From discrete monomeric complexes to hydrogen-bonded dimeric assemblies based on sterically encumbered square planar palladium(ii) ONN-pincers

Article abstract of DOI:10.1039/c3dt50176k

The 2-(3-biphenyl-2-ol)-6-iminepyridines, 2-(3-C₁₂H ₈-2-OH)-6-(CHNAr)C₅H₃N (Ar = 2,6-i-Pr ₂C₆H₃ (L1a-H), 2,4,6-Me₃C ₆H₂ (L1b-H)), have been prepared in high yield via sequential Suzuki coupling, deprotection and condensation reactions from 2-methoxybiphenyl-3-ylboronic acid and 2-bromo-6-formylpyridine. Treatment of L1-H with Pd(OAc)₂ or (MeCN)₂PdCl₂ results in deprotonation of L1-H to afford the discrete square planar ONN-chelates, [{2-(3-C₁₂H₈-2-O)-6-(CHNAr)C₅H ₃N}Pd(OAc)] (Ar = 2,6-i-Pr₂C₆H₃ (1a), 2,4,6-Me₃C₆H₂ (1b)) and [{2-(3-C ₁₂H₈-2-O)-6-(CHNAr)C₅H₃N}PdCl] (Ar = 2,6-i-Pr₂C₆H₃ (2a), 2,4,6-Me₃C ₆H₂ (2b)), in good yield, respectively; conversion of 1 to 2 using aqueous sodium chloride has been demonstrated. Selective reduction of the imino unit in L1-H with LiAlH₄ proceeds smoothly to yield the 2-(3-biphenyl-2-ol)-6-(methylamine)pyridines, 2-(3-C₁₂H ₈-2-OH)-6-(CH₂-NHAr)C₅H₃N (Ar = 2,6-i-Pr₂C₆H₃ (L2a-H), 2,4,6-Me ₃C₆H₂ (L2b-H)), which on reaction with Pd(OAc)₂ give [{2-(3-C₁₂H₈-2-O)-6-(CH ₂-NHAr)C₅H₃N}Pd(OAc)] (Ar = 2,6-i-Pr ₂C₆H₃ (3a), 2,4,6-Me₃C ₆H₂ (3b)). Depending on the temperature of the reaction, the oxidised aldimine products 1a or 1b can also be observed as a competitive side-product during the formation of 3a or 3b. Similarly, ketimine-containing, [{2-(3-C₁₂H₈-2-O)-6-(CMeN(2,6-i-Pr₂C ₆H₃))C₅H₃N}Pd(OAc)] (5), can be detected during the preparation of chiral [{2-(3-C₁₂H ₈-2-O)-6-(CMeH-NH(2,6-i-Pr₂C₆H ₃))C₅H₃N}Pd(OAc)] (4) from 2-(3-C ₁₂H₈-2-OH)-6-(CH₂-NH(2,6-i-Pr₂C ₆H₃))C₅H₃N (L3-H) and Pd(OAc) ₂. Complexes 3a, 3b and 4 all exist as dimeric species in the solid state in which two anti-aligned square planar monomers are held together by two intermolecular NH_amine...O_phenolate interactions resulting in palladium-palladium separations of between 3.141-3.284 A. The structurally related chloride-containing dimeric assemblies, [{2-(3-C ₁₂H₈-2-O)-6-(CH₂-NHAr)C₅H ₃N)}PdCl] (Ar = 2,6-i-Pr₂C₆H₃ (6a), 2,4,6-Me₃C₆H₂ (6b)), can also be isolated on treatment of 3 with aqueous sodium chloride or by reaction of L3-H with (MeCN)₂PdCl₂. Single crystal X-ray diffraction studies have been performed on L1a-H, L3-H, 1a, 1b, 2a, 2b, 3a, 3b, 4, 6a and 6b. The Royal Society of Chemistry 2013.

Full text of DOI:10.1039/c3dt50176k

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From discrete monomeric complexes to hydrogen-
bonded dimeric assemblies based on sterically
encumbered square planar palladium(II) ONN-pincers†
Cite this: Dalton Trans., 2013, 42, 7710
Okoh Adeyi, Warren B. Cross, Gregory Forrest, Luke Godfrey, Eric G. Hope,
Andrew McLeod, Amandeep Singh, Kuldip Singh, Gregory A. Solan,* Yining Wang
and Luka A. Wright
The 2-(3-biphenyl-2-ol)-6-iminepyridines, 2-(3-C12H8-2-OH)-6-(CHvNAr)C5H3N (Ar = 2,6-i-Pr2C6H3 (L1a-
H), 2,4,6-Me3C6H2 (L1b-H)), have been prepared in high yield via sequential Suzuki coupling, deprotec-
tion and condensation reactions from 2-methoxybiphenyl-3-ylboronic acid and 2-bromo-6-formylpyri-
dine. Treatment of L1-H with Pd(OAc)2 or (MeCN)2PdCl2 results in deprotonation of L1-H to afford the
discrete square planar ONN-chelates, [{2-(3-C12H8-2-O)-6-(CHvNAr)C5H3N}Pd(OAc)] (Ar = 2,6-i-Pr2C6H3
(1a), 2,4,6-Me3C6H2 (1b)) and [{2-(3-C12H8-2-O)-6-(CHvNAr)C5H3N}PdCl] (Ar = 2,6-i-Pr2C6H3 (2a), 2,4,6-
Me3C6H2 (2b)), in good yield, respectively; conversion of 1 to 2 using aqueous sodium chloride has been
demonstrated. Selective reduction of the imino unit in L1-H with LiAlH4 proceeds smoothly to yield the
2-(3-biphenyl-2-ol)-6-(methylamine)pyridines, 2-(3-C12H8-2-OH)-6-(CH2-NHAr)C5H3N (Ar = 2,6-i-Pr2C6H3
(L2a-H), 2,4,6-Me3C6H2 (L2b-H)), which on reaction with Pd(OAc)2 give [{2-(3-C12H8-2-O)-6-(CH2-NHAr)-
C5H3N}Pd(OAc)] (Ar = 2,6-i-Pr2C6H3 (3a), 2,4,6-Me3C6H2 (3b)). Depending on the temperature of the reac-
tion, the oxidised aldimine products 1a or 1b can also be observed as a competitive side-product during
the formation of 3a or 3b. Similarly, ketimine-containing, [{2-(3-C12H8-2-O)-6-(CMevN(2,6-i-Pr2C6H3))-
C5H3N}Pd(OAc)] (5), can be detected during the preparation of chiral [{2-(3-C12H8-2-O)-6-(CMeH-NH(2,6-
i-Pr2C6H3))C5H3N}Pd(OAc)] (4) from 2-(3-C12H8-2-OH)-6-(CH2-NH(2,6-i-Pr2C6H3))C5H3N (L3-H) and
Pd(OAc)2. Complexes 3a, 3b and 4 all exist as dimeric species in the solid state in which two anti-aligned
square planar monomers are held together by two intermolecular NHamine⋯Ophenolate interactions result-
ing in palladium–palladium separations of between 3.141–3.284 Å. The structurally related chloride-
containing dimeric assemblies, [{2-(3-C12H8-2-O)-6-(CH2-NHAr)C5H3N)}PdCl] (Ar = 2,6-i-Pr2C6H3 (6a),
2,4,6-Me3C6H2 (6b)), can also be isolated on treatment of 3 with aqueous sodium chloride or by reaction
of L3-H with (MeCN)2PdCl2. Single crystal X-ray diffraction studies have been performed on L1a-H, L3-H,
1a, 1b, 2a, 2b, 3a, 3b, 4, 6a and 6b.
Received 17th January 2013,
Accepted 13th March 2013
DOI: 10.1039/c3dt50176k
www.rsc.org/dalton
the aromatisation–dearomatisation processes that can occur at
Introduction
the pyridine core during certain bond activations has help
Pyridine-based pincer-type complexes, in which the hetero- further fuel the research area.2
aromatic defines the central donor, have attracted considerable
With regard to palladium(II) chemistry, pyridine-based
interest in recent years due, in large part, to their important pincer complexes have been reported for a raft of different tri-
applications in organic synthesis, homogeneous catalysis, dentate ligand sets including symmetrical (e.g., PNP,3 NNN,4
bond activation and design of new materials.1 The amenability CNC,5 SNS6) and non-symmetrical (e.g., NNC,7 ONC8)
of the exterior donor atoms of the tridentate ligand to impart examples. In contrast, those based on non-symmetric ONN-
electronic and steric flexibility to the metal centre has no frameworks are considerably more scarce with anionic
doubt impacted on these advances. Moreover, recognition of O-substituted N,N-bipyridines/phenanthrolines9 and neutral
2-imine-6-(methylalcohol)pyridines10 representative.
With a view to developing new ligand systems that may have
Department of Chemistry, University of Leicester, University Road, Leicester LE1
catalytic applications, we have been interested in pincers that
7RH, UK. E-mail: gas8@leicester.ac.uk
can not only promote the formation of a sterically protected
metal-containing pocket, but also have the potential to
†CCDC 919243–919253. For crystallographic data in CIF or other electronic
format see DOI: 10.1039/c3dt50176k
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Fig. 1 Monoanionic 2-(3-biphenyl-2-olate)-6-iminepyridine (L1), 2-(3-biphenyl-2-olate)-6-(methylamine)pyridine (L2) and 2-(3-biphenyl-2-olate)-6-(ethylamine)-
pyridine (L3).
facilitate intermolecular hydrogen-bonding interactions11,12 reduced by addition of lithium aluminium hydride to yield the
within the pocket. To this end, we targeted an ONN ligand 2-(3-biphenyl-2-ol)-6-(methylamine)pyridines, 2-(C12H8-2-OH)-
framework incorporating a central pyridine group appended 6-(CH2-NHAr)C5H3N (Ar = 2,6-i-Pr2C6H3 (L2a-H), 2,4,6-Me3-
by both an anionic oxygen donor and a neutral secondary C6H2 (L2b-H)), while the 2-(3-biphenyl-2-ol)-6-(ethylamine)pyr-
amine (or imine) donor.13 It was envisaged that the coordi- idine, 2-(3-C12H8-2-OH)-6-(CMeH-NH(2,6-i-Pr2C6H3))C5H3N
nated amine donor could also serve as a directional hydrogen (L3-H), could be prepared by treating L1a-H with trimethyl-
bond donor (D) and the bound oxygen as an acceptor (A). aluminium followed by hydrolysis; this latter approach having
Herein, we report the synthesis of the protonated forms of the been used to derivatize a range of different imine com-
non-symmetrical 2-(biphenyl-2-olate)-6-iminepyridine, L1, and pounds.15 The five new compounds, L1a-H, L1b-H, L2a-H,
the reduced 2-(biphenyl-2-olate)-6-(alkylamine)pyridines, L2 L2b-H and L3-H, have been characterised using a combination
1
and L3, and then explore their coordination chemistry with of electrospray mass spectrometry, IR, H NMR and 13C NMR
palladium(II) (Fig. 1).
spectroscopy (see Experimental section).
