METALLORADICAL CHEMISTRY OF COBALT(II) PORPHYRINS - THE SYNTHESES, STRUCTURE, AND REACTIVITY OF TRIPHENYLTIN(II) AND TRIHALOMETHYLCOBALT(III) OCTAETHYLPORPHYRIN

Stannanes R3SnH (R = n-Bu, Ph) reacted with Co-III(OEP)CH3 or Co-II(OE P) to afford Co-III(OEP)SnR3 and CH4 or H-2, respectively. Co-III(OEP) SnR3 was more efficiently prepared by reaction of Co-I(OEP)(-) with R3 SnCl. Co-III(OEP)SnPh3, C54H59CoN4Sn, crystallized in the triclinic sp ace group P (1) over bar (Z = 2) with unit cell dimensions a = 12.124( 5) Angstrom, b = 14.700(5) Angstrom, c = 15.221(7) Angstrom, alpha = 1 09.56(4)degrees, beta = 91.44(5)degrees, gamma = 113.27(1)degrees, and V = 2308.4(1.8) Angstrom(3) at 295(2) K. The structure resembled that of five-coordinate alkylcobalt(III) porphyrin complexes with a square -pyramidal Co atom displaced 0.077 Angstrom out of the porphyrin plane toward Sn and a Co-Sn bond length of 2.510(2) Angstrom. The bond diss ociation energy of the Co-Sn bond was considerably larger than that of the Co-C bond in alkylcobalt(III) porphyrin complexes. Co-III(OEP)SnP h3 was air stable in solution and decomposed by homolysis slowly at 12 0 degrees C in toluene. The Co-Sn bond was rapidly cleaved, though, wh en oxidized by It or by electrochemical means. In contrast, the Co-C b onds in Co-III(OEP)CX3 (X = Cl, Br, I) were substantially weaker than in the Co-C bond in alkylcobalt(III) porphyrin complexes and weakened progressively with heavier halogens. Co-III(OEP)CX3 complexes were pre pared by reaction of Co-I(OEP)(-) with CX4 (X = Cl, Br) or by reaction of Co-II(OEP) with CBrCl3 or CX4 (X = Pr, I). The reaction of Co-I(OE P)- with CX4 (X = Cl, Br, I) also afforded small amounts of Co-III(OEP )CHX2 complexes, which were obtained in greater yield by reaction of C o-I(OEP)(-) with CHX3. The substitution of one hydrogen for a halogen stabilized the Co-III(OEP)CHX2 complexes relative to the corresponding Co-III(OEP)CX3 complexes.