Synthesis, spectroscopy and electrochemistry of rhenium(V) imido complexes of pyridine and a comparative study with oxo and nitrido analogues; crystal structure of [Rev(NMe)(py)3(OEt)Cl]ClO4(py = pyridine)

Abstract

A series of novel cationic methylimidorhenium(V) complexes, trans-[Re^v(NMe)(py)₂(PPh₃)(OEt)Cl]⁺1, cis-[Re^v(NMe)(py)₂(PPh₃)(OEt)Cl]⁺2, [Re^v(NMe)(py)₃(OEt)Cl]⁺3 and [Re^v(NMe)(4Me-py)₂(PPh₃)(OEt)Cl]⁺4(py = pyridine) have been synthesized as their perchlorate salts. The crystal structure of 3 has been determined:monoclinic, space group P2₁/c, a= 10.223(4), b= 17.663(2), c= 25.222(3)Å, β= 90.70(2)° and Z= 4. The structure of 3 reveled an almost linear Re–N–Me geometry, consistent with a four-electron donor formulation for the methylimido unit. Spectroscopic studies on 1–4 and their nitrido and oxo analogues, [Re^v(N)(py)₂(PPh₃)₂Cl]ClO₄5 and [Re^v(O)₂(py)₃(PPh₃)]ClO₄6 all show low energy (d_xy)→(d_π·) electronic absorption bands at 400–500 nm.