The synthesis and crystal structures of the first examples of six-membered inorganic iridacycles containing the [(Ph2PE)2N]- ligand (E=S or Se)

Article abstract of DOI:10.1016/S0022-328X(99)00351-4

The reaction of the potassium salt of either imidotetraphenyldithiodiphosphinate (L¹) or imidotetraphenyldiselenodiphosphinate (L²) with [Cp*IrCl(μ-Cl)]₂ in THF yields the complexes Cp*Ir{Ph₂P(S)NP(S)Ph₂-S,S′}Cl (1) and Cp*Ir{Ph₂P(Se)NP(Se)Ph₂-Se,Se′}Cl (2), respectively. Compounds 1 and 2 can be further converted into a range of new mononuclear species comprising mixed [Cp*,E₃] donor sets by metathetic exchange of the chloro ligand for either thiocyanate or selenocyanate. These are the first examples of neutral monomeric Ir(III) complexes which have this ligand set. All compounds were characterised by a combination of NMR spectroscopy (¹H and ³¹P{¹H}), IR spectroscopy, microanalysis and X-ray crystallography.

Full text of DOI:10.1016/S0022-328X(99)00351-4

www.elsevier.nl/locate/jorganchem
Journal of Organometallic Chemistry 588 (1999) 99–106
The synthesis and crystal structures of the first examples of
six-membered inorganic iridacycles containing the [(Ph2PE)2N]−
ligand (E=S or Se)
Jonathan Parr *, Martin B. Smith 1, Alexandra M.Z. Slawin
Department of Chemistry, Loughborough Uni6ersity, Loughborough, Leicstershire LE11 3TU, UK
Received 28 April 1999
Abstract
The reaction of the potassium salt of either imidotetraphenyldithiodiphosphinate (L1) or imidotetraphenyldiselenodiphosphinate
(L2) with [Cp*IrCl(m-Cl)]2 in THF yields the complexes Cp*Ir{Ph2P(S)NP(S)Ph2-S,S%}Cl (1) and Cp*Ir{Ph2P(Se)NP(Se)Ph2-
Se,Se%}Cl (2), respectively. Compounds 1 and 2 can be further converted into a range of new mononuclear species comprising
mixed [Cp*,E3] donor sets by metathetic exchange of the chloro ligand for either thiocyanate or selenocyanate. These are the first
examples of neutral monomeric Ir(III) complexes which have this ligand set. All compounds were characterised by a combination
of NMR spectroscopy (1H and 31P{1H}), IR spectroscopy, microanalysis and X-ray crystallography. © 1999 Elsevier Science S.A.
All rights reserved.
Keywords: Crystal structure; Inorganic heterocycle; Iridacycle; NMR spectroscopy; Phosphorus(V) ligands; Pseudo-halides
A search of the chemical literature reveals no neu-
tral monomeric complexes of the type Cp*Ir‘E’3,
where ‘E’3 represents any ligand set which coordinates
to the iridium through three sulfurs, three seleniums
or a mixture of sulfur and selenium, irrespective
of the substitution at the chalcogen. The most closely
related compounds are the remarkable series of
complexes reported by Herberhold et al. with general
formula [Cp*Ir(PMe3)h2-Sn], where n=5, 6 or 7
[2]. The dimeric compounds [(Cp*Ir)2S8] reported
by Chen and Angelici [3] and {[Cp*Ir(SiPr)]2h2-Sn}
where n=2 or 9 reported by Hidai and co-workers
[4] and the cubane-like tetrameric complexes
[Cp*M(m3-E)]4 (M=Rh, Ir, E=S, Se) [5] indicated
that there may be the possibility of preparing
monomeric compounds if the correct ligand set were
used. Starting from this premise, compounds 1 and 2
were metathesised with the pseudo-halides thiocyanate
and selenocyanate to prepare complexes of general
formula Cp*Ir‘E’3 where ‘E’3 represents ligands with
the donor set [S, S%, S%%], [S, S%, Se], [Se, Se%, S] or [Se,
Se%, Se%%].
