The conversion of AsF5 and SbF5 into novel arsenic- and antimony(V) pseudohalogen species: preparation, characterization and hybrid DFT computation of Lewis base stabilized M(N3)5 species (M=As, Sb)

Journal of Fluorine Chemistry 109 (2001) 151±162

The conversion of AsF5 and SbF5 into novel arsenic- and antimony(V) pseudohalogen species: preparation, characterization and hybrid DFT computation of Lewis base stabilized M(N3)5 species (M ˆ As, Sb) Thomas M. KlapoÈtke*, Thomas SchuÈtt Department of Chemistry, Ludwig-Maximilians-University, Munich, Butenandtstr. 5-13 (Haus D), D-81377 Munich, Germany Received 29 January 2001; accepted 28 February 2001

Abstract When reacted with ®ve equivalents of trimethylsilylazide and one equivalent of a Lewis base (LB ˆ pyridine, quinoline, NH3, N2H4 and NH2CN), AsF5 and SbF5 form 1:1 adducts: As(N3)5
LB and Sb(N3)5
LB. The adducts are stable at ambient temperature, but highly explosive towards mechanical impact or increasing temperature. Vibrational and multinuclear NMR spectra and theoretical calculations show that all compounds are nitrogen-coordinated donor±acceptor adducts, and that the strengths of the nitrogen bridges (determined by calculating the bond dissociation enthalpy) increase in the order NH2CN, pyridine, NH3 to N2H4 and from As(N3)5 to Sb(N3)5. As(N3)5
LB and Sb(N3)5
LB (LB ˆ pyridine, quinoline, NH3, N2H4 and NH2CN) were obtained by reacting AsF5 and SbF5 with ®ve equivalents of Me3SiN3 in the presence of LB. Vibrational and multinuclear NMR spectra and theoretical calculations (B3LYP) show that all compounds are nitrogen-coordinated donor±acceptor adducts. # 2001 Elsevier Science B.V. All rights reserved. Keywords: Azides; Arsenic penta¯uoride; Antimony penta¯uoride; Lewis acid±base adducts; Hybrid DFT

1. Introduction Our research group is interested in the chemistry of main group elements in high oxidation states, and therefore, we have recently investigated the chemistry of Lewis acid±base adducts of nitrogen bases with arsenic and antimony penta¯uoride [1±4]. AsF5 and SbF5 which are known as very strong Lewis acids build weak acceptor±donor complexes with carbonyl halides [5]. While AsCl5 is very unstable [6,7] and only AsCl5
OP(Ph)3 is known as a stable adduct of arsenic pentachloride [8], SbCl5 can be stabilized by several nitrogen- or oxygen donors [9±12]. Our intention has now been to ®nd new pseudohalogen species of arsenic and antimony in the oxidation state (V), which can be stabilized in donor±acceptor complexes by Lewis bases. We are also interested in the chemistry of covalent azides of arsenic and antimony. Recently, we reported the binary arsenic- and antimony azide species As(N3)3, As(N3)4‡ [13,14], As(N3)6 [15,16] and Sb(N3)3 [17]. Therefore, we synthesized the novel arsenic and antimony pseudohalogen species M(N3)5 (M ˆ As, Sb) and investigated their *

Corresponding author. Tel: ‡49-89-2180-7491; fax: ‡49-89-2180-7492. E-mail address: [email protected] (T.M. KlapoÈtke).

behavior as Lewis acids. Here, we report the synthesis, spectroscopic and theoretical characterization of As(N3)5
LB and Sb(N3)5
LB, (LB ˆ pyridine, quinoline, NH3, N2H4 and NH2CN). 2. Results and discussion 2.1. Synthesis and properties The adducts were prepared by the stoichiometric reaction of the respective group 15 penta¯uoride with trimethylsilylazide and the respective Lewis base according Eq. (1). MF5 ‡ 5Me3 SiN3 ‡ LB

CH2 Cl2 or SO2

!

M…N3 †5
LB ‡ 5Me3 SiF (1)

where M ˆ As/Sb, LB ˆ pyridine, quinoline, NH3, N2H4 and NH2CN. In the case of the NH3 and N2H4 methylene chloride was used as solvent due to the reaction of NH3 and N2H4 with SO2. It is important to note, that before reaction with the Lewis bases all ¯uorine atoms have to be replaced by azide ligands. Otherwise no ¯uoride±azide exchange could be observed due to the kinetic inertness of six coordinate As

0022-1139/01/$ ± see front matter # 2001 Elsevier Science B.V. All rights reserved. PII: S 0 0 2 2 - 1 1 3 9 ( 0 1 ) 0 0 3 8 7 - 6

152

T.M. KlapoÈtke, T. SchuÈtt / Journal of Fluorine Chemistry 109 (2001) 151±162

and Sb. Attempts to isolate the ligand free As(N3)5 or Sb(N3)5, respectively failed because of the high explosive character of these compounds. In solution and in the presence of resulting trimethylsilyl¯uoride, the generated As(N3)5 and Sb(N3)5, can be handled safely. The prepared compounds are stable at ambient temperature and can be handled in the solid state. Exposed to electrical discharge, mechanical impact or increasing temperature the compounds explode violently. 2.2. Vibrational spectroscopy Tables 1±3 summarize the computed and observed vibrational frequencies of the compounds synthesized in this study. The computed (B3LYP) vibrations are close enough to the measured frequencies to allow assignment. The excellent ®t between measured frequencies and calculated leave no doubt that these complexes are N-coordinated donor±acceptor adducts (in the case of NH2CN via the CN-unit). In the case of the quinoline adducts it should be noted that we have not carried out computations for these adducts due to the high similarity of quinoline and pyridine. The measured IR and Raman spectra show clearly the presence of azide ligands bonded covalently to arsenic and antimony. The antisymmetric stretching vibration of the azide group can be detected in the vibrational spectra at about 2100 cm 1. This vibration mode should show more signals if more than one azide group is present in the molecule. This vibration can be divided into the nasN3 Ð in phase-vibration and the nasN3 Ð out of phase-vibration mode. From our calculations the nasN3 Ð in phase-vibration mode appears at higher frequencies. The in phase-vibration mode is a vibration which does not change the symmetry of the molecule, whereas the symmetry changes for the out of phase-vibrations. Similar in/out of phase vibrations can be assigned to the symmetric stretching vibrations of the azide group which appears normally at about 1200±1300 cm 1. From our calculations the deformation vibration of the azide group should show four signals; two for the vibration in and out of phase of one plane (634±687 cm 1) (IR active), and two for in and out of phase to a plane perpendicular to the ®rst plane (508±626 cm 1) (Raman active). The dN3 Ð in phase-vibration appears at higher frequencies in contrast to the dN3 Ð out of phase-vibration. The arsenic- and antimony±nitrogen stretching vibration can be divided into a symmetrical and a antisymmetrical mode. The deformation mode of the As±N bond and Sb±N bond, respectively can be assigned to the signals in the region about 229±283 cm 1. The covalent donor±acceptor nature of the prepared compounds can be justi®ed by the appearance of As±NLewis base and Sb±NLewis base stretching and deformation modes. In the case of the pyridine and quinoline adducts, the stretching mode appears at 173±216 cm 1 and the deformation mode of this bonding at 111±139 cm 1. The NH2CN adducts show the same stretching modes with strong bands at 429 (IR) and 430 cm 1 (Raman) for the As(N3)5 compound

