The first example of Re(IV)-mediated nitrile-hydroxylamine coupling

Article abstract of DOI:10.1016/j.inoche.2006.04.010

The metal-mediated coupling between the acetonitriles in cis-[Re^IVCl₄(MeCN)₂] and the N,N-dibenzylhydroxylamines R₂³ NOH (R³ = CH₂Ph, CH₂C₆H₄C1-p

Full text of DOI:10.1016/j.inoche.2006.04.010

Inorganic Chemistry Communications 9 (2006) 732–735
www.elsevier.com/locate/inoche
The first example of Re(IV)-mediated nitrile–hydroxylamine coupling
b,
*
Konstantin V. Luzyanin a,b, Vadim Yu. Kukushkin
,
c
a,
*
Matti Haukka , Armando J.L. Pombeiro
a
Centro de Quimica Estrutural, Complexo I, Instituto Superior Te´cnico, Av. Rovisco Pais, 1049-001 Lisbon, Portugal
b
Department of Chemistry, St. Petersburg State University, 198504 Stary Petergof, Russian Federation
c
Department of Chemistry, University of Joensuu, P.O. Box 111, FIN-80101 Joensuu, Finland
Received 24 March 2006; accepted 10 April 2006
Available online 9 June 2006
Abstract
The metal-mediated coupling between the acetonitriles in cis-[ReIVCl4(MeCN)2] and the N,N-dibenzylhydroxylamines R3NOH
2
(R3 = CH2Ph, CH2C6H4C1-p) proceeds smoothly in CH2Cl2/MeCN at 20–25 ꢀC for ca. 15 min to accomplish new imino species
cis-½ReCl4fNH@CðMeÞONR3g ꢀ (R3 = CH2Ph, 1, CH2C6H4C1-p, 2) in ca. 70% yield. The structures of the isolated compounds were
2
2
based on elemental analyses (C, H, N), IR, FAB+-MS and on X-ray data for 1.
ꢁ 2006 Published by Elsevier B.V.
Keywords: Nitriles; Rhenium(IV) complexes; Nucleophilic addition; Metal-mediated reactions; Dibenzylhydroxylamines; Imino complexes
Nucleophilic addition to nitriles, RC„N, represents an
attractive way to new organic and coordination com-
pounds with a variety of applications, e.g. in polymer
industry, pharmacology, and environmental protection
[1,2]. The reactivity of organonitriles has already been sum-
marized in some comprehensive reviews [1,3,4], giving an
idea that nitriles, in particular unreactive RCN species with
donor R groups, should be subjected to additional electro-
philic activation in order to perform the nucleophilic addi-
tion. One of the most effective routes to reach this
activation is coordination to a metal center [1], and the
benefits in reactivity could be so significant that coupling
of coordinated nitriles might proceed with even weak
HON-nucleophiles (i.e. oximes) to accomplish imino spe-
cies, and the reaction opens up (upon liberation of the
obtained ligands) a route to new uncommon or even
unknown compounds in organic chemistry.
[5]. In the case of oximes and in the presence of a metal salt
(viz. NiCl2), the reaction proceeds via the formation of
intermediate complex A (Fig. 1), generated through the
double nucleophilic addition of R1R2C@NOH species by
the oxygen to a nitrile carbon, which further reacts with
2 equiv. of phthalonitriles to form metal–Pcs [5].
Furthermore, it was recently observed [6] that the use
of N,N-dialkylhydroxylamines, HONR32, as alternative
HON-nucleophiles in the synthesis of PCs, leads to an
enhancement of the reactivity, which suggests that the
hydroxylamines have a higher nucleophilicity than the oxi-
mes. This relative behaviour has recently been confirmed
by a kinetic study [7].
However, in contrast with the diversity of the addition
reactions of various oximes to nitriles, coordinated to dif-
ferent metal centers, e.g. (PtIV, ReIV, RhIII) [8a,8b,8c,8d],
there are only a few works devoted to the hydroxyl-
amine–nitrile coupling [7,9]. Thus, our previous studies
demonstrate that the reaction of dialkyl- and dibenzylhydr-
Recently we discovered that HON-nucleophiles, such as
oximes and dialkylhydroxylamines, can effectively promote
the conversion of phthalonitriles to phthalocyanines (PCs)
oxylamines ðHONR3; R3 ¼ Me; Et; CH2Ph; CH2C6H4-
2
Cl-pÞ with coordinated nitriles in the platinum(II) and
platinum(IV) complexes [PtCln(RCN)2] (n = 2,4) and [Ph3-
PCH2Ph][PtCln(RCN)] (n = 3,5) affords, upon addition of
the hydroxylamine oxygen to the carbon atom of the
*
Corresponding authors.
