Preparation of half-sandwich diazoalkane complexes of osmium

Article abstract of DOI:10.1016/j.poly.2015.11.021

Diazoalkane complexes [OsCl(η⁶-p-cymene)(N₂CAr1Ar2){PPh(OEt)₂}]BPh₄ (1, 2) [Ar1 = Ar2 = Ph; Ar1 = Ph, Ar2 = p-tolyl; Ar1 = H, Ar2 = COOEt] were prepared by allowing compounds OsCl₂(η⁶-p-cym

Full text of DOI:10.1016/j.poly.2015.11.021

Polyhedron 104 (2016) 46–51
Contents lists available at ScienceDirect
Polyhedron
journal homepage: www.elsevier.com/locate/poly
Preparation of half-sandwich diazoalkane complexes of osmium
⇑
Gabriele Albertin , Stefano Antoniutti, Matia Forcolin, Dario Gasparato
Dipartimento di Scienze Molecolari e Nanosistemi, Università Ca’ Foscari Venezia, Dorsoduro 2137, 30123 Venezia, Italy
a r t i c l e i n f o
a b s t r a c t
Article history:
Diazoalkane complexes [OsCl(
Ar1 = Ph, Ar2 = p-tolyl; Ar1 = H, Ar2 = COOEt] were prepared by allowing compounds OsCl2(
ene)[PPh(OEt)2] to react with diazoalkane in ethanol. Diazo-pyridine derivatives [OsCl(
g
6-p-cymene)(N2CAr1Ar2){PPh(OEt)2}]BPh4 (1, 2) [Ar1 = Ar2 = Ph;
6-p-cym-
6-p-cymene)
1-(4-C5H4N)(Ph)CN2}L]BPh4 (3, 4) [L = PPh(OEt)2, P(OEt)3] were also prepared by reacting chloro-
compounds OsCl2(
6-p-cymene)L with 4-[diazo(phenyl)methyl]pyridine, (4-C5H4N)PhCN2, in ethanol.
Treatment of diazoalkane complexes 1 and 2 with CH2@CH2 (1 atm) and PhC„CH in ethanol led to
ethylene [OsCl(
2-CH2@CH2)( 6-p-cymene){PPh(OEt)2}]BPh4 (5) and carbene [OsCl{@C(CH2Ph)(OEt)}
6-p-cymene){PPh(OEt)2}]BPh4 (6) derivatives.
Received 1 October 2015
Accepted 15 November 2015
Available online 2 December 2015
g
g
{
j
g
Keywords:
Osmium
Half-sandwich
Diazoalkane
Synthesis
g
g
(
g
Ó 2015 Elsevier Ltd. All rights reserved.
Phenyldiethoxyphosphine
1. Introduction
complexes could be prepared and how their properties change.
The results are given here.
Diazoalkanes Ar1Ar2CN2 can coordinate to transition metals,
giving stable and isolable complexes [1–6]. The properties of these
complexes are of current interest, not only thanks to the close rela-
tionship with dinitrogen fixation [7,8] but also for their rich and
various reactivity [1–6]. Thus, extrusion of dinitrogen with forma-
2. Experimental
2.1. General comments
tion of carbene M = CAr1Ar2 was observed in
g
2-CN coordinated
species [3f,9,10], whereas
g
1-bonded diazoalkane gave dinitrogen
All synthetic work was carried out in an appropriate atmo-
sphere (Ar, N2) using standard Schlenk techniques or a vacuum
atmosphere dry-box. All solvents were dried over appropriate
drying agents, degassed on a vacuum line, and distilled into vac-
uum-tight storage flasks. OsO4 was a Pressure Chemical Co. (USA)
product, used as received. Phosphites P(OMe)3, P(OEt)3 and
triisopropylphosphine P(iPr)3 were Aldrich products, purified by
distillation, whereas phenyldiethoxyphosphine PPh(OEt)2 and
diphenylethoxyphosphine PPh2OEt were prepared by the method
of Rabinowitz and Pellon [12]. Diazoalkanes were prepared follow-
ing the known methods [13]. Other reagents were purchased from
commercial sources in the highest available purity and used as
received. Infrared spectra were recorded on Perkin-Elmer Spec-
trum One FT-IR spectrophotometer. NMR spectra (1H, 13C, 31P)
were obtained on AVANCE 300 Bruker spectrometer at tempera-
tures between À80 and +30 °C, unless otherwise noted. 1H and
13C spectra are referenced to internal tetramethylsilane; 31P{1H}
chemical shifts are reported with respect to 85% H3PO4, with
downfield shifts considered positive. The COSY, HMQC and HMBC
NMR experiments were performed using their standard programs.
The iNMR software package [14] was used to treat NMR data. The
conductivity of 10À3 mol dmÀ3 solutions of the complexes in
CH3NO2 at 25 °C were measured with a Radiometer CDM 83.
[M]–N2 complexes [3f], transfer of carbene to imine [9f], or
cleavage of the NAN bond of the Ar1Ar2CN2 group [3g]. Dipolar
(3 + 2) cycloaddition of coordinate diazoalkane with alkene and
alkyne affording 3H-pyrazole derivatives has recently been
reported [5], as well as hydrolysis of [M]–N2CAr1Ar2 yielding
g
2-diazene derivatives [6].
