Regioselective Cobalt(II) Catalyzed C-H Functionalization and [3 + 2] Annulation of N-Arylguanidines with 1,3-Diynes.

8-Quinolinyl directed N-arylguanidines were subjected to cobalt(II) catalyzed C-H functionalization/1,3-diyne annulation under mild conditions to afford 40 alkynylated indole guanidines in 34% to 92% yields. The scope of the substrates was explored. The reported procedure is mostly regioselective and tolerates various functional groups in the substrates. The regioselectivity of the reactions was assessed with the aid of multinuclear NMR spectroscopy and X-ray crystallography. Competition and labeling experiments were carried out to support the proposed mechanism.

Syntheses, structural, photophysical and theoretical studies of heteroleptic cycloplatinated guanidinate(1-) complexes bearing acetylacetonate and picolinate ancillary ligands.

Cycloplatination of symmetrical N,N',N''-triarylguanidines, (ArNH)2C[double bond, length as m-dash]NAr with cis-[Pt(TFA)2(S(O)Me2)2] in toluene afforded cis-[Pt(TAG)(TFA)(S(O)Me2)] (TAG = triarylguanidinate(1-)-κC,κN; TFA = OC(O)CF3; 6-9) in 75-82% yields. The reactions of 6-9 and the previously known cis-[Pt(TAG)X(S(O)Me2)] (X = Cl (1) and TFA (2-5)) with acetylacetone (acacH) or 2-picolinic acid (picH) in the presence of a base afforded [Pt(TAG)(acac)] (acac = acetylacetonate-κ2O,O'; 10-18) and [Pt(TAG)(pic)] (pic = 2-picolinate-κN,κO; 19) in high yields. The new complexes were characterised by analytical, IR and multinuclear NMR spectroscopies. Further, molecular structures of 11, 12, 13·0.5 toluene and 14-19 were determined by single crystal X-ray diffraction. Absorption spectra of 10-19 in solution and their emission spectra in crystalline form were measured. Platinacycles 10-19 are bluish green light emitter in the crystalline form, and emit in the λPL = 488-529 nm range (11 and 13-19) while 12 emits at λPL = 570 nm. Unlike other platinacycles, the emission band of 12 is broad, red shifted, and this pattern is ascribed to the presence of an intermolecular N-H⋯Pt interaction involving the endocyclic amino unit of the six-membered [Pt(TAG)] ring and the Pt(ii) atom in the adjacent molecule in an asymmetric unit of the crystal lattice. Lifetime measurements were carried out for all platinacycles in crystalline form, which revealed lifetime in the order of nanoseconds. The origin of absorption and emission properties of 11, 15, 18 and 19 were studied by TD-DFT calculations.

Influence of the Steric/Electronic Properties of N-Aryl Substituents in Cycloplatinated Guanidinate(1-) Complexes on the Formation of Discrete Pt → Ag Complexes and One-Dimensional Coordination Polymer.

The reactions of cycloplatinated guanidinate(1-) complexes 1-6 with AgTFA (TFA = OC(O)CF3) in 1:1 and 1:2 PtII/AgI molar ratios afforded complexes containing three types of Pt2Ag2 skeletons (7-10, 11, and 13), one 1D CP containing Pt2Ag3 skeleton (16), and a Pt2Ag4 complex (17) in 91-95% (method 1), 73-82% (method 2) (7-10), and 54-79% (11, 13, 16, and 17) yields. The reactions of 11 with 2,6-XylNC (2,6-Xyl = 2,6-Me2C6H3) and 4-DMAP (4-dimethylaminopyridine) gave a neutral complex 18 and an ionic complex 19, respectively. Molecular structures of 12 complexes were unambiguously determined by single-crystal X-ray diffraction. Ten complexes contain unprecedented PtAg skeletons and are shown to contain multiple number of dative Pt → Ag bonds supported by the TFA ligand, platinated carbon of the TAG ligand, or both these ligands in conjunction with the Ag-Ag contacts stabilized by argentophilic interaction. Further, the new complexes were characterized by analytical, IR, and multinuclear NMR (19F, 1H, 13C{1H}, and 195Pt) spectroscopies, powder X-ray diffraction, and TGA/DTA. In solution, 9 and 19 exist in more than one form as identified by multinuclear NMR, and this behavior is ascribed to the restricted (N2)C-N(H)Ar single-bond rotation of the TAG ligand. The photophysical properties of 9 and 11 are reported.

