Phosphine-tethered carbene ligands: Template synthesis and reactivity of cyclic and acyclic functionalized carbenes

Article abstract of DOI:10.1021/om100841j

Reaction of the phosphine-tethered isocyanide iron(II) complex 1, [CpFe(CO)(PCN)]I, with primary and secondary amines forms the corresponding acyclic (diamino)carbene complexes [CpFe(CO)(PCXNH)]I; X = n-butylamine (4), 4-methylaniline (5), dihexylamine (6

Full text of DOI:10.1021/om100841j

Organometallics 2010, 29, 6065–6076 6065
DOI: 10.1021/om100841j
Phosphine-Tethered Carbene Ligands: Template Synthesis and Reactivity
of Cyclic and Acyclic Functionalized Carbenes
Insun Yu,† Christopher J. Wallis,† Brian O. Patrick,† Paula L. Diaconescu,‡ and
Parisa Mehrkhodavandi*,†
†Department of Chemistry, University of British Columbia, 2036 Main Mall, Vancouver, British Columbia,
Canada, and Department of Chemistry & Biochemistry, University of California, Los Angeles,
‡
California, United States
Received August 30, 2010
Reaction of the phosphine-tethered isocyanide iron(II) complex 1, [CpFe(CO)(PCN)]I, with
primary and secondary amines forms the corresponding acyclic (diamino)carbene complexes
[CpFe(CO)(PCXNH)]I; X=n-butylamine (4), 4-methylaniline (5), dihexylamine (6). Five- and six-
membered cyclic (diamino)carbene complexes [CpFe(CO)(PCNHN-nCy)]I (n = 5 (9), 6 (10)) are
generated in two steps from the reaction of 1 with 2-chloroethyl and 3-chloropropylamine, first
forming acyclic diaminocarbene complexes [CpFe(CO)(PCNXNH)]I (X = chloroethyl (7), chloro-
propyl (8)), respectively, followed by deprotonation and intramolecular cyclization. This method-
ology is not effective for alcohols; however, acyclic (oxy)(amino)carbene complexes are produced
in two steps by the reaction of 1 with potassium methoxide, ethoxide, and isopropoxide to form
the corresponding ylidene complexes CpFe(CO)(PCO(X)N) (X = Me (11), Et (12), i-Pr (13)), which,
in the second step, can be protonated with an equimolar amount of HBF4 to form acyclic (oxy)-
(amino)carbene complexes [CpFe(CO)(PCO(X)NH)]BF4 (X=Me (14), Et (15), i-Pr (16)). Five and
six-membered cyclic (oxy)(amino)carbene complexes [CpFe(CO)(PCNO-nCy)]Cl (n =5 (17), 6 (18))
are formed by the concerted reaction of 1 with 2-chloroethoxide and 3-chloropropoxide followed
by intramolecular cyclization. The reversible conversion of acyclic (silyl)(amino)carbene complex
[CpFe(CO)(PPhCSi(Ph)3NH)]BF4 (20) to its ylidene precursor CpFe(CO)(PPhCSi(Ph)3N) (19) via slow
deprotonation with an equivalent of NaHB(OAc)3 is demonstrated, and the structure of 20 is
reported. All complexes were characterized by IR and NMR spectroscopy and, where possible, by
single-crystal X-ray diffraction. DFT calculations were used to support the electronic structure of
complexes deduced from structural and spectroscopic data.
Introduction
based on two donors to stabilize the carbene (push-push
carbenes), early work on acyclic carbenes8-11 and recent
expansion to stable cyclic (alkyl)(amino)carbenes12,13 have
reinforced the importance of investigating unconventional
carbene ligands.
The two main routes to metal-carbene complexes are ligand
substitution using the free carbenes or their precursor imida-
zoliumsalts, andtemplate synthesis using a modification of an
existing metal-C(ligand) functionality.14-16 While ligand sub-
stitution is the most versatile and generally applicable route to
The excellent properties of stable, singlet N-heterocyclic
carbenes (NHCs) as ligands for transition metals1-3 have
prompted a massive effort to modify their electronic and steric
properties by varying the carbene-bound substituents and
developing multidentate donor-functionalized analogues.4-7
Although the major focus in the literature has been on ligands
*To whom correspondence should be addressed. E-mail: mehr@
chem.ubc.ca.
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2010 American Chemical Society
Published on Web 10/15/2010
pubs.acs.org/Organometallics

6066 Organometallics, Vol. 29, No. 22, 2010
Yu et al.
metalcarbene complexes, inthe pastfew yearstherehasbeena
resurgence of the classic template synthesis of Fischer car-
benes to enable formation of unusual and difficult to obtain
complexes.17-21
Scheme 1. Synthesis of Phosphine-Tethered Diaminocarbene
Complexes from 136
Nucleophilic attack on the coordinated carbon of a metal-
bound isocyanide is an attractive and commonly used route
for the formation of aminocarbene metal complexes with
sufficiently electrophilic metals.14,15 Precursor metal isocya-
nide complexes have long been used in the reaction with
protic nucleophiles, such as primary and secondary amines
or alcohols, to yield acyclic diamino- and (alkoxy)(amino)-
carbene complexes.22-24 They can also be used to afford
NHC complexes (cyclic diamino-, (oxy)(amino)-, and (thio)-
(amino)carbenes) by spontaneous, base-promoted, 1,3-dipo-
larophile- and 1,3-dipole-promoted cyclization.25-29 Com-
plexes with benzannulated carbenes (benzoxazolylidenes
and benzimidazolinylidenes) can be formed from the use of
2-hydroxyaryl isocyanide and 2-aminoarylisocyanide as pre-
cursors by spontaneous cyclization, though they must be
protected before metalation.30-35
Scheme 2. Synthesis of Acyclic Diaminocarbene Complexes 3-6
In 1995, Liu and co-workers36 reported the synthesis of
an acyclic diamino carbene iron(II) complex from the reac-
tion of phosphino-isocyanide chelated iron(II) complex 1
with n-propylamine. Complex 1, a piano stool iron(II) com-
plex bearing a chelating isocyanide-phosphine ligand, is gen-
erated by reacting a phosphinimine-phosphine compound
with CpFe(CO)2I (Scheme 1). In the course of our studies of
phosphinimine donor complexes of late transition metals,37,38
we have recently communicated our methodology for the
synthesis of rare, acyclic (phosphino)(amino)- and (silyl)-
(amino)carbenes using complex 1 as a starting scaffold.39
Herein, we report an expanded family of acyclic and cyclic
tethered carbene complexes. Their electronic properties and
reactivity have been systematically studied, and DFT calcula-
tions have been used to understand the trends observed.
Results and Discussion
Acyclic Diaminocarbene Complexes. We have repeated
Liu’s initial experiment as well as synthesized the tert-butyl
analogue of the proligand Ph3PdN(CH2)3P(t-Bu)2, which
formed the (tert-butyl)phosphine-functionalized isocyanide
complex 2.36 The IR spectrum of 2 shows peaks corresponding
(17) Ruiz, J.; Garcia, G.; Mosquera, M. E. G.; Perandones, B. F.;
Gonzalo, M. P.; Vivanco, M. J. Am. Chem. Soc. 2005, 127, 8584–8585.
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to the isocyanide (νCN = 2089 cm-1) and carbonyl (νCO
=
1999 cm-1) moieties. The 13C{1H} NMR spectrum of 2
shows signals for the isocyanide and carbonyl carbons at
183.1 and 214.2 ppm, respectively. These data confirm the
formation of the isocyanide complex 2 and Ph3PdO and
suggest a nucleophilic attack of the iminophosphorane at
the carbonyl ligand. The 31P{1H} NMR spectrum of the
reaction mixture containing 2 shows a signal at 29.9 ppm for
Ph3PdO as well as a signal at 53.8 ppm, which indicates
the formation of a phosphino moiety coordinated to the
metal center (87.7 ppm for 1).
Angew. Chem., Int. Ed. 2005, 44, 3759–3763.
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Organometallics 1996, 15, 1055–1061.
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569–570.
Reactions of the iron isocyanide complexes 1 and 2 with
excess n-butyl-, dihexyl-, or 3-methylphenylamine at room
temperature in CH2Cl2 yield the acyclic, diaminocarbene
complexes 3-6 in greater than 70% yield (Scheme 2). The
1
characteristic features of 3 are two singlets in the H NMR
spectrum at 5.96 and 7.97 ppm, corresponding to the N-H
protons, an upfield-shifted 31P{1H} NMR signal at 77.9 ppm,
and a significant downfield shift of the 13C{1H} NMR signal
to 221 ppm. The NMR spectral features of carbene complexes
4-6 are similar to those of 3; complex 5, which was formed
from a secondary amine, shows only one singlet for the N-H
proton, at 7.75 ppm. The average νCO and νCN stretching
frequencies for 3-6 are 1950 and 1541 cm-1, respectively,
indicating minimal electronic changes with ligand substitu-
tion. Although it is possible to form orthometalated amino-
carbene complexes of electron-poor metals substituted with a
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Mehrkhodavandi, P. Organometallics 2009, 28, 3889–3895.

