Propargylic C(sp3)-H Bond Activation for Preparing η3-Propargyl/Allenyl Complexes of Yttrium

Article abstract of DOI:10.1021/acs.organomet.7b00395

Propargylic C(sp³) - H bond activation of 1-substituted-1-propynes, such as 1-trimethylsilyl-1-propyne, 2-hexyne, and 1-phenyl-1-propyne, was achieved by treatment with an alkylyttrium complex 8 bearing an ene-diamido ligand to give the corresponding (η³-propargyl/allenyl)yttrium complexes 7a-c. A unique delocalized η³-propargyl/allenyl structure of these three complexes was revealed by NMR spectroscopy and X-ray single crystal analyses. To elucidate the reactivity of the η³-propargyl/allenyl unit of complexes 7a-c, we conducted two reactions with N-methylaniline and N,N′-dicyclohexylcarbodiimine. For protonation by N-methylaniline, we found that the product distribution of monosubstituted internal alkynes and allenes depended on the substituent on the η³-propargyl/allenyl moiety: 7a and 7b afforded the corresponding internal alkynes as the major products, whereas the major protonation product of 7c was phenylallene. For the insertion of N,N′-dicyclohexylcarbodiimine, complex 7a selectively yielded η³-{N,N′-dicyclohexyl-2-(3-trimethylsilylpropargyl)amidinate}yttrium 12a, while complex 7c produced η³-{N,N′-dicyclohexyl-2-(1-phenylallenyl)amidinate}yttrium complex 13c, though complex 7b gave a mixture of η³-{N,N′-dicyclohexyl-2-(3-normalpropylpropargyl)amidinate}yttrium complex 12b and η³-{N,N′-dicyclohexyl-2-(1-normalpropylallenyl)amidinate}yttrium 13b in an 83:17 ratio. On the basis of the product distributions in these two-types of reactions, (η³-propargyl/allenyl)yttrium complexes were shifted into preferentially favorable η¹-allenyl species or η¹-propargyl species depending on the substituents prior to the reaction with electrophiles via a four-membered cyclic mechanism.

Full text of DOI:10.1021/acs.organomet.7b00395

Article
pubs.acs.org/Organometallics
Propargylic C(sp3)−H Bond Activation for Preparing η3‑Propargyl/
Allenyl Complexes of Yttrium
Haruki Nagae, Abhinanda Kundu, Hayato Tsurugi,* and Kazushi Mashima*
Department of Chemistry, Graduate School of Engineering Science, Osaka University, Toyonaka, Osaka 560-8531, Japan
S
* Supporting Information
ABSTRACT: Propargylic C(sp3)H bond activation of 1-
substituted-1-propynes, such as 1-trimethylsilyl-1-propyne, 2-
hexyne, and 1-phenyl-1-propyne, was achieved by treatment
with an alkylyttrium complex 8 bearing an ene-diamido ligand
to give the corresponding (η3-propargyl/allenyl)yttrium
complexes 7a−c. A unique delocalized η3-propargyl/allenyl
structure of these three complexes was revealed by NMR
spectroscopy and X-ray single crystal analyses. To elucidate the
reactivity of the η3-propargyl/allenyl unit of complexes 7a−c,
we conducted two reactions with N-methylaniline and N,N′-
dicyclohexylcarbodiimine. For protonation by N-methylaniline,
we found that the product distribution of monosubstituted
internal alkynes and allenes depended on the substituent on the η3-propargyl/allenyl moiety: 7a and 7b afforded the
corresponding internal alkynes as the major products, whereas the major protonation product of 7c was phenylallene. For the
insertion of N,N′-dicyclohexylcarbodiimine, complex 7a selectively yielded η3-{N,N′-dicyclohexyl-2-(3-trimethylsilylpropargyl)-
amidinate}yttrium 12a, while complex 7c produced η3-{N,N′-dicyclohexyl-2-(1-phenylallenyl)amidinate}yttrium complex 13c,
though complex 7b gave a mixture of η3-{N,N′-dicyclohexyl-2-(3-normalpropylpropargyl)amidinate}yttrium complex 12b and
η3-{N,N′-dicyclohexyl-2-(1-normalpropylallenyl)amidinate}yttrium 13b in an 83:17 ratio. On the basis of the product
distributions in these two-types of reactions, (η3-propargyl/allenyl)yttrium complexes were shifted into preferentially favorable
η1-allenyl species or η1-propargyl species depending on the substituents prior to the reaction with electrophiles via a four-
membered cyclic mechanism.
INTRODUCTION
■
Propargyl and allenyl functionalities are important structural
motifs in pharmaceuticals and other materials, and their
versatile reactivity is often used for further chemical trans-
formations.1,2 These functional groups are catalytically and
stoichiometrically introduced via allenyl- and propargyl-metal
species, whose reactions with polar and nonpolar unsaturated
bonds have been comprehensively well-investigated. In general,
a propargyl-metal species gives the corresponding allenyl
products, while an allenyl-metal species yields the correspond-
ing propargyl products via cyclic intermediates (Figure 1a and
b).3 Noteworthy is that propargyl-metal complexes and allenyl-
metal complexes are in equilibrium, probably through η3-
Figure 1. Plausible mechanism for the reaction of propargyl- and
propargyl/allenyl complexes (Scheme 1),3b,d−g,j,m,n,4 and
allenyl complexes with unsaturated compounds.