E-mail addresses: kukushkin@VK2100.spb.edu (V.Yu. Kukushkin),
pombeiro@ist.utl.pt (A.J.L. Pombeiro).
1387-7003/$ - see front matter ꢁ 2006 Published by Elsevier B.V.
doi:10.1016/j.inoche.2006.04.010

K.V. Luzyanin et al. / Inorganic Chemistry Communications 9 (2006) 732–735
733
R2
CH2C6H4Cl-p, 2) in ca. 70% yield [11]. The isolated com-
pounds were characterized by elemental analyses (C, H,
N), IR, FAB+-MS and also 1 by a single crystal X-ray dif-
fraction [12]. Despite the numerous attempts to obtain the
corresponding products of addition of dialkylhydroxylam-
ines, R32NOH (R3 = Me, Et), or monosubstituted
alkylhydroxylamine, R3NHOH (R3 = Me), to cis-
[ReCl4(MeCN)2], we were unable to isolate any significant
quantities of the expected imine products, presumably due
to their instability and/or occurrence of side reactions.
Compounds 1 and 2 gave satisfactory C, H, and N ele-
mental analyses. The FAB+-MS spectra of both com-
pounds display the molecular ion peaks and those
derived from fragmentation, corresponding to the sequen-
tial loss of Cl ligands, viz. [MꢁnCl]+, as observed previ-
ously for [ReCl4(imine)2] complexes [8b]. In the IR
spectra, 1 and 2 display no band that could be assigned
to a m(C„N) stretching vibration (such a band appears
at 2293 cmꢁ1 for the parent cis-[ReCl4(MeCN)2] [13]), but
show one intense band in the range of 1660–1595 cmꢁ1
assigned to m(C@N) of the newly formed imino group
C@NH. These data match well with those obtained for
the related complexes, e.g. cis-½ReCl4fNH@CðMeÞON@
CR1R22g2ꢀ [8b], derived from the addition of oximes to
Re-bound acetonitriles. The molecular structure of 1 has
been determined by single-crystal X-ray diffraction analysis
(Fig. 2).
R1
O
R2
2+
R1
NH2
N
N
(Cl–)2
N
O
R
R
R
R
N
N
Ni
N
O
H2N
R1
O
R2
A
R2
R1
Fig. 1.
RC„N ligands, structurally relevant PtII- and PtIV-imino
species ½PtClnfNH@CðEtÞONR3g ꢀ or ½Ph3PCH2Phꢀ-
2
2
½PtClnfNH@CðEtÞONR3gꢀ, correspondingly [9].
2
In order to widen the application of the higher nucleo-
philicity of dialkylhydroxylamines towards coordinated
organonitriles as compared to oximes, we decided to
extend the work to other metal-centers and focused our
attention on ReIV nitrile complexes. Moreover, it is known
that Re centers can activate nitriles towards either electro-
philic or nucleophilic additions depending on the metal oxi-
dation state (in contrast with the PtII,IV-centers for which
only electrophilic activation of nitriles is known [1]). In
fact, the electron-rich ReI-phosphinic centers trans- and
cis-{ReCl(Ph2PCH2CH2PPh2)2} strongly activate nitrile
ligands towards electrophilic but not nucleophilic addition
[10]. Thus, we have now investigated the activation of nitr-
iles by the electron-poor ReIV center and report herein the
first example of a ReIV-mediated nitrile–hydroxylamine
Crystallographic data are summarized in [14,15], while
selected bond lengths and angles are given in the legend
to Fig. 2. The rhenium(IV) imino complex 1 has a slightly
distorted octahedral geometry and both imino ligands are
HONR3 (R3 = CH2Ph, CH2C6H4Cl-p) coupling.
