Insertion reaction of elemental sulfur into the Ln–C bond: Synthesis and characterization of [(C5H4SiMe2Bu)2Ln(μ-SR)]2 (R = Me,Ln = Yb,Er, Dy,Y; R = Bu,Ln = Yb,Dy)

Treatment of (C₅H₄SiMe₂^tBu)₂LnR with 1 equiv of elemental sulfur in toluene at ambient temperature gives dimeric complexes [(C₅H₄SiMe₂^tBu)₂Ln(μ-SR)]₂ [R = Me, Ln = Yb (1), Er (2), Dy (3), Y (4); R = ⁿBu, Ln = Yb (5), Dy (6)]. All these complexes have been characterized by elemental analysis, IR and mass spectroscopies. The structures of complexes 1, 3, 5 and 6 are also determined through X-ray single crystal diffraction analysis, indicating that only one sulfur atom from elemental sulfur inserts into Ln–C σ-bond.     

Synthesis of aluminium complexes bearing a piperazine-based ligand system

Aluminium complexes bearing the N,N-chelating ligand 1,4-bis(2-hydroxy-3,5-di-tert-butyl)piperazine (1) have been synthesised. Both monometallic and bimetallic aluminium methyl complexes (2 and 3, respectively) were prepared by treatment of 1 with the appropriate amount of AlMe₃. Complex 2 can be converted to 3 by addition of excess AlMe₃. Bimetallic aluminium-ethyl complex 4 was also prepared. Treatment of 1 with AlEt₂Cl afforded the monometallic chloride complex 5. Treatment of this latter complex with potassium alkoxides (KOR, R = Me, Et, ⁱPr, ^tBu) or AgOTf afforded the corresponding aluminium alkoxide complexes (6, R = Et; 7, R = Me; 8, R = ⁱPr; 9, R = ^tBu; 10, R = OTf) in good yields. Aluminium ethoxide complex 6 was also synthesised by treatment of 1 with AlEt₂OEt. All of these complexes were tested as potential catalysts in the ring-opening polymerisation of rac-lactide and caprolactone with limited success.     

New route to alkylaluminum hydroxides via hydrolysis of cyclopentadienylaluminum complexes

A novel, very simple and effective synthetic method for the formation of alkylaluminum complexes with terminal hydroxy group via hydrolysis of cyclopentadienylaluminum compounds has been found. Investigations of the hydrolysis of cyclopentadienylaluminum complexes (L)Al(Me)Cp (1) and (L)Al(Et)Cp (2) (L = HC[(CMe)(2,6-ⁱPr₂C₆ H₃N)]₂) have shown that the reaction leads to the formation of (L)Al(Me)OH (3) and (L)Al(Et)OH (4), respectively. The high selectivity of the hydrolysis was revealed. The crystal structures of 1, 2 and 4 were determined.     

Heteroleptic tin (II) dialkoxides stabilized by intramolecular coordination Sn(OCH2CH2NMe2)(OR) (R = Me, Et, Pr, Bu, Ph). Synthesis, structure and catalytic activity in polyurethane synthesis

A straightforward method of synthesis of heteroleptic tin (II) alkoxides stabilized by one intramolecular coordination bond was developed. Addition of one equivalent of dimethylamino ethanol to diamide Sn(N(SiMe₃)₂)₂ (5) yields alkoxy-amido derivative Sn(OCH₂CH₂NMe₂)(N(SiMe₃)₂) (2). Further addition of alcohol leads to corresponding heteroleptic dialkoxides Sn(OCH₂CH₂NMe₂)(OR) (R = Me (6), Et (7), ⁱPr (8), ^tBu (9), Ph (10)). Catalytic activity of tin (II) compounds in polyurethane formation was tested.     

