Phosphasilene 1a and phosphagermene 1b, featuring unprecedented substitution patterns (donors on Si or Ge and acceptor on P), were synthesized utilizing a one-step synthetic approach: direct coupling of dilithiosilane/dilithiogermane and dichlorophosphine. The structural features of both 1a and 1b based on their NMR and X-ray crystal data are discussed, as well as their one-electron reduction forming persistent phosphasilene and phosphagermene anion-radicals.Multiple bonding between the main group elements heavier than the elements of the second row is one of the main themes in contemporary heteroatomic and organometallic chemistry. Being well established in the case of homonuclear derivatives of the types -E 13 dE 13 -, >E 14 dE 14 <, or -E 15 dE 15 -(E 13 , E 14 , or E 15 = group 13, 14, or 15 elements), 1 the chemistry of heteronuclear combinations, particularly those of different group elements of the types -E 13 dE 15 -, -E 13 dE 14 <, and >E 14 dE 15 -, is much less developed. 1 Of the heavy doubly bonded derivatives of the main group elements, those of group 14 and group 15 elements are particularly interesting, since they contain two reactive sites in one molecule: an E 14 dE 15 π-bond and lone electron pair on the E 15 element. 2 Several compounds of the type >E 14 dE 15have been reported, including phosphasilenes >SidP-, phosphagermenes >GedP-, phosphastannenes >SndP-, and arsasilenes >SidAs-. 3 The double bond between silicon/germanium and phosphorus is polarized, >E δ+ dP δ--(E = Si or Ge), because of the difference in electronegativity between Si (or Ge) and P atoms: 1.90 (or 2.01) vs 2.19 (Pauling scale). Such bond polarization results in the enhanced reactivity of both >SidP-and >GedP-. Using substituents with opposing electronic effects on the >EdP-bond (E = Si or Ge), namely, electron-donating groups (D) on silicon/germanium and electron-accepting groups (A) on phosphorus ("push-pull" substitution pattern), one can expect that such double-bond polarization would be decreased or even reversed as in D 2 E δ-dP δ+ -A. However, this interesting synthetic challenge, directed toward a changed electron distribution in the group 14-15 element double bonds, has not yet been achieved experimentally. 2 In this communication, we report the synthesis of phosphasilene and phosphagermene derivatives with such a substitution pattern (electron-releasing silyl substituents on Si or Ge and an electron-withdrawing aryl group on P). The onestep procedure used takes advantage of the high and selective reactivity of ( t Bu 2 MeSi) 2 ELi 2 (E = Si, Ge) reagents. The structural features of these phosphasilene and phosphagermene compounds, based on their structures as determined by X-ray crystallography and their NMR and UV spectroscopic data, are discussed, and their reduction with potassium graphite to form persistent anion-radical species is described.Previously reported phosphasilenes and phosphagermenes are typically prepared employing a two-step procedure: initial coupling of phosphorus and silicon/germanium units ...

The multiply bonded derivatives of the heavier main group elements are among the most challenging targets for synthetic pursuits. Those of them featuring a double bond between the silicon and group 15 element are represented mostly by the silaimines -N═Si< and phosphasilenes -P═Si< with a very few examples of arsasilenes -As═Si<. In this contribution, we report on the synthesis and structural elucidation of the first stable stibasilene and novel phosphasilene and arsasilene derivatives, featuring an identical substitution pattern. A systematic comparison within the series phosphasilene-arsasilene-stibasilene is made on the basis of their experimental and computational studies.

The first compound featuring an As[double bond, length as m-dash]Ge double bond, arsagermene Mes*As[double bond, length as m-dash]Ge(SiMetBu2)2, was synthesized, isolated and fully characterized. Crystallographic studies revealed that arsagermene has a planar Ge[double bond, length as m-dash]As bond of 2.2731(8) Å, which is notably shorter than the standard Ge-As single bond. The double bond character of arsagermene was further supported by computational data.