Article
Organometallics, Vol. 29, No. 22, 2010 6067
Figure 1. Molecular structures of complexes 3 (left) and 5 (right) (depicted with thermal ellipsoids at 50% probability and most H
˚
atoms omitted for clarity). Selected distances (A) and angles (deg) for 3: C1-Fe1 1.742(3), C2-Fe1 1.958(3), P1-Fe1 2.287(9), C1-O1
1.152(3), C2-N1 1.332(4), C2-N2 1.342(4), N1-C2-N2 115.1(3), N1-C2-Fe1 126.7(2), N2-C2-Fe1 117.9(2), Fe1-C1-O1
175.8(2), Cl-Fe1-C2 95.93(12), C1-Fe1-P1 89.58(10), C2-Fe1-P1 94.55(9). For 5: C1-Fe1 1.749(3), C2-Fe1 1.992(3), P1-Fe1
2.2029(8), C1-O1 1.151(3), C2-N1 1.345(3), C2-N2 1.356(3), N1-C2-N2 113.6(2), N1-C2-Fe1 122.7(2), N2-C2-Fe1 123.6(2),
Fe1-C1-O1 175.6(3), C2-N1-C10 128.1, C2-N2-C23 124.1(2), C2-N2-C29 122.7(2), C1-Fe1-C2 95.23(12), C1-Fe1-P1
89.00(10), C2-Fe1-P1 95.03(8).
Table 1. Comparison of Electronic Parameters for the Cations of 3, 4, and 5a
Fe-Ccarbene NMb
bond order
(Mayer)
NP-Ccarbene NMb,c
bond order
(Mayer)
N-Ccarbene NMb
bond order
(Mayer)
Hirshfeld charge
of Fe (Mulliken)
Hirshfeld charge
of Ccarbene (Mulliken)
complex
3
4
5
0.85 (0.88)
0.83 (0.90)
0.79 (0.90)
1.44 (1.21)
1.45 (1.22)
1.44 (1.20)
1.46 (1.20)
1.46 (1.20)
1.45 (1.30)
0.02 (-0.08)
0.00 (-0.16)
0.02 (-0.11)
0.06 (0.25)
0.05 (0.26)
0.05 (0.24)
a Numbers in parentheses represent a different value for the same parameter, as indicated at the top of each column. b NM is Nalewajski-Mrozek
bond order calculated from two-electron valence indices (three-index set). cNP is the nitrogen part of the same cycle as the phosphine.
Scheme 3. Synthesis of Cyclic Diaminocarbene Complexes 9 and 10
phenyl group,40 orthometalation is not observed with com-
plex 6 due to the electronically saturated iron center.
for half-sandwich iron(II) NHC complexes likely due to their
acyclic nature.45 These results indicate that there are no
significant differences between primary and secondary amino
substituents on the carbene carbon.
The above electronic interpretation, which is based on
structural characteristics, is supported by the results of DFT
calculations performed on the cations of 3, 4, and 5. The
comparison between the two primary amine complexes (3
and 4) and between the primary (4) and secondary (5) amine
complexes indicates that all the electronic parameters inves-
tigated are similar for the three complexes (Table 1).
Cyclic Diaminocarbene Complexes. Analogous tethered
N-heterocyclic carbene complexes are generated via a
two-step route (Scheme 3). Reactions of 1 with 4 equiv of
2-chloroethylamine or 3-chloropropylamine afford the cor-
responding acyclic diaminocarbene complexes 7 and 8 in
greater than 90% yield. Subsequent dehydrohalogenations
of 7 and 8 by excess NaOEt yield the air-stable, five- and six-
membered, cyclic diaminocarbene complexes 9 and 10 in
The molecular structures of 3 and 5 were determined by
single-crystal X-ray diffraction and show piano-stool iron
centers with a distorted octahedral geometry coordinated to
˚
planar carbenes (Figure 1). The Fe-Ccarbene (3, 1.958 A; 5,
˚
˚
˚
1.992 A), Ccarbene-N1 (3, 1.332 A; 5, 1.345 A), and
˚
˚
Ccarbene-N2 (3, 1.342 A; 5, 1.356 A) distances are longer
than those of the parent isocyanide complex 1 (Fe-Cisocyanide
1.77 A and Cisocyanide-N, 1.20 A). The Fe-Ccarbene-N1
angles (∼120°) are more acute than the Fe-C-N angle in 1
(169°). The N1-Ccarbene-N2 angles (3, 115.1°; 5, 113.6°) are
intermediate between free acyclic diaminocarbenes (121°)41,42
and NHCs (104.7° and 102.2°),43,44 but larger than reported
,
36
˚
˚
(40) Yam, V. W. W.; Chu, B. W. K.; Cheung, K. K. Chem. Commun.
1998, 2261–2262.
(41) Alder, R. W.; Allen, P. R.; Murray, M.; Orpen, A. G. Angew.
Chem., Int. Ed. Engl. 1996, 35, 1121–1123.
(42) Alder, R.; Blake, M. E. Chem. Commun. 1997, 1513–1514.
(43) Arduengo, A. J.; Harlow, R. L.; Kline, M. J. Am. Chem. Soc.
1991, 113, 361–363.
(44) Arduengo, A. J.; Goerlich, J. R.; Marshall, W. J. J. Am. Chem.
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130, 17174–17186.

6068 Organometallics, Vol. 29, No. 22, 2010
Yu et al.
Figure 4. Molecular structure of complex 10 (depicted with
thermal ellipsoids at 50% probability and most H atoms as well
˚
as solvent molecules omitted for clarity). Selected distances (A)
Figure 2. 1H NMR spectra of (a) the acyclic diaminocarbene
complexes, 7(left) and8 (right), and(b) thefive-andsix-membered
cyclic diaminocarbene complexes, 9 (left) and 10 (right).
and angles (deg): C1-Fe1 1.751(7), C2-Fe1 1.972(7), P1-Fe1
2.1958(19), C1-O1 1.137(9), C2-N1 1.336(9), C2-N2 1.336(10),
N1-C2-N2 116.7(6), N1-C2-Fe1 127.2(6), N2-C2-Fe1
116.1(5), Fe1-C1-O1 172.9(6), C2-N1-C5 123.7(6), C1-
Fe1-C2 96.5(3), C1-Fe1-P1 88.5(2), C2-Fe1-P1 93.4(2).
The electronic similarity between 7 and 9 and between 9
and 10 deduced from structural characteristics is supported
by the results of DFT calculations performed on the cations
for the three complexes. The comparison between the three
complexes indicates that all the electronic parameters inves-
tigated are similar to each other and to those for complexes
3-5 (Table 2).
Formation of the intermediate species 7 and 8 suggests a
mechanism different from that proposed for the reaction
of haloamines with isocyanide complexes.15 In one case, the
formation of the cyclic diaminocarbene palladium com-
plexes is proposed to occur by initial nucleophilic attack of
the bromoethylamine on the palladium-bound isocyanide
carbon to yield an imino intermediate (I) with subsequent
deprotonation and ring closure in the presence of a further
molecule of 2-chloroethylamine (Scheme 4). However, inter-
mediate I was neither observed nor proposed in this and
other similar systems.47-49
We propose a similar first step; however, in our system this
is followed by proton transfer in intermediate I from the
amine to the imido to give the acyclic diaminocarbene com-
plex 7, which is not observed nor proposed in the case of the
palladium complexes.15 The NOE spectrum of 7, in which
we selectively saturated the N2-H signal, shows that N1-H
(6.69 ppm) and N2-H (8.84 ppm) are not close enough to
show dipole-dipole coupling. In addition, the four methylene
protons of the chloroethyl functionality are close enough to
have a through-space interaction with the saturated N2-H
resonance (Figure 5). Deprotonation of 7 by the addition of
NaOEt results in a spontaneous intramolecular cyclization to
yield complex 9.
Figure 3. Molecular structure of complex 7 (depicted with thermal
ellipsoids at 50% probability and most H atoms omitted for
clarity). Selected distances (A) and angles (deg): C1-Fe1 1.744(3),
C2-Fe1 1.949(3), P1-Fe1 2.192(8), C1-O1 1.147(4), C2-N1
1.330(4), C2-N2 1.344(4), N1-C2-N2 115.7(3), N1-C2-Fe1
127.2(2), N2-C2-Fe1 117.1(2), Fe1-C1-O1 177.5(3), C2-
N1-C10 127.2(2), C1-Fe1-C2 93.38(13), C1-Fe1-P1 89.66(10),
C2-Fe1-P1 95.23(9).
˚
greater than 80% yield. Transformation of the acyclic dia-
minocarbene 7 to the five-membered cyclic diaminocarbene
1
9 is readily monitored by H NMR spectroscopy: the two
broad singlets for the N-H protons at 6.69 and 8.84 ppm of
7 are replaced by one broad resonance at 8.31 ppm for 9
(Figure 2a). Similar results are observed for the transforma-
tion of 8 to 10 (Figure 2b).
The molecular structures of 7 and 10 were determined by
single-crystal X-ray diffraction and show similar octahedral
piano-stool iron centers, consistent with those of the acyclic
diaminocarbene complexes 3 and 5 (Figures 3 and 4). The
carbonyl stretching frequencies of the acyclic (νCO = 1948-
1959 cm-1) and cyclic (νCO = 1949-1952 cm-1) diamino-
carbene fragments are also similar, indicating very little
electronic difference between the two species. More pro-
nounced differences in CO frequencies are reported between
acyclic (νCO av of 2021 cm-1) and saturated cyclic (νCO av
of 2038 cm-1) square-planar carbene complexes such as
cis-(CO)2Rh(carbene)Cl.46
(Oxy)(amino)carbene Complexes. The chemistry of the
diamino carbenes can be expanded to (oxy)(amino)carbenes.
Literature reports show that the reaction of some metal-
activated isocyanide ligands with alcohols can form cyclic
and acyclic (oxy)(amino)carbenes in one step.15 However,
Hahn et al. have reported that the enhanced back-bonding
(47) Motschi, H.; Angelici, R. J. Organometallics 1982, 1, 343–349.
(48) Belluco, U.; Crociani, B.; Michelin, R.; Uguagliati, P. Pure Appl.
Chem. 1983, 55, 47–54.
(46) Herrmann, W. A.; Ofele, K.; von Preysing, D.; Herdtweck, E.
J. Organomet. Chem. 2003, 684, 235–248.
(49) Belluco, U.; Michelin, R. A.; Uguagliati, P. J. Organomet. Chem.
1983, 250, 565–587.

