Nickel-Manganese Sulfido Carbonyl Cluster Complexes. Synthesis, Structure, and Properties of the Unusual Paramagnetic Complexes Cp₂Ni ₂Mn(CO)₃(μ₃-E)₂, E = S, Se

The reaction of Mn₂(CO)₇(μ-S₂) with [CpNi(CO)]₂ yielded the paramagnetic new compound Cp ₂Ni₂Mn(CO)₃(μ₃-S)₂ (1) and a new hexanuclear metal product Cp₂Ni₂Mn ₄(CO)₁₄(μ₆-S₂)(μ ₃-S)₂ (2). Structurally, compound 1 contains two triply bridging sulfido ligands on opposite sides of an open Ni₂Mn triangular cluster. EPR and temperature-dependent magnetic susceptibility measurements of 1 show that it contains one unpaired electron. The electronic structure of 1 was determined by Fenske-Hall molecular orbital calculations which show that the unpaired electron occupies a low lying antibonding orbital delocalized unequally across the three metal atoms. The selenium homologue Cp₂Ni₂Mn(CO)₃(μ₃-Se)₂ (3) was obtained from the reaction of a mixture of Mn₂(CO) ₁₀ and [CpNi(CO)]₂ with elemental selenium and Me ₃NO·₂H₂O. It also has one unpaired electron. Compound 1 reacted with elemental sulfur to yield the dinickeldimanganese compound, Cp₂Ni₂Mn ₂(CO)₆(μ₄-S₂)(μ ₄-S₅), 4, which can also be made from the reaction of Mn₂(CO)₇(μ-S₂) with [CpNi(CO)]₂ and sulfur. Compound 4 was converted back to 1 by sulfur abstraction using PPh₃. The reaction of Mn₂(CO)₁₀ with [CpNi(CO)]₂ in the presence of thiirane yielded the ethanedithiolato compound CpNiMn(CO)₃(μ-SCH₂CH₂S) (5), which was also obtained from the reaction of Mn₄(CO)₁₅(μ ₃-S₂)(μ₄-S₂) with [CpNi-(CO)]₂ in the presence of thiirane. Compound 5 reacted with additional quantities of thiirane to yield the new compound CpNiMn(CO) ₃[μ-S(CH₂CH₂S)₂], 6, which contains a 3-thiapentanedithiolato ligand that bridges the two metal atoms. Compound 6 was also obtained from the reaction of Mn₂(CO) ₁₀ with CpNi(CO)12 and thiirane. The molecular structures of the new compounds 1-6 were established by single-crystal X-ray diffraction analyses.