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A. Saito et al. / Journal of Organometallic Chemistry 691 (2006) 5746–5752
previous findings that the reactions of 1 and 2 with MP
afford the clusters consisting of MP bridging between
two Ir atoms may suggest that this trimerization using 4
probably proceeds via the initial formation of the analo-
gous alkyne adduct, followed by the successive insertion
of two MP molecules into the Ir–C bonds. Exceptionally,
high regioselectivity favoring 1,3,5-substituted trimer
observed for this system might be ascribable to this mech-
anism featuring the bimetallic site. Indeed, treatment of
the MP adduct 8 with 100 equiv. of MP in MeCN at
J = 8 Hz, 4H, CH ), 2.77–2.84 (m, 2H, CH ), 3.01–3.08
2 2
ꢁ
1
(m, 2H, CH ). IR (KBr, cm ): 2244 (C„N).
2
3.3. Preparation of 5
This compound was prepared similarly from 3 (43 mg,
*
0.050 mmol) and [(Cp RhCl)(l-Cl) ] (16 mg, 0.025 mmol)
2
as red crystals (48 mg, 81% yield). Anal. Calc. for
C H N S Cl Ir Rh requires C, 37.01; H, 4.57; N, 2.40.
3
6
53
2
3
2
2
1
Found: C, 36.55; H, 4.66; N, 2.72%. H NMR (d, CD CN):
1.51, 1.57, 1.62 (s, 15H each, Cp ), 2.40–2.44 (m, 2H, CH ),
3
*
6
0 ꢀC resulted in the formation of the trimer 9 with reten-
2
tion of the cluster cores of all 8, although the yield was
low (TON = 1.3 after 24 h).
2.48 (t, J = 8 Hz, 2H, CH ), 2.67–2.78 (m, 2H, CH ), 2.93–
2
2
ꢁ
1
3.05 (m, 2H, CH ). IR (KBr, cm ): 2245 (C„N). A single
2
In contrast, other cyclotrimerization reactions catalyzed
by numerous transition metal complexes generally proceed
via the mechanism involving the mononuclear metallacyclo-
pentadiene complexes as key intermediate stages, which
tend to result in the formation of a mixture of 1,3,5- and
crystal of 5 used for the X-ray analysis was sealed in a glass
capillary without drying, which contained two solvating
acetonitrile molecules per one cluster molecule.
3.4. Reaction of 4 with XyNC to give 6 and 7
1
,2,4-substituted trimers from terminal alkynes with the lat-
ter predominant [10]. Significant difference in the catalytic
Complex 4 Æ 1.75MeCN (67 mg, 0.050 mmol), XyNC
activity between the Ir cluster 4 and the Ir Rh cluster 5 indi-
(29 mg, 0.22 mmol), and KPF (31 mg, 0.17 mmol) were
added into MeCN (5 cm ) and the mixture was stirred for
31 h at 60 ꢀC. The resultant mixture was filtered and ether
was added to the concentrated filtrate, affording a 2:3 mix-
ture of 6 and 7 as orange microcrystals (55 mg) together
3
2
6
3
cates that the Rh center is involved in the active site of the
latter, which might also support indirectly this dinuclear
mechanism.
3
. Experimental
with small amounts of pure 6 Æ 0.5Et O as pale-yellow crys-
2
tals (1 mg) and 7 as red crystals (6 mg) that are separable
manually. Additional amounts of pure crystals of 6 and 7
were obtained by recrystallizing the microcrystalline mix-
3
.1. General
All manipulations were carried out under N using stan-
ture of these two. 6 Æ 0.5Et O: 43% yield. Anal. Calc. for
2
2
dard Schlenk techniques. Solvents were dried by common
C H N O F PSIr requires C, 46.20; H, 4.93; N, 4.90.
3
3
42
3
0.5 6
1
methods and distilled under N before use. Complex 3,
Found: C, 46.25; H, 4.51; N, 4.79%. H NMR (d, CD CN):
2
3
*
*
[
(Cp MCl) (l-Cl) ] (M = Ir, Rh) were prepared according
2.14 (s, 15H, Cp ), 2.43 (s, 12H, Me in Xy), 2.55, 2.72 (t,
2
2
to the literature methods [12], while other chemicals used in
this study were obtained commercially and used as received.
NMR and IR spectra were measured on a JEOL alpha-
J = 6.9 Hz, 2H each, CH ), 7.20–7.35 (m, 6H, C H ). IR
2
6
3
ꢁ
1
(KBr, cm ): 2249w (CH C„N), 2186s, 2155s (XyN„C).
2
7: 74% yield. Anal. Calc. for C H N F PS Ir requires
4
1
52
3
6
2
2
4
00 or a JASCO FT/IR-420 spectrometer at room temper-
C, 41.72; H, 4.44; N, 3.56. Found: C, 41.83; H, 4.33; N,
1
*
ature. Characterization of organic compounds by GC–MS
methods was carried out using a Shimadzu GC–MS QP-
5
3.84%. H NMR (d, CD CN): 1.84 (s, 30H, Cp ), 2.26 (s,
3
12H, Me in Xy), 2.38, 2.84 (t, J = 7.5 Hz, 2H each, CH ),
2
ꢁ1
050 spectrometer, and determination of their quantities
6.80–6.95 (m, 6H, C H ). IR (KBr, cm ): 2252w
6 3
by GLC methods was on a Shimadzu GC-14B gas chro-
matograph equipped with a 25 m · 0.25 mm CBP 10 fused
silica capillary column. Elemental analyses were done with
a Perkin–Elmer 2400 series II CHN analyzer.
(CH C„N), 2131s (XyN„C).
2
3.5. Reactions of 4 with MP
(1) A mixture of 4 Æ 1.75MeCN (67 mg, 0.050 mmol),
3
.2. Preparation of 4
KPF (28 mg, 0.15 mmol), and MP (17 mg, 0.20 mmol) in
6
3
1
MeCN (5 cm ) was stirred at 60 ꢀC for 12 h. The
H
3
Into
a
MeCN solution (150 cm ) of
3
(1.29 g,
NMR spectrum of the product mixture containing Ph CH
3
*
1
0
.50 mmol) was added [(Cp IrCl) (l-Cl) ] (598 mg,
.751 mmol), and the mixture was stirred at room temper-
(25 mg) as an internal standard showed that the yield of 9
was 0.99 mol/mol 4 charged, while 4 present in the product
solution was 92% of the amount initially charged. From the
2
2
ature for 20 h. The resultant mixture was dried up in vacuo
and the residue was washed with ether. Crystallization of
the remained solid from MeCN–ether afforded
1
H NMR criteria, the trimer 9 was the sole organic product
and the cluster 4 was the only detectable Ir-containing
compound.
4
Æ 1.75MeCN as red crystals (1.51 g, 76%). Anal. Calc.
for C39.5H58.25N3.75S Cl Ir requires C, 35.69; H, 4.42; N,
(2) As for the typical catalytic reaction, a mixture of
4 Æ 1.75MeCN (15 mg, 0.011 mmol), KPF6 (7 mg,
0.05 mmol), and MP (108 mg, 1.28 mmol) in MeCN
3
2
3
1
3
.95. Found: C, 35.47; H, 4.44; N, 4.06%. H NMR (d,
*
*
CD CN): 1.55 (s, 30H, Cp ), 1.59 (s, 15H, Cp ), 2.46 (t,
3