Synthesis of a Tris(phosphaalkene)phosphine Ligand and Fundamental Organometallic Reactions on Its Sterically Shielded Metal Complexes

Article abstract of DOI:10.1021/acs.organomet.6b00250

A new tris(phosphaalkene)phosphine ligand (1) was synthesized via phospha-Wittig methodology. Metalation of 1 with [RhCl(C₂H₄)₂]₂ and [IrCl(COE)₂]₂ (COE = cyclooctene) produced trigonal bip

Full text of DOI:10.1021/acs.organomet.6b00250

Article
pubs.acs.org/Organometallics
Synthesis of a Tris(phosphaalkene)phosphine Ligand and
Fundamental Organometallic Reactions on Its Sterically Shielded
Metal Complexes
†
†
†
†
†
Preston M. Miura-Akagi, Mika L. Nakashige, Caitlin K. Maile, Shelly M. Oshiro, Joshua R. Gurr,
†
§
⊥
‡
⊥
Wesley Y. Yoshida, A. Timothy Royappa, Colleen E. Krause, Arnold L. Rheingold,
,†
Russell P. Hughes, and Matthew F. Cain*
†
Department of Chemistry, University of Hawai‘i at Manoa, 2545 McCarthy Mall, Honolulu, Hawaii 96822, United States
̅
‡
Department of Chemistry, University of Hartford, 200 Bloomfield Avenue, West Hartford, Connecticut 06117, United States
§
6
128 Burke Laboratory, Department of Chemistry, Dartmouth College, Hanover, New Hampshire 03755, United States
⊥
Department of Chemistry, University of California, San Diego, 9500 Gilman Drive, La Jolla, California 92093, United States
*
S Supporting Information
ABSTRACT: A new tris(phosphaalkene)phosphine ligand (1) was synthesized
via phospha-Wittig methodology. Metalation of 1 with [RhCl(C H ) ] and
2
4 2 2
[
IrCl(COE) ] (COE = cyclooctene) produced trigonal bipyramidal metal
2 2
chlorides 2a (M = Rh) and 2b (M = Ir) in which the ligand coordinates in a
tetradentate fashion. X-ray crystallographic studies on 1·1.5THF, 2a·5CHCl3,
and 2b·2.5CHCl combined with DFT calculations revealed a pronounced
3
change in hybridization of the phosphaalkene phosphorus atoms upon
coordination to the Rh/Ir centers, resulting in highly sterically congested
metal complexes. Nucleophilic substitution on 2a with NaN afforded Rh−N
3
3
15
1
complex 3; computational analysis, IR spectroscopy, and N{ H} NMR
spectroscopy on isotopologue N-3 provided additional structural insights.
1
5
Halide abstraction of the chloride in 2b with AgOTf in the presence of acetonitrile afforded cationic Ir−NCMe complex 4.
Evidence of the bound acetonitrile unit was obtained by 2D NMR spectroscopy and deuterium labeling studies.
INTRODUCTION
The guiding principle of using sterics to dictate metal-
■
6
1
centered reactivity is evolving as ligands capable of electroni-
Tetradentate ligands featuring sterically demanding groups are
becoming increasingly popular, as the resulting metal center
contains a highly crowded, but well-defined binding pocket for
the activation of small molecules. Schrock and co-workers
successfully exploited bulky TREN ligand derivatives (TREN =
,2′,2′′-triaminotriethylamine; HIPT = hexaisopropylterphenyl,
shown in Scheme 1) to direct dinitrogen coordination into a
sterically protected trigonal bipyramidal (TBP) Mo pocket.
Subsequent treatment of the bound N unit with a proton
source and reducing agent resulted in the first example of
homogeneous and catalytic ammonia production.
7
2
cally influencing reactivity have experienced a surge of interest.
The most common examples of ligands engaging in this redox-
8
3
active/noninnocent behavior are pincer-derived metal com-
plexes, which undergo metal−ligand cooperativity via dear-
9
omatization/aromatization processes or by ligand-centered
2
reduction through easily accessible, low-lying, and extended π
10
4
networks. Recently though, the Peters lab has directly
observed this electronic influence with tetradentate XP -
3
2
11
12
13
14
supported (X = Si, C, B, and N ) TBP first-row metal
5
complexes designed to catalyze dinitrogen reduction (Scheme
15
16
17
1
). Fe and Co complexes ligated by the BP ligand
3
facilitated the catalytic conversion of N to NH (in the
2
3
Scheme 1. Two Different Modes of Metal-Catalyzed
Dinitrogen Reduction Featuring Tetradentate Ligands
presence of HBAr and KC ), while the performance of SiP
F
8
3
and CP analogues was stoichiometric at best; no N reduction
3
2
17
has been reported with the NP ligand set. Trivalent boranes
BAr ) are often counted as zero-electron ligands, but recent
3
1
8
(
3
evidence has suggested that the tricoordinate boron unit (BAr3)
in BP3 can act as a zero-, one-, or two-electron ligand
19
depending on the oxidation state of the metal complex. This
Received: March 29, 2016
©
XXXX American Chemical Society
A
DOI: 10.1021/acs.organomet.6b00250
Organometallics XXXX, XXX, XXX−XXX

Organometallics
Article
embedded ligand “flexibility” is believed to be the source of the
Scheme 2. Synthesis of 1
16,17
enhanced reactivity of the BP -supported metal complexes.
3
In designing a new tetradentate ligand capable of enforcing
reactivity at a single site, we wanted to combine the advantages
associated with steric control, while simultaneously introducing
an electronic component capable of enhancing reactivity
through redox-active/noninnocent processes. Electronically,
phosphaalkenes (R′PCHR) are analogues of the ubiquitous
2
0
CO ligand, possessing low-lying π* orbitals capable of acting
2
1
as π acceptors and recently implicated in several metal-
22
mediated bond activation events. However, unlike carbon in
CO, the phosphorus donor atom of a phosphaalkene exerts an
element of significant steric control. In order to prevent
oligomerization of the PC fragment, phosphorus must be
kinetically stabilized by a sterically substantial group such as
23
about the P−Mes* bonds on the NMR time scale; both t-Bu
signals were sharp and integrated in a 2:1 ratio. Mass
spectrometry and X-ray crystallography unequivocally con-
firmed the assignment of 1 (Figure 1). Although phosphaal-
Mes* (Mes* = 2,4,6-tri-tert-butylbenzene). If the organic
scaffolding of the targeted ligand (1) is based on tris(2-
24
carboxyaldehyde)triphenylphosphine, the installment of three
2
5
PMes* moieties creates a sterically protected binding pocket
for a TBP metal complex, which will be incorporated into a
potentially redox-active/noninnocent framework. The rigid
three-carbon linker between the apical P and the phosphaal-
kene donor atoms should enforce tetradentate binding, as
calculations indicated the apical P should adopt an endo
26
configuration (Chart 1). We report here the successful
synthesis of a tris(phosphaalkene)phosphine ligand and
reactivity of its corresponding Rh and Ir chloride complexes.
