Oxidative addition reactions of Rh(SbPh3)3(CO)X (X = Cl, Br) with organic phenyl-substituted propargyl compounds. Rhodium(III) phenylpropargyl products and their conversion to rhodiacyclic complexes

Article abstract of DOI:10.1016/S0020-1693(01)00457-1

Reactions of Rh(SbPh₃)₃(CO)X (X = Cl (1), Br (2)) with PhC≡CCH₂Y (Y = OTs, Cl, Br) in CH₂Cl₂ at ambient temperature lead to formation of the oxidative addition products Rh(SbPh₃)₂(CO)X(Y)(η¹-CH₂C ≡CPh) (X = Cl, Y = OTs (3), Cl (4), Br (5); X = Br, Y = OTs (6), Br (7)). Complexes 3 and 6 each react with pyridine at room temperature to afford the rhodiacyclopent-3-ene-2-ones Rh(SbPh₃)₂(py)X(η²-C(O)C(Ph)=C(OTs)CH ₂) (X = Cl (8), Br (9)). Treatment with AgOTs converts 8 to Rh(SbPh₃)₂(py)(OTs)(η²-C(O)C(Ph)=C(OTs) CH₂) (10). Addition of AgOTf (or AgBF₄) and then immediately an excess of PhC≡CCH₂Br to a CH₂Cl₂ solution of 1 at ambient temperature affords an orange solid that is formulated tentatively as [Rh(SbPh₃)₂(CO)Cl(η³-CH₂ CCPh)]OTf (or -BF₄) (11a and 11b). All new complexes were characterized by a combination of elemental analysis, FAB mass spectrometry, IR and NMR (¹H and ¹³C{¹H}) spectroscopy and conductance measurements.

Full text of DOI:10.1016/S0020-1693(01)00457-1

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Inorganica Chimica Acta 319 (2001) 187–193
Oxidative addition reactions of Rh(SbPh3)3(CO)X (X=Cl, Br)
with organic phenyl-substituted propargyl compounds.
Rhodium(III) phenylpropargyl products and their conversion to
rhodiacyclic complexes
Asgar Kayan 1, Andrew Wojcicki *
Department of Chemistry, The Ohio State Uni6ersity, 100 West 18th A6enue, Columbus, OH 43210-1185, USA
Received 8 March 2001; accepted 6 April 2001
Abstract
Reactions of Rh(SbPh3)3(CO)X (X=Cl (1), Br (2)) with PhCꢀCCH2Y (Y=OTs, Cl, Br) in CH2Cl2 at ambient temperature
lead to formation of the oxidative addition products Rh(SbPh3)2(CO)X(Y)(h1-CH2CꢀCPh) (X=Cl, Y=OTs (3), Cl (4), Br (5);
X=Br, Y=OTs (6), Br (7)). Complexes 3 and 6 each react with pyridine at room temperature to afford the rhodiacyclopent-3-
ene-2-ones Rh(SbPh3)2(py)X(h2-C(O)C(Ph)ꢁC(OTs)CH2) (X=Cl (8), Br (9)). Treatment with AgOTs converts
8 to
Rh(SbPh3)2(py)(OTs)(h2-C(O)C(Ph)ꢁC(OTs)CH2) (10). Addition of AgOTf (or AgBF4) and then immediately an excess of
PhCꢀCCH2Br to a CH2Cl2 solution of 1 at ambient temperature affords an orange solid that is formulated tentatively as
[Rh(SbPh3)2(CO)Cl(h3-CH2CCPh)]OTf (or ꢂBF4) (11a and 11b). All new complexes were characterized by a combination of
elemental analysis, FAB mass spectrometry, IR and NMR (1H and 13C{1H}) spectroscopy and conductance measurements.
© 2001 Elsevier Science B.V. All rights reserved.
Keywords: Oxidative addition; Rhodium complexes; Propargyl complexes; Rhodiacyclic complexes
1. Introduction
reactions of 1 and 2 with various phenyl-substituted
propargyl compounds PhCꢀCCH2Y (Y=OTs, Cl, Br)
which invariably yield rhodium(III) h1-propargyl com-
plexes, Rh(SbPh3)2(CO)X(Y)(h1-CH2CꢀCPh). Some
products were converted to the rhodiacyclic complexes
Rh(SbPh3)2(py)X(h2-C(O)C(Ph)ꢁC(Y)CH2) and to a
cationic complex that we formulate tentatively as
an h3-allenyl/propargyl, [Rh(SbPh3)2(CO)Cl(h3-CH2-
CCPh)]+. Our preliminary communication [8a] has ad-
dressed aspects of this chemistry.