1. Introduction
Imidotetraaryldichalcogenodiphosphinates of gen-
eral formula [(R2PE)2N]−, where E=O, S or Se,
have a well-defined coordination chemistry, with ex-
amples of simple complexes known for elements from
each block of the periodic table [1]. These complexes
are usually characterised by their high thermal and
chemical stability and their ease of preparation. Com-
plexes of metals with this class of ligand have found
applications in catalysis [1e] as NMR shift reagents
[1f] and in metal-selective extraction technology [1h].
We report here the use of two such ligands, where
R=Ph, E=S (L1) or Se (L2), to prepare complexes
comprising the first examples of the six-membered in-
organic iridacycles Ir(EPNPE) (E=S, 1 and E=Se,
2).
* Corresponding author. Fax: +44-01519-223925.
1 Also corresponding author.
E-mail addresses: j.parr@lboro.ac.uk (J. Parr), m.b.smith
@lboro.ac.uk (M.B. Smith)
0022-328X/99/$ - see front matter © 1999 Elsevier Science S.A. All rights reserved.
PII: S0022-328X(99)00351-4

Table 1
Analytical and spectroscopic data for 1–7
Compound
31P (ppm)
1H(arom) (ppm)
1H(Cp*) (ppm)
C(calc)
H(calc)
N(calc)
w(CH) Cp*
w(CN)
w(PE)
w(P2Nasym) (cm−1
)
[1J(77Seꢀ31P) Hz]
(cm−1
)
(cm−1
)
(cm−1
)
1
2
3
4
5
6
7
31.0
18.3 [572]
29.3
15.7 [567]
29.0
15.5 [572]
29.7
8.20–6.90
8.25–6.86
8.04–7.13
8.05–7.10
7.98–7.11
8.05–7.05
8.10–6.92
1.34
1.39
1.43
1.47
1.46
1.50
1.50
45.25 (45.20)
45.15 (45.10)
50.30 (50.40)
44.95 (45.30)
47.70 (47.70)
42.85 (43.10)
51.65 (52.00)
4.05 (3.90)
3.75 (3.90)
4.30 (4.25)
3.95 (3.80)
3.90 (4.00)
3.45 (3.65)
4.35 (4.45)
1.45 (1.50)
1.25 (1.55)
3.45 (3.35)
3.15 (3.00)
3.40 (3.15)
2.70 (2.85)
1.30 (1.50)
2914
2914
2912
2910
2913
2913
2919
–
–
571
540
570
542
569
542
567
1189, 1173, 1104
1193, 1174
2101
2101
2107
2108
–
1190, 1178, 1105
1229, 1181, 1153
1195, 1177, 1105
1232, 1181
1181, 1106 a
/
a Bands partially obscured by the intense (SꢁO) stretches associated with the sulfonyl group of the counter ion.
Table 2
Crystal data for 1–7
1
2
3
4
5
6
7
Formula
Colour
C34H35ClIrNP2S2.CHCl3
Orange
C34H35ClIrN2P2Se2.CHCl3
Orange
C35H35IrN2P2S3
Orange
C35H35IrN2P2SSe2
Orange
C35H35IrN2P2S2Se
Red
C35H35IrN2P2Se3
Orange
C41H42IrNO3P2S3
Green
Crystal size (mm)
0.36×0.4×0.4
10.8707(3)
11.8831(3)
0.16×0.36×0.36
10.91310(10)
12.58110(10)
14.3903(3)
0.1×0.23×0.3
11.69110(10)
18.9620(10)
15.84980(10)
0.03×0.06×0.13
11.8638(5)
19.0625(9)
0.1×0.1×0.25
11.7340(10)
19.0872(2)
0.1×0.1×0.2
11.87670(10)
19.0646(4)
0.06×0.1×0.25
15.3812(2)
11.8593(2)
,
a (A)
588
,
b (A)
)
,
c (A)
17.1741(4)
16.0809(7)
15.9826(2)
16.1446(3)
22.4774(3)
h (°)
i (°)
k (°)
Volume (A )
System
109.6890(10)
94.2810(10)
111.8020(10)
1888.07(8)
75.3620(10)
88.740(10)
80.0790(10)
1882.57(5)
104.60(10)
105.2790(10)
104.610(10)
105.1900(10)
98.7600(10)
106
3
,
3400.22(4)
Monoclinic
P21/n
3508.2(3)
Monoclinic
P21/n
3464.00(6)
Monoclinic
P21/n
3527.82(10)
Monoclinic
P21/n
4052.28(10)
Monoclinic
P21/c
Triclinic
Triclinic
(
(
Space group
Z
P1
2
P1
2
4
4
4
4
4
Total data
Unique data
Rint
Absorption correction
R
Rw
8335
5396
0.0284
None
0.0231
0.0586
