REACTIONS OF [IR(COD)(PME3)3]CL WITH BENZENE, PYRIDINE, FURAN, AND THIOPHENE - C-H CLEAVAGE VS RING-OPENING

Reactions between [Ir(COD)(PMe3)3]Cl, 1, and a number of aromatic hydr ocarbons (benzene, pyridine, furan, thiophene, and benzothiophene) wer e investigated where [Ir(COD)(PMe3)3]Cl acts as a convenient source of ''Ir(PMe3)3Cl''. Reactions between 1 and benzene, pyridine, and furan lead to the formation of products derived from oxidative addition of a C-H bond. The benzene addition product, 2, is mer-(Me3P)3Ir(H)(Ph)(C l) which crystallized in the monoclinic space group P2(1)/n with a = 9 .877(2) angstrom, b = 11.894(3) angstrom, c = 17.964(5) angstrom, beta = 94.29-degrees, and V = 2104.5(9) angstrom3 for Z = 4. The stereoche mistry of 2 has the H and Cl trans to each other and the phenyl group trans to PMe3. NMR evidence indicates that there is hindered rotation about the Ir-phenyl bond. The pyridine addition product, 3, is mer-(Me 3P)3Ir(pyr)(H)(Cl) which crystallized in the orthorhombic space group Cmca with a = 13.340(4) angstrom, b = 11.999(3) angstrom, c = 26.315 a ngstrom, and V = 4212(2) angstrom3 for Z = 8. The stereochemistry of 3 is different from that of 2 in that 3 has pyridine trans to chloride and H trans to PMe3. The pyridine exclusively adds the C-H bond a to t he nitrogen. The furan addition product, 4, crystallized in the monocl inic space group P2(1)/n with a = 9.723(2) angstrom, b = 11.583(3) ang strom, c = 17.790(5) angstrom, beta = 94.68(2)-degrees, and V = 1996.7 (9) angstrom3 for Z = 4. The stereochemistry of 4 is the same as 2: H trans to Cl and furanyl trans to PMe3 with the C-H bond a to oxygen be ing the one that adds. In contrast to the above cases of C-H addition, thiophene reacts via a ring-opening C-S oxidative addition reaction t o form mer-(Me3P)3Ir(CI){SC(H)=C(H)C(H)=C(H)}, 5a. The benzothiophene adduct, 5b, crystallized in the orthorhombic space group P2(1)2(1)2, w ith a = 11.550(3) angstrom, b = 13.598(2) angstrom, c = 14.362(4) angs trom, and V = 2255.7(9) angstrom3 for Z = 4. The stereochemistry of th e addition results in C trans to Cl and S trans to PMe3. The structure and bonding of 5b is compared with other thiairidametallacycles repor ted in the literature.