Complexes [Rh(μ-RCOO)(CO₂)]₂, where R = H, CH ₃, CF₃ (I, II, III, respectively) are synthesized by reacting anhydrous carboxylic acids with Rh(Acac)(CO₂) crystals. In compounds I, II, III, and trans-Rh(RCOO)(PPh₃)₂(CO), where R = H, CH₃, CF₃ (IV, V, VI, respectively), ν(CO) and ¹J(CRh) increase and δ¹³C decreases with the increasing electronegativity of R (CH₃ < H < CF₃). In the case complexes IV, V, and VI, the values of δ³¹P and ¹J(PRh) decrease in the same order. Complexes I and V are studied by X-ray diffraction analysis. Intramolecular (2.946 Å) and intermolecular (3.127 Å) Rh-Rh distances in a columnar structure I are close, i.e., the structure contains infinite chains of metal atoms. Interaction of IV with chlorinated solvents results in trans-RhCl(PPh₃)₂(CO). When heated with an excess of PPh₃ in propanol-2, compound IV transforms to HRh(PPh₃)₃(CO). The latter reaction was suggested as a basis of a new method that can be used to obtain HRh(PPh ₃)₃(CO).