Reactions of Trialkyl Phosphates with Trialkyls of Aluminum and Gallium: New Route to Alumino- and Gallophosphate Compounds via Dealkylsilylation

Synthesis, Characterization, and Stability of Dealkylated Salen-Supported Aluminum Phosphates

Three salen aluminum bromide compounds salen(^tBu)AlBr (1) (salen = N,N'-ethylenebis(3,5-di-tert-butylsalicylideneimine)), salpen(^tBu)AlBr (2) (salpen = N,N'-propylenebis(3,5-di-tert-butylsalicylideneimine)), and salophen(^tBu)AlBr (3) (salophen = N,N'-o-phenylenenebis(3,5-di-tert-butylsalicylideneimine) were evaluated for their potential use as dealkylation agents with a series of organophosphates. These reactions led to the aluminum phosphate compounds containing six-coordinate aluminum centers and hydrolytically stable P-O-C bonds: 4 = [salen(^tBu)AlOP(O)(OMe)₂]_n, 5 = [salen(^tBu)AlOP(O)(OEt)₂]_n, 6 = [salen(^tBu)AlOP(O)(OPh)₂]_n, 7 = [salophen(^tBu)AlOP(O)(OMe)₂]_n, 8 = [salpen(^tBu)AlOP(O)(OⁱPr)₂]₂, 9 = (salen(^tBu)AlO)₃PO, 10 = (salpen(^tBu)AlO)₃PO, 11 = (salophen(^tBu)AlO)₃PO. All the compounds were characterized by ¹H, ¹³C, ²⁷Al, and ³¹P NMR, IR, and mass spectrometry. Furthermore, compounds 4-8 were structurally characterized by single-crystal X-ray diffraction. The potential hydrolysis of these compounds was modeled with 4 and demonstrated the unique stability of the final product and ease of isolation.

Synthesis and Characterization of Silylated Phosphonium [P(OSiMe3)4]+ and Phosphate [O2P(OSiMe3)2]- Salts

Starting from an optimized synthesis of silylated phosphoric acid, OP(OSiMe₃)₃, a borate salt bearing the [P(OSiMe₃)₄]⁺ cation was generated in the reaction of OP(OSiMe₃)₃ with [Me₃Si-H-SiMe₃][B(C₆F₅)₄], isolated, and fully characterized. Analogously to the protonated species, phosphoric acid (H₃PO₄) reaction of OP(OSiMe₃)₃ with a base led to the formation of the unknown [O₂P(OSiMe₃)₂]^- anion, which could be crystallized as potassium salt and structurally characterized, too. Both [P(OSiMe₃)₄]⁺ and [O₂P(OSiMe₃)₂]^- can be regarded as the formal autoprotolysis products of OP(OSiMe₃)₃.

Linear coordination polymers based on aluminum phosphates: synthesis, crystal structure and morphology

Several aluminum tris(diorganophosphates) have been synthesized and characterized via elemental analysis, NMR, FT-IR and Raman spectroscopy, as well as powder XRD, and SEM. Single-crystal X-ray diffraction studies revealed that the aluminum tris(diethylphosphate) crystal structure comprises two crystallographically nonequivalent catena-Al[O2P(OEt)2]3 chains propagating along the c-axis. Their parallel orientation favors the formation of closely packed hexagonal domains. PXRD data suggest that other homologues have a similar structure, with the interchain distance closely corresponding to the dimensions of organic ligands. They are also susceptible to a reversible dissociation to ionic species under the effect of primary amines. This feature can be utilized for the synthesis of epoxy nanocomposites.

Synthetic strategies to achieve further-functionalised monoaryl phosphate primary building units: crystal structures and solid-state aggregation behavior

The synthesis of a new class of functionalized organophosphates, potential building units in materials and zeolite chemistry, has been reported.

