Synthesis of mono-, di-, and triaminobismuthanes and observation of C–C coupling of aromatic systems with bismuth(iii) chloride

Mono-, di- or triaminobismuthanes were synthesized depending on the sterical demand of the organic substituent. In one case, a C–C coupling product was observed as main product in the reaction of BiCl₃ with Mes*(SiMe₃)NLi.

Intramolecular amine-induced [1,3]-sigmatropic rearrangement in the reactions of aminophosphinites or phosphites with elemental sulfur or selenium

Ether- and thioether-functionalized cyclodiphosphazanes cis-[tBuNP(OCH2CH2EMe)]2 (E = O, 1; E = S, 2) react with 2 equiv of elemental sulfur or selenium to produce dichalcogenides cis-[tBuNP(E)(OCH2CH2EMe)]2 (4-6), whereas the similar reaction of amine-functionalized cyclodiphosphazane cis-[tBuNP(OCH2CH2NMe2)]2 (3) with elemental chalcogen results in the formation of thio- or selenophosphates trans-[tBuNP(O)(ECH2CH2NMe2)]2 (E = S, 7; E = Se, 8) through [1,3]-sigmatropic rearrangement. The X-ray crystal structure of 8 confirms the rearranged product as the trans isomer with a planar P2N2 ring. The equimolar reaction of P(OCH2CH2OMe)3 (9) with elemental sulfur or selenium produces the simple sulfide and selenide E=P(OCH2CH2OMe)3 (E = S, 11; E = Se, 12) derivatives, respectively. In contrast, the reaction between P(OCH2CH2NMe2)3 (10) and S or Se furnishes the rearranged products (13 and 14). The rearrangement reaction was monitored by (31)PNMR spectroscopy, which confirms the formation of selenophosphinic acid as the first step of the rearrangement. The [1,3]-sigmatropic rearrangement presumably takes place through chalcogen-nitrogen interactions.

Bis(1°-amino)cyclodistib(III)azanes: the First Structural Characterization of cis and trans Isomers of a Single Cyclodipnict(III)azane

The dichlorocyclodistib(III)azane [ClSb(mu-NtBu)]2 (1) has been shown to exist as the cis isomer in the solid state. A series of bis(1 degree-amino)cyclodistib(III)azanes [R'NHSb(mu-NtBu)]2 (2, R' = tBu; 3, R' = Dipp; 4, R' = Dmp) has been prepared by the reaction of 1 with 2 equiv. of LiNHR'. On the basis of NMR solution spectra, all three derivatives are formed as a mixture of cis and trans isomers. In the case of 3, the structures of both the cis and trans isomers have been determined by X-ray crystallography; cis-3 adopts an endo, endo arrangement for the amido protons of the DippNH groups. Isomerization of trans-3 into cis-3 occurs slowly in solution. Deprotonation of 2 with 2 equiv. of nBuNa or trans-3 with nBuLi produces [Na2Sb2(mu-NtBu)4] (5) and [Li2Sb2(mu-NtBu)2(mu-NDipp)2] (6), whose solvated cubane structures were established by X-ray crystallography. In contrast, the reaction of cis-3 with 2 equiv. of nBuLi produces the tricyclic compound [Li2Sb(mu-NtBu)2(mu-NDipp)(mu-NHDipp)] (7).

Dissociation of 2,4-Bis(2,4,6-tri-tert-butylphenyl)-cyclo-1,3-dipnicta-2,4-diazanes (pnict = P, As, Sb) Imposed by Substituent Steric Strain: A Cyclobutane/Olefin Analogy

Three 2,4-bis(Mes)-cyclo-1,3-dipnicta-2,4-diazanes, 2PnX, have been synthesized as 1,3-dichloro- (Pn = As; X = Cl) or 1,3-bis(triflato)- (Pn = P, Sb; X = OTf) derivatives (Mes = 2,4,6-tri-tert-butylphenyl; OTf = triflato = trifluoromethanesulfonoxy). The compounds have been structurally characterized as cyclodimers, but spectroscopic characterization of melts and solutions indicates facile dissociation of the diphosphadiazane 2POTf derivative to give the corresponding iminophosphine 1POTf and of the diarsadiazane 2AsCl derivative to give the corresponding iminoarsine 1AsCl. 1,3-Bis(triflato)-2,4-bis(Mes)-cyclo-1,3-distiba-2,4-diazane (2SbOTf) does not dissociate in the melt or in solution. The presence of the sterically bulky Mes substituent does not preclude association of N-Pn olefin analogues to give single bonded cyclobutane analogues. The facile dissociation of 2POTf and isolation of 1POTf implicates a relatively high degree of substituent steric strain in the dimer. In comparison, dissociation of 2AsCl is only apparent in the melt and in solution, likely the result of the lower substituent strain in the larger N(2)As(2) framework. The largest N(2)Pn(2) framework in 2SbOTf provides sufficient space for the Mes substituents, and the monomer is not observed under the conditions examined.

Identification of new N-Sb topologies: understanding the sequential dehydrochloride coupling of primary amines and trichloropnictines

Subtle steric strain imposed by 2,6-dimethylphenyl substituents on N-Sb frameworks has enabled identification of the first acyclic dipnictadiazane and the first six-membered cyclotristibatriazane providing insight into the dehydrohalide coupling reaction of amines with halopnictines.

