Ligand substitution in the osmium carbonyl cluster Os2(CO)8(μ3-SbPh)Os(CO)3(Cl)2: Towards derivatives of the osmostibine metalloligand

Derivatisation of the osmium carbonyl cluster Os-2(CO)(8)(mu(3)-SbPh)Os(CO)(3)(Cl)(2), 1, the precursor to the metalloligand Os-2(CO)(8)(mu-SbPh), 2, was explored as a route to derivatives of the latter. The reaction of 1 with PPh3 in different stoichiometries and under trimethylamine N-oxide activation in CH3CN led to mono-, di-, tri- and tetra-substitution by PPh3 and CH3CN. The first substitution occurred at the Os(CO)(3)Cl-2 "spike" and although subsequent substitution favoured CH3CN at the osmostibine moiety, the latter was not readily displaced by PPh3. Substitution at the "spike" also shut down release of the substituted osmostibine. The CH3CN-substituted osmostibine could, however, be generated in situ through the bis-acetonitrile derivative of 1 by conversion of the Os(CO)(2)(NCCH3)Cl-2 "spike" back into its removable Os(CO)(3)Cl-2 form through reaction with CO gas, and was then trapped with W(CO)(5)(NCCH3). (C) 2021 Elsevier B.V. All rights reserved.