6 Group 13–15 Needle-Shaped Oligomers and Nanorods: Structures. . .
209
Fig. 6.2 Structures of [RMYR ] 4 tetramers on the example of (a) cubane-type [HAlN i Pr] 4
cluster tetrakis(μ 3 -isopropylimido)-tetrahydrido-tetra-aluminium [94] and (b) tetrahedral cluster
tetrakis((N-(2,6-Di-isopropylphenyl)trimethylsilylamino)-aluminium(I)) Al 4 (NRR ) 4 [93]. Aluminum atoms are colored in pink, nitrogen in blue, silicon in yellow, and carbon in gray. Hydrogen
atoms are omitted for clarity
1,2-diisopropyldiazene molecule i PrN=N i Pr, but this adduct decomposes upon
sublimation to give pure [HAlN i Pr] 4 cubane (Fig. 6.2a) [94].
It was supposed that interaction of weakly M-Y bonded cubanes with strong
Lewis bases will result in opening of the M 4 Y 4 cage, yielding ladder-type structures.
Tensimetry study of interaction of phosphorus-containing cubane-type clusters
[RMPR ] 4 (M = Ga, In) toward pyridine showed that M 4 P 4 core is stable and
does not react with Py, although computations show that process is energetically
favorable at low temperatures [97].
Nevertheless, several group 13–15 ladder compounds of [ClMYR] 4 D 2 composition are known and structurally characterized [98–100]. They are formed when
donor-acceptor interactions with Lewis base D prevent formation of [ClMYR] n
cages due to much lower M-Y bond energies in P-, As-, and Sb-containing cubanes
[43]. Upon the removal of donor molecules, closure of ladder structure to tetramer
or hexamer is expected. Indeed, when synthesis of [ClAlPSi i Pr 3 ] 4 ·2OEt 2 (Fig.
6.3) was carried out in absence of OEt 2 , hexameric compound [ClAlPSi i Pr 3 ] 6 was
formed [98].
Mixed metal ladder compounds are also known. Molecular structure of
[(ClGa) 2 (BPh) 2 (N t Bu) 4 ] with Ga 2 B 2 N 4 core (Fig. 6.3c) was reported in work
[101]. Analogous indium compound with In 2 B 2 N 4 core incorporates bissolvated
lithium chloride molecule in the indium complex, resulting in coordination number
5 on In center.
Mixed group 13 element and mixed pnictogen tetramers are not yet
experimentally realized. [(M x M y M z )Y 4 ]H 8 and [M 4 (Y x Y y Y z )]H 8 (x+y+z=4;
M,M ,M =Al,Ga,In; Y,Y ,Y =N,P,As) compounds were computationally studied
in [44]. Their structural parameters resemble those of individual cubanes. The
209
Fig. 6.2 Structures of [RMYR ] 4 tetramers on the example of (a) cubane-type [HAlN i Pr] 4
cluster tetrakis(μ 3 -isopropylimido)-tetrahydrido-tetra-aluminium [94] and (b) tetrahedral cluster
tetrakis((N-(2,6-Di-isopropylphenyl)trimethylsilylamino)-aluminium(I)) Al 4 (NRR ) 4 [93]. Aluminum atoms are colored in pink, nitrogen in blue, silicon in yellow, and carbon in gray. Hydrogen
atoms are omitted for clarity
1,2-diisopropyldiazene molecule i PrN=N i Pr, but this adduct decomposes upon
sublimation to give pure [HAlN i Pr] 4 cubane (Fig. 6.2a) [94].
It was supposed that interaction of weakly M-Y bonded cubanes with strong
Lewis bases will result in opening of the M 4 Y 4 cage, yielding ladder-type structures.
Tensimetry study of interaction of phosphorus-containing cubane-type clusters
[RMPR ] 4 (M = Ga, In) toward pyridine showed that M 4 P 4 core is stable and
does not react with Py, although computations show that process is energetically
favorable at low temperatures [97].
Nevertheless, several group 13–15 ladder compounds of [ClMYR] 4 D 2 composition are known and structurally characterized [98–100]. They are formed when
donor-acceptor interactions with Lewis base D prevent formation of [ClMYR] n
cages due to much lower M-Y bond energies in P-, As-, and Sb-containing cubanes
[43]. Upon the removal of donor molecules, closure of ladder structure to tetramer
or hexamer is expected. Indeed, when synthesis of [ClAlPSi i Pr 3 ] 4 ·2OEt 2 (Fig.
6.3) was carried out in absence of OEt 2 , hexameric compound [ClAlPSi i Pr 3 ] 6 was
formed [98].
Mixed metal ladder compounds are also known. Molecular structure of
[(ClGa) 2 (BPh) 2 (N t Bu) 4 ] with Ga 2 B 2 N 4 core (Fig. 6.3c) was reported in work
[101]. Analogous indium compound with In 2 B 2 N 4 core incorporates bissolvated
lithium chloride molecule in the indium complex, resulting in coordination number
5 on In center.
Mixed group 13 element and mixed pnictogen tetramers are not yet
experimentally realized. [(M x M y M z )Y 4 ]H 8 and [M 4 (Y x Y y Y z )]H 8 (x+y+z=4;
M,M ,M =Al,Ga,In; Y,Y ,Y =N,P,As) compounds were computationally studied
in [44]. Their structural parameters resemble those of individual cubanes. The