Reaction of complex [Cp2Mo2(CO)4(micro,eta 2-P2)] (Cp=C5H5 (1)) with CuPF6, AgX (X=BF4, ClO4, PF6, SbF6, Al{OC(CF3)3}4) and [(Ph3P)Au(THF)][PF6] (THF=tetrahydrofuran), respectively, results in the facile formation of the dimers 3 b-h of the general formula [M2({Cp2Mo2 (CO)4(micro,eta 2:eta 2-P2)}2)({Cp2Mo2(CO)4 (micro,eta 2:eta 1:eta 1-P2)}2)][X]2 (M=Cu, Ag, Au; X=BF4, ClO4, PF6, SbF6, Al{OC(CF3)3}4). As revealed by X-ray crystallography, all these dimers comprise dicationic moieties that are well-separated from the weakly coordinating anions in the solid state. If 1 is allowed to react with AgNO2 and LAuCl (L=CO or tetrahydrothiophene), respectively, the dimer [Ag2{Cp2Mo2 (CO)4(micro,eta 2:eta 1:eta 1-P2)}2(eta 2-NO2)2] (5) and the complex [AuCl{Cp2Mo2(CO)4(micro,eta 2:eta 1-P2)}] (6) are formed, which have also been characterised by X-ray crystallography. In compounds 5 and 6, the anions remain coordinated to the Group 11 metal centres. Spectroscopic data suggest that the dimers 3 b-h display dynamic behaviour in solution and this is discussed by using the comprehensive results obtained for 3 g (M=Ag; X=Al{OC(CF3)3}4) as a basis. The interpretation of the experimental results is facilitated by density functional theory (DFT) calculations on 3 g (structures, energetics, NMR shielding tensors). The 31P magic angle spinning (MAS) NMR spectra recorded for the dimers 3 b (M=Cu; X=PF6) and 3c (M=Ag; X=BF4) as well as that of the previously reported one-dimensional (1 D) polymer [Ag2{Cp2Mo2(CO)4(micro,eta 2:eta 1:eta 1-P2)}3(micro,eta 1:eta 1-NO3)]n[NO3]n (4) are also discussed herein and the strong dependence of the chemical shift of the phosphorus atoms within each compound on subtle structural differences in the solid state is demonstrated. Furthermore, the X-ray crystallographic and 31P MAS NMR spectroscopic characterisation of a new polymorph of 1 is reported.