Bis(azido) compounds of Pd and Pt with bulky phosphine ligands (dppn=1,8-bis(diphenylphosphino)naphthalene, dppf=1,1′-bis(diphenylphosphino)ferrocene, 1-dpn=1-diphenylphosphino-naphthalene): Preparation, structures, and reactivity toward isocyanides

Article abstract of DOI:10.1016/j.molstruc.2005.12.024

Pd-bis(azido) compounds [Pd(dppn)(N₃)₂] and [Pd(dppf)(N₃)₂], which contain bulky chelating bis(phosphine) ligands (dppn=1,8-bis(diphenylphosphino)naphthalene, dppf=1,1′-bis(diphenylphosphino)ferrocene), were prepared from the corresponding chlorides and NaN₃. We also prepared the Pt-bis(azido) compound [Pt(1-dpn)(SMe₂)(N₃)₂] containing a bulky monodentate phosphine (1-dpn=1-diphenylphosphino-naphthalene). All these compounds underwent [2+3] cycloaddition with isocyanides (R-NC, R=cyclohexyl, tert-butyl, 2,6-dimethylphenyl) to convert azido ligands to five-membered, C-coordinated tetrazolate rings. In addition, we observed the [Pd(dppn)Cl₂]-mediated C-C coupling of PhC{triple bond, short}CH to generate the η²-PhC{triple bond, short}C-C{triple bond, short}CPh ligand. All compounds have been structurally characterized by X-ray diffraction.

Full text of DOI:10.1016/j.molstruc.2005.12.024

Journal of Molecular Structure 789 (2006) 209–219
www.elsevier.com/locate/molstruc
Bis(azido) compounds of Pd and Pt with bulky phosphine
ligands (dppnZ1,8-bis(diphenylphosphino)naphthalene,
dppfZ1,10-bis(diphenylphosphino)ferrocene,
1-dpnZ1-diphenylphosphino-naphthalene): Preparation,
structures, and reactivity toward isocyanides
*
Hyun Sue Huh, Yeon Kyoung Lee, Soon W. Lee
Department of Chemistry (BK21), Institute of Basic Science, Sungkyunkwan University, Natural Science Campus, Suwon 440-746, South Korea
Received 19 November 2005; received in revised form 30 December 2005; accepted 30 December 2005
Available online 13 February 2006
Abstract
Pd-bis(azido) compounds [Pd(dppn)(N3)2] and [Pd(dppf)(N3)2], which contain bulky chelating bis(phosphine) ligands (dppnZ1,8-bis
(diphenylphosphino)naphthalene, dppfZ1,10-bis(diphenylphosphino)ferrocene), were prepared from the corresponding chlorides and NaN3. We
also prepared the Pt-bis(azido) compound [Pt(1-dpn)(SMe2)(N3)2] containing a bulky monodentate phosphine (1-dpnZ1-diphenylphosphino-
naphthalene). All these compounds underwent [2C3] cycloaddition with isocyanides (R–NC, RZcyclohexyl, tert-butyl, 2,6-dimethylphenyl) to
convert azido ligands to five-membered, C-coordinated tetrazolate rings. In addition, we observed the [Pd(dppn)Cl2]-mediated C–C coupling of
PhCbCH to generate the h2-PhCbC–CbCPh ligand. All compounds have been structurally characterized by X-ray diffraction.
q 2006 Elsevier B.V. All rights reserved.
Keywords: dppn; dppf; 1-dpn; Pd- and Pt-bis(azido) compounds; Isocyanide
1. Introduction
carbodiimido and C-tetrazolato ligands, formed by concomitant
N–C coupling with N2 elimination (for the carbodiimido ligand)
and [2C3] cycloaddition (for the C-tetrazolato ligand). In
addition, we have studied cycloaddition of alkynes mediated by
Pd and Rh complexes for several years [14–17]. In particular, we
found that [Pd(dppf)Cl2] mediated the trimerization of pheny-
lethynes (PhCbCH) in the presence of triethylamine in ethanol
to give [Pd(dppf)(2,3,5-triphenylfulvene)], which contains a
fulvene group [15].
[2C3] Cycloaddition of unsaturated organic compounds,
such as isocyanide, nitrile, carbon disulfide, and alkyne, to the
metal–azido bond has long been attracted [1–11]. These
reactions usually give C- or N-coordinated tetrazolato or
triazolato metal compounds, depending on the nature of the
unsaturated compounds and spectator ligands.
We previously reported the preparation, structure, and
reactivity of the Pt-bis(azido) compound, [Pt(dppf)(N3)2],
which contains a bulky chelating ligand 1,10-bis(diphenylpho-
sphino)ferrocene (dppf) [12]. Reactions of [Pt(dppf)(N3)2] with
isocyanide (R–NC, RZtert-butyl or cyclohexyl) gave C-coor-
dinated tetrazolatoPtcompounds. Wealsoreportedthestructure
of a cyclic dimer [Pd2(C8H4N6)2(PMe3)4], which was prepared
from Pd(PMe3)2(N3)2 and 1,4-phenylene diisocyanide
(C6H4(NC)2) [13]. This cyclic compound contains both
As a continuous research, we decided to investigate the
reactivity of bis(azido) compounds of Pd and Pt that contain
bulky phosphine ligands, including dppf, 1,8-bis(diphenylpho-
sphino)naphthalene (dppn), and 1-(diphenylphosphino)-
naphthalene (1-dpn). Our study was focused on the reactivity
of these compounds toward isocyanides (R–NC, RZcyclo-
hexyl, tert-butyl, 2,6-dimethylphenyl). Herein, we report the
preparation, structures, and reactivity of [Pd(dppn)(N3)2] (1),
[Pd(dppf)(N3)2] (4), and [Pt(1-dpn)(SMe2)(N3)2] (6).
