Substitution Reactions of Aluminum Organoamide Complexes [Al(μ-NR2)nCl3-n]2 (R = Et, iPr; n ? 3) with LiNR‘R‘‘ (R‘ = R‘‘ = iPr, Et; R‘ = H, R‘‘ = iPr): Crystal Structure of [Al(μ-NEt2)(NiPr2)X]2 (X = Cl, H) and AlCl3(NiPrH2)2{Al(NH3)(NH2)[Al(NiPrH)(NiPr)

Substitution Reactions of Aluminum Organoamide Complexes [Al(

µ-NR

2

)

n

Cl

3-n

]

2

(R

)

Et,

i

Pr; n e 3) with LiNR′R′′

(R′

)

R′′

)

i

Pr, Et; R′

)

H, R′′

)

i

_{Pr): Crystal Structure of}

[Al(

µ-NEt

2

)(N

i

Pr

2

)X]

2

(X

)

Cl, H) and AlCl

3

(N

i

_PrH

2

)

2

{Al(NH

3

)(NH

2

)[Al(N

i

PrH)(N

i

Pr)Cl]

2

}

2

Chung-Cheng Chang,*

,†

_{Mung-Dar Li,}

†

_{Michael Y. Chiang,}

†

_{Shie-Ming Peng,}

‡

_{Yu Wang,}

‡

_and

Gene-Hsiang Lee

‡

Department of Chemistry, National Sun Yat-Sen University, Kaohsiung, Taiwan, ROC, and

Department of Chemistry, National Taiwan University, Taipei, Taiwan, ROC

Recei

V

ed May 4, 1995

X

As part of our ongoing study of different substituents of Al

2

N

2

ring systems, the synthesis, structural characterization,

and spectroscopic studies on several amido derivatives of four-coordinated aluminum are described. The compounds

Al

2

(NEt

2

)

2

(N

i

Pr

2

)

2

Cl

2

, 1, Al

2

((N

i

Pr

2

)

4

Cl

2

, 2, Al((N

i

Pr

2

)

3

, 3, Al(NEt

2

)

3

, 4,

{

Al(N

i

PrH)

3

}

3

, 5, Al

2

(NEt

2

)

2

(N

i

Pr

2

)

2

H

2

,

6, and AlCl

3

(N

i

PrH

2

)

2

{

Al(NH

3

)(NH

2

)[Al(N

i

PrH)(N

i

Pr)Cl]

2

}

2

, 7, were synthesized by substitution reactions and

characterized by mass spectra, IR spectra, elemental analysis, and

1

_H,

13

_{C, and}

27

_{Al NMR data. The structures}

of three compounds,

V

iz., 1, 6, and 7, have been determined by single-crystal X-ray diffraction analysis. Crystal

data with Mo K

R

(1 and 7,

λ

)

0.710 73 Å) or Cu K

R

(6,

λ

)

1.541 78 Å) radiation: (1) Al

2

N

4

C

20

H

48

Cl

2

, a

)

7.747(2) Å, b

)

9.648(2) Å, c

)

10.110(3) Å,

R

)

102.91(2)

°

,

β

)

83.54(2)

°

,

γ

)

110.19(2)

°

, triclinic, space

group P1

h

, Z

)

1, R

)

0.053 for 1789 (I

>

3

σ(I)) reflections; (6) Al

2

N

4

C

20

H

50

, a

)

15.088(2) Å, b

)

14.506(3)

Å, c

)

12.439(3) Å, orthorhombic, space group Cmca (No. 64), Z

)

4, R

)

0.045 for 701 (I

>

3

σ(I)) reflections;

(7) Al

7

N

14

C

30

H

86

Cl

7

, a

)

29.914(9) Å, b

)

10.197(3) Å, c

)

20.525(5) Å,

β

)

90.99(4)

°

, monoclinic, space

group C2/c, Z

)

4, R

)

0.042 for 2472 (I

>

2

σ(I)) reflections.

Introduction

Recently compounds with group 13 and 15 bonds were shown

to be potential precursors for semiconductor systems.

1-12

Noteworthy are the organoaluminum compounds, which are

precursors for aluminum nitride. Most amido or imido

deriva-tives of aluminum tends to form oligomers with strong metal

-nitrogen

σ bonds. In complexes involving imido ligands,

especially (imino)aluminum monomers, the lone pairs on

nitrogen may not be involved in

σ-bonding and may in principle

contribute to the partial

π-bonds between aluminum and nitrogen

centers. Power and co-workers have reported the Al

-

N bond

in compounds possessing a possible weak

π-interaction.

13

_Low

valency, unsaturated coordination, and fascinating bonding are

noticeably emphasized in Al

-

N chemistry recently.

14

_Our

previous studies focused mainly on the reactivity of Al

-

N and

Mg

-

C bonds.

