Daniel F. Moser

Crystal structure of the stable silylene, N, N'-di-tert-butyl-1,3-diaza-2-silacyclopent-4-en-2-ylidene

Comment The title compound was isolated in 1994 as the first known room temperature divalent, dicoordinate silicon species [ 11 F.xtensive studies of this silylene indicate that it is stabilized both by electron donation from nitrogen to silicon and by aromatic delocalization in its six π-electron ring |2.3| In 1994. in spite of several attempts, a single crystal X-ray structure could not be obtained for the silylene Its structure was instead established by gas phase electron diffraction [1] The crystal structure for the prototypical silylene (Figure 1) has at last been determined and is

[1+4]-Cycloadditions of silylenes to 2,4,6-tri-tert-butyl-1,3,5-triphosphabenzene

2,4,6-Tri-tert-butyl-1,3,5-triphosphabenzene 1 undergoes [1 + 4]-cycloaddition with the stable bis(amino)silylenes Si[(NCH2But)2C6H4-1,2] 3, Si[(NBut)2C2H2] 4 and Si[(NBut)2C2H4] 7 to afford the structurally characterised 5, 6 and 11. The intermediate aminosilylsilylene resulting from the dissociation of the disilene [Si{(NBut)2C2H4}]49 was trapped as its [1 + 4]-cycloadduct with 1, which was also structurally characterised. The reversibility of the cycloaddition was demonstrated for 5 through reaction with [Mo(CO)4(nbd)] to afford [Mo(CO)3(η6-P3C3But3)] (13) and a mixture of cis- (14a) and trans-[Mo(CO)4(3)2] (14b) of which 14b has been structurally characterised by a single crystal X-ray diffraction study.

Mono- and Bimetallic Cyclodiphosph(V)Azane Complexes

The 2,4-bis(amino)cyclodiphosph(V)azanes cis-[R(H)N(E=PNtBu)2N(H)R] (R = Ph, E = S(2), Se(3); R = tBu, E = p-Tol (4)) were synthesized and X-ray structurally characterized. Treatment of 4 or cis-[tBu(H)N(E=PNtBu)2N(H)tBu] with TiCl4 afforded monometallic complexes of the type {[tBu(H)N(E=PNtBu)2NtBu]TiCl3] E = S(5), Se(6), NPh. Deprotonation of 2 and cis-[tBu(H)N(E=PNtBu)2N(H)tBu] with nBuLi, afforded dilithium complexes of the general formula {[(THF2·LiRN)(E=PNtBu)2(NRLi·THF2)]} R = Ph(7), R = tBu(8). Treatment of [tBu(H)N(E=PNtBu)2N(H)tBu] with trimethylaluminum produced {(Me2AI)[(tBuN)(E=PNtBu)2(NtBu)](AlMe2)}, E = O(9), S(10), p-Tol(11). Single-crystal X-ray analyses demonstrated that the monometallic 5 and 6 are bispirocyclic complexes, while the bimetallic 7–11 were shown to be trispirocyclic complexes.