Branched and dendritic metallo-carbosiloxanes with OCH2PPh2MLn end-grafted units

A straightforward method for the preparation of metallo carbosiloxanes of type Si(OCH₂CH₂CH₂SiMe₂[OCH₂PPh₂M(CO)_n])₄ (n = 3, M = Ni, 7a; n = 4, M = Fe, 7b; n = 5: M = Mo, 7c; M = W, 7d), Si(OCH₂CH₂CH₂SiMe[OCH₂PPh₂Ni(CO)₃]₂)₄ (8) and Me₂Si(OCH₂CH₂CH₂SiMe[OCH₂PPh₂Ni(CO)₃]₂)₂ (11) is described. The reaction of Si(OCH₂CH₂CH₂SiMeXCl)₄ (1: X = Me, 2: X = Cl) or Me₂Si(OCH₂CH₂CH₂SiMeCl₂)₂ (9) with HOCH₂PPh₂ (3) produces Si(OCH₂CH₂CH₂SiMe₂(OCH₂PPh₂))₄ (4), Si(OCH₂CH₂CH₂SiMe(OCH₂PPh₂)₂)₄ (5) or Me₂Si(OCH₂CH₂CH₂SiMe(OCH₂PPh₂)₂)₂ (10) in presence of DABCO. Treatment of the latter molecules with Ni(CO)₄ (6a), Fe₂(CO)₉ (6b), M(CO)₅(Thf) (6c: M = Mo; 6d: M = W), respectively, gives the title compounds 7a-7d, 8 and 11 in which the PPh₂ groups are datively bound to a 16-valence-electron metal carbonyl fragment.The formation of analytical pure and uniform branched and dendritic metallo carbosiloxanes is based on elemental analysis, and IR, ¹H, ¹³C{¹H}, ²⁹Si{¹H} and ³¹P{¹H} NMR spectroscopic studies. In addition, ESI-TOF mass spectrometric studies were carried out.     

Rare earth metal bis(alkyl) complexes bearing amino phosphine ligands: Synthesis and catalytic activity toward ethylene polymerization

Reactions of neutral amino phosphine compounds HL^1-3 with rare earth metal tris(alkyl)s, Ln(CH₂SiMe₃)₃(THF)₂, afforded a new family of organolanthanide complexes, the molecular structures of which are strongly dependent on the ligand framework. Alkane elimination reactions between 2-(CH₃NH)-C₆H₄P(Ph)₂ (HL¹) and Lu(CH₂SiMe₃)₃(THF)₂ at room temperature for 3 h generated mono(alkyl) complex (L¹)₂Lu(CH₂SiMe₃)(THF) (1). Similarly, treatment of 2-(C₆H₅CH₂NH)-C₆H₄P(Ph)₂ (HL²) with Lu(CH₂SiMe₃)₃(THF)₂ afforded (L²)₂Lu(CH₂SiMe₃)(THF) (2), selectively, which gradually deproportionated to a homoleptic complex (L²)₃Lu (3) at room temperature within a week. Strikingly, under the same condition, 2-(2,6-Me₂C₆H₃NH)-C₆H₄P(Ph)₂ (HL³) swiftly reacted with Ln(CH₂SiMe₃)₃(THF)₂ at room temperature for 3 h to yield the corresponding lanthanide bis(alkyl) complexes L³Ln(CH₂SiMe₃)₂(THF)_n (4a: Ln = Y, n = 2; 4b: Ln = Sc, n = 1; 4c: Ln = Lu, n = 1; 4d: Ln = Yb, n = 1; 4e: Ln = Tm, n = 1) in high yields. All complexes have been well defined and the molecular structures of complexes 1, 2, 3 and 4b-e were confirmed by X-ray diffraction analysis. The scandium bis(alkyl) complex activated by AlEt₃ and [Ph₃C][B(C₆F₅)₄], was able to catalyze the polymerization of ethylene to afford linear polyethylene.     

Synthesis and crystal structures of boratranes with methyl substituents on the atrane cage

Three monomeric boratranes B[(OCH₂CH₂)_nN(CH₂CMe₂O)_3−n] (n = 0, 1; n = 1, 2; n = 2, 3) have been synthesized by the reaction of B(OMe)₃ with a series of triethanolateamines such as [(OCH₂CH₂)_nN(CH₂CMe₂O)_3−n]³⁻ (n = 0, L1; n = 1, L2; n = 2, L3), where the number of CMe₂ groups adjacent to the OH functionality varied from 3 (L1H₃) to 2 (L2H₃) to 1 (L3H₃). These boratranes 1-3 have been characterized by solution ¹H, ¹³C{¹H} and ¹¹B NMR, and the crystal structures of 1 and 2 have been determined by single crystal X-ray diffraction.     

