Construction of the First Rhodium(I) Cyclic Pentameric Structure [Rh(CO)Cl{(μ‑NtBuP)2(CCPh)2}]5 Using (Phenylethynyl)cyclodiphosphazanes

To examine the steric effect of the phosphorus substituents in cyclodiphosphazanes, two less sterically demanding alkynyl-functionalized cis-[(μ-NtBuP)2(CCPh)2] (1) and trans-[(μ-NtBuP)2(CCPh)2] (2) were synthesized. The cis isomer 1, with a large subtending angle (135.8°) upon treatment with [Rh­(CO)2Cl]2, afforded the first rhodium­(I) cyclic pentameric macrocycle [Rh­(CO)­Cl­{(μ-NtBuP)2(CCPh)2}]5 (3). The crystal structure of the cyclic pentamer 3 closely resembles a classical “Ferris wheel”.