Thermal reactivity of Group 9 transition metal pinacolate complexes: Heterocumulene cleavage and C-O bond formation

Article abstract of DOI:10.1016/S0020-1693(02)01234-3

The reactions of Group 9 transition metal pinacolate complexes Cp*M(pin) (M=Co (1), Rh (2), Ir (3)) with heterocumulenes (Y=C=Z) are described. In these transformations the C=Z bond of the heterocumulene is cleaved, and the pinacolate ligand is incorporated into an organic heterocycle (pin)C=Y. In some cases a clean organometallic product of the general formula Cp*MZ₂C=Y is also produced. The regiochemistry of these reactions has been explored and found to follow expected trends, and evidence suggests a mechanism involving initial heterocumulene insertion into an M-O bond yielding a 7-membered metallacycle, followed by 1,2 elimination.

Full text of DOI:10.1016/S0020-1693(02)01234-3

Inorganica Chimica Acta 341 (2002) 99ꢁ106
/
www.elsevier.com/locate/ica
Thermal reactivity of Group 9 transition metal pinacolate complexes:
heterocumulene cleavage and CÃO bond formation
/
Andrew W. Holland, Robert G. Bergman *
Department of Chemistry and Center for New Directions in Organic Synthesis, University of California, Berkeley, CA 94720, USA
Received 6 May 2002; accepted 13 August 2002
Dedicated to Professor Ken Raymond on the occasion of his 60th birthday, in recognition of his outstanding contributions to inorganic chemistry,
and in honor of our many years as friends and colleagues
Abstract
The reactions of Group 9 transition metal pinacolate complexes Cp*M(pin) (Mꢀ
(YÄCÄZ) are described. In these transformations the CÄZ bond of the heterocumulene is cleaved, and the pinacolate ligand is
incorporated into an organic heterocycle (pin)CÄY. In some cases a clean organometallic product of the general formula
Cp*MZ2CÄY is also produced. The regiochemistry of these reactions has been explored and found to follow expected trends, and
O bond yielding a 7-membered metallacycle,
/Co (1), Rh (2), Ir (3)) with heterocumulenes
/
/
/
/
/
evidence suggests a mechanism involving initial heterocumulene insertion into an MÃ
/
followed by 1,2 elimination.
# 2002 Elsevier Science B.V. All rights reserved.
Keywords: Metal glycolate; Alkoxide complexes; Rhodium; Iridium; Heterocumulene; Insertion reactions
1. Introduction
we recently prepared a series of Group 9 pinacolate
complexes and found that their photolysis results in the
oxidative cleavage of the central CÃC bond of the
pinacolate to produce acetone [18].
Because of their relevance to both biological and
/
synthetic catalytic systems [1ꢁ
/
5], organometallic com-
pounds containing late metalꢁoxygen bonds have been
/
The nucleophilic potential of glycolate ligands bound
to late metals has been overlooked as well. The
nucleophilicity of related mono-alkoxide groups is well
documented [1,6], and the potential availability of two
such moieties at one metal center may be expected to
yield novel reactivity. Additionally, alkoxides stabilize
coordinatively unsaturated metal centers via p-donation
[19], so glycolate ligands may support unusually reactive
metal centers. We report here that studies of the
reactions of the coordinatively unsaturated pinacolate
studied increasingly in recent years [1,6,7]. Advances in
their syntheses have allowed for thorough investigations
of many late metal-alkoxo and -aryloxo species, but this
realm of study has only very rarely been extended to
include chelating bis-alkoxo complexes [8]. This omis-
sion is surprising, given the diverse reactivity and
synthetic relevance of those metal glycolate complexes
that have been prepared. These complexes frequently
exhibit rich electrocyclic chemistry, and such reactions
have been exploited to catalyze a variety of important
complexes Cp*M(pin) (MꢀCo (1), Rh (2), Ir (3)) with
/
synthetic transformations [9ꢁ/17]. To further explore the
heterocumulenes have allowed us to realize both these
possibilities. In these transformations the pinacolate
ligand is lost as part of an organic heterocycle, the
heterocumulene is cleaved, and a reactive organometal-
lic fragment is generated.
participation of late-metal glycolates in such reactions,
* Corresponding author. Fax: ꢂ
/
1-510-642 7714
E-mail address: bergman@cchem.berkeley.edu (R.G. Bergman).
0020-1693/02/$ - see front matter # 2002 Elsevier Science B.V. All rights reserved.
PII: S 0 0 2 0 - 1 6 9 3 ( 0 2 ) 0 1 2 3 4 - 3

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A.W. Holland, R.G. Bergman / Inorganica Chimica Acta 341 (2002) 99ꢁ106
/
2. Results
All three pinacolate complexes react with CS2 to yield
thiocarbonate 9 and apparent organometallic trithiocar-
In the course of attempting to prepare stable adducts
bonates 10ꢁ12 in high yield (Eq. (4)). These inorganic
/
of complexes 1ꢁ
/
3, we found that cobalt complex 1 and
products feature broad NMR spectra, but their infrared
spectra, mass spectra, and elemental analyses are con-
rhodium complex 2 react with CO rapidly on mixing to
form the organic cyclic carbonate 4 and dicarbonyl
complexes 5 and 6 (Eq. (1)). This observation led us to
explore the reactions of the pinacolate complexes with a
sistent with formulations 10ꢁ12. We presume the
/
broadness in the NMR spectra of these compounds is
a consequence of reversible oligomerization through
additional Mꢁ
/
S contacts, but due to the insolubility of
variety of MÃ
/
O insertion candidates, and we observed
clean reactivity with several heterocumulenes at room
complexes 10ꢁ
/
12 at low temperature we were unable to
slow this apparent fluctionality and observe meaningful
NMR data. Treatment of these products with PMe3
temperature.
yields the corresponding adducts 13ꢁ15 (Eq. (5)) which
/
exhibit all the expected spectroscopic features including
sharp NMR spectra.