15-18

Herein we report the synthesis,

character-ization, and crystal structures of Al

2

(NR

2

)

2

(NR

′

2

)

2

X

2

(R

)

Et,

i

_{Pr; R}

′

)

i

_{Pr, X}

)

Cl, H) and a novel adduct AlCl

3

(N

i

-PrH

2

)

2

{

Al(NH

3

)(NH

2

)[Al(N

i

PrH)(N

i

Pr)Cl]

2

}

2

. The adduct

con-tains unusually short Al

-

N bonds indicating a possible

π-in-teraction or strong ionic attraction in the Al

-

N moieties.

Experimental Section

Apparatus and Materials. All manipulations were carried out in

a N2-flushed glovebag, drybox, or vacuum system. Solvents were

distilled and degassed prior to use. Lithium amides were synthesized by following a reported procedure.14 _{Single-crystal X-ray diffraction}

data were obtained using an Enraf Nonius CAD-4 diffractometer. All

1_H,13_{C, and}27_{Al NMR spectra were measured on a Varian VXR-300}

spectrometer. Chemical shifts are referenced relative to either TMS (1_{H) or benzene-d}

6(1H,δ 7.15;13C{1H},δ 128.00), while27Al NMR

spectra were referenced relative to Al(H2O)63+

. Mass spectral data were obtained on a VG-7025 GC/MS/MS spectrometer. IR spectra were recorded as Nujol mulls between KBr disks on a BIO-RAD FT-IR spectrometer. Elemental analyses (C, H, N) were performed at the Analytische Laboratorien, Lindlar, Germany. Deviations in the results of the elemental analyses from calculated values are attributed to the extremely air sensitive and hygroscopic nature of these compounds.

Synthesis of Al2(NR2)2(NR′2)2Cl2(R)Et, R′)

i_{Pr, 1; R}

)R′)

i_{Pr, 2). Bis((µ-dialkylamido)dichloroaluminum), Al}

2(NR2)2Cl415(R)

†_{National Sun Yat-Sen University.} ‡_{National Taiwan University.}

X_{Abstract published in Ad}Vance ACS Abstracts, April 1, 1997. (1) Liao, B.; Li, Y.; Lu, Y. J. Mater. Chem. 1993, 3 (2), 117. (2) Lindsell, W. E. In ComprehensiVe Organometallic Chemistry;

Wilkin-son, G., Stone, F. G. A., Abel, E. W., Eds.; Pergamon, Oxford, U.K., 1982; Vol. 1, Chapter 6, and references cited therein.

(3) Laubengayer, A. W.; Smith, J. D.; Ehrlich, G. G. J. Am. Chem. Soc. 1961, 83, 542.

(4) Gosling, K.; Smith, J. D.; Wharmby, D. H. W. J. Chem. Soc. A 1969, 1738.

(5) Alford, K. J.; Gosling, K.; Smith, J. D. J. Chem. Soc., Dalton Trans. 1972, 2203.

(6) (a) Hitchcock, P. B.; Smith, J. D.; Thomas, K. M. J. Chem. Soc., Dalton

Trans. 1976, 1433. (b) Amirkhalili, S.; Hitchcock, P. B.; Smith, J.

D. J. Chem. Soc., Dalton Trans. 1979, 1206.

(7) Amirkhalili, S.; Hitchcock, P. B.; Jenkins, A. D.; Nyathi, J. Z.; Smith, J. D. J. Chem. Soc., Dalton Trans. 1981, 377.

(8) Atwood, J. L.; Stucky, G. D. J. Am. Chem. Soc. 1970, 92, 285. (9) McLaughlin, G. M.; Sim, G. A.; Smith, J. D. J. Chem. Soc., Dalton

Trans. 1972, 2197.

(10) Dozzi, G.; Cucinella, S.; Mazzei, A. J. Organomet. Chem. 1979, 164, 1.

(11) Piero, G. D.; Cesari, M.; Dozzi, G.; Mazzei, A. J. Organomet. Chem. 1977, 129, 281.

(12) (a) Sze, S. M. Physics of Semiconductor DeVices, 2nd ed.; Wiley: New York, 1981. (b) Rockeususs, W.; Roesky, H. W. AdV. Mater.

1993, 5, 443.

(13) Brothers, P. J.; Wehmschulte, R. J.; Olmstead, M. M.; Ruhlandt-senge, K.; Parkin, S. R.; Power, P. P. Organometallics 1994, 13, 2792. (14) (a) Collum, D. B. Acc. Chem. Res. 1993, 26, 227 and references cited

therein. (b) Lappert, W. F.; Power, P. P.; Sanger, A. R.; Srivastava, R. C. Metal and Metalloid Amides; Ellis-Horwood: Chichester, U.K., 1980; and references cited therein.

(15) Her, T. Y.; Chang, C. C.; Tsai, J. O.; Lai, Y. Y.; Liu, L. K.; Chang, H. C.; Chen, J. H. Polyhedron 1993, 12, 731.

(16) Her, T. Y.; Chang, C. C.; Liu, L. K. Inorg. Chem. 1992, 31, 2291. (17) Her, T. Y.; Chang, C. C.; Lee, G. H.; Peng, S. M.; Wang, Yu Inorg.