Structural studies of phosphor-1,1-diselenoato Mn(I) and Re(I) complexes

Mononuclear complexes of the type, M(CO)₄[Se₂P(OR)₂] (M = Mn, R = ⁱPr, 1a; Et, 1b; M = Re, R = ⁱPr, 3a; Et, 3b) can be prepared from either [-Se(Se)P(OⁱPr)₂]₂ (A) or [Se{-Se(Se)P(OEt)₂}₂] (B) with M(CO)₅Br. O,O′-dialkyl diselenophosphate ([(RO)₂PSe₂]^-, abbreviated as dsep) ligands generated from A and B act as a chelating ligand in these complexes. Upon refluxing in acetonitrile, these mononuclear complexes yield dinuclear complexes with a general formula of [M₂(CO)₆{Se₂P(OR)₂}₂] (M = Mn, R = ⁱPr, 2a; Et, 2b; M = Re, R = ⁱPr, 4a; Et, 4b). Dsep ligands display a triconnective, bimetallic bonding mode in the dinuclear compounds and this kind of connective pattern has never been identified in any phosphor-1,1-diselenoato metal complexes. Compounds 2b, 3b, and 4 are structurally characterized. Compounds 2b and 3b display weak, secondary Se?Se interactions in their lattices.     

Synthesis, structures, and catalytic properties for ethylene polymerization of bridged [η,η-C5H4CHPhArO]TiCl2 complexes

A number of bridged half-sandwich titanium complexes [η⁵:η¹-2-C₅H₄CHPh-4-R¹-6-R²C₆H₂O]TiCl₂ [R¹ = H (5), Me (6), ^tBu (7, 8); R² = H (6, 7), ^tBu (5, 8)] were synthesized from the reaction of their corresponding trimethylsilyl substituted ligand precursors 2-Me₃SiC₅H₄CHPh-4-R¹-6-R²C₆H₂OSiMe₃ [R¹ = H (1), Me (2), ^tBu (3, 4); R² = H (2, 3), ^tBu (1, 4)] with TiCl₄ in hexane. All new complexes were characterized by ¹H and ¹³C NMR spectroscopy. Molecular structures of complexes 5 and 8 were determined by single crystal X-ray diffraction analysis. Upon activation with AlⁱBu₃/Ph₃CB (C₆F₅)₄, complexes 5-8 exhibit reasonable catalytic activity for ethylene polymerization and copolymerization with 1-hexene, producing polyethylene and poly(ethylene-co-1-hexene) with moderate molecular weights.     

Substituted lithiumtrimethylsiloxysilanides LiSiRR′(OSiMe3) - Investigations of their synthesis, stability and reactivity

The reactions of the trimethylsiloxychlorosilanes (Me₃SiO)RR′SiCl (1a-h: R′ = Ph, 1a: R = H, 1b: R = Me, 1c: R = Et, 1d: R = ⁱPr, 1e: R = ^tBu, 1f: R = Ph, 1g: R = 2,4,6-Me₃C₆H₂ (Mes), 1h: R = 2,4,6-(Me₂CH)₃C₆H₂ (Tip); 1i: R = R′ = Mes) with lithium metal in tetrahydrofuran (THF) at −78 °C and in a mixture of THF/diethyl ether/n-pentane in a volume ratio 4:1:1 at −110 °C lead to mixtures of numerous compounds. Dependent on the substituents silyllithium derivatives (Me₃SiO)RR′SiLi (2b-i), Me₃SiO(RR′Si)₂Li (3a-g), Me₃SiRR′SiLi (4a-h), (LiO)RR′SiLi (12e, 12g-i), trisiloxanes (Me₃SiO)₂SiRR′ (5a-i) and trimethylsiloxydisilanes (6f^∗, 6h^∗, 6i^∗) are formed. All silyllithium compounds were trapped with Me₃SiCl or HMe₂SiCl resulting in the following products: (Me₃SiO)RR′SiSiMe₂R″ (6b-i: R″ = Me, 7c-i: R″ = H), Me₃SiO(RR′Si)₂SiMe₂R″ (8a-g: R″ = Me, 9a-g: R″ = H), Me₃SiRR′SiSiMe₂R″ (10a-h: R″ = Me, 11a-h: R″ = H) and (HMe₂SiO)RR′SiSiMe₂H (13e, 13g-i). The stability of trimethylsiloxysilyllithiums 2 depends on the substituents and on the temperature. (Me₃SiO)Mes₂SiLi (2i) is the most stable compound due to the high steric shielding of the silicon centre. The trimethylsiloxysilyllithiums 2a-g undergo partially self-condensation to afford the corresponding trimethylsiloxydisilanyllithiums Me₃SiO(RR′Si)₂Li (3a-g). (Me₃)Si-O bond cleavage was observed for 2e and 2g-i. The relatively stable trimethylsiloxysilyllithiums 2f, 2g and 2i react with n-butyllithium under nucleophilic butylation to give the n-butyl-substituted silyllithiums ⁿBuRR′SiLi (15g, 15f, 15i), which were trapped with Me₃SiCl. By reaction of 2g and 2i with 2,3-dimethylbuta-1,3-diene the corresponding 1,1-diarylsilacyclopentenes 17g and 17i are obtained.X-ray studies of 17g revealed a folded silacyclopentene ring with the silicon atom located 0.5 Å above the mean plane formed by the four carbon ring atoms.     

