Allylation of Phosphorus, Arsenic, and Antimony Trihalides by Allylic Stannanes. Synthesis, Spectroscopic Characterization, and Quantum Chemical Investigations of Allylic Phosphines, Arsines, and Stibines

Abstract

The reaction between an allylic tributylstannane and a phosphorus, arsenic, or antimony trihalide led to the corresponding allylic phosphine, arsine, or stibine dihalides. With phosphorus derivatives, only the gamma-regioselection was observed, as shown by the formation of (1-methyl-2-propenyl)- (2e,f)or (1,1-dimethyl-2-propenyl)dihalophosphines (2g,h) starting from crotylstannanes 1c,c' or prenylstannane 1d, respectively, and PCl(3) or PBr(3). On heating at 80 degrees C, some of these phosphines led to the corresponding thermodynamic products. Allylic dichloroarsines 3a-d were also prepared and kinetic compounds 3c,d completely rearranged at room temperature into the corresponding crotyl- (3e,e') and prenyldichloroarsines (3f). For antimony derivatives, even at low temperature (-90 degrees C), crude mixtures containing only the thermodynamic products were observed. While allylic dihalophosphines and -arsines are not efficient allylation reagents of electrophiles, allylic dichlorostibines 4a,c reacted with benzaldehyde to lead to the corresponding homoallyl alcohols. Syn and anti products were mainly produced starting from crotyldichlorostibines (4e,e'). The primary allylic phosphines 7a-f, arsines 8a-f, and stibines 9a,bhave been prepared by the chemoselective reduction of the corresponding allylic dihalophosphines, -arsines, or -stibines with LAH in tetraglyme or with Bu(3)SnH as reducing agent and characterized by (1)H and (13)C NMR spectroscopy and mass spectrometry. The primary allylic arsines and stibines are the first elements of new classes of compounds. Several allylic phosphines and arsines were investigated by ab initio quantum chemical methods and photoelectron spectroscopy. The most stable structure of these compounds is when the C-E (E = P, As) bond is out of the plane of the allyl system. This conformation is stabilized by the hyperconjugation between the pi-orbital and the C-E sigma-bond. Due to this geometrical arrangement, the phosphorus (arsenic) lone pair interacts strongly and unprecedently with the pi-system. The strength of this interaction is due to the close proximity of the pi and the n(P) (n(As)) levels.

Iron(0) and ruthenium(0) complexes with tridentate phosphonite ligands and their potential for ketene formation from methyl iodide, CO and a base

“…Instead the iodo complexes 22-29 were obtained. The iron-acetyl complexes (34)(35)(36)(37) proved to be much more acidic than the related ruthenium-acetyl complexes (30)(31)(32)(33). In all the deprotonation experiments, we were unable to observe any ketene-metal intermediate.…”

“…The reaction was carried out with irradiation and found to be faster in the presence of a radical initiator (AIBN), therefore a radical character of the substitution was proposed. However, the reaction was reported [33] later to also proceed without photolysis and in the presence of duroquinone or acrylonitrile. Thus, an anionic process cannot be excluded.…”

“…The initial deprotonation experiments carried out in dichloromethane at room temperature and under a carbon monoxide atmosphere showed that no reaction occurred with the ruthenium acetyl complexes (30)(31)(32)(33) and that the iron acetyl complexes (34-37) reacted very slowly as evidenced by the presence of a small amount of protonated BEMP in the 31 P NMR spectra after four days of reaction. The deprotonation experiments with BEMP can be conveniently monitored by 31 P NMR spectroscopy.…”

Structurally Defined Allyl Compounds of Main Group Metals: Coordination and Reactivity

“…The main decomposition pathway is the coupling of allyl ligands to give 1,5‐hexadiene with concomitant formation of M 0 109. 110b The allyl ligands show an η 1 bonding mode in the liquid phase94, 106, 109 and a weak β effect has been suggested for derivatives of As and Sb (see Section 4.5) 111. A dynamic behavior of the allyl ligands has not been reported for the homoleptic compounds, although high‐temperature scenarios have not been investigated.…”

“…However, rearrangement reactions have been observed in the case of butenyl and prenyl dihaloarsines and stibines. Such compounds with the Group 15 fragment at the less‐substituted terminus of the allylic system are the thermodynamically more‐stable isomers 111. In halogenated or cationic derivatives of allyl bismuth, [Bi(C 3 H 5 ) 2 (I)] and [Bi(C 3 H 5 ) 2 (thf) 2 ] + , the allyl ligands show dynamic behavior in solution 109.…”