Chem. 1994, 33, 99.

(18) Chang, C. C.; Lee, W. H.; Her, T. Y.; Lee, G. H.; Peng, S. M.; Wang, Y. J. Chem. Soc., Dalton Trans. 1994, 315.

S0020-1669(95)00539-8 CCC: $14.00

© 1997 American Chemical Society

Downloaded by NATIONAL TAIWAN UNIV on August 14, 2009

Et, a; R)

i_{Pr, b; 3.0 mmol; 1.02 g, a; 1.20 g, b), was added slowly to}

an ether solution (100 cm3_{) of LiNR}′′

2(R′′)Et, 0.48 g, 6.0 mmol; R′′ )

i_{Pr, 0.65 g, 6.0 mmol) under nitrogen at}

-30°C. The reaction

mixture was brought back to room temperature slowly, and after 1 h the solution was centrifuged to remove LiCl powder. Crude products of compound 1 and 2 were obtained after the removal of ether. Transparent colorless crystals of Al2(NR2)2(NR′2)2Cl2were obtained

by vacuum sublimation (compound 1) and recrystallization of the crude product from toluene (compound 2). Analytical data for 1 and 2 follows. Compound Al2(NEt2)2(NiPr2)2Cl2(1): Mp 96-97°C; yield

75%; IR (Nujol mull) 2980 (s), 2960 (s), 2910 (s), 2860 (s), 2810 (m), 1460 (m), 1370 (m), 1185 (br), 1055 (br), 690 (br) cm-1. Anal. Found: C, 51.3; H, 10.3; N, 11.8. Calcd: C, 51.2; H, 10.3; N, 11.9. Analysis by mass spectroscopy gave the fragments expressed as m/z (EI: 70 eV, relative intensity (%) and assignment in parentheses): 468 (9.3, [M]+), 453 (17.5, [M -CH₃] +), 433 (9.1, [M -Cl] +), 390 (13.3, [M-(C3H7+Cl)] +), 368 (74.4, [M -N(C3H7)2] +), 334 (19.5, [MH -(Cl+N(C3H7)2)] +), 269 (19.5, [MH -2(N(C3H7)2)] +), 233 (26.4 [M-(Cl+2N(C3H7)2)] +), 219 (100, [M/2 -CH3] +), 303 (9.3, [M + Cl-N(C3H7)2] +). 1H NMR (C 6D6): δ 1.09 (t, 12H, CH3of NEt2, 3_J H-H )6.6 Hz), 1.27 (d, 24H, CH3of N i_Pr 2,3JH-H )6.6 Hz), 2.94, 2.97, 3.37, 3.41 (quart, 8H, CH2of NEt2,3JH-H )6.6 Hz), 3.26 (sep, 4H, CH of Ni_Pr 2,3JH-H )6.6 Hz). 13_{C NMR (C} 6D6): δ 12.40 (CH3 of NEt2), 25.50 (CH3of NiPr2), 40.23 (CH2of NEt2), 46.69 (CH of Ni_Pr 2). 27Al NMR (C6D6): δ 89 ppm (br). Compound Al2(NiPr2)4Cl2

(2): Mp (dec) 77°C; yield 40%; IR (in KBr pellets) 2965 (s), 2945 (s), 2890 (s), 1335 (m), 1230 (m), 1132 (w), 1063 (m), 817 (br), 641 (br) cm-1

. Anal. Found: C, 57.2; H, 11.0; N, 9.73; Cl, 11.9. Calcd: C, 54.8; H, 10.7; N, 10.6; Cl, 13.5. Analysis by mass spectroscopy gave the fragments expressed as m/z (EI: 70 eV, relative intensity (%) and assignment in parentheses): 524 (5.2, [M]+

), 509 (18.2, [M -CH3]+ ), 489 (13.3, [M-Cl] + ), 446 (12.1, [M-(C3H7+Cl)] + ), 424 (8.7, [M-N(C3H7)2] + ), 390 (12.7, [MH-(Cl+N(C3H7)2)] + ), 226 (32.6, [Al(N(C3H7)2-H] + ), 183 (32.6, [AlN(C3H7)2)-(C3H7+H)] + ), 126 (72.2, [AlNC3H7 - H] + ), 100 (100, [N(C3H7)2]+ ). 1_{H NMR} (C6D6): δ 1.25 (d, 36H, CH3of NiPr2,3JH-H )6.6 Hz), 3.40 (sep, 4H, CH of Ni_Pr 2,3JH-H )6.6 Hz). 13_{C NMR (C} 6D6): δ 23.71 (CH3of Ni_Pr 2), 45.31 (CH of NiPr2). 27Al NMR (C6D6): δ 112 ppm (br). Synthesis of Al(NR′R′′)3(R′)R′′) i_{Pr, 3; R}′ )R′′)Et, 4; R′ ) i_{Pr, R}′′ )H, 5). Bis((µ-dialkylamido)dichloroaluminum), Al2(NR2)2 -Cl415(R)Et, a;