Cobalt(II)-Catalyzed Directed C-H Functionalization/[3+2] Annulation of N-Arylguanidines with Alkynes.

A family of N,N'-diaryl-N″-(quinolin-8-yl)guanidines were prepared by two methods, and these guanidines were subjected to Co(II)-catalyzed C-H functionalization/annulation with terminal and internal alkynes under mild conditions to afford a family of indole guanidines. Substrates with a range of electronic and steric properties were tolerated. The fluxional behavior of two guanidines and molecular structures of nine compounds are reported. Several key experiments were carried out to support the proposed mechanism of alkyne annulation.

Reactions of Cycloplatinated Guanidine Complexes with Hg(OC(O)CF3)2: Formation of a One-Dimensional Coordination Polymer Containing a Pt2Hg(µ2-S(O)Me2-S,O) Repeating Unit versus a Discrete Pt2Hg2 Complex.

Separate reactions of cycloplatinated 2-tolyl- and 2-anisylguanidine complexes, [Pt{κ2(C,N)}(OC(O)CF3)(S(O)Me2)] (1 and 2), with Hg(OC(O)CF3)2 in 1:0.5 and 1:1 molar ratios afforded the one-dimensional coordination polymer (1D CP) {[PtIII{κ2(C,N)}(OC(O)CF3)2]2Hg0}(µ2-S(O)Me2-S,O)·C7H8 (3·C7H8) as bright red crystals and the discrete tetrametallic complex [PtII{κ2(C,N)}(µ2-OC(O)CF3)2HgI-]2 (4) as yellow crystals in good yields. The two different products obtained in the aforementioned reactions are ascribed to the subtle differences in the N substituent of the guanidinate(1-) ligands in 1 and 2. The plausible mechanisms of formation of 3 and 4 are outlined. Complexes 3 and 4 were characterized by elemental analyses and IR and multinuclear NMR (1H, 13C{1H}, 19F, and 195Pt) spectroscopy. Complex 4 was also characterized by 199Hg NMR spectroscopy. The molecular structures of 3·C7H8 and 4 were determined by single-crystal X-ray diffraction studies. 1D CP 3·C7H8 contains a Pt(III)-Hg(0)-Pt(III)(µ2-S(O)Me2-S,O) repeating unit with a pair of unsupported Pt-Hg covalent bonds, while 4 contains a Pt(II)-Hg(I)-Hg(I)-Pt(II) chain with a pair of trifluoroacetate ligand supported Pt→Hg coordinate bonds. 1D CP 3·C7H8 falls apart into a mixture of three species, namely 6-8 and 9-11 in C6D6 and CDCl3, respectively, as revealed by multinuclear NMR spectroscopy. In CDCl3, 4 partially isomerizes to [PtII(OC(O)CF3)(µ2-OC(O)CF3){κ3µ2(C,N,O)}HgI-]2 (12), wherein each Pt→Hg coordinate bond is supported by one µ2-bridging trifluoroacetate ligand and one chelating bridging guanidinate(1-) ligand, as inferred from variable-temperature 1H and 19F NMR spectroscopy. Complex 12 is the major species and 4 is the minor species in CDCl3, while opposite situation prevails in C6D6. The observance of a mixture of two solution species for 4 is ascribed to a rapid "carboxylate shift" process induced by the oxygen atom of the ═N(C6H4(OMe)-2) unit of the guanidinate(1-) ligand through neighboring-group participation. UV-visible absorption and emission spectra of 4 were measured in CHCl3, and from the outcome of the investigation, the possible existence of [Cl2(H)C-Cl···PtII(OC(O)CF3)(µ2-OC(O)CF3){κ3µ2(C,N,O)}HgI-]2 (12″) was suggested, which is likely to have a pair of Pt-Hg covalent bonds made possible by CHCl3 coordination on the sixth site of the Pt(II) atom.

