Interactions of Rh(III)−Dihydrido−Bis(phosphine) Complexes with Semicarbazones

• Published in: Inorganic chemistry 2005-03, Vol.44 (5), p.1482-1491
• Main Authors: Ezhova, Maria B., Patrick, Brian O., Sereviratne, Kapila N., James, Brian R., Waller, Francis J., Ford, Michael E.
• Format: Article
• Language: English
• ISSN: 0020-1669; 1520-510X
• DOI: 10.1021/ic0489185

Interaction of cis,trans,cis-[Rh(H)2(PR3)2(acetone)2]PF6 complexes (R = aryl or R3 = Ph2Me, Ph2Et) under H2 with E-semicarbazones gives the Rh(III)−dihydrido−bis(phosphine)−semicarbazone species cis,trans-[Rh(H)2(PR3)2{R‘(R‘ ‘)CNN(H)CONH2}]PF6, where R‘ and R‘ ‘ are Ph, Et, or Me. The complexes are generally characterized by elemental analysis, 31P{1H} NMR, 1H NMR, and IR spectroscopies, and MS. X-ray analysis of three PPh3 complexes reveals chelation of E-semicarbazones by the imine-N atom and the carbonyl-O atom. In contrast, the corresponding reaction of [Rh(H)2(PPhMe2)2(acetone)2]PF6 with acetophenone semicarbazone gives the ortho-metalated-semicarbazone species cis-[RhH(PPhMe2)2{o-C6H4(Me)CN−N(H)CONH2}]PF6. The X-ray structure of E-propiophenone semicarbazone is also reported. Rhodium-catalyzed, homogeneous hydrogenation of semicarbazones was not observed even at 40 atm H2.