N-Triisopropylphenyl-substituted N,N-py,O pincers as supports for mononuclear palladium(II) complexes and hydrogen-bonded dimeric assemblies

• Published in: Polyhedron Vol. 59; pp. 124 - 132
• Main Authors: Cross, Warren B., Hope, Eric G., Forrest, Gregory, Singh, Kuldip, Solan, Gregory A.
• Format: Journal Article
• Language: English
• Published: OXFORD Elsevier 01.08.2013
• Subjects: Chemistry; Chemistry, Inorganic & Nuclear; Crystallography; Physical Sciences; Science & Technology; 2-(3-Biphenyl-2-olate)-6-iminepyridine; OXIDATION; N-Triisopropylphenyl-substituted; Self-assembly; ACTIVATION; LIGANDS; 2-(3-Biphenyl-2-olate)-6-methylaminepyridine; Palladium; Hydrogen bonding; METALATION REACTIONS
• ISSN: 0277-5387
• DOI: 10.1016/j.poly.2013.04.049

Treatment of the sterically bulky 2-(3-biphenyl-2-ol)-6-iminepyridine, 2-(3-C12H8-2-OH)-6-(CH=N(2,4,6-i-Pr3C6H2))C5H3N (HL1(tripp)), with Pd(OAc)(2) or (MeCN)(2)PdCl2 results in deprotonation of HL1(tripp) to afford the discrete square planar O,N-py,N-pincer complexes, [(L1(tripp))Pd(OAc)] (1) and [(L1(tripp))PdCl] (2) respectively, in good yield; conversion of 1 directly to 2 using aqueous sodium chloride or to [(L1(tripp))Pdl] (3) using aqueous sodium iodide has been demonstrated. Selective reduction of the imino unit in HL1(tripp) with LiAlH4 proceeds smoothly to yield the 2-(3-biphenyl-2-ol)-6-methylaminepyridine, 2-(3-C12H8-2-OH)-6-(CH2-NH(2,4,6-i-Pr3C6H2))C5H3N (HL2(tripp)), which on reaction with Pd(OAc)(2) at low temperature gives [L2(tripp))Pd(OAc)] (4) as the sole product. Complex 4 exists as a dimeric species in the solid state in which two square planar monomers are linked together by two intermolecular NHamine ... O-acetate interactions resulting in a Pd ... Pd separation of 6.255 angstrom. The corresponding chloride complex, [(L2(tripp))PdCl] (5), formed by reaction of 4 with aqueous sodium chloride, also exists as a dimeric assembly in the solid state but in this case the presence of two intermolecular NHamine ... O-phenolate interactions has the effect of compressing the palladium-palladium separation to 3.2580(11) angstrom. Single crystal X-ray diffraction studies have been performed on 1, 2 center dot CH2Cl2, 2.C6H6, 3, 4 and 5. (c) 2013 Elsevier Ltd. All rights reserved.