Synthesis and X-ray structure determination of the Ir–Ag–Ir donor–acceptor metal–metal bonded complex [{(η⁵-C₅Me₅)(CO)₂Ir}₂Ag][BF₄]

Abstract

. Can. J. Chem. 67, 1832 (1989). The title complex (2) has been synthesized from the reaction of ( q 5 -~5~e 5 ) 1 r (~0 ) 2(1) with AgBF4. Complex 2 crystallizes in the monoclinic space group P21/c with a = 12.355(2) A, b = 13.713(2) A, c = 16.672(3) A, P = 97.70(1)", and Z = 4.The structure was solved by using 3131 observed reflections ( I 2 2.5u(I)) in the range 0" < 20 < 50" to final discrepancy indices of RF = 0.032 and RWF = 0.038. The cation may be described as consisting of two molecules of 1 bound to Ag+ by donor-acceptor Ir + Ag bonds. The Ir-Ag-Ir skeleton is nearly linear (angle 173.67(6)"). The Ag-Ir bond lengths are equal (2.659(1) A), and the two molecules of 1 are disposed mutually trans, to give the cation approximate (noncrystallographic) C2h symmetry.Key words: complex, iridium, silver, metal-metal bond, X-ray, crystal, structure, carbonyl, donor-acceptor, pentamethylcyclopentadienyl. Mots cle's : complexe, iridium, argent, liaison metal-metal, rayons X, cristal, structure, carbonyle, donneur-accepteur, pentamtthylcyclopentaditnyle.[Traduit par la revue] I IntroductionThere is considerable current interest in heteronuclear metalmetal bonded complexes (I), and one subset includes those i which can be formulated in a simplistic way to contain a heteropolar (or dative), metal-metal bond that is not "supported by the presence of concurrent bridging ligands (i.e., M -+ M ' ) (see, for example, ref. 2). Recently, two X-ray structures have been published involving complexes with unbridged Ir -+ Ag bonds (3), and in this paper we describe the synthesis and X-ray structure of a further example, [{(r15-C5Mes)(~~)2~r)2~g]- [BFdI (2). Results Synthesis and characterizationThe addition of AgBF, to the iridium complex (r15-C5Me5)- (1) itself. In the 'H NMR spectrum, the r 1 5 -C 5~e 5 resonance is at 6 2.37 ppm, shifted downfield by comparison with 1. Both effects are consistent with the withdrawal of electron density from Ir as a result of the formation of formal Ir -+ Ag+ donor-acceptor bonds.The fast-atom-bombardment (FAB) technique employing a thioglycerol matrix and xenon bombardment gave an excellent mass spectrum (FABMS) of the parent cation ( Fig. 1) X-ray structureThe structure consists of discrete [ { ( r 1 5 -~5~e 5 ) (~~) 2 1 r ) 2 cations and [BF4]-anions with no unusually short interionic contacts. A view of the structure of the cation is given in Fig. 2. The cation features two crystallographically distinct ( q 5 -C 5~e 5 ) I r ( C 0 ) 2 moieties bound to Ag+ such that the Can. J. Chem. Downloaded from www.nrcresearchpress.com by 54.245.55.244 on 05/11/18For personal use only.

Chemical Redox Agents for Organometallic Chemistry

“…First, silver(I) salts are efficient halide abstraction reagents. , Second, they may bind to the oxygen, sulfur {where the reaction of the thiocarbonyl [W(CO)(CS)(dppe) 2 ], to give [Ag{(μ-SC)W(CO)(dppe) 2 } 2 ] + , contrasts with the simple oxidation of [W(CO) 2 (dppe) 2 ] to [W(CO) 2 (dppe) 2 ] + 61 }, or nitrogen 52 atoms of coordinated ligands. Third, there are now many examples of the formation of Ag−metal bonds; ,− particularly impressive are recent studies of cluster formation by the sequential condensation of Ag + and [Fe(CO) 4 ] 2- ions, culminating in the one-electron oxidation of [Ag 13 {Fe(CO) 4 } 8 ] 4- to [Ag 13 {Fe(CO) 4 } 8 ] 3- . In many of these alternative reaction modes, the substrate is redox-active with a formal potential negative of that of silver(I); under the experimental conditions described, coordination is prefered even though one-electron transfer is exergonic.…”

Unprecedented stabilisation of the Ag22+-ion by two hydrido-iridium(iii) complexes

“…The Ag-O bond length of 239.2 (7) pm is in good agreement with that found in [Ag 3 (OSO 2 CF 3 ) 3 (PPh 3 ) 3 ]. 15 The iridium-silver distances are 291.07 (11) 6 A significantly shorter bond length of 265.9(1) pm was determined for a direct Ag-Ir bond interaction in [{(h 5 -C 5 Me 5 )(CO) 2 Ir} 2 Ag][BF 4 ], 5 which is close to the sum of covalent radii of iridium and silver (261 pm). 16 The hydride ligands could not be positioned on the basis of the data obtained by single crystal diffraction methods, due to the absence of rest electron density.…”

“…So far, the shortest contact of 267 pm was found in the bis[1,3-diphenyltriazenido-silver(I)]. 4 Ag + -ions are known to form adducts with transition-metal fragments, such as in [{(h 5 Addition of 1 equiv. of AgOSO 2 CF 3 to the iridium(III) complex (h 5 -C 5 Me 5 )(Ph 3 P)Ir(OEt)(H) 9 (1) in dichloromethane solution readily affords [{(h 5 -C 5 Me 5 )(Ph 3 P)Ir(m-H) 2 } 2 Ag 2 (O-SO 2 CF 3 ) 2 ] (2), which is isolated as a greenish-yellow crystalline solid in 85% yield (Scheme 1).…”

Silver(i) and thallium(i) cations as unsupported bridges between two metal bases

“…29 While Ag + cations have served as unsupported bridges between monovalent Group 9 metal-ligand fragments (e.g. C, Scheme 1) [17][18][19][20]37 and other low-valent species, when Group 10 metal bases are concerned, only examples containing divalent Pt II L n fragments are known. [38][39][40] It is somewhat counterintuitive that no examples exist in which more electron-rich zerovalent Pt 0 L n fragments act as Lewis bases to Ag + .…”

“…15,16 However, halfsandwich compounds were used for isolation of unsupported transition metal-silver bonds in the complex [{(Z 5 -C 5 H 5 )(OC)-(Ph 3 P)Rh} 2 (m-Ag)] + (C) (Scheme 1). [17][18][19][20] Metallocryptates are a class of inorganic cage complexes that are able to encapsulate a variety of metal ions via coordination either through strong Lewis base interactions of the donor groups of the ligands or through metallophilic interactions. 21 In particular, the groups of Balch and Catalano investigated M-M 0 metallophilic interactions between late transition metals and guest metal ions, for example with iridium complexes of the form [(OC) 2 X 2 (m-dpma) 2 Ir 2 (m-Tl)] + (D) and platinum compound [(m-P 2 phen) 3 Pt 2 (m-Tl)] (P 2 phen = 2,9-bis(diphenylphosphino)-1,10-phenanthroline).…”