Synthesis of heteroboroxines with MB₂O₃ core (M = Sb, Bi, Sn)--an influence of the substitution of parent boronic acids

The synthesis and structure of stiba-, stanna- and bismaheteroboroxines of a general formula L(E)M[(OBR)2O] supported by a N,C,N-chelating ligand L [where L = C6H3-2,6-(CH2NMe2)2, M, E = Sb, lone pair or Sn, Ph or Bi, lone pair] is reported. The target compounds are prepared by straightforward one-step reactions between oxides (LMO)2 (M = Sb or Bi) or organotin(iv) carbonate L(Ph)Sn(CO3) with four or two molar equivalents of corresponding organoboronic acid. All compounds were characterized with the help of elemental analysis, multinuclear NMR spectroscopy and on several occasions the molecular structure was determined using single-crystal X-ray diffraction analysis. The influence of both the substitution of the parent organoboronic acid and the central atom used on the feasibility of the condensation reaction was addressed. Furthermore, several heteroboroxines containing nitrogen donor functionality (i.e. NH2, NMe2, CN or 4-pyridyl) included in the boronic acid residue were synthesized and characterized with the aim to prepare boroxine-based covalent frameworks (through intermolecular N→B interactions) containing metal atoms in their structures. Although no such intermolecular bonding was detected in solution of these compounds, it was shown that the organotin(iv) heteroboroxine substituted by 4-pyridyl group forms an infinite polymeric chains via N→B interactions in the solid state. This polymer collapsed back to monomeric units upon dissolution.

Mononuclear Schiff Base Boron Halides: Synthesis, Characterization, and Dealkylation of Trimethyl Phosphate

A series of mononuclear boron halides of the type LBX(2) [LH = N-phenyl-3,5-di-tert-butylsalicylaldimine, X = Cl (2), Br (3)] and LBX [LH2 = N-(2-hydroxyphenyl)-3,5-di-tert-butylsalicylaldimine, X = Cl (7), Br (8); LH2 = N-(2-hydroxyethyl)-3,5-di-tert-butylsalicylaldimine, X = Cl (9), Br (10); and LH2 = N-(3-hydroxypropyl)-3,5-di-tert-butylsalicylaldimine, X = Cl (11), Br (12)] were synthesized from their borate precursors LB(OMe)2 (1) (LH = N-phenyl-3,5-di-tert-butylsalicylaldimine) and LB(OMe) [LH2 = N-(2-hydroxyphenyl)-3,5-di-tert-butylsalicylaldimine (4), N-(2-hydroxyethyl)-3,5-di-tert-butylsalicylaldimine (5), N-(3-hydroxypropyl)-3,5-di-tert-butylsalicylaldimine (6)]. The boron halide compounds were air and moisture sensitive, and upon hydrolysis, compound 7 resulted in the oxo-bridged compound 13 that contained two seven-membered boron heterocycles. The boron halide compounds dealkylated trimethyl phosphate in stoichiometric reactions to produce methyl halide and unidentified phosphate materials. Compounds 8 and 12 were found to be the most effective dealkylating agents. On reaction with tert-butyl diphenyl phosphinate, compound 8 produced a unique boron phosphinate compound LB(O)OPPh2 (14) containing a terminal phosphinate group. Compounds 1-14 were characterized by 1H, 13C, 11B, 31P NMR, IR, MS, EA, and MP. Compounds 5, 6, and 11-14 also were characterized by single-crystal X-ray diffraction.

A Supramolecular Hexameric Ring from Alumazene and Methylsulfonate

A dealkylsilylation reaction of alumazene [2,6-(i-Pr)2C6H3NAlMe]3 (1) with trimethylsilyl methylsulfonate in a 1:2 molar ratio in toluene afforded a supramolecular cyclic hexamer {Me[2,6-(i-Pr)2C6H3NAl]3(O3SMe)2}6 (2) composed of six intact alumazene rings and possessing two types of bridging sulfonate groups. Changing the reagent molar ratio to 1:3 caused the third sulfonate to partially substitute the last alumazene methyl group in an eta2 fashion and introduced a disorder in the crystal lattice.

Aluminum Phosphinate and Phosphates of Salen Ligands

A new dealkylation reaction between organophosphate esters and Salen aluminum bromide compounds has been used to prepare three new aluminum salen compounds salen((t)Bu)AlOP(O)Ph2 (1) (salen = N,N'-ethylenebis(3,5-di-tert-butylsalicylideneimine)), [(MeOH)Alsalen((t)Bu)[OMePO2(O)]Alsalen((t)Bu)[OMePO2(O)]Alsalen((t)Bu)]Br (2), and [salpen((t)Bu)AlO]2[(BuO)2PO]2 (3) (salpen = N,N'-propylenebis(3,5-di-tert-butylsalicylideneimine)). Compounds 1.MeOH, 2, and 3 were characterized by single-crystal X-ray diffraction. Compound 1 is the first example of a monomeric aluminum Schiff base phosphinate. Compound 2 is a cationic Salen aluminum phosphate, and compound 3 contains an aluminophosphate ring. This work is the first example of the intentional use of an aluminum-based dealkylation reaction to form new compounds.