Syntheses, crystal structures and coordination modes of tri- and di-organotin derivatives with 2-mercapto-4-methylpyrimidine

The organotin (IV) derivatives of 2-mercapto-4-methylpyrimidine (Hmpymt) R₃SnL (R = Ph 1, PhCH₂2, n-Bu 3), R₂SnCl_mL_n (m = 1, n = 1, R = CH₃4, Ph 5, n-Bu 6, PhCH₂7; m = 0, n = 2, R = CH₃8, n-Bu 9, Ph 10, PhCH₂11) were obtained by the reaction of the organotin(IV) chlorides R₃SnCl or R₂SnCl₂ with 2-mercapto-4-methylpyrimidine hydrochloride (HCl · Hmpymt) in 1:1 or 1:2 molar ratio. All complexes 1-11 were characterized by elemental analyses, IR, ¹H, ¹³C and temperature-dependent ¹¹⁹Sn NMR spectra. Except for complexes 3 and 6, the structures of complexes 1, 2, 4, 5, 7, 8-11 were confirmed by X-ray crystallography. Including tin-nitrogen intramolecular interaction, the tin atoms of complexes 1-7 are all five-coordinated and their geometries are distorted trigonal bipyramidal. While the tin atoms of complexes 8-11 are six-coordinated and their geometries are distorted octahedral. Besides, the ligand adopts the different coordination modes to bond to tin atom between the complexes 1, 6, 7 and 2, 3, 4, 5, 8-11. Furthermore, intermolecular Sn?N or Sn?S interactions were recognized in crystal structures of complexes 4, 7 and 11, respectively.     

New synthesis and thermal studies of palladacycloalkanes and their precursors

A series of new palladacycloalkanes of formula cis-[PdL₂(CH₂)_n] (9. n = 6, L = PPh₃; 10. n = 6, L₂ = dppe; 11. n = 8, L = PPh₃; 12. n = 8, L₂ = dppe) have been prepared by two routes. In the first route, the precursor bis(1-alkenyl) complexes cis-[PdL₂((CH₂)_nCHCH₂)₂] (1. n = 2, L = PPh₃, 2. n = 2, L₂ = dppe, 3. n = 3, L = PPh₃, 4. n = 3, L₂ = dppe) were allowed to react with Grubb’s 2nd generation catalyst to give the palladacycloalkenes, cis-[PdL₂(CH₂)_nCHCH(CH₂)_n] (5. n = 2, L = PPh₃, 6. n = 2, L₂ = dppe, 7. n = 3, L = PPh₃, 8. n = 3, L₂ = dppe), which were then hydrogenated to the palladacycloalkanes, 9-12. In the second route, the di-Grignard reagents BrMg(CH₂)_nMgBr (n = 6, 8) were reacted with the palladium complex [PdCl₂(COD)] followed by immediate ligand displacement to form the respective palladacycloalkanes 10 and 12. The complexes obtained were characterized by a range of spectroscopic and analytical techniques. Thermal decomposition studies were carried out on the palladacycloalkanes 9-12 and the main organic products shown to be 1-alkenes and 2-alkenes.     

Carbosilane dendrimers containing peripheral cyclopentadienyl niobium- and tantalum-imido complexes

Anilines Gn-{(C₆H₄)N(SiMe₃)₂}_m, based on simple or dendritic carbosilanes, have been used to synthesized (imido)tantalum compounds Gn-{(C₆H₄)NTaCl₂Cp^∗}_m (1, n = 0, m = 1; 2, n = 1, m = 4; Cp^∗ = η⁵-C₅Me₅), by the reaction with [TaCl₄Cp^∗] and elimination of SiMe₃Cl. (Imido)niobocene compounds of general formula (3-5; n = 0, 1, 2; m = 1, 4, 8, respectively) have been readily prepared from their corresponding half-sandwich complexes Gn-{(C₆H₄)NNbCl₂Cp′}_m by the reaction with m equiv. of LiCp′ (Cp′ = η⁵-C₅H₄SiMe₃). Compounds 1-5 are all found to be exceedingly moisture sensitive, and in the case of the (imido)niobocene materials the hydrolytic reaction selectively leads to the formation of (6). The molecular structure of 6 has been determined by X-ray diffraction studies.     

