A benzene (~10 ml) solution of HS₂P(OPr-n)₂ (0.818 g; 3.82 mmol) was added to benzene (~15 ml) solution of Cp₂TiCl₂ (0.475 g; 1.91 mmol) dropwise with stirring at room temperature. The reaction mixture was refluxed for ~5 hour, during which the color of the reaction mixture changed from color red to dark red. The excess solvent was removed under reduced pressure and the product washed repeatedly by n-hexane and the desired product was finally dried under reduced pressure.

Bioactivity studies were conducted using three bacterial strains; Escherichia coli, Bacillus cereus, and Pseudomonas aeruginosa as test microorganisms.

Susceptibility of the microorganisms to the novel chemical compounds was determined using the Agar diffusion method and in accordance with the CLSI (formerly NCCLS) guidelines [21] . This method was used as a qualitative method to determine whether each bacterium is resistant, intermediately resistant or susceptible to the synthesized chemicals. The broth cultures of the microorganisms were first grown until they had an optical density (OD) or absorbance of 0.8 - 1.0 at a 600 nm wavelength. Inoculum of approximately 10⁶ colony forming unit (CFU) of each isolate was plated on to the Mueller-Hinton Agar plates to form a confluent or lawn growth. The test chemical (400 ug/ml) or control (70% ethanol, v/v) was applied to sterile disks and placed on the inoculated plates and incubated at 37˚C for 24 h.

The zones of inhibition/clearance of microbial growth around the disks containing the extracts/control were measured. The zone of inhibition was defined as the shortest distance (in mm) from the outside margin of the initial point of microbial growth. Three replicates were made for each test organism.

IR spectra of biscyclopentadienyl titanium bis (dialkyl and alkylenedithiophosphate), have been recorded in the region 4000 - 400cm⁻¹ [22] [23] . The band shown by the parent acids in the region 2544 - 2400 cm⁻¹, due to SH stretching vibration, are absent for biscyclopentadienyl titanium bis(dialkyl and alkylenedithiophosphate) derivatives, indicating the formation of Ti-S bond with the appearance a new band in the regions 428 - 400 cm⁻¹ [22] [24] . The bands present in the region 1104.0 - 1014.5 cm⁻¹ and 937.3 - 800 cm⁻¹ have been assigned to ν (P)-O-C and νP-O-(C) stretching vibrations respectively. Strong bands in the region 995 - 921.9 cm⁻¹¹ are due to dioxaphospholane and dioxaphosphorinane ring vibrations [25] - [27] . The bands observed present in the region 704.0- 638.0 cm⁻¹¹ can be assigned to ν P=S vibrations [28] . The bands in medium intensities in the region 602 - 513.0 cm⁻¹¹ may be attributed to vibration of νP-S asymmetric and symmetric vibrations [29] . Details regarding the individual bands have been included in Table 2.

s = strong, m = medium, w = weak and b = broad absorption band.

The ¹H NMR spectra Biscyclopentadienyl titanium bis (dialkyl and alkylenedithiophosphate) recorded in CDCl₃, show the characteristic resonance due to alkoxy and glycoxy (dithio moiety) protons. These ¹H NMR spectral data are given in Table 3. The singlet peak at (3.1 - 3.5 ppm) in the parent dithiophosphoric acids and assigned to SH proton, is absent from the spectra of Titanium bis (dithiophosphate) derivatives indicating deprotonation of SH group and forming of Ti -S bond [30] .

The ¹³C NMR spectra of biscyclopentadienyl titanium bis (dialkyl and alkylenedithiophosphate) complexes were recorded in deuterated chloroform at ambient temperature (Table 4). The spectra show very small chemical shifts when compared to those obtained for the parent dithiophosphoric acids and indicate no substantial difference in the structure [31] .

The proton decoupled ³¹P NMR spectra of biscyclopentadienyl titanium (IV) bis (dialkyl and alkylenedithiophosphate) derivatives, Table 3, show only one signal peak for each complex in the region 77.9 - 93.7 ppm. The observation of only one sharp singlet for all compounds reflects the equivalent nature of phosphorous nuclei and the purity of the compound. However, no notable difference was observed in comparison to the parent acids [32] [33] . According to Glidewell, these small shifts indicate monodentate behavior of the ligand [34] .

Considering the normal mode of bonding of dithiophosphate with the metal as bidentate chelating ligand and based on the above spectral studies of the complexes using IR, NMR (¹H, ¹³C, ¹³P), molecular weight determination and elemental analyses. We suggest the following structure (Figure 1 and Figure 2).

The preliminary results show that the chemical compounds slightly inhibited the growth of Escherich coli and Bacillus cereus after a 24 h incubation period, but had little or no effect on Pseudomonas aeruginosa under similar conditions. See (Table 5) and Figure 3. The results are means of three replicate experiments. Escherichia coli a Gram-negative bacterium commonly found in the lower intestine of warm-blooded organisms [35] appeared to be the most susceptible to all chemicals tested with zones of inhibition ranging from 5.0 ± 0.76 (Cp₂Ti [S₂P(OPr-n)₂]₂) to 11.1 ± 0.54 for (Cp₂Ti [S₂P(OEt)₂]₂). The test chemicals had very little inhibitory effect on Pseudomonas aeruginosa.