Construction of Larger Molecular Aluminophosphate Cages from the Cyclic Four-Ring Building Unit
作者:Jan Chyba、Zdenek Moravec、Marek Necas、Sanjay Mathur、Jiri Pinkas
DOI:10.1021/ic500083a
日期:2014.4.7
New molecular aluminophosphates of different nuclearity are synthesized by a stepwise process and structurally characterized. The alkane elimination reaction of bis(trimethylsiloxy)phosphoric acid, OP-(OH)(OSiMe3)(2), with trialkylalanes, AlR3 (R = Me, Et, Bu-i), provides the cyclic dimeric aluminophosphates, [(AlR2mu(2)-O2P(OSiMe3)(2)})(2)) (R = Me (1), Et (2), Bu-i (3)). Unsymmetrically substituted cyclic aluminophosphonate [(AlMe2mu(2)-O2P(OSiMe3)((c)Hex)})(2)] (cis/trans-4) is prepared by dealkylsilylation reaction of (c)HexP(O)(OSiMe3)(2) with AlMe3. Molecules 1-4 containing the [Al-2(mu(2)-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. Reaction of 1 with 4 equiv of Hhfacac leads to new cyclic aluminophosphate [(Al(hfacac)(2)mu(2)-O2P(OSiMe3)(2)})(2)] (5), existing in two isomeric (D-2 and C-2h) forms. Reaction of 1 with 2 equiv of OP(OH)(OSiMe3)(2) and 1 equiv of Hhfacac provides a molecular aluminophosphate [AlMeAl(hfacac)}(2)mu(3)-O3P(OSiMe3)}(2)mu(2)-O2P(OSiMe3)(2)}(2)OP-(OSiMe3)(3)}] (6), while by adding first the Hhfacac and using 3 equiv of OP(OH)(OSiMe3)(2) we isolate [AlAl(hfacac)}(2)mu(3)-O3P(OSiMe3)}(2)mu(2)-O2P(OSiMe3)(2)}(2)HOP(O)(OSiMe3)(2)}(2)] (7). These molecules contain units in their cores that imitate 4=1 SBU of zeolite frameworks. Reaction with the order of component mixing 1, Hhfacac, OP(OH)(OSiMe3)(2) at a 1:2:2 molar ratio lead to formation of a larger cluster [(Al(AlMe)Al(hfacac)}mu(3)-O3P(OSiMe3)}(2)mu(2)-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)}mu(3)-O3P(OSiMe3)}(2)mu(2)-O2P(OSiMe3)(2)}(3))(2)] (9). Both molecules display Al centers in three different coordination environments.