Formation and structural characterization of mercury complexes from Te(R)CH2SiMe3 (R = Ph, CH2SiMe3) and HgCl2

The reaction of HgCl₂ and Te(R)CH₂SiMe₃ [R = CH₂SiMe₃ (1), Ph (2)] in ethanol yielded a mononuclear complex [HgCl₂{Te(R)CH₂SiMe₃}₂] (R = Ph, 3a; R = CH₂SiMe₃, 3b). The recrystallization of 3a or 3b from CH₂Cl₂ produced a dinuclear complex [Hg₂Cl₂(μ-Cl)₂{Te(R)CH₂SiMe₃}₂] (R = Ph, 4a; R = CH₂SiMe₃, 4b). When 3a was dissolved in CH₂Cl₂, the solvent quickly removed, and the solid recrystallized from EtOH, a stable ionic [HgCl{Te(Ph)CH₂SiMe₃}₃]Cl·2EtOH (5a·2EtOH) was obtained. Crystals of [HgCl₂{Te(CH₂SiMe)₂}]·2HgCl₂·CH₂Cl₂ (6b·2HgCl₂·CH₂Cl₂) were obtained from the CH₂Cl₂ solution of 3b upon prolonged standing. The complex formation was monitored by ¹²⁵Te-, and ¹⁹⁹Hg NMR spectroscopy, and the crystal structures of the complexes were determined by single crystal X-ray crystallography.     

Selective synthesis of monomeric or dimeric titanatranes via fine tuning in triethanolateamine ligand

Monomeric titanatrane i-PrOTi(OCMe₂CH₂)₃N (1) and dimeric titanatranes [i-PrOTi(OCH₂CH₂)_nN(CH₂CMe₂O)_3−n]₂ (n = 1, 2; n = 2, 3) were synthesized by the reaction of Ti(O-i-Pr)₄ with a series of triethanolateamines such as (OCH₂CH₂)_nN(CH₂CMe₂O)_3−n³⁻ (n = 0, Lig¹; n = 1, Lig²; n = 2, Lig³), which vary by the number of CMe₂ groups adjacent to a OH functionality from 3 (Lig¹H₃) to 2 (Lig²H₃) to 1 (Lig³H₃). The resultant titanatranes 1–3 have been characterized by solution ¹H and ¹³C{¹H} NMR and their solid state structures have been determined by X-ray crystallography. Whereas compound 1 is monomeric in the solid state, compounds 2 and 3 are dimeric, due to the reduction of the steric congestion in the vicinity of the Ti.     

Structural diversity of di and triorganotin complexes with 4-sulfanylbenzoic acid: Supramolecular structures involving intermolecular Sn?O, O-H?O or C-H?X (X = O or S) interactions

Twelve new organotin complexes with 4-sulfanylbenzoic acid of two types: R_nSn[S(C₆H₄COOH)]_4−n (I) (n = 3: R = Me 1, n-Bu 2, Ph 3; PhCH₂4; n = 2: R = Me 5; n-Bu 6, Ph 7, PhCH₂8) and R₃Sn(SC₆H₄COO)SnR₃ · mEtOH (II) (m = 0: R = Me 9, n-Bu 10, PhCH₂12; m = 2: R = Ph 11), along with the 4,4′-bipy adduct of 9, [Me₃Sn(SC₆H₄COO)SnMe₃]₂(4,4-bipy) 13, have been synthesized. The coordination behavior of 4-sulfanylbenzoic acid is monodentate in 1-8 by thiol S atom but not carboxylic oxygen atom. While, in 9-13 it behaves as multidenate by both thiol S atom and carboxylic oxygen atoms. The supramolecular structures of 6, 11 and 13 have been found to consist of 1D molecular chains built up by intermolecular O-H?O, C-H?O or C-H?S hydrogen bonds. The supramolecular aggregation of 7 is 2D network determined by two C-H?O hydrogen bonds. Extended intermolecular C-H?O interactions in the crystal lattice of 9 link the molecules into a 2D network.     

