Lipophilicity coefficients of potential tumor imaging agents, positron-labeled O(6)-benzylguanine derivatives

Novel radiolabeled O(6)-benzylguanine (O(6)-BG) derivatives, 6-O-[(11)C]-[(methoxymethyl)benzyl]guanines ([(11)C]p-O(6)-MMBG, 1a; [(11)C]m-O(6)-MMBG, 1b; [(11)C]o-O(6)-MMBG, 1c), 2-amino-6-O-[(11)C]-[(methoxymethyl)benzyloxy]-9-methyl purines ([(11)C]p-O(6)-AMMP, 2a; [(11)C]m-O(6)-AMMP, 2b; [(11)C]o-O(6)-AMMP, 2c), 2-amino-6-O-[(11)C]-[(methoxymethyl)benzyloxy]-9-benzyl purines ([(11)C]p-O(6)-AMBP, 3a; [(11)C]m-O(6)-AMBP, 3b; [(11)C]o-O(6)-AMBP, 3c), 2-amino-6-O-benzyloxy-9-[(11)C]-[(methoxycarbonyl)methyl]purine ([(11)C]ABMMP, 4), and 2-amino-6-O-benzyloxy-9-[(11)C]-[(4'-methoxycarbonyl)benzyl]purine ([(11)C]ABMBP, 5), have been synthesized for evaluation as potential novel positron emission tomography tumor imaging agents. The ability of O(6)-BG analogs to penetrate the blood--brain barrier in brain tumor could be due, at least in part, to their lipophilicity. In this paper, we measured lipophilicity coefficients (log P) of compounds 1--5 by the C(18) HPLC method. These log P values were compared, and correlations between lipophilicity and biological activity of selected analogs were made. The results suggest the appropriate level of lipophilic character in this class of compounds as useful imaging agents appears to be in the range of 1.4--2.6.     

Adventures in crystallization. Crystalline salts containing one, two, or even three chemically distinct cations obtained from solutions of [(cyclohexyl isocyanide)(4)Rh(I)]+

By judicious selection of crystallization conditions, it has been possible to obtain the salts of a common building block, [(RNC)4Rh(I)]+, in single-crystal form suitable for X-ray diffraction. Salts that contain a single type of cation include deep green [(C6H11NC)12Rh(I)3](SbF6)3, deep green [(C6H11NC)12Rh(I)3](AsF6)3, and straw yellow [(C6H11NC)8Rh(II)2Cl2](BF4)2 (in addition to the previously isolated trimeric deep green [(i-PrNC)12RhI3]Cl3 x 4.5 H2O, monomeric, [(C6H11NC)4 Rh(I)](BPh4), and [(i-PrNC)4Rh(I)](BPh4) (both yellow), and red, dimeric [(C6H11NC)8Rh(I)2]Cl2 x 0.5C6H6 x 2H2O). Ordered crystals of [(C6H11NC)12Rh(I)3](SbF6)3 contain linear Rh3 units, while those of [(C6H11NC)12Rh(I)3](AsF6)3 show disorder which is consistent with the presence of linear or bent Rh3 units. The formation of green [(C6H11NC)12Rh(V/III)3Cl2][(C6H11NC)12Rh(I)3]Cl6, and brown [(C6H11NC)12Rh(V/III)3Cl2][(C6H11NC)8Rh(I)2][(C6H11NC)4RhI]Cl6 x 16H2O x 3C6H6 along with unidentified red-brown cubes from an air-exposed solution of [(C6H11NC)4Rh(I)]Cl is reported. As their formulas indicate, green [(C6H11NC)12Rh(V/III)3Cl2][(C6H11NC)12Rh(I)3]Cl6, and brown [(C6H11NC)12Rh(V/III)3Cl2][(C6H11NC)8Rh(I)2][(C6H11NC)8Rh(I)]Cl6 x 16H2O x 3C6H6 contain two or three chemically distinct cations, respectively, but again are built from a common precursor, [(C6H11NC)4Rh(I)]+.     

