Divalent silicon, germanium, and tin compounds with element—heteroatom bonds

New paramagnetic N-heterocyclic stannylenes: An EPR study

“…EPR spectra of compounds 4 and 5 in toluene solution remain for several hours after discontinuance of irradiation at 220 K. At ambient temperature these complexes decompose faster. Irradiation of toluene solution containing 1 and Co 2 (CO) 8 at 220 K results in a weak broad singlet in EPR spectrum, which disappears under further irradiation or increase temperature. When Mn 2 (CO) 10 and Re 2 (CO) 10 were used as radical sources, we were unable to detect any EPR signals both under ambient temperature and when cooled.…”

“…The enhanced stability of the latter was explained by the following: a weak ancillary coordination bond between germanium and ethoxy group causes considerable steric hindrances in the coordination sphere of germanium, and thus prevents addition of the second radical [6b]. Taking into account the fact, that the tetracoordinate state is more usual for tin(II) than for germanium(II) derivatives [8], we proposed, that the product of above mentioned phenoxyl addition to stannylene 1 would show even higher stability.…”

New tin(II) and tin(IV) amidophenolate complexes

“…Dihedral angles between the planar central Sn (1) [15]), and it is in clear agreement with the sum of covalent radii of nitrogen and tin (2.10 Å [8]). It should be noted that existence of dimer divalent tin derivatives having such Sn-O bonding is rather usual [16].…”

Germylene and stannylene (Me2NCH2CH2O)2E as strong σ-donor ligands for transition metal complexes [ML(CO)n] (E=Ge, Sn; M=Cr, Mo, W, n=4 or 5; M=Fe, n=4). Synthesis, spectroscopic and theoretical study

“…Ligand dissociation energies (D 0 ) were calculated as energy difference between the relaxed structures of complexes [CrL(CO) 5 ], [FeL(CO) 4 ] and isolated fragments L and [Cr(CO) 5 ] and [Fe(CO) 4 ]. For both chromium and iron complexes ligand dissociation energies increase in the order Ph 3 P < 2$1 < dmiy.…”

“…Kinetic stabilization is achieved by the introduction of bulky substituents (steric stabilization, types A [2] and B [3]), while thermodynamic stabilization stems from electronic effects [4] such as: (i) introduction of acceptor substituents X on the central atom E (type C [5]); (ii) formation of intramolecular coordination bonds Y ? E (Y -heteroatom bearing a lone electron pair, N, P, O, S; type D [6]); (iii) conjugation and delocalization (types E [7] and F [8]).…”