title: Bis(diphenylphosphido) derivatives of the heavier group 2 elements.
abstract: A number of heavier alkaline-earth (Ae) diphenylphosphides have been prepared by protonolysis of the corresponding bis(trimethylsilyl)amides and completely characterized in the solid state and in solution. Through careful control of the reaction and workup conditions, preparations performed with tetrahydrofuran (THF) as the only donor solvent crystallize as octahedral tetrakis-solvated THF adducts [Ae(PPh2)2(THF)4] when Ae=Ca and Sr. Both structures are similar and contain the two diphenylphosphide substituents in a trans disposition. In contrast, the analogous reaction performed upon the barium amide yielded a one-dimensional polymeric complex containing both five- and six-coordinated Ba centers in which the polymer is propagated via bridging diphenylphosphide units. Further strictly mononuclear derivatives of the Ca and Ba diphenylphosphides may be straightforwardly prepared by treatment of the THF adducts with 18-crown-6. Although the THF-solvated species are evidently labile to loss of solute, solution (diffusion-ordered spectroscopy NMR, THF-d8) studies indicate that, under catalytically relevant conditions, a similar mononuclear constitution is most likely retained.
authors.affiliation: Department of Chemistry, Imperial College London, Exhibition Road, South Kensington, London SW7 2AZ, UK.
authors.forename: Mark R
authors.initials: MR
authors.lastname: Crimmin
authors.forename: Anthony G M
authors.initials: AG
authors.lastname: Barrett
authors.forename: Michael S
authors.initials: MS
authors.lastname: Hill
authors.forename: Peter B
authors.initials: PB
authors.lastname: Hitchcock
authors.forename: Panayiotis A
authors.initials: PA
authors.lastname: Procopiou
mesh_terms: D000577:Amides / Q000737:chemistry; D018360:Crystallography, X-Ray; D005663:Furans / Q000737:chemistry; D009682:Magnetic Resonance Spectroscopy; D008673:Metals, Alkaline Earth / Q000737:chemistry*; D008958:Models, Molecular; D008968:Molecular Conformation; D015394:Molecular Structure; D009942:Organometallic Compounds / Q000138:chemical synthesis* / Q000737:chemistry; D009943:Organophosphorus Compounds / Q000138:chemical synthesis* / Q000737:chemistry
chemical_list: D000577:Amides; D005663:Furans; D008673:Metals, Alkaline Earth; D009942:Organometallic Compounds; D009943:Organophosphorus Compounds; C018674:tetrahydrofuran