Carbon Dioxide Chemistry. Synthesis, Properties, and Structural Characterization of Stable Bis(carbon dioxide) Adducts of Molybdenum

Article abstract of DOI:10.1021/ja00269a026

The bis(carbon dioxide) adduct,trans-Mo(CO2)2(PMe3)4, 1, has been prepared from the reaction of cis-Mo(N2)2(PMe3)4 with CO2 under pressure (4-5 atm).The interaction of 1 with several small molecules has been studied.In particular, reaction with COS affords a seven-coordinate S,S'-dithiocarbonate, Mo(S2CO)(CO)2(PMe3)3, 2, while interaction with various isocyanides yields the new carbon dioxide complexes trans,mer-Mo(CO2)2(CNR)(PMe3)3, 3 (R = Me, 3a; i-Pr, 3b; t-Bu, 3c; Cy, 3d; CH2C6H5, 3e).The new compounds have been characterized by analytical and spectroscopic (IR and 1H, 13C, and 31P NMR) studies.The molecular structures of 2, 3b, and 3e have been determined by X-ray crystallography.Compound 2 is orthorhombic and belongs to the space group Pna2₁ with a = 14.003 (2) Angstroem, b = 9.767 (2) Angstroem, c = 15.127 (2) Angstroem, D_c = 1.52 g*cm^-3, and Z = 4.Refinement was achieved on 1939 independent observed reflections, leading to a final R value of 0.038. 3b crystallizes in the monoclinic space group C2/c with unit cell parameters a = 24.47 (3) Angstroem, b = 13.01 (1) Angstroem, c = 16.77 (1) Angstroem, β = 132.41 (3) deg, and D_c = 1.35 g*cm^-3 for Z = 8.Least-squares refinement based on 3493 independent observed reflections led to a final R value of 0.076.Crystals of 3e are monoclinic, space group P2₁/c with a = 11.563 (8) Angstroem, b = 11.792 (7) Angstroem, c = 18.57 (1) Angstroem, β = 90.42 (4) deg, D_c = 1.39 g*cm^-3, and Z = 4, 1907 reflections were considered observed (I >/= 3?(I)), and the final R value based on them was 0.093. 3b and 3e are isostructural, with the Mo atom bonded to two trans, staggered CO2 molecules, the overall molecular geometry being approximately octahedral.