ð1Þ
As we have since reported elsewhere [20], treatment of
iridium complex 3 with 2 equiv. of carbodiimide for 2
days at 22 8C yields cyclic carbamate complex 7 and
organometallic guanidinate 8 (Eq. (2)). In these two
products, 1 equiv. of the carbodiimide has been cleaved
ð4Þ
across the CÄ
/
N double bond and its fragments CÄ
/NTol
and NTol incorporated into the organic and organome-
tallic products, respectively. A second equivalent of
carbodiimide is consumed to generate the organometal-
lic product. While the reactions of pinacolate complexes
1 and 2 with carbodiimides do not yield clean organo-
metallic products, they do afford organic product 7 (Eq.
(3), Table 1).
ð5Þ
Treatment of any of the three pinacolate complexes
1ꢁ3 with TolNCO affords the cyclic carbonate 6 as the
/
lone organic product. The reaction of the iridium
starting material 3 yields a ureylene complex 16 (Eq.
(6)) in addition to the organic carbonate. When a
catalytic amount of rhodium pinacolate 2 was treated
with tolyl isocyanate in the presence of pinacol, catalytic
condensation of these substrates to acyclic mono-
carbamate 17 was observed (Eq. (7)). This reaction
ð2Þ
ð3Þ
ð6Þ
Table 1
Regiochemical selectivity and NMR yields
Entry Reagent
Y
Z
Organic product
NMR yield from 1
NMR yield from 2
NMR yield from 3
1
2
3
4
5
6
7
8
CO
SÄCÄS
6
9
95
95
90
95
25
95
95
95
95
90
95
85
95
85
10
95
90
65
95
85
65
S
S
S
S
OÄCÄS
O
NAr
6
ArNÄCÄS
ArNÄCÄNAr
OÄCÄNAr
R2CÄCÄO
OÄCÄO
7
NAr NAr
7
O
R2C
NAr
O
6
20
No reaction
ꢁ/
ꢁ/
ꢁ/

A.W. Holland, R.G. Bergman / Inorganica Chimica Acta 341 (2002) 99ꢁ
/106
101
does not proceed at a significant rate at room tempera-
ture without a catalyst.
of the starting material begins to occur at elevated
temperatures.
ð7Þ
ð9Þ
Tolyl isothiocyanate reacts with both the cobalt and
rhodium complexes 1 and 2 to afford the cyclic
carbamate 7 in high yields, but neither of these reactions
produces a clean organometallic product (Eq. (8)). The
reactions of the isothiocyanate with iridium complex 3
afford very different results (Scheme 1). When the
reagents are combined at relatively high concentrations
(0.014 M in 3), a single new product 18 with a 1H NMR
spectrum featuring one Cp* signal and six non-Cp*
ð10Þ
methyl resonances (d 0.9ꢁ2.2 ppm) is formed. The
/
number and inequivalency of these methyl groups
suggest the structure shown at the top of Scheme 1, in
which one molecule of isothiocyanate has been inserted
3. Discussion
into an IrÃ
/
O bond, and another has occupied the open
Given the formally vacant site at the metal center, we
presume that the reaction of 1 and 2 with carbon
monoxide proceeds by initial coordination of CO
site at the iridium center. The mass spectrum and
elemental analysis of this product are also consistent
with this assignment. Neither thermolysis nor photolysis
of complex 18 effects its further conversion to any
tractable products. When the same reaction is conducted
under more dilute conditions (0.013 M), cyclic carba-
mate 7 and iridium dithiocarbamate 19 are produced.
(yielding 21), followed by its insertion into the MÃ
/O
bond to yield an intermediate 6-membered metallacycle
22 (Scheme 2). Subsequent reductive elimination in this
species (or perhaps its CO adduct) and trapping of the
resulting fragment by CO would yield the observed
dicarbonyl complex. This general mechanism has pre-
cedent among the reactions of other bis-alkoxides with
CO [21,22], although in these reported reactions some
oxalate product resulting from double CO insertion was
observed. The greater selectivity in this system could be
a consequence of the cyclic geometry of intermediate 22,
which may facilitate reductive elimination or disfavor a
second CO insertion.
ð8Þ
All three complexes 1ꢁ3 react with carbonylsulfide to
/
give cyclic carbonate 4 in high yield (Eq. (9)), and with
trimethylsilyl ketene to afford the alkene 20 in moderate
yield (Eq. (10)), but multiple organometallic products
are formed in each of these reactions. None of the
pinacolates react with 1 atm CO2 before decomposition
The CO result led us to explore reactions involving
other insertion-prone molecules, and we found that
many heterocumulenes exhibit related reactivity. In all
of these reactions (Eq. (11)) we observed cleavage of a
CÄ
/
Z double bond, and incorporation of the remaining
CÄ
/
Y fragment into an organic heterocycle containing
Scheme 2. Proposed mechanism of reactions between pinacolates and
CO.
Scheme 1. Reactions of isothiocyanate with iridium pinacolate 3.

