dehydrogenation reaction in the con-
densed phase to give a platinum(ii)-bound Schiff base ligand
NH2CH2CH NCH2CH2NH2.[18]
CID
n = 1, 2, 3
ϪnH2
[Pt(Me5dien)N Ϫ nH2]ϩ
ϪHCN
[Pt(Me5dien)N]ϩ
CID
CID
[Pt(Me5dien)N Ϫ HCN Ϫ nH2]ϩ
ϪHCN
ϪnH2
[Pt(Me5dien)N Ϫ HCN]ϩ
ϪNH2
CID
ϪNH2
CID
ϪnH2
[Pt(Me5dien)N Ϫ HCN Ϫ NH2]ϩ
[Pt(Me5dien)N Ϫ HCN Ϫ NH2 Ϫ nH2
Scheme 5. Gas-phase reactions of [Pt(Me5dien)N3]+ and derived
species.
Gas-Phase Fragmentation of [Pt(dien)N − NH3 + L]+
ϪNH3 297.1
(a)
342.1 (1)
314.5 (8)
100
80
60
40
20
0
Surprisingly, the fragmentation of [Pt(dien)N − NH3 + L]+
(where L = MeOH, MeCN, and Me2CO) yields similar prod-
ucts to those observed via CID of [Pt(terpy)N + L]+.[10]
All the adducts [Pt(dien)N − NH3 + L]+ fragment, via the
loss of the neutral reagent L, to yield the parent complex
ion [Pt(dien)N − NH3]+ (Reaction (6) in Scheme 2). Only
[Pt(dien)N − NH3 + MeOH]+ fragments via the additional
pathway shown in Reaction (7), involving loss of CH2O
to yield [Pt(dien)N − NH3 + H2]+. Interestingly, the bare
platinum cation reacts with MeOH to give PtH+2 , amongst
other ionic products, while PtCH+2 behaves quite differ-
ently towards MeOH.[19] In order to determine whether this
oxidation occurs for other alcohols, ethanol and isopropanol
were also examined. Both [Pt(dien)N − NH3 + EtOH]+
and[Pt(dien)N − NH3 + PriOH]+ form[Pt(dien)N − NH3 +
H2]+ via the loss of CH3CHO and Me2CO respectively upon
CID (Reaction (7)).
∗
314.2
314.9
#
ϪCN[15N]H
329.0
4
324.8
269.1
250 260 270 280 290 300 310 320 330 340 350
ϪND3 297.2
(b)
345.1 (1)
100
317.0 (8)
ϪND2H
298.1
80
60
40
20
0
ϪCN2D2H2
271.2
270.2
255.1
∗
ϪNDH2
299.1
317.2
312.1
285.1
[Pt(dien)N − NH3 + R1R2CH(OH)]+
324.9
→ [Pt(dien)N − NH3 + H2]+ + R1R2CO
(7)
250 260 270 280 290 300 310 320 330 340 350
m/z
The formation of [Pt(dien)N − NH3 + H2]+ from
[Pt(dien)N − NH3 + RꢀOH]+ (where Rꢀ = Me, Et, and Pri)
indicates that [Pt(dien)N − NH3 + RꢀOH]+ activates both the
OH and CH bonds of the primary and secondary alcohols
examined. In order to evaluate the influence of the OH bond
in this reaction, the CID reactions of the adduct formed from
an ether, [Pt(dien)N − NH3 + Et2O]+ were also examined.
Upon CID, [Pt(dien)N − NH3 + Et2O]+ fragments to give
[Pt(dien)N − NH3 + EtOH]+ (Reaction (8)), which further
Fig. 3. CID of (a) [195Pt(15N2dien)N]+ and (b) [195Pt(D5dien)N]+.
∗ Denotes the precursor ion; # denotes the MeOH adduct. The number
in bracket denotes the width of the isolation window (in Th) used in the
mass-selection process.
protons of the dien ligand are more acidic than the C–H pro-
tons and this will be enhanced on coordination of the ligand to
a platinum centre.[16] To our surprise, then, [Pt(D5dien)N]+
lost both ND3, ND2H and possibly NDH2 upon CID

Gas-Phase Reactivity of the Azido(diethylenetriamine)platinum(ii) Cation
1205
ϩ
ϩ
ϩ
H
H
N
N
N
PtII
N
PtII
N
H
PtII
N
H
N
H
N
H
N
H
H
H
H
H
H
H
N
N
N
H
H
H
H
H
H
(12)
(13)
(14)
Scheme 6. Proposed structures of [Pt(dien)N]+ containing a modified dien framework.