Synthesis and structural characterization of organotin(IV) carboxylates based on different heterocyclic substituents

Six novel organotin(IV) carboxylates have been successfully synthesized, namely, the polymer (C₆H₅)₃Sn(L1)_∞ (1) [HL1 = 4-imidazolyl benzoic acid], the mononuclear (C₆H₅)₃Sn(L2) (2) [HL2 = 4-pyrazolylbenzoic acid], (C₆H₅)₃Sn(L3)·CH₃OH (3) [HL3 = 4-triazolylbenzoic acid] and (C₆H₅)₃Sn(L4) (4) [HL4 = 4-tetrazolyl benzoic acid] and the tetranuclear [(n-Bu₂Sn)₄(L2)₂O₂(OCH₃)₂] (5) and [(n-Bu₂Sn)₄(L3)₂O₂(OCH₃)₂] (6). X-ray diffraction analyses show 1D infinite chain of polymer 1, single molecular structures of isomorphous complexes 2 and 4, single molecule structures of complex 3 containing solvent CH₃OH molecule and similar ladder-type structures of complexes 5 and 6. The photoluminescence of ligands and 1-6 were also measured in the solid state at room temperature.     

Syntheses and crystal structures of di- and triorganotin derivatives with 2,5-dimercapto-1,3,4-thiodiazole

A series of organotin(IV) complexes with 2,5-dimercapto-1, 3, 4-thiodiazole (HHdmt) of the type (R_nSnCl_m)₂(dmt) (m=0, n=3, R=Ph 1, PhCH₂2, n-Bu 3; m=1, n=2, R=Ph 4) and [R₂Sn(dmt) · L]_n (L=0.5C₆H₆, R=CH₃5; L=0, n=5, R=n-Bu 6) have been synthesized. All complexes 1-6 were characterized by elemental analysis, IR, ¹H and ¹³C NMR spectra. And except for 3, complexes 1, 2, 4, 5 and 6 were also determined by X-ray crystallography. The tin atoms of complexes 1, 2, 3 and 4 are all five-coordinated. The geometries at tin atoms of 1, 2, 3 and 4 are distorted trigonal bipyramidal. The tin atoms of complexes 5 and 6 are six-coordinated and their geometries are distorted octahedral.     

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.     

Mesogens based on palladium orthometallated complexes with carboxylato bridges: tuning and shaping a non-planar molecule

The binuclear cyclopalladated compounds [Pd₂(μ-OH)₂(Lⁿ)₂] (1) derived from imines HLⁿ = p-C_nH_2n + 1O-C₆H₄-CHN-C₆H₄-OC_nH_2n + 1-p (n = 6,10) react with carboxylic acids to give the derivatives [Pd₂(μ-ox)₂(Lⁿ)₂] (2) with a planar core for oxalic acid, and [Pd₂(μ-OOCR)₂(Lⁿ)₂] (3-7) compounds with a non-planar ridge tent structure for other RCOOH acids: (3) R = C_mH_2m + 1 (m = 1, 3, 5, 7, 9, 11, 13, 15, 17); (4) R = CH₂(OCH₂CH₂)_pOCH₃ (p = 1, 2); (5) R = CH₂-C₆H₄-OC_qH_2q + 1-p (q = 2, 4, 6, 8, 10, 12); (6) R = C₆H₄-OC_rH_2r + 1-p (r = 4, 10); (7) R = C*H(OH)CH₃. The acids used were designed to explore the effect on the thermal properties of the compounds prepared of systematic variations in the type of carboxylato ligand, which induce structure, packing, and polarity changes, and in the length of the carboxylato chain. Most of the complexes prepared, even when far from planar, show liquid crystal behavior and display nematic, smectic A and smectic C phases.     

Synthesis of mono and doubly alkynyl substituted ferrocene and its crystal engineering using -C-H···O supramolecular synthon

Mono and doubly alkynyl substituted ferrocene complexes, [Fc(CH₂OCH₂CCH)_n], 2-3 (2: n = 1; 3: n = 2; Fc = ferrocene) have been synthesized from the room temperature reaction of mono and 1,1′-dihydroxymethyl ferrocene, Fc(CH₂OH)_n , 1a-b (1a: n = 1; 1b: n = 2) and propargyl bromide, in modest to good yields. These new ferrocene derivatives have been characterized by mass, IR, ¹H, ¹³C NMR spectroscopy, and molecular structures of compound 2 and 3 were unequivocally established by single crystal X-ray diffraction study. The crystal structure analysis revealed that 2 and 3 consist of infinite 1D zig-zag hydrogen bonded chains and 2D microporous hydrogen bonded network of molecules, linked by intermolecular C-H···O hydrogen bonding. The molecular structures of both 2 and 3 are further stabilized by C-H···π interactions.     

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.     

