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Four-membered and five-membered metallocycles of methylnickel compounds

1991; Elsevier BV; Volume: 189; Issue: 2 Linguagem: Inglês

10.1016/s0020-1693(00)80199-1

1873-3255

H.‐F. Klein, Thomas Wiemer,

N-Heterocyclic Carbenes in Organic and Inorganic Chemistry

Square planar methylnickel phenoxides trans-NiMe(OR)(PMe3)2(R =3−NO2C6H4 (1a), 4−NO2C6H4, (2a), 4−CHOC6H4 (3a), C6F5 (4a), 4−C6H5N2C6H4 (5a) were prepared from [NiMe(OMe)(PMe3)]2 and the corresponding phenol in the presence of trimethylphosphine. Without the phosphine only one of the dinuclear methylnickel phenoxides [NiMe(OR)(PMe3)]2 (R=C6F5, 4) could be obtained, while triphenylsilanol gave cis/trans-[NiMe(OSiPh3)(PMe3)]2 (6) or cis-Ni2Me2(OMe)(OSiPh3)(PMe3)2 (7) that do not add trimethylphosphine. 2-Hydroxopyridine forms both types of complex, 8a and 8, without utilizing its N-donor functions. Five-membered O,N-chelate rings are exclusively formed by 2-hydroxo- methylpyridine and pyridine-2-carboxylic acids giving NiOXC5H4N(Me)(PMe3) (X = CH2 (9), CO (10)) and dinuclear Ni2Me2(PMe3)3(NC5H3-2,3-COO-N:O:O) (11). Triethylphosphine complexes trans- NiMe(X)(PEt3)2 (X= Cl (12), Br (13)) and [NiMe(OR)(PEt3)]2 (R= CH3 (14), H (15), C6H5(16)) are also described as related to chelate complexes NiMe(quinoline-8-oxo-N:O)(PEt3) (17) and trans- [NiMe(PEt3)]2C2O4 (18).