Palladium(II)-Mediated Addition of Benzenediamines to Isocyanides: Generation of Three Types of Diaminocarbene Ligands Depending on the Isomeric Structure of the Nucleophile

Article abstract of DOI:10.1021/acs.organomet.5b00936

Coupling of the palladium-bis(isocyanide) complexes cis-[PdCl₂(CNR)₂] (R = 2,6-Me₂C₆H₃ 1, 2-Cl-6-MeC₆H₃ 2) with benzene-1,3-diamine (BDA1) leads to the diaminocarbene species cis-[PdCl₂(CNR){C(NHR)=NH(1,3-C₆H₄NH₂)}] (5 and 6, respectively). In this reaction, BDA1 behaves as a monofunctional nucleophile that adds to one of the RNC ligands by one amino group. By contrast, the reaction of 1 and 2 with benzene-1,4-diamine (BDA2) involves both amino functionalities of the diamine and leads to the binuclear species [cis-PdCl₂(CNR){ΜC(NHR)=NH(1,4-C₆H₄)NH=C(NHR)}-(cis)-PdCl₂(CNR)] (6 and 7) featuring two 1,4-bifunctional diaminocarbene ligands. The reaction of cis-[PdCl₂(CNR)₂] (R = cyclohexyl 3) with either BDA1 or BDA2 does not afford any isolable carbene derivatives. The most versatile chemistry was observed when 1-3 were treated with benzene-1,2-diamine (BDA3) and the relevant substituted 1,2-diamines, viz., 4,5-dimethylbenzene-1,2-diamine (BDA4) and 4,5-dichlorobenzene-1,2-diamine (BDA5). The addition of these diamines brings about the formation of the monocarbene cationic complexes cis-[PdCl(CNR){C(NHR)=NHC₆H₂X₂NH₂}]Cl (X = H, Me, Cl) (8-16), the Chugaev-type C,C-bound bis-carbenes cis-[PdCl₂{C(NHR)=NHC₆H₂X₂NH=C(NHR)}] (17, 18), and the bis(C,N-chelated)carbene complexes cis-[Pd{C(NHR)=NHC₆H₂X₂NH₂}₂]Cl₂ (19-24). All prepared complexes (with the exception of 17 and 18) were isolated as colorless or pale yellow solids and characterized by elemental analyses (C, H, N), HRESI^±-MS, IR, ¹H and ¹³C{¹H} NMR spectroscopies, and 4, 7, 13, 16, and 24 by X-ray diffraction. Complexes 17 and 18 were characterized by HRESI^±-MS and IR spectroscopy, and their structures were established by X-ray crystallography.

Full text of DOI:10.1021/acs.organomet.5b00936

Article
pubs.acs.org/Organometallics
Palladium(II)-Mediated Addition of Benzenediamines to Isocyanides:
Generation of Three Types of Diaminocarbene Ligands Depending
on the Isomeric Structure of the Nucleophile
Mikhail A. Kinzhalov,† Svetlana A. Timofeeva,† Konstantin V. Luzyanin,*,†,‡ Vadim P. Boyarskiy,*,†
Anton A. Yakimanskiy,† Matti Haukka,§ and Vadim Yu. Kukushkin†
†Saint Petersburg State University, 7/9 Universitetskaya Nab., Saint Petersburg 199034, Russia
‡Department of Chemistry, University of Liverpool, Crown Street, Liverpool L69 7ZD, United Kingdom
§Department of Chemistry, University of Jyvaskyla, P.O. Box 35, FI-40014 Jyvaskyla, Finland
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S
* Supporting Information
ABSTRACT: Coupling of the palladium-bis(isocyanide) complexes cis-
[PdCl2(CNR)2] (R = 2,6-Me2C6H3 1, 2-Cl-6-MeC6H3 2) with benzene-1,3-
diamine (BDA1) leads to the diaminocarbene species cis-[PdCl2(CNR){C-
(NHR)NH(1,3-C6H4NH2)}] (5 and 6, respectively). In this reaction, BDA1
behaves as a monofunctional nucleophile that adds to one of the RNC ligands by
one amino group. By contrast, the reaction of 1 and 2 with benzene-1,4-diamine
(BDA2) involves both amino functionalities of the diamine and leads to the
binuclear species [cis-PdCl2(CNR){μ-C(NHR)NH(1,4-C6H4)NHC-
(NHR)}-(cis)-PdCl2(CNR)] (6 and 7) featuring two 1,4-bifunctional diamino-
carbene ligands. The reaction of cis-[PdCl2(CNR)2] (R = cyclohexyl 3) with
either BDA1 or BDA2 does not afford any isolable carbene derivatives. The most
versatile chemistry was observed when 1−3 were treated with benzene-1,2-
diamine (BDA3) and the relevant substituted 1,2-diamines, viz., 4,5-dimethyl-
benzene-1,2-diamine (BDA4) and 4,5-dichlorobenzene-1,2-diamine (BDA5). The
addition of these diamines brings about the formation of the monocarbene cationic complexes cis-[PdCl(CNR){C(NHR)
NHC6H2X2NH2}]Cl (X = H, Me, Cl) (8−16), the Chugaev-type C,C-bound bis-carbenes cis-[PdCl2{C(NHR)
NHC6H2X2NHC(NHR)}] (17, 18), and the bis(C,N-chelated)carbene complexes cis-[Pd{C(NHR)NHC6H2X2NH2}2]Cl2
(19−24). All prepared complexes (with the exception of 17 and 18) were isolated as colorless or pale yellow solids and
characterized by elemental analyses (C, H, N), HRESI -MS, IR, 1H and 13C{1H} NMR spectroscopies, and 4, 7, 13, 16, and 24
by X-ray diffraction. Complexes 17 and 18 were characterized by HRESI -MS and IR spectroscopy, and their structures were
established by X-ray crystallography.
bis-isocyanides with ambident N-phenylbenzamidine proceeds
regioselectively to afford C,N-chelated species, and the
regioselectivity is controlled by the nature of R in RNCs
(Route C).18 Reaction of palladium-CNRs with such heterocyclic
imines as 1,3-diiminoisoindolines and 3-iminoisoindolin-1-ones
produces C,N-chelated diaminocarbenes (Route D).19−21
Finally, the reaction of (RNC)PdII species with aminopyridines
leads to the binuclear complexes containing the bridging
aminocarbene ligand; this reaction proceeds through the
intermediate generation of the mononuclear carbene species
that further attacks the starting palladium−isocyanide complex
(Route E).22,23
INTRODUCTION
■
Metal-mediated addition of N-nucleophiles to coordinated
isocyanides is known to afford complexes bearing acyclic
diaminocarbene ligands (M-ADCs).1−4 These species are
recognized as efficient organometallic catalysts,5−13 with
corresponding palladium derivatives demonstrating outstand-
ing performance in cross-coupling processes,5,6,10,11 whereas
platinum-ADCs are efficient in hydrosilylation of alkenes.8
The vast majority of known palladium-ADC species are
monodentate and are generated through nucleophilic addition
of monofunctional N-nucleophiles (e.g., amines) to metal-bound
CNR ligands.1−3 The addition of bifunctional N,N-nucleophiles
is so far limited to few examples.4 Thus, the interplay between
bis-isocyanide palladium(II) complexes and aliphatic 1,2-
diamines proceeds via the attack by both amino groups on
two CNR ligands leading to C,C-chelated bis-carbene derivatives
(Scheme 1, Route A).14,15 Closely related addition of aliphatic
hydrazines brings about the formation of the Chugaev-type4
C,C-bound bis-carbenes (Route B).16,17 Coupling of palladium
Although regioselectivity of the addition of bifunctional
reagents to RNC ligands was studied, the effect of the isomeric
composition of polyfunctional nucleophiles on structure of the
product formed has never been investigated. Thus, while in the
Received: November 11, 2015
© XXXX American Chemical Society
A
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Scheme 1. Coupling of Isocyanides in cis-[PdCl2(CNR)2] with Various Ambident Nucleophiles
case of benzene-1,n-diamines (n = 2−4), Belluco and co-
workers reported24 the reaction of benzene-1,2-diamine with a
coordinated isocyanide in cis-[PdCl2(CNPh)2] leading to the
conventional monodentate Pd-ADC complex cis-[PdCl2-
(CNPh){C(NHPh)NH(1,2-C6H4NH2)}] (Scheme 2), no
reaction with the isomeric benzene-1,3- and 1,4-diamines was
studied.
