Reactivity of hydridoirida-β-diketones with bases: the selective formation of new di-μ-acyl-μ-hydridodiiridium(iii) or dihydridoirida-β-diketone complexes and heterometallic Ir(iii)–Rh(i) derivatives

Abstract

The hydridoirida-β-diketone [IrHCl{(PPh₂(o-C₆H₄CO))₂H}] (1a) reacts with bases such as KOH or NaHCO₃ in methanol to undergo dehydrodechlorination and acyl-bridge formation affording [Ir₂H₂(PPh₂(o-C₆H₄CO))₂(μ-PPh₂(o-C₆H₄CO))₂] (2) with two acylphosphine chelate-bridging ligands, in a head-to-tail disposition, and terminal hydrides. The acyl bridges can be broken by pyridine, PPh₃, CO or dimethylsulfoxide affording selectively mononuclear diacylhydrido neutral derivatives [IrH(PPh₂(o-C₆H₄CO))₂L] (3–6). 1a reacts with KOH or NaHCO₃ in refluxing methanol to afford a novel dihydridoirida-β-diketone [IrH₂{(PPh₂(o-C₆H₄CO))₂H}] (7), via dehydrodechlorination to afford 2, which then undergoes hydrogenation and protonation. The reaction of 1a with NEt₃ affords 2 and [NHEt₃]Cl. Further reaction affords [Ir₂(μ-H){μ-PPh₂(o-C₆H₄CO)}₂(PPh₂(o-C₆H₄CO))₂]⁺ (8), with two acylphosphine chelate-bridging ligands and a bridging hydride. Neutral or cationic hydridoirida-β-diketone complexes react with [Rh(cod)(OMe)]₂ (cod = 1,5-cyclooctadiene) to afford hydridoirida-β-diketonaterhodium(I) complexes [IrHCl(μ-PPh₂(o-C₆H₄CO))₂Rh(cod)] (9) or [IrHL(μ-PPh₂(o-C₆H₄CO))₂Rh(cod)]ClO₄ (L = py, 10; CO, 11), respectively that isomerise to the thermodynamically stable isomers of [IrCl(PPh₂(o-C₆H₄CO))(μ-H))(μ-PPh₂(o-C₆H₄CO))Rh(cod)] (12) or [Ir(py)(PPh₂(o-C₆H₄CO))(μ-H))(μ-PPh₂(o-C₆H₄CO))Rh(cod)]ClO₄ (13). The reaction of 7 with [Rh(cod)(OMe)]₂ affords [Ir(PPh₂(o-C₆H₄CO))₂(μ-H)₂Rh(cod)] (14). All the complexes were fully characterised spectroscopically. Single-crystal X-ray diffraction analysis was performed on 2, 4, 7, [8]ClO₄ and 9.