8183
5304
0.0228
None
0.0264
0.0632
14794
4922
0.0175
SADABS
0.0193
0.0487
21371
8211
0.0744
14584
4951
0.0897
20623
8241
0.1419
17224
5834
0.1832
Semi-emp. C scans SADABS
0.0494
0.0992
Semi-emp. C scans Semi-emp. C scans
0.0388
0.0618
0.0395
0.0802
0.0423
0.0695

J. Parr et al. / Journal of Organometallic Chemistry 588 (1999) 99–106
101
2. Experimental
2.1. Materials
All reactions were carried out under an atmosphere
of dry oxygen-free nitrogen. All solvents were distilled
prior to use. [Cp*IrCl(m-Cl)]2 [6] and K[(Ph2PE)2N]
(E=S [7] or Se [8]) were prepared according to pub-
lished procedures. Ag(SCN), Ag(C7H7SO3), NH4(SCN)
and K(SeCN) were obtained commercially and used as
received.
2.2. Instrumentation
IR spectra were recorded as KBr pellets over the
range 4000–200 cm−1 using a Perkin–Elmer system
2000 FT spectrometer. The 1H-NMR spectra were
recorded on a Bruker AC250 FT spectrometer (250
MHz) with chemical shifts (l) reported relative to
external TMS (see Table 1). The 31P{1H}-NMR spectra
were recorded on a Jeol FX90Q spectrometer (36.2
MHz) with chemical shifts (l) reported relative to
external 85% H3PO4; all NMR spectra were recorded in
CDCl3 solutions. Elemental analyses were performed
using a Perkin–Elmer 2400 CHN elemental analyser by
the Loughborough University Microanalytical Service
within the Department of Chemistry.
2.3. X-ray crystallography
The X-ray crystallographic studies were performed
on 1–7 at ambient temperatures using a Siemens
SMART diffractometer with graphite-monochromated
,
MoꢀKa radiation (u=0.71073 A) and ꢀ scans. The
crystal data, a summary of the data collections and the
Scheme 1. The preparation of 1 and 2.
Scheme 2. The preparation of 3–6.

102
J. Parr et al. / Journal of Organometallic Chemistry 588 (1999) 99–106
Fig. 1. The molecular structures of 1 and 2 (H atoms omitted for clarity, solvate molecule not shown).
Fig. 2. The molecular structures of 3 and 4 (H atoms omitted for clarity).
structure refinements for these compounds are given in
Table 2; selected bond lengths and angles are collected
in Table 3. All structures were solved by direct methods
and all of the non-hydrogen atoms refined with an-
isotropic displacement parameters. Refinement was by
full-matrix least-squares methods on F2, calculations
were performed using the program SHELXTL-PC [9].
the product was obtained as orange crystals after va-
pour diffusion of 60:80 petroleum. The product 1 was
collected by suction filtration and dried in vacuo. Yield:
0.044 g, 80%.
2.4.2. Ir(C5(CH3)5)p2-{Ph2P(Se)NP(Se)Ph2-Se,Se%}Cl
(2)
To a solution of [Cp*IrCl(m-Cl)]2 (0.031 g, 0.0389
mmol) in THF (5 ml) was added K[L2] (0.047 g, 0.0808
mmol) as a solid. The solution was stirred at r.t. for 30
min, after which the solvent was removed under re-
duced pressure. The orange residue was extracted into 4
ml of CH2Cl2 and filtered through a Celite pad. The
volume was reduced to 1 ml and addition of 60:80
petroleum (10 ml) gave the product 2 as an orange solid
which was collected by suction filtration and dried in
vacuo. Yield: 0.054 g, 77%.
