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The synthesis of the phosphinito complexes [(C5H5)Co{P(O)R2}3Co{R2(O)P}3}Co(C5H5)] (R = C2H5 (Ib), CH2C6H5 (Id), C6H5 (Ie), p-C6H4Cl (If)), starting from secondary phosphine oxides and cobaltocene is described. Ib and Id are shown to react with cyanide to give the anionic half-sandwich complexes [(C5H5)Co{P(O)R2}3]− (R = C2H5 (IIb), CH2C6H5 (IId)), which behave like oxygen tripod ligands. With metal ions, e.g. Mn+ = Al3+, Ce4+, Pr3+, Eu3+, Fe3+, in aqueous solution IIb for instance forms the complexes [(C5H5)Co{P(O)(C2H5)2}3M{(C2H5)2(O)P}3Co (C5H5)](n-2)+. Secondary phosphine oxides, HP(O)R2, react with nickelocene to yield the potentially bidentate oxygen ligands [(C5H5)Ni{P(O)R2}{P(OH)R2}] (R = CH3, C2H5, C6H5). Contrastingly the isostructural bidentate sulfur ligand [(C5H5)Ni{P(S)R2}2]− (R = OCH3) can be prepared from nickelocene and HP(S)(OCH3)2 only via an indirect route. The dimeric nickel compounds [{(C5H5)NiP(S)R2}2] (R = CH3 (Xa), cyclo-C6H11 (Xc), C6H5 (Xe), OCH3 (Xg)) are primary products of the reaction of nickelocene with HP(S)R2. Xg is cleaved by an excess of HP(S)(OCH3)2 in the presence of Zn2+ ions to yield [(C5H5)Ni{P(S)(OCH3)2}2Zn{(CH3O)2(S)P}2Ni(C5H5)] (XIg). Na[(C5H5)Ni{P(S)(OMe)2}2], the sodium salt of the bidentate sulfur ligand in XIg, can be isolated by treating XIg with Na2S. |
