Monomeric Aluminum Research Articles

Insertion, Reduction, and Carbon–Carbon Coupling Induced by Monomeric Aluminum Hydride Compounds Bearing Substituted Pyrrolyl Ligands

A monomeric aluminum hydride complex bearing substituted pyrrolyl ligands, AlH[C(4)H(3)N(CH(2)NMe(2))-2](2) (1), was synthesized and structurally characterized. To further confirm the presence of Al--H bonds, the compound AlD[C(4)H(3)N(CH(2)NMe(2))-2](2) ([D]1) was synthesized by reacting LiAlD(4) with [C(4)H(4)N(CH(2)NMe(2))-2]. Compound 1 and [D]1 react with phenyl isothiocyanate yielding Al[C(4)H(3)N(CH(2)NMe(2))-2](2)[eta(3)-SCHNPh] (2) and Al[C(4)H(3)N(CH(2)NMe(2))-2](2)[eta(3)-SCDNPh] ([D]2) by insertion. The reactions of 1 with 9-fluorenone and benzophenone generated the unusual aluminum alkoxide complexes 3 and 4, respectively, through intramolecular proton abstraction and C-C coupling. A mechanistic study shows that 9-fluorenone coordinates to [D]1 and releases one equivalent of HD followed by C-C coupling and hydride transfer to yield the final product. Reduction of benzil with 1 affords aluminum enediolate complex 5 in moderate yield. Mechanistic studies also showed that the benzil was inserted into the aluminum hydride bond of [D]1 through hydroalumination followed by proton transfer to generate the final product [D]5. All new complexes have been characterized by (1)H and (13)C NMR spectroscopy and X-ray crystallography.

Retrospective Analyses and Future Predictions of Snowmelt-Induced Acidification: Example from a Heavily Impacted Stream in the Czech Republic

We have combined a long-term hydrochemistry model (MAGIC) with a model that predicts short-term transient changes in hydrochemistry (pBDM) during hydrological events in order to improve the temporal resolution of retrospective analyses and future predictions of streamwater acidification. The model has been applied to a heavily impacted catchment in the Czech Republic. Spring flood acid-neutralizing capacity (ANC), pH, and inorganic monomeric aluminum (Ali(n+)) were simulated for the years of 1860, 1900, 1930, 1950, 1965, and 1985, measured in 1999, and predicted for 2030 using two different emission control scenarios. If the emission reduction according to the current legislation scenario is implemented, the model predicts that the spring flood pH, ANC, and Ali(n+) will recover close to the level of the 1950s by 2030. This will occur despite the annual average chemistry being farfrom having recovered to that level. The results suggest that the recovery of spring flood events is faster then the recovery of annual average chemistry and that much of what is won by further emission reduction will not be fully realized on an annual time scale.

Diffusive Gradients in Thin Films Sampler Predicts Stress in Brown Trout (Salmo trutta L.) Exposed to Aluminum in Acid Fresh Waters

Increased levels of aluminum ions released from nutrient-poor soils affected by acid rain have been the primary cause of fish deaths in the acidified watersheds of southern Norway. The complex aluminum chemistry in water requires speciation methods to measure the gill-reactive species imposing toxic effects toward fish. Previously, aluminum speciation has mainly followed the fractionation principles outlined by Barnes/Driscoll, and several analogues of these fractionation principles have been used both in situ and in the laboratory. Due to rapid transformation processes, aluminum speciation in water samples may change even during short storage times. Thus, results obtained by laboratory fractionation methods might be misleading for the assessment of potentially toxic aluminum species in the water. Until now, all in situ field fractionation methods have been time and labor consuming. The DGT technique (diffusive gradients in thin films) is a new in situ sampler collecting a fraction of dissolved metal weighted according to the rate of diffusion and dissociation kinetics. In a field experiment with acid surface water we studied the DGT sampler as a new prediction tool for the gill accumulation of aluminum in trout (Salmo trutta L.) and the induced physiological stress responses measured as changes in blood glucose and plasma chloride. Aluminum determined with DGT (DGT-AI) was higher than labile monomeric aluminum (Ali) determined with a laboratory aluminum fractionation procedure (PCV--a pyrocatechol violet analogue of Barnes/Driscoll), a difference due to collection of a fraction of organically complexed aluminum by DGT and a reduction of the Ali fraction during sample storage. DGT-AI predicted the gill uptake and the aluminum-induced physiological stress responses (increased blood glucose and decreased plasma chloride, r2 from 0.6 to 0.9). The results indicate that DGT-AI is a better predictor for the stress response than laboratory-determined Ali, because the DGT sampler collects a more correct fraction of the gill-reactive aluminum species that induces the stress.