*
Corresponding author. Tel.: C82 31 290 7066; fax: C82 31 290 7075.
E-mail address: swlee@chem.skku.ac.kr (S.W. Lee).
2. Experimental
All reactions have been performed at room temperature
under argon. Sodium azide, cyclohexyl isocyanide, tert-butyl
0022-2860/$ - see front matter q 2006 Elsevier B.V. All rights reserved.
doi:10.1016/j.molstruc.2005.12.024

210
H.S. Huh et al. / Journal of Molecular Structure 789 (2006) 209–219
isocyanide, 2,6-dimethylphenyl isocyanide, and phenylethyne
(phenylacetylene, PhCbCH) were purchased. [Pd(dppn)Cl2]
[18], [Pd(dppf)Cl2] [19], and [Pt(1-dpn)(SMe2)Cl2] [18] were
prepared by the literature methods. All products were
recrystallized from CH2Cl2-pentane.
(CDCl3): d 26.4 (1P, d, JZ73.3 Hz), 9.5 (1P, d, JZ73.3 Hz).
Anal. Calcd for C50H36P2Pd: C, 74.59; H, 4.51. Found:
C, 74.85; H, 4.38. Mp (dec.): 144–146 8C. IR (KBr): 2156
(CbC) cmK1
.
1H, 13C{1H}, and 31P{1H} NMR spectra were recorded with
a Varian Unity Inova 500 MHz spectrometer. IR spectra were
recorded with a Nicolet 320 FT IR spectrophotometer.
Elemental analyses were performed by the Korea Basic
Science Center.
2.4. Preparation of [Pd(dppf)(N3)2] (4)
NaN3 (0.075 g, 1.038 mmol) was added to 30 ml of CH2Cl2
containing [Pd(dppf)Cl2] (0.20 g, 0.346 mmol), and then the
resulting slurry was stirred for 48 h. The solvent was removed
under vacuum to give dark orange solids, which were extracted
with 30 ml of CH2Cl2. The solvent was evaporated under
vacuum and washed with hexane (2!10 ml) to give orange
2.1. Preparation of [Pd(dppn)(N3)2] (1)
1
NaN3 (0.064 g, 0.891 mmol) was added to 30 ml of THF
containing [Pd(dppn)Cl2] (0.20 g, 0.297 mmol), and then the
resulting slurry was stirred for 48 h. The solvent was removed
under vacuum to give yellow solids, which were extracted with
30 ml of CH2Cl2. The solvent was evaporated under vacuum
and washed with hexane (2!10 ml) to give yellow solids of 1
solids of 4 (0.185 g, 0.249 mmol, 72%). H NMR (CDCl3): d
7.80–7.26 (20H, m, PPh2), 4.42 (4H, d, JZ1.5 Hz, C5H4), 4.23
(4H, d, JZ1.5 Hz, C5H4). 13C{1H} NMR (CDCl3): d 135.1–
129.4 (PPh2), 76.86–74.54 (C5H4). 31P{1H} NMR (CDCl3): d
32.8. Anal. Calcd for C34H28N6P2FePd: C, 54.83; H, 3.79; N,
11.28. Found: C, 54.85; H, 3.95; N, 11.04. Mp (dec.): 225–
(0.17 g, 0.248 mmol, 84%). H NMR (CDCl3): d 8.21 (2H, d,
226 8C. IR (KBr): 2043 (N3) cmK1
.
1
JZ3.5 Hz, Np), 7.54 (2H, t, JZ7.5 Hz, Np), 7.44 (2H, m, Np),
7.41–7.23 (20H, m, PPh2). 13C{1H} NMR (CDCl3): d
139.1–120.1 (NpCPPh2). 31P{1H} NMR (CDCl3): d 20.2.
Anal. Calcd for C34H26N6P2Pd: C, 59.45; H, 3.81; N, 12.23.
Found: C, 60.01; H, 3.98; N, 11.99. Mp (dec.): 143–145 8C. IR
2.5. Preparation of [Pd(dppf)(CN4-t-Bu)2] (5)
This compound was prepared similarly to compound 2.
Compound 4 (0.10 g, 0.134 mmol) was treated with excess
tert-butyl isocyanide (0.067 g, 0.806 mmol) to give yellow
(KBr): 2063 (N3) cmK1
.
1
solids of 5 (0.058 g, 0.064 mmol, 48%). H NMR (CDCl3): d
2.2. Preparation of [Pd(dppn)(CN4–Cy)2] (2)
8.21–6.63 (20H, broad, m, PPh2), 4.82 (2H, s, C5H4), 4.36 (2H,
s, C5H4), 4.25 (2H, s, C5H4), 3.83 (2H, s, C5H4), 1.22 (18H, s, t-
Bu). 13C{1H} NMR (CDCl3): d 138.3–128.7 (PPh2), 77.9–72.7
(C5H4), 58.88 (CMe3), 30.20 (CMe3). 31P{1H} NMR (CDCl3):
d 13.4. Anal. Calcd for C44H46N8P2FePd: C, 58.01; H, 5.09; N,
12.30. Found: C, 58.85; H, 5.30; N, 11.99. Mp (dec.): 148–
To a yellow solution of compound 1 (0.10 g, 0.148 mmol) in
25 ml of CH2Cl2 was added excess cyclohexyl isocyanide
(0.097 g, 0.885 mmol). The resulting solution was stirred for
6 h, and the solvent was removed under vacuum and washed
with hexane (2!10 ml) to give bright yellow solids of 2
(0.056 g, 0.062 mmol, 42%). d 8.16 (2H, d, JZ7.0 Hz, Np),
7.52–7.46 (4H, m, Np), 7.35–7.12 (20H, broad, m, PPh2), 4.67
(2H, m, cyclohexyl), 1.67–1.07 (20H, broad, m, cyclohexyl).
