Syntheses, crystal structures, and electrochemical and spectroscopic properties of ruthenium complexes of the N,S-bidentate ligand 2-(2-pyridyl)benzenethiol
作者:Alexander M. W. Cargill Thompson、David A. Bardwell、John C. Jeffery、Leigh H. Rees、Michael D. Ward
DOI:10.1039/a606650j
日期:——
Conversion of the amino group of 2-(2-aminophenyl)pyridine into a
thiol to give the N,S-donor chelating ligand 2-(2-pyridyl)benzenethiol
(HL) afforded the oxidised disulfide L–L which was
crystallographically characterised. It shows an interesting example of
an intermolecular
N · · · S–S
interaction (N · · · S
distances are 2.778 and 2.724 Å;
N · · · S–S angles are
both ca. 11°) in which the pyridyl lone pair interacts
weakly with the σ* orbital of the S–S bond.
Reaction of L–L with
[Ru(bipy)
2
Cl
2
]·2H
2
O
(bipy = 2,2′-bipyridine) and
RuCl
3
·xH
2
O afforded
[Ru
II
(bipy)
2
L][PF
6
] 1 and
[Ru
III
L
3
] 2 respectively (following
in situ reduction of the disulfide) which have N
5
S
and mer-N
3
S
3
donor sets respectively (N
of pyridyl, S of benzenethiolate). Both were crystallographically
characterised and have the expected pseudo-octahedral geometries. An
interesting feature of both structures is that the relatively large
Ru–S distances (compared to the Ru–N) prevent the pyridyl
rings from approaching the metal centre as closely as they would if they
were not constrained, so the Ru–N distances are longer than usual.
Electrochemical studies show that the benzenethiolate ligands are more
effective electron donors to ruthenium (both +2 and +3) than are
phenolates: for example, the Ru
II
–Ru
III
couple of 1 is at -0.07 V vs.
ferrocene–ferrocenium, whereas the same couple of the related
N
5
O-co-ordinated complex (O from phenolate) was at +0.03 V.
Similarly the Ru
III
–Ru
IV
couple of
2 was at -0.21 V, compared to +0.14 V for the
N
3
O
3
-co-ordinated analogue. Complex 2
also shows a reversible ligand-based oxidation which is absent for
1, arising from stabilisation of the sulfur-based radical
cation by interaction with the lone pair on an adjacent sulfur atom in
the co-ordination sphere of the complex, which cannot happen for
1. Electronic spectral properties show that the sulfur donor of
1 weakens the ligand field with respect to
[Ru(bipy)
3
]
2+
, and that 2 has an intense
sulfur-to-Ru
III
ligand-to-metal charge-transfer band.
通过将 2-(2-氨基苯基)吡啶的氨基转化为硫醇,得到 N、S 供体螯合配体 2-(2-吡啶基)苯硫酚 (HL),从而得到氧化二硫化物 L-L,并对其进行了晶体学表征。它展示了分子间 N - - - S - S 相互作用的有趣实例(N - - - S 距离分别为 2.778 和 2.724 Å;N - - - S - S 角度均约为 11°),其中吡啶基孤对与 S-S 键的σ* 轨道相互作用微弱。
L-L 与 [Ru(bipy) 2 Cl 2 ]-2H 2 O(bipy = 2,2′-联吡啶)和 RuCl 3 -xH 2 O 反应,分别得到 [Ru II (bipy) 2 L][PF 6 ] 1 和 [Ru III L 3 ] 2(二硫化物原位还原后),它们分别具有 N 5 S 和 mer-N 3 S 3 供体组(N 为吡啶基,S 为苯硫酚)。这两种结构都经过了晶体学表征,并具有预期的假八面体几何结构。这两种结构的一个有趣特征是,相对较大的 Ru-S 间距(与 Ru-N 间距相比)使吡啶基环无法像不受制约时那样接近金属中心,因此 Ru-N 间距比通常情况下要长。
电化学研究表明,苯硫酸盐配体比苯酚盐更能有效地为钌(+2 和 +3)提供电子:例如,1 的 Ru II -Ru III 对映电压为 -0.07 V。
同样,2 的 Ru III -Ru IV 偶联为 -0.21 V,而 N 3 O 3 共配位类似物为 +0.14 V。络合物 2 还显示出 1 所没有的基于配体的可逆氧化作用,这是因为硫基阳离子与络合物配位层中相邻硫原子上的孤对作用使硫基阳离子趋于稳定,而这在 1 中是不可能发生的。电子光谱特性表明,1 的硫供体削弱了[Ru(bipy) 3 ] 2+ 的配体场,2 具有一个强烈的硫-Ru III 配体-金属电荷转移带。