Cycloaddition of Phosphaalkynes to High-Oxidation-State Metal Alkylidenes:  Synthesis and Characterization of a Unique Phosphametallacyclobutene via an Alkoxide Ligand Shift

Abstract

The phosphametallacycle 3, [ArN][RO]MoC(t-Bu)P(OR)C(H)(t-Bu) (Ar = 2,6-(i-Pr)2-C6H3, R = CMe(CF3)2), is formed from the cycloaddition of tert-butylphosphaacetylene to the high-oxidation-state molybdenum alkylidene [ArN][RO]2MoC(H)(t-Bu), accompanied by an alkoxide metal-to-ligand shift. The 1-phospha-3-molybdacyclobut-2-ene has been characterized by multinuclear NMR spectroscopy and its molecular structure determined by X-ray crystallographic analysis.

Synthesis and Characterization of a Molybdenum Alkylidyne Supported by a Trianionic OCO3– Pincer Ligand

“…The η 2 -bound tert -butylacetylene and THF ligands occupy the remaining vertices. The MoC1 bond length of 1.9072(11) Å within 6 is significantly longer than the MoC bond length of 1.7676(13) Å observed in 5 and is comparable to other similar structurally characterized neutral Mo­(VI)-disubstituted alkylidenes, whose MoC bond lengths typically range from 1.87 to 1.96 Å. ,− Best described as a metallacyclopropene the η 2 -bound tert -butylacetylene has an elongated C37−C38 bond length of 1.3020(16) Å ( cf . 1.2 Å for a typical CC) , and a ∠C37−C38−C39 angle of 143.65(11)°.…”

Evidence for single metal two electron oxidative addition and reductive elimination at uranium

“…If a terminal imido complex were ever to exist as an intermediate, then it would undergo a [2 + 2]-cycloaddition to yield a metallacyclobutadiene-type complex formation. However, a range of alkynes (MeC≡CMe, PhC≡CPh, Bu t C≡CH, Me 3 SiC≡CH) are found experimentally to not react, and even the polar and thus reactive Bu t C≡P does not react where it has previously been found to be much more reactive than PhC≡CPh 68 – 71 . These observations, however, are in agreement with the calculated reaction profile (see Supplementary Fig.…”

Phospha‐Organic Chemistry: Panorama and Perspectives

“…(37)]. [103] The initial [2þ2] cycloaddition, which shows the expected regiochemistry (P d+ ÀC dÀ ), is followed by the [1,3] migration of an alkoxy group from the molybdenum to the phosphorus center. The groups of Grobe and Weber have also shown that a [2þ2] cycloaddition can be performed between a diphosphene and a phosphaalkyne [Eq.…”