13C{1H} NMR (CDCl3): d 164.8 (dd, JC–PZ166 (trans), 25
(cis), CN4), 138.9–123.4 (NpCPPh2), 58.9 (cyclohexyl), 54.1
(cyclohexyl), 33.8 (cyclohexyl), 25.9 (cyclohexyl). 31P{1H}
NMR (CDCl3): d 13.4. Anal. Calcd for C48H48N8P2Pd: C,
63.68; H, 5.34; N, 12.38. Found: C, 63.54; H, 5.47; N, 12.55.
150 8C. IR (KBr): 2236 (s) cmK1
.
2.6. Preparation of [Pt(1-dpn)(SMe2)(N3)2] (6)
This compound was prepared similarly to compound 4.
[Pt(1-dpn)(SMe2)Cl2] (0.30 g, 0.468 mmol) was treated with
excess NaN3 (0.09 g, 1.415 mmol) to give yellow solids of 6
1
(0.27 g, 0.398 mmol, 87%). H NMR (CDCl3): d 8.37 (1H, d,
JZ8.5 Hz, Np), 8.00 (2H, d, JZ8.0 Hz, Np), 7.93 (2H, d, JZ
8.0 Hz, Np), 7.77–7.40 (10H, broad, m, PPh2), 7.22 (2H,
quartet, JZ7.0 Hz, Np), 2.06 (6H, s, SMe2). 13C{1H} NMR
(CDCl3): d 134.9–128.7 (NpCPPh2), 29.7–22.3 (SMe2).
31P{1H} NMR (CDCl3): d 5.43 (Jpt–pZ3554 Hz).Anal. Calcd
for C24H23SPN6Pt: C, 44.10; H, 3.55; N, 12.86. Found: C,
44.25; H, 3.38; N, 12.65. Mp (dec.): 163–166 8C. IR (KBr):
Mp (dec.): 178–180 8C. IR (KBr): 2127 (s) cmK1
.
2.3. Preparation of [Pd(dppn)(h2-PhCbC–CbCPh)] (3)
To a yellow solution of [Pd(dppn)Cl2] (0.15 g, 0.214 mmol)
in 25 ml of CH2Cl2 and 15 ml of ethanol was added 0.12 ml of
NEt3 (0.087 g, 0.860 mmol) and 0.23 ml of PhCbCH (0.22 g,
2.15 mmol). The solution was stirred for 10 h, and the resulting
solution was concentrated under vacuum to give a bright brown
powder. The resulting precipitates were filtered and washed
with diethyl ether (2!10 ml) and hexane (2!10 ml) to give
yellow solids of 3 (0.083 g, 0.105 mmol, 49%). d 8.21–8.14
(2H, m, Np), 7.53–7.39 (4H, m, Np), 7.37–7.17 (30H, m,
PPh2Cphenyl). 13C{1H} NMR (CDCl3): d 139.6–122.0 (NpC
PPh2Cphenyl), 81.8 (CbC), 74.1 (CbC). 31P{1H} NMR
2053 (N3) cmK1
.
2.7. Preparation of [Pt(t-Bu–NC)2(CN4–t-Bu)2] (7)
This compound was prepared similarly to compound 2.
Compound 6 (0.10 g, 0.153 mmol) was treated with excess
tert-butyl isocyanide (0.08 g, 0.99 mmol) to give pale-yellow
1
solids of 7 (0.057 g, 0.093 mmol, 61%). H NMR (CDCl3): d
1.78 (18H, s, CN4–t-C4H9), 1.43 (18H, s, t-C4H9–NC).

H.S. Huh et al. / Journal of Molecular Structure 789 (2006) 209–219
211
13C{1H} NMR (CDCl3): d 31.2, 30.9, 29.9 (t-C4H9). Anal.
Calcd for C20H36N10Pt: C, 39.27; H, 5.93; N, 19.63. Found: C,
39.45; H, 6.18; N, 20.02. Mp (dec.): 108–111 8C. IR (KBr):
53.79; H, 4.51; N, 17.42. Found: C, 54.17; H, 4.40; N, 17.61.
Mp (dec.): 154–156 8C. IR (KBr): 2216 (s) cmK1
.
2197 (s) cmK1
.
2.9. X-ray structure determination
2.8. Preparation of
[Pt(2,6-Me2–C6H3–NC)2(CN4–2,6-Me2–C6H3)2] (8)
All X-ray data were collected on a Siemens P4 diffract-
ometer equipped with a Mo X-ray tube. Intensity data were
empirically corrected for absorption with j-scan data. All
calculations were carried out with the use of the SHELXTL
programs [20]. All crystal structures were solved by direct
methods. All non-hydrogen atoms were anisotropically, unless
otherwise specified. All hydrogen atoms were generated in
ideal positions and refined in a riding model. In the crystal of
2$pentane, the co-crystallized pentane showed extreme
structural disorder and its carbon atoms were refined
isotropically. Details on crystal data and intensity data are
given in Table 1.
