Novel Carbonyliridium and ‐rhodium Complexes Containing 2,6‐Bis[(4′S)‐4′‐isopropyloxazolin‐2′‐yl]pyridine (iPr‐pybox) and 2,6‐Bis[(4′R)‐4′‐phenyloxazolin‐2′‐yl]pyridine (Ph‐pybox) Ligands

Metal/Ligand Proton Tautomerism Facilitates Dinuclear H2Reductive Elimination

“…The 1 H NMR signals attributed to the new species are broad but consistent with equivalent pyrazolyl arms (i.e., κ 3 -coordination of N­(NN H ) 2 ). The observed ν co is similar to those reported for cationic square planar monocarbonyls of Ir . These observations are consistent with CO dissociation from the bis-carbonyl [ 4-LH ] + resulting in a mixture of [ 4-LH ] + and the square planar monocarbonyl [ 2-LH ] + (Figure ).…”

“…The observed ν co is similar to those reported for cationic square planar monocarbonyls of Ir. 36 ). Apparently, the metal center has become the thermodynamic site of protonationthe proton of the bound pyrazole has migrated to the transition metal.…”

Alkene and alkyne insertion into the Ir–H bond: Synthesis of new mono- and dinuclear alkyl and alkenyl iridium–pybox complexes

“…The ethyl and bridging chlorine groups are located in a nearly trans orientation. The Ir(1)-Cl(2) and Ir(2)-Cl(2) distances [2.543(2) and 2.521(2) Å, respectively] are considerably longer than the Ir(1)-Cl(1) and Ir(2)-Cl (3) (4) and 158.5(3)-158.6(4)°] fall in the range observed for mononuclear iridiumpybox complexes [3,5]. The Ir-C distances [2.060(11) Å for Ir(1)-C(35); 2.096(11) Å for Ir(2)-C(37)] are in the range observed for other Ir(III)-Et bonds (ranges 2.086À2.192 Å) [6].…”

“…Their analytical, spectroscopic ( 1 H and 13 C{ 1 H} NMR, and IR) and conductance data are in accordance with the proposed formulations (see Section 4 for details). Significant spectroscopic data are given: (a) the IR spectra show m(C@O) absorptions in the range of 1710-1684 cm À1 as expected for uncoordinated CO 2 R groups; (b) the 1 H NMR resonance shows the olefinic hydrogens as two doublets [9.09 and 4.40 ppm (4) and 8.94 and 4.38 ppm (5)] with a large coupling constant [J HH = 15.7 Hz (4) and J HH = 15.8 Hz) (5)] as expected for a trans arrangement; (c) the 13 C{ 1 H} NMR spectra show singlet signals for the alkenyl carbons at 140.1 (IrCH) and 122.4 (CHCO 2 R) ppm (4) and 139.8 (IrCH) and 122.8 (CHCO 2 R) ppm (5). In addition, the carboxylate carbon resonates at 162.4 (4) and 161.9 (5) ppm.…”

Cationic mono and dicarbonyl pincer complexes of rhodium and iridium to assess the donor properties of PCcarbeneP ligands

“…A related PNP system containing phosphinato donor arms is significantly less donating, with a n CO stretch of 2010 cm −1 found for its monocarbonyl cation. 44 Other systems, including SNS, 42 NNS, 45 and NNN 46,47 pincer complexes are all less donating than the ligands in compounds 3 and 5 by this criterion.…”