Synthesis and crystal structure of new polynuclear rhodium complexes formed by reaction of bis(η-ethylene)(η5-indenyl)rhodium with t-butylphospha-acetylene

Treatment of bis(η-ethylene)(η5indenyl)rhodium (1) or (cyclo-octa-1,5-diene)(η5-indenyl)rhodium (2) with t-butylphospha-acetylene (3) yields [η4-2,4-di(t-butyl)-1,3-diphosphacyclobutadiene](η5-indenyl)rhodium (4) as the main product together with two other rhodium complexes(5) and (6) that contain derivatives of the new ligated systems 1,2,4,5-tetraphosphabenzenediyl and 1-rhoda-2,5-diphosphacyclopentenediyl, respectively. Phosphorus-31, 1H, and 13C n.m.r. data are reported and are discussed in relation to the structures, which in the case of (5) and (6) were established by X-ray diffraction analyses. The n.m.r. spectra of (6) reveal restricted rotation of one of the indenyl groups.