Publication details

Construction of Larger Molecular Aluminophosphate Cages from the Cyclic Four-Ring Building Unit



Year of publication 2014
Type Article in Periodical
Magazine / Source Inorganic Chemistry
MU Faculty or unit

Central European Institute of Technology

Field Inorganic chemistry
Keywords aluminophosphates; bis(trimethysiloxy)phosphoric acid; secondary building units
Description New molecular aluminophosphates of different nuclearity are synthesized by a stepwise process and structurally characterized. The alkane elimination reaction of bis(trimethysiloxy)phosphoric acid, OP(OH)(OSiMe3)2, with trialkylalanes, AlR3 (R = Me, Et, iBu), provides the cyclic dimeric aluminophosphates, [(AlR2{m2-O2P(OSiMe3)2})2] (R = Me (1), Et (2), iBu (3)). Unsymmetrically substituted cyclic aluminophosphonate [(AlMe2{m2-O2P(OSiMe3)(cHex)})2] (cis/trans 4), is prepared by dealkylsilylation reaction of cHexP(O)(OSiMe3)2 with AlMe3. The molecules 1-4 containing the [Al2(m2-O2P)2] inorganic core are structural and spectroscopic models for the single four-ring (S4R) secondary building units (SBU) of zeolite frameworks. Compound 1 serves as a starting point in construction of larger molecular units by reactions with OP(OH)(OSiMe3)2 as a cage-extending reagent, and with diketones, such as Hhfacac (1,1,1,5,5,5-hexafluoropentan-2,4-dione) and Hacac (pentan-2,4-dione), as capping reagents. The reaction of 1 with four eq. of Hhfacac lead to new cyclic aluminophosphate [(Al(hfacac)2{m2-O2P(OSiMe3)2})2] (5), existing in two isomeric (D2 and C2h) forms. The reaction of 1 with two eq. of OP(OH)(OSiMe3)2 and one eq. of Hhfacac provides a molecular aluminophosphate [AlMe{Al(hfacac)}2{m3-O3P(OSiMe3)}2{m2-O2P(OSiMe3)2}2{OP(OSiMe3)3}] (6) while by adding first the Hhfacac and using three eq. of OP(OH)(OSiMe3)2, we isolate [Al{Al(hfacac)}2{m3-O3P(OSiMe3)}2{m2-O2P(OSiMe3)2}2H{OP(O)(OSiMe3)2}2] (7). These molecules contain units in their cores that imitate 4=1 SBU of zeolite frameworks. The reaction with the order of component mixing 1, Hhfacac, OP(OH)(OSiMe3)2 at the 1:2:2 molar ratio lead to the formation of a larger cluster [(Al(AlMe){Al(hfacac)}{m3-O3P(OSiMe3)}2{m2-O2P(OSiMe3)2}3)2] (8) containing both S4R and 4=1 structural units. Similarly, Hacac (pentan-2,4-dione) provides an isostructural [(Al(AlMe){Al(acac)}{m3-O3P(OSiMe3)}2{m2-O2P(OSiMe3)2}3)2] (9).
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