This compound was prepared similarly to compound 7.
Compound 6 (0.10 g, 0.153 mmol) was treated with excess 2,6-
dimethylphenyl isocyanide (0.120 g, 0.92 mmol) to give pale-
yellow solids of 8 (0.074 g, 0.092 mmol, 60%). 1H NMR
(CDCl3): d 7.28–7.19 (6H, m, CN4–2,6-Me2–C6H3), 7.10–7.04
(6H, m, 2,6-Me2–C6H3–NC), 2.20 (12H, m, CN4–2,6-Me2–
C6H3), 1.74 (12H, s, 2,6-Me2–C6H3–NC). 13C{1H} NMR
(CDCl3): d 136.4–125.3 (phenyl), 18.9 (CN4–2,6-Me2–C6H3).
18.6 (2,6-Me2–C6H3–NC). Anal. Calcd for C36H36N10Pt: C,
Table 1
X-ray data collection and structure refinement details
1
2$Pentane
3
4$CH2Cl2
5$CH2Cl2
6
7
8
Formula
C
34H26N6P2Pd C53H60N8P2Pd C50H36P2Pd
C35H30Cl2-
FeN6P2Pd
829.74
C45H48Cl2-
FeN8P2Pd
996.00
C24H23N6PPtS C20H36N10Pt
C36H36N10Pt
Fw
686.95
977.43
805.13
653.60
611.68
803.84
Temp (K)
Crystal color
Crystal shape
Crystal size
(mm3)
296(2)
296(2)
296(2)
296(2)
295(2)
296(2)
295(2)
296(2)
Yellow
Rod
Yellow
Orange
Block
Red
Brown
Yellow
Block
White
White
Rod
Rod
Block
Block
Block
0.80!0.42
!0.38
0.70!0.42
!0.38
0.26!0.16
!0.12
0.82!0.20
!0.16
0.48!0.40
!0.34
0.20!0.18
!0.08
0.42!0.12
!0.06
0.36!0.26
!0.16
Cryst syst
Space group
Triclinic
PK1
Monoclinic
P21/c
Triclinic
P-1
Monoclinic
P21/n
Triclinic
PK1
Monoclinic
P21
Monoclinic
P21/c
Monoclinic
P21/c
˚
a (A)
˚
b (A)
˚
c (A)
10.052(6)
12.308(7)
14.111(7)
101.721(4)
108.953(6)
111.223(7)
1434(1)
2
20.260(2)
12.947(2)
18.670(2)
10.371(2)
13.864(3)
14.521(3)
98.00(3)
91.43(1)
111.80(1)
1913.0(7)
2
11.126(3)
18.170(4)
17.686(4)
10.535(3)
11.615(2)
20.755(4)
76.671(8)
80.90(1)
66.94(1)
2267.3(8)
2
9.397(3)
12.833(2)
10.905(2)
9.958(3)
23.841(4)
12.384(2)
15.518(2)
10.994(2)
21.767(4)
a (8)
b (8)
g (8)
97.416(9)
107.10(2)
108.03(2)
107.80(1)
110.34(1)
3
˚
V (A )
4857(1)
4
3417(1)
4
1250.5(5)
2
2799.4(9)
4
3482(1)
4
Z
Dcalcd
(g cmK3
1.591
1.337
1.398
1.613
1.459
1.736
1.451
1.533
)
m (mmK1
F(000)
Tmax
)
0.796
696
0.493
2040
0.604
824
1.237
1672
0.947
1020
5.782
636
5.037
1216
4.070
1600
0.8765
0.5902
3.5–50
5175
0.3148
0.2807
3.5–50
8644
0.8441
0.5077
3.5–50
7019
0.4140
0.3472
3.5–50
6273
0.6287
0.5767
3.5–50
8381
0.8046
0.4191
3.5–50
2433
0.8090
0.4283
3.5–50
5210
0.7314
0.2861
3.5–50
7885
Tmin
2q Range (8)
No. of reflns
measured
No. of unique
reflns
4872
8360
6777
527
6623
3247
478
5948
4644
425
7910
7182
533
2286
4914
2729
281
6081
4630
425
No. of reflns
with IO2s(I)
No. of params
refined
4438
1688
389
299
Max in Dr
K3
0.618
K0.605
1.000
K0.952
0.423
K0.521
0.631
K0.584
0.705
K0.55
1.048
K0.715
0.718
K0.627
0.544
K0.613
˚
(e A
)
Min in Dr
K3
˚
(e A
)
GOF on F2
R1a
1.088
0.0315
0.0837
P
1.030
0.998
1.011
1.04
1.044
1.001
1.019
0.0476
0.1251
0.0740
0.1155
0.0359
0.0763
0.0306
0.0763
0.0475
0.0799
0.0574
0.0950
0.0339
0.0690
wR2b
P
a
R1Z jjFojKjFjj= jFoj.
P
P
b
wR2Z ½wðFo2 KFc2Þ ꢀ= ½wðFo2Þ ꢀ
.
2
2 1=2

212
H.S. Huh et al. / Journal of Molecular Structure 789 (2006) 209–219
spectrum of 1 shows a strong absorption band at 2063 cmK1
corresponding to the azide group.