The effect of titanium alkoxides in the synthesis of heterobimetallic complexes by titanocene(III) alkoxide-induced metal-metal bond cleavage of metal carbonyl dimers

A series of titanocene(III) alkoxides L₂Ti(III)OR where L = Cp, R = Et(1b), ^tBu(1a), 2,6-Me₂C₆H₃(1c), 2,6-^tBu₂-4-Me-C₆H₂(1d), or L = Cp*, R = Me(2e), ^tBu(2a), Ph(2f) was synthesized and subjected to reaction with [CpM(CO)₃]₂ [M = Mo, W], [CpRu(CO)₂]₂, and Co₂(CO)₈. The Ti(III) precursors 1a, 1c, 2a, 2e, and 2f reacted with [CpM(CO)₃]₂ [M = Mo, W] to form heterobimetallic complexes L₂Ti(OR)(μ-OC)(CO)₂MCp [M = Mo, W], of which Ti and M are linked by an isocarbonyl bridge. Reactions of these Ti(III) complexes with Co₂(CO)₈ resulted in formation of Ti-Co₁ heterobimetallic complexes, from 2a, 2e, or 2f, or Ti-Co₃ tetrametallic complexes, Cp₂Ti(O^tBu)(μ-OC)Co₃(CO)₉ from 1a, 1b, or 1c. The products were characterized by NMR, IR, and X-ray crystallography. Reaction mechanisms were proposed from these results, in particular, from steric/electronic effects of titanium alkoxides.     

Synthesis of the first examples of stable heterometallic isopropoxides of an organometallic RSn(IV) moiety

Five-, six-, and seven-coordinate volatile butyltin(IV) heterobimetallic derivatives, respectively of the types, [BuSn{(μ-OPrⁱ)₂Al(OPrⁱ)₂}Cl₂] (1), [BuSn{(μ-OPrⁱ)₂Al(OPrⁱ)₂}₂Cl] (2), and BuSn{(μ-OPrⁱ)₂M(OPrⁱ)_x − 2}₃ (3:M = Al (x = 4); 4:M = Ga (x = 4); 5:M = Nb (x = 6)) have been synthesized by the reactions of BuSnCl₃ with potassium tetraisopropoxoaluminate in 1:1, 1:2, and 1:3 molar ratios. Replacement reactions of chloride in (1) and (2) with appropriate alkoxometallate (tetraisopropoxoaluminate, tetraisopropoxogallate, or hexaisopropoxoniobate) ligands result in the formation of novel BuSn(IV) heterotri- and tetra-metallic derivatives. All of these derivatives have been characterized by elemental analyses, molecular weight measurements, and spectroscopic (IR, ¹H, ²⁷Al, and ¹¹⁹Sn NMR) studies. Based on these studies, plausible structures for the new derivatives involving bidentate ligation of the alkoxometallate ligands have been suggested.     