Oxidative addition reactions of propargyl halides and
tosylates to various d8 and d10 metal centers afford
h1-allenyl and h1-propargyl complexes [1–7]. We have
recently reported [8] that reactions of Rh(SbPh3)3-
(CO)X (X=Cl (1), Br (2)) with HCꢀCCH2Y (Y=OTs,
OBs, Cl, Br; OTs=p-MeC6H4SO3, OBs=PhSO3) lead
to formation of h1-allenyl complexes, Rh(SbPh3)2-
(CO)X(Y)(h1-CHꢁCꢁCH2), when Y=OTs or OBs, and
of rhodiacyclopent-3-ene-2-one complexes, Rh(SbPh3)3-
(X or Y)(h2-C(O)CHꢁC(Y or X)CH2), when Y=Cl or
Br. In this paper we present a complementary study on
2. Experimental
2.1. General procedures and measurements
* Corresponding author. Tel.: +1-614-2924750; fax: +1-614-
2921685.
E-mail address: wojcicki.1@osu.edu (A. Wojcicki).
1 Present address: Kocaeli Universitesi, Fen.-Ed. Fak., Kimya
Bolumu, 41300 Izmit, Turkey.
Reactions and manipulations of air-sensitive com-
pounds were carried out under an atmosphere of argon
by the use of standard procedures [9]. Solvents were
0020-1693/01/$ - see front matter © 2001 Elsevier Science B.V. All rights reserved.
PII: S0020-1693(01)00457-1

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A. Kayan, A. Wojcicki / Inorganica Chimica Acta 319 (2001) 187–193
1
dried [10], distilled under argon and degassed before
use. Elemental analyses were performed by M-H-W
Laboratories, Phoenix, AZ. IR, NMR (1H and
13C{1H}) and FAB mass spectra were obtained as
previously described [8b]. Conductance measurements
on approximately 1 mM solutions of rhodium com-
plexes in CH2Cl2 were carried out at room temperature
with a YSI Model 35 conductivity apparatus.
(CHCl3, cm−1): w(CO) 2061. H NMR (CDCl3): l=
2
7.82–6.95 (m, 35H, Ph), 2.83 (d, JRhH=3.2 Hz, 2H,
CH2). 13C{1H} NMR (CDCl3): l=183.51 (d, JRhC
=
1
63.7 Hz, CO), 138.00–127.48 (m, Ph), 100.86 (s, ꢀCPh),
1
86.22 (s, CH2Cꢀ), −2.85 (d, JRhC=17.8 Hz, CH2).
FAB MS; m/z: 987.1 (M++2−Cl), 871.8 (M++2−
Cl−C9H7), 843.8 (M++2−Cl−C9H7−CO). Anal.
Found: C, 52.36; H, 3.54. Calc. for C46H37Cl2ORhSb2:
C, 54.00; H, 3.65%.
2.2. Materials
2.3.3. Reaction of 1 with PhCꢀCCH2Br
Reagents were procured from various commercial
sources and used as received, except as noted below.
Procedures used in the literature were employed to
synthesize the organic propargyl compounds PhCꢀ
CCH2Cl [11], PhCꢀCCH2Br [12] and PhCꢀCCH2OTs
[12]. The complex Rh(SbPh3)3(CO)Cl (1) [13–17] was
prepared by the method of Vallarino [18], but without
recrystallization, which causes loss of SbPh3 and forma-
tion of Rh(SbPh3)2(CO)Cl [17]. The analogous bromide
Rh(SbPh3)3(CO)Br (2) was obtained from 1 and LiBr as
reported earlier [8b]. It was characterized by compari-
son of its spectroscopic properties with those published
for 2 [17].
