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Syntheses and structural aspects of six-membered palladacyclic complexes derived from ,′,′′-triarylguanidines with N- or S-thiocyanate ligands
Six-membered palladacyclic complexes derived from N , N ′, N ′′-triarylguanidines, [Pd{ κ 2 ( C , N )}(μ-NCS)] 2 ( 1-4 ), trans -[Pd{κ 2 ( C , N )}(NCS)L] (L = nitrogen based planar Lewis bases, 5-7 ) and cis -[Pd{κ 2 ( C , N )}(X)L] (L = phosphorus based conical Lewis bases, X = NCS or SCN) that co...
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| Published in: | New journal of chemistry 2019-01, Vol.43 (5), p.237-2327 |
|---|---|
| Main Authors: | , , , |
| Format: | Article |
| Language: | English |
| Online Access: | Get full text |
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| Summary: | Six-membered palladacyclic complexes derived from
N
,
N
′,
N
′′-triarylguanidines, [Pd{
κ
2
(
C
,
N
)}(μ-NCS)]
2
(
1-4
),
trans
-[Pd{κ
2
(
C
,
N
)}(NCS)L] (L = nitrogen based planar Lewis bases,
5-7
) and
cis
-[Pd{κ
2
(
C
,
N
)}(X)L] (L = phosphorus based conical Lewis bases, X = NCS or SCN) that contained N bound thiocyanate (
8
and
10-16
) and S bound thiocyanate (
9
) were isolated in good yields.
trans
-[Pd(κ
1
C
-guanidine)(NCS)(PMe
3
)
2
] (
17
and
18
) were isolated in good yields in order to understand the factors that decide the thiocyanate coordination modes in
5-16
. The new complexes were characterized by analytical techniques, IR and multinuclear NMR (
1
H,
31
P and
13
C) spectroscopy and further the molecular structures of thirteen complexes were determined by single crystal X-ray diffraction. The Pd(
ii
) atom in
5
·CH
2
Cl
2
and
6
·PhMe revealed a
trans
configuration while that in the remaining structurally characterized monomeric palladacycles revealed a
cis
configuration. Palladacycles
8
·2/3PhMe and
9
·MeOH represent the first pair of structurally characterized linkage isomers of organopalladium complexes to be reported. The influence of solvents on thiocyanate coordination modes in
8
·2/3PhMe and
9
·MeOH is discussed. Theoretical studies were carried out on the
8
and
9
pair and on their model complexes,
8′
and
9′
, and in both cases an N bound isomer was found to be more stable than their S bound counterpart by 6.14 and 4.64 kcal mol
−1
, respectively. In the case of methanol bridged dimers of
8′
and
9′
, namely
8′′
and
9′′
, the N bound isomer (
8′′
) is more stable by 8.11 kcal mol
−1
suggesting the possible role of lattice methanol and its intermolecular interactions with
9
in the crystal lattice for the observance of a S bound thiocyanate coordination mode. The Wiberg bond index calculations were carried out on
8′
and
9′
which suggested the dominance of Pd ← N&z.dbd;C&z.dbd;S (
F
) and Pd ← S-C&z.tbd;N (
H
) resonance forms, respectively.
Linkage isomers
8
·2/3PhMe and
9
·MeOH were synthesized, isolated and structurally characterized by SCXRD and the role of solvent of crystallization in the formation of these linkage isomers identified. |
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| ISSN: | 1144-0546 1369-9261 |
| DOI: | 10.1039/c8nj04167a |