C(5)
N(4)
C(3)
C(6)
C(2)
N(1)
N(7)
Pt
N(8)
N(9)
N(10)
Fig. 4. A diagram of the [Pt(dien)N3]+ cation showing the atom
labelling scheme. Ellipsoids are scaled to the 20% probability level.
Table 1. Selected bond length [Å] and angle [◦] data for the
cation [Pt(dien)N3]+
Fig. 5. A stacking diagram of the [Pt(dien)N3]+ cations. Ellipsoids
are scaled to the 20% probability level. The dashed lines illustrate the
weak interaction between atoms N(8), N(9), and N(10) with the platinum
centres of the adjacent [Pt(dien)N3]+ cations stacked along the b-axis
direction.
Pt–N(1)
Pt–N(4)
Pt–N(7)
Pt–N(8)
2.054(11)
2.064(11)
2.020(8)
2.030(10)
N(1)–Pt–N(4)
N(1)–Pt–N(7)
N(1)–Pt–N(8)
N(4)–Pt–N(7)
N(4)–Pt–N(8)
N(7)–Pt–N(8)
84.4(5)
167.6(6)
92.9(5)
83.3(4)
161.5(5)
98.4(5)
potential use in our ongoing study of this azido complex and
related systems. A diagram of the [Pt(dien)N3]+ complex is
presented in Figure 4. Large anisotropic temperature factors
for the fluorine and oxygen atoms of the triflate counterion
were indicative of disorder, however attempts to model these
atoms with split occupancies were unsuccessful and resulted
in unreasonable geometries.
Selected structural parameters for [Pt(dien)N3]+ are pre-
sented in Table 1. The platinum centre is of distorted square-
planar geometry due to: (a) the restricted bite angle of dien
which is less than 90◦; and (b) the non-coplanarity of atom
N(8) of the azido ligand with the plane defined by Pt–N(1)–
N(4)–N(7) (the mean deviation of the plane Pt–N(1)–N(4)–
N(7) is 0.0088 Å, with the maximum deviation from the
plane to be 0.0157 Å by the platinum centre). However,
atom N(8) of the azido ligand deviates from the plane by
0.61 Å. The non-coplanarity of the azido ligand with the
plane Pt–N(1)–N(4)–N(7) may be due to the weak interaction
between atoms N(8), N(9), and N(10) of the azido ligand with
the platinum centres of the adjacent [Pt(dien)N3]+ cations
stacked along the b-axis direction (Fig. 5). (The distances
between N(8), N(9), and N(10) and the platinum centres
fragments to give [Pt(dien)N − NH3 + H2]+ (Equation (7)).
[Pt(dien)N − NH3 + Et2O]+
→ [Pt(dien)N − NH3 + EtOH]+ + CH2 CH2 (8)
Since it is not possible to delineate between the various
structural possibilities for [Pt(dien)N]+, and consequently
[Pt(dien)N − NH3]+, it is premature to speculate on the way
in which alcohols and ethers might interact with this latter
system. The same is true for comments on the mechanistic
basis of these interesting reactions.
Crystallography of [Pt(dien)N3]CF3SO3
We carried out a single-crystal X-ray diffraction study of the
[Pt(dien)N3]+ in order to furnish structural information for

1206
R. A. J. O’Hair et al.
of the adjacent [Pt(dien)N3]+ cations vary from 3.374 to
3.939 Å. These distances, which are longer than the sum of
the van derWaals radii for N and Pt (3.35 Å),[20] infers that the
interactionbetweentheazidoligandwiththeplatinumcentres
of the adjacent [Pt(dien)N3]+ cations is indeed very weak.)
As observed with the azido ligand in the [Pt(terpy)N3]+
system,[10] there is also a kink at the azido ligand in
the [Pt(dien)N3]+ system, with an angle N(8)–N(9)–N(10)
of 159(3)◦.
