Aliphatic versus aromatic carbon-hydrogen activation and the x-ray crystal structure of [IrH(H2O)(7,8-benzoquinolinato)(PPh3)2]SbF6

Chlorohydrido[2(1H)-pyridonato-N,O]bis[tris(1-methylethyl)phosphine]iridium(III)

“…Although the refined hydride position corresponded approximately to the sixth octahedral site in direction, the IrmH bond distance of 1.18 (12)/~ was well outside that of other metal-hydride bond distances established by neutron diffraction (see, for example, Garlaschelli, Khan, Bau, Longoni & Koetzle, 1985). Therefore, we did not consider the hydride position to be accurately determined; a situation that has been encountered by others (Lavin, Holt & Crabtree, 1989;Luo, Schulte & Crabtree, 1990). We subsequently removed the proposed hydride atom and performed the final refinement of the parameters given here.…”

“…The IroN distance [2.214 (7)/~], however, somewhat exceeds the largest value [2.166 (6)/~; Steed & Tocher, 1992] found for this class of complex. The high trans influence of the hydrido ligand may be responsible for this lengthening of the Ir--N bond (Lavin, Holt & Crabtree, 1989). (16) 0.1471 (6) 0.097 (7) 0.0167 (18) 0.1951 (6) 0.094 (7) 0.0984 (14) 0.1663 (6) 0.067 (5) 0.…”

Agostic bonds in cyclometalation

“…25 kcal/mol, is cleaved. The MeC bond strength in the product 10 must therefore be at least 25 kcal/mol stronger than the MeC bond in the hypothetical oxidative addition product from 8-methylquinoline [45].…”

“…However, Crabtree et al [45] reported in 1989 that, under mild reaction conditions the reaction of 8-methylquinolines with an Table 3) iridium complex gives agostic compounds, and the reaction of benzoquinoline with the iridium complex gives a cyclometalated product 10. The proposed reaction scheme is shown in Scheme 3 [45]: in the first step, the nitrogen atom coordinates to the iridium atom, and then, the cyclometalation reaction proceeds via the agostic interaction and CeH activation.…”

“…The proposed reaction scheme is shown in Scheme 3 [45]: in the first step, the nitrogen atom coordinates to the iridium atom, and then, the cyclometalation reaction proceeds via the agostic interaction and CeH activation. The benzylic CeH bond of the 8-methylquinoline binds in an agostic fashion, while the arene CeH of benzoquinoline, which must be stronger by ca.…”