Chemistry of aluminium(i)

In this article, we discuss the synthesis of tetrameric and monomeric aluminium(I) compounds. These compounds are prepared by reduction of the respective Al-X (X = halide) bond containing precursor. The tetrameric aluminium(I) compounds are synthesized by using sterically bulky ligands whereas a stable monomeric aluminium(I) compound is obtained using a monovalent chelating ligand. Theoretical studies are carried out on the monomer to understand the Lewis basicity. The presence of a lone pair of electrons plays an important role in the preparation of aluminium containing heterocyclic compounds, main group-main group and transition metal-main group compounds having donor-acceptor bonds by carrying out reactions with unsaturated compounds and Lewis acids.

Landscape influences on aluminium and dissolved organic carbon in streams draining the Hubbard Brook valley, New Hampshire, USA

Concentrations of both aluminium (Al) and dissolved organic carbon (DOC) in stream waters are likely to be regulated by factors that influence water flowpaths and residence times, and by the nature of the soil horizons through which waters flow. In order to investigate landscape-scale spatial patterns in streamwater Al and DOC, we sampled seven streams draining the Hubbard Brook valley in central New Hampshire. We observed considerable variation in stream chemistry both within and between headwater watersheds. Across the valley, concentrations of total monomeric aluminium (Alm) ranged from below detection limits (<0·7 µmol l−1) to 22·3 µmol l−1. In general, concentrations of Alm decreased as pH increased downslope. There was a strong relationship between organic monomeric aluminium (Alo) and DOC concentrations (R2 = 0·92). We observed the highest Alm concentrations in: (i) a watershed characterized by a steep narrow drainage basin and shallow soils and (ii) a watershed characterized by exceptionally deep forest floor soils and high concentrations of DOC. Forest floor depth and drainage area together explained much of the variation in ln Alm (R2 = 0·79; N = 45) and ln DOC (R2 = 0·87; N = 45). Linear regression models were moderately successful in predicting ln Alm and ln DOC in streams that were not included in model building. However, when back-transformed, predicted DOC concentrations were as much as 72% adrift from observed DOC concentrations and Alm concentrations were up to 51% off. This geographic approach to modelling Al and DOC is useful for general prediction, but for more detailed predictions, process-level biogeochemical models are required. Copyright © 2005 John Wiley & Sons, Ltd.