2.4. Preparation of complexes
2.4.1. Ir(C5(CH3)5)p2-{Ph2P(S)NP(S)Ph2-S,S%}Cl (1)
To a solution of [Cp*IrCl(m-Cl)]2 (0.025 g, 0.031
mmol) in THF (5 ml) was added K[L1] (0.04 g, 0.068
mmol) as a solid. The solution was stirred at room
temperature (r.t.) for 30 min, after which the solvent
was removed under reduced pressure. The orange
residue was extracted into 2 ml of CHCl3 from which

J. Parr et al. / Journal of Organometallic Chemistry 588 (1999) 99–106
103
Fig. 3. The molecular structures of 5 and 6 (H atoms omitted for clarity).
solid. The solution was stirred at r.t. for 40 h, after
which the solvent was removed under reduced pressure.
The residue was extracted into 4 ml of CH2Cl2 and
filtered through a Celite pad. The volume was reduce to
1 ml and addition of 60:80 petroleum (9 ml) gave
complex 4. The solid was collected by suction filtration
and dried in vacuo. Yield: 0.021 g, 70%.
2.4.3. Ir(C5(CH3)5)p2-{Ph2P(S)NP(S)Ph2-S,S%}SCN (3)
To a solution of 1 (0.04 g, 0.049 mmol) in THF (5
ml) was added Ag(SCN) (0.009 g, 0.054 mmol) as a
solid. The solution was stirred at r.t. for 30 min, during
which time a fine white precipitate formed. The solvent
was removed under reduced pressure, and the orange
residue was extracted into 2 ml of CHCl3 and filtered
through a Celite pad. Vapour diffusion of 60:80
petroleum into this solution gave the product 3 as
orange–red crystals. Yield: 0.034 g, 67%.
2.4.5. Ir(C5(CH3)5)p2-{Ph2P(S)NP(S)Ph2-S,S%}SeCN
(5)
To a solution of 1 (0.05 g, 0.061 mmol) in THF (5
ml) was added K(SeCN) (0.010 g, 0.068 mmol) as a
solid. The solution was stirred at r.t. for 3 h, after
which the solvent was removed under reduced pressure.
The orange–red residue was extracted into 2 ml of
CHCl3 and filtered through a Celite pad. Vapour diffu-
sion of 60:80 petroleum into this solution gave the
product 5 as red crystals. Yield: 0.035 g, 64%.
2.4.4. Ir(C5(CH3)5)p2-{Ph2P(Se)NP(Se)Ph2-Se,Se%}
SCN (4)
To a solution of 2 (0.029 g, 0.032 mmol) in THF (5
ml) was added NH4(SCN) (0.010 g, 0.131 mmol) as a
2.4.6. Ir(C5(CH3)5)p2-{Ph2P(Se)NP(Se)Ph2-Se,Se%}-
SeCN] (6)
To a solution of 2 (0.029 g, 0.032 mmol) in THF (5
ml) was added K(SeCN) (0.020 g, 0.139 mmol) as a
solid. The solution was stirred at r.t. for 24 h, after
which the solvent was removed under reduced pressure.
The residue was extracted into 4 ml of CH2Cl2 and the
solution filtered through a Celite pad. The volume was
reduced to 1 ml and addition of 60:80 petroleum (10
ml) gave complex 6, which was collected by suction
filtration and dried in vacuo. Yield: 0.026 g, 84%.
2.4.7. [Ir(C5(CH3)5)p2-{Ph2P(S)NP(S)Ph2S,S%}]-
(C7H7SO3) (7)
To a solution of 1 (0.035 g, 0.043 mmol) in THF (5
ml) was added Ag(C7H7SO3) (0.014 g, 0.048 mmol) as a
solid. The solution was stirred at r.t. for 30 min, during
Fig. 4. The structure of the cation in 7 (H atoms omitted for clarity,
anion not shown).

104
J. Parr et al. / Journal of Organometallic Chemistry 588 (1999) 99–106
which time a white precipitate formed and the solution
turned a deep green colour. The solvent was removed
under reduced pressure and the green residue was ex-
tracted into 2 ml of THF. The product was obtained as
green–black crystals after slow diffusion of diethyl
ether. Yield: 0.029 g, 72%.
