Notice of Pre-AIA or AIA Status
The present application, filed on or after March 16, 2013, is being examined under the first inventor to file provisions of the AIA .
The amendments filed 7/27/26 overcome the rejections set forth in the office action mailed 4/29/26 except for the rejection over Kim, which is maintained below. The discussion of the rejection has been updated as necessitated by the amendments. Claims 8 and 10 continue to be objected to as being dependent upon a rejected base claim, but would be allowable if rewritten in independent form including all of the limitations of the base claim and any intervening claims.
Claim Rejections - 35 USC § 103
Claims 1, 4-7, 9, and 13-19 are rejected under 35 U.S.C. 103 as being unpatentable over Kim (Kim, T.H., Lee, H.M., Park, H.S., Kim, S.D., Kwon, S.J., Tahara, A., Nagashima, H., Lee, B.Y., “MAO‐free and extremely active catalytic system for ethylene tetramerization”, Appl. Organometal Chem., 2019, 33, e4829).
In the abstract, Scheme 5 (page 7 of the reference) and Table 3 (page 8 of the reference), Kim discloses performing ethylene tetramerization using an organochromium catalyst and an organoboron cocatalyst, where the ligands of the organochromium catalyst have a PNP structure. The chromium forms a coordination complex with the ligands in accordance with claims 13-14, and the cocatalyst meets the limitations of claim 15. In sections 3.4 and 2.5, Kim indicates that the chromium is derived from CrCl3(THF)3 (chromium(III) chloride tetrahydrofuran), as recited in claim 16, and the organoboron is [H(OEt2)2]+[B(C6F5)4]-, which meets the limitations of formula 8 of claim 17. The tetramerization of ethylene to form a product comprising 1-octene and 1-hexene (1-C8 and 1-C6 in Table 3 of Kim) using the catalyst of Kim meets the method limitations of claims 18-19.
In Scheme 5 and entries 16-17 of Table 3, Kim discloses a PNP ligand 13 which is similar to the ligand of claims 1, 4, 7, and 9 where the R1 through R4 groups are tributylsilyl groups and R5 is an isopropyl group, except for the tributylsilyl groups being in the para position rather than the meta position. Kim also discloses in Scheme 5 and entry 15 of Table 3 a PNP ligand 12 having a trimethylsilyl substituent in the meta position. Both 13 and 12 are effective in catalyzing the tetramerization of ethylene.
It therefore would have been obvious to one of ordinary skill in the art to prepare the ligand of Kim to have both an isopropyl group bound to the nitrogen and a tributylsilyl substituent in the meta position, since the teachings of Kim that ligands having these characteristics would be effective in catalyzing the tetramerization of ethylene. While the data provided in Table 3 of Kim indicates that the activity of such a catalyst would be decreased at low temperature compared to the exemplified para-substituted catalysts or the catalysts having a longer-chain alkyl bound to the nitrogen, "A known or obvious composition does not become patentable simply because it has been described as somewhat inferior to some other product for the same use." In re Gurley, 27 F.3d 551, 554, 31 USPQ2d 1130, 1132 (Fed. Cir. 1994). It is also noted that a comparison of entries 9 and 11 in Table 3 indicates that replacing the trimethylsilyl substituents of ligand 12 with tributylsilyl substituents would be expected to increase activity, and that the difference in activity would be smaller at higher temperatures, with likely increased selectivity as well (compare entries 17 and 13 in Table 3 of Kim). Claims 1, 4, 7, 9, and 13-19 are therefore rendered obvious by Kim.
Additionally, since Kim teaches that both trimethylsilyl and tributylsilyl substituted ligands are effective in forming chromium catalysts for the tetramerization of ethylene, one of ordinary skill in the art would understand that tripropylsilyl substituted analogues, meeting the limitations of claims 1 and 5-6 (Formula 2-7 of claim 6), would also be effective in forming chromium catalysts for the tetramerization of ethylene, since propyl groups have a chain length in between that of methyl and butyl groups, and because Kim teaches in the discussion on page 8 that bulky trialkylsilyl substituents are effective. Claims 5-6 are therefore also rendered obvious by Kim, as well as claim 1 for the case where the R1 through R4 groups are tripropylsilyl.
