doi:10.1039/d0dt02713hengParker, A.Lamata, P.Viguri, F.Rodríguez, R.López, J.A.Lahoz, F.J.García-Orduña, P.Carmona, D.Half-sandwich complexes of osmium containing guanidine-derived ligandsART-2020-120565Pyridinyl- and phosphano-guanidino complexes of formula [(¿6-p-cymene)OsCl(H2L)][SbF6] (cymene = MeC6H4iPr; H2L = N, N'-bis(p-Tolyl)-N''-(2-pyridinylmethyl)guanidine, H2L1 (1) and N, N'-bis(p-Tolyl)-N''-(2-diphenylphosphanoethyl)guanidine, H2L2 (2)) have been prepared from the dimer [{(¿6-p-cymene)OsCl}2(µ-Cl)2] and H2L in the presence of NaSbF6. Treatment of complex 2 with HCl renders the phosphano-guanidinium complex [(¿6-p-cymene)OsCl2(H3L2)][SbF6] (3). Compounds 1 and 2 react with AgSbF6 rendering the cationic aqua complexes [(¿6-p-cymene)Os(H2L)(OH2)][SbF6]2 (H2L = H2L1 (4), H2L2 (5)). Addition of monodentate ligands L to compound 4 affords complexes of formula [(¿6-p-cymene)Os(H2L1)L][SbF6]2 (L = py (6), 4-(NHMe)py (7), CO (8), P(OMe)3 (9)). Treatment of complexes 4 and 5 with NaHCO3 renders the monocationic complexes [(¿6-p-cymene)Os(¿3N, N', N''-HL1)][SbF6] (10) and [(¿6-p-cymene)Os(¿3N, N', P-HL2)][SbF6] (11), respectively, in which the HL ligand adopts a fac-¿3 coordination mode. The new complexes have been characterised by analytical and spectroscopic means, including the determination of the crystal structures of the compounds 1-4, 6, 8, and 11, by X-ray diffractometric methods. The phosphano-guanidino complexes 2 and 5 exhibit a temperature dependent fluxional process in solution. The new 18 electron complexes 1, 2, 6, and 8-10 are active catalysts for the Friedel-Crafts reaction between trans-ß-nitrostyrene and N-methyl-2-methylindole. Conversions greater than 90% were obtained. Proton NMR studies support a mechanism involving the Brønsted-acid activation of trans-ß-nitrostyrene through the NH functionalities of the coordinated guanidine ligands.2020http://zaguan.unizar.es/record/13129810.1039/d0dt02713hhttp://zaguan.unizar.es/record/131298oai:zaguan.unizar.es:131298info:eu-repo/grantAgreement/ES/MICINN/CTQ2017-83421-Pinfo:eu-repo/grantAgreement/ES/MICINN/CTQ2018-095561-BI00info:eu-repo/grantAgreement/ES/MINECO/RYC-2013-13800Dalton Transactions 49, 39 (2020), 13601-13617All rights reservedhttp://www.europeana.eu/rights/rr-f/info:eu-repo/semantics/openAccess