i_{Pr, b) (4.0 mmol; 1.36 g, a; 1.60 g, b), was added}

dropwise to an ether solution (100 cm3_{) of lithium diisopropylamide}

(1.71 g, 16 mmol) or lithium diethylamide (1.26 g; 16 mmol) under nitrogen at-30°C. The reactions took place when the temperature

was raised to room temperature. After 2.5 h the solution was centrifuged to remove the white precipitate. The crude product was recrystallized and characterized to be Al(NR′R′′)3(R′)R′′)

i_{Pr, 3;}

R′)R′′)Et, 4; R′)

i_{Pr, R}′′

)H, 5).

The compounds Al(NR′R′′)3(3-5) were also obtained from the

reaction of Al2Cl6with LiNR′R′′(R′)R′′)

i_{Pr for 3; R}′

)R′′)Et

for 4, R′)

i_{Pr, R}′′

)H for 5) in a molar ratio of 1:6. Analytical data

for 3-5 follows. Compound Al(N

i_Pr

2)3 (3): Solid; mp 58-59°C;

yield, 80%. 3 was purified by sublimation at 50°C, 10-3Torr. IR (KBr pellets): 2998 (s), 2976 (s), 2895 (s), 1441 (m), 1410 (m), 1111 (m), 1102 (w), 995 (m), 911 (br), 643 (br) cm-1. Anal. Found: C, 58.5; H, 11.7; N, 11.1. Calcd: C, 66.0; H, 12.9; N, 12.8. Analysis by mass spectroscopy gave the fragments expressed as m/z (EI: 70 eV, relative intensity (%) and assignment in parentheses): 328 (2.2, [M+

H]+ ), 313 (4.5, [M+H-CH3] + ), 298 (5.2, [M+H-2Me] + ), 283 (5.1, [M+H-3Me] + ), 226 (12.8, [M-H-N(C3H7)2] + ), 211 (32.6, [AlN(C3H7)2-H-Me] + ), 183 (10.6, [AlN(C3H7)2)-(C3H7+H)] + ), 126 (32.6, [AlNC3H7 - H] + ), 100 (72.2, [N(C3H7)2]+ ), 58 (100, [HNC3H7]+ ). 1_{H NMR (C} 6D6): δ 1.27 (d, 36H, CH3of NiPr2,3JH-H )6.6 Hz), 3.41 (sep, 4H, CH of N i_Pr 2,3JH-H )6.6 Hz). 13_{C NMR} (C6D6): δ 25.66 (CH3of NiPr2), 46.24 (CH of NiPr2) and27Al NMR

(C6D6): δ 162 ppm (br). Compound Al(NEt2)3(4): Solid; mp 68-70

°C; yield, 60%; IR (Nujol mull) 2994 (s), 2980 (s), 2891 (m), 1456 (w), 1412 (m), 1370 (m), 1080 (m), 1035 (m), 990 (br), 960 (m) cm-1. Anal. Found: C, 58.9; H, 12.2; N, 17.1. Calcd: C, 59.2; H, 12.4; N, 17.3. Analysis by mass spectroscopy gave the fragments expressed as

m/z (EI: 70 eV, relative intensity (%) and assignment in parentheses):

487 (18.7, [2M+H] +), 413 (5.5, [Al 2(NEt2)5-H] +), 398 (12.3, [Al 2 -(NEt2)5-Me-H] +, 384 (15.6, [Al 2(NEt2)5-2Me-H] +), 340 (17.2, [Al2(NEt2)4-2H] +), 313 (13.8, [Al(NEt 2)4-2H] +), 272 (72.3, [EtAl-(NEt2)3]+), 242 (92.3, [M -H] +) 171 (33.0, [Al(NEt 2)2]+), 100 (100, [HAl(NEt2)]+). 1H NMR (C 6D6): δ 1.24 (t, 15H, CH3of NEt2,3JH-H )6.6 Hz), 3.14 (quart, 8H, CH₂of NEt₂, 3_J H-H )6.6 Hz). 13_{C NMR} (C6D6): δ 12.38 (CH3of NEt2), 39.75 (CH2of NEt2). 27Al NMR

(C6D6): δ 157 ppm (br). Compound{Al(NiPrH)3}3(5): Mp (dec)