Compounds, L1a-H, L1b-H, L2a-H, L2b-H and L3-H, all
display protonated molecular ions peaks in their electrospray
mass spectra and downfield shifted signals for the phenolic
protons (range: δ 14.1–15.2) in their 1H NMR spectra. In
addition, broad ν(OH) absorption bands centered ca.
Results and discussion
(a) Preparation of pro-ligands L1-H–L3-H
The 2-(3-biphenyl-2-ol)-6-iminepyridines, 2-(3-C12H8-2-OH)- 2600 cm−1 in their IR spectra are consistent with strong intra-
6-(CHvNAr)C5H3N (Ar = 2,6-i-Pr2C6H3 (L1a-H), 2,4,6-Me3C6H2 molecular hydrogen bonds. In the 1H NMR spectrum of imine-
(L1b-H)), have been prepared in high yield via sequential based L1-H, the CHvN protons are seen as singlets at δ ca. 8.3
Suzuki coupling, deprotection and condensation reactions with the corresponding imino carbon appearing at δ ca. 161.0
from 2-methoxybiphenyl-3-ylboronic acid and 2-bromo-6-for- in their 13C NMR spectra. The CH2-NH moiety in reduced L2-H
mylpyridine (Scheme 1) using general methodologies we have can be seen as a singlet for the methylene protons [δ 4.22 (L2a-
described elsewhere.14 The imino unit in L1-H could be readily H), 4.46 (L2b-H)] and a broad singlet for the NH proton at δ ca.
Scheme 1 Reagents and conditions: (i) 2-Br-6-(CHO)C5H3N, cat. Pd(PPh3)4, toluene, K2CO3 (aq.), ethanol, 90 °C; (ii) BBr3, CH2Cl2, −78 °C; (iii) ArNH2, ethanol, 40 °C;
(iv) LiAlH4, THF, −78 °C; (v) H2O; (vi) AlMe3, toluene, 100 °C.
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Fig. 2 Molecular structure of L1a-H including
a partial atom numbering
scheme. All hydrogen atoms, apart from H1 and H12, have been omitted for
clarity.
Scheme 2 Reagents and conditions: (i) Pd(OAc)2, toluene, 60 °C; (ii) (MeCN)2-
PdCl2, THF, RT; (iii) NaCl (aq.), CHCl3, RT.
neighbouring phenol oxygen as a result of a hydrogen-bonding
interaction between the phenol hydrogen atom and the pyri-
dine nitrogen [O(1)⋯N(1) 2.540 (L1a-H), 2.543 Å (L3-H)].14
Some tilting of the plane of the 3-phenyl substituent with
respect to the neighbouring phenol is evident in both struc-
tures [tors. C(1)–C(2)–C(25)–C(26) 48.3(4)° (L1a-H), 45.4(5)°
(L3-H)] in a manner similar to that found in 2-hydroxy-
biphenyl.16
Fig. 3 Molecular structure of L3-H including
a partial atom numbering
scheme. All hydrogen atoms, apart from H1, H2 and H12, have been omitted
for clarity.
(b) Palladium(II) complexes of L1
Table 1 Selected bond lengths (Å) and angles (°) for L1a-H and L3-H
Interaction of L1-H with either Pd(OAc)2 at 60 °C in toluene or
(MeCN)2PdCl2 in tetrahydrofuran at room temperature gave,
on work-up, [{2-(3-C12H8-2-O)-6-CHvNAr)C5H3N}Pd(OAc)] (Ar =
2,6-i-Pr2C6H3 (1a), 2,4,6-Me3C6H2 (1b)) and [{(2-(3-C12H8-2-O)-
6-CHvNAr)C5H3N}PdCl] (Ar = 2,6-i-Pr2C6H3 (2a), 2,4,6-Me3-
C6H2 (2b)), respectively, in good yield (Scheme 2). Alternatively,
1 can be converted to 2 in near quantitative yield by treatment
of a chloroform solution of 1 with aqueous sodium chloride.
The complexes are air stable and have been characterised
using a combination of FAB mass spectrometry, IR and NMR
(1H and 13C) spectroscopy and elemental analyses (see Experi-
mental section). In addition, crystals of each complex have
been the subject of single crystal X-ray diffraction studies.
The molecular structures of 1a, 1b, 2a, and 2b are closely
related and will be discussed together. Perspective views of 1a
and 2b are given in Fig. 4 and 5; selected bond distances and
angles are collected for all the structures in Tables 2 and 3.
There are two independent molecules for 1a in the unit cell
(molecules A and B) and five for 2b (molecules A–E) which
differ most noticeably in the inclination of the N-aryl plane to
the adjacent imine unit (vide infra). Each structure consists of
a single palladium centre bound by a tridentate monoanionic
L1a-H
L3-H
Bond lengths
C(1)–O(1)
C(2)–C(25)
C(6)–C(7)
C(12)–N(2)
1.348(3)
1.489(4)
1.482(3)
1.262(3)
1.429(3)
1.366(3)
1.486(5)
1.470(4)
1.482(4)
1.425(4)
C(13)–N(2)
Bond angles
C(11)–C(12)–N(2)
C(12)–N(2)–C(13)
122.0(2)
119.2(2)
112.5(3)
115.2(3)
1
3.4 in their H NMR spectra. Similarly, the CMeH-NH proton
in L3-H appears as a broad singlet at δ 3.48 while a mutually
coupled doublet and quartet are seen for the CMeH-NH and
CMeH-NH protons, respectively. Further confirmation of the
composition of L1a-H and L3-H was achieved in the form of
single crystal X-ray determinations.
Perspective views of L1a-H and L3-H are depicted in Fig. 2
and 3; selected bond distances and angles for both structures
are listed in Table 1. Each structure consists of a central pyri-
dine ring that is substituted at its 2-position by a 3-biphenyl-2-
ol group but differs at the 6-position with a trans-configured N-
arylimine unit for L1a-H [C(12)–N(2) 1.262(3) Å] or a saturated
CHMeNH(2,6-i-Pr2C6H3) unit for L3-H. In general, the pyridine
nitrogen atoms adopt a cis configuration with respect to the
2-(3-biphenyl-2-olate)-6-iminepyridine ligand along with
a
monodentate O-bound acetate (1) or chloride (2) to complete a
distorted square planar geometry. Within the ONN-ligand
7712 | Dalton Trans., 2013, 42, 7710–7723
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there are both 5- and 6-membered chelate rings with the bite 9.2(11)A, 8.8(11)B (1a), 2.1(12)° (1b)]. For a given complex, the
angle for the 6-membered ring being more compatible with Pd–N(imine) bond distance is the longest of the three metal–
the geometrical requirements of the palladium(II) centre [O(1)– ligand interactions involving the ONN-ligand followed by the
Pd(1)–N(1)6-membered: 94.5(2)A, 92.9(2)B (1a), 94.9(3) (1b), 92.6(2) Pd–N(pyridine) distance and then by the Pd–O(phenolate) dis-
(2a), 93.3(3)av.° (2b) vs. N(2)–Pd(1)–N(1)5-membered 83.1(3)A, tance which is best exemplified for complex 1b [Pd(1)–
83.8(3)B (1a), 81.8(3) (1b), 82.1(2) (2a), 82.0(3)av.° (2b)]. In all N(2)imine 2.004(6)
> Pd(1)–N(1)pyridine 1.973(6) > Pd(1)–
cases some twisting of the phenolate unit with respect to the O(1)phenolate 1.942(5) Å]. Replacing a chloride for an O-bound
pyridyl plane is apparent [tors. N(1)–C(13)–C(2)–C(1) 6.0(10) acetate has little effect on the trans Pd–N(pyridine) distance
(2a), 13.4(15)av.° (2b) compared with tors. N(1)–C(13)–C(2)–C(1) [1.958(6)A/B (1a), 1.973(6) (1b), 1.986(5) (2a), 1.968(8)av. Å (2b)].
The N-aryl groups are inclined towards orthogonality with
regard to the neighbouring CvNimine vector [tors. C(18)–N(2)–
C(19)–C(20) 105.6(8)A, 86.9(9)B (1a), 75.2(10) (1b), 98.5(7) (2a),
72.9(13)A–103.4(11)E° (2b)], while the 3-phenyl group is tilted
[tors. C(1)–C(6)–C(7)–C(12) 53.4(10)A, 50.4(12)B (1a), 44.6(12)
(1b), 49.5(10) (2a), 44.0(14)av.° (2b)] with respect to the adjacent
phenolate group. There are no intermolecular contacts of note.
The closest crystallographically characterised comparators to 1
and 2 are [2-(2,2′-bipyridin-6-yl)phenolate]PdCl9b and [3-fluoro-
2-(1,10-phenanthrolin-2-yl)phenolate]Pd(OAc),9d which display
similar bonding characteristics.
Table 2 Selected bond lengths (Å) and angles (°) for 1a and 1b
1a
1b
Fig. 4 Molecular structure of 1a (molecule A) including a partial atom number-
ing scheme. All hydrogen atoms have been omitted for clarity.
Molecule A
Molecule B
Bond lengths
Pd(1)–O(1)
Pd(1)–O(2)
Pd(1)–N(1)
Pd(1)–N(2)
C(18)–N(2)
C(6)–C(7)
C(31)–O(2)
C(31)–O(3)
1.934(5)
1.997(5)
1.958(6)
1.973(6)
1.292(8)
1.483(10)
1.303(9)
1.225(9)
1.948(5)
2.004(5)
1.958(6)
1.993(6)
1.297(8)
1.503(11)
1.293(9)
1.224(8)
1.942(5)
2.018(5)
1.973(6)
2.004(6)
1.299(10)
1.508(12)
1.313(11)
1.234(10)
Bond angles
N(1)–Pd(1)–N(2)
N(1)–Pd(1)–O(1)
N(2)–Pd(1)–O(2)
O(1)–Pd(1)–O(2)
N(1)–Pd(1)–O(2)
83.1(3)
94.5(2)
95.0(2)
87.3(2)
176.8(2)
83.8(3)
92.9(2)
94.7(2)
88.6(2)
178.2(2)
81.8(3)
94.9(3)
95.5(3)
88.0(2)
176.7(2)
Fig. 5 Molecular structure of 2b (molecule A) including a partial atom number-
ing scheme. All hydrogen atoms have been omitted for clarity.