By a similar procedure, 1 (0.20 g, 0.16 mmol) and
PhCꢀCCH2Br (0.100 ml, 0.156 g, 0.800 mmol) afforded
Rh(SbPh3)2(CO)Cl(Br)(h1-CH2CꢀCPh) (5) as a yellow
solid in 89% yield (0.155 g). IR (CHCl3, cm−1): w(CO)
1
2060. H NMR (CDCl3): l=7.84–6.95 (m, 35H, Ph),
2
2
2.90 (d, JRhH=3.50 Hz, 2H, CH2), 2.82 (d, JRhH
=
3.15 Hz, CH2, minor product). 13C{1H} NMR (CDCl3):
1
1
l=183.66 (d, JRhC=64 Hz, CO), 183.50 (d, JRhC
=
62 Hz, CO, minor product), 136.52–124.26 (m, Ph),
101.35 (s, ꢀCPh, minor product), 100.76 (s, ꢀCPh),
86.91 (s, CH2Cꢀ, minor product), 86.81 (s, CH2Cꢀ),
1
0.18 (d, JRhC=18.42 Hz, CH2, minor product), −2.6
1
(d, JRhC=18.42 Hz, CH2). \m=0.27 V−1 cm2 mol−1
.
Anal. Found: C, 51.58; H, 3.70. Calc. for
2.3. Reactions of Rh(SbPh3)3(CO)X (X=Cl (1), Br
(2)) with organic propargyl compounds
C46H37BrClORhSb2: C, 51.75; H, 3.49%.
2.3.4. Reaction of 2 with PhCꢀCCH2OTs
2.3.1. Reaction of 1 with PhCꢀCCH2OTs
Reaction of
2
(0.42 g, 0.33 mmol) with
A stirred solution of 1 (0.88 g, 0.72 mmol) in 15 ml
of CH2Cl2 was treated with PhCꢀCCH2OTs (0.29 g, 1.0
mmol) in 3 ml of CH2Cl2 at room temperature. The
color of the resultant solution changed from red to pale
yellow in 1 h as stirring continued for 1.5 h. The
volume was then reduced to approximately 3 ml, and a
solid was precipitated by the addition of 20 ml of
hexane. The yellow Rh(SbPh3)2(CO)Cl(OTs)(h1-
CH2CꢀCPh) (3) was collected on a filter frit, washed
with hexane (2×15 ml) and dried under vacuum for 3
days. Yield, 0.71 g (85%). IR (CDCl3, cm−1): w(CO)
PhCꢀCCH2OTs (0.11 g, 0.38 mmol), conducted simi-
larly to the preceding reactions, gave Rh(SbPh3)2-
(CO)Br(OTs)(h1-CH2CꢀCPh) (6) as a yellow solid in
1
80% yield (0.32 g). IR (CDCl3, cm−1): w(CO) 2073. H
NMR (CDCl3): l=7.85–6.70 (m, 39H, Ph, C6H4), 3.11
2
(d, JRhH=3.55 Hz, 2H, CH2), 2.30 (s, Me).
2.3.5. Reaction of 2 with PhCꢀCCH2Br
By
a
similar procedure, Rh(SbPh3)2(CO)Br2(h1-
CH2CꢀCPh) (7) was obtained as a yellow solid in 90%
yield (0.16 g) from 2 (0.203 g, 0.160 mmol) and
PhCꢀCCH2Br (0.100 ml, 0.156 g, 0.800 mmol). IR
1
2071. H NMR (CDCl3): l=7.81–6.71 (m, 39H, Ph,
2
C6H4), 3.09 (d, JRhH=3.4 Hz, 2H, CH2), 2.29 (s, 3H,
1
(CDCl3, cm−1): w(CO) 2060. H NMR (CDCl3): l=
1
Me). 13C{1H} NMR (CDCl3): l=183.18 (d, JRhC
=
2
7.88–6.92 (m, 35H, Ph), 2.89 (d, JRhH=3.37 Hz, 2H,
64.6 Hz, CO), 139.82–123.70 (m, Ph, C6H4), 99.73
(s, ꢀCPh), 88.93 (s, CH2Cꢀ), 21.23 (s, Me), −5.74
(d, 1JRhC=17.9 Hz, CH2). FAB MS; m/z: 987.0 (M++
2−OTs), 959.0 (M++2−OTs−CO), 844.1 (M++
2−OTs−CO−C9H7). Anal. Found: C, 54.80; H,
4.06. Calc. for C53H44ClO4RhSSb2: C, 54.93; H, 3.83%.
1
CH2). 13C{1H} NMR (CDCl3): l=183.40 (d, JRhC
=
63.72 Hz, CO), 139.60–124.26 (m, Ph), 101.41
1
(s, ꢀCPh), 86.75 (s, CH2Cꢀ), −2.66 (d, JRhC=17.42
Hz, CH2).
