A contribution to 1-azapentadienylmetal chemistry: Si, Sn(II), Fe(II) and Co(II) complexes

Complexes of three related 1-azapentadienyl ligands [N(SiMe2R1)C(But)(CH)3SiMe2R]−, abbreviated as L (R = But, R1 = Me), L′ (R = Me = R1), and L″ (R = But = R1), are described. The crystalline compounds Sn(L)2 (1), Sn(L′)2 (2), [Sn(L′)(μ-Cl)]2 (3) and [Sn(L″)(μ-Cl)]2 (4) were prepared from SnCl2 and 2 K(L), 2 K(L′), K(L′) and K(L″), respectively, in thf. Treatment of the appropriate lithium 1-azapentadienyl with Si(Cl)Me3 yielded the yellow crystalline Me3Si(L) (5) and the volatile liquid Me3Si(L′) (6) and Me3Si(L″) (7), each being an N,N,C-trisilyldieneamine. The red, crystalline Fe(L)2 (8) and Co(L′)2 (9) were obtained from thf solutions of FeCl2 with 2 Li(L)(tmeda) and CoCl2 with 2 K(L′), respectively. Each of 1–9 gave satisfactory C, H, N analyses; 6 and 7 (GC–MS) and 1, 2, 8 and 9 (MS) showed molecular cations and appropriate fragments (also 3 and 4). The 1H, 13C and 119Sn NMR (1–4) and IR spectra support the assignment of 1–4 as containing Sn–N(SiMe2R1)-C(But)(CH)3SiMe2R moieties and 5–7 as N(SiMe3)(SiMe2R1)C(But)(CH)3SiMe2R molecules; for 1–4 this is confirmed by their X-ray structures. The magnetic moments for 8 (5.56 μB) and 9 (2.75 μB) are remarkably close to the appropriate Fe and Co complex [M{η3-N(SiMe3)C(But)C(H)SiMe3}2]; hence it is proposed that 8 and 9 have similar metal-centred, centrosymmetric, distorted octahedral structures.

The crystalline compounds Sn(L)2, Sn(L′)2, [Sn(L′)(μ-Cl)]2, [Sn(L″)(μ-Cl)]2 (X-ray data), Me3Si(L), the high-spin Fe(L)2 and the low-spin Co(L′)2, as well as the liquid Me3Si(L′) and Me3Si(L″), have been prepared and characterised.Figure optionsDownload as PowerPoint slide