Organometallic Platinum Complexes Research Articles

Metal complexes of benzodiazepines. Part 3. Synthesis and characterization of organometallic complexes of platinum(II)

The complexes cis-[PtMe2(Me2SO)L1] and [PtR2L2](R = Me or Ph) are easily obtained by reaction in CH2Cl2 of the complexes [PtMe2(Me2SO)2] or [{PtPh2(Et2S)}2] with L1= 2,3-dihydro-2,2,4-trimethyl-1H-1,5-benzodiazepine or L2= bromazepam = 7-bromo-1,3-dihydro-5-(2-pyridyl)-2H-1,4-benzodiazepin-2-one. They are the first examples of simple organometallic adducts of benzodiazepines with platinum(II). Their 1H and 13C NMR spectra suggest the co-ordination of L1 through N5, while L2 acts as a bidentate ligand by means of the imine and pyridine nitrogen atoms. The co-ordinated heterocyclic rings show a notable increase in their inversion barrier.

Structural characterization of cisplatin analogues by fast atom bombardment (FAB) and laser microprobe mass spectrometry (LAMMA)

The present study is concerned with the investigation of the potentials and limitations of fast atom bombardment (FAB) and laser microprobe mass spectrometry (LAMMA) for the structural characterization of a series of cisplatin analogues. The limiting factors for obtaining good quality FAB spectra are the solubility and the stability of the organometallic platinum complexes in the FAB matrix. In the case of a suitable matrix being found, molecular weight information is derived from the (M + H) + and/or (M — H) − ions. Drawbacks of the application of FAB are (i) the low signal intensities of the molecular ion-like species as compared to the matrix signals and (ii) the scarcity of fragmentation necessary for structure determination. Combination of FAB with tandem mass spectrometry was used to overcome these problems. LAMMA provides a valuable alternative for the direct mass spectral analysis of cisplatin analogues. For some compounds, LAMMA results in useful mass spectra, whereas FAB fails. The abundant fragmentation yields structural information which is complementary for positive and negative ions. The laser power density applied to the sample is of critical importance for the quality of the spectra.

3,6-bis(2′-pyridyl)pyridazine-based ligands. Synthesis and organometallic complexes of platinum(II)

In order to improve the solubility of bimetallic complexes in organic solvents, some new 3,6-bis(2′-pyridyl)pyridazine-based molecules have been synthesised and tested as ligands in platinum(II) organometallic complexes. The reaction of 3,6-bis(2′-pyridyl)-1,2,4,5-tetrazine with terminal acetylenes gives 3,6-bis(2′-pyridyl)-4-substituted pyridazines. Their further reactivity toward (DMSO) 2Pt(CH 3) 2 or (COD)Pt(C 6H 5) 2 (1:1 molecular ratio) is reported. The characterisation of the newly synthesised compound by IR, 1H NMR and electronic spectroscopy is described.

Tumor animal models used for evaluating the antineoplastic activity of platinum coordination complexes

The number of organometallic platinum complexes synthesized and tested for antitumor activity, after the discovery of the antineoplastic properties of cis-dichlorodiammineplatinum(II) (cisplatin), is very high, indicating the interest of numerous scientists in this field. Many experimental models of transplantable animal tumors have been employed for estimating the antitumor potency of these derivatives. Rodent tumors growing in ascitic form, such as Ehrlich ascites carcinoma, sarcoma 180, L1210 lymphoid leukemia and P388 lymphocytic leukemias were widely employed and their use has characterized the first 10 years of research. Solid tumors were used as well. The interest was first addressed to the solid forms of s.c.-implanted Ehrlich ascites carcinoma and of sarcoma 180, and particularly to the s.c.-growing ADJPC6 Plasmocytoma on which many analogs have been tested. B16 melanoma, Lewis lung carcinoma, and specialized forms of implant of human and animal xenografts, in the nude mouse and in the subrenal capsule of the mouse respectively, have elicited the interest of scientists in recent years. In addition, several other transplantable animal tumors have been used: Yoshida sarcoma, Walker 256-carcinosarcoma, VX2 carcinoma, mouse fibrosarcomas. Leukemias such as Dunning ascitic leukemia, Pausher leukemia, MPOC 104E plasmocytoma, and myeloid and lymphatic leukemias of the rat have been used during the last 15 years, giving a clear indication of the broad spectrum of the antineoplastic activity of cisplatin. It is worth noting that, in many instances, more than one single tumor mode1 has been used, although L1210 lymphoid leukemia seems to be the tumor line which has received the most interest, being present alone or with other tumors in almost all of the scientific works from the end of the Sixties. Detailed examination of the tumor models employed in the research for cisplatin analogs shows that, although some old tumors such as Ehrlich ascites carcinoma are still used for studying drug-cell interactions, an even greater interest is devoted by researchers towards an improvement in the selection of experimental tumors endowed with more similarities with those commonly encountered in humans, which are thus more predictive of activity in the human patient.

Formation of organometallic complexes of platinum(II) and platinum(IV) in reactions of PtCl 62− with alkanes, olefins and aromatics induced by γ-irradiation

γ- Irradiation of solutions of the ion PtCl 6 2− and n-hexane (or alkene) in MeCO 2H affords a π-olefin complex of platinum(II); σ-aryl complexes of platinum(IV) are formed in analogous reactions with aromatic compounds.

Electron microscopic studies of platinum catalysts prepared via decomposition of Al2O3-anchored metal complexes

Reduced alumoplatinum and alumoplatinum-tin catalysts prepared via interaction of an organometallic platinum complex and platinum-tin compounds of various composition with Al2O3 mainly contain platinum particles of ≤10 A.