Effective modular assembling of novel ligands starting from (Thio)phosphorylated anilines

Article abstract of DOI:10.1080/10426507.2012.743129

A series of novel oligodentate ligands has been designed by the modular assembly of ortho-(thio)phosphorylated anilines with a range of commercially available carbonyl compounds. The new ligands readily form complexes with a series of metal ions (Pd(II), Cu(II), Ni(II), and Re(I)) both in neutral and deprotonated forms, providing OO, SN, ONO, SNO, SNS, SNN, and ONN donor sets. The structure and composition of the resulting complexes depend on the nature and mutual disposition of the donating groups as well as on the reaction conditions.

Full text of DOI:10.1080/10426507.2012.743129

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Phosphorus, Sulfur, and Silicon and the
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Effective Modular Assembling
of Novel Ligands Starting from
(Thio)Phosphorylated Anilines
Vladimir A. Kozlov a , Valentina Yu. Aleksenko a , Diana V.
Aleksanyan a , Elena V. Sharova a , Oleg I. Artyushin a & Irina L.
Odinets a
a A. N. Nesmeyanov Institute of Organoelement Compounds, Russian
Academy of Sciences , Moscow , Russian Federation
Published online: 08 May 2013.
To cite this article: Vladimir A. Kozlov , Valentina Yu. Aleksenko , Diana V. Aleksanyan , Elena V.
Sharova , Oleg I. Artyushin & Irina L. Odinets (2013) Effective Modular Assembling of Novel Ligands
Starting from (Thio)Phosphorylated Anilines, Phosphorus, Sulfur, and Silicon and the Related Elements,
188:1-3, 79-83, DOI: 10.1080/10426507.2012.743129
To link to this article: http://dx.doi.org/10.1080/10426507.2012.743129
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Phosphorus, Sulfur, and Silicon, 188:79–83, 2013
Copyright ꢀC Taylor & Francis Group, LLC
ISSN: 1042-6507 print / 1563-5325 online
DOI: 10.1080/10426507.2012.743129
EFFECTIVE MODULAR ASSEMBLING OF NOVEL
LIGANDS STARTING FROM (THIO)PHOSPHORYLATED
ANILINES
Vladimir A. Kozlov, Valentina Yu. Aleksenko,
Diana V. Aleksanyan, Elena V. Sharova, Oleg I. Artyushin,
and Irina L. Odinets
A. N. Nesmeyanov Institute of Organoelement Compounds, Russian Academy of
Sciences, Moscow, Russian Federation
GRAPHICAL ABSTRACT
Abstract A series of novel oligodentate ligands has been designed by the modular assembly
of ortho-(thio)phosphorylated anilines with a range of commercially available carbonyl com-
pounds. The new ligands readily form complexes with a series of metal ions (Pd(II), Cu(II),
Ni(II), and Re(I)) both in neutral and deprotonated forms, providing OO, SN, ONO, SNO, SNS,
SNN, and ONN donor sets. The structure and composition of the resulting complexes depend on
the nature and mutual disposition of the donating groups as well as on the reaction conditions.
Keywords Oligodentate phosphorus ligands; modular assembling; transition metal complexes
INTRODUCTION
Rational design of readily tunable ligand systems is at the heart of modern coordina-
tion chemistry. Oligodentate ligands with variable donor centers are of particular interest
because they offer the opportunity of a more rigid control of the properties of a metal center
Received 27 August 2012; accepted 16 October 2012.
This work was supported by the Russian Foundation for Basic Research (project no. 12-03-00793-a).
Address correspondence to Diana V. Aleksanyan, A. N. Nesmeyanov Institute of Organoelement Com-
pounds, Russian Academy of Sciences, 28 Vavilov Street, Moscow 119991, Russian Federation. E-mail:
aleksanyan.diana@gmail.com, fos@ineos.ac.ru
79