Chart 1. Design Parameters of Tetradentate Ligand 1
Figure 1. X-ray crystal structure of 1·1.5THF. The solvent and
disorder are not shown.
kenes are known to display remarkable stability to oxidation
29
and hydrolysis, we were pleased that 1 could also be handled,
manipulated, and purified under aerobic conditions. In both the
solid state and solution over the course of months, 1 showed no
RESULTS AND DISCUSSION
Ligand Synthesis. The desired ligand 1 was prepared in a
31
1
■
signs of decomposition by P{ H} NMR spectroscopy.
Electrochemistry on 1. In an effort to gauge potential
redox-active behavior of 1, its redox properties were probed
straightforward manner using well-precedented phospha-Wittig
2
7
31
methodology. Treatment of a frozen benzene mixture of
electrochemically. Cyclic voltammetry studies of 1 in
2
8
32
Mes*PCl2 and Zn dust with a room-temperature (RT)
dichloromethane (DCM) revealed a quasi-reversible system
solution of PMe in benzene generated the phosphinidene
at −1.56 V, while in tetrahydrofuran (THF), the wave was
3
29
transfer agent Mes*PPMe (A). Addition of a freshly
shifted to −1.81 V (Figure 2). Similar reductions with
3
filtered solution of A to triphenylphosphine-derived tris-
phosphaalkene-based pincer ligands have been attributed to
2
4
32a,33
(
aldehyde) B, followed by heating to 60 °C for 16 h,
the accessibility of the low-lying π* orbitals.
An additional
afforded 1 in 79% yield (Scheme 2).
anodic peak was observed at 0.62 V in DCM, tentatively
assigned as oxidation of the apical phosphorus. However, bulky
triphenylphosphine derivatives can exhibit complicated electro-
chemical behavior due to an interplay between more stable
The expected doublet/quartet pattern of 1 was observed by
3
1
1
4
30
1
P{ H} NMR spectroscopy ( J = 30 Hz).
H NMR
PP
spectroscopy revealed that the phosphaalkene units were all
present in the E conformation (δ 8.57, J = 25 Hz).
2
27
34
radical cations and pronounced structural reorganization. In
HP
Restricted rotation about the P−Mes* bonds was indicated by
THF, a more complicated series of weak anodic features was
noted at −0.12, 0.48, and 0.99 V, respectively. The origin of
these secondary electrochemical waves is unidentified.
1
the presence of one broad and one sharp t-Bu signal in the H
NMR spectrum. Warming to 60 °C resulted in fast rotation
B
DOI: 10.1021/acs.organomet.6b00250
Organometallics XXXX, XXX, XXX−XXX

Organometallics
Article
Likewise, reaction of 1 with 0.6 equiv of [IrCl(COE)2]2
COE = cyclooctene) in benzene at 40 °C afforded trigonal
bipyramidal Ir(I) complex 2b in 58% yield. The P{ H} NMR
(
31
1
spectrum displayed a distinctly shifted doublet/quartet pattern
2
with increased J coupling (34 Hz), indicating the ligand had
PP
coordinated in a tetradentate fashion. Complex 2b was further
1
13
1
characterized by H and C{ H} NMR spectroscopy, mass
spectrometry, and X-ray crystallography (Figure 4).
Figure 2. Cyclic voltammograms of 1 in a 0.1 M solution of
[
nBu N][PF ] in DCM (left, in blue) and THF (right, in red). Scan
4 6
+
rate = 100 mV/s, referenced to the Fc/Fc couple.
Synthesis of Rh(I) and Ir(I) Chloride Complexes.
Despite its substantial steric profile, we envisioned 1 acting as
a multidentate ligand to a single metal center. Addition of a
solution of 1 in benzene to 0.5 equiv of [RhCl(C H ) ]
2
4 2 2
resulted in the generation of trigonal bipyramidal Rh(I)
35
complex 2a (Scheme 3).
Scheme 3. Synthesis of 2a/b
Figure 4. X-ray crystal structure of 2b·2.5CHCl . The solvent and
3
disorder are not shown.
A comparison of the solid-state structures of 1 and 2a/b
provided an opportunity to analyze the effect of coordination
on the new tris(phosphaalkene)phosphine ligand. Selected
bond lengths and angles are documented in Table 1.
Table 1. Selected Bond Lengths (Å) and Angles (deg)
Highlight the Structural Consequences of Coordination of 1
to Rh and Ir Centers
The tetradentate binding mode of 1 in Rh(I) complex 2a was
31
1
confirmed by P{ H} NMR spectroscopy, which displayed the
1
2
anticipated doublet of doublets pattern ( J
= 169, J = 44
Rh−P
PP
1
2a·CHCl3
1.817(3)
2b·CHCl3
Hz) for the equivalent phosphaalkene groups and (over-
a
1
2
P
1
−C
1.838(2)
1.825(2)
lapping) doublet of quartets ( J
= 99, J = 44 Hz)
Rh−P
PP
1
1
.840(2)
.838(2)
1.820(3)
splitting for the apical phosphorus unit. Recrystallization from a
concentrated chloroform solution layered with acetonitrile
afforded 2a in 95% yield. The structure of 2a was
unambiguously determined by X-ray crystallography (Figure 3).
1.826(3)
a
P C
1.679(2)
1.677(2)
1.677(2)
101.74(9)
1.673(4)
1.679(3)
2
P C
1.673(4)
3
P C
1.673(4)
4
a
C−P −C
103.84(16)
103.91(16)
102.93(16)
111.80(17)
111.91(17)
109.88(17)
bound P sp
103.48(9)
1
1
1
02.05(9)
00.54(9)
a
C−P C
100.91(10)
100.11(10)
99.93(10)
111.11(12)
2
C−P C
3
C−P C
4
.92
2.25
1.26
2.33
hybridization of P1
lone pair sp0
bound P sp
bound P sp
hybridization of P2,3,4 lone pair sp0.50 bound P sp
1.34
a
Three-fold axis present.
Undoubtedly, the most striking feature upon coordination of
1
to Rh(I) and Ir(I) centers was the increase in the C−PC
angles. The free ligand displayed typical bond angles (C−P
C) around 100 degrees, consistent with high p character in the
36
P−C sigma bonds. However, the formation of complexes 2a/
b resulted in an enlargement of the angles about all three
phosphaalkene phosphorus atoms, indicating a significant
increase in the s character of the P−C sigma bonds; DFT
Figure 3. X-ray crystal structure of 2a·5CHCl . The solvent and
3
disorder are not shown.
C
DOI: 10.1021/acs.organomet.6b00250
Organometallics XXXX, XXX, XXX−XXX

Organometallics
Article
3
7
calculations support this finding (Table 1). Le Floch and co-
workers observed similar structural adaptions with a
dibenzofuran-derived phosphaalkene ligand upon generation
purified by filtration and fully characterized by NMR
spectroscopy, mass spectrometry, and elemental analysis.3
9
In agreement with related late metal azide complexes, the
29
−1
of group 11 metal complexes. The widening of the C−PC
angles forces the Mes* groups into closer proximity to the
metal center, creating a binding pocket that is more narrow and
sterically protected than we expected.
