Phosphaniminato-Komplexe des Arsens. Kristallstrukturen von [AsCl(NPMe3)]2Cl2, [AsCl(NPMe3)2SbCl4]SbCl6 und [AsCl(NPMe3)2SnCl4] · CH3CN

Synthesis of a Molecule with Five Different Adjacent Pnictogens

The first molecular compound with all five pnictogens was obtained by a multi-step reaction. Lithiation of the (bisamido)diazadiarsetidine (tBuNAs)2 (tBuNH)2 in aliphatic solvents leads to the dimeric metallated species [(tBuNAs)2 (tBuNLi)2 ]2 (12 ). Upon reactions with AsCl3 , SbCl3 and BiCl3 the polycyclic compounds [(tBuNAs)2 (tBuN)2 ]PnCl (Pn=As (2), Sb (3), Bi (4)) can be obtained. Conversion of 2-4 with [tBu2 SbP(tBu)Li(OEt2 )]2 leads to the remarkable interpnictogens [(tBuNAs)2 (tBuN)2 ]PnP(tBu)SbtBu2 (Pn=As (5), Sb (6), Bi (7)), whereby 7 is the first example of a molecule containing all five Group 15 elements. The compound with adjacent AsNBiPSb-chains is surprisingly stable and does not show high sensibility against light as the labile Bi-P bond might suggest.

Synthesis of a Molecule with Four Different Adjacent Pnictogens

The synthesis of a molecule containing four adjacent different pnictogens was attempted by conversion of a Group 15 allyl analogue anion [Mes*NAsPMes*](-) (Mes*=2,4,6-tri-tert-butylphenyl) with antimony(III) chloride. A suitable precursor is Mes*N(H)AsPMes* (1) for which several syntheses were investigated. The anions afforded by deprotonation of Mes*N(H)AsPMes* were found to be labile and, therefore, salts could not be isolated. However, the in situ generated anions could be quenched with SbCl3 , yielding Mes*N(SbCl2 )AsPMes* (4).

An Unusual Reaction: a GaCl3-Assisted Methyl/Chlorine Exchange in Silylated Hydrazinodichloroarsane

N,N',N'-[Tris(trimethylsilyl)]hydrazino(dichloro)arsane, (Me3Si)2N-N(SiMe3)-AsCl2 (1), has been transformed into the corresponding N-trimethylsilyl-N',N'-bis-(dimethylchlorosilyl)hydrazinodimethylarsane in a two-step synthesis: (i) Addition of GaCl3 to 1 results in the formation of the corresponding hydrazinodimethylarsane GaCl3 adduct (2). (ii) Reaction of 2 with 4-(dimethylamino)pyridine (DMAP) yielded the adduct-free hydrazinodimethylarsane (3). The intriguing methyl/chlorine exchange with GaCl3 as transfer/exchange reagent represents a new synthetic route to the hitherto unknown N-trimethylsilyl-N',N'-bis-(dimethylchlorosilyl)hydrazinodimethylarsane in contrast to the same reaction of the phosphorus analogue that results in the formation of triazadiphospholes. The new exchange reaction was unambiguously proven by NMR and X-ray studies (1: monoclinic, P2(1)/c, a = 9.5002(19) A, b = 13.840(3) A, c = 17.226(5) A, beta = 120.12(2) degrees ; V = 1959.1(8) A3, Z = 4; 2: orthorhombic, Pbca; a = 11.7766(2) A, b = 13.9927(2) A, c = 28.3298(4) A; V = 4668.37(12) A3, Z = 4; 3: monoclinic, P2(1)/c, a = 12.015(2) A, b = 12.466(3) A, c = 13.031(3) A, beta = 98.20(3) degrees ; V = 1931.8(7) A3, Z = 4). Structural comparisons of the hydrazinoarsanes with their GaCl3 adducts provide interesting similarities and differences. Computations at the B3LYP level reveal that the exchange process is -34 kcal/mol exergonic.

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.