Volume 40, Issue 3-4

In this review the structural parameters of 20 mononuclear Pt(II) coordination complexes with an inner coordination sphere of PtPX 3 (X=O, N, Cl, S, I or Te) are summarized and analyzed. The P-donor ligands are organomonophosphines. These complexes are crystallized in two crystal systems: monoclinic and triclinic (each ×10). The X-donor ligands are mono-: O, N, C, S, or I; bi-: O/O; N/N; S/S and ter-: N/N/N; S/S/S, or Te/Te/Te-dentate. The mean Pt-X (homo-trans) bond distances elongate in the order: 2.00 Å (O)<2.02 Å (N)<2.302 Å (Cl)<2.325 Å (S)<2.590 Å (Te)<2.638 Å (I). The mean Pt-P (trans to X) bond distances are in the order: 2.218 Å (X=N)<2.230 Å (Cl)<2.233 Å (O)<2.258 Å (I)<2.287 Å (S)<2.308 Å (Te). The chelating ligands form four-, five-, and six-membered metallocyclic rings.

This review includes more than 100 monomeric derivatives in which the Pt(II) atom is in a distorted square planar environment with inner coordination spheres of PtP 2 X 2 (X=Br, I, Se, Si or Te). The P-donor ligands are organomonophosphanes. These complexes crystallize in three crystal systems: orthorhombic (5.7%), triclinic (37.5%) and monoclinic (56.8%). The X-donor ligands are mono- Br, Se, Si, I or Te or bi- Se, Si, Te, dentate. The chelating ligands form a wide variety of three-, four-, five-, six-, and even seven-membered metallocycles. There are at least two types of isomerism: cis - trans and distortion. Several relationships were found and are discussed.

The lead(II) chloride [{N^N iPr }PbCl] ( 1 ), where {N^N} − is a bulky, monoanionic, bidentate iminoanilide ligand, was synthesised by salt metathesis between [{N^N iPr }Li] and PbCl 2 . The complex was characterised by X-ray diffraction crystallography and 207 Pb nuclear magnetic resonance (NMR) spectroscopy. It exists in the molecular solid state as a monometallic three-coordinate species, with two independent, similar but not identical molecules per asymmetric unit. The differences between the first coordination sphere of 1 and that of Fulton’s structurally related β-diketiminato complex [{N^N iPr }PbCl] are illustrated. The synthesis of 1 offers a convenient handle in the still underdeveloped organometallic and inorganic chemistry of lead(II), as exemplified by the synthesis of the alkyl complex [{N^N iPr }PbCH(CH 3 ) 2 ] ( 3 ). The iodo complex [{N^N iPr }PbI] ( 2 ) was also synthesised, but, unlike 1 , it showed limited stability in solution.

A new one-dimensional (1D) coordination polymer, [Pb 2 (psa)(phen) 2 (NO 3 ) 2 ] n , has been synthesized by the method of hydrothermal reaction and characterized by elemental analysis, FT-IR and X-ray single-crystal diffraction (where H 2 psa is phenylsuccinic acid and phen is 1,10-phenanthroline). The single-crystal X-ray analysis showed that the complex has a dinuclear core stabilized by bridging phenylsuccinic acids and nitrate anions. The coordination number of the two Pb(II) atoms are 7 and 6, with the stereochemically active lone pair, resulting in the hemidirected geometry for the complex. The complex contain a 1D chain, which is further extended into two-dimensional supramolecular architecture through hydrogen bonds, C-H···π, and π···π interactions.

The aldol addition of acyldiazomethane with aromatic aldehydes, vinyl aldehyde and aliphatic aldehydes was carried out efficiently in the presence of MgI 2 etherate and i Pr 2 EtN (DIPEA) using untreated reagent-grade CH 2 Cl 2 under atmospheric conditions in good to excellent yields. Iodide counterion and a non-coordinating reaction media (i.e. CH 2 Cl 2 ) are among the critical factors for the unique reactivity of this reaction system.

Five new triphenyltin complexes of N- (5-bromosalicylidene)-α-amino acids, 5-Br-2-HOC 6 H 3 C(H)=NCH(R)COOSnPh 3 (where R=H, 1 ; Me, 2 ; i -Pr, 3 ; i -Bu, 4 ; s -Bu, 5 ), were synthesized by one-step reactions of triphenyltin hydroxide, 5-bromosalicylaldehyde, and α-amino acid in 1:1:1 molar ratios and characterized by elemental analysis, IR, and NMR ( 1 H, 13 C, and 119 Sn) spectra. The crystal structures of 5-Br-2-HOC 6 H 3 C(H)=NCH( i -Pr)COOSnPh 3 ( 3 ) and 5-Br-2-HOC 6 H 3 C(H)=NCH( s -Bu)COOSnPh 3 ( 5 ) were determined and showed that the tin atom is five-coordinated and adopts a polymeric trans -O 2 SnC 3 trigonal bipyramidal configuration with the axial positions occupied by a carboxylate oxygen from the ligand and the phenolic oxygen of the ligand in an adjacent complex. Bioassay results indicated that these compounds have stronger cytotoxic activity against three human tumor cell lines, HeLa, CoLo205 and MCF-7, than that of cis -platin used clinically.

The crystal structures of two adducts of 2-methoxycarbonylethyltin trichloride with hexamethylphosphoryltriamide (HMPA) and 1,10-phenanthroline (phen), CH 3 OCOCH 2 CH 2 SnCl 3 ·L (L=HMPA, 1 ; L=phen, 2 ), have been determined. The tin atom in 1 is six-coordinated and adopts a distorted [CSnCl 3 O 2 ] octahedral geometry involving an oxygen atom of HMPA and an oxygen atom of intramolecularly coordinating carbonyl group (Sn-O 2.462(2) Å). The tin atom in 2 is also six-coordinated and possesses a distorted [CSnCl 3 N 2 ] octahedral geometry with two nitrogen atoms of a chelating phenanthrolin. The carbonyl oxygen atom does not coordinate to the tin center (Sn···O 4.985(2) Å).