The space-filling diagram depicted in Figure 5 highlights this
pronounced effect. A side view of 2a appears to show an “all-
IR spectrum of 3 showed a strong band at 2048 cm (DFT
−
1
37
15
15
predicted: 2044 cm ), with the N isotopologue ( N-3),
15
synthesized from Na N (98% terminally labeled; CAS:
3
−1
609374), displaying a stretching vibration at 2037 cm . The
P{ H} NMR spectrum (CDCl ) of N-3 exhibited additional
31
1
15
3
splitting of the apical P resonance, indicative of the introduction
15
of another NMR-active nuclei ( N, I = 1/2). At RT, the
15
1
N{ H} NMR spectrum (CDCl ) showed a single signal (δ
3
−
242.2); however, upon cooling to −60 °C, the expected two
signals were observed at −246.5 (singlet, N ) and −346.2 (dd,
χ
1
2
J
= 32, J
= 15 Hz, N ) ppm, consistent with an intact
Rh−N
P−N α
15
40
Rh− N unit (Figure 6). Related temperature-dependent
3
Figure 5. Space-filling diagrams of 2a. On the left is a side view; on the
right is a top view looking down the Rh−Cl bond. The hydrogens are
included in the top view.
carbon cavity”, and only the smallest sections of phosphorus
atoms can be observed (gold-colored atoms). However, viewing
the space-filling diagram down the Rh−Cl bond reveals a
narrow and sterically encumbered access point (chlorine =
Figure 6. 15N{ H} NMR spectrum (CDCl , −60 °C) of 15N-3.
1
3
1
3
1
1
broadening and sharpening of NMR signals have been reported
green-colored atom). In addition, the C{ H} and H NMR
spectra of 2a and 2b show the presence of restricted rotation
about the P−Mes* bond, rendering all six carbon atoms on the
aryl ring including both protons and the ortho t-Bu signals
with 15N-labeled phosphazide-based (RNN NPPh ) tungsten
15
3
complexes and were attributed to an unidentified dynamic
process. Alternatively, the NMR observations may be the
result of adjacent N quadrupole nuclei.
DFT calculations established the bent azide isomer was
considerably lower in energy than the linear isomer (∼10 kcal/
mol). In fact, the linear azide is not a minimum, but a second-
order saddle point between bent azide forms and, therefore, not
a true viable species. Any bent to linear conversion is low
energy and would be fast on the NMR time scale.
41
14
1
inequivalent. Variable-temperature H NMR experiments reveal
this behavior is maintained up to 60 °C.
Substitution on Rh(I) Complexes. Despite the congested
environment of 2a, we anticipated that small nucleophiles
would enter the coordination sphere and displace the chloride,
generating Rh-based precursors of interest. Treatment of a
37
A
solution of 2a in chloroform with 15 equiv of NaN resulted in
3
computed structure of 3 is shown in Figure 7.
smooth, but slow conversion (∼72 h) to azido complex 3 in
near-quantitative yield (Scheme 4). The sluggish reaction is
Scheme 4. Synthesis of 3
likely due to solubility problems, as the use of a more soluble
azide source such as [PNN][N ] (PPN = bis-
3
38
(
triphenylphosphine)iminium; Ph PNPPh ) accelerated
3
3
the reaction rate considerably. The conversion of 2a to 3 was
1
monitored by H NMR spectroscopy, which revealed a
pronounced shift in the phosphaalkene (ArCHPMes*)
Figure 7. Computed structure of 3 displaying the bent azide
functionality.
signal (CDCl : δ 8.16 to 7.86). The crude product (3) was
3
D
DOI: 10.1021/acs.organomet.6b00250
Organometallics XXXX, XXX, XXX−XXX

Organometallics
Article
It is well documented that M−N complexes will extrude N
CONCLUSIONS
3
2
■
4
2
43
photochemically and/or thermally, producing highly
reactive terminal metal nitrogen species. Recently, Smith and
co-workers harnessed this reactivity with a tris(carbene)borate-
This Article reported the synthesis and potential applications of
new tris(phosphaalkene)phosphine ligand 1. Upon coordina-
tion to a Rh(I)/Ir(I) center, the C−PC angles of 1
incorporating the phosphaalkene P atoms increased signifi-
cantly and created highly shielded late metal chlorides 2a and
supported Fe(II)−N /Fe(IV)N system to generate a
3
4
4
synthetic cycle for the aziridination of styrenes. We are
interested in developing related processes associated with
2
b, respectively. Rh−Cl complex 2a was converted into azido
4
5
ammonia production and other N atom functionalization
complex 3 by nucleophilic substitution, while Ir−Cl complex
4
6
with Rh and hypothesize the implementation of a metal−
2
b underwent halide abstraction to generate cationic Ir−NCMe
ligand framework with a sterically protected M−N unit will
3
complex 4. Future investigations using 3 and 4 as precursors
control reactivity and selectivity.
will target new bond activation and catalytic processes.
Halide Abstraction on Ir(I) Complexes. Similar sterically
shielded and potentially reactive sites should also be accessible
from 2b. To investigate if a vacant coordinate site could be
generated, we treated 2b with AgOTf in the presence of
EXPERIMENTAL SECTION
■
All manipulations were conducted under a nitrogen or argon
atmosphere in a MBraun drybox or using Schlenk techniques unless
otherwise specified. All glassware was oven-dried prior to use.
Anhydrous-grade acetonitrile, pentane, toluene, benzene, ether,
dichloromethane, and THF were purchased from commercial
suppliers (Aldrich or Acros) and pumped directly into the glovebox.
All solvents were stored over oven-activated 4 Å molecular sieves
CH CN at RT to afford the acetonitrile-trapped Ir(I) salt 4
3
4
7
(
Scheme 5).
Scheme 5. Synthesis of 4
(
Aldrich). The starting materials and reagents [RhCl(C H ) ] ,
2 4 2 2
15
[
IrCl(COE) ] , AgOTf, NaN (and Na N ), and Zn dust were
2 2 3 3
purchased from commercial suppliers. PMe3 was purchased from
28
Strem and dried over molecular sieves prior to use. Mes*PCl and
2
2
4
tris(aldehyde) B were prepared according to literature protocols.
NMR spectra were obtained on Varian spectrometers operating at
either 300 or 500 MHz; all spectra shown in the Supporting
Information are on the 500 MHz spectrometer. NMR chemical shifts
are reported as ppm relative to tetramethylsilane and are referenced to
1
3
1
the residual proton or C signal of the solvent ( H CDCl , 7.27 ppm;
3
1
13
13
H C D , 7.16 ppm; C CDCl , 77.16 ppm; C C D , 128.06 ppm).
6
6
3
6
6
Mass spectrometry was conducted at the University of California at
Irvine (Dr. J. Greaves) on compound 1. Other mass spectroscopic data
were obtained at the University of Hawai‘i at Manoa on an Agilent
̅
6
545 Accurate-Mass Q-TOF LC/MS (NSF CHE-1532310). Analytical
data were obtained from the CENTC Elemental Analysis Facility at
the University of Rochester, funded by NSF CHE-0650456. All X-ray
quality crystals were analyzed at the Small Molecule X-ray
Crystallography Facility located at the University of California at
San Diego.
