Details

Autor(en) / Beteiligte

• Murugesan, Sathiyamoorthy
• Stöger, Berthold
• Carvalho, Maria Deus
• Ferreira, Liliana P
• Pittenauer, Ernst
• Allmaier, Günter
• Veiros, Luis F
• Kirchner, Karl

Titel

Synthesis and Reactivity of Four- and Five-Coordinate Low-Spin Cobalt(II) PCP Pincer Complexes and Some Nickel(II) Analogues

Ist Teil von

• Organometallics, 2014-11, Vol.33 (21), p.6132-6140

Ort / Verlag

United States: American Chemical Society

Erscheinungsjahr

2014

Quelle

Alma/SFX Local Collection

Beschreibungen/Notizen

• Anhydrous CoCl2 or [NiCl2(DME)] reacts with the ligand PCPMe-iPr (1) in the presence of nBuLi to afford the 15e and 16e square planar complexes [Co­(PCPMe-iPr)­Cl] (2) and [Ni­(PCPMe-iPr)­Cl] (3), respectively. Complex 2 is a paramagnetic d7 low-spin complex, which is a useful precursor for a series of Co­(I), Co­(II), and Co­(III) PCP complexes. Complex 2 reacts readily with CO and pyridine to afford the five-coordinate square-pyramidal 17e complexes [Co­(PCPMe-iPr)­(CO)­Cl] (4) and [Co­(PCPMe-iPr)­(py)­Cl] (5), respectively, while in the presence of Ag+ and CO the cationic complex [Co­(PCPMe-iPr)­(CO)2]+ (6) is afforded. The effective magnetic moments μeff of all Co­(II) complexes were derived from the temperature dependence of the inverse molar magnetic susceptibility by SQUID measurements and are in the range 1.9 to 2.4 μB. This is consistent with a d7 low-spin configuration with some degree of spin–orbit coupling. Oxidation of 2 with CuCl2 affords the paramagnetic Co­(III) PCP complex [Co­(PCPMe-iPr)­Cl2] (7), while the synthesis of the diamagnetic Co­(I) complex [Co­(PCPMe-iPr)­(CO)2] (8) was achieved by stirring 2 in toluene with KC8 in the presence of CO. Finally, the cationic 16e Ni­(II) PCP complex [Ni­(PCPMe-iPr)­(CO)]+ (10) was obtained by reacting complex 3 with 1 equiv of AgSbF6 in the presence of CO. The reactivity of CO addition to Co­(I), Co­(II), and Ni­(II) PCP square planar complexes of the type [M­(PCPMe-iPr)­(CO)] n (n = +1, 0) was investigated by DFT calculations, showing that formation of the Co species, 6 and 8, is thermodynamically favorable, while Ni­(II) maintains the 16e configuration since CO addition is unfavorable in this case. X-ray structures of most complexes are provided and discussed. A structural feature of interest is that the apical CO ligand in 4 deviates significantly from linearity, with a Co–C–O angle of 170.0(1)°. The DFT-calculated value is 172°, clearly showing that this is not a packing but an electronic effect.