A phosphine-mediated through-space exchange coupling pathway for unpaired electrons in a heterobimetallic lanthanide-transition metal complex

摘要

The reaction of P(CH2OH)(3) with methyl anthranilate NH2C6H4-2-CO2Me produced the ligand precursor P(CH2NHCH6-2-CO2Me)(3) (1). The reaction of 1 with [Y{N(SiMe3)(2)}3] produced hexadentate yttrium complex [Y{P(CH2NC6H4-2-CO2Me)(3)}] (2), in which the metal centre is coordinated by three amido donors and the three carbonyl oxygen atoms of the ester groups. The P-31{H-1) NMR spectrum features (1)J(Y,P) = 15 Hz, and DFT calculations demonstrate that through-space interaction between the minor lobe of the phosphine lone pair and the yttrium centre allows a large Fermi contact contribution to this spin coupling constant. The EPR spectrum of the analogous paramagnetic Gd complex [Gd{P(CH2NC6-2-CO2Me)(3)}] (3) can be modelled by using a B-20 crystal field parameter of +/- 0.19 cm(-1). Heterodinuclear complexes were prepared by the reactions of 1 and 3 with [5,10,15,20-tetrakis(4-methoxyphenyl)porphinato]-cobalt(II), by binding of the phosphine lone pair to the d(7) cobalt centre. The solid-state EPR spectrum of the heterodinuclear yttrium complex 4 exhibits large superhyperfine coupling to the phosphorus nucleus, indicative of an S=(1)/2, complex in which the unpaired electron resides in the cobalt d(z)(2),, orbital directed at the phosphine donor. The magnetic susceptibility of the heterodinuclear Gd-Co complex 5 demonstrates that through-space antiferromagnetic coupling occurs between unpaired electrons on the gadolinium and cobalt centres.