The reaction of tetramethyldiphosphine with butadiene

Abstract

Exclusive 1.4-addition of tetramethyldiphosphine to butadiene occurs slowly above 100"; the reaction is catalysed by azobis(isobutyronitri1e). The formation of cis-and trans-l,4-bis(dimethylphosphino) but-2-ene is discussed in terms of a dimethylphosphino-radical addition involving an allyl radical intermediate, the more reactive primary carbon atom of which abstracts Me,p from the diphosphine. The isomers have been identified by a comparison of their l H n.m.r. spectra with that of the independently prepared trans-compound. The i.r. spectra of the isomers are recorded. Complexes of both isomers with PtII are apparently polymeric; they have been separated by use of their solubility difference. P.O. Box

Influence of Charge and Coordination Number on Bond Dissociation Energies, Distances, and Vibrational Frequencies for the Phosphorus–Phosphorus Bond

“…The homolytic and heterolytic P–P dissociations of 5 have enthalpies that are similar to those of 1 , and the former pathway is preferred in both compounds. For 1 , these observations are consistent with its reactivity toward unsaturated systems, for example 1,3-butadiene, which results in the formation of the homolytic P–P cleavage product 1,4-bis(dimethylphosphino)-but-2-ene . Heterolytic dissociation of the P–P bond appears to be prohibitively endothermic in all cases except 2 1+ , 3 2+ , and 6 1+ in which P–P dissociation can occur without separation of oppositely charged ions.…”

“…For 1, these observations are consistent with its reactivity toward unsaturated systems, for example 1,3-butadiene, which results in the formation of the homolytic P−P cleavage product 1,4bis(dimethylphosphino)-but-2-ene. 18 Heterolytic dissociation of the P−P bond appears to be prohibitively endothermic in all cases except 2 1+ , 3 2+ , and 6 1+ in which P−P dissociation can occur without separation of oppositely charged ions. The relatively small heterolytic dissociation energy for 2 1+ and 6 1+ predicts that these cations may undergo displacement of the PMe 3 group by a stronger donor such as an N-heterocyclic carbene (NHC) to give the corresponding [NHC-P(S)Me 2 ] 1+ cations, a derivative of which has been prepared via a different synthetic route.…”

Preparation and Nuclear Magnetic Resonance Study of Phosphorus Compounds Containing Alkenyl Functional Groups

“…data on phosphines containing alkenyl groups is available even though they have been shown to function as chelates with a large n~~m b e r of transition metals (2)(3)(4)(5)(6)(7)(8). The determination of the structure of metal-phosphorus complexes is frequently based on the assignment of their ' H and 31P spectra.…”

Diphosphination of 1,3-Dienes with Diphosphines under Visible-Light-Promoted Photoredox Catalysis

“…The aforementioned advances recently appeared in the diphosphination reaction leading to DPPEs with relatively small bite angles; however, the related synthesis of 1,4-bis­(diphenyl­phosphino)­butanes (DPPBs) with larger bite angles still remains largely elusive. Theoretically, the regioselective diphosphination of 1,3-dienes with diphosphines can form the DPPB-type skeletons in a straightforward manner, but there is only one successful example in the literature, where the parent 1,3-butadiene reacted with especially reactive tetramethyldiphosphine under harsh conditions (neat, >100 °C) . Thus, the development of new protocols to accommodate more versatile diene and phosphine substrates is greatly appealing.…”

“…Theoretically, the regioselective diphosphination of 1,3-dienes with diphosphines can form the DPPB-type skeletons in a straightforward manner, but there is only one successful example in the literature, where the parent 1,3-butadiene reacted with especially reactive tetramethyldiphosphine under harsh conditions (neat, >100 °C). 11 Thus, the development of new protocols to accommodate more versatile diene and phosphine substrates is greatly appealing. Herein, we report a bromine cation initiated diphosphination of 1,3-dienes with tetraaryldiphosphines (Ar 2 P−PAr 2 ) under Ir(ppy) 3 -promoted photoredox catalysis.…”