80
V. A. KOZLOV ET AL.
owing to multiple options for directed structural modifications. An effective approach to
complex ligand systems can be based on the modular assembling of a single basic block
with a range of commercially available embedded blocks, opening the way to a whole
library of ligands with diverse structures. Therewith, such a basic fragment must have an
appropriate anchor function that can be used for its functionalization. Taking this into ac-
count, we decided to choose as suitable basic blocks ortho-phosphorylated aniline and its
thio-analog. Note that the complexing features of phosphine-substituted aniline1 and oligo-
dentate ligands2 on its base have been thoroughly explored, while the coordination potential
of the related four-coordinated phosphorus derivatives still remains underappreciated.
RESULTS AND DISCUSSION
The key phosphorylated aniline 1a3 and its thio-analog 1b4 are readily available
from 2-diphenylphosphinoaniline5 by oxidation with H2O2 and addition of elemental sul-
fur, respectively. Various carbonyl compounds were reacted with these basic blocks to
yield novel oligodentate ligands (Scheme 1). Thus, the condensation of 1a,b with sodium
1
enolate of benzoyl acetaldehyde led to enaminoketone derivatives 2a,b. According to H
NMR spectroscopic data, the introduction of an ancillary (thio)phosphoryl group, capable
of participating in hydrogen bonding, affords the unexpected stabilization of a trans–trans
isomer in a nonpolar solvent, such as CDCl3, and Z-s-E isomeric form in polar media
(DMSO, CD3OD), which is rarely detected in the case of nonfunctionalized enaminoke-
tones. The condensation of starting anilines with salicylaldehyde, smoothly performed in
ethanol under reflux, furnished salicylaldimines 3a,b (Scheme 1). Furthermore, the reaction
of thiophosphorylated aniline 1b with picolinic acid in the presence of triphenylphosphite
as a dehydrating agent afforded amide 4, while the treatment of 1a,b with in situ generated
dichlorosubstituted picolinic acid chloride gave its counterparts 5a,b, which can provide a
P(X)Ph2
P(X)Ph2
CHO
OH
O
Ph
ONa
N
OH
NH
O
HC
Ph
X = S 58% (2a)
X = O 78% (2b)
X = S 88% (3a)
X = O 91% (3b)
P(S)Ph2
N
COOH
P(X)Ph2
P(X)Ph2
NH2
O
Ph2PCH2COOH
PCl3
NH
(PhO)3P, Py
NHC
O
PPh2
N
O
1a,b
O
63% (4)
X = O 55% (6a)
X = S 69% (6b)
X = O (a)
X = S (b)
P(X)Ph2
NH
Cl
N
COOH
P(X)Ph2
P(X)Ph2
O
/SOCl2
Cl
Ph2PSNa
Cl
ClCH2CCl
N
Cl
Et3N
NHC
O
NHC
O
PPh2
S
O
X = O 87% (7a)
X = S 99% (7b)
X = O 79% (6c)
X = S 77% (6d)
Cl
X = O 79% (5a)
X = S 63% (5b)
Scheme 1

NOVEL PHOSPHORUS LIGANDS VIA MODULAR ASSEMBLING
81
Ph
Ph
Ph
NiCl2.6H2O
or
Cu(OAc)2.H2O
Ph
O
P(X)Ph2
Re(CO)5Br
or
(PhCN)2PdCl2
Ph
P
O
N
P
X
P
Ln
M
M
NH
O
N
O
O
N
O
Ph
Ph
Ph
Ph
Ph
2a,b
M = Re, Ln = (CO)3:
X = O 88%
M = Pd, Ln = Cl:
X = S 52%
M = Ni 75%
M = Cu 88%
X = S 83%
Scheme 2
possibility of estimating additional steric and electronic factors. Finally, the direct acetyla-
tion of (thio)phosphorylated anilines 1a,b with in situ generated diphenylphosphoryl acetic
acid chloride or reaction of 1a,b with chloroacetyl chloride followed by the treatment of
the resulting chloroacetyl derivatives 7a,b with Ph2PSNa resulted in novel P(X)-modified
carbamoylmethylphosphine oxides (CMPO) and sulfides (CMPS) 6a–d (Scheme 1).
The complexation features of the ligands derived were studied by the direct interaction
with metal salts (Cu(OAc)2 · H2O, NiCl2 · 6H2O) or displacement of labile ligands from
their complexes (Re(CO)5Br, (PhCN)2PdCl2), preformed either in the presence of a base
(mostly in the case of Re(I) derivatives) or without a base. Thus, the reaction of P(X)-
modified (X O, S) ketoenamines 2a,b with Re(I), Pd(II), Ni(II), and Cu(II) precursors
readily afforded complexes with two six-membered fused metallocycles, in which the
ligands adopt a tridentate monoanionic coordination mode (Scheme 2). Therewith, the
composition of the resulting complexes depended on the substituent X at the P(X)-group in
2a,b. Note that in all cases the deprotonated ligands were stabilized in the Z-s-Z isomeric
form.
Salicylaldimines 3a,b, in which the donor group amenable to deprotonation is shifted
to the side, also readily formed complexes of different compositions in the presence of Et3N
(except for Cu(II) complex), in each case featuring κ3-XNO monoanionic coordination mode
(Scheme 3).
Note that both the palladium and copper complexes can be obtained by the template
assembling of starting anilines 1a,b and salicylaldehyde on the metal ion. At the same time,
the reaction of 1a with salicylaldehyde copper complex was found to be slow enough to
enable isolation of a half-condensation product. Owing to the presence of the salicylalde-
hyde entity, the latter can be reacted with other primary amines, leading to unsymmetrical
Schiff-base products (Scheme 4).
Ph
Ph
P(X)Ph2
P
NiCl2.6H2O
or
Cu(OAc)2.H2O
Ph
Re(CO)5Br
or
(PhCN)2PdCl2
Ph
X
O
N
P
Ln
O
P
M
N
OH
O
N
M
O
O
HC
N
Ph
M=Pd, L=Cl:
X=S 92%
Ph
3a,b
M=Re, Ln=(CO)3:
X=O 87%
M = Ni 87%
M = Cu 87%
X= S 85%
Scheme 3

