Formation of an Unsymmetrical Pt−Ir Tetraalkynyl Complex and Investigation into Subsequent Construction of Multimetallic Systems

Abstract

The reactions between [Pt(C⋮CR)4]2- (R = Ph, t-Bu, SiMe3) and [Ir(μ-Cl)(COD)]2 have been studied, but the formation of an unsymmetrical heterobinuclear complex (NBu4)[(COD)Ir(μ-1κC α:η2-C⋮CSiMe3)(μ-2κC α:η2-C⋮CSiMe3)Pt(C≡CSiMe3)2], (NBu4)[{Ir−Pt}(C⋮CSiMe3)2], 1 was only observed with the homoleptic species [Pt(C⋮CSiMe3)4]2-. Complex 1 exhibits in the solid state a bent σ,π double-alkynyl bridging system, which is formed through a migration of one σ-alkynyl group from platinum to iridium. The stability of the remaining Pt-acetylide σ-bonds in 1 and its possible application in the assembly of multimetallic compounds containing the {Ir−Pt} “pincer” unit has been investigated. Treatment of (NBu4)[{Ir−Pt}(C⋮CSiMe3)2] (1) with neutral [cis-M(C6F5)2(THF)2] (THF = tetrahydrofuran, M = Pt, Pd) or cationic [Rh(COD)(acetone) x ]+ or [Pd(η3-C3H5)S x ]+ solvento species (the latter generated “in situ”) leads to very unusual anionic (NBu4)[{Ir−Pt}(μ-2κC α:η2-C⋮CSiMe3)2M(C6F5)2] (M = Pt, 2; Pd, 3) or neutral heterotrimetallic complexes [{Ir−Pt-}(μ-2κC α:η2-C⋮CSiMe3)2Rh+(COD)] (4) and [{Ir−Pt-}(μ-2κC α:η2-C⋮CSiMe3)2Pd+(η3-C3H5)] (5), respectively. The molecular structure of 4 confirms the presence of a formally heterotrimetallic zwitterion [(COD)Ir(μ-1κC α:η2-C⋮CSiMe3)(μ-2κC α:η2-C⋮CSiMe3)Pt-(μ-2κC α:η2-C⋮CSiMe3)2Rh+(COD)], formed by the binuclear anionic fragment [(COD)Ir(μ-1κC α:η2-C⋮CSiMe3)(μ-2κC α:η2-C⋮CSiMe3)Pt(C⋮CSiMe3)2]-, which in its turn acts as a chelating dimetallo bidentate ligand toward the cationic [Rh(COD)]+ unit. However, a similar neutralization reaction of 1 with 1 equiv of AgClO4 produces an unusual hexanuclear trimetallic complex [(η2-{Ir−Pt}(C⋮CSiMe3)2)2Ag2] (6), in which the heterobimetallic diyne anionic substrate [{Ir−Pt}(C⋮CSiMe3)2]- acts as a μ-η2:η2 bridging ligand of two different silver(I) centers.

Ethynyltolan Platinum Complexes with (Arylalkynyl)phosphane Ligands

“…The approximate calculated activation energy is similar for the ortho-fluorine (∆G ‡ 273K = 50.01 kJ mol -1 ) and for the meta-fluorine atoms (∆G ‡ 268K = 50.63 kJ mol -1 ). The equivalence of the o-F atoms (and the m-F ones as well) at high temperature can be explained either by assuming a rapid rotation of the C 6 F 5 groups around the Pt-C bonds, as previously suggested in other systems with "cis-Pt(C 6 F 5 ) 2 " fragments, [79][80][81][82][83] or by a fast intramolecular exchange of the "cis-Pt(C 6 F 5 ) 2 " unit below and above the platinum coordination plane. This second possibility has been suggested in related derivatives [3,57,84] stabilized by a double alkynyl bridging system and assumes the existence of a formal inversion of the PtC 4 Pt central skeleton, which could take place via intermediate species with one or two µ-η 1 -bonded alkynyl ligands.…”

Novel Luminescent Mixed‐Metal PtTl‐Alkynyl‐Based Complexes: The Role of the Alkynyl Substituent in Metallophilic and η2(π⋅⋅⋅Tl)‐Bonding Interactions

“…[71] and can tentatively be related to the small h 2 -covalent contribution to the Tl I Àacetylenic bonding interactions, the electrostatic interaction between the platinate entities and the Tl I centers probably being the driving force and the main contribution to the stability of these species. Interaction of naked metal (Ni 0 [74,75] and Pt 0 [76] ), cations (Cu I , Ag I ) [77] or M'Ln fragments [77,78] with metal-acetylenic entities LnMCCR usually causes a shift of the n(CC) absorption to lower wavenumbers. The size of the Dñ shift relative to the precursor is related to the extent of the interaction with the M À C(a)C(b) À R entity.…”

Use of the MnCC system in organometallic and organic synthesis

“…In contrast, the substitution of CO by PPh 3 in 78 (reaction (40)) resulted in C 3 O migration from Pt to the vinylidene C 1 atom, the Pt Pt bond splitting and formation of the unusual complex 79 [110]. According to the X-ray study, the benzylideneketene [PhC 2 H C 1 C 3 O] ligand in 79 serves as an 3 -allylic ligand on one of the Pt atoms, and forms a C 1 Pt -bond with the second Pt.…”

“…The vinylidene carbonylation reactions do not have common features. At the same time, carbonylation of carbene and carbyne (intra-and intermolecular) resulting in the formation of free ketenes, 2 -ketene, 1 -and 2 -ketenyl ligands, is well-known and has been intensively investigated [5b, [110][111][112]. Organometallic compounds participating in similar reactions are considered as models of probable intermediates in the Fischer-Tropsch process [41a,113].…”