recently, some η3-propargyl/allenyl complexes were prepared
by four synthetic routes:5 (a) oxidative addition of Pt(0) into 1-
formation of alkanes as byproducts, though only electropositive
metal−alkyl complexes have been applicable. Bazan and Bercaw
independently prepared η3-propargyl/allenyl complexes of
zirconium 49a and yttrium 54a by the corresponding reactions
of Cp*(TBM)ZrCH3 (TBM = tribenzylidenemethane) and
phenyl-3-bromo-1-propyn followed by replacement of the
bromide anion by AgOTf for 1,6a (b) abstraction of a hydroxyl
group of prop-2-yl-1-ol in the presence of HBF4·Et2O for 2,7a
(c) transmetalation of Cp2ZrMe(Cl) with a Grignard reagent,
PhCCCH2MgBr, for 3,8a and (d) a propargylic C−H bond
activation of internal alkynes by metal alkyl complexes for 4, 5,
and 6 (Figure 2).9 Among them, the latter method is regarded
as the most straightforward and clean reaction with only the
Received: June 1, 2017
© XXXX American Chemical Society
A
DOI: 10.1021/acs.organomet.7b00395
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typically observed for η1-propargyl- and η1-allenyl complexes of
various transition metals, as depicted in Figure 1.
Scheme 1. Equilibrium between Propargyl- and Allenyl-
Metal Species via the η3-Propargyl/Allenyl Moiety
RESULTS AND DISCUSSION
■
Synthesis and Characterization of (η3-Propargyl/
allenyl)yttrium Complexes 7b and 7c. The alkylyttrium
complex 8 having a dianionic ene-diamido ligand reacted with
2-hexyne and 1-phenly-1-propyne in hexane at 60 °C for 3 h to
give the corresponding (η3-propargyl/allenyl)yttrium com-
plexes 7b and 7c as a consequence of selective C(sp3)H
bond activation at the propargylic methyl group of the
corresponding substituted propynes (eq 1), though we
previously reported the synthesis and characterization of
complex 7a obtained in a similar manner.9c
Complexes 7b and 7c were fully characterized as a
delocalized π-bonded η3-propargyl/allenyl structure, as clearly
differing from a tautomeric mixture of (η1-propargyl)yttrium
and (η1-allenyl)yttrium based on the NMR spectral data as well
as a crystallographic study of 7c and 7a (Tables 1 and 2). Table
1 summarizes the chemical shift values and corresponding
Figure 2. Representative examples of η3-propargyl/allenyl complexes.
1
1JC−H and JY−C coupling constants of the η3-propargyl/allenyl
moiety in NMR spectroscopy for 7a−7c, together with some
related yttrium complexes such as CnY(η3-CH2CCMe) (5: Cn
= 1,4,7-trimethyl-1,4,7-triazacyclonane)4a and Cp*2Y(η3-
CH2CCPh) (6-Y).9b Resonances due to methylene protons
bound to C3 and C3 carbon of the η3-propargyl/allenyl moiety
were observed at δH 2.64 and δC 40.8 for 7b and δH 3.23 and δC
47.7 for 7c, values that were almost the same as those found for
the reported complex 7a (δH 2.60 and δC 37.8)9c and those of
6-Y (δH 2.60 and δC 37.8), while methylene protons bound to
C3 and C3 carbon of 5 were observed in a lower field (δH 3.87
and δC 55.5) than those found for 7a−7c and 6-Y. The C−H
coupling constants of methylene bound to C3 of the η3-
propargyl/allenyl moiety for 7a−7c were ca. 160 Hz assignable
to typical sp2-carbons.10 Chemical shifts of the quaternary C2
carbon of 7b and 7c were observed at δC 151.4 for 7b and δC
163.3 for 7c values, which were similar to the reported values of
CnYMe3 (Cn = 1,4,7-trimethyl-1,4,7-triazacycolononane) with
2-butyne, and Hessen reported two η3-propargyl/allenyl
complexes of group 3 metals, 6-Y and 6-La, by treating
Cp*2LnCH(SiMe3)2 with 1-phenyl-1-propyne in the presence
of hydrogen.9b Recently, we synthesized a η3-propargyl/allenyl
yttrium complex 7a by treating 1-trimethylsilyl-1-propyne with
an alkylyttrium complex 8 supported by an ene-diamido
ligand,9c and expanded our synthetic approach to other (η3-
propargyl/allenyl)yttrium complexes 7b and 7c by, respectively,
treating 8 with 2-hexyne and 1-phenyl-1-propyne. Moreover, to
elucidate the reaction pattern of the η3-propargyl/allenyl
moiety bound to the yttrium atom depending on the
substituents, we carried out two reactions of 7a−c with N-
methylaniline and N,N′-dicyclohexylcarbodiimine, whose re-
actions proceeded according to a different pattern than that
1
Table 1. H and 13C NMR Spectral Data for η3-Propargyl/Allenylyttrium Moiety of 7a−c, 5, and 6-Y
B
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Table 2. Selected Bond Lengths and Angles (Å and Deg) for the η3-Propargyl/Allenylyttrium Moiety of 7a, 7c, 1, 3, and 6-Y
η3-propargyl/allenyl yttrium complexes 7a (δC 162.6), 5 (δC
169.2), and 6-Y (δC 155.1) being completely different from the
chemical shifts of quaternary C2 carbons of typical η1-propargyl
complexes (δC 60100)3,6a,11 and η1-allenyl complexes (δC
same as the reported structure of 7a. The bond length of
C27C28 (1.366(8) Å) is shorter than that of a typical C−C
single bond (1.45 Å) and longer than that of a typical C−C
double bond (1.31 Å), while the bond length of C28C29
(1.259(8) Å) is regarded as an intermediate between a C−C
double bond and a C−C triple bond (1.20 Å). Accordingly, the
η3-propargyl/allenyl coordination mode was confirmed based
on the observed bond lengths along with a slightly bent C27
C28C29 angle (160.3(6)°) and larger C28C29C30
angle (137.8(6)°) than the ideal angle of sp2 carbon found for
some η1-allenyl complexes.12 Furthermore, the bond length of
Y−C29 (2.522(6) Å) in 7c is the shortest among the three
yttrium−carbon bonds (Y−C27 = 2.817(5) Å and Y−C28 =
2.556(5) Å), indicating the η3-propargyl/allenyl coordination
mode. Such an observation is in good accord with the large JY−C
value (17 Hz) for a C1 carbon (vide supra).