2.4. Reactions of rhodium(III) p1-propargyl complexes
with pyridine
2.3.2. Reaction of 1 with PhCꢀCCH2Cl
Reaction between
1 (1.0 g, 0.82 mmol) and
PhCꢀCCH2Cl (0.800 ml, 1.15 g, 7.66 mmol) and subse-
quent work-up were conducted similarly to those for 1
and PhCꢀCCH2OTs. Yield of Rh(SbPh3)2(CO)Cl2(h1-
CH2CꢀCPh) (4), a yellow solid, was 0.75 g (90%). IR
2.4.1. Reaction of Rh(SbPh3)2(CO)Cl(OTs)-
(p1-CH2CꢀCPh) (3) with pyridine
Pyridine (0.110 ml, 0.107 g, 1.37 mmol) was added to
a stirred solution of 3 (0.27 g, 0.23 mmol) in 10 ml of

A. Kayan, A. Wojcicki / Inorganica Chimica Acta 319 (2001) 187–193
189
CH2Cl2 at room temperature. The color of the solution
2.6. Reaction of Rh(SbPh3)3(CO)Cl (1) with sil6er(I)
salts and PhCꢀCCH2Br
changed from yellow to pale red in a few minutes. The
mixture was stirred for 1 h, and solvent was removed
under vacuum to leave an oily solid which was washed
with hexane (2×5 ml). The hexane wash containing
excess pyridine was removed by decantation to leave an
A stirred solution of 1 (0.20 g, 0.16 mmol) in 10 ml
of CH2Cl2 at room temperature was treated first with
AgOTf (0.042 g, 0.16 mmol) and then immediately with
PhCꢀCCH2Br (0.100 ml, 0.156 g, 0.800 mmol). The
mixture was stirred for 1 h and filtered to remove a pale
yellow solid, shown to be AgBr by oxidation to Br2
with H2O2/HNO3 in the presence of 1,2-dichloroethane.
The filtrate was evaporated to dryness, and the residue
was dissolved in approximately 2 ml of toluene. Addi-
tion of hexane (20 ml) with stirring induced precipita-
tion of a pale orange solid, which was collected on a
filter frit and washed with 10 ml of hexane. The solid
was recrystallized from toluene–hexane and dried un-
der vacuum for a few days. Yield, 0.14 g (75% of
proposed 11a). IR (CDCl3, cm−1): w(CO) 2068. 1H
NMR (CDCl3): l=7.85–6.89 (m, 35H, Ph), 4.43
(s, 2H, CH2). 13C{1H} NMR (CDCl3): l=183.37
(d, 1JRhC=63.73 Hz, CO), 139.94–121.79 (m, Ph),
101.25 (s, CPh), 87.92 (s, CH2C), 80.70 (s, CH2). FAB
MS; m/z: 987.1 (M++2) (for M+ꢁ[Rh(SbPh3)2(CO)-
Cl(h3-CH2CCPh)]+). \m=21.55 V−1 cm2 mol−1. Sat-
isfactory elemental analysis for [Rh(SbPh3)2(CO)Cl(h3-
CH2CCPh)]OTf (11a) could not be obtained.
orange
solid,
Rh(SbPh3)2(py)Cl(h2-C(O)C(Ph)ꢁ
C(OTs)CH2) (8) which was dried under vacuum for 3
days. Yield, 0.28 g (97%). IR (CDCl3, cm−1): w(CꢁO)
1
1626. H NMR (CDCl3): l=9.06–8.76, 8.42–6.46 (dd,
2
m, 44H, py, Ph, C6H4), 3.69 (d, JHH=18.10 Hz, 1H of
CH2), 3.26 (d, 2JHH=18.10 Hz, 1H of CH2), 2.24
(s, 3H, Me). 13C{1H} NMR (CDCl3): l=232.84
(d, 1JRhC=30.75 Hz, CꢁO), 166.41 (s, ꢁCOTs), 153.92–
151.33 (2s, py), 149.79 (s, ꢁCPh), 147.54–123.86
1
(m, Ph, C6H4, py), 24.08 (d, JRhC=25.41 Hz, CH2),
21.31 (s, Me). Anal. Found: C, 56.59; H, 4.34. Calc. for
C58H49ClNO4RhSSb2: C, 56.27; H, 3.99%.