189°C; yield, 45%; IR (Nujol mull) 3340 (w), 3290 (w), 2950 (m), 2920 (s), 2850 (w), 1460 (m), 1370 (w), 1295 (w), 1190 (s), 1105 (w), 1065 (m), 1050 (m), 1010 (w), 925 (m), 840 (m), 760 (br), 690 (br), 650 (w) cm-1. Analysis by mass spectroscopy gave the fragments expressed as m/z (EI: 30 eV, relative intensity (%) and assignment in parentheses): 603 (55.3, [3Al(Ni_PrH) 3]+), 601 (100, [3Al(NiPrH) 3 -2H]+), 559 (5.5, [3Al(NiPrH) 3 -i_Pr -H] +), 549 (52.2, [2Al(NiPrH) 3 +H2Al(N i_PrH 2)]+ ), 384 (5.2, [2Al(Ni_PrH) 3-Me-H] + ), 143 (7.7, [Al(Ni_PrH) 2]+ ), 71 (4.3, [HAli_Pr]+ ), 57 (6.4, [i_PrN]+ ), 44 (23.2, [HC3H7]+ ), 43 (24.7, [C3H7]+ ). 1_{H NMR (C} 7D8): δ 0.19 (br, NH of Ni_{PrH), 1.23 (d, CH} 3oftNiPrH,3JH-H )6.3 Hz), 1.38 (d, CH3of b_Ni -PrH,3_J H-H )6.3 Hz), 3.40, 3.41 (sep, CH of N i_PrH,3_J H-H )6.3 Hz). 13_{C NMR (C} 7D8): δ 29.59 (CH3oftNiPrH), 29.74 (CH3ofbNiPrH), 44.84 (CH oft_Ni_{PrH), 46.83 (CH of}b_Ni_PrH). 27_{Al NMR (C} 6D6): δ 111 ppm (br).

Reaction of Al2(NEt2)2(NiPr2)2Cl2 (1) with LiNiPrH. Bis((

µ-dialkylamido)chloro(diisopropylamido)aluminum), Al2(NEt2)2(NiPr2)2

-Cl2(1.87 g, 4.0 mmol), was added slowly to an ether solution (100

cm3_{) of lithium isopropylamide (2.60g; 24.0 mmol) under nitrogen at}

-30 °C. The reaction took place when the reaction mixture was

warmed to room temperature. The solution was centrifuged to remove the white precipitate. The products Al2(NEt2)2(NiPr2)2H2(6) and{Al(Ni

-PrH)3}3(5) were obtained by gradient vacuum sublimation (10-3Torr) at 115 and 185°C, respectively. Analytical data for Al2(NEt2)2(Ni

-Pr2)2H2(6): Mp (dec) 145°C; yield 10%; IR (Nujol mull) 2980 (s),

2960 (s), 2910 (s), 2860 (s), 1725 (m), 1460 (m), 1370 (m), 1185 (br), 1055 (br), 690 (br) cm-1. Anal. Found: C, 59.0; H, 12.3, N, 12.7. Calcd: C, 59.2; H, 12.6; N, 14.0. Analysis by mass spectroscopy gave the fragments expressed as m/z (EI: 70 eV, relative intensity (%) and assignment in parentheses): 401 (8.7, [M+H] +), 385 (17.2, [M -CH3]+), 384 (8.3, [M -H -Me] +), 357 (5.2, [M -C3H7] +), 300 (5.2, [M-N(C₃H₇)₂] +, 258 (12.7, [MH -(C3H7+N(C3H7)2)] +), 201 (12.7, [M/2+H] +), 100 (100, [N(C 3H7)2)]+), 58 (57.2, [HNC 3H7]+), 43 (72.3, [C3H7]+). 1H NMR (C 7D8): δ-0.20 (br, 2H, Al-H), 1.08 (t, 12H, CH3of NEt2,3JH-H )6.6 Hz), 1.24 (d, 24H, CH₃of N i_Pr 2, 3_J H-H )6.6 Hz), 2.97, 3.00, 3.34, 3.37 (q, 8H, CH₂of NEt₂, 3_J H-H ) 6.6 Hz), 3.24 (sep, 4H, CH of Ni_Pr 2, 3JH-H ) 6.6 Hz). 13_{C NMR} (C7D8): δ 12.40 (CH3of NEt2), 25.53 (CH3of NiPr2), 40.30 (CH2of NEt2), 46.77 (CH of NiPr2). 27Al NMR (C7D8): δ 108 ppm (br).

Synthesis of AlCl3(NiPrH2)2{Al(NH3)(NH2)[Al(NiPrH)(NiPr)Cl]2}2

(7). Al2Cl6 (2.67 g; 10.0 mmol) was added slowly to a solution

containing an ether solution (100 cm3_{) of lithium isopropylamide (2.14}

g; 60.0 mmol) with excess isopropylamine (20.0 mmol) under nitrogen at-30°C. The reaction took place when the temperature returned to

room temperature. The crude product was obtained after removal of solvent and LiCl precipitate. The product AlCl3(NiPrH2)2{[Al(NH3

)-(NH2)[Al(NiPrH)(NiPr)Cl]2}2(7) was obtained from recrystallization

from a hexane/toluene mixture (1:1).

