Bis(pentamethylcyclopentadienyl)magnesium:  Unexpected Determination of the Until Now Unknown Molecular Structure of the Crystalline Compound

Abstract

The structure of bis(pentamethylcyclopentadienyl)magnesium, Mg(C 5 Me 5 ) 2 ( 1), in the solid state has been determined by X-ray diffraction. The experimental results are described and discussed in comparison to structural properties of the higher alkaline-earth metallocenes MCp* 2 (M ) Ca, Sr, Ba) as determined in the gas phase or in the solid state. Structural trends of 1 in comparison to the isoelectronic species [LiCp* 2 ] -, BeCp* 2 , and [AlCp* 2 ] + are also presented.

Butenyl‐Substituted Alkaline‐Earth Metallocenes: A First Step towards Olefin Complexes of the Alkaline‐Earth Metals

“…The structural investigations show that only the magnesium complex 1 satisfies the strict arrangement of a sandwich structure with a parallel arrangement of the cyclopentadienyl ring planes above and below the central metal atom, an arrangement that was also found for [Mg(C 5 H 5 ) 2 ] [17] and [Mg(C 5 Me 5 ) 2 ]. [18] Two independent molecules are located in the unit cell that differ only slightly in the angles Cp1 cen -Mg1-Cp2 cen (175.848) and Cp1 cen -Mg2-Cp2 cen (1808) and in the torsion angles: C1r-Cp1 cen -Cp2 cenC6r = À32.1(1)8 and C1r-Cp1 cen -Cp1' cenC1r' = À1808 (Figure 1, cen = ring centroid). The respective distance between the centers of the two cyclopentadienyl ligands (3.930 and 3.926 , respectively, Table 1) corresponds to the value determined for [Mg(C 5 Me 5 ) 2 ] (3.94 ).…”

“…The respective distance between the centers of the two cyclopentadienyl ligands (3.930 and 3.926 , respectively, Table 1) corresponds to the value determined for [Mg(C 5 Me 5 ) 2 ] (3.94 ). [18] The two butenyl side chains are directed away from the magnesium center above and below, respectively. The compounds with the heavy alkaline-earth metals, 2-4, have in principal the same molecular structure with C 2 symmetry (3) or approximate C 2 symmetry (2, 4; see Figure 2).…”

Alkaline Earth Organometallics

“…Steric crowding presumably leads to the change in bonding arrangement. 232 The stable carbene 1,3,4,5tetramethylimidazol-2-ylidene reacts with (C 5 Me 5 ) 2 Mg to generate the (C 5 Me 5 ) 2 Mg(1,3,4,5-Me 4 -C 3 N 2 ) adduct. 184 Applications in CVD Various techniques of thin film deposition, including CVD (also abbreviated as MOCVD, metalloorganic chemical-vapor deposition) have been under intensive development for the s-block elements, and particularly the alkaline earth metals, since the late 1980s.…”

[AlCp2]+: Structure, Properties and Isobutene Polymerization

“…The structure of the cationic AlCp 2 ϩ -ion is given in Figure 2. In 2a the Cp rings are η 5bonded (stagger angle β ϭ 30.55°) [14] with an average XϪAl distance of 178.9 pm (X is the distance between the center of the Cp-rings and the aluminum atom) and an XϪAlϪX angle of 179.5°. The average AlϪX distances in [AlCp* 2 ] ϩ (1) and [AlCpЈ 2 ] ϩ (3) are 178 pm and 176.5 pm respectively [1,2].…”