Hydrophosphinylation of Styrenes Catalysed by Well‐Defined s‐Block Bimetallics

Abstract

Advancing the applications of s-block heterobimetallic complexes in catalysis, we report the use of potassium magnesiate (PMDETA) 2 K 2 Mg(CH 2 SiMe 3 ) 4 [PMDETA = N,N,N',N',N''-pentamethyldiethylenetriamine] for the catalytic hydrophosphinylation of styrenes under mild conditions. Exploiting chemical cooperation, this bimetallic approach offers greater catalytic activity and chemoselectivity than the single-metal components KCH 2 SiMe 3 and Mg(CH 2 SiMe 3 ) 2 . Stoichiometric studies between (PMDETA) 2 K 2 Mg(CH 2 SiMe 3 ) 4 and Ph 2 P(O)H help to elucidate the constitution of the active catalytic species, and illustrate the influence of donors on the potassium cation coordination, and how this may impact catalytic activity. Mechanistic investigations support that the rate determining step is the insertion of the olefinic substrate.

Diphenylacetylene stabilised alkali-metal nickelates: synthesis, structure and catalytic applications

“…Moving to the lithium nickelate Li 4 (Et 2 O) 4 Ph 4 Ni 2 {µ 2 -η 2 :η 2 -Ph-CuC-Ph} (1a, entry 3) led to a considerable increase to 74% conversion. Contrasting with other catalytic studies using alkali-metal magnesiates, [51][52][53][54][55] no apparent alkali-metal effect was observed, with comparable conversions observed for the sodium nickelate 1b (73%, entry 4) and potassium nickelate 1c (78%, entry 5), indicating that the alkali-metal does not appear to play an active role in catalysis. Using compound 1d as a catalyst gave a slightly improved conversion (85%, entry 6) suggesting that the more electron-rich 4-t Bu-C 6 H 4 substituents enhances the catalytic activity when compared to 1a.…”

Low-Coordinate Magnesium Sulfide and Selenide Complexes

“…The Mg–O bond distance to the anionic diphenyl­phosphinite is only slightly shorter than that to the neutral triphenyl­phosphinoxide (Mg1–O2 1.9000(16) versus Mg1–O1 1.9243(14)), and the P–O bond in the P V ligand (P1–O1 1.4972(13)) is, as expected, shorter than that in the phosphinite (P2–O2 1.5459(17)). These features compare well to those of other alkaline earth metal complexes with diphenylphosphinite ligands. − …”

Alkaline‐earth metal dimesitylphosphinites and their ether adducts – A structural study in solution and in the crystalline state

“…[3] In addition, heterobimetallic sodium and potassium magnesates are also suitable catalysts, but lithium magnesates are inactive in this catalytic hydrophosphorylation reaction. [4] The compound class of s-block metal diarylphosphinites AOPAr 2 and Ae(OPAr 2 ) 2 is well known for many decades and has easily been accessible by reduction of Ar 2 P(O)Cl with the s-block metals or conversion of the phosphane oxides Ar 2 P(O)H with the metals or their organometallic reagents. [5] Another procedure is the selective cleavage of a CÀ P bond in triphenylphosphane oxide by sodium, quantitatively leading to NaOPPh 2 .…”

“…However, suitability of the s‐block metal diarylphosphinites as catalysts for this hydrofunctionalization strongly depends on size and hardness of the s‐block metal ion with increasing reactivity of the softer metal ions such as potassium, rubidium and cesium as well as barium, whereas lithium, magnesium and calcium compounds show no reactivity in this catalytic processes [3] . In addition, heterobimetallic sodium and potassium magnesates are also suitable catalysts, but lithium magnesates are inactive in this catalytic hydrophosphorylation reaction [4] …”