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

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.

顺,反,顺-[Rh(H)₂(PR₃)₂(丙酮)₂]PF₆ 配合物（其中R为芳基，或R₃为Ph₂Me、Ph₂Et）在氢气氛围下与E型缩氨基脲（E-semicarbazones）反应，可生成Rh(III)-二氢-双(膦(phosphine))-缩氨基脲（semicarbazones）类物种顺,反-[Rh(H)₂(PR₃)₂{R’(R’’)C=N-N(H)CONH₂}]PF₆，其中R’与R’’可为Ph、Et或Me。该类配合物通常通过元素分析、磷-31{质子}核磁共振谱(³¹P{¹H} NMR)、氢-1核磁共振谱(¹H NMR)、红外光谱(IR)以及质谱(MS)进行表征。对三个三苯基膦(PPh₃)配合物的X射线衍射分析表明，E型缩氨基脲通过亚胺氮原子（imine-N）与羰基氧原子（carbonyl-O）发生螯合配位。与之相对，[Rh(H)₂(PPhMe₂)₂(丙酮)₂]PF₆与苯乙酮缩氨基脲的对应反应，则生成了邻位金属化缩氨基脲（ortho-metalated-semicarbazone）类物种顺-[RhH(PPhMe₂)₂{o-C₆H₄(Me)C=N-N(H)CONH₂}]PF₆。本研究还报道了E型苯丙酮缩氨基脲的X射线晶体结构。即使在40 atm的氢气压力下，也未观察到铑催化的缩氨基脲均相氢化（homogeneous hydrogenation）反应。