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Capturing a Ghost. Synthesis and Structural Characterization of Pd(dba)[P(o‑Tol)3]2
journal contribution
posted on 2013-06-24, 00:00 authored by Brennen A. Harding, Patrick R. Melvin, William Dougherty, Scott Kassel, Felix E. GoodsonIn
an effort to improve upon a literature synthesis of bis[tris(o-tolyl)phosphine]palladium(0) (1) from tris(o-tolyl)phosphine and Pd2(dba)3, we
instead isolated a new compound which proved to have the composition
Pd(dba)[P(o-Tol)3]2 (2), upon analysis by X-ray crystallography. While this is
not the first known palladium compound containing both dba and phosphine
ligands, it is, to our knowledge, the first containing dba and tris(o-tolyl)phosphine. This is significant, because mixtures
of Pd2(dba)3 and tris(o-tolyl)phosphine
are routinely used in cross-coupling protocols, and palladium complexes
containing dba and tris(o-tolyl)phosphine have been
cited as intermediates in organometallic and polymerization reactions.
The most interesting crystallographic parameter for 2 is an abnormally long Pd–P bond length of 2.388(1) Å,
which we believe is the cause of this complex’s metastability.
We also present an alternative synthesis of 1 that does
not require a large excess of phosphine.