2.4.2. Reaction of Rh(SbPh3)2(CO)Br(OTs)-
(p1-CH2CꢀCPh) (6) with pyridine
By
a
similar procedure, Rh(SbPh3)2(py)Br(h2-
C(O)C(Ph)ꢁC(OTs)CH2) (9) was obtained as an orange
solid from 6 (0.29 g, 0.24 mmol) and pyridine (0.20 ml,
0.19 g, 2.4 mmol). Yield, 0.30 g (97%). IR (CDCl3,
cm−1): w(CꢁO) 1625. 1H NMR (CDCl3): l=9.08–
8.85, 8.61–6.55 (dd, m, 44H, py, Ph, C6H4), 3.81
A similar reaction of 1, AgBF4 and PhCꢀCCH2Br
yielded the corresponding BF4− salt, 11b. Its IR w(CO)
and 1H and 13C{1H} NMR spectra were essentially
identical with those of 11a. FAB MS; m/z: 987.1 (M+
+2) (for M+ꢁ[Rh(SbPh3)2(CO)Cl(h3-CH2CCPh)]+).
2
2
(d, JHH=17.66 Hz, 1H of CH2), 3.28 (d, JHH=17.66
Hz, 1H of CH2), 2.31 (s, 3H, Me). 13C{1H} NMR
1
(CDCl3): l=232.79 (d, JRhC=30.63 Hz, CꢁO), 167.12
(s, ꢁCOTs), 154.65–152.01 (2s, py), 149.74 (s, ꢁCPh),
1
\m=21.70 V−1 cm2 mol−1
.
147.42–124.60 (m, Ph, C6H4, py), 24.55 (d, JRhC
=
25.29 Hz, CH2), 21.29 (s, Me).
3. Results and discussion
2.5. Reaction of Rh(SbPh3)2(py)Cl(p2-C(O)C(Ph)ꢁ
C(OTs)CH2) (8) with sil6er tosylate
3.1. Rhodium(III) p1-propargyl complexes
Silver tosylate (0.069 g, 0.24 mmol) was added to a
stirred solution of 8 (0.30 g, 0.24 mmol) in 10 ml of
CH2Cl2 at room temperature. Stirring was continued
for 2 h, and the mixture was filtered to remove silver
chloride. Solvent was evaporated from the filtrate, and
the remaining orange solid Rh(SbPh3)2(py)(OTs)(h2-
C(O)C(Ph)ꢁC(OTs)CH2) (10) was dried under vacuum
for 3 days. Yield, 0.32 g (97%). IR (CDCl3, cm−1):
Reactions of Rh(SbPh3)3(CO)X (X=Cl (1), Br (2))
with PhCꢀCCH2Y (Y=OTs, Cl, Br) in CH2Cl2 at
room temperature give complexes 3–7 as yellow solids
in 80–90% yield (Eq. (1)).
1
w(CꢁO) 1637. H NMR (CDCl3): l=8.97–8.73, 8.47–
2
6.79 (dd, m, 48H, py, Ph, C6H4), 4.53 (dd, JHH=18.29
2
Hz, 2JRhH=2.38 Hz, 1H of CH2), 3.44 (dd, JHH
=
2
18.29 Hz, JRhH=2.76 Hz, 1H of CH2), 2.32 (s, 6H,
1
Me). 13C{1H} NMR (CDCl3): l=227.60 (d, JRhC
=
30.63 Hz, CꢁO), 167.21 (s, ꢁCOTs), 152.68–151.60 (2s,
2
py), 146.22 (d, JRhC=5.98 Hz, ꢁCPh), 147.31–124.58
1
(m, Ph, C6H4, py), 25.88 (d, JRhC=26.10 Hz, CH2),
21.03 (s, Me).
