ligand with [Pd(COD)(CH3CN)Cl]BF4 resulted in the formation
of palladium black in all cases.
References
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˚
The short C1–N3 bond in 5b (1.313(7) A), compared to that
˚
observed in 3b (1.343(5) A), indicates a greater double-bond
character for the exocyclic imine of the imidazole-2-imine ring.
Structure A (Scheme 2) more closely represents the actual nature
of the ligand once coordinated to palladium, despite the slightly
elongated C1–N3 bond over that reported for IPrNH.11 This
assessment is further supported by the longer C1–N1 and C1–
N2 bond in 5b compared to the corresponding ones in 3b.
2 F. T. Edelmann, Chem. Soc. Rev., 2009, 38, 2253.
˚
Similarly, the N3–C4 bond in 5b at 1.321(7) A is also slightly
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˚
longer than that observed in the precursor salt (1.307(5) A). The
˚
N3–C4 and C4–N4 bond length of 1.321(7) and 1.332(7) A in
5b are consistent with the coordination with palladium, which
also results in a smaller C4–N4–C6 bond angle of 118.8(5)◦ in
5b compared to 123.5(3)◦ observed for 3b. In contrast to that
for 3b, the 2,6-diisopropylphenyl rings attached to N1 and N2
in 5b are approximately crystallographically equivalent due to a
pseudo-mirror plane that is orthogonal to the imidazole ring and
that passes through the exocyclic iminic bond. The angles between
the best plane passing through C1, N3, C4, C5, N4, C6 and those
formed by the imidazole ring and the 2,6-dimethylphenyl group
are 75.6◦ and 82.4◦, respectively. The plane passing through the
bimetallic palladium bridge is tilted off by 65.8◦ from the best
plane formed by N3, C4, C5, N4, C6. The remaining bond lengths
and bond angles are normal and lie within the expected range.
In summary, we have synthesised and structurally characterised
the new family of imine imidazol-2-imine ligands and their
corresponding titanium(IV) and palladium(II) complexes. Two
different coordination modes were observed depending on the
nature of the metal centre itself. We are currently exploring the
coordination chemistry of these new complexes and expanding
the scope of the ligands to other early and late transition metals.
Catalytic activities in various organic transformations are also
being evaluated.
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GGL gratefully acknowledges financial support from the Ontario
Ministry of Research and Innovation for an Early Researcher
Award, the Natural Sciences and Engineering Research Council
for a Discovery Grant and a Research and Tools Instrumentation
Grant, the Canadian Foundation for Innovation and the Ontario
Research Fund for infrastructure funding, and York University
for start-up funds.
6946 | Dalton Trans., 2010, 39, 6943–6946
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The Royal Society of Chemistry 2010
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