A new complexes of Cp 2Ti[S 2P(OR) 2] 2 (where R = Et, Pr-n, Pr-i, Bu-i and Ph) and Cp 2Ti[S 2POGO] 2 (where G = -CH 2CMe 2CH 2-, -CH 2CEt 2CH 2- and -CMe 2CMe 2-) were prepared by the dropwise addition of the appropriate O, O’-dialkyl or -alkylenedithiophosphoric acid to biscyclopentadienyl titanium dichloride in 1:2 molar ratio and refluxed in benzene solution. These novel deep red colored complexes were characterized by elemental analyses, molecular weight measurements and spectroscopic techniques (IR., NMR 1H, 13C and 31P NMR). These titanium (IV) dithio complexes have also been screened for their antibacterial activities.
The synthesis of coordination compounds with sulfur containing ligands has been in the center of interest in chemical research for many years [
Before discussing the results of the above reactions, it may be relevant to mention the structural features of the Cp2TiCl2 [
Stringent precautions were taken to exclude moisture. Solvents (benzene, n-hexane) were dried by standard methods. Glycols were distilled before use; Titanocene (Merck) was used as received. Dialkyl and alkylenedithiophosphoric acids were prepared by the reaction of phosphorus pentasulfide and alcohols in a 1:4 ratio, and in a 1:2 ratio with glycols as described in the literature [
1H and 13C spectra were recorded on a Jeol-FT NMR spectrometer-LA300 and using TMS as the internal reference. 31P NMR spectra were recorded in CHCl3 using H3PO4 as an external reference on the same instrument. The following synthetic details for a specific 1:2 reaction represent the procedure used to synthesize all compounds.
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 [
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.
Biscyclopentadienyl titanium bis (dialkyl and alkylenedithiophosphate) have been synthesized by the reaction of biscyclopentadienyl titanium dichloride (Titanocene) with dialkyl and alkylenedithiophosphoric acids in 1:2 molar ratios in refluxing benzene as in Equations (1) and (2).
where R = Et, Pr-n, Pr-i, Bu-i and Ph
G = -CH2CMe2CH2-, -CH2CEt2CH2- and -CMe2CMe2.
The color of the reaction medium changed from red to deep red color with the progress of reaction. Biscyclopentadienyl titanium bis (dialkyl and alkylenedithiophosphate) derivatives are deep red color solids in open and cyclic chain complexes. All these compounds are soluble in common organic solvents like benzene, dichloromethane and chloroform. The molecular weight of all these products determined by cryoscopic method in benzene indicated the monomeric nature of these products (
IR spectra of biscyclopentadienyl titanium bis (dialkyl and alkylenedithiophosphate), have been recorded in the region 4000 - 400cm−1 [
SI. No. | Compounds | Physical State | M. P. ˚C | Mol. Wt. Found/(Calc.) | % H Found/(Calc.) | %C Found/(Calc.) | % S Found/(Calc.) | % Ti Found/(Calc.) | |
---|---|---|---|---|---|---|---|---|---|
1 | Cp2Ti[S2P(OEt)2]2 | Deep Red Solid | 137˚ | 542.22/(548.50) | 5.54/(5.51) | 38.99/(39.41) | 22.43 / (23.38) | 7.10/(8.72) | |
2 | Cp2Ti[S2P(OPr-n)2]2 | Deep Red solid | 153˚ | 598.54/(604.61) | 6.38/(6.33) | 43.8/(43.7) | 20.88 / (21.21) | 7.80/(7.91) | |
3 | Cp2Ti[S2P(OPr-i)2]2 | Deep Red Solid | 121˚ | 598.69/(604.61) | 6.29/(6.33) | 43.92/(43.70) | 20.98 / (21.21) | 7.83/(7.91) | |
4 | Cp2Ti[S2P(OBu-i)2]2 | Deep Red Solid | 195˚ | 659.32/(660.72) | 7.23/(7.01) | 47.16/(47.26) | 18.94 / (19.41) | 6.88/(7.24) | |
5 | Cp2Ti[S2P(OPh)2]2 | Deep Red Solid | 217˚ | 738.11/(740.67) | 4.23/(4.08) | 54.89/(55.13) | 16.47/ (17.32) | 5.91/(6.46) | |
6 | Cp2Ti[S2POCH2CMe2CH2O]2 | Deep Red Solid | 187˚ | 568.67/(572.52) | 5.48/(5.28) | 42.16/(41.95) | 21.97/ (22.40) | 7.95./(8.36) | |
7 | Cp2Ti[S2POCH2CEt2CH2O]2 | Deep Red Solid | 173˚ | 627.78/(628.63) | 5.98/(6.09) | 46.22/(45.85) | 19.97 / (20.40) | 7.81./(7.61) | |