Synthesis, structures and ε-caprolactone polymerization activity of aluminum N,N′-dimethyloxalamidates

Alkyl aluminum N,N′-dimethyloxalamidates R₄Al₂(dmoa) (1, R = Me; 2, R = Et; 3, R = ⁱBu; 4, R = ^tBu) (dmoa-H₂ = N,N′-dimethyloxalamide) have been prepared and characterized. Molecular structures of the compounds 1 and 4 have been determined by X-ray crystallography. The centrosymmetric molecules of the compounds consist of one N,N′-dimethyloxalamidate unit bonded to two four-coordinated aluminum atoms. Each of the aluminum atoms is bonded to two alkyl groups, and oxygen and nitrogen atoms originating from two different amidate groups. A skeleton framework of the molecules of 1 and 4 consists of two fused AlNOC₂ heterocyclic rings, which are flat and positioned in one plane. It was shown that compounds 1-3 were initiators in a process of ring opening polymerization (ROP) of ε-caprolactone. The compound 4 exhibited low activity in ROP.     

Reactions of trimethylsiloxychlorosilanes with lithium metal - On the mechanism of the formation of trimethylsiloxysilyllithium compounds LiSiRR’(OSiMe3)

The reaction pathway for the formation of the trimethylsiloxysilyllithium compounds (Me₃SiO)RR′SiLi (2a: R = Et, 2b: R = ⁱPr, 2c: R = 2,4,6-Me₃C₆H₂ (Mes); 2a-c: R′ = Ph; 2d: R = R′ = Mes) starting from the conversion of the corresponding trimethylsiloxychlorosilanes (Me₃SiO)RR′SiCl (1a-d) in the presence of excess lithium in a mixture of THF/diethyl ether/n-pentane at −110 °C was investigated.The trimethylsiloxychlorosilanes (Me₃SiO)RPhSiCl (1a: R = Et, 1b: R = ⁱPr, 1c: R = Mes) react with lithium to give initially the trimethylsiloxysilyllithium compounds (Me₃SiO)RPhSiLi (2a-c). These siloxysilyllithiums 2 couple partially with more trimethylsiloxychlorosilanes 1 to produce the siloxydisilanes (Me₃SiO)RPhSi-SiPhR(OSiMe₃) (Ia-c), and they undergo bimolecular self-condensation affording the trimethylsiloxydisilanyllithium compounds (Me₃SiO)RPhSi-RPhSiLi (3a-c). The siloxydisilanes I are cleaved by excess of lithium to give the trimethylsiloxysilyllithiums (Me₃SiO)RPhSiLi (2). In the case of the two trimethylsiloxydisilanyllithiums (Me₃SiO)RPhSi-RPhSiLi (3a: R = Et, 3b: R = ⁱPr) a reaction with more trimethylsiloxychlorosilanes (Me₃SiO)RPhSiCl (1a, 1b) takes place under formation of siloxytrisilanes (Me₃SiO)RPhSi-RPhSi-SiPhR(OSiMe₃) (IIa: R = Et, IIb: R = ⁱPr) which are cleaved by lithium to yield the trimethylsiloxysilyllithiums (Me₃SiO)RPhSiLi (2a, 2b) and the trimethylsiloxydisilanyllithiums (Me₃SiO)RPhSi-RPhSiLi (3a, 3b). The dimesityl-trimethylsiloxy-silyllithium (Me₃SiO)Mes₂SiLi (2d) was obtained directly by reaction of the trimethylsiloxychlorosilane (Me₃SiO)Mes₂SiCl (1d) and lithium without formation of the siloxydisilane intermediate. Both silyllithium compounds 2 and 3 were trapped with HMe₂SiCl giving the products (Me₃SiO)RR′Si-SiMe₂H and (Me₃SiO)RPhSi-RPhSi-SiMe₂H.     