and at 419 cm 1 (Raman) for the Sb(N3)5 compound. The deformation mode of this bonding appears in both cases at ca. 130 cm 1. In addition to this, the nCN stretching mode is very characteristic for the donor±acceptor interaction. It appears between 2327 cm 1 (As(N3)5) and 2350 cm 1 (Sb(N3)5) in the IR spectra, and is therefore, 118± 141 cm 1 shifted to higher frequency compared with the uncoordinated NH2CN (2209 cm 1). This is nicely in agreement with theory since cyanides are better s-donors than pacceptors and the nCN frequencies of the complexes are generally higher than the value for the free NH2CN [12,18]. For the ammonia adducts, the stretching vibration of the As± NLewis base and Sb±NLewis base bonds could not be resolved, only the deformation mode shows a band at 135 cm 1 for the As(N3)5
NH3 adduct. According to our calculations the stretching vibration of the As±NLewis base and Sb±NLewis base bonds for the hydrazine adducts should appear at ca. 430± 454 cm 1, but it can be detected only for the As(N3)5
N2H4 adduct at 430 cm 1 as a band with medium activity in the Raman spectra. The deformation mode of the As±N2H4 and Sb±N2H4 bonds appears only for the Sb(N3)5
N2H4 adduct at 147 cm 1. It is not possible to compare the vibrations of the As± NLewis base and Sb±NLewis base bonds of all compounds prepared due to the different ligand systems of the Lewis bases used. 2.3. NMR spectra The results of our multinuclear NMR study are summarized in Table 4. A useful method for the characterization of nitrogen bonded Lewis acid±base adducts and covalently bonded azides is undoubtedly the 14 N NMR method. For the covalently bound azide species, three well resolved resonances have been found in the 14 N NMR spectra and assignment of the individual resonances to Na, Nb and Ng (connectivity: M±Na±Nb±Ng) was made on the basis of the arguments given in the literature [14±16,19±22]. The Nb atom shows a resonance at ca. d ˆ 140, the Ng atom at ca. d ˆ 170, and the Na atom as expected, a very broad resonance at d ˆ 240 to 271 ppm. 19 F NMR spectra of the compounds were recorded, but no signals could be detected; complete ¯uoride±azide exchange can be proclaimed. The resonances of the nitrogen atoms of the Lewis bases are shifted signi®cantly upon coordination compared to the resonances of the free Lewis bases [23]. It is important to stress that these adducts form stable complexes even in solution (CH2Cl2, SO2, DMSO) and not only in the solid state. The 14 N NMR resonances of the pyridine and quinoline adducts are shifted up to 116 ppm towards high®eld and appear to be larger for the stronger Lewis acid ``Sb(N3)5'' and for the stronger Lewis base pyridine. The 14 N NMR resonances of the ammonia adducts appear at 349 (Sb) and 359 ppm (As) and are shifted towards lower ®eld

As(N3)5
pyridine a

Sb(N3)5
pyridine b

Calculated

Raman

IR

2242 2235 1325 1318 698 677 589 579 425 390 279 3265 1633 231 132

2115 (2.5) 2096 (1)

2081 vs

a b

(773) (136) (122) (230) (68) (38) (17) (6) (112) (19) (11) (4) (5) (3) (1)

1261 (2) 684 (0.5) 669 (1) 420 (10) 274 3097 1610 216 121

(3) (2.5) (2) (1.5) (5)

1256 s 680 s 608 vw 574 w

3110 m 1609 m

Values in parenthesis: IR intensity (km mol 1). Values in parenthesis: relative Raman intensity.

a

Calculated 2250 2234 1323 1319 669 666 591 587 417 381 252 3255 1639 176 111

(802) (85) (249) (66) (60) (25) (10) (5) (80) (3) (70) (6) (7) (4) (2)

As(N3)5
quinoline b

b

Sb(N3)5
quinoline b

Assignment

Raman

IR

Raman

IR

Raman

IR

2092 (2.5)

2088 vs 1255 s 683 m

2085 vs 1269 vs

2092 (3.5) 2080 (3.5) 1269 (0.5)

2078 vs

1259 (1)

2113 (4) 2089 (3) 1273 (1)

666 (2) 410 (10) 249 3101 1637 171 111

(3) (2) (1) (4) (2)

577 vw 405 w 3099 m 1629 m

669 630 522 415

(2.5) (0.5) (3.5) (10)

267 3071 1620 200 123

(3.5) (3) (1.5) (1) (7)

682 m 626 w 412 w 3088 w 1617 m

667 (2) 519 410 392 229 3073 1636 173 139

(4) (8) (10) (3) (4) (2) (3) (2)

1252 s 665 574 508 416

s w w s

3071 w 1635 s

nasN3 Ð in phase nasN3 Ð out of phase nsN3 Ð in phase nsN3 Ð out of phase dN3 Ð in phase dN3 Ð out of phase dN3 Ð in phase/908 dN3 Ð out of phase/908 nasM±Nazide nsM±Nazide dM±Nazide nC±H nC±C nM±NLewis base dM±NLewis base

T.M. KlapoÈtke, T. SchuÈtt / Journal of Fluorine Chemistry 109 (2001) 151±162

Table 1 Selected observed and calculated vibrational data for As(N3)5
pyridine, Sb(N3)5
pyridine, As(N3)5
quinoline and Sb(N3)5
quinoline

153

T.M. KlapoÈtke, T. SchuÈtt / Journal of Fluorine Chemistry 109 (2001) 151±162

154

Table 2 Selected observed and calculated vibrational data for As(N3)5
NCNH2 and Sb(N3)5
NCNH2 As(N3)5
NCNH2 a

Sb(N3)5
NCNH2 b

a

Assignment b

Calculated

Raman

IR

Calculated

Raman

IR

2244 2231 1327 1310 675 664 590 580 421 391 284 2360 1144 555 437 127

2119 2092 1287 1264 670

2101 vw 2081 vs 1294 s

2265 2232 1346 1318 666 654 596 587 413 388 236 2347 1176 569 422 131

2109 (1.5) 2097 (2)

2126 w

a b

(526) (398) (161) (252) (34) (10) (8) (8) (91) (16) (32) (274) (1) (148) (69) (25)

(4) (3) (1) (2) (1.5)

417 (8) 283 (2.5) 500 (2.5) 429 (10) 127 (7.5)