Synthesis and application of isocyanates radiolabeled with carbon-11

Carbon-11 labeled isocyanates are efficiently prepared by dehydration of [(11) C]carbamate salts, which in turn are easily formed from cyclotron-produced [(11) C]CO(2) and amines in the presence of a CO(2) fixation agent. The [(11) C]isocyanates are useful radiosynthons for the synthesis of a variety of [carbonyl-(11) C]-labeled asymmetrical ureas and carbamate esters. The method is well suited to incorporate any isotope of carbon, and is especially useful for positron emission tomography (PET) radiotracers for in vivo imaging. This is demonstrated by using the method to make [carbonyl-(11) C]-6-hydroxy-[1,1'-biphenyl]-3-yl cyclohexylcarbamate which is a novel radiotracer for PET imaging of fatty acid amide hydrolase.     

Microfluidic reactions using [11C]carbon monoxide solutions for the synthesis of a positron emission tomography radiotracer

Microfluidic technology has been used to perform [(11)C]carbonylation reactions using solutions containing [(11)C]CO in the form of the complex, copper(i)tris(3,5-dimethylpyrazolyl)borate-[(11)C]carbonyl (Cu(Tp*)[(11)C]CO). The synthesis of the model compound [(11)C]N-benzylbenzamide and the known tracer molecule [(11)C]trans-N-[5-(2-flurophenyl)-2-pyrimidinyl]-3-oxospiro[5-azaisobenzofurane-1(3H),1'-cyclohexane]-4'-carboxamide ([(11)C]MK-0233), a ligand for the neuropeptide Y Y5 receptor, have been performed using this technique. Following semi-preparative HPLC purification and reformulation, 1262 ± 113 MBq of [(11)C]MK-0233 was produced at the end of the synthesis with a specific activity of 100 ± 30 GBq μmol(-1) and a >99% radiochemical purity. This corresponds to a decay corrected radiochemical yield of 7.2 ± 0.7%. Using a 3 mL vial as the reaction vessel, and following semi-preparative HPLC purification and reformulation, 1255 ± 392 MBq of [(11)C]MK-0233 was produced at the end of the synthesis with a specific activity of 100 ± 15 GBq μmol(-1) and a >99% radiochemical purity. This corresponds to a decay corrected radiochemical yield of 7.1 ± 2.2%.     

Cu(I)-catalyzed (11)C carboxylation of boronic acid esters: a rapid and convenient entry to (11)C-labeled carboxylic acids, esters, and amides

Rapid and direct: the carboxylation of boronic acid esters with (11)CO(2) provides [(11)C]carboxylic acids as a convenient entry into [(11)C]esters and [(11)C]amides. This conversion of boronates is tolerant to diverse functional groups (e.g., halo, nitro, or carbonyl).     

Photoinitiated carbonylation with [(11)C]carbon monoxide using amines and alkyl iodides

Photoinitiated radical carbonylation with [(11)C]carbon monoxide at low concentration was employed in syntheses of carbonyl-(11)C-labeled amides using alkyl iodides and amines as precursors. Eleven (11)C-amides were synthesized in up to 74% decay-corrected radiochemical yields with reaction times of 400 s and with up to 95% conversion of carbon monoxide. Starting with 26.3 GBq of [(11)C]carbon monoxide, 10.6 GBq of 1-cyclohexane [(11)C]carbonyl-4-phenyl-piperazine (15) was obtained within 35 min from the end of bombardment (33 microA) and with a specific radioactivity of 192 GBq/micromol at the same time point. The influence of solvents was investigated. The described procedure extends the range of accessible labeling methods. The method may also be useful for preparation of (13)C- and (14)C-substituted compounds.     

Variation in crystallization conditions allows the isolation of trimeric as well as dimeric and monomeric forms of [(alkyl isocyanide)4RhI]+

Trimeric green [(i-PrNC)12Rh(I)3]Cl3.4.5H2O, monomeric [(C6H11NC)4Rh(I)](BPh4) and [(i-PrNC)4Rh(I)](BPh4) (both yellow), and red, dimeric [(C6H11NC)8Rh(I)2]Cl2.0.5C6H6.2H2O have been crystallized.     

