BINDING OF LEAD(II), ANTIMONY(III), AND OTHER ISOELECTRONIC MAIN-GROUP IONS TO IRIDIUM IN THE METALLOMACROCYCLE IR2(CO)2CL2(MU-(PH2PCH2)2ASPH)2

The ability of the metallomacrocycle Ir2(CO)2Cl2(mu-dpma)2 (1; dpma is bis(diphenylphosphinomethyl)phenylarsine) to coordinate a variety of main-group ions (Pb(II), Sn(II), Ge(II), Tl(I), In(I), Sb(III), Bi(III) with an s2 electron configuration is surveyed. Reaction of 1 with sodium iodide, lead(II) iodide, and ammonium hexafluorophosphate yields magenta [Ir2-(PbI)(CO)2I2(mu-dpma)2](PF6).CH2Cl2, which crystallizes in the triclinic space group PlBAR (No. 2) with a = 15.963 (6) angstrom, b = 16.146 (6) angstrom, c =16.869 (9) angstrom, alpha = 95.68 (1)-degrees, beta = 104.49 (1)-degrees, gamma = 117.83 (1)-degrees at 130 K and Z = 2. Refinement of 8994 reflections with 456 parameters yielded R = 0.059, R(w) = 0.057. The structure of the cation consists of a PbI unit suspended at the center of the metallomacrocycle through two Pb-Ir bonds (Pb-Ir distances, 2.855 (2), 2.831 (2) angstrom), which are shorter than the Pb-1 bond (2.892 (2) angstrom). Antimony(III) fluoride and sodium tetrafluoroborate react with 1 to yield [Ir2(SbF2)(CO)2Cl2(mu-dpma)2](BF4), which crystallizes in the orthorhombic space group Pmnb (No. 62) with a = 19.800 (5) angstrom, b = 19.832 (4) angstrom, c = 19.865 (4) angstrom at 130 K with Z = 4. Refinement of 3789 reflections and 233 parameters yielded R = 0.083, R(w) = 0.070. The structure consists of the cation, which has crystallographic mirror symmetry, with an SbF2+ unit (that lies in the mirror plane) bound to two iridium atoms with two equivalent Sb-Ir distances of 2.655 (1) angstrom. The arrangement of the two dpma ligands in the macrocycle differs from other adducts because the relative orientation of the lone pairs on the arsenic atoms is trans (i.e., they lie on opposite sides of the rough P4Ir2 plane). This implies either inversion of the configuration at arsenic or dissociation of a dpma ligand during formation of the cationic complex. Spectroscopic features of these adducts are compared to those of related complexes with Tl+ and (SnCl)+ bound to the center of the metallomacrocycle. All show intense absorption in the visible spectrum and luminescence from solutions.