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Synthesis and Oligonuclear Structures of Strontium and Barium Complexes with Protonated and Deprotonated N-Mesityl-P,P-diphenylphosphinic Amide Ligands.

ABSTRACT: Metalation of N-mesityl-P,P-diphenylphosphinic amide Ph₂P(O)-NHMes (HL, I) with MgBu₂ and Ae{N(SiMe₃)₂}₂ (Ae = Ca, Sr, and Ba) yields alkaline-earth metal complexes with the compositions of [(thf)_nAe(L·HL)₂] [Ae/n = Mg/0 (II), Ca/2 (III)] as well as of [Sr₂L₃(L·HL)(HL)] (1), [Ba₂L₃(L·HL)(HL)] (2), [Ba₃L₆] (3), and [(thf)₂Ba₃L₆] (4). In III, 1, 2, and 3, the alkaline-earth metal atoms are in severely distorted octahedral environments, and the structural distortions are partially caused by the small O-Ae-N bite angles of the chelating Ph₂P(O)-NMes anions. The substructures (L·HL) contain N-H···N hydrogen bridges, stabilizing the arrangement of the ligands in complexes II, III, 1, and 2. In the trinuclear barium complex [Ba(μ-L)₃Ba(μ-L)₃Ba] (3), a rigid adjustment of the anionic L bases leads to a C₃-symmetric molecule in the crystalline state with bridging oxygen atoms. Due to the small O-Ba-N bite angles of the chelating anions, vacant coordination sites are available at the outer barium centers. Coordination of thf bases in these gaps yields the complex [(thf)Ba(μ-L)₃Ba(μ-L)₃Ba(thf)] (4). However, THF is unable to deaggregate the trinuclear complexes into smaller barium-containing moieties. Increasing the radius of the alkaline-earth metals and increasing the nuclearity of these compounds lead to decreasing solubility in common organic solvents. NMR studies verify that the molecular structures of these alkaline-earth metal complexes are maintained in ethereal solvents and toluene.

SUBMITTER: Schonherr PRW

PROVIDER: S-EPMC8444311 | biostudies-literature |

REPOSITORIES: biostudies-literature

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