Lithium and aluminium complexes supported by chelating phosphaguanidinates

Diisopropylcarbodiimide, (i)PrN[double bond, length as m-dash]C[double bond, length as m-dash]N(i)Pr, inserts into the lithium-phosphorus bond of in situ prepared "Ph(2)PLi(THF)(n)" to afford the lithium salt, [Li(Ph(2)PC{N(i)Pr}(2))(THF)(n)](x)(2a); alternatively, this compound can be made by deprotonation of the neutral phosphaguanidine, Ph(2)PC{N(i)Pr}{NH(i)Pr}(1a) with (n)BuLi. Displacement of the THF solvate in 2a is readily achieved with TMEDA to afford Li(Ph(2)PC{N(i)Pr}(2))(TMEDA)(3a). X-Ray crystallographic analyses show that 2a exists as a dimer in the solid state with a folded ladder structure and an N,N' chelating phosphaguanidinate, while 3a is monomeric with N,P-coordination of the ligand to lithium. Compound 2a reacts via a transmetallation pathway with AlMe(2)Cl to afford the dimethylaluminium complex, Al(Ph(2)PC{N(i)Pr}(2))Me(2)(4a), which can also be prepared by protonation of a methyl group of AlMe(3) using 1a. The formation of a series of dialkylaluminium compounds has been investigated employing this latter pathway using both 1a and the N,N'-dicyclohexyl analogue, Ph(2)PC{NCy}{NHCy}(1b), affording Al(Ph(2)PC{NR}(2))Et(2)(5a,b), Al(Ph(2)PC{NR}(2))(i)Bu(2)(6a,b) and the diphenylaluminium compound Al(Ph(2)PC{N(i)Pr}(2))Ph(2)(7a). The oily nature of most of the dialkyl compounds and high sensitivity to oxygen and moisture lead to difficulty in manipulation and characterization; however, NMR spectroscopy indicated highly pure products (>95%) upon removal of the solvent. The molecular structures of the crystalline examples 4a and 7a are reported, showing monomeric aluminium species with symmetrically chelating phosphaguanidinate ligands. The series of aluminium compounds AlLCl(2){L=[EC{NiPr}(2)](-): A, E=Me; B, E=Me(2)N; C, E=(Me(3)Si)(2)N and D, E=Ph(2)P} were investigated using density functional theory. In the more simple cases A and B, the delocalized electron density of the metallacycle was represented by a combination of the HOMO and an orbital of lower energy (A, HOMO-5; B, HOMO-6). The HOMO-1 in B was pi-bonded across the Me(2)N-C bond suggesting delocalization of electron density into the metallacycle. In the more complex systems C and D, delocalization within the metallacycle was less extensive due to the (Me(3)Si)(2)N- and Ph(2)P-moieties. A number of occupied orbitals in D, however, display phosphorus 'lone-pair' characteristics, indicating that these species have the potential to behave as Lewis bases in the formation of poly(metallic) systems.

Stream acidification and mortality of brook trout (Salvelinus fontinalis) in response to timber harvest in Catskill Mountain watersheds, New York, USA

Effects of clear-cut and timber-stand improvement (TSI) harvests on water chemistry and mortality of caged brook trout (Salvelinus fontinalis) were evaluated in a study of three Catskill Mountain streams, 1994–2000. Harvests removed 73% of tree basal area (BA) from a clearcut subbasin, 5% BA from a TSI subbasin, and 14% BA at a site below the confluence of both streams. A fourth nonharvested site served as a control. Water quality and trout mortality were affected only in the clearcut stream. Acidity and concentrations of nitrate and inorganic monomeric aluminum (Alim) increased sharply during high flows after the first growing season (fall 1997). Acid–Alim episodes were severe during this period and decreased steadily in magnitude and duration thereafter. All trout at this site died within 7 days during spring 1998 and 85% died during spring 1999. Only background mortality was observed in other years at this site and at the other three sites during all tests. The absence of mortality in TSI watersheds indicates that limited harvests should not harm brook trout populations in acid-sensitive streams. Effects of tree harvests on fish communities are of concern, however, because many stream-dwelling species are more sensitive to acidified waters than brook trout.

Dermatitis, branchitis and mortality in empire gudgeon Hypseleotris compressa exposed naturally to runoff from acid sulfate soils

