Lanthanide(II) and ‐(III) Porphyrinogens − Rational Synthesis and Derivatisation of Mononuclear, Alkali‐Metal‐Free Lanthanide(II) and ‐(III) meso‐Octaalkylporphyrinogen Complexes

Abstract

Modifying the porphyrinogen framework in lanthanide porphyrinogen complexes by trans-N,NЈ-dimethylation results in Sm II and Sm III derivatives that are remarkably simple in structure and formulation, and are amenable to highly controllable further reaction chemistry. The Sm II bis(tetrahydrofuran) adduct, Sm III chloride and bis(trimethylsilyl)amide

Sm(ii) reduction chemistry of heteroalkynes: stable adducts, reductive coupling, reductive C–C/C–N bond cleavage and trapping of the tert-butyl fragment with bulky nitriles, phosphaalkynes and isonitriles

“…2. The Sm centre binds to the macrocycle in its typical h 5 :h 1 :h 5 :h 1 -binding mode with the Sm-C/N distances to the macrocycle in accord with previous reports for Sm(III) centres, 16 which are clearly distinguished from Sm(II) examples featuring the larger metal ion, including that of the nitrile adduct [(Me 2 N 4 )Sm(N≡C-t-Bu)] 4, see below. The structure reveals the (t-BuC=N-t-Bu)ligand to bind h 2 -to the Sm centre, as is commonly found for transition metal complexes.…”

Synthesis and reactivity of trans-N,N′-dimethyl-meso-octaalkylporphyrinogen Sm(II), Eu(II) and Yb(II) complexes: Metal-based influences on the reduction of t-butyl-1,4-diazabuta-1,3-diene

“…The EueN(pyr) and EueO bond lengths in the bis(THF) adduct 4 are longer than those observed in mono(THF) adduct 5 by 3.1e5.2%, consistent with this reduction in coordination number. Similar trends are observed in the isostructural Sm(II) complexes [(Me 2 N 4 ) Sm(THF) 2 ] 1 and [(Me 2 N 4 )Sm(THF)] 3 [9]. The distance of the metal centre from the plane of the macrocycle appears to be very sensitive to both the ionic radius of the metal and steric strain between the macrocycle and ancillary ligands, see below.…”

“…The analogous reaction performed in THF using the THF adduct [(C 5 Me 5 ) 2 Sm (THF) 2 ] has been reported by us [9] as an unusual pentamethylcyclopentadienyl elimination reaction route to [(Me 2 N 4 )Sm (THF) 2 ] 1. This reaction promised to offer an extended route into macrocyclic complexes of the (Me 2 N 4 ) 2À ligand across the whole series (where metathetical exchanges involving LnX 3 salts and direct macrocycle metallations have universally failed thus far).…”

“…The increased steric influences of the (Me 2 N 4 ) 2À macrocyclic ligand on ancillary ligands relative to the bis(pentamethylcyclopentadienyl) ligand set has previously been established through a number of comparative structural studies [9,21]. In particular, the macrocycle exhibits a relatively short binding groove for accommodating ancillary ligands that is limited by the meso-ethyl substituents that have no spatial counterparts in metallocene chemistry.…”

“…We have previously reported the synthesis and reactivity of the bis(tetrahydrofuran) adduct of the Sm(II) complex [9] of the doubly deprotonated trans-N,N 0 -dimethyl-meso-octaethylporphyrinogen, (Me 2 N 4 ) 2À , that we introduced into organometallic chemistry, [(Me 2 N 4 )Sm(THF) 2 ], 1. It forms an unusual 2:1 stoichiometric complex [10] on reaction with 1,4-di-t-butyl-1,4-diazabuta-1,3-diene, t-Bu-DAB, in toluene giving the dinuclear complex [{(Me 2 N 4 ) Sm} 2 (t-Bu-DAB)], 2.…”