Synthesis of Binuclear Complexes Bound in an Enlarged Tetraphosphamacrocycle: Two Diphosphine Metal Units Linked in Front-to-Front Style

A large-hole tetraphosphamacrocycle 2, with four phosphorus centers separated at the corners of a 3.7 Å wide and 9.7 Å long rectangle, was synthesized by a stepwise cyclization reaction between PCl-bridged [1.1]ferrocenophane and bisphenol A in a 2:2 ratio. The macrocycle 2 could incorporate two Ag⁺ or Pt⁰ fragments in the hole to provide binuclear complexes, which were identified as μ-2-[Ag(NCMe)₂]₂(BF₄)₂ (3) and μ-2-[Pt(PhCCPh)]₂ (5), respectively, using X-ray and spectroscopic analysis. The X-ray structure of 3 demonstrates that the macrocycle 2 serves as a framework in which two diphosphine silver units are aligned in a front-to-front style, while that of 5 indicates that 2 can also bind two bulky Pt(PhCCPh) fragments by the flexible change of its conformation.