Applications of the Laddering Principle — A Two-Stage Approach to Describe Lithium Heterocarboxylates

Abstract

Since the development of the laddering principle in the mid‐1980s, it has become a useful concept for describing structural features in a wide variety of organoalkali metal (particularly organolithium) and other main‐group element oligomers. Here a brief account of the laddering principle is given, and a two‐stage approach to understanding structural diversity is described for several lithium heterocarboxylates. “Primary laddering” describes the initial aggregation of monomeric units, whereas “secondary laddering” deals with the assembly of these primary laddered units into larger structures. Both homo‐ and heteromolecular clusters can be formed by these processes. In this context, several examples are discussed, with particular emphasis on the effects of solvation and heteroatoms.

A Gallium(I) β‐Amido‐Imino‐Phosphorane: A Five‐Membered N‐Heterocyclic Gallylene with Enhanced Nucleophilicity

“…4 is dimeric in the solid state consisting of a tricyclic [5.3.0.0] ring system featuring a planar, diamond-shaped four-membered Li 2 N 2 central ring. In contrast to transoid primary laddering typically observed for lithium complexes of N,N 0 -chelates [58][59][60], a cisoid geometry is observed here, likely because it allows a better separation of the bulkyl substituents. The N1-Li1-N2 angle of 89.0(3)° is significantly smaller compared to other dimeric lithium amides [61] but resembles values of previously reported N,N 0 ,N 0 -substituted 1,2-ethanediamides (91.35(14)°) [62].…”

A Gallium(I) β‐Amido‐Imino‐Phosphorane: A Five‐Membered N‐Heterocyclic Gallylene with Enhanced Nucleophilicity

“…4 is dimeric in the solid state consisting of a tricyclic [5.3.0.0] ring system featuring a planar, diamond-shaped four-membered Li 2 N 2 central ring. In contrast to transoid primary laddering typically observed for lithium complexes of N,N 0 -chelates [58][59][60], a cisoid geometry is observed here, likely because it allows a better separation of the bulkyl substituents. The N1-Li1-N2 angle of 89.0(3)° is significantly smaller compared to other dimeric lithium amides [61] but resembles values of previously reported N,N 0 ,N 0 -substituted 1,2-ethanediamides (91.35(14)°) [62].…”

New Lanthanide Alkynylamidinates and Diiminophosphinates

“…In the solid state, both lithium propiolamidinates crystallize in the triclinic space group P-1 with one dimeric molecule in the unit cell. The bond lengths and bond angles are in good agreement with similar structures of amidinate ligands [48][49][50][51][52][53][54][55][56][57][58]. The N-C distances in the amidinate N-C-N unit are 1.321(2) and 1.330(2) Å in 1 and 1.3201 (13)…”

Mono- and dinuclear β-oxo-δ-diiminate (BODDI) based catalysts for the ring-opening polymerization of l -lactide

“…mol weight 473 g mol −1 ). Aggregation of lithium complexes is well known 11 and in lithium β-diketiminates for example, secondary interactions with aromatic carbons of neighbouring molecules can be involved. 12 Given the steric strain imposed by the BODDI ligand, we assume that related secondary interactions are also involved in the tetramerization of (BODDI)Li 2 .…”

A Gallium(I) β‐Amido‐Imino‐Phosphorane: A Five‐Membered N‐Heterocyclic Gallylene with Enhanced Nucleophilicity

“…4 is dimeric in the solid state consisting of a tricyclic [5.3.0.0] ring system featuring a planar, diamond-shaped four-membered Li 2 N 2 central ring. In contrast to transoid primary laddering typically observed for lithium complexes of N,N 0 -chelates [58][59][60], a cisoid geometry is observed here, likely because it allows a better separation of the bulkyl substituents. The N1-Li1-N2 angle of 89.0(3)° is significantly smaller compared to other dimeric lithium amides [61] but resembles values of previously reported N,N 0 ,N 0 -substituted 1,2-ethanediamides (91.35(14)°) [62].…”

New Lanthanide Alkynylamidinates and Diiminophosphinates

“…In the solid state, both lithium propiolamidinates crystallize in the triclinic space group P-1 with one dimeric molecule in the unit cell. The bond lengths and bond angles are in good agreement with similar structures of amidinate ligands [48][49][50][51][52][53][54][55][56][57][58]. The N-C distances in the amidinate N-C-N unit are 1.321(2) and 1.330(2) Å in 1 and 1.3201 (13)…”

Mono- and dinuclear β-oxo-δ-diiminate (BODDI) based catalysts for the ring-opening polymerization of l -lactide

“…mol weight 473 g mol −1 ). Aggregation of lithium complexes is well known 11 and in lithium β-diketiminates for example, secondary interactions with aromatic carbons of neighbouring molecules can be involved. 12 Given the steric strain imposed by the BODDI ligand, we assume that related secondary interactions are also involved in the tetramerization of (BODDI)Li 2 .…”

A Gallium(I) β‐Amido‐Imino‐Phosphorane: A Five‐Membered N‐Heterocyclic Gallylene with Enhanced Nucleophilicity

“…4 is dimeric in the solid state consisting of a tricyclic [5.3.0.0] ring system featuring a planar, diamond-shaped four-membered Li 2 N 2 central ring. In contrast to transoid primary laddering typically observed for lithium complexes of N,N 0 -chelates [58][59][60], a cisoid geometry is observed here, likely because it allows a better separation of the bulkyl substituents. The N1-Li1-N2 angle of 89.0(3)° is significantly smaller compared to other dimeric lithium amides [61] but resembles values of previously reported N,N 0 ,N 0 -substituted 1,2-ethanediamides (91.35(14)°) [62].…”

New Lanthanide Alkynylamidinates and Diiminophosphinates

“…In the solid state, both lithium propiolamidinates crystallize in the triclinic space group P-1 with one dimeric molecule in the unit cell. The bond lengths and bond angles are in good agreement with similar structures of amidinate ligands [48][49][50][51][52][53][54][55][56][57][58]. The N-C distances in the amidinate N-C-N unit are 1.321(2) and 1.330(2) Å in 1 and 1.3201 (13)…”

Mono- and dinuclear β-oxo-δ-diiminate (BODDI) based catalysts for the ring-opening polymerization of l -lactide

“…mol weight 473 g mol −1 ). Aggregation of lithium complexes is well known 11 and in lithium β-diketiminates for example, secondary interactions with aromatic carbons of neighbouring molecules can be involved. 12 Given the steric strain imposed by the BODDI ligand, we assume that related secondary interactions are also involved in the tetramerization of (BODDI)Li 2 .…”