Five-Coordinate Aluminum Bromides: Synthesis, Structure, Cation Formation, and Cleavage of Phosphate Ester Bonds

The alkane elimination reaction between Salen((t)Bu)H(2) ligands and diethylaluminum bromide was used to prepare three Salen aluminum bromide compounds salen((t)Bu)AlBr (1) (salen = N,N'-ethylenebis(3,5-di-tert-butylsalicylideneimine)), salpen((t)Bu)AlBr (2) (salpen = N,N'-propylenebis(3,5-di-tert-butylsalicylideneimine)), and salophen((t)Bu)AlBr (3) (salophen = N,N'-o-phenylenenebis(3,5-di-tert-butylsalicylideneimine)). The compounds contain five-coordinate aluminum either in a distorted square pyramidal or a trigonal bipyramidal environment. The bromide group in these compounds could be displaced by triphenylphosphine oxide or triphenyl phosphate to produce the six-coordinate cationic aluminum compounds [salen((t)Bu)Al(Ph(3)PO)(2)]Br (4), [salpen((t)Bu)Al(Ph(3)PO)(2)]Br (5), [salophen((t)Bu)Al(Ph(3)PO)(2)]Br (6), and [salophen((t)Bu)Al[(PhO)(3)PO)](2)]Br (7). All the compounds were characterized by (1)H, (13)C, (27)Al, and (31)P NMR, IR, mass spectrometry, and melting point. Furthermore, compounds 1-3 and 5-7 were structurally characterized by single-crystal X-ray diffraction. Compounds 1-3 dealkylated a series of organophosphates in stoichiometric reactions by breaking the ester C-O bond. Also, they were catalytic in the dealkylation reaction between trimethyl phosphate and added boron tribromide.

Transformations of molecules and secondary building units to materials: a bottom-up approach

A variety of complex inorganic solids with open-framework and other fascinating architectures, involving silicate, phosphate, and other anions, have been synthesized under hydrothermal conditions. The past few years have also seen the successful synthesis and characterization of several molecular compounds that can act as precursors to form open-framework and other materials, some of them resembling secondary building units (SBUs). Transformations of rationally synthesized molecular compounds to materials constitute an important new direction in both structural inorganic chemistry and materials chemistry and enable possible pathways for the rational design of materials. In this article, we indicate the potential of such a bottom-up approach, by briefly examining the transformations of molecular silicates and phosphates. We discuss stable organosilanols and silicate secondary building units, phosphorous acids and phosphate secondary building units, di- and triesters of phosphoric acids, and molecular phosphate clusters and polymers. We also examine the transformations of metal dialkyl phosphates and molecular metal phosphates.

Adamantane-like aluminum amide-phosphate from alumazene

A dealkylsilylation reaction between alumazene [2,6-(i-Pr)(2)C(6)H(3)NAlMe](3) (1) and tris(trimethylsilyl) ester of phosphoric acid (2) in a 1:3 molar ratio provides the heteroadamantane molecule (MeAl)[2,6-(i-Pr)(2)C(6)H(3)N](3)[Al[OP(OSiMe(3))(3)]](2)(O(3)POSiMe(3)) (3). Compound 3 was characterized by analytical and spectroscopic methods, and its molecular structure was established by a single-crystal X-ray diffraction experiment. Moreover, trialkyl and triaryl phosphates and dialkyl phosphonates react with 1 at elevated temperature to afford an intractable mixture of products. The reaction of phosphonic acids with 1 proceeds under decomposition to yield 2,6-diisopropylaniline and aluminophosphonates.