Table 3 Selected bond lengths (Å) and angles (°) for 2a and 2b
2b
2a
Molecule A
Molecule B
Molecule C
Molecule D
Molecule E
Bond lengths
Pd(1)–O(1)
Pd(1)–N(1)
Pd(1)–N(2)
Pd(1)–Cl(1)
C(18)–N(2)
C(6)–C(7)
1.976(4)
1.986(5)
2.010(5)
2.299(2)
1.289(7)
1.492(14)
1.943(6)
1.959(7)
1.981(8)
2.287(3)
1.257(11)
1.494(12)
1.934(6)
1.969(8)
1.999(8)
2.287(3)
1.305(11)
1.451(13)
1.950(6)
1.966(8)
2.006(8)
2.298(3)
1.276(11)
1.484(13)
1.946(6)
1.973(8)
1.990(8)
2.286(3)
1.283(11)
1.491(13)
1.937(6)
1.973(8)
1.990(8)
2.291(3)
1.271(11)
1.500(13)
Bond angles
N(1)–Pd(1)–N(2)
N(1)–Pd(1)–O(1)
N(2)–Pd(1)–Cl(1)
O(1)–Pd(1)–Cl(1)
N(1)–Pd(1)–Cl(1)
N(2)–Pd(1)–O(1)
82.1(2)
92.6(2)
95.08(16)
90.18(13)
177.21(16)
173.4(2)
82.5(3)
93.5(3)
95.4(2)
88.66(19)
175.3(2)
176.0(3)
82.5(3)
93.9(3)
95.9(2)
87.7(2)
177.3(2)
176.0(3)
82.2(3)
93.7(3)
95.7(3)
88.5(2)
177.6(2)
173.9(3)
80.9(3)
92.0(3)
96.1(2)
90.73(19)
175.5(2)
172.1(3)
82.0(3)
93.4(3)
95.7(2)
88.8(2)
175.6(2)
175.1(3)
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Scheme 3 Reagents and conditions: (i) Pd(OAc)2, toluene, 60 °C. Relative ratios determined by 1H NMR spectroscopy.
Complexes 1a, 1b, 2a and 2b, all display molecular ion toluene affording, on work-up, almost exclusively 3a, 3b and 4.
peaks in their FAB mass spectra along with fragmentation The three new complexes have been characterised using a com-
peaks corresponding to the loss of an acetate or a chloride, bination of FAB mass spectrometry, IR and NMR (1H and 13C)
respectively. Their imine stretching frequencies shift by spectroscopy along with elemental analyses (see Experimental
ca. 35 cm−1 to lower wavenumber on imine-coordination (in section). In addition, crystals of each complex have been the
comparison with free L1-H) as is seen in related palladium(II) subject of single crystal X-ray diffraction studies.
complexes.17 In 1a and 2a two distinct doublets are seen for
The molecular structures of 3a, 3b and 4 are similar and
1
the isopropyl methyl groups in their H NMR spectra consist- will be discussed together. Views of 3a and 5 are shown in
ent with some restricted rotation about the N-aryl bond in Fig. 6 and 7; selected bond distances and angles are collected
solution. The acetate methyl groups in 1 can be seen at δ ca. for all three structures in Tables 4 and 5. Each structure com-
1
1.6 in their H NMR spectra with the MeC(O)O carbon atoms prises two anti-parallel aligned square planar {2-(3-biphenyl-
observable at δ ca. 176.7 in their 13C NMR spectra. In addition 2-olate)-6-alkylamine-pyridine}Pd(OAc) monomeric units linked
strong bands assignable to the symmetric and asymmetric together by two NamineH⋯Ophenolate hydrogen bonding inter-
ν(COO) vibrations in 1, are in agreement with those expected actions [N(2)⋯O(1A) 3.038 (3a), 2.929 (3b), 3.000 (4) Å]19 to
for monodentate acetate ligands.18
form a dimeric assembly. Like 1 and 2, the ONN-tridentate
ligand in each monomer contain both 5- and 6-membered
chelate rings with the bite angle for the 6-membered ring
(c) Palladium(II) complexes of L2 and L3
Initially, the preparation of [{2-(3-C12H8-2-O)-6-(CH2-NHAr)- again being better matched with the geometrical requirements
C5H3N}Pd(OAc)] (Ar = 2,6-i-Pr2C6H3 (3a), 2,4,6-Me3C6H2 (3b)) of the palladium(II) centre [O(1)–Pd(1)–N(1)6-membered: 90.48(18)
was carried out using the conditions employed to synthesise 1 (3a), 92.2 (3b), 92.5° (4) vs. N(2)–Pd(1)–N(1)5-membered 84.59(19)
(viz. by reacting the pro-ligand with Pd(OAc)2 in toluene at (3a), 85.3(3) (3b), 83.4(3)° (4)]. The twisting of the phenolate
60 °C). However, monitoring of the reactions using 1H NMR unit with respect to the neighbouring pyridyl plane is,
spectroscopy revealed the presence of both 3 and aldimine- however, even more noticeable [tors. N(1)–C(13)–C(2)–C(1) 28.9
containing 1, the relative ratio being dependent on the nature (9) (3a), 25.0(11) (3b), 31.3(12)° (4)] when compared to 1 and 2,
of the aryl group (relative ratio: 3a–1a 47 : 53 and 3b–1b 90 : 10) presumably to compensate for the puckering at the methylene
(Scheme 3). Similarly, the reaction of L3-H with Pd(OAc)2 gave (CH2NHAr (3) or CHMeNHAr (4)) carbon atoms. There are no
[{2-(3-C12H8-2-O)-6-(CMeH-NH(2,6-i-Pr2C6H3))C5H3N}Pd(OAc)] interactions of note between dimeric assemblies.
(4) and ketimine-containing [{2-(3-C12H8-2-O)-6-(CMevN(2,6-
The palladium–palladium separations in 3b (3.177(2) Å)
i-Pr2C6H3))C5H3N}Pd(OAc)] (5) in a 81 : 19 ratio. To circumvent and 4 (3.1409(15) Å) are shorter than the sum of the van der
this apparent oxidation of 3 or 4, the reaction of the cor- Waals radii (3.26 Å) while in 3a (3.284 Å) the separation
responding pro-ligand with Pd(OAc)2 was carried out at 0 °C in is slightly longer. In comparison with previously reported
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Table 4 Selected bond lengths (Å) and angles (°) for 3a and 3ba
3a
3b
Bond lengths
Pd(1)–O(1)
Pd(1)–O(2)
Pd(1)–N(1)
Pd(1)–N(2)
C(18)–N(2)
C(6)–C(7)
C(31)–O(2)
C(31)–O(3)
1.990(4)
2.019(4)
1.955(5)
2.078(4)
1.505(6)
1.477(8)
1.257(7)
1.221(7)
3.284
1.972(5)
2.049(6)
1.976(6)
2.033(6)
1.495(9)
1.456(12)
1.124(11)
1.284(11)
3.177(2)
Pd(1)⋯Pd(1A)
Bond angles
N(1)–Pd(1)–N(2)
N(1)–Pd(1)–O(1)
N(2)–Pd(1)–O(2)
O(1)–Pd(1)–O(2)
N(1)–Pd(1)–O(2)
N(2)–Pd(1)–O(2)
84.59(19)
90.48(18)
94.99(17)
89.43(15)
176.25(19)
94.99(17)
85.5(3)
92.2(3)
90.4(2)
91.6(2)
175.3(3)
90.4(2)
a The ‘A’ atoms denote the neighbouring palladium atom in the dimer;
for 3b it been generated by symmetry: symmetry operation −x + 1, −y,
−z.
Fig. 6 Molecular structure of 3a including a partial atom numbering scheme.
All hydrogen atoms, apart from H2, have been omitted for clarity.
Table 5 Selected bond lengths (Å) and angles (°) for 4a
Bond lengths
Pd(1)–O(1)
Pd(1)–O(2)
Pd(1)–N(1)
Pd(1)–N(2)
C(18)–N(2)
C(6)–C(7)
C(32)–O(2)
1.959(5)
2.025(5)
1.971(6)
2.038(6)
1.557(10)
1.462(11)
1.260(9)
1.250(9)
3.1409(15)
C(32)–O(3)
Pd(1)⋯Pd(1A)
Bond angles
N(1)–Pd(1)–N(2)
N(1)–Pd(1)–O(1)
N(2)–Pd(1)–O(2)
O(1)–Pd(1)–O(2)
N(1)–Pd(1)–O(2)
N(2)–Pd(1)–O(2)
83.4(3)
92.5(2)
92.8(2)
91.2(2)
176.1(2)
92.8(2)
a The ‘A’ atoms have been generated by symmetry: symmetry operation
−x + 1, −y, −z.
Fig. 7 Molecular structure of 4 including a partial atom numbering scheme.
All hydrogen atoms, apart from H2, have been omitted for clarity.
Compounds 3a, 3b and 4 all show fragmentation peaks cor-
responding to the loss of an acetate group from both the
dimeric and monomeric species in their ESI mass spectra. The
covalently bridged palladium(II) dimers,20 the Pd⋯Pd dis-
tances in 3a, 3b and 4 fall at the top end of the range
(2.55–3.05 Å) but are comparable with that found in the related
hydrogen-bonded dimer [Pd(OPh)2(pyrrolidine)2] (3.0960(3)
Å).21 Interestingly, d8–d8 bonding interactions have been high-
lighted recently during a computational investigation on a
range of palladium(II) dimers (Pd⋯Pd 2.55–3.05 Å)22 and in
the model compound [Pd(CN)2(PH3)2]2 (Pd⋯Pd 3.107 Å).20b
Moreover, it has been suggested that the Pd–Pd bonding inter-
action is related to the separation between the palladium
centres implying some interaction may be present in 3a, 3b
and 4, albeit weak.