Synthesis and characterization of phosphorous-bridged bisphenoxy titanium complexes and their application to ethylene polymerization

Phosphorous-bridged bisphenoxy titanium complexes were synthesized and their ethylene polymerization behavior was investigated. Bis[3-tert-butyl-5-methyl-2-phenoxy](phenyl)phosphine tetrahydrofuran titanium dichloride (4a) was obtained by treatment of 3 equiv of n-BuLi with bis[3-tert-butyl-2-hydroxy-5-methylphenyl](phenyl)phosphine hydrochloride salt (3a) followed by TiCl₄(THF)₂ in THF. THF-free complexes 5a-5d were synthesized more conveniently by the direct reaction of MOM-protected ligands (2a-2d) with TiCl₄ in toluene. X-ray analysis of 4a revealed that the ligand is bonded to the octahedral titanium (IV) center in a facial fashion and two chlorine atoms possess cis-geometry. Complexes 4a and 5a-5d were utilized as catalyst precursors for ethylene polymerization. Complex 5c gave high molecular weight polyethylene (M_w = 1,170,000, M_w/M_n = 2.0) upon activation with Al(ⁱBu)₃/[Ph₃C][B(C₆F₅)₄] (TB). Ethylene polymerization activity of 5d activated with Al(ⁱBu)₃/TB reached 49.0 × 10⁶ g mol (cat) ⁻¹ h⁻¹.     

Binuclear Salan borate compounds with three-coordinate boron atoms

A series of binuclear boron compounds supported by Salan(^tBu)H₄ ligands have been prepared. They are of the general formula Salan(^tBu)[B(OR)]₂. The compounds are Salean(^tBu)(BOR)₂ [Salean(^tBu) = (N,N′-ethylenebis(3,5-di-tert-butyl-salicylamine)), R = Me (1), SiMe₃ (4)], Salban(^tBu)(BOR)₂[Salban(^tBu) = (N,N′-butylenebis(3,5-di-tert-butyl-salicylamine)), R = Me (2), SiMe₃ (5)], and Salhan(^tBu)(BOR)₂ [Salhan(^tBu) = (N,N′-hexylenebis(3,5-di-tert-butyl-salicylamine)), R = Me (3)]. All of the compounds were characterized by spectroscopic (¹H NMR, ¹¹B NMR, IR) and physical (mp, EA) techniques. Also, 1, 2 and 4 were structurally characterized by single crystal X-ray diffraction studies.     

Bis(pyrazole)- and bis(pyrazolyl)-palladium complexes as phenylacetylene polymerization catalysts

Two types of pyrazole-based palladium complexes were used to catalyze the polymerization of phenylacetylene. Catalysts with electron-withdrawing linkers, [{1,3-(3,5-R₂pzCO)₂C₆H₄}Pd₂Cl₂(μ-Cl)₂] (R = ^tBu (1), Ph (2), Me (3), [{2,6-(3,5-R₂pzCO)₂C₅H₃N)}PdCl₂] (R = ^tBu (4), Me (5)), show high conversion; whilst those with simple pyrazole ligands, [(3,5-R₂pz)₂PdCl₂] (R = H (6), Me (7), ^tBu (8)), [(3,5-^tBu₂pz)₂PdCl(Me)] (9), have much lower conversions. Conversion greatly improved when 9 was used to catalyze the co-polymerization of sulfur dioxide and phenylacetylene. Both types of catalysts produce predominantly trans–cisoidal polyphenylacetylene.     

Arene ruthenium β-diketonato triazolato derivatives: Synthesis and spectral studies (β-diketones: 1-phenyl-3-methyl-4-benzoyl pyrazol-5-one, acetylacetone derivatives)