A number of diazoalkane complexes have been reported [1–6]
for several metal centres, displaying a variety of coordination
modes (Chart 1) and reactivities. However, in contrast with Fe
and Ru, diazoalkane complexes of osmium are very rare and, apart
from [OsH(N2CAr1Ar2)L4]BPh4, described 15 years ago [11], no
other example of this metal has been reported.
We are interested in the chemistry of diazoalkane complexes
and have recently reported the synthesis and reactivity of
half-sandwich ruthenium derivatives with p-cymene [4],
cyclopentadienyl [5a,b] and indenyl [5c] as supporting ligands.
The interesting properties shown by these compounds prompted
us to extend our study to osmium, to test whether diazoalkane
⇑
Corresponding author. Fax: +39 0412348594.
E-mail address: albertin@unive.it (G. Albertin).
http://dx.doi.org/10.1016/j.poly.2015.11.021
0277-5387/Ó 2015 Elsevier Ltd. All rights reserved.

G. Albertin et al. / Polyhedron 104 (2016) 46–51
47
Ar1
Ar2
Ar1
C
N
N
Ar1
C
C
N
N
N
Ar2
N
M
M
Ar2
I I
II I
M
I
Ar1
C
Ar1
C
Ar1
M
Ar2
N
C
N
N
Ar2
N
Ar2
N
N
M
M
M
M
V I
IV
V
Chart 1. Diazoalkane coordination modes.
Elemental analyses were determined in the Microanalytical Labo-
ratory of the Dipartimento di Scienze del Farmaco of the University
of Padua, Italy.
calc.: C, 64.17; H, 5.66; Cl, 3.27; N, 2.58. Found: C, 64.02; H, 5.78;
Cl, 3.13; N, 2.65%.
2.4. [OsCl(g
6-p-cymene){N2C(H)COOEt}{PPh(OEt)2}]BPh4 (2)
2.2. Synthesis of complexes
In a 25-mL three-necked round-bottomed flask were placed
100 mg (0.17 mmol) of solid [OsCl2(
6-p-cymene){PPh(OEt)2}], an
excess of NaBPh4 (0.34 mmol, 116 mg), an excess of ethyldiazoac-
etate N2C(H)COOEt (0.68 mmol, 71 L) and 10 mL of ethanol. The
reaction mixture was stirred at room temperature for 6 h and then
concentrated to about 2 mL by removing the solvent under
reduced pressure. The resulting solution was cooled to À25 °C
and the yellow solid which slowly separated out was filtered and
g
Compounds [OsCl(l-Cl)(g g
6-p-cymene)]2 and [OsCl2( 6-p-
cymene)L] [L = P(OMe)3, P(OEt)3, PPh(OEt)2, PPh2OEt, P(iPr)3] were
prepared following the reported methods [15,16].
l
2.3. [OsCl(g
6-p-cymene)(N2CAr1Ar2){PPh(OEt)2}]BPh4 (1)
[Ar1 = Ar2 = Ph (a); Ar1 = Ph, Ar2 = p-tolyl (b)].
crystallised from ethanol. Yield: 76 mg (45%). IR (KBr pellet): mN
2
1960 (m), mCO 1727 (s) cmÀ1 1H NMR (CD2Cl2, 25 °C) d: 7.95–
.
In a 25-mL three-necked round-bottomed flask were placed
6.87 (m, 25H, Ph), 5.58, 5.37, 5.30, 5.08 (d, 4H, Ph p-cym), 4.26,
3.98 (m, 4H, CH2 phos), 3.62 (q, 2H, CH2 COOEt), 2.47 (m, 1H, CH
Pri), 1.92 (s, 3H, CH3 p-cym), 1.38 (m, 3H, CH3 COOEt + 6H, CH3
phos), 1.19, 1.17 (d, 6H, CH3 Pri). 31P{1H} NMR (CD2Cl2, 25 °C) d:
91.3 (s) ppm. KM = 52.2 ΩÀ1 molÀ1 cm2. C48H55BClN2O4OsP
(991.43): Anal. calc.; C, 58.15; H, 5.59; Cl, 3.58; N, 2.83. Found: C,
57.97; H, 5.63; Cl, 3.45; N, 2.71%.
100 mg (0.17 mmol) of solid [OsCl2(g
6-p-cymene){PPh(OEt)2}], an
excess of the appropriate diazoalkane Ar1Ar2CN2 (0.5 mmol), an
excess of NaBPh4 (0.34 mmol, 116 mg) and 4 mL of ethanol. The
reaction mixture was stirred at room temperature for 4 h and then
the solid that formed was filtered and crystallised from CH2Cl2 and
EtOH. Yield: 138 mg (76%) for 1a, 144 mg (78%) for 1b.
1a: IR (KBr pellet): mN 1897 (m) cmÀ1
.
1H NMR (CD2Cl2, 25 °C)
2
d: 7.75–6.85 (m, 35H, Ph), 5.68, 5.65, 5.58, 5.48 (d, 4H, Ph p-cym),
3.82 (m, 4H, CH2), 2.45 (m, 1H, CH Pri), 2.05 (s, 3H, CH3 p-cym), 1.22
(d, 6H, CH3 Pri), 1.14 (t, 6H, CH3 phos). 31P{1H} NMR (CD2Cl2, 25 °C)
2.5. [OsCl(
(OEt)2 (3), P(OEt)3 (4)]
g j
6-p-cymene){ 1-(4-C5H4N)(Ph)CN2}L]BPh4 (3, 4) [L = PPh
d:
92.9 ppm. KM = 52.6 ΩÀ1 molÀ1 cm2.
