Synthesis and reactivity investigation of iridium maleonitriledithiolate complexes. Redox studies and extended Hueckel molecular orbital calculations on Cp*IrL(mnt) (where L = PMe3, PPh3, CN-t-Bu)

Article abstract of DOI:10.1016/0022-328X(94)05385-O

The reaction between the cyclopentadienyliridium complexes Cp^*Ir(L)Cl2 (where L = PMe3, PPh3, CN-t-Bu) and disodium maleonitriledithiolate (Na2mnt) yields the corresponding mnt-substituted compounds Cp^*Ir(PMe3)(mnt) (1), Cp^*Ir(PPh3)(mnt) (2) and Cp^*Ir(CN-t-Bu)(mnt) (3).All of these new compounds have been isolated in high yield and characterized in solution by IR and NMR spectroscopy.The solid state structures of 2 and 3 were determined by single-crystal X-ray diffraction analysis. 2 crystallizes in the triclinic space group P<*> with a = 10.4557(8) Angstroem, b = 10.630(1) Angstroem, c = 14.894(1) Angstroem, α = 91.382(8) deg, β = 90.141(6) deg, γ = 118.182(7) deg, V = 1458.5(3) Angstroem³ and Z = 2.Full-matrix least-squares refinement yielded R = 0.0281 for 3425 (I > 3?(I)) reflections. 3 crystallizes in the monoclinic space group P2₁/n with a = 8.9609(7) Angstroem, b = 20.343(1) Angstroem, c = 11.9115(9) Angstroem, β = 94.168(6) deg, V = 2165.6(3) Angstroem³ and Z =4.Full-matrix least-squares refinement yielded R = 0.0245 for 2266 (I > 3?(I)) reflections.The redox properties of 1-3 have been explored by cyclic and rotating disc electrode voltammetric techniques in MeCN and CH2Cl2 solvents.Each of these compounds exhibit a well-defined one-electron oxidation wave that is assigned to the 0/+1 redox couple, along with a +1/+2 redox wave, the reversibility of which is highly dependent on the nature of the ancillary two-electron donor ligand (L) and the solvent.Extended Hueckel calculations have been performed on the model compounds CpIr(PH3)(mnt) and CpIr(CNH)(mnt), with the results used in a discussion of the nature of the HOMO and LUMO levels in 1-3.Keywords: Iridium; Hueckel molecular orbital calculations; Electrochemistry; Maleonitriledithiolate complexes; Cyclopentadienyl derivatives