Photochemistry of ring-coupled group VI bimetallic compounds I: phosphine substitution without disproportionation. The molecular structures of Mo 2(CO) 5[P(C 6 H 5) 3]( μ- η5, η5-C 5H 4–CR 2–C 5H 4) and Mo 2(CO) 4[P(CH 3) 3] 2( μ- η5, η5-C 5H 4–CR 2–C 5H 4)

Abstract

Solution photolysis of ring-coupled bimetallic compounds of the formula M 2(CO) 6( μ- η 5, η 5-C 5H 4–CR 2–C 5H 4), where M=Mo or W and R=H or CH 3, in the presence of triphenylphosphine or trimethylphosphine yields simple substitution derivatives M 2(CO) 5L( μ- η 5, η 5-C 5H 4–CR 2–C 5H 4) or M 2(CO) 4L 2( μ- η 5, η 5-C 5H 4–CR 2–C 5H 4). The compounds have been fully characterized by IR and NMR spectroscopy and elemental analysis. Phosphine ligands are found to occupy positions trans to the M–M bond. No evidence was found for disproportionation processes such as those found for similar reactions of the non-ring-coupled species. The molecular structures of two compounds have been determined: ( μ- η 5, η 5-C 5H 4–CH 2–C 5H 4)Mo 2(CO) 5(PPh 3): monoclinic, P2 1/ c, a=22.871(8), b=16.415(6), c=15.957(9) Å, β=94.29(3)°, V=5974(4) Å 3, Z=8, R( F)=8.87%; ( μ- η 5, η 5-C 5H 4–CH 2–C 5H 4)Mo 2(CO) 4(PMe 3) 2: monoclinic, P2 1/ c, a=9.843(5), b=15.343(7), c=31.514(6) Å, β=97.28(3)°, V=4720(4) Å 3, Z=8, R( F)=4.38%.