An extended planar C5 conformation and a 310-helical structure of peptide foldamer composed of diverse alpha-ethylated alpha,alpha-disubstituted alpha-amino acids

Optically active peptide foldamers Tfa-[(S)-(alphaEt)Leu]-[(S)-(alphaEt)Nva]-Deg-[(S)-(alphaEt)Nle]-OEt (10) and Tfa-[(S)-(alphaEt)Val]-[(S)-(alphaEt)Leu]-[(S)-(alphaEt)Nva]-Deg-[(S)-(alphaEt)Nle]-OEt (11) composed of diverse alpha-ethylated alpha,alpha-disubstituted alpha-amino acids were synthesized. The dominant conformation of these peptides in solution was an unusual, fully extended planar conformation, and that in the crystal state was both right-handed (P) and left-handed (M) 3(10)-helical structures in 10 and a P 3(10)-helical structure in 11, respectively. The preferred planar C(5) conformation of the peptides prepared from chiral alpha-ethylated alpha,alpha-disubstituted alpha-amino acids was drastically different from the 3(10)-helical structure of the peptides prepared from chiral alpha-methylated alpha,alpha-disubstituted alpha-amino acids.     

(11)C] Carbon monoxide in selenium-mediated synthesis of (11)C-carbamoyl compounds

Using either amines, amino alcohols, or alcohols in selenium-mediated synthesis with [(11)C]carbon monoxide, 3 ureas, 6 carbamates, and 1 carbonate were labeled. Tetrabutylammonium fluoride ((TBA)F) was discovered to form a soluble and reactive complex with selenium and drastically increase the radiochemical yields. Of the selected carbamoyl compounds, one was a receptor ligand, one was an enzyme inhibitor, and one was a muscular relaxant pharmaceutical. The (11)C-target compounds were obtained in radiochemical yields ranging from low to almost quantitative and with specific radioactivity up to 1300 GBq/micromol. The radiochemical purity of the final products exceeded 98%. In one case, the corresponding (13)C-substituted compound was produced to verify the position of the (11)C-label. In a typical experiment starting with 16.4 GBq [(11)C]carbon monoxide, 7.0 GBq of LC-purified 5-phenyl-1,3-oxazolidin-[2-(11)C]-2-one was obtained within 20 min from start of the carbonylation reaction (84% decay-corrected radiochemical yield). The presented approach is an interesting alternative to the use of [(11)C]phosgene in labeling chemistry.     

Aryl triflates and [11C]/(13C)carbon monoxide in the synthesis of 11C-/13C-amides

Palladium(0)-mediated carbonylation reactions using aryl triflates, amines, and a low concentration of [(11)C]carbon monoxide were used in the syntheses of 13 (11)C-labeled amides. Lithium bromide was used as an additive to facilitate the reaction. The (11)C-labeled products were obtained with decay-corrected radiochemical yields in the range of 2-63%. The radiochemical purity of the final products exceeded 98%. As an example, a reaction starting with 1.79 GBq [(11)C]carbon monoxide gave 0.38 GBq of LC-purified N-isopropyl-4-nitro-[(11)C]benzamide within 27 min from the start of the carbonylation reaction (54% decay-corrected radiochemical yield). The specific radioactivity of this compound was 191 GBq/micromol, 35 min after the end of a 10 microAh bombardment. N-Benzylisoquinoline-1-((13)C)carboxamide was prepared and analyzed by NMR for confirmation of the labeling position. The triflates 16, 20, 21, and 22 were synthesized from the corresponding alcohols and trifluoromethanesulfonic anhydride. The reference compounds 30a and 30b were prepared from the corresponding carboxylic acids and benzylamine. The other nine reference compounds 32a to 32i were synthesized from the respective acid chlorides and amines. The presented report shows that the sometimes more easily obtainable aryl triflates can be a useful alternative to the commonly used aryl halides in palladium(0)-mediated synthesis of (11)C/(13)C-amides.     

