THE SYNTHESIS, X-RAY STRUCTURE AND HYDROLYSIS KINETICS OF LORO(2-AMINOMETHYLPYRIDINE)(TRIAMINE)CHROMIUM(III) SALTS

The chloro(diamine) (triamine)chromium(III) complexes, [CrCl(ampy)(dpt )](ClO4)(2) (1) and [CrCl(ampy)(2,3-tri)]ZnCl4.H2O (2) were prepared f rom [CrCl3(tri)] and 2-aminomethylpyridine (ampy) (tri = dpt = 1,5,9-t riazanonane or 2,3-tri = 1,4,8-triazaoctane) and the isomeric configur ations were established by single crystal X-ray structural analysis. 1 : orthorhombic, P2(1)2(1)2(1), a = 8.281(1), b=13.390(1), c=19.091(2) Angstrom, V=2116.73(30) Angstrom(3), Z=4. 2: orthorhombic, P2(1)2(1)2( 1), a=8.515(1), 6=9.636(1), c=26.542(1) Angstrom, V=2177.79(26) Angstr om(3), Z=4. In both complexes the tridentate polyamine adopts the mer configuration with the sec-N proton remote (exo) from the coordinated chloro ligand. For the dpt system the pyridine end of the ampy ligand is trans to the chloro ligand, but in the 2,3-tri system the pyridine end of the ampy ligand is trans to the sec-NH group of the tridentate. Thus the cations are formulated as exo-trans(py)-mer-[CrCl(ampy)(dpt) ](2+) (1) and exo-cis(py)-mer-[CrCl(ampy)(2,3-tri)](2+) (2). The rates of thermal acid hydrolysis (k(H)), Hg2+-assisted acid hydrolysis (k(H g)) and base hydrolysis (k(OH)) have been measured for 1 and 2. Kineti c parameters (k(x) (25 degrees C), Delta H-# (kJ mol(-1)), Delta S-# ( J K-1 mol(-1))) for 1 are 10(7) k(H)=3.16 s(-1) 101, -32; 10(6) k(Hg)= 57.2 M(-1) s(-1), 102, +16; k(OH)=2.17 M(-1) s(-1), 113, +140 and for 2 are 10(7) k(H)=0.21 s(-1), 109, -25. 10(6) k(Hg)=4.4 M(-1) s(-1), 10 6, +9; k(OH)=0.355 M(-1) s(-1), 108, +110. The incorporation of a coor dinated pyridine ligand cis to the leaving group in 2 does not appear to have a significant acceleratory role in the base hydrolysis, with r espect to the analogous exo-mer-[CrCl(en)(2,3-tri)](2+) cation.