Jonathan L. Bookham

The disecondary phosphines [PhHP(CH2)nPHPh] (n = 2-4, 6): improved syntheses, NMR spectra and complexation behaviour with group VI Transition metal hexacarbonyls

Abstract Improved preparations of the disecondary phosphines PhHP(CH2)nPHPh (n = 2, mppe; n = 3, mppp; n = 4, mpppb; n = 6 mpph) by the lithium cleavage of the corresponding ditertiary phosphine Ph2P(CH2)nPPH2 are described and various NMR parameters are reported; a 12 13 C isotope effect upon δ(13P) is observed in the case of mppe. Reactions of mppe and mppp with [M(CO)6] (M = Cr, Mo, W) yield 1:1 complexes; both the meso and the rac isomers are produced, are separated and are unequivocally characterized by elemental analysis, vibrational spectroscopy and 1H, 13C and 31P NMR spectroscopy.

The synthesis, nuclear magnetic resonance spectra, crystal structure, and solid-state and solution conformations of tris(diphenylphosphino)ethene (tppee)

Abstract The synthesis of tris(diphenylphosphino)ethene (tppee) by addition of Ph2PH to Ph2PCCPPh2, or by the reaction of Ph2PCl with Ph2PCli:CHPPh2, and its crystal structure are described. Crystals of tppee are monoclinic, space group C2/c with a 3553.0(4), b1044.1(1), c 1855.7(2) pm, β 93.40(1)°, and Z = 8; final R = 0.0597 for 4585 observed reflections. The proton, 13C and 31P NMR parameters are reported, and the PP and PC coupling constants suggest a solution conformation that is close to that found by X-ray diffraction on the solid; that is, a close approach of the electron lone pairs of the cis-vicinal phosphorus atoms, and opposition of those on the geminal phosphorus atoms.

Stereoselective addition reactions of diphenylphosphine to pyridyl and pyrimidylalkynes: chiral 1,2-diheteroaryl-1,2-bis(diphenylphosphino)ethanes and their Group 6 metal carbonyl complexes

Abstract The base-catalysed addition of diphenylphosphine to the diarylethynes RCCR′ (R=R′=2-pyridyl 1 ; R=R′=3-pyridyl 2 ; R=2-pyridyl, R′=3-pyridyl 3 ; R=phenyl, R′=2-pyridyl 4 , 3-pyridyl 5 , 2-pyrimidyl 6 ) yield diphosphines of general formula Ph 2 PCH(R)CH(R′)PPh 2 together with alkene by-products Ph 2 PC(R)CHR′ and HC(R)C(R′)PPh 2 in all cases except 1 . Selected P,P′ -coordinated M(CO) 4 complexes (M=Mo, W) of the diphosphines have been prepared and their 1 H-, 13 C- and 31 P-NMR data are presented. The pattern of 13 CO-NMR signals for the tetracarbonyl complexes was used unambiguously to determine the stereochemistry of the parent diphosphine. At moderately elevated temperatures, nitrogen coordination of 2-pyridyl and 2-pyrimidyl groups occurred for tetracarbonyl complexes of meso - or erythro -stereochemistry, but not for complexes of rac - or threo -form, to yield corresponding fac -tricarbonyl complexes. At 162°C the complex cis-rac -(CO) 4 W{ P,P′ -Ph 2 PCH(R)CH(R)PPh 2 } (R=R′=2-pyridyl) is converted quantitatively into fac-erythro -(CO) 3 W{ P,P′ , N -Ph 2 PCH(R)CH(R)PPh 2 } via an inversion/ N -coordination pathway.

Sterically hindered diphosphines (Ph2P)2C=CHR (R=Me or Ph) and their derivatives

Reactions of (Ph2P)2CCHR (R = Me or Ph) with E (E = S or Se) yielded the corresponding mono- and di-chalcogenides and the mixed S/Se derivatives, 1H, 13C and 31P NMR parameters for which are reported. These are rationalized in terms of conformational preferences associated with the relative P–E and phosphorus-lone pair orientations. The complexes [M(CO)4{(Ph2P)2CCHR}](M = Mo or W, R = Me or Ph) have also been prepared and have NMR parameters which can be accounted for similarly. The crystal structure of (Ph2P)2CCHMe has been determined by single-crystal X-ray diffraction and shows that the solid-state conformation is similar to that deduced in solution on the foregoing basis.