Metallaboranes of the Early Transition Metals: Direct Synthesis and Characterization of [{(eta5-C5Me5)Ta}2BnHm] (n=4, m=10; n=5, m=11), [{(eta5-C5Me5)Ta}2B5H10(C6H4CH3)], and [{(eta5-C5Me5)TaCl}2B5H11

Reaction of [Cp*TaCl4] (Cp*=eta5-C5Me5) with a sixfold excess of LiBH(4)thf followed by BH3thf in toluene at 100 degrees C led to the isolation of hydrogen-rich metallaboranes [(Cp*Ta)2B4H10] (1), [(Cp*Ta)2B5H11] (2), [(Cp*Ta)2B5H10(C6H4CH3)] (3), and [(Cp*TaCl)2B5H11] (4) in modest yield. Compounds 1-3 are air- and moisture-sensitive but 4 is reasonably stable in air. Their structures are predicted by the electron-counting rules to be a bicapped tetrahedron (1), bicapped trigonal bipyramids (2, 3), and a nido structure based on a closo dodecahedron 4. Yellow tantalaborane 1 has a nido geometry with C2v symmetry and is isostructural with [(Cp*M)2B4H8] (M=Cr and Re); whereas 2 and 3 are C3v-symmetric and isostructural with [(Cp*M)2B5H9] (M=Cr, Mo, W) and [(Cp*ReH)2B5Cl5]. The most remarkable feature of 4 is the presence of a hydride ligand bridging the ditantalum center to form a symmetrical tantalaborane cluster with a long Ta--Ta bond (3.22 A). Cluster 4 is a rare example of electronically unsaturated metallaborane containing four TaHB bonds. All these new metallaboranes have been characterized by mass spectrometry, 1H, 11B, and 13C NMR spectroscopy, and elemental analysis, and the structural types were unequivocally established by crystallographic analysis of 1-4.     

Guest driven rearrangements of protonation and hydrogen bonding in decavanadate anions as their tetraalkylammonium salts

Single crystal X-ray structure determinations of [(n-C5H11)4N]3[H3V10O28].2(CH3)2CO (TAA-acetone), [(n-C5H11)4N]8[H3V10O28]2[H4V10O28].7C4H8O2 (TAA-dioxane), [(n-C5H11)4N]3[H3V10O28] (TAAh) and [(n-C6H13)4N]2[H4V10O28].4C4H8O2 (THA-dioxane) revealed that protonation and hydrogen bond formation of decavanadate anions in their tetraalkylammonium salts are influenced by the nature of the solvent molecules incorporated as guests into the crystals. When crystallized with acetone molecules, the decavanadate anion forms a self-associated hydrogen-bonded dimer of ([H3V10O28](3-))2 to hide the protons from the aprotic protophobic acetone molecules. When crystallized with 1,4-dioxane molecules, the decavanadate anion exposes its protons to the aprotic protophilic 1,4-dioxane molecules to form a hydrogen-bond assisted solvation complex of ((C4H8O2)4...[H4V10O28)](2-)). Size effects of the tetraalkylammonium cations on crystallizing these hydrogen-bonded assemblies were also examined.     

Formation of a bridging planar trimethylenemethane dianion from a neopentyl precursor via sequential beta-alkyl elimination and C-H activation

The reaction of neopentyllithium, Me3CCH2Li, with [(C5Me5)2Sm][(mu-Ph)2BPh2], 1, was investigated as a route to the unsolvated alkyl, [(C5Me5)2Sm(CH2CMe3)]x, and found to generate the first f element trimethylenemethane dianion complex, [(C5Me5)2Sm]2[mu-eta3:eta3-C(CH2)3], 2. Formation of the [C4H6]2- trimethylenemethane ligand from the [C5H11]1- neopentyl precursor can be explained by a combination of a beta-methyl elimination reaction to form isobutene and [(C5Me5)2SmMe]3, 3, with subsequent C-H activation reactions. This sequence has been modeled in several ways, including the synthesis of 2 from reactions of 3 with CH2=CMe2 and 3 with the 2-methylallyl complex, (C5Me5)2Sm[CH2C(Me)CH2], 4.     