Mononuclear neutral arene ruthenium(II) β-diketonato complexes of the general formula (η⁶-arene)Ru(LL)Cl [LL = 1-phenyl-3-methyl-4-benzoyl pyrazol-5-one (L1), arene = C₆H₆ (1), p-ⁱPrC₆H₄Me (2), C₆Me₆ (3); arene = p-ⁱPrC₆H₄Me, LL = 1-benzoylacetone (L3) (8); arene = p-ⁱPrC₆H₄Me, LL = dibenzoylmethane (L4) (9)] have been synthesized and their subsequent substitution reactions with NaN₃ in alcohol at room temperature yielded the corresponding neutral terminal azido complexes (η⁶-arene)Ru(LL)N₃ [LL = 1-phenyl-3-methyl-4-benzoyl pyrazol-5-one (L1), arene = C₆H₆ (4), p-ⁱPrC₆H₄Me (6), C₆Me₆ (7); arene = p-ⁱPrC₆H₄Me, LL = dibenzoylmethane (L4) (10)] as well as a cationic complex [(η⁶-p-ⁱPrC₆H₄Me)Ru(L4) (PPh₃)]BF₄ (12) with PPh₃. The [3 + 2] cycloaddition reaction of selective azido complexes with the activated alkynes dimethyl and diethyl acetylenedicarboxylates produced the arene triazolato complexes [(η⁶-arene)Ru(LL){N₃C₂(CO₂R)₂}] [arene = p-ⁱPrC₆H₄Me, LL = L1, R = Me (13); arene = C₆Me₆, LL = L1, R = Me (14); arene = C₆Me₆, LL = acetyl acetone (L2), R = Me (15); arene = C₆Me₆, LL = L3, R = Me (16); arene = p-ⁱPrC₆H₄Me, LL = L1, R = Et (17); arene = C₆Me₆, LL = L1, R = Et (18); arene = C₆Me₆, LL = L2, R = Et (19); arene = C₆Me₆, LL = L3, R = Et (20)]. With fumaronitrile the reaction yielded the triazoles [(η⁶-arene)Ru(LL)(N₃C₂HCN)] [arene = p-ⁱPrC₆H₄Me, LL = L1 (21), arene = C₆Me₆, LL = L1 (22), arene = C₆Me₆, LL = L2 (23), arene = C₆Me₆, LL = L3 (24)]. In the above triazolato complexes only N(2) isomer was obtained. The complexes were characterized on the basis of spectroscopic data. Crystal structure of representatives complexes were determined by single crystal X-ray diffraction.     

Synthesis of arene ruthenium triazolato complexes by cycloaddition of the corresponding arene ruthenium azido complexes with activated alkynes or with fumaronitrile

The neutral arene ruthenium azido complexes [(η⁶-p-cymene)Ru(LL)(N₃)], [LL = acetylacetonato (acac) (4), benzoylacetonato (bzac) (5) diphenylbenzoyl methane (dbzm) (6)] undergo [3+2] cycloaddition reaction with a series of activated alkynes and fumaronitrile to produce the arene ruthenium triazolato complexes: [(η⁶-p-cymene)Ru(LL){N₃C₂(CO₂R)₂}] [LL = (acac), R = Me (7); LL = (bzac), R = Me (8); LL = (dbzm), R = Me (9); LL = (acac), R = Et (10); LL = (bzac), R = Et (11); LL = (dbzm), R = Et (12) and [(η⁶-p-cymene)Ru(LL)(N₃C₂HCN)]; LL = acac (13), bzac (14); dbzm (15). However, cationic azido complexes, [(η⁶-p-cymene)Ru(dppe)(N₃)]⁺ and [(η⁶-p-cymene)Ru(dppm)(N₃)]⁺ do not undergo such cycloaddition reactions. The complexes were characterized on the basis of microanalyses, FT-IR and NMR spectroscopic data. Crystal structures of representative complexes were determined by single crystal X-ray diffraction.     

Synthesis and structural characterization of metallated bioconjugates: C-terminal labeling of amino acids with aminoferrocene

Aminoferrocene, H₂N-Fc, has been substituted to the C-terminus of six amino acids using the HBTU/HOBt coupling protocol. The synthesized bioconjugates Boc-Aaa-NH-Fc, Aaa = Gly (1), Leu (2), Phe (3), Val (4), Cys(Acm) (5), Tyr(^tBu) (6) (Acm = acetamidomethyl, ^tBu = tert-butyl), have been characterized by ¹H NMR, ¹³C NMR, EI-MS, EI-HRMS, UV and CD spectroscopies. In addition, a VT NMR study on 4 and the X-ray structure of 1 are presented.     

