Structure and stereodynamics of [M(CO)5{P(C6H4Me-o)3}](M = Cr, Mo or W) and [Cr(CO)3{P(C6H4Me-o)3}]

Abstract

The crystal structure of [Cr(CO)₅{P(C₆H₄Me-o)₃}] has been determined. It reveals an exo₂ conformation for the phosphine ligand, in agreement with molecular mechanics calculations. Barriers to P–C rotation in the series [M(CO)₅{P(C₆H₄Me-o)₃}](M = Cr, Mo or W) are in the range 36–42 kJ mol^–1; restricted M–P rotation is also evident in the low-temperature ¹³CO NMR spectrum of [Cr(CO)₅{P(C₆H₄Me-o)₃}]. The crystal structure of the π complex [Cr(CO)₃{P(C₆H₄Me-o)}₃] is most consistent with an electron-acceptor character for the P(C₆H₄Me-o)₂ substituent. Crystal data: [Cr(CO)₅{P(C₆H₄Me-o)₃}], monoclinic, space group P2₁/n, a= 10.774(2), b= 14.951(5), c= 14.687(7)Å, β= 91.45(2)°, Z= 4, R′= 0.0980 for 209 variable parameters and 2326 observed reflections; [Cr(CO)₃{P(C₆H₄Me-o)₃}], monoclinic, space group P2₁/a, a= 16.725(2), b= 7.340(1), c= 17.675(4), β= 92.66(2)°, Z= 4, R′= 0.1187 for 263 variable parameters and 1848 observed reflections.