Biosynthetic pathways to isocyanides and isothiocyanates; precursor incorporation studies on terpene metabolites in the tropical marine sponges Amphimedon terpenensis and Axinyssa n.sp

The biosynthetic origins of the isocyanide and isothiocyanate functional groups in the marine sponge metabolites diisocyanoadociane (1), 9-isocyanopupukeanane (10) and 9-isothiocyanatopupukeanane (11) are probed by the use of [(14)C]-labelled precursor experiments. Incubation of the sponge Amphimedon terpenensis with [(14)C]-labelled thiocyanate resulted in radioactive diisocyanoadociane (1) in which the radiolabel is specifically associated with the isocyanide carbons. As expected, cyanide and thiocyanate were confirmed as precursors to the pupukeananes 10 and 11 in the sponge Axinyssa n.sp.; additionally these precursors labelled 2-thiocyanatoneopupukeanane (12) in this sponge. To probe whether isocyanide-isothiocyanate interconversions take place at the secondary metabolite level, the advanced precursor bisisothiocyanate 17 was supplied to A. terpenensis, but did not result in significant labelling in the natural product isocyanide 1. In contrast, in the sponge Axinyssa n.sp., feeding of [(14)C]-9-isocyanopupukeanane (10) resulted in isolation of radiolabelled 9-isothiocyanatopupukeanane 11, while the feeding of [(14)C]-11 resulted in labelled isocyanide 10. These results show conclusively that isocyanides and isothiocyanates are interconverted in the sponge Axinyssa n.sp., and confirm the central role that thiocyanate occupies in the terpene metabolism of this sponge.     

Radical-mediated carboxylation of alkyl iodides with [11C]carbon monoxide in solvent mixtures

[reaction: see text] [carboxyl-(11)C]Carboxylic acids were prepared from alkyl iodides via photoinitiated radical reactions using 10(-)(8) mol of [(11)C]carbon monoxide in binary and ternary homogeneous solvent mixtures. Short- (isobutyric), medium-, and long-chain saturated fatty acids (heptadecanoic) were labeled with isolated decay-corrected radiochemical yields ranging from 55% to 70% in 5-7-min reactions. The conversion of [(11)C]carbon monoxide to products reached 80-90%. To obtain good yields in the reactions performed in water-acetonitrile and water-THF mixtures, the addition of tetrabutylammonium hydroxide or potassium hydroxide was essential. The carboxylation was efficient for primary and secondary alkyl iodides. The carboxylation of tertiary iodides was feasible for 1-iodoadamantane but not for tert-butyl iodide. The dependence of the radiochemical yields on reaction time, photoirradiation conditions, and organic and inorganic additives was studied. The method provides a one-step route to [carboxyl-(11)C]carboxylic acids; traditional methods, in contrast, would require several steps. For example, using the devised reaction conditions, 3.19 GBq of purified [1-(11)C]1,10-decanedicarboxylic acid (specific radioactivity 188 GBq/mumol) was obtained within 35 min of the end of 10 muAh bombardment. (1-(13)C)4-Phenylbutyric acid was synthesized using ((13)C)carbon monoxide for identifying the labeling position with (1)H and (13)C NMR.     

