Zwitterionic Si‐C‐Si‐P and Si‐P‐Si‐P Four‐Membered Rings with Two‐Coordinate Phosphorus Atoms

Abstract

It's hip to be square: The reaction of amidinato chlorosilylene (PhC(NtBu)2SiCl) with adamantyl phosphaalkyne and white phosphorus affords the formation of Si‐C‐Si‐P and Si‐P‐Si‐P (see picture) four‐membered rings. Both compounds were characterized by single‐crystal X‐ray studies and by solution and solid‐state NMR spectroscopy. DFT calculations elucidated the bonding situation.

Different Reactivity of As4 towards Disilenes and Silylenes

“…[5] Later, Driess et al reported on as tepwise insertion of al ow-valent silicon(II) center into two opposing PÀPb onds of the P 4 tetrahedron (B and C). [7] The same compound was reported by Inoue et al from the reaction of LSiP(SiMe 3 ) 2 (L = PhC(NtBu) 2 )w ith Ph 3 PCl 2 . [7] The same compound was reported by Inoue et al from the reaction of LSiP(SiMe 3 ) 2 (L = PhC(NtBu) 2 )w ith Ph 3 PCl 2 .…”

Advances in Phosphasilene Chemistry

“…Due to the presence of the benzamidinate ligand,the phosphorusa nd silicon atoms in 34 are significantly more shielded compared to those in 28 and 28'.I nf act, in the NMR spectra of 34,s ignals were observed at d( 31 P) = Figure 17. [58,63,64] is distinctly different to that of cyclobuta-1,3-diene (all carbon) derivatives. The distorted Si 2 P 2 ring in 35 adopts ar hombic geometry.I ti s planar,p erpendicular to the adjacent amidinate rings and consists of four equivalent SiÀPb onds of about 2.171 ,whichcan be assigned as elongated double bonds.…”

“…The delocalized 4π‐electron system of 2,4‐disila‐1,3‐diphospha‐cyclobuta‐1,3‐diene 35 (Figure ) is distinctly different to that of cyclobuta‐1,3‐diene (all carbon) derivatives. The distorted Si 2 P 2 ring in 35 adopts a rhombic geometry.…”

“…DFT calculations at the B3LYP level support a delocalization of π‐electron density in the Si 2 P 2 ring of 35 . The WBI values for the Si−P, Si ⋅⋅⋅ Si, and P ⋅⋅⋅ P bonds of 35 are 1.1424, 0.2832, and 0.2754, respectively.…”

New Route to Access an Acyl‐Functionalized Phosphasilene and a Four‐Membered Si‐P‐C‐O Heterocycle

“…The nitrogen atom in axial position has a longer bond length and is thus weaker coordinated than the amidinato nitrogen atom in equatorial position (Si1N1: 1.945(2), 1.946(2) Å and Si1N2: 1.822(2), 1.824(2) Å) similar to other five‐coordinate silicon compounds18 as well as compound 4 . The siliconphosphorus bond length of 2.2384(10) and 2.2414(9) Å is in the range of a siliconphosphorus single bond (compare 2.2838(12) Å in compound 1 and 2.095(3) Å in compound 2 )5a and longer than in other four‐membered rings with siliconphosphorus bonds (2.1894(7) and 2.2012(7) Å in LSi‐P‐SiL‐C(Ad), and 2.1737(6) and 2.1742(6) Å in (LSiP) 2 ) 22. The carbon–phosphorus double bond of 1.732(3) and 1.733(3) Å in compound 5 is in the range of other phosphorus–carbon double bonds in heterocycles (1.699(2), 1.705(1), 1.729(3), and 1.755(2) Å)20, 21 and longer than the average carbon–phosphorus bond length in acyclic phosphaalkenes (average: 1.67 Å, range 1.63–1.80 Å) 23…”