Synthesis and characterisation of bulky guanidines and phosphaguanidines: precursors for low oxidation state metallacycles

Bulky guanidinate stabilized homoleptic magnesium, calcium and zinc complexes and their catalytic activity in the Tishchenko reaction

“…The 1 H NMR spectrum exhibits a singlet at 4.79 ppm for the NeH resonance. The 13 C { 1 H} NMR spectrum, the carbon atom of the guanidine core i.e., N3C resonates at 148.7 ppm, that is well in agreement with other reported bulky guanidines (N3C 140e159 ppm) [24].…”

“…The compounds 1 and 2 display solid state structures comparable to those of previously characterized bulky guanidine (L 1 H) and its alkali salt (L 1 K) n compounds [24]. Four different isomeric forms exist for guanidine and related amidines, due to CeN bond rotation and C]N bond isomerization (E anti , E syn , Z anti , Z syn ).…”

“…ArN]C] NAr (Ar ¼ 2,6-i Pr 2 -C 6 H 3 ) and followed by aqueous work up [24]. In our hands, deprotonation of L 1 H upon treatment with MR 2 (M ¼ Mg, Ca; R ¼ N(SiMe 3 ) 2 or salt metathesis reaction between potassium salt of L 1 H i.e., L 1 K with MX 2 (M ¼ Mg, Ca; X ¼ halide) led to the formation of mixture of products; major product free ligand (L 1 H) was noticed by NMR analysis of reaction mixture.…”

Synthesis and Crystal Structures of Bulky Guanidinato Zirconium(IV) and Hafnium(IV) Chloride Complexes

“…Melting points were determined in sealed glass capillaries under dinitrogen and are uncorrected. The compound GisoH was prepared by the literature method [2], whilst all other reagents were used as received.…”

“…In recent years we have developed a variety of extremely bulky guanidinate ligands, e.g. [(DipN) 2 CN(C 6 H 11 ) 2 ] -Giso (Dip = C 6 H 3-Pr 2 i -2,6) [2], and have utilized these for the stabilization of low oxidation state and/or low coordination number complexes incorporating metals from every block of the periodic table [3]. Given these prior successes, we believed the steric bulk of the Giso ligand could allow us access to complexes of the heavier group 4 metals, zirconium and hafnium, with those metals in oxidation states lower than ?4.…”