The preparation and structural elucidation of uranium (VI) complexes and salts of the phosphorus ylides Ph3PCHCOPh, Ph3PC(COMe)(COPh) and Ph3PCHCOOCH2CH3

Anhydrous TEMPO-H: reactions of a good hydrogen atom donor with low-valent carbon centres

“…As suggested by Kalyanasundari et al,28 this planarity also supports the resonance delocalization model. It is reflected again in the torsion angles for this region of the molecule, P1-C19-C20-O1 = 175.35(10) • , P1-C19-C20-O2 = -6.3(2) • , C19-C20-O1-N1 = -10.72 (18) • and O2-C20-O1-N1 = 170.70 (11) • , all values similar to those reported by Spencer et al 29 and Kalyanasundari et al 28 The non-bonded distance between P1 and O2 is 2.94 Å , significantly less than the sum of the van der Waals radii for phosphorus and oxygen (3.3 Å ). 30 As described by both Spencer et al 29 and Kalyanasundari et al, 26 this suggests that there is a strong intramolecular interaction between the P + and O -charge centres of the enolate resonance contributor, which in turn leads to the molecule adopting a cis orientation.…”

The synthesis and structural characterisation of the mercury (II) halide complexes of the phosphorus ylide carbethoxymethylenetriphenylphosphorane

“…The significant elongation of the P1-C19 and C19-C20 bonds in complexes 1, 2 and 3 with respect to the free ylide [14] (1.706(2) Å and 1.408(2) Å , respectively) is consistent with the loss of resonance delocalisation within the ylide ligands upon complexation. The non-bonding distance between the phosphorus and oxygen atoms of the ylide molecules are 3.048(4) Å (1), 3.155(8) Å (2), and 3.013(5) Å (3).…”

Mercury(II) complexes of stabilized phosphine–phosphonium ylide derived from bis(diphenylphosphino)methane: Synthesis, spectra and crystal structures

“…As shown, both the phosphine and ylidic components are devoid of steric Table 2 Selected bond distances (Å) and angles (°) in compounds 2, 3 and 4. 113.03 (7) 112.62 (8) 120.07 (5) [P(4)-Hg(2)-I(4) = 112.94(5)] X(1) -Hg(1) -P (2) 112.41 (7) 117.46 (9) 118.92 (5) [P(4)-Hg (2) bond lengths within the ylidic fragment are comparable to those observed for the other monoketo ylides [22,23]. No steric or electronic effects due to the presence of -CH 2 PPh 2 is thus anticipated.…”

“…The monoketo ylides derived from bisphosphines, viz., Ph 2 PCH 2 PPh 2 @C(H)C(O)R, Ph 2 PCH 2 CH 2 PPh 2 @ C(H)C(O)R (R = Me, Ph or OMe) [4] contain a P donor site in addition to C donor (the ylidic C) or O donor (the carbonyl O) sites for coordination, and therefore can engage in different kinds of bonding with metal ions. We have been interested in studying the coordination modes adopted by the resonance stabilized ylides when ligated to Hg(II) and U(VI) [5]. Hg(II) forms C-coordinated complexes with Ph 3 P@C(H)C(O)Ph [6,7] and Ph 3 P@C(H)CO(OCH 2 -CH 3 ) [8], whereas, regiospecific O-coordination of the acetyl oxygen had been observed with Ph 3 P@C(COPh)(COMe) [9].…”