190210).3,6a,11b−d Noteworthy were the JY−C values of C1
1
and C3 carbons, which demonstrated the bonding nature
between the carbons of the η3-propargyl/allenyl moiety and the
yttrium center. The 1JY−C value (3 Hz) was observed for the C3
1
carbon of complexes 7a and 7b, while the JY−C for the C3
1
carbon was not observed for complex 7c. Much larger JY−C
values of 7a (12 Hz), 7b (14 Hz), and 7c (17 Hz) were
observed for the C1 carbon, suggesting that the bond between
the C1 carbon and the yttrium center was stronger than the
C3Y bond and consistent with the corresponding crystallo-
graphic data (vide infra).
Figure 3 shows the molecular structure of complex 7c. The
selected bond lengths and angles of 7c are summarized in Table
Protonation and Insertion Reactions of (η3-Propargyl/
allenyl)yttrium Complexes 7a−c. With three (η3-propargyl/
allenyl)yttrium complexes 7a−c in hand, we conducted
protonation by N-methylaniline (1 equiv) and an insertion
reaction of N,N′-dicyclohexcylcarbodiimide to clarify the
substituent-dependent preference of η1-propargyl or η1-allenyl
species generated in situ from η3-propargyl/allenyl complexes.
Protonation of the η3-propargyl/allenyl moiety bound to the
yttrium atom afforded internal alkynes 10 and allenes 11
together with the formation of an amido complex 9 (Scheme
2): reactions of 7a and 7b, having electron-donating substituent
Scheme 2. Protonation of (η3-Propargyl/allenyl)yttrium
Complexes 7a−c by N-Methylaniline
Figure 3. ORTEP drawing of the η3-propargyl/allenyl-yttrium
complex 7c with 50% thermal ellipsoids. All hydrogen atoms and
solvent molecules are omitted for clarity. Selected bond lengths (Å)
and angles (deg): YN1, 2.200(5); YN2, 2.209(5); YC27,
2.917(5); YC28, 2.556(5); YC29, 2.522(6); N1C1, 1.411(7);
N2C2, 1.413(7); C1C2, 1.351(9); C27C28, 1.366(8); C28
C29, 1.259(8); C27C28C29, 160.3(6); C28C29C30,
137.8(6); O1Y−N2, 147.97(15); and O2Y1N1, 117.81(15).
on the η3-propargyl/allenyl ligand, with N-methylaniline gave
the corresponding alkynes, 1-trimethylsilyl-1-propyne (10a)
and 2-hexyne (10b), with contamination of the corresponding
minor allenes 11a and 11b in the ratios of 10a/11a = 91:9 and
10b/11b = 76:24. On the other hand, treatment of 7c, which
has an electron-deficient group on the η3-propargyl/allenyl
ligand, with N-methylaniline mainly producing phenylallene
2 together with those for 7a and some η3-propargyl/allenyl
complexes 1, 3, and 6-Y. Complex 7c adopts a distorted
trigonal bipyramidal molecular geometry, where the O1 and N2
atoms occupy axial positions, and the yttrium atom has one
chelating ene-diamido ligand, two THF, and one η3-propargyl/
allenyl ligand, and the overall structure of 7c is essentially the
C
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(11c) accompanied by a minor product of 1-phenyl-1-propyne
(10c) in a 10c/11c = 22:78 ratio.
Treatment of 7a with N,N′-dicyclohexylcarbodiimide re-
sulted in the selective formation of complex 12a supported by
an η3-amidinate ligand whose central carbon was attached by a
propargyl group with a terminal trimethylsilyl substituent
(Scheme 3). The 1H and 13C{1H} NMR spectra of 12a
propargyl form as the active species because of the formation of
the corresponding alkynes as major products and a smaller
1JY−C value (12 Hz for 7a and 15 Hz for 7b) for the C1 carbon
1
and an observable JY−C value (3 Hz for 7a and 7b) for the C3
carbon in NMR spectroscopy. In contrast, the major product of
the reaction of 7c with N-methylaniline was phenylallene (11c),
and the 1JY−C value (17 Hz) for the carbon (C1), as well as the
lack of a coupling constant for the C3 carbon in NMR
spectroscopy for 7c, suggested the favorable contribution of the
allenyl canonical form for 7c; therefore, we assumed that the
preference of the active species of 7c was an η1-allenyl species
prior to being protonated via a typical four-membered δ-bond
metathesis pathway.14 On the basis of these preferences of the
reactive species for protonation, it was assumed that the η1-
propargyl species for 7a and 7b reacted with N,N′-
dicyclohexylcarbodiimide to give the corresponding (η3-
propargylamidinate)yttrium complexes 12a and 12b via a
four-membered cyclic transition state, while the preference of
η1-allenyl species for 7c selectively yields the (η3-
allenylamidinate)yttrium complex 13c as the major product
through the same cyclic transition state (Scheme 4).
