Small-Molecule Activation within the Group 6 Complexes (η5-C5Me5)[N(iPr)C(Me)N(iPr)]M(CO)(L) for M = Mo, W and L = N2, NCMe, η2-Alkene, SMe2, C3H6O

Article abstract of DOI:10.1021/acs.organomet.6b00131

A series of midvalent monocyclopentadienyl monoamidinate (CPAM) group 6 complexes of the general formula Cp?[N(ⁱPr)C(Me)N(ⁱPr)]M(CO)(L) (II), where Cp? = η⁵-C₅Me₅ and M = Mo, W, have been prepared, and most of them have been structurally characterized. Treatment of the ditungsten "end-on-bridged" dinitrogen complex {Cp?[N(ⁱPr)C(Me)N(ⁱPr)]W}₂(μ-η¹:η¹-N₂) (3) with excess NCMe under a CO atmosphere produced the ditungsten bridging diimido complex {Cp?[N(ⁱPr)C(Me)N(ⁱPr)]W}₂[μ-η¹:η¹-NC(Me)=(Me)N] (4). Photolysis of Cp?[N(ⁱPr)C(Me)N(ⁱPr)]M(CO)₂, where M = Mo (6), W (7), or treatment of Cp?[N(ⁱPr)C(Me)N(ⁱPr)]Mo(CO)(NCMe) (1a) with excess alkene provided Cp?[N(ⁱPr)C(Me)N(ⁱPr)]M(CO)(L) for M = Mo and L = η²-ethene (8), M = W and L = η²-ethene (9), M = Mo and L = η²-norbornene (10), M = W and L = η²-norbornene (11), M = W and L = η²-cyclopentene (12), M = Mo and L = η²-cyclopentene (13), and M = Mo and L = η²-styrene (14). When isobutene was employed as the alkene, C-H bond activation occurred to produce Cp?[N(ⁱPr)C(Me)N(ⁱPr)]W(H)(η³-C₄H₇) (15). Photolysis of 7 in the presence of SMe₂ provided Cp?[N(ⁱPr)C(Me)N(ⁱPr)]W[κ-C,O-C(O)Me](SMe) (16) through oxidative C-S bond activation of a coordinated SMe₂, followed by 1,1-carbonyl migratory insertion into the new W-C bond. Finally, reaction of 1a with propylene oxide (C₃H₆O) provided the 16-electron complex Cp?[N(ⁱPr)C(Me)N(ⁱPr)]Mo[C(O)CH(Me)CH₂O] (19) via similar oxidative C-O bond activation of coordinated C₃H₆O, followed by 1,1-carbonyl migratory insertion into the Mo-C bond of an intermediate metallaoxetane. Under a CO atmosphere, 19 is converted to the 18-electron complex Cp?[N(ⁱPr)C(Me)N(ⁱPr)]Mo[C(O)CH(Me)CH₂O](CO) (20). These results provide additional support for the development of new stoichiometric and catalytic transformations that are mediated by CPAM group 6 metal complexes and that are relevant to the goal of small-molecule fixation.

Full text of DOI:10.1021/acs.organomet.6b00131

Article
pubs.acs.org/Organometallics
Small-Molecule Activation within the Group 6 Complexes
(η5‑C5Me5)[N(iPr)C(Me)N(iPr)]M(CO)(L) for M = Mo, W and L = N2,
NCMe, η2‑Alkene, SMe2, C3H6O
Wesley S. Farrell, Brendan L. Yonke, Jonathan P. Reeds, Peter Y. Zavalij, and Lawrence R. Sita*
Department of Chemistry and Biochemistry, University of Maryland, College Park, Maryland 20742, United States
S
* Supporting Information
ABSTRACT: A series of midvalent monocyclopentadienyl
monoamidinate (CPAM) group 6 complexes of the general
formula Cp*[N(iPr)C(Me)N(iPr)]M(CO)(L) (II), where
Cp* = η5-C5Me5 and M = Mo, W, have been prepared, and
most of them have been structurally characterized. Treatment
of the ditungsten “end-on-bridged” dinitrogen complex
{Cp*[N(iPr)C(Me)N(iPr)]W}2(μ-η1:η1-N2) (3) with excess
NCMe under a CO atmosphere produced the ditungsten
bridging diimido complex {Cp*[N(iPr)C(Me)N(iPr)]W}2[μ-
η1:η1-NC(Me)C(Me)N] (4). Photolysis of Cp*[N(iPr)C-
(Me)N(iPr)]M(CO)2, where M = Mo (6), W (7), or
treatment of Cp*[N(iPr)C(Me)N(iPr)]Mo(CO)(NCMe)
(1a) with excess alkene provided Cp*[N(iPr)C(Me)N(iPr)]-
M(CO)(L) for M = Mo and L = η2-ethene (8), M = W and L = η2-ethene (9), M = Mo and L = η2-norbornene (10), M = W and
L = η2-norbornene (11), M = W and L = η2-cyclopentene (12), M = Mo and L = η2-cyclopentene (13), and M = Mo and L = η2-
styrene (14). When isobutene was employed as the alkene, C−H bond activation occurred to produce Cp*[N(iPr)C(Me)-
N(iPr)]W(H)(η3-C4H7) (15). Photolysis of 7 in the presence of SMe2 provided Cp*[N(iPr)C(Me)N(iPr)]W[κ-C,O-
C(O)Me](SMe) (16) through oxidative C−S bond activation of a coordinated SMe2, followed by 1,1-carbonyl migratory
insertion into the new W−C bond. Finally, reaction of 1a with propylene oxide (C3H6O) provided the 16-electron complex
Cp*[N(iPr)C(Me)N(iPr)]Mo[C(O)CH(Me)CH2O] (19) via similar oxidative C−O bond activation of coordinated C3H6O,
followed by 1,1-carbonyl migratory insertion into the Mo−C bond of an intermediate metallaoxetane. Under a CO atmosphere,
19 is converted to the 18-electron complex Cp*[N(iPr)C(Me)N(iPr)]Mo[C(O)CH(Me)CH2O](CO) (20). These results
provide additional support for the development of new stoichiometric and catalytic transformations that are mediated by CPAM
group 6 metal complexes and that are relevant to the goal of small-molecule fixation.