Synthesis, characterisation and reactivity of germanium(II) amidinate and guanidinate complexes

Reactions of lithium salts of the bulky guanidinate ligands, [ArNC(NR2)NAr](-) (NR2 = N(C6H11)2 (Giso-) and cis-NC5H8Me2-2,6 (Pipiso-); Ar = C6H3Pri2-2,6), with GeCl2.dioxane afforded the heteroleptic germylenes, [(Giso)GeCl] and [(Pipiso)GeCl], the former of which was structurally characterised. The further reactivity of these and the related complexes, [(Piso)GeCl] and [(Priso)GeCl] (Piso- = [ArNC(Bu(t))NAr]-, Priso- = [ArNC(NPri2)NAr]-) has been investigated. Salt elimination reactions have yielded the new monomeric complexes, [(Piso)Ge(NPri2)] and [(Piso)GeFeCp(CO)2], whilst a ligand displacement reaction afforded the heterometallic species, [(Piso)Ge(Cl)(W(CO)5)]. Chloride abstraction from [(Priso)GeCl] with GaCl3 has given the structurally characterised contact ion pair, [(Priso)Ge][GaCl4]. In addition, the inconclusive outcome of a number of attempts to reduce the germanium halide complexes are discussed.     

Biosynthetic pathways to dichloroimines; precursor incorporation studies on terpene metabolites in the tropical marine sponge Stylotella aurantium

The biosynthetic origin of the dichloroimine functional group in the marine sponge terpene metabolites stylotellanes A (3) and B (4) was probed by the use of [(14)C]-labelled precursor experiments. Incubation of the sponge Stylotella aurantium with [(14)C]-labelled cyanide or thiocyanate resulted in radioactive terpenes in which the radiolabel was shown by hydrolytic chemical degradation to be associated specifically with the dichloroimine carbons. Additionally, label from both precursors was incorporated into farnesyl isothiocyanate (2). A time course experiment with [(14)C]-cyanide revealed that the specific activity for farnesyl isothiocyanate decreases over time, but increases for stylotellane B (4), consistent with the rapid formation of farnesyl isothiocyanate (2) from inorganic precursors followed by a slower conversion to stylotellane B (4). The advanced precursors farnesyl isothiocyanate (2) and farnesyl isocyanide (5) were supplied to S. aurantium, and shown to be incorporated efficiently into stylotellane A (3) and B (4). Feeding of [(14)C]-farnesyl isothiocyanate (2) resulted in a higher incorporation of label than with [(14)C]-farnesyl isocyanide (5). Farnesyl isocyanide was incorporated into farnesyl isothiocyanate in agreement with labelling studies in other marine sponges. Both farnesyl isocyanide and isothiocyanate were further incorporated into axinyssamide A (11) as well as the cyclized dichloroimines (12)-(14), (16) that represent more advanced biosynthetic products of this pathway. These results identify the likely biosynthetic pathway leading to the major metabolites of S. aurantium.     

Synthesis and structural characterization of new divanada- and diniobaboranes containing chalcogen atoms

The reaction of [Cp(n) MCl(4-x) ] (M=V: n=2, x=2; M=Nb: n=1, x=0; Cp=η(5) -C(5) H(5) ) with LiBH(4) ?THF followed by thermolysis in the presence of dichalcogenide ligands E(2) R(2) (E=S, Te; R=2,6-(tBu)(2) -C(6) H(2) OH, Ph) and 2-mercaptobenzothiazole (C(7) H(5) NS(2) ) yielded dimetallaheteroboranes [{CpV(μ-TePh)}(2) (μ(3) -Te)BH?thf] (1), [(CpV)(2) (BH(3) S)(2) ] (2), [(CpNb)(2) B(4) H(10) S] (3), [(CpNb)(2) B(4) H(11) S(tBu)(2) C(6) H(2) OH] (4), and [(CpNb)(2) B(4) H(11) TePh] (5). In cluster 1, the V(2) BTe atoms define a tetrahedral framework in which the boron atom is linked to a THF molecule. Compound 2 can be described as a dimetallathiaborane that is built from two edge-fused V(2) BS tetrahedron clusters. Cluster 3 can be considered as an edge-fused cluster in which a trigonal-bipyramidal unit (Nb(2) B(2) S) has been fused with a tetrahedral core (Nb(2) B(2) ) by means of a common Nb(2) edge. In addition, thermolysis of an in-situ-generated intermediate that was produced from the reaction of [Cp(2) VCl(2) ] and LiBH(4) ?THF with excess BH(3) ?THF yielded oxavanadaborane [(CpV)(2) B(3) H(8) (μ(3) -OEt)] (6) and divanadaborane cluster [(CpV)(2) B(5) H(11) ] (7). Cluster 7 exhibits a nido geometry with C(2v) symmetry and it is isostructural with [(Cp*M)(2) B(5) H(9+n) ] (M=Cr, Mo, and W, n=0; M=Ta, n=2; Cp*=η(5) -C(5) Me(5) ). All of these new compounds have been characterized by (1) H?NMR, (11) B?NMR, and (13) C?NMR spectroscopy and elemental analysis and the structural types were established unequivocally by crystallographic analysis of compounds?1-4, 6, and 7.     