Scheme 3. Reaction of (η3-Propargyl/allenyl)yttrium
Complexes 7a−c and N,N′-Dicyclohexylcarbodiimide
Scheme 4. Proposed Reaction Mechanism to Give Amidinate
Complexes 12 and 13
displayed a singlet resonance at δH 3.12 and a triplet resonance
at δC 17.1 (1JC−H = 125 Hz) assignable to a methylene moiety
between the amidinate moiety and the CC moiety, clearly
indicating that N,N′-dicyclohexylcarbodiimide was inserted into
the η1-propargylyttrium species of 7a. Complex 7b was found
to give a propargyl-attached complex 12b as a major product
(83% selectivity) with the same tendency as 7a. In sharp
contrast, the reaction of 7c with N,N′-dicyclohexylcarbodiimide
yielded η3-N,N′-dicyclohexyl-2-(1-phenylallenyl)amidinate yt-
trium complex 13c as a single product in 72% isolated yield, in
which the CN bond of N,N′-dicyclohexylcarbodiimide
inserted into a preferential (η1-allenyl)yttrium species of 7c
1
(Scheme 3). Complex 13c was characterized by its H and
13C{1H} NMR spectra: a singlet signal due to the typical
terminal vinylidene protons was observed at δH 4.97, and the
internal carbon and terminal vinylidene carbon of the allenyl
unit were observed as a singlet signal at δC 205.3 and a triplet
CONCLUSION
■
We demonstrated that a unique propargylic C(sp3)-H bond
activation was applicable for preparing (η3-propargyl/allenyl)-
yttrium complexes 7a−c by treating the alkylyttrium complex 8
with the corresponding internal alkynes, such as 1-trimethyl-
silyl-1-propyne, 1-hexyne, and 1-phenyl-1-propyne. On the
basis of the two types of reactions of 7a−c with N-
methylaniline and N,N′-dicyclohexylcarbodiimine, we proposed
a four-membered cyclic mechanism for the protonation and
insertion with selectivity in which the propargyl canonical form
produced internal alkynes upon protonation and η3-{N,N′-
dicyclohexyl-2-(3-substitutedpropargyl)amidinate}yttrium com-
plexes 12 for the insertion reactions, whereas the allenyl
canonical form afforded allenes upon protonation and η3-
{N,N′-dicyclohexyl-2-(1-substitutedallenyl)amidinate}yttrium
complexes 13 for the insertion reaction, presumably consistent
with the general tendency that early transition metal complexes
favor σ-bond metathesis and a four-membered cyclic transition
state in polymerization and amine-insertion reactions.15 This is
the first example of a regioselective insertion reaction of the
CN bond into the η3-propargyl/allenyl complex. It is
1
resonance at δC 79.3 with a large JC−H coupling constant
(1JC−H = 168 Hz).11 The molecular structure of 13c was
determined by a preliminary X-ray diffraction study of the
single crystal (Figure S23),13 though the structural feature of
13c was not precisely discussed due to its low accuracy,
indicating that the yttrium atom adopts a five-coordinated
distorted trigonal bipyramidal structure surrounded by one ene-
diamido, one allenylamidinate, and one THF, and the allenyl
carbon with a phenyl group attaches to the central carbon atom
of the η3-amidinate ligand.
These two reactions and bonding characteristics, evidenced
from the NMR spectroscopy, led us to propose a four-
membered cyclic mechanism for the reactions of η3-propargyl/
allenylyttrium complexes with electrophiles, such as N-
methylaniline and N,N′-dicyclohexylcarbodiimine, reflecting
the substituent-dependent preference of the reactive species,
i.e., η1-propargylyttrium or η1-allenylyttrium derived from η3-
propargyl/allenylyttrium. Complexes 7a and 7b favored the η1-
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C43H59N2O2Y: C, 71.25; H, 8.20; N, 3.86. Found: C, 71.39; H, 8.0; N,
3.86. The small deviation of the E.A. values is due to the high
sensitivity of 7c to air.
noteworthy that such selectivity is clearly distinguished from
the general tendency that η1-propargyl complexes of late-
transition metals afford the corresponding allenyl products,
while η1-allenyl complexes of late-transition metals favorably
yield the corresponding propargyl products via cyclic
intermediates, as demonstrated in Figure 1a and b.