Scheme 2. Reported Addition of Benzene-1,2-diamine to
PdII-Bound Isocyanides24
Figure 1. Isomeric benzene-1,n-diamines BDA1−BDA5.
affords typical monodentate diaminocarbene palladium species
4 or 5 (76−80%; Scheme 3), and these results agree with those
reported by Belluco et al. for benzene-1,2-diamine.24 The
products were separated by filtration, and HRESI -MS
monitoring of the filtrate indicated the absence of any other
palladium complexes apart from 4 or 5 that exist in the mixture
with some organic species.
In the framework of our projects on metal-involving reac-
tions of RNCs1,4,10,11,18,19,21−23,25−27 and catalytic activity of
(ADC)M systems,5,8,10,11,20,21,28,29 we undertook a systematic
study aimed at the recognition of the influence of isomeric
composition of aromatic benzene-1,n-diamines (n = 2−4) on
the structure of the carbene product formed upon reaction with
palladium-bound isocyanides. We observed that isomeric
composition strongly affects the nature of ADC formed, and
our results are disclosed in the sections that follow.
Scheme 3. Reactions of 1 and 2 with BDA1 and BDA2
RESULTS AND DISCUSSION
■
For this study, we addressed, on the one hand, the known
palladium−isocyanide complexes cis-[PdCl2(CNR)2] [R =
2,6-Me2C6H3 (Xyl) 1, 2-Cl-6-MeC6H3 2, and cyclohexyl (Cy)
3]22,30 and, on the other hand, the isomeric benzene-1,n-
diamines (Figure 1), i.e., benzene-1,3-diamine (BDA1), benzene-
1,4-diamine (BDA2), and benzene-1,2-diamine (BDA3). In
addition, substituted 1,2-diamines such as 4,5-dimethylbenzene-
1,2-diamine (BDA4), and 4,5-dichlorobenzene-1,2-diamine
(BDA5) were employed as reactants.
(i). Reactions of Palladium-Isocyanide Complexes 1−3
with Benzene-1,3-diamine (BDA1). Owing to the absence
of conjugation between the two amino groups, benzene-1,3-
diamine BDA1, among the isomeric benzene-1,n-diamines, is the
most related to aniline. Consequently, the reaction of BDA1 and
complexes 1 (or 2) in a molar ratio 1:1 (RT, MeCN, overnight)
B
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In agreement with the IR and NMR data (see Experimental
Section), both 4 and 5 possess pendant unprotonated amino
groups. We attempted to involve both the amino group of
BDA1 in the reaction with the RNC ligand by refluxing a
mixture of complex 1 (2) with BDA1 in molar ratios 1:1 and
2:1 in MeCN (4 h) or CHCl3 (4 h). Monitoring of the reaction
mixture by HRESI -MS indicated the presence of palladium
complex of 4 (5) and [PdCl(CNR){C(NHR)NH(1,3-
C6H4NH2)}{1,3-C6H4(NH2)2}]+ along with a broad range of yet
unidentified Pd species. Our attempts to isolate any individual palla-
dium compound from these reaction mixtures were unsuccessful.
Furthermore, treatment of one equiv of bis(isocyanide)
complex 1 with 4 (or bis(isocyanide) complex 2 with 5) does
not lead to the coupling of the unreacted amino group with the
RNC ligands either. All of these observations indicate that the
nucleophilic addition of one amino group of BDA1 to PdII-
activated RNC reduces the nucleophilicity of the pendant
NH2-moiety, and it loses its reactivity toward the isocyanide
ligands. It is noteworthy that the reaction of complex 3 with
BDA1 at RT or under reflux yielded a mixture of yet unidentified
products along with traces of metallic Pd.
Scheme 4. Nucleophilic Additions of 1,2-Diamines
BDA3−BDA5 to the Isocyanides in 1−3
(ii). Coupling of Palladium−Isocyanide Complexes 1−3
with Benzene-1,4-diamine (BDA2). The reaction between
benzene-1,4-diamine (BDA2) and any one of 1−3 in an MeCN
solution at RT yielded Pd black, and no pure palladium
complex was isolated from those reaction mixtures. Monitoring
of these mixtures by HRESI -MS indicated the presence of
[PdCl(CNR){C(NHR)NH(1,4-C6H4NH2)}]+, [PdCl-
(CNR){C(NHR)NH(1,4-C6H4NH2)}(1,4-C6H4(NH2)2)]+
ions, and some unidentified Pd complexes. However, reflux of
complexes 1 or 2 and BDA2 in a molar ratio 1:1 in CHCl3
instead of MeCN for 4 h led to the formation of binuclear
species 6 or 7, where both amino groups are involved in the
generation of the carbene moieties (Scheme 3); approximately,
a half of the starting diamine remains unreacted as verified by
1H NMR. The reaction of bis(isocyanide) complexes 1 or 2
with BDA2 in a molar ratio 2:1 (CHCl3, reflux, 4 h) afforded 6
or 7 in good yields (74% and 80%, respectively), which were
separated by filtration after cooling the reaction mixture to RT.
We believe that the reason for the difference in reactivity between
the 1,3- and 1,4-diamines is due to the higher nucleophilicity of
benzene-1,4-diamine.31 Noticeably, complex 3 is reduced to Pd
black by diamine BDA2 in a CHCl3 solution.
(iii). Coupling of Palladium−Isocyanide Complexes
1−3 with 1,2-Diamines BDA3−BDA5. The reaction of 1−3
and BDA3−BDA5 (molar ratio 1:1, CHCl3 or CH2Cl2, RT,
overnight) in all possible combinations gave monocationic
aminocarbene complexes 8−16 in 69−82% isolated yields
(Route A, Scheme 4; see Table 1 for compound numbering).
On the basis of the X-ray data, in 8−16, the aminocarbene
ligands are coordinated to the metal centers in a bidentate
mode, i.e., through the carbene carbon and via the second
amine group of the 1,2-diamine moiety, thus leading to the
C,N-coordination. The close similarities of the IR spectra of
8−16 in the solid state (either in Nujol or in KBr) and in a
solution (CHCl3) indicate that 8−16 in the solution also exist
in the chelated form. This coordination mode was previously
reported for the range of ambident nucleophiles (Scheme 2,
products of C−E).4
Table 1. Numbering for Compounds 8−16 and 19−24
(for the Latter Are Given in Parentheses)
R in starting complex cis-[PdCl2(CNR)2]
benzene-1,n-diamine used
Cy
Xyl
2-Cl-6-MeC6H3
BDA3 (X = H)
8 (19)
11 (22)
14 (−)
9 (20)
12 (23)
15 (−)
10 (21)
13 (24)
16 (−)
BDA4 (X = 4,5-Me2)
BDA5 (X = 4,5-Cl2)
crystals were mechanically separated and characterized by IR
spectroscopy and X-ray diffraction indicating that 17 and 18 are
the Chugaev-type4 C,C-chelated bis-carbene derivatives.
We believe that the appearance of 17 and 18 in the system is
the result of the palladium(II)-mediated intramolecular nucleo-
philic addition of the pendant amine moiety to the CNR ligand
in 13 and 16 that occurs similarly to other reported insertions
of ambident nucleophiles (see section 2.4 of our review4).
However, all attempts to develop high yielding synthetic routes
to 17 and 18 by either treatment of 13 and 16 with the
corresponding CNRs or by treatment of 13 and 16 with excess
(n-Bu4N)Cl were not successful. If in the former case, we
obtained broad mixtures with no 17 and 18; in the latter case,
no reaction was observed.