Article
Organometallics, Vol. 29, No. 22, 2010 6069
Table 2. Comparison of Electronic Parameters for the Cations of 7, 9, and 10a
Fe-Ccarbene NMb
bond order
(Mayer)
NP-Ccarbenec NMb
bond order
(Mayer)
N-Ccarbene NMb bond
order
(Mayer)
Hirshfeld
charge of
Fe (Mulliken)
Hirshfeld
charge of Ccarbene
(Mulliken)
complex
7
9
10
0.83 (0.90)
0.84 (0.91)
0.81 (0.88)
1.46 (1.22)
1.43 (1.25)
1.45 (1.28)
1.44 (1.17)
1.43 (1.17)
1.44 (1.17)
0.00 (-0.18)
0.01 (-0.16)
0.00 (-0.16)
0.05 (0.26)
0.04 (0.28)
0.05 (0.27)
a Numbers in parentheses represent a different value for the same parameter, as indicated at the top of each column. b NM is Nalewajski-Mrozek
bond order calculated from two-electron valence indices (three-index set). cNP is the nitrogen part of the same cycle as the phosphine.
Scheme 4. The Two Proposed Mechanisms for the Formation of
9
from the electron-rich CpFe fragments can deactivate a
coordinated isocyanide carbon toward nucleophilic attack
from an alcohol.34,35 The lack of a reaction between the
coordinated isocyanide in 1 and protic alcohols prompted
us to use a two-step route comprised of the direct nucleo-
philic attack on the isocyanide by an alkoxide (a more
nucleophilic fragment than alcohol), followed by proton-
ation of the resulting ylidene to form carbene complexes
(Scheme 5).39
Figure 5. (a) 1H NMR spectrum and (b) the nuclear Overhauser
effect (NOE) spectrum of complex 7 saturating the N2-H signal
at 8.84 ppm.
Reactions of complex 1 with KOR (R = Me, Et, i-Pr) form
ylidene complexes 11-13 in quantitative yield. These com-
plexes lead to the acyclic (oxy)(amino)carbene complexes
14-16 in 90% isolated yield upon subsequent protonations
of the imido nitrogen with HBF4 (Scheme 5). The carbonyl
stretching frequencies of the ylidene complexes are approxi-
mately 20 cm-1 lower than those of the carbene complexes,
indicating a more electron-rich iron center with a formally
anionic carbon ligand in the case of the ylidene complexes.
The respective average CdN stretching frequencies of com-
plexes 11-13 (∼1560 cm-1) and 14-16 (1550 cm-1) suggest a
greater electronic communication through thecarbene carbon
and the lone pair on the neighboring oxygen.
Scheme 5. Synthesis of Acyclic (Oxy)(amino)carbanion and
Carbene Complexes 11-13 and 14-16, Respectively
Five- and six-membered cyclic (oxy)(amino)carbene com-
plexes 17 and 18 were synthesized by the reaction of lithium
2-chloroethoxide or 3-chloropropanoxide with complex 1 in
1
DFT calculations performed on the full molecule of 11 and
the cation of 14 also indicate that there are larger electronic
differences between these two complexes than between any
other pair/series considered (Table 3). As expected, the
N-Ccarbene bond order is higher for 11 than for 14, while
the opposite is true for the O-Ccarbene bond order. In
addition, although the iron and Ccarbene charges are similar
for the two complexes, the Fe-Ccarbene bond order is higher
for 14 than for 11, in agreement with a larger electron
delocalization in 14.
CH2Cl2 at room temperature (Scheme 6). The H NMR
spectrum of each complex shows new methine resonances,
while the 13C{1H} NMR spectra show downfield-shifted
carbene carbon signals at 229.0 and 231.3 ppm for 17 and
18, respectively. The IR spectra of 17 and 18 show CdN
absorptions at 1529 cm-1 for both complexes, a ∼34 cm-1
decrease in νCO compared to 1. The carbonyl stretch in 18
(1966 cm-1) is similar to that in the acyclic analogues 14-16
and higher than in the ylidene complex 11 (1937 cm-1),
suggesting a more electron-rich iron center in the latter
compounds. These results also suggest that, as with the cyclic
diaminocarbene complexes, the change in ring size does not
have a significant effect on the electronic properties of the
complexes.
1
The H NMR spectra of the ylidene complexes 11-13
show characteristic resonances for the methyl and methine
groups of the alkoxide substituents at high fields. The spec-
tra of the corresponding carbene complexes 14-16 show
one additional broad singlet for the N-H resonance at
∼8.7 ppm. The 13C{1H} NMR spectra of 14-16 show
signals that are ∼40 ppm downfield of 11-13, signifying
a slight difference of electron density between the carbene
and ylidene carbons. The molecular structure of 11 was deter-
mined by X-ray crystallography (Figure 6). The Cylidene-Fe
The molecular structure of 18 was determined by
X-ray crystallography (Figure 7). The Fe-Ccarbene distance
(1.976 A) is slightly longer than the analogous distance in the
˚
˚
ylidene complex 11 (1.965 A), but the difference is within
experimental error. As with previously discussed complexes,
˚
the Ccarbene-N1 distance of 18 (1.322 A) is longer than that
of the acyclic (oxy)(amino) ylidene complex 11 (1.260 A) and
˚
˚
˚
distance in 11 (1.965 A) is similar to that of 3 (1.958 A)
˚
and about 0.19 A greater than that of isocyanide complex 1
˚
that of the isocyanide complex 1 (1.20 A). The Ccarbene-O2
distance of 18 (1.330 A) is shorter than that of complex 11
36
˚
(1.77 A).
˚

6070 Organometallics, Vol. 29, No. 22, 2010
Table 3. Comparison of Electronic Parameters for Complex 11 and the Cations of 14 and 18a
Yu et al.
Fe-Ccarbene NMb
bond order
(Mayer)
N-Ccarbene NMb
bond order
(Mayer)
O-Ccarbene NMb
bond order
(Mayer)
Hirshfeld
charge of Fe
(Mulliken)
Hirshfeld
charge of Ccarbene
(Mulliken)
complex
11
14
18
0.79 (0.85)
0.91 (0.95)
0.87 (0.92)
1.90 (1.78)
1.50 (1.25)
1.48 (1.30)
1.18 (0.90)
1.33 (1.01)
1.33 (1.01)
0.00 (-0.20)
0.01 (-0.21)
0.00 (-0.21)
0.04 (0.38)
0.08 (0.44)
0.08 (0.44)
a Numbers in parentheses represent a different value for the same parameter, as indicated at the top of each column. b NM is Nalewajski-Mrozek
bond order calculated from two-electron valence indices (three-index set).
Figure 7. Molecular structure of 18 (depicted with thermal elli-
psoids at 50% probability and all H atoms omitted for clarity).
Selected distances (A) and angles (deg): C1-Fe1 1.742(4),
Figure 6. Molecular structure of complex 11 (depicted with
thermal ellipsoids at 50% probability and all H atoms as well
˚
as solvent molecules omitted for clarity). Selected distances (A)
˚
C1-O1 1.146(5), C2-Fe1 1.976(5), P1-Fe1 2.185(7), C2-N1
1.322(9), C2-O2 1.330(11), N1-C2-O2 122.8(7), N1-C2-
Fe1 127.6(5), O2-C2-Fe1 109.5(5), Fe1-C1-O1 176.9(3),
C2-N1-C10 123.6(8), C2-N1-C23 122.5(9), C10-N1-C23
113.8(9), C1-Fe1-C2 92.0(2), C1-Fe1-P1 93.27(19), C2-
Fe1-P1 93.5(3).
and angles (deg): C1-Fe1 1.744(6), C1-O1 1.160(7), C2-Fe1
1.965(6), P1-Fe1 2.263(5), C2-N1 1.260(6), C2-O2 1.403(6),
O2-C2-N1 114.9(5), O2-C2-Fe1 174.41(1), N1-C2-Fe1
134.8(4), C2-O-C11 116.09(7), C2-N1-C8 120.2(4), Cl-Fe1-
C2 92.4(2), C1-Fe1-P1 90.96(18), C2-Fe1-P1 90.48(16).
Scheme 6. Synthesis of Five- and Six-Membered Cyclic
(Oxy)(amino)carbene Complexes 17 and 18
Scheme 7. Reversible Reaction of Acyclic (Silyl)(amino) Ylidene
(19) and Carbene (20) Complexes
˚
˚
(1.403 A). Interestingly, the Ccarbene-N1 (1.332 A) and
agreement with the ionic nature of 20. The Ccarbene-N1
distance (1.302 A) of the (silyl)(amino)carbene complex 20
˚
˚
Ccarbene-O2 (1.330 A) distances are similar. DFT calcula-
tions on the full cation of 18 agree with the crystallographic
observations: similar distances were found for Fe-Ccarbene in
11 (1.99 A) and 18 (1.95 A) and for Ccarbene-N1 (1.34 A) and
Ccarbene-O2 (1.35 A). A comparison between the electronic
parameters for 14 (acyclic carbene) and 18 (cyclic carbene)
shows that the two complexes are similar (Table 3).
Acyclic (Silyl)(amino)carbene Complexes. We have com-
municated the first examples of donor-functionalized acyclic
(phosphino)- and (silyl)(amino)carbenes, which were gener-
ated via a two-step template synthesis on a piano-stool
iron(II) complex.39 Spectroscopic analysis of these com-
plexes indicates that, although they are both “push-spectator”
carbenes, they are, nevertheless, electronically distinct. We
showed that reacting complex 1 with KSiPh3 yielded the
ylidene complex 19, which upon protonation formed the
carbene complex 20 (Scheme 7).
˚
is longer than that of the ylidene complex 19 (1.289 A). The
˚
Ccarbene-Si distance (1.933 A) in 20 is shorter than that of
complex 19 (1.913 A). The distances and angles of 20 are
consistent with those in the only other reported (silyl)-
˚
˚
˚
˚
˚
(amino)carbene complex, (COD)(Cl)RhdC(NMe2)(SiMePh2)
(C-N 1.316 A, C-Si 1.927 A, C-Rh 1.993 A).50 The structural
data support the fact that the silyl substituent acts as a spectator,
as observed previously.
˚
˚
˚
The above interpretation is supported by the results of
DFT calculations performed on the full molecule of 19 and
the cation of 20 (Table 4). These results are also compared to
those obtained from a geometry optimization on the full
molecule (COD)(Cl)RhdC(NMe2)(SiMePh2).50 The com-
parison between the three complexes indicates that all the
electronic parameters investigated are similar to each other
and to those for the complexes discussed herein. The most
noticeable difference is the Hirshfeld and Mulliken charges,
The molecular structure of 20 has since been elucidated by
X-ray crystallography and shows a distorted-octahedral iron
center similar to that of 19 (Figure 8). The Fe-Ccarbene
(50) Canac, Y.; Conejero, S.; Donnadieu, B.; Schoeller, W. W.;
Bertrand, G. J. Am. Chem. Soc. 2005, 127, 7312–7313.
˚
˚
distance (1.943 A) of 20 is shorter than that of 19 (2.005 A), in