Critical Role of Anions in Platinum(II) Precursors upon the Structural Motifs of Six-Membered Cycloplatinated N,N',N″-Triarylguanidines.

The reactions of cis-[Pt(OAc)2(DMSO)2] with 2 equiv of sym N,N',N″-triarylguanidines, [ArN=C(NHAr)2], in toluene under reflux condition for 8 h afforded six-membered cycloplatinated guanidines, [Pt{κ2(C,N)}(OAc){κ1 N(ArN=C(NHAr)2)}] [sym = symmetrical; Ar = 2-MeC6H4 (1) and 2,4-Me2C6H3 (2)], in 82 and 84% yields, respectively. The salt metathesis reaction of 1 with 1 equiv of AgTFA in CH2Cl2 at room temperature (RT) afforded [Pt{κ2(C,N)}(TFA){κ1 N(ArN=C(NHAr)2)}] (3) in 94% yield. The reaction of cis-[Pt(TFA)2(DMSO)2] with 1 equiv of [ArN=C(NHAr)2] in toluene under reflux condition for 8 h afforded six-membered cycloplatinated guanidines, [Pt{κ2(C,N)}(TFA)(DMSO)] [Ar = 2-MeC6H4 (4), 4-MeC6H4 (5), 2,4-Me2C6H3 (6), and 2-(MeO)C6H4 (7)], in ≥73% yields. The reaction of trans-[PtCl2(PhCN)2] with 2 equiv of [ArN=C(NHAr)2] in toluene under reflux condition for 48 h afforded trans-[PtCl2{ArN=C(NHAr)2}2] [Ar = 2-MeC6H4 (8) and 2,4-Me2C6H3 (9)] in 90 and 45% yields, respectively. Complexes 8 and 9 were separately refluxed in MeOH for 8 h to afford six-membered cycloplatinated guanidines, [Pt{κ2(C,N)}(µ-Cl)]2 (10 and 11), in 93 and 96% yields, respectively, with concomitant formation of the respective guanidinium salts, [(ArNH)3C]Cl, as the byproduct. Platinacycle 10 was treated with 2 equiv of AgTFA in CH2Cl2 at RT to afford six-membered cycloplatinated guanidine, [Pt{κ2(C,N)}(µ-TFA)]2 (12), in 94% yield. The new compounds were characterized by analytical techniques and multinuclear NMR (1H, 13C, and 195Pt) spectroscopy, and further, molecular structures of 10 compounds were determined by single-crystal X-ray diffraction. The structural motif in 1·1/2CH2Cl2 and 3 is novel in that it contains a planar six-membered [Pt{κ2(C,N)}] unit and a nonplanar eight-membered [Pt{κ2(N,O)}] ring, wherein OAc and the guanidine ligands are linked through a N-H···O hydrogen bond. The six-membered cycloplatinated structural motifs present in 10/11·C7H8 and 12·CH2Cl2 are also unprecedented in the literature. The number and nature of solution species of new complexes were unambiguously investigated by detailed NMR studies. The critical role of anions in Pt(II) precursors upon the course of cycloplatination and thus the motifs in the products were addressed. Plausible mechanisms of cycloplatination reactions are discussed.

Dual role of acetate as a nucleophile and as an internal base in cycloplatination reaction of sym-N,N',N″-triarylguanidines.