Severe dermatitis and branchitis are described in a wild population of empire gudgeon Hypseleotris compressa, an Australian eleotrid, exposed naturally to runoff from acid sulfate soils (ASS) in a drained estuarine embayment in eastern Australia. After at least 2 d exposure to pH < 4, and up to 7 d exposure to pH < 6, approximately 50% of the fish sampled had moderate to severe diffuse epidermal hyperplasia, usually at scale margins, and scattered areas of moderate to severe, focal to locally extensive, subacute, necrotising dermatitis. Saprolegnia spp. had invaded epidermis in some inflamed areas. In gills, there was moderate to severe hyperplasia and necrosis of secondary lamellar epithelium, with fusion of adjacent secondary lamellae. Inorganic monomeric aluminium and calcium concentrations in water at the site during the event were 27.7 and 16.6 mg l(-1), respectively. Large numbers of empire gudgeons at the study site had died after at least 8 d exposure to pH < 4, and up to 13 d exposure to pH < 6. These findings provide clear evidence that acidification of estuarine systems by runoff from ASS has deleterious effects on aquatic biota. Furthermore, study findings suggest a mechanism whereby lesions of epizootic ulcerative syndrome (EUS) may be initiated in estuarine fishes by a combination of sublethal exposure to ASS runoff and Aphanomyces invadans infection, a suggestion consistent with the geographic and temporal distribution of EUS outbreaks in Australian estuaries.

Role of dimeric and monomeric aluminum chlorides as catalysts is aromatic electrophilic substitution

Aromatic electrophilic substitution reactions were simulated by ab initio calculations of the intermediate complexes and transition states involving the dimeric and monomeric forms of aluminum chloride. With the monomeric form, breaking of the catalytic cycle should be expected due to formation of a stable intermediate complex. With the dimeric form, no such complex was revealed, implying a key role this form plays in the catalysis.

Spectroscopic evidence of monomeric aluminium phthalocyanine tetrasulphonate in aqueous solutions

Aqueous solutions of aluminium phthalocyanine tetrasulphonate (AlPcS 4) were investigated by means of absorption and fluorescence spectroscopy. The absorption spectrum of AlPcS 4 is independent of concentration in a wide range (from 10 −8 to 10 −4 M). The fluorescence spectrum measured with a standard setup is strongly dependent on AlPcS 4 concentration, and the fluorescence maximum is gradually red-shifted with increasing concentration. Calculations that take into account reabsorption of fluorescence (inner-filter effect) fit the experimental observations at low concentrations (up to 10 −6 M). Disagreement between the calculations and spectra recorded at higher concentrations (above 10 −5 M) shows that the reabsorbed light may be reemitted as fluorescence. The influence of inner-filter effects on the spectral shape was demonstrated by the experiments where a fibre-optic front-face fluorescence setup was applied: Under such conditions the shape of the fluorescence spectra for a high concentration (10 −3 M) coincided with that of a low concentration (10 −8 M). In conclusion, the present spectroscopic results show that AlPcS 4 does not form aggregates and is a very stable compound in aqueous solutions.

Transformation of positively charged aluminium-species in unstable mixing zones following liming

Liming is widely used to counteract chronic toxicity of positively charged monomeric aluminium species (Al i). Immediately after liming, unstable mixing zones are formed due to the sudden increase in pH. Transformation of monomeric Al i species takes place instantaneously and transient positively charged Al polymers, being acute toxic to fish, are formed in the mixing zones. Using in situ hollow fibre ultrafiltration interfaced with ion chromatography in unstable mixing zone field experiments performed in two river systems situated south and southwest of Norway, information on time-dependent transformations of low molecular mass (LMM) and high molecular mass (HMM) positively charged Al i-species has been followed. The formation of HMM Al i species from LMM Al i occurred rapidly following liming. HMM Al i species have a certain lifetime and are transformed to high molecular mass neutral Al-species (HMM Al o) and then to non-reactive colloidal Al species (HMM Al c). Concentration levels of transient Al-species formed in the mixing zone and the rate of transformation depend on the concentrations of LMM Al i species, Al complexing ligands (DOC and Si) in the input water and on pH in the mixing zone after liming. A dynamic model describing transformation processes influencing the Al speciation in mixing zones following a sudden increase in pH is suggested. Based on the experimental results, associated rate constants and half-lives for transient Al-species were estimated.

