Table 1.

Summary of the experimental observations and suggested mechanisms for the oxidative addition of ArX to complexes 2–4.

		Pd(1-AdPtBu2)2	Pd(CyPtBu2)2	Pd(PCy3)n n = 2,3	General Conclusion
ArI	Order in ArI	1	1	1	The ArI reacts with the PdL2 species
	Order in L	Zeroth	Zeroth	-1 for n = 3, 0 for n = 2
	Conclusion	Irreversible associative displacement of L by ArI		Reaction of ArI with L2Pd
ArCl	Order ArCl	1	1	1	The C–X bond cleavage step occurs after reversible dissociation or displacement of one phosphine from PdL2 to form PdL or LPd–ArX
	Order in L	-1	-1	-1
	Conclusion	Reversible exchange of L with PhCl prior to C–X bond cleavage.
ArBr	Order ArBr	1	1	1	The C–X bond cleavage step appears to occur by two pathways of similar energy. One major pathway clearly occurs by reaction of ArBr with the L2Pd(0) species. This step could occur by irreversible displacement of one L to form LPd–ArX or by irreversible direct C-X bond cleavage. The second, less defined pathway is zeroth order in ArBr, and appears to occur by irreversible dissociation of L to form LPd.
	y-intercept of kobs vs [ArBr]	non-zero	non-zero	zero
	Order in L	Zeroth	Zeroth	Nearly zeroth
	Conclusion	One path by reaction of the ArBr with L2Pd, most likely by associative displacement of L to form LPd–ArX. A second competing pathway appears to occur that is zeroth order in ArBr, most likely by initial dissociation of L, followed by rapid reaction with ArBr.		Reaction of the ArBr with the bisphosphine complex L2Pd as the major pathway (by nearly irreversible associative displacement of L by PhBr prior to C–X bond cleavage or nearly irreversible direct oxidative addition)