Addition of 2 equiv of BDA3 or BDA4 to a suspension (for 1
and 2) or a solution (for 3) of 1 equiv of the corresponding
isocyanide complex (MeCN, RT) led to a rapid precipitation of
bis-carbenes 19−24 (Scheme 4, Route C; Table 1) except for
the reaction between 3 and BDA4 that proceeded for ca. 2 h
only at 70 °C. Complexes 19−24 were also obtained by the
reaction of 8−13 with BDA3 or BDA4 (a molar ratio 1:1) in
MeCN (80−93%) (Scheme 4, Route D). The reactions of
BDA5 with any one of 1−3 (a molar ratio 2:1) furnished only
corresponding monocarbene products 14−26 (via Route B)
and no bis(C,N-chelated)carbene complexes were detected in
the reaction mixture even after reflux of 1−3 (1 equiv) in an
MeCN solution in the presence of a large excess of BDA5
(4 equiv) for 24 h.
Complexes 8−16 are stable upon reflux in CHCl3 or MeCN
for ca. 24 h. However, after 2 months at RT a small amount
of crystalline material (17 and 18; Scheme 4, Route B) was
released from solutions of 13 and 16, correspondingly. These
It should be mentioned that the lower reactivity of the
second isocyanide ligand toward nucleophilic addition is
C
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commonly observed for bis-isocyanide metal species, e.g., cis-
[PdCl2(CNR)2]. A possible rationale for this behavior is that
the carbene ligand formed, being a stronger donor compared to
the isocyanide, deactivates the second CNR ligand toward the
nucleophilic addition.5 In this study, we found that the reaction
of palladium bis-isocyanides with 1,2-diaminobenzenes pro-
ceeds at both isocyanide ligands and that, most likely, the
chelation drives the second addition.
Characterization of the Aminocarbene Complexes.
Complexes 4−16 and 19−24 were obtained as colorless or
pale yellow solids and characterized by elemental analyses
1
(C, H, N), and HRESI -MS, IR, H, and 13C{1H} NMR
spectroscopies. In addition, the structures of 4, 7, 13, 16, and
24 were elucidated by single-crystal X-ray diffraction studies.
Complexes 17 and 18 were characterized by IR spectroscopy
and HRESI -MS, and their structures were determined by
X-ray crystallography.
Complexes 4−16 and 19−24 gave satisfactory CHN-
microanalyses that are consistent with the proposed formulas.
In the HRESI+-MS of 4−16 and 19−24, ions [M−Cl]+ and/or
[M−2Cl−H]+ with the characteristic isotopic distribution were
detected. In addition, the m/2 peaks from [M−2Cl]2+ were
observed in the mass spectra of 6 and 7. The HRESI−-MS of 5,
12, and 22−24 display ion peaks [M−H]− and/or [M−Cl−
2H]−. The IR spectra of 4−24 indicated the formation of
the carbene moiety; thus, the intense absorption at 1570−
1545 cm−1 was assigned to ν(N−Ccarbene), and corresponding
ν(N−H) bands emerge in the range of 3250−3040 cm−1,
whereas δ(N−H) is closer to 1500 cm−1. The IR spectra of
4−16 display one strong ν(CN) stretching vibration in the
range between 2240 and 2198 cm−1 belonging to one unreacted
isocyanide ligand, whereas starting complexes 1−3 display
two overlapped ν(CN) bands in the interval 2265−
2208 cm−1.22,30,32,33 The IR spectra of 17−24 display no
bands in the range between 2300 and 2190 cm−1 corresponding
to ν(CN), thus supporting the transformation of both
isocyanide ligands into aminocarbenes.
Figure 2. View of 4 with the atomic numbering scheme. Thermal
ellipsoids are drawn with 50% probability. Hydrogen labels are omitted
for simplicity. Selected bond lengths (Å) and angles (deg): Pd1−C16
1.929(3) Pd1−C1 1.979(3); Pd1−Cl2 2.3289(8); Pd1−Cl1
2.3843(7); N1−C1 1.320(3); N1−C2 1.446(3); N2−C1 1.329(4);
N2−C10 1.440(3); N3−C12 1.388(4); N4−C16 1.156(4); N4−C17
1.405(4); C16−Pd1−C1 90.49(11); C16−Pd1−Cl2 175.94(8);
C1−Pd1−Cl2 86.49(8); C16−Pd1−Cl1 89.84(8); C1−Pd1−Cl1
175.53(8); Cl2−Pd1−Cl1 93.39(3); C1−N1−C2 125.7(2);
C1−N2−C10 126.3(2); C16−N4−C17 171.5(3); N1−C1−N2
118.0(3); N1−C1−Pd1 119.6(2); N2−C1−Pd1 122.3(2); and
N4−C16−Pd1 175.9(2).
The 13C{1H} NMR data also confirmed the structures of the
synthesized species. Addition of BDA1−BDA5 to 1−3 is
accompanied by a pronounced downfield δ 13C shift of one or
both of the isocyanide quaternary C atom to the range that is
specific for ADC Pd−Ccarbene (δC 160−224 ppm).11,15,19,22,34
The CcarbeneNH 13C signals in 4−16 were found to resonate
in the range of δC 173−184 ppm, that is ca. 70 ppm downfield
shifted vs 1 (e.g., δC 115 ppm for CN). These δ values for
the CcarbeneNH 13C signal are upfield relatively to those (δC
197−201 ppm) reported for the series of palladium complexes
bearing the chelating acyclic aminocarbene ligands [PdCl{C-
(NC(C6R2R3R4R5CON))N(H)R1}(CNR1)].19 In the
13C{1H} NMR spectra of 19−24, the Ccarbene−NH signals were
found to resonate in the range of δC 183−188 ppm, which is
slightly (5−10 ppm) downfield from the signals of monocarbene
complexes 4−16.
Figure 3. View of 7 with the atomic numbering scheme. Thermal
ellipsoids are drawn with 50% probability. Hydrogen labels are omitted
for simplicity. Selected bond lengths (Å) and angles (deg): Pd1−C12
1.935(6); Pd1−C1 1.974(5); N3−C12 1.159(7); N3−C(13)
1.385(7); N2−C1 1.326(6); N2−C(10) 1.432(6); N1−C1 1.312(6);
N1−C2 1.443(7); C12−Pd1−C1 86.8(2); C1−N1−C2 122.9(4);
N1−C1−N2 119.3(5); C12−N3−C(13) 176.1(5); N3−C12−Pd1
176.0(4); N2−C1−Pd1 118.2(4); and N1−C1−Pd1 122.5(4).
The crystallographic data and processing parameters for 4, 7,
13, 16−18, and 24 are listed in (Table S1); the plots for the
structures can be found in Figures 2−6.
Complexes 4, 7, 13, 16−18, and 24 exhibit a slightly
distorted square planar geometry around the metal centers. The
Pd−Ccarbene distances are typical for the single Pd−C bond and
are comparable to those reported for the relevant palladium
aminocarbene complex cis-[PdCl2{C(N(H)NCPh2)
N(H)Xyl}(CNXyl)] (1.924(3) Å)11 and cis-[PdCl2{C(Ind)
N(H)Cy}(CNCy)] (1.976(3) Å).25 In all studied complexes,
the carbene moieties are roughly planar, and the angles around
the carbene carbon atoms are close to 120°. All of the C−N
bonds of the carbene fragments have similar length and lie
between single CN bond distances (1.469(10) Å in amines35)
and double CN bond distances (1.279(8) Å in imines35). In the
D
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Figure 4. View of 13 (left) and 16 (right) with the atomic numbering schemes. Thermal ellipsoids are drawn with the 50% probability. Hydrogen
labels are omitted for simplicity. Selected bond lengths (Å) and angles (deg) for 13: Pd1−C17 1.942(3); Pd1−C1 1.974(3); Pd1−N3 2.063(2);
Pd1−Cl1 2.3439(7); N1−C1 1.339(3); N1−C2 1.419(3); N2−C1 1.332(3); N2−C(9) 1.418(3); N4−C17 1.152(4); N4−C18 1.397(4); C17−
Pd1−C1 94.32(11); C1−Pd1−N3 86.80(10); N2−C1−N1 114.4(2); and C17−N4−C18 169.4(3). Selected bond lengths (Å) and angles (deg) for
16: Pd1−C15 1.950(7); Pd1−C1 1.998(6); Pd1−N3 2.061(5); Pd1−Cl1 2.3315(16); Pd1−C15B 1.942(7); Pd1−C1 2.003(6); Pd1−N3B
2.052(5); Pd1−Cl1 2.3264(15); N2−C1 1.331(7); N1−C1 1.334(7); N4−C15 1.143(8); N4−C16 1.398(8); C15−Pd1−C1 96.4(2); C15−Pd1−
N3 177.7(2); C1−Pd1−N3 85.2(2); N2−C1−N1 113.9(5); and C15−N4−C16 172.6(6).