Reaction of cis-[Cl(2)Pt(S(O)Me(2))(2)] with 1 equiv of sym-N,N',N″-triarylguanidines, ArN═C(NHAr)(2) (sym = symmetrical; Ar = 2-MeC(6)H(4) (LH(2)(2-tolyl)), 2-(MeO)C(6)H(4) (LH(2)(2-anisyl)), 4-MeC(6)H(4) (LH(2)(4-tolyl)), 2,5-Me(2)C(6)H(3) (LH(2)(2,5-xylyl)), and 2,6-Me(2)C(6)H(3) (LH(2)(2,6-xylyl))) in toluene under reflux condition for 3 h afforded cis- or trans-[Cl(2)Pt(S(O)Me(2))(ArN═C(NHAr)(2))] (Ar = 2-MeC(6)H(4) (1), 2-(MeO)C(6)H(4) (2), 4-MeC(6)H(4) (3), 2,5-Me(2)C(6)H(3) (4), and 2,6-Me(2)C(6)H(3) (5), respectively) in 83-96% yield. Reaction of cis-[Cl(2)Pt(S(O)Me(2))(2)] with 1 equiv of LH(2)(2-tolyl) and LH(2)(4-tolyl) in the presence of 1 equiv of NaOAc in methanol under reflux condition for 3 h afforded acetate-substituted products, cis-[(AcO)ClPt(S(O)Me(2))(ArN═C(NHAr)(2))] (Ar = 2-MeC(6)H(4) (6) and 4-MeC(6)H(4) (7)) in 83% and 84% yields, respectively. Reaction of cis-[Cl(2)Pt(S(O)Me(2))(2)] with 1 equiv of LH(2)(2-anisyl) and LH(2)(2-tolyl) in the presence of 1 equiv of NaOAc in methanol under reflux condition for 3 and 12 h afforded six-membered [C,N] platinacycles, [Pt{κ(2)(C,N)-C(6)H(3)R-3(NHC(NHAr)(═NAr))-2}Cl(S(O)Me(2))] (Ar = 2-RC(6)H(4); R = OMe (8) and Me (9)), in 92% and 79% yields, respectively. The new complexes have been characterized by analytical and spectroscopic techniques, and further the molecular structures of 1, 2, 4, 5, 6, and 8 have been determined by single-crystal X-ray diffraction. The platinum atom in 1, 4, and 5 exhibited the trans configuration, while that in 2, 6, and 8 exhibited the cis configuration. Complex 6 is shown to be the precursor for 9, and the former is suggested to transform to the latter possibly via an intramolecular C-H activation followed by elimination of AcOH. The solution behavior of new complexes has been studied by multinuclear NMR ((1)H, (195)Pt, and (13)C) spectroscopy. The new complexes exist exclusively as a single isomer (trans (1 and 5) and cis (6 and 7)), a mixture of cis and trans isomers with the former isomer being predominant in the case of 2 and the latter isomer being predominant in the case of 3. Complex 5 in the trans form revealed the presence of one isomer at 0.007 mM concentration and two isomers in about 1.00:0.12 ratio at 0.154 mM concentration as revealed by (1)H NMR spectroscopy, and this has been ascribed to the restricted Pt-S bond rotation at higher concentration. Platinacycle 8 exists as one isomer, while 9 exists as a mixture of seven isomers in solution. The influence of steric factor, π-acceptor property of the guanidine, subtle solid-state packing forces upon the configuration of the platinum atom, and the number of isomers in solution have been outlined. Factors that accelerate or slow down the cycloplatination reaction, the role of NaOAc, and a plausible mechanism of this reaction have been discussed.

Synthesis, reactivity studies, structural aspects, and solution behavior of half sandwich ruthenium(II) N,N',N''-triarylguanidinate complexes.

