Diaminoarylnickel(II) "Pincer" Complexes: Mechanistic Considerations in the Kharasch Addition Reaction, Controlled Polymerization, and Dendrimeric Transition Metal Catalysts

Accounts of Chemical Research

Volumn 31, Issue 7, 1998, Pages 423-431

  Gossage, Robert A ^a,b,c,d   Van De Kuil, Lucia A ^a,e,f,g   Van Koten, Gerard ^a,f,h,i  

^a UTRECHT UNIVERSITY   (Netherlands)

^b Canadian Institute of Chemistry   (Canada)

^c UNIVERSITY OF GUELPH   (Canada)

^d UNIVERSITY OF VICTORIA   (Canada)

^e St Bonifatius College   (Netherlands)

^f UTRECHT UNIVERSITY   (Netherlands)

^g Hercules European Research Center   (Netherlands)

^h UNIVERSITY OF AMSTERDAM   (Netherlands)

ⁱ Laboratory for Organic Chemistry ^*

Author keywords

[No Author keywords available]

Indexed keywords

EID: 0000064895     PISSN: 00014842     EISSN: None     Source Type: Journal    
DOI: 10.1021/ar970221i     Document Type: Article

References (149)

1. (a) Kharasch, M. S.; Jensen, E. V.; Urry, W. H. Science 1945, 102 128.
2. (b) Kharasch, M. S.; Jensen, E. V.; Urry, W. H. J. Am. Chem. Soc. 1945, 67, 1626.
3. (c) Kharasch, M. S.; Jensen, E. V.; Urry, W. H. J. Am. Chem, Soc. 1946, 60, 154-155.
4. (d) Kharasch, M. S.; Jensen, E. V.; Urry, W. H. J. Am. Chem. Soc. 1947, 69, 1100-1105.
5. (e) Kharasch, M. S.; Reinmuth, O.; Urry, W. H. J. Am. Chem. Soc. 1947, 69, 1105-1110.
6. In some circles this process is called the Prins Reaction, but this term often causes confusion with respect to the addition of formaldehyde to olefins, which is also referred to as the Prins reaction. See: March, J. Advanced Organic Chemistry, 4th ed:, John-Wiley & Sons: London, 1992; Section 5-33. Kharasch addition is an example of what is currently being referred to as "Atom Transfer Radical Addition" (ATRA).
7. Hey, D. H.; Waters, W. A. Chem. Rev. 1937, 21, 169-208.
8. Kharasch, M. S.; Engelmann, H.; Mayo, F. R. J. Org. Chem 1938, 2, 288-302.
9. Dowbenko, P. J. Am. Chem. Soc. 1964, 86, 946-947.
10. (a) Rijnenbrij, P. P. M.; Loven, R.; Wijnberg, J. B. P. A.; Speckamn, W. N.; Huisman, H. O. Tetrahedron Lett. 1972, 1425-1428.
11. (b) Bellus, D. Pure Appl. Chem. 1985, 57, 1827-1838.
12. (c) Martin, P.; Steiner, J.; Winkler, T.; Bellus, D. Tetrahedron 1985, 41, 4057-4078.
13. (d) Martin, P.; Streith, J.; Rihs G.; Winkler, T.; Bellus, D. Tetrahedron Lett. 1985, 26, 3947-3950.
14. Klemmensen, P. D.; Kolind-Andersen, H.; Madsen, H. B.; Svendsen, A. J. Org. Chem. 1979, 44, 416-420.
15. (a) Hayes, T. M.; Villani, R.; Weinreb, S. M. J. Am. Chem. Soc. 1988, 110, 5533-5543 and references therein.
16. (b) Nagashima, H.; Ara, K.; Wakamatsu H.; Itoh, K. J. Chem. Soc., Chem. Commun. 1985, 518-519.
17. (c) Nagashima, H.; Wakamatsu, H. J. Chem. Soc., Chem Commun. 1984, 652-653.
18. (d) Matsumoto, H.; Ohkawa, K.; Ikemori, S.; Nakamo, T.; Nagai, Y. Chem. Lett. 1979, 1011-1014.
19. (e) Takano, S.; Nishizawa, S.; Akiyama, M.; Ogasawara, K. Heterocycles 1984, 22, 1179-1188.