(OAT), nitrene group transfer (NGT), or sulfur atom transfer
(SAT) processes.5,6,10−12,14 Other structures within this same
family of CPAM group 6 metal complexes have been proposed
as key intermediates in novel strong bond-breaking or bond-
making reactions, such as IIf for cleaving the N−N double
bond of nitrous oxide (N2O).6 Intriguingly, all of the structures
of Chart 1 can be viewed as having been derived from
coordination of a strong A−B multiple bond of a small
molecule (e.g. OCO, RNCO, and RNCO for IIa−c) to
a 16-electron, coordinatively unsaturated M(II,d4) complex,
Cp*M[N(iPr)C(R)N(iPr)](X) (M = Mo, W; R = Me, Ph; X =
CNR, CO) (III), that has been invoked as a transient
intermediate in OAT, NGT, and SAT catalytic cycles. Given
the growing apparent ubiquity of II and III for small-molecule
fixation schemes based on CPAM group 6 metal complexes, a
next logical step to take was to conduct a wider survey of what
other derivatives of II might be accessible through the
INTRODUCTION
■
Identification of early-transition-metal complexes that can
“activate” abundant and inexpensive small molecules, such as
dinitrogen (N2), for subsequent “fixation” through metal-
mediated bond-cleaving, atom-functionalization, and product-
forming reactions is critical for the development of new classes
of sustainable and environmentally friendly “green” chemical
processes.1 In this regard, over the past decade we have been
exploring the ability of the monocyclopentadienyl monoamidi-
nate (CPAM) ligand set within group 4−6 metal complexes of
the general formula (η5-C5R5)[N(R1)C(R3)N(R2)]M(X)(Y)
(I), to support a remarkably broad array of stoichiometric and
catalytic transformations that are relevant to the goal of small-
molecule fixation.2−14 In each of these reports, the formal 18-
electron M(II,d4) or M(IV,d2) Cp*[N(iPr)C(R)N(iPr)]M(X)-
(L) (M = Mo, W; R = Me, Ph; Cp* = η5-C5Me5; X = CNR,
CO; L = small molecule) complexes IIa−e in Chart 1 have
been isolated, structurally characterized, and experimentally
confirmed to be intermediates in catalytic small-molecule
fixation cycles that proceed through key oxygen atom transfer
Received: February 16, 2016
© XXXX American Chemical Society
A
DOI: 10.1021/acs.organomet.6b00131
Organometallics XXXX, XXX, XXX−XXX

Organometallics
Article
Chart 1
Scheme 1
fragment is observed. Figure 1 provides the solid-state
molecular structure and selected geometric parameters of 4 as
coordination of other categories of small molecules to III, or a
relevant synthon for this highly reactive species, in a manner
that might facilitate novel chemical transformations and
ultimately lead to the discovery of other catalytic processes of
potential value. Herein, we now report the results of such an
investigation in which different synthetic routes to additional
examples of monocarbonyl CPAM group 6 metal complexes,
Cp*[N(iPr)C(Me)N(iPr)M(CO)(L) (II for R = Me and X =
CO), have been established for L = acetonitrile (NCMe),
several η2-alkenes, dimethyl sulfide (SMe2), and propylene
oxide (C3H6O). Gratifyingly, in each of these new examples of
II, small-molecule activation pathways involving either novel
bond-breaking or bond-forming reactions have been docu-
mented.
Figure 1. Molecular structure (30% thermal ellipsoids) of compound
4. Hydrogen atoms have been omitted for the sake of clarity. Selected
bond lengths (Å) and angles (deg): W1−N3 1.7624(15), N3−C19
1.381(2), C19−C19A 1.374(4); W1−N3−C19 173.04(14), N3−
C19−C19A 122.7(2).16
RESULTS AND DISCUSSION
■
Complexes of II in which L = NCMe, N2. We have
previously reported that the structurally characterized, formal
Mo(II), monocarbonyl, mono(acetonitrile) complexes Cp*[N-
(iPr)C(R)N(iPr)]Mo(CO)(NCMe), where R = Me (1a), Ph
(1b), can serve as effective chemical synthons for III (M = Mo
and L = CO) through facile ligand substitution of NCMe by a
small molecule serving to displace the Lewis base.10,12 In these
previous studies, 1a,b were conveniently prepared in high yield
through reaction of the corresponding dimolybdenum “end-on-
bridged” dinitrogen complexes {Cp*[N(iPr)C(R)N(iPr)]-
Mo}2(μ-η1:η1-N2), where R = Me (2a), Ph (2b),4,12 with
excess amounts of NCMe in benzene solution under an
atmosphere of CO (1 atm). With this useful synthetic route
established, we next sought to prepare the analogous tungsten
complex Cp*[N(iPr)C(Me)N(iPr)]W(CO)(NCMe) through
an identical procedure.
determined by a single-crystal X-ray analysis. The W1−N3
bond length of 1.7624(15) Å is in keeping with the
corresponding W−N value of 1.753(2) Å obtained for the
previously reported mononuclear CPAM W(IV) imido
complex Cp*[N(iPr)C(Me)N(iPr)]WNCMe3.10 These
structural data, along with a central C19−C19A bond length
of 1.374(4) Å, support the depicted assignment of the two
coupled NCMe groups being associated with a single diimido
moiety that bridges two W(IV) centers, rather than the
alternative formalization in which a diiminato [NC(Me)C-
(Me)N] group that is coupling two W(III) centers through
W−N single bonds.15f−h
Regarding a mechanism for the formation of 4 from 3, it is
important to note that no reaction of 3 with excess amounts of
NCMe occurred in benzene solution in the absence of CO.
Accordingly, it seemed reasonable to postulate that prior
coordination of CO to the W centers of 3 is a prerequisite for
weakening W−N2 π back-bonding17 through introduction of a
competing W−CO π interaction to the extent that NCMe can
now displace the coordinated N2 ligand. As Scheme 1 shows,
support for this hypothesis was obtained by exposing 3 to CO
(1 atm) in benzene-d6 solution and monitoring the reaction by
1H NMR until a near-quantitative yield of a single new C1-
symmetric species was observed to have occurred, prior to the
appearance of the known dicarbonyl species Cp*W[N(iPr)C-
As summarized in Scheme 1, treatment of the ditungsten
end-on-bridged dinitrogen compound {Cp*[N(iPr)C(Me)N-
(iPr)]W}2(μ-η1:η1-N2) (3)4 with excess NCMe under a CO
atmosphere did not produce the desired monocarbonyl
mono(acetonitrile) product; rather, the ditungsten “bridging”
diimido complex {Cp*[N(iPr)C(Me)N(iPr)]W}2[μ-η1:η1-NC-
(Me)C(Me)N] (4), in which two acetonitrile ligands have
undergone reductive coupling,15 was obtained in high yield
instead.16 In benzene-d6 solution, complex 4 displays Cs
1
symmetry, as determined by H NMR spectroscopy, in which
only a single methyl group resonance for the bridging diimido
B
DOI: 10.1021/acs.organomet.6b00131
Organometallics XXXX, XXX, XXX−XXX

Organometallics
Article
(Me)N(iPr)](CO)2.4,5,16 Subsequent isolation of an analytically
pure sample of this new compound and determination of its
molecular structure through single-crystal X-ray analysis quite
surprisingly revealed it to be the ditungsten end-on-bridged
dinitrogen 1,4-dicarbonyl complex {Cp*[N(iPr)C(Me)N-
(iPr)]W(CO)}2(μ-η1:η1-N2) (5). Figure 2 presents the solid-
state molecular structure and selected geometric parameters for
5.16
Scheme 2
carbonyl mono(alkene) complexes Cp*[N(iPr)C(Me)N(iPr)]-
M(CO)(L), where M = Mo and L = η2-ethene (8), M = W and
L = η2-ethene (9), M = Mo and L = η2-norbornene (10), M =
W and L = η2-norbornene (11), and M = W and L = η2-
cyclopentene (12), were observed.16 However, the scale-up of
this procedure for obtaining larger quantities of materials was
found to be practical only for the tungsten derivatives 9 and 11,
which could be isolated in modest to high yields as analytically
1
pure, orange crystalline materials. Indeed, although H NMR
Figure 2. Molecular structure (30% thermal ellipsoids) of compound
5. Hydrogen atoms have been omitted for the sake of clarity. Selected
bond lengths (Å) and angles (deg): W1−N5 2.0231(15), N5−N6
1.144(3), W1−C37 1.932(2), C37−O1 1.171(2); W1−N5−N6
176.69(9), C37−W1−N5 79.64(7).
confirmed a high yield of 12, the noncrystalline nature of this
compound frustrated all attempts to obtain it in pure form for
complete analytical characterization. Furthermore, in contrast
to the ready formation of 12, photolysis of 6 in the presence of
excess cyclopentene did not lead to any discernible formation
of the corresponding molybdenum derivative, as determined by
1H NMR spectroscopy. Finally, attempts to employ non-
symmetric styrene as the alkene trap for III provided a complex
inseparable mixture of compounds for both M = Mo and M =
W.