667 m

416 w 2327 1138 497 430

s m w m

(464) (830) (73) (182) (39) (16) (12) (7) (66) (3) (9) (389) (1) (184) (23) (17)

1252 (0.5) 668 (2) 634 (2)

1260 s 669 w

407 (5.5) 233 (3.5) 1177 (0.5) 419 (6)

2350 s

nasN3 Ð in phase nasN3 Ð out of phase nsN3 Ð in phase nsN3 Ð out of phase dN3 Ð in phase dN3 Ð out of phase dN3 Ð in phase/908 dN3 Ð out of phase/908 nasM±Nazide nsM±Nazide dM±Nazide nN±C nC±NH2 dN±C±NH2 nM±NLewis base dM±NLewis base

Values in parenthesis: IR intensity (km mol 1). Values in parenthesis: relative Raman intensity.

compared to free NH3 ( 388 ppm). The 1 H NMR spectra of these two adducts show very broad resonances at ca. 7.1 ppm. For the hydrazine adducts, two resonances can be detected in the 14 N NMR spectra. They can be assigned to the nitrogen atom coordinated to the group 15 metal ( 358 ppm) and to the uncoordinated nitrogen atom ( 334 ppm), which comes close to free hydrazine ( 331 ppm) [23]. As for the ammonia adducts the 1 H NMR spectra of the hydrazine compounds show broad singlet resonances at 6.90 ppm (As) and 7.30 ppm (Sb). The 14 N NMR spectra of the NH2CN complexes show, in addition to the signals assigned to the azide groups, two signals for the NH2CN moiety in the spectra of the antimony compound. One can be assigned to the nitrogen atom of the ± NH2 unit ( 359 ppm). This signal is not shifted signi®cantly compared with free NH2CN [23]. The other signal can be assigned to the nitrogen atom of the cyanide unit ( 153 ppm). This signal is shifted signi®cantly towards lower ®eld compared with free cyanamide ( 196 ppm) [23]. Since only, the nitrogen atom of the cyanide unit is shifted, it is possible to conclude that only the adduct is formed coordinated via the cyanide unit. The 14 N NMR spectra of As(N3)5
NCNH2 adduct shows, in addition to the azide signals, only one signal at ( 359 ppm). The assignment follows the Sb(N3)5
NCNH2 adduct. The nitrogen atom of the cyanide unit could not be detected. Furthermore, the 13 C NMR spectra of the cyanamide adducts show well resolved signals shifted about 40 ppm towards lower ®eld compared to free NCNH2, as expected from the deshielding of these nuclei by the electron-withdrawing effect of the Lewis acids. In addition to the 14 N NMR study, 75 As and 121 Sb NMR spectra were recorded. The chemical shifts of these spectra appear as broad singlet resonances at about ‡1 up to

‡20 ppm. The relatively sharp signals indicate a very symmetrical environment at the central As and Sb atom since due the large quadruple moment of the 75 As and 121 Sb nuclei these elements can only be detected in very symmetrical environment [15,16,24±27]. 2.4. Structures The calculated structures of the prepared compounds are shown in the Fig. 1 and the calculated structural parameters are summarized in Table 5. The arsenic and antimony atoms exhibit a slightly distorted octahedral environment and are bound to six nitrogen atoms, ®ve from the azide ligands and one from the Lewis base. All computed structures are true minimum structures (NIMAG ˆ 0). The bond angles between the N1 atom of the axial azide group and the nitrogen atoms of the Lewis base are almost linear and lie in a range between 174.0 and 177.08. The bond angles between the nitrogen atoms of the axial azide ligand and the equatorial azide groups are between 94.8 and 97.68 resulting in an almost ideal octahedral structure. The computed bond lengths and angles of the azide groups are in very good agreement with experimentally observed bond lengths and angles of covalently bonded arsenic and antimony azides [15,16,28]. The N1±N2 disÊ , the tances are in the range between 1.234 and 1.241 A bond order is between one and two. The covalent radius Ê [29] for a single bonded nitrogen atom is r cov ˆ 0:7, 0.6 A Ê for a triple for a double bonded nitrogen atom and 0.55 A bonded nitrogen atom. The bond order for the N2±N3 Ê ) is between two and three. The angle of the (1.137±1.142 A azide group (N±N±N) is about 1748, the angle between the arsenic and antimony atom, respectively and the azide group (M±N±N) is about 1188 in good agreement with

Table 3 Selected observed and calculated vibrational data for As(N3)5
NH3, Sb(N3)5
NH3, As(N3)5
N2H4 and Sb(N3)5
N2H4

a

Sb(N3)5
NH3

Calculated

Raman

2250 2231 1324 1308 689 674 592 584 422 377 280 3610 3458 1654

2125 2085 1266 1248

(599) (150) (147) (189) (37) (29) (12) (7) (118) (4) (1) (56) (42) (28)

332 (18) 128 (1) a b

b

(4) (3) (1.5) (1)

664 (3) 416 378 271 3042

(10) (2) (1) (0.5)

135 (6)

a

As(N3)5
N2H4 b

IR

Calculated

Raman

IR

2084 s 2048 s

2253 2230 1325 1317 666 658 591 584 411 388 238 3600 3457 1632

2104 (2) 2088 (2) 1260 (0.5)

2082 s 1258 m

1245 s 687 s 668 s 575 s 407 vs 3099 w

(953) (41) 301) (132) (27) (17) (11) (6) (60) (2) (48) (59) (43) (27)

344 (4) 129 (3) 1

Values in parenthesis: IR intensity (km mol ). Values in parenthesis: relative Raman intensity.

659 (0.5)

667 w

400 (3) 237 (10) 3042 (3)

3133 m

a

Sb(N3)5
N2H4 b

a

Assignment b

Calculated

Raman

IR

Calculated

Raman

IR

2256 2230 1327 1318 685 672 593 588 421 382 248 3546 3448 1641 974 454 111

2101 (1.5) 2088 (1) 1273 (0.5)

2105 w

2096 (2)

2097 w

1269 (1)

1271 s

667 (1.5)

666 m

2254 2234 1324 1314 693 660 595 583 415 384 247 3540 3445 1641 964 431 138

(704) (155) (149) (130) (25) (25) (12) (6) (110) (12) (3) (69) (17) (54) (188) (62) (1)

407 (10) 390 (5) 3150 (0.5) 968 (0.5) 430 (3)

1280 s

580 w

3203 m 1610 w

(950) (162) (241) (152) (92) (29) (9) (6) (83) (4) (46) (70) (4) (58) (117) (55) (1)

655 (1) 395 (5) 3101 (1) 964 (0.5) 147 (8)

665 w 577 w

3197 m 1605 w 950 s

nasN3 Ð in phase nasN3 Ð out of phase nsN3 Ð in phase nsN3 Ð out of phase dN3 Ð in phase dN3 Ð out of phase dN3 Ð in phase/908 dN3 Ð out of phase/908 nasM±Nazide nsM±Nazide dM±Nazide nasN±H nsN±H dN±H3 nN±N nM±NLewis base dM±NLewis base