The compound AlCl3(NiPrH2)2{Al(NH3)(NH2)[Al(NiPrH)(NiPr)Cl]2}2

(7) (solid) was purified by sublimation at 55°C, 10-3Torr: Mp 73

-75°C; yield, 38%; IR (Nujol mull) 3361 (w), 3295 (w), 3205 (w), 2980 (s), 2958 (s), 2950 (s), 2870 (s), 1460 (m), 1370 (m), 1172 (br), 1151 (br), 893 (m), 651 (br) cm-1

. Anal. Found: C, 38.3; H, 6.7; N, 15.0. Calcd: C, 33.3; H, 8.2; N, 18.1. Analysis by mass spectroscopy gave the fragments expressed as m/z (EI: 70 eV, relative intensity (%) and assignment in parentheses): 568 (17.2, [AlCl2(NiPrH2) +

[Al(NH3)(NH2)[Al(NiPrH)(NiPr)Cl]2 - 2H] + ), 509 (47.2, [AlCl2 + [Al(NH3)(NH2)[Al(NiPrH)(NiPr)Cl]2-2H] + ), 435 (5.2, [AlCl3(NiPrH2)2 +Al(N i_Pr 2)(NiPrH)]+ ), 413 (2.1, [Al(NH3)(NH2)[Al(NiPrH)(NiPr)Cl2 -2H] +), 378 (7.2, [AlCl 3(NiPrH2)2+Al(N i_Pr 2)]+), 224 (8.6, [Al(Ni -PrH)(Ni_Pr)Cl +AlCl-Me] +), 69 (5.4, [AliPr -H] +), 58 (21.8, [Ni -PrH]+), 44 (61.8, [HiPr]+), 43 (100, [iPr]+). 1H NMR (C 6D6): δ 0.87 (br, 10H, Al(NH2)(NH3)), 0.95 (d, 12H, CH3of NiPrH2,3JH-H )6.6 Hz), 1.23 (d, 24H, CH3of NiPr,3JH-H )6.6 Hz), 1.26 (br, 4H, NH of Ni_PrH 2), 1.31 (br, 24H, CH3of NiPrH), 2.80 (br, 2H, CH of NiPrH2,

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3_J H-H )6.6 Hz), 3.23 (sep, 4H, CH of N i_Pf,3_J H-H )6.6 Hz), 3.38 (sep, 4H, CH of Ni_PrH,3_J H-H )6.6 Hz), 3.89 (br, 4H, NH of N i_PrH, 3_J H-H )6.6 Hz). 13_{C NMR (C} 6D6): δ 23.70 (CH3of NiPrH2), 25.66 (CH3of NiPrH), 25.90 (CH3of NiPr), 46.01 (CH of NiPrH2), 46.29 (CH of Ni_{PrH), 65 45 (CH of N}i_Pr). 27_{Al NMR (C} 6D6): δ 112 ppm (br).

X-ray Structure Analysis. Single crystals for X-ray measurements

were sealed in glass capillaries. Intensity data were collected using theθ-2θ scan mode and corrected for absorption and decay. All

structures were solved by direct methods and refined with full-matrix least squares on F. In the final cycle all non-hydrogen atoms were fixed at idealized positions. Scattering factors for neutral atoms and anomalous scattering coefficients for non-hydrogen atoms were taken from the literature.19 _{All calculations were carried out with either a}

Micro VAX 3600 computer using the NRCVAX program package20a

(for 6) or a SGI R4000 computer using the teXsan program package20b

(for 1 and 7). Data collection and crystal parameters are summarized in Table 1, and selected bond distances and angles of 1, 6, and 7 are listed in Table 2. The final positional parameters of the refined atoms are presented in Table 3.

Results and Discussion

The compound

{

Al(NR

′

R

′′

)

3

}

n

can be synthesized either by

the reaction of aluminum hydride with amine or by treatment

of aluminum chloride with amine and lithium amide.

2,29

_The

latter reaction can be controlled by stoichiometry. For the main

group metals, substitution reaction via lithium amide is a

common method to generate Al/NR

2

/halide ternary compounds.

In order to study the selectivity in substitution and stabilization

of the Al

2

(NR

2

)

n

Cl

6-n

complexes, we have used different

stoichiometric ratios of aluminum complexes and lithium amide

to form the new Al

2

(NR

2

)

n

Cl

6-n

complexes.

The X-ray

structural determinations of the complexes are described in the

following section.

Description of Structures. Compound Al(NEt

2

)(N

i

Pr

2

)Cl

uses diethylamide as a bridging group to form dimer 1, and the

dimer sits on an inversion center as shown in Figure 1. The

four atoms Al, N(2), Al

′

, and N(2

′

) form a coplanar

four-membered ring with equal Al

-

N distances of 1.967(4) Å, and

the internal angles of the Al

2

N

2

ring are all near 90

°

. In the

terminal amide the Al, N(1), C(1), and C(4) atoms lie on a plane

as a result from the sp

2

_{hybridization of the N(1) atom.}

However, the Al

-

N(1) bond distance is quite short (1.791(4)

Å) reaching the lowest values found in the literature (1.79

-(19) Ibers, J. A., Hamilton, W. C., Eds. International Tables for X-ray

Crystallography; Kynoch Press: Birmingham, U.K., 1974; Vol. IV,

Tables 2.2.B and 2.3.1.