C57H59BClN2O2OsP
(1071.56): Anal. calc.: C, 63.89; H, 5.55; Cl, 3.31; N, 2.61. Found:
In a 25-mL three-necked round-bottomed flask were placed
0.17 mmol of solid [OsCl2(
6-p-cymene)L], an excess of dia-
C, 63.68; H, 5.47; Cl, 3.43; N, 2.67%.
g
1b: IR (KBr pellet): mN 1925 (m) cmÀ1
.
1H NMR (CD2Cl2, 25 °C)
zoalkane (4-C5H4N)(Ph)CN2 (0.51 mmol, 100 mg), an excess of
NaBPh4 (0.34 mmol, 116 mg) and 4 mL of ethanol. The reaction
mixture was stirred for 24 h and then the solid that formed was fil-
tered and crystallised from CH2Cl2 and EtOH. Yield: 160 mg (88%)
for 3, 163 mg (92%) for 4.
2
d: 7.60–6.87 (m, 34H, Ph), 5.66, 5.64, 5.56, 5.47 (d, 4H, Ph p-cym),
3.81, 3.64 (m, 4H, CH2), 2.45 (m, 1H, CH Pri), 2.39 (s, 3H, CH3 p-tol),
2.04 (s, 3H, CH3 p-cym), 1.16, 1.13 (t, 6H, CH3 phos), 1.11, 1.10 (d,
6H, CH3 Pri). 31P{1H} NMR (CD2Cl2, 25 °C) d: 94.1. 13C{1H} NMR
(CD2Cl2, 25 °C) d: 160–119 (m, Ph), 110. 6 (d, C4 p-cym), 82.9 (br,
CN2), 93.2, 82.1 (d), 80.7 (br), 79.5 (d) (Ph p-cym), 63.85 (d,
JCP = 7.1 Hz, CH2), 31.12 (s, CH Pri), 23.0, 22.6 (s, CH3 Pri), 21.3 (s,
JCP = 6.5, CH3 p-tol), 18.5 (s, CH3 p-cym), 16.5 (d, CH3 phos) ppm.
KM = 51.9 ΩÀ1 molÀ1 cm2. C58H61BClN2O2OsP (1085.58): Anal.
3: IR (KBr pellet): mN 2044 (s) cmÀ1
.
1H NMR (CD2Cl2, 25 °C) d:
2
8.32–6.72 (m, 34H, Ph + Py), 5.58, 5.56, 5.31, 5.22 (d, 4H, Ph p-
cym), 4.11, 4.03, 3.90, 3.82 (m, 4H, CH2), 2.54 (m, 1H, CH Pri),
2.12 (s, 3H, CH3 p-cym), 1.39, 1.32 (t, 6H, CH3 phos), 1.16, 1.14
(d, 6H, CH3 Pri). 31P{1H} NMR (CD2Cl2, 25 °C) d: 98.9 ppm.

48
G. Albertin et al. / Polyhedron 104 (2016) 46–51
KM = 52.6 ΩÀ1 molÀ1 cm2. C56H58BClN3O2OsP (1072.55): Anal.
calc.: C, 62.71; H, 5.45; Cl, 3.31; N, 3.92. Found: C, 62.54; H, 5.52;
Cl, 3.19; N, 3.80%.
5.48 (d, HA p-cym, JAB = 6.7, JAC = 0.4, JAD = 0.8 Hz), 5.42 (d, HB p-
cym, JBC = 0.8, JBD = 0.4), 5.40 (d, HC p-cym, JCD = 6.7), 5.33 (d, HD
p-cym), 5.37, 2.98 [d, 2H, JHH = 13.2, @C(CH2Ph)], 4.41, 4.32 [m,
2H, @C(OCH2CH3)], 4.11, 3.98 (m, 4H, CH2 phos), 2.60 (m, 1H,
CH), 1.98 (s, 3H, CH3 p-cym), 1.48, 1.42 (t, 6H, JHH = 7.0, CH3 phos),
1.38 [t, 3H, JHH = 7.0, @C(OCH2CH3)], 1.16, 1.14 (d, 6H, JHH = 7.1, CH3
Pri). 31P{1H} NMR (CD2Cl2, 25 °C) d: 95.8 (s). 13C{1H} NMR (CD2Cl2,
25 °C) d: 286.5 (d, JCP = 15.9, Os = C), 165–122 (m, Ph), 119.26 (d, br,
JCP = 1.4, C1 p-cym), 105.20 (br, C4 p-cym), 93.02 (d, JCP = 3.4, C3 p-
cym), 88.30 (d, JCP = 3.1, C6 p-cym), 86.90 (d, JCP = 5.9, C2 p-cym),
86.38 (s, br, C5 p-cym), 76.56 [s, @C(OCH2CH3)], 65.1, 64.5 (d,
JCP = 9.9, JCP = 7.3, CH2 phos), 54.3 [br, @C(CH2Ph)], 31.1 (s, CH),
22.25, 21.95 (s, CH3 iPr), 17.98 (s, p-CH3 p-cym), 16.30, 16.28 (d,
4: IR (KBr pellet): mN 2050 (s) cmÀ1
.