102
A.W. Holland, R.G. Bergman / Inorganica Chimica Acta 341 (2002) 99ꢁ106
/
the pinacolate ligand. In some cases, both the Z
fragment and a second equivalent of heterocumulene
are incorporated into a clean organometallic product as
well. By analogy to the CO reaction described above, we
propose (Scheme 3) that these reactions proceed by
initial substrate coordination to the open site of the
metal center (yielding 23), and subsequent heterocumu-
unimolecular elimination reaction within intermediate
24 proceeds more quickly than trapping, resulting in
products 7 and 19. While we have been unable to
observe the heterocumulene adducts 23 or the insertion
products 24 directly at room temperature or below, the
observation of complex 18 under appropriate conditions
argues for the viability of both these classes of com-
plexes.
lene insertion to yield 7-membered metallacycle 24. A 1ꢁ
/
2 elimination within this cycle would produce the
observed heterocycle, leaving behind a metal sulfido,
imido, or oxo intermediate (25). This highly reactive
species could then potentially undergo a cycloaddition
reaction with a second equivalent of heterocumulene to
yield an organometallic product. Clearly the last step of
this mechanism does not proceed smoothly in the many
cases where no clean inorganic product is observed.
Such cycloadditions are well known for monomeric
metal imido complexes, including late metal imido
complexes very similar to the intermediates proposed
here [23,24]. Reaction of these intermediates with
additional heterocumulene is apparently faster than
dimerization; imido-dimer 26 is not observed in these
reactions, and does not react with carbodiimide below
75 8C (Eq. (12)).
The formation of acyclic carbamate 17 upon the
addition of pinacol to pinacolate 2 and TolNCO also
provides indirect evidence for the intermediacy of
metallacycles 24. While we intended for the pinacol to
react with transient imido complex 25 to liberate amine
and pinacolate 2, it appears that the diol instead reacts
with intermediate 24 to produce carbamate 17 and
regenerate pinacolate 2 before elimination of 6 occurs
(Scheme 4). Pinacol does not react directly with
isocyanates at room temperature, and the lack of
dicarbamate Me4C2(OCONTolH)2 even at long reaction
times (with excess TolNCO) implies that protonolysis of
species 24, rather than some more general Lewis acid or
base catalyzed condensation, is the operative process
here.
Treatment of a pinacolate complex with an unsym-
metrical heterocumulene (YÄ
/
CÄ
/
Z where Y"
/
Z) offers
Y or CÄ
two possible regiochemical outcomes; either CÄ
/
/
ð11Þ
Z can be incorporated into the organic product, and
either Z or Y can be incorporated into the resulting
organometallic species. In all cases, we observed ex-
cellent regiochemical selectivity in this respect (Table 1).
In general, we observed an order of preference Sꢀ
NArꢀO for the incorporation of a given group Z
into the organometallic product, and correspondingly
/
ð12Þ
/
the opposite order of preference for incorporation of CÄ
/
The insertion step of this mechanism is lent some
credence by the observation of product 18 in the
reaction of iridium pinacolate 3 with TolNCS at high
concentrations (Scheme 1). In this transformation it
appears that the 7-membered metallacycle resulting
Y into the organic product.
This selectivity is likely a result of two complimentary
trends. Of the groups in question, sulfur generally forms
the strongest bonds to late metals [25], and NR groups
bind more tightly to electron-deficient late metal centers
than does oxygen [25]. Additionally, the selectivity
from insertion (24, Zꢀ
/
S, YꢀNTol) is trapped by a
/
second equivalent of TolNCS before the elimination
step occurs. Notably, at lower concentrations the
observed preserves the stronger p bond present: CÄ
/
Scheme 3. Proposed mechanism of reactions between pinacolates and
heterocumulenes.
Scheme 4. Proposed mechanism of condensation catalyzed by rho-
dium pinacolate 2.

A.W. Holland, R.G. Bergman / Inorganica Chimica Acta 341 (2002) 99ꢁ
/106
103
5. Experimental
5.1. Methods and materials
General experimental information has been reported
elsewhere [29,30]. All NMR spectra were obtained at
room temperature using a Bruker AMX-400 MHz
spectrometer. All degassing was achieved by two free-
Fig. 1. Intermediates 23 and 24 (see Table 1) both form and preserve
stronger bonds than those in isomers 23? and 24?.
zeꢁ
/
pumpꢁthaw cycles, and unless otherwise noted
/
Oꢀ
/
CÄ
/
Nꢀ
/
CÄ
/
S [26ꢁ28]. Both of these considerations
/
solids were collected by filtration. Unless otherwise
noted, reagents were purchased from commercial sup-
pliers and used without further purification. Solvent
purification techniques have been reported elsewhere
[29,31]. Celite (Aldrich) was dried in vacuo at 250 8C for
48 h. Trimethylphosphine (Aldrich) was vacuum-trans-
ferred from sodium metal and p-tolyl isocyanate (Al-
drich) was filtered through Celite prior to use. Carbon
should affect the relative stabilities of adducts 23 and 23?
(Fig. 1), as well as those of possible insertion products
24 and 24?, and we presume that it is in the formation of
these intermediates that the regiochemical outcome of
the reaction is determined. The cycloaddition of hetero-
cumulene to intermediate 25 also appears to proceed
selectively in the formation of ureylene 16 and dithio-
carbamate 19 (we have observed similar regiochemistry
in related systems [20]); this selectivity can be explained
by precisely the same thermodynamic trends.
˚
disulfide was distilled from 4 A molecular sieves and di-
p-tolyl carbodiimide (Aldrich) was recrystallized from
pentane. Cp*Co(pin) (1), Cp*Rh(pin) (2), and
Cp*Ir(pin) (3) were prepared according to literature
procedures [18]. All reaction mixtures containing 1 or 2
were protected from ambient light whenever possible.