1
methylene CH2-NH protons in the H NMR spectra of 3a and
3b are inequivalent and appear as two doublet of doublets [at
δ 4.58 and 4.16 (3a); 4.76 and 4.02 (3b)], while in 4 the CHMe-
NH proton appears as a doublet of quartets at δ 4.31. Each
isopropyl-methyl proton in 3a and 4 are inequivalent leading
to four separate doublets. The NH proton in each complex
is shifted by ca. 4 ppm downfield compared to that observed
in the free pro-ligand, supportive of a hydrogen bonding inter-
action being maintained in solution.
It is uncertain as to the mechanism of oxidation that occurs
during the formation of imines 1 and 5 on reaction of L2-H or
L3-H with palladium acetate, respectively. Notably, palladium
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Table 6 Selected bond lengths (Å) and angles (°) for 6a and 6ba
6a
6b
Bond lengths
Pd(1)–O(1)
Pd(1)–N(1)
Pd(1)–N(2)
Pd(1)–Cl(1)
C(18)–N(2)
C(6)–C(7)
Pd(1)⋯Pd(1A)
Bond angles
2.001(4)
1.973(4)
2.058(4)
2.2982(14)
1.510(7)
1.485(8)
3.2412(10)
1.999(10)
1.966(12)
2.049(12)
2.302(4)
1.456(19)
1.49(2)
3.291
N(1)–Pd(1)–N(2)
N(1)–Pd(1)–O(1)
N(2)–Pd(1)–Cl(1)
O(1)–Pd(1)–Cl(1)
N(1)–Pd(1)–Cl(1)
N(2)–Pd(1)–O(1)
84.59(18)
90.92(17)
92.77(13)
92.07(11)
176.34(14)
170.17(16)
83.6(5)
91.3(4)
93.6(4)
92.3(3)
174.4(3)
167.6(4)
Scheme 4 Reagents and conditions: (i) NaCl (aq.), CHCl3, RT; (ii) (MeCN)2PdCl2,
THF, RT.
a The ‘A’ atoms denote the neighbouring palladium atom in the dimer;
for 6a it been generated by symmetry: symmetry operation −x + 2, −y +
2, −z + 1.
acetate–pyridine mixtures have has been used as catalysts to
promote the aerobic oxidation of secondary amines to imines
(e.g., Ar-CH2NHPh to Ar-CHvN-Ph).23 It would therefore seem
plausible that adventitious amounts of oxygen may have con-
tributed to the product distribution; we cannot however, rule
out a mechanism involving metal–ligand cooperation via aro-
matisation–dearomatisation involving the pyridine core.2
The palladium chloride analogues of 3a and 3b, [{2-(3-
C12H8-2-O)-6-(CH2-NHAr)C5H3N}PdCl] (Ar = 2,6-i-Pr2C6H3 (6a),
2,4,6-Me3C6H2 (6b)), could be readily prepared by treatment of
a chloroform solution of 3a or 3b with aqueous sodium chlor-
ide (Scheme 4). Attempts at reacting L2-H with (MeCN)2PdCl2
in tetrahydrofuran gave only modest yields of 6a and 6b and
involved multiple crystallisations. Both 6a and 6b have been
molecular NamineH⋯Ophenolate hydrogen bonding interactions
[N(2)⋯O(1A) 2.955 (6a), 2.918 Å (6b)]19 supporting the dimeric
assembly. Replacement of an acetate (3) with a chloride (6)
appears to have little effect on the M⋯M separations with dis-
tances of 3.2412(10) and 3.291 Å in 6a and 6b, respectively.
The spectroscopic properties of 6a and 6b are similar to those
found in 3a and 3b with the N–H proton again shifted down-
field (ca. 5.8) in comparison with L2a-H and L2b-H.
fully characterised including by single crystal X-ray diffraction Conclusions
studies.
Protonated forms of the new ONN pincer-type ligands, 2-(3-
Complexes 6a and 6b are isostructural; a view of 6a is
shown in Fig. 8 while selected bond distances and angles for
both structures are given in Table 6. As with 3a and 3b, two
square planar (2-(3-biphenyl-2-olate)-6-alkylamine-pyridine)PdCl
monomeric units align in an anti-parallel fashion with inter-
biphenyl-2-olates)-6-iminepyridines (L1) and 2-(3-biphenyl-
2-olates)-6-(alkylamine)pyridines (L2 and L3), have been suc-
cessfully synthesised and provide convenient access to square
planar complexes in which the ONN-ligand’s substituents
sterically shelter the metal-bound acetate or halide site. We
have shown the presence of an amine donor in L2 or L3 to
facilitate the self assembly of dimeric species through inter-
molecular hydrogen bonding. This synthetic chemistry sets the
stage for an investigation of these and related systems in
various applications. These results will be reported in due
course.
Experimental
General
All operations, unless otherwise stated, were carried out under
an inert atmosphere of dry, oxygen-free nitrogen using stan-
dard Schlenk and cannular techniques or in a nitrogen purged
glove box. Solvents were distilled under nitrogen from appro-
priate drying agents24 or were employed directly from a Solvent
Purification System (Innovative Technology, Inc). The electro-
spray (ESI) mass spectra were recorded using a micromass
Quattra LC mass spectrometer with acetonitrile or methanol
Fig. 8 Molecular structure of 6a including a partial atom numbering scheme.
All hydrogen atoms, apart from H2, have been omitted for clarity.
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as the matrix. FAB mass spectra (including high resolution) charged with 2-(2-methoxybiphenyl-3-yl)-6-formylpyridine
were recorded on Kratos Concept spectrometer with NBA as (2.380 g, 8.24 mmol), dichloromethane (40 mL) and the solu-
matrix. The infrared spectra were recorded in the solid state tion cooled to −78 °C. A 1 M solution of boron tribromide
with Universal ATR sampling accessories on a Perkin Elmer (18 mL, 18 mmol) was added at −78 °C forming an orange
Spectrum One FTIR instrument. NMR spectra were recorded solution. The solution was allowed to warm to room tempera-
on a Bruker DPX 300 spectrometer operating at 300.03 (1H) ture and left to stir overnight. Water (40 mL) was added care-
and 75.4 MHz (13C) or a Bruker DRX400 spectrometer at fully and the mixture neutralised with potassium carbonate.
400.13 (1H) and 100.61 MHz (13C) at ambient temperature The organic layer was separated and the aqueous phase
unless otherwise stated; chemical shifts (ppm) are referred to washed repeatedly with chloroform (3 × 100 mL). All organic
the residual protic solvent peaks and coupling constants are extracts were combined and the solvent removed on the rotary
expressed in hertz (Hz). Melting points (mp) were measured evaporator yielding 2-(3-biphenyl-2-ol)-6-formylpyridine as a
1
on a Gallenkamp melting point apparatus (model MFB-595) in green/gold foamy solid (1.830 g, 81%). Mp: 67–68 °C. H NMR
open capillary tubes and were uncorrected. Elemental analyses (400 MHz, CDCl3): δ 6.96 (t, JHH = 6.8, 1H, Ar-H), 7.21–7.39 (m,
were performed at the Science Technical Support Unit, London 4H, Ar-H), 7.55 (d, JHH = 6.8, 2H, Ar-H), 7.86 (d, JHH = 7.7, 1H,
Metropolitan University. The reagents 2,6-diisopropylaniline, Ar-H/Py-H), 7.92 (d, JHH = 7.7, 1H, Ar-H/Py-H), 8.07 (t, JHH
=
2,4,6-trimethylaniline, lithium aluminium hydride, trimethyl- 7.7, 1H, Py-H), 8.13 (d, JHH = 6.9, 1H, Py-H), 10.17 (s, 1H,
aluminium (2 M solution in toluene) and boron tribromide CHvO), 14.22 (br s, 1H, OH). 13C{1H} NMR (100 MHz, CDCl3):
(1 M solution in dichloromethane) were purchased from δ 117.2, 118.1, 118.7, 119.6, 123.3, 125.0, 126.3, 127.1, 128.9,
Aldrich Chemical Co. and used without further purification. 133.5, 137.0, 149.0, 156.3, 158.2, 189.8 (CHvO). IR (cm−1):
The compounds tetrakis(triphenylphosphine)palladium(0),25 1712 (CvO), 1591 (CvNpyridine). ESIMS (+ve): m/z 276
2-methoxybiphenyl-3-ylboronic acid,26 2-bromo-6-formylpyri- [M + H]+. ESIMS (−ve): m/z 274 [M − H]+. HRMS (FAB): Calcd
dine27 and bis(acetonitrile)dichloropalladium(II)28 were pre- for C18H14NO2 [M + H]+ 275.09463, found 275.09469.
pared using literature procedures. All other chemicals were
obtained commercially and used without further purification.
Synthesis of 2-(3-C12H8-2-OH)-6-(CHvNAr)C5H3N (L1-H).
(a) Ar = 2,6-i-Pr2C6H3 (L1a-H). To a round bottomed flask
Synthesis of 2-(3-biphenyl-2-ol)-6-formylpyridine. The title equipped with stir bar was added 2-(3-biphenyl-2-ol)-6-formyl-
compound was prepared in two steps. Step 1 (Suzuki coup- pyridine (1.830 g, 6.65 mmol), 2,6-diisopropylaniline (1.760 g,
ling): a Schlenk flask equipped with stir bar was charged with 9.98 mmol) and absolute ethanol (13 mL). The suspension was
2-bromo-6-formylpyridine (2.180 g, 11.7 mmol), Pd(PPh3)4 stirred and heated to 40 °C and after 15 min. a catalytic
(0.269 g, 0.23 mmol), toluene (30 mL) and an aqueous 2 M amount of formic acid added. After further stirring at 40 °C
solution of potassium carbonate (12 mL, 23.4 mmol). The overnight a yellow precipitate formed which was allowed to
mixture was stirred at room temperature for 15 min. followed cool to room temperature. The precipitate was filtered, washed
by the addition of 2-methoxybiphenyl-3-ylboronic acid with ethanol and further dried under reduced pressure to give
(3.470 g, 15.2 mmol, 1.3 eq.) in ethanol (20 mL). The solution L1a-H as a yellow solid (1.990 g, 69%). Mp: 127–130 °C. 1H
was heated to 90 °C and stirred at this temperature for 42 h. NMR (400 MHz, CDCl3): δ 1.18 (d, JHH = 6.9, 12H, CH(CH3)2),
On cooling to room temperature hydrogen peroxide (10 mL, 2.95 (sept, JHH = 6.9, 2H, CH(CH3)2), 7.04 (t, JHH = 7.7, 1H, Ar-
30 wt% in water) was added and the solution left to stir for H), 7.09–7.14 (m, 3H, Ar-H), 7.35 (t, JHH = 7.4, 1H, Ar-H),
1 h. Following extraction with diethyl ether (3–100 mL) and 7.35–7.45 (m, 3H, Ar-H), 7.66 (d, JHH = 7.1, 2H, Ar-H), 7.88 (dd,
washing with a brine solution (1 × 50 mL), the combined JHH = 8.1, 1.4, 1H, Ar-H), 8.03 (t, JHH = 7.9, 1H, Py-H), 8.11 (d,
organic extracts were dried over magnesium sulfate. Filtration JHH = 7.7, 1H, Py-H), 8.24 (d, JHH = 7.5, 1H, Py-H), 8.33 (s, 1H,
followed by removal of the solvent on the rotary evaporator NvCH), 14.20 (br s, 1H, OH). 13C{1H} NMR (100 MHz, CDCl3):
gave the crude product as a viscous brown oil. Catalyst residues δ 23.4 (CH(CH3)2), 27.9 (CH(CH3)2), 118.8, 118.9, 119.2, 121.3,
were removed by a short silica column using a dichloro- 123.1, 124.7, 126.0, 127.0, 128.1, 129.5, 131.4, 133.0, 137.0,
methane–hexane (80 : 20) solvent mixture as the eluent 138.4, 138.6, 148.2, 150.9, 157.0, 158.2, 161.0 (NvC–H). IR
affording 2-(2-methoxybiphenyl-3-yl)-6-formylpyridine as
a
(cm−1): 2962 (C-H), 2600 (br, OH), 1641 (CvNimine), 1589
1
yellow oil (2.920 g, 86%). H NMR (400 MHz, CDCl3): δ 3.27 (s, (CvNpyridine). ESIMS: m/z 435 [(M + H)]+, 457 [(M + Na)]+.