Synthesis
Preparation of N,N-Bis[2-(p-tolylsulfonyloxy)ethyl]-
p-toluenesulfonamide
N,N-Bis[2-(p-tolylsulfonyloxy)ethyl]-p-toluenesulfonamide was pre-
pared according to a literature procedure.[21]
Preparation of N,N-Bis[2-(phthalimido)ethyl]-
p-toluenesulfonamide
N,N-Bis[2-(phthalimido)ethyl]-p-toluenesulfonamide was prepared
according to a literature procedure.[22]
Conclusions
Preparation of N-(2-aminoethyl)ethane-1,2-diamine (dien)
The complex [Pt(dien)N3]+ behaves in a similar way to
[Pt(terpy)N3]+ in the gas phase but the behaviour of the
CID-derived species [Pt(dien)N]+ and [Pt(terpy)N]+ is quite
different. The complex [Pt(terpy)N]+ does not undergo frag-
mentation reactions although it readily forms adducts with
neutral reagents (alcohols, acetonitrile, and acetone). In con-
trast, [Pt(dien)N]+ undergoes ready fragmentation in the gas
phase via the loss of NH3, whereas it is involved in very slow
substitution reaction with neutral reagents. Our observations
of the behaviour of [Pt(dien)N]+ with neutral reagents and
the study of the fragmentation of [Pt(15N2dien)N3]+ appear
to rule out (5) (a platinum(ii) nitrene) or (6) (a platinum(iv)
nitride) as structures for this complex. Potential structures of
[Pt(dien)N]+ are proposed to be four-coordinate complexes
containing an amide ligand (NH2) such as complexes (7), (8),
(12), (13), and (14). This proposition is based on the frag-
mentation behaviour of [Pt(D5dien)N]+, which establishes
that the hydrogen atoms of NH3 lost in this process origi-
nate from both the amino group and the carbon backbone of
the dien ligand. These results indicate that the fragmentation
reactions of platinum complexes containing polymethylene-
linked donor atoms, and indeed complexes of other met-
als, are likely to be more complicated and varied than
one might anticipate from comparisons with the condensed
phase.
N,N-Bis[2-(phthalimido)ethyl]-p-toluenesulfonamide (5.51 g, 0.0106
moles)wasaddedto30%HBr/HOAc(200 mL)andthesolutionrefluxed
for 3 d. The solvent was evaporated and the residue was then extracted
with water (30 mL). Insoluble solids were removed by filtration, and the
pH of the filtrate was adjusted to pH ∼ 11 by addition of a saturated
aqueous solution of NaOH. The total volume of the resulting solution
was then reduced to 30 mL by evaporation on the steambath. Continuous
extraction of the solution with CHCl3 for 36 h, followed by removal
of the CHCl3 under reduced pressure afforded dien (60%). The NMR
spectrum of the product was identical to that of a pure sample of dien.[23]
Preparation of N,N-Bis[2-([15N]phthalimido)ethyl]-
p-toluenesulfonamide and N-(2-[15N1]aminoethyl)ethane–
1,2-(2-[15N1]diamine (15N2dien)
These compounds were prepared in the same way as the unlabelled
analogues using potassium [15N]phthalimide in place of the unlabelled
analogue.
Preparation of [Pt(15N2 dien)Cl]Cl
This complex was prepared by according to a literature method[24] using
15N2dien in place of dien.
Preparation of Complexes for Mass Spectrometry
A literature procedure[25] was used to prepare the complex [Pt(dien)-
N3]NO3.
The complex [Pt(15N2dien)N3]+ was prepared in situ by stirring
a mixture of [Pt(15N2dien)Cl]Cl (0.103 g, 2.77 × 10−4 mol) and NaN3
(0.178 g, 2.74 × 10−3 mol) in water (9 mL) for 24 h. The solution was
then diluted to 0.1 g mL−1 before mass spectrometric analysis.
The complex [Pt(D5dien)N3]+ was prepared in situ by stirring
[Pt(dien)N3]NO3 in D2O for 22 h. It was then diluted to 0.1 mg mL−1
in D2O before mass spectrometric analysis.
All the adducts [Pt(dien)N − NH3 + L]+ fragment via the
loss of the neutral reagent L to yield the parent complex
ion [Pt(dien)N – NH3]+. Only [Pt(dien)N − NH3 + RꢀOH]+
adduct ions (Rꢀ = Me, Et, and Pri) fragment via an addi-
tional pathway to yield [Pt(dien)N − NH3 + H2]+ ions with
concomitant oxidation of the alcohols.
