Lubricating oil compositions

1. A lubricating oil composition comprising (a) at least one oil of lubricating viscosity and (b) an effective amount of at least one thio-functionalized phenylenediamine compound of the general formula:

wherein R 1 is a straight or branched, substituted or unsubstituted, C 1 -C 30 alkyl, a substituted or unsubstituted C 3 -C 30 cycloalkyl, a substituted or unsubstituted C 3 -C 30 cycloalkenyl, a substituted or unsubstituted C 5 -C 30 aryl, a substituted or unsubstituted C 5 -C 30 arylalkyl, a substituted or unsubstituted C 5 -C 30 heteroaryl, a substituted or unsubstituted C 3 -C 30 heterocyclic ring or a C 1 -C 20 ester;

R 2 and R 3 together with the nitrogen atom to which they are bonded are joined together to form a heterocyclic group optionally containing one or more additional heterocyclic atoms;

R 4 is independently a straight or branched, substituted or unsubstituted, C 1 -C 30 alkyl, a substituted or unsubstituted C 3 -C 30 cycloalkyl, a substituted or unsubstituted C 3 -C 30 cycloalkenyl, a substituted or unsubstituted C 5 -C 30 aryl, a substituted or unsubstituted C 5 -C 30 arylalkyl, a substituted or unsubstituted C 5 -C 30 heteroaryl, a substituted or unsubstituted C 3 -C 30 heterocyclic ring or a C 1 -C 20 ester, and n is 1.

2. The lubricating oil composition of claim 1 , wherein R 1 is a substituted or unsubstituted C 5 -C 30 aryl.

3. The lubricating oil composition of claim 1 , wherein R 1 is a substituted or unsubstituted phenyl group.

4. The lubricating oil composition of claim 1 , further comprising least one lubricating oil additive selected from the group consisting of anti-wear agents, detergents, rust inhibitors, dehazinq agents, demulsifyinq agents, metal deactivating agents, friction modifiers, pour point depressants, antifoaming agents, co-solvents, package compatibilisers, corrosion-inhibitors, ashless dispersants, dyes, and extreme pressure agents.

5. The lubricating oil composition of claim 1 , wherein the at least one oil of lubricating viscosity has a viscosity of about 1.5 to about 2000 centistokes (cSt) at 100° C.

6. The lubricating oil composition of claim 1 , further comprising at least one lubricating oil additive selected from the group consisting of an alkylated diphenylamine, alkylated hindered phenolic, alkylated substituted or unsubstituted phenylenediamine, alkylated oil soluble copper compound, phenothiazines, sulfurized olefins, thiocarbamates, sulfur bearing hindered phenolics, zinc dialkyldithiophosphates.

7. A lubricating oil composition comprising (a) at least one oil of lubricating viscosity and (b) an effective amount of at least one thio-functionalized phenylenediamine compound of the general formula:

wherein R 1 is a straight or branched, substituted or unsubstituted, C 1 -C 30 alkyl, a substituted or unsubstituted C 3 -C 30 cycloalkyl, a substituted or unsubstituted C 3 -C 30 cycloalkenyl, a substituted or unsubstituted C 5 -C 30 aryl, a substituted or unsubstituted C 5 -C 30 arylalkyl, a substituted or unsubstituted C 5 -C 30 heteroaryl, a substituted or unsubstituted C 3 -C 30 heterocyclic ring or a C 1 -C 20 ester; R 2 and R 3 are independently hydrogen, a straight or branched, substituted or unsubstituted, C 1 -C 30 alkyl, a substituted or unsubstituted C 3 -C 30 cycloalkyl, a substituted or unsubstituted C 3 -C 30 cycloalkenyl, a substituted or unsubstituted C 5 -C 30 aryl, a substituted or unsubstituted C 5 -C 30 arylalkyl, a substituted or unsubstituted C 5 -C 30 heteroaryl, a substituted or unsubstituted C 3 -C 30 heterocyclic ring or a C 1 -C 20 ester with the proviso that only one of R 2 and R 3 can be hydrogen or R 2 and R 3 together with the nitrogen atom to which they are bonded are joined together to form a heterocyclic group optionally containing one or more additional heterocyclic atoms; R 4 is independently a straight or branched, substituted or unsubstituted, C 1 -C 30 alkyl, a substituted or unsubstituted C 3 -C 30 cycloalkyl, a substituted or unsubstituted C 3 -C 30 cycloalkenyl, a substituted or unsubstituted C 5 -C 30 aryl, a substituted or unsubstituted C 5 -C 30 arylalkyl, a substituted or unsubstituted C 5 -C 30 heteroaryl, a substituted or unsubstituted C 3 -C 30 heterocyclic ring or a C 1 -C 20 ester, and n is 2.

8. The lubricating oil composition of claim 7 , wherein R 1 is a substituted or unsubstituted C 5 -C 30 aryl.

9. The lubricating oil composition of claim 7 , wherein R 1 is a substituted or unsubstituted C 5 -C 30 aryl, R 2 is hydrogen, R 3 is a straight or branched, substituted or unsubstituted, C 1 -C 30 alkyl.

10. The lubricating oil composition of claim 7 , wherein R 1 is a substituted or unsubstituted phenyl group, R 2 is hydrogen, R 3 is a straight or branched C 1 -C 6 alkyl.

11. The lubricating oil composition of claim 7 , wherein R 2 and R 3 together with the nitrogen atom to which they are bonded are joined together to form a heterocyclic group, optionally containing one or more additional heterocyclic atoms.

12. The lubricating oil composition of claim 7 , wherein the at least one oil of lubricating viscosity has a viscosity of about 1.5 to about 2000 centistokes (cSt) at 100° C.

13. The lubricating oil composition of claim 7 , further comprising at least one lubricating oil additive selected from the group consisting of anti-wear agents, detergents, rust inhibitors, dehazing agents, demulsifying agents, metal deactivating agents, friction modifiers, pour point depressants, antifoaming agents, co-solvents, package compatibilisers, corrosion-inhibitors, ashless dispersants, dyes, and extreme pressure agents.

14. The lubricating oil composition of claim 7 , further comprising at least one lubricating oil additive selected from the group consisting of an alkylated diphenylamine, alkylated hindered phenolic, alkylated substituted or unsubstituted phenylenediamine, alkylated oil soluble copper compound, phenothiazines, sulfurized olefins, thiocarbamates, sulfur bearing hindered phenolics, and zinc dialkyldithiophosphates.