T.M. KlapoÈtke, T. SchuÈtt / Journal of Fluorine Chemistry 109 (2001) 151±162

As(N3)5
NH3

155

T.M. KlapoÈtke, T. SchuÈtt / Journal of Fluorine Chemistry 109 (2001) 151±162

156

Table 4 Multinuclear NMR shifts of the M(N3)5
LB adducts, d in ppm 1

As(N3)5
NC5H5

13

H

6.58 8.30 6.74 8.10 7.71 7.86 8.10 8.97

m (2-H), d (1-H) m (2-H), d (1-H) m (2-H), m (7-H), m (3-H), m (1-H)

Sb(N3)5
NC9H7

7.97 8.13 8.31 9.15

m m m m

As(N3)5
NH3

7.15 (broad)

Sb(N3)5
NH3

7.14 (broad)

As(N3)5
NCNH2

7.84

156.7

Sb(N3)5
NCNH2

7.88

155.9

As(N3)5
N2H4

6.90 (very broad)

Sb(N3)5
N2H4

7.30 (very broad)

Sb(N3)5
NC5H5 As(N3)5
NC9H7

7.02 m (3-H), 6.94 m (3-H), 7.74 m (6-H), 8.05 m (5-H), 8.57 m (8-H),

(2-H), 8.06 m (6-H), (7-H), 8.28 m (5-H), (3-H), 9.03 m (8-H), (1-H)

14

C

125.0 142.8 124.2 139.8 121.9 128.6 129.2 141.0 148.1 121.8 129.6 130.7 139.7 146.8

bond angles of arsenic and antimony azides reported in the literature [15,16,28]. The calculated As±Nazide and Sb±Nazide (for assignment, see Fig. 1) for the pyridine, ammonia and hydrazine adducts agree very well with the experimental observed bond lengths for the As(N3)6 anion [15,16] and SbCl(N3)2 [28]. It is interesting that in both cases (As and Sb) the shortest M±NLB bond lengths can be found in the hydrazine (2.121 Ê ) adducts followed by the ammonia (2.134 and and 2.275 A Ê 2.284 A) and then the pyridine compounds (2.178 and Ê ). The cyanamide adducts show signi®cantly longer 2.290 A Ê ). Upon strong M±NLB bond lengths (2.500 and 2.660 A complexation, the As±Nazide and Sb±Nazide bond lengths increase due the donation of the s-lone pair into the antibonding s-orbital of the As±Nazide and Sb±Nazide bond. This is in good agreement with the calculated As±Nazide and Sb±Nazide bond lengths, where the cyanamides show the shortest distances. These calculated bond lengths are in good agreement with the resulting stability of the prepared complexes (see Section 2.5). 2.5. Stability of the complexes The structures and energies and vibrational data of the As(N3)5
LB and Sb(N3)5
LB adducts were computed at the

s (2-C), d (1-C) s (2-C), d (1-C) s (2-C), s (5-C), s (7-C), s (3-C), s (1-C) s (2-C), s (5-C), s (7-C), s (3-C), s (1-C)

127.4 m (3-C), 126.4 m (3-C), 125.7 129.0 132.4 144.9

s s s s

(6-C), (4-C), (8-C), (9-C),

122.2 129.8 135.6 145.1

s s s s

(6-C) (4-C), (8-C), (9-C),

75

N 142 161 141 180 115 165

(Nb), 151 (py) (Ng), 263 (Na) (Nb), 173 (Ng) (py), 268 (Na) (qui) 141 (Nb), (Ng), 260 (Na)

141 (Nb), 170 (Ng),

141 265 141 251 141 249 141 172 359 139 242 334 358 139 242 334 358

160 (qui) 251 (Na)

(Nb), 165 (Ng) (Na), 359 (NH3) (Nb), 172 (Ng), (Na), 349 (NH3) (Nb), 164 (Ng) (Na), 359 (NCNH2) (Nb), 153 (NCNH2) (Ng), 252 (Na), (NCNH2) (Nb), 166 (Ng) (Na) (As-NH2±NH2) (As-NH2±NH2) (Nb), 173 (Ng) (Na) (Sb-NH2±NH2) (Sb-NH2±NH2)

As/121 Sb

‡20 ‡4 ‡7

‡1

‡8 ‡3 ‡9 ‡4 ‡11

‡5

B3LYP/6-31G (d, p) level of theory with quasi-relativistic pseudopotentials for As and Sb (see Section 3). The dissociation energies according Eq. (2) can be used to get an appreciation for the As/Sb±NLB bond strengths in the adducts. M…N3 †5 LB ! M…N3 †5 ‡ LB

(2)

where M ˆ As/Sb, LB ˆ pyridine, NH3, N2H4 and NH2CN. The calculated total energies (Table 6) can be used to predict theoretically the reaction enthalpy values for the dissociation. The dissociation energies were calculated, and, after correction [30] for zero-point energies (zpe, Table 6), differences in rotational (DU rot ˆ …3=2†RT) and translational (DU tr ˆ …3=2†RT) d.f., and the work term (PDV ˆ RT), converted into the gas phase dissociation enthalpies at room temperature. Therefore, the bond dissociation enthalpy value (BDE) for the 1:1 adducts decreases in the order of the Lewis bases N2H4, NH3, pyridine and NH2CN, and of the Lewis acids from Sb(N3)5 to As(N3)5. The value of 0 DH298 ˆ ‡31:1 kcal mol 1 for the Sb(N3)5
N2H4 adduct, 0 DH298 ˆ ‡23:7 kcal mol 1 for the As(N3)5
N2H4 adduct, 0 DH298 ˆ ‡25:8 kcal mol 1 for the Sb(N3)5
NH3 adduct and 0 DH298 ˆ ‡25:3 kcal mol 1 for the Sb(N3)5
pyridine adduct corresponds to a ``strong'' Lewis acid±base As/Sb±NLB

T.M. KlapoÈtke, T. SchuÈtt / Journal of Fluorine Chemistry 109 (2001) 151±162

157

Fig. 1. Calculated structures for the M(N3)5
LB adducts (M ˆ As, Sb; LB ˆ pyridine, NH3, NCNH2 and N2H4). 0 bond. The values of DH298 ˆ ‡17:0 kcal mol 1 for the 0 As(N3)5
NH3 adduct, DH298 ˆ ‡17:1 kcal mol 1 for the 0 Sb(N3)5
NCNH2 adduct and DH298 ˆ ‡15:5 kcal mol 1 for the As(N3)5
pyridine adduct correspond to a ``normal'' Lewis acid±base As/Sb±NLB bond strength [30]. However, for the As(N3)5
NCNH2 adduct the BDE is only 9.9 kcal mol 1 which suggests a very weak and only loosely bound adduct. The results of the calculation of the bond dissociation enthalpies are qualitatively in good agreement with the calculated As/Sb±NLB bond lengths.