Complex 4 was easily identified by 31P{ H} NMR spectros-
1
copy (C D ) due to its significantly upfield shifted
phosphaalkene and apical P signals. In addition, the H
NMR spectrum (C D ) displayed a new singlet at 2.39 ppm,
integrating in a 1:1 ratio (3H:3H) with the phosphaalkene
protons. A 13C− H NMR HSQC experiment confirmed this
signal corresponds to the methyl group of the bound
6
6
48
1
Synthesis of 1. Mes*PCl (100 mg, 0.288 mmol) and Zn dust (94
2
6
6
mg, 1.44 mmol, 5 equiv) were combined in a vial, and 2 mL of
benzene was added. The heterogeneous mixture was cooled in the
glovebox freezer (−35 °C) for 15 min. Treatment of the frozen
1
benzene mixture with a room-temperature solution of PMe (56 mg,
3
0
.736 mmol, 2.6 equiv) in 3 mL of benzene resulted in an olive green
acetonitrile unit. Conducting the halide abstraction in
CD CN resulted in the disappearance of the H NMR signal
reaction mixture. The reaction mixture was stirred for 2−2.5 h at room
temperature and filtered through a Celite plug. The bright yellow-
1
3
31
at 2.39 ppm, lending further support to our assignment.
orange filtrate (Mes*PPMe , P NMR (C H ): δ 4.2 and 134.3, J =
3
6
6
1
3
1
19
1
Complex 4 was further characterized by C{ H} and F{ H}
NMR spectroscopy and mass spectrometry.
580 Hz) was added to solid tris(aldehyde) B (20 mg, 0.058 mmol, 1/5
equiv), affording a homogeneous bright yellow solution. The solution
was transferred to a J-Young tube, sealed, brought outside of the
Generating open coordination sites on metal complexes
ligated by multidentate ligands provides the opportunity to
introduce typically unreactive substrates into a reactive
31
glovebox, and heated to 60 °C for 16 h. P NMR spectroscopy
confirmed complete conversion to the desired product. Identifiable
byproducts included unreacted Mes*PPMe , PMe (O) (δ 31),
3
3
4
,5
coordination sphere.
For example, pioneering work by
PMe (δ −62), and PH Mes* (δ −130). The contents of the J-Young
3
2
tube were then transferred to a vial (and exposed to oxygen) and
concentrated under vacuum. The yellow residue was dissolved in 3 mL
of pentane and filtered through a Celite plug. The filtrate was
concentrated under vacuum and recrystallized from 5 mL of a 50:50
solution of THF and acetonitrile at −20 °C to afford a yellow
crystalline solid (50 mg, 0.044 mmol, 76%). Crystals suitable for X-ray
diffraction were obtained by dissolving 25 mg of the ligand in 4 mL of
a 50:50 solution of THF and acetonitrile at 0 °C. On scale-up to 1 g of
Jensen and co-workers demonstrated that an unsaturated 14-
+
electron Ir(PCP) pincer fragment can dehydrogenate alkanes
49,50
to afford alkenes.
Milstein has shown late metal complexes
(
usually Ru or Ir) featuring vacant coordination sites and
dearomatized PNN and PNP pincer ligands can activate other
inert and difficult to functionalize substrates such as water,
9
ammonia, and related molecules with strong bonds. Upcoming
Mes*PCl , 467 mg of 1 was isolated (79% yield); 1/5.5 equiv of B is
2
studies will investigate exposing the “naked” Ir center to
typically unreactive substrates with the goal of uncovering new
modes of reactivity.
employed. Elemental analysis data were consistently low (three
attempts) in carbon, for example: Anal. Calcd for C H102P4: C, 79.89;
75
H, 9.12. Found: C, 79.33; H, 9.30. HRMS: m/z calcd for C H102P4Na
7
5
E
DOI: 10.1021/acs.organomet.6b00250
Organometallics XXXX, XXX, XXX−XXX

Organometallics
Article
+
31
1
(
M + Na) 1149.6830, found 1149.6853. P{ H} NMR (CD Cl ): δ
vacuum, affording the product as a dark brown solid (69 mg, 0.54
2
2
2
66.5 (d, J = 30 Hz, 3P, PC), −32.3 (quartet, J = 30 Hz, 1P, PAr ).
mmol, 98%). Anal. Calcd for C H P RhN : C, 70.79; H, 8.08; N,
3
75 102
4
3
1
H NMR (CD Cl ): δ 8.57 (dd, J = 25, 5.5 Hz, 3H, Mes*PCHAr),
3.30. Found: C, 70.52; H, 8.37; N, 3.15. HRMS: m/z calcd for
2
2
3
1
1
7
7
1
.88 (br m, 3H, Ar), 7.30 (t, J = 7.5 Hz, 3H, Ar), 7.25 (6H, Mes*),
.11(t, J = 7.5 Hz, 3H, Ar), 6.55 (dd, J = 7.5, 4.5 Hz, 3H, Ar), 1.30 and
.17 (overlapping singlets, 1 sharp and 1 broad, 81H, Mes*). C{ H}
[C75H P RhN ] 1271.6079, found 1271.6071. P{ H} NMR
102 4 3
(CDCl
): δ 230.3 (dd, JRh−P = 168, JPP = 48 Hz, PC), 37.0
3
13
1
1
(overlapping doublet of quartets, JRh−P = 97, JPP = 48 Hz, apical P). H
NMR (CD Cl ): δ 173.5 (dd, J = 36, 20.5 Hz, PC), 154.2 (Ar),
NMR (CDCl
3
): δ 7.86 (br, 3H, PC), 7.39−7.34 (overlapping, 9H, 2
2
2
1
49.7 (Ar), 145.3 (dd, J = 25, 14 Hz, Ar), 139.8 (d, J = 56 Hz, Ar),
35.1 (Ar), 134.8 (t, J = 11 Hz, Ar), 129.3 (Ar), 128.3 (Ar), 127.1 (d, J
Mes* and Ar), 7.09 (t, J = 7.5 Hz, 3H, Ar), 7.06 (t, J = 7.5 Hz, 3H, Ar),
1
6.25 (dd, J = 7.5, 12 Hz, 3H, Ar), 1.45 (27H, t-Bu), 1.29 (27H, t-Bu),
1.06 (27H, t-Bu). 13C{ H} NMR (CDCl ): δ 155.4 (Ar), 153.3 (Ar),
1
=
(
27 Hz, Ar), 121.9 (Ar), 38.2 (CMe ), 35.2 (t-Bu), 33.7 (CMe ), 31.5
3
3
3
t-Bu). 13C NMR assignments were aided by DEPT experiments.
Synthesis of 2a. A solution of 1 (126 mg, 0.112 mmol) in 5 mL of
152.9 (br, PC), 150.1 (Ar), 144.3 (d, J = 12 Hz, Ar), 133.1 (Ar),
132.6 (br, Ar), 130.9 (two overlapping Ar signals), 126.8 (d, J = 8 Hz,
Ar), 123.2 (Ar), 122.9 (Ar), 116.1 (br), 39.5 (CMe ), 38.6 (CMe ),
benzene was added to [RhCl(C H ) ] (22 mg, 0.057 mmol, 0.5
2
4
2
2
3
3
1
3
equiv), producing a dark reaction mixture. The reaction mixture was
stirred for 24 h at room temperature and then concentrated under
vacuum. Subsequently, the crude product was dissolved in 3 mL of
chloroform and filtered through a Celite plug. The filtrate was layered
with acetonitrile (10 mL) and placed in the freezer at −35 °C. After
standing overnight, a dark solid precipitated (134 mg, 0.106 mmol,
34.8 (CMe ), 34.0 (t-Bu), 33.9 (t-Bu), 31.2 (t-Bu). C NMR
3
1
5
assignments were aided by DEPT experiments. The N-labeled
isotopologue 15N-3 was synthesized in an analogous fashion. N{ H}
15
1
15
1
NMR (CDCl , RT): δ −242.2. N{ H} NMR (CDCl , −60 °C): δ
3
3
−246.5 (singlet, N ), −346.2 (dd, J
= 32, J
= 15 Hz, N ).
