The cross‐coupling of organotin reagents with a variety of organic electrophiles, catalyzed by palladium, provides a novel method for generating a carbon‐carbon bond. Because this mild, versatile reaction is tolerant of a wide variety of functional groups on either coupling partner, is stereospecific and regioselective, and gives high yields of product, it is ideal for use in the synthesis of elaborate organic molecules. When the coupling reaction is carried out in the presence of carbon monoxide, instead of a direct coupling, carbon monoxide insertion takes place, stitching the two coupling partners together and generating a ketone.

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A theoretical analysis of two aspects of the mechanism of reductive elimination is presented—how the choice of central metal and peripheral ligands affects the activation energy for reductive elimination from a four-coordinate MR2(PR3)2 complex and how ligand asymmetry controls cis-trans rearrangements and elimination pathways proceeding through three-coordinate intermediates. The following conclusions emerge: (1) In the four-coordinate complex, the better the σ-donating capability of the leaving groups, the more facile the elimination; (2) Stronger donor ligands trans to the leaving groups will increase the barrier to elimination; (3) The reductive elimination barrier in four-coordinate complexes is controlled by the energy of an antisymmetric b2 orbital, which in turn depends on the energy of the metal levels. The activation energy for such direct reductive elimination should be, and is, substantially lower for Ni than for Pt or Pd; (4) T-shaped trans PdLR2, arising from dissociation of L in PdL2R2, will encounter a substantial barrier to polytopal rearrangement to cis PdLR2, which in turn has an open channel for reductive elimination of R2; (5) If the leaving groups are poor donors, cis-trans isomerization in the three-coordinate manifold should be easier than elimination.

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