Bis-ortho-chelated Diaminoaryl Platinum Compounds with σ-Acetylene Substituents. Investigations into Their Stability and Subsequent Construction of Multimetallic Systems. The Crystal Structure of [(μ²-[(η²-NCN)Pt(η¹-CO)C⋮CSiMe₃])Co₂(CO)₆] (NCN = 2,6-Bis[(dimethylamino)methyl]phenyl)

Abstract

A series of related platinum σ-acetylide complexes {Pt}CtCR ({Pt} ) [Pt(C 6 H 3 {Me 2 NCH 2 } 2 -2,6)] + ) were prepared by reacting lithium acetylides with {Pt}Cl (1) in order to investigate the stability of the Pt-acetylide σ-bond and their possible application in the assembly of multimetallic compounds containing the {Pt} "pincer" unit. This may be achieved by η 2coordination of the acetylide or by incorporating a second ligating site in the acetylide anion. Both of these approaches are demonstrated herein. {Pt}CtCSiMe 3 (2) was reacted with [M][BF 4 ] ([M] ) [Cu(NCMe) 4 ], Ag) and different forms of Cu(I) halides. Only with the former was the formation of stable π-coordinated M(I) compounds observed. [(η 2 -[{Pt}CtCSiMe 3 ] 2 )-Cu][BF 4 ] exhibits η 2 -coordination of both acetylenic units to a formal Cu(I) metal center, thus forming a heterotrimetallic compound. In the presence of halide ions, 2 undergoes cleavage of the Pt-CtC σ-bond with concomitant formation of {Pt}X (X ) Cl or I). The reaction of 2 with Co 2 (CO) 8 leads via π-coordination to the formation of a trimetallic dicobaltatetrahedrane. The structure of [(µ 2 -[(η 2 -NCN)Pt(η 1 -CO)CtCSiMe 3 ])Co 2 (CO) 6 ] in the solid state shows that one ortho-CH 2 NMe 2 substituent of the NCN ligand is no longer coordinated to the Pt metal center. Instead, a CO ligand coordinates trans to the Pt-N bond, yielding a metal center with four different ligand donor atoms. Attempts to obtain related Pt(IV) acetylides by reaction of 2 with CuCl 2 resulted in the formation of {Pt}Cl 3 , [CuX] n , and [CuCtCSiMe 3 ] n . The reaction with I 2 gave neither a Pt(IV) diiodide nor a Pt(II) η 1 -Ι 2 complex, but instead led to Pt-C(acetylide) bond cleavage and formation of {Pt}I and ICtCSiMe 3 . The reaction of {Pt}CtCC 6 H 4 CN-4 with [{Pt}H 2 O][BF 4 ] and {Ru}NtN{Ru} ({Ru} ) [RuCl 2 (C 5 H 3 N{CH 2 NMe 2 } 2 -2,6)]) gives air-stable well-defined bimetallic compounds.In contrast, the reaction of {Pt}CtCC 6 H 4 CN-4 with [AuCl 3 ] 2 or Au(CO)Cl leads to the formation of a gold mirror, NCC 6 H 4 (CtC) 2 C 6 H 4 CN, and {Pt}Cl 3 or {Pt}Cl, respectively. Cyclic voltammetry studies with representative Pt-acetylides show irreversible oxidative processes which are shifted to a more negative potential upon substitution of Cl by acetylide.

Mixed Metal Acetylides: The PtII Aryl Acetylide “[PtC6H2(CH2NMe2)22,6-(C≡C)-4]” as a Connective Fragment

“…This mirrors results obtained with the Pt monochloride [PtCl(C 6 H 3 {CH 2 NMe 2 } 2 -2,6)]. [16] The carbon atoms of the Pt-bound acetylenic unit exhibit signals at chemical shifts that are comparable to those of other known Ptacetylides. [4] Due to the low intensity of the C ipso atom signals of the NCN unit [C(1)] and the platinum bonded acetylide ligands, 195 Pt-C satellites could not be detected.…”

“…These values lie in the range reported for this type of vibration. [4,16] In the 1 H NMR spectra of compounds 2؊5 and 7؊9, a common general feature can be observed with respect to the chemical shift of the signals of the CH 2 NMe 2 units. A comparison with the chloridesubstituted Pt compounds 1 and 6 reveals that upon substitution of Cl by an acetylide, the singlet of the NMe 2 unit experiences a slight but diagnostic low-field shift, as does the resonance signal of the benzylic protons (Table 1).…”

“…The formation of Pt monoacetylides containing the anionic potentially tridentate NCN ''pincer'' ligand (NCN ϭ [C 6 H 3 (CH 2 NMe 2 ) 2 -2,6] Ϫ ) has been previously reported. [16] Results and Discussion…”

“…We tested this different approach because Cu I catalysed reactions for the formation of Pt monoacetylides of this type have failed. [16] The deprotection of the acetylenic unit of compounds 1؊4 yields the mono-substituted acetylenes 7؊9 (Equation 2). [15] The compound HCϵC{Pt}Cl (6) has been described elsewhere.…”

Ruthenium‐to‐Platinum Interactions in η6,η1 NCN‐Pincer Arene Heterobimetallic Complexes: An Experimental and Theoretical Study

“…Cyclic voltammetry in acetonitrile showed, for each NCN-pincer platinum-containing complex, an electrochemically irreversible oxidation wave, which was shown to correspond to a Pt II Ǟ Pt IV oxidation. [38][39][40] These oxidation potentials are also reported in Table 2. Although the measured oxidation potentials do not correspond to an electrochemically reversible process, their evolution fully confirms the trends observed by 195 Pt NMR spectroscopy.…”