A convenient synthesis of complexes of the type [Rh2Cl2(all)4](all = allyl, 1-methyl-, 2-methyl-, or 2-chloro-allyl) is described from the oxidative hydrolysis of [Rh2Cl2(CO)4] in the presence of an allylic chloride (allCl) in aqueous methanol. If the synthesis is carried out in the presence of potassium hydroxide the reactions are much faster and the yields higher; [Rh2Cl2(1-phenylallyl)4] was prepared by this method. With 2-methylallyl chloride and [Rh2Cl2(CO)4] reacting in aqueous methanol at ca. 0° the major product is [Rh2Cl2(2-methylallyl)4] but at 60° only [Rh2Cl2(2,5-dimethylhexa-1,5-diene)2] was isolated. Deuteriation and other studies show that reversible protonation of the 2-methylallyl groups plays an essential part in the formation of the 2,5-dimethylhexa-1,5-diene ligand. Complexes of the type [Rh2Cl2(all)4] contain asymmetrically bonded allylic groups, the nature of which is discussed. Some complexes of the type [Rh2Cl2(all)4] react with alcoholic potassium hydroxide to give an olefin (allH). They can also be used to prepare complexes of the types: [Rh2X2(all)4](X = Br, l, or Ac); [RhCl(all)2L] and [Rh(all)2py2]+(L = py, PR3, or AsR3); [RhCl(PPh3)3]; [Rh2Cl2(cyclo-octa-1,5-diene)]; [Rh(acac)(all)2]; [Rh(σ-all)(π-all)(C5H5)]; [RhCl2(all)]x and [Rh(all)3]. [Rh(all)3] reacts with Na2PdCl4 to give [Rh2Cl2(all)4] and [Pd2Cl2(all)2], or with PPh3 to give [Rh(all)(PPh3)2]. Complexes of the types [RhCl2(all)L2](L = py or PMe2Ph) and [Rh2Cl4(all)2(CO)2], and the complex [RhCl2(C5H5)]x are described. Near-infrared, far-infrared, and nuclear magnetic resonace data are given and discussed.