1H NMR (CD2Cl2, 25 °C) d:
2
8.44 (d, 2H, JHH = 7.2 Hz, H2, H6 Py), 7.60–6.85 (m, 27H, Ph + H3,
H5 Py), 5.58, 5.57, 5.42, 5.24 (d, 4H, Ph p-cym), 3.90 (m, 4H,
CH2), 2.63 (m, 1H, CH Pri), 2.14 (s, 3H, CH3 p-cym), 1.22 (t, 6H,
CH3 phos), 1.18 (d, 6H, CH3 Pri). 31P{1H} NMR (CD2Cl2, 25 °C) d:
70.5. 13C{1H} NMR (CD2Cl2, 25 °C) d: 165–118 (m, Ph + C3 Py),
155.19 (d, JCP = 2.6, C2, C6 Py), 111.06 (d, JCP = 5.0, C4 p-cym),
97.91 (d, JCP = 2.2, C1 p-cym), 82.87 (d, JCP = 2.6), 81.69 (d,
JCP = 2.0), 81.62 (d, JCP = 2.7), 78.09 (d, JCP = 2.6) (C2, C3, C5, C6
p-cym), 63.66 (d, JCP = 7.1, CH2), 30.85 (s, CH Pri), 22.61, 21.81
(s, CH3 Pri), 18.18 (s, CH3 p-cym), 16.18 (d, JCP = 6.5, CH3 phos)
ppm. KM = 53.5 ΩÀ1 molÀ1 cm2. C52H58BClN3O3OsP (1040.50):
Anal. calc.: C, 60.02; H, 5.62; Cl, 3.41; N, 4.04. Found: C, 59.84; H,
5.70; Cl, 3.29; N, 4.13%.
JCP = 7.3, CH3 phos), 14.59 [s, @C(OCH2CH3)] ppm. KM = 53.6 ΩÀ1
-
molÀ1 cm2. C54H61BClO3OsP (1025.53): C, 63.24; H, 6.00; Cl, 3.46.
Found: C, 63.07; H, 6.09; Cl, 3.35%.
3. Results and discussion
2.6. [OsCl(
g
2-CH2@CH2)(
g
6-p-cymene){PPh(OEt)2}]BPh4 (5)
3.1. Preparation of diazoalkane complexes
A
solution of [OsCl(g
6-p-cymene){N2C(Ph)(p-tolyl)}{PPh
(OEt)2}]BPh4 (1b) (100 mg, 0.09 mmol) in CH2Cl2 (7 mL) was stir-
red under an ethylene atmosphere (1 atm) for 3 h. The solvent
was removed under reduced pressure to leave an oil, which was
triturated with ethanol (2 mL) containing an excess of NaBPh4
(0.18 mmol, 62 mg). A yellow solid slowly separated out from the
resulting solution, which was filtered and crystallised from CH2Cl2
and ethanol. Yield: 56 mg (67%). 1H NMR (CD2Cl2, 25 °C) d: 7.85–
6.87 (m, 25H, Ph), ABCDX, dA 5.53, dB 5.61, dC 5.0 7, dD 5.67,
JAB = 5.9, JAC = 0.6, JAD = 1.0, JAX = 0.6, JBC = 1.0, JBD = 0.6, JBX = 1.7,
JCD = 5.9, JCX = 1.6, JDX = 1.5 Hz (4H, Ph p-cym), EFGHX spin syst
(X = 31P), dE = dG 4.24, dF = dH 3.12, JEG = JFH = 9.5, JEH = JFG = 9.2,
JEF = JGH = 0.6, JEX = JGX = 3.8, JFX = JHX = 2.1 (4H, CH2 ethylene), 4.02
Diazoalkane complexes [OsCl(
(OEt)2}]BPh4 (1) were prepared by reacting the chlorocompound
[OsCl2(
6-p-cymene){PPh(OEt)2}] with an excess of diazoalkane
g
6-p-cymene)(N2CAr1Ar2){PPh
g
in ethanol, as shown in Scheme 1.
The reaction proceeds with the substitution of one chloride by
Ar1Ar2CN2 and the formation of cationic complexes 1 and 2.
Crucial for successful synthesis is the presence of NaBPh4 salt
which, labilising the ClÀ ligand, favours the formation of dia-
zoalkane complexes, separated as BPhÀ4 salts and characterised.
The reaction with diazoalkane was extended to analogous
p-cymene complexes containing ligands different from PPh(OEt)2,
such as phosphites P(OR)3 (R = Me, Et), phosphinite PPh2OEt, or
phosphines PPh3 and P(iPr)3, but in no case were stable diazoalkane
complexes separated. The reaction did proceed with a colour
change of the solution, but no stable compounds were isolated, sug-
i
(m, 4H, CH2 phos), 2.28 (m, 1H, CH Pr), 1.68 (s, 3H, CH3 p-cym),
1.39 (JHH = 7.0), 1.32 (JHH = 7.0) (t, 6H, CH3 phos), 1.09 (JHH = 6.7),
1.07 (JHH = 6.6) (d, 6H, CH3 iPr). 31P{1H} NMR (CD2Cl2, 25 °C) d:
84.2 (s). 13C{1H} NMR (CD2Cl2, 25 °C) d: 165–122 (m, Ph), 116.25
(d, JCP = 1.8, C1 p-cym), 104.04 (s, C4), 91.65 (d, JCP = 2.3, C5),
90.39 (d, JCP = 3.7, C3), 86.55 (d, JCP = 5.8, C6), 81.22 (d, JCP = 5.2,
C2), 66.98, 66.92, 66.26 (d, JCP = 11.0, CH2 phos), 51.00 (d,
gesting that only the fragment [OsCl(g
6-p-cymene)L]+ containing
phenyldiethoxyphosphine PPh(OEt)2 can stabilise diazoalkane
derivatives. Probably, only with this phosphine the electronic and
steric factors of the ligand allow the separation of stable complexes
1 and 2.
