Jump to main content
Jump to site search

Issue 7, 2012
Previous Article Next Article

Stabilization of coordinatively unsaturated Ir4 clusters with bulky ligands: a comparative study of chemical and mechanical effects

Author affiliations

Abstract

The synthesis and characterization of new cluster compounds represented by the series Ir4(CO)12−xLx (L = tert-butyl-calix[4]-arene(OPr)3(OCH2PPh2); x = 2 and 3) is reported using ESI mass spectrometry, NMR spectroscopy, IR spectroscopy and single-crystal X-ray diffraction. Thermally driven decarbonylation of the cluster compound series represented by x = 1–3 according to the formula above is followed viaFTIR and NMR spectroscopies, and dynamic light scattering in toluene solution. The propensity of these clusters to decarbonylate in solution is shown to be directly correlated with number density of adsorbed calixarene phosphine ligands and controlled via Pauli repulsion between metal d and CO 5σ orbitals. The tendency for cluster aggregation unintuitively follows a trend that is exactly opposite to the cluster's propensity to decarbonylate. No cluster aggregation is observed for clusters consisting of x = 3, even after extensive decarbonylationvia loss of all bridging CO ligands and coordinative unsaturation. Some of the CO lost during thermal treatment viadecarbonylation can be rebound to the coordinatively unsaturated cluster consisting of x = 3. In contrast, the clusters consisting of x = 1 and x = 2 both aggregate into large nanoparticles when treated under identical conditions. Clusters in which the calixarene phosphine ligand is replaced with a sterically less demanding PPh2Me ligand 6 lead to significantly less coordinative unsaturation upon thermal treatment. Altogether, these data support a mechanical model of accessibility in coordinatively unsaturated metal clusters in solution, which hinges on having at least three sterically bulky organic ligands per Ir4 core.

Graphical abstract: Stabilization of coordinatively unsaturated Ir4 clusters with bulky ligands: a comparative study of chemical and mechanical effects

Back to tab navigation

Supplementary files

Publication details

The article was received on 13 Sep 2011, accepted on 08 Nov 2011 and first published on 21 Dec 2011


Article type: Paper
DOI: 10.1039/C1DT11734C
Citation: Dalton Trans., 2012,41, 2091-2099

  •   Request permissions

    Stabilization of coordinatively unsaturated Ir4 clusters with bulky ligands: a comparative study of chemical and mechanical effects

    A. Okrut, O. Gazit, N. D. Silva, R. Nichiporuk, A. Solovyov and A. Katz, Dalton Trans., 2012, 41, 2091
    DOI: 10.1039/C1DT11734C

Search articles by author

Spotlight

Advertisements