The molecular structure of 1 with the atom-numbering
scheme is shown in Fig. 1, which displays one chelating dppn
and two azido (NK3 ) ligands. The coordination sphere of the Pd
metal can be described as a distorted square plane. The
equatorial plane, defined by N1, N4, P1, P2, and Pd1, is roughly
˚
planar with an average atomic displacement of 0.121 A. The
naphthalene plane is twisted by 39.5(1)8 with respect to the
equatorial plane. The N–N–N bond angles of the azido ligands
are 176.4(4) and 176.1(4)8. In the azido ligands, all N–N bond
˚
lengths (1.140(5)–1.155(4) A) are equal within experimental
Scheme 1.
error, which indicates the azido ligands prefer the resonance
form II [2]. On the other hand, several Pd–azido complexes
containing different N–N bond lengths, in which N(bound)–
N(central) lengths are distinctly longer than N(central)–
N(distant) lengths, were recently reported [21–23].
3. Results and discussions
All compounds (1–8) in this study are air-stable both in the
solid state and in solution and have been fully characterized by
spectroscopy (NMR and IR), elemental analysis, and X-ray
diffraction.
3.1. Preparation, structure, and reactivity of 1
[Pd(dppn)Cl2] reacted with excess sodium azide (NaN3) to
give [Pd(dppn)(N3)2] (1) in 84% yield (Scheme 1). The IR
As mentioned in Introduction, reactions of metal–azido
compounds with isocyanides frequently convert the azido
˚
Fig. 1. ORTEP drawing of 1 showing the atom-labeling scheme and 50% probability thermal ellipsoids. Selected bond distances (A) and bond angles (8): Pd1–N1
2.035(3), Pd1–N4 2.056(3), Pd1–P2 2.1999(11), Pd1–P1 2.2188(11), N1–N2 1.155(4), N2–N3 1.152(4), N4–N5 1.151(4), N5–N6 1.140(5); N1–Pd1–N4 90.72(13),
N1–Pd1–P2 92.96(10), N4–Pd1–P2 176.32(8), N1–Pd1–P1 166.93(9), N4–Pd1–P1 89.54(9), P2–Pd1–P1 86.86(2), N2–N1–Pd1 129.6(3), N3–N2–N1 176.4(4), N5–
N4–Pd1 121.6(2), N6–N5–N4 176.1(4).

H.S. Huh et al. / Journal of Molecular Structure 789 (2006) 209–219
213
Fig. 2. ORTEP drawing of 2. Pd1–C35 2.039(4), Pd1–C42 2.046(4), Pd1–P2 2.2936(10), Pd1–P1 2.3017(11), N1–C35 1.347(5), N1–N2 1.356(5), N1–C36 1.452(5),
N2–N3 1.273(6), N3–N4 1.364(5), N4–C35 1.322(5), N5–C42 1.344(5), N5–N6 1.357(5), N5–C43 1.461(5), N6–N7 1.285(6), N7–N8 1.362(5), N8–C42 1.336(5);
C35–Pd1–C42 87.35(16), N2–Pd1–P1 87.07(4), N4–C35–N1 106.6(3), N8–C42–N5 106.3(3).
ligand to the C-coordinated tetrazolate ring, a five-membered
heterocycle, resulting from the [2C3] cycloaddition of the
azido and the isocyanide groups [2–11]. In a similar way,
treating metal–azido compounds with nitriles, alkynes, and
CS2 gives N-coordinated tetrazolato [4,5,9], triazolato [3,4,9],
and thiatriazolato [2,4,10] compounds, respectively. On the
basis of these facts, we have carried out similar cycloaddition
reactions with several isocyanides.
square planar. The equatorial plane, defined by C35, C42, P1,
P2, and Pd1, is relatively planar with an average atomic
˚
displacement of 0.094 A. Two tetrazolate rings are essentially
planar with average atomic displacements of 0.001 and
˚
0.005 A. These two rings are mutually perpendicular with a
dihedral angle of 75.1(1)8, and also virtually perpendicular to
the equatorial plane with dihedral angles of 74.0(1) and
60.6(1)8. The naphthalene plane is twisted out of the equatorial
plane by 40.7(1)8.
The Pd-bis(azido) compound 1 reacted with excess
cyclohexyl isocyanide in CH2Cl2 to give [Pd(dppn)(CN4–
Cy)2] (2), which contains two C-coordinated tetrazolate rings
(Scheme 1). These results indicate that compound 1 prefers to
undergo [2C3] cycloaddition, rather than N–C coupling to
give a carbodimido (NaCaN) group, in spite of steric
congestion due to the bulky, chelating dppn ligand that might
suppress the cycloaddition reactivity. The same reactivity was
also observed for the platinum analog [Pt(dppf)(N3)2] [12]. In
the IR spectrum of compound 2, the N3 absorption band at
2063 cmK1 in the starting compound 1 disappeared, and a new
absorption appeared at 2127 cmK1, presumably due to the
formation of the tetrazolato ligand.