JCP = 1.5, CH2 ethylene), 30.76 (s, CH Pr), 21.95, 21.53 (s, CH3 iPr),
i
17.30 (s, CH3 p-cym), 16.30 (JCP = 6.7), 16.20 (JCP = 6.6 Hz) (d, CH3
phos) ppm. KM = 52.3 ΩÀ1 molÀ1 cm2. C46H53BClO2OsP (905.38):
C, 61.02; H, 5.90; Cl, 3.92. Found: C, 59.79; H, 5.83; Cl, 3.73%.
Diaryldiazoalkanes with Ph and p-tolyl substituents give stable
complexes 1a and 1b, whereas with diazofluorene they turned out
to be unstable and were not isolated in pure form. Instead, ethyl-
diazoacetate N2C(H)COOEt gave a stable isolable derivative (2).
Comparison of our results with those of related fragments [RuCl
HE
HF
C
C
(g
6-p-cymene)L]+ [L = P(OR)3, PPh(OEt)2] [4] indicates that stable
[Os]
diazoalkane complexes can be prepared with both metals, but
not with the diazofluorene ligand, which gives unstable species
in both cases. Instead, different behaviour by the two metals was
observed in the reaction of the triisopropylphosphine precursor
HH
HG
[RuCl2(
which afforded the new sandwich complex [Ru(
rene)(
6-p-cymene)]+ [4], in the case of ruthenium. Neither sand-
g
6-p-cymene){P(iPr)3}] (M = Ru, Os) with diazofluorene,
g
5-alkoxyfluo-
g
2.7. [OsCl{@C(CH2Ph)(OEt)}(
g
6-p-cymene){PPh(OEt)2}]BPh4 (6)
wich complexes nor diazoalkane derivatives, but only
decomposition products, were obtained with osmium.
An excess of phenylacetylene PhC„CH (0.27 mmol, 30
l
L) was
Chlorocomplexes [OsCl2(
g
6-p-cymene)L] (L = PPh(OEt)2,
P
added to a solution of [OsCl(
g
6-p-cymene){N2C(Ph)(p-tolyl)}{PPh
(OR)3] were also treated with 4-[diazo(phenyl)methyl]pyridine
(4-C5H4N)(Ph)CN2 in the presence of NaBPh4, and the reaction
was seen to proceed with the substitution of one ClÀ ligand
(OEt)2}]BPh4 (1b) (100 mg, 0.09 mmol) in CH2Cl2 (5 mL) and the
reaction mixture was stirred for 3 h. The solvent was removed
under reduced pressure to leave an oil, which was triturated with
ethanol (3 mL) containing an excess of NaBPh4 (0.18 mmol, 62 mg).
A yellow solid slowly separated out from the resulting solution,
which was filtered and crystallised from CH2Cl2 and ethanol. Yield:
71 mg (75%). 1H NMR (CD2Cl2, 25 °C) d: 7.56–6.87 (m, 30H, Ph),
and the formation of
1-(4-C5H4N)(Ph)CN2}L]BPh4 (3, 4), which were isolated and
characterised (Scheme 2).
j g
1-pyridine complexes [OsCl( 6-p-cymene)
{j
In this case, the pyridinic nitrogen atom does bind to osmium
instead of the diazo group: it affords a new pyridine complex with

G. Albertin et al. / Polyhedron 104 (2016) 46–51
49
+
exc. Ar1Ar2CN2
Os
-
Os
BPh4
NaBPh4, EtOH
Cl
Cl
Cl
N
PPh(OEt)2
PPh(OEt)2
1, 2
Ar1
N
C
( I )
Ar2
Scheme 1. Ar1 = Ar2 = Ph (1a); Ar1 = Ph, Ar2 = p-tolyl (1b); Ar1 = H, Ar2 = COOEt (2).
N
+
CN2
exc.
Ph
-
Os
Os
BPh4
NaBPh4
Cl
Cl
Cl
N
L
L
CN2
3, 4
Ph
Scheme 2. L = PPh(OEt)2 (3), P(OEt)3 (4).
a free diazo group which, however, is not favoured in competition
with the pyridine for the metal centre.
matching the NPy coordination of the (4-C5H4N)(Ph)CN2 group.
The presence of this ligand was confirmed by both 1H and 13C
NMR spectra, which showed the characteristic signals of the pyri-
dine substituent and of the ancillary ligands p-cymene and PPh
(OEt)2. In the temperature range between +20 and À80 °C, the
31P NMR spectra show a singlet at 98.9 (3) and 70.5 (4) ppm, fitting
the proposed formulations for the complexes.
The new diazoalkane complexes [OsCl(g
6-p-cymene)
(N2CAr1Ar2){PPh(OEt)2}]BPh4 (1, 2) were isolated as yellow-
orange solids stable in air and in solution of polar organic solvents,
in which they behave as 1:1 electrolytes [17]. Analytical and spec-
troscopic (IR, NMR) data support the proposed formulations.