(20) (a) Gabe, E. J.; Le Page, Y.; White, P. S.; Lee, F. L. Acta Crystallogr. 1987, A43, S294. (b) teXsan: Crystal Structure Analysis Package; Molecular Structure Corp.: College Station, TX, 1985, 1992. Table 1. Crystallographic Data Refinement Details for Compounds 1, 6, and 7 compound 1 6 7 formula C20H48Al2N4Cl2 C24H50Al2N4 C30H88Al7N14Cl7 fw 469.49 400.51 1082.15 a, Å 7.747(2) 15.088(2) 29.914(9) b, Å 9.648(2) 14.506(3) 10.197(3) c, Å 10.110(3) 12.439(3) 20.525(5) R, deg 102.91(2) β, deg 83.54(2) 90.99(4) γ, deg 110.19(2)

cryst system triclinic orthorhombic monoclinic space group P1 Cmca (No. 64) C2/c

2θ range, deg 16.66-28.06 60.9-78.3 15.50-20.00 cryst size, mm 0.25× 0.30 × 0.50 0.16× 0.45 × 0.45 0.25× 0.50 × 0.55 V, Å3 _{691(1) 2722(1) 6260(3)} Z 1 4 4 Dcalc, Mg M-3 1.129 0.977 1.148 µ, mm-1 0.31 1.02 (Cu K R) 0.45 λ, Å 0.710 70 1.541 78 0.710 70 no. of rflns measd 2449 1162 4068 no. of unique rflns 2423 4068 no. of rflns I0>2.0σ(I0) 1789 697 (I0>3.0σ) 2472 transm factors (min; max) 0.942; 0.997 0.883; 1.000 RF 0.062 0.051 0.047 Rw 0.053 0.042 0.043 GoF 4.47 3.61 1.76 max∆/σ 0.015 0.01 0.023

Figure 1. ORTEP view of the compound Al2(µ-NEt2)2(NiPr2)2Cl2(1).

Table 2. Selected Bond Distances (Å) and Angles (deg) for

Compounds 1, 6, and 7 Compound 1 Al-N(1) 1.791(4) N(2)-C(7) 1.50(1) Al-N(2) 1.967(4) C(1)-C(2) 1.53(1) Al-Cl 2.127(2) C(7)-C(8) 1.52(1) N(1)-C(4) 1.46(1) Al-N(2)-Al′ 91.4(2) Al-N(1)-C(4) 124.9(3) N(2)-Al-N(2′) 88.6(2) C(1)-N(1)-C(4) 113.1(3) Cl-Al-N(2) 105.8(1) Al-N(2)-C(7) 112.6(3) Cl-Al-N(1) 115.2(1) C(2)-C(1)-C(3) 109.1(4) Al-N(1)-C(1) 122.0(3) N(2)-C(7)-C(8) 115.0(4) Compound 6 Al(1)-N(1) 1.792(5) N(2)-C(5) 1.49(1) Al(1)-N(2) 1.962(3) C(1)-C(2) 1.51(1) Al(1)-H(14) 1.67 C(5)-C(6) 1.51(1) N(1)-C(1) 1.47(1)

Al(1)-N(2)-Al(1′) 92.0(2) Al(1)-N(1)-C(3) 122.4(4)

N(2)-Al(1)-N(2′) 88.0(2) C(1)-N(1)-C(3) 112.3(5) N(2)-Al(1)-H(14) 107.5 Al(1)-N(2)-C(5) 115.6(2) N(1)-Al(1)-H(14) 114.4 C(2)-C(1)-C(2′) 109.6(6) Al(1)-N(1)-C(1) 125.3(4) N(2)-C(5)-C(6) 115.6(2) Compound 7 Al(1)-N(1) 1.926(4) Al(3)-N(7) 1.874(6) Al(1)-N(2) 1.926(4) Al(1)-Cl(1) 2.124(2) Al(1)-N(3) 1.784(4) N(1)-C(1) 1.50(1) Al(2)-N(4) 1.788(5) N(3)-C(7) 1.51(1) Al(3)-N(3) 1.718(4) Al(4)-Cl(4) 2.169(2) Al(3)-N(4) 1.735(4) Al(4)-N(5) 2.037(4) Al(3)-N(6) 1.880(6) N(5)-C(13) 1.51(1)

Al(1)-N(1)-Al(2) 86.9(2) Al(2)-N(4)-Al(3) 122.9(2)

N(1)-Al(1)-N(2) 84.3(2) Al(1)-N(3)-C(7) 123.8(3) Cl(1)-Al(1)-N(1) 113.1(1) Al(3)-N(3)-C(7) 113.5(3) Cl(1)-Al(1)-N(3) 123.1(2) N(6)-Al(3)-N(7) 106.8(3) Al(1)-N(1)-C(1) 123.3(3) N(7)-Al(3)-N(3) 110.4(3) Al(2)-N(1)-C(1) 122.1(3) N(7)-Al(3)-N(4) 110.1(3) Al(1)-N(3)-Al(3) 122.7(2) C(2)-C(1)-C(3) 111.0(5) N(3)-Al(3)-N(4) 109.0(2)

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1.85 Å).