Article
Organometallics, Vol. 29, No. 22, 2010 6071
which have negative values for the carbene carbon of the
three silyl complexes, while these parameters have a positive
value for all the other compounds investigated.
The (silyl)(amino)carbene complex 20 can be converted
back to the ylidene complex 19 via reaction with 6 equiv of
sodium triacetoxyborohydride (NaHB(OAc)3) in CH2Cl2, at
room temperature under static vacuum overnight. The con-
version was monitored by 31P{1H} NMR spectroscopy. The
reaction is slow; about 30% of complex 20 is converted to 19
in one day without any further decomposition. The full
conversion of 20 to 19 requires four evacuations of the
reaction mixture in four days. A more reactive hydride
source such as LiAlH4 reacts rapidly (1 h) at room tempera-
ture and even at -35 °C; however, many byproducts are
observed along with the desired product 19.
Conclusions
Herein we describe the synthesis and characterization of a
family of phosphine-tethered ylidene and carbene complexes
of iron(II) via template synthesis from a half-sandwich com-
plex bearing a chelating isocyanide-phosphine ligand.
The acyclic diamino carbene complexes are prepared by
the reaction of the isocyanide iron(II) complex with primary
and secondary amines, while the five- and six-membered cyclic
analogues are synthesized using routes reported in the litera-
ture, via spontaneous cyclization and base-promoted cycliza-
tion, respectively. A new mechanism for the formation of
cyclic diaminocarbene complexes is proposed on the basis of
in situ observation and crystallographic identification of inter-
mediates.
The direct reaction of alcohols, phosphines,39 and silanes
with the isocyanide iron(II) complex does not form XCN
carbene complexes (X = O, P, or Si). These complexes may
be generated, however, via a two-step procedure involving
the synthesis of ylidene complexes via nucleophilic attack on
the iron-bound isocyanide carbon followed by protonation
of the resulting cyclic imine to form the carbene complexes.
Diagnostic 13C{1H} NMR data for the resulting carbenes
show a distinct trend with the nature of the substituent:
Ccarbene-N (∼219 ppm) < Ccarbene-O (∼230 ppm) <
Ccarbene-P (∼276 ppm)39 <Ccarbene-Si (∼299 ppm). The
shifts correlate well with the donor-acceptor properties of
Figure 8. Molecular structure of complex 20 (depicted with
thermal ellipsoids at 50% probability and most H atoms
˚
omitted for clarity). Selected distances (A) and angles (deg):
C1-Fe1 1.750(3), C1-O1 1.149(4), C2-Fe1 1.943(3), P1-Fe1
2.2094(9), C2-N1 1.302(4), C2-Si(1) 1.933(3), Si1-C2-N1
110.6(2), Si1-C2-Fe1 121.90(16), N1-C2-Fe1 127.5(2),
C2-N1-C10 127.7(3), Fe1-C1-O1 178.1(3).
Table 4. Comparison of Electronic Parameters for 19, the Cation of 20, and (COD)(Cl)RhdC(NMe2)(SiMePh2)a
M-Ccarbene NMb
bond order
(Mayer)
N-Ccarbene NMb
bond order
(Mayer)
Si-Ccarbene NMb
bond order
(Mayer)
Hirshfeld
charge of M
(Mulliken)
Hirshfeld
charge of Ccarbene
(Mulliken)
complex
19
20
0.84 (0.91)
1.00 (1.03)
0.99 (0.54)
1.96 (1.72)
1.64 (1.33)
1.61 (1.42)
0.86 (0.75)
0.83 (0.77)
0.87 (0.87)
0.00 (-0.09)
0.01 (-0.10)
0.27 (0.63)
-0.08 (-0.29)
-0.05 (-0.30)
-0.07 (-0.46)
[Rh]c
a Numbers in parentheses represent a different value for the same parameter, as indicated at the top of each column. b NM is Nalewajski-Mrozek
bond order calculated from two-electron valence indices (three-index set). c [Rh] is (COD)(Cl)RhdC(NMe2)(SiMePh2).50
Figure 9. 31P{1H} NMR (CH2Cl2) spectra for conversion of complex 20 to complex 19 by reacting with (a) 6 (at 24 h), (b) 12 (at 48 h),
and (c) 24 (at 96 h) equiv of NaHB(OAc)3.

6072 Organometallics, Vol. 29, No. 22, 2010
Yu et al.
the substituent X in XCN carbene complexes. The greater
degree of Ccarbene-X interaction, where X=N rather than
X = O, P,39 and Si, is reflected in the greater shielding of
Ccarbene in aminocarbene complexes. IR spectroscopic data
on these octahedral iron complexes are not as diagnostic
for determining the different electronic properties of the
carbene complexes. DFT calculations were used to support
the electronic interpretations based on crystallographic and
NMR spectroscopic data. For a series of complexes with
different Ccarbene substituents, the Fe-Ccarbene Mayer bond
order increases from 4 (0.90) to 14 (0.95) and to 20 (1.03).
This systematic study of the template synthesis of acyclic and
cyclic carbenes on a model system has enabled us to directly
compare a diverse family of functionalized carbene ligands.
Experimental Section
General Methods. Unless otherwise specified, all procedures
were carried out using standard Schlenk techniques or in an
MBraun glovebox. A Bruker Avance 300 MHz spectrometer
and Bruker Avance 400dir MHz spectrometer were used to
record the 1H NMR, 13C{1H} NMR, and 31P{1H} NMR
spectra. 1H NMR chemical shifts are given in ppm versus
residual protons in deuterated solvents as follows: δ 5.32 for
CD2Cl2 and δ 7.27 for CDCl3. 13C{1H} NMR chemical shifts
are given in ppm versus residual 13C in solvents as follows: δ
54.00 for CD2Cl2 and δ 77.23 for CDCl3. 31P{1H} NMR chemi-
cal shifts are given in ppm versus 85% H3PO4 set at 0.00 ppm. A
Waters/Micromass LCT mass spectrometer equipped with an
electrospray (ESI) ion source and a Kratos-50 mass spectro-
meter equipped with an electron impact ionization (EI) source
were used to record low-resolution and high-resolution spectra.
IR spectra were obtained on a Thermo Scientific FT-IR spectro-
meter (Nicolet 4700). Diffraction measurements for X-ray
crystallography were made on a Bruker X8 APEX II diffraction
with graphite-monochromated Mo KR radiation. The structure
was solved by direct methods and refined by full-matrix least-
squares using the SHELXTL crystallographic software of
Bruker-AXS (Table 6). Unless specified, all non-hydrogen
atoms were refined with anisotropic displacement parameters,
and all hydrogen atoms were constrained to geometrically
calculated positions but were not refined. ESI mass spectra were
obtained on a Waters/Micromass LCT time-of-flight (TOF)
mass spectrometer equipped with an electrospray ion source.
CHN analysis was performed using a Carlo Erba EA1108 ele-
mental analyzer. The elemental composition of an unknown
sample is determined by using a calibration factor. The calibration
factor is determined by analyzing a suitable certified organic
standard (OAS) of a known elemental composition.
˚
All solvents were degassed and dried using 3 A molecular
sieves in an MBraun solvent purification system. THF, Et2O,
and C6H6 (C6D6) were further dried over Na/benzophenone and
distilled under N2. CH3CN (CD3CN), CH2Cl2 (CD2Cl2), and
CHCl3 (CDCl3) were dried over CaH2 and vacuum-transferred
to a Strauss flask and then degassed through a series of freeze-
pump-thaw cycles. Deuterium-labeled NMR solvents were
purchased from Cambridge Isotope Laboratory. Other chemi-
cals and solvents were purchased from Aldrich, Fisher, Alfa
Aesar, or Strem and were used without further purification.
1-Azido-3-chloropropane,51 N-(3-chloroprophyl)triphenylpho-
sphinimine,36 N-(3-(diphenylphosphino)propyl)triphenylphos-
phinimine,36 CpFe(CO)2I, and complexes 19 and 2039 were pre-
pared according to literature procedures.
Synthesis of Complex 1. The preparation of complex 1 is
a modification of a literature procedure.36 A solution of
(51) Yao, L.; Smith, B. T.; Aube, J. J. Org. Chem. 2004, 69, 1720–
1722.