Compound 5 is stable in solution and the solid state, and it
does not show any propensity to lose CO or N2 under vacuum.
A solid-state infrared (IR) spectrum (KBr pellet) for this
compound provided νCO 1768 cm−1 for the stretching
frequency of the metal-bound carbonyl ligands, and this value
is suggestive of a strong degree of π back-donation from filled
metal orbitals into the π* orbital of the C−O bond.17 As
hypothesized, this strong M−CO bonding interaction further
appears to deplete π back-donation into the analogous π*
orbital of the bridging N2 group, as evidenced by the N5−N6
bond length of 1.144(3) Å, which is significantly shorter than
the corresponding N−N bond length value of 1.277(8) Å that
was previously determined for 3.4
Fortunately, as Scheme 3 reveals, an alternative synthetic
route to the desired monocarbonyl η2-alkene derivatives of II
Scheme 3
Complexes of II in which L = η2-Alkene. Given the
various η2-coordination bonding modes involving A−B double
bonds of small molecules already displayed by the structures of
Chart 1, it seemed reasonable to explore the possibility of
preparing a series of η2-alkene derivatives of II for the purpose
of investigating the nature of metal−alkene σ donation, π back-
donation bonding interactions.
As shown in Scheme 2, a few of the desired monocarbonyl
mono(alkene) derivatives of II were successfully prepared
through simple photolysis of the previously reported dicarbonyl
complexes Cp*[N(iPr)C(Me)N(iPr)]M(CO)2, where M = Mo
(6), W (7),4,5 in benzene-d6 solutions containing excess
amounts of a symmetric alkene lacking accessible β hydrogens
that can engage in strong metal−hydrogen agostic inter-
actions18 (e.g., ethene, norbornene, and cyclopentene) within a
Pyrex tube using a Rayonet carousel of medium-pressure Hg
lamps.16,19 As previously proposed, photolysis of 6 and 7
generates III as a transient intermediate that is then quickly
trapped by coordination of the alkene. When the reaction was
for M = Mo was successfully developed that involved simply
adding excess amounts of the alkene to a benzene solution of
the monocarbonyl mono(acetonitrile) complex 1a.16,20 In
addition to clean and near-quantitative conversions being
1
observed by H NMR, this thermal route could now be easily
scaled to provide practical quantities of all the CPAM
molybdenum η2-alkene derivatives in high yield as orange-red,
crystalline materials.16 The clean nature of this alternative route
also proved to be essential for the successful synthesis, isolation,
and analytical characterization of the cyclopentene and styrene
derivatives 13 and 14, respectively (see Scheme 3).
1
monitored by H NMR, using durene as an internal standard,
near-quantitative conversions to the corresponding mono-
C
DOI: 10.1021/acs.organomet.6b00131
Organometallics XXXX, XXX, XXX−XXX

Organometallics
Article
Figure 3. Molecular structures (30% thermal ellipsoids) of (a) 8, (b) 10, (c) 13, and (d) 14. Hydrogen atoms have been omitted for the sake of
clarity.
All of the new crystalline compounds presented in Schemes 2
and 3 were subjected to structural analysis by X-ray
crystallography and IR spectroscopy in order to assess the
relative degree of π back-donation from the metal center to the
CO and η2-alkene ligands. Figure 3 presents the solid-state
molecular structures of the series of molybdenum derivatives 8,
10, 13, and 14, and Table 1 presents a correlation of M−C and
C−C bond lengths for the η2-alkene ligand and the νCO
stretching frequencies for the CO group for these compounds
along with the tungsten derivatives 9 and 11. To begin, it is
important to note that reports of structurally characterized
second- and third-row group 6 M(II,d4) carbonyl, η2-alkene
complexes are extremely rare.19−22 In the present work, all of
the Cp*[N(iPr)C(Me)N(iPr)]M(CO)(η2-alkene) derivatives
of II are diamagnetic, thermally stable complexes in solution
and do not display any evidence of dynamic rotation about a
1
centralized M−alkene bond axis at room temperature by H
NMR spectroscopy. In keeping with these observations, the
metal−carbon and carbon−carbon bond lengths associated
with the M−(η2-alkene) bonding interaction are consistent
with a metallacyclopropane resonance structure in which a large
degree of π back-donation of electron density from the metal
into the π* C−C antibonding orbital exists (see Table 1).17 On
comparison of second- and third-row metal effects for the same
η2-alkene ligand, νCO stretching frequencies consistently
indicate a stronger M−CO π back-donation interaction for M
= W over M = Mo (cf. νCO 1867 cm−1 for 8 vs 1858 cm−1 for 9
and 1859 cm−1 for 10 vs 1844 cm−1 for 11 in Table 1). Finally,
within the series of molybdenum complexes presented in
Figure 3 and Table 1, M−CO π back-donation decreases in the
order 10 (L = η2-norbornene) > 8 (L = η2-ethene) > 14 (L =
η2-styrene), and these data suggest the opposite correlation of
14 > 8 > 10 in the strength of M−(η2-alkene) bonding.
Although further reactivity studies are warranted, at the present
time, we have not observed any unique reactions involving the
metal−carbon bonds of the formal metallacyclopropane
Table 1. Selected Structural Parameters and IR CO
Stretching Frequencies for
Cp*[N(iPr)C(Me)N(iPr)]M(CO)(η2-alkene)
a
a
c
compd
M
d(M−Calkene) (Å)
d(C−C) (Å)
νCO (cm−1
)
8
9
Mo
W
2.2522(16), 2.008(15)
2.236(5), 2.174(5)
2.284(4), 2.224(4)
2.231(2), 2.192(2)
2.278(2), 2.224(4)
2.2340(11), 2.2605(11)
1.433(2)
1.452(8)
1.433(5)
1.478(3)
1.449(3)
1.4452(15)
1867
1858
1859
1844
1861
1880
b
10
Mo
W
11
b
13
Mo
Mo
14
a
b
Bond lengths for M−-(η2-alkene) interaction. Parameters selected
from one of two or three unique molecules within the asymmetric unit
cell.16 Solid-state IR (KBr).
c
D
DOI: 10.1021/acs.organomet.6b00131
Organometallics XXXX, XXX, XXX−XXX

Organometallics
Article
moieties of these Cp*[N(iPr)C(Me)N(iPr)]M(CO)(η2-al-
kene) derivatives of II, such as 1,1-carbonyl migratory insertion.
C−H Bond Activation: Synthesis and Characterization
of Cp*[N(iPr)C(Me)N(iPr)]W(H)(η3-C4H7) (15). When alkenes
bearing β hydrogens (e.g. propene, 1-butene, and cyclohexene)
that are accessible for formation of agostic interactions within a
M(η2-alkene) complex were employed in the reactions of
Schemes 2 and 3, only formation of complex mixtures of
multiple unidentifiable products were observed. The use of
isobutene as the alkene trap in the photolysis of the tungsten
dicarbonyl 7, however, proved to be an important exception.
More specifically, as Scheme 4 reveals, photolysis of a solution
2.235(4) Å and carbon−carbon bond lengths of C19−C20
1.411(7) Å and C20−C21 1.409(7) Å. In benzene-d6 solution,
the 13C{1H} NMR (125 MHz, benzene-d6) spectrum of 15 also
displays 13C resonances at δ 53.2 and 45.7 ppm with
1J(13C−183W) = 12 and 19 Hz, respectively, for the terminal
carbon atoms of the η3-methallyl ligand.16 The groups of
Legzdins and Henderson have previously reported the
formation of W(II) η3-allyl complexes through C−H bond
activation pathways.23 In the present case, it is reasonable to
propose that photolyic loss of CO from a Cp*[N(iPr)C(Me)-
N(iPr)]W(CO)(η2-isobutene) intermediate provides an open
coordination site for formation of a β hydrogen agostic
interaction of one of the distal methyl groups of the η2-
isobutene ligand with the tungsten center, followed by
complete C−H activation to provide 15.
