Rotaxanes Derived from Dimetallic Polyynediyl Complexes: Extended Axles and Expanded Macrocycles

A new 35-membered macrocycle <b>3b</b> derived from 1,10-phenanthroline and two 2,9-<i>p</i>-C₆H₄O­(CH₂)₆O substituents that tether a 2,7-naphthdiyl moiety is synthesized. CuI complexes of <b>3b</b> and a previously reported analog in which the naphthdiyl is replaced by a <i>m</i>-C₆H₄ group (<b>3a</b>) are reacted with the hexatriynyl complex <i>trans</i>-(C₆F₅)­(<i>p</i>-tol₃P)₂Pt­(CC)₃H (1.0:2.5 mol ratios) in the presence of K₂CO₃ (4.0–5.0 equiv) and I₂ (1.3–1.8 equiv) in THF at 55 °C. Workups afford the rotaxanes <b>5·3a</b> and <b>5·3b</b> (45–23%), in which the macrocycles are threaded by the sp carbon chain of the diplatinum dodecahexaynediyl complex <i>trans,trans</i>-(C₆F₅)­(<i>p</i>-tol₃P)₂Pt­(CC)₆Pt­(P<i>p</i>-tol₃)₂(C₆F₅) (<b>5</b>), which is also obtained as a byproduct. The yields of <b>5·3a</b> and <b>5·3b</b> are much higher than in the case with octatetraynediyl (C₈) analogs, and their spectroscopic properties and crystal structures are analyzed in detail, especially with reference to recent DFT studies

Mechanism of Me–Re Bond Addition to Platinum(II) and Dioxygen Activation by the Resulting Pt–Re Bimetallic Center

Unusual cis-oxidative addition of methyltrioxorhenium (MTO) to [PtMe₂(bpy)], (bpy = 2,2′-bipyridine) (<b>1</b>) is described. Addition of MTO to <b>1</b> first gives the Lewis acid–base adduct [(bpy)­Me₂Pt–Re­(Me)­(O)₃] (<b>2</b>) and subsequently affords the oxidative addition product [(bpy)­Me₃PtReO₃] (<b>3</b>). All complexes <b>1</b>, MTO, <b>2</b>, and <b>3</b> are in equilibrium in solution. The structure of <b>2</b> was confirmed by X-ray crystallography, and its dissociation constant in solution is 0.87 M. The structure of <b>3</b> was confirmed by extended X-ray absorption fine structure and X-ray absorption near-edge structure in tandem with one- and two-dimensional NMR spectroscopy augmented by deuterium and ¹³C isotope-labeling studies. Kinetics of formation of compound <b>3</b> revealed saturation kinetics dependence on [MTO] and first-order in [Pt], complying with prior equilibrium formation of <b>2</b> with oxidative addition of Me–Re being the rate-determining step. Exposure of <b>3</b> to molecular oxygen or air resulted in the insertion of an oxygen atom into the platinum–rhenium bond forming [(bpy)­Me₃PtOReO₃] (<b>4</b>) as final product. Density functional theory analysis on oxygen insertion pathways leading to complex <b>4</b>, merited on the basis of Russell oxidation pathway, revealed the involvement of rhenium peroxo species