Analysis of Toxic Aluminium Species in Natural Waters

Aluminium is known to be toxic to a wide range of aquatic organisms under certain conditions. Monomeric hydroxy ions have been found to be primarily responsible for aluminium aquatic toxicity. A survey of aluminium toxicity and a brief discussion of speciation schemes are presented. The fast reaction of Al3+ with pyrocatechol violet (PCV) followed by spectrophotometric analysis is a frequently used method for aluminium speciation. By using a flow system, one obtains fairly exact and reproducible control of the reaction time, and as a result it provides a direct method of analysis for “free” aluminium (including inorganic monomeric aluminium). The PCV-method has been adapted for the determination of aluminium in carbonate-rich natural waters using an improved buffering system. Thus it is possible to monitor aluminium concentrations in lake water as well as in pore water of the sediments of eutrophicated hardwater lakes that has been treated with aluminium salts as a restoration measure.

Sensitivity of Blacknose Dace (Rhinichthys Atratulus) to Moderate Acidification Events in Shenandoah National Park, U.S.A.

Shenandoah National Park (SNP) receives more acid deposition than any other national park in the United States of America. As part of an effort to assess the impact of acidification upon fish in the park, in situ sub-lethal stress bioassays (measured by monitoring hematocrit) were conducted with acid sensitive blacknose dace Rhinichthys atratulus. Study streams experienced moderate acidification events that resulted in reduced pH (the largest reductionbeing 6.18 to 5.37) and increased total monomeric aluminum (TMA) concentration (the largest being 15 to 39 μg L-1). Although some of these acidification events were within the pH and TMA range expected to result in blacknose dace stress, none was detected by monitoring hematocrit. In an acid-sensitive stream, mean baseflow (pre-event) hematocrit ± SD, was 33.5±4.5%, and hematocrit during the largest event was 31.5±4.9%, A moderate acidification event also occurred in a less acid sensitive stream; pH dropped from 7.18 to 6.38 but TMA remained below 10 μg L-1. Mean hematocrit during baseflowin this stream was 32.3±2.8%, and hematocrit during event flow was 34.1±5.0%. At the time of this bioassay, acidificationevents that would result in acute toxicity for most species of fish did not occur, however the conditions documented in this investigation do not represent the most acute acidification events that have been observed in SNP. It should be noted that a chronic sub-lethal stress, measured by condition indices, has been observed among blacknose dace in SNP streams.

The significance of the North Atlantic Oscillation (NAO) for sea-salt episodes and acidification-related effects in Norwegian rivers.

Acidification of Norwegian surface waters, as indicated by elevated concentrations of sulfate and a corresponding reduction in acid neutralizing capacity and pH, is a result of emission and subsequent deposition of sulfur and nitrogen compounds. Episodic sea-salt deposition during severe weather conditions may increase the effects of acidification by mobilizing more toxic aluminum during such episodes. Changes in climatic conditions may increase the frequency and strength of storms along the coast thus interacting with acidification effects on chemistry and biota. We found that the North Atlantic Oscillation (NAO) is linked to sea-salt deposition and sea-salt induced water chemistry effects in five rivers. Particularly, toxic levels of aluminum in all rivers were significantly correlated with higher NAO index values. Further, temporal trends were studied by comparing tendencies for selected statistical indices (i.e. frequency distributions) with time. The selected indices exhibited strong correlations between the NAO index, sea-salt deposition and river data such as chloride, pH and inorganic monomeric aluminum, pointing at the influence of North Atlantic climate variability on water chemistry and water toxicity. The potentially toxic effects of sea-salt deposition in rivers seem to be reduced as the acidification is reduced. This suggests that sea-salt episodes have to increase in strength in order to give the same potential negative biological effects in the future, if acid deposition is further reduced. More extreme winter precipitation events have been predicted in the northwest of Europe as a result of climate change. If this change will be associated with more severe sea-salt episodes is yet unknown.

