Di-manganese carbonyl compounds containing bis(dicyclohexylphosphino)methane (dcpm) ligation

Abstract

The reaction of [Mn 2(CO) 10] with bis(dicyclohexylphosphino)methane (dcpm) in refluxing cyclohexane yields the simple substitution products [Mn 2(dcpm)(CO) 8] ( 1) and [Mn 2(dcpm) 2(CO) 6] ( 2). The solid state structures of 1 and 2 show the dcpm ligands to be bridging the di-manganese core with a pseudo-octahedral coordination about each Mn metal center. The 13C NMR spectra of 1 and 2 show the carbonyl ligands to be non-fluxional on the NMR time scale at 30 °C. Attempts to thermally induce decarbonylation of 2 at 174 °C in refluxing n-decane failed. However, photolysis of 2 in benzene was found to efficiently produce the complex [Mn 2(dcpm) 2(CO) 5] ( 3) shown to contain a semi-bridging carbonyl ligand both in solution v(MCO)=1637 cm −1, and in the solid state (X-ray diffraction). The MnMn distance of 2.928(2) Å in 3 is shorter than the values of 2.976(2) and 3.025(2) Å found for 1 and 2, respectively. Crystal data at 293 K for Mn 2P 2O 8C 33H 46 ( 1): a=13.097(1), b=11.6635(9), c=23.501(2) Å, β=101.035(7)°, Z=4 in space group P2 1/ n; for Mn 2P 4O 6C 68H 120 ( 2·2C 6H 14) at 293 K: a=20.714(5), b=15.856(2), c=20.910(5) Å, β=94.34(2)°, Z=4 in space group C2/ c; for Mn 2P 4O 5C 55H 92 ( 3) at 293 K: a=11.0309(9), b=12.319(2), c=21.518(2) Å, α=83.361(9), β=76.293(7), γ=85.646(9)°, Z=2 in space group P 1 [kw]Crystal structures; Manganese complexes; Carbonyl complexes; Bidentate ligand complexes; Dinuclear complexes