Binuclear palladium macrocycles synthesized via the weak-link approach

The "weak-link approach" to metallomacrocycle synthesis has been employed t o synthesize a series of Pd(II) macrocycles in high yield. Although this ap proach has been used to construct several Rh(I) complexes with a variety of ligands, the generality of this methodology with respect to transition met als has not been demonstrated. When added to [Pd(NCCH3)(4)][BF4](2), the ph osphinoalkyl ether or thioether ligands produce "condensed intermediates", [(mu-(1,4(PPh2CH2CH2X2)-Y2Pd2)][BF4](4) (4, X = O, Y = 2,3,5,6-((CH3)(4)C-6 ); 5, X = O, Y = C6H4; 6, X = S, Y = C6H4), containing strong P-Pd bonds an d weaker O-Pd or S-Pd bonds. The weak bonds of these intermediates can be q uantitatively broken through simple ligand substitution reactions to genera te the macrocyclic structures [(mu-(1,4-(PPh2CH2CH2X)(2)-Y)(2)(Z)(4)Pd-2)][ BF4](n) (7, X = O, Y = 2,3,5,6-((CH3)(4)C-6), Z = CH3CN, n = 4; 8, X = O, Y = C6H4, Z = CH3CN, n = 4; 9, X = O, Y = 2,3,5,6-((CH3)(4)C-6), Z = CN, n = 0; 10, X = O, Y = C6H4, Z = CN, n X = S, Y = C6H4, Z = CN, n = O), in quan titative yields. The extension of this approach to Pd(II) should provide ne w pathways for modifying the binding and catalytic capabilities of these co mplexes. Solid-state structures as determined by single-crystal X-ray diffr action studies are presented for compounds 6, 8, and 9.