Abstract
The reaction between CpMo(CO) 3 Na and trans-1-chloropenta-2,4-diene in tetrahydrofuran at -78 °C gives CpMo(CO) 3 (η 1 -pentadienyl) (1). In photolytic reaction, 1 undergoes η 1 → syn-η 3 → η 5 conversion and yields CpMo(CO) 2 (syn-η 3 -pentadienyl) (2) and CpMo(CO)(η 5 -pentadienyl) (3). In solution, 2 exists in two stereoisomers characterized as the endo-syn-η 3 and exosyn-η 3 forms, its solid structure is the exo form which crystallized in the monoclinic space group P2 1 /n with a = 12.647 (5) Å, b = 8.703 (2) Å, c = 13.817 (3) Å, β = 102.59 (3)°, V = 1143.11 Å 3 , and Z = 4. For 3, the pentadienyl configuration is unsymmetric η 5 -S-shaped as inferred from its 1 H and 13 C NMR spectra. © 1986 American Chemical Society.