Synthesis of cyclo-2,4,6-Triarsa-1,3,5-triazanes from cyclo-2,4-Diarsa-1,3-diazanes Demonstrating the General Influence of Substituent Steric Strain on the Relative Stability of Pnictazane Oligomers

2,4-Dichloro-1,3-diaryl-cyclo-2,4-diarsa-1,3-diazanes (aryl = 2,6-dimethylphenyl, Dmp, or 2,6-diisopropylphenyl, Dipp) have been transformed into the corresponding 2,4,6-trichloro-cyclo-2,4,6-triarsa-1,3,5-triazanes on reaction with GaCl(3) followed by 4-(dimethylamino)pyridine (DMAP). The nitrogen bound Dmp and Dipp substituents impose "medium" substituent steric strain on the heterocycles influencing the relative thermodynamic stability of potential oligomers in favor of the trimers. This ring expansion disproportionation reaction is initiated by chloride ion abstraction, and the intermediate 2,4-dichloro-1,3,5-tris(2,6-diisopropylphenyl)-cyclo-2,4-diarsa-1,3,5-triazane-6-arsenium tetrachlorogallate has been isolated and structurally characterized. Subsequent reaction with 4-(dimethylamino)pyridine (DMAP) effects release of chloride ion from the gallate anion and consequential formation of a covalent As-Cl bond in the trimer. The observations are analogous to those for the phosphorus derivatives demonstrating a general applicability of this new synthetic procedure for the development and diversification of cyclopnictazane chemistry.

Inorganic heterocyclic bis(phosphines): syntheses and structures of a 1,2-bis(diazasilaphosphetidino)ethane and its nickel, molybdenum, and rhodium complexes

Synthesis and characterization of a new, highly electron-rich, chelating bis(phosphine), based on the ethanediyl-linked inorganic heterocycle [Me(2)Si(mu-N(t)Bu)(2)P], are reported. Treatment of nickel chloride with this bis(phosphine) afforded square-planar cis-[[Me(2)Si(mu-N(t)Bu)(2)PCH(2)](2)NiCl(2)], which features isometric nickel-chloride (2.2220(8) A) and nickel-phosphorus (2.1572(8) A) bonds. The ligand reacted with cis-[(piperidine)(2)Mo(CO)(4)] to form colorless cis-[[Me(2)Si(mu-N(t)Bu)(2)PCH(2)](2)Mo(CO)(4)], which has distorted octahedral geometry and long Mo-P bonds (2.5461(18) A). Because of its potential applications in hydrogenation catalysis cis-[[Me(2)Si(mu-N(t)()Bu)(2)PCH(2)](2)Rh(COD)]BF(4) was synthesized. This square-planar, cationic rhodium(I) complex, having symmetrical Rh-P (2.250(2) A) and Rh-C (2.305(6) A) bonds, is structurally related to bis(phospholano)- and bis(phosphetano)rhodium species.

Sequential dehydrochloride coupling of trichlorophosphine with 2,6-di-isopropylaniline: aminophosphine precursors to phosphetidines

Various stoichiometric combinations of PCl3 with DippNH2 (Dipp = 2,6-di-isopropylphenyl) have been examined using 31P NMR spectroscopy. The dehydrochloride coupling reaction is mediated by the moderate steric bulk of the Dipp substituent. Isolation procedures and characterization data are reported for the aminodichlorophosphine (1), the aminotetrachlorodiphosphine (4), and the dichlorophosphetidine (7). The observations offer new appreciation of dehydrochloride coupling products of halophosphines with primary amines.Key words: phosphorus, nitrogen, phosphazanes, phosphetidines, iminophosphine.

Synthesis and structural comparison of triaryl(sulfonylimino)pnictoranes

Triarylphosphanes 1 (Ar(3)P; Ar = Ph, 4-MeC(6)H(4)), triphenylarsane (2), and triarylstibanes 3 (Ar(3)Sb; Ar = 2-MeC(6)H(4), 2-MeOC(6)H(4)) reacted with trifluoromethanesulfonamide (7a) in the presence of equimolar diethyl azodicarboxylate to afford the corresponding triaryl(sulfonylimino)pnictoranes [Ar(3)M=NSO(2)CF(3); 8 (M = P), 9 (M = As), 10 (M = Sb)]. The Kirsanov-type reaction of triarylantimony dichlorides 5 (Ar(3)SbCl(2); Ar = 2-MeC(6)H(4), 2-MeOC(6)H(4)) and triarylbismuth dichlorides 6 (Ar(3)BiCl(2); Ar = 2-MeC(6)H(4), 2-MeOC(6)H(4), 2,4,6-Me(3)C(6)H(2)) with sulfonamides 7 (H(2)NSO(2)R; R = CF(3), 4-MeC(6)H(4), Me) in the presence of 2 equiv of potassium tert-butoxide yielded triaryl(sulfonylimino)-lambda(5)-stibanes 10 and -bismuthanes 11, respectively. The ortho-substitution in aryl ligands of 10 and 11 has been found to bring about considerable kinetic stabilization of the reactive Sb=N and Bi=N bonds. A structural comparison was made for a series of triaryl(sulfonylimino)pnictoranes 8-11 by IR spectroscopy and X-ray crystallography. In the IR spectra of 9-11, SO(2) asymmetric stretching absorptions (nu(SO2)) were observed at lower wavenumbers as compared to those of phosphorus counterparts 8. The difference in frequency (Deltanu(SO2)) from 8 increased progressively as the pnictogen element being utilized moved down the group 15 column on the periodic table. X-ray crystallographic analyses of eight of the triaryl(sulfonylimino)pnictoranes prepared confirmed the increasing single-bond character of the M=N bond, with the contribution from the canonical structure M(+)-N=S(O)-O(-) increasing in importance in the order P < As < Sb < Bi. Among all triaryl(sulfonylimino)pnictoranes examined, only imino-lambda(5)-bismuthanes 11 oxidized alcohols to carbonyl compounds.