Scheme 4
Complexes of II in Which L = SMe2. One of the goals of
exploring new examples of II was to obtain derivatives in which
L can be displaced even more easily than NCMe in ligand
substitution reactions (vide supra, Scheme 3). To this end,
photolysis of toluene solutions of 6 and 7 containing excess
amounts of dimethyl sulfide, SMe2, as a Lewis base σ donor,
was pursued.24 Although these studies were not productive for
6, in the case of 7, clean formation of the W(IV) methyl sulfido
η2-acyl complex Cp*[N(iPr)C(Me)N(iPr)]W[κ-C,O-C(O)-
Me](SMe) (16) occurred to provide this compound in a
modest isolated yield as an orange, crystalline material
according to Scheme 5.16 Figure 5 presents the molecular
of 7 in benzene under an atmosphere of isobutene (15 psi)
resulted in clean production of a new C1-symmetric species.
1
1
The existence of a H resonance in the H NMR (400 MHz,
benzene-d6) spectrum occurring at δ −0.88 ppm with coupling
to 183W (1J(1H−183W) = 55 Hz), as well as the lack of a 13C
resonance for a carbonyl ligand in the 13C{1H} NMR (125
MHz, benzene-d6) spectrum, suggested that this product, 15,
likely resulted from C−H bond activation of an initial η2-alkene
complex. Indeed, this hypothesis was confirmed through
isolation and analytical characterization of a pure sample of
15, including a single-crystal X-ray analysis, which provided the
molecular structure presented in Figure 4 along with selected
geometric parameters. As can be seen, compound 15 is a
W(IV) η3-methallyl hydride complex with the empirical
formula Cp*[N(iPr)C(Me)N(iPr)]W(H)(η3-C4H7), as de-
picted in Scheme 4. In the solid state, the η3-methallyl
fragment is associated with tungsten−carbon bond lengths of
W1−C19 2.250(5) Å, W1−C20 2.187(4) Å, and W1−C21
Scheme 5
structure of 16 along with selected geometric parameters as
determined by a single-crystal X-ray analysis. The observed η2
coordination of the acyl ligand is supported by the relatively
short W1−O1 distance of 2.209(2) Å and the C20−O1 bond
length of 1.282(4) Å, which is in keeping with structural data
reported for other midvalent η2-acyl complexes of tungsten.25
Additional structural information for 16 was obtained by
conducting the photolysis using 13C-labeled (99%) (13CO)2-7
to provide the corresponding isotopically labeled [η2-13C(O)-
Me]-16, which displayed a strong 13C resonance at δ 276 ppm
Figure 4. Molecular structure (30% thermal ellipsoids) of compound
15. Hydrogen atoms have been omitted for the sake of clarity, with the
exception of the W hydride, which is represented by a white sphere.
Selected bond lengths (Å) and angles (deg): W1−H1 1.94(5), W1−
C19 2.250(5), W1−C20 2.187(4), W1−C21 2.235(4), C19−C20
1.411(7), C20−C21 1.409(7), C20−C22 1.520(6); C19−C20−C21
111.5(4).
1
with J(13C−183W) = 72 Hz in the 13C{1H} NMR (125 MHz,
benzene-d6) spectrum.25 It is reasonable to assume that
formation of 16 proceeds according to Scheme 5, in which
initial generation of the desired 17 is followed by formal
oxidative addition involving C−S bond activation to produce
E
DOI: 10.1021/acs.organomet.6b00131
Organometallics XXXX, XXX, XXX−XXX

Organometallics
Article
a 16-electron, Mo(IV) complex, it is not surprising that
introduction of CO (10 psi) into a benzene solution of this
compound slowly produced the formal 18-electron complex
Cp*[N(iPr)C(Me)N(iPr)]Mo(CO)[κ-C,O-C(O)CH(CH3)-
CH2O] (20), which was isolated as a crystalline material in high
yield.16 The molecular structures of 19 and 20 as determined
by single-crystal X-ray analyses are presented in Figure 6 along
with selected geometric parameters.
Figure 5. Molecular structure (30% thermal ellipsoids) of compound
16. Hydrogen atoms have been omitted for the sake of clarity. Selected
bond lengths (Å) and angles (deg): W1−S1 2.4708(8), S1−C19
1.818(4), W1−C20 1.973(3), W1−O1 2.209(2), C20−O1 1.282(4),
C20−C21 1.484(5); W1−S1−C19 109.98(12), W1−C20−C21
156.4(3), W1−C20−O1 82.54(19).
the intermediate 18. Subsequent 1,1-carbonyl insertion into the
new tungsten-bound methyl group of 18 then provides 16. To
the best of our knowledge, only a handful of transition-metal
complexes that occur as a result of oxidative C−S bond
activation of a thioether have been isolated and structurally
characterized.26
Complexes of II in which L = Propylene Oxide
(C3H6O). Given the ease with which the proposed intermediate
17 engages in C−S bond activation of a coordinated thioether
(see Scheme 5), it was of significant interest to investigate the
chemistry of related derivatives of II in which L is coordinated
propylene oxide (C3H6O). As summarized in Scheme 6,
Scheme 6
Figure 6. Molecular structures (30% thermal ellipsoids) of (a) 19 and
(b) 20. Hydrogen atoms have been omitted for the sake of clarity.
Selected bond lengths (Å) and angles (deg): for 19, Mo1−C19
2.1468(12), C19−O1 1.2190(15), C19−C20 1.5664(18), C20−C21
1.5151(19), O2−C21 1.4167(15), Mo1−O2 1.9675(9), Mo1−C19−
C20 107.38(8), C19−Mo1−O2 79.37(4), Mo1−O2−C21 118.26(7);
for 20, Mo1−O2 2.0579(9), O2−C21 1.3987(15), C21−C20
1.5236(19), C19−C20 1.5408(19), Mo1−C19 2.3120(12), C19−O1
1.2042(16), Mo1−C23 1.9504(13), C23−O3 1.1575(16), C19−
Mo1−C23 66.26(5), C21−O2−Mo1 115.97(8), O2−Mo1−C19
71.83(4), Mo1−C19−C20 112.25(9).
Although exhaustive reactivity profile studies for 19 have yet
to be undertaken, it is of interest to comment here on the
thermal stability of this compound. More specifically, upon
gentle heating of a benzene solution of 19 (generated in situ),
elimination of methacrolein and formation of the known
terminal oxo complex Cp*[N(iPr)C(Me)N(iPr)]Mo(O)
addition of C3H6O to a toluene solution of 1a at room
temperature cleanly produced the new C1-symmetric, ring-
opened product Cp*[N(iPr)C(Me)N(iPr)]Mo[κ-C,O-C(O)-
CH(CH3)CH2O] (19), which could be isolated in high yield
as a black, crystalline material. It is reasonable to propose that
formation of 19 proceeds through oxidative C−O bond
activation of coordinated propylene oxide within a derivative
of II (M = Mo, L = C3H6O), to form a transient
metallaoxetane,27 followed by 1,1-migratory insertion of CO
into the new molybdenum−carbon bond.28 Since 19 is formally
(21),5 according to Scheme 7, was observed by H NMR
1
spectroscopy. Since compound 21 can be converted back to the
dicarbonyl 6 under an atmosphere of CO,5 efforts are currently
underway to develop a new catalytic cycle for a “green”
chemical conversion of propylene oxide to methacrolein.