(1)

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A. Kayan, A. Wojcicki / Inorganica Chimica Acta 319 (2001) 187–193
stereochemistry of 3–7 is based on the assumed trans
These products have been characterized as rhodium-
(III) h1-propargyl complexes by a combination of IR
and NMR (1H and 13C{1H}) spectroscopy, FAB mass
spectrometry, conductance measurements and elemen-
tal analysis. Because of the near identical spectroscopic
properties of 3–7 (cf. Section 2.3), elemental analysis
determination was not considered necessary for all
complexes. The molar conductivity value \m=0.75
oxidative addition of PhCꢀCCH2 and Y to a square
planar Rh center, formed by dissociation of one SbPh3
ligand from five-coordinate 1 or 2. This proposal is
supported by the recently elucidated structure of the
iridium(III) h1-allenyl complex Ir(PPh3)2(CO)(NHSO2-
Ph)Cl(h1-CHꢁCꢁCH2) [26] which has been related
stereochemically to the product of the reaction between
trans-Ir(PPh3)2(CO)Cl and HCꢀCCH2Br [3,6,26].
In contrast to reactions of metal complexes with
HCꢀCCH2Y which generally afford h1-allenyls
MCHꢁCꢁCH2 [1–3,6,7], reactions of metal complexes
with phenyl-substituted propargyls, PhCꢀCCH2Y, yield
h1-propargyls MCH2CꢀCPh [1,4,21,22]. An exception
to the latter behavior is provided by the oxidative
addition reaction of Pd(PPh3)4 with PhCꢀCCH2Br
which gives an equilibrium mixture of trans-Pd(PPh3)2-
Br(h1-CH2CꢀCPh) and trans-Pd(PPh3)2Br(h1-C(Ph)ꢁ
CꢁCH2) [27]. Related examples of h1-propargyl–h1-
allenyl tautomer chemistry include isomerization of
trans-Pt(PPh3)2X(h1-CH2CꢀCPh) to trans-Pt(PPh3)2-
X(h1-C(Ph)ꢁCꢁCH2) (X=Cl, Br, I) [7a] and prepara-
tion of each Cp(CO)2Ru(h1-CH2CꢀCPh) and Cp(CO)2-
Ru(h1-C(Ph)ꢁCꢁCH2) by the use of different synthetic
routes [22,28]. In the present case, heating 4 in THF at
60oC for 2 h effected no conversion to a corresponding
h1-allenyl complex.
V
−1 cm2 mol−1 for 5 in CH2Cl2 supports a nonionic,
six-coordinate formulation. Solutions of 1:1 electrolytes
of comparable concentration in CH2Cl2 give substan-
tially
−1 cm2 mol−1 [19,20].
The IR spectra of 3–7 show one w(CO) band at
2073–2060 cm−1, with the tosylate complexes 3 and 6
absorbing at the highest energy, 2071 and 2073 cm−1
higher
molar
conductivities
(10.3–23.8
V
,
respectively, as expected. The presence of the h1-
CH2CꢀCPh ligand is evidenced by the appearance of a
1H resonance of the CH2 group at l 3.11–2.83 with a
small coupling constant, 2JRhH=3.15–3.55 Hz. The
observed chemical shift is in the range appropriate for
2
metal h1-propargyl complexes [4,21,22], and the JRhH
is that expected for a RhCH2 fragment [23,24]. The
13C{1H} NMR spectra also support the phenylpropar-
gyl formulation, with the ꢀCPh signals occurring at l
101.41–99.73, CH2Cꢀ signals at l 88.93–86.22 and
1
CH2 signals at l −2.6 to −5.74 with JRhC=17.4–
1
18.4 Hz. The magnitude of the JRhC of RhCH2 com-
3.2. Rhodiacyclopent-3-ene-2-one complexes
pares very well with that reported for Rh(SbPh3)2-
(CO)Cl(OTs)(h1-CH2CꢀCMe) [8b] and Rh(SbPh3)2-
(CO)Cl(Br)(h1-CH2CHꢁCH2) [25]. The 13C{1H} NMR
spectra also show a signal of the CO ligand at l
183.66–183.16 with 1JRhC=63.7–64.4 Hz. Both of
these values are similar to those obtained for
Treatment of 3 and 6 with pyridine in CH2Cl2 at
room temperature affords complexes 8 and 9, respec-
tively, as orange solids in 97% yield (Eq. (2)).