The IR spectra of complexes 1 and 2 show a medium-intensity
band at 1960–1897 cm-1, attributed to the mN@N@C of the dia-
zoalkane ligand. Comparison of these values with those of dia-
zoalkane complexes of known structure [1,5] suggested singly-
bent geometry I (Scheme 1) for the Ar1Ar2CN2 group. In addition,
3.2. Reactions with alkenes and alkynes
Diazoalkane complexes [OsCl(g
6-p-cymene)(N2CAr1Ar2){PPh
(OEt)2}]BPh4 (1, 2) were treated with ethylene and pheny-
lacetylene under mild conditions. The results are shown in
Scheme 3.
the spectrum of the ethyldiazoacetate complex [OsCl(g
6-p-
cymene){N2C(H)COOEt}{PPh(OEt)2}]BPh4 (2) shows a strong band
at 1727 cmÀ1, due to the mCO of the COOEt substituent.
In mild conditions (1 atm, RT), CH2@CH2 reacts with complexes
1, 2 to give the ethylene complex [18] [OsCl(g -
6-p-cymene)(g2
Besides the signals of the ancillary ligands p-cymene and PPh
(OEt)2 and the anion BPhÀ4 , the proton NMR spectra show the char-
acteristic resonances of substituents of the diazo group. In particu-
lar, the methyl group of the p-tolyl of 1b is a singlet at 2.39 ppm,
whereas the spectrum of 2 shows a quartet at 3.62 and a triplet
at 1.38 ppm of the ethyl group of the COOEt substituent. The CH
proton is masked by the multiplets of the methylene protons of
PPh(OEt)2. In the 13C NMR spectra of 1b, the broad signal at
82.9 ppm was attributed to the CN2 carbon resonance of the dia-
zoalkane, whereas the singlet at 21.3 ppm was due to the methyl
group of the p-tolyl substituent. The signals of the p-cymene and
PPh(OEt)2 ligands were also present. In the temperature range
+20 to À80 °C, the 31P NMR spectra of 1 and 2 are singlets at
94.1–91.3 ppm, fitting the proposed formulations for the
complexes.
CH2@CH2){PPh(OEt)2}]BPh4 (5), which was isolated and charac-
terised. The reaction proceeds with the substitution of diazoalkane
and the formation of the
somewhat surprising, since diazoalkanes coordinated to the half-
sandwich fragment [Ru(
5-C5H5)(PPh3)L]+ (L = phosphite) often
g
2-CH2@CH2 derivative 5. This result was
g
undergo (3 + 2) cycloaddition to ethylene, affording 3H-pyrazole
derivatives [5a,b]. Instead, our Os p-cymene fragment did not
appear to be able to activate the coordinated N2CAr1Ar2 to
cyclisation, and substitution was the only observed reaction.
Phenylacetylene also reacts with 1, 2 to give the alkoxycarbene
complex [OsCl{@C(OEt)(CH2Ph)}(
(6), the formation of which probably involves substitution of N2-
g
6-p-cymene){PPh(OEt)2}]BPh4
CAr1Ar2 with phenylacetylene to afford an
g
2-alkyne intermediate
([B], Scheme 4).
The IR spectra of the pyridine-diazo complexes [OsCl(g
6-p-
Tautomerisation [19] of
p-alkyne on the metal centre gives
cymene){j
1-(4-C5H4N)(Ph)CN2}L]BPh4 (3, 4) show a strong band
vinylidene intermediate [C], which undergoes nucleophilic attack
[20] by ethanol, yielding final carbene derivatives 6. Therefore,
phenylacetylene also substitutes the diazoalkane bonded to the
at 2050–2044 cm-1, attributed to the mN of the diazoalkane. This
2
value is only slightly shifted with respect to free diazoalkane,

50
G. Albertin et al. / Polyhedron 104 (2016) 46–51
+
+
CH2
CH2 (1 atm)
Os
CH2Cl2 / EtOH
Cl
+
PPh(OEt)2
5
Os
Cl
N
PPh(OEt)2
Ar1
N
C
PhC
CH2Cl2 / EtOH
CH
1, 2
Os
OEt
Cl
C
Ar2
PPh(OEt)2
6
CH2Ph
Scheme 3.
H
+
+
Ar1
C
PhC
CH
[Os]
N
N
C
[Os]
C
Ar2
H
Et
Ph
O
H
+
OEt
C
+
[Os]
C
C
[Os]
Ph
CH2Ph
[Os] =
Os
Cl
PPh(OEt)2
Scheme 4. Reaction path.
osmium fragment, affording the known alkoxycarbene derivative
[20] as final product.
the carbene ligand is the 13C NMR spectrum, which shows a dou-
blet at 286.5 ppm (JCP = 15.9 Hz), characteristic of the carbene car-
bon resonance. In addition, the signals of the substituents OC2H5
and CH2Ph as well as those of the supporting ligands p-cymene
and PPh(OEt)2 are also present, in agreement with the proposed
formulation.
