ARTICLE DOI: 10.1002/zaac.201300287 Keggin-type Polyoxometalates [PW 11 O 39 MCl] 5– with Noble Metals (M = Rh and Ir): Novel Synthetic Entries and ESI-MS Directed Reactivity Screening Maxim N. Sokolov,* [a,b] Sergey A. Adonin, [a,b] Pavel L. Sinkevich, [b] Cristian Vicent, [c] Dmitry A. Mainichev, [a] and Vladimir P. Fedin [a,b] Keywords: Polyoxometalate; Rhodium; Iridium; Thiocyanate; Mass-spectrometry Abstract. A new synthetic entry to iridium Keggin-type polyoxomet- alate complexes from [PW 11 O 39 ] 7– and K 3 [IrCl 6 ] under harsh condi- tions is reported. The complex [PW 11 O 39 IrCl] 5– (1 5– ) featuring an IrCl functionality was obtained in high yield and characterized by NMR spectroscopic and ESI-MS techniques. The presence of Li + (3–4 M) is essential for a quantitative yield of 1 5– . The reactivities of 1 5– and its rhodium analogue [PW 11 O 39 RhCl] 5– in ligand substitution at the noble metal site were studied. Thiocyanate coordination success- fully yielded (Bu 4 N) 5 [PW 11 O 39 M(SCN)] [M = Rh (2a), Ir, (3a)]. In Introduction Polyoxometalates (POM) represent a huge family of polynu- clear metal-oxide complexes. This class of compounds is char- acterized by diversity of composition and structural types (up to nanoscale discrete polyoxoanions containing hundreds of metal atoms), which results in high variety of chemical proper- ties. [1] Research in this field is inspired both by fundamental interest and its importance for different applied areas such as catalysis, [2] molecular magnetism, [3] biochemical and biomedi- cal studies, [4] materials science and nanoscience, [5] etc., mak- ing it a “hot topic” of modern inorganic chemistry. Among the whole class of POM, chemistry of noble metal- containing complexes attracts a particular attention. [6] These compounds are expected to provide synergism from combining POM fragments and noble metal atoms, both known by their outstanding catalytic properties. This hypothesis is strongly supported by the known examples of their chemical behavior: for example, Ru-, Ir- and Rh-containing POMs demonstrate activity in oxidation of water [7] and various organic sub- * Prof. Dr. M. N. Sokolov Fax: +7-383-330-94-89 E-Mail: caesar@niic.nsc.ru [a] Nikolaev Institute of Inorganic Chemistry SB RAS 630090, Lavrentyeva St. 3 Novosibirsk, Russia [b] Novosibirsk State University 630090, Pirogova St. 2 Novosibirsk, Russia [c] Serveis Centrals d’Instrumentació Cientifica Universitat Jaume I Avda. Sos Baynat s/n 12071 Castelló, Spain Supporting information for this article is available on the WWW under http://dx.doi.org/10.1002/zaac.201300287 or from the au- thor. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim Z. Anorg. Allg. Chem. 2014, 640, (1), 122–127 122 both cases, the SCN ligands are coordinated by sulfur atoms, according to 13 C NMR and IR spectroscopic data. Gas-phase fragmentation reactions of compounds 2a and 3a were also investigated by collision-induced dissociation (CID) experiments. Reaction of [PW 11 O 39 RhCl] 5– with NaN 3 resulted in Cl – to OH – replacement ac- companied by the liberation of the RhCl fragment, whereas 1 5– proved unreactive with NaN 3 . Attempts to coordinate NO 2 – are adversely af- fected by competing noble metal excision with formation of free [PW 11 O 39 ] 7– . strates; [8] Ru-POM species may act as nitrogen atom transfer- ring agents. [9] At the moment, the most studied structural type of noble metal-containing POM complexes is based on monol- acunary Keggin anions [XW 11 O 39 ] n– (X = P, Si, B etc.). About half of them are ruthenium complexes: there have been pub- lished numerous papers on synthesis, characterization, cata- lytic and computational studies. [10] Complexes of all other noble metals remain significantly less studied. A series of Keggin-type POM containing rhodium was first reported by Pope et al. in 1997–1998. Apart from the expected product of single rhodium atom incorporation ([XW 11 O 39 Rh(L)] n– ) [11] it has been shown that [XW 11 O 39 ] n– (X = P, n = 7; X = Si, n = 8) can also react with Rh(II) carboxylate complexes [Rh 2 (O 2 CR) 4 ] to give [XW 11 O 39 Rh 2 (O 2 CR) 2 ] n– . [12] Reaction between [XW 11 O 39 ] n– (X = P, Si) and RhCl 3 in acetate buffer leads to direct C–H bond metalation of the acet- ate, yielding [XW 11 O 39 Rh(CH 2 COOH)] n– – the first organo- metallic derivatives of POM with sigma bonds between a tran- sition metal atom and carbon atom. It is noteworthy that this compound was produced under conditions highly unusual for organometallic chemistry (120 °C, aqueous solution). Our interest is focused on the preparation and reactivity studies of the Keggin-type [PW 11 O 39 MCl] 5– (M = Rh or Ir) POM. We have shown that [PW 11 O 39 RhCl] 5– also reacts with a number of organic substrates (boronic acids, organotin compounds etc.) to give water- and air-stable organometallic complexes with Rh–C σ bond [PW 11 O 39 Rh(R)] 5– (R = Me, Ph, Fc). [13] The first iridium-substituted Keggin-type complex, [PW 11 O 39 Ir(H 2 O)] 4– was obtained and the substitution behavior of the aqua ligand was studied by ESI-MS. [14] Herein we report (a) a new syn- thetic entry to access [PW 11 O 39 IrCl] 5– in high yield from con- ventional reagents; (b) some reactivity at the single M = Rh or