Solvothermal synthesis of cobalt PCP pincer complexes from [Co(2)(CO)(8)]

Treatment of [Co(2)(CO)(8)] with the ipso-substituted P(C-X)P(Y) ligands (X = Br, Cl; R = iPr, tBu) bearing Y = NH and CH(2) linkers under solvothermal conditions affords the five-coordinate Co(I) and Co(III) complexes [Co(I)(PCP(Y)-R)(CO)(2)] and [Co(III)(PCP(Y)-R)X(2)]. The later are paramagnetic exhibiting a solution magnetic moment in the range of 3.0–3.3 μ(B) which is consistent with a d(6) intermediate spin system corresponding to two unpaired electrons. In the case of P(C-X)P(Y) ligands (X = Br, Cl; R = tBu; Y = NH) the formation of the square planar Co(II) complex [Co(PCP(NH)-tBu)X] was favored. This complex gives rise to a magnetic moment of 1.8 μ(B) being consistent with a d(7) low spin system corresponding to one unpaired electron. All complexes are characterized by means of spectroscopic techniques (NMR, IR), HR-MS. Representative complexes were also characterized by X-ray crystallography. GRAPHICAL ABSTRACT: [Image: see text] SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1007/s00706-023-03123-x.