Zinc(II) bis(O,O′-dialkyl dithiophosphates): complexation behaviour with pyridine and other multidentate nitrogen donor molecules. The crystal and molecular structures of the 1:1 complexes of bis(O,O′-di-isopropyl dithiophosphato)zinc(II) with pyridine, 2,2′-bipyridine, and 2,2′ : 6′,2″-terpyridine and of (1,11-diamino-3,6,9-triazaundecane)zinc(II) bis(O,O′-diethyl dithiophosphate)

Abstract

Fifteen complexes of zinc(II) bis(O,O′-dialkyl dithiophosphates), Zn[S₂P(OR)₂]₂(R = Et or Prⁱ), with a variety of nitrogen donor ligands, L [L = pyridine (py), pyridazine (pydz), ethylenediamine (en), 2,2′-bipyridine (bipy), N,N′-diethylethylenediamine (deen), 1,10-phenanthroline (phen), 2,2′ : 6′,2″-terpyridine (terpy), and 1,11 -diamino-3,6,9-triazaundecane (datau)], all of 1:1 stoicheiometry, have been synthesised. The crystal structures of four, Zn[S₂P(OPrⁱ)₂]₂·L[L = py (1), bipy (2), or terpy (3)] and the datau complex of Zn[S₂P(OEt)₂]₂, (4), have been determined by the heavy-atom method with intensity data collected by a four-circle diffractometer using Mo-K_α radiation (λ= 0.7107 Å). Crystals of Zn[S₂P(OPrⁱ)₂]₂·py are monoclinic, space group P2₁/n, with a= 16.289(3), b= 8.331(2), c= 21.316(3)Å, β= 99.56(2)°, Z= 4, final R= 0.0499 from 3 558 independent reflections. Crystals of Zn[S₂P(OPrⁱ)₂]₂·bipy are triclinic, space group P, with a= 9.020(2), b= 8.502(2), c= 21.267(2)Å, α= 83.1 2(2), β= 97.96(2), γ= 103.46(2)°, Z= 2, final R= 0.0988 from 2 463 independent reflections. Crystals of Zn[S₂P(OPrⁱ)₂]₂·terpy are monoclinic, space group P2₁/n, with a= 8.847(2), b= 25.21 5(2), c= 15.740(2)Å, β= 90.74(2)°, U= 4, final R= 0.0988 from 3 959 independent reflections. Crystals of [Zn(datau)][S₂P(OEt)₂]₂ are monoclinic, space group P2₁/c, with a= 8.1 83(2), b= 25.161(2), c= 14.981(2)Å, β= 99.72(2)°, z= 4, final R= 0.0616 from 3 068 independent reflections. The complexes (1)–(3) exhibit molecular structures in which the nitrogen donor ligand co-ordinates to the zinc atom. In (1), one S₂P(OPrⁱ)₂ ligand chelates the zinc almost symmetrically [Zn–S 2.352(2), 2.496(2)Å], whilst the other is strongly anisobidentate [Zn–S 2.273(2), 3.041(2)Å]. The pyridine nitrogen atom completes a distorted tetrahedral geometry about zinc [Zn–N 2.028(4)Å]. The zinc atom in (2) is chelated by the ligand [Zn–N 2.09(1), 2.14(1)Å], with one anisobidentate [Zn–S 2.365(5), 2.711(4)Å] and one unidentate [Zn–S 2.327(4), 3.822(5)Å] S₂P(OPrⁱ)₂ attached to the metal. Both S₂P(OPrⁱ)₂ groups are unidentate in (3)[Zn–S 2.334(4), 3.523(5)Å(ligand 1); 2.339(3), 3.977(5)Å(ligand 2)], with all three nitrogen atoms within bonding distance of the metal [Zn–N 2.21(1), 2.12(1), 2.17(1)Å]. The geometries at zinc in both (2) and (3) are irregular. Complexation of bis(O,O′-diethyl dithiophosphato)zinc(II) by datau results in the ionisation of both S₂P(OEt)₂ groups, and crystals of the complex comprise [Zn(datau)]²⁺ cations and S₂P(OEt)₂^– anions [closest Zn ⋯ S contact 4.153(3)Å]. All five of the nitrogen atoms of the datau ligand are bonded to the zinc in the cation to give a distorted trigonal-bipyramidal geometry [Zn–N 2.047(6)–2.191(6)Å; N_eq–Zn–N_eq angles 117.4(3),115.5(3),126.8(3)°; N_ax–Zn–N_ax angle 161.3(3)°]. The bonding parameters of the S₂P(OR)₂ groups exhibit small variations with the change in bonding environment in complexes (1)–(4). Principal ligand i.r. vibration data are also reported for the complexes and related compounds, and are remarkably insensitive as a probe for the mode of bonding.