Polyphosphorus ligands. II: The new pentaphosphorus ligand bis(2,2-bis(diphenylphosphino)ethyl)phenylphosphine and its sulphides

Abstract The preparation of the title compound and its progressive reaction with elemental sulphur to give nine from a possible total of 19 different phosphine sulphides are described. One- and two-dimensional 31P NMR experiments are used to disentangle the complicated spectra given by the unseparated reaction mixtures, and the 31P NMR parameters are found to be strongly dependent on conformational influences.

Polyphosphorus ligands—IV. The asymmetric unsaturated biphosphine 1,1-bis(diphenylphosphino)prop-1-ene☆

Abstract The new ligand 1,1-bis(diphenylphosphino)prop-1-ene is valuable as a precursor of other polyphosphorus ligands and metal complexes in which the lowered symmetry induced by the methyl group can introduce diastereoisomerism and can facilitate the measurement of 2 J PP .

Rearrangements of the unsaturated ligand 1,1-bis(diphenylphosphinomethyl)ethene and its chalcogenides and group VI metal carbonyl complexes

Abstract In contrast to the behaviour of other unsaturated organophosphines, treatment of the new ligand (Ph2PCH2)2CCH2 with Ph2PH in the presence of KOBut does not result in addition to the double bond; instead, an allylic rearrangement occurs to give cis and trans Ph2PCHC(CH3)CH2PPh2 in a 3:7 ratio. In the case of (Ph2P(E)CH2)2CCH2 [E = S, Se] only the trans isomer is obtained from this reaction, while under similar conditions (CO)4M(Ph2PCH2)2CCH2 [M = Cr, Mo, W] yields only a cis product in which the two phosphorus atoms remain chelated. The products of these and related reactions are characterized by elemental analysis and 13C and 31P NMR spectroscopy.

Chiral ligands: unambiguous assignment of absolute configuration by NMR spectroscopy

Two-dimensional rotating-frame nuclear Overhauser enhancement (ROESY) spectra are used to determine the relative configurations at the chiral carbon atoms in the two diastereoisomers of [o-[graphic omittted]d(Ph2PCHMeCHMePPh2)]+PF6– derived from (+) Ph2PCHMeCHMePPh21 and [o-[graphic omittted]dCl]2 of known configurations, and hence to show that the (+) form of 1 has the R,Rconfiguration.

An NMR study of the solution conformations of di(tertiary phosphine) complexes of orthopalladated 1-phenyl-1-(N,N-dimethylamino)ethane

NOE intensities derived primarily from 2-D NMR ROESY spectra were used to study the solution conformations of the chelate rings of the (R)- and (S)-[1-phenyl-1-(N,N-dimethylamino)ethane][(2R,3R)-bis(diphenylphosphino)butane]palladium(II) cations, 3 and 4. In each, the diphosphine ring adopts a conformation with both N-methyl groups equatorial owing to potential unfavourable trans-annular methyl–phenyl interactions in the alternative conformation with axial methyl groups. For the orthometallated chelate ring the population of the conformer with C-methyl equatorial is less than 10% in 4, but is close to 55% in 3. This contrasting behaviour is attributed to inter-annular steric interactions between the N-methyl and the P-phenyl groups which also lead to a weakening of the Pd–N bond in 3 and can account for the enantioselectivity of the orthopalladated 1-phenyl-1-(N,N-dimethylamino)ethane moiety when used as a resolving agent.

An unusual ready inversion of sp3 skeletal carbon in an organometallic complex

Abstract Quantitative inversion at the chiral sp 3 hybridised carbon atoms in the octahedral tetracarbonyl tungsten(0) chelate complex of the C 2 chiral diphosphine Ph 2 PCHArCHArPPh 2 (Ar = 2-pyridyl) occurs at moderately elevated temperatures.