Synthesis, spectroscopic characterization and reactivities of linear and butterfly chromium/selenium complexes containing substituted cyclopentadienyl ligands: crystal structures of [{η5-MeC5H4Cr(CO)2}2Se] and [{η5-EtO2CC5H4Cr(CO)2}2Se2]

Electronic Structure of Ni2E2 Complexes (E = S, Se, Te) and a Global Analysis of M2E2 Compounds: A Case for Quantized E2n– Oxidation Levels with n = 2, 3, or 4

“…The single sharp peak at 880 ppm indicates chemical equivalence of the two Se atoms in solution, consistent with the solid-state structure. Transition metal complexes bearing the Se 2 2– ion show 77 Se NMR resonances at <−250 ppm, whereas resonances for Se 2– species have appeared as disparately as −996 ppm or +1241 ppm. , Therefore, the Se NMR data disfavor a Se 2 2– assignment, ruling out case A . The 125 Te NMR spectrum of 3 displays a single sharp peak at 822 ppm, which also suggests that the two Te atoms are equivalent in solution as in solid state.…”

Novel Organometallic Macrocycles Containing Linear Cr2E Structural Units: Synthesis and Characterization of {[(CO)2Cr⋮E⋮Cr(CO)2][η5-C5H4C(O)CH2]2}n (E = Se, S; n = 1, 2)

“…The 77 Se NMR spectra of 1 and 2 exhibited one singlet at 2693.9 and 2589.2 ppm for their Se atoms, respectively. It follows that the two Se atoms in 2 have identical magnetic environments, and the 77 Se NMR chemical shifts of 1 and 2 are very close to those of their noncyclic analogues [( η 5 -RC 5 H 4 )Cr(CO) 2 ] 2 Se (R = H (2574 ppm), Me (2580.9 ppm), MeCO (2589.8 ppm),8b MeO 2 C (2604.6 ppm 8b )). In addition, it is worth pointing out that the ESI mass spectrum of dimeric macrocycle 2 showed its molecular ion at m / z 1016, whereas the mass spectrum of dimeric macrocycle 4 displayed its molecular ion at m / z 921.…”

“…This molecule could be regarded as a 17-membered macrocycle, if all the carbon atoms of the two Cp rings C(5) through C(9) and C(14) through C(18) are all involved in counting the ring size. The bond angle around Se (163.08(6)°) in macrocycle 1 is obviously smaller than those in their noncyclic analogues [ (η 5 -MeO 2 CC 5 H 4 )Cr(CO) 2 ] 2 Se (167.90(8)°),8b [( η 5 -MeC 5 H 4 )Cr(CO) 2 ] 2 Se (178.70(6)°), and [CpCr(CO) 2 ] 2 Se (178.3(1)°),8a whereas the average Cr−Se bond length (2.2176(16) Å) of 1 is close to those of [( η 5 -MeO 2 CC 5 H 4 )Cr(CO) 2 ] 2 Se (2.1935(16) Å),8b [( η 5 -MeC 5 H 4 )Cr(CO) 2 ] 2 Se (2.2105(2) Å), and [CpCr(CO) 2 ] 2 Se (2.22085(1) Å) 8a. In addition, it is worthy of note that the considerable shortening of the Cr−Se bond lengths in comparison with the sum of the covalent radii of chromium ( r Cr = 1.46 Å) and selenium ( r Se = 1.17 Å) atoms is in agreement with triple bonding between chromium and selenium atoms in those Cr⋮Se⋮Cr units of such complexes.…”

Tuning of Cr–Cr Magnetic Exchange through Chalcogenide Linkers in Cr2 Molecular Dimers

“…The possibility of utilizing selenium bridged transition-metal dimer complexes as catalysts for organic reactions has been studied over the past few decades. − Chemistry of the linear Cr 2 Se and butterfly Cr 2 Se 2 complexes has been explored by different synthetic and characterization approaches. − In this work, we report the synthesis, crystal structure, and properties of three new molecular compounds Cr 2 Q 2 (en) 4 X 2 ( Q : S, Se; X : Br, Cl; en : ethylenediamine), all with a Cr 2 Q 2 rhombus core. An important feature of these compounds is that the bridging selenium atoms are not connected to any other organic ligands.…”