2
The coupling between the acetonitriles in cis-[ReCl4
(MeCN)2] and the dibenzylhydroxylamines R32NOH
(R3 = CH2Ph, CH2C6H4Cl-p), Scheme 1, proceeds smoothly
in CH2Cl2/MeCN at 20–25 ꢀC for ca. 15 min and the sub-
sequent workup provides the isolation of the new imino
species cis-½ReCl4fNH@CðMeÞONR3g ꢀ (R3 = CH2Ph, 1,
2
2
Cl
N
Cl
N
ReIV
Cl
+
HO
2
N
Cl
R3
R3
C
C
Me
Me
Fig. 2. The crystal structure of cis-[ReCl4{NH@C(Me)ON(CH2Ph)2}2]
˚
(1). Selected bond lengths (A) and angles (ꢀ) for 1 are Re(1)AN(1) 2.105(2),
Cl
Cl
R3
CH2Ph
CH2(C6H4Cl-p)
Re(1)AN(3) 2.108(2), Re(1)ACl(1) 2.3322(5), Re(1)ACl(2) 2.3638(5),
N(1)AC(1) 1.277(3), C(1)AO(10) 1.351(2), O(1)AN(2) 1.482(2), N(2)A
C(3) 1.486(3), C(1)AC(2) 1.482(3), Cl(1)ARe(1)ACl(2) 81.31(2),
N(1)ARe(1)ACl(1) 172.18(5), N(1)ARe(1)ACl(2) 83.52(5), C(1)AN(1)A
Re(1) 137.27(14), N(1)AC(1)AO(10) 121.4(2), C(1)AO(10)AN(2)
112.10(15), N(1)AC(1)AC(2) 127.0(2); hydrogen bond: N(1)AH(1) 0.89,
H(1) ꢂ ꢂ ꢂ N(2) 2.16 N(1) ꢂ ꢂ ꢂ N(2) 2.590(2), N(1)AH(1) ꢂ ꢂ ꢂ N(2) 113.1,
N(3)AH(3) 0.91, H(3) ꢂ ꢂ ꢂ N(4) 2.16, N(3) ꢂ ꢂ ꢂ N(4) 2.658(2), N(3)A
H(3) ꢂ ꢂ ꢂ N(4) 113.4.
Me
Cl ReIV Cl
1
H
N
N
R3
R3
2
O
N
H
O
Me
N
R3
R3
Scheme 1. ReIV-mediated nitrile–hydroxylamine coupling.

734
K.V. Luzyanin et al. / Inorganic Chemistry Communications 9 (2006) 732–735
[6] M.N. Kopylovich, V.Yu. Kukushkin, K.V. Luzyanin, A.J.L. Pom-
beiro, unpublished results.
mutually cis and in the E-configuration. The ReACl bond
lengths [2.105(2) and 2.108(2) A] and all bond angles
˚
[7] K.V. Luzyanin, V.Yu. Kukushkin, M.L. Kuznetsov, A.D. Ryabov,
M. Galanski, M. Haukka, E.V. Tretyakov, V.I. Ovcharenko, M.N.
Kopylovich, A.J.L. Pombeiro, Inorg. Chem. 45 (2006) 2296.
[8] (a) V.Yu. Kukushkin, T.B. Pakhomova, Yu.N. Kukushkin, R.
Herrmann, G. Wagner, A.J.L. Pombeiro, Inorg. Chem. 37 (1998)
6511;
around the Re center are as expected [16], and they are in
a good agreement with those obtained for the related com-
plexes cis-[ReCl4{NH@C(Me)ON@C(R)}2] (R = C5H10,
C9H18) [8b]. The two C@NH bonds in 1 are equal within
˚
3r [1.277(3) and 1.286(3) A] and they correspond to typical
(b) G. Wagner, A.J.L. Pombeiro, N.A. Bokach, V.Yu. Kukushkin, J.
Chem. Soc., Dalton Trans. (1999) 4083;
˚
values (1.26–1.29 A) [16] for C@N double bonds. All other
bond lengths and angles for compound 1 are not unusual
and are within the expected limits [16]. Inspection of the
NAH and NHꢂ ꢂ ꢂN distances and values of the HANꢂ ꢂ ꢂH
angles in the imine ligands clearly indicates that the E-con-
figuration of these species is stabilized by a NAHꢂ ꢂ ꢂH
hydrogen bond between the imine hydrogen and the
hydroxylamine N atom.
(c) V.Yu. Kukushkin, I.V. Ilichev, G. Wagner, J.J.R. Frau´sto da
Silva, A.J.L. Pombeiro, J. Chem. Soc., Dalton Trans. (1999)
3047;
(d) D.A. Garnovskii, M.F.C. Guedes da Silva, T.B. Pakhomova, G.
Wagner, M.T. Duarte, J.J.R. Frau´sto da Silva, A.J.L. Pombeiro,
V.Yu. Kukushkin, Inorg. Chim. Acta 300–302 (2000) 499.
[9] K.V. Luzyanin, V.Yu. Kukushkin, A.D. Ryabov, M. Haukka, A.J.L.
Pombeiro, Inorg. Chem. 44 (2005) 2944.
[10] (a) A.J.L. Pombeiro, D.L. Hughes, R.L. Richards, Chem. Commun.
(1988) 1052;
Thus, we extended the nitrile–hydroxylamine coupling,
previously observed only at Pt centers [7,9], to another
metal and reported the first example of a ReIV-mediated
integration between nitriles and hydroxylamines.
