Rhodium(I) complexes of α-keto-stabilised 1,2-bis(diphenylphosphino)alkane mono ylides
Rhodium(I) complexes of the hybrid ylide-phosphine ligands, Ph2P(CH2)nPPh2(CHC(O)C6H5) (n = 1: dppm-yl, or 2: dppe-yl) have been synthesised from [Rh(μ-C1)(COD)]2 (COD = 1,5-cyclooctadiene) and characterized by NMR spectroscopic and X-ray structural methods. The dppe-yl behaves as an ambidentate ligand; it functions as a monodentate P-donor ligand with a dangling ylidic carbon in the neutral chloro complex, [(COD)Rh(Cl)(dppe-yl)] (1), whereas replacement of the chloride by a non-coordinating counter anion results in the formation of the complexes, [(COD)Rh(L-L’)]+ (L-L’ = dppe-yl (2) or dppm-yl (3)) respectively in which the ligands are bonded to the metal via the phosphorus and the ylidic carbon atoms. The 1,5-cyclooctadiene (COD), present in the Rh(I) precursor, remains intact in the products. The structures of1,2 and3 have been confirmed by X-ray crystallography.
Theoretical studies of n-membered ring chelate complexes of Ni(II), Pd(II) and Pt(II) derived from bidentate phosphorus ylides
Abstract The structural and electronic properties of a series of transition metal complexes of bidentate phosphorus ylides, namely [(R 2 P(CH 2 ) n PR 2 C(H)C(O)R)MX 2 ], have been investigated using density functional theory (DFT) calculations at the B3LYP/LanL2DZ level of theory. The substituent R on the phosphorus atoms (R = Me, Ph), metal atoms (M = Ni, Pt, Pd), halogen atoms (X = Cl, Br, I) and (CH 2 ) n groups ( n  = 1–3) are combined to make different complexes with five-, six- and seven-membered chelate rings. The results of this work provide valuable guidelines for the synthesis of new bidentate phosphorus ylides and their complexes to be used in industry, catalysis or biological activities. The final geometry of the formed complexes indicates that the X atoms have a cis orientation in five- and six-membered complexes, whilst in seven-membered complexes they have a trans orientation. The general trends of the electronic and structural properties are derived from the free ligands and the corresponding complexes. For all the complexes, the M–P(1) and M–C(2) bonds have the longest bond lengths for Pd(II) complexes, which nicely reflects the Lanthanide contraction. The computed binding energies have shown that a six-membered chelate ring complex, for both the methyl and phenyl substituted ligands, is the most stable form of the n-membered chelate ring complexes. In this regard, the sequence of the binding energies was found as Pt > Pd > Ni; Cl > Br > I; Me > Ph. The results of gap energies indicate that Ni can be considered as the most reactive metal, Ph as the most reactive R group and I as the most reactive halogen. The natural bonding orbital analyses show that the M–P(1) bond has a stronger covalent character than the M–C(2) bond. There is a decrease in the charge distribution on the ligands, reflecting electron transfer from the ligands to the metal and halogen co-ligands so that the M–C bonding orbitals are polarized towards the carbon atom and the M–P bonds are also polarized towards the phosphorus atom. The changing R groups substituted on the phosphorus atom have an effect on the structure and molecular properties of the complexes.
Mono- and bi-nuclear four-membered methanide auracycles; synthesis and reactivity. X-Ray structure of cis-[Au(C6F5)2(SPPh2O)(CH2PPh2Me)]
The complexes [Au(C6F5)2Cl(SPh2PCH2PPh2CH2R)]ClO4(R = H or Ph) react with Na2CO3 or NaH to give four-membered methanide auracycles [[graphic omitted]HPPh2CH2R)]ClO4 or [[graphic omitted]PPh2CH2R)], respectively; these complexes can be interconverted by reaction with with NaH or HClO4. The neutral derivatives can be used to form homobinuclear complexes [[graphic omitted]C(AuX)PPh2Me}](X = C6F5 or Cl) and [[graphic omitted](AuPPh3)PPh2Me}]BF4 and react with water to give [Au(C6F5)2(SPPh2O)(CH2PPh2CH2R)]. The structure of [Au(C6F5)2(SPPh2O)(CH2PPh2Me)] has been solved by X-ray crystallography.