2.6. Conclusion The structures and normal modes of the different As(N3)5
LB and Sb(N3)5
LB (LB ˆ pyridine, quinoline, NH3, N2H4 and NH2CN) complexes have been calculated, discussed and agree well with the experimental values. The adducts were also characterized by multinuclear NMR spectroscopy. The 14 N NMR spectra show signi®cantly shifted resonances compared with the corresponding Lewis bases. 75 As and 121 Sb NMR spectra point to a very symmetrical environment at the central group 15 elements. Adduct structures which represent true minima were found for all M(N3)5
LB (M ˆ As, Sb) species. The

agreement between calculated structural parameters and experimentally observed structures of arsenic [15,16] and antimony azide [28] species is reasonably good. The structures show a six-coordinated As- and Sb-atom, which is surrounded in an octahedral fashion by ®ve azide ligands and one N atom of the respective Lewis bases. On the basis of quantum chemical calculations, the bond dissociation enthalpy was calculated for all adducts to give more information about the stability of those adducts. The stability increases in the order NH2CN, pyridine, NH3 to N2H4 and from As(N3)5 to Sb(N3)5. 3. Experimental 3.1. General remarks 3.1.1. Caution Arsenic and antimony azide compounds are toxic and potentially explosive! Safety equipment like leather gloves and face-shield is recommended. All of the reported compounds, here are moisture sensitive. Consequently, all manipulations were carried out under dinitrogen using glass vessels ®tted with poly(tetra¯uoroethylene)

T.M. KlapoÈtke, T. SchuÈtt / Journal of Fluorine Chemistry 109 (2001) 151±162

158

Table 5 Computed structural parameters for the M(N3)5
LB adducts

Symmetry Ê) d(As±N1) (A Ê) d(As±N4) (A Ê) d(N1±N2) (A Ê) d(N2±N3) (A Ê) d(As±NLB) (A Ê) d(NLB±C) (A Ê) d(H2N±NH2) (A <(As±N1±N2) (8) <(N1±N2±N3) (8) <(N1±As±N4) (8) <(N1±As±NLB) (8) <(As±NLB±C) (8) <(NLB±C±NH2) (8) <(As±NLB±NH2) (8) Symmetry Ê) d (Sb±N1) (A Ê) d (Sb±N4) (A Ê) d (N1±N2) (A Ê) d (N2±N3) (A Ê) d (Sb±NLB) (A Ê) d (NLB±C) (A Ê) d (H2N±NH2) (A <(Sb±N1±N2) (8) <(N1±N2±N3) (8) <(N1±Sb±N4) (8) <(N1±Sb±NLB) (8) <(Sb±NLB±C) (8) <(NLB±C±NH2) (8) <(Sb±NLB±NH2) (8)

As(N3)5
py

As(N3)5
NH3

As(N3)5
NCNH2

As(N3)5
N2H4

C1 1.922 1.937 1.234 1.141 2.178 1.344

C1 1.918 1.940 1.235 1.141 2.134

C1 1.845 1.928 1.241 1.137 2.660 1.167

C1 1.918 1.947 1.235 1.141 2.121

117.6 175.1 94.8 176.6 120.2

118.6 174.7 96.5 175.2

116.6 172.9 96.5 177.0 139.8 177.0

Sb(N3)5
py

Sb(N3)5
NH3

Sb(N3)5
NCNH2

Sb(N3)5
N2H4

C1 2.093 2.098 1.234 1.142 2.290 1.346

C1 2.087 2.097 1.235 1.141 2.284

C1 2.039 2.098 1.237 1.139 2.500 1.169

C1 2.085 2.103 1.235 1.141 2.275

119.2 174.9 95.6 176.6 120.0

119.7 174.8 97.6 174.5

118.5 173.4 95.6 175.6 137.3 176.7

valves, or in an inert gas dry-box containing dinitrogen. Volatile materials were handled with the help of a steel vacuum line. SO2 (Messer±Griesheim) was condensed into a one bulb vessel and dried over CaH2. NH3 (Messer±Griesheim) was

1.440 118.7 174.6 96.2 175.6 120.3

1.451 119.8 174.7 97.4 174.0 118.8

dried over sodium, N2H4 (Merck) was dried over NaOH, BaO and sodium and NH2CN (Aldrich) has been stored at 08C over P4O10. Traces of HF in SbF5 (Aldrich) were removed by keeping SbF5 for an extended period of time

Table 6 Computed structural parameters and energies for As(N3)5
LB and Sb(N3)5
LB Compound B3LYP/6-31G (d, p) As(N3)5 As(N3)5
N2H4 As(N3)5
NH3 As(N3)5
NC5H5 As(N3)5
NCNH2 Sb(N3)5 Sb(N3)5
N2H4 Sb(N3)5
NH3 Sb(N3)5
NC5H5 Sb(N3)5
NCNH2 N2H4 NH3 C5H5N NH2CN

E (au)

827.124455 939.026445 883.709235 1075.434971 975.921013 826.362834 938.276560 882.961719 1074.689287 975.171689 111.863035 56.556411 248.287074 148.783189

Zero-point energies (zpe) (kcal mol 1)

NIMAG

41.5 77.8 66.3 98.9 63.8 40.4 76.7 65.2 97.9 63.1 33.3 21.6 55.8 21.4

0 0 0 0 0 0 0 0 0 0 0 0 0 0

BDE (kcal mol 1)

