The series of 2-substituted diphenylphosphine pyridines 1−5 were synthesized and subsequently oxidized with silyl or aryl azides to give the series of pyridine−phosphinimine ligands 2-(Me3SiNPPh2)C5H4N (9), 2-(2,6-Me2C6H3NPPh2)C5H4N (10), 2-(2,6-i-Pr2C6H3NPPh2)C5H4N (11), 2-(2,6-Me2C6H3NPPh2)-6-MeC5H4N (12), 2-(2,6-i-Pr2C6H3NPPh2)-6-MeC5H4N (13), 2-(2,6-Me2C6H3NPPh2)-6-BnC5H4N (14), 2-(2,6-i-Pr2C6H3NPPh2)-6-BnC5H4N (15), 2-(2,6-Me2C6H3NPPh2)-6-SiMe3C5H4N (16), 2-(2,6-i-Pr2C6H3NPPh2)-6-SiMe3C5H4N (17), 2-(2,6-Me2C6H3NPPh2)-6-PhC5H4N (18), and 2-(2,6-i-Pr2C6H3NPPh2)-6-PhC5H4N (19). Attempts to oxidize the fluorinated phosphine 2-P(C6F5)2-6-PhC5H3N (6) were unsuccessful. The ligand 9 reacted with PdCl2(PhCN)2 to the give the square-planar, diamagnetic compound (L)PdCl2 (20; L = 9), while the remaining ligands were used to prepare (L)NiBr2 and (L)FeCl2 complexes 21−30 and 31−40 (L = 10-19), respectively. In these complexes the P atoms become part of the chelate backbone. In addition, the pyridine−phosphinimines 2-(Ph3PNCH2)(C5H4N) (44), 2-(Ph3PNCH2)-6-Me(C5H3N) (45), and 2-(Ph3PNCH2)-6-Ph(C5H3N) (46) were also prepared from the reaction of 2-azidomethyl−pyridines with PPh3. In a similar fashion the complexes (L)PdCl2 (47, 48; L = 44, 45), (L)NiBr2 (49−51; L = 44−46), (L)FeCl2 (52, 53), and (L)CoCl2 (54, 55; L = 44, 45) were prepared. In addition, the imidazole−phosphines 1-Me-2-(PPh2)C3H2N2 (58), 1-Me-2-(PPh2)-4,5-Ph2C3N2 (59), and 1-Me-2-(PPh2)C7H6N2 (60) were prepared and oxidized to give the imidazole−phosphinimines 1-Me-2-(2,6-Me2C6H3NPPh2)C3H2N2 (61), 1-Me-2-(2,6-i-Pr2C6H3NPPh2)C3H2N2 (62), 1-Me-2-(2,6-Me2C6H3NPPh2)-4,5-Ph2C3N2 (63), 1-Me-2-(2,6-i-Pr2C6H3NPPh2)-4,5-Ph2C3N2 (64), 1-Me-2-(2,6-Me2C6H3NPPh2)C7H6N2 (65), 1-Me-2-(2,6-i-Pr2C6H3NPPh2)C7H6N2 (66) and 1-Me-2-(2,6-i-Pr2C6H3NPPh2)-4-(t-Bu)C3HN2 (67). Subsequent complexation afforded the species (L)PdCl2 (68; L = 61), (L)NiBr2 (69−75; L = 61−67), and (L)FeCl2 (76−82; L = 61−67). Preliminary screening for activity as catalyst precursors for ethylene polymerization indicated that ethylene oligomerization may be occurring. In the case of complexes 30, 40, 74, and 82 activation with Et2AlCl(ClC6H5) at 35 °C under 300 psi of ethylene effected modest catalytic dimerization of ethylene to mainly C4 alkenes. DFT computations suggested that inclusion of P into the ligand results in diminished electrophilicity at the metal and thus a weakened ethylene−metal interaction, accounting for the modest catalytic activity. X-ray structure determinations were obtained for 2, 20, 26, 27, 35, 37, 40, 49−51, 54, 68, 79, and 82.

No abstract

No abstract

In aprotic solvents, reactions of [NiCl4]2-with preformed or generated in situ thiolates from pyridine-2-thiol (py2SH) and pyrimidine-2-thiol (pm2SH) afford the distorted octahedral thiolato complexes [Ni(S2py)3]-and [Ni(S2pm)3]", respectively. (Et4N)[Ni(S2py)3] (3) crystallizes in the monoclinic space group P2¡/c with a = 18.958 (5) Á, b = 9.311 (3) Á, c = 15.090 (4) Á, 0 = 104.91 (2)°, V = 2574 (1) Á3, and Z = 4. The structure of 3 was refined to R = 4.68% on the basis of 2636 unique (F2 > 3a(F02)) data. (Ph4P)[Ni(S2pm)3]-CH3CN (4b) also crystallizes in the monoclinic space group P2¡/c with a = 18.002 (7) A, b = 9.951 (4) Á, c = 22.791 (1) Á, ß = 112.27 (3)°, V = 3778 (3) Á3, and Z = 4. On the basis of 2565 unique data, the structure of 4b was refined to R = 4.66%. These discrete thiolato complexes of nickel(II) contain three four-membered N,S-chelate rings with exceptionally small N-Ni-S "bite" angles of ca. 67°. The average Ni(II)-N and Ni(II)-Sth (th = thiolate) distances are 2.052 (4) and 2.528 (1) Á (in 3) and 2.043 (5) and 2.495 (2) Á (in 4b) respectively. Both complexes are isolated as the mer isomer.Various spectroscopic studies show that pm2S" is the stronger ligand and gives rise to a nickel(II) complex that is more resistant to oxidation. The three complexes reported in this paper belong to a relatively scarce class of octahedral nickel(II) thiolates. Unlike the tetrahedral thiolato complexes [Ni(SAr)4]2-, these octahedral species are quite stable in presence of protic solvents like alcohols.

No abstract