Preparation of (2,6-iPr2C6H3-DAD)Y[(NCy)2C−CH2C
CSiMe3)](THF)2 (12a). 7a (68.2 mg, 9.45 μmol) and N,N′-
dicyclohexylcarbodiimide (18.9 mg, 9.17 μmol) were reacted in
benzene at room temperature for 3 h. Then, all volatiles were
evaporated. The remaining solid was dried to give 12a as a brown
1
powder in 89% yield (72.1 mg, 8.43 μmol), mp 97−99 °C (dec). H
EXPERIMENTAL SECTION
■
NMR (400 MHz, C6D6 and 14 equiv of THF-d8, 30 °C): δ 0.16 (s,
9H, Si(CH3)3), 0.96−1.11 (br m, 2H, Cy), 1.11−1.31 (br m, 8H, Cy),
General. All manipulations involving air- and moisture-sensitive
organometallic compounds were carried out under argon using the
standard Schlenk technique or argon-filled glovebox. Yttrium
complexes 7a and 8 were prepared according to the literature.9c
Dicyclohexylcarbodiimide and N-methylaniline were purchased and
purified by distillation over CaH2. Hexane, pentane, toluene, and
benzene-d6 were distilled over CaH2 and thoroughly degassed by trap-
to-trap distillation before use. NMR spectra were recorded on a Bruker
AV 400 MHz spectrometer in a 5 mm NMR tube. Chemical shifts
were reported in parts per million and referenced to a residual proton
signal of the solvent (1H benzene-d6, δ = 7.16; chloroform, δ = 7.26)
or the solvent itself (13C{1H} benzene-d6, δ = 128.06; chloroform, δ =
77.16). Melting points were recorded by a BUCHI Melting Point M-
565. The elemental analyses were recorded by using PerkinElmer 2400
at the Faculty of Engineering Science, Osaka University.
3
1.35 (d, 24H, JHH = 6.4 Hz CH(CH3)2), 1.45 (br s, 8H, β-CH2 of
THF and THF-d8), 1.52−1.61 (br m, 2H, Cy), 1.64−1.75 (br m, 4H,
Cy), 1.82−1.88 (br m, 4H, Cy), 3.21 (br m, 2H, Cy), 3.25 (s, 2H,
CH23CCSi), 3.56 (br m, 8H, α-CH2 of THF + THF-d8), 3.75 (sept,
4H, JHH = 6.8 Hz, CH(CH3)2), 5.61 (s, 2H, CHCH), 7.06 (t, 2H,
3
1
3JHH = 7.6 Hz, p-Ar), 7.20 (d, 4H, JHH = 7.6 Hz, m-Ar). H NMR
(400 MHz, C6D6, 30 °C): δ 0.24 (s, 9H, Si(CH3)3), 0.92−1.04 (m,
2H, Cy), 1.09 (br s, 4H, β-CH2 of THF), 1.15−1.33 (br m, 8H, Cy),
1.34−1.62 (br m, 26H, CH(CH3)2 and Cy), 1.61−1.75 (br s, 4H, Cy),
1.77−1.98 (br s, 4H, Cy), 3.03−3.40 (br, 2H, Cy), 3.20 (s, 2H,
CH2CCSi), 3.57 (br s, 4H, α-CH2 of THF), 3.67 (br s, 4H,
3
CH(CH3)2), 5.69 (s, 2H, CHCH), 7.10 (t, 2H, JHH = 7.2 Hz, p-
Ar), 7.27 (d, 4H, 3JHH = 7.2 Hz, m-Ar). 13C NMR (100 MHz, C6D6, 30
°C): δ 0.2 (q, 1JCH = 131 Hz, Si(CH3)3), 17.3 (td, 1JCH = 134 Hz, 3JYC
= 2 Hz, CCH2CCSi), 25.2 (β-CH2 of THF), 25.4 (CH(CH3)2),
Preparation of (2,6-iPr2C6H3-DAD)Y(buten-2-ynyl)(THF)2
(7b). To a solution of 8 (200 mg, 0.287 mmol) in hexane was
added a solution of 2-hexyne (25.9 mg, 0.316 mmol) via syringe at
room temperature. The color of the reaction mixture turned to brown.
The reaction mixture was stirred at 60 °C for 3 h, and then all volatiles
were evaporated. After drying the remaining solid in vacuo, 7b was
isolated as a brown powder in 58% yield (115 mg, 0.166 mmol), mp
1
26.3 (2 carbon of Cy), 28.4 (br, CH(CH3)2), 37.1 (t, JCH = 126 Hz,
1
Cy), 56.9 (d, JCH = 126 Hz, Cy), 70.8 (α-CH2 of THF), 86.0
2
(CCH2CCSi), 102.2 (t, JCH = 12 Hz, CCH2CCSi), 114.0 (d,
1
1JCH = 166 Hz, CHCH), 121.2 (d, JCH = 161 Hz, p-Ar), 123.5 (br
1
2
d, JCH = 149 Hz, m-Ar), 141.2 (br s, o-Ar), 150.9 (d, JYC = 3 Hz, i-
Ar), 171.2 (s, CCH2CCSi). Anal. Calcd for C49H77N4OSiY: C,
68.82; H, 9.08; N, 6.55. Found: C, 68.98; H, 10.12; N, 6.54. A small
deviation of the E.A. values is due to high sensitivity of 12a to air.
Reaction of 7b with N,N′-Dicyclohexylcarbodiimide. 7b (87.4
mg, 0.127 mmol) and N,N′-dicyclohexylcarbodiimide (25.6 mg, 0.124
mmol) were reacted in benzene at room temperature for 3 h. Then, all
volatiles were evaporated. The remaining solid was dried to give a
brown solid in total 86% yield. Analysis of the product by 1H NMR in
C6D6 showed the presence of two compounds in a 12b/13b = 83:17
ratio, as evidenced by two sets of signals attributable to the ligand
backbone proton (CHCH). The major product appears to be 12b.