Ê) d (M

N) (A

23.7 17.0 15.5 9.9

2.121 2.134 2.178 2.660

31.1 25.8 25.3 17.1

2.275 2.284 2.290 2.500

T.M. KlapoÈtke, T. SchuÈtt / Journal of Fluorine Chemistry 109 (2001) 151±162

under dynamic vacuum at 08C. SbF5 was than condensed directly into the reaction vessel. AsF5 (Matheson) and CH3SiN3 (Aldrich) were used as received. CH2Cl2 (Merck), pyridine (Aldrich) and quinoline (Aldrich) were freshly distilled prior to use. Raman spectra were recorded on a Perkin-Elmer Spectrum 2000R NIR FT with the 1064 nm exciting line of a Nd:YAG-laser, using sealed glass tubes as sample containers. IR spectra were recorded on a Perkin-Elmer Spectrum One FT-IR spectrometer between KBr plates. NMR spectra were recorded as DMSO-d6 or CD2Cl2 solutions using a JEOL EX 400e instrument. Chemical shifts are relative to (CH3)4Si (1 H, 13 C), KAsF6 (75 As), NEt4SbCl6 (121 Sb) and CH3NO2 (14 N). 3.2. Calculations The structures, vibrational data and the bond dissociation enthalpies for the arsenic and antimony pentaazide Lewis base adducts were calculated using the density functional theory with the program package Gaussian'98 [31]. The calculations were carried out at the electron correlated B3LYP level of theory [32±35] which includes a mixture of Hartree±Fock exchange with DFT exchange±correlation. For C, H and N a standard 6-31G (d, p) double-zeta basis set was used and for As and Sb, a quasi-relativistic pseudopotential (As: ECP28MWB; Sb: ECP46MWB) [36] and a (5s5p1d)/[3s3p1d]-DZ ‡ P basis set [37]. Becke's three parameter functional, where the non-local correlation is provided by the LYP expression (Lee, Yang, Parr correlation functional) was used which is implemented in Gaussian'98. 3.3. Synthesis 3.3.1. As(N3)5
NC5H5 At 1968C AsF5 [0.170 g (1.00 mmol)] was condensed onto a frozen solution of (CH3)3SiN3 [0.66 ml (5.00 mmol)] in 10 ml SO2 on one side of a two bulb vessel. The reaction mixture was warmed slowly to room temperature and stirred for 24 h. On the other side of the two bulb vessel, pyridine [0.08 ml (1.00 mmol)] were dissolved in 10 ml SO2. Both sides were reacted together at room temperature and stirred for 12 h. SO2 and resulting (CH3)3SiF were removed under dynamic vacuum. A yellow solid remained. Yield: 94%. IR (KBr): ~nˆ 3110 (m), 2081 (vs, nasN3), 1636 (m), 1609 (m), 1538 (m), 1488 (m), 1256 (s, nsN3), 1165 (w), 1058 (w), 750 (s), 680 (s, dN3), 608 (vw, dN3), 574 (w, dN3), 482 (vw). Raman (310 scans, 100 mW, 180, 208C): ~nˆ 3097 (2.5), 2115 (2.5, nasN3), 2096 (1, nasN3), 1610 (1), 1261 (2, nsN3), 1211 (1), 1018 (4), 684 (0.5, dN3), 669 (1, dN3), 420 (10, nasAsN3), 274 (3, dAsN3), 216 (1.5), 121 (5). 1 H NMR (CD2Cl2, 400 MHz, 258C): d ˆ 6:58 (m, 2-H), 7.02 (m, 3H), 8.30 (d, 1-H). 13 C NMR (CD2Cl2, 101 MHz, 258C): d ˆ 125:0 (s, 2-C), 127.4 (m, 3-C), 142.8 (d, 1-C). 14 N NMR (CD2Cl2, 29 MHz, 258C): d ˆ 142 (s, Nb), 151 (s, Npy),

161 (s, Ng), 263 (s, Na). 258C): d ˆ 20 (s).

159 75

As NMR (CD2Cl2, 69 MHz,

3.3.2. Sb(N3)5
NC5H5 At 1968C SbF5 [0.217 g (1.00 mmol)] was condensed onto a frozen solution of (CH3)3SiN3 [0.66 ml (5.00 mmol)] in 10 ml SO2 on one side of a two bulb vessel. The reaction mixture was warmed slowly to room temperature and stirred for 24 h. On the other side of the two bulb vessel, pyridine [0.08 ml (1.00 mmol)] were dissolved in 10 ml SO2. Both sides were reacted together at room temperature and stirred for 12 h. SO2 and resulting (CH3)3SiF were removed under dynamic vacuum. A yellow solid remained. Yield: 92%. IR (KBr): ~nˆ 3099 (m), 2088 (vs, nasN3), 1629 (m), 1603 (w), 1550 (m), 1479 (w), 1255 (s, nsN3), 1161 (m), 1040 (s), 683 (m, dN3), 608, 577 (vw, dN3), 405 (w, nasSbN3). Raman (200 scans, 150 mW, 180, 208C): ~nˆ 3101 (2), 2092 (2.5, nasN3), 1637 (1), 1259 (1, nsN3), 1201 (2), 1010 (4.5), 666 (2, dN3), 638 (1.5), 410 (10, nasSbN3), 334 (3), 298 (2), 249 (3, dSbN3), 171 (4), 111 (5). 1 H NMR (CD2Cl2, 400 MHz, 258C): d ˆ 6:74 (m, 2-H), 6.94 (m, 3-H), 8.10 (d, 1-H). 13 C NMR (CD2Cl2, 101 MHz, 258C): d ˆ 124:2 (s, 2-C), 126.4 (m, 3-C), 139.8 (d, 1-C). 14 N NMR (CD2Cl2, 29 MHz, 258C): d ˆ 141 (s, Nb), 173 (s, Ng), 180 (s, Npy), 268 (s, Na). 121 Sb NMR (CD2Cl2, 96 MHz, 258C): d ˆ 4 (s). 3.3.3. As(N3)5
NC9H7 At 1968C AsF5 [0.170 g (1.00 mmol)] was condensed onto a frozen solution of (CH3)3SiN3 [0.66 ml (5.00 mmol)] in 10 ml SO2 on one side of a two bulb vessel. The reaction mixture was warmed slowly to room temperature and stirred for 24 h. On the other side of the two bulb vessel, quinoline [0.12 ml (1.00 mmol)] were dissolved in 10 ml SO2. Both sides were reacted together at room temperature and stirred for 12 h. SO2 and resulting (CH3)3SiF were removed under dynamic vacuum. A brown-yellow solid remained. Yield: 97 %. IR (KBr): ~nˆ 3088 (w), 2085 (vs, nasN3), 1617 (m), 1612 (m), 1530 (w), 1488 (m), 1269 (vs, nsN3), 1170 (m), 1030 (w), 750 (s), 682 (m, dN3), 626 (w, dN3), 412 (w, nasAsN3). Raman (500 scans, 150 mW, 180, 208C): ~nˆ 3071 (3), 2113 (2.5, nasN3), 2089 (3, nasN3), 1620 (1.5), 1585 (2), 1375 (4), 1273 (1, nsN3), 1055 (1), 769 (5), 669 (2.5, dN3), 630 (0.5, dN3), 522 (3.5, dN3), 415 (10, nasAsN3), 267 (3.5, dAsN3), 200 (1), 123 (7). 1 H NMR (CD2Cl2, 400 MHz, 258C): d ˆ 7:71 (m, 2-H), 7.74 (m, 6-H), 7.86 (m, 7-H), 8.05 (m, 5-H), 8.10 (m, 3-H), 8.57 (m, 8-H), 8.97 (m, 1-H). 13 C NMR (CD2Cl2, 101 MHz, 258C): d ˆ 121:9 (s, 2-C), 125.7 (m, 6-C), 128.6 (s, 5-C), 129.0 (s, 4-C), 129.2 (s, 7-C), 132.4 (s, 8-C), 141.0 (s, 3-C), 144.9 (s, 9-C), 148.1 (s, 1-C). 14 N NMR (CD2Cl2, 29 MHz, 258C): d ˆ 115 (s, Nqui), 141 (s, Nb), 165 (s, Ng), 260 (s, Na). 75 As NMR (CD2Cl2, 69 MHz, 258C): d ˆ 7 (s). 3.3.4. Sb(N3)5
NC9H7 At 1968C SbF5 [0.217 g (1.00 mmol)] was condensed onto a frozen solution of (CH3)3SiN3 [0.66 ml (5.00 mmol)]