Rh(SbPh3)2(CO)Cl(OTs)(h1-CH2CꢀCMe)
[8b],
Rh(SbPh3)2(CO)Cl(Br)(h1-CH2CHꢁCH2) [25] and re-
lated six-coordinate rhodium(III) h1-allenyl complexes
[8].
The foregoing spectroscopic data suggest formation
of only a single product for each of 3, 4, 6 and 7. For
5, the occurrence of duplicate H and 13C{1H} NMR
1
(2)
resonances in the spectra (cf. Section 2.3.3) indicates
that another, minor, species, probably an isomer of the
main product, is present as well. No attempt was made
to separate the two complexes. The proposed ligand
The structurally analogous 10 was obtained by re-
placement of bromide in 9 with tosylate from AgOTs
(Eq. (3)).
(3)

A. Kayan, A. Wojcicki / Inorganica Chimica Acta 319 (2001) 187–193
191
Scheme 1. X=Cl, Br; L=SbPh3.
The IR and 13C{1H} NMR spectra of 8–10 closely
match those of the rhodiacyclic complexes Rh(SbPh3)3-
(X or Y)(h2-C(O)CHꢁC(Y or X)CH2), obtained from
Rh(SbPh3)3(CO)X and HCꢀCCH2Y, and, especially,
those of the pyridine substitution product Rh(SbPh3)2-
(py)Cl(h2-C(O)CHꢁC(Cl)CH2) [8b]. Three of those
complexes have been characterized by X-ray diffraction
techniques [8]. In the IR spectra of 8–10 the w(CꢁO)
band of the rhodiacyclopent-3-ene-2-one ring is ob-
served at 1637–1625 cm−1, and in the 13C{1H} NMR
spectra the signal of this CꢁO occurs at l 232.84–
same group, viz., OTs, in 8–10.2 A similar criterion was
used to assign the location of X and Y (Rh or ring
CH2Cꢁ) in the rhodiacyclics derived from Rh(SbPh3)3-
(CO)X and HCꢀCCH2Y [8b].
The CH2 protons of 8–10 are inequivalent in their
NMR spectra and appear as an AB pattern with l
2
4.53–3.69 and 3.44–3.26 and JHH=17.7–18.3 Hz, as
reported previously for Rh(SbPh3)2(py)Cl(h2-C(O)CHꢁ
C(Cl)CH2) [8b]. In the spectrum of 10, additional small
coupling to 103Rh is discernible (2JRhH=2.38 and 2.76
Hz). The inequivalence of the CH2 protons is likely due
to the presence of a chiral Rh center, which would
result from the two SbPh3 ligands assuming cis posi-
tions.
227.60 with substantial coupling to 103Rh (1JRhC
=
30.6–30.8 Hz). Other important 13C{1H} resonances
are those at l 167.21–166.41 (CH2C(OTs)ꢁ), 149.79–
146.22 (ꢁCPh) and 25.88–24.08 (CH2), the latter a
1
doublet with JRhC=26.1–25.3 Hz. The magnitude of
2 However, an alternative, zwitterionic rhodiacyclopent-3-ene-2-one
structure of the same composition as 8–10, in which pyridine is
bonded to the ring CH2Cꢁ and tosylate is bonded to the rhodium
center, cannot be ruled out on the basis of the spectroscopic data.
this coupling constant indicates RhꢂCH2 bonding
[8b,25,29,30]. The very similar chemical shifts for the
ring CH2Cꢁ suggest that this carbon is bonded to the

192
A. Kayan, A. Wojcicki / Inorganica Chimica Acta 319 (2001) 187–193
The formation of complexes 8 and 9 may be rational-
phenylpropargyl bromide in the reaction is important,
as phenylpropargyl chloride gives a mixture of unchar-
acterized rhodium products. Reaction of 5 with AgOTf
resulted in precipitation of AgCl, but the solid iso-
lated from the filtrate also could not be characterized.
Thus, abstraction of halide by silver(I) occurs from
PhCꢀCCH2X rather than from rhodium, and is favored
by X=Br.
ized by an adaptation of the mechanism proposed for
the reactions of 1 and 2 with HCꢀCCH2Y leading to
rhodiacyclic products [8b]. This modified mechanism is
shown in Scheme 1. Briefly, it starts with replacement
of ligated tosylate with pyridine, and then dissociation
of one stibine and tautomerization of h1-propargyl to
h1-allenyl (overall 3, 6 to III). This is followed by
migration of C(Ph)ꢁCꢁCH2 ligand of III to CO to yield
IV, which undergoes coordination of the allenyl CbꢁCg
to rhodium with formation of V. Addition of tosylate
to ligated CꢁC of V completes the cycloaddition
process.