1H NMR (400 MHz, C6D6, 30 °C) major product: δ 0.94 (t, 3H, 3JHH
= 7.2 Hz, CH3CH2CH2), 1.12 (br s, 4H, β-CH2 of THF), 1.18−1.35
(m, 8H, Cy), 1.36−1.63 (br m, 30H, CH(CH3)2, Cy, and
CH3CH2CH2), 1.64−1.78 (br s, 4H, Cy), 1.82−2.00 (m, 4H, Cy),
2.07 (t, 2H, 3JHH = 6.8 Hz, CH3CH2CH2), 3.18 (s, 2H, YCH2CC),
3.31 (br s, 2H, Cy), 3.61 (br s, 4H, α-CH2 of THF), 3.68 (br s, 4H,
1
78−80 °C (dec). H NMR (400 MHz, C6D6, 30 °C): δ 1.04 (t, 3H,
3JHH = 7.2 Hz, CH3CH2CH2), 1.10 (br s, 8H, β-CH2 of THF), 1.38 (d,
3
3
24H, JHH = 6.8 Hz, CH(CH3)2), 1.67 (sext, JHH = 7.2 Hz, 2H,
3
5
CH3CH2CH2), 2.30 (tt, JHH = 7.1 Hz, JHH = 2.7 Hz, 2H,
CH3CH2CH2), 2.65 (t, JHH = 2.8 Hz, 2H, YCH2), 3.53 (br s, 8H,
5
3
α-CH2 of THF), 3.82 (sept, 4H, JHH = 6.8 Hz, CH(CH3)2), 5.70 (s,
2H, CHCH), 7.14 (t, 2H, 3JHH = 8.0 Hz, p-Ar), 7.24 (t, 4H, 3JHH
=
8.0 Hz, m-Ar). 13C{1H} NMR (100 MHz, C6D6, 30 °C): δ 14.2 (q,
1JCH = 121 Hz, CH3CH2CH2), 25.2 (t, JCH = 133 Hz, β-CH2 of
1
THF), 25.4 (q, 1JCH = 123 Hz, CH(CH3)2), 25.8 (CH3CH2CH2), 28.4
(d, 1JCH = 124 Hz, CH(CH3)2), 28.8 (t, 1JCH = 129 Hz, CH3CH2CH2),
40.9 (dt, 1JCH = 157 Hz, 1JYC = 3 Hz, YCH2C), 71.0 (t, 1JCH = 148 Hz,
α-CH2 of THF), 108.6 (d, 1JYC = 14 Hz, YCH2CC), 113.5 (dd, 1JCH
2
1
= 165 Hz, JYC = 2 Hz, CH = CH), 122.1 (d, JCH = 157 Hz, p-Ar),
123.4 (d, 1JCH = 152 Hz, Hz m-Ar), 143.8 (o-Ar), 151.4 (YCH2CC),
2
152.6 (d, JYC = 4 Hz, ipso-Ar). Anal. Calcd for C40H61N2O2Y: C,
69.54; H, 8.90; N, 4.06. Found: C, 69.15; H, 8.85; N, 4.45. Small
deviation of the E.A. values is due to high sensitivity of 7b to air.
Preparation of (2,6-iPr2C6H3-DAD)Y(3-(phenyl)prop-2-ynyl)-
(THF)2 (7c). To a solution of 8 (300 mg, 0.432 mmol) in hexane was
added 1-phenyl-1-propyne (50.2 mg, 0.432 mmol) via syringe at room
temperature. The color of the reaction mixture turned to orange. The
reaction mixture was stirred at 60 °C for 3 h, and then all volatiles
were evaporated. After drying the remaining solid in vacuo, 7c was
isolated as an orange powder in 44% yield (139 mg, 0.192 mmol), mp
85−87 °C (dec). 1H NMR (400 MHz, C6D6, 30 °C): δ 1.08 (br s, 8H,
3
CH(CH3)2), 5.70 (s, 2H, CHCH), 7.10 (t, 2H, JHH = 7.6 Hz, p-
Ar), 7.27 (d, 4H, 3JHH = 7.6 Hz, m-Ar). 13C NMR (100 MHz, C6D6, 30
3
°C): δ 13.7 (CH3CH2CH2), 16.2 (d, JYC = 3 Hz, CCH2CCnPr),
21.2 (CH3CH2CH2), 22.6 (CH3CH2CH2), 25.2 (β-CH2 of THF), 25.4
(CH(CH3)2), 26.3 (2 carbon of Cy), 29.1 (CH(CH3)2), 37.2 (Cy),
56.8 (Cy), 70.9 (α-CH2 of THF), 75.9 (CCH2CCnPr), 81.4
(CCH2CCnPr), 114.1 (CHCH), 121.2 (p-Ar), 123.5 (br, m-Ar),
141.5 (br, o-Ar), 150.9 (d, 2JYC = 4 Hz, ipso-Ar), 172.7 (d, 2JYC = 2 Hz,
1
CCH2CCnPr). Selected H NMR data for the minor product 13b:
3
3
β-CH2 of THF), 1.30 (d, 24H, JHH = 6.8 Hz, CH(CH3)2), 3.24 (s,
1H NMR (400 MHz, C6D6, 30 °C) δ 0.98 (t, 3H, JHH = 7.2 Hz,
2H, YCH2), 3.58 (br s, 8H, α-CH2 of THF), 3.77 (sept, 4H, 3JHH = 6.8
CH3CH2CH2), 2.11−2.19 (m, 2H, CH3CH2CH2), 4.69 (t, 2H, 5JHH
=
3
4.0 Hz, H2CCC), 5.76 (s, 2H, CHCH). Selected 13C NMR
Hz, CH(CH3)2), 5.80 (s, 2H, CH = CH), 6.98 (t, 1H, JHH = 7.2 Hz,
p-Ph), 7.11−7.16 (m, 4H, p-Ar and m-Ph), 7.22 (d, 4H, 3JHH = 7.6 Hz,
m-Ar), 7.45 (d, 2H, 3JHH = 7.2 Hz, o-Ph). 13C NMR (100 MHz, C6D6,
30 °C): δ 25.2 (t, 1JCH = 134 Hz, β-CH2 of THF), 25.3 (q, 1JCH = 120
data for minor product 13b: 13C NMR (100 MHz, C6D6, 30 °C) δ
3
76.5 (H2CCC), 98.0 (d, JYC = 3 Hz, H2CCC), 174.1
(H2CCC(nPr)C), 203.6 (H2CCC).