20. (f) Nagashima, H.; Wakamatsu, H.; Itoh, K.; Tomo, Y.; Tsuji, J. Tetrahedron Lett. 1983, 24, 2395-2398.
21. Grigg, R.; Devlin, J.; Ramasubbu A.; Scott, R. M.; Stevenson, P. J. Chem. Soc., Parkin Trans. 1 1987, 1515-1520.
22. Maruoka, K.; Sano, H.; Fukutani, Y.; Yamamoto, H. Chem. Lett. 1985, 1689-1691.
23. Takeyama, Y.; Ichinose, Y.; Oshima, K.; Utimoto, K. Tetrahedron Lett. 1989, 30, 3159-3162
24. Freidlina, R. Kh.; Velichko, F. K. Synthesis 1977, 145-154.
25. See, for example: Kondakov, S. E.; Smirnov, V. V. Kinet. Catal. 1995, 36, 315-319.
26. (a) Minisci, F. Acc. Chem. Res. 1975, 8, 165-171.
27. (b) Also see: Fouassier, J. P.; Rabek, J. F., Eds. Radiation Curing in Polymer Science and Technology. Vol. 11: Photoinitiating Systems; Elsevier: London, 1993; Chapter 6.
28. (a) Steiner, E.; Martin, P.; Bellus, D. Helv Chim. Acta 1982, 65, 983-985.
29. (b) Badanyan, Sh. O.; Voskanyan, M. G.; Chobanyan, Zh. O. Russ. Chem. Rev. 1981, 50, 1074-1086 and references therein.
30. (c) Vit, Z.; Hájek, M. Collect. Czech. Chem. Commun. 1987, 52, 1280-1292 and references therein.
31. (d) Laurent, P.; Blancou, H.; Commeyres, A. J. Fluorine Chem. 1993, 64, 125-127 and references therein.
32. (a) Murai, S.; Tsutsumi, S. J. Org. Chem. 1966, 31, 3000-3003.
33. (b) Burton, D. J.; Kehoe, L. J. J. Org. Chem 1971, 36, 2596-2599 and references therein.
34. (c) Mitani, M.; Nakayama, M.; Koyoma, K. Tetrahedron Lett. 1980, 21, 4457-4460.
35. (d) Nondek L.; Hun, L. G.; Wicherlová, B.; Krupicka, S. J. Mol. Catal. 1987, 42, 51-55.
36. (e) Afanas'ev, I. B.; Samokhvalov, A. Russ. Chem. Rev. 1969, 38, 318-329 and references therein.
37. (f) Kotora, M.; Adarnek, F.; Hajek, M. Catal. Lett. 1993, 18, 345-348 and references therein.
38. (g) Hirao, T.; Ohshiro, O. Synlett 1990, 217-218.
39. (h) Boutevin, B.; Dongala, E. B. Tetrahedron Lett. 1977, 4315-4316.
40. Hogeveen, H.; Elzinga, J. J. Org. Chem. 1980, 45, 3957-3969.
41. (a) Davis, R.; Groves, I. F. J. Chem. Soc., Dalton Trans. 1982, 2281-2287.
42. (b) Davis, R.; Durrant, J. L. A.; Khazaal, N. M. S.; Bitterwolf, T. E. J. Organomet. Chem. 1990, 386, 229-239.
43. Fuchikami, T.; Ojima, I. Tetrahedron Lett. 1984, 25, 307-308.
44. (a) Davis, R.; Khazaal, N. M. S.; Maistry, V. J. Chem. Soc., Chem. Commun. 1986, 1387-1389.
45. (b) Kerber, R. C.; Waldbaum, B. R. J. Organomet. Chem. 1996, 513, 277-280.
46. Davis, R.; Khazal, N. M. S.; Bitterwolf, T. E. J. Organomet. Chem. 1990, 397, 51-58.
47. Ishihava, T.; Kuroboshi, M.; Okada, Y. Chem. Lett. 1986, 1895-1896.
48. Nagashima, H.; Tsuji, J.; Sato, K. Tetrahedron 1985, 41, 393-397 and references therein.
49. (a) Inoue, Y.; Ohno, S.; Hashimoto, H. Chem. Lett. 1978, 367-368.
50. (b) Saushkina, T. P.; Zubritskn, L. M.; Petrova, A. A. Zh. Org. Khim. 1990, 26, 722-725.
51. (a) Murai, S.; Sugise, R.; Sonada, N. Angew. Chem. 1981, 93, 481-482.
52. (b) Cable, C. J.; Adams H.; Bailey, N. A.; Crosby, J.; White, C. J. Chem. Soc., Chem. Commun. 1991, 165-166.
53. (c) Pereira.S; Srebnik, M. J. Am. Chem. Soc. 1996, 118, 909-910.