3.2. Preparation and structure of 3
As mentioned in Section 1, we previously reported the
[Pd(dppf)Cl2]-mediated trimerization of phenylethynes
(PhCbCH) in the presence of triethylamine in ethanol to
give [Pd(dppf)(2,3,5-triphenylfulvene)] [15]. Under the same
reaction conditions except the spectator ligand (dppf/dppn),
we treated [Pd(dppn)Cl2] with PhCbCH. This reaction did not
produce the expected compound [Pd(dppn)(2,3,5-triphenylful-
vene)], but it proceeded to give the unexpected compound
[Pd(dppn)(h2-PhCbC–CbCPh)] (3) (Eq. (1)). Unfortunately,
we cannot give a reasonable explanation for the different
reactivity between [Pd(dppf)Cl2] and compound 3. The
structural formula of compound 3 tells us that phenylethyne
The molecular structure of 2 is presented in Fig. 2, which
shows two C-coordinated tetrazolate rings and one chelating
dppn ligand. The coordination sphere of Pd can be described as

214
H.S. Huh et al. / Journal of Molecular Structure 789 (2006) 209–219
underwent C–C coupling to give 1,4-diphenyl-1,3-butadiyne,
which is bound to the Pd metal in the p manner. We speculate
that the base NEt3 deprotonates the Ph–CbC–H proton to give
Ph–CbCK, which binds to the metal to give the intermediate
[Pd(dppn)(Ph–CbC)2]. The phenylethynyl ligands in the
intermediate then undergo C–C coupling to give h2-PhCbC–
CbCPh in compound 3.
displays a strong absorption band at 2043 cmK1 assigned to the
azide group.
The molecular structure of 4 is shown in Fig. 4, which shows
a square-planar complex with one chelating dppf and two azido
ligands. The equatorial plane, defined by N1, N4, P1, P2, and
Pd1, is roughly planar with an average displacement of
˚
0.013 A. The N–N–N bond angles of the azido ligands are
175.1(4) and 175.5(4)8. As is the case of compound 1, the azido
ligands in compound 4 appear to adopt the resonance form II,
in which the N–N bond lengths are essentially same.
Two Cp rings are not perfectly parallel but twisted from
each other with a dihedral angle of 3.7(3)8. The torsion angle of
P1–C1–C6–P2 is 38.0(2)8, indicating a gauche conformation of
the two Cp rings. For comparison, the ideal torsion angles for
the gauche and eclipsed conformation are 36 and 728,
respectively. The distances of Fe–Ct (Ct is the centroid of the
˚
Cp ring) are 1.636 and 1.641 A, and the angle of the Ct1–Fe–
Ct2 (Ct1: C1–C5; Ct2: C6–C10) is 179.718. In addition, the
˚
P1$$$P2 distance is 3.489(1) A. The above bonding parameters
The molecular structure of 3 is shown in Fig. 3. The square-
planar compound 3 has one chelating dppn and one h2-
butadiyne ligand. The dihedral angle between Plane 1 (Pd1, P1,
and P2) and Plane 2 (Pd1, C41, and C42) is 3.5(7)8. The phenyl
groups in dppn are extremely twisted out of the naphthalene
plane with dihedral angles in the range of 66.6(2)–77.4(2)8. Six
carbon atoms (C35 and C41–C45) in the butadiyne framework
are essentially coplanar with an average atomic displacement
within a ferrocene moiety are relatively consistent with those
found for square-planar palladium complexes in which the
dppf group acts as a ligand [24]. The distance of Pd$$$Fe is
˚
of 0.007 A.
˚
4.236(1) A, which clearly rules out direct bonding interaction
between the two metals.
3.3. Preparation, structure, and reaction of 4
Like compound 1, compound 4 underwent [2C3] cyclo-
addition with isocyanide to convert the azido ligand to the
C-coordinated tetrazolate ring. Compound 4 reacted with
excess tert-butyl isocyanide in CH2Cl2 to give [Pd(dppf)(CN4–
Like compound 1, [Pd(dppf)(N3)2] (4) was prepared from
[Pd(dppf)Cl2] and NaN3 by the simple and straightforward
metathesis (Scheme 2). The Pt analog [Pt(dppf)(N3)2] was
previously reported by our group [12]. The IR spectrum of 4
Fig. 3. ORTEP drawing of 3. Pd1–C41 2.051(8), Pd1–C42 2.054(8), Pd1–P1 2.271(2), Pd1–P2 2.283(2), C35–C41 1.459(10), C41–C42 1.267(11), C42–C43
1.404(11), C43–C44 1.214(11), C44–C45 1.400(11); C41–Pd1–C42 35.9(3), P1–Pd1–P2 88.18(8), C42–C41–C35 139.0(8), C41–C42–C43 145.8(9), C44–C43–
C42 178.1(10), C43–C44–C45 178.4(9).

H.S. Huh et al. / Journal of Molecular Structure 789 (2006) 209–219
215
angles of 80.0(1) and 80.5(1)8. The tert-butyl groups on two
tetrazolate rings seem to orient as far as possible, which
probably arises from the steric congestion.
Bonding parameters in the dppf moiety in compound 5 are
essentially the same as those in compound 4. Two Cp rings
have a dihedral angle of 3.2(2)8. The P1–C1–C6–P2 torsion
angle of 39.9(1)8 indicates a slight distortion from a gauche
conformation of the two Cp rings. The distances of Fe–Ct (Ct is
˚
the centroid of the Cp ring) are 1.647 and 1.646 A, and the
angle of the Ct1–Fe–Ct2 (Ct1: C1–C5; Ct2: C6–C10) is
179.718. The distances of P1$$$P2 and Pd$$$Fe are 3.679(1)
˚
and 4.335(1) A, respectively.
Scheme 2.
3.4. Preparation, structure, and reaction of 6
t-Bu)2] (5) (Scheme 2). As is the case for the conversion of
compound 1 to compound 2, the IR spectrum of compound 5
shows a new strong absorption band at 2236 cmK1, which is
absent in that of the starting compound 4 that exhibits the azide
We have so far used bulky chelating bis(phosphine) ligands,
dppf and dppn, in preparing compounds 1–5. For a comparison
study, we decided to examine the reactions of isocyanides with
[Pt(1-dpn)(SMe2)(N3)2] (6), which contains a bulky mono-
dentate phosphine ligand, 1-(diphenylphosphino)naphthalene
(1-dpn). Compounds 6 was prepared from [Pt(1-dpn)(SMe2)-
Cl2] and NaN3 (Scheme 3). The IR spectrum of 6 shows a
strong absorption band at 2053 cmK1 corresponding to the
azide group.
band at 2043 cmK1
.
