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was investigated by conducting reactions of 2 with 10 equiv of
and upon reaction of [{(h3-allyl)NiBr}2] with NO to form
[3a]
=
À
=
TMEDA and 10–30 equiv of alkene in THF solution at room
temperature (Table 1). Dinitrosoalkane adducts were only
isolated from reactions with strained and non-enolizable
[NiBr(NO)(CH2 CH CH NOH)].
In summary, a simple high-yielding synthesis of the novel
metal dinitrosyl complex [RuCl2(NO)2(THF)] from [{(cy-
mene)RuCl2}2] is reported. In the solid state, the former
compound displays nitric oxide ligands with both bent and
linear geometries. In solution, in the presence of a variety of
chelating ligands, [RuCl2(NO)2(THF)] reacts with simple
alkenes to form the corresponding six-coordinate dinitroso-
alkane complexes. We are continuing to investigate new
organometallic reagents for controlling the reactivity of NO
and the application of the reaction reported herein to the
asymmetric diamination of alkenes and will report our
findings in subsequent publications.
Table 1: Scope of the reaction of 2, 10 equiv of TMEDA and 10–30 equiv
of alkene in THF at room temperature.
Alkene
Product
t
Yield
[h] [%][a]
n=1
n=2
4a
4b
2
2
57
66
R1 =R3 =CO2Me
R2 =R4 =H
4c 0.5 60
3
4
=
R ,R =-(CH
CHCH2)-
4d
2
75
Experimental Section
R1 =R2 =H
Synthesis of 2: A Schlenk flask containing a slurry of [{RuCl2-
(cymene)}2] (2.00 g, 3.26 mmol) in THF (50 mL) was attached to a
manifold fitted with a nitric oxide inlet. The reaction mixture was
freeze–pump–thaw degassed and the apparatus isolated under
vacuum. Nitric oxide was then introduced and the reaction mixture
stirred under 1 atm NO. A fast reaction occurred and the solution
turned deep brown with solid [{RuCl2(cymene)}2] being consumed in
the first 30 min. Once the reaction was complete, the solvent was
removed in vacuo and the resulting brown/black crystalline solid
washed with pentane (3 ꢁ 20 mL) and dried under vacuum overnight.
[RuCl2(NO)2THF] (1.74 g, 5.72 mmol, 88%) was isolated as a brown
4e
2
81[b]
R1 =Me
R1 =iPr
4 f 0.5 93[b]
4g
24[b]
3
R1 =Me
R1 =Ph
4h 0.5 66[b]
4i
2
56[b]
1
solid. H NMR (CD2Cl2, 400 MHz, 298 K): d = 4.60 (m, 4H, THF),
R1 =Ph
4j
1
81[b]
2.20 ppm (m, 4H, THF); 13C NMR (CD2Cl2, 100 MHz, 298 K): d =
R1 =CH2(tBu)
R1 =iPr
4k 0.5 88[b]
4l 0.5 44[b]
75.5, 26.7 ppm; IR (solid): n = 1859, 1615 cmÀ1; Elemental analysis
~
calcd for C4H8N2O3RuCl2: C 15.80, H 2.65, N 9.21; found: C 16.23, H
2.48, N 8.54.
Synthesis of 4a: In a glovebox, TMEDA (190 mg, 1.64 mmol,
10 equiv) and norbornadiene (151 mg, 1.64 mmol, 10 equiv) were
weighed into a scintillation vial and dissolved in THF (2.5 mL). This
mixture was then added to a solution of 2 (50 mg, 0.164 mmol) in THF
(2.5 mL) in a 20 mL scintillation vial. The reaction mixture was stirred
for 2 h at room temperature. The vial containing the reaction mixture
was removed from the glovebox and the crude mixture chromato-
graphed on silica gel using chloroform as an eluent. 4a was isolated as
a red/brown crystalline solid (40.7 mg, 0.0927 mmol, 57%). 1H NMR
(CDCl3, 400 MHz, 298 K): d = 1.52 (d, 1H, J = 9.6 Hz), 1.63 (d, 1H,
J = 9.6 Hz), 2.39–2.46 (m, 2H), 2.50–2.56 (m, 2H), 2.61 (s, 6H), 2.90 (s,
6H), 3.57 (m, 2H), 4.01 (m, 2H), 6.37 ppm (m, 2H); 13C NMR
(CDCl3, 100 MHz, 298 K): d = 45.3, 49.3, 50.5, 51.2, 59.7, 100.3,
[a] Reactions conducted in THF at room temperature using 10 equiv of
TMEDA, 1 equiv of 2, and 10 equiv of alkene; reported yields are
following isolation by silica gel chromatography. [b] 30 equiv of alkene
was used.
alkenes (4a–e). For both 1,1-disubstituted and 1,1,2-trisub-
stituted alkenes, compounds containing a single nitrosoalkane
and oxime functional group were isolated (4 f–l). Attempts to
extend this methodology to both cyclic and acyclic, cis- and
trans-1,2-dialkyl alkenes failed to yield products that were
isolable by chromatography on silica gel.
Tautomerization was detected by not only the acidic
oxime proton signal, observed as a broad resonance between
d = 6.0–6.6 ppm and d = 7.6–9.2 ppm for 4 f–i and 4j–l,
respectively, in CDCl3 solution by 1H NMR spectroscopy,
but also distinctive resonances at d = 155–175 ppm in the
13C NMR spectra characteristic of the sp2-oxime carbon. In
140.1 ppm; IR (solid): n = 2910, 1460, 1397, 1326, 1270 cmÀ1; HR-MS
~
(ESI, [MÀCl]+) calcd for C13H24ClN4O2Ru 405.0631, found 405.0626.
Elemental analysis calcd for C13H24Cl2N4O2Ru: C 35.46, H 5.49, N
12.72; found: C 35.23, H 5.55, N 12.60.
Full experimental details including single-crystal X-ray diffrac-
tion studies are provided in the Supporting Information.
CCDC 810236 (2) and 810237 (4a) contain the supplementary
crystallographic data for this paper. These data can be obtained
free of charge from The Cambridge Crystallographic Data Centre via
À
addition, broad n(O H) absorptions were observed in the
infrared spectra between 3100–3250 cmÀ1. The connectivity of
4l was determined unambiguously following a single-crystal
X-ray diffraction experiment; however, the poor resolution of
the data limits any informative discussion (see the Supporting
Information, Figure S2). It is noteworthy that while analogous
tautomerization products have not been observed in the
alkene/[CpCo(NO)2] reaction,[2] a similar tautomerization has
been observed in the insertion reaction of [NO][PF6] with
[CpCr(NO)2Me] to yield [CpCr(NO)2{N(OH)CH2}][PF6],[14]
Received: February 1, 2011
Published online: April 7, 2011
Keywords: coordination compounds · nitrosyl ligands ·
.
nitric oxide · nitrosoalkanes · ruthenium
ꢀ 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Angew. Chem. Int. Ed. 2011, 50, 4484 –4487