Figure 5. View of 17 (left) and 18 (right) with the atomic numbering schemes. Thermal ellipsoids are drawn with 50% probability. Hydrogen labels
are omitted for simplicity. Selected bond lengths (Å) and angles (deg) for 17: Pd1−C1 1.961(7); Pd1−C17 1.974(7); Pd1−Cl2 2.3742(18);
Pd1−Cl1 2.3777(18); Pd1−C1 1.961(7); Pd1−C17B 1.970(7); Pd1−Cl1 2.3693(19); Pd1−Cl2B 2.3778(18); N3−C17 1.333(9); N4−C17
1.306(9); N4−C18 1.427(9); N2−C1 1.324(9); N1−C1 1.336(9); N1−C2 1.459(9); C1−Pd1−C17 84.7(3); Cl2−Pd1−Cl1 94.09(7); C1−Pd1−
C17B 86.3(3); Cl1−Pd1−Cl2B 92.50(7); N4−C17−N3 119.2(6); C17−N4−C18 126.2(6); C1−N1−C2 124.4(6); and N2−C1−N1 118.3(6).
Selected bond lengths (Å) and angles (deg) for 18: Pd1−C1 1.960(3); Pd1−C15 1.958(3); Pd1−Cl2 2.3683(9); Pd1−Cl1 2.3755(8); N1−C1
1.319(4); N2−C1 1.338(4); N3−C15 1.334(4); N4−C15 1.326(4); C15−Pd1−C1 86.82(13); Cl2−Pd1−Cl1 93.24(3); N1−C1−N2 119.2(3);
and N4−C15−N3 118.1(3).
isocyanide ligand, the CN bond [C17−N4 1.152(4) for 13 and
C15−N4 1.143(8) for 16, Å] has a normal value for the triple
CN bond in Pd-CNR species.36−38
the route for preparation of a wide range of aminocarbene
species of different structure. Thus, a reaction of equimolar
amounts of 1,2-diamines BDA3−BDA5 and bis-isocyanide
complexes 1−3 (a molar ratio 1:1) affords aminocarbene
monocationic complexes 8−16. Some of them (13 and 16) are
able to form Chugaev-type C,C-chelated bis-carbene complexes
17 and 18 at long time exposition of the reaction mixture. The
addition of 2-fold excess of BDA3 or BDA4 (2 equiv) to
isocyanide complexes 1−3 leads to C,N-chelated bis-carbene
complexes 19−24.
Second, prepared diaminocarbene complexes represent
different types of aminocarbene palladium species, and they
might be potentially interesting as acyclic diaminocarbene-
based catalysts for cross-coupling reactions.5,6 In this context,
palladium complexes with monodentate aminocarbene li-
gands10,11,28,29 as well as with C,C- and C,N-chelated bidentate
aminocacarbenes14,17,21 have demonstrated an outstanding
catalytic efficiency in different organic transformations, including
FINAL REMARKS
■
The results from this work may be considered from at least two
perspectives. First, we found that the direction of the reaction
between the isocyanide−palladium species and benzene-1,n-
diamines (n = 2−4) depends on the position of the amino
group in the benzene ring, viz. on different basicity and
nucleophilicity of these nucleophiles.31 Benzene-1,3-diamine
BDA1 reacts with only one isocyanide group of complexes 1
and 2 leading to the typical monodentate Pd-ADC complexes 4
and 5, respectively. The reaction between benzene-1,4-diamine
(BDA2) and complexes 1 and 2 includes participation of
both amino groups of the nucleophile accomplishing binuclear
Pd-ADC 6 and 7. By contrast, the reaction of benzene-1,2-
diamines BDA3−BDA5 with palladium−isocyanides opens up
E
DOI: 10.1021/acs.organomet.5b00936
Organometallics XXXX, XXX, XXX−XXX

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Article
solved by direct methods using the SHELXS-9741 or by the charge
flipping method using Superflip42 programs. A semiempirical or
analytical absorption correction (SADABS43 or CrysAlisPro40) was
applied to all data. Structural refinements were carried out using
SHELXL-97.41 Because of slight disorder, the carbon C16 in structure
7 was restrained so that its Uij components approximate to isotropic
behavior. In 13, the chlorine and methyl substituents (Cl2 and C8) on
one of the aromatic rings were disordered over alternative sides of the
ring with an occupancy ratio of 0.76/0.24. The C−C and C−Cl
distances were restrained to be similar on both sides of the ring. Also,
the anisotropic displacement parameter of the alternative C and Cl
were set to be equal. The crystals of 16 and 17 were diffracting only
weakly. All 1-chloro-3-methylbenzene groups in these structures were
disordered in such a way that the Me and Cl groups were flipping over
alternative sides of the ring. Therefore, a series of geometric and
displacement restraints and constraints were applied to these
disordered groups. In 18, the chlorine (Cl3 and Cl6) and the methyl
(C8 and C22) substituents on the aromatic rings were again
disordered over alternative sides of the ring with occupancy ratios of
0.61/0.39 and 0.77/0.23. The C−Cl and C−C distances were
restrained to be similar on both sides of the ring, and the anisotropic
displacement parameters of the disordered C and Cl atoms were set to
be equal. The NH and NH2 hydrogen atoms were located from the
difference Fourier map or positioned geometrically and refined
Figure 6. View of 24 with the atomic numbering scheme. Thermal
ellipsoids are drawn with 50% probability. Hydrogen labels are omitted
for simplicity. Selected bond lengths (Å) and angles (deg): Pd1−C1
2.008(3); Pd1−C17 2.027(3); Pd1−N3 2.095(2); Pd1−N(6)
2.105(2); N3−C16 1.438(4); N1−C1 1.329(4); N1−C2 1.434(4);
N2−C1 1.332(4); N2−C(9) 1.420(4); N4−C17 1.331(4); N4−C18
1.443(4); N5−C17 1.333(4); N5−C25 1.420(4); N(6)−C32
1.443(4); C1−Pd1−N3 84.04(11); C17−Pd1−N(6) 84.68(11);
N1−C1−N2 117.6(3); C1−N1−C2 126.4(3); and N4−C17−N5
116.3(3).
isotropically or constrained to ride on their parent atom, with Uiso
=
1.2 Ueq(parent atom). Other hydrogen atoms were positioned geo-
metrically and constrained to ride on their parent atoms, with C−H =
0.95−1.00 and Uiso = 1.2−1.5 Ueq(parent atom). The crystallographic
details are summarized in Table S1. Supplementary crystallographic
data for this paper have been deposited at Cambridge Crystallographic
Data Centre (CCD 1435500−1435506) and can be obtained free of
charge via www.ccdc.cam.ac.uk/data_request/cif.
Synthetic Work. Synthesis of 4 and 5. Solid BDA1 (0.1 mmol)
was added to the suspension of the isocyanide complex (1 or 2,
0.1 mmol) in MeCN (5 mL). The reaction mixture was stirred at RT
for 3 h and then left overnight. The precipitate was filtered off, washed
with Et2O (three 1 mL portions), and dried in air at RT.
catalysts that outperform the most active phosphine- and
NHC-based complexes. At the same time, application of these
compounds in other catalyzed organic transformations, e.g.,
Buchwald−Hartwig amination, or Heck reaction is significantly
less studied but worth exploring, and works in this direction are
underway in our group.
4: Yield 76%. Calc. for C24H26N4Cl2Pd: C, 52.62; H, 4.78; N, 10.23.