The molecular structure of the square-planar compound 5 is
presented in Fig. 5. Compound 5 has two C-coordinated
tetrazolate rings (CN4–t-Bu) and one bidentate dppf ligand.
The equatorial plane, defined by C35, C40, P1, P2, and Pd1, is
relatively planar with an average atomic displacement of
˚
0.005 A. Two tetrazolate rings (C35, N1–N4; C40, N5–N8) are
essentially planar with average atomic displacements of 0.002
˚
and 0.004 A, respectively. These two rings are mutually
The molecular structure of 6 is shown in Fig. 6, which
displays one dppn and SMe2 and two azido ligands. The
coordination sphere of the Pt metal can be described as square
planar. The equatorial plane, defined by N1, N4, P1, S1, and
Pd1, is roughly planar with an average atomic displacement of
perpendicular with a dihedral angle of 77.3(1)8 and are
virtually perpendicular to the equatorial plane with dihedral
Fig. 4. ORTEP drawing of 4. Pd1–N4 2.069(3), Pd1–N1 2.072(3), Pd1–P1 2.2832(11), Pd1–P2 2.2882(10), N1–N2 1.170(4), N2–N3 1.147(5), N4–N5 1.194(4), N5–
N6 1.156(5); N4–Pd1–N1 90.52(13); N4–Pd1–P1 176.45(9), N1–Pd1–P1 86.45(10), N4–Pd1–P2 83.50(9), N1–Pd1–P2 173.97(1), P1–Pd1–P2 99.50(4), N2–N1–
Pd1 121.2(3), N3–N2–N1 175.1(4), N5–N4–Pd1 118.8(3), N6–N5–N4 175.5(4).

216
H.S. Huh et al. / Journal of Molecular Structure 789 (2006) 209–219
Fig. 5. ORTEP drawing of 5. Pd1–C40 2.056(3), Pd1–C35 2.062(3), Pd1–P1 2.3643(8), Pd1–P2 2.3762(7), N1–N2 1.365(3), N1–C35 1.373(3), N1–C36 1.497(4),
N2–N3 1.296(4), N3–N4 1.376(4), N4–C35 1.301(4), N5–N6 1.367(3), N5–C40 1.370(3), N5–C41 1.497(4), N6–N7 1.288(4), N7–N8 1.383(3), N8–C40 1.285(4);
C40–Pd1–C35 84.55(10), P1–Pd1–P2 101.79(3), N4–C35–N1 107.6(2), N8–C40–N5 107.2(2).
˚
0.027 A. With respect to the equatorial plane, the naphthalenyl
ring (C1–C10) has a dihedral angle of 65.8(3)8. The P1–Pt1–S1
bond angle is 95.6(1)8.
(7) or 2,6-dimethylphenyl (8)) on the two tetrazolate rings
seem to orient as far as possible.
Kim and co-workers recently reported a couple of papers on
the reactions between 2,6-dimethylphenyl isocyanide (2,6-
Me2C6H3–NC) and Pd-bis(azido) complexes [Pd(PR3)2(N3)2]
(PR3ZPMe3, PMe2Ph, PEt3, PMePh2, PEt3, depe, dppp, dppe)
[25,26]. According to their results, those compounds
containing small phosphines gave either (carboimido)(tetrazo-
lato) complexes [Pd(PR3)2(NaCaN–R)(CN4–R)] or bis(car-
The Pt-bis(azido) compound 6 reacted with excess tert-butyl
isocyanide and 2,6-dimethylphenyl isocyanide in CH2Cl2 to
give [Pt(t-Bu–NC)2(CN4–t-Bu)2] (7) and [Pt(2,6-Me2–C6H3–
NC)2(CN4–2,6-Me2–C6H3)2] (8), respectively (Scheme 3). In
these reactions, the incoming isocyanides replaced both the
1-dpn and SMe2 ligands during the reactions.
The molecular structures of compounds 7 and 8 are shown
in Figs. 7 and 8, respectively. Each square-planar compound
has two C-coordinated tetrazolate rings and two isocyanide
ligands. The equatorial plane, defined by two carbon atoms of
the tetrazolate ring, two carbon atoms of the isocyanide, and
the Pt metal, is somewhat planar with an average atomic
boimido)
complexes
[Pd(PR3)2(NaCaN–R)2].
By
contrast, those compounds containing bulky chelating bis(pho-
sphine) ligands (depe, dppp, dppe) exclusively produced
˚
displacement of 0.216 (for 7) or 0.001 A (for 8). Consistent
with our expectation, compounds 7 and 8 have new absorption
bands at 2197 and 2216 cmK1, respectively, arising from the
newly formed tetrazolate rings.
˚
Bond lengths (1.97(1)–1.99(1) A) between Pt and the
isocyanide carbon (Pt–C(RNC)) are a little shorter than those
(2.01(1)–2.04(1)) between Pt and the C-tetrazolate carbon (Pt–
C(CN4)). Two tetrazolate rings in each compound are
essentially planar with an average atomic displacement of
˚
0.003–0.008 A. These two rings are mutually perpendicular
with a dihedral angle of 85.1(4) (7) or 70.4(2)8 (8), and are also
essentially perpendicular to the equatorial plane with a dihedral
angle of 78.5(4) (7) or 66.4(2)8 (8). The substituents (tert-butyl
Scheme 3.

