Efficient Synthesis and Multisite Reactivity of a Phosphinidene-Bridged Mo-Re Complex. A Platform Combining Nucleophilic and Electrophilic Features.

The heterometallic complex [MoReCp(μ-PR*)(CO)] () was prepared in 60% overall yield from -[MoCp(PHR*)(CO)] via a three-step procedure involving complexes -[MoCp(PClR*)(CO)] and [MoReCp(μ-PR*)(CO)] as intermediate species (R* = 2,4,6-CHBu). The PR* ligand in displays a novel asymmetric interaction with the dimetal center, involving a double bond with one atom (Mo) and a dative single bond with the other one (Re). Compound underwent thermal isomerization involving a C-H bond cleavage to yield the hydride [MoReCp(μ-H){μ-P(CHCMe)CHBu}(CO)] and reacted with I to give [MoReCpI(μ-PR*)(CO)], which displays a symmetrical phosphinidene bridge. Its reaction with methyl propiolate at 293 K proceeded with [2 + 2] cycloaddition of the alkyne and decarbonylation to yield the phosphapropenylidene-bridged complex [MoReCp{μ-κ:η-PRCHC(COMe)}(CO)] as the major product, whereas its reaction with excess CN(4-CHOMe) at 273 K proceeded with formal [2 + 1] cycloaddition of the isocyanide and further isocyanide addition at the Re site to yield the complex [MoReCp{μ-η:κ-PRCN(4-CHOMe)}(CO){CN(4-CHOMe)}], which displays an azaphosphaallene ligand in a novel bridging coordination mode.