Complexes of electropositive metals with a hemilabile ether phosphine. Crystal structures of [TiCl4L], [FeL2(O3SCF3)2] and [Mo(CO)3L2][L = PhCH2P(CH2CH2OEt)2]

Abstract

New complexes containing some early transition metals with benzylbis(2-ethoxyethyl)phosphine (L) have been prepared. Reaction of this potentially hemilabile terdentate ligand with TiCl₄ afforded [TiCl₄L]1. The crystal structure shows the metal to have a distorted-octahedral geometry, where the ligand acts as a P,O-bonding chelate. Reaction of 1 with AgBF₄ and AgO₃SCF₃ afforded yellow oils which could not be fully characterised, but are tentatively assigned as [TiCl₃L][BF₄] and [TiCl₃L][O₃SCF₃] respectively. The reaction of [Cr(MeCN)₃(CO)₃] with L resulted in the formation of [Cr(CO)₄L₂]2 in poor yield. This complex can be prepared in high yield by the reaction of [Cr(MeCN)₂(CO)₄] with L. The reaction of [M(CO)₃(C₆H₃Me₃-2,4,6)](M = Mo or W) with L gave the complex fac-[Mo(CO)₃L₂]3 and [M(CO)₄L₂](M = Mo 4 or W 5) depending upon reaction conditions. The crystal structure of 3 shows the metal to have a distorted-octahedral geometry, where one L bonds as a P,O chelate and the other as a P-donor. ³¹P-{¹H} NMR spectroscopy indicates this complex to be fluxional in solution, where the two ligands readily interchange at high temperatures. The iron(II) complex [FeL₂(O₃SCF₃)₂]6 was prepared by the reaction of L and FeCl₂·4H₂O with AgO₃SCF₃. Its crystal structure shows the metal to have a distorted-octahedral geometry with trans ligands (through phosphorus and oxygen) and trans-co-ordinating triflates.