A Fully Phosphane‐Substituted Disilene

Abstract

There is growing interest in compounds containing functionalized E=E multiple bonds (E=Si, Ge, Sn, Pb) because of their potential to exhibit novel physical and chemical properties. However, compounds containing multiple functionalizations are rare, with scarcity increasing with increasing degree of substitution. The first ditetrelene R2E=ER2 in which the E=E bond is substituted by four heteroatoms (other than Si) is described. The tetraphosphadisilene {(Mes)2P}2Si=Si{P(Mes)2}2 (7) is readily isolated from the reaction between SiBr4 and [(Mes)2P]Li, the latter of which acts as a sacrificial reducing agent. The structure of 7 is presented, while the bonding in, and stability of 7 were probed using DFT calculations.

Reduction of a Bicyclo[1.1.0]tetrasil-1(3)-ene with LiAlH4 Leading to an Isolable Cyclotrisilenide

“…The Si1–Si2 distance [2.1451(7) Å] falls within the range of the SiSi double bond in reported cyclotrisilenes (2.118–2.186 Å) and is comparable to those of phosphanyl-substituted acyclic disilenes (2.1542–2.1968 Å). , The Si1–P1 distance [2.2746(7) Å] is similar to those of reported phosphanyl disilenes (2.2367(12)–2.3126(10) Å) . In the 29 Si NMR spectrum of 7 in benzene- d 6 , signals assigned to the Si1 and Si2 nuclei were observed at 141.3 and 107.0 ppm, respectively, which were downfield shifted compared with those of reported acyclic phosphanyl disilenes (52.5–111.7 ppm) . The 1 J (Si,P) coupling constant of Si1 nucleus [214.8 Hz] is significantly larger than those of reported phosphanyl disilenes [ 1 J (Si,P) = 115–133 Hz], suggesting an increased s-character of the orbital of the silicon atom in the P–Si bond .…”

“…Single-crystal XRD analysis of 7 (Figure ) disclosed that the geometry around the unsaturated Si2 atom is perfectly planar [the angle sums of the Si2 atoms is 360.00°], while a slight pyramidalization of Si1 is observed [the angle sums of the Si1 atoms is 355.99°]. The Si1–Si2 distance [2.1451(7) Å] falls within the range of the SiSi double bond in reported cyclotrisilenes (2.118–2.186 Å) and is comparable to those of phosphanyl-substituted acyclic disilenes (2.1542–2.1968 Å). , The Si1–P1 distance [2.2746(7) Å] is similar to those of reported phosphanyl disilenes (2.2367(12)–2.3126(10) Å) . In the 29 Si NMR spectrum of 7 in benzene- d 6 , signals assigned to the Si1 and Si2 nuclei were observed at 141.3 and 107.0 ppm, respectively, which were downfield shifted compared with those of reported acyclic phosphanyl disilenes (52.5–111.7 ppm) .…”

“…In the 29 Si NMR spectrum of 7 in benzene- d 6 , signals assigned to the Si1 and Si2 nuclei were observed at 141.3 and 107.0 ppm, respectively, which were downfield shifted compared with those of reported acyclic phosphanyl disilenes (52.5–111.7 ppm) . The 1 J (Si,P) coupling constant of Si1 nucleus [214.8 Hz] is significantly larger than those of reported phosphanyl disilenes [ 1 J (Si,P) = 115–133 Hz], suggesting an increased s-character of the orbital of the silicon atom in the P–Si bond . The UV–vis absorption spectrum of 7 in hexane exhibits a longest-wavelength absorption band at 430 nm, which is bathochromically shifted compared with those of 4 and 6 [373 and 414 nm], suggesting the presence of the n−π interaction between the phosphorus lone pair and the SiSi bond in 7 (See also Figure S55).…”

A Stabilized Bisphosphanylsilylene and Its Heavier Congeners

“…Single crystals suitable for X‐ray diffraction have been obtained for 8 (Figure ). In the molecular structure of 8 the Si‐P distances of 2.3369(8) and 2.3275(8) Å are elongated compared with the tetravalent dihalosilanes Fe(C 5 H 4 P t Bu) 2 SiX 2 (X=Cl, Br, I; 2.2380(5)–2.2548(8) Å) and the recently published tetraphosphanyldisilene (2.2666(8)‐2.2392(8) Å) but are very similar to those in NHC adducts of monophosphanyl substituted silylenes ((2.3460(11) Å, 2.3748(7) Å)). One might be tempted to attribute this elongation to hyperconjugative electron donation from the σ PSiP orbital to the electron acceptor N ‐heterocycle, but second order perturbation theory analysis on the NBO basis reveals only weak (2–3 kcal mol −1 ) interactions between the P−Si bonds and the antibonding orbitals of the NHC unit.…”

Comparison of Two Phosphinidenes Binding to Silicon(IV)dichloride as well as to Silylene

“…The latter was supported by only NMR spectroscopy. 10 Compounds 2 and 3 were characterized by 1 H, 13 C{ 1 H}, 31 P{ 1 H}, 29 Si{ 1 H} NMR spectroscopy and elemental analysis. In the 29 Si{ 1 H} NMR spectrum of 2 and 3, both display triplets at δ= 28.9 ppm ( 1 J SiP = 169 Hz) and δ= +6.9 ppm ( 1 J SiP = 174 Hz), respectively, thus indicating the coupling with the phosphorus atoms.…”