A series
of Ni complexes [Ni(Cl)2(PR3)2] with
R = Me (1-Me),
n
Pr (1-
n
Pr), and
n
Bu (1-
n
Bu) and nickelocenes
[Ni(η5-C5H4R′)2] with R′ = H (2-H), Me (2-Me),
and SiMe3 (2-SiMe
3
) were synthesized and characterized. From these complexes, the synthesis
of the Ni complexes [NiCl(PR3)(η5-C5H4R′)] R = Me, R′ = H (3-Me), R=
n
Bu, R′ = H (3-
n
Bu), R =
n
Pr, R′ = H (3-
n
Pr), R = Et, R′
= Me (4), and R = Et, R′ = SiMe3 (5) was achieved. All complexes were fully characterized, including
single crystal X-ray crystallography. Complexes 3-R, 4, and 5 were then used to obtain homobimetallic
Ni complexes with rare examples of unbridged Ni–Ni bonds [{Ni(η5-C5H5)(PR3)}2],
with R = Me (7-Me) and R =
n
Pr (7-
n
Pr) being structurally characterized by single crystal X-ray
diffraction. In order to probe the effect of bridging ligands on the
Ni–Ni bond, the bridged complex [{Ni(μ:η5-C5H4CH2CH2P(
t
Bu)2)}2] (8) was synthesized from the monomeric precursor [Ni(Cl)(κ1-η5-C5H4CH2CH2P
t
Bu2)] (6). The Ni–Ni distances in 7-Me, 7-
n
Pr, and 8 were found to be 2.407(1), 2.3931(6), and 2.6027(17)
Å, respectively, the latter seemingly lengthened compared to
the other two due to the tethered nature of the bridging ligand. DFT
calculations confirm the presence of unbridged σ-bonds between
the Ni atoms in 7-Me and 7-
n
Pr and show that the bridging
ligand in 8 has a minimal effect on the character of
the Ni–Ni bond.