[(η(6)-C(10)H(14))RuCl(µ-Cl)](2) (η(6)-C(10)H(14) = η(6)-p-cymene) was subjected to a bridge-splitting reaction with N,N',N''-triarylguanidines, (ArNH)(2)C═NAr, in toluene at ambient temperature to afford [(η(6)-C(10)H(14))RuCl{κ(2)(N,N')((ArN)(2)C-N(H)Ar)}] (Ar = C(6)H(4)Me-4 (1), C(6)H(4)(OMe)-2 (2), C(6)H(4)Me-2 (3), and C(6)H(3)Me(2)-2,4 (4)) in high yield with a view aimed at understanding the influence of substituent(s) on the aryl rings of the guanidine upon the solid-state structure, solution behavior, and reactivity pattern of the products. Complexes 1-3 upon reaction with NaN(3) in ethanol at ambient temperature afforded [(η(6)-C(10)H(14))RuN(3){κ(2)(N,N')((ArN)(2)C-N(H)Ar)}] (Ar = C(6)H(4)Me-4 (5), C(6)H(4)(OMe)-2 (6), and C(6)H(4)Me-2 (7)) in high yield. [3 + 2] cycloaddition reaction of 5-7 with RO(O)C-C≡C-C(O)OR (R = Et (DEAD) and Me (DMAD)) (diethylacetylenedicarboxylate, DEAD; dimethylacetylenedicarboxylate, DMAD) in CH(2)Cl(2) at ambient temperature afforded [(η(6)-C(10)H(14))Ru{N(3)C(2)(C(O)OR)(2)}{κ(2)(N,N')((ArN)(2)C-N(H)Ar)}]·xH(2)O (x = 1, R = Et, Ar = C(6)H(4)Me-4 (8·H(2)O); x = 0, R = Me, Ar = C(6)H(4)(OMe)-2 (9), and C(6)H(4)Me-2 (10)) in moderate yield. The molecular structures of 1-6, 8·H(2)O, and 10 were determined by single crystal X-ray diffraction data. The ruthenium atom in the aforementioned complexes revealed pseudo octahedral "three legged piano stool" geometry. The guanidinate ligand in 2, 3, and 6 revealed syn-syn conformation and that in 4, and 10 revealed syn-anti conformation, and the conformational difference was rationalized on the basis of subtle differences in the stereochemistry of the coordinated nitrogen atoms caused by the aryl moiety in 3 and 4 or steric overload caused by the substituents around the ruthenium atom in 10. The bonding pattern of the CN(3) unit of the guanidinate ligand in the new complexes was explained by invoking n-π conjugation involving the interaction of the NHAr/N(coord)Ar lone pair with C═Nπ* orbital of the imine unit. Complexes 1, 2, 5, 6, 8·H(2)O, and 9 were shown to exist as a single isomer in solution as revealed by NMR data, and this was ascribed to a fast C-N(H)Ar bond rotation caused by a less bulky aryl moiety in these complexes. In contrast, 3 and 10 were shown to exist as a mixture of three and five isomers in about 1:1:1 and 1·0:1·2:2·7:3·5:6·9 ratios, respectively in solution as revealed by a VT (1)H NMR, (1)H-(1)H COSY in conjunction with DEPT-90 (13)C NMR data measured at 233 K in the case of 3. The multiple number of isomers in solution was ascribed to the restricted C-N(H)(o-tolyl) bond rotation caused by the bulky o-tolyl substituent in 3 or the aforementioned restricted C-NH(o-tolyl) bond rotation as well as the restricted ruthenium-arene(centroid) bond rotation caused by the substituents around the ruthenium atom in 10.

Factors dictating the nuclearity/aggregation and acetate coordination modes of lutidine-coordinated zinc(II) acetate complexes.