Syntheses and structures of non-symmetric guanidinato zirconium and hafnium complexes and their catalytic behavior for ethylene polymerization

Equivalent addition reactions of PhN(Li)SiMe₃ to nitriles, RCN (R = dimethylamido, 1-piperidino), generated non-symmetric guanidinato lithium [(Et₂O)LiN(SiMe₃)C(NMe₂)N(Ph)]₂ (1) or [(THF)LiN(SiMe₃)C(NMe₂)N(Ph)]₂ (2) and [(Et₂O)LiN(SiMe₃)C(N(CH₂)₅)N(Ph)]₂ (5) which further reacted with zirconium or hafnium tetrachloride to form Zr and Hf guanidinato complexes with the general formula [PhNC(R)NSiMe₃]₃MCl (R = dimethylamido, M = Zr (3), Hf (4); R = 1-piperidino, M = Zr (6), Hf (7)). Complexes 1-4, 6 and 7 were well characterized by ¹H, ¹³C NMR and microanalysis, the single crystal X-ray diffraction analysis data for complexes 1, 3, 4 and 7 were also provided. Furthermore, complexes 3, 4, 6 and 7 were found to be active for ethylene polymerization. The influences of cocatalyst, pressure, reaction temperature and Al/M ratio on activity were investigated.     

Germylene and stannylene (Me2NCH2CH2O)2E as strong σ-donor ligands for transition metal complexes [ML(CO)n] (E = Ge, Sn; M = Cr, Mo, W, n = 4 or 5; M = Fe, n = 4). Synthesis, spectroscopic and theoretical study

A series of germylene and stannylene (Me₂NCH₂CH₂O)₂E (E = Ge, 1; E = Sn, 2) complexes of group 6 metals and iron carbonyls L·M(CO)_n (M = Cr, Mo, W, n = 5 (3-8), n = 4 (9, 10); M = Fe, n = 4 (11, 12)) were prepared. These complexes were characterized by ¹H, ¹³C NMR, FTIR and elemental analysis. Ligand properties of 1 and 2 were compared to PPh₃ and dmiy (N,N′-dimethylimidazolin-2-ylidene) using theoretical calculations (PBE/TZ2P) and FTIR. Ligand dissociation energies increase in the order Ph₃P < 2∼1 < dmiy, while donor strength rise in the order PPh₃ < dmiy < 2 < 1.     

New alkenyl-substituted group 4 C-ansa-metallocene complexes. Reactivity of the substituent at the carbon ansa bridge

The allyl-substituted group 4 metal complexes [M{(R)CH(η⁵-C₅Me₄)(η⁵-C₅H₄)}Cl₂] [M = Ti, R = CH₂CHCH₂, (2); R = CH₂C(CH₃)CH₂ (3); M = Zr, R = CH₂CHCH₂ (4), R = CH₂C(CH₃)CH₂ (5)] have been synthesized by the reaction of allyl ansa-magnesocene derivatives and the tetrachloride salts of the corresponding transition metal. The dialkyl complexes ] [M = Ti, R = CH₂=CHCH₂, R′ = Me (6), R′ = CH₂Ph (7); R = CH₂C(CH₃)CH₂, R′ = Me (8), R′ = CH₂Ph (9); M = Zr, R = CH₂CHCH₂, R′ = Me (10), R′ = CH₂Ph (11); R = CH₂C(CH₃)CH₂, R′ = Me (12), R′ = CH₂Ph (13)] have been synthesized by the reaction of the corresponding ansa-metallocene dichloride complexes 2-5 and two molar equivalents of the alkyl Grignard reagent. Compounds 2-5 reacted with H₂ under catalytic conditions (Wilkinson’s catalyst or Pd/C) to give the hydrogenation products [M{(R)CH(η⁵-C₅Me₄)(η⁵-C₅H₄)}Cl₂] [M = Ti and R = CH₂CH₂CH₃ (14) or R = CH₂CH(CH₃)₂ (15); M = Zr and R = CH₂CH₂CH₃ (16) or R = CH₂CH(CH₃)₂ (17)]. The reactivity of 2-5 has also been tested in hydroboration and hydrosilylation reactions. The hydroboration reactions of 3, 4 and 5 with 9-borabicyclo[3.3.1]nonane (9-BBN) yielded the complexes [M{(9-BBN)CH₂CH(R)CH₂CH(η⁵-C₅Me₄)(η⁵-C₅H₄)}Cl₂] [M = Ti and R = H (18); M = Zr and R = H (19) or R = CH₃ (20)]. The reaction with the silane reagents HSiMe₂Cl gave the corresponding [M{ClMe₂SiCH₂CHRCH₂CH(η⁵-C₅Me₄)(η⁵-C₅H₄)}Cl₂] [M = Ti and R = H (21); M = Zr and R = H (22) or R = CH₃ (23)]. The reaction of 22 with t-BuMe₂SiOH produced a new complex [Zr{t-BuMe₂SiOSi(Me₂)CH₂CH₂CH₂CH(η⁵-C₅Me₄)(η⁵-C₅H₄)}Cl₂] (24) through the formation of Si-O-Si bonds. On the other hand, reactivity studies of some zirconocene complexes were carried out, with the insertion reaction of phenyl isocyanate (PhNCO) into the zirconium-carbon σ-bond of [Zr{(n-Bu)CH(η⁵-C₅Me₄)(η⁵-C₅H₄)}₂Me₂] (25) giving [{(n-Bu)CH(η⁵-C₅Me₄)(η⁵-C₅H₄)]}Zr{Me{κ²-O,N-OC(Me)NPh}] as a mixture of two isomers 26a-b. The reaction of [Zr{(n-Bu)(H)C(η⁵-C₅Me₄)(η⁵-C₅H₄)}(CH₂Ph)₂] (27) with CO also provided a mixture of two isomers [{(n-Bu)CH(η⁵-C₅Me₄)(η⁵-C₅H₄)]}Zr(CH₂Ph){κ²-O,C-COCH₂Ph}] 28a-b. The molecular structures of 4, 11, 16 and 17 have been determined by single-crystal X-ray diffraction studies.     