Found: C, 52.60; H, 4.78; N, 10.20. HRESI+-MS (70 V, MeOH, m/z):
calc. for C24H26N4ClPd+ 511.0875, found 511.0881 [M − Cl]+, calc.
for C24H25N4Pd+ 475.1109, found 475.1110 [M − 2Cl − H]+.
HRESI−-MS (−70 V, MeOH, m/z): calc. for C24H25N4Cl2Pd−
545.0497, found 545.0509 [M − H]−. IR (KBr, selected bands,
cm−1): ν(N−H) 3322−3268 (m) and 3157 (m), ν(C−H) 2991 (m),
ν(CN) 2198 (s), ν(N−Ccarbene) 1551 (s), δ(N−H) 1505 (s), δ(C−
H Ar) 775 (s). δH (400.130 MHz, DMSO-d6): 2.25 (6H, s, CH3), 2.31
EXPERIMENTAL SECTION
■
Materials and Instrumentation. Solvents, PdCl2, benzenedi-
amines, and isocyanides were obtained from commercial sources and
used as received, whereas CHCl3 was purified by the conventional
distillation over calcium chloride. Complexes 1−3 were prepared by
known procedures.22 C, H, and N elemental analyses were carried out
on a Euro EA 3028HT CHNSO analyzer. Mass spectra were obtained
on a Bruker micrOTOF spectrometer equipped with an electrospray
ionization (ESI) source, and MeOH, MeCN, or MeOH/DMSO
mixture were used as the solvents. The instrument was operated both
at positive and negative ion modes using an m/z range of 50−3000.
The capillary voltage of the ion source was set at −4500 V (ESI+) or
3500 V (ESI−) and the capillary exit at (70−150) V. The nebulizer
gas pressure was 0.4 bar and drying gas flow 4.0 L/min. The most
intensive peak in the isotopic pattern is reported. Infrared spectra
(4000−400 cm−1) were recorded on a Shimadzu FTIR 8400S instru-
ment in KBr pellets. 1D (1H, 13C{1H}, DEPT) NMR spectra were
acquired on Bruker Avance 400 spectrometers, while 2D (1H,1H−
COSY, 1H,13C-HMQC/HSQC, and 1H,13C-HMBC) NMR correla-
tion experiments were recorded on Bruker Avance II+ 500 MHz
(UltraShield Magnet) spectrometers, at ambient temperature.
3
(6H, s, CH3), 5.41 (2H, br, NH2), 6.51 (1H, d, JH,H = 8.0 Hz, HAr),
6.59 (1H, s, HAr), 7.08 (1H, t, 3JH,H = 8.0 Hz, HAr), 7.14−7.23 (4H, m,
3
3
HAr), 7.27 (2H, d, JH,H = 7.5 Hz, HAr), 7.38 (1H, t, JH,H = 7.5 Hz,
HAr), 9.40 (1H, s, NH), 10.74 (1H, s, NH). δC (100.613 MHz,
DMSO-d6): 18.3 and 18.4 (CH3), 111.3, 112.9, and 113.7 (CHAr),
118.5 (C, CN), 125.5 (CAr), 126.6, 128.8, 129.0, 129.4, and 130.8
(CHAr), 134.9, 135.7, 135.8, and 141.5 (CAr), 178.3 (Ccarbene).
5. Yield 80%. Calc. for C22H20N4Cl4Pd: C, 44.89; H, 3.42; N, 9.52.
Found: C, 45.32; H, 3.40; N, 9.48. HRESI+-MS (70 V, MeOH, m/z):
calc. for C22H20N4Cl3Pd+ 550.9783, found 550.9791 [M − Cl]+, calc.
for C22H19N4Cl2Pd+ 515.0016, found 515.0018 [M − 2Cl − H]+. IR
(KBr, selected bands, cm−1): ν(N−H) 3416-3188 (m) and 3067 (m),
ν(C−H) 2924 (m), ν(C−H) 2854 (m), ν(C−H) 2806 (m), ν(CN)
2197 (s), ν(N−Ccarbene) 1553 (s), δ(N−H) 1497 (s), δ(C−H Ar) 781
(s). δH (400.130 MHz, DMSO-d6): 2.26 (3H, s, CH3), 2.34 (3H, s,
CH3), 6.52−6.58 (2H, m, HAr), 7.22−7.59 (8H, m, HAr), 9.76 (1H, s,
X-ray Structure Determinations. The crystals of 4, 7, 13, 16−
18, and 24 were immersed in Fomblin oil (Aldrich), mounted in a
Nylon loop, and measured at 100−123 K. The X-ray diffraction data
were collected on a Bruker Kappa Apex II, Bruker Kappa Apex II Duo,
or Agilent SuperNova diffractometer using Mo Kα radiation (λ =
0.710 73 Å). The Apex239 or CrysAlisPro40 program packages were
used for cell refinements and data reductions. The structures were
F
DOI: 10.1021/acs.organomet.5b00936
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Article
NH), 11.08 (1H, s, NH). δC (100.613 MHz, DMSO-d6): 18.3 and 18.4
(CH3), 111.3, 112.9, and 113.7 (CHAr), 118.5 (C, CN), 125.5
(CAr), 126.6, 128.8, 129.0, 129.4, and 130.8 (CHAr), 134.9, 135.7,
135.8, and 141.5 (CAr), 178.3 (Ccarbene).
(20H, m, CH2), 3.65−3.80 (1H, m, CH from Cy), 3.85−4.00 (1H, m,
3
CH from Cy), 6.94 (1H, d, JH,H = 7.3 Hz, HAr), 7.05−7.12 (2H, m,
3
3
HAr), 7.23 (1H, d, JH,H = 7.3 Hz, HAr), 9.60 (1H, d, JH,H = 8.8 Hz,
Ccarbene−NH−Cy), 11.07 (1H, s, NH). δC (100.613 MHz, CD2Cl2):
22.7, 24.5, 24.7, 24.9, 31.9, and 33.8 (CH2 from Cy), 55.8 and 59.2
(CH from Cy), 121.3, 121.9, 125.0, and 126.9 (CHAr), 128.2 and
135.9 (CAr), 178.9 (Ccarbene); the signal from isocyanide C was not
detected.
Synthesis of 6 and 7. The mixture containing BDA2 (0.05 mmol)
and isocyanide complex (1 or 2, 0.10 mmol) in CHCl3 (10 mL) was
refluxed for 4 h. The yielded precipitate was filtered off, washed with
CHCl3 (two 1 mL portions), and dried in air at RT.
6. Yield 74%. Calc. for C42H44N6Cl4Pd2: C, 51.08; H, 4.49; N, 8.51.
Found: C, 51.01; H, 4.48; N, 8.43. HRESI+-MS (70 V, MeOH, m/z):
calc. for C42H44N6Cl3Pd2+ 949.0757, found 949.0764 [M − Cl ]+, calc.
for C42H44N6Cl2Pd22+ 459.0536, found 459.0552 [M−2Cl]2+. IR (KBr,
selected bands, cm−1): ν(N−H) 3286−3269 (m), ν(C−H) 2953−
2851 (m), ν(CN) 2199 (s), ν(N−Ccarbene) 1550 (s), δ(N−H) 1516
(s), δ(C−H Ar) 775 (s). δH (400.130 MHz, DMSO-d6): 2.28 (6H, s,
CH3), 2.38 (6H, s, CH3), 7.30−7.60 (12H, m, HAr), 7.70−7.90 (4H,
m, HAr), 9.99 (1H, s, NH), 11.25 (1H, s, NH). δC (100.613 MHz,
DMSO-d6): 18.6 and 19.0 (8CH3), 128.9−136.0 (30C, CHAr), 179.4
(Ccarbene); the isocyanide C signal was not detected.