Interestingly, CO2 did not react with pinacolates 1ꢁ
In following with the arguments above, we attribute this
primarily to the less favorable tradeoff between a CÄO p
bond in CO2 and an MÃO s-bond in the intermediate
/3.
/
/
24 that would result from its insertion. Additionally, this
reaction would be disfavored by the presumed relative
instability of the metal-oxo intermediate 25 that would
result from elimination of carbonate 4. Monomeric oxo
complexes of the Group 9 metals are not known and
rarely postulated. In an attempt to generate an oxo
5.2. General procedure for NMR-scale reactions of
Cp*M(pin) (1ꢁ3) with heterocumulenes
/
In a typical experiment, pinacolate 3 (8.8 mg, 20 mol)
was dissolved in C6D6 (250 mL), and internal standard
1,3,5-trimethoxybenzene (1.7 mg, 10 mmol) was added.
The resulting solution was loaded into an NMR tube
which was then capped with a septum, and an initial 1H
NMR spectrum was acquired to calibrate the quantity
of starting material with respect to the internal standard.
Di-p-tolyl carbodiimide (8.8 mg, 40 mmol) was then
added to the tube as a solid and the tube walls were
rinsed with C6D6 (50 ml). (Trimethylsilylketene, p-tolyl
isocyanate and carbon disulfide were added by syringe,
and CO and OCS were added by vacuum transfer using
a known volume bulb.) The tube was then flame-sealed
under vacuum, shaken, and allowed to stand for 2 days
at room temperature. The yield was then measured by
1H NMR integration of product (6: d 0.72; 7: 0.90, 0.83;
9: 0.67; 20: 0.91, 0.30 ppm.) versus internal standard (d
3.30 ppm). In all cases, only one of the possible organic
products was observed. Yields of these products are
reported in Table 1.
complex we treated complexes 1ꢁ3 with a bulky ketene
/
and observed incorporation of its C2 moiety into the
organic product (Eq. (10)). This suggests that the oxo
complexes may be formed, although they do not yield
clean products. Attempts to trap the transient oxo using
CO2 or TolNCNTol were similarly unsuccessful, and
use of other traps was complicated by the reactivity of
the starting materials.
4. Conclusion
In summary, we have observed a general reaction of
heterocumulenes with a series of Group 9 metal
pinacolate complexes in which the heterocumulene is
cleaved and a heterocycle is produced. Additionally, the
ultimate organometallic products of the reaction appear
to result from the transient formation of highly reactive
monomeric late metal sulfido and imido complexes.
These results highlight both the remarkable degree of
reactivity possible in coordinatively unsaturated late
metal bis-alkoxide complexes, and their potential utility
in delivering two preorganized alkoxide groups to a
single substrate.
5.3. Reaction of Cp*Co(pin) (1) with CO
Pinacolate 1 (174 mg, 0.561 mmol) was dissolved in
C6H6 (10 ml) and both the solution and a stirbar were
loaded into a 200-ml glass vessel equipped with a Teflon
stopcock. The solution was degassed on a vacuum line,
the vessel was charged with CO (724 torr) and sealed,
and the mixture was stirred at room temperature for 10

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A.W. Holland, R.G. Bergman / Inorganica Chimica Acta 341 (2002) 99ꢁ106
/
h. A color change first to green, then to orange resulted.
The solution was degassed, and the remaining volatile
materials were vacuum transferred at 45 8C to a new
vessel. This left behind 6 (78 mg, 98%) as a white solid,
and yielded an orange solution. The solvent was then
removed in vacuo at 10 8C, yielding orange solid 4 (103
ArCH3), 1.93 (3H, s, ArCH3), 1.22 (15H, s, C5Me5)
ppm. These data match those we have previously
reported for this compound prepared by a different
procedure [20].
5.6. Cp*CoS2CS (10)
1
mg, 75%). 4: H NMR (400 MHz, CDCl3): d 1.60 ppm
(lit: d 1.61 [32]). IR (KBr, cmꢃ1): 2018 (s), 1966 (s) (lit:
2016, 1965 [32]). 6: 1H NMR (400 MHz, CDCl3): d 1.40
ppm (lit: d 1.41 [33]). IR (KBr, cmꢃ1): 1779 (s) (lit:
1779, nujol [33]).
Pinacolate 1 (110 mg, 0.355 mmol) was dissolved in
C6H6 (5 ml) in a vial, and CS2 (50 ml, 0.84 mmol) was
added by syringe. A gradual color change to brownꢁ
/
green was observed over 24 h. The solution was then
evaporated to dryness in vacuo and washed with cold
pentane (1 ml), yielding 10 (93 mg, 84%) as a brown
powder. No signals were observed in the NMR spectra
of this material. IR (KBr, cmꢃ1): 2959 (s), 2913 (s), 1457
5.4. Reaction of Cp*Rh(pin) (2) with CO
Pinacolate 2 (165 mg, 0.481 mmol) was dissolved in
C6H6 (10 ml) and both the solution and a stirbar were
loaded into a 200-ml glass vessel equipped with a Teflon
stopcock. The solution was degassed on the line, and the
vessel was charged with CO (736 torr), sealed, and
stirred at room temperature for 10 h. A color change
(m), 969 (s). MS (EI): m/zꢀ
302 (Mꢂ). Anal. Calc. for
C11H15CoS3: C, 43.69; H, 5.00. Found: C, 43.99; H,
5.22%.