1
1
Preparation of (2,6-iPr2C6H3-DAD)Y[(NCy)2C−C(Ph)C
CH2)](THF) (13c). 7c (148 mg, 0.204 mmol) and N,N′-dicyclohex-
ylcarbodiimide (42.1 mg, 0.204 mmol) were reacted in benzene at
room temperature for 3 h. All volatiles were evaporated, and the
remaining solid was dried to give 13c as a brown powder in 74% yield
Hz, CH(CH3)2), 28.5 (d, JCH = 127 Hz, CH(CH3)2), 47.7 (t, JCH
=
1
156 Hz, YCH2CC), 71.2 (t, JCH = 151 Hz, α-CH2 of THF), 113.7
1
2
1
(dd, JCH = 165 Hz, JYC = 2 Hz, CH = CH), 113.8 (d, JYC = 17 Hz,
YCH2CC), 122.3 (d, 1JCH = 157 Hz, p-Ar), 123.4 (d, 1JCH = 152 Hz,
1
1
m-Ar), 125.4 (d, JCH = 160 Hz, p-Ph), 128.5 (d, JCH = 157 Hz, m-
Ph), 130.3 (d, 1JCH = 158 Hz, o-Ph), 135.6 (i-Ph), 143.8 (o-Ar), 152.5
1
(130 mg, 0.151 mmol), mp 120−122 °C (dec). H NMR (400 MHz,
2
(d, JYC = 3.9 Hz, i-Ar), 163.4 (YCH2CC). Anal. Calcd for
C6D6 + 9 eq. of THF, 30 °C): δ 0.99−1.89 (m, Cy, CH(CH3)2, and β-
E
DOI: 10.1021/acs.organomet.7b00395
Organometallics XXXX, XXX, XXX−XXX

Organometallics
Article
CH2 of THF, integration is not given due to broadness in this region),
ASSOCIATED CONTENT
* Supporting Information
The Supporting Information is available free of charge on the
ACS Publications website at DOI: 10.1021/acs.organo-
met.7b00395.
■
3.18−3.28 (br m, 2H, Cy), 3.57 (br s, 10H, α-CH2 of THF and THF-
S
3
d8), 3.75 (sept, 4H, JHH = 6.4 Hz, CH(CH3)2), 5.00 (s, 2H, H2C
CC), 5.74 (s, 2H, CHCH), 7.04−7.12 (m, 3H, p-Ph and p-Ar),
7.22−7.30 (m, 6H, m-Ar and m-Ph), 7.59 (d, 2H, 3JHH = 6.8 Hz, o-Ph).
1H NMR (400 MHz, C6D6, 30 °C): δ 0.98−1.89 (m, Cy, CH(CH3)2,
and β-CH2 of THF, integration is not given due to broadness in this
region), 3.26−4.13 (br m, 10H, Cy, α-CH2 of THF, and CH(CH3)2),
4.98 (s, 2H, H2CCC), 5.80 (s, 2H, CHCH), 7.06 (t, 1H, 3JHH
= 7.6 Hz, p-Ph), 7.14 (p-Ar, overlapped with C6D6), 7.25−7.32 (m,
NMR spectra for the metal complexes and protonation
of 7a−c by PhNHCH3 (PDF)
Accession Codes
CCDC 1551191−1551192 contain the supplementary crystal-
lographic data for this paper. These data can be obtained free of
charge via www.ccdc.cam.ac.uk/data_request/cif, or by email-
ing data_request@ccdc.cam.ac.uk, or by contacting The
Cambridge Crystallographic Data Centre, 12 Union Road,
Cambridge CB2 1EZ, UK; fax: +44 1223 336033.
3
6H, m-Ar and m-Ph), 7.64 (d, 2H, JHH = 7.6 Hz, o-Ph). 13C NMR
(100 MHz, C6D6, 30 °C): δ 25.3 (br, β-CH2 of THF), 26.1 (br,
CH(CH3)2, 2 carbon of Cy), 28.4 (br, CH(CH3)2), 37.1 (br, Cy), 58.2
(d, 1JCH = 129 Hz, Cy), 71.1 (br, α-CH2 of THF), 79.0 (t, 1JCH = 170
3
Hz, H2CCC), 102.0 (d, JYC = 3 Hz, H2CCC), 114.3 (br d,
1JCH = 151 Hz, CHCH), 121.5 (d, 1JCH = 164 Hz, p-Ar), 123.5 (br,
1
m-Ar), 126.4 (d, JCH = 158 Hz, o-Ph), 129.2 (m-Ph), 133.9 (i-Ph),
AUTHOR INFORMATION
Corresponding Authors
*E-mail: tsurugi@chem.es.osaka-u.ac.jp.