H.S. Huh et al. / Journal of Molecular Structure 789 (2006) 209–219
217
Fig. 6. ORTEP drawing of 6. Pt1–N1 2.00(2), Pt1–N4 2.070(17), Pt1–P1 2.252(5), Pt1–S1 2.277(5), N1–N2 1.10(3), N2–N3 1.19(3), N4–N5 1.14(2), N5–N6
1.17(3), N1–Pt1–N4 88.4(9); P1–Pt1–S1 95.64(19), N2–N1–Pt1 120.2(18), N1–N2–N3 174(3), N5–N4–Pt1 123.5(18), N4–N5–N6 176(2).
Fig. 7. ORTEPdrawing of 7. Pt1–C1 1.970(13), Pt1–C6 1.996(12), Pt1–C11 2.012(11), Pt1–C16 2.032(10), N3–C11 1.343(12), N3–N4 1.359(12), N3–C12 1.495(13),
N4–N5 1.312(12), N5–N6 1.348(12), N6–C11 1.351(12), N7–C16 1.337(12), N7–N8 1.362(12), N7–C17 1.493(14), N8–N9 1.289(13), N9–N10 1.364(13), N10–C16
1.344(12); C1–Pt1–C6 92.0(5), C11–Pt1–C16 86.3(4), C1–N1–C2 172.5(13), C6–N2–C7 176.6(13), N1–C1–Pt1 178.3(12), N2–C6–Pt1 175.1(12).

218
H.S. Huh et al. / Journal of Molecular Structure 789 (2006) 209–219
Fig. 8. ORTEP drawing of 8. Pt1–C1 1.968(6), Pt1–C10 1.978(5), Pt1–C19 2.029(5), Pt1–C28 2.042(5), N3–C19 1.357(7), N3–N4 1.338(7), N3–C20
1.433(7), N4–N5 1.282(8), N5–N6 1.368(7), N6–C19 1.319(7), N7–C28 1.355(6), N7–N8 1.371(6), N7–C29 1.429(7), N8–N9 1.290(6), N9–N10 1.356(6),
N10–C28 1.323(6); C1–Pt1–C10 87.9(2), C1–Pt1–C28 175.0(2), C1–N1–C2 179.5(7), C10–N2–C11 174.5(5).
bis(carboimido) complexes. However, our results in this study
revealed that Pd- and Pt-bis(azido) complexes containing bulky
phosphine ligands (dppf, dppn, 1-dpn), chelating or mono-
dentate, underwent only [2C3] cycloaddition with isocyanides
(R–NC, RZcyclohexyl, tert-butyl, 2,6-dimethylphenyl) to
convert azido ligands to C-coordinated tetrazolate rings.
Considering the steric bulk of the phosphine ligands, such
results are somewhat unusual. In addition, among the four
azido complexes (2, 5, 7, and 8) only complex 2 exhibited
phosphorus–carbon (in the terazolato ring) couplings in the
form of a double of a doublet [JC–PZ166 (trans), 25 (cis)] in its
13C{1H} NMR spectrum. The fact that the other three
compounds do not exhibit the peaks corresponding to the
coordinated carbon in the tetrazolato ring can probably be due
to the quaternary nature of this carbon.
rings. In particular, in the reactions of [Pt(1-dpn)(SMe2)(N3)2],
the incoming isocyanides replaced both the 1-dpn and SMe2
ligands, together with the conversion of the azido ligands to the
tetrazolate rings. Consequently, these reactions gave bis(te-
trazolato) compounds, which do not contain carbodimido
ligands resulting from the N–C coupling with N2 elimination.
In addition, we observed the [Pd(dppn)Cl2]-mediated C–C
coupling of PhCbCH to generate the h2-PhCbC–CbCPh
ligand.
5. Supplementary material
Crystallographic data for the structural analysis have been
deposited at the Cambridge Crystallographic Data Center:
CCDC No. 282328 for 1, 282329 for 2$pentane, 282330 for 3,
282331 for 4$CH2Cl2, 282332 for 5$CH2Cl2, 282333 for 6,
282334 for 7, and 282335 for 8. Copies of this information may
be obtained free of charge from: The director, CCDC, 12 Union
Road, Cambridge, CB2 1EZ, UK (fax: C44 1223 336 033;
E-mail: deposit@ccdc.cam.ac.uk or www: http://www.ccdc.
cam.ac.uk).
4. Conclusions
We have prepared two Pd-bis(azido) compounds containing
bulky chelating bis(phosphine) ligands, [Pd(dppn)(N3)2] and
[Pd(dppf)(N3)2], as well as one Pt-bis(azido) containing a
bulky monodentate phosphine ligand [Pt(1-dpn)(SMe2)(N3)2].
In spite of the steric bulk of the phosphine ligands, all those
bis(azido) compounds underwent only [2C3] cycloaddition
with isocyanides to convert the azido ligands to the
corresponding five-membered, C-coordinated tetrazolate
Acknowledgements
This work was supported by the 63 Research Fund of
Sungkyunkwan University (2004–2005).

H.S. Huh et al. / Journal of Molecular Structure 789 (2006) 209–219
[14] H.-J. Kim, S.W. Lee, Bull. Korean Chem. Soc. 20 (1999) 1089.
219
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