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-[Rev(NMe)(py)2(PPh3)(OEt)Cl]+ 1, cis-[Rev(NMe)(py)2(PPh3)(OEt)Cl]+ 2, [Rev(NMe)(py)3(OEt)Cl]+ 3 and [Rev(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, [Rev(N)(py)2(PPh3)2Cl]ClO 4 5 and [Rev(O)2(py)3(PPh3)]ClO4 6 all show low energy (dxy) → (dπ*) electronic absorption bands at 400-500 nm.