Organometallic Derivatives of Ruthenium ( II & III ) ligated by Quinazole-2-thione-4-one

Mixed ligand phosphine and arsine complexes of ruthenium (II & III) ligated by Quinazole-2thione-4-one (QTH) of composition [Ru(Pφ 3 ) 2 (QT) 2 ], [RuX(CO)(Eφ 3 ) 2 (QT)] and [RuX 2 (Eφ 3 ) 2 (QT)] (E = P/As; X = Cl/Br; QT = monobasic bidentate N,S-chelating ligand) are prepared and investigated. The identities of complexes are established by elemental analysis, conductivity measurements, magnetic susceptibility and spectral methods (IR, UV-vis, 1 H NMR). An octahedral geometry has been tentatively proposed for all these complexes.


INTRODUCTION
Quinazole-2-thione-4-one (Str.I) contains amide and thioamide groups having interesting donor sites. 1 We have reported some complexes of low-valent 2 and high-valent 3 metal ions with this ligand in our earlier communication.The present paper reports synthesis, spectral characterization and structural investigation of some ruthenium (II & III) chelates with this ligand.

EXPERIMENTAL
All chemicals used in this work were either of Anal R grade or chemically pure grade.

Preparation of new ruthenium (II) complexes
All new ruthenium (II) complexes of composition [RuCl(CO)(Eφ 3 ) 2 (QT)] (E = As/P) were prepared by the ligand substitution in benzene using precursor complexes and ligand reported in our previous method. 12The other ruthenium (II) complex of composition [Ru(Pφ 3 ) 2 (QT) 2 ] was prepared by direct reaction of [RuCl 2 (Pφ 3 ) 4 ] with ligand (QTH) following our previous method. 13e analysis of C, H and N were performed at CDRI, Lucknow, India.The IR spectra of ligand and complexes were recorded on a Perkin-Elmer Model-577 Spectrophotometer in the range of 4000-200 cm -1 as KBr pillets.The magnetic measurements were made on a Gouy balance and diamagnetic corrections for the ligand molecule were applied.Electronic spectra were recorded with Beckmann DU-6 spectrophotometer.The molar conductance of complexes (10 -3 M) were measured in DMF using Wiss-Wekstatter Weighein obb type LBR conductivity meter.The 1 H NMR spectra were recorded on Bruker 400 MHz using TMS as reference.

RESULTS AND DISCUSSION
The ligand directly reacts with precursors and yielded solid products without change in oxidation state of ruthenium : The analytical data is consistent with the proposed stoichiometeries of the complexes.In all the above reactions, the thioamide ligand behaves as mononegative bidentate ligand.All isolated solid products are air stable in the solid state at room temperature and are non-hygroscopic in nature.All synthesized complexes are soluble in DMF, DMSO and acetonitrile producing intense coloured solution.The molar conductance in DMF (10 -3 M) are found in the range of 10.16 -15.5 Λ -1 cm 2 mol -1 indicating their non-electrolytic nature. 15The chloride or bromide ion in corresponding complexes are present in the inner sphere and coordinated nature.

IR Spectra
A comparison of the IR spectra (table 1) of the ligand (QTH) and ruthenium (II & III) complexes brings out the following facts to light : which is attributed due to terminally coordinated carbonyl group and is observed at higher frequency than in the precursor complexes. 23(iv) Thioamide bands [24][25][26] I, II, III and IV are observed at 1530 (s), 1295 (m), 960 (m) and 790 (m) cm -1 in the spectrum of ligand (QTH).Band I splits, Band II blue shift to higher frequency, while band III and band IV red shift with reduction in intensity.1][32]  Thus, the thioamide ligand acts as N, S-chelating mononegative bidentate nature in octahedral structure.

H NMR Spectra
1 H NMR spectra of ligand and some complexes (Sl.No. 1, 2 & 3) were recorded in CDCl 3 / TMS to substantiate further metal-ligand bonding.The aromatic protons signals are observed at δ7.8 -8.6 PPM and the aromatic proton at position -5 is deshielded by carbonyl oxygen so the extreme signal at δ8.3 PPM is considered to be due to this proton.The imino protons of the ligand observed at δ3.2 -3.6 PPM found to be absent in complexes indicating deprotonation of imino group.The 1 H NMR spectra of complexes show a multiplet around δ6.2-7.7 PPM which is assigned to aromatic protons of Pφ 3 /Asφ 3 . 33he resonances in the region δ7.68 PPM, δ8.2 PPM and δ 8.8 PPM assignable to the protons of Pyridine ligand along with the resonances due to aromatic protons in complexes. 34us, on the basis of physico-chemical, conductometric, magnetic, UV-vis, IR and 1 H NMR data octahedral structure of both Ru(II) and Ru(III) complexes may be reasonably assigned.
(i) The medium broad nN-H bands of the ligand at 3446 and 3350 cm -1 are severely affected on coordination.The 3446 cm -1 band almost disappears indicating displacement of N-H hydrogen by means of Ru(II)/Ru(III) ion and formation of Ru(II)-N/ Ru(III)-N bond.While the 3350 cm -1 band shift to lower frequency and gets split.(ii) The nC=O band of the ligand at 1710 cm -1 is found to be almost at the same place in the spectra of complexes indicating absence of bonding through carbony oxygen atom. 22(iii) All carbonyl complexes of ruthenium (II) display a new strong band in the region 1955-1960 cm -1 (vi) The single Ru(III)-Cl stretching mode in [RuCl 2 (Eφ 3 ) 2 (QT)] indicates two mutual chlorine atoms are at Trans-position in octahedral structure (Str.III).