160

T.M. KlapoÈtke, T. SchuÈtt / Journal of Fluorine Chemistry 109 (2001) 151±162

in 10 ml SO2 on one side of a two bulb vessel. The reaction mixture was warmed slowly to room temperature and stirred for 24 h. On the other side of the two bulb vessel, quinoline [0.12 ml (1.00 mmol)] were dissolved in 10 ml SO2. Both sides were reacted together at room temperature and stirred for 12 h. SO2 and resulting (CH3)3SiF were removed under dynamic vacuum. A brown-yellow solid remained. Yield: 95 %. IR (KBr): ~nˆ 3071 (w), 2078 (vs, nasN3), 1635 (s), 1597 (s), 1558 (m), 1489 (m), 1252 (s, nsN3), 1148 (m), 1133 (m), 1050 (w), 809 (s), 771 (m), 665 (s, dN3), 574 (w, dN3), 508 (w, dN3), 474 (w), 416 (s, nasSbN3), 334 (m). Raman (450 scans, 150 mW, 180, 208C): ~nˆ 3073 (4), 2092 (3.5, nasN3), 2080 (3.5, nasN3), 1636 (2), 1598 (2), 1395 (4), 1381 (4.5), 1269 (0.5, nsN3), 1150 (1), 1053 (3), 769 (4), 667 (2, dN3), 519 (4, dN3), 410 (8, nasSbN3), 392 (10, nsSbN3), 334 (7), 229 (3, dSbN3), 210 (2), 173 (3), 139 (2). 1 H NMR (CD2Cl2, 400 MHz, 258C): d ˆ 7:97 (m, 2-H), 8.06 (m, 6-H), 8.13 (m, 7-H), 8.28 (m, 5-H), 8.31 (m, 3-H), 9.03 (m, 8-H), 9.15 (m, 1-H). 13 C NMR (CD2Cl2, 101 MHz, 258C): d ˆ 121:8 (s, 2C), 122.2 (m, 6-C), 129.6 (s, 5-C), 129.8 (s, 4-C), 130.7 (s, 7C), 135.6 (s, 8-C), 139.7 (s, 3-C), 145.1 (s, 9-C), 146.8 (s, 1C). 14 N NMR (CD2Cl2, 29 MHz, 258C): d ˆ 141 (s, Nb), 160 (s, Nqui), 170 (s, Ng), 251 (s, Na). 121 Sb NMR (CD2Cl2, 96 MHz, 258C): d ˆ 1 (s). 3.3.5. As(N3)5
NH3 At 1968C AsF5 [0.170 g (1.00 mmol)] was condensed onto a frozen solution of (CH3)3SiN3 [0.66 ml (5.00 mmol)] in 10 ml CH2Cl2 on one side of a two bulb vessel. The reaction mixture was warmed slowly to room temperature and stirred for 24 h. On the other side of the two bulb vessel, NH3 [0.017 g (1.00 mmol)] were dissolved in 10 ml CH2Cl2. Both sides were reacted together at room temperature and stirred for 12 h. A slightly yellow solid precipitates. CH2Cl2 and resulting (CH3)3SiF were removed under dynamic vacuum. A slightly yellow solid remained. Yield: 79%. IR (KBr): ~n ˆ 3099(w), 2084 (s, nasN3), 2048 (s, nasN3), 1393 (w), 1245 (s, nsN3), 837 (w), 687 (s, dN3), 668 (s, dN3), 575 (s, dN3), 407 (vs, nasAsN3), 314 (m). Raman (310 scans, 150 mW, 180, 208C): ~n ˆ 3042 (0.5), 2125 (4, nasN3), 2085 (3, nasN3), 1344 (0.5), 1266 (1.5, nsN3), 1248 (1, nsN3), 664 (3, dN3), 416 (10, nasAsN3), 378 (2, nasAsN3), 271 (1, dAsN3), 164 (3.5), 135 (6). 1 H NMR (d6-DMSO, 400 MHz, 258C): d ˆ 7:15 (s, NH3). 14 N NMR (d6-DMSO, 29 MHz, 258C): d ˆ 141 (s, Nb), 165 (s, Ng), 265 (s, Na), 359 (s, NH3). 75 As NMR (d6-DMSO, 69 MHz, 258C): d ˆ 8 (s). 3.3.6. Sb(N3)5
NH3 At 1968C SbF5 [0.217 g (1.00 mmol)] was condensed onto a frozen solution of (CH3)3SiN3 [0.66 ml (5.00 mmol)] in 10 ml CH2Cl2 one side of a two bulb vessel. The reaction mixture was warmed slowly to room temperature and stirred for 24 h. On the other side of the two bulb vessel, NH3 [0.017 g (1.00 mmol)] were dissolved in 10 ml CH2Cl2. Both sides were reacted together at room temperature and