54. Ma, S.; Lu, X. J. Chem. Soc., Perkin Trans. 1 1990, 2031-2033 and references therein.
55. (a) Matsumoto, H.; Motegi, T.; Nakano, T.; Nagai, Y. J. Organomet. Chem. 1979, 174, 157-161 and references therein.
56. (b) Sasson, Y.; Rempel, G. L. Synthesis 1975, 448-450.
57. (c) Derouet, D.; Brosse, J. C. Eur. Polym. J. 1991, 27, 537-547.
58. (a) Kameyama, M.; Kamigata, N.; Kobayashi, M. J. Org. Chem. 1987, 52, 3312-3316 and references therein.
59. (b) Kameyama, M.; Kamigata, N. Bull. Chem. Soc. Jpn. 1989, 62, 648-650.
60. (c) Kamigata, N.; Fukushima, T.; Terakawa, Y.; Yoshida, M.; Sawada, H. J. Chem. Soc., Perkin Trans, 1 1991, 627-633 and references therein.
61. Phelps, J. C.; Bergbreiter, D. E.; Lee, G. M.; Villani, R.; Weinreb, S. M. Tetrahedron Lett. 1989, 30, 3915-3918.
62. (a) Asscher, M.; Vofsi, D. J. Chem. Soc. 1961, 2261-2264, 1963, 1887-1896, 3291-3297.
63. (b) Asscher, M.; Vofsi, D. J. Chem. Soc. B 1968, 947-952.
64. (c) Asscher, M.; Vofsi, D. J. Chem. Soc., Perkin Trans. 2 1973, 1000-1002.
65. Minisci, F., Ed. Free Radicals in Organic Synthesis and Biology; Kluwer: Dordrecht, The Netherlands, 1989.
66. (a) Matyjaszewski, K.; Patten, T. E.; Xia, J. J. Am. Chem. Soc. 1997, 119, 674-680.
67. (b) Patten, T. E.; Xia, J.; Abernathy, T.; Matyjaszewski, K. Science 1996, 272, 866-868.
68. (c) Webster, O. W. Science 1991, 251, 887-893.
69. (d) Haddleton, D. M.; Jasieczek, C. B.; Hannon, M. J.; Shooter, A. J. Macromolecules 1997, 30, 2190-2193.
70. (e) Percec, V.; Barboiu, B. Macromolecules 1995, 28, 7970-7972.
71. (a) Kochi, J. K. Organometallic Mechanisms and Catalysis; Academic Press: London, 1978; pp 197-203.
72. (b) Tsuji, J. Organic Synthesis by Means of Transition Metal Complexes; Springer-Verlag: Heidelberg, 1975; pp 61-64.
73. (a) Bland, W. J.; Davis, R.; Durrant, J. L. A. J. Organomet. Chem. 1984, 267, C45-C48.
74. (b) Bland, W. J.; Davis, R.; Durrant, J. L. A. J. Organomet. Chem. 1985, 200, 397-406.
75. (c) Davis, R.; Furze, J. D.; Cole-Hamilton, D. J.; Pogorzelec, P. J. Organomet. Chem. 1992, 440, 191-196.
76. (a) Bradley, J. S.; Connor, D. E.; Dolphin, D.; Labinger, J. A.; Osborn, J. A. J. Am. Chem. Soc. 1972, 94, 4043-4044.
77. (b) Labinger, J. A.; Kramer, A. V.; Osborn, J. A. J. Am. Chem. Soc. 1973, 95, 7903-7904.
78. (c) Lappert, M. F.; Lednor, P. W. J. Chem. Soc., Chem. Commun. 1973, 948-949.
79. (d) Hargreaves, N. G.; Puddephatt, R. J.; Sutcliffe, L. H.; Thompson, P. J. J. Chem. Soc., Chem. Commun. 1973, 861-862.
80. (e) Also see: Byers, B. H.; Brown, T. L. J. Am. Chem. Soc. 1977, 99, 2527-2532.
81. (a) van Koten, G. Pure Appl. Chem. 1989, 61, 1681-1694.
82. (b) Rietveld, M. H. P.; Grove, D. M.; van Koten, G. New J. Chem, 1997, 21, 751-771.
83. (a) van Beek, J. A. M.; van Koten, G.; Stufkens, D. J.; van der Linden, J. G. M. J. Am. Chem. Soc. 1986, 108, 5010-5011.
84. (b) van Koten, G. Pure Appl. Chem. 1990, 62, 1155-1159.