A couple of comments are warranted. First, the
rhodium(III) h1-propargyl complexes that react cleanly
with pyridine to afford rhodiacyclic products are those
that contain coordinated tosylate. In contrast, com-
plexes 4 and 5, each without ligated tosylate, gave
mixtures of uncharacterized rhodium products when
treated with pyridine under similar conditions. Higher
molar conductivity values of the tosylato rhodium com-
plexes compared to the analogous halogeno rhodium
complexes [8] suggest that tosylate may promote cy-
cloaddition by undergoing more extensive dissociation
in CH2Cl2 solution. Second, the mechanism proposed
in Scheme 1 requires rearrangement of CH2CꢀCPh to
C(Ph)ꢁCꢁCH2, which is generally thought to proceed
via an h3-allenyl/propargyl intermediate (II in Scheme
1) [4,7a]. Interestingly, such a short-lived cationic inter-
mediate would appear to be identical in composition
with the isolable products of likely formula
(4)
The presence of a h3-CH2CCPh ligand in 11a is
evidenced by the appearance of a H NMR signal at l
1
4.43 and of 13C{1H} NMR signals at l 101.25 (CPh),
87.92 (CH2C) and 80.70 (CH2), all with no discernible
coupling to 103Rh. With the exception of the CH2
resonance, which occurs at a lower field than that
observed for various metal h3-allenyl/propargyl com-
plexes, these resonances are in line with the proposed
ligand formulation [31,32]. The 13C{1H} NMR spec-
trum also shows a signal at l 183.37 as a doublet with
1JRhC=63.73 Hz, which is assigned to a CO ligand. A
strong IR w(CO) absorption at 2068 cm−1 confirms the
presence of CO. The corresponding spectroscopic prop-
erties of 11b are very similar to those of 11a. The ionic
nature of 11a and 11b is indicated by their molar
[Rh(SbPh3)2(CO)Cl(h3-CH2CCPh)]+(OTf or BF4−
)
(11a and 11b), considered in the next section. However,
it should be noted that the proposed intermediate II,
unlike 11a and 11b, is present in the chemical environ-
ment of free SbPh3, pyridine and tosylate, which allows
it to react further eventually to yield 8 or 9.
conductivity values of 21.55 and 21.70 V−1 cm2 mol−1
,
respectively, in CH2Cl2 solution, which are normal for
1:1 electrolytes [19,20]. The FAB mass spectra agree
with the formulation of the cationic complex; unfortu-
nately, satisfactory chemical analyses could not be ob-
tained. Attempts to grow crystals suitable for X-ray
diffraction analysis proved unsuccessful. Therefore, the
proposed structure of 11 is to be considered somewhat
tentative at this time.
3.3. Rhodium(III) p3-allenyl/propargyl complexes
Addition of AgOTf and then an excess of
PhCꢀCCH2Br to a CH2Cl2 solution of 1 at room
temperature affords after work-up a red solid, which
appears to be [Rh(SbPh3)2(CO)Cl(h3-CH2CCPh)]OTf
1
(11a) on the basis of its IR and H and 13C{1H} NMR
Acknowledgements
spectra, molar conductivity in solution and FAB mass
spectrum (Eq. (4)). The pale yellow precipitate formed
in the course of this reaction was characterized as
AgBr. The corresponding BF4− salt of the rhodium
complex (11b) was obtained by use of AgBF4 in place
of AgOTf. The isolated cationic complex may be
analogous to the h3-allyls [Rh(SbPh3)2(CO)X(h3-
CH2CHCH2)]+ prepared by treatment of Rh(SbPh3)2-
(CO)Cl first with CH2ꢁCHCH2X (X=Cl, Br) and then
with AgClO4 or of Rh(SbPh3)2(CO)Cl(X)(h1-CH2CHꢁ
CH2) (X=Br) with AgClO4 [25]. In our study, use of
This study was supported in part by the National
Science Foundation and The Ohio State University.
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