Allowable Subject Matter
Claims 8 and 10 are objected to as being dependent upon a rejected base claim, but would be allowable if rewritten in independent form including all of the limitations of the base claim and any intervening claims. Claims 8 and 10 require the claimed ligand to have tributylsilyl substituents in the meta position of the phenyl groups, and also to have specific hydrocarbon substituents on the nitrogen atoms. Kim, as discussed above, discloses similar ligands having tributylsilyl substituents in the meta position, but only discloses alkyl substituents on the nitrogen group. Lee (U.S. PG Pub. No. 2021/0229084) discloses similar ligands to those of Kim and discloses that an aryl group can be bound to the nitrogen, but does not provide any teaching of the aryl, cyclopentyl, or substituted cyclohexyl groups recited in claims 8 and 10. Lee also teaches only para-substituted phenyl groups. One of ordinary skill in the art would not have any motivation to modify Lee or Kim in order to arrive at the ligands of claims 8 and 10. As discussed in the rejection, Lee indicates that the nitrogen-bound substituent affects the activity of the catalyst, so one of ordinary skill in the art could not simply substitute in any hydrocarbyl substituent.
Blann and McGuinness render obvious a ligand having alkyl substituents on the meta position of the phenyl ring and an indanyl group bound to the nitrogen, but there would be no motivation to replace the alkyl substituents of Blann and McGuinness with tributylsilyl groups, which are outside the scope of the substituents disclosed by Blann and McGuinness.
A STIC Structure search was performed and did not identify any references which disclose or render obvious claims 8 and 10.
Response to Arguments
Applicant's arguments filed 7/27/26 have been fully considered but they are not persuasive. Applicant argues that Table 3 of Kim teaches away from meta-substituted ligands relative to para-substituted ligands. In the right column of page 7 of the reference, Kim discloses that “The introduction of a -SiMe3 substituent at the meta-position also improved the activity, but the improvement was not as dramatic as that for the introduction at the para-position”. Kim’s teaching that the meta-substitution improves the activity, albeit not as much as the para-substitution, is not a teaching away. As noted in the rejection, "A known or obvious composition does not become patentable simply because it has been described as somewhat inferior to some other product for the same use." In re Gurley, 27 F.3d 551, 554, 31 USPQ2d 1130, 1132 (Fed. Cir. 1994). As also noted in the rejection, a comparison of entries 9 and 11 in Table 3 indicates that replacing the trimethylsilyl substituents of ligand 12 with tributylsilyl substituents would be expected to increase activity, and that the difference in activity would be smaller at higher temperatures, with likely increased selectivity as well (compare entries 17 and 13 in Table 3 of Kim). The examiner therefore maintains the position taken in the rejection.
Applicant also points to the data provided in Tables 1-2 of the current specification as providing evidence that the catalyst activity of a prior art catalyst provides “remarkably lower” catalyst activity than the currently claimed compounds. Applicant does not specifically argue that the results are unexpected (See MPEP 716.02), but in any case, Comparative Synthetic Example 5, which is a PNP ligand where the benzene rings are methyl-substituted at both the meta- and para-positions, is not the closest prior art in light of Kim’s teachings of ligands where the rings are para-substituted with trialkylsilyl groups. In order to successfully overcome a prima facie case of obviousness with a showing of unexpected results, applicant must provide a comparison with closest prior art. See MPEP 716.02(e).
Conclusion
THIS ACTION IS MADE FINAL. Applicant is reminded of the extension of time policy as set forth in 37 CFR 1.136(a).
A shortened statutory period for reply to this final action is set to expire THREE MONTHS from the mailing date of this action. In the event a first reply is filed within TWO MONTHS of the mailing date of this final action and the advisory action is not mailed until after the end of the THREE-MONTH shortened statutory period, then the shortened statutory period will expire on the date the advisory action is mailed, and any nonprovisional extension fee (37 CFR 1.17(a)) pursuant to 37 CFR 1.136(a) will be calculated from the mailing date of the advisory action. In no event, however, will the statutory period for reply expire later than SIX MONTHS from the mailing date of this final action.
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/JAMES C GOLOBOY/Primary Examiner, Art Unit 1771
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