Article
Organometallics, Vol. 29, No. 22, 2010 6073
N-(3-(diphenylphosphino)propyl)triphenylphosphinimine (2.52 g,
5.01 mmol) and CpFe(CO)2I (1.52 g, 5.01 mmol) in toluene
(200 mL) was stirred at room temperature overnight. A yellow
precipitate was collected on a fine frit. The yellow solid was washed
with toluene and THF to remove triphenylphosphine oxide com-
pletely and then dried under vacuum to yield 1 as a yellow solid
(2.44 g, 92% yield). IR (CDCl3): 2089 cm-1 (νCN) and 1999 cm-1
(νCO). 1H NMR (300 MHz, CDCl3): δ 1.90-2.18 (m, -CH2, 1H),
2.18-2.47 (m, -CH2, 1H), 2.73 (td, J = 13.42, 9.25 Hz, -CH2,
1H), 3.39 (ddd, J = 14.50, 4.45, 4.34 Hz, -CH2, 1H), 3.78-3.98
(m, -CH2, 1H), 4.80 (ddd, J = 14.90, 8.74, 4.23 Hz, -CH2, 1H),
5.02 (d, J = 1.14 Hz, Cp H, 5H), 7.42-7.79 (m, aryl H, 10H).
13C{1H} NMR (75.44 MHz, CDCl3): δ 28.45 (d, J = 6.13 Hz,
-CH2, 1C), 31.66 (d, J = 32.20 Hz, -CH2, 1C), 48.76 (s, -CH2,
1C), 85.90 (s, Cp C, 5C), 123.44, 134.95 (m, aryl C, 12C), 183.58
(d, J = 35.27 Hz, Cisocyanide), 212.51 (d, J = 23.00 Hz, Ccarbonyl).
31P{1H} NMR (121.44 MHz, CDCl3): δ 53.8.
Synthesis of Complex 2. The preparation of complex 2 fol-
lowed the same procedure as complex 1 with the corresponding
proligand N-(3-(di(tert-butyl)phosphino)propyl)triphenylphos-
phinimine (0.92 g, 1.98 mmol). Complex 2 was obtained as a
yellow solid (0.56 g, 73%). IR (CDCl3): 2090 cm-1 (νCN) and
2001 cm-1 (νCO). 1H NMR (300 MHz, CDCl3): δ 1.28 (d, J =
13.9 Hz, -CH3, 9H), 1.49 (d, J=13.7 Hz, -CH3, 9H), 1.69-
1.83 (m, -CH2, 1H), 2.60-2.86 (m, -CH3, 3H), 3.51 (dd, J =
15.1, 4.6 Hz, -CH2, 1H), 4.04-4.14 (m, -CH2, 1H), 5.16 (s, Cp
H, 5H). 13C{1H} NMR (75.44 MHz, CDCl3): δ 26.50 (d, J =
22.41 Hz, -CH2, 1C), 29.54 (d, J = 5.17 Hz, -CH2, 1C), 29.69
(d, J = 2.30 Hz, -CH3, 3C), 31.02 (br s, -CH3, 3C), 39.06 (d,
J = 10.92 Hz, -CH2, 1C), 40.57 (d, J = 12.64 Hz, -C(CH3)3,
1C), 48.78 (s, -C(CH3)3, 1C), 84.03 (s, Cp C, 5C), 183.14 (d, J =
29.88 Hz, Cisocyanide), 214.18 (d, J = 19.54 Hz, Ccarbonyl). 31P{1H}
NMR (121.44 MHz, CDCl3): δ 87.74. Anal. Calcd for 2
(C18H29FeINOP): N, 2.86; C, 44.20; H, 5.98. Obtained: N,
3.13; C, 44.37; H, 5.86.
Synthesis of Complex 3. An excess amount of n-butylamine
(5 mL, 50.6 mmol) was added to a solution of complex 2 (500
mg, 0.945 mmol) in CH2Cl2 (20 mL) at room temperature. The
reaction mixture was stirred overnight, and it was concentrated
in vacuo. Et2O (10 mL) was added to precipitate the yellow solid,
complex 3. Complex 3 was collected on a fine frit and dried
in vacuo (0.423 g, 89%). Complex 3: IR (CDCl3) 19450 cm-1
1
(νCO). H NMR (400 MHz, CDCl3): δ 1.17 (d, J = 12.46 Hz,
-CH3, 9H), 1.24 (d, J = 12.12 Hz, -CH3, 9H), 1.29-1.49 (m,
-CH3, 3H), 1.54 (br s, -CH2, 2H), 1.79 (br s, -CH2, 3H), 1.97
(br s, -CH2, 1H), 2.10-2.31 (m, -CH2, 1H), 2.48-2.65 (m,
-CH2, 1H), 3.22 (br s, -CH2, 1H), 3.27-3.48 (m, -CH2, 2H),
3.98-4.13 (m, -CH2, 1H), 4.75 (s, Cp C, 5H), 5.96 (br s, -NH,
1H), 7.97 (br s, -NH, 1H). 13C{1H} NMR (100.58 MHz,
CDCl3): δ 13.48 (s, -CH3, 1C), 19.84 (s, -CH2, 1C), 25.67 (s,
-CH2, 1C), 28.90 (d, J = 9.69 Hz, -CH2, 1C), 29.60 (br s,
-CH3, 3C), 29.81 (br s, -CH3, 3C), 30.25 (s, -CH2, 1C), 37.52
(d, J = 17.99 Hz, -CH2, 1C), 38.40 (d, J = 17.99 Hz, -CH2,
1C), 45.94 (s, -C(CH3)3, 1C), 46.78 (s, -C(CH3)3, 1C), 84.30 (s,
Cp C, 5C), 210.71 (d, Ccarbonyl, 1C), 221.00 (d, J = 31.83 Hz,
C
Anal. Calcd for 3 (C22H41FeIN2OP): N, 4.97; C, 46.91; H, 7.34.
Obtained: N, 5.48; C, 46.54; H, 7.19.
carbene, 1C). 31P{1H} NMR (121.44 MHz, CDCl3): δ 77.88.
Synthesis of Complex 4. An excess amount of n-butylamine
(5 mL, 50.6 mmol) was added to a solution of complex 1 (500
mg, 0.945 mmol) in CH2Cl2 (20 mL) at room temperature. The
reaction mixture was stirred overnight, and the solution was
concentrated in vacuo. Et2O (10 mL) was added to precipitate
the yellow solid and dried in vacuo to obtain complex 4 (0.524 g,
)
)
1
92%). IR (CDCl3): 1948.91 cm-1 (νCO). H NMR (400 MHz,
CDCl3): δ 0.98 (t, J = 7.31 Hz, -CH3, 3H), 1.16-1.39 (m,
-CH2, 2H), 1.42-1.64 (m, -CH2, 2H), 1.64-1.85 (m, -CH2,
2H), 2.09-2.31 (m, -CH2, 1H), 2.68-2.85 (m, -CH2, 1H),
3.45-3.72 (m, -CH2, 3H), 4.13-4.36 (m, -CH2, 1H), 4.54 (s,
Cp H, 5H), 6.50 (br s, -NH, 1H), 7.10 - 7.58 (m, aryl H, 10H),

