Transition‐Metal‐Like Reversible Cycloadditions of [tBuSP‐W(CO)₅] with Alkenes and Alkynes

Abstract

tert‐Butylthiophosphinidene complex [tBuSP‐W(CO)5] was generated by dissociation of 1‐(tert‐butylthio)phosphirane–W(CO)5 complex under mild conditions. The formation of transient [tBuSP‐W(CO)5] was indicated by trapping reactions with 2,3‐dimethyl‐1,3‐butadiene, alkynes, phenanthrene‐9,10‐dione, and methanol. The LUMO of [MeSP‐W(CO)5] is significantly lower in energy than those of [Me2NP‐W(CO)5], [MeOP‐W(CO)5], and [Me2PP‐W(CO)5]. The HOMO of [MeSP‐W(CO)5] contains a significant contribution from the in‐plane lone pair of P and the LUMO shows a typical π* characteristic. Since stabilized by sulfur lone pair and coordinated by W(CO)5, [tBuSP‐W(CO)5] undergoes facile and reversible cycloadditions with alkenes and alkynes.

Insight into fragmentation of a phosphirane to form phosphinidene complexes: an illustration with the 1-phenylselenylphosphirane W(CO)5 complex

“…The different P⋯C distances of TS1 support the above explanation. In addition, the calculated Se–P bond length of [PhSeP–W(CO) 5 ] 2 (2.20 Å) is shorter than that of 1 (2.30 Å) which is similar to the previous observation in [ t -BuSW(CO) 5 ], 10 which reflects the interaction between the Se lone pair and phosphinidene.…”

“…Since stabilized by the selenium lone pair, [PhSeP–W(CO) 5 ] undergoes transition metal like 24 reversible cycloadditions with alkynes (Scheme 3). Similar phosphinidene transfer reactions have been observed with amino-substituted 9 and thio-substituted 10 phosphinidene complexes.…”

“…9 We recently disclosed the fragmentation of a thio-substituted phosphinidene complex by dissociation of a related phosphirane complex. 10 Based on the aforementioned calculation and experimental results, we hypothesize that strong π-donation from the adjacent atom centre to the LUMO of phosphinidene affects the interaction between phosphinidene complexes and alkenes, which facilitates the [1 + 2] retroaddition of phosphiranes.…”

“…Our recent studies on phosphiranes chemistry 10,21 allow us to facilely synthesize the 1-phenylselenylphosphoriane W(CO) 5 complex 1 through the reaction of the phosphiranide complex 4 with phenylselenyl chloride. As shown in Scheme 2a, the starting material 1 was prepared by a one-pot reaction from β-chloroethylphosphine complex 3 21 a in 80% overall yield.…”

Challenging an old paradigm by demonstrating transition metal-like chemistry at a neutral nonmetal center

“…At ambient temperature no reaction was observed, but upon warming to 70 °C, suddenly, the selective formation of a diastereomeric mixture of phosphirane complexes 10a (34:66) and 10b and (36:64) with 31 P NMR chemical shifts of −137.7 ppm ( cis −10a, 1 J W,P = 258.8 Hz) and −145.4 ppm ( trans −10a, 2 J P,H = 19.6 Hz, 1 J W,P = 259.7 Hz), and −137.4 ppm ( cis −10b, 1 J W,P = 258.9 Hz) and −145.5 ppm ( trans −10b, 2 J P,H = 15.2 Hz, 1 J W,P = 260.2 Hz) was observed, indicating a ligand dissociation prior to the rapid [2 + 1] cycloaddition of the transient terminal phosphinidene complex 4 . At this point it should be also noted that π-systems such as alkenes can coordinate reversibly to phosphinidene complexes to form respective phosphirane complexes if terminal alkenes are used as solvent 83 , 84 .…”