Synthesis and Characterization of Some  Triphenylantimony(V) Derivatives of Ν, Ο and S  Containing Monofunctional Bidentate Ligands  Pankaj K. Sharma, Rajendra K. Sharma, A.K. Rai and Y.P. Singh* Department of Chemistry, University of Rajasthan, Jaipur - 302 004, India e-mail: vp sinzh07(a),vahoo.co.in ABSTRACT  Triphenylantimony(V)isopropoxide, Ph 3 Sb(OPr')2, reacts with monofunctional bidentate benzothiazoline ligands of the type HNC 6 H 4 SC(R)CH 2 C(0)R' [where R = CH 3 , R'=CH 3 (1); R=CH 3 , R'=C 6 H 5 (2); R=CH 3 ,R'=4-CH 3 C 6 H 4 (3); R=CH 3 ,R'=4-C1C 6 H 4 (4); and R=CF 3 ,R'=C 6 H 5 (5)] in 1:1 molar ratio in refluxing benzene solution to give corresponding triphenylantimony(V) derivatives, Ph 3 Sb(OPr')[SC 6 H 4 N: C(R)CH 2 C(0)R']. These newly synthesized compounds have been characterized by elemental analyses, molecular weight measurements and IR as well as NMR ('Η and 13 C) spectral studies. These studies show the bidentate nature of the ligands and a hexa-coordination around the central antimony atom in these complexes. INTRODUCTION  The compounds of organoantimony are well known for their applications in chemotherapy as antimony compounds exhibit antiparasitic /l/, antitumor 111, and antifertility 131 activity. Interest in the chemistry of higher co-ordinated organoantimony(V) derivatives has increased in the last two decades, with special interest in their molecular structure, as antimony may attain a co-ordination number of 5,6 and even 7 in some special cases /4-10/. A number of R 3 Sb(V) (R=alkyl or aryl group) derivatives of multidentate ligands have been synthesized and characterized /4-10/ and in some cases it has been observed that the co-ordination number of antimony is seven /4,5/. Benzothiazolines constitute an important class of multidentate ligands and some Al /11/, Ga and In l\2l derivatives of benzothiazolines have been reported, in which these ligands have been reported to behave as bifunctional tridentate ligands. In view of the reported bifunctional tridentate behaviour of these benzothiazolines, it was thought that organoantimony(V) derivatives of these ligands would have a higher coordination number, but in the present case the nature of these ligands is found to be mono-functional bidentate and thus resulted organoantimony(V) derivatives have hexa-coordination around the central antimony atom. In view of this we report in this communication the synthesis and characterisation of triphenylantimony(V) derivatives of these ligands. 51