The 95Mo NMR spectra of a series of seven-coordinate molybdenum(II) isocyanide complexes of the types [Mo(CNR) 7- n L n ](PF 6) 2 (R = CH 3, CHMe 2, CMe 3, C 6H 11, CH 2Ph; L = py, bpy, Me 2bpy, phen, dppe, P-n-Bu 3; n = 0,1,2) [Mo(CNC-Me 3) 6X]PF 6 (X = Cl, Br, I) and [{Mo(CNCMe 3) 4(NN)} 2(μ-CN)](PF 6) 3 (NN = bpy, Me 2bpy, phen) have been studied. The 95Mo chemical shift range for this group of complexes is about 1100 ppm. An increase in the size of the R group attached to the isocyanide ligand generally tends to shield the 95Mo nucleus. Replacement of the isocyanide ligand with a phosphorus ligand also increases the shielding, whereas the replacement of isocyanide with a heterocyclic nitrogen donor leads to deshielding by 800–900 ppm. This group of complexes shows a normal halogen dependence, i.e. replacement of Cl − by Br − and I − increases the shielding of the 95Mo nucleus. The cyano-bridged cations [{Mo(CNCMe 3) 4(NN)} 2(μ-CN)] 3+ (NN = bpy, Me 2bpy, or phen) show two 95Mo NMR signals, one for the molybdenum coordinated to the carbon of the bridging CN and one for the N-coordinated molybdenum. Comparison of the chemical shifts and linewidths of the cyano-bridged species with those of the corresponding mononuclear molybdenum(II) complexes [Mo(CNCMe 3) 5(NN)](PF 6) 2 leads to the assignment of the more deshielded signal to the N-coordinated molybdenum. The 14N and 31P NMR spectra for these complexes have also been measured, as have the 13C NMR spectra of the pairs of complexes [Mo(CNCMe 3) 5(NN)](PF 6) 2 and [{Mo(CNCMe 3) 4(NN)} 2(μ-CN)](PF 6) 3 (NN = bpy or phen). The 183W NMR spectra for [W(CNR) 5(bpy)](PF 6) 2 (R = CMe 3 and CH 2Ph), show that the δ( 183W)/δ( 95Mo) chemical shift ratios for isocyanide complexes are different from the ratio found for M 0 and M VI.