(b) J.J.R. Frau´sto da Silva, M.F.C. Guedes da Silva, R.A. Henderson,
A.J.L. Pombeiro, R.L.J. Richards, Organomet. Chem. 461 (1993)
141;
(c) A.J.L. Pombeiro, M.F.C. Guedes da Silva, J. Organomet. Chem.
617 (2001) 65;
(d) M.F.C. Guedes da Silva, J.J.R. Frau´sto da Silva, A.J.L.
Pombeiro, Inorg. Chem. 41 (2002) 219;
Supplementary material
Crystal data for cis-[ReCl4{NH@C(Me)ON(CH2Ph)2}2]
have been deposited at the Cambridge Crystallographic
Data Centre (CCDC) with deposition No. 601861. Copies
of this information may be obtained free of charge from
deposit@ccdc.cam.ac.uk or www: http://www.ccdc.cam.
ac.uk. Supplementary data associated with this article can
be found, in the online version, at doi (manuscript code
here).
(e) S.M.P.R. Cunha, M.F.C. Guedes da Silva, A.J.L. Pombeiro,
Inorg. Chem. 42 (2003) 2157;
(f) M.L. Kuznetsov, A.A. Nazarov, A.J.L. Pombeiro, J. Phys. Chem.,
A 109 (2005) 8187.
[11] Reaction of cis-[ReCl4(MeCN)2] with HONR32 (R3 = CH2Ph,CH2-
C6H4Cl-p). A solution of the appropriate dibenzylhydroxylamine
(0.20 mmol) in CH2C12 (1.0 mL) was added to a suspension of cis-
[ReCl4(MeCN)2] [13] (41 mg, 0.10 mmol) in MeCN (5.0 mL) and the
mixture was kept for 2 h at room temperature, whereupon the slightly
greenish crystalline product formed (in the case of 1, suitable for X-
ray diffraction analysis) was separated by filtration, washed twice with
3 mL-portions of dry diethyl ether and dried in vacuo at room
temperature. Yields are 70%, based on Re.
Acknowledgements
[12] cis-[ReCl4{NH@C(Me)ON(CH2Ph)2}2] (1): Anal. Calcd. for
This work has been partially supported by the Fundac¸ao
˜
C
32H36N4Cl4O2Re: C, 45.94; H, 4.34; N, 6.70. Found: C, 45.47; H,
para a Cieˆncia e a Tecnologia (FCT), Portugal, and its
POCI 2010 program (FEDER funded). K.V.L. express
gratitude to FCT and the POCTI program (FEDER
funded), Portugal, for a fellowship (Grant SFRH/BD/
10464/2002). V.Yu.K. is very much obliged to the Russian
Fund for Basic Research for the Grants (06-03-32065 and
05-03-32140). M.H. thanks the Academy of Finland for
financial support of his studies.
4.32; N, 6.50%. FAB+-MS, m/z: 835 [M]+, 799 [MꢁClꢁH]+. IR,
cmꢁ1: 3268 m-w m(NAH), 1612 m(C@N), 1192 m m(CAO). cis-
[ReCl4{NH@C(Me)ON(CH2C6H4Cl-p)2}2] (2): Anal. Calcd. for
C
32H32N4Cl8O2Re: C, 39.44; H, 3.31; N, 5.75. Found: C, 40.21; H,
3.12; N, 5.25%. FAB+-MS, m/z: 973 [M]+, 903 [Mꢁ2Cl]+. IR, cmꢁ1
:
3262 m-w m(NAH), 1609 s m(C@N), 1206 m m(CAO).
[13] G. Rouschias, G. Wilkinson, J. Chem. Soc. A (1968) 489.
[14] X-ray structure determination of 1: The X-ray diffraction data were
collected on a Nonius KappaCCD diffractometer using Mo Ka
˚
radiation (k = 0.71073 A). The Denzo-Scalepack [15a] program
package was used for cell refinements and data reduction. The
structure was solved by direct methods using the SIR2002 program
[15b]. An empirical absorption correction based on equivalent
reflections [15c] was applied to the data (Tmax/Tmin was 0.3806/
0.7692). The structure refinement was carried out with the
SHELXL97 program [15d] and the WinGX graphical user interface
[15e]. NH hydrogen was located from the difference Fourier but not
refined. Other hydrogens were placed in idealized position and
constrained to ride on their parent atom. Crystal data for 1:
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˚
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˚
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K.V. Luzyanin et al. / Inorganic Chemistry Communications 9 (2006) 732–735
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