These results show that diazoalkane is labile in half-sandwich
osmium complexes 1 and 2 and allows the preparation of ethylene
and carbene derivatives. Both ethylene 5 and carbene 6 com-
pounds were isolated as yellow stable solids and characterised
by analytical and spectroscopic data. Significant appears the proton
spectrum of the CH2@CH2 complex 5, which shows two multiplets
at 4.24 and 3.12 ppm, attributed to the protons of the coordinated
ethylene. The multiplicity of signals is due to the presence of a chi-
ral centre in the molecule which makes the protons of ethylene
two-by-two diastereoisotopic, thus appearing at different chemical
shift values and coupled with the phosphorus of the phosphine.
The multiplet may be simulated by an EFGHX model (X = 31P) with
the parameters reported in the Experimental section and the good
fit between the experimental and calculated spectra strongly
supports the proposed attributions.
4. Conclusions
This paper reports that the half-sandwich fragment [OsCl(
cymene)L]+ with PPh(OEt)2 as a supporting ligand can stabilise dia-
zoalkane complexes.
1-Pyridine-diazoalkane derivatives [OsCl
6-p-cymene){ 1-(4-C5H4N)(Ph)CN2}L]BPh4 were also prepared.
Reaction of [OsCl(
6-p-cymene)(N2CAr1Ar2){PPh(OEt)2}]BPh4
g
6-p-
j
(g
j
g
with ethylene and phenylacetylene proceeds with substitution of
the Ar1Ar2CN2 group, yielding new derivatives.
Besides the signals of ancillary ligands, the 1H NMR spectra of
the alkoxycarbene complex 6 show the characteristic resonance
of the OC2H5 and CH2Ph substituents of the carbene, which appear
as a quartet and a triplet the former, and as two doublets at 5.37
and 2.98 ppm the latter. However, diagnostic for the presence of
Acknowledgment
We thank Mrs. Daniela Baldan, from the Università Ca’ Foscari
Venezia, for her technical assistance.

G. Albertin et al. / Polyhedron 104 (2016) 46–51
[7] (a) D. Sutton, Chem. Rev. 93 (1993) 995;
51
References
(b) M. Hidai, Y. Mizobe, Chem. Rev. 95 (1995) 1115.
[8] (a) H. Kisch, P. Holzmeier, Adv. Organomet. Chem. 34 (1992) 67;
(b) D. Sellmann, Angew. Chem. Int. Ed. 32 (1993) 64;
(c) H. Zollinger, Diazo Chemistry II, VCH, Weinheim, Germany, 1995.
[9] (a) H. Seino, D. Watanabe, T. Ohnishi, C. Arita, Y. Mizobe, Inorg. Chem. 46
(2007) 4784;
[1] (a) Y. Mizobe, Y. Ishii, M. Hidai, Coord. Chem. Rev. 139 (1995) 281;
(b) M. Dartiguenave, M.J. Menu, E. Deydier, Y. Dartiguenave, H. Siebald, Coord.
Chem. Rev. 178–180 (1998) 623.
[2] (a) R. Ben-Shoshan, J. Chatt, G.J. Leigh, W. Hussain, J. Chem. Soc., Dalton Trans.
(1980) 771;
(b) R.A. Zarkesh, A.F. Heyduk, Organometallics 28 (2009) 6629;
(c) S.K. Russell, E. Lobkovsky, P.J. Chirik, J. Am. Chem. Soc. 131 (2009) 36;
(d) M.A. Alvarez, M.E. García, R. Gonzalez, M.A. Ruiz, Organometallics 29
(2010) 5140;
(e) E.M. Matson, P.E. Fanwick, S.C. Bart, Eur. J. Inorg. Chem. (2012) 5471;
(f) J. Egloff, M. Ranocchiari, A. Schira, C. Schotes, A. Mezzetti, Organometallics
32 (2013) 4690;
(g) V.M. Iluc, G.L. Hillhouse, J. Am. Chem. Soc. 136 (2014) 6479;
(h) W. Ren, E. Zhou, B. Fang, G. Hou, G. Zi, D.-C. Fang, M.D. Walter, Angew.
Chem. Int. Ed. 42 (2014) 11310.
(b) M. Hidai, S. Aramaki, K. Yoshida, T. Kodama, T. Takahashi, Y. Uchida, Y.
Mizobe, J. Am. Chem. Soc. 108 (1986) 1562;
(c) A. Nakamura, T. Yoshida, M. Cowie, S. Otsuka, J.A. Ibers, J. Am. Chem. Soc.
99 (1977) 2108;
(d) K.D. Schramm, J.A. Ibers, Inorg. Chem. 19 (1980) 1231;
(e) K.D. Schramm, J.A. Ibers, Inorg. Chem. 19 (1980) 2435;
(f) K.D. Schramm, J.A. Ibers, Inorg. Chem. 19 (1980) 2441;
(g) G.L. Hillhouse, B.L. Haymore, J. Am. Chem. Soc. 104 (1982) 1537;
(h) M. Cowie, S.J. Loeb, I.R. McKeer, Organometallics 5 (1986) 854;
(i) A.W. Kaplan, J.L. Polse, G.E. Ball, R.A. Andersen, R.G. Bergman, J. Am. Chem.
Soc. 120 (1998) 11649;
(j) H. Kwen, V.G. Young Jr., E.A. Maatta, Angew. Chem. Int. Ed. 38 (1999) 1145;
(k) E.L. Dias, M. Brookhart, P.S. White, J. Am. Chem. Soc. 123 (2001) 2442;
(l) H. Werner, N. Mahr, J. Wolf, A. Fries, M. Laubender, E. Bleuel, R. Garde, P.