ano-stool’ geometries. Both L1 and L2 act as chelating
ligands through their respective chalcogens, and so
adopt a cis geometry at the metal centre. For 1 and 2
(Fig. 1) the conformation of the (Ir–E–P–N–P–E)
ring is best described as boat like, where the Ir and the
N represent the ‘bow’ and ‘stern’, whilst in the other
structures the ring can be loosely described as puckered
(Figs. 2 and 3). Global comparisons of the bond lengths
of HL1 [10] and HL2 [8] in the solid state with the
complexes 1, 3, 5 and 2, 4, 6, respectively reveals some
distinct trends (Table 3). Most noticeably, the length of
the (PE) bond is increased on deprotonation and coor-
3. Results and discussion
The dimeric complex [Cp*IrCl(m-Cl)]2 reacts with
K[L1] and K[L2] in THF solution to form the
monomeric complexes 1 and 2, respectively (Scheme 1)
using a method similar to that previously reported for
the rhodium analogues [1b]. These complexes can be
used as the starting point for the preparation of a range
of substituted products by exchange of the labile chloro
ligand for thiocyanate (3, 5) and selenocyanate (4, 6)
ligands, Scheme 2. The products from these reactions
are rare examples of monomeric Cp*IrE3 complexes,
where E3 represents a three atom donor set of either
mixed or single chalcogens as the donor site of a ligand.
Analytical data for complexes 1–7 are presented in
Table 1.
,
dination (between 2.035(2) and 2.013(1) A in 1, 3, 5, c.f.
1
,
1.950(1) and 1.937(1) A in HL ; between 2.191(2) and
,
,
2.171(2) A for 2, 4, 6, c.f. 2.101(1) and 2.085(1) A in
HL2) and the (PN) bond length is reduced (between
,
1.601(3) and 1.573(3) A in 1, 3, 5, c.f. 1.683(2) and
1
,
,
1.672(2) A in HL ; between 1.595(4) and 1.575(6) A for
2
,
2, 4, 6, c.f. 1.684(4) and 1.678(4) A in HL ). These
changes can be rationalised in terms of a delocalisation
of the charge and bonds within the iridacycle formed,
such that the (PE) bond in the complex has far more
single-bond character than in the free ligand, and the
(PN) bond experiences an effective increase in bond
order. The values for the 1J(77Seꢀ31P) coupling con-
stants are smaller than those seen for HL2, again in-
dicative of a reduction in the (PSe) bond order. The
changes in bond lengths are entirely consistent with the
changes seen for other complexes of these ligands with
transition metals [1b–d,g,8]. For each of these products
1–6, there is a small but seemingly consistent variation
in some of the structural parameters, which may indi-
cate that there is at least in the solid state a preponder-
ance of one of the contributing canonical forms rather
than a true averaging such as would be expected in a
fully delocalised system. The distances [IrꢀE(1)] and
[IrꢀE(2)] vary by up to 10% in some complexes, and
there are distinct differences in [P(1)ꢀN(1)], [P(2)ꢀN(1)]
and [E(1)ꢀP(1)] [E(2)ꢀP(2)] bond lengths. It is not clear
whether this variation is significant and carried through
to the solution state or is an artefact of the solid state
structure, but it has been cited previously as an indica-
tion of incomplete delocalisation within the metallacy-
cle [8].
A similar observation has been made by Valderrama
and Contreras in the solid state structure of the cation
in the complex [Cp*Ir{PO(OMe)2}{h2-(SPPh2)2CH2-
S,S%]BF4 containing the disulfide of bis(diphenylphos-
phino)methane (dppm) as a ligand [11]. In this case the
(PꢀS) bonds are the same within 0.5%, but in the same
complex the (IrꢀS) bonds differ by ca. 2%. Since this
ligand is entirely symmetrical with no delocalisation, it
may well indicate that the asymmetry observed in the
bond lengths of 1–6 is not a real effect of incomplete
delocalisation at all.
All of the complexes isolated are stable microcrys-
talline solids with good solubility in common organic
solvents. Spectroscopic analysis of 1–7 reveals a high
degree of similarity in their IR and NMR responses.
Further, within the two groups of complexes, those
with L1 (1, 3, 5, and 7) and those with L2 (2, 4, and 6),
the similarities are even more pronounced.