Metal β-diketiminates revisited: ansa-CH2-bridged bis(β-diketiminate)s of lithium and aluminium having diverse structures

The metal β-diketiminato ligand-to-metal binding modes are briefly reviewed, with reference particularly to our previous work on metal complexes using the ligands [{N(R¹)C(R²)}₂CH] (R¹ = SiMe₃ = R and R² = Ph; or R¹ = C₆H₃Prⁱ₂-2,6 and R² = Me). The syntheses of the β-diketimines H[{N(R)C(Ar)}₂CH] 1 (Ar = Ph) and 2 (Ar = C₆H₄Me-4) and the ansa-CH₂-bridged bis(β-diketimine)s 3 (Ar = Ph) and 4 (Ar = C₆H₄Me-4) are reported. Thus, from the appropriate compound Li[{N(R)C(Ar)}₂CH] and H₂O, (CH₂Br)₂ or CH₂Br₂ the product was 2, 3 or 4. Compound 1 was prepared from K[{N(R)C(Ph)}₂CH] and (CH₂Br)₂. Each of 3 or 4 with LiBuⁿ surprisingly yielded the bicyclic dilithium compound 5 (Ar = Ph) or 6 (Ar = C₆H₄Me-4) in which each of the β-diketiminato fragments is an N,N′-bridge between the two lithium atoms and the CH₂ moiety joins the two ligands through their central carbon atoms. However, 4 with AlMe₃ yielded the expected ansa-CH₂-bridged-bis[(β-diketiminato)(dimethyl)alane] 7, which was also obtained from 6 and Al(Cl)Me₂. X-ray structures of the known compounds 2 and 3, and of 5, 6 and 7 are presented; the ¹H NMR spectra of 6 in toluene-d₈ show that there is restricted rotation about the NC-C₆H₄Me-4 bond.     

Cation-anion interactions involving hydrogen bonds: Syntheses and crystal structures study of hexafluorotitanate(IV) salts with pyridine and methyl substituted pyridines

Fluorotitanates (LH)₂[TiF₆]·nH₂O (1: R = pyridine, n = 1, 2: R = 2-picoline, n = 2, 3: R = 2,6-lutidine, n = 0, 4: R = 2,4,6-collidine, n = 0) and (LH)[TiF₅(H₂O)] (3a: L = 2,6-lutidine) have been synthesized by the reaction of pyridine or corresponding methyl substituted pyridines and titanium dioxide dissolved in hydrofluoric acid. The crystal structures of ionic compounds 1, 2, 3, 3a and 4 have been determined by single-crystal X-ray diffraction analysis. The hydrogen bonding led to the formation of discrete (LH)₂[TiF₆] units (4), chains (1-3), and layers (3a). The additional π-π interactions present in 1, 2, and 4 results in chain structures of 1 and 4 and in a layer structure of 2. The [TiF₆]²⁻ and [TiF₅(H₂O)]⁻ anions were observed by ¹⁹F NMR spectroscopy in aqueous solutions of 1, 2, 3, 3a and 4.