χ
Rh−N
P−N
α
Synthesis of 4. A solution of 2b (36 mg, 0.027 mmol) in 1 mL of
benzene with three drops of acetonitrile was added to solid AgOTf (8
mg, 0.032 mmol, 1.2 equiv) and stirred for 1 h at room temperature.
The resulting dark red solution was filtered through a Celite plug. The
filtrate was layered with pentane and placed in the freezer at −35 °C,
95%, 2 crops) from solution. X-ray quality crystals were obtained from
an additional recrystallization of 10 mg of 2a in 1 mL of chloroform
layered with 3 mL of acetonitrile at −35 °C. Elemental analysis data
were consistently low (3 attempts) in carbon, for example: Anal. Calcd
for C H P RhCl: C, 71.16; H, 8.12. Found: C, 69.87; H, 8.05.
75
102
4
resulting in the precipitation of a dark red solid (22 mg, 0.015 mmol,
+
+
HRMS: m/z calcd for [C H P RhCl (M + H) ]: 1265.5754, found
55%). HRMS: m/z calcd for [C H105IrNP4 (M − NCMe) ]
75
103
4
77
265.5740. 31P{ H} NMR (CDCl ): δ 241.1 (dd, J
1
= 169, JPP = 44
= 99, JPP = 44
31
1
1
1360.6827, found 1360.6849. P{ H} NMR (C D ): δ 198.2 (d, J =
3
Rh−P
6 6
Hz, PC), 39.2 (overlapping doublet of quartets, J
37 Hz, PC), −15.0 (quartet, J = 37 Hz, apical P). An unidentified
Rh−P
1
1
Hz, apical P). H NMR (CDCl ): δ 8.16 (br, 3H, PC), 7.39 (t, J =
impurity is present at 24.9 ppm (singlet). H NMR (C D ): δ 8.23 (br,
3
6
6
7
.5 Hz, 3H, Ar), 7.32 (3H, Mes*), 7.27 (3H, Mes*), 7.15 (br t, J = 6
3H, PC), 7.75 (3H, Mes*), 7.57 (3H, Mes*), 6.95 (t, J = 7.5 Hz,
3H, Ar), 6.69 (overlapping, 6H, 2 Ar), 6.32 (dd, J = 7.5, 13 Hz, 3H,
Ar), 2.39 (3H, NCMe), 1.47 (27H, t-Bu), 1.37 (27H, t-Bu), 1.20
(27H, t-Bu). 13C{ H} NMR (C D ): δ 154.7 (Ar), 153.5 (Ar), 153.0
Hz, 3H, Ar), 7.09 (t, J = 7.5 Hz, 3H, Ar), 6.32 (dd, J = 8, 12 Hz, 3H,
Ar), 1.28 (27H, t-Bu), 1.25 (27H, t-Bu), 1.08 (27H, t-Bu). 13C{ H}
1
1
NMR (CDCl ): δ 155.7 (Ar), 151.9 (Ar), 150.3 (PC), 149.7 (Ar),
3
6
6
144.4 (d, J = 12 Hz, Ar), 133.5 (Ar), 130.7 (br, likely two overlapping
(Ar), 144.6 (br, PC), 143.6 (d, J = 11 Hz, Ar), 133.5 (d, J = 7 Hz,
Ar signals), 129.0 (Ar), 126.4 (Ar), 122.7 (Ar), 122.3 (Ar), 115.7 (br,
Ar), 39.9 (CMe ), 38.8 (CMe ), 34.8 (CMe ), 34.5 (t-Bu), 33.3 (t-Bu),
3
Ar), 131.8 (Ar), 130.9 (br, Ar), 124.5 (Ar), 124.0 (Ar), 39.9 (CMe ),
3
3
3
3
39.3 (CMe ), 35.5 (CMe ), 34.1 (t-Bu), 32.9 (t-Bu), 31.5 (t-Bu), 4.4
3
3
1.2 (t-Bu). 13C NMR assignments were aided by DEPT experiments.
Synthesis of 2b. A solution of 1 (100 mg, 0.087 mmol) in 4 mL of
(
NCMe). 19F{ H} NMR (C D ): δ −77.8 (OTf). Note: Some of the
1
6
6
13 1
Ar peaks are obscured by the strong C D /C H signal. The C{ H}
and H NMR are complicated by the fact that complex 4 is somewhat
6
6
6
6
1
benzene was added to [IrCl(COE) ] (48 mg, 0.052 mmol, 0.6 equiv),
2
2
producing a dark reaction mixture. The reaction mixture was
transferred to a screw-top Teflon Schlenk bomb, heated at 40 °C
for 24 h with stirring, and then concentrated under vacuum. The crude
product was dissolved in pentane and filtered through a Celite plug.
The filtrate was concentrated under vacuum, and the residue was
washed with cold acetonitrile (−35 °C) to wash away any remaining
COE. The crude solid was dissolved in 1 mL of chloroform and
layered with 1 mL of acetonitrile, resulting in the precipitation of a
dark crystalline solid at room temperature (70 mg, 0.050 mmol, 58%, 2
crops). Dissolving 10 mg of 2b in a 3 mL 1:2 solution of chloroform
and acetonitrile at −35 °C produced X-ray quality crystals. Elemental
analysis data were consistently off (three attempts), for example: Anal.
Calcd for [C H P IrCl]: C, 66.47; H, 7.59. Found: C, 70.90; H,
unstable; prolonged exposure to vacuum, the presence of CHCl , and
even standing in solution resulted in unidentified decomposition
pathways.
3
DFT Computational Details. Full-molecule calculations were
5
1
carried out using the hybrid M06 functional and the LACV3P**
5
2
53
basis, as implemented in the Jaguar suite of programs. Natural
5
4
bond orbital calculations were performed on the optimized structure
5
5
using NBO 6.0, as implemented in Jaguar. Computed structures
were confirmed as minima by calculating the vibrational frequencies
using second-derivative analytic methods and confirming the absence
of imaginary frequencies for minima. Thermodynamic quantities were
calculated assuming an ideal gas and zero point energy corrected.
Graphical representations of structures were made using the CYLView
75
102 4
+
8
.26. HRMS: m/z calcd for [C H P IrCl (M + H) ] 1355.6328,
56
75
103
4
program.
