98394-13-9Relevant academic research and scientific papers
Pyrazolyl-bridged iridium dimers. 8. Two-center, electrophilic addition of activated acetylenes to bis(cycloocta-1,5-diene)bis(μ-pyrazolyl)diiridium(I) leading to a diiridacyclobutene configuration: Regular, parallel coordination of methyl propiolate
Bushnell, Gordon W.,Decker, Michael J.,Eadie, Donald T.,Stobart, Stephen R.,Vefghi, Rahmatollah,Atwood, Jerry L.,Zaworotko, Michael J.
, p. 2106 - 2111 (2008/10/08)
The activated alkynes hexafluorobut-2-yne (HFB), dimethyl acetylenedicarboxylate (DMAD), and methyl propiolate (MPL) react under mild conditions with [Ir(COD)(μ-pz)]2 (1) to afford 1:1 adducts 2-4, respectively, for which 1H and 13C NMR measurements suggest parallel alkyne addition, generating a diiridacyclobutene configuration in which the two metal centers are formally d7 Ir(II). By contrast the related diiridium(I) complex [Ir(CO)(PPh3)(μ-pz)]2 (5) forms a similar adduct (6) only with DMAD; with HFB alkyne polymerization occurs, attributed to PPh3 dissociation from 5. Compounds 3 and 4 have been structurally characterized by using X-ray diffractometry, showing the geometry in each case to resemble that communicated earlier for 2 and substantiating the interpretation of the spectroscopic data. Crystal data for 3: space group P21/c, a = 11.318 (3) A?, b = 11.543 (3) A?, c = 42.091 (9) A?, β = 98.07 (3)°. Crystal data for 4: space group P1, a = 10.983 (4) A?, b = 12.585 (6) A?, c = 9.862 (4) A?, α = 92.96 (4)°, β = 110.29 (3)°, γ = 99.41 (4)°. The adjacent Ir(II) centers in each molecule are spin paired via Ir-Ir bond formation, with single bond distances of 2.633 (2), 2.642 (2) A? (3, two independent molecules), and 2.637 (1) A? (4), to accommodate which terminal COD ligands are rotated to occupy axial positions at each Ir with alkyne coordination in equatorial sites. Coordination of the unsymmetrical MPL bridging unit is regular with Ir-CMPL distances equal at 2.094 (mean) A?.