Ligand-tetrahydrofuran coupling in chelated aluminum phosphinates

When the reagents LAlMe (L = N,N'-(alkylene or arylene)bis(3,5-di-tert-butyl)salicylideneimine (alkylene = ethylene (Salen(tBu))(1), propylene (Salpen(tBu))(2), and butylene (Salben(tBu)) (3); arylene = phenylene (Salophen(tBu) (4), 3,4-dimethylphenylene (Salomphen(tBu) (5)) are combined with Ph(H)P(O)OH in tetrahydrofuran (thf) the unique aluminophosphinate compounds, [L(tBu)Al[O(2)P(H)Ph]](n) with L, n = Salen,(infinity)(6), Salpen, 2 (7), Salben, 2 (8), Salophen, (infinity)(9) and Salomphen, (infinity)(10) are produced. The yields for the latter two reactions are low, and it was subsequently found that the unique thf-coupled compounds appear in the thf filtrates of the original reaction mixture. These compounds are, [L-thf(tBu)Al[O(2)P(H)Ph]](2), L = Salophen (13) and Salomphen (14). The thf connects through an alpha-carbon to only one of the two possible imine carbons of the ligand. While trying to determine how this coupling proceeds, the six-coordinate, solution-state species LAlMe(thf) (L = Salophen (11) and Salomphen (12) were discovered and implicated as intermediates. All of the compounds are characterized by melting point, NMR, IR, and X-ray analyses for 5-8, 13, and 14. A possible mechanism for the thf coupling event is presented.

Synthesis and Structural Characterization of Functionalized Dimeric Aluminophosphonates and a Monomeric Gallophosphonate Anion

Reaction of t-BuP(O)(OSiMe(3))(OH) with Me(3)Al leads to the formation of [Me(2)Al(mu-O)(2)P(OSiMe(3))(t-Bu)](2) (1) whereas Me(2)AlCl reacts with Ph(2)P(O)(OH) to yield [(Cl)(Me)Al(mu-O)(2)PPh(2)](2) (2). These compounds represent the first examples of functionalized dimeric four-ring type aluminophosphonate systems. The double four-ring type gallophosphonate, namely, [t-BuPO(3)GaMe](4), reacts with n-Bu(4)NHF(2) under ambient conditions, resulting in the formation of a monomeric gallophosphonate [n-Bu(4)N][MeGa[t-BuPO(2)(OH)](3)] (3). These derivatives have been adequately characterized using various spectroscopic techniques and X-ray diffraction studies.

Application of n-Bu4NHF2 as a fluorinating agent for the preparation of fluoroanions: synthesis and crystal structure of the anions [t-BuPO3AlF2]2(2-), [PhPO3AlF2]2(2-), and [(O-i-Pr)3Ti(mu-F)2(mu-O-i-Pr)Ti(O-i-Pr)3]-

The first phosphonate anions of aluminum-containing fluorine and an anionic bridged fluoroalkoxy derivative of titanium have been realized using n-Bu4NHF2 as a fluorinating agent in organometallic synthesis. Reactions of [RPO3AlMe]4 [R = Ph (1), t-Bu] with n-Bu4NHF2 yield organic-soluble compounds of the type [n-Bu4N]2[RPO3AlF2]2 [R = Ph (2), t-Bu (3)], whereas the reaction of Ti(O-i-Pr)4 with n-Bu4NHF2 results in the formation of [n-Bu4N][O-i-Pr)3Ti(mu-F)2(mu-O-i-Pr)Ti(O-i-Pr)3] (4). These compounds have been obtained in high yields and have been adequately characterized through spectroscopic techniques and X-ray diffraction studies.

Metal alkoxides as versatile precursors for group 4 phosphonates: synthesis and X-ray structure of a novel organosoluble zirconium phosphonate

Reactions of Ph2P(O)(OH) and t-BuP(O)(OSiMe3)(OH) with Ti(O-i-Pr)4 in equimolar ratios gave titanium phosphonates of the type [(O-i-Pr)3Ti(mu-O)2PR1R2]2 (1, R1 = R2 = Ph; 2, R1 = t-Bu, R2 = OSiMe3) as colorless crystalline solids in moderate yields. Reactions of Ph2P(O)(OH) and the isopropoxides of zirconium and hafnium resulted in products of the composition [(O-i-Pr)3M(mu-O-i-Pr)2(mu-OPOPh2)M(O-i-Pr)2]Ph2P(O)(OH) (M = Zr (3), Hf (4)) in high yields. The compounds were characterized by 1H, 31P, and 29Si NMR, infrared (IR), and mass spectroscopic (MS) techniques. The molecular structures of 2 and 3 were confirmed by X-ray crystallography.