Synthesis and Reactions of the First Room Temperature Stable Li/Cl Phosphinidenoid Complex

<i>P</i>-Trityl substituted Li/Cl phosphinidenoid tungsten(0) complex (OC)₅W­{Ph₃CP­(Li/12-crown-4)­Cl} (<b>3</b>) was prepared via chlorine/lithium exchange in complex (OC)₅W­{Ph₃CPCl₂} (<b>2</b>) using ^<i>t</i>BuLi in the presence of 12-crown-4 in tetrahydrofuran (THF) at low temperature; complex <b>3</b> possesses significantly increased thermal stability in contrast to previously reported analogue derivatives. Terminal phosphinidene-like reactivity of <b>3</b> was used in reactions with benzaldehyde and isopropyl alcohol as oxaphosphirane complex (OC)₅W­{Ph₃CPC­(Ph)­O} (<b>5</b>) and phosphinite complex (OC)₅W­{Ph₃CP­(H)­O^<i>i</i>Pr} (<b>6</b>) were obtained selectively. Reaction of <b>3</b> with phosgene allowed to obtain the first kinetically stabilized chloroformylphosphane complex (OC)₅W­{Ph₃CP­(Cl)­C­(O)­Cl} (<b>4</b>). Density functional theory (DFT) calculations revealed remarkable differences in the degree of P–Li bond dissociation <b>3a–d</b>: using a continuum model <b>3</b> displays a covalent character of P–Li bond (COSMO (THF)) (<b>a</b>), which becomes elongated if 12-crown-4 is coordinated to lithium (<b>b</b>) and is cleaved if a dimethylether unit is additionally coordinated to lithium (<b>c</b>). A similar result was obtained for the case of <b>3</b>(thf)₄ in which also a solvent-separated ion pair structure is present (<b>d</b>). All products were unambiguously characterized by various spectroscopic means and, in the case of <b>2</b> and <b>4</b>–<b>6</b>, by single-crystal X-ray diffraction analysis. In all structures very long P–C bonds were determined being in the range from 1.896 to 1.955 Å