[Pt(Me5dien)Cl]ClO4 was prepared according to a literature
method.[9]
The complex [Pt(Me5dien)N3]+ (1.24 g, 2.46 × 10−3 mol) was gen-
erated in situ by treatment of [Pt(Me5dien)Cl]+ with one equivalent
of Ag+ followed by removal of the precipitated AgCl. NaN3 (0.385 g,
5.92 × 10−3 mol) was added to the filtrate which was then diluted to
0.1 mg mL−1 for subsequent ESI-MS experiments.
Experimental
Materials and Techniques
Solvents and reagents used in sample preparation were of either lab-
oratory or analytical reagent (LR, AR) grade; those used for ESI-MS
were of HPLC grade. NMR spectra were recorded on a UnityPlus 300
(Varian) spectrometer; 1H shifts are given in ppm relative to CDCl3
(δH 7.24). ESI-MS were recorded using a quadrupole ion trap mass
spectrometer (Finnigan-MAT model LCQ) equipped with electrospray
ionization.Typically, samples were diluted (0.1 mg mL−1) prior to being
introduced to the mass spectrometer at a flow rate of 3.0 µL min−1 via
electrospray ionization (ESI conditions were spray voltage 4.0–5.5 kV,
capillary temperature 100–250◦C, nitrogen sheath gas pressure
20–80 psi, and auxiliary gas flow rates 0 (arbitrary units); the capillary
voltage and tube lens offset were optimized by examining the ion current
as a function of voltage, which was varied from −135 to +135 V and
−200 to +200 V respectively).
Gas-Phase Ion Chemistry Experiments
For [Pt(L3)N3]+ (where L3 = dien and Me5dien), and their derivatives
(except [Pt(dien)N]+), either a single isotope (arising from 195Pt) or the
isotope envelope (consisting of the 194Pt, 195Pt, and 196Pt isotopes) was
mass selected with a 1 amu or a 3 amu window respectively. Only the
product fragment ion [Pt(dien)N]+ was isolated with an 8 amu window.
Mass-selected cations were subjected to CID and IMR to investigate
their fragmentation reactions and their reactivity with neutral reagents.
Typically CID conditions were activation amplitude 0.5–1.5V, activation
(Q) 0.25V, and activation time 30 ms. Ion–molecule reactions were car-
ried out as previously described.[12] Neutral reagents were introduced
into the ion trap via the helium line. Reaction times were varied from
30 ms to 10 s.

Gas-Phase Reactivity of the Azido(diethylenetriamine)platinum(ii) Cation
1207
X-Ray Crystallography
Soc. 1998, 120, 12 646. (b) R. A. J. O’Hair, Chem. Comm.
2002, 20] and metal oxo ions [(c) P. Dalgaard, C. J. McKenzie,
J. Mass Spectrom. 1999, 34, 1033].
Crystals of [Pt(dien)N3]CF3SO3 suitable for diffraction studies were
grown by mixing saturated aqueous solution of [Pt(dien)N3]NO3
and NaCF3SO3 and allowing the mixture to stand at room tem-
perature for 2 d. The best crystal, a rod of approximate dimensions
0.4 × 0.12 × 0.1 mm, was selected for data collection. Intensity data
were collected at 20◦C with a Bruker SMARTApex CCD detector using
MoKα radiation (graphite crystal monochromator, λ 0.71073 Å).[26]
Accurate cell parameters and crystal orientation were obtained by least-
squares refinement of 2762 reflections with θ values between 3◦ and
27◦. Data were reduced using the program SAINT[26] and corrected for
absorption (ratio of max/min transmission 0.41).[26] 4829 data were col-
lected with 2774 unique (Rint = 0.0406) and 2408 observed (I > 2σ(I)).
A thermal ellipsoid plot which depicts 20% ellipsoids is presented in
Figure 4.
The structure was solved by direct methods and difference Fourier
synthesis. Hydrogen atoms were included in calculated positions. Full-
matrix least-squares refinement on F2, using all data, was carried out
with anisotropic displacement parameters applied to all non-hydrogen
atoms. The weighting scheme employed was of the type w = [σ2(Fo2) +
(0.07680P)2]−1 where P = (Fo2 + 2Fc2)/3. In the final difference map
the maximum and minimum peak heights were 3.1 and −1.5 e A−3
respectively.
