Taming reactive phosphorus intermediates with organic and inorganic carriers

Abstract

Complexes (THF)₀-₂E[P₃Nb(ODipp)₃]₂ (E = Sn, Pb; Dipp = 2,6-iPr₂C₆H₃) were prepared and characterized as potential precursors to new tetrel phosphides. Treatment of (THF)Sn[P₃Nb(ODipp)₃]₂ with pyridine-N-oxide effected the formation of ONb(ODipp)₂(py)₂ and a new tin phosphide, [(THF)SnP₆]x, characterized using a multitude of techniques. Additionally, P₃Nb(ODipp)₂(py)₂, prepared from [Na(THF)₃][[P₃Nb(ODipp)₃] in the presence of pyridine and salts of coordinating cations, was found to successfully produce AsP₃ upon treatment with AsCl₃ Dimer [P₂Nb(ODipp)₃]₂ has been obtained via a novel "2(3-1)" synthetic strategy. The mononuclear diphosphorus complex P₂Nb(ODipp)₃ proposed to be generated transiently by formal P- abstraction from previously reported [Na(THF)₃][P₃Nb(ODipp)₃] undergoes irreversible dimerization to form the [P₂Nb(ODipp)₃]₂ complex, and is alternatively trapped reversibly by a 1,3-cyclohexadiene (CHD) to form in situ C₆H₈P₂Nb(ODipp)₃ Unprotected dibenzo-7[lambda]³A3-phosphanorbornadiene derivatives RPA (A= C₁₄H₁₀ or anthracene; R = tBu, dbabh, HMDS, iPr₂N, cis-Me₂ Pip, Cy₂N, Me₂N) were synthesized by treatment of the corresponding phosphorus dichloride RPCl₂ with MgA-3THF. Thermolysis of RPA benzene-d₆ solutions leads to anthracene extrusion. Experimental and computational thermodynamic activation parameters suggest this process occurs through the intermediacy of a singlet phosphinidene for the iPr₂N derivative. The [RP] unit could be transferred to CHD, a carbene and an ortho-benzoquinone, with formation of the corresponding anti-7-phosphanorbornene, phosphaalkene and phospholane. The anthracene diphosphorus adduct P₂A₂ was synthesized from Me₂NPA, through isolated intermediates CIPA and [P₂A₂Cl][AlCl₄]. P₂A₂ was found to transfer P₂ efficiently to N-₃ CHD, 1,3-butadiene and (C₂H₄)Pt(PPh₃)₂ to form 1,2-cyclo-[P₂N₃]-, P₂(CHD)₂, P₂(BD)₂ and (P₂)[Pt(PPh₃)₂]₂ . A complete kinetic and computational study of the P₂(CHD)₂ formation from P₂A₂ suggests P₂ is a productive intermediate in solution. Additionally, a molecular beam mass spectrometry study on the thermolysis of solid P₂A₂ reveals the direct detection of molecular fragments of only P₂ and anthracene thus establishing a link between solution-phase P₂-transfer chemistry and production of gas-phase P₂ by mild thermal activation of a molecular precursor. The HCP precursor Ph₃PC(H)PA was synthesized directly from C1PA. The activation of P₄ with [Na][SnPh₃ ] and sodium naphthalenide led to the synthesis of phosphide compounds [Na(benzo-15-crown-5)][P(SnPh₃)₂], P(SnPh₃)₃, (XL)₂InP(SnPh₃)₂, (Ph₃P)AuP(SnPh₃)₂, P₇(SnPh₃)₃ and P7(SiMe₃)₃, characterized using a variety of techniques.