85. Sutter, J. P.; Grove, D. M.; Beley, M.; Collin, J.-P.; Veldman, N.; Spek, A. L.; Sauvage, J.-P.; van Koten, G. Angew. Chem., Int. Ed. Engl. 1994, 33, 1282-1284.
86. (a) James, S. L.; Veldman, N.; Spek, A. L.; van Koten, G. Chem. Commun. 1996, 1309-1310.
87. (b) Davis, P. J.; Veldman, N.; Grove, D. M.; Spek, A. L.; Lutz, B. T. G.; van Koten, G. Angew. Chem., Int. Ed. Engl. 1996, 35, 1959-1961.
88. (c) Steenwinkel, P.; James, S. L.; Grove, D. M.; Kooijman, H.; Spek, A. L.; van Koten, G. Organometallics 1997, 16, 513-515.
89. (d) Davis, P. J.; Grove, D. M.; van Koten, G. Organometallics 1997, 16, 800-802.
90. (e) Lagunas, M.-C.; Gossage, R. A.; Spek, A. L.; van Koten, G. Organometallics 1998, 17, 731-741.
91. (a) Grove, D. M.; van Koten, G.; Ubbels, H. J. C.; Zoet, R.; Spek, A. L. Organometallics 1984, 3, 1003-1009.
92. (b) van Beek, J. A. M.; van Koten, G.; Ramp, M. J.; Coenjaarts, N. C.; Grove, D. M.; Goubitz, K.; Zoutberg, M. C.; Stam, C. H.; Smeets, W. J. J.; Spek, A. L. Inorg. Chem. 1991, 30, 3059-3068.
93. (c) van de Kuil, L. A.; Luitjes, H.; Grove, D. M.; Zwikker, J. W.; van der Linden, J. G. M.; Roelofsen, A. M.; Jenneskens, L. W.; Drenth, W.; van Koten, G. Organometallics 1994, 13, 468-477.
94. (d) van de Kuil, L. A.; Veldhuizen, Y. S. J.; Grove, D. M.; Zwikker, J. W.; Jenneskens, L. W.; Drenth, W.; Smeets, W. J. J.; Spek, A. L.; van Koten, G. Red. Trav. Chim. Pays-Bas 1994, 113, 267-277.
95. (e) Schimmelpfennig, U.; Zimmering, R.; Scheinitz, K. D.; Stösser, R.; Wenschuh, E.; Baumeister, U.; Hartung, H. Z. Anorg. Allg. Chem. 1993, 679, 1931-1938.
96. (a) Grove, D. M.; van Koten, G.; Zoet, R.; Murrall, N. W.; Welch, A. J. J. Am. Chem. Soc. 1983, 105, 1379-1380.
97. (b) Grove, D. M.; van Koten, G.; Mul, W. P.; van der Zeijden, A. A. H.; Terheijden, J.; Zoutberg, M. C.; Stam, C. H. Organometallics 1986, 5, 322-326.
98. (c) Grove, D. M.; van Koten, G.; Mul, P.; Zoet, R.; van der Linden, J. G. M.; Legters, J.; Schmitz, J. E. J.; Murrall, N. W.; Welch, A. J. Inorg. Chem. 1988, 27, 2466-2473.
99. (d) van de Kuil, L. A.; Veldhuizen, Y. S. J.; Grove, D. M.; Zwikker, J. W.; Jenneskens, L. W.; Drenth, W.; Smeets, W. J. J.; Spek, A. L.; van Koten, G. J. Organomet. Chem. 1995, 488, 191-197.
100. (e) For related Ni(III) compounds containing only Ni-C bonds, see: Alonso, P. J.; Falvello, L. R.; Forniés, J.; Martín, A.; Menjón, B.; Rodríguez, G. Chem. Commun. 1997, 503-504.
101. Haines, R. I.; McAuley, A. Coord. Chem. Rev. 1981, 39, 77-119.
102. (a) Grove, D. M.; van Koten, G.; Verschuuren, A. H. M. J. Mol. Catal. 1988, 45, 169-174.
103. (b) Grove, D. M.; Verschuuren, A. H. M.; van Koten, G.; van Beek, J. A. M. J. Organomet. Chem. 1989, 372, C1-C6.
104. van de Kuil, L. A.; Grove, D. M.; Gossage, R. A.; Zwikker, J. W.; Jenneskens, L. W.; Drenth, W.; van Koten, G. Organometallics, 1997, 16, 4985-4994.
105. van de Kuil, L. A. Ph.D. Thesis (Proefschrift), Universiteit Utrecht, 1993.
106. Stryker, L. Biochemistry, Freeman Publishing Co.: San Francisco, 1981; pp 103-184.
