Reaction of Phosphaalkynes with [Ru₄(CO)₁₃(μ₃-PPh)]:  Synthesis of Unsymmetrically Capped Bisphosphinidene Complexes

Abstract

The 62-electron cluster [Ru 4 (CO) 13 (µ 3 -PPh)] (1) reacts with phosphalkynes RCtP [(R ) tBu, Ar′ (2,4,6-tBu 3 C 6 H 2 )] to yield a series of unsymmetrically capped bisphosphinidene clusters characterized by a ketene substituted µ 4 -PR ligand. The reaction pathway was followed by 31 P-NMR spectroscopy and reveals that, in the first step of the reaction, a CO substitution of 1 occurs in order to form an intermediate with a σ-or π-bonded phosphaalkyne. After scavenging of CO the chain compound [Ru 4 (CO) 12 (µ 3 -PPh)(µ 3 -PC(CO)R)] [R ) tBu (2), Ar′ ( 7)] is created. Further CO elimination leads to the closo-complexes [Ru 4 (CO) 10 (µ-CO)-(µ 4 -PPh)(µ 4 -PC(CO)R)] [R ) tBu (3), Ar′ (4)]. Due to steric reasons the nido-cluster [Ru 3 (CO) 9 (µ 3 -PPh){µ 3 -PC(CO)tBu}] (5) is the final product in the reaction starting from Ar′CtP. The molecular structures of the complexes 2-5 are discussed.1 provides an opportunity to explore the chemistry of RCtP on cluster frames, and our findings are presented herein. Results and DiscussionThe reactions of [Ru 4 (CO) 13 (µ 3 -PPh)] (1) with different phosphaalkynes lead to various ketene ligand-containing clusters. The ligand tBuCtP reacts with 1 at ambient temperatures to yield the complex [Ru 4 (CO) 12 -(µ 3 -PPh)(µ 3 -PC(CO)tBu)] (2) (Scheme 1), whereas at 60 °C the closo-complex [Ru 4 (CO) 10 (µ-CO)(µ 4 -PPh)(µ 4 - † Dedicated to Professor W. Siebert on the occasion of his 60th birthday.

Cyclooligomerization Reactions of Different Phosphaalkynes in the Presence of [W(CO)5thf] − A Route to Tungsten-Stabilised Phosphorus Heterocycles

“…Sol-vents were purified and degassed by standard procedures and distilled prior to use. Ϫ NMR spectra were recorded on a Bruker 6 in a UV apparatus for 2 h. tBuCϵP was synthesised as described in reference [2]. MesCϵP was obtained as published in ref.…”

“…For tBu as well as the mesityl substituents, cycloaddition is the predominant reaction pathway (Scheme 1). By elimination of W(CO) 6 as the driving force [30] a 1,3-diphosphete ring system capped by a W(CO) 4 group is generated to give compound 3. After further elimination of CO, RCϵPǞW(CO) 5 is coordinated side-on to give the complexes 2, 4, and 5, respectively.…”

“…[3,4] Investigations involving phosphaalkynes with a residue R different from tBu, however, are scarce. Only a few examples of complexes derived from AdCϵP [5] (Ad ϭ C 10 H 15 ) and Mes*CϵP [6,7] (Mes* ϭ 2,4,6-tBu 3 C 6 H 2 ) are known in the literature. Our interest is focussed on the reactivity of RCϵP towards cluster frameworks such as e.g.…”

“…Our interest is focussed on the reactivity of RCϵP towards cluster frameworks such as e.g. nido-[Ru 4 (CO) 13 (µ 3 -PPh)], [6] and especially on the use of phosphaalkynes in the metathesis reaction with alkoxides of the type [(RO) 3 WϵW(OR) 3 ]. [8,9] The goal of the latter chemistry has been the development of an efficient procedure for the synthesis of phosphido complexes of the type [(RO) 3 WϵP].…”