The "weak-link approach" to metallomacrocycle synthesis has been employed to synthesize a series of Pd(II) macrocycles in high yield. Although this approach has been used to construct several Rh(I) complexes with a variety of ligands, the generality of this methodology with respect to transition metals has not been demonstrated. When added to [Pd(NCCH3)4[BF4]2, the phosphinoalkyl ether or thioether ligands produce "condensed intermediates", [(μ-(1,4-(PPh2CH2 CH2X)2-Y)2Pd2)] [BF4]4 (4, X = O, Y = 2,3,5,6- ((CH3)4C6); 5, X = O, Y = C6H4; 6, X = S, Y = C6H4), containing strong P-Pd bonds and weaker O-Pd or S-pd bonds. The weak bonds of these intermediates can be quantitatively broken through simple ligand substitution reactions to generate the macrocyclic structures [(μ-(1,4-(PPh2CH2 CH2X)2-Y)2(Z)4Pd2)] BF4]n (7, X = O, Y = 2,3,5,6-((CH3)4 C6), Z = CH3CN, n = 4; 8, X = O, Y = C6H4, Z = CH3CH, n = 4; 9, X = O, Y = 2,3,5,6-((CH3)4C6), Z = CN, n = 0; 10, X = O, Y = C6H4, Z = CN, n = 0; 11, X = S, Y = C6H4, Z = CN, n = 0), in quantitative yields. The extension of this approach to Pd(II) should provide new pathways for modifying the binding and catalytic capabilities of these complexes. Solid-state structures as determined by single-crystal X-ray diffraction studies are presented for compounds 6, 8, and 9.
ASJC Scopus subject areas
- Physical and Theoretical Chemistry
- Organic Chemistry
- Inorganic Chemistry