31
1
found 1355.6351. P{ H} NMR (CDCl ): δ 211.0 (d, J = 34 Hz, P
3
Electrochemistry Experimental Details. All electrochemical
measurements were conducted on a CHI 1040 electrochemical
analyzer with a three-electrode system. A glassy carbon electrode, a
1
C), −8.4 (quartet, J = 34 Hz, apical P). H NMR (C D ): δ 8.22 (br,
6
6
3
6
1
H, PC), 7.58 (6H, overlapping Mes*), 6.96 (t, J = 7.5 Hz, 3H, Ar),
.85 (t, J = 6 Hz, 3H, Ar), 6.72 (t, J = 7.5 Hz, 3H, Ar), 6.58 (dd, J = 8,
2.5 Hz, 3H, Ar), 1.57 (27H, t-Bu), 1.39 (27H, t-Bu), 1.31 (27H, t-
+
platinum wire, and a Ag/Ag electrode were employed as the working,
+
auxiliary, and reference electrodes, respectively. The Fc/Fc couple
13
1
Bu). C{ H} NMR (CDCl ): δ 155.7 (Ar), 151.9 (Ar), 149.9 (Ar),
3
was employed as the internal standard. Cyclic voltammetry (CV) was
1
1
44.2 (d, J = 11 Hz, Ar), 140.0 (br, PC), 133.4 (Ar), 130.5 (Ar),
performed in a 0.1 M solution of [Bu N][PF ] in anhydrous
4
6
30.0 (br, Ar), 127.5 (Ar), 125.4 (d, J = 10 Hz, Ar), 122.8 (Ar), 122.0
dichloromethane or tetrahydrofuran at room temperature under a
nitrogen atmosphere. Individual CV plots are shown in the Supporting
Information.
(
Ar), 114.0 (br, Ar), 39.9 (CMe ), 39.1 (CMe ), 34.8 (CMe ), 34.3 (t-
3 3 3
13
Bu), 33.0 (t-Bu), 31.2 (t-Bu). C NMR assignments were aided by
DEPT experiments.
Synthesis of 3. A solution of 2a (70 mg, 0.055 mmol) in 3 mL of
chloroform was added to NaN (54 mg, 0.83 mmol, 15 equiv) and
ASSOCIATED CONTENT
3
■
stirred for 72 h at room temperature. The progress of the reaction can
*
S
Supporting Information
1
be tracked by H NMR spectroscopy (CDCl , [Rh]−Cl phosphaal-
3
The Supporting Information is available free of charge on the
ACS Publications website at DOI: 10.1021/acs.organo-
met.6b00250.
kene signal: δ 8.19 to [Rh]−N phosphaalkene signal: δ 7.89). After
full conversion to the azide complex, the dark reaction mixture was
3
filtered through a Celite plug, and the filtrate was concentrated under
F
DOI: 10.1021/acs.organomet.6b00250
Organometallics XXXX, XXX, XXX−XXX

Organometallics
Complete experimental details with NMR spectra
Article
(11) Mankad, N. P.; Whited, M. T.; Peters, J. C. Angew. Chem., Int.
Ed. 2007, 46, 5768−5771.
included, expanded details on electrochemistry and
individual CV plots, and full details on DFT computa-
tional methodology (PDF)
(
1
(
12) Creutz, S. E.; Peters, J. C. J. Am. Chem. Soc. 2014, 136, 1105−
115.
13) Synthesis of BP : Bontemps, S.; Bouhadir, G.; Dyer, P. W.;
3
X-ray structures (CIF)
Miqueu, K.; Bourissou, D. Inorg. Chem. 2007, 46, 5149−5151.
14) MacBeth, C. E.; Harkins, S. B.; Peters, J. C. Can. J. Chem. 2005,
(
(
CIF)
CIF)
(
83, 332−340.
Optimized Cartesian coordinates (XYZ)
(15) Chatt, J.; Dilworth, J. R.; Richards, R. L. Chem. Rev. 1978, 78,
5
(
89−625.
16) Anderson, J. S.; Rittle, J.; Peters, J. C. Nature 2013, 501, 84−87.
(17) Del Castillo, T. J.; Thompson, N. B.; Suess, D. L. M.; Ung, G.;
AUTHOR INFORMATION
Corresponding Author
E-mail: mfcain@hawaii.edu.
■
Peters, J. C. Inorg. Chem. 2015, 54, 9256−9262.
*
(18) (a) Hill, A. F. Organometallics 2006, 25, 4741−4743.
b) Crossley, I. R.; Hill, A. F.; Willis, A. C. Organometallics 2008,
(
Notes
2
(
7, 312−315.
The authors declare no competing financial interest.
19) (a) Moret, M.-E.; Zhang, L.; Peters, J. C. J. Am. Chem. Soc. 2013,
1
35, 3792−3795. (b) Moret, M.-E.; Peters, J. C. Angew. Chem., Int. Ed.
ACKNOWLEDGMENTS
M.F.C. thanks the University of Hawai‘i at Manoa for generous
■
2011, 50, 2063−2067.
(20) Le Floch, P. Coord. Chem. Rev. 2006, 250, 627−681.
(21) Magnuson, K. W.; Oshiro, S. M.; Gurr, J. R.; Yoshida, W. Y.;
Gembicky, M.; Rheingold, A. L.; Hughes, R. P.; Cain, M. F.
Organometallics 2016, 35, 855−859.
̅
start-up funds and laboratory space. M.F.C. also acknowledges
the UHM faculty for support and access to their chemical
inventories and the Strem Chemical Co., Sigma-Aldrich,
Chemglass Life Sciences, Fisher Scientific, and Wilmad-
Labglass for their generous discounts on chemicals and/or
laboratory equipment and supplies. In addition, Dr. Christian
Ehm provided excellent feedback on an early draft of the
manuscript, and William Brennessel (University of Rochester)
conducted elemental analyses on the new compounds.
(
22) (a) Chang, Y.-H.; Nakajima, Y.; Tanaka, H.; Yoshizawa, K.;
Ozawa, F. J. Am. Chem. Soc. 2013, 135, 11791−11794. (b) Chang, Y.-
H.; Nakajima, Y.; Tanaka, H.; Yoshizawa, K.; Ozawa, F. Organo-
metallics 2014, 33, 715−721. (c) Chang, Y.-H.; Takeuchi, K.; Wakioka,
M.; Ozawa, F. Organometallics 2015, 34, 1957−1962. (d) Lin, Y.-F.;
Nakajima, Y.; Ozawa, F. Dalton Trans. 2014, 43, 9032−9037.
(e) Nakajima, Y.; Okamoto, Y.; Chang, Y.-H.; Ozawa, F. Organo-
1
4
15
Discussions on N/ N NMR with Tom Apple (UHM)
were also extremely valuable.
metallics 2013, 32, 2918−2925. (f) Chang, Y.-H.; Nakajima, Y.; Ozawa,
F. Organometallics 2013, 32, 2210−2215. (g) Lin, Y.-F.; Ichihara, N.;
Nakajima, Y.; Ozawa, F. Organometallics 2014, 33, 6700−6703.
(h) Nakajima, Y.; Shiraishi, Y.; Tsuchimoto, T.; Ozawa, F. Chem.
Commun. 2011, 47, 6332−6334. (i) Nakajima, Y.; Nakao, Y.; Sakaki,
S.; Tamada, Y.; Ono, T.; Ozawa, F. J. Am. Chem. Soc. 2010, 132,
REFERENCES
■
(
1) (a) Schrock, R. R. Acc. Chem. Res. 1997, 30, 9−16. (b) Naiini, A.
A.; Menge, W. M. P. B.; Verkade, J. C. Inorg. Chem. 1991, 30, 5009−
9
(
2
(
934−9936.