3H, OMe), 7.11–7.41 (m, 5H, Ar-H), 7.56–7.65 (m, 2H, Ar-H), HRMS (FAB): Calcd. C30H31N2O [M + H]+ 435.24286, found
7.85 (dd, JHH = 7.7, 1.8, 1H, Py-H), 7.92–7.96 (m, 2H, Py-H, 435.24247.
Ar-H), 8.13 (dd, JHH = 6.9, 1.4, 1H, Py-H), 10.16 (s, 1H, CHvO).
(b) Ar = 2,4,6-Me3C6H2 (L1b-H). Employing a similar pro-
13C{1H} NMR (100 MHz, CDCl3): δ 61.0 (OCH3), 118.8, 123.7, cedure to that described for L1a-H with 2-(3-biphenyl-2-ol)-
125.9, 126.9, 127.3, 128.2, 129.8, 131.4, 132.2, 134.9, 136.0, 6-formylpyridine (2.734 g, 9.93 mmol), 2,4,6-trimethylaniline
137.3, 151.7, 154.6, 156.0, 192.8 (CHvO). IR (cm−1): 1712 (2.014 g, 14.80 mmol) and absolute ethanol (20 mL) gave L1b-
(CvO), 1585 (CvNpyridine). ESIMS: m/z 290 [M + H]+. HRMS H as a yellow solid (2.729 g, 70%). Mp: 139–144 °C. H NMR
1
(FAB): Calcd for C19H15NO2 [M + H]+ 290.11770, found (300 MHz, CDCl3): δ 2.05 (s, 6H, Ar-o-Me), 2.21 (s, 3H, Ar-p-
290.11775.
Step 2 (deprotection): a Schlenk flask equipped with stir bar (m, 4H, Ar-H/Py-H), 7.56 (d, JHH = 7.1, 2H, Py-H), 7.79 (dd, JHH
was initially evacuated and backfilled with nitrogen and then 8.1, 1.6, 1H, Ar-H), 7.94 (t, JHH = 7.9, 1H, Ar-H), 8.01 (d, JHH
Me), 6.81 (s, 2H, Ar-H), 6.95 (t, JHH = 7.7, 1H, Ar-H), 7.24–7.39
=
=
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7.3, 1H, Ar-H), 8.13 (d, JHH = 7.5, 1H, Py-H), 8.25 (s, 1H, evacuated and backfilled with nitrogen and loaded with L1a-H
NvCH), 14.10 (br s, 1H, OH). 13C{1H} NMR (75 MHz, CDCl3): (0.600 g, 1.38 mmol) and toluene (20 mL). A 2 M trimethyl-
δ 18.3 (o-Me), 20.8 (p-Me), 118.8, 118.9, 119.1, 121.2, 126.0, aluminium solution (2.1 mL, 4.15 mmol) was added dropwise
126.8, 127.1, 128.2, 129.0, 129.6, 131.4, 133.0, 133.8, 138.5, and the reaction mixture stirred and heated to 100 °C over-
138.6, 147.5, 151.1, 157.1, 158.1, 161.4 (NvC–H). IR (cm−1): night. On cooling to room temperature, all volatiles were
2963 (CH), 2602 (br, OH), 1640 (CvNimine), 1592 (CvNpyridine). removed under reduced pressure. Diethyl ether (20 mL) was
ESIMS: m/z 393 [(M + H)]+. HRMS (FAB): Calcd. C27H25N2O added to the flask followed by careful dropwise addition of
[M + H]+ 393.1967, found 393.1965.
water (20 mL). After stirring for 3 h the organic layer was separ-
Synthesis of 2-(3-C12H8-2-OH)-6-(CH2-NHAr)C5H3N (L2-H). ated and the aqueous layer extracted with diethylether (3 ×
(a) Ar = 2,6-i-Pr2C6H3 (L2a-H). Two Schlenk flasks equipped 30 mL). All organic extracts were combined and dried over
with stir bars were evacuated and backfilled with nitrogen. To magnesium sulfate. Following filtration, the solvent was
one of the flasks was added lithium aluminium hydride removed under reduced pressure affording L3-H as yellow-
1
(0.131 g, 3.46 mmol) and tetrahydrofuran (10 mL) and the brown solid (0.454 g, 73%). Mp: 95–98 °C. H NMR (300 MHz,
resulting suspension stirred and cooled to 0 °C. To the second CDCl3): δ 1.00 (d, JHH = 6.8, 6H, CH(CH3)2), 1.19 (d, JHH = 6.8,
flask was added L1a-H (0.300 g, 0.69 mmol) and tetrahydro- 6H, CH(CH3)2), 1.63 (d, JHH = 6.8, 3H, N-CHMe), 3.10 (sept, JHH
furan (10 mL) and the contents stirred until dissolution. The = 6.9, 2H, CH(CH3)2), 3.48 (br s, 1H, N-H), 4.23 (q, JHH = 6.8,
solution of L1a-H was then transferred via cannular (dropwise) 1H, N-CHMe), 6.98–7.05 (m, 5H, Ar-H), 7.38 (m, 1H, Ar-H),
to the cooled LiAlH4 suspension. The reaction mixture was 7.40 (dd, JHH = 7.2, 1.2, 1H, Ar-H), 7.45 (t, JHH = 7.4, 2H, Ar-H/
allowed to warm to room temperature and stirred for 90 min. Py-H), 7.68–7.71 (m, 3H, Ar-H), 7.80–7.90 (m, 2H, Ar-H/Py-H),
Water (2 mL) was carefully added followed by chloroform 14.80 (br s, 1H, OH). 13C{1H} NMR (75 MHz, CDCl3): δ 19.7
(30 mL) and more water (30 mL). The organic phase was separ- (N-CH(CH3)), 23.0 (CH(CH3)2), 23.2 (CH(CH3)2), 26.7 (CH
ated and the aqueous layer extracted with chloroform (3 × (CH3)2), 59.5 (N-CH(CH3)), 117.1, 117.6 , 118.2, 118.8, 122.5.
50 mL). All organic extracts were combined and dried over 122.6, 124.8, 126.0, 127.0, 128.6, 130.0, 131.6, 137.0, 137.5,
magnesium sulfate. Filtration followed by removal of the 139.9, 141.3, 156.3, 157.0, 159. 1 (C). IR (cm−1): 2962 (C-H),
solvent under reduced pressure gave L2a-H as a yellow brown 2581 (br, OH), 1594 (CvNpyridine), 1567. ESIMS (+ve): m/z 451
1
oil (0.230 g, 76%). H NMR (300 MHz, CDCl3): δ 1.21 (d, JHH
=
[M + H]+, 473 [M + Na]+. ESIMS (−ve): m/z 449 [M − H]+. HRMS
6.8, 12H, CH(CH3)2), 3.28 (sept, JHH = 6.8, 2H, CH(CH3)2), 3.45 (FAB): Calcd for C31H35N2O [M
+
H]+ 451.2749, found
(s, 1H, N-H), 4.22 (s, 2H, NH-CH2), 6.89 (t, JHH = 7.7, 1H, Ar-H), 451.2760.
6.95–7.01 (m, 3H, Ar-H), 7.24 (t, JHH = 8.1, 1H, Ar-H), 7.30–7.40
Synthesis of [{2-(3-C12H8-2-O)-6-(CHvNAr)C5H3N}Pd(OAc)]
(m, 4H, Ar-H/Py-H), 7.57 (d, JHH = 7.0, 2H, Ar-H), 7.80–7.70 (m, (1). (a) 1a. A Schlenk flask equipped with stir bar was
3H, Ar-H), 15.2 (br s, 1H, OH). 13C{1H} NMR (75 MHz, CDCl3): evacuated and backfilled with nitrogen and loaded with
δ 21.4 (CH(CH3)2), 23.2 (CH(CH3)2), 26.7 (CH(CH3)2), 55.4 Pd(OAc)2 (0.065 g, 0.29 mmol), L1a-H (0.126 g, 0.29 mmol)
(NHCH2), 117.0, 117.5, 117.6, 118.0, 118.8, 121.7, 122.6, 123.4, and toluene (10 mL). After stirring at 60 °C overnight, the reac-
124.8, 125.9, 127.0, 128.5, 130.1, 131.4, 131.6, 137.4, 137.5, tion mixture was cooled to room temperature and filtered
139.2, 141.1, 141.9, 155.5, 155.3, 156.8. IR (cm−1): 2962 (C-H), through celite and the celite cake washed thoroughly with
2600 (br, OH), 1592 (CvNpyridine), 1589. ESIMS (+ve): m/z 437 dichloromethane. The filtrate was concentrated to ca. 1 mL
[M + H]+. ESIMS (−ve): m/z 435 [M − H]+. HRMS (FAB): Calcd whereupon diethyl ether (ca. 8 mL) was added. The resulting
for C30H33N2O [M + H]+ 437.2593, found 437.2599.