/
5.7. Cp*RhS2CS (11)
first to blue, then to redꢁorange resulted. The solution
/
was degassed, and the remaining volatile materials were
vacuum transferred at 65 8C to a new vessel. This left
behind 6 (66 mg, 93%) as a white solid, and yielded an
orange solution. The solvent was then removed in vacuo
Pinacolate 2 (131 mg, 0.382 mmol) was dissolved in
C6H6 (5 ml) in a vial, and CS2 (50 ml, 0.84 mmol) was
added by syringe. A gradual color change to brown and
precipitation of brown solid was observed over 2 h. The
solution was evaporated to dryness in vacuo and washed
with cold pentane (5 ml), yielding 11 (113 mg, 86%) as a
at 10 8C, yielding redꢁorange solid 5 (115 mg, 84%). 5:
/
1H NMR (400 MHz, CDCl3): d 2.01 ppm (lit: 2.02 [32]).
IR (KBr, cmꢃ1): 2034 (s), 1968 (s) (lit: 2037, 1971 [32]).
redꢁbrown powder. No signals were observed in the
/
NMR spectra of this material. IR (KBr, cmꢃ1): 2560 (s),
2915 (s), 1457 (m), 1377 (m), 1019 (s), 983 (s). MS (EI):
5.5. Reaction of Cp*Ir(pin) (3) with di-p-tolyl
carbodiimide
m/zꢀ
346 (Mꢂ). Anal. Calc. for C11H15RhS3: C, 38.14;
H, 4.37. Found: C, 38.00; H, 4.01%.
/
Pinacolate 3 (222 mg, 0.500 mmol) and di-p-tolyl
carbodiimide (225 mg, 1.02 mmol) were dissolved in
pentane (35 ml), and the solution was allowed to stand
at room temperature for 72 h. At the end of this time the
color of the solution had changed from red to green, and
green crystals of guanidinate 8 (265 mg, 81%) had
formed. The supernatant was concentrated to 5 ml in
vacuo and filtered through Celite to yield a pale green
5.8. Reaction of Cp*Ir(pin) (3) with CS2
Pinacolate 3 (252 mg, 0.567 mmol) was dissolved in
C6H6 (5 ml) in a vial, and CS2 (70 ml, 1.2 mmol) was
added by syringe. A color change to orange was
observed over 24 h. The solution was evaporated to
dryness in vacuo and washed with cold pentane (1
solution. This was chilled to ꢃ
off-white crystals of cyclic carbamate 7 (59 mg, 51%). 7:
1H NMR (400 MHz, C6D6): d 7.28 (2H, d, Jꢀ
8.2 Hz,
Ar), 7.02 (2H, d, Jꢀ8.2 Hz, Ar), 2.12 (3H, s, ArCH3),
0.90 (6H, s, C(CH3)2), 0.83 (6H, s, C(CH3)2) ppm.
13C{1H} NMR (100 MHz, C6D6): d 151.8 (s, C Ä
N),
/
30 8C for 72 h, yielding
portion, 5 ml), leaving 12 (198 mg, 80%) as an orangeꢁ
brown powder. The wash was evaporated to dryness in
vacuo and recrystallized from ether (1 ml) at ꢃ30 8C
/
/
/
/
yielding 9 (51 mg, 56%) as white crystals. 12: No signals
were observed in the NMR spectra of this material. IR
(KBr, cmꢃ1): 2958 (s), 2913 (s) 1482 (m), 990 (m). MS
/
145.1 (s, Ar), 132.3 (s, Ar), 128.9 (s, Ar), 124.2 (s, Ar),
84.7 (s, C(CH3)2), 84.3 (s, C(CH3)2), 22.2 (s, C(CH3)2),
22.1 (s, C(CH3)2), 21.3 (s, ArCH3) ppm. IR (KBr,
cmꢃ1): 2983 (s), 2920 (w), 1705 (s), 1613 (w), 1510 (m),
1293 (m), 1139 (m), 1012 (m), 994 (m), 821 (m). MS (EI):
(EI): m/zꢀ
/
436 (Mꢂ). Anal. Calc. for C11H15IrS3: C,
1
30.32; H, 3.47. Found: C, 30.25; H, 3.41%. 9: H NMR
(400 MHz, CDCl3): d 1.49 ppm (lit: d 1.50 [34]). M.p.:
154ꢁ155 8C (lit: 156 8C [34]).
/
m/zꢀ
/
233 (Mꢂ). M.p. 81ꢁ
/
83 8C. Anal. Calc. for
5.9. Cp*(PMe3)CoS2CS (13)
C14H19NO2: C, 72.07; H, 8.21; N, 6.00. Found: C,
71.85; H, 8.04; N, 5.76%. 8: 1H NMR (400 MHz, C6D6):
Complex 10 (87 mg, 0.29 mmol) was dissolved in
toluene (10 ml) and the solution and a stirbar were
loaded into a 50-ml glass vessel equipped with a Teflon
d 7.40 (2H, br, Ar), 7.01 (4H, d, Jꢀ
/
7.2 Hz, Ar), 7.00
(2H, br, Ar), 6.72 (4H, d, Jꢀ7.2 Hz, Ar), 2.17 (6H, s,
/

A.W. Holland, R.G. Bergman / Inorganica Chimica Acta 341 (2002) 99ꢁ
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105
stopcock. The solution was degassed and PMe3 (17
torrꢄ500 ml, 0.46 mmol) was added by vacuum
transfer using a known-volume-bulb. The sample was
then stirred for 16 h at room temperature, and the
resulting orange solution was concentrated to 2 ml in
vacuo. This was layered with pentane (5 ml), and left at
C5Me5), 14.9 (d, Jꢀ
IR (KBr, cmꢃ1): 2957 (s), 2914 (s) 1475 (m), 985 (m).