*E-mail: mashima@chem.es.osaka-u.ac.jp.
ORCID
Haruki Nagae: 0000-0002-5589-7375
Notes
The authors declare no competing financial interest.
2
2
■
141.8 (br, o-Ar), 150.8 (d, JYC = 3 Hz, i-Ar), 171.7 (d, JYC = 1 Hz,
H2CCC(Ph)C), 205.4 (t, 2JCH = 3 Hz H2CCC), p-Ph signal
is overlapped with the C6D6 signal.
Protonation of 7a−c. To a solution of 7a−c (1.5 × 10−2 mmol)
in C6D6 (0.5 mL) was added N-methylaniline (1.5 × 10−2 mmol). The
solution was transferred into an NMR tube and analyzed by NMR
spectroscopy. In all cases, amidoyttrium complex 9 was observed
together with the protonated organic products: for the amidoyttrium
complex 9, 1H NMR (400 MHz, C6D6, 30 °C) δ 1.06 (br s, 8H, β-CH2
3
of THF), 1.34 (d, 24H, JHH = 6.8 Hz, CH(CH3)2), 2.96 (s, 3H,
NCH3), 3.55 (br s, 8H, α-CH2 of THF), 3.68 (sept, 4H, 3JHH = 6.8 Hz,
ACKNOWLEDGMENTS
■
3
CH(CH3)2), 5.67 (s, 2H, CHCH), 6.60 (d, 2H, JHH = 8.0 Hz, o-
H.N. acknowledges financial support by JSPS KAKENHI,
Grant Number JP16H06934, Grant-in-Aid for Research
Activity Start-up of The Ministry of Education, Culture, Sports,
Science, and Technology, Japan. A.K. acknowledges the JICA
Friendship Program of Osaka University, IIT Hyderabad. H.T.
acknowledges financial support by JSPS KAKENHI, Grant
Number JP15KT0064, Grant-in-Aid for Scientific Research (B)
of The Ministry of Education, Culture, Sports, Science, and
Technology, Japan.
Ph), 6.67 (t, 1H, 3JHH = 8.0 Hz, p-Ph), 7.09−7.16 (m, 2H, p-Ar), 7.24
3
3
(d, 4H, JHH = 7.2 Hz, m-Ar), 7.30 (t, 2H, JHH = 8.0 Hz, m-Ph).
The spectroscopic data for alkyne 10a: 1H NMR (400 MHz, C6D6,
30 °C) δ 0.20 (s, 9H, Si(CH3)3), 1.51 (s, 3H, CH3CCSi); for allene
11a, 1H NMR (400 MHz, C6D6, 30 °C) δ 0.10 (s, 9H, Si(CH3)3), 4.28
4
4
(d, 2H, JHH = 7.2 Hz, H2CCCH), 4.89 (t, 1H, JHH = 7.6 Hz,
H2CCCH).
The spectroscopic data for alkyne 10b: 1H NMR (400 MHz, C6D6,
3
30 °C) δ 0.89 (t, 3H, JHH = 7.2 Hz, CH3CH2CH2), 1.39−1.44 (m,
2H, CH3CH2CH2), 1.57 (t, 5JHH = 2.8 Hz, 3H, CH3CCCH2), 1.99−
REFERENCES
1
■
2.06 (m, 2H, CH3CH2CH2); for allene 11b, H NMR (400 MHz,
C6D6, 30 °C) δ 0.83 (t, 3H, 3JHH = 7.6 Hz, CH3CH2CH2), 1.39−1.44
(m, 2H, CH3CH2CH2), 1.81−1.93 (m, 2H, CH3CH2CH2), 4.59−4.63
(m, 2H, H2CCCH), 5.00−5.06 (m, 1H, H2CCCH).
The spectroscopic data for alkyne 10c: 1H NMR (400 MHz, C6D6,
30 °C): δ 1.65 (s, 3H, CH3CC), 6.96−7.02 (m, 3H, m- and p-Ph),
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4
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X-ray Crystallographic Analysis. All crystals were handled
similarly. The crystals were mounted on the CryoLoop (Hampton
Research Corp.) with a layer of light mineral oil and placed in a
nitrogen stream at 113(2) K. All measurements were made on a
Rigaku RAXIS RAPID imaging plate area detector with graphite
monochromated Mo−Kα (0.71075 Å) radiation. Crystal data and
structure refinement parameters are listed in Supporting Information.
The structures were solved by SHELXL-9716 and SIR2008,17 refined
on F2 by a full-matrix least-squares method, using SHELXL-97.16 Non-
hydrogen atoms were anisotropically refined. H atoms were included
in the refinement on calculated positions riding on their carrier atoms.
The function minimized was [Σw(Fo2 − Fc2)2] (w = 1/[σ2 (Fo2) +
(aP)2 + bP]), where P = (Max(Fo2,0) + 2Fc2)/3 with σ2(Fo2) from
counting statistics. The functions R1 and wR2 were (Σ∥Fo| − |Fc∥)/Σ|
Fo| and [Σw(Fo2 − Fc2)2/Σ(wFo4)]1/2, respectively. The ORTEP-3
program was used to draw the molecule.18
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DOI: 10.1021/acs.organomet.7b00395
Organometallics XXXX, XXX, XXX−XXX