107. Granel, C.; Dubois, Ph.; Jérôme, R.; Teyssié, Ph. Macromolecules 1996, 29, 8576-8582.
108. Connor, J. A.; Riley, P. I. J. Chem. Soc., Dalton Trans. 1979, 1318-1323.
109. (a) Winter, C. M.; Veal, W. R.; Garner, C. M.; Gladysz, J. A. J. Am. Chem. Soc. 1989, 111, 4766-4776.
110. (b) Peng, T.-S.; Winter, C. H.; Gladysz, J. A. Inorg. Chem. 1994, 33, 2534-2542.
111. (c) Pathak, D. D.; Adams, H.; White, C. J. Chem. Soc., Chem. Commun. 1994, 733-734.
112. (d) Conroy-Lewis, F. M.; Redhouse, A. D.; Simpson, S. J. J. Organomet. Chem. 1989, 366, 357-367.
113. (e) Kulawiec, R. J.; Faller, J. W.; Crabtree, R. H. Organometallics 1990, 9, 745-755.
114. (f) Arndtsen, B. A.; Bergman, R. G. Science 1995, 270, 1970-1973.
115. (g) Burk, M. J.; Segmuller, B.; Crabtree, R. H. Organometallics 1987, 6, 2241-2246.
116. (h) Van Seggan, D. M.; Anderson, O. P.; Strauss, S. H. Inorg. Chem. 1992, 31, 2987-2990.
117. (i) Kulawiec, R. J.; Crabtree, R. H. Coord. Chem. Rev. 1990, 99, 89-115 and references therein.
118. (a) Lehmkuhl, H.; Näser, J.; Mehler, G.; Keil, T.; Danoski, F.; Benn, R.; Mynott, R.; Schroth, G.; Gabor, B.; Krüger, C.; Betz, P. Chem. Ber. 1991, 124, 414-425.
119. (b) Schmitt, H.-J.; Weidenhammer, K.; Ziegler, M. L. Chem. Ber. 1976, 109, 2558-2564.
120. (c) Krüger, C. Chem. Ber. 1976, 109, 3574-3580.
121. (d) Cámpora, J.; Gutiérrez, E.; Poveda, M. L.; Ruìz, C.; Carmona, E. J. Chem. Soc., Dalton Trans. 1992, 1769-1774.
122. (e) Scatturin, V.; Tureo, A. J. Inorg. Nucl. Chem. 1958, 447-451.
123. (f) Stalick, J. K.; Ibers, J. A. Inorg. Chem. 1970, 9, 453-458.
124. (a) Jackson, S. A.; Eisenstein, O.; Martin, J. D.; Albeniz, A. C.; Crabtree, R. H. Organometallics 1991, 10, 3062-3069.
125. (b) McWeeny, R.; Mason, R.; Towl, A. D. C. Faraday Discuss. Chem. Soc. 1969, 47, 20-25.
126. (c) Basolo, F.; Pearson, R. G. Prog. Inorg. Chem. 1962, 4, 381-453.
127. (d) Grünberg, A. A. Acta Physicochim. URSS 1935, 3, 573-576; Bull. Acad. Sci. URSS, Cl. Sci. Chem. 1943, 350-356.
128. (d) Grünberg, A. A. Acta Physicochim. URSS 1935, 3, 573-576; Bull. Acad. Sci. URSS, Cl. Sci. Chem. 1943, 350-356.
129. van der Zeijden, A. A. H.; van Koten, G.; Wouters, J. M A.; Wijsmuller, W. F. A.; Grove, D. M.; Smeets, W. J. J.; Spek, A. L. J. Am. Chem. Soc. 1988, 110, 5354-5361.
130. Preliminary molecular modelling studies (MM2 and ZINDO) have shown that such a hypercoordinate carbon species is a viable intermediate: Grove, D. M. Unpublished results.
131. For an example of block copolymer synthesis via "living" carbocationic followed by "living" radical polymerization, see: Coca, S.; Matyjaszewski, K. Macromolecules 1997, 30, 2808-2810. This form of polymerization is also called "Atom Transfer Radical Polymerization" (ATRAP); see ref 2.
132. Thomson, A. J. Nature 1982, 298, 602-603.
133. (a) Lancaster, J. R., Jr. FEBS Lett. 1980, 115, 285-288.
134. (b) Albracht, S. P. J.; Graf, E.-G.; Thauer, R. K. FEBS Lett. 1982, 140, 311-313.
135. (c) Cammack, R.; Patil, D.; Aguirre, R.; Hatchikian, E. C. FEBS Lett. 1982, 142, 289-292.
