Communications Base-Free Phosphine-Sulfonate Nickel Benzyl Complexes Xiaoyuan Zhou, Se ´bastien Bontemps, and Richard F. Jordan* Department of Chemistry, The UniVersity of Chicago, 5735 South Ellis AVenue, Chicago, Illinois 60637 ReceiVed July 31, 2008 Summary: Base-free [2-PR 2 -4-Me-benzenesulfonate)]Ni(η 3 -ben- zyl) complexes (R ) 2-OMe-Ph (4a), Cy (4b)) were prepared and tested for ethylene polymerization. 4a produces low- molecular-weight polyethylene (M n ) 1300) that contains 10 Me branches/10 3 C and terminal and internal olefin units. The polymer yield and structure are unaffected by the ethylene pressure (60-300 psi). 4b is less actiVe than 4a and produces a polymer with higher M n , fewer branches, and a higher fraction of terminal olefin units. Palladium alkyl complexes that contain o-phosphinoarene- sulfonate ligands ([PO] - ) catalyze the copolymerization of ethylene and polar monomers to linear functionalized polyeth- ylenes. In-situ-generated and discrete [PO]PdR species copo- lymerize ethylene with carbon monoxide, 1 alkyl acrylates, 2 acrylonitrile, 3 vinyl ethers, 4 vinyl fluoride, 5 functionalized norborenes, 6 N-vinylpyrrolidinone and N-isopropylacrylamide, 7 and copolymerize vinyl acetate with carbon monoxide. 8 Analo- gous [PO]NiR species are of interest because nickel catalysts are often more reactive and are less expensive than palladium catalysts and thus are more attractive for practical applications. 9,10 In-situ-generated [PO]NiR species were reported to oligo- merize ethylene to C 4 -C 20 R-olefins 11 and to polymerize ethylene. 2a Rieger showed that discrete (2-PAr 2 -benzene- sulfonate)Ni(Ph)(PPh 3 ) complexes (Ar ) Ph, 2-Me-Ph, 2-OMe- Ph) polymerize ethylene to low-molecular-weight (M w ) 1000-4000), moderately branched (15-25 branches/10 3 C) polymers in the presence of phosphine scavengers (B(C 6 F 5 ) 3 or Ni(COD) 2 , where COD ) 1,5-cyclooctadiene). 12 Low activi- ties were observed in the absence of a scavenger. [PO]NiR catalysts are inhibited by methyl methacrylate and poisoned by * E-mail: rfjordan@uchicago.edu. (1) (a) Drent, E.; Dijk, R.; Ginkel, R.; Oort, B.; Pugh, R. I. Chem. Commun. 2002, 964. (b) Hearley, A. K.; Nowack, R. J.; Rieger, B. Organometallics 2005, 24, 2755. (c) Newsham, D. K.; Borkar, S.; Sen, A.; Conner, D. M.; Goodall, B. L. Organometallics 2007, 26, 3636. (d) Bettucci, L.; Bianchini, C.; Claver, C.; Suarez, E. J. G.; Ruiz, A.; Meli, A.; Oberhauser, W. Dalton Trans. 2007, 5590. (2) (a) Drent, E.; Dijk, R.; Ginkel, R.; Oort, B.; Pugh, R. I. Chem. Commun. 2002, 744. (b) Drent, E.; Pello, D. H. L. European Patent 0632084, 1995. (c) Kochi, T.; Yoshimura, K.; Nozaki, K. Dalton Trans. 2006, 25. (d) Skupov, K. M.; Marella, P. R.; Simard, M.; Yap, G. P. A.; Allen, N.; Conner, D.; Goodall, B. L.; Claverie, J. P. Macromol. Rapid Commun. 2007, 28, 2033. (3) Kochi, T.; Noda, S.; Yoshimura, K.; Nozaki, K. J. Am. Chem. Soc. 2007, 129, 8948. (4) Luo, S.; Vela, J.; Lief, G. R.; Jordan, R. F. J. Am. Chem. Soc. 2007, 129, 8946. (5) Weng, W.; Shen, Z.; Jordan, R. F. J. Am. Chem. Soc. 2007, 129, 15450. (6) (a) Liu, S.; Borkar, S.; Newsham, D.; Yennawar, H.; Sen, A. Organometallics 2007, 26, 210. (b) Skupov, K. M.; Marella, P. R.; Hobbs, J. L.; McIntosh, L. H.; Goodall, B. L.; Claverie, J. P. Macromolecules 2006, 39, 4279. (7) Skupov, K. M.; Piche, L.; Claverie, J. P. Macromolecules 2008, 41, 2309. (8) Kochi, T.; Nakamura, A.; Ida, H.; Nozaki, K. J. Am. Chem. Soc. 2007, 129, 7770. (9) (a) Ittel, S. D.; Johnson, L. K.; Brookhart, M. Chem. ReV. 2000, 100, 1169. (b) Britovsek, G. J. P.; Gibson, V. C.; Wass, D. F. Angew. Chem., Int. Ed. 1999, 38, 429. (c) Gibson, V. C.; Spitzmesser, S. K. Chem. ReV. 2003, 103, 283. (10) (a) Johnson, L. K.; Killian, C. M.; Brookhart, M. J. Am. Chem. Soc. 1995, 117, 6414. (b) Liu, W.; Malinoski, J. M.; Brookhart, M. Organometallics 2002, 21, 2836. (c) Malinoski, J. M.; Brookhart, M. Organometallics 2003, 22, 5324. (d) Daugulis, O.; Brookhart, M. Orga- nometallics 2002, 21, 5926. (e) Kim, J. S.; Pawlow, J. H.; Wojcinski, L. M., II; Murtuza, S.; Kacker, S.; Sen, A. J. Am. Chem. Soc. 1998, 120, 1932. (11) Murray, R. E. U.S. Patent 4,689,437, 1987. (12) Nowack, R. J.; Hearley, A. K.; Rieger, B. Z. Anorg. Allg. Chem. 2005, 631, 2775.  Copyright 2008 American Chemical Society Volume 27, Number 19, October 13, 2008 10.1021/om800741w CCC: $40.75  2008 American Chemical Society Publication on Web 09/11/2008