Computational Study of Aluminum Chloride Activation for Toluene Chlorination

Aluminum chloride, in the absence of solvent and moisture, was observed to exert a negligible catalytic effect upon the chlorination of toluene, but in the presence of atmospheric moisture, a very large catalytic effect was evident. DFT calculations were performed on a number of possible intermediates involved in the chlorination process. The calculations suggest that dimeric aluminum chloride predominates in the absence of solvents or moisture, and it is not active as a catalyst. It is suggested that HCl is produced by reaction of water with the aluminum chloride leading to the formation of monomeric complexes with molecular chlorine. These complexes are believed to serve as the electrophile during catalytic toluene chlorination. The results further suggest that very strong complexes can form between water and monomeric aluminum chloride. Complexes between aluminum chloride and toluene were also identified in the calculations, but their catalytic significance remains unclear.

C−H Activation by AlCl Monomers: Characterization of HAl(Cl)CH3 as the Product of the Photoactivated Reaction Between AlCl and CH4 in a Solid Ar Matrix at 12 K

AbstractIn a solid Ar matrix at 12 K and upon photoactivation AlCl inserts into the C−H bond of CH4 to give the new monomeric aluminium hydride HAl(Cl)CH3, which was identified and characterized with the aid of the IR spectra recorded for several isotopomers [Cl(H)Al12CH3, Cl(D)Al12CD3, and Cl(H)Al13CH3], comparison with the known IR properties of related molecules and detailed quantum chemical calculations. Calculations yield a Cs symmetric global energy minimum structure for this compound, and that the reaction is slightly exothermic (reaction energy of −43.2 kJ·mol−1). This work demonstrates impressively how reactive photoactivated AlCl molecules are. (© Wiley‐VCH Verlag GmbH &amp; Co. KGaA, 69451 Weinheim, Germany, 2003)

Synthesis and structural characterization of silver(I), aluminium(III) and cobalt(II) complexes with 4-isopropyltropolone (hinokitiol) showing noteworthy biological activities. Action of silver(I)-oxygen bonding complexes on the antimicrobial activities

Through two unequivalent oxygen donor atoms of the hinokitiol (Hhino; C10H12O2; 4-isopropyltropolone) ligand that showed noteworthy biological activities, the dimeric, silver(I)-oxygen bonding complex [Ag(hino)]21, the monomeric aluminium(III) complex [Al(hino)3]·0.5H2O 4 and the cobalt(II) complex “[Co(hino)2]2 ·H2O” 6 were synthesized and characterized with elemental analysis, thermogravimetric and differential thermal analysis (TG/DTA), FTIR and solution (1H and 13C) NMR spectroscopy. The crystal structure of 1 was determined by Rietveld analysis based on X-ray powder diffraction (XPD) data and those of [Al(hino)3]·MeOH 4a and [Co(hino)2(EtOH)]26a, being obtained as yellow block crystals and red platelet crystals, respectively, by crystallization of 4 and 6, were determined by single-crystal X-ray analysis. The antimicrobial activities of 1, 4 and 6, evaluated with minimum inhibitory concentration (MIC; μg ml−1), were compared with those of other metal complexes (M=Na, Li, Cs, Ca, V, Zn) with the hino− ligand. The antimicrobial activities observed in the alkali-metal salts strongly suggested that they were attributed to the effect of the anionic hino− species. The antimicrobial activities of 1 were significantly enhanced, whereas those of other metal complexes were suppressed, compared with those of the neutral Hhino and anionic hino− molecules. The antimicrobial activities observed in 1 were comparable with those of other recently found silver(I)-oxygen bonding complexes, the ligands of which had no activity. Thus, it is proposed that the antimicrobial activities of the silver(I)-oxygen bonding complexes are due to a direct interaction or complexation of the silver(I) ion with biological ligands such as protein, enzyme and membrane, and the coordinating ligands of the silver(I) complexes play the role of a carrier of the silver(I) ion to the biological system.

