High-Valent Pyrazolate-Bridged Platinum Complexes: A Joint Experimental and Theoretical Study

Abstract

Complexes [{Pt(C^C*)(μ-pz)} 2 ] (HC^C* A = 1-(4-(ethoxycarbonyl)phenyl)-3-methyl-1 H -imidazol-2-ylidene 1a , HC^C* B = 1-phenyl-3-methyl-1 H -imidazol-2-ylidene 1b ) react with methyl iodide (MeI) at room temperature in the dark to give compounds [{Pt IV (C^C*)Me(μ-pz)} 2 (μ-I)]I (C^C* A 2a , C^C* B 2b ). The reaction of 1a with benzyl bromide (BnBr) in the same conditions afforded [Br(C^C* A )Pt III (μ-pz) 2 Pt III (C^C* A )Bn] ( 5a ), which by heating in BnBr(l) became [{Pt IV (C^C* A )Bn(μ-pz)} 2 (μ-Br)]Br ( 6a ). Experimental investigations and density functional theory (DFT) calculations on the mechanisms of these reactions from 1a revealed that they follow a S N 2 pathway in the two steps of the double oxidative addition (OA). Based on the DFT investigations, species such as [(C^C* A )Pt III (μ-pz) 2 Pt III (C^C* A )R]X (RX = MeI Int-Me , BnBr Int-Bn ) and [(C^C* A )Pt II (μ-pz) 2 Pt IV (C^C* A )(R)X] (RX = MeI Int′-Me , BnBr Int′-Bn ) were proposed as intermediates for the first and the second OA reactions, respectively. In order to put the mechanisms on firmer grounds, Int-Me was prepared as [(C^C* A )Pt III (μ-pz) 2 Pt III (C^C* A )Me]BF 4 ( 3a′ ) and used to get [I(C^C* A )Pt III (μ-pz) 2 Pt III (C^C* A )Me]( 4a ), [(C^C* A )Pt II (μ-pz) 2 Pt IV (C^C* A )(Me)I]( Int′-Me ), and [{Pt IV (C^C*)Me(μ-pz)} 2 (μ-I)]BF 4 ( 2a′ ). The single-crystal X-ray structures of 2a , 2b , 3a′ , and 5a along with the mono- and bi-dimensional 1 H and 195 ...

Molecular Flytraps Held Together by Platinum–Platinum Intermetallic Bonds

“…Formal intermetallic bonds are generally formed by fine‐tuning the oxidation states of two (not necessarily identical) metal centers to form a bond that can have substantial covalent character [22, 23] . In most cases, this is facilitated by the use of bridging ligands that bring the two metals close together in space prior to the formation of a metal‐metal bond [24–27] . The use of bridging ligands also contributes to the overall stability of the structure by supporting the intermetallic bond with covalent bonds within the ligand.…”

“…[22,23] In most cases, this is facilitated by the use of bridging ligands that bring the two metals close together in space prior to the formation of a metal-metal bond. [24][25][26][27] The use of bridging ligands also contributes to the overall stability of the structure by supporting the intermetallic bond with covalent bonds within the ligand. Metal complexes with unsupported metal-metal bonds are also known, but they are much less common in the literature.…”

N,C,N-Pincers in Platinum Bimetallic Complexes: Influence of the Pincer and Bridging Ligands on the Metal–Metal Bond and the Photophysical Properties

“…The first type is based on two platinum subunits, which contain an orthometalated phenyl- N -heterocycle, linked by a double bridge formed by two bidentate ligands resulting from the deprotonation of molecules type: thiazolthiol, quinolinyl- and pyridylthiol, hydroxyquinoline, hydroxypyridine, pyrazol, triazole, and terminal alkyne . The second one is constructed in a similar way, changing the N -donor heterocycle by an NHC group and using pyrazolate or formamidinate as bridges. The separation between the platinum centers is usually governed by the bridging ligands, giving rise to two class of structures: rigid and flexible.…”