9. Yield 78%. Calc. for C24H26N4Cl2Pd: C, 52.62; H, 4.78; N, 10.23.
Found: C, 52.64; H, 4.80; N, 10.23. HRESI+-MS (70 V, MeOH): calc.
for C24H26N4ClPd+ 511.0875, found m/z 511.0883 [M − Cl ]+. IR
(KBr, selected bands, cm−1): ν(N−H) 3447 (m), ν(C−H) 2950 (m),
ν(CN) 2207 (s), ν(N−Ccarbene) 1552 (s), δ(N−H) 1503 (s), δ(C−
H Ar) 776 (m). δH (400.130 MHz, CD2Cl2): 2.14 (6H, s, CH3), 2.57
(6H, s, CH3), 6.79−7.33 (10H, m, HAr), 11.06 (1H, s, NH), 12.35
(1H, s, NH). δC (100.613 MHz, CD2Cl2): 18.3 and 19.9 (CH3), 121.2,
122.3, and 125.5 (CHAr), 127.2 (CAr), 127.3, 127.8, 128.1, and 128.3
(CHAr), 129.3 (CAr), 130.1 (CHAr), 135.2, 135.6, and 137.8 (CAr),
183.7 (Ccarbene); the signal from isocyanide C was not detected.
10. Yield 72%. Calc. for C22H20N4Cl4Pd: C, 48.89; H, 3.42; N, 9.52.
Found: C, 48.93; H, 3.44; N, 9.53. HRESI+-MS (70 V, MeOH): calc.
for C22H20N4Cl3Pd+ 550.9783, found m/z 550.9788 [M − Cl ]+. IR
(KBr, selected bands, cm−1): ν(N−H) 3446-3130 (m), ν(C−H) 2962
(m), ν(CN) 2210 (s), ν(N−Ccarbene) 1556 (s), δ(N−H) 1503 (s),
δ(C−H Ar) 784 (m). δH (400.130 MHz, CD3OD): 2.50 (3H, s, CH3),
2.59 (3H, s, CH3), 7.14−7.63 (10H, m, HAr). δC (100.613 MHz,
CD3OD): 17.4 and 17.8 (CH3), 121.9, 122.4, 126.6, 126.7, 127.5, and
128.0 (CHAr), 129.2 (CAr), 129.3 (CHAr), 129.8 (CAr), 130.0 and
130.4 (CHAr), 130.9 and 131.4 (CAr), 131.8 (CHAr), 132.6, 135.3,
138.0, and 139.2 (CAr), 177.0 (Ccarbene); the signal from isocyanide C
was not detected.
7. Yield 80%. Calc. for C38H32N6Cl8Pd2: C, 42.69; H, 3.02; N, 7.86.
Found: C, 42.59; H, 3.00; N, 7.79. HRESI+-MS (70 V, MeOH, m/z):
+
calc. for C38H32N6Cl7Pd2 1028.8572, found 1028.8586 [M − Cl ]+,
2+
calc. for C38H32N6Cl6Pd2 498.9427, found 498.9477 [M−2Cl]2+. IR
(KBr, selected bands, cm−1): ν(N−H) 3230−3180 (m), ν(C−H)
2957−2852 (m), ν(CN) 2200 (s), ν(N−Ccarbene) 1544 (s), δ(N−
H) 1508 (s), δ(C−H Ar) 777 (s). δH (400.130 MHz, DMSO-d6): 2.28
(6H, s, CH3), 2.38 (6H, s, CH3), 7.30−7.60 (12H, m, HAr), 7.70−7.90
(4H, m, HAr), 9.99 (1H, s, NH), 11.25 (1H, s, NH); δC (100.613 MHz,
DMSO-d6): 18.8 and 19.3 (4C, CH3), 124.1−129.2 (30C, CHAr), 180.4
(Ccarbene); the isocyanide C signal was not detected.
Synthesis of 8−16. The solid benzenediamines (BDA3−BDA5;
0.1 mmol) were added to the solution or suspension of any one of
1−3 (0.1 mmol) in CH2Cl2 (2 mL), and the reaction mixture left at
RT overnight. The yielded precipitate was filtered off, washed with
CH2Cl2 (0.5 mL), and dried in air at RT (portion 1). The initial
solution and the filtrate were combined, dried in vacuo at RT, washed
with a cooled mixture of Et2O and CH2Cl2 9:1 (1 mL), then Et2O
(two 1 mL portions), and dried in air at RT (portion 2).
8. Yield 69%. Calc. for C20H30N4Cl2Pd: C, 47.68; H, 6.00; N, 11.12.
Found: C, 47.67; H, 5.96; N, 11.13. HRESI+-MS (70 V, MeOH): calc.
for C20H30N4ClPd+ 467.1188, found m/z 467.1191 [M − Cl ]+. IR
(KBr, selected bands, cm−1): ν(N−H) 3429 (m), ν(C−H) 2932−
2852 (m), ν(CN) 2233 (s), ν(N−Ccarbene) 1570 (s), δ(N−H) 1500
(s), δ(C−H Ar) 757 (s). δH (400.130 MHz, CD2Cl2): 0.95−2.20
11. Yield 77%. Calc. for C22H34N4Cl2Pd: C, 49.68; H, 6.44; N,
10.53. Found: C, 49.78; H, 6.50; N, 10.48. HRESI+-MS (70 V,
MeOH): calc. for C22H34N4ClPd+ 495.1501, found m/z 495.1503
[M − Cl ]+. IR (KBr, selected bands, cm−1): ν(N−H) 3430 (m),
ν(C−H) 2935−2850 (m), ν(CN) 2235 (s), ν(N−Ccarbene) 1570
(s), δ(N−H) 1500 (s), δ(C−H Ar) 755 (s). δH (400.130 MHz,
CDCl3): 0.76−2.00 (20H, m, CH2), 2.09 (3H, s, CH3), 2.18 (3H, s,
CH3), 3.55−3.70 (1H, m, CH), 3.77−3.87 (1H, m, CH), 6.72 (1H, s,
HAr), 6.92 (1H, s, HAr), 9.40 (1H, d, 3JH,H = 8.9 Hz, Ccarbene−NH−Cy),
10.90 (1H, s, NH). δC (100.613 MHz, CDCl3): 19.1, 22.7, 24.5, 24.7,
24.9, and 31.9 (CH2), 55.6 and 59.1 (CH), 122.4 and 122.9 (CHAr),
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DOI: 10.1021/acs.organomet.5b00936
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125.2, 133.4, 133.7, and 135.2 (CAr), 178.5 (Ccarbene); the signal from
isocyanide C was not detected.
15. Yield 60%. Calc. for C24H24N4Cl4Pd: C, 46.74; H, 3.92; N, 9.08.
Found: C, 46.80; H, 3.97; N, 9.10. HRESI+-MS (70 V, MeOH): calc.
for C24H24N4Cl3Pd+ 579.0096, found m/z 579.0098 [M − Cl ]+. IR
(KBr, selected bands, cm−1): ν(N−H) 3286−3012 (m), ν(C−H)
2831−2756 (m), ν(CN) 2203 (s), ν(N−Ccarbene) 1553 (s), δ(N−
H) 1476 (s), δ(C−H Ar) 801 (s). δH (400.130 MHz, CD3OD): 2.41
(6H, s, CH3), 2.52 (6H, s, CH3), 7.24−7.40 (6H, m, HAr), 7.42 (1H, s,
HAr), 7.73 (1H, s, HAr). δC (100.613 MHz, CD3OD): 17.2 and 17.5
(CH3), 123.4, 124.0, 128.1, and 129.0 (CHAr), 129.1 (CAr), 129.5
(CHAr), 133.8, 134.9, 135.2, and 136.3 (CAr), 177.0 (Ccarbene); the
signal from isocyanide C was not detected.
12. Yield 73%. Calc. for C26H30N4Cl2Pd: C, 54.23; H, 5.25; N, 9.73.
Found: C, 54.17; H, 5.19; N, 9.68. HRESI+-MS (70 V, MeOH): calc.
for C26H30N4ClPd 539.1188, found m/z 539.1194 [M − Cl ]+.
