Pd(η3-1-PhC3H4)(η5-C5H5), an Unusually Effective Catalyst Precursor for Suzuki–Miyaura Cross-Coupling Reactions Catalyzed by Bis-Phosphine Palladium(0) Compounds

• Published in: Organometallics Vol. 31; no. 6; pp. 2470 - 2475
• Main Authors: Fraser, Andrew W, Besaw, Jessica E, Hull, Laura E, Baird, Michael C
• Format: Journal Article
• Language: English
• Published: American Chemical Society 26.03.2012
• ISSN: 0276-7333; 1520-6041
• DOI: 10.1021/om300154m

It has previously been shown that the easily handled, heat- and air-stable compound Pd(η3-1-PhC3H4)(η5-C5H5) (Vb) reacts rapidly with a wide variety of tertiary phosphines L to produce near-quantitative yields of the corresponding Pd(0) compounds PdL2, which are widely believed to be the active species in many often-used cross-coupling catalyst systems based on Pd(PPh3)4 (I), Pd2(dba)3 (II), PdCl2 (III), and Pd(OAc)2 (IV). However, catalyst precursors I–IV are in fact known to preferentially generate sterically hindered, three-coordinate Pd(0) species rather than two-coordinate PdL2, and thus Vb is hypothetically expected to be a better catalyst precursor for e.g. Suzuki–Miyaura cross-coupling reactions. Utilizing the conventional Suzuki–Miyaura cross-coupling reaction of phenylboronic acid with bromoanisole, comparisons are made of the efficacies of catalyst systems based on Vb with those based on compounds I–IV (L = the representative phosphines PPh3, PCy3, PBu t 3). As anticipated, catalysts generated from Vb are significantly more competent and, as a bonus, Vb makes palladium(0) complexes PdL2 available under rigorously anhydrous conditions.