Elke Bleuel

The First Example of Linkage‐Isomeric Ketene Metal Complexes

With [(C9H7)Rh(PiPr3)] as molecular unit and diphenylketene as ligand, it has been possible for the first time to isolate linkage-isomeric ketene metal complexes (1 and 2). With regard to the hard/soft acid/base (HSAB) concept, it is surprising that the η2(C,O)-bonded isomer is thermodynamically more stable than the η2(C,C)-bonded counterpart.

DER ERSTMALIGE NACHWEIS BINDUNGSISOMERER KETEN-METALLKOMPLEXE

Mit [(C9H7)Rh(PiPr3)] als Molekulgerust und Diphenylketen als Ligand ist erstmals die Isolierung bindungsisomerer Ketenkomplexe 1 und 2 gelungen. Im Hinblick auf das HSAB-Konzept erstaunt es, das das η2-(C,O)-gebundene Isomer 2 thermodynamisch stabiler als das η2-(C,C)-gebundene ist.

Diphenylcarbene rhodium complexes: of the halfsandwich type with (η5-C5H4SiMe3)Rh as a molecular unit

Abstract The square-planar rhodium(I) complexes trans -[RhCl(=CPh 2 )(L) 2 ] (L = Sb i Pr 3 , P i Pr 3 , PPh 3 ) react with LiC 5 H 4 SiMe 3 to give the halfsandwich type compounds [(η 5 -C 5 H 4 SiMe 3 )Rh(=CPh 2 )(L)] 7–9 in good to excellent yields. While the phosphine complexes 8 and 9 are rather inert toward Lewis bases, the stibine derivative 7 reacts with CO, CN t Bu and PMe 3 to afford the corresponding substitution products [(η 5 -C 5 H 4 SiMe 3 )Rh(=CPh 2 )(L′] 10–12 . In contrast, the reaction of 7 with C 2 H 4 leads to the displacement of the carbene ligand and to the formation of the ethene complex [(η 5 -C 5 H 4 SiMe 3 )Rh(C 2 H 4 )(Sb i Pr 3 )] 14 together with the C−C coupling product Ph 2 C=CHCH 3 13 . Upon treatment of 9 (L = PPh 3 ) with an equimolar amount of HCl, the chloro(hydrido)rhodium(III) compound [{η 5 -C 5 H 3 )(CHPH 2 )(SiMe 3 )}RhHCl(PPh 3 )] 15 is formed. With an excess of HCl, a mixture of two products is obtained, one of which, with the composition [η 5 -C 5 H 4 )CHPh 2 )RhCl 2 (PPH 3 )] 17 has been independently prepared from η 5 -C 5 H 5 )Rh(=CPh 2 )(PPh 3 ] 18 and 2 equiv of HCl.