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There is unceasing interest toward transformations of phosphine derivatives, which are facilitated by transition metals. We report a facile Pd(II)- and Pt(II)-assisted P-C bond cleavage in a luminescent 2-phenylbenzothiazole-based α-methylaminophosphine ( PCN , 1 ). Specifically, reactions between 1 and [M(COD)Cl 2 ] (M = Pd, Pt; COD = cycloocta-1,5-diene) in different solvents (methylene chloride, acetonitrile, pyridine, toluene) resulted in the formation of PPh 2 - , captured either as a bridging ligand in binuclear complexes with a {M 2 (PPh 2 ) 2 } moiety or as an adduct to COD in [Pt 2 (PPh 2 COD) 2 Cl 2 ]. The heterocyclic part transforms to annulated c-CN + species with a 1,2-dihydroquinazoline cycle formed. In the presence of pyridine as a base, annulated form c-CN + destabilizes and undergoes reverse cyclization transforming to deprotonated CN form. Quantum-chemical density functional theory (DFT) calculations predict that a crucial step in the reactions involves proton transfer from the N atom of the amino group of PCN to a neighboring molecule. A combination of high photophysical sensitivity of c-CN + toward its immediate environment and rich structural capabilities in assembling ( c-CN ) 2 2+ pairs in different crystal packings in a family of phases with the general formula ( c-CN ) 2 [M 2 (PPh 2 ) 2 Cl 4 ] allows one to fine-tune the luminescence properties of the latter. The results were rationalized as a variation of π-π intercationic spacings, which tunes the degree of excited-state charge transfer between c-CN + cations. As a result, compounds with relatively short interplanar π-π-separation between the cations show a stronger charge-transfer-mediated bathochromic shift.

Heterometallic complexes [Cp* 2 Ln(μ- iso CO) 2 {Cr 2 (μ-P)Cp 2 (CO) 2 }] [Ln = Yb ( 1 ), Sm ( 2 )] were obtained in reactions of [Cp* 2 Ln(thf) 2 ] (Ln = Sm, Yb) with [{CpCr(CO) 2 } 2 (μ,η 2:2 -P 2 )] ( 4 ). An analogous yttrium compound [Cp* 2 Y(μ- iso CO) 2 {Cr 2 (μ-P)Cp 2 (CO) 2 }] ( 3 ) was synthesized using a three-component reaction between [Cp* 2 Y(BPh 4 )], 4 , and KC 8 . Compounds 1 - 3 were isolated as solvent-free crystalline phases; in the case of 2 , the 2·0.5C 7 H 8 solvate was also obtained. The structures of all crystalline phases were determined by single-crystal X-ray diffraction analysis. All compounds contain a unique {((CO) 2 CpCr═P═CrCp(CO) 2 )} - unit, which is linked to Ln 3+ ions through CO ligands in the isocarbonyl mode. Compounds 1 and 3 have a molecular structure, while compound 2 contains polymeric chains of triangular [Cp* 2 Sm(μ- iso CO) 2 {Cr 2 (μ-P)Cp 2 (CO) 2 }] units linked by μ- iso CO-ligands. 31 P NMR studies demonstrated similar dramatic downfield shifts for complexes 1 - 3 . To realize the electronic structure of 1 - 3 and to elucidate the nature of the high downfield chemical 31 P shift, quantum chemical calculations were performed both for 1 - 3 and for related Cr- and Fe-phosphido complexes. Calculations show that the anomalously high downfield chemical shifts for 1 - 3 are due to the anisotropic effect of the Cr═P double bonds.

Complexes of divalent ytterbium (1) and europium (2) with a dianionic o-amidophenolate ligand were prepared by both the direct reduction of 4,6-di-tert-butyl-N-(2,6-diisopropylphenyl)-o-iminobenzoquinone (dpp-IQ) and the salt metathesis reaction of potassium o-amidophenolate with LnI2 (Ln = Yb, Eu). Oxidation of o-amidophenolates 1, 2 with one equivalent of dpp-IQ as well as the salt metathesis reaction of potassium o-iminosemiquinolate with LnI2 afforded ligand mixed-valent o-iminosemiquinonato-amidophenolato complexes of trivalent ytterbium (3) and europium (4). All novel complexes 1-4 were fully characterized, including the solid state structures of 1 and 2 determined by single crystal X-ray diffraction. The magnetic properties of paramagnetic 2-4 were examined.