Synthesis and reactivity of asymmetrically substituted ansa-bridged zirconocene complexes: X-ray crystal structures of [Zr{R(H)C(η-C5Me4)(η-C5H4)}Cl2] (R = Bu, Bu) and [Zr{Bu(H)C(η-C5Me4)(η-C5H4)}(CH2Ph)2]

The dialkyl complexes, (R = Prⁱ, R′ = Me (2a), CH₂Ph (3a); R = Buⁿ, R′ = Me (2b), CH₂Ph (3b); R = Bu^t, R′ = Me (2c), CH₂Ph (3c); R = Ph, R′ = Me (2d), CH₂Ph (3d)), have been synthesized by the reaction of the ansa-metallocene dichloride complex, [Zr{R(H)C(η⁵-C₅Me₄)(η⁵-C₅H₄)}Cl₂] (R = Prⁱ (1a), Buⁿ (1b), Bu^t (1c), Ph (1d)), and two molar equivalents of the alkyl Gringard reagent. The insertion reaction of the isocyanide reagent, CNC₆H₃Me₂-2,6, into the zirconium-carbon σ-bond of 2 gave the corresponding η²-iminoacyl derivatives, [Zr{R(H)C(η⁵-C₅Me₄)(η⁵-C₅H₄)}{η²-MeCNC₆H₃Me₂-2,6}Me] (R = Prⁱ (4a), Buⁿ (4b), Bu^t (4c), Ph (4d)). The molecular structures of 1b, 1c and 3b have been determined by single-crystal X-ray diffraction studies.     

Self-assembly of di- and triorganotin(IV) complexes: Syntheses, characterization and crystal structures of 1D polymeric chain containing O,O-diethyl or O,O-diisopropyl phosphoric acid ligands

A series of organotin(IV) complexes with O,O-diethyl phosphoric acid (L¹H) and O,O-diisopropyl phosphoric acid (L²H) of the types: [R₃Sn · L]_n (L = L¹, R = Ph 1, R = PhCH₂2, R = Me 3, R = Bu 4; L = L², R = Ph 9, R = PhCH₂10, R = Me 11, R = Bu 12), [R₂Cl Sn · L]_n (L = L¹, R = Me 5, R = Ph 6, R = PhCH₂7, R = Bu 8; L = L², R = Me 13, R = Ph 14, R = PhCH₂15, R = Bu 16), have been synthesized. All complexes were characterized by elemental analysis, TGA, IR and NMR (¹H, ¹³C, ³¹P and ¹¹⁹Sn) spectroscopy analysis. Among them, complexes 1, 2, 3, 5, 8, 9 and 11 have been characterized by X-ray crystallography diffraction analysis. In the crystalline state, the complexes adopt infinite 1D infinite chain structures which are generated by the bidentate bridging phosphonate ligands and the five-coordinated tin centers.     

Thermal behaviour of hexanuclear titanium(IV) oxo isopropoxide carboxylates,and their usability as a single-source TiO2 CVD precursors

Hexanuclear oxo titanium(IV) isopropoxide carboxylates, of the general formula [Ti₆O₆(OPrⁱ)₆(O₂CR)₆] (R = Bu^t (1), CH₂Bu^t (2)) and [Ti₆O₆(OPrⁱ)₆(O₂CC(CH₃)₂Et)₆] · 0.5(C₇H₈) (3), have been synthesized as polycrystalline powders in order to study their thermal properties and usability as TiO₂ CVD precursors. Analysis of thermogravimetric and variable temperature (VT-IR) data shows that the thermal stability of the synthesized complexes decreases as follows 3 > 2 > 1. The composition of the vapors formed during the thermolysis of 1–3 were qualitatively analysed with VT-IR methods and mass spectrometry (MS-EI). According to obtained results, the decomposition of 1 and 2 proceeds with a partial decomposition and the formation of a volatile and stable titanium species, sufficient for their transport in vapors. The formation of volatile titanium-containing derivatives is an important factor that decides the application of 1 and 2 as precursors in CVD experiments. The high stability of 3 causes the thermal decomposition of this complex to be observed just above 573 K, and volatile titanium-containing derivatives were not detected in vapors. These results indicate that 3 could not be used as a precursor in CVD processes.