On the Reactivity of Dihydridoirida-β-diketones with 2‑Aminopyridines. Formation of Acylhydrido Complexes with New PCN Terdentate Ligands

2-Aminopyridines (H2NC5H3RN) react
with [IrH2{(PPh2(o-C6H4CO))2H}] (1) in refluxing methanol
to afford [IrH­(PPh2(o-C6H4CO))­(PPh2(o-C6H4CHNHC5H3RN))] (R = H (2), R = CH3 (3)) containing new terdentate
PCN ligands in a facial disposition with the phosphorus atom trans to H and the new alkyl fragment trans to the other phosphorus atom. The formation of 2 and 3 requires imination of the hydroxycarbene moiety in 1, iridium to carbon hydrogen transfer, and coordination of
the nitrogen atom of pyridine to iridium. In refluxing methanol the
reaction of 1 with the N-substituted 2-(methylamino)­pyridine
leads to [IrH­(PPh2(o-C6H4CO))­(PPh2(o-C6H4C­(OH)­N­(CH3)­C5H4N))] (4), containing a PCN ligand with a hydroxyalkyl
moiety trans to phosphorus and the nitrogen atom
of pyridine trans to hydride. By performing this
reaction in the presence of KOH, complex [IrH­(PPh2(o-C6H4CO))­(PPh2(o-C6H4C­(OCH3)­N­(CH3)­C5H4N))] (5), with a methoxyalkyl
moiety in the PCN ligand and similar stereochemistry to that of 2 and 3, is obtained. In chloroform solution 5 transforms, with retention of the stereochemistry, into
[IrH­(PPh2(o-C6H4CO))­(PPh2(o-C6H4C­(OH)­N­(CH3)­C5H4N))]
(6), an isomer of 4. Formation of complexes 4–6 is proposed to occur via OH----HIr
hydrogen bond formation and hydrogen evolution. Single-crystal X-ray
diffraction analysis was performed on 3, 4, 5, and 6.