Synthesis and Reactivity of Bis(ethene) Rhodium(I) and Iridium(I) Carboxylato Complexes

[Rh(μ‐O 2 CCH 3 )(C 2 H 4 ) 2 ] 2 ( 3 ) and analogous carboxylatobis‐(olefin)rhodium(I) complexes [Rh(μ‐O 2 CR)(olefin) 2 ] 2 ( 4–6 ) were almost quantitatively prepared under heterogeneous conditions from [RhCl(C 8 H 14 ) 2 ] 2 ( 1 ) or [RhCl(C 2 H 4 ) 2 ] 2 ( 2 ) and CH 3 CO 2 Na · 3 H 2 O or RCO 2 H/NaOH, respectively. The X‐ray crystal structure analysis of 3 confirmed the bridging position of the acetato ligands. The synthesis of [Ir(μ‐O 2 CCH 3 )(C 2 H 4 ) 2 ] 2 ( 10 ) was carried out similarly by using [IrCl(C 2 H 4 ) 2 ] 2 ( 8 ) and CH 3 CO 2 Na · 3 H 2 O as starting materials. The monoethene complex trans ‐[Ir(η 1 ‐O 2 CCH 3 )(C 2 H 4 )‐(P i Pr 3 ) 2 ] ( 11 ) was obtained from 10 and P i Pr 3 ; it reacted with H 2 and HCCPh by oxidative addition to give [IrH 2 (η 2 ‐O 2 CCH 3 )(P i Pr 3 ) 2 ] ( 12 ) and [IrH(CCPh)(η 2 ‐O 2 CCH 3 )(P i Pr 3 ) 2 ] ( 14 ), respectively. Compound 12 was also prepared from [IrH 2 Cl(P i Pr 3 ) 2 ] ( 13 ) and CH 3 CO 2 Na · 3 H 2 O. The new bis‐(ethene)complexes 3 , [Rh(μ‐O 2 CC 6 H 5 )(C 2 H 4 ) 2 ] 2 ( 6 ) and 10 are catalytically less active than 2 in the reaction of C 2 H 4 and Ph 2 CN 2 and gave as C–C coupling product not only 1,1‐diphenylpropene ( 16 ) but also mixtures of 16 and 1,1‐diphenylcyclopropane ( 17 ) in different ratios.