HRESI−-MS (−70 V, MeOH, m/z): calc. for C26H28N4ClPd+
537.1043, found 537.1044 [M − Cl−2H]−. IR (KBr, selected bands,
cm−1): ν(N−H) 3446 (m), ν(C−H) 2950 (m), ν(CN) 2203 (s),
ν(N−Ccarbene) 1555 (s), δ(N−H) 1513 (s), δ(C−H Ar) 781 (m δH
(400.130 MHz, CDCl3): 1.99 (3H, s, CH3), 2.09 (6H, s, CH3), 2.15
(3H, s, CH3), 2.54 (6H, s, CH3), 6.74−6.82 (3H, m, HAr), 6.84 (1H, s,
HAr), 6.98−7.00 (3H, m, HAr), 7.15−7.19 (1H, m, HAr), 10.70 (1H, s,
NH), 12.14 (1H, s, NH). δC (100.613 MHz, CDCl3): 18.5 (2C, CH3),
18.9 and 19.0 (CH3), 20.1 (2C, CH3), 122.3 and 123.4 (CHAr), 124.3
(CAr), 127.8 and 127.9 (CHAr), 128.2 (CAr), 128.3 and 130.1 (CHAr),
133.0, 134.3, 135.2, 135.7, and 135.8 (CAr), 137.8 (CHAr), 183.0
(Ccarbene); the signal from isocyanide C was not detected.
16. Yield 66%. Calc. for C22H18N4Cl6Pd: C, 40.19; H, 2.76; N, 8.52.
Found: C, 40.27; H, 2.86; N, 8.44. HRESI+-MS (70 V, MeOH): calc.
for C22H18N4Cl5Pd+ 618.9003, found m/z 618.9012 [M − Cl ]+. IR
(KBr, selected bands, cm−1): ν(N−H) 3443−3111 (m), ν(C−H)
2924 (m), ν(CN) 2208 (s), ν(N−Ccarbene) 1550 (s), δ(N−H) 1487
(s), δ(C−H Ar) 780 (s). δH (400.130 MHz, CD3OD): 2.47 (6H, s,
CH3), 2.57 (6H, s, CH3), 7.35−7.54 (7H, m, HAr), 7.72 (1H, s, HAr).
δC (100.613 MHz, CD3OD): 17.4 and 17.8 (CH3), 123.4, 123.8,
127.4, 128.0, and 129.2 (CHAr), 129.3 and 129.9 (CAr), 130.0 and
130.6 (CHAr), 130.9, 131.2, and 131.6 (CAr), 131.8 (CHAr), 132.2
(CAr), 137.9 and 139.4 (CH, Ar), 177.6 (Ccarbene); the signal from
isocyanide C was not detected.
13. Yield 82%. Calc. for C24H24N4Cl4Pd: C, 46.74; H, 3.92; N, 9.08.
Found: C, 46.71; H, 3.98; N, 9.03. HRESI+-MS (70 V, MeOH): calc.
for C24H24N4Cl3Pd+ 579.0096, found m/z 579.0102 [M − Cl ]+. IR
(KBr, selected bands, cm−1): ν(N−H) 3440 (m), ν(C−H) 2960 (m),
ν(CN) 2210 (s), ν(N−Ccarbene) 1556 (s), δ(N−H) 1500 (s), δ(C−
H Ar) 785 (m). δH (400.130 MHz, CD2Cl2): 2.13 (3H, s, CH3), 2.17
(3H, s, CH3), 2.25 (3H, s, CH3), 2.29 (3H, s, CH3), 6.82−6.90
(3H, m, HAr), 7.08 (1H, s, HAr), 7.11−7.37 (4H, m, HAr), 11.25 (1H, s,
NH), 12.54 (1H, s, NH). δC (100.613 MHz, CD2Cl2): 18.7, 18.8, 18.9,
and 19.8 (CH3), 122.4−138.0 (18C, CAr), 182.9 (Ccarbene); the signal
from isocyanide C was not detected.
Synthesis of 17 and 18. The solutions of 13 and 16 (0.05 mmol)
in MeCN (10 mL) were evaporated slowly at RT for 2 months. A few
formed crystals of 17 and 18 were mechanically separated and studied
by HRESI-MS and X-ray crystallography.
17. HRESI+-MS (70 V, MeOH, m/z): calc. for C24H24N4Cl3Pd+
579.0096, found 579.0081 [M − Cl ]+. IR (KBr, selected bands,
cm−1): ν(N−H) 3217−3085 (m), ν(C−H) 2960 (m), ν(N−Ccarbene
1560 (s), δ(N−H) 1505 (s), δ(C−H Ar) 785 (s).
)
14. Yield 52%. Calc. for C20H28N4Cl4Pd: C, 41.94; H, 4.93; N, 9.78.
Found: C, 42.07; H, 4.96; N, 9.73. HRESI+-MS (70 V, MeOH): calc.
for C20H28N4Cl3Pd+ 535.0409, found m/z: 535.0415 [M − Cl ]+. IR
(KBr, selected bands, cm−1): ν(N−H) 3483−3175 (m), ν(C−H)
2935−2857 (m), ν(CN) 2240 (s), ν(N−Ccarbene) 1566 (s), δ(N−
H) 1586 (s). δH (400.130 MHz, CD3OD): 1.22−2.18 (20H, m, CH2),
4.00−4.10 (1H, m, CH), 4.10−4.20 (1H, m, CH), 7.61 (1H, s, HAr),
7.62 (1H, s, HAr). δC (100.613 MHz, CD3OD): 22.2, 24.3, 24.5, 24.4,
31.3, and 31.9 (CH2), 54.7 and 55.4 (CH), 123.0 and 123.1 (CHAr),
128.4, 129.3, 129.4, and 135.6 (CAr), 173.7 (Ccarbene); the signal from
isocyanide C was not detected.
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18. HRESI+-MS (70 V, MeOH, m/z): calc. for C22H18N4Cl5Pd+
618.9003, found 618.8989 [M − Cl]+. IR (KBr, selected bands, cm−1):
ν(N−H) 3243−3090 (m), ν(C−H) 2940 (m), ν(N−Ccarbene) 1560
(s), δ(N−H) 1500 (s), δ(C−H Ar) 780 (s).
7.44−7.50 (2H, m, HAr), 7.60−7.65 (2H, m, HAr). δC (100.613 MHz,
CD3OD): 17.8 (2C, CH3), 122.0, 123.3, 126.0, 126.2, 128.0, 129.9,
and 130.2 (CHAr), 131.2, 131.8, 131.9, 132.1, 132.2, 135.3, 135.4,
138.6, and 138.7 (CAr), 186.7 (Ccarbene).
22. Yield 85%. Calc. for C30H46N6Cl2Pd: C, 53.94; H, 6.94; N,
12.58. Found: C, 53.97; H, 6.98; N, 12.56. HRESI+-MS (70 V,
MeOH): calc. for C30H46N6ClPd+ 631.2502, found 631.2507 [M −
Cl]+, calc. for C30H45N6Pd+ 595.2735, found m/z 595.2742 [M − 2Cl −
H]+. HRESI−-MS (−70 V, MeOH, m/z): calc. for C30H45N6Cl2Pd−
665.2123, found m/z 665.2131 [M − H]−, calc. for C30H44N6ClPd
629.2356, found m/z 629.2362 [M − Cl−2H]−. IR (KBr, selected
bands, cm−1): ν(N−H) 3430 (m), ν(C−H) 2935−2850 (m), ν(N−
Ccarbene) 1560 (s), δ(N−H) 1500 (s), δ(C−H Ar) 753 (s). δH (400.130
MHz, CD3OD): 2.48−3.64 (20H, m, CH2), 2.23 and 2.25 (16H, s,
CH3), 3.19−3.24 and 3.87−3.93 (2H, m, CH), 6.92, 6.97, 7.12, 7.23,
7.28, and 7.91 (4H, s, HAr). δC (100.613 MHz, CD3OD): 17.71, 17.77,
17.81, 17.88, 24.6−25.0, 31.7, 31.9, 32.1, 31.8, 34.5, 52.5, 53.5, 58.5,
59.2, 122.3, 122.4, 122.5, 122.6,122.9, 123.0, 123.1, 128.1, 128.5, 128.8,
132.8, 133.0, 133.2, 133.3, 133.7, 134.0, 134.2, 134.4, 134.5, 134.6, 134.7,
183.1, and 189.9 (Ccarbene).
