Substitution and Hydrogenation Reactions on Rhodium(I)−Ethylene Complexes of the Hydrotris(pyrazolyl)borate Ligands Tp‘ (Tp‘ = Tp, Tp^Me2)^†

The bis(ethylene) Rh species TpMe2Rh(C2H4)2 (1*) (TpMe2 = tris(3,5-dimethyl-1-pyrazol-1-yl)hydroborate) has been obtained from [RhCl(C2H4)2]2 and KTpMe2. Complex 1* easily decomposes in solution to give mainly the butadiene species TpMe2Rh(η4-C4H6). In the solid state its thermal decomposition follows a different course and the allyl TpMe2RhH(syn-C3H4Me) is cleanly obtained as a mixture of exo and endo isomers. The complexes Tp‘Rh(C2H4)2 (Tp‘ = Tp, TpMe2) afford the monosubstituted species Tp‘Rh(C2H4)(PR3) upon reaction with PR3 but react differently with L = CO or CNR: the Tp compound gives dinuclear [TpRh]2(μ-L)3 complexes, while, in the case of 1*, TpMe2Rh(C2H4)(L) species are obtained. The ethylene ligand of complexes TpMe2Rh(C2H4)(PR3) is labile, and several peroxo compounds of composition TpMe2Rh(O2)(PR3) have been isolated by their reaction with O2. All the mononuclear Rh(I) complexes are formulated as 18e- trigonal bipyramidal species on the basis of IR and NMR spectroscopic studies. A series of dihydride complexes of Rh(III) of formulation Tp‘RhH2(PR3) have been prepared by the hydrogenation of the corresponding ethylene derivatives. Complexes [TpRh]2(μ-CNCy)3, TpMe2Rh(C2H4)(PEt3), and TpMe2Rh(O2)(PEt3) have been further characterized by X-ray diffraction studies.双(乙烯)合铑物种TpMe2Rh(C₂H₄)₂ (1*) [其中TpMe2为三(3,5-二甲基-1-吡唑基)氢硼酸盐(tris(3,5-dimethyl-1-pyrazol-1-yl)hydroborate)]，可由二聚氯双(乙烯)合铑([RhCl(C₂H₄)₂]₂)与三(3,5-二甲基-1-吡唑基)氢硼酸钾(KTpMe2)反应制得。配合物1*在溶液中易发生分解，主要生成丁二烯合铑物种TpMe2Rh(η⁴-C₄H₆)。在固态状态下，其热分解路径截然不同，可干净地得到烯丙基合铑物种TpMe2RhH(syn-C₃H₄Me)，该产物为外向(exo)与内向(endo)异构体的混合物。配合物Tp'Rh(C₂H₄)₂ [其中Tp'为三(吡唑基)氢硼酸盐(Tp)与TpMe2] 与膦配体PR₃反应时，可生成单取代配合物Tp'Rh(C₂H₄)(PR₃)；但与配体L（CO或异腈配体CNR）反应时则表现出不同的反应性：以Tp为配体的配合物会生成双核桥联配合物[TpRh]₂(μ-L)₃，而对于配合物1*，则生成TpMe2Rh(C₂H₄)(L)物种。TpMe2Rh(C₂H₄)(PR₃)的乙烯配体具有配位不稳定性，其与氧气(O₂)反应可得到一系列组成为TpMe2Rh(O₂)(PR₃)的过氧合铑配合物，此类配合物均已被分离得到。基于红外(IR)与核磁共振(NMR)光谱研究，所有单核Rh(I)配合物均被归属为18电子三角双锥构型物种。一系列组成为Tp'RhH₂(PR₃)的Rh(III)二氢配合物，可通过对应乙烯衍生物的氢化反应制备得到。配合物[TpRh]₂(μ-CNCy)₃、TpMe2Rh(C₂H₄)(PEt₃)与TpMe2Rh(O₂)(PEt₃)，已通过X射线衍射分析得到进一步的结构表征。