The reactions of Zn(OAc)(2).2H(2)O with various positional isomers of lutidine were explored with a view to understand the factors responsible for the nuclearity/aggregation and acetate coordination modes of the products. The reactions of Zn(OAc)(2).2H(2)O with 3,5-lutidine, 2,3-lutidine, 2,4-lutidine, and 3,4-lutidine in a 1:1 ratio in methanol at ambient temperature afforded three discrete trinuclear complexes [Zn(3)(OAc)(2)(mu(2)-eta(2):eta(1)-OAc)(2)(mu(2)-eta(1):eta(1)-OAc)(2)(H(2)O)(2)(3,5-lutidine)(2)] (1), [Zn(3)(mu(2)-eta(1):eta(1)-OAc)(4)(mu(2)-eta(2):eta(0)-OAc)(2)L(2)] [L = 2,3-lutidine (2) and 2,4-lutidine (3)], and a one-dimensional coordination polymer [Zn(OAc)(mu(2)-eta(1):eta(1)-OAc)(3,4-lutidine)] (4) in 93, 79, 81, and 94% yields, respectively. Complexes 1-4 were characterized by microanalytical, IR, solution ((1)H and (13)C), and solid-state cross-polarization magic angle spinning (13)C NMR spectroscopic techniques and single-crystal X-ray diffraction data. Complex 1 is unique in that it contains three types of acetate coordination modes, namely, monodentate, bridging bidentate, and asymmetric chelating bridging. Variable-temperature (1)H NMR data indicated that complex 1 partially dissociates in solution, and the remaining undissociated 1 undergoes a rapid "carboxylate shift" even at 218 K. The plausible mechanism of formation of complexes 1-4 was explained with the aid of a point zero charge (pzc) model, according to which the nuclearity/aggregation observed in complexes 1-4 depends upon the number and nature of equilibrating species formed upon dissolution of the reactants in methanol, and these in turn depend upon the subtle basic/steric properties of lutidines. Further, noncovalent interactions play a crucial role in determining the nuclearity/aggregation and acetate coordination modes of the products.

Comparisons of phosphorus ligation properties in P(CH2NR)3P.

Bicyclic P(CH2NMe)3P was synthesized, and its reactions with MnO2, elemental sulfur, p-toluenesulfonyl azide, BH3.THF, and W(CO)5(THF) were shown to furnish a variety of products in which the PC3 and/or the PN3 phosphorus are oxidized/coordinated. In contrast, reactions of the previously known P(CH2NPh)3P with Mo(0) and Ru(II) precursors were shown to afford products in which only the PC3 phosphorus is coordinated. The contrast in reactivity of P(CH2NR)3P (R = Me, Ph) with the aforementioned reagents is discussed in terms of steric and electronic factors. The new compounds are characterized by analytical and spectroscopic (IR, 1H, 31P, and 13C NMR) methods. The results of crystal and molecular structure X-ray analyses of the previously known compounds P(CH2O)3P and P(CH2NPh)3P and 6 of the 14 new compounds obtained in this investigation are presented. Salient features of these structures and the analysis of the Tolman cone angles calculated from their structural parameters are discussed in terms of the effects of constraint in the bicyclic moieties. Evidence is presented for greater M-P sigma bonding effects on coordination of the PC3 phosphorus of P(CH2NR)3P (R = Me, Ph) than are present in PMe3 analogues of group 6B metal carbonyls. From 1JBP data on the BH3 adducts of P(CH2NMe)3P, it is suggested that the free bases MeC(CH2NMe)3P < P(CH2NMe)3P < (Me2N)3P < P(MeNCH2CH2)3N increase in Lewis basicity at the PN3 phosphorus in the order shown. Substantial differences in 31P chemical shifts in the bicyclic compounds discussed herein relative to their acyclic analogues do not seem to be associated with the relatively small bond angle changes that occur around either the PN3 or the PC3 trivalent phosphorus atoms.

Synthesis and photoelectron spectroscopic studies of N(CH2CH2NMe)3P=E (E = O, S, NH, CH2).

