Bimetallic systems. Part 22. Molybdenum(0)– and manganese(I)-iron(0) carbonyl complexes containing one bridging Ph2PCH2PPh2 ligand, including the reversible uptake of carbon monoxide: crystal structure of [(OC)4Fe(µ-Ph2PCH2PPh2)Mo(CO)4]·0.5 C6H5Cl

Abstract

Treatment of [Fe₂(CO)₉] with dppm (Ph₂PCH₂PPh₂) in tetrahydrofuran gave [Fe(CO)₄(dppm-P)] and other products. Treatment of [Fe(CO)₄(dppm-P)] with [Mn(CO)₅Br] gave [(OC)₄Fe(µ-dppm)-Mn(CO)₃Br] in 58% yield. This bimetallic complex reacted reversibly with carbon monoxide, breaking the metal–metal bond to give [(OC)₄Fe(µ-dppm)Mn(CO)₄Br]. Treatment of [Fe(CO)₄(dppm-P)] with [Mo(CO)₄(nbd)]{nbd = norbornadiene (bicyclo[2.2.1]hepta-2,5-diene)} gave [(OC)₄Fe(µ-dppm)Mo(CO)₄] in 47% yield. This bimetallic complex reacts with carbon monoxide to give a complex, formulated as [(OC)₄Fe(µ-dppm)Mo(CO)₅], which was not isolated. Analogous reactions with the diphosphine CH₂C(PPh₂)₂ are described. Crystals of [(OC)₄Fe(µ-dppm)-Mo(CO)₄] are tetragonal, space group I4₁cd(no. 110), with a= 1 853.1(4), c= 4 106.8(9) pm, and Z= 16; final R= 0.0633 for 3 357 observed reflections. The structure shows that there is a metal–metal bond [Fe–Mo 302.4(5) pm] formulated as a donor → acceptor bond, viz. Fe → Mo.