SYNTHESEN MIT 1-PHENYLBORA-2,5-CYCLOHEXADIEN. KOMPLEXE VON EISEN, COBALT UND NICKEL MIT TEILWEISE HYDRIERTEN BORABENZOL-LIGANDEN

Article abstract of DOI:10.1016/S0022-328X(00)99580-9

Phenylbora-2,5-cyclohexadiene (LH) is a versatile ligand precursor in reactions with Fe(CO)5, Co2(CO)8, Ni(CO)4, and Ni(η⁴-1,5-COD)2.Photochemical reaction with Fe(CO)5 gives (η⁵-LH)Fe(CO)3 which under irradiation slowly converts to the known borabenzene derivative <(η⁶-L)Fe(CO)2>2 (Fe-Fe).LH reacts with Co2(CO)8 to give the known complex (η⁶-L)Co(CO)2 and two isomers (η⁴-LH2)Co(CO)3 with the novel bora-5-cyclohexen-2-yl and bora-3-cyclohexen-2-yl ligands, respectively.Ni(CO)4 similarly yields two isomers Ni(η⁶-L)(η⁴-LH2), whereas Ni(η⁴-1,5-COD)2 gives Ni(η⁶-L)(1,4,5-η³-C8H13).Complexes with ligands of the η⁴-2-bora-3-buten-1-yl show strong metal-boron interactions as evidenced by a Ni-B distance of 217 pm in the corresponding isomer Ni(η⁶-L)(η⁴-LH2) and by δ(11B) values ranging from 19.6 to 24.4 ppm.In contrast to this, complexes with ligands of the type η⁴-1-bora-3-buten-2-yl show weak metal-boron interactions as revealed by a comparatively long Co-B distance of 248.1(7) pm in the corresponding isomer Co(CO)2(PMe3)(η⁴-LH2) and by δ(11B) values at significantly lower field, ranging from 41.5 to 30.8 ppm.