Chromium, molybdenum, and tungsten carbonyl complexes of phenyldibenzophosphole

Article abstract of DOI:10.1021/om00098a006

A series of complexes of 1-phenyldibenzophosphole (DBP) of the type (DBP)_nM(CO)_6-n (M = Cr, Mo, W; n = 1-3) have been prepared and characterized by elemental analysis, physical properties, and infrared and ¹H, ¹H{³¹P}, ¹³C{¹H}, ¹⁷O, ³¹P{¹H}, and ⁹⁵Mo NMR spectroscopy. The structures of (DBP)Cr(CO)₅ (1), cis-(DBP)₂Cr(CO)₄ (2), and mer-(DBP)₃Cr(CO)₃ (3) complexes have been determined from three-dimensional X-ray data collected by counter methods. Compound 1 crystallized in space group P2₁/c with a = 7.962 (3) ?, b = 23.122 (9) ?, c = 11.212 (4) ?, β = 95.27 (3); and Z = 4. Compound 2 crystallizes in space group P2₁ with a = 11.295 (4) ?, b = 13.381 (5) ?, c = 10.948 (3) ?, β = 103.24 (2); and Z = 2. Compound 3 crystallizes in space group P1 with a = 10.621 (3) ?, b = 12.476 (2) ?, c = 20.489 (4) ?, α = 92.86 (2)°, β = 101.441 (2)°, γ = 108.07 (2)°, and Z = 2. The three structures were refined by least squares methods with R = 0.070 for 1, R = 0.067 for 2, and R = 0.068 for 3 for 2696, 2347, and 6106 unique reflections with I/ σ(I) ≥ 3.0 for 1, 2, and 3, respectively. Attractive interactions between two adjacent dibenzophosphole planes exist for cis-(DBP)₂Cr(CO)₄ and mer-(DBP)₃Cr(CO)₃ in the solid state. This interaction is shown by diamagnetic anisotropy effects in the ¹H and ¹³C{¹H} NMR spectra to be present in solution as well for all the cis-(DBP)₂M(CO)₄ and mer-(DBP)₃M(CO)₃ complexes stabilizing a mutually cis orientation of two DBP ligands. The CO force constants for these molecules have been calculated by the Cotton-Kraihanzel method, and the Graham σ/π parameters of DBP have been evaluated to allow a comparison of the donor properties of DBP with those of other phosphorus donors. Correlations between these force constants and the chemical shifts of the various nuclei and among the chemical shifts of the various nuclei are discussed.