precipitate was filtered and dried under reduced pressure
(b) Ar = 2,4,6-Me3C6H2 (L2b-H). Employing a similar pro- forming 1a as a dark red powder (0.158 g, 91%). Red blocks
cedure to that described for L2a-H with L1b-H (0.300 g, suitable for an X-ray diffraction study could be grown by
0.76 mmol) and lithium aluminium hydride (0.145 g, slow diffusion of hexane into a dichloromethane solution
3.81 mmol) gave L2b-H as a pale yellow solid (0.141 g, 47%). of the complex. Mp: >260 °C. 1H NMR (400 MHz, CDCl3):
1
Mp: 96–98 °C. H NMR (400 MHz, CDCl3): δ 2.21 (s, 6H, Ar-o- δ 1.11 (d, JHH = 6.9, 6H, CH(CH3)2), 1.33 (d, JHH = 6.9, 6H, CH
Me), 2.22 (s, 3H, Ar-p-Me), 3.49 (br s, 1H, NH), 4.26 (s, 2H, (CH3)2), 1.65 (s, 3H, CH3CO2), 3.43 (sept, JHH = 6.7, 2H, CH
NH-CH2), 6.81 (s, 2H, Ar-H), 6.99 (t, JHH = 7.7, 1H, Ar-H), (CH3)2), 6.83 (t, JHH = 8.1, 1H, Ar-H), 7.18 (d, JHH = 7.6, 1H, Ar-
7.30–7.35 (m, 2H, Ar-H), 7.38 (dd, JHH = 7.4, 1.3, 1H, Ar-H), H), 7.22 (d, JHH = 7.8, 2H, Ar-H), 7.30 (m, 3H, Ar-H), 7.40 (d,
7.44 (t, JHH = 7.6, 2H, Ar-H), 7.64 (d, JHH = 7.4, 2H, Py-H), JHH = 7.0, 1H, Ar-H), 7.64 (d, JHH = 7.1, 1H, Ar-H), 7.76 (d, JHH
=
7.79–7.88 (m, 3H, Ar-H/Py-H), 14.81 (br s, 1H, OH). 13C{1H} 7.1, 2H, Ar-H), 7.88 (d, JHH = 8.5, 1H, Py-H), 8.02 (s, 1H,
NMR (100 MHz, CDCl3): δ 17.2 (o-Me), 19.5 (p-Me), 52.6 NvC-H), 8.15 (t, JHH = 8.3, 1H, Py-H), 8.52 (d, JHH = 8.8, 1H,
(NHCH2), 116.9, 117.6, 118.0, 118.9, 124.8, 125.9, 127.0, 128.5, Py-H). 13C{1H} NMR (100 MHz, CDCl3): δ 21.3 (H3CCOO), 21.9
129.1, 130.1, 130.9, 131.6, 137.4, 137.5, 141.4, 155.8, 156.2, (CH(CH3)2), 24.2 (CH(CH3)2), 27.5 (CH(CH3)2), 114.9, 119.3,
156.7. IR (cm−1): 2962 (C-H), 2599 (br, OH), 1596 (CvNpyridine). 122.4, 123.6, 125.5, 125.9, 126.5, 127.3, 127.6, 129.0, 132.5,
ESIMS (+ve): m/z 395 [M + H]+. HRMS (FAB): Calcd for 133.3, 136.6, 138.9, 140.2, 141.0, 151.1, 151.7, 160.4, 165.0
C27H27N2O [M + H]+ 395.2123, found 395.2119.
Synthesis of 2-(3-C12H8-2-OH)-6-{CMeH-NH(2,6-i-Pr2C6H3)}- (CvNimine), 1582 (COO)asymm/CvNpyridine), 1383 (COO)symm
C5H3N (L3-H). A Schlenk flask equipped with stir bar was FABMS m/z: 599 [M]+, 540 [M − OAc]+. Anal Calc. for
(NvCH), 176.5 (H3CCOO). IR (cm−1): 2961 (C-H), 1615
.
7718 | Dalton Trans., 2013, 42, 7710–7723
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(C32H32N2O3Pd): C, 64.16; H, 5.38; N, 4.68. Found: C, 64.21; 1H, Ar-H), 7.33 (t, JHH = 7.6, 2H, Ar-H), 7.46 (dd, JHH = 7.0, 1.4,
H, 5.21; N, 4.72%. 1H, Ar-H), 7.74 (d, JHH = 7.2, 1H, Ar-H), 7.79 (d, JHH = 7.2, 2H,
(b) 1b. Employing a similar procedure to that described for Ar-H/Py-H), 7.86 (dd, JHH = 8.0, 1.6, 1H, Ar-H), 7.91 (s, 1H,
1a using L1b-H (0.114 g, 0.29 mmol) and Pd(OAc)2 (0.065 g, NvC-H), 8.15 (t, JHH = 7.2, 1H, Py-H), 8.50 (d, JHH = 8.8, 1H,
0.29 mmol) gave 1b as a red solid (0.126 g, 78%). Red blocks Py-H). IR (cm−1): 2963 (C-H), 1615 (CvNimine), 1583
suitable for an X-ray diffraction study could be grown by slow (CvNpyridine). FABMS m/z: 533 (M + H)+, 497 (M − Cl)+. Anal
diffusion of hexane into a dichloromethane solution of the Calc. for (For C27H23ClN2OPd): C, 60.80; H, 4.35; N, 5.25.
1
complex. Mp: >260 °C. H NMR (300 MHz, CDCl3): δ 1.58 (s, Found: C, 60.73; H, 4.23; N, 5.19%.
3H, CH3CO2), 2.26 (s, 3H, Ar-p-Me), 2.31 (s, 6H, Ar-o-Me), 6.80
Conversion of 1 to 2
(td, JHH = 7.8, 0.9, 1H, Ar-H), 6.85 (s, 2H, Ar-H), 7.19 (t, JHH
=
7.3, 1H, Ar-H), 7.29 (t, JHH = 7.5, 2H, Ar-H), 7.39 (dd, JHH = 7.2, A round bottomed flask equipped with stir bar and open to
1.2, 1H, Ar-H), 7.55 (d, JHH = 7.0, 1H, Ar-H), 7.70 (d, JHH = 7.4, the air was loaded with 1 (0.054 mmol), chloroform (10 mL)
2H, Ar-H/Py-H), 7.87 (dd, JHH = 8.2, 1.2, 1H, Ar-H), 7.97 (s, 1H, and brine (10 mL). After stirring vigorously at room tempera-
NvC-H), 8.10 (t, JHH = 7.9, 1H, Py-H), 8.52 (d, JHH = 8.7, 1H, ture overnight the organic phase was separated and the
Py-H). 13C{1H} NMR (75 MHz, CDCl3): δ 17.3 (o-Me), 19.97 aqueous phase washed with chloroform (3 × 10 mL). All
(p-Me), 21.0 (H3CCOO), 114.9, 119.0, 123.5, 125.4, 125.6, 126.4, organic extracts were combined and dried over magnesium
127.3, 127.7, 128.0, 128.9, 129.2, 132.4, 133.4, 136.2, 136.6, sulfate. Following filtering, all volatiles were removed under
138.8, 141.4, 151.6, 165.7 (NvCH), 176.9 (H3CCOO). IR (cm−1): reduced pressure affording 2 as red powders (0.031 g, 98%
2963 (C-H), 1610 (CvNimine), 1587 (COOasymm/CvNpyridine), (2a), 0.026 g, 89% (2b)). The spectroscopic data obtained for 2a
1381 (COOsymm). FABMS m/z: 556 [M]+, 539 [M − OAc]+. Anal and 2b were consistent with that given above.
Calc. for (C29H26N2O3Pd): C, 62.54; H, 4.71; N, 5.03. Found:
Synthesis of [{2-(3-C12H8-2-O)-6-(CH2-NHAr)C5H3N}Pd(OAc)]
C, 62.77; H, 4.69; N, 5.01%.