23) Shah, S.; Protasiewicz, J. D. Coord. Chem. Rev. 2000, 210, 181−
01.
24) Whitnall, M. R.; Hii, K. K.; Pett-Thornton, M.; Kee, T. P. J.
Organomet. Chem. 1997, 529, 35−50.
25) Yam, M.; Chong, J. H.; Tsang, C.-W.; Patrick, B. O.; Lam, A. E.;
Gates, D. P. Inorg. Chem. 2006, 45, 5225−5234.
26) Sidorkin, V. F.; Doronina, E. P. Organometallics 2009, 28, 5305−
315.
27) (a) Shah, S.; Protasiewicz, J. D. Chem. Commun. 1998, 1585−
586. (b) Shah, S.; Protasiewicz, J. D. Coord. Chem. Rev. 2000, 210,
81−201. (c) de Vaumas, R.; Marinetti, A.; Ricard, L.; Mathey, F. J.
5
(
2
012. (c) Verkade, J. G. Acc. Chem. Res. 1993, 26, 483−489.
2) (a) Sietzen, M.; Wadepohl, H.; Ballmann, J. Organometallics
014, 33, 612−615. (b) Sietzen, M.; Wadepohl, H.; Ballmann, J. Inorg.
Chem. 2014, 53, 4144−4153. (c) Sietzen, M.; Batke, S.; Merz, L.;
Wadepohl, H.; Ballmann, J. Organometallics 2015, 34, 1118−1128.
(
(
4
(
(
6
4
d) Sietzen, M.; Wadepohl, H.; Ballmann, J. Inorg. Chem. 2015, 54,
094−4103.
(
5
(
1
1
3) Schrock, R. R. Angew. Chem., Int. Ed. 2008, 47, 5512−5522.
4) (a) Yandulov, D. V.; Schrock, R. R. J. Am. Chem. Soc. 2002, 124,
252−6253. (b) Yandulov, D. V.; Schrock, R. R. Inorg. Chem. 2005,
4, 1103−1117. (c) Yandulov, D. V.; Schrock, R. R.; Rheingold, A. L.;
Ceccarelli, C.; Davis, W. M. Inorg. Chem. 2003, 42, 796−813.
Am. Chem. Soc. 1992, 114, 261−266. (d) Marinetti, A.; Mathey, F.
Angew. Chem., Int. Ed. Engl. 1988, 27, 1382−1384. (e) Mathey, F. Acc.
Chem. Res. 1992, 25, 90−96.
(
d) Ritleng, V.; Yandulov, D. V.; Weare, W. W.; Schrock, R. R.; Hock,
A. S.; Davis, W. M. J. Am. Chem. Soc. 2004, 126, 6150−6163.
e) Weare, W. W.; Schrock, R. R.; Hock, A. S.; Muller, P. Inorg. Chem.
006, 45, 9185−9196. (f) Reithofer, M. R.; Schrock, R. R.; Muller, P. J.
Am. Chem. Soc. 2010, 132, 8349−8358. (g) Chin, J. M.; Schrock, R. R.;
Mu
(
2
̈
(28) Cowley, A. H.; Norman, N. C.; Pakulski, M. Inorg. Synth. 1990,
27, 235−240.
̈
(29) Deschamps, E.; Deschamps, B.; Dormieux, J. L.; Ricard, L.;
̈
ller, P. Inorg. Chem. 2010, 49, 7904−7916.
5) Yandulov, D. V.; Schrock, R. R. Science 2003, 301, 76−78.
6) (a) Knowles, W. S. Acc. Chem. Res. 1983, 16, 106−112. (b) Burk,
(
(
́
Mezailles, N.; Le Floch, P. Dalton Trans. 2006, 594−602.
(30) Glueck, D. S. Coord. Chem. Rev. 2008, 252, 2171−2179.
(31) (a) Geiger, W. E. Organometallics 2011, 30, 28−31. (b) Pinter,
B.; Smith, K. T.; Kamitani, M.; Zolnhofer, E. M.; Tran, B. L.; Fortier,
S.; Pink, M.; Wu, G.; Manor, B. C.; Meyer, K.; Baik, M.-H.; Mindiola,
D. J. J. Am. Chem. Soc. 2015, 137, 15247−15261.
M. J. Acc. Chem. Res. 2000, 33, 363−372.
(
(
(
1
5
7) Chirik, P. J.; Wieghardt, K. Science 2010, 327, 794−795.
8) Chirik, P. J. Inorg. Chem. 2011, 50, 9737−9740.
9) (a) Gunanathan, C.; Milstein, D. Chem. Rev. 2014, 114, 12024−
2087. (b) Gunanathan, C.; Milstein, D. Acc. Chem. Res. 2011, 44,
88−602. (c) Butschke, B.; Fillman, K. L.; Bendikov, T.; Shimon, L. J.
(32) Observations of a peak current ratio (ipa/ipc) of less than 1 and a
slowly increasing separation of peaks with increasing scan rate are
consistent with a quasi-reversible process: (a) Jouaiti, A.; Geoffroy, M.;
Terron, G.; Bernardinelli, G. J. Am. Chem. Soc. 1995, 117, 2251−2258.
(b) Bush, P. M.; Whitehead, J. P.; Pink, C. C.; Gramm, E. C.; Eglin, J.
L.; Watton, S. P.; Pence, L. E. Inorg. Chem. 2001, 40, 1871−1877.
(33) Nakajima, Y.; Ozawa, F. Organometallics 2012, 31, 2009−2015.
W.; Diskin-Posner, Y.; Leitus, G.; Gorelsky, S. I.; Neidig, M. L.;
Milstein, D. Inorg. Chem. 2015, 54, 4909−4926.
10) (a) Chirik, P. J. Acc. Chem. Res. 2015, 48, 1687−1695. (b) Hoyt,
J. M.; Schmidt, V. A.; Tondreau, A. M.; Chirik, P. J. Science 2015, 349,
60−963. (c) Darmon, J. M.; Yu, R. P.; Semproni, S. P.; Turner, Z. R.;
Stieber, S. C. E.; DeBeer, S.; Chirik, P. J. Organometallics 2014, 33,
423−5433.
(
9
́
(34) (a) Bullock, J. P.; Bond, A. M.; Boere, R. T.; Geitz, T. M.;
Roemmele, T. L.; Seagrave, S. D.; Masuda, J. D.; Parvez, M. J. Am.
5
G
DOI: 10.1021/acs.organomet.6b00250
Organometallics XXXX, XXX, XXX−XXX

Organometallics
Article
Chem. Soc. 2013, 135, 11205−11215. (b) Schiavon, G.; Zecchin, S.;
Cogoni, G.; Bontempelli, G. J. Electroanal. Chem. Interfacial Electro-
chem. 1973, 48, 425−431.
E. D.; Landis, C. R.; Weinhold, F. Wiley Interdisciplinary Reviews:
Computational Molecular Science 2012, 2, 1−42. (c) Weinhold, F.;
Landis, C. R. Valency and Bonding: A Natural Bond Orbital Donor-
Acceptor Perspective; Cambridge University Press: Cambridge, 2005.
(d) Reed, A. E.; Curtiss, L. A.; Weinhold, F. Chem. Rev. 1988, 88,
899−926.