6074 Organometallics, Vol. 29, No. 22, 2010
Yu et al.
8.15 (br s, -NH, 1H). 13C{1H} NMR (100.58 MHz, CDCl3): δ
13.54 (d, J = 8.30 Hz, -CH3, 1C), 19.91 (s, -CH2, 1C), 24.68
(s, -CH2, 1C), 30.44 (s, -CH2, 1C), 35.35 (m, J = 22.14 Hz,
-CH2, 1C), 41.80 (s, -CH2, 1 C), 45.68 (s, -CH2, 1C), 46.07
(s, -CH2, 1C), 84.76 (s, Cp C, 5C), 128.07 (d, J = 9.69 Hz, aryl
C, 2C), 128.61 (d, J = 9.69 Hz, aryl C, 2C), 129.68 (d, J = 8.30
Hz, aryl C, 2C), 131.82 (d, J = 11.07 Hz, aryl C, 2C) 132.43 (d,
J = 8.30 Hz, aryl C, 2C) 132.83 (s, aryl C, 1 C), 138.75 (m, J =
48.44 Hz, aryl C, 1C), 209.61 (d, J = 24.91 Hz, Ccarbonyl, 1C),
218.05 (d, J = 31.83 Hz, Ccarbene, 1C). 31P{1H} NMR (121.44
MHz, CDCl3): δ 56.70. Anal. Calcd for 4 (C26H32FeIN2OP): N,
4.65; C, 51.85; H, 5.36. Obtained: N, 5.38; C, 51.64; H, 5.80.
Synthesis of Complex 5. The preparation of complex 5 fol-
lowed the same procedure as complex 4 with the corresponding
amine (5 mL, 21.3 mmol). Complex 5 was obtained as a yellow
solid (0.628 g, 93%). IR (CDCl3): 1947.76 cm-1 (νCO). 1H NMR
(400 MHz, CDCl3): δ 0.82-0.91 (m, -CH3, 6H), 1.30 (d, J =
3.58 Hz, -CH2, 9H), 1.43-1.60 (m, -CH2, 2H), 1.60-1.86 (m,
-CH2, 3H), 1.93 (br s, -CH2, 1H), 2.11-2.33 (m, -CH2, 1H),
2.60-2.72 (m, -CH2, 1H), 2.82-2.91 (m, -CH2, 1H), 3.08-
3.20 (m, -CH2, 1H), 3.43 (dt, J = 13.61, 6.76 Hz, -CH2, 1H),
3.64-3.81 (m, -CH2, 2H), 3.95-4.06 (m, -CH2, 1H),
4.29-4.43 (m, -CH2, 2H), 4.50 (s, Cp H, 5H), 4.78 (br s, aryl
H, 2H), 7.03-7.11 (m, aryl H, 2H), 7.18-7.25 (m, aryl H, 2H),
7.32-7.44 (m, aryl H, 2H), 7.47-7.56 (m, aryl H, 2H), 7.75 (br s,
-NH, 1H). 13C{1H} NMR (100.58 MHz, CDCl3): δ 13.82 (d,
J = 13.56 Hz, -CH3, 2C), 22.24 (s, -CH2, 1C), 22.35 (s, -CH2,
2C), 24.51 (s, -CH2, 1C), 26.41 (s, -CH2, 1C), 26.70 (s, -CH2,
1C), 26.94 (s, -CH2, 1C), 28.97 (s, -CH2, 1C), 31.41 (d, J =
3.70 Hz, -CH2, 2C), 35.11 (d, -CH2, 1C), 49.90 (s, -CH2, 1C),
59.78 (s, -CH2, 1C), 85.21 (s, Cp C, 5C), 128.00 (d, J = 9.86 Hz,
aryl C, 2C), 128.80 (d, J = 9.86 Hz, aryl C, 2C), 129.72 (d, J =
8.63 Hz, aryl C, 2C), 129.95 (s, aryl C, 1C), 130.82 (s, aryl C, 1C),
132.47 (d, J = 46.86 Hz, aryl C, 1C), 133.29 (d, J = 9.86 Hz, aryl
C, 2C), 139.28 (d, J = 51.79 Hz, aryl C, 1C), 210.00 (d, J = 20.96
Hz, Ccarbonyl, 1C), 219.16 (d, J = 36.99 Hz, Ccarbene, 1C).
31P{1H} NMR (121.44 MHz, CDCl3): δ 55.87. Anal. Calcd
for 5 (C34H48FeIN2OP): N, 3.92; C, 57.16; H, 6.77. Obtained: N,
4.12; C, 57.72; H, 7.33.
(m, -CH2, 1H), 2.67-2.75 (m, -CH2, 1H), 2.82-2.92 (m, -CH2,
1H), 3.44 (ddd, J = 14.63, 9.76, 5.06 Hz, -CH2, 1H), 3.88-3.96
(m, -CH2, 2H), 4.01-4.09 (m, -CH2, 1H), 4.24-4.31 (m,
-CH2, 1H), 4.35 (ddd, J = 14.59, 7.23, 7.10 Hz, -CH2, 1H),
4.50-4.57 (m, Cp H, 5H), 6.69 (t, J = 5.57 Hz, -NH, 1H), 7.23
(dd, J = 10.63, 7.68 Hz, aryl H, 2H), 7.38 (td, J = 7.68, 1.92 Hz,
aryl H, 2H), 7.42-7.53 (m, aryl H, 6H), 8.84 (br s, -NH, 1H).
13C{1H} NMR (100.58 MHz, CDCl3): δ 24.71 (s, -CH2, 1C),
35.56 (d, J = 22.19 Hz, -CH2, 1C), 43.99 (s, -CH2, 1C), 45.50
(br s, -CH2, 1C), 47.52 (s, -CH2, 1C), 84.67 (s, Cp C, 5C),
128.92 (d, J = 9.86 Hz, aryl C, 2C), 129.16 (d, J = 8.63 Hz, aryl
C, 2C), 129.93 (d, J = 8.63 Hz, aryl C, 2C), 130.39 (d, J = 2.46
Hz, aryl C, 1C), 131.33 (d, J = 2.47 Hz, aryl C, 1C), 132.59 (s,
aryl C, 1C), 132.91 (d, J = 9.87 Hz, aryl C, 1C), 138.33 (d, J =
49.31 Hz, aryl C, 1C), 211.35 (d, J = 28.36 Hz, Ccarbonyl, 1C),
218.11 (d, J = 32.06 Hz, Ccarbene, 1C). 31P{1H} NMR (121.44
MHz, CDCl3): δ 56.44. Anal. Calcd for 7 (C24H27ClFeIN2OP):
N, 4.60; C, 47.36; H, 4.47. Obtained: N, 4.66; C, 47.58; H, 4.52.
Synthesis of Complex 8. A solution of 3-chloropropylamine
hydrochloride (0.79 g, 6.05 mmol, [Cl(CH2)2NH3]Cl) was trea-
ted with a solution of an equimolar amount of NaOEt (0.41 g,
6.03 mmol) in EtOH (2 mL) at room temperature. The reaction
mixture was continuously stirred for 10 min to complete the
formation of 2-chloroethylamine as well as a NaCl salt. The
amine solution was filtered through a glass fiber membrane filter
and added dropwise to a solution of complex 1 (0.80 mg, 1.51
mmol) in CH2Cl2 (10 mL) at room temperature, and then the
mixture was stirred overnight. The reaction mixture was then
concentrated under vacuum. Et2O (10 mL) was added to the
residue, and a yellow solid precipitated and was collected on a
frit, washed with pentane (2 ꢀ 5 mL), and taken to dryness under
vacuum to yield complex 8 as a yellow solid (0.89 g, 95%). IR
(CDCl3): 1952.12 cm-1 (νCO). 1H NMR (300 MHz, CDCl3): δ
1.27-1.51 (m, -CH2, 1H), 2.08-2.47 (m, -CH2, 3H) 2.64-2.96
(m, -CH2, 2H) 3.38-3.59 (m, -CH2, 1H), 3.66-4.05 (m,
-CH2, 4H), 4.14-4.39 (m, -CH2, 1H), 4.56 (d, J = 1.37 Hz, Cp
H, 5H), 6.84 (br s, -NH, 1H), 7.18 (dd, J = 10.62, 7.42 Hz, aryl
H, 2H), 7.30-7.38 (m, aryl H, 2H), 7.39-7.56 (m, aryl H, 6H),
8.41 (br s, -NH, 1H). 13C{1H} NMR (100.58 MHz, CDCl3): δ
24.74 (s, -CH2, 1C), 31.17 (s, -CH2, 1C), 35.34 (d, J = 22.20
Hz, -CH2, 1C), 43.11 (s, -CH2, 2C), 45.56 (d, J = 2.47 Hz,
-CH2, 1C), 84.83 (s, Cp C, 5C), 128.44 (d, J = 9.86 Hz, aryl C,
2C), 128.87 (d, J = 8.63 Hz, aryl C, 2C), 129.80-130.15 (m, aryl
C, 3C), 130.77 (s, aryl C, 1C), 132.73 (d, J = 9.86 Hz, aryl C, 2C),
133.15 (s, aryl C, 1C), 138.99 (d, J = 49.32 Hz, aryl C, 1C),
211.04 (d, J = 24.66 Hz, Ccarbonyl, 1C), 218.16 (d, J = 32.06 Hz,
Ccarbene, 1C). 31P{1H} NMR (121.44 MHz, CDCl3): δ 56.45.
Anal. Calcd for 8 (C25H29ClFeIN2OP): N, 4.50; C, 48.22; H,
4.69. Obtained: N, 4.43; C, 48.14; H, 4.67.
Synthesis of Complex 9. A suspension of complex 7 (200 mg,
0.328 mmol) in CH2Cl2 (10 mL) was reacted with a 5 mL EtOH
solution of four equimolar amount of NaOEt (89.3 mg, 1.312
mmol) at room temperature. After stirring overnight, the solu-
tion mixture was taken to dryness and the residue was dissolved
in the minimum amount of CH2Cl2 (3 mL). The solution was
filtered through Celite for removal of a NaCl salt and excess
NaOEt. The filtrate was concentrated, and Et2O (10 mL) was
added to filter the solution and obtain a yellow precipitate, 9
(0.156 g, 83%). IR (CDCl3): 1948.77 cm-1 (νCO). 1H NMR (400
MHz, CDCl3): δ 1.51 (br s, -CH2, 1H), 1.79 (br s, -CH2, 1H),
2.64-2.80 (m, -CH2, 1H), 2.87-3.04 (m, -CH2, 1H), 3.37-
3.57 (m, -CH2, 2H), 3.57-3.73 (m, -CH2, 4H), 4.75 (s, Cp H,
5H), 7.13-7.23 (m, aryl H, 2H), 7.28-7.41 (m, aryl H, 3H),
7.42-7.48 (m, aryl H, 1H), 7.51 (t, J = 6.49 Hz, aryl H, 2H),
7.55-7.63 (m, aryl H, 2H), 8.31 (br s, -NH, 1H). 13C{1H} NMR
(100.58 MHz, CDCl3): δ 23.04 (s, -CH2, 1C), 34.24 (d, J =
24.54 Hz, -CH2, 1C), 44.75 (s, -CH2, 1C), 48.39 (s, -CH2, 1C),
52.31 (s, -CH2, 1C), 85.47 (s, Cp C, 5C), 128.61 (d, J = 10.73
Hz, aryl C, 2C), 129.23 (d, J = 9.20 Hz, aryl C, 2C), 130.43 (s,
aryl C, 1C), 130.74 (s, aryl C, 1C), 131.22 (d, J = 9.20 Hz, aryl C,
Synthesis of Complex 6. The preparation of complex 6 fol-
lowed the same procedure as complex 4 with the corresponding
amine (0.409 g, 3.82 mmol) and complex 1 (0.505 g, 0.96 mmol).
Complex 6 was obtained as a yellow solid (0.550 g, 90%). IR
(CDCl3): 1954.00 cm-1 (νCO). 1HNMR(400MHz, CDCl3):δ1.01
(br s, -CH2, 1H), 1.95-2.19 (m, -CH2, 1H), 2.23 (s, -CH3, 3H),
2.70 (t, J = 15.19 Hz, -CH2, 1H), 3.04 (br s, -CH2, 1H), 3.38 (dd,
J = 13.83, 6.83 Hz, -CH2, 1H), 3.59-3.77 (m, -CH2, 1H), 4.43
(br s, -CH2, 1H), 4.64 (br s, Cp H, 5H), 7.11 (br s, -NH, 1H),
7.19-7.26 (m, aryl H, 6H), 7.33(brs,aryl H, 6H), 7.45(brs, aryl H,
2H), 9.38 (br s, -NH, 1H). 13C{1H} NMR (100.58 MHz, CDCl3):
δ 21.77 (br s, -CH3, 1C), 24.15 (br s, -CH2, 1C), 34.55 (d, J =
25.89 Hz, -CH2, 1C), 45.17 (br s, -CH2, 1C), 73.52 (br s, aryl H,
2C), 85.60 (br s, Cp C, 5C), 127.63-135.68 (m, aryl H, 16C), 217.92
(d, J = 28.36 Hz, Ccarbonyl, 1C), 234.63 (d, J = 25.89 Hz, Ccarbene
,
1C). 31P{1H} NMR (121.44 MHz, CDCl3): δ 57.90. Anal. Calcd
for 6 (C29H30FeIN2OP): N, 4.40; C, 54.74; H, 4.75. Obtained: N,
4.26; C, 54.99; H, 4.84.
Synthesis of Complex 7. A solution of 2-chloroethylamine
hydrochloride (0.70 g, 6.05 mmol) was treated with a solution
of an equimolar amount of NaOEt (0.41 g, 6.03 mmol) in EtOH
(2 mL) at room temperature. The reaction mixture was con-
tinuously stirred for 10 min to complete the formation of
2-chloroethylamine as well as a NaCl salt. The amine solution
was filtered through a glass fiber filter and added dropwise to a
solution of complex 1 (0.80 g, 1.51 mmol) in CH2Cl2 (10 mL) at
room temperature. The mixture was stirred overnight. A yellow
precipitate was collected, washed with Et2O (2 ꢀ 10 mL), and
dried under vacuum. Complex 7 was obtained as a yellow solid
(0.85 g, 93%). IR (CDCl3): 1958.83 cm-1 (νCO). 1H NMR
(600 MHz, CDCl3): δ 11.32-1.42 (m, -CH2, 1H), 2.14-2.29

