| Title | Spectroscopic Characterization of Nonconcerted [4 + 2] Cycloaddition of 1,3-Butadiene with Lanthanacyclopropene To Form Lanthanum-Benzene in the Gas Phase. |
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| Authors | Hewage, D.; Cao, W.; Kim, J.Hyun; Wang, Y.; Liu, Y.; Yang, D.S. |
| Journal | J Phys Chem A |
| DOI | 10.1021/acs.jpca.6b12239 |
| Abstract |
The reaction between La atoms and 1,3-butadiene is carried out in a laser-vaporization molecular beam source. Metal-hydrocarbon species with formulas La(CnHn) (n = 2, 4, and 6) and La(CmHm+2) (m = 4 and 6) are observed with time-of-flight mass spectrometry and characterized with mass-analyzed threshold ionization spectroscopy. A lanthanum-benzene complex [La(C6H6)] is formed by 1,3-butadiene addition to lanthanacyclopropene [La(C2H2)] followed by molecular hydrogen elimination. Lanthanacyclopropene is an intermediate generated by the primary reaction between La and 1,3-butadiene. Two other intermediates produced by the La + 1,3-butadiene reaction are La[η(4)-(1-buten-3-yne)] [La(C4H4)] and 1-lanthanacyclopent-3-ene [La(C4H6)]. The La(benzene) complex exhibits distinctive metal-ligand bonding from that of the three intermediates as shown by the adiabatic ionization energies and ground electron configurations. |
See more Lanthanum products. Lanthanum (atomic symbol: La, atomic number: 57) is a Block F, Group 3, Period 6 element with an atomic weight of 138.90547. 
The number of electrons in each of lanthanum's shells is [2, 8, 18, 18, 9, 2] and its electron configuration is [Xe] 5d1 6s2. The lanthanum atom has a radius of 187 pm and a Van der Waals radius of 240 pm. Lanthanum was first discovered by Carl Mosander in 1838. In its elemental form, lanthanum has a silvery white appearance.
It is a soft, malleable, and ductile metal that oxidizes easily in air. Lanthanum is the first element in the rare earth or lanthanide series. It is the model for all the other trivalent rare earths and it is the second most abundant of the rare earths after cerium. Lanthanum is found in minerals such as monazite and bastnasite. The name lanthanum originates from the Greek word Lanthaneia, which means 'to lie hidden'.