The synthesis and the crystal and molecular structure of N(CH(2)CH(2)NMe)(3)P=CH(2) is reported. The P-N(ax) distance is rather long in N(CH(2)CH(2)NMe)(3)P=CH(2). The ylide N(CH(2)CH(2)NMe)(3)P=CH(2) proved to be a stronger proton acceptor than proazaphosphatrane N(CH(2)CH(2)NMe)(3)P, since it was shown to deprotonate N(CH(2)CH(2)NMe)(3)PH(+). The extremely strong basicity of the ylide is in accordance with its low ionization energy (6.3 eV), which is the lowest in the presently investigated series N(CH(2)CH(2)NMe)(3)P=E (E: CH(2), NH, lone pair, O and S), and to the best of our knowledge it is the smallest value observed for a non-conjugated phosphorus ylide. Computations reveal the existence of two bond strech isomers, and the stabilization of the phosphorus centered cation by electron donation from the equatorial and the axial nitrogens. Similar stabilizing effects operate in the case of protonation of E. A fine balance of these different interactions determines the P-N(ax) distance, which is thus very sensitive to the level of the theory applied. According to the quantum mechanical calculations, methyl substitution at the equatorial nitrogens flattens the pyramidality of this atom, increasing its electron donor capability. As a consequence, the PN(ax) distance in the short-transannular bonded protonated systems and the radical cations is longer by about 0.5 A in the N(eq)(Me) than in the N(eq)(H) systems. Accordingly, isodesmic reaction energies show that a stabilization of about 25 and 10 kcal/mol is attributable to the formation of the transannular bond in case of N(eq)(H) and the experimentally realizable N(eq)(Me) species, respectively.

An investigation of Staudinger reactions involving cis-1,3,5-triazidocyclohexane and tri(alkylamino)phosphines.

The reaction of 1,3,5-cis-triazidocyclohexane with the electron-rich tris(dialkylamino)phosphines P(NMe(2))(3) (1) and N(CH(2)CH(2)NMe)(3)P (2b) in acetonitrile for 3 h furnished the corresponding tris-phosphazides 1,3,5-cis-(R(3)PN(3))(3)C(6)H(9), 3a (R(3)P = 1) and 3b (R(3)P = 2b), in 90% and 92% yields, respectively. The same reaction with the relatively electron-poor tris(dialkylamino)phosphine MeC(CH(2)NMe)(3)P (4) for 2 days gave the tris-iminophosphorane, 1,3,5-cis-(R(3)PN)(3)C(6)H(9), 5a (R(3)P = 4), in 60% yield. Compound 3b is a thermally stable solid that did not lose dinitrogen when refluxed in toluene for 24 h or when heated as a neat sample at 100 degrees C /0.5 Torr for 10 h. By contrast, tris-phosphazide 3a decomposed to the tris-iminophosphorane 1,3,5-cis-(R(3)PN)(3)C(6)H(9), 5b (R(3)P = 1), in 3 h in quantitative yield upon heating to 100 degrees C in toluene. Factors influencing the formation of the phosphazides or the iminophosphoranes in these reactions are discussed. The reaction of 3b with 4 equiv of benzoic acid gave [N(CH(2)CH(2)NMe)(3)P=NH(2)]PhCO(2) ([6bH]PhCO(2)) in quantitative yield along with benzene (56% yield) and dinitrogen. The same reaction with 3a gave [(Me(2)N)(3)P=NH(2)]PhCO(2) ([7aH]PhCO(2)) (quantitative yield), benzene (15% yield), and dinitrogen(.) Treatment of [6bH]PhCO(2) with KO(t)Bu afforded N(CH(2)CH(2)NMe)(3)P=NH (6b) in 40% overall yield. Compound 6b upon treatment with PhCH(2)CH(2)Br produced [6bH]Br in 90% yield along with styrene. The new compounds were characterized by analytical and spectroscopic methods, and selected compounds (3b, 5a, and [6bH]Br) were structured by X-ray crystallography. A special feature of 3b is its capability to function as a starting material for 6b, which was not accessible by other synthetic routes.

Reactions of tris(amino)phosphines with arylsulfonyl azides: product dependency on tris(amino)phosphine structure.