21

_{This possibly indicates more s-character in the Al}

-N(1) bonding. The Al

-

Cl(1) bond distance of 2.127(2) Å is

in the same range as found in other organoaluminum chloride

compounds.

22-25

A molecular plot of compound Al(NEt

2

)(N

i

Pr

2

)H (6), a dimer

with a center of inversion, is shown in Figure 2. The selected

bond lengths and bond angles are shown in Table 2. Both

compound 6 and compound 1 possess an identical framework.

The Al

2

N

2

four-membered ring skeleton is nearly square planar.

The distance of 1.792(4) Å between Al(1) and terminal N(1)

atom is the same as that in 1.

13

_{Although the Al}

-

H distance

may not be reliable in the X-ray analysis, the observed Al(1)

-H(14) distance of 1.67 Å falls between that in a

trialkylalumi-num (1.75(3) Å)

26

_{and that in a lithium organotrihydroaluminate}

(1.61(2) Å).

27

_{The H}

-

Al

-

N angles involving H(14) (108,

114

°

) are consistent with distorted tetrahedral geometry around

the aluminum atom.

Compound 7 is composed of two parts of

{

Al(NH

3

)(NH

2

)-[Al(N

i

_PrH)(N

i

_Pr)Cl]

2

}

2

(X) with one part of AlCl

3

(N

i

PrH

2

)

2

(Y).

The exact molecular symmetry of 7 is C

2

with the 2-fold axis

passing through Al(4) and Cl(3). Coordinated to the seven

aluminum atoms are ammonia, amide, imide, and free amine

as shown in Figure 3. The selected bond lengths and bond

angles are given in Table 2. The X part contains a plane formed

from atoms Al(1), N(3), N(4), and Al(2) and a

cyclobutane-like Al

2

N

2

ring made of Al(1), Al(2), N(1), and N(2) atoms. In

the three-coordinate N(3) moiety, the Al(1), N(3), C(7), and

Al(3) atoms lie on a plane caused by the sp

2

_{hybridization of}

N(3) atom, and so is the N(4) atom. The short distances of

Al

-

N involving N(3) (1.784(4), 1.718(4) Å) and N(4)

(1.735-(4) and 1.788(5) Å) could be caused by ionic resonance effects.

14

The Y molecule is an amine adduct of electronically neutral

AlCl

3

. Hence, the X molecule is also neutral. The nitrogen

ligands coordinated to Al(3) have to be neutral amine and amido

anion in order to balance the charge on X. After careful

examination of the final difference electron density map, the

N(7) is assigned as belonging to the amine ligand and N(6) is

assigned as belonging to the amido ligand.

Stoichiometric Reaction of Compound Al

2

(NR

2

)

2

Cl

4

(R

)

Et, a; R

)

i

_{Pr, b) with LiN}

i

_Pr

2

. The reactions of Al

2

(NR

2

)

2

-Cl

4

(R

)

Et, a; R

)

i

_{Pr, b) and lithium diisopropylamide, LiN}

i

-Pr

2

, in 1:2 stoichiometric ratio produced 1 and 2 as shown in

eq 1. The

1

_{H NMR spectrum of 1 displayed a chemical shift}

at

δ

)

1.09 (t, 6H), 2.98 (q, 4H), and 3.28 (q, 4H) due to the

methyl and methylene protons in the ethyl groups and at

δ

)

1.27 (d, 12H) and 3.38 (sep, 4H) due to the methyl and methine

protons in the isopropyl groups. The

13

_{C NMR spectrum}

showed a chemical shift at

δ

)

12.40 and 40.23 for the methyl

and methylene groups of the ethyl and at

δ

)

25.50 and 46.69

(21) Vieth, M. Chem. ReV. 1990, 90, 1.

(22) Bott, S. G.; Elgamal, H.; Atwood, J. L. J. Am. Chem. Soc. 1985, 107, 1796.

(23) Robinson, G. H.; Self, M. F.; Sangokoya, S. A.; Pennington, W. T. J.

Am. Chem. Soc. 1989, 111, 1520.

(24) Piero, G. D.; Perego, G.; Cucinella, S.; Cesari, M.; Mazzei, A. J.

Organomet. Chem. 1977, 136, 13.

(25) Cucinella, S.; Salvatori, T.; Busetto, C.; Perego, G.; Mazzei, A. J.

Organomet. Chem. 1974, 78, 185.

(26) Uhl, W. Z. Anorg. Allg. Chem. 1989, 570, 37.

(27) Eaborn, C.; Gorrell, I. B.; Hitchcock, P. B.; Smith, J. D.; Tavakkoli, K. