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

The hydridoirida-beta-diketone [IrHCl{(PPh2(o-C6H4CO))(2)H}] (1a) reacts with bases such as KOH or NaHCO3 in methanol to undergo dehydrodechlorination and acyl-bridge formation affording [Ir2H2(PPh2(o-C6H4CO))(2)(mu-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))(2)L] (3-6). 1a reacts with KOH or NaHCO3 in refluxing methanol to afford a novel dihydridoirida-beta-diketone [IrH2{(PPh2(o-C6H4CO))(2)H}] (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 [Ir-2(mu-H){mu-PPh2(o-C6H4CO)}(2)(PPh2(o-C6H4CO))(2)](+) (8), with two acylphosphine chelate-bridging ligands and a bridging hydride. Neutral or cationic hydridoirida-beta-diketone complexes react with [Rh(cod)(OMe)](2) (cod = 1,5-cyclooctadiene) to afford hydridoirida-beta-diketonaterhodium(I) complexes [IrHCl(mu-PPh2(o-C6H4CO))(2)Rh(cod)] (9) or [Ir(py)(PPh2(o-C6H4CO))(2)Rh(cod)]ClO4 (L = py, 10; CO, 11), respectively that isomerise to the thermodynamically stable isomers of [IrCl(PPh2(o-C6H4CO))(mu-II))(mu-PPh2(o-C6II4CO)) Rh(cod)] (12) or [Ir(py)(PPh2(o-C6H4CO))(mu-H))(mu-PPh2(o-C6H4CO)) Rh(cod)]ClO4 (13). The reaction of 7 with [Rh(cod)(OMe)](2) affords [Ir(PPh2(o-C6H4CO))(2)(mu-H)(2)Rh(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.