ARGENTOTROPISM IN (PENTAMETHYLCYCLOPENTADIENYL)IRIDIUM COMPLEXES WITHPYRAZOLE LIGANDS - MULTINUCLEAR DNMR EXPERIMENTS

The dynamic behavior of the heterobimetallic compounds [(eta5-C5Me5)Ir (pz)3Ag(PPh3)] (2), [(eta5-C5Me5)Ir(mu-pz)3{Ag(PPh3)}2]BF4 (3), [(eta5 -C5Me5)Ir(pz)2 PPh3] (4), and [(eta5-C5Me5)Ir(PPh3)(mu-pz)2Ag(PPh3)]BF 4 (5) has been studied by multinuclear (H-1, C-13, N-15, P-31, and Ag- 109) NMR. The results demonstrate that argentotiropism accounts for th e observed spectra of compounds 2 (DELTAH = 8.3 kcal mol-1, DELTAS = - 13 eu) and 3 (DELTAH = 7.6 kcal mol-1, DELTAS = -20 eu); in the case o f compound 4, the dynamic behavior is due to a slow rotation about the P-Ir bond, and for compound 5, the dynamic behavior corresponds to a flipping of the central heteroring Ir(N)4Ag. Several new heteronuclear coupling constants have been determined, some of them [such as 1J(P-3 1-Ag-107(109)] being related to the structure and dynamical properties of the complex.