F
DOI: 10.1021/acs.organomet.6b00131
Organometallics XXXX, XXX, XXX−XXX

Organometallics
Article
(6H, d, J = 6.5 Hz), 1.62 (6H, s), 1.94 (30H, s), 3.56 (2H, sp, J = 6.7
Hz), 3.59 (2H, sp, J = 6.5 Hz). IR (KBr): νCO 1768 cm−1.
Scheme 7
Synthesis of Cp*[N(iPr)C(Me)N(iPr)]Mo(CO)(C2H4) (8). A
solution of 1a (0.060 g, 0.14 mmol) in benzene-d6 was prepared in
a Pyrex J. Young NMR tube equipped with a Teflon seal. The
headspace was evacuated, the tube was charged with ethene (15 psi),
and the mixture was shaken vigorously and allowed to react for 16 h, at
1
which point complete consumption of 1a was observed by H NMR.
Volatiles were removed in vacuo, the crude material was extracted in
pentane, and the extract was filtered through a pad of Celite and
pumped down to dryness. The resulting red crystals were dissolved in
minimal pentane and cooled to −30 °C to furnish 8 as red crystals
(0.043 g, 75% yield). Data for 8 are as follows. Anal. Calcd for
C21H36N2OMo: C, 58.86; H, 8.43; N, 6.57. Found: C, 58.87; H, 8.47;
CONCLUSION
■
Given the previously well established role that derivatives of II
play in catalytic OAT, SAT, and NGT processes, the present
study serves to expand the range of such CPAM group 6 metal
complexes. In each case, unique reaction pathways involving
strong bond cleavage and new bond formation involving the
coordinated small-molecule ligand L have been documented.
These results support ongoing efforts to develop new metal-
mediated stoichiometric and catalytic transformations that are
relevant to the goal of small-molecule fixation.
1
N, 6.54. H NMR (400 MHz, benzene-d6): 0.94 (3H, d, J = 6.9 Hz),
1.00 (3H, d, J = 6.9 Hz), 1.02 (1H, m), 1.10 (3H, d, J = 6.5 Hz), 1.26
(3H, d, J = 6.4 Hz), 1.31 (1H, m), 1.46 (3H, s), 1.64 (15H, s), 2.15
(1H, m), 3.07 (1H, sp, J = 6.9 Hz), 3.32 (1H, m), 3.61 (1H, sp, J = 6.4
Hz). IR (KBr): νCO 1867 cm−1.
Synthesis of Cp*[N(iPr)C(Me)N(iPr)]W(CO)(C2H4) (9). A sol-
ution of 7 (0.060 g, 0.12 mmol) in 1 mL of benzene-d6 was prepared
in a Pyrex J. Young NMR tube equipped with a Teflon seal. The
headspace was evacuated, and the tube was charged with ethene (15
psi), at which point the tube was shaken vigorously and the mixture
photolyzed for 16 h. The headspace was evacuated and the tube
charged with ethene again, and the solution was photolyzed for 9 h
longer, at which point complete consumption of 7 was observed by 1H
NMR. Volatiles were removed in vacuo, the resulting crude material
was extracted in pentane, the extract was filtered through a pad of
Celite, and the filtrate was concentrated and cooled to −30 °C to
furnish 9 as orange crystals (0.041 g, 67% yield). Data for 9 are as
follows. Anal. Calcd for C21H36N2OW: C, 48.85; H, 7.03; N, 5.42.
Found: C, 48.91; H, 6.67; N, 5.44. 1H NMR (400 MHz, benzene-d6):
0.95 (3H, d, J = 6.7 Hz), 0.98 (3H, d, J = 6.9 Hz), 0.99 (1H, m), 1.07
(3H, d, J = 6.5 Hz), 1.23 (3H, d, J = 6.3 Hz), 1.27 (1H, m), 1.41 (3H,
s), 1.74 (15H, s), 1.84 (1H, m), 3.00 (1H, sp, J = 6.8 Hz), 3.01 (1H,
m), 3.48 (1H, sp, J = 6.3 Hz). IR (KBr): νCO 1858 cm−1.
EXPERIMENTAL SECTION
■
General Considerations. All manipulations with air- and
moisture-sensitive compounds were carried out under an N2 or Ar
atmosphere with standard Schlenk or glovebox techniques. Et2O and
THF were dried over Na/benzophenone and distilled under N2 prior
to use. Toluene and pentane were dried and deoxygenated by passage
over activated alumina and GetterMax 135 catalyst (purchased from
Research Catalysts, Inc.) and collected under N2 prior to use. Benzene-
d6, toluene-d8, styrene, and cyclopentene were dried over Na/K alloy
and isolated by vacuum transfer prior to use. Acetonitrile and dimethyl
sulfide were dried over CaH2 and distilled under N2 prior to use.
Norbornene was dried over molten Na and distilled under vacuum
prior to use. Gaseous reagents were purchased from Sigma-Aldrich and
used as received. Compounds 1a, 3, 6, and 7 were prepared according
to reported methods in similar yield and purity.4,10 Celite was oven-
dried (150 °C for several days) before use in the glovebox. Cooling
was performed in the internal freezer of a glovebox maintained at −30
Synthesis of Cp*[N(iPr)C(CH3)N(iPr)]Mo(CO)(C7H10) (10). A
solution of 1a (0.035 g, 0.08 mmol) and norbornene (0.021 g, 0.22
mmol) in benzene-d6 was prepared and transferred to a Pyrex J. Young
NMR tube equipped with a Teflon seal. After 2 h, complete
consumption of 1a was observed by 1H NMR. Volatiles were removed
in vacuo, the crude material was extracted with pentane, the extract
was filtered through a pad of Celite, and the filtrate was concentrated
and cooled to −30 °C to furnish 10 as red-orange crystals (0.026 g,
66% yield). Data for 10 are as follows. Anal. Calcd for C26H42N2OMo:
1
°C. H and 13C{1H} NMR spectra were recorded at 400 and 125
MHz, respectively. Photolysis reactions were performed using a
Rayonet Photochemical Reactor containing a carousel of medium
pressure Hg lamps. Elemental analyses were carried out by Midwest
Microlab LLC.
Synthesis of {Cp*[N(iPr)C(Me)N(iPr)]W}2[μ-η1:η1-NC(Me)C-
(Me)N] (4). A solution of 3 (0.038 g, 0.04 mmol) and NCMe (0.5 mL,
0.10 mmol) in 0.6 mL of benzene-d6 was prepared and transferred to a
J. Young NMR tube equipped with a Teflon seal. The headspace was
evacuated and charged with CO (1 atm), and the mixture was shaken
and allowed to react for 2 days, at which point 1H NMR confirmed the
consumption of 3. Volatiles were removed in vacuo, and the resulting
crude material was dissolved in a minimal amount of pentane and
cooled to −30 °C to furnish 4 as green crystals (0.032 g, 80% yield).
Data for 4 are as follows. Anal. Calcd for C40H70N6W2: C, 47.89; H,
7.04; N, 8.38. Found: C, 48.06; H, 6.87; N, 8.28. 1H NMR (400 MHz,
benzene-d6): 1.01 (12H, d, J = 6.3 Hz), 1.26 (12H, d, J = 6.3 Hz), 1.51
(6H, s), 2.08 (30H, s), 2.60 (6H, s), 3.22 (4H, sp, J = 6.3 Hz).
