Synthetic Pathway, Structural Chemistry and Structural Elucidation Based Upon Spectral Studies [IR, NMR (*Η, 13 C and U9 Sn)] of Some Mixed Ligand Complexes of Diorganotin (IV) Derived from Sterically Demanding HeterocyclicxvutsronmkjihgedcaVUTSRPONJIDCBA ß-Diketones and N-Protected Amino Acids. Anurag Joshi, Shashi Verma, Asha Jain and Sanjiv Saxena* Department of Chemistry, University of Rajasthan, Jaipur-302 004, India E-mail: saxenas348@sify.com ABSTRACT A series of new mixed ligand diorganotin (IV) complexes of general formula Bu 2 SnLA [where LH = RCOC:C(OH)N(C 6 H 5 )N:CCH 3 ; R = -C 6 H 5 , -C 2 H S , -CH, and AH = C(0)C 6 H 4 C(0)NCH R'COOH; R' = -H, - CH,, -CH(CH,) 2 , -CH 2 C 6 H 5 , -CHR' = -CH 2 CH 2 - was synthesized by the interaction of dibutyltin (IV) dichloride with the corresponding ligands in the presence of triethylamine in 1:1:1:2 molar ratios in dry refluxing benzene solution. The plausible structures of these newly synthesized complexes have been proposed on the basis of physico-chemical and spectral studies. The central tin atom is bonded by heterocyclic ß-diketone and N-protected amino acid ligands. The ll9 Sn NMR spectral studies of some of these complexes reveal the presence of hexacoordinated tin centres in these complexes. INTRODUCTION The chemistry of organotin (IV) complexes derived from various organic ligands such as Schiff bases /1,2/, ß-diketones /3/, dithiocarbazates /4/, mono and dithiophosphates 15,61, dipeptides 111, semi- and thiosemicarbazones /8/, N-protected amino acids /9,10/ and oximes /11,12/ has been extensively studied during the last few decades. There has been continuous interest in the chemistry of organotin (IV) complexes /13-16/ and the studies on organotin (IV) complexes are mainly concerned with their synthetic and structural aspects. The modern physical techniques may be applied for the study of the structural aspects of organotin(IV) complexes. The organotin(IV) complexes exhibit significant biological activities /17-23/ and find applications as biocides /24,25/, industrial catalysts /26,27/ and polymers /28/. N-protected amino acids and sterically demanding heterocyclic ß-diketones are the potential organic ligands because of their interesting bonding patterns /29-3I/ and potential biological applications of their metal complexes /17,32,33/. A good deal of 123