Bis(phosphinoselenoic amides) as versatile chelating ligands for alkaline earth metal (Mg, Ca, Sr and Ba) complexes: syntheses, structure and ε-caprolactone polymerisation.
We report here a series of heavier alkaline earth metal complexes with N,N'-(ethane-1,2-diyl)bis(P,P-diphenylphosphinoselenoic amide) using two synthetic routes. In the first route, the heavier alkaline earth metal bis(trimethylsilyl)amides [M{N(SiMe3)2}2(THF)n] (M = Ca, Sr, Ba), when treated with phosphinoselenoic amine [Ph2P(Se)NHCH2CH2NHPPh2(Se)] (1), afforded the corresponding alkaline earth metal complexes of the composition [(THF)3M{Ph2P(Se)NCH2CH2NPPh2(Se)}] [M = Ca (2), Sr (3), Ba (4)]. The metal complexes 2-4 were also obtained from a one-pot reaction, where potassium phosphinoselenoic amide was generated in situ by the reaction of compound 1 and [KN(SiMe3)2], followed by the addition of the respective metal diiodides in THF at room temperature. The magnesium complex [(THF)3Mg{Ph2P(Se)NCH2CH2NPPh2(Se)}] (5) was also prepared. The solid-state structures of alkaline earth metal complexes 2-5 were established by single crystal X-ray diffraction analysis. In the solid state, all the metal complexes are monomeric but in complexes 2-4, ligand 1 is chelated in a tetra-dentate fashion to each metal ion but in complex 5, ligand 1 behaves as a bidentate ligand. Complexes 2-4 were tested as catalysts for the ring-opening polymerisation of ε-caprolactone and a high level of activity for the barium complex 4 was observed, with narrow polydispersity. We also report the synthesis and structure of the bis(amidophosphino borane) ligand [Ph2P(BH3)NHCH2CH2NHPPh2(BH3)] (6) and the corresponding barium complex [(THF)2Ba{Ph2P(BH3)NCH2CH2NPPh2(BH3)}]2 (7).
Department of Chemistry, Indian Institute of Technology Hyderabad, Ordnance Factory Estate, Yeddumailaram 502205, Andhra Pradesh, India. tpanda@iith.ac.in.
Ravi K
RK
Kottalanka
Harinath
H
Adimulam
Jayeeta
J
Bhattacharjee
H
H
Vignesh Babu
Tarun K
TK
Panda
D002208:Caproates / Q000737:chemistry*; D002614:Chelating Agents / Q000737:chemistry*; D007783:Lactones / Q000737:chemistry*; D008024:Ligands; D008673:Metals, Alkaline Earth / Q000737:chemistry*; D008958:Models, Molecular; D015394:Molecular Structure; D009942:Organometallic Compounds / Q000138:chemical synthesis* / Q000737:chemistry*; D009943:Organophosphorus Compounds / Q000737:chemistry*; D016566:Organoselenium Compounds / Q000737:chemistry*; D058105:Polymerization
D002208:Caproates; D002614:Chelating Agents; D007783:Lactones; D008024:Ligands; D008673:Metals, Alkaline Earth; D009942:Organometallic Compounds; D009943:Organophosphorus Compounds; D016566:Organoselenium Compounds; C121056:caprolactone