(3). (a) 3a. A Schlenk flask equipped with stir bar was evacu-
Synthesis of [{2-(3-C12H8-2-O)-6-(CHvNAr)C5H3N}PdCl] ated and backfilled with nitrogen and loaded with Pd(OAc)2
(2). (a) 2a. A Schlenk flask equipped with stir bar was evacu- (0.065 g, 0.29 mmol), L2a-H (0.126 g, 0.29 mmol) and toluene
ated and backfilled with nitrogen and loaded with (10 mL). After stirring at 0 °C overnight, the reaction mixture
(MeCN)2PdCl2 (0.060 g, 0.231 mmol), L1a-H (0.110 g, was filtered through celite and the celite cake washed
0.254 mmol) and tetrahydrofuran (25 mL). After stirring over- thoroughly with dichloromethane. The filtrate was concen-
night at room temperature, the reaction mixture was concen- trated to ca. 1 mL whereupon diethyl ether (ca. 8 mL) was
trated to ca. 2 mL and hexane (15 mL) added. The precipitate added. The resulting precipitate was filtered and dried under
was filtered, washed with hexane and dried under reduced reduced pressure forming 3a as a yellow powder (0.100 g,
pressure to give 2a as dark red powder (0.071 g, 53%). Red 58%). Yellow plates suitable for an X-ray diffraction study
blocks suitable for an X-ray diffraction study could be grown could be grown by slow diffusion of hexane into a dichloro-
by slow diffusion of hexane into a dichloromethane solution of methane solution of the complex. Mp: >260 °C. 1H NMR
1
the complex. Mp: >260 °C. H NMR (300 MHz, CDCl3): δ 1.00 (400 MHz, CDCl3): δ 1.16 (d, JHH = 6.8, 3H, CH(CH3)2), 1.17 (d,
(d, JHH = 6.9, 6H, CH(CH3)2), 1.34 (d, JHH = 6.6, 6H, CH(CH3)2), JHH = 6.4, 3H, CH(CH3)2), 1.33 (d, JHH = 6.5, 3H, CH(CH3)2),
3.22 (sept, JHH = 7.0, 2H, CH(CH3)2), 6.83 (dd, JHH = 8.4, 7.2, 1.58 (s, 3H, CH3CO2), 1.68 (d, JHH = 6.8, 3H, CH(CH3)2), 3.24
1H, Ar-H), 7.20–7.28 (m, 3H, Ar-H), 7.33–7.40 (m, 3H, Ar-H), (sept, JHH = 6.7, 1H, CH(CH3)2), 4.16 (dd, JHH = 17.3, 9.2, 1H,
7.53 (dd, JHH = 7.2, 1.6, 1H, Ar-H), 7.77 (dd, JHH = 7.2, 0.9, 1H, HN-CHaHb), 4.58 (dd, JHH = 17.2, 10.0, 1H, HN-CHaHb), 5.21
Ar-H), 7.86 (d, JHH = 7.1, 2H, Py-H/Ar-H), 7.90 (dd, JHH = 8.6, (sept, JHH = 6.7, 1H, CH(CH3)2), 6.77 (t, JHH = 7.8, 1H, Ar-H),
1.6, 1H, Ar-H), 7.99 (s, 1H, NvC-H), 8.16 (dd, JHH = 8.7, 7.2, 6.84 (t, JHH = 7.6, 1H, Ar-H), 7.07 (dd, JHH = 6.4, 3.2, 1H, Ar-H),
1H, Py-H), 8.51 (d, JHH = 8.7, 1H, Py-H). 13C{1H} NMR (75 MHz, 7.18 (t, JHH = 7.2, 1H, Ar-H), 7.20–7.32 (m, 4H, Ar-H), 7.52 (dd,
CDCl3): δ 22.1 (CH(CH3)2), 22.6 (CH(CH3)2), 27.6 (CH(CH3)2), JHH = 7.8, 1.6, 1H, Ar-H), 7.54 (br t, JHH = 8.0, 1H, HN-CHaHb),
115.4, 119.5, 122.4, 124.4, 125.6, 126.4, 126.6, 127.6, 127.7, 7.73–7.79 (m, 3H, Py-H/Ar-H), 7.89 (d, JHH = 8.0, 1H, Py-H). 13
C
129.1, 132.9, 133.4, 137.0, 138.8, 139.6, 142.6, 151.1, 151.4, {1H} NMR (75 MHz, CDCl3): δ 21.5 (H3CCOO), 22.3 (CH(CH3)2),
159.9, 166.8 (NvCH). IR (cm−1): 2961 (C-H), 1614 (CvNimine), 23.5 (CH(CH3)2), 23.6 (CH(CH3)2), 24.9 (CH(CH3)2), 27.0 (CH
1589 (CvNpyridine). FABMS m/z: 575 [M + H]+, 539 [M − Cl]+. (CH3)2), 27.7 (CH(CH3)2), 62.3 (HN-CH2), 114.5, 114.9, 119.7,
Anal Calc. for (C30H29ClN2OPd): C, 62.62; H, 5.08; N, 4.87. 122.6, 123.2, 125.1, 126.4, 126.5, 128.1, 128.9, 131.7, 132.5,
Found: C, 62.61; H, 5.00; N, 4.81%.
137.2, 137.8, 139.22, 140.0, 141.8, 152.8, 160.1, 161.2, 177.3
(b) 2b. Employing a similar procedure to that described for (H3CCOO). IR (cm−1): 3224 (NH), 2954 (C-H), 1585 (COOasymm
/
2a using L1b-H (0.100 g, 0.255 mmol) and (MeCN)2PdCl2 CvNpyridine), 1384 (COOsymm). ESIMS: m/z 1141 [M2 − OAc],
(0.060 g, 0.231 mmol) gave 2b as a red solid (0.114 g, 93%). 541 [M − OAc]. FABMS m/z 601 [M + H]+, 540 [M − OAc]+. Anal
Red/orange blocks suitable for an X-ray diffraction study could Calc. for (C32H34N2O3Pd): C, 63.95; H, 5.70; N, 4.66. Found:
be grown by slow diffusion of hexane into a dichloromethane C, 64.01; H, 5.55; N, 4.89%.
solution of the complex. Mp: >260 °C. 1H NMR (400 MHz,
(b) 3b. Employing a similar procedure to that described
CDCl3): δ 2.23 (s, 3H, Ar-p-Me), 2.26 (s, 6H, Ar-o-Me), 6.79 (s, for 3a using L2b-H (0.114 g, 0.29 mmol) and Pd(OAc)2
2H, Ar-H), 6.86 (td, JHH = 7.6, 1.2, 1H, Ar-H), 7.19 (t, JHH = 7.4, (0.065 g, 0.29 mmol) gave 3b as a yellow solid (0.119 g, 74%).
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Yellow needles suitable for an X-ray diffraction study could be at room temperature overnight the organic phase was separ-
grown by slow diffusion of hexane into a dichloromethane ated and the aqueous phase washed with chloroform (3 ×
solution of the complex. Mp: >260 °C. 1H NMR (300 MHz, 10 mL). All organic extracts were combined and dried over
CDCl3): δ 1.65 (s, 3H, CH3CO2), 2.20 (s, 3H, Ar-p-Me), 2.41 magnesium sulfate. Following filtering, all volatiles were
(br s, 3H, Ar-o-Me), 3.08 (br s, 3H, Ar-o-Me), 4.02 (dd, JHH
=
removed under reduced pressure affording 6a as yellowy brown
17.4, 6.4, 1H, HN-CHaHb), 4.76 (dd, JHH = 17.3, 7.7, 1H, powder (0.026 g, 87%). Yellow blocks suitable for an X-ray diffr-
HN-CHaHb), 6.71 (t, JHH = 7.7, 1H, Ar-H), 6.78 (br, 2H, Ar-H), action study could be grown by slow diffusion of hexane into a
6.80–6.84 (m, 1H, Ar-H), 7.19 (t, JHH = 7.3, 1H, Ar-H), 7.23–7.32 dichloromethane solution of the complex. Mp: >260 °C. 1H
(m, 3H, Py-H/Ar-H), 7.40–7.52 (m, 2H, Ar-H/HN-CHaHb), NMR (400 MHz, CDCl3): δ 0.73 (d, JHH = 6.8, 3H, CH(CH3)2),
7.55–7.72 (m, 4H, Py-H/Ar-H). 13C{1H} NMR (100 MHz, CDCl3, 1.02 (br s, 3H, CH(CH3)2), 1.20 (br s, 3H, CH(CH3)2), 1.48 (d,
low solubility) signals seen at δ 20.6 (o-Me), 22.7 (H3CCOO), JHH = 6.5, 3H, CH(CH3)2), 3.34 (dd, JHH = 17.7, 1.8, 1H,
61.4 (HN-CH2), 115.3, 115.8, 120.2, 123.4, 126.2, 127.4, 128.9, HN-CHaHb), 3.72 (br s, 1H, CH(CH3)2), 4.21 (sept, JHH = 6.5,
129.9, 131.8, 132.8, 136.5, 137.8, 139.9. IR (cm−1): 2924 (C-H), 1H, CH(CH3)2), 4.99 (dd, JHH = 17.7, 7.9, 1H, HN-CHaHb), 5.98
1580 (COOasymm/CvNpyridine), 1382 (COOsymm). ESIMS: m/z (br s, 1H, HN-CH2), 6.60 (t, JHH = 7.5, 1H, Ar-H), 7.05–7.24 (m,
1057 [M2 − OAc], 559 [M + H]+, 499 [M − OAc]. FABMS 7H, Py-H/Ar-H), 7.26 (t, JHH = 7.5, 2H, Ar-H), 7.35 (br s, 2H, Py-
m/z: 558 [M]+, 499 [M
(C29H28N2O3Pd·CH2Cl2): C, 55.96; H, 4.70; N, 4.35. Found: C, (CH), 1598 (CvNpyridine). ESIMS m/z 1118 [M2 − Cl]+, 539 [M −
55.93; H, 4.51; N, 4.55%.
Cl]+. FABMS m/z 576 [M]+, 539 [M − Cl]+. Anal Calc. for
−
OAc]+. Anal Calc. for H), 7.88 (d, JHH = 8.1, 2H, Ar-H). IR (cm−1): 3223 (NH), 2955
Synthesis of [{2-(3-C12H8-2-O)-6-(CMeH-NH(2,6-i-Pr2C6H3))- (C30H31ClN2OPd): C, 62.40; H, 5.41; N, 4.85. Found: C, 62.69;
C5H3N}Pd(OAc)] (4) and [{2-(3-C12H8-2-O)-6-(CMevN(2,6-i- H, 5.25; N, 4.92%.
Pr2C6H3))C5H3N}Pd(OAc)] (5). A Schlenk flask equipped with
(b) 6b. Employing a similar procedure to that described
stir bar was evacuated and backfilled with nitrogen and loaded for 6a using 3b (0.030 g, 0.054 mmol) gave 6b as
a
with Pd(OAc)2 (0.065 g, 0.29 mmol), L3-H (0.130 g, 0.29 mmol) yellowy brown solid (0.020 g, 70%). Yellow plates suitable
and toluene (10 mL). After stirring at 60 °C overnight, the reac- for an X-ray diffraction study could be grown by slow diffusion
tion mixture was filtered through celite and the celite cake of hexane into
thoroughly washed with dichloromethane. The filtrate was complex. Mp: >260 °C. H NMR (400 MHz, CDCl3): δ 2.11 (s,
concentrated to ca. 1 mL whereupon hexane (ca. 8 mL) was 3H, Ar-p-Me), 2.48 (s, 3H, Ar-o-Me), 2.50 (br s, 3H, Ar-o-Me),
a
dichloromethane solution of the
1
added. The resulting precipitate was filtered and dried under 3.35 (d, JHH
= 17.7, 1H, HN-CHaHb), 5.21 (br s, 1H,
reduced pressure forming a mixture of 4 and 5 as a red powder HN-CHaHb), 5.71 (br s, 1H, HN-CH2), 6.55 (t, JHH = 7.5, 1H, Ar-
(0.099 g, 56%). Complex 4 (83% of mixture): 1H NMR H), 6.70 (s, 2H, Ar-H), 7.05–7.25 (m, 5H, Py-H/Ar-H), 7.26
(400 MHz, CDCl3): δ 0.99 (d, JHH = 6.8, 3H, CH(CH3)2), 1.17 (d, (t, JHH = 7.5, 2H, Ar-H), 7.48 (br s, 1H, Py-H), 7.81 (d, JHH
=
JHH = 6.4, 3H, CH(CH3)2), 1.28 (d, JHH = 6.5, 3H, CH(CH3)2), 8.1, 2H, Ar-H). IR (cm−1): 3224 (N-H), 2917 (C-H), 1582
1.51 (d, JHH = 6.5, 3H, HNCH(CH3)), 1.58 (s, 3H, CH3CO2), 1.71 (COOasymm/CvNpyridine), 1383 (COOsymm). ESIMS m/z 1035
(d, JHH = 6.8, 3H, CH(CH3)2), 3.21 (sept, JHH = 6.7, 1H, CH [M2 − Cl]+, 535 [M + H]+, 499 [M − Cl]+. FABMS m/z: 535 [M]+,
(CH3)2), 4.31 (dq, JHH = 8.8, 7.0, 1H, HN-CHMe), 5.25 (sept, JHH 499 [M − Cl]+, IR (cm−1): 3224 (N-H), 2917 (C-H), 1582
= 6.7, 1H, CH(CH3)2), 6.67 (t, JHH = 7.6, 1H, Ar-H), 6.81 (d, JHH (COOasymm/CvNpyridine), 1383 (COOsymm). Anal Calc. for
= 7.4, 1H, Ar-H), 7.04 (d, JHH = 7.4, 1H, Ar-H), 7.09–7.24 (m, (C27H25ClN2OPd): C, 60.57; H, 4.71; N, 5.23. Found: C, 60.22;
6H, Ar-H), 7.44 (d, JHH = 8.2, 1H, Py-H), 7.65 (d, JHH = 8.0, 2H, H, 4.51; N, 5.01%.