8 | Cp2Ti[S2POCMe2CMe2O]2 | Deep Red Solid | 203˚ | 599.43/(600.58) | 5.98/(5.70) | 43.62/(43.99) | 21.41/ (21.36) | 7.60/(7.97) |
SI. No. | Compounds | ν(P)-O-C | νP-O-(C) | Ring Vibration | ν P=S | νP-S | ν (Ti-S) |
---|---|---|---|---|---|---|---|
1 | Cp2Ti[S2P(OEt)2]2 | 1014.5 s | 817.8 s | -- | 644.2 m | 530.0 w | 400.0 m |
2 | Cp2Ti[S2P(OPr-n)2]2 | 1060.0 m | 827.4 m | -- | 655.8 m | 520.0 m | 408.0 w |
3 | Cp2Ti[S2P(OPr-i)2]2 | 1022.2 m | 800.4 m | -- | 638.0 m | 540.0 w | 400.0 m |
4 | Cp2Ti[S2P(OBu-i)2]2 | 1018.3 s | 804.3 s | -- | 661.5 m | 550.0 m | 406.0 w |
5 | Cp2Ti[S2P(OPh)2]2 | 1104.0 s | 820.8 s | -- | 682.5 s | 513.0 w | 409.0 w |
6 | Cp2Ti[S2POCH2CMe2CH2O]2 | 10415 s | 815.8 m | 987.5 s | 667.3 m | 601.7 m | 410.0 w |
7 | Cp2Ti[S2POCH2CEt2CH2O]2 | 1066.6 s | 937.3 m | 995.0 s | 671.2 m | 602.0 m | 428 0 m |
8 | Cp2Ti[S2POCMe2CMe2O]2 | 1022.5 s | 800.4 s | 921.9 m | 704.0 m | 584.4 m | 414.0 m |
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
The 13C NMR spectra of biscyclopentadienyl titanium bis (dialkyl and alkylenedithiophosphate) complexes were recorded in deuterated chloroform at ambient temperature (
The proton decoupled 31P NMR spectra of biscyclopentadienyl titanium (IV) bis (dialkyl and alkylenedithiophosphate) derivatives,
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 (
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 (
SI. No. | Compounds | 1H chemical shift in δ ppm in CDCl3 | 31P chemical (parent acid) |
---|---|---|---|
1 | Cp2Ti[S2P(OEt)2]2 | 1.14, t (J = 6.5 Hz), 12H(CH3), 3.7, q (J = 6.0 Hz), 8H(OCH2) 6.42, s, 10H(C5H5) | 86.0. (85.7) |
2 | Cp2Ti[S2P(OPr-n)2]2 | 0.76, t (J = 7.5 Hz), 12H(CH3) 1.34, m (J = 6.5 Hz), 8H(CH2) 4.0 - 4.1, t (J = 7.5 Hz, 8H(OCH2) 6.6, s, 10H(C5H5) | 86.2 (86.1) |
3 | Cp2Ti[S2P(OPr-i)2]2 | 1.21, d (J = 6.6 Hz), 24H(CH3) 4.40 - 4.42, m J (PH) = 12 Hz, 4H(OCH) 6.42, s, 10H(C5H5) | 82.3 (82.3) |
4 | Cp2Ti[S2P(OBu-i)2]2 | 0.8, d (J = 7 Hz), 24H(CH3) 1.92, m (J = 6.5 Hz), 4H(CH) 3.80, d (J = 7 Hz), 8H(OCH2) 6.60, s, 10H(C5H5) | 85.6 (85.7) |
5 | Cp2Ti[S2P(OPh)2]2 | 7.2 - 7.4, m, 2OH(OC6H5) 6.4, s, 10H(C5H5 ) | 79.9 (79.9) |
6 | Cp2Ti[S2POCH2CMe2CH2O]2 | 0.82, s, 12H(CH3) 4.10, d, 8H(OCH2), J(PH) = 15.6 Hz 6.35, s, 10H(C5H5) | 77.4 (77.3) |
7 | Cp2Ti[S2POCH2CEt2CH2O]2 | 0.71, t (J = 7.5 Hz), 12H(CH3) 1.11, q (J = 7.5 Hz), 8H(CH2) 4.02, d, 8H(OCH2), J(PH) = 16 Hz 6.28, s, 10H(C5H5) | 78.3 (78.5) |
8 | Cp2Ti[S2POCMe2CMe2O]2 | 1.06, s, 24H(CH3) 6.50, s, 10H(C5H5) | 93.4 (93.1) |
SI. No. | Compound | 13C Chemical shift, in ppm | |||||
---|---|---|---|---|---|---|---|
CH3 | CH2 | CH | C | CO | C5H5 | ||
2 | Cp2Ti[S2P(OPr-n)2]2 | 10.0 s | 23.0 s | 70.2 s | 120.4 s | ||
4 | Cp2Ti[S2P(OBu-i)2]2 | 18.8 s | 28.5 s | 74.2 s | 120.4 s | ||
7 | Cp2Ti[S2POCH2CEt2CH2O]2 | 6.8 s | 22.2 s | 36.9 s | 76.2 s | 120.7 s |
TEST chem. compounds | Escherichia coli | Bacillus cereus | Pseudomonas aeruginosa |
---|---|---|---|
Cp2Ti[S2P(OEt)2]2 | 11.1 ± 0.54 | 5.1 ± 0.32 | 2.45 ± 1.5 |
Cp2Ti[S2P(OPr-n)2]2 | 5.0 ± 0.76 | 5.0 ± 0.78 | 0.00 |
Cp2Ti[S2P(OPr-i)2]2 | 5.8 ± 0.81 | 2.3 ± 0.21 | 0.00 |
Cp2Ti[S2P(OBu-i)2]2 | 6.3 ± 0.41 | 4.2 ± 0.46 | 0.00 |
Cp2Ti[S2P(OCH2C(Et)2CH2O)2]2 | 6.7 ± 0.72 | 3.9 ± 0.18 | 2.00 ± 3.0 |
We have successfully synthesized and characterized the new biscyclopentadienyl titanium (IV) bis (O,O dialkyl and alkylenedithiophosphate) compounds. The molecular weight of all these products determined by cryoscopic method in benzene indicated the monomeric nature of these products. The IR, 1H, 13C and 31P NMR spectra and the elemental analysis of all of these titanium complexes are consistent with the proposed tentative structure: (see
The authors are thankful for financial support from Evans-Allen Federal Appropriated Funds. The authors also wish to express their profound appreciation for the support received from Dr. L. Walker, Prof. Matthew Edwards, Dean Chance M. Glenn, Ms. Dianne Kirnes and Shonda Scott.