Synthesis of {Cp*[N(iPr)C(Me)N(iPr)]W(CO)}2(μ-η1:η1-N2) (5). A
solution of 3 (0.043 g, 0.05 mmol) was prepared in 0.6 mL of
benzene-d6 and transferred to a J. Young NMR tube equipped with a
Teflon seal. The headspace was evacuated, the tube was charged with
CO (8 psi), and the mixture was allowed to react for 15 h to produce a
dark green solution. Volatiles were removed in vacuo, and the residue
was dissolved in minimal pentane and cooled to −30 °C to furnish 5
as dark green crystals (0.024 g, 53% yield). Data for 5 are as follows.
Anal. Calcd for C38H64N6O2W2: C, 45.41; H, 6.42; N, 8.37. Found: C,
1
C, 63.14; H, 8.56; N, 5.66. Found: C, 63.04; H, 8.55; N, 5.53. H
NMR (400 MHz, benzene-d6): 0.89 (3H, d, J = 7.0 Hz), 0.99 (1H, d, J
= 9.5 Hz), 1.04 (3H, d, J = 7.0 Hz), 1.14 (1H, m), 1.21 (3H, d, J = 6.3
Hz), 1.34 (3H, d, J = 6.3 Hz), 1.42 (2H, m), 1.50 (3H, s), 1.66 (15H,
s), 1.87 (1H, d, J = 5.6 Hz), 2.04 (2H, m), 2.28 (1H, br), 2.35 (1H, d, J
= 5.6 Hz), 3.14 (1H, sp, J = 7.0 Hz), 3.31 (1H, br), 3.70 (1H, sp, J =
6.3 Hz). IR (KBr): νCO 1859 cm−1.
Synthesis of Cp*[N(iPr)C(CH3)N(iPr)]W(CO)(C7H10) (11). A
solution of 7 (0.052 g, 0.10 mmol) and norbornene (0.103 g, 1.10
mmol) in 1 mL of benzene-d6 was prepared and transferred to a Pyrex
J. Young NMR tube equipped with a Teflon seal and photolyzed for 20
1
h, at which point complete consumption of 7 was observed by H
NMR. Volatiles were removed in vacuo, the crude material was
extracted with pentane, and the extract was filtered through a pad of
Celite and pumped down to dryness to furnish 11 as orange crystals
(0.057 g, 97% yield). Data for 11 are as follows. Anal. Calcd for
C26H42N2OW: C, 53.61; H, 7.27; N, 4.81. Found: C, 53.63; H, 7.00;
1
N, 4.73. H NMR (400 MHz, benzene-d6): 0.92 (3H, d, J = 6.8 Hz),
1.00 (3H, d, J = 6.8 Hz), 1.11 (1H, d, J = 9.8 Hz), 1.17 (3H, d, J = 6.6
Hz), 1.28 (3H, d, J = 6.6 Hz), 1.36 (1H, m), 1.46 (3H, s), 1.51 (2H,
m), 1.75 (15H, s), 1.91 (1H, d, J = 6.5 Hz), 2.21 (2H, m), 2.28 (2H,
m), 3.06 (1H, sp, J = 6.8 Hz), 3.24 (1H, br), 3.60 (1H, sp, J = 6.6 Hz).
IR (KBr): νCO 1844 cm−1.
1
45.39; H, 6.22; N, 8.12. H NMR (400 MHz, benzene-d6): 1.11 (6H,
d, J = 6.5 Hz), 1.17 (6H, d, J = 6.7 Hz), 1.21 (6H, d, J = 6.7 Hz), 1.28
G
DOI: 10.1021/acs.organomet.6b00131
Organometallics XXXX, XXX, XXX−XXX

Organometallics
Article
Synthesis of Cp*[N(iPr)C(CH3)N(iPr)]Mo(CO)(C5H8) (13). A
solution of 1a (0.035 g, 0.08 mmol) and cyclopentene (35 μL, 0.38
mmol) in 0.6 mL of benzene-d6 was prepared in a Pyrex J. Young
NMR tube equipped with a Teflon seal, and the mixture was allowed
to react for 2 h, at which point complete consumption of 1a was
was added propylene oxide (73 μL, 1.06 mmol) at room temperature.
The resulting solution was stirred overnight, at which point volatiles
were removed in vacuo, the crude product was extracted with pentane,
and the extract was filtered through a pad of Celite, concentrated
under vacuum, and cooled to −30 °C to furnish 19 as black crystals
(0.017 g, 72% yield). Data for 19 are as follows. Anal. Calcd for
C22H38N2O2Mo: C, 57.64; H, 8.35; N, 6.11. Found: C, 57.29; H, 8.39;
1
observed by H NMR. Volatiles were removed in vacuo, the crude
material was extracted with pentane, and the extract was filtered
through a pad of Celite. The filtrate was concentrated and cooled to
−30 °C to furnish 13 as red crystals (0.020 g, 54% yield). Data for 13
are as follows. Anal. Calcd for C24H40N2OMo: C, 61.53; H, 8.60; N,
5.98. Found: C, 61.21; H, 8.31; N, 6.09. 1H NMR (400 MHz,
benzene-d6): 0.96 (3H, d, J = 6.8 Hz), 1.05 (3H, d, J = 6.8 Hz), 1.12
(3H, d, J = 6.5 Hz), 1.24 (3H, d, J = 6.4 Hz), 1.47 (3H, s), 1.65 (15H,
s), 1.82 (2H, m), 1.98 (1H, m), 2.56 (1H, t, J = 5.4 Hz), 2.83 (2H, m),
3.18 (3H, m), 3.65 (1H, sp, J = 6.5 Hz). IR (KBr): νCO 1861 cm−1.
Synthesis of Cp*[N(iPr)C(CH3)N(iPr)]Mo(CO)(C8H8) (14). A
solution of 1a (0.023 g, 0.05 mmol) and styrene (116 μL, 1.01
mmol) in a small amount of toluene was prepared in a screw-cap vial
and stirred for 3 h. Volatiles were removed in vacuo, the crude material
was extracted with pentane, and the extract was filtered through a pad
of Celite. The filtrate was concentrated and cooled to −30 °C to
furnish 14 as orange crystals (0.021 g, 80% yield). Data for 14 are as
follows. Anal. Calcd for C27H40N2OMo: C, 64.27; H, 7.99; N, 5.55.
Found: C, 64.35; H, 8.00; N, 6.57. 1H NMR (400 MHz, benzene-d6):
0.98 (3H, d, J = 6.8 Hz), 1.00 (3H, d, J = 6.8 Hz), 1.04 (3H, d, J = 6.8
Hz), 1.15 (3H, d, J = 6.8 Hz), 1.54 (3H, s), 1.59 (15H, s), 1.78 (1H,
dd, J = 8.0, 3.3 Hz), 1.91 (1H, dd, J = 10.5, 3.3 Hz), 3.14 (1H, sp, J =
6.8 Hz), 3.61 (1H, sp, J = 6.4 Hz), 3.80 (1H, dd, J = 10.3,8.2 Hz), 7.10
(1H, t, J = 7.1 Hz), 7.35 (2H, d, J = 7.3 Hz), 7.41 (2H, t, J = 7.2 Hz).
IR (KBr): νCO 1879 cm−1.
1
N, 5.91. H NMR (400 MHz, benzene-d6): 0.99 (3H, d, J = 6.8 Hz),
1.01 (3H, d, J = 6.8 Hz), 1.14 (3H, d, J = 6.5 Hz), 1.35 (3H, d, J = 6.8
Hz), 1.40 (3H, d, J = 6.8 Hz), 1.71 (3H, s), 1.75 (15H, s), 3.45 (1H,
dd, J = 10.3 Hz, J = 9.8 Hz), 3.64 (3H, m), 5.19 (1H, dd, J = 9.9 Hz, J
= 7.2 Hz). 13C-labeled 19 was prepared by an identical procedure
using 13C-labeled 1a. 13C{1H} NMR (125.6 MHz, benzene-d6): 282.35
ppm.