MS (EI): m/zꢀ PMe3). Anal. Calc.
512 (Mꢂ), 436 (Mꢃ
for C14H24IrPS3: C, 32.85; H, 4.73. Found: C, 32.61; H,
4.65%.
/
39 Hz, PMe3), 9.5 (s, C5Me5) ppm.
/
/
/
ꢃ
/
30 8C for 24 h. Orange crystals of 13 (79 mg, 73%
5.12. Cp*Ir((NTol)2CO) (16)
1
yield) were then collected. H NMR (400 MHz, C6D6):
d 1.14 (15H, d, Jꢀ
/
1.2 Hz, C5Me5), 0.93 (9H, d, Jꢀ
/
9.8
Hz, PMe3) ppm. 31P{1H} NMR (162 MHz, C6D6): d
12.38 ppm. 13C{1H} NMR (100 MHz, C6D6): d 94.2 (s,
Pinacolate 3 (227 mg, 0.510 mmol) and p-tolyl
isocyanate (135 mg, 1.02 mmol) were dissolved in
pentane (30 ml), and the solution was allowed to stand
at room temperature for 72 h. At the end of this time the
color of the solution had changed from red to green, and
green crystals of ureylene 16 (248 mg, 86%) had formed.
C5Me5), 90.1, 15.1 (d, Jꢀ
ppm. IR (KBr, cmꢃ1): 2960 (s), 2914 (s), 1471 (m), 975
(s). MS (EI): m/zꢀ PMe3). Anal.
378 (Mꢂ), 302 (Mꢃ
Calc. for C14H24CoPS3: C, 44.43; H, 6.79. Found: C,
44.24; H, 6.50%.
/
31 Hz, PMe3), 9.8 (s, C5Me5)
/
/
16: 1H NMR (400 MHz, CD2Cl2): d 7.11 (4H, d, Jꢀ
Hz, Ar), 1.05 (4H, d, Jꢀ8.0 Hz, Ar), 2.32 (6H, s,
/8.0
/
ArCH3), 1.81 (15H, s, C5(CH3)5) ppm. These data
match those we have previously reported for this
compound prepared by a different procedure [20].
5.10. Cp*(PMe3)RhS2CS (14)
Complex 11 (105 mg, 0.303 mmol) was dissolved in
toluene (10 ml) and the solution and a stirbar were
loaded into a 50-ml glass vessel equipped with a Teflon
stopcock. The solution was degassed and PMe3 (18
5.13. C(OH)(CH3)2C(CH3)2OCONHTol (17)
Pinacol (249 mg, 2.11 mmol) and p-tolyl isocyanate
(293 mg, 2.20 mmol) were combined in pentane (20 ml),
pinacolate 2 (14 mg, 0.040 mmol) was added, and the
resulting orange solution was left at room temperature
for 24 h. At the end of this time, pale yellow crystals of
torrꢄ500 ml, 0.49 mmol) was added by vacuum
/
transfer using a known-volume-bulb. The sample was
then stirred for 16 h at room temperature, and the
resulting orange solution was concentrated to 2 ml in
vacuo. This was layered with pentane (5 ml), and left at
1
carbamate 17 (462 mg, 87%) were collected. H NMR
ꢃ
/
30 8C for 24 h. Yellowꢁ
65% yield) were then collected. H NMR (400 MHz,
C6D6): d 1.32 (15H, d, Jꢀ3.0 Hz, C5Me5), 0.97 (9H, d,
Jꢀ
9.5 Hz, PMe3) ppm. 31P{1H} NMR (162 MHz,
C6D6): d 2.3 (d, Jꢀ
149 Hz) ppm. 13C{1H} NMR (100
MHz, C6D6): d 99.3 (d, JRhÃC 8.8 Hz, C5Me5), 77.8,
15.3 (d, Jꢀ32 Hz, PMe3), 9.8 (s, C5Me5) ppm. IR (KBr,
cmꢃ1): 2561 (s), 2916 (s), 1459 (m), 1373 (m), 1019 (s).
MS (EI): m/zꢀ PMe3). Anal. Calc.
422 (Mꢂ), 346 (Mꢃ
/
orange crystals of 14 (84 mg,
(400 MHz, C6D6): d 7.15 (2H, br, Ar), 6.88 (2H, d, Jꢀ
/
1
8.1 Hz, Ar), 6.02 (1H, s, NH), 4.28 (1H, s, OH), 2.03
(3H, s, ArCH3), 1.43 (6H, s, C(CH3)2), 1.17 (6H, s,
C(CH3)2) ppm. 13C{1H} NMR (100 MHz, C6D6): d
/
/
/
154.3 (s, C Ä
/
N), 136.1 (s, Ar), 132.5 (s, Ar), 129.4 (s, Ar),
ꢀ
/
119.2 (s, Ar), 88.6 (s, C(CH3)2), 74.9 (s, C(CH3)2), 25.3
(s, C(CH3)2), 22.2 (s, C(CH3)2), 20.4 (s, ArCH3) ppm.
IR (KBr, cmꢃ1): 3292 (s), 3253 (s), 2992 (s), 1688 (s),
1604 (m), 1542 (s), 1516 (m), 1406 (m), 1318 (m), 1261
/
/
/
for C14H24PRhS3: C, 39.80; H, 5.73. Found: C, 39.72;
H, 5.65%.
(s), 1158 (s), 1108 (m), 1055 (s), 816 (m). MS (EI): m/zꢀ
/
251 (Mꢂ). Anal. Calc. for C14H21NO3: C, 66.90; H,
8.42; N, 5.58. Found: C, 66.86; H, 8.38; N, 5.43%.