1
The H-NMR data for 1–7 (Table 1) show very little
variation in the position of the (C5(CH3)5) resonance
(1.34–1.50 ppm), a result that is indicative of the
similarity of these complexes, and the resonances due to
the aromatic protons are found to be similarly consis-
tent. The 31P{1H}-NMR data also reflect this congruity
with a more pronounced dependence upon whether the
ligand is L1 or L2 rather than any coherent dependence
upon the nature of the monodentate ligand X. For both
types of complex, the largest value for the chemical
shift is seen for X=Cl, but shows very little variation
between X=SCN or SeCN. The 1J(77Se–31P) couplings
observed for 2, 4 and 6 are reduced by approximately
100 Hz with respect to the value observed for K[L2]
(1J(77Seꢀ31P)=687 Hz). This similarity within the two
types of complex is continued in the IR data for 1–7
where the values of w(PE) for 1, 3, 5, 7 vary by only 4
cm−1, and for 2, 4, 6 by only 2 cm−1. The wasym(PN)
values are also strongly convergent, while the w(CN)
responses indicate that in 3–6 the pseudohalide is E-
bound.
Crystallographic studies (Tables 2 and 3) reveal
structures for 1–6 that are very much in keeping with
simple predictions, with overall pseudo tetrahedral ‘pi-

J. Parr et al. / Journal of Organometallic Chemistry 588 (1999) 99–106
105
The ligands HL1 and HL2 have a pronounced simi-
larity to the dichalcogenides of dppm, and the literature
for these ligands contains examples of h2 coordination
through both chalcogens [11–13] or, when deproto-
nated, through a [C, S] donor set [14,15] and even h3
coordination through a [C, Se, Se%] donor set [16].
Although there are examples of L1 and L2 binding
metals in a similar fashion, using [N, S] [17] and [N, Se,
Se%] donor sets [18], there is no evidence so far to
suggest that these different binding modes are available
to complexes of Ir(III).
Compound 7 is rather unusual in that after removal
of the chloro ligand by reaction with silver p-tolylsul-
fonate, the coordinatively unsaturated cation formed
does not under the conditions used readily accept a
molecule of solvent as a ligand, nor does it form even a
weak interaction with the anion in the solid state (Fig.
4). Further, there is no evidence for any agostic interac-
tions with other areas of the cation or any tendency to
dimerise. Instead, the cation rearranges to give a per-
pendicular arrangement of the Cp* with respect to the
plane defined by [IrꢀS(1)ꢀS(2)] (90.1°), a similar struc-
tural motif to that seen for the related ruthenium
complexes reported by Mashima et al. [19]. The ion in
7 is formally 16-electron, which in Ir(I) is usually
associated with a square planar geometry, although
examples of Ir(III) with this geometry are less well
known. Comparison of the crystallographic data ob-
tained for 7 with 1–6 shows that in the cation the (IrꢀS)
bonds are shortened, consistent with the Ir in 7 having
a greater Lewis acid character. The angle defined by
(PꢀNꢀP) is also significantly compressed (125.9(3) in 7
c.f. 131.7(2)–134.1(3)° 1–6) as are both the (SꢀPꢀN)
angles (116.7(2) and 116.8(2) 7, c.f. 118.0(2)–118.9(1)°
1–6).
cies, and will continue to be the subject of much
research.
5. Supplementary material
Data have been deposited in the Cambridge Crystal-
lographic Database as CCDC nos. 118867–72 (com-
pounds 1–6) and CCDC no. 118896 (compound 7).
Copies of this information may be obtained free of
charge from the Director, CCDC, 12, Union Road,
Cambridge CB2 1EZ (Fax: +44-1223-336-033; email:
deposit@ccdc.cam.ac.uk or www: http://www.ccdc.
cam.ac.uk).
Acknowledgements
The authors thank Johnson Matthey plc. for the
generous loan of iridium salts.
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364.
The reaction of 2 with silver p-tolylsulphonate yields
a green solution and a yellow solid which precipitates
from the THF solution. Examination of the solution by
31P{1H}-NMR showed one major component at l +
21.9 ppm, in addition to a small amount of unreacted 2.
We tentatively ascribe this major component to a com-
pound analogous to 7, as [Cp*Ir{Ph2P(Se)NP-
(Se)Ph2ꢀSe,Se%}](C7H7SO3) (8). Isolation of the crude
yellow solid by filtration and examination by 31P{1H}-
NMR indicated the presence of a major species at l
+10.2 ppm and a small amount of 2. The identity of
both species awaits further elucidation and these results
will be reported in due course.
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