Synthesis of Cp*[N(iPr)C(CH3)N(iPr)]Mo(CO)[C(O)CH(CH3)-
CH2O] (20). A solution of 19 (0.034 g, 0.07 mmol) was prepared in
0.6 mL of benzene-d6 and transferred to a J. Young NMR tube
equipped with a Teflon seal. The headspace was evacuated and the
tube charged with CO (10 psi). The tube was shaken and the mixture
allowed to react for 2 days, at which point volatiles were removed in
vacuo, and the resulting brown residue was dissolved in a minimal
amount of pentane and cooled to −30 °C to furnish 20 as red-orange
crystals (0.028 g, 78% yield). Data for 20 are as follows. Anal. Calcd
for C23H38N2O3Mo: C, 56.78; H, 7.87; N, 5.76. Found: C, 56.43; H,
1
7.84; N, 5.80. H NMR (400 MHz, benzene-d6): 1.00 (3H, d, J = 6.7
Hz) 1.12 (3H, d, J = 6.7 Hz), 1.15 (3H, d, J = 6.7 Hz), 1.28 (3H, d, J =
6.7 Hz), 1.47 (3H, d, J = 7.0 Hz), 1.60 (15H, s), 1.70 (3H, s), 3.09
(1H, m), 3.66 (1H, sp, J = 6.7 Hz), 3.96 (1H, t, J = 9.9 Hz), 4.04 (1H,
sp, J = 6.7 Hz), 5.19 (1H, dd, J = 9.6 Hz, J = 7.2 Hz). IR (KBr): νCO
1875 cm−1.
Synthesis of Cp*[N(iPr)C(CH3)N(iPr)]W(H)(η3-C4H7) (15). A
solution of 7 (0.047 g, 0.09 mmol) in 0.6 mL of benzene-d6 was
prepared and transferred to a Pyrex J. Young NMR tube equipped with
a Teflon seal. The headspace was evacuated, the tube was charged with
isobutene (15 psi), and the solution was photolyzed for 17 h. Again
the headspace was evacuated, the tube was charged with isobutene,
and the solution was photolyzed for 20 h. This process was repeated
once more, at which point nearly complete consumption of 7 was
ASSOCIATED CONTENT
* Supporting Information
The Supporting Information is available free of charge on the
ACS Publications website at DOI: 10.1021/acs.organo-
met.6b00131.
■
S
Crystallographic data (CIF)
1
observed by H NMR. Volatiles were removed in vacuo, the crude
material was extracted with pentane, and the extract was filtered
through a pad of Celite, concentrated, and cooled to −30 °C to furnish
15 as yellow crystals (0.032 g, 68% yield). Data for 15 are as follows.
Anal. Calcd for C22H40N2W: C, 51.17; H, 7.81; N, 5.42. Found: C,
50.03; H, 7.57; N, 5.31. 1H NMR (400 MHz, benzene-d6): −0.87 (1H,
t, JHH = 3.5 Hz, JWH = 54.7 Hz), 0.57 (1H, dd, J = 5.08 Hz, J = 1.8
Hz), 1.09 (3H, d, J = 6.9 Hz), 1.14 (3H, d, J = 6.9 Hz), 1.26 (3H, d, J
= 6.7 Hz), 1.33 (3H, d, J = 6.9 Hz), 1.36 (1H, br), 1.47 (1H, d, J = 3.2
Hz), 1.59 (3H, s), 1.73 (15H, s), 2.36 (1H, dd, J = 5.2 Hz, J = 5.0 Hz),
3.05 (3H, s), 3.50 (1H, sp, J = 7.0 Hz), 3.68 (1H, sp, J = 6.8 Hz).
13C{1H} NMR (125 MHz, benzene-d6): 11.2, 21.1, 24.2, 25.2, 26.0,
AUTHOR INFORMATION
Corresponding Author
*E-mail for L.R.S.: lsita@umd.edu.
Notes
■
3
1
The authors declare no competing financial interest.
ACKNOWLEDGMENTS
We thank the National Science Foundation (CHE-1361716)
for financial support of this work.
■
26.7, 30.5, 45.7, 47.6, 52.8, 53.3, 79.0, 100.4, 165.3.
Synthesis of Cp*[N(iPr)C(CH3)N(iPr)]W[η2-C(O)CH3](SCH3)
(16). A solution of 7 (0.075 g, 0.15 mmol) and dimethyl sulfide (65
μL, 0.89 mmol) in 4 mL of toluene was prepared and transferred to a
Pyrex J. Young NMR tube equipped with a Teflon seal. The solution
was photolyzed for 24 h, at which point volatiles were removed in
vacuo, and the resulting orange-red oil was extracted with pentane and
the extract filtered through a pad of Celite and pumped down to
dryness. The crude material was dissolved in minimal Et2O and cooled
to −30 °C to furnish 16 as an orange crystalline material (0.047 g, 59%
yield). Data for 16 are as follows. Anal. Calcd for C21H38N21OSW: C,
45.83; H, 6.96; N, 5.09. Found: C, 45.82; H, 6.82; N, 5.06. H NMR
(400 MHz, benzene-d6): 0.88 (3H, d, J = 7.2 Hz), 1.15 (3H, d, J = 7.2
Hz), 1.41 (3H, d, J = 6.5 Hz), 1.63 (3H, d, J = 6.5 Hz), 1.74 (3H, s),
1.91 (15H, s), 2.41 (3H, s), 2.43 (3H, s, JWH = 2.8 Hz), 3.03 (1H, sp, J
= 6.9 Hz), 4.13 (1H, sp, J = 6.9 Hz). 13C-labeled 16 was prepared by
an identical procedure using 13C-labeled 7. 13C{1H} NMR (125.6
REFERENCES
■
(1) Sustainable Industrial Chemistry. Principles, Tools and Industrial
Examples; Cavani, F., Centi, G., Perathoner, S., Trifiro, F., Eds.; Wiley-
VCH: Weinheim, Germany, 2009.
(2) Hirotsu, M.; Fontaine, P. P.; Epshteyn, A.; Zavalij, P. Y.; Sita, L.
R. J. Am. Chem. Soc. 2007, 129, 9284−9285.
(3) Hirotsu, M.; Fontaine, P. P.; Zavalij, P. Y.; Sita, L. R. J. Am. Chem.
Soc. 2007, 129, 12690−12692.
(4) Fontaine, P. P.; Yonke, B. L.; Zavalij, P. Y.; Sita, L. R. J. Am.
Chem. Soc. 2010, 132, 12273−12285.
(5) Yonke, B. L.; Reeds, J. P.; Zavalij, P. Y.; Sita, L. R. Angew. Chem.,
Int. Ed. 2011, 50, 12342−12346.
(6) Reeds, J. P.; Yonke, B. L.; Zavalij, P. Y.; Sita, L. R. J. Am. Chem.
Soc. 2011, 133, 18602−18605.
(7) Yonke, B. L.; Keane, A. J.; Zavalij, P. Y.; Sita, L. R. Organometallics
2012, 31, 345−355.
1
MHz, benzene-d6): δCO 275.7, JWC = 72 Hz.