Synthesis of 19−24. A solution of diamine (BDA3 or BDA4,
0.22 mmol) in MeCN (1 mL) was slowly added at RT to a solution or
suspension of any one of 1−3 (0.10 mmol) in MeCN (2 mL). The
color of the reaction mixture turned immediately from light yellow to
bright yellow, which gradually turned back to the light yellow. For all
complexes except 22, the reaction mixture was stirred for 1 h at RT
until a crystalline precipitate formed; complex 22 was obtained via
heating up to 70 °C for 2 h and cooling to RT. The formed
precipitates were filtered off, washed with MeCN (1 mL) and Et2O
(two 1 mL portions) and dried in air at RT.
19. Yield 80%. Calc. for C26H38N6Cl2Pd: C, 51.03; H, 6.26; N,
11.59. Found: C, 50.98; H, 6.25; N, 13.73. HRESI+-MS (70 V,
MeOH): calc. for C26H38N6ClPd+ 575.1876, found m/z 575.1883
[M − Cl ]+, calc. for C26H37N6Pd+ 539.2109, found m/z 539.2113
[M − 2Cl − H]+. IR (KBr, selected bands, cm−1): ν(N−H) 3429 (m),
ν(C−H) 2932−2855 (m), ν(N−Ccarbene) 1562 (s), δ(N−H) 1500 (s),
δ(C−H Ar) 754 (s). δH (400.130 MHz, CD3OD): 1.10−2.10 (20H,
m, CH2), 3.85−4.05 (2H, m, NH−CH), 7.10−7.35 (5H, m, Ar), 7.35−
7.45 (1H, m, HAr), 7.45−7.56 (2H, m, HAr). δC (100.613 MHz,
CD3OD): 24.5, 24.9, and 31.8 (CH2), 52.6 (CH-NH), 121.4, 122.3,
125.2, and 125.7 (CHAr), 130.8 and 135.8 (CAr), 183.5 (Ccarbene).
23. Yield 93%. Calc. for C34H42N6Cl2Pd: C, 57.35; H, 5.95; N,
11.80. Found: C, 57.37; H, 5.48; N, 11.83. HRESI+-MS (70 V,
MeOH): calc. for C34H42N6ClPd+ 675.2189, found m/z 675.2195
[M − Cl]+, calc. for C34H41N6Pd+ 639.2422, found m/z 639.2419
[M − 2Cl − H]+. HRESI−-MS (−70 V, MeOH, m/z): calc. for
C34H40N6ClPd− 673.2043, found m/z 673.2047 [M − Cl−2H]−. IR
(KBr, selected bands, cm−1): ν(N−H) 3423 (m), ν(C−H) 2958 (m),
ν(N−Ccarbene) 1546 (s), δ(N−H) 1511 (s), δ(C−H Ar) 780 (s). δH
(400.130 MHz, CD3OD): 2.21 (6H, s, CH3), 2.25 (6H, s, CH3), 2.37
(12H, s, CH3), 6.97 (2H, s, HAr), 7.20−7.30 (6H, m, HAr), 7.39 (2H, s,
HAr). δC (100.613 MHz, CD3OD): 19.0−19.2 (8C, CH3), 124.1 and
125.5 (CHAr), 129.9 (CAr), 130.2 and 130.3 (CHAr), 134.2, 135.1,
135.7, 136.0, and 136.9 (CAr), 186.9 (Ccarbene).
20. Yield 91%. Calc. for C30H34N6Cl2Pd: C, 54.93; H, 5.22; N,
12.81. Found: C, 54.94; H, 5.23; N, 12.83. HRESI+-S (70 V, MeOH):
calc. for C30H34ClN6Pd+ 619.1563, found m/z 619.1567 [M − Cl]+,
calc. for C30H33N6Pd+ 583.1796, found m/z 583.1799 [M − 2Cl −
H]+. IR (KBr, selected bands, cm−1): ν(N−H) 3410 (m), ν(C−H)
2980 (m), ν(N−Ccarbene) 1545 (s), δ(N−H) 1500 (s), δ(C−H Ar)
780 (m). δH (400.130 MHz, CD3OD): 2.38 (12H, s, CH3), 7.20−7.35
(12H, m, HAr), 7.55−7.65 (2H, m, HAr). δC (100.613 MHz, CD3OD):
18.0 (4C, CH3), 122.3, 123.8, 126.3, 126.4, 129.3, and 129.5 (CHAr),
131.8, 134.1, 135.8, and 135.9 (CAr), 186.3 (Ccarbene).
21. Yield 87%. Calc. for C28H28N6Cl4Pd: C, 48.26; H, 4.05; N,
12.06. Found: C, 48.27; H, 4.07; N, 12.08. HRESI+-MS (70 V,
MeOH): calc. for C28H28N6Cl3Pd+ 659.0470, found m/z 659.0473
[M − Cl ]+, calc. for C28H27N6Cl2Pd+ 623.0704, found m/z 623.0709
[M − 2Cl − H]+. IR (KBr, selected bands, cm−1): ν(N−H) 3408 (m),
ν(C−H) 2979 (m), ν(N−Ccarbene) 1546 (s), δ(N−H) 1502 (s),
δ(C−H Ar) 778 (m). δH (400.130 MHz, CD3OD): 2.44 (3H, s, CH3),
2.46 (3H, s, CH3), 7.22−7.27 (6H, m, HAr), 7.36−7.41 (4H, m, HAr),
24. Yield 88%. Calc. for C32H36N6Cl4Pd: C, 51.05; H, 4.82; N,
11.16. Found: C, 51.07; H, 4.80; N, 11.13. HRESI+-MS (70 V,
MeOH): calc. for C32H35N6Cl2Pd+ 679.1330, found m/z 679.1334
[M − 2Cl − H]+. HRESI−-MS (−70 V, MeOH, m/z): calc. for
C32H34N6Cl3Pd− 713.0951, found 713.0948 [M − Cl−2H]−. IR (KBr,
selected bands, cm−1): ν(N−H) 3424 (m), ν(C−H) 2973 (m), ν(N−
Ccarbene) 1546 (s), δ(N−H) 1515 (s), δ(C−H Ar) 779 (s). δH
(400.130 MHz, CD3OD): 2.22 (6H, s, CH3), 2.26 (6H, s, CH3),
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2.42 (3H, s, CH3), 2.43 (3H, s, CH3), 6.99 (2H, s, HAr), 7.36−7.39
(6H, m, HAr), 7.43−7.46 (2H, m, HAr). δC (100.613 MHz, CD3OD):
19.1−19.2 (6C, CH3), 124.2, 125.4, and 129.3 (CHAr), 129.8 (CAr),
131.3 and 131.5 (CHAr), 133.2, 133.3, 133.5, 133.7, 134.2, 135.8,
136.2, and 140.0 (CAr), 187.6 (Ccarbene).
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ASSOCIATED CONTENT
* Supporting Information
The Supporting Information is available free of charge on the ACS
Publications website at DOI: 10.1021/acs.organomet.5b00936.
■
S
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Crystal data and structure refinement data (PDF)
CIF file for complex 4 (CIF)
CIF file for complex 7 (CIF)
CIF file for complex 13 (CIF)
CIF file for complex 17 (CIF)
CIF file for complex 24 (CIF)
CIF file for complex 16 (CIF)
CIF file for complex 18 (CIF)
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AUTHOR INFORMATION
Corresponding Authors
*(K.V.L.) E-mail: konstantin.luzyanin@liv.ac.uk.
*(V.P.B.) E-mail: v.boiarskii@spbu.ru.
■
Notes
The authors declare no competing financial interest.
ACKNOWLEDGMENTS
■
This work was supported by Russian Science Foundation
(grant 14-43-00017). S.A.T. is grateful to Saint Petersburg State
University for the postdoctoral fellowship (12.50.2525.2013).
Physicochemical studies were performed at the Center for
Magnetic Resonance and Center for Chemical Analysis and
Materials Research (all belong to Saint Petersburg State
University).
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