5.11. Cp*(PMe3)IrS2CS (15)
5.14. Cp*(TolNCS)Ir(O(C(CMe2)2OC(NTol)S)
(18)
Complex 12 (185 mg, 0.424 mmol) was dissolved in
toluene (10 ml) and the solution and a stirbar were
loaded into a 50-ml glass vessel equipped with a Teflon
stopcock. The solution was degassed and PMe3 (18
Pinacolate 3 (121 mg, 0.273 mmol) was and p-
tolylisothiocyanate (89 mg, 0.60 mmol) were dissolved
in toluene (2 ml) and the resulting red solution was left
at room temperature for 24 h. Over the course of this
torrꢄ500 ml, 0.49 mmol) was added by vacuum
/
transfer using a known-volume-bulb. The sample was
then stirred for 16 h at room temperature, and the
resulting orange solution was concentrated to 3 ml in
vacuo. This was layered with pentane (10 ml), and left at
1
time, orange crystals of 18 (130 mg, 64%) formed. H
NMR (400 MHz, C6D6): d 7.50 (2H, d, Jꢀ
7.37 (2H, d, Jꢀ8.3 Hz, Ar), 7.22 (d, 2H, Jꢀ
Ar), 7.06 (2H, d, Jꢀ8.2 Hz, Ar), 2.23 (3H, s, ArCH3),
/
8.2 Hz, Ar),
/
/8.3 Hz,
ꢃ
/
30 8C for 24 h. Yellow crystals of 15 (184 mg, 80%)
/
1
were then collected. H NMR (400 MHz, C6D6): d 1.34
(15H, d, Jꢀ2.0 Hz, C5Me5), 1.08 (9H, d, Jꢀ10.3 Hz,
PMe3) ppm. 31P{1H} NMR (162 MHz, C6D6): d ꢃ
33.9
ppm. 13C{1H} NMR (100 MHz, C6D6): d 94.0 (s,
2.12 (3H, s, ArCH3), 1.96 (3H, s, OC(CH3)), 1.43 (3H, s,
OC(CH3)), 1.27 (15H, s, C5Me5), 1.12 (3H, s, OC(CH3)),
0.89 (3H, s, OC(CH3)) ppm. 13C{1H} NMR (100 MHz,
/
/
/
THF-d8): d 183.4 (OÃ
/
C(SIr)Ä
/
N), 167.1 (IrÃ
/
NÄ
/
C Ä
/S),

106
A.W. Holland, R.G. Bergman / Inorganica Chimica Acta 341 (2002) 99ꢁ106
/
148.7 (s, Ar), 141.9 (s, Ar), 134.6 (s, Ar), 130.2 (s, Ar),
129.5 (s, Ar), 129.2 (s, Ar), 125.6 (s, Ar), 122.9 (s, Ar),
95.0 (OC(CH3)2), 87.3 (s, C5Me5), 86.4 (OC(CH3)2),
25.3 (s, ArCH3), 25.0 (s, ArCH3), 23.6 (OC(CH3)), 21.2
(OC(CH3)), 21.1 (OC(CH3)), 18.1 (OC(CH3)), 8.6 (s,
C5Me5) ppm. IR (CD2Cl2, cmꢃ1): 2986 (m), 2920 (s),
2194 (m), 1557 (s), 1501 (s), 1382 (w), 1030 (w), 897 (m),
Acknowledgements
We thank the NSF (Grant # CHE-0094349) for
funding this work.
References
818 (w). MS (EI): m/zꢀ
742 (Mꢂ). Anal. Calc. for
C32H41IrN2O2S2: C, 51.80; H, 5.57; N, 3.78. Found: C,
/
[1] H.E. Bryndza, W. Tam, Chem. Rev. 88 (1988) 1163.
[2] C. Masters, Homogeneous Transition Metal Catalysis, Chapman
and Hall, New York, 1981.
51.72; H, 5.56; N, 3.76%.
[3] D.T. Sawyer, Oxygen Chemistry, Oxford University Press, New
York, 1991.
[4] R.A. Sheldon, J.K. Kochi, Metal Catalyzed Oxidation of Organic
Compounds, Academic Press, New York, 1981.
[5] L.I. Simandi, Catalytic Activation of Dioxygen by Metal Com-
plexes, Kluwer, Dordrecht, 1992.
5.15. Cp*Ir(S2C(NTol)) (19)
Pinacolate 3 (118 mg, 0.266 mmol) and p-tolyl
isothiocyanate (85 mg, 0.570 mmol) were dissolved in
pentane (20 ml) and the resulting red solution was left at
[6] J.R. Fulton, A.W. Holland, D.J. Fox, R.G. Bergman, Acc. Chem.
Res. 35 (2002) 44.
[7] R.G. Bergman, Polyhedron 14 (1995) 3227.
[8] M.A. Andrews, G.L. Gould, Organometallics 10 (1991) 387.
[9] D.P. Steinhuebel, S.J. Lippard, J. Am. Chem. Soc. 121(1999)11762.
[10] J.E. McMurry, Chem. Rev. 89 (1989) 1513.