136. Kitazume, T.; Ikeya, T. J. Og. Chem. 1988, 53, 2350-2352. The authors of this article incorrectly refer to urease as a "porphin" enzyme. The Ni centers in this enzyme are thought to be in a pseudo-octahedral geometry and ligated by five N and/or O donor atoms and a single S atom. Although urease carries out Kharasch-type addition, there is no evidence that this enzyme contains a Ni center in the +3 oxidation state or that urease is involved in any form of redox cycle during catalysis (unlike the hydrogenases and membrane-bound Ni compounds discussed above). Therefore, the mechanism of action of this enzyme must be distinctly different from that of the [Ni(NCN)X] complexes described in this Account (see: (i) Cammack, R. Catalysis by Nickel in Biological Systems. In Bioinorganic Catalysis; Reedijk, J. Ed., Marcel Dekker: New York, 1993; Chapter 7. (ii) Finnegan, M. G.; Kowal, A. T.; Werth, M. T.; Clark, P. A.; Wilcox, D. E.; Johnson, M. K. J. Am. Chem. Soc. 1991, 113, 4030-4032. (iii) Clark, P. A.; Wilcox, D. E.; Scott, R. A. Inorg. Chem. 1990, 29, 579-581). We thank the comments of the reviewers in this area.
137. Kitazume, T.; Ikeya, T. J. Og. Chem. 1988, 53, 2350-2352. The authors of this article incorrectly refer to urease as a "porphin" enzyme. The Ni centers in this enzyme are thought to be in a pseudo-octahedral geometry and ligated by five N and/or O donor atoms and a single S atom. Although urease carries out Kharasch-type addition, there is no evidence that this enzyme contains a Ni center in the +3 oxidation state or that urease is involved in any form of redox cycle during catalysis (unlike the hydrogenases and membrane-bound Ni compounds discussed above). Therefore, the mechanism of action of this enzyme must be distinctly different from that of the [Ni(NCN)X] complexes described in this Account (see: (i) Cammack, R. Catalysis by Nickel in Biological Systems. In Bioinorganic Catalysis; Reedijk, J. Ed., Marcel Dekker: New York, 1993; Chapter 7. (ii) Finnegan, M. G.; Kowal, A. T.; Werth, M. T.; Clark, P. A.; Wilcox, D. E.; Johnson, M. K. J. Am. Chem. Soc. 1991, 113, 4030-4032. (iii) Clark, P. A.; Wilcox, D. E.; Scott, R. A. Inorg. Chem. 1990, 29, 579-581). We thank the comments of the reviewers in this area.
138. Kitazume, T.; Ikeya, T. J. Og. Chem. 1988, 53, 2350-2352. The authors of this article incorrectly refer to urease as a "porphin" enzyme. The Ni centers in this enzyme are thought to be in a pseudo-octahedral geometry and ligated by five N and/or O donor atoms and a single S atom. Although urease carries out Kharasch-type addition, there is no evidence that this enzyme contains a Ni center in the +3 oxidation state or that urease is involved in any form of redox cycle during catalysis (unlike the hydrogenases and membrane-bound Ni compounds discussed above). Therefore, the mechanism of action of this enzyme must be distinctly different from that of the [Ni(NCN)X] complexes described in this Account (see: (i) Cammack, R. Catalysis by Nickel in Biological Systems. In Bioinorganic Catalysis; Reedijk, J. Ed., Marcel Dekker: New York, 1993; Chapter 7. (ii) Finnegan, M. G.; Kowal, A. T.; Werth, M. T.; Clark, P. A.; Wilcox, D. E.; Johnson, M. K. J. Am. Chem. Soc. 1991, 113, 4030-4032. (iii) Clark, P. A.; Wilcox, D. E.; Scott, R. A. Inorg. Chem. 1990, 29, 579-581). We thank the comments of the reviewers in this area.
139. Kitazume, T.; Ikeya, T. J. Og. Chem. 1988, 53, 2350-2352. The authors of this article incorrectly refer to urease as a "porphin" enzyme. The Ni centers in this enzyme are thought to be in a pseudo-octahedral geometry and ligated by five N and/or O donor atoms and a single S atom. Although urease carries out Kharasch-type addition, there is no evidence that this enzyme contains a Ni center in the +3 oxidation state or that urease is involved in any form of redox cycle during catalysis (unlike the hydrogenases and membrane-bound Ni compounds discussed above). Therefore, the mechanism of action of this enzyme must be distinctly different from that of the [Ni(NCN)X] complexes described in this Account (see: (i) Cammack, R. Catalysis by Nickel in Biological Systems. In Bioinorganic Catalysis; Reedijk, J. Ed., Marcel Dekker: New York, 1993; Chapter 7. (ii) Finnegan, M. G.; Kowal, A. T.; Werth, M. T.; Clark, P. A.; Wilcox, D. E.; Johnson, M. K. J. Am. Chem. Soc. 1991, 113, 4030-4032. (iii) Clark, P. A.; Wilcox, D. E.; Scott, R. A. Inorg. Chem. 1990, 29, 579-581). We thank the comments of the reviewers in this area.
140. (a) van de Kuil, L. A.; Grove, D. M.; Zwikker, J. W.; Jenneskens, L. W.; Drenth, W.; van Koten, G. Chem. Mater. 1994, 6, 1675-1683.
141. (b) Pathmamanoharan, C.; Wijkens, P.; Grove, D. M.; Philipse, A. P. Langmuir 1996, 12, 4372-4377.
142. (c) Knapen, J. W. J.; van der Made, A. W.; de Wilde, J. C.; van Leeuwen, P. W. N. M.; Wijkens, P.; Grove, D. M.; van Koten, G. Nature 1994, 372, 659-663.
143. (a) Fréchet, J. M. J. Science 1994, 263, 1710-1715.
144. (b) Tomalia, D. M. Sci. Am. 1995, 272, 62-68.
145. (a) Roovers, J.; Zhou, L. L.; Toporowski, P. M.; van der Zwan, M.; Iatrou, H.; Hadijchristidis, N. Macromolecules 1993, 26, 963-968 and references therein.
146. (b) van der Made, A. W.; van Leeuwen, P. W. N. M.; de Wilde, J. C.; Brandes, R. A. C. Adv. Mater. 1993, 5, 466-468 and references therein.
147. (a) Knapen, J. W. J.; van der Made, A. W.; de Wilde, J. C.; van Leeuwen, P. W. N. M.; Wijkens, P.; Grove, D. M.; van Koten, G.; Gossage, R. A.; Kleij, A. W.; Kragl, U.; Brinkmann, N. Manuscript in preparation.
148. (b) Kleij, A. W.; Gossage, R. A.; Kleijn, H.; van Koten, G.; Kragl, U.; Brinkmann, N. KNCV Katalyse Symposium, May 12-13, 1997, Kerkrade, The Netherlands, poster 37.
149. (c) Kragl, U.; Dreisbach, C.; Wandrey C. In Applied Homogeneous Catalysis with Organometallic Compounds, Cornils, B., Herrmann, W. A., Eds. Vol. 2; VCH: Weinheim, 1996; Chapter 3.2.3.