Reaction of [Mn(CO)₅X] (X = Cl or Br) with L–L {L–L = dppm (Ph₂PCH₂PPh₂), dppe (Ph₂PCH₂CH₂PPh₂), dppp (Ph₂PCH₂CH₂CH₂PPh₂), C₆H₄(PPh₂)₂-o, C₆H₄(PH₂)₂-o, dpae (Ph₂AsCH₂CH₂AsPh₂), diars [C₆H₄(AsMe₂)₂-o], dpsp (Ph₂SbCH₂CH₂CH₂SbPh₂) or dmsp (Me₂SbCH₂CH₂CH₂SbMe₂)} or with two molar equivalents of L (= PPh₂H, PCy₂H or PPhH₂) in refluxing CHCl₃ yielded the neutral manganese(I) complexes [MnX(CO)₃(L–L)] and [MnX(CO)₃L₂] as yellow or orange solids. Infrared spectroscopic studies confirmed the fac-tricarbonyl arrangement and ¹H, ¹³C-{¹H}, ³¹P-{¹H} and ⁵⁵Mn NMR spectroscopy have been used to probe the solution behaviour. For a given halide ⁵⁵Mn NMR spectroscopic studies showed some dependence of δ(⁵⁵Mn) on halide, chelate ring size, substituent and donor atom. X-Ray crystallographic analyses on [MnCl(CO)₃{C₆H₄(PPh₂)₂-o}], [MnBr(CO)₃(dppe)] and the diprimary phosphine complex [MnCl(CO)₃{C₆H₄(PH₂)₂-o}]·CH₂Cl₂ confirmed a fac-tricarbonyl arrangement, with the ditertiary or diprimary phosphine chelating. The structure of [MnBr(CO)₃(PPhH₂)₂] also shows a fac-tricarbonyl arrangement with the primary phosphine ligands mutually cis.