[11] R.R. Schrock, S.F. Pedersen, M.R. Churchill, J.W. Ziller,
Organometallics 3 (1984) 1574.
room temperature for 48 h. Over the course of this time,
1
yellowꢁ
NMR (400 MHz, C6D6): d 8.12 (2H, d, Jꢀ
7.19 (2H, d, Jꢀ8.3 Hz, Ar), 2.17 (3H, s, ArCH3), 1.52
/orange crystals of 19 (142 mg, 72%) formed. H
/8.3 Hz, Ar),
/
(15H, s, C5Me5) ppm. 13C{1H} NMR (100 MHz, THF-
d8): d 148.2 (s, Ar), 135.7 (s, Ar), 129.6 (s, Ar), 126.3 (s,
Ar), 91.5 (s, C5Me5), 21.1 (s, Ar-CH3), 9.0 (s, C5Me5)
ppm. IR (KBr, cmꢃ1): 2957 (w), 2919 (w), 1601 (w),
1553 (s), 1499 (s), 1240 (s), 1030 (m), 897 (m), 836 (m).
[12] W.A. Herrmann, D. Marz, E. Herdtweck, A. Schafer, W.
Wagner, H.-J. Kneuper, Angew. Chem., Int. Ed. Eng. 26 (1987)
462.
[13] Z. Zhu, A.M. Al-Ajlouni, J.H. Espenson, Inorg. Chem. 35 (1996)
1408.
MS (EI): m/zꢀ
509 (Mꢂ). Anal. Calc. for C32H41Ir-
N2O2S2: C, 42.41; H, 4.56; N, 2.75. Found: C, 42.51; H,
4.56; N, 2.52%.
/
[14] K.P. Gable, E.C. Brown, Organometallics 19 (2000) 944.
[15] K.P. Gable, J.J.J. Juliette, J. Am. Chem. Soc. 118 (1996) 2625.
[16] G.K. Cook, M.A. Andrews, J. Am. Chem. Soc. 118 (1996) 9448.
[17] H.C. Kolb, M.S. VanNieuwenhze, K.B. Sharpless, Chem. Rev. 94
(1994) 2483.
[18] A.W. Holland, D.S. Glueck, R.G. Bergman, Organometallics 20
(2001) 2250.
[19] K.G. Caulton, New J. Chem. 18 (1994) 25.
[20] A.W. Holland, R.G. Bergman, J. Am. Chem. Soc. 124 (2002)
9010.
5.16. C2(CH3)4)O2CCH(SiMe3) (20)
Pinacolate 2 (157 mg, 0.458 mmol) was dissolved in
pentane (10 ml) and trimethylsilylketene (118 mg, 1.10
mmol) was added. The solution turned brown immedi-
[21] H.E. Bryndza, Organometallics 4 (1985) 1686.
[22] G. Fachinetti, T. Funaioli, D. Masi, C.J. Mealli, Organomet.
Chem. 417 (1992) C32.
[23] D.S. Glueck, J. Wu, F.J. Hollander, R.G. Bergman, J. Am. Chem.
Soc. 113 (1991) 2041.
ately, and was then chilled to ꢃ30 8C for 16 h. Brown
solid precipitated during this time, and the brown
supernatant was filtered through Celite, concentrated
/
[24] A.A. Danopoulos, G. Wilkinson, T.K.N. Sweet, M.B. Hurst-
house, J. Chem. Soc., Dalton Trans. (1996) 3771.
[25] F.A. Cotton, G. Wilkinson, Advanced Inorganic Chemistry, 5th
ed., Wiley, New York, 1988.
to 2 ml in vacuo, and left at ꢃ30 8C for approximately 4
/
weeks. Brown solid precipitated during this time, and
the supernatant was again filtered through Celite. The
filtrate was evaporated to leave pale brown oil 20 (28
[26] T.H. Lowry, K.S. Richardson, Mechanism and Theory in Organic
Chemistry, 3rd ed., Harper Collins Publishers, New York, 1987.
[27] C.M. Hadad, P.R. Rablen, K.B. Wiberg, J. Org. Chem. 63 (1998)
8668.
1
mg, 29%) in vacuo. H NMR (400 MHz, C6D6): d 3.48
(1H, s, CÄ
(CH3)2), 0.30 (9H, s, CÄ
NMR (100 MHz, C6D6): d 84.4 (s, C(CH3)2), 83.5 (s,
C(CH3)2), 73.1 (s, C ÄCH(SiMe3)), 59.6 (s, CÄ
CH(SiMe3)), 22.1 (s, C(CH3)2), 22.0 (s, C(CH3)2), 1.1
(s, CÄ
CH(Si(CH3)3) ppm. IR (KBr, cmꢃ1): 1979 (m),
1956 (m), 2901 (m), 1642 (s), 1456 (m), 1246 (m), 1149
(m), 1011 (m), 855 (s). MS (FAB): m/zꢀ
214 (Mꢂ).
/
CH(Si(CH3)3), 0.91 (12H, s, C(CH3)2C-
[28] H. Egsgaard, D. Suelzle, H. Schwarz, L. Carlsen, Chem. Ber. 124
(1991) 1265.
/
CH(Si(CH3)3) ppm. 13C{1H}
[29] D.M. Tellers, R.G. Bergman, Organometallics 20 (2001) 4819.
[30] P.J. Alaimo, B.A. Arndtsen, R.G. Bergman, Organometallics 19
(2000) 2130.
/
/
[31] P.J. Alaimo, D.W. Peters, J. Arnold, R.G. Bergman, J. Chem.
Educ. 78 (2001) 64.
/
[32] I.R. Lyatifov, G.M. Jafarov, V.N. Babin, P.V. Petrovskii, V.D.
Zagoresvskii, J. Organomet. Chem. 368 (1989) 223.
[33] T. Ida, T. Itaya, Tetrahedron 49 (1993) 10511.
[34] J. Daub, J. Kappler, K.H. Jogun, J.J. Stezowski, H. Binder, J.
Organomet. Chem. 240 (1982) 239.
/
HRMS Calc. for C11H22O2Si: 214.1839. Found:
214.1836.