Nickel(II) and nickel(0) complexes containing 2-pyridylphosphine ligands, including water-soluble species

The paramagnetic, S = 1, NiX 2 L 2 (X  Cl or Br, L  PPh 3− n py n , n = 1–3), and diamagnetic NiBr 2 [d(py)pe] ( 4b ) complexes have been isolated, generally as solvates, where py = 2-pyridyl and d(py)pe = py 2 P(CH 2 ) 2 Ppy 2 . Also isolated are the diamagnetic Ni(CO) 2 (PPh 2 py) 2 ( 5 ), Ni(CO) 2 [d(py)pe] ( 7 ), Ni(PPh 2 py) 4 , Ni(PPhpy 2 ) 4 and Ni[d(py)pe] 2 , sometimes as hydrates. The complexes, except for 5 which contains paramagnetic impurities, analyze well, and have been characterized by 1 H and 31 P{ 1 H} NMR (for diamagnetic species), IR (for the carbonyls) or magnetic moment data (for the paramagnetic species). NMR evidence for in situ formation of Ni(CO) 2 (PPhpy 2 ) 2 and Ni(Ppy 3 ) 4 is also presented. Of note, NiX 2 L 2 , 4b and 7 are water-soluble, possibly because of protonation of the pyridyl-N atoms, although this remains to be established; even non-aqueous solutions of these Ni(II) species are moisture-sensitive. In contrast to Ni(PPh 3 ) 4 , at ambient conditions the NiL 4 species show little tendency to dissociate in benzene or toluene.