The Staudinger reaction of N(CH2CH2NR)3P [R = Me (1), Pr (2)] with 1 equiv of N3SO2C6H4Me-4 gave the ionic phosphazides [N(CH2CH2NR)3PN][SO2C6H4Me-4] [R = Me (3), R = Pr (5a)], and the same reaction of 2 with N3SO2C6H2Me3-2,4,6 gave the corresponding aryl sulfinite 5b. On the other hand, the reaction of 1 with 0.5 equiv of N3SO2Ar (Ar = C6H4Me-4) furnished the novel ionic phosphazide [[N(CH2CH2NMe)3P]2(mu-N3)][SO2Ar] (6). Data that shed light on the mechanistic pathway leading to 3 were obtained by low temperature 31P NMR spectroscopy. A crystal and molecular structure analysis of the phosphazide sulfonate [N(CH2CH2NMe)3PN3][SO3C6H4Me-4] (4), obtained by atmospheric oxidation of 3, indicated an ionic structure, the cationic part of which is stabilized by a transannular P-N bond. A crystal and molecular structure analysis of 6 also indicated an ionic structure in which the cation features two untransannulated N(CH2CH2NMe)3P cages bridged by an azido group in an eta 1: mu: eta 1 fashion. The reaction of P(NMe2)3 with N3SO2Ar (Ar = C6H4Me-4) in a 1:0.5 molar ratio furnished [[(Me2N)3P]2(mu-N3)][SO2-Ar] (11) in quantitative yield. On the other hand, the same reaction involving a 1:1 molar ratio of P(NMe2)3 and N3SO2Ar produced a mixture of 11, [(Me2N)3PN3][SO2Ar] (12), and the iminophosphorane (Me2N)3P=NSO2Ar (10). In contrast, the bicyclic tris(amino)phosphines MeC(CH2NMe)3P (7) and O=P(CH2NMe)3P (8) reacted with N3SO2-Ar (Ar = C6H4Me-4) to give the iminophosphorane MeC(CH2NMe)3P=NSO2Ar (14) (structured by X-ray means) and O=P(CH2NMe)3P=NSO2Ar (16) via the intermediate phosphazides MeC(CH2NMe)3PN3SO2Ar (13) and O=P(CH2NMe)3PN3SO2Ar (15), respectively. The variety of products obtained from the reactions of arylsulfonyl azides with proazaphosphatranes (1 and 2), acyclic P(NMe2)3, bicyclic tris(amino)phosphines 7 and 8 are rationalized in terms of steric and basicity variations among the phosphorus reagents.

Oxidative Addition of Tetrachloro-1,2-benzoquinone to lambda(3)-Cyclotriphosphazanes. An Unusual Ring Contraction-Rearrangement.

The lambda(3)-cyclotriphosphazanes, [EtNP(OR)](3) [R = 2,6-Me(2)C(6)H(3) (1), 4-BrC(6)H(4) (2), or CH(2)CF(3)(3)], on treatment with tetrachloro-1,2-benzoquinone (TCB) give the lambda(5)-cyclodiphosphazanes, [EtNP(O(2)C(6)Cl(4))(OR)][EtNP(O(2)C(6)Cl(4)){N(Et)P(OR)(2)}] (5-7) by an unusual ring contraction-rearrangement. The reaction of the mixed substituent lambda(3)-cyclotriphosphazane, [(EtN)(3)P(3)(OR)(2)(OR')] [R = 2,6-Me(2)C(6)H(3), R' = 4-BrC(6)H(4)] (4), with TCB gives the lambda(5)-cyclodiphosphazane, [EtNP(O(2)C(6)Cl(4))(OR')][EtNP(O(2)C(6)Cl(4)){N(Et)P(OR)(2)}] (8), in which 4-bromophenoxide resides on one of the ring phosphorus atoms. The lambda(3)-bicyclic tetraphosphapentazane, (EtN)(5)P(4)(OPh)(2), on treatment with TCB undergoes a double ring contraction-rearrangement to give the lambda(5)-cyclodiphosphazane, (EtN)[(EtN)(2)P(2)(O(2)C(6)Cl(4))(2)(OPh)](2) (9). Variable-temperature and high-field (31)P NMR studies indicate the presence of more than one isomer in solution for the rearranged products 5-9. The solid state structure of 8 reveals a trans arrangement of the substituents with respect to the P(2)N(2) ring in contrast to the gauche arrangement observed for 5.