stirred for 12 h. A slightly yellow solid precipitates. CH2Cl2 and resulting (CH3)3SiF were removed under dynamic vacuum. A slightly yellow solid remained. Yield: 73%. IR (KBr): ~n ˆ 3133 (m), 2082 (s, nasN3), 1403 (s), 1258 (m, nsN3), 1047 (m), 798 (m), 667 (s, dN3). Raman (500 scans, 200 mW, 180, 208C): ~n ˆ 3042 (3), 2104 (2, nasN3), 2088 (2, nasN3), 1409 (0.5), 1260 (0.5, nsN3), 659 (0.5, dN3), 446 (0.5), 400 (3, nasSbN3), 237 (10, dSbN3). 1 H NMR (d6DMSO, 400 MHz, 258C): d ˆ 7:14 (s, NH3). 14 N NMR (d6DMSO, 29 MHz, 258C): d ˆ 141 (s, Nb), 172 (s, Ng), 251 (s, Na), 349 (s, NH3). 121 Sb NMR (d6-DMSO, 96 MHz, 258C): d ˆ 3 (s). 3.3.7. As(N3)5
N2H4 At 1968C AsF5 [0.170 g (1.00 mmol)] was condensed onto a frozen solution of (CH3)3SiN3 [0.66 ml (5.00 mmol)] in 10 ml CH2Cl2 on one side of a two bulb vessel. The reaction mixture was warmed slowly to room temperature and stirred for 24 h. On the other side of the two bulb vessel, N2H4 [0.03 ml (1.00 mmol)] were dissolved in 10 ml CH2Cl2. Both sides were reacted together at room temperature and stirred for 12 h. A brown solid precipitates. CH2Cl2 and resulting (CH3)3SiF were removed under dynamic vacuum. A brown solid remained. Yield: 83%. IR (KBr): ~n ˆ 3203 (m), 2105 (w, nasN3), 1610 (w), 1401 (vw), 1280 (s, nsN3), 837 (vw), 666 (m, dN3), 580 (w, dN3), 334 (w). Raman (400 scans, 200 mW, 1808, 208C): ~n ˆ 3150 (0.5), 2101 (1.5, nasN3), 2088 (1, nasN3), 1273 (0.5, nsN3), 1081 (0.5), 667 (1.5, dN3), 430 (3), 407 (10, nasAsN3), 390 (5, nsAsN3), 268 (1). 1 H NMR (d6-DMSO, 400 MHz, 258C): d ˆ 6:90 (s, N2H4). 14 N NMR (d6-DMSO, 29 MHz, 258C): d ˆ 139 (s, Nb), 166 (s, Ng), 242 (s, Na), 334 (s, AsNH2NH2), 358 (s, AsNH2NH2). 75 As NMR (d6-DMSO, 69 MHz, 258C): d ˆ 11 (s). 3.3.8. Sb(N3)5
N2H4 At 1968C SbF5 [0.217 g (1.00 mmol)] was condensed onto a frozen solution of (CH3)3SiN3 [0.66 ml (5.00 mmol)] in 10 ml CH2Cl2 on one side of a two bulb vessel. The reaction mixture was warmed slowly to room temperature and stirred for 24 h. On the other side of the two bulb vessel, N2H4 [0.03 ml (1.00 mmol)] were dissolved in 10 ml CH2Cl2. Both sides were reacted together at room temperature and stirred for 12 h. A dark-brown solid precipitates. CH2Cl2 and resulting (CH3)3SiF were removed under dynamic vacuum. A dark-brown solid remained. Yield: 78%. IR (KBr): ~n ˆ 3197 (m), 2097 (w, nasN3), 1605 (w), 1399 (vw), 1271 (s, nsN3), 1077 (m), 950 (s), 665 (w, dN3), 577 (w, dN3). Raman (300 scans, 150 mW, 1808, 208C): ~n ˆ 3101 (1), 2096 (2, nasN3), 1269 (1, nsN3), 1087 (0.5), 964 (0.5), 655 (1, dN3), 395 (5, nasSbN3), 325 (10), 147 (8). 1 H NMR (d6-DMSO, 400 MHz, 258C): d ˆ 7:30 (s, N2H4). 14 N NMR (d6-DMSO, 29 MHz, 258C): d ˆ 139 (s, Nb), 173 (s, Ng), 242 (s, Na), 334 (s, SbNH2NH2), 358 (s, SbNH2NH2). 121 Sb NMR (d6-DMSO, 96 MHz, 258C): d ˆ 5 (s).

T.M. KlapoÈtke, T. SchuÈtt / Journal of Fluorine Chemistry 109 (2001) 151±162

3.3.9. As(N3)5
NCNH2 At 1968C AsF5 [0.170 g (1.00 mmol)] was condensed onto a frozen solution of (CH3)3SiN3 [0.66 ml (5.00 mmol)] in 10 ml SO2 on one side of a two bulb vessel. The reaction mixture was warmed slowly to room temperature and stirred for 24 h. On the other side of the two bulb vessel, NCNH2 [0.042 g (1.00 mmol)] were dissolved in 10 ml SO2. Both sides were reacted together at room temperature and stirred for 12 h. SO2 and resulting (CH3)3SiF were removed under dynamic vacuum. A red-brown solid remained. Yield: 92%. IR (KBr): ~n ˆ 3302 (w), 2327 (s), 2101 (vw, nasN3), 2081 (vs, nasN3), 1634 (m), 1539 (m), 1294 (s, nsN3), 1200 (m), 1138 (m), 1034 (m), 919 (m), 729 (s), 667 (m, dN3), 497 (w), 430 (m), 416 (w, nasAsN3). Raman (385 scans, 150 mW, 180, 208C): ~n ˆ 3193 (0.5), 2119 (4, nasN3), 2092 (3, nasN3), 1561 (3), 1287 (1, nsN3), 1264 (2, nsN3), 1069 (2.5), 1038 (1), 703 (1), 670 (1.5, dN3), 500 (2.5), 429 (10), 417 (8, nasAsN3), 283 (2.5, dAsN3), 127 (7.5). 1 H NMR (d6-DMSO, 400 MHz, 258C): d ˆ 7:84 (s, NCNH2). 13 C NMR (d6-DMSO, 101 MHz, 258C): d ˆ 156:7 (s, NCNH2). 14 N NMR (d6-DMSO, 29 MHz, 258C): d ˆ 141 (s, Nb), 164 (s, Ng), 249 (s, Na), 359 (s, NCNH2). 75 As NMR (d6-DMSO, 69 MHz, 258C): d ˆ 9 (s). 3.3.10. Sb(N3)5
NCNH2 At 1968C SbF5 [0.217 g (1.00 mmol)] was condensed onto a frozen solution of (CH3)3SiN3 [0.66 ml (5.00 mmol)] in 10 ml SO2 on one side of a two bulb vessel. The reaction mixture was warmed slowly to room temperature and stirred for 24 h. On the other side of the two bulb vessel, NCNH2 [0.042 g (1.00 mmol)] were dissolved in 10 ml SO2. Both sides were reacted together at room temperature and stirred for 12 h. SO2 and resulting (CH3)3SiF were removed under dynamic vacuum. A brown solid remained. Yield: 88%. IR (KBr): ~n ˆ 3280 (w), 2350 (s), 2126 (w, nasN3), 1489 (w), 1382 (w), 1260 (s, nsN3), 1019 (s), 898 (m), 798 (w), 669 (m, dN3). Raman (400 scans, 130 mW, 180, 208C): ~n ˆ 3204 (0.5), 2109 (1.5, nasN3), 2097 (2, nasN3), 1639 (0.5), 1573 (1), 1395 (1.5), 1252 (0.5, nsN3), 1177 (0.5), 989 (0.5), 764 (2), 668 (2, dN3), 634 (2, dN3), 419 (6), 407 (5.5, nasAsN3), 349 (10), 233 (3.5, dSbN3), 143 (2.5). 1 H NMR (d6-DMSO, 400 MHz, 258C): d ˆ 7:88 (s, NCNH2). 13 C NMR (d6DMSO, 101 MHz, 258C): d ˆ 155:9 (s, NCNH2). 14 N NMR (d6-DMSO, 29 MHz, 258C): d ˆ 141 (s, Nb), 153 (s, NCNH2), 172 (s, Ng), 252 (s, Na), 359 (s, NCNH2). 121 Sb NMR (d6-DMSO, 96 MHz, 258C): d ˆ 4 (s). Acknowledgements Financial support of this work by the University of Munich and the Fonds der Chemischen Industrie is gratefully acknowledged. We are indebted to and thank Dr. B. Krumm for recording the NMR spectra. We also thank the

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