Reaction of [{Cr(cp)(CO)3}2](cp =η5-C5H5) with elemental phosphorus. Isolation of [Cr2(cp)2(P5)] as a thermolysis product and its X-ray crystal structure

Abstract

The reaction of [{Cr(cp)(CO)₃}₂](1) with 2 mol equivalents of P₄ in toluene at 90 °C produces a mixture of [Cr₂(cp)₂(CO)₄(µ-η²-P₂)](2), [Cr(cp)(CO)₂(η³-P₃)](3), [{Cr(cp)(CO)₂}₅(P₁₀)](4), and [Cr₂(cp)₂(η⁵-P₅)](5), the relative proportion of which is dependent on the duration of the reaction. This, coupled with thermolysis studies on (2)–(4), demonstrates that these three complexes are the primary products of the reaction, whereas (5) arises mainly from the thermolysis of (2), which also yields (3) and [{Cr(cp)(CO)₂}₂](6). Complex (5) has been isolated from a reaction of (1) with P₄ at 110 °C after ca. 5 h. A single-crystal X-ray diffraction study of (5) shows it to be a triple-decker sandwich complex with a cyclic P₅ ring bonded to two Cr(cp) groups. Crystal data: monoclinic, space group P2₁/n, a= 7.921 (2), b= 15.04(1), c= 11.704(4)Å, β= 104.08(2)°, and Z= 4. The spectral features of complex (5) are also presented.