Carbene- and Carbyne-like Behavior of the Mo−P Multiple Bond in a Dimolybdenum Complex Inducing Trigonal-Pyramidal Coordination of a Phosphinidene Ligand

The phosphinidene complex [Mo2Cp(μ-κ1:κ1,η5-PC5H4)(CO)2(η6-R*H)] (2; Cp = η5-C5H5; R* = 2,4,6-C6H2tBu3) has substantially
different Mo−P bonds and displays a high reactivity located at the
short Mo−P bond. Sideways cycloaddition or addition processes
are observed toward RC⋮CR, HCl, and [Fe2(CO)9], to give
respectively metallacyclobutene and arylphosphide-bridged and
heterometallic phosphinidene-bridged derivatives, a behavior
reminiscent of the nucleophilic mononuclear phosphinidene complexes (carbene-like behavior), which is in good agreement with
the ground-state electronic structure of 2 derived from density
functional theory calculations. However, the reaction of 2 with [Co2(CO)8] implies the addition of two cobalt fragments to its short
Mo−P bond and thus reveals a carbyne-like behavior of compound
2. In most of the new products, the P atom displays an
unprecedented trigonal-pyramidal-like environment, instead of the
expected tetrahedral distribution of bonds.