(
(
(
35) Takaoka, A.; Peters, J. C. Inorg. Chem. 2012, 51, 16−18.
36) Le Floch, P. Coord. Chem. Rev. 2006, 250, 627−681.
37) Full details on the DFT calculations are in the Supporting
Information.
38) Ruff, J. K.; Schlientz, W. J.; Dessy, R. E.; Malm, J. M.; Dobson,
G. R.; Memering, M. N. Inorg. Synth. 2007, 15, 84−90.
39) (a) Scepaniak, J. J.; Young, J. A.; Bontchev, R. P.; Smith, J. M.
(55) (a) Glendening, E. D.; Landis, C. R.; Weinhold, F. J. Comput.
Chem. 2013, 34, 1429−1437. (b) Glendening, E. D.; Badenhoop, J. K.;
Reed, A. K.; Carpenter, J. E.; Bohmann, J. A.; Morales, C. M.; Landis,
C. R.; Weinhold, F. NBO 6.0; Theoretical Chemistry Institute;
University of Wisconsin; Madison, 2013.
(
(
Angew. Chem., Int. Ed. 2009, 48, 3158−3160. (b) Vreeken, V.; Siegler,
M. A.; de Bruin, B.; Reek, J. N. H.; Lutz, M.; van der Vlugt, J. I. Angew.
Chem., Int. Ed. 2015, 54, 7055−7059. (c) Gloaguen, Y.; Rewbreyend,
C.; Lutz, M.; Kumar, P.; Huber, M.; van der Vlugt, J. I.; Schneider, S.;
de Bruin, B. Angew. Chem., Int. Ed. 2014, 53, 6814−6818.
́
(56) Legault, C. Y. CYLview, 1.0b; Universite de Sherbrooke, 2009.
(
40) Albertin, G.; Antoniutti, S.; Bacchi, A.; Celebrin, A.; Pelizzi, G.;
Zanardo, G. Dalton Trans. 2007, 661−668.
41) Hillhouse, G. L.; Goeden, G. V.; Haymore, B. L. Inorg. Chem.
982, 21, 2064−2071.
̈
42) Some recent examples: (a) Scheibel, M. G.; Wu, Y.; Stuckl, A.
(
1
(
C.; Krause, L.; Carl, E.; Stalke, D.; de Bruin, B.; Schneider, S. J. Am.
Chem. Soc. 2013, 135, 17719−17722. (b) Scepaniak, J. J.; Young, J. A.;
Bontchev, R. P.; Smith, J. M. Angew. Chem., Int. Ed. 2009, 48, 3158−
3
160. (c) Scheibel, M. G.; Askevold, B.; Heinemann, F. W.; Reijerse, E.
J.; de Bruin, B.; Schneider, S. Nat. Chem. 2012, 4, 552−558.
43) Some recent examples: (a) Schoffel, J.; Rogachev, A. Y.; George,
S. D.; Burger, P. Angew. Chem., Int. Ed. 2009, 48, 4734−4738.
b) Gloaguen, Y.; Rewbreyend, C.; Lutz, M.; Kumar, P.; Huber, M.;
van der Vlugt, J. I.; Schneider, S.; de Bruin, B. Angew. Chem., Int. Ed.
014, 53, 6814−6818.
44) Munoz, S. B.; Lee, W.-T.; Dickie, D. A.; Scepaniak, J. J.; Subedi,
D.; Pink, M.; Johnson, M. D.; Smith, J. M. Angew. Chem., Int. Ed. 2015,
4, 10600−10603.
45) Schlo
(
̈
(
2
(
̃
5
(
(
(
̈
gl, R. Angew. Chem., Int. Ed. 2003, 42, 2004−2008.
46) van der Vlugt, J. I. Chem. Soc. Rev. 2010, 39, 2302−2322.
47) (a) Yuan, J.; Hughes, R. P.; Golen, J. A.; Rheingold, A. L.
Organometallics 2010, 29, 1942−1947. (b) Huang, H.; Rheingold, A.
L.; Hughes, R. P. Organometallics 2009, 28, 1575−1578. (c) Bourgeois,
C. J.; Huang, H.; Larichev, R. B.; Zakharov, L. N.; Rheingold, A. L.;
Hughes, R. P. Organometallics 2007, 26, 264−271.
(
48) (a) Nakajima, Y.; Nakatani, M.; Hayashi, K.; Shiraishi, Y.;
Takita, R.; Okazaki, M.; Ozawa, F. New J. Chem. 2010, 34, 1713−1722.
b) Chang, Y.-H.; Takeuchi, K.; Wakioka, M.; Ozawa, F. Organo-
metallics 2015, 34, 1957−1962.
49) Initial reports: (a) Gupta, M.; Hagen, C.; Flesher, R. J.; Kaska,
(
(
W. C.; Jensen, C. M. Chem. Commun. 1996, 2083−2084. (b) Gupta,
M.; Hagen, C.; Kaska, W. C.; Cramer, R. E.; Jensen, C. M. J. Am.
Chem. Soc. 1997, 119, 840−841. (c) Gupta, M.; Kaska, W. C.; Jensen,
C. M. Chem. Commun. 1997, 461−462.
(
50) (a) Choi, J.; MacArthur, A. H. R.; Brookhart, M.; Goldman, A.
S. Chem. Rev. 2011, 111, 1761−1779. (b) Morales-Morales, D.; Lee, D.
W.; Wang, Z.; Jensen, C. M. Organometallics 2001, 20, 1144−1147.
(
c) Liu, F.; Pak, E. B.; Singh, B.; Jensen, C. M.; Goldman, A. S. J. Am.
Chem. Soc. 1999, 121, 4086−4087.
51) (a) Zhao, Y.; Truhlar, D. G. Theor. Chem. Acc. 2008, 120, 215−
41. (b) Zhao, Y.; Truhlar, D. G. Acc. Chem. Res. 2008, 41, 157−167.
52) (a) Dunning, T. H.; Hay, P. J. In Modern Theoretical Chemistry,
(
2
(
Vol. 4: Applications of Electronic Structure Theory; Schaefer, H. F., III,
Ed.; Plenum: New York, 1977. (b) Wadt, W. R.; Hay, P. J. J. Chem.
Phys. 1985, 82, 284−298. (c) Hay, P. J.; Wadt, W. R. J. Chem. Phys.
1
985, 82, 299−310. (d) Hay, P. J.; Wadt, W. R. J. Chem. Phys. 1985,
82, 270−283.
(
53) (a) Bochevarov, A. D.; Harder, E.; Hughes, T. F.; Greenwood, J.
R.; Braden, D. A.; Philipp, D. M.; Rinaldo, D.; Halls, M. D.; Zhang, J.;
Friesner, R. A. Int. J. Quantum Chem. 2013, 113, 2110−2142.
(
̈
b) Jaguar, versions 7.0−8.9; Schrodinger, LLC: New York, NY,
2
007−2015.
54) (a) Weinhold, F.; Landis, C. R. Discovering Chemistry with
Natural Bond Orbitals; John Wiley & Sons: NJ, 2012. (b) Glendening,
(
H
DOI: 10.1021/acs.organomet.6b00250
Organometallics XXXX, XXX, XXX−XXX