Major differences between preferred tetracarbagallane and tetracarbalane structures

Publication date: Available online 2 February 2018 Source:Journal of Organometallic Chemistry Author(s): Amr A.A. Attia, Alexandru Lupan, R. Bruce King The complete series of tetracarbagallanes C4Ga n–4Me n (6 ≤ n ≤ 14) has been examined by density functional theory. The lowest-energy C4Ge6Me10 structure is a very symmetrical T d tetracapped octahedral structure with an adamantane-like surface very similar to the experimentally known R'4C4Ga6R6 structures and to the lowest energy structure for the tetracarbalane C4Al6Me10. This structure is the only lowest energy C4Ga n–4Me n (n = 6 to 14) structure containing isolated carbon atoms. The remaining low-energy tetracarbagallane structures consist of Ga n–4 subpolyhedra having faces capped by aggregates of two to four carbon atoms. The most commonly encountered partitions of the four carbon atoms in the C4Ga n–4Me n structures are C3 + C or 2 × C2. Such capping often leads to significant distortion of the Ga n–4 subpolyhedron including lengthening of some of the original edges beyond bonding distances. Many of the low-energy 6- to 9-vertex C4Ga n–4Me n structures are recognized as nido structures in accord with their 2n + 4 skeletal electrons determined by the Wade-Mingos procedure. Such structures can be derived from an (n + 1)-vertex deltahedron by removal of a degree 5 or 6 vertex and thus have a pentagonal or hexagonal open face. The low-energy structures for the 6- and 7-vertex t...

Source: Journal of Organometallic Chemistry - February 2, 2018 Category: Chemistry Source Type: research