Tri(pyridylmethyl)phosphine: The Elusive Congener of TPA Shows Surprisingly Different Coordination Behavior
journal contributionposted on 17.06.2013, 00:00 by Christopher J. Whiteoak, James D. Nobbs, Evgeny Kiryushchenkov, Sandro Pagano, Andrew J.P. White, George J.P. Britovsek
Tri(pyridylmethyl)phosphine (TPPh), the remarkably elusive congener of tri(pyridylmethyl)amine (TPA), has been prepared, as well as the relative tri(N-methyl-pyridylamino)phosphine (TPAMP). The coordination properties of these new ligands have been evaluated for chromium(III), iron(II), and ruthenium(II) complexes and compared with the related TPA complexes. In all cases, a different coordination behavior has been observed whereby TPPh and TPAMP always act as tridentate ligands. A chromium(III) complex [Cr(TPPh)Cl3] has been prepared, which has shown low ethylene oligomerization activity. Octahedral low spin iron(II) complexes [Fe(TPPh)2]2+ and [Fe(TPAMP)2]2+ were obtained with two ligands bound to the metal center. Ruthenium(II) chloro complexes of TPA and TPPh undergo ligand exchange reactions in acetonitrile, and the ruthenium(II) complex [Ru(MeCN)2(TPA)]2+ can be oxidized by m-CPBA in acetonitrile to give a transient ruthenium(IV) oxo complex [Ru(O)(MeCN)(TPA)]2+. Attempts to generate high valent ruthenium(IV) oxo TPPh or TPAMP complexes could not be achieved, probably due to insufficient stabilization by these strong field ligands.