[4] Redox reactions have been used to generate gas-phase peptide
radicals from metal complexes: (a) S. Wee, R. A. J. O’Hair,
W. D. McFadyen, Rapid Commun. Mass Spectrom. 2002, 16,
884. (b) I. K. Chu, C. F. Rodriquez, T. C. Lau, A. C. Hopkinson,
K. W. M. Siu, J. Phys. Chem. B 2000, 104, 3393.
[5] (a) M. Y. Combariza, R. W. Vachet, J. Am. Soc. Mass Spectrom.
2002, 13, 813. (b) R. W. Vachet, J. R. Hartman, J. W. Gertner,
J. H. Callahan, Int. J. Mass Spectrom. 2001, 204, 101. (c)
R. W. Vachet, J. H. Callahan, J. Mass Spectrom. 2000, 35, 311.
(d) R. W. Vachet, J. A. R. Hartman, J. H. Callahan, J. Mass
Spectrom. 1998, 33, 1209.
[6] (a) L.-S. Wang, X.-B. Wang, J. Phys. Chem. A 2000, 104,
1978. (b) X.-B. Wang, L.-S. Wang, J. Am. Chem. Soc. 2000,
122, 2339.
[7] (a) L. A. Posey, Adv. Met. Semicond. Clusters 2001, 5, 145.
(b) T. G. Spence, B. T. Trotter, L. A. Posey, J. Phys. Chem.
A 1998, 102, 7779.
[8] S.-W. Lee, S. Chang, D. Kossakovski, H. Cox, J. L. Beauchamp,
J. Am. Chem. Soc. 1999, 121, 10 152.
[9] M. L. Styles, R. A. J. O’Hair, W. D. McFadyen, L. Tannous,
R. J. Holmes, R. W. Gable, J. Chem. Soc. Dalton Trans 2000, 93.
[10] S. Wee, M. J. Grannas, W. D. McFadyen, R. A. J. O’Hair,
Aust. J. Chem. 2001, 54, 245.
[Pt(dien)N3]CF3SO3: C5H13N6F3O3SPt, M 489.36, monoclinic,
space group C2, a 24.553(2), b 6.6616(5), c 8.4808(6) Å, β 104.446(1);
V 1343.27(17) Å3, Z 8, Dx 2.395 g cm−3, T 293 K, amber rod,
0.40 × 0.12 × 0.1 mm; µ 10.65 mm−1, 2θmax 54.96◦; 4829 reflections
collected, 2774 unique (Rint 0.0406, 172 parameters, wR 0.1209 for all
data, R 0.0464 for 2408 data with I > 2σ(I)).
[11] M. L. Styles, Ph.D. Thesis 2001, Ch. 4 (University of Melbourne:
Melbourne).
[12] G. E. Reid, R. A. J. O’Hair, M. L. Styles, W. D. McFadyen,
R. J. Simpson, Rapid Commun. Mass Spectrom. 1998, 12, 1701.
[13] S. Gronert, J. Am. Soc. Mass Spectrom. 1998, 9, 845.
[14] J. E. McClellan, J. P. Murphy, J. J. Mulholland, R. A. Yost, Anal.
Chem. 2002, 74, 402.
Acknowledgments
[15] (a) H. Deng, P. Kebarle, J. Am. Chem. Soc. 1998, 120, 2925.
(b) H. Deng, P. Kebarle, J. Phys. Chem. A 1998, 102, 571.
(c) D. V. Zagorevskii, J. L. Holmes, C. H. Watson, J. R. Eyler,
Eur. Mass Spectrom. 1997, 3, 27.
[16] M. M. Jones, Ligand Reactivity and Catalysis 1968 (Academic:
New York, NY).
[17] V. G. Albano, G. Natile, A. Panunzi, Coord. Chem Rev. 1994,
133, 67.
[18] F. Schwarz, H. Schollhorn, U. Thewalt, B. Lippert, J. Chem.
Soc., Chem. Commun. 1990, 18, 1282.
W.D.McF. thanks the NHMRC for financial support. R.A.J.O.
thanks the Australian Research Council for financial sup-
port and the University of Melbourne for funds to purchase
the LCQ. S.W. acknowledges the award of the following
awards: IPRS (International Postgraduate Research Schol-
arship) and MIRS (Melbourne International Research Schol-
arship).We thank Dr Michelle L. Styles for carrying out some
preliminary experiments.
[19] M. Broenstrup, D. Schroeder, H. Schwarz, Organometallics
1999, 18, 1939.
[20] A. Bondi, J. Phys. Chem. 1964, 68, 441.
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1
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[3] Decarboxylation has been used to synthesize a range of novel
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