Cycloaddition and C–S Bond Cleavage Processes in Reactions of Heterometallic Phosphinidene-Bridged MoRe and MoMn Complexes with Alkynes and Phenyl Isothiocyanate

Reactions of [MoReCp(μ-PMes*)(CO)6] with internal alkynes RC≡CR yielded the phosphapropenylidene-bridged complexes [MoReCp(μ-κ2P,C:η3-PMes*CRCR)(CO)5] (Mes* = 2,4,6-C6H2tBu3; R CO2Me, Ph). Terminal HC≡CR1 gave mixtures isomers [MoReCp(μ-κ2P,C:η3-PMes*CHCR1)(CO)5] and [MoReCp(μ-κ2P,C:η3-PMes*CR1CH)(CO)5], first isomer being major (R1 CO2Me) or unique tBu), indicating relevance steric repulsions during [2 + 2] cycloaddition step between Mo═P C≡C bonds in these reactions. Similar reactions were observed for [MoMnCp(μ-PMes*)(CO)6]. Addition ligands to promoted rearrangement phosphapropenylidene ligand into allyl-like μ-η3:κ1C mode, as shown by reaction [MoReCp(μ-κ2P,C:η3-PMes*CHC(CO2Me)}(CO)5] CN(p-C6H4OMe) give [MoReCp{μ-η3:κ1C-PMes*CHC(CO2Me)}(CO)5{CN(p-CH4OMe)}2]. The MoRe phosphinidene complex reacted S═C═NPh products phosphametallacyclic [MoReCp{μ-κ2P,S:κ2P,S-PMes*C(NPh)S}(CO)5] its thiophosphinidene-bridged [MoReCp(μ-η2:κ1S-SPMes*)(CO)5(CNPh)]. product follows from a C═S bonds, specific formation P─C whereas second one would arise alternative involving P─S more favored on grounds. prevalence μ-η2:κ1S coordination mode SPMes* over μ-η2:κ1p was investigated theoretically conclude that congestion favors while kinetic barrier interconversion is low any case.