Article
Organometallics, Vol. 29, No. 22, 2010 6075
2C), 131.54 (d, J = 9.20 Hz, aryl C, 2C), 211.54 (d, J = 27.60 Hz,
C
NMR (121.44 MHz, CDCl3): δ 56.95. Anal. Calcd for 9
(C24H26FeIN2OP): N, 4.90; C, 50.38; H, 4.58. Obtained: N,
5.38; C, 50.08; H, 4.91.
7.48-7.61 (m, aryl H, 3H). 13C{1H} NMR (100.58 MHz,
CDCl3): δ 14.99 (s, -CH3, 1C), 24.78 (s, -CH2, 1C), 35.38 (d,
J = 22.19 Hz, -CH2, 1C), 49.94 (br s, -CH2, 1C), 61.14 (s,
-CH2, 1 C), 83.46 (s, Cp C, 5C), 127.76 (d, J = 9.86 Hz, aryl C,
2C), 128.19 (d, J = 8.63 Hz, aryl C, 2C), 129.26 (s, aryl C, 1C),
129.49 (s, aryl C, 1C), 130.84 (d, J = 8.63 Hz, 2C), 132.61 (d, J =
8.63 Hz, 2C), 133.56, (d, J = 17.26 Hz, 1 C), 136.67 (d, 1C),
197.64 (d, J = 30.83 Hz, 1C, Cylidene), 221.22 (d, J = 32.06 Hz,
1C, Ccarbonyl). 31P{1H} NMR (121.44 MHz, CDCl3): δ 61.09.
Anal. Calcd for 12 (C24H26FeNO2P): N, 3.13; C, 64.44; H, 5.86.
Obtained: N, 3.12; C, 64.47; H, 5.90.
Synthesis of Complex 13. The preparation of complex 13 fol-
lowed the same procedure as complex 11 with KOtBu (0.22 g,
1.96 mmol) in 2-propanol (iPrOH) (5 mL) and complex 1 (1.01 g,
1.91 mmol) in THF (10 mL). Complex 13 was obtained as a
yellow solid (0.819 g, 93%). IR (CDCl3): 1935.67 cm-1 (νCO). 1H
NMR (400 MHz, CDCl3): δ 1.20 (d, J = 6.14 Hz, -CH3, 3H),
1.30 (d, J = 6.14 Hz, -CH3, 3H), 1.35-1.52 (m, -CH2, 1H),
1.75-1.93 (m, -CH2, 1H), 2.48-2.61 (m, -CH2, 1H), 2.72 (m,
J = 13.48, 13.48, 6.32, 3.41 Hz, -CH2, 1H), 3.52 (dd, J = 12.37,
9.47 Hz, -CH2, 1H), 3.69-3.81 (m, -CH2, 1H), 4.40 (s, Cp H,
5H), 5.24 (spt, J = 6.17 Hz, -CH, 1H), 7.27-7.33 (m, aryl H,
3H) 7.39-7.47 (m, aryl H, 5H), 7.52-7.65 (m, aryl H, 2H).
13C{1H} NMR (100.58 MHz, CDCl3): δ 22.49 (s, -CH3, 1C),
22.80 (s, -CH3, 1C), 24.77 (s, -CH2, 1C), 35.45 (d, J = 22.57
Hz, -CH2, 1C), 50.19 (d, J = 5.37 Hz, -CH2, 1C), 65.27 (s,
-CH, 1C), 83.52 (s, Cp C, 5C), 127.71 (d, J = 9.67 Hz, aryl C,
2C), 128.22 (d, J = 9.67 Hz, aryl C, 2C), 129.24 (s, aryl C, 1 C),
129.47 (s, aryl C, 1C), 130.95 (d, J = 8.60 Hz, aryl C, 2C), 132.86
(d, J = 9.67 Hz, aryl C, 2C), 136.79 (d, J = 45.13 Hz, aryl C,
1C), 140.00 (d, J = 39.76 Hz, aryl C, 1C), 196.27 (d, J = 33.31
Hz, Cylidene, 1C) 221.37 (d, J = 33.31 Hz, Ccarbonyl, 1C). 31P{1H}
NMR (121.44 MHz, CDCl3): δ 61.28. Anal. Calcd for 13
(C25H28FeNO2P): N, 3.04; C, 65.09; H, 6.12. Obtained: N,
3.00; C, 64.91; H, 6.07.
Synthesis of Complex 14. An equivalent amount of 6.2 M
HBF4 (0.12 mL, 0.744 mmol) in Et2O was added dropwise to a
solution of complex 11 (0.304 g, 0.702 mmol) in CH2Cl2 (10 mL)
at room temperature. The reaction solution was stirred over-
night. The solution was concentrated in vacuo, and a yellow solid
of complex 14 was precipitated by addition of diethyl ether to
the residue. The yellow precipitate, complex 14 (0.340 g, 93%),
was collected on a fine frit. IR (CDCl3): 1960.15 cm-1 (νCO). 1H
NMR (400 MHz, CDCl3): δ 1.67 (br s, -CH2, 1H), 1.89 (br s,
-CH2, 1H), 2.88 (br s, -CH2, 2H), 3.87 (br s, -CH2, 2H), 4.02
(br s, -CH3, 3H), 4.59 (br s, Cp H, 5H), 7.10-7.26 (m, aryl H,
2H), 7.32-7.47 (m, aryl H, 3H), 7.52 (br s, aryl H, 5H), 8.81 (br s,
-NH, 1H). 13C{1H} NMR (100.58 MHz, CDCl3): δ 24.28 (s,
-CH3, 1C), 34.63 (d, J = 27.60 Hz, -CH2, 1C), 45.10 (s, -CH2,
1C), 57.50 (s, -CH2, 1C), 85.56 (s, Cp C, 5C), 128.17-130.00
(m, aryl C, 5C), 130.30-132.20 (m, aryl C, 7C), 218.25 (d, J =
27.60 Hz, Ccarbonyl, 1C) 237.08 (d, J = 27.60 Hz, Ccarbene, 1C).
31P{1H} NMR (121.44 MHz, CDCl3): δ 55.59. Anal. Calcd for
14 (C23H25BF4FeNO2P): N, 2.69; C, 53.01; H, 4.84. Obtained:
N, 2.63; C, 52.74; H, 4.98.
Synthesis of Complex 15. The preparation of complex 15
followed the same procedure as complex 14 with 6.2 M HBF4
(0.11 mL, 0.682 mmol) in Et2O and complex 12 (0.298 g, 0.666
mmol) in CH2Cl2 (10 mL). Complex 15 was obtained as a yellow
solid (0.324 g, 91%). IR (CDCl3): 1958.49 cm-1 (νCO). 1H NMR
(400 MHz, CDCl3): δ 1.51 (br s, -CH3, 3H), 1.71 (br s, -CH2,
1H), 1.90 (br s, -CH2, 1H), 2.87 (br s, -CH2, 2H), 3.86 (br s,
-CH2, 2H), 4.25 (br s, -CH2, 2H), 4.58 (br s, Cp H, 5H),
7.16-7.26 (m, aryl H, 1H), 7.33-7.47 (m, aryl H, 3H), 7.53 (br s,
aryl H, 6H), 8.73 (br s, -NH, 1H). 13C{1H} NMR (100.58 MHz,
CDCl3): δ 13.88 (br s, -CH3, 1C), 24.15 (br s, -CH2, 1C), 34.22
(d, J = 24.66 Hz, -CH2, 1C), 44.83 (br s, -CH2, 1C), 66.22 (br
s, -CH2, 1C), 85.43 (br s, Cp C, 5C), 127.98-129.44 (m, aryl C,
4 C), 130.17-132.12 (m, aryl C, 5C), 132.25-135.96 (m, aryl C,
3C), 218.09 (d, J = 27.13 Hz, Ccarbonyl, 1C), 236.34 (d, J = 29.59 Hz,
carbonyl, 1C), 218.81 (d, J = 29.14 Hz, Ccarbene, 1C). 31P{1H}
Synthesis of Complex 10. A suspension of complex 8 (200 mg,
0.321 mmol) in CH2Cl2 (10 mL) was reacted with a 5 mL EtOH
solution of four equimolar amount of NaOEt (87.4 mg, 1.284
mmol) at room temperature. After stirring overnight, the solu-
tion mixture was taken to dryness and the residue was dissolved
in the minimum amount of CH2Cl2 (3 mL). The solution was
filtered through Celite for removal of NaCl and excess NaOEt.
The filtrate was concentrated and Et2O (10 mL) was added to
filter the solution and obtain a yellow precipitate, 10 (0.152 g,
1
81%). IR (CDCl3): 1952.24 cm-1 (νCO). H NMR (400 MHz,
CDCl3): δ 1.02-1.20 (m, -CH2, 1H), 1.78-1.94 (m, -CH2,
1H), 1.96-2.09 (m, -CH2, 1H), 2.09-2.32 (m, -CH2, 1H),
2.61-2.77 (m, -CH2, 1H), 2.94-3.06 (m, -CH2, 1H), 3.11 (d,
J=12.63 Hz, -CH2, 1H), 3.26-3.53 (m, -CH2, 4H), 4.26 (dd,
J=14.59, 9.47 Hz, -CH2, 1H), 4.67 (s, Cp H, 5H), 7.20-7.33
(m, aryl H, 4H), 7.36 (br s, aryl H, 4H), 7.43-7.53 (m, aryl H,
2H), 8.00 (br s, -NH, 1H). 13C{1H} NMR (100.58 MHz,
CDCl3): δ 20.87 (s, -CH2, 1C), 22.02 (s, -CH2, 1C), 34.26 (d,
J = 22.14 Hz, -CH2, 1C), 41.17 (s, -CH2, 1 C), 49.42 (s, -CH2,
1C), 56.29 (br s, -CH2, 1C) 84.84 (s, Cp C, 5C), 128.32 (d, J =
11.07 Hz, aryl C, 2C), 128.80 (d, J = 8.30 Hz, aryl C, 2C), 129.87
(d, J = 8.30 Hz, aryl C, 2C), 130.74 (s, aryl C, 2C), 132.87 (d, J =
8.30 Hz, aryl C, 2C), 133.38 (s, aryl C, 1C), 139.22 (d, J = 47.06
Hz, aryl C, 1C), 205.75 (d, J = 24.91 Hz, Ccarbonyl, 1C), 218.25
(d, J = 33.22 Hz, Ccarbene, 1C). 31P{1H} NMR (121.44 MHz,
CDCl3): δ 56.21. Anal. Calcd for 10 (C25H28FeIN2OP CH2Cl2):
3
N, 4.46; C, 48.72; H, 4.65. Obtained: N, 4.38; C, 48.38; H, 4.74.
Synthesis of Complex 11. A solution of potassium tert-but-
oxide, KOtBu (0.22 g, 1.96 mmol), in methanol (MeOH) (5 mL)
was added to a solution of complex 1 (1.01 g, 1.91 mmol) in THF
(10 mL) at room temperature. The solution mixture was stirred
overnight, after which the solvent was removed completely
in vacuo and the remaining residue dissolved in benzene. The
solution was filtered through Celite to remove KI. The filtrate
was evaporated in vacuo to obtain the desired product 11 as a
yellow solid (0.745 g, 90%). IR (CDCl3): 1936.99 cm-1 (νCO). 1H
NMR (400 MHz, CDCl3): δ 1.33-1.49 (m, -CH2, 1H), 1.83-
2.01 (m, -CH2, 1H), 2.52-2.64 (m, -CH2, 1H), 2.73-2.85 (m,
-CH2, 1H), 3.54 (dd, J = 12.46, 9.73 Hz, -CH2, 1H), 3.72 (s,
-CH3, 3H), 3.81 (dd, J = 12.29, 7.17 Hz, -CH2, 1H), 4.46 (d,
J = 1.37 Hz, Cp H, 5H), 7.26-7.34 (m, aryl H, 3H), 7.36-7.44
(m, aryl H, 5H), 7.51-7.58 (m, aryl H, 2H). 13C{1H} NMR
(100.58 MHz, CDCl3): δ 24.75 (s, -CH2, 1C), 35.71 (d, J =
22.14 Hz, -CH2, 1C), 49.99 (d, J = 4.15 Hz, -CH2, 1C), 53.76
(s, -CH3, 1C), 83.27 (s, Cp C, 5C), 127.91 (d, J = 9.69 Hz,
aryl C, 2C), 128.30 (d, J = 8.30 Hz, aryl C, 2C), 129.26 (s, aryl C,
1C), 129.66 (s, aryl C, 1C), 130.63 (d, J = 9.69 Hz, aryl C, 2C),
132.90 (d, J = 9.69 Hz, aryl C, 2C), 136.04 (d, J = 45.67 Hz,
aryl C, 1C), 140.36 (d, J = 41.52 Hz, aryl C, 1C), 198.03 (d, J =
33.22 Hz, Cylidene, 1C), 221.08 (d, J = 31.83 Hz, Ccarbonyl, 1C).
31P{1H} NMR (121.44, CDCl3): δ 60.55. Anal. Calcd for 11
(C23H24FeNO2P): N, 3.23; C, 63.76; H, 5.58. Obtained: N, 3.32;
C, 64.11; H, 5.67.
Synthesis of Complex 12. The preparation of complex 12 fol-
lowed the same procedure as complex 11 with KOtBu (0.22 g,
1.96 mmol) in ethanol (EtOH) (5 mL) and complex 1 (1.01 g,
1.91 mmol) in THF (10 mL). Complex 12 was obtained as a
yellow solid (0.760 g, 89%). IR (CDCl3): 1937.11 cm-1 (νCO). 1H
NMR (400 MHz, CDCl3): δ 1.30 (t, -CH3, J = 7.08 Hz, 3H),
1.34-1.52 (m, -CH2, 1H), 1.73-1.96 (m, -CH2, 1H), 2.48-
2.64 (m, -CH2, 1H), 2.74 (m, J = 13.46, 13.46, 6.36, 3.41 Hz,
-CH2, 1H), 3.43-3.59 (m, -CH2, 1H), 3.74 (dd, J = 12.37, 7.77
Hz, -CH2, 1H), 4.02 (dq, J = 10.37, 7.01 Hz, -CH2, 1H), 4.17
(dq, J = 10.39, 7.06 Hz, -CH2, 1H), 4.43 (d, J = 1.02 Hz, Cp H,
5H), 7.22-7.33 (m, aryl H, 2H), 7.33-7.43 (m, aryl H, 5H),