Photolytically Induced Reaction of Monomeric AlCl with Dihydrogen in a Solid Ar Matrix at 12 K: Generation and Characterization of the Previously Unknown Monomeric Aluminium Hydride ClAlH2.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Photolytically Induced Reaction of Monomeric AlCl with Dihydrogen in a Solid Ar Matrix at 12 K: Generation and Characterization of the Previously Unknown Monomeric Aluminium Hydride ClAlH2

AbstractMonomeric AlCl is shown to react with H2 under photoactivation to yield the new monomeric aluminium hydride ClAlH2. The planar, C2v symmetric molecule is characterized by its IR spectra, taking in the effects of isotopic substitution (H2, D2 and HD), allied with detailed quantum chemical calculations. A normal coordinate analysis is performed to calculate accurate force constants. The properties of this species are compared to the ones of other related compounds featuring either an Al‐H or an Al‐Cl bond. Finally, the dimerization to give the D2h symmetric H2Al(μ‐Cl)2AlH2 is investigated theoretically. This dimer is of interest as a possible reagent to prepare dialane, Al2H6. The enthalpy for the reaction of H2Al(μ‐Cl)2AlH2 in the gas‐phase with solid LiAlH4 to give gaseous Al2H6 and solid LiCl is calculated.

Fascinating transformations of donor-acceptor complexes of group 13 metal (Al, Ga, In) derivatives with nitriles and isonitriles: from monomeric cyanides to rings and cages.

Formation of the donor-acceptor complexes of group 13 metal derivatives with nitriles and isonitriles X(3)M-D (M = Al,Ga,In; X = H,Cl,CH(3); D = RCN, RNC; R = H,CH(3)) and their subsequent reactions have been theoretically studied at the B3LYP/pVDZ level of theory. Although complexation with MX(3) stabilizes the isocyanide due to the stronger M-C donor-acceptor bond, this stabilization (20 kJ mol(-1) at most) is not sufficient to make the isocyanide form more favorable. Relationships between the dissociation enthalpy DeltaH degrees (298)(diss), charge-transfer q(CT), donor-acceptor bond energy E(DA), and the shift of the vibrational stretching mode of the CN group upon coordination Deltaomega(CN) have been examined. For a given metal center, there is a good correlation between the energy of the donor-acceptor bond and the degree of a charge transfer. Prediction of the DeltaH degrees (298)(diss) on the basis of the shift of CN stretching mode is possible within limited series of cyanide complexes (for the fixed M,R); in contrast, complexes of the isocyanides exhibit very poor Deltaomega(CN) - DeltaH degrees (298)(diss) correlation. Subsequent X ligand transfer and RX elimination reactions yielding monomeric (including donor-acceptor stabilized) and variety of oligomeric cage and ring compounds with [MN]n, [MC]n, [MNC]n cores have been considered and corresponding to thermodynamic characteristics have been obtained for the first time. Monomeric aluminum isocyanides X(2)AlNC are more stable compared to Al-C bonded isomers; for gallium and indium situation is reversed, in qualitative agreement with Pearson's HSAB concept. Substitution of X by CN in MX(3) increases the dissociation enthalpy of the MX(2)CN-NH(3) complex compared to that for MX(3)-NH(3), irrespective of the substituent X. Mechanisms of the initial reaction of the X transfer have been studied for the case X = R = H. The process of hydrogen transfer from the metal to the carbon atom in H(3)M-CNH is thermodynamically favorable and is likely to be intramolecular. By contrast, intramolecular hydrogen transfer in H(3)M-NCH has been definitely ruled out. Head-to-tail dimeric species [H(3)M-(NC)H](2) are formed exothermically and exhibit low H.H distances, which can assist in hydrogen transfer, and are likely to be the starting point for H(2) elimination. Elimination of H(2), CH(4), and C(2)H(6) from X(3)M-(NC)R adducts is very favorable thermodynamically; by contrast, elimination of HCl and CH(3)Cl is highly unfavorable even if formation of oligomer species takes place. Thus, high-temperature generation of gas-phase rings and clusters has been predicted viable in the cases X = H,CH(3) and their presence in the reactor media should not be neglected. Moderate stability of [HMCH(2)NH](4) clusters (especially in the cases M = Ga, In) makes these species viable intermediates of gas-phase reactions. Their formation may be responsible for the carbon contamination in the course of metal organic chemical vapor deposition processes of group 13 binary nitrides.