Ar-H), 7.68 (br d, JHH = 8.0, 1H, HN-CHMe), 7.72–7.82 (m, 2H,
Py-H/Ar-H). Complex 5 (17% of mixture): 1H NMR (400 MHz,
CDCl3): signals identifiable, δ 1.05 (d, JHH = 6.9, 6H, CH
Crystallographic studies
(CH3)2), 1.37 (d, JHH = 6.9, 6H, CH(CH3)2), 1.50 (s, 3H, Data for L1a-H, L3-H, 1a, 1b, 2a, 2b, 3a, 3b, 4, 6a and 6b
CH3CO2), 2.21 (s, 3H, NvCMe), 3.22 (sept, JHH = 6.7, 2H, CH were collected on a Bruker APEX 2000 CCD diffractometer.
(CH3)2), 6.83 (t, JHH = 8.1, 1H, Ar-H), 8.05 (t, JHH = 8.3, 1H, Py- Details of data collection, refinement and crystal data are
H), 8.52 (d, JHH = 8.8, 1H, Py-H). Orange blocks of 4 suitable listed in Table 7. The data were corrected for Lorentz and
for an X-ray diffraction study could be grown by slow diffusion polarisation effects and empirical absorption corrections
of hexane into a dichloromethane solution of the mixture. Mp: applied. Structure solution by direct methods and
>260 °C. IR (cm−1): 2960 (C-H), 1589 (COO)asymm/CvNpyridine), structure refinement based on full-matrix least-squares on F2
1385 (COO)symm. ESIMS: m/z 1171 [M2 − OAc], 555 [M − OAc]. employed SHELXTL version 6.10.29 Hydrogen atoms
FABMS m/z 615 [M + H]+, 554 [M − OAc]+. Anal Calc. for were included in calculated positions (C–H = 0.96–1.00 Å)
(C33H36N2O3Pd): C, 64.44; H, 5.90; N, 4.55. Found: C, 64.09; H, riding on the bonded atom with isotropic displacement para-
5.75; N, 4.79%.
meters set to 1.5Ueq(C) for methyl H atoms and 1.2Ueq(C) for
Synthesis of [{2-(3-C12H8-2-O)-6-(CH2-NHAr)C5H3N)}PdCl] all other H atoms. All non-H atoms were refined with anisotro-
(6). (a) 6a. A round bottomed flask equipped with stirrer bar pic displacement parameters. Disordered solvent was omitted
and open to the air was loaded with 3a (0.032 g, 0.054 mmol), using the SQUEEZE option in PLATON for L1a-H, 1b, 4
chloroform (10 mL) and brine (10 mL). After stirring vigorously and 6a.30
7720 | Dalton Trans., 2013, 42, 7710–7723
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Table 7 Crystallographic and data processing parameters for L1a-H, L3-H, 1a, 1b, 2a, 2b, 3a, 3b, 4, 6a and 6ba
Complex
L1a-H
34H40N2O2
508.68
0.25 × 0.23 ×
0.12
L3-H
1a
1b
2a
2b
Formula
C
C31H34N2O
450.60
0.21 × 0.15 ×
0.14
C65H66ClN4O6Pd2 C39H49Cl2N2O3Pd C30H29ClN2OPd
1282.92 771.10 575.40
0.14 × 0.10 × 0.09 0.16 × 0.15 × 0.12 0.33 × 0.27 ×
0.18
C138H121Cl11N10O5Pd5
2921.40
0.20 × 0.15 × 0.08
M
Crystal size (mm3)
Temperature (K)
150(2)
Triclinic
ˉ
P1
150(2)
Monoclinic
P2(1)/c
9.646712)
24.689(3)
11.3413(15)
90
110.409(3)
90
2531.5(6)
4
1.182
968
0.071
150(2)
Monoclinic
P2(1)/c
15.311(2)
11.6253(17)
32.923(5)
90
90.364(4)
90
5869.0(15)
4
1.454
2632
0.760
150(2)
Tetragonal
I4(1)/a
20.075(8)
20.075(8)
28.842(17)
90
150(2)
Monoclinic
P2(1)/c
9.941(4)
12.678(5)
20.671(8)
90
97.076(7)
90
2585.3(17)
4
1.478
1176
0.847
150(2)
Triclinic
ˉ
P1
13.427(8)
17.856(11)
26.730(16)
76.396(13)
86.289(14)
86.280(15)
6208(6)
Crystal system
Space group
a (Å)
b (Å)
c (Å)
8.9542(16)
12.028(2)
14.082(3)
89.451(3)
85.613(4)
81.432(4)
1495.3(5)
2
α (°)
β (°)
γ (°)
90
90
U (Å3)
Z
11 624(10)
16
1.763
6416
0.872
2
Dc (Mg m−3
F(000)
)
1.130
548
0.070
1.563
2952
1.008
μ(Mo-Kα) (mm−1
)
Reflections collected
Independent reflections
Rint
Restraints/parameters
Final R indices (I > 2σ(I)) R1 = 0.0613
wR2 = 0.1362
10 849
5210
0.0850
0/303
18 269
4462
0.1632
0/313
R1 = 0.0638
wR2 = 0.1102
R1 = 0.1604
wR2 = 0.1375
0.808
45 009
11 515
0.2017
0/720
R1 = 0.0699
wR2 = 0.1035
R1 = 0.1671
wR2 = 0.1271
0.841
41 787
5124
19 633
5077
0.1370
679/429
R1 = 0.0697
wR2 = 0.1413
R1 = 0.1204
wR2 = 0.1608
0.958
48 941
24 098
0.1753
1475/1536
R1 = 0.0792
wR2 = 0.0993
R1 = 0.2329
wR2 = 0.1346
0.797
0.2088
0/320
R1 = 0.0753
wR2 = 0.1631
R1 = 0.1453
wR2 = 0.1854
0.966
All data
R1 = 0.1155
wR2 = 0.1513
Goodness of fit on F2 (all 0.825
data)
Complex
3a
3b
4
6a
6b
Formula
C33H36Cl2N2O3Pd
685.94
0.15 × 0.13 × 0.04
150(2)
C30H29Cl3N2O3Pd
678.3
0.24 × 0.08 × 0.05
150(2)
C52H79Cl3N2O3Pd
992.92
0.17 × 0.11 × 0.10
150(2)
C39H54ClN2O2Pd
724.69
0.18 × 0.13 × 0.12
150(2)
C28H27Cl3N2OPd
629.27
0.17 × 0.11 × 0.04
150(2)
M
Crystal size (mm3)
Temperature (K)
Crystal system
Space group
a (Å)
b (Å)
c (Å)
Monoclinic
P2(1)/c
13.471(3)
14.913(3)
16.595(4)
90
108.732(4)
90
3157.1(12)
4
Monoclinic
P2(1)/c
13.216(10)
18.856(14)
11.977(9)
90
100.468(17)
90
2935(4)
Rhombohedral
R3
Triclinic
P1
Triclinic
P1
ˉ
ˉ
ˉ
22.469(7)
22.469(7)
22.469(7)
115.655(6)
115.655(6)
115.655(6)
5952(3)
6
10.5900(16)
10.9142(16)
14.160(2)
92.595(3)
95.184(3)
105.297(3)
1568.1(4)
2
9.632(9)
11.597(11)
13.229(12)
90.597(19)
108.415(19)
112.533(18)
1280(2)
2
α (°)
β (°)
γ (°)
U (Å3)
Z
4
Dc (Mg m−3
F(000)
)
1.443
1408
0.792
1.535
1376
0.939
1.662
3156
0.724
1.535
762
0.717
1.609
628
1.063
μ(Mo-Kα) (mm−1
)
Reflections collected
Independent reflections
Rint
Restraints/parameters
Final R indices (I > 2σ(I))
24 097
6204
0.1722
0/357
R1 = 0.0644
wR2 = 0.0905
R1 = 0.1428
wR2 = 0.1070
0.860
22 755
5773
0.1950
0/356
R1 = 0.0785
wR2 = 0.1467
R1 = 0.1792
wR2 = 0.1757
0.937
46 610
7800
0.3336
351/358
R1 = 0.0781
wR2 = 0.1533
R1 = 0.1881
wR2 = 0.1769
0.819
12 345
6069
0.0958
0/320
R1 = 0.0584
wR2 = 0.1216
R1 = 0.0849
wR2 = 0.1289
0.873
10 113
4967
0.1186
0/319
R1 = 0.1151
wR2 = 0.3053
R1 = 0.1526
wR2 = 0.3219
1.100
All data
Goodness of fit on F2 (all data)
1
a Data in common: graphite-monochromated Mo-Kα radiation, λ = 0.71073 Å; R1 = Σ||Fo| − |Fc||/Σ|Fo|, wR2 = [Σw(Fo − Fc2)2/Σw(Fo ) ] , w
=
2
2 2
−1
2
[σ2(Fo)2 + (aP)2], P = [max(Fo2,0) + 2(Fc2)]/3, where a is a constant adjusted by the program; goodness of fit = [Σ(Fo2 − Fc2)2/(n − p)]1/2 where n is the
number of reflections and p the number of parameters.
Acknowledgements
References
We thank the University of Leicester for financial assistance.
Johnson Matthey PLC are thanked for their generous loan of
palladium salts.
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Dalton Trans., 2013, 42, 7710–7723 | 7723