有机膦、胂、(月弟)合钨、钼聚多酸盐的研究 Ⅳ.烷基膦合钼聚多酸盐的制备

本文是作者在合成了一系列有机胂、有机(月弟)的钨、钼聚多酸盐后,有关若干有机膦合钼聚多酸“柄状”化合物的合成报导以及一些光学性质的测定。有关有机基团是C_2H_5,n-C_3H_7,n-C_4H_9,n-C_5H_(11)及C_6H_5CH_2。发现pH为3～5时,在不同的投料比例下都只形成一种类型的化合物[(RP)_2Mo_5O_(21)]~(4-),与相应的有机胂衍生物既可形成[(RAs)_2Mo_5O_(21)]~(4-)又可形成[(RAs)_2Mo_6O_(24)]~(4-)有较大的差异。     

Boron and aluminum complexes of sterically demanding phosphinimines and phosphinimides

Reactions of sterically demanding phosphinimines R3PNH [R=i-Pr (1), t-Bu (2)] were examined. Reactions with B(C6F5)3 formed the adducts (R3PNH)B(C6F5)3 [R=i-Pr (3), t-Bu (4)] in high yield. On the other hand, 2 reacts with HB(OBu)2, evolving H2 to give t-Bu3PNB(OBu)2 (5). The reaction of 2 equiv of 2 with BH3.SMe2 affords the species (t-Bu3PN)2BH (6). In contrast, the reaction of n-Bu(t-Bu)2PNH with BH3.SMe2 results in the formation of the robust adduct n-Bu(t-Bu)2PNH.BH3 (8). An alternative route to borane-phosphinimide complexes involves Me3SiCl elimination, as exemplified by the reaction of BCl2Ph with n-Bu3PNSiMe3, which gives the product n-Bu3PNBCl(Ph) (9). The corresponding reactions of the parent phosphinimines 1 and 2 with AlH3.NMe2Et give the dimers [(mu-i-Pr3PN)AlH2]2 (10) and [(mu-t-Bu3PN)AlH2]2 (11). Species 11 reacts further with Me3SiO3SCF3 to provide [(mu-t-Bu3PN)AlH(OSO2CF3)]2 (12). The reaction of the lithium salt [t-Bu3PNLi]4 (13) with BCl3 proceeds smoothly to give t-Bu3PNBCl2 (14), which is readily alkylated to give t-Bu3PNBMe2 (15). Subsequent reaction of 15 with B(C6F5)3 results in methyl abstraction and the formation of [(mu-t-Bu3PN)BMe]2[MeB(C6F5)3]2 (16). The reaction of 13 in a 2:1 ratio with BCl3 gives the salt [(t-Bu3PN)2B]Cl (17). This species can be methylated to give (t-Bu3PN)2BMe (18), which undergoes subsequent reaction with [Ph3C][X] (X=[B(C6F5)4], [PF6]) to form the related salts [(t-Bu3PN)2B][B(C6F5)4] (19) and [(t-Bu3PN)2B][PF6] (20), respectively. Analogous reactions with [Ph3C][BF4] afforded [t-Bu3PNBF2]2 (21). Compounds 3, 4, 6, 8, 11, 12, 17, 19, and 21 were characterized by X-ray crystallography.