Synthesis and Characterization of Some Trivalent and Tetravalent Derivatives of 2-Hydroxy-1-naphthoic Acid

The trivalent derivatives (B, Al, As, Sb & Fe) and tetravalent derivatives (Si,Ti & Se) of 2-hydroxy-1-naphthoic acid have been prepared by the interaction of their corresponding isopropoxide with letter in different molar ratio viz. 1:3 &1:4 in benzene medium. The prepared compounds generally obtained as coloured solids and amongst them those containing isopropoxy groups were found to be hygroscopic. All these compound were characterized by azeotrope and elemental analysis as well as by IR, PMR and mass spectral measurements. These spectral data have facilitated in elucidating the mode of bonding of the said metals and nonmetals in these compounds with 2-hydroxy-1-naphthoic acid.


Introduction
The reactivity of metal / non metal alkoxides provides a simple and convenient method for preparations of a variety of metallo-organic / non-metallo-organic compounds.

Materials
All the chemicals used during the study were of analytical grade reagents.The solvents were dried by standard procedures. 52-Hydroxy-1-napthoic acid were used after re-crystallization from 50% (v/v) aqueous ethanol.B, Al, Fe, As or Sb triisopropoxides and Si and Se tetraisopropoxides were prepared by already reported methods 6 .Titanium tetraisopropoxides were used as such.

General Procedure for the synthesis of trivalent and tetravalent derivatives
The tri/tetravalent isopropoxide and 2,1 hna in appropriate stoichiometry in dry benzene are refluxed on a wax bath at 90-100 0 C.After several hrs (Table 1) of reflux, the isopropanolbenzene was fractionated out and the amount of isopropanol liberated was estimated by an oxidimetric method 7,8 to monitor the completion of the reaction .This yielded colored solid which was washed with dry benzene followed by dry ether and finally dried under suction.

Characterization
Melting points were recorded on an electro thermal CAT No. IA 8103 digital m.p. apparatus.The IR spectra was recorded on a Bruker IFS 66 v FT-IR spectrometer, using KBr pellets in the region 4000-400 cm -1 , while the PMR spectra were taken in DMSO-d 6 solution and recorded on a JEO GSX 400 NB FT-NMR 400 MHz spectrometer, using TMS as an internal standard.The electrospray mass spectra were recorded on a Micromass Quatro II triple quadrapole mass electrospray spectrometer.

Results and Discussion
The reaction occurring between tri and tetravalent metal and non-metal isopropoxide and LH 2 may be illustrated as under: IR and PMR spectrum of trivalent (III) and tetravalent (IV) compounds 9,11 The IR and PMR spectrum are already known 4 .M(III) (LH 2 ) 3 , M(IV) (LH 2 ) 4 shows weak and medium absorption in the region 3100-2880 cm -1 indicate the overlapping of free hydroxy and νC-H of the aromatic ring, while the other absorptions in the region 3100-2880 cm -1 corresponds to the overlapping of νC-H of the aromatic ring and isopropoxide group in case of M(IV) (LH 2 ) 3 (OPr i ).The absorption in the region 1645-1620 cm -1 shows the overlapping of ν as COO and νC=C of the aromatic ring and other absorption at 1440 -1420 cm -1 assigned to ν s COO of the carboxylate group.Thus a shift of 10-20 cm -1 ν s COO in comparison to the ligand suggests bonding of the carboxylate oxygen to the corresponding metal / non-metal.Further the separation value (ν as COO-ν s COO) ∆νCOO, 185-230 cm -1 suggests the presence of a bridged or coordinated carboxylate group.The weak absorptions in the region 1390-1360 cm -1 in M(IV) (LH) 3 (OPr i ) exhibits C-H bending of the gem-dimethyl structure of the isopropoxy group and other absorption in the region 1345-1210 cm -1 because of the v C-O of the hydroxyl group, while the absorption in the region 1160-1140 cm -1 in M(IV) (LH 2 ) 3 (OPr i ) correspond to νC-O of the isopropoxy group.The new bands around 1360-1350 cm -1 and 580-475 cm -1 correspond to νB-O and νM-O (M = Br, Al, Sb, Fe, As, Si, Ti &, Se).

* Molecular weight obtained by Mass Spectrum in several representative cases.
The multiplet between 7.20-8.15corresponds to the naphthyl ring protons.The doublet and multiplet in the region 1.20-1.55and 4.10-4.55due to -CH 3 and ≡CH protons of the isopropoxy group in M(IV)(LH 2 ) 3 (OPr i ).A hump in the region 6.44-5.85suggests that the hydroxy group remains intact.The signal due to the protons of the carboxylic acid observed in 2.1hna disappear in these compounds and no additional peaks have been observed to occur which indicates the participation of carboxylate groups in bonding with the corresponding metal / non-metal.