Vinylidene Transition‐metal complexes, VI. The rhodium compounds C 5 H 5 Rh(CCHR)P i Pr 3 as building blocks for the synthesis of heterometallic Di‐ and trinuclear vinylidene‐bridged complexes

The vinylidene rhodium complex C 5 H 5 Rh( C CH 2 )P i Pr 3 ( 1 ) reacts with C 6 H 6 Cr(CO) 3 upon UV irradiation and with C 5 H 5 Mn(CO) 2 THF at room temperature to give the heterometallic dinuclear compounds [C 5 H 5 (P i Pr 3 )Rh(μ‐CCH 2 )(μ‐CO)Cr(CO)‐C 6 H 6 ] ( 4 ) and [C 5 H 5 (P i Pr 3 )Rh(μ‐CCH 2 (μ‐CO)Mn(CO)C 5 H 5 ] ( 6 ), respectively. Treatment of 6 with HBF 4 in ether leads, after metathetical exchange of the anion with NH 4 PF 6 , to the PF 6 salt of the μ‐ethylidyne cation [C 5 H 5 (P i Pr 3 )Rh(μ‐CCH 3 )(μ‐CO)Mn(CO)C 5 H 5 ] + (7). The reactions of 1 and C 5 H 5 Rh‐(CCHR)P i Pr 3 ( 2 : R = Me; 3 : R = Ph) with Fe 2 (CO) 9 give the dinuclear complexes [C 5 H 5 (P i Pr 3 )Rh(μ‐CCHR)(μ‐CO)Fe(CO) 3 ] ( 11 – 13 ) as the main products. In addition, small amounts of the trinuclear clusters [(μ 3 ‐η 1 ,η 2 ‐CCHR)(μ‐CO) 2 Fe 2 Rh(CO) 4 (P i Pr 3 )C 5 H 5 ] ( 14 – 16 ) are formed. The protonation of 11 – 13 with HBF 4 gives the ionic compounds [C 5 H 5 (P i Pr 3 )Rh(μ‐CCH 2 R)‐(μ‐CO)Fe(CO) 3 ]BF 4 ( 17 – 19 ). The crystal and molecular structures of 6, 11 and 14 have been determined. The two dinuclear complexes 6 and 11 contain unsymmetrical bridging ligands (CO and CCH 2 ) probably as a consequence of the different electronic configuration of the metal atoms. The core of the trinuclear cluster 14 consists of an open RhFeFe triangle which is triply bridged by the CCH 2 unit.