Synthesis of Cp*[N(iPr)C(CH3)N(iPr)]Mo[C(O)CH(CH3)CH2O]
(19). To a solution of 1a (0.023 g, 0.05 mmol) in 2 mL of toluene
(8) Keane, A. J.; Zavalij, P. Y.; Sita, L. R. J. Am. Chem. Soc. 2013, 135,
9580−9583.
H
DOI: 10.1021/acs.organomet.6b00131
Organometallics XXXX, XXX, XXX−XXX

Organometallics
Article
(9) Keane, A. J.; Yonke, B. L.; Hirotsu, M.; Zavalij, P. Y.; Sita, L. R. J.
Am. Chem. Soc. 2014, 136, 9906−9909.
(26) For a recent review of stoichiometric and catalytic C−S bond
activation reactions, see: Wang, L.; He, W.; Yu, Z. Chem. Soc. Rev.
2013, 42, 599−621.
(27) For a recent review regarding the chemistry of metallaoxetanes,
see: Dauth, A.; Love, J. A. Chem. Rev. 2011, 111, 2010−2047.
(28) For an example of insertion of CO into a M−C bond of a
metallaoxetane, see: Hartwig, J. F.; Bergman, R. G.; Andersen, R. A.
Organometallics 1991, 10, 3344−3362.
(10) Yonke, B. L.; Reeds, J. P.; Fontaine, P. P.; Zavalij, P. Y.; Sita, L.
R. Organometallics 2014, 33, 3239−3242.
(11) Yonke, B. L.; Reeds, J. P.; Zavalij, P. Y.; Sita, L. R. Z. Anorg. Allg.
Chem. 2015, 641, 61−64.
(12) Farrell, W. S.; Zavalij, P. Y.; Sita, L. R. Angew. Chem., Int. Ed.
2015, 54, 4269−4273.
(13) Keane, A. J.; Farrell, W. S.; Yonke, B. L.; Zavalij, P. Y.; Sita, L. R.
Angew. Chem., Int. Ed. 2015, 54, 10220−10224.
(14) Farrell, W. S.; Zavalij, P. Y.; Sita, L. R. Submitted for publication.
(15) (a) Finn, P. A.; King, M. S.; Kilty, P. A.; McCarley, R. E. J. Am.
Chem. Soc. 1975, 97, 220−221. (b) Cotton, F. A.; Hall, W. T. Inorg.
Chem. 1978, 17, 3525−3528. (c) Cotton, F. A.; Hall, W. T. J. Am.
Chem. Soc. 1979, 101, 5094−5095. (d) Duchateau, R.; Williams, A. J.;
Gambarotta, S.; Chiang, M. Y. Inorg. Chem. 1991, 30, 4863−4866.
(e) Young, C. G.; Philipp, C. C.; White, P. S.; Templeton, J. L. Inorg.
Chem. 1995, 34, 6412−6414. (f) Tsai, Y.; Johnson, M. J. A.; Mindiola,
D. J.; Cummins, C. C.; Klooster, W. T.; Koetzle, T. F. J. Am. Chem.
Soc. 1999, 121, 10426−10427. (g) Segerer, U.; Blaurock, S.; Sieler, J.;
Hey-Hawkins, E. Organometallics 1999, 18, 2838−2842. (h) Tsai, Y.;
Stephens, F. H.; Meyer, K.; Mendiratta, A.; Gheorghiu, M. D.;
Cummins, C. C. Organometallics 2003, 22, 2902−2913. (i) Cross, J. L.;
Garrett, A. D.; Crane, T. W.; White, P. S.; Templeton, J. L. Polyhedron
2004, 23, 2831−2840.
(16) Additional details are provided in the Experimental Section.
(17) (a) Dewar, M. J. S. Bull. Chem. Soc. Fr. 1951, 18, C71−C79.
(b) Chatt, J.; Duncanson, L. A. J. Chem. Soc. 1953, 2939−2947.
(18) For reviews on transition-metal agostic interactions, see:
(a) Brookhart, M.; Green, M. L. H. J. Organomet. Chem. 1983, 250,
395−408. (b) Brookhart, M.; Green, M. L. H.; Wong, L.-L. Prog. Inorg.
Chem. 1988, 36, 1−124. (c) Brookhart, M.; Green, M. L. H.; Parkin,
G. Proc. Natl. Acad. Sci. U. S. A. 2007, 104, 6908−6914.
(19) For a review of group 6 carbonyl η2-alkene complexes, see:
́
Szymanska-Buzar, T. Coord. Chem. Rev. 2006, 250, 976−990.
(20) For examples of group 6 carbonyl η2-alkene complexes prepared
thermally, see: (a) King, R. B.; Fronzaglia, A. F. Inorg. Chem. 1966, 5,
1837−1846. (b) Lai, C.-H.; Cheng, C.-H.; Chou, W.-C.; Wang, S.-L.
Organometallics 1993, 12, 1105−1112.
(21) For the molecular structures of selected tungsten carbonyl η2-
alkene complexes prepared photolytically, see: (a) Gor
A.; Szymanska-Buzar, T. Organometallics 2004, 23, 3037−3046.
(b) Gorski, M.; Kochel, A.; Szymanska-Buzar, T. Inorg. Chem.
Commun. 2006, 9, 136−138.
́
ski, M.; Kochel,
́
́
́
(22) For molecular structures of non-carbonyl group 6 metal η2-
alkene complexes, see: (a) Sharp, P. R. Organometallics 1984, 3, 1217−
1223. (b) Blomberg, M. R. A.; Siegbahn, P. E. M.; Svensson, M. J. Phys.
Chem. 1992, 96, 9794−9800. (c) Dyer, P. W.; Gibson, V. C.; Howard,
J. A. K.; Whittle, B.; Wilson, C. Polyhedron 1995, 14, 103−111.
(d) Tsang, W. C. P.; Jamieson, J. Y.; Aeilts, S. L.; Hultzsch, K. C.;
Schrock, R. R.; Hoveyda, A. H. Organometallics 2004, 23, 1997−2007.
(e) Marinescu, S. C.; King, A. J.; Schrock, R. R.; Singh, R.; Muller, P.;
Takase, M. K. Organometallics 2010, 29, 6816−6828. (f) Hanna, B. S.;
MacIntosh, A. D.; Ahn, S.; Tyler, B. T.; Palmore, G. T. R.; Williard, P.
G.; Bernskoetter, W. H. Organometallics 2014, 33, 3425−3432.
(g) Zhang, Y.; Williard, P. G.; Bernskoetter, W. S. Organometallics
2016, 35, 860−865.
(23) (a) Henderson, R. A.; Hughes, D. L.; Macdonald, C. J.; Oglieve,
K. E. Inorg. Chim. Acta 1997, 259, 107−117. (b) Adams, C. S.;
Legzdins, P.; Tran, E. J. Am. Chem. Soc. 2001, 123, 612−624. (c) Ng,
S. H. K.; Adams, C. S.; Hayton, T. W.; Legzdins, P.; Patrick, B. O. J.
Am. Chem. Soc. 2003, 125, 15210−15223. (d) Chow, C.; Patrick, B.
O.; Legzdins, P. Organometallics 2012, 31, 8159−8171.
(24) For examples of structurally characterized group 6 compounds
bearing sulfide ligands, see: Adams, R. D.; Blankenship, C.; Segmuller,
̈
B. E.; Shiralian, M. J. Am. Chem. Soc. 1983, 105, 4319−4326.
(25) Debad, J. D.; Legzdins, P.; Batchelor, R. J.; Einstein, F. W. B.
Organometallics 1993, 12, 2094−2102.
I
DOI: 10.1021/acs.organomet.6b00131
Organometallics XXXX, XXX, XXX−XXX