Lahuerta, Organometallics 22 (2003) 3566.
[10] (a) W.A. Herrmann, Angew. Chem. Int. Ed. 17 (1978) 800;
(b) M.P. Doyle, Chem. Rev. 86 (1986) 919;
(c) W.R. Roper, J. Organomet. Chem. 300 (1986) 167;
(d) M. Putala, D.A. Lemenovskii, Russ. Chem. Rev. 63 (1994) 197;
(e) H. Werner, J. Organomet. Chem. 500 (1995) 331;
(f) C.-M. Che, J.-S. Huang, F.-W. Lee, Y. Li, T.-S. Lai, H.-L. Kwong, P.-F. Teng, W.-
S. Lee, W.-C. Lo, S.-M. Peng, Z.-Y. Zhou, J. Am. Chem. Soc. 123 (2001) 4119;
(g) D.J. Mindiola, G.L. Hillhouse, J. Am. Chem. Soc. 124 (2002) 9976;
(h) W. Kirmse, Angew. Chem. Int. Ed. 42 (2003) 1088;
(i) X. Dai, T.H. Warren, J. Am. Chem. Soc. 126 (2004) 10085;
(j) I.V. Shishkov, F. Rominger, P. Hofmann, Organometallics 28 (2009) 1049.
[11] G. Albertin, S. Antoniutti, E. Bordignon, B. Carrera, Inorg. Chem. 39 (2000)
4646.
[3] (a) L. Messerle, M.D. Curtis, J. Am. Chem. Soc. 102 (1980) 7789;
(b) C. Woodcock, R. Eisenberg, Organometallics 4 (1985) 4;
(c) M.D. Curtis, L. Messerle, J.J. D’Errico, W.M. Butler, M.S. Hay,
Organometallics 5 (1986) 2283;
(d) Y. Gao, M.C. Jennings, R.J. Puddephatt, H.A. Jenkins, Organometallics 20
(2001) 3500;
(e) B.D. Rowsell, S.J. Trepanier, R. Lam, R. McDonald, M. Cowie,
Organometallics 21 (2002) 3228;
(f) R. Cohen, B. Rybtchinski, M. Gandelman, H. Rozenberg, J.M.L. Martin, D.
Milstein, J. Am. Chem. Soc. 125 (2003) 6532;
(g) S.C. Bart, A.C. Bowman, E. Lobkovsky, P.J. Chirik, J. Am. Chem. Soc. 129
(2007) 7212;
(h) R.G. Samant, T.W. Graham, B.D. Rowsell, R. McDonald, M. Cowie,
Organometallics 27 (2008) 3070;
(i) J. Zhang, M. Gandelman, L.J.W. Shimon, D. Milstein, Organometallics 27
(2008) 3526;
(j) N.P. Mankad, J.C. Peters, Chem. Commun. (2008) 1061;
(k) C. Khosla, A.B. Jackson, P.S. White, J.L. Templeton, Organometallics 31
(2012) 987.
[12] R. Rabinowitz, J. Pellon, J. Org. Chem. 26 (1961) 4623.
[13] (a) L.I. Smith, K.L. Howard, Organic Syntheses, Wiley, New York, 1955, p. 351.
vol. III;
(b) J.B. Miller, J. Org. Chem. 24 (1959) 560;
(c) R. Baltzly, N.B. Mehta, P.B. Russel, R.E. Brooks, E.M. Grivsky, A.M. Steinberg,
J. Org. Chem. 26 (1961) 3669.
[14] G. Balacco, <http://www.inmr.net/>.
[15] J.A. Cabeza, P.M. Maitlis, J. Chem. Soc., Dalton Trans. (1985) 573.
[16] (a) G. Albertin, S. Antoniutti, J. Castro, Eur. J. Inorg. Chem. (2009) 5352;
(b) G. Albertin, S. Antoniutti, J. Castro, S. Paganelli, J. Organomet. Chem. 695
(2010) 2142.
[17] W.J. Geary, Coord. Chem. Rev. 7 (1971) 81.
[18] G. Albertin, A. Albinati, S. Antoniutti, M. Bortoluzzi, S. Rizzato, J. Organomet.
Chem. 702 (2012) 45.
[19] (a) V. Cadierno, M.P. Gamasa, I. Gimeno, Coord. Chem. Rev. 248 (2004) 1627;
(b) M.I. Bruce, Chem. Rev. 91 (1991) 197;
(c) M.C. Puerta, P. Valerga, Coord. Chem. Rev. 193–195 (1999) 977;
(d) J.M. Lynam, Chem. Eur. J. 10 (2010) 8238.
[20] G. Albertin, S. Antoniutti, J. Castro, Organometallics 30 (2011) 1558.
[4] G. Albertin, S. Antoniutti, F. Callegaro, J. Castro, Organometallics 28 (2009)
4475.
[5] (a) G. Albertin, S. Antoniutti, D. Baldan, J. Castro, G. Comparin, Organometallics
32 (2013) 3157;
(b) G. Albertin, S. Antoniutti, A. Botter, J. Castro, M. Giacomello,
Organometallics 33 (2014) 3570;
(c) G. Albertin, S. Antoniutti, J. Castro, G. Dottorello, Dalton Trans. 44 (2015)
9289.
[6] G. Albertin, S. Antoniutti, A. Botter, J. Castro, Inorg. Chem. 54 (2015) 2091.