Pd···H−C Interactions. Preparation and Structure of Orthometalated Tetranuclear Complexes of Palladium(II) and Platinum(II)

The reaction of 2-(1-naphthyl)benzothiazoline with
palladium(II) acetate leads to helical mononuclear
and
orthometalated tetranuclear products. The molecular structures of
mononuclear palladium(II) [Pd(H1-nabz)2]
(1)
(H21-nabz =
2-N-(1-naphthylmethylideneamino)benzenethiolate),
tetranuclear palladium(II)
[Pd4(1-nabz)4]
(2)
and tetranuclear platinum(II)
[Pt4(1-nabz)4] (3) have
been determined by single-crystal X-ray diffraction
method.
Crystal data for complex 1 are as follows: 
a = 14.208(3) Å, b = 18.227(4) Å,
c = 14.398(8) Å; β =
94.55(3)°;
V = 3717.0(23) Å3; space group =
P21/n, Z = 4.
Crystal data for the complex 2 are as follows: 
a = b =
15.798(3) Å, c = 23.728(4) Å; V =
5921.7(20) Å3; space group =
I41/a, Z = 16 for the
Pd(1-nabz) unit. Crystal
data for the complex 3 are as follows:  a =
b = 15.496(2) Å, c = 24.348(3) Å;
V = 5846.3(20) Å3; space
group
= I41/a, Z = 16 for
the Pt(1-nabz) unit. The mononuclear palladium(II)
complex reveals short ortho-hydrogen···palladium distances of 2.66(7) and 2.48(7)
Å. These short distances and 1H NMR studies provide
a
M···H−C interaction which can be regarded as a three-center
four-electron interaction. The molecular structures
of 2 and 3 confirm the formation of unusual
tetranuclear compounds featuring a rare C,N,S-tridentate
ligand
derived from orthometalation of pendant side arm. The structural
and chemical properties of the mononuclear
palladium(II) complex 1 clearly suggest that
1 is a potential intermediate in the formation of the
tetranuclear
complex 2 by orthometalation reactions.