Phosphine-borane adduct studies

The proton n.m.r. spectra of these adducts have been intensively studied. The BH3 resonance in the spectrum of CHjPHj BH3 consists of a 1 1 1 1 quartet due of coupling between the boron nucleus ( B, 80% natural abundance /= 3/2) and the directly bonded protons (/bh" = 99 Hz). Each component of the quartet is further split into a doublet of triplets due to coupling with the phosphorus nucleus (/pH" = 16 Hz) and the two protons bonded to phosphorus, respectively. The PH -signal is, as is typical for phosphine-borane adducts, a doublet with/pH = 375 Hz. All n.m.r. data for the two types of adducts are given in Table 11. 

Stereochemistry — The conformational analysis of various deuteriated ethyl-phosphine-borane adducts and dimethyl methylphosphonates were based on vibrational spectral data. The stereochemistry of diethylphosphonyl acetamide,the unusual vinyl compounds (60 X = L.E.P., O, and a number of l,3,2-dioxaphosphorinanes have been studied. It was found that the Raman-active ring vibration is related to the orientation of the phosphoryl group. Conformational data for dioxaphosphepane was compared with calculated parameters. A low-temperature study of several cyclopropyl-phosphonates (61) revealed rotational isomerization about the P-O bonds but not about the P-C bond. The variable temperature i.r. and Raman spectra of the silyl phosphates (62) also revealed rotational isomerism. ... 

Nucleophilic attack at other atoms. The chemistry of phosphine-borane adducts has continued to generate interest. Simple borane adducts of primary vinyl-, ethynyl- and allenyl-phosphines have been prepared and studied by a range of spectroscopic and theoretical techniques. The same group has also shown that attachment of the BH3 unit to a variety of primary phosphines results in a substantial increase in the intrinsic acidity of the system in the gas-phase. Group III halide adducts of the type Bu 2PH EX3 (E = B, Al, Ga or In X = Cl or Br) are accessible from the reactions of the secondary phosphine with the trihalides at room temperature. The solid state structure and reactivity of these adducts was also reported. Treatment of l,8-bis(diphenylphosphino)naphthalene with the borane-dimethylsulfide complex in ether solvents affords a simple monoborane adduct of the diphosphine irrespective of the molar ratio of the... 

Photolysis of (244) in the presence of alcohols likewise results in the formation of esters of methyl(phenyl)phosphinic acid. However, O-isotopic labelling studies provide evidence of, at least, the partial involvement of a pentacovalent phosphorus intermediate in this reaction, and so the previous assumption of the intermediacy of (245) may not be the whole story. The phosphole oxide dimers (246) have been shown to undergo regioselective reduction and complexation on treatment with the dimethylsulfide-borane adduct, to form the bicyclic system (247). Treatment of the propadienylphosphine oxide... 

The reaction between a Lewis acid R3M and a Lewis base ER3 is of fundamental interest in main group chemistry. Synthetic and computational chemists have investigated the influence of both the Lewis acid and the base on the solid state structure and the thermodynamic stability of the corresponding adduct, that is usually expressed in terms of the dissociation enthalpy De. This led to a sophisticated understanding of the nature of dative bonding interactions. In particular, reactions of boranes, alanes and gallanes MR3 with amines and phosphines ER3, typically leading to adducts of the type R3M <— ER3, have been studied.10... 

Adducts of secondary phosphines have also been studied in the context of MO VCD precursors,29 as well as the dehydrocoupling of borane and phosphines to form B-P bond-based polymers.158 Low to medium molecular weight poly(phenylphosphino-boranes) were isolated in the B(C6F5)3 catalyzed dehydrocoupling of PhPH2 BH3. 

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