82
V. A. KOZLOV ET AL.
Ph
Ph
P
Ph
Ph
O
P
O
PPh2
H
O
N
O
O
Cu
N
O
O
O
O
NH2
NH2
N
Cu
Cu
H
O
O
O
H
H
Scheme 4
Ph
S
Ph
O
P
M = Re, Ln = (CO)3 75%
M = Pd, Ln = Cl 85%
M = Cu, Ln = OAc 57%
Ln
M
N
N
Cl
Ph
S
O
Ph
Ph
N
Cl
P
Ph
Re(CO)5Br,
(PhCN)2PdCl2,
or Cu(OAc)2.H2O
P
S
N
OAc
Cu
Pd
N
70%
X = S
Re(CO)5Br
N
S
P
N
Cl
Ph
O
P(S)Ph2
Cl
N
Ph
O
93%
Cl
Cu(OAc)2.H2O
NH
Cl
Cl
N
Ph
Ph
O
Ph
O
Ph
O
Cl
Cln
P
P
O
N
X
(PhCN)2PdCl2
N
77%
Re(CO)3
N
Cu
4,5a,b
n = 0,2
N
N
X = O
O
Cl
O
N
P
X = O 70%
X = S 75%
Cl
Ph
Ph
Cl
Cl
Scheme 5
Both unsubstituted thiophosphorylated picolinylamide 4 and its dichlorinated analogs
5a,b readily underwent metallation at the nitrogen atom in reactions with Re(I) and Cu(II)
precursors to form 5,6-memebred κ3-SNN complexes (Scheme 5). Again the nature of
the substituent X at the phosphorus atom affected the composition of the final products.
The effect of additional steric hindrances in the case of ligand 5b was best manifested
for the palladium derivative, leading only to the bidentately bonded complex, lacking the
coordination of the pyridine moiety, while its unsubstituted counterpart 4 readily afforded
κ3-SNN complex.
The reaction of carbamoylmethylphosphine oxides and sulfides 6a–d with the Re(I)
and Pd(II) precursors easily furnished κ3-XNY complexes with two six-membered fused
metallocycles (Scheme 6). Thus, unlike the known CMP derivatives, the coordination of a
carbamoyl moiety occurs via the nitrogen atom rather than the oxygen atom. The interaction
of 6a with Re(CO)5Br without addition of a base gave κ2-OO ten-membered metallocycle
lacking the coordination of an amide fragment. This molecular complex can be readily
transformed into κ3-ONO complex with the deprotonated ligand under the action of Et3N,
and, therefore, is likely to be considered as an intermediate in the reaction with the base.

NOVEL PHOSPHORUS LIGANDS VIA MODULAR ASSEMBLING
83
The structures of the ligands and their complexes were unambiguously assigned on
1
the basis of multinuclear NMR (31P, H, and 13C) and IR spectroscopic data as well as
single-crystal X-ray diffraction investigations.
Ph
Ph
Ph
Ph
Ph
Ph
P
P
P
X
X
X
Re(CO)5Br
(PhCN)2PdCl2
Cl
Re(CO)3
X
Pd
NH
X
N
N
Y
PPh2
PPh2
PPh2
O
O
O
6a-d
X = S, Y = O 81%
X = O, Y = S 75%
X = Y = S 97%
X = O 81%
X = S 72%
Scheme 6
CONCLUSION
To summarize the results presented, simple modular assembling procedures of the
available building-blocks, ortho-(thio)phosphorylated anilines, and a number of carbonyl
derivatives afforded several series of oligodentate ligands with donor centers of variable
nature, therewith, offering ample opportunities for fine-tuning of their electronic and steric
properties. The ligands derived show wide coordination diversity, forming complexes with
different metal ions both in neutral and deprotonated forms, depending on the nature of
donating groups, metal ions, and reaction conditions.
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