6076 Organometallics, Vol. 29, No. 22, 2010
Yu et al.
Ccarbene, 1C). 31P{1H} NMR (121.44 MHz, CDCl3): δ 55.60.
Anal. Calcd for 15 (C24H27BF4FeNO2P): N, 2.62; C, 53.87; H,
5.09. Obtained: N, 2.49; C, 54.14; H, 5.22.
removed in vacuo. Et2O (10 mL) was added to the residue, and a
yellow solid was precipitated and collected on a fine frit, washed
with pentane (5 mL), and dried in vacuo to yield complex 18 as
a yellow powder (0.798 g, 90%). IR (CDCl3): 1966.33 cm-1 (νCO).
1H NMR (300 MHz, CDCl3): δ 1.33 (br s, -CH2, 1H), 1.95-
2.15 (m, -CH2, 1H), 2.15-2.30 (m, -CH2, 2H), 2.73-2.93 (m,
-CH2, 1H), 3.07-3.31 (m, -CH2, 2H), 3.73-3.97 (m, -CH2,
2H), 4.32-4.50 (m, -CH2, 2H), 4.50-4.62 (m, -CH2, 1H), 4.76
(s, Cp H, 5H), 7.24-7.58 (m, aryl H, 10H). 13C{1H} NMR
(100.58 MHz, CDCl3): δ 20.93 (s, -CH2, 1C), 21.31 (s, -CH2,
1C), 33.77 (d, J = 24.91 Hz, -CH2, 1C), 48.50 (s, -CH2, 1C),
66.99 (s, -CH2, 1C), 84.78 (br s, Cp C, 5C), 128.28 (d, J = 9.69
Hz, aryl C, 2C), 128.65 (d, J = 9.69 Hz, aryl C, 2C), 129.92 (br s,
aryl C, 3C), 130.60 (s, aryl C, 1C), 131.91 (d, J = 8.30 Hz, aryl C,
2C), 133.02 (d, J = 48.44 Hz, aryl C, 1C), 137.19 (s, aryl C, 1C),
217.97 (d, J = 29.06 Hz, Ccarbonyl, 1C), 231.32 (d, J = 29.06 Hz,
Synthesis of Complex 16. The preparation of complex 16
followed the same procedure as complex 14 with 6.2 M HBF4
(0.11 mL, 0.682 mmol) in Et2O and complex 13 (0.299 g, 0.648
mmol) in CH2Cl2 (10 mL). Complex 16 (0.310 g, 87%) as a
yellow solid was obtained. IR (CDCl3): 1958.91 cm-1 (νCO). 1H
NMR (400 MHz, CDCl3): δ 1.46 (d, J = 25.13 Hz, -CH3, 6H),
1.67 (br s, -CH2, 1H), 1.97 (br s, 1H), 2.86 (br s, -CH2, 2H),
3.89 (br s, -CH2, 2H), 4.54 (br s, Cp H, 5H), 5.02 (br s, -CH,
1H), 7.24 (br s, aryl H, 1H), 7.31-7.47 (m, aryl H, 3H), 7.52 (br s,
aryl H, 6 H), 8.55 (br s, -NH, 1H). 13C{1H} NMR (100.58
MHz, CDCl3): δ 21.77 (br s, -CH3, 1C) 21.97 (br s, -CH3, 1C)
24.15 (br s, -CH2, 1C) 34.55 (d, J = 25.89 Hz, -CH2, 1C)
45.17 (br s, -CH2, 1C) 73.52 (br s, -CH, 1C) 85.60 (br s, Cp C,
5C) 127.63-135.68 (m, aryl C, 12C) 217.92 (d, J = 28.36 Hz,
C
carbene, 1C). 31P{1H} NMR (121.44 MHz, CDCl3): δ 56.30.
C
carbonyl, 1C) 234.63 (d, J = 25.89 Hz, Ccarbene, 1C). 31P{1H}
Anal. Calcd for 18 (C25H27FeINO2P): N, 2.39; C, 51.13; H, 4.63.
Obtained: N, 2.50; C, 51.66; H, 4.69.
NMR (121.44 MHz, CDCl3): δ 56.02. Anal. Calcd for 16
(C25H29BF4FeNO2P): N, 2.55; C, 54.68; H, 5.32. Obtained: N,
2.49; C, 54.20; H, 5.27.
Reversible Reaction of Acyclic (Silyl)(amino) Carbene (20)
to Ylidene (19) Complexes. A suspension of NaHB(OAc)3
(15.2 mg, 0.40 mmol) in CH2Cl2 (2 mL) was added to a solution
of complex 20 (50.1 mg, 0.07 mmol) in CH2Cl2 (5 mL) at room
temperature and was kept under static vacuum overnight. This
step was repeated four days to complete the conversion from
complex 20 to complex 19 while adding more equivalents of
the reducing reagent each day. The solution was concentrated
in vacuo for an NMR sample.
Synthesis of Complex 17. To a solution of 2-chloroethanol
(0.3 mL, 4.46 mmol) in THF (3 mL) at room temperature was
added 1.6 M n-BuLi in n-hexane (1 mL, 1.6 mmol), followed by
the complex 1 (800 mg, 1.51 mmol) in CH2Cl2 (10 mL), and the
reaction mixture was stirred overnight. The mixture was dried
in vacuo, and the resulting yellow solid was dissolved in the
minimum amount of CH2Cl2 (3 mL). The solution was then
filtered through Celite to remove salt, and then the solvent was
removed in vacuo. Et2O (10 mL) was added to the residue, and a
yellow solid was precipitated and collected on a fine frit, washed
with pentane (5 mL), and dried in vacuo to yield complex 17
(0.788 g, 91%). IR (CDCl3): 1963.60 cm-1 (νCO). 1H NMR (300
MHz, CDCl3): δ 1.78 (br s, -CH2, 1H) 1.85 (br s, -CH2, 1H)
2.78-2.94 (m, -CH2, 1H) 3.03-3.23 (m, -CH2, 1H) 3.83-4.14
(m, -CH2, 4H), 4.66 (t, -CH2, J = 9.71 Hz, 2H), 4.73 (d, J =
1.14 Hz, Cp H, 5H) 7.22-7.33 (m, aryl H, 2H) 7.38-7.50 (m,
aryl H, 3H) 7.57 (d, J = 5.48 Hz, aryl H, 5H). 13C{1H} NMR
(100.58 MHz, CDCl3): δ 22.35 (s, -CH2, 1C), 33.75 (d, J =
27.58 Hz, -CH2, 1C), 47.15 (s, -CH2, 1C), 52.27 (s, -CH2, 1C),
70.04 (s, -CH2, 1C), 85.78 (s, Cp C, 5C), 128.56 (d, J = 10.11
Hz, aryl C, 2C), 128.94 (d, J = 10.11 Hz, aryl C, 2C), 130.07 (d,
J = 9.19 Hz, aryl C, 2C), 130.34 (s, aryl C, 1C), 131.12 (s, aryl C,
1C), 131.67 (d, J = 10.11 Hz, aryl C, 2C), 135.35 (d, J = 46.88
Hz, aryl C, 2C), 217.62 (d, J = 26.66 Hz, Ccarbonyl, 1C), 229.00
(d, J = 28.50 Hz, Ccarbene, 1C). 31P{1H} NMR (121.44 MHz,
CDCl3): δ 55.79. Anal. Calcd for 17 (C24H25FeINO2P): N, 2.44;
C, 50.29; H, 4.40. Obtained: N, 2.58; C, 50.56; H, 4.92.
DFT Calculations.52 The Amsterdam Density Functional
(ADF) package (version ADF2009.01)53,54 was used to do
geometry optimizations on Cartesian coordinates as specified
in the text. All structures were optimized in the gas phase start-
ing with geometries obtained from the X-ray crystal structures.
For all atoms, standard triple-ζ STA basis sets from the ZORA
ADF database TZP with frozen cores were employed. The local
density approximation (LDA) by Becke-Perdew was used
together with the exchange and correlation corrections that
are employed by default by the ADF2009.01 program suite.
Calculations for all complexes were carried out using the scalar
spin-orbit relativistic formalism.
Acknowledgment. The authors thank UBC, NSERC,
CFI, and BCKDF for funding. P.L.D. thanks UCLA and
the Sloan Foundation for support.
Supporting Information Available: Computational details.
This material is available free of charge via the Internet at
http://pubs.acs.org.
Synthesis of Complex 18. To a solution of 3-chloroethanol
(0.3 mL, 3.59 mmol) in THF (3 mL) at room temperature was
added 1.6 M n-BuLi in n-hexane (1 mL, 1.6 mmol), followed
by complex 1 (800 mg, 1.51 mmol) in CH2Cl2 (10 mL), and the
reaction mixture was stirred overnight. The mixture was dried
in vacuo, and the resulting yellow solid was dissolved in the
minimum amount of CH2Cl2 (3 mL). The solution was then
filtered through Celite to remove salt, and then the solvent was
(52) ADF2009.01; SCM; http://www.scm.com: Theoretical Chemistry,
Vrije Universiteit: Amsterdam, The Netherlands.
(53) Velde, G. T.; Bickelhaupt, F. M.; Baerends, E. J.; Guerra, C. F.;
Van Gisbergen, S. J. A.; Snijders, J. G.; Ziegler, T. J. Comput. Chem.
2001, 22, 931–967.
(54) Guerra, C. F.; Snijders, J. G.; te Velde, G.; Baerends, E. J. Theor.
Chem. Acc. 1998, 99, 391–403.