Notizen: Isomerism in the Linear Tetratertiary Phosphine 1,1,4,7,10,10-Hexaphenyl-1, 4,7,10-Tetraphosphadecane

Abstract

Two isomers of the linear tetratertiary phosphine (C6H5)2ΡCH2CH2Ρ(C6H5)CH2H2Ρ(C6H5)CH2CH2Ρ- (C6H5)2 with widely differing solubilities and melting points can be obtained from the base-catalyzed addition of C6H5P(H)CH2CH2P(H)C6H5 to two equivalents of diphenylvinylphosphine; these appear to be the dl and meso diastereoisomers arising from the two equivalent asymmetric phosphorus atoms.

Iron(II) Complexes of the Linear rac-Tetraphos-1 Ligand as Efficient Homogeneous Catalysts for Sodium Bicarbonate Hydrogenation and Formic Acid Dehydrogenation

“…5a In an NMR-scale experiment, we reacted the monohydride 3•BPh 4 with CO 2 (1 atm) in d 8 -THF, obtaining as expected the formate complex cis-α-[Fe(η 2 -O 2 CH)(rac-P4)](BPh 4 ) (6•BPh 4 ; Scheme 4), having 31 P{ 1 H} NMR signals at δ P 106.0 (t) and 76.5 (t, 2 J PP = 29.5 Hz). In the corresponding 13 C{ 1 H} NMR spectrum, apart from the signal at δ C 162.4 ppm due to BPh 4 − , a broad singlet at 174.6 ppm compatible with a coordinated formate anion was observed. By repetition of the test using in situ generated 3•BF 4 and 13 CO 2 , the singlet at 174.6 ppm turned as expected into a doublet with 1 J CH = 208.8 Hz in the corresponding protoncoupled 13 C NMR spectrum.…”

“…The linear tetradentate phosphine ligand 1,1,4,7,10,10-hexaphenyl-1,4,7,10-tetraphosphadecane (tetraphos-1, P4) exists as a mixture of rac ( S , S ; R , R ) and meso ( S , R ) diastereoisomers (hereafter rac- P4 and meso- P4, respectively), which can be separated by fractional crystallization. , Despite the fact that the existence of these stereoisomers was recognized as early as 1974, the importance of this isomerism was not fully appreciated until the work of Brown and Canning . The configurations that these diastereoisomers can adopt in an octahedral complex are denoted as cis-α, cis-β, and trans (Chart ).…”

“…While the meso isomer can adopt only a trans or cis-β configuration, all three configurations are physically possible for the rac isomer. Nevertheless, the rac isomer is known for its propensity to form cis-α complexes. , Since the original preparation of tetraphos-1 by King and co-workers, there have been a number of reports on its coordination behavior. − By a close perusal of the available literature, we noticed that the chemistry of the meso isomer is far more developed than that of the rac isomer. Only complexes [FeBr­(P4)]­[BPh 4 ] and trans - [FeH­(N 2 )­(P4)] have been characterized crystallographically, and in both the ligand exhibits a meso configuration.…”

New dihydrogen complexes: the synthesis and spectroscopic properties of iron(II), ruthenium(II), and osmium(II) complexes containing the meso-tetraphos-1 ligand

“…[7]). THF [7] trans-RuH(C1)L + NaOEt tran~-Ru(H)~L + unidentified products was FeL'; the loss of hydride ligands under these conditions is not uncommon (34).…”

“…To better understand this intramolecular hydrogen atom exchange, we have prepared new dihydrogen complexes of the tetradentate phosphine Ph2PCH2CH2P(Ph)CH2CH2P(Ph)CH2CH2-PPh2 (tet-1). This ligand exists as a mixture of two diastereomers, the meso (S,R) and rac (S,S; R,R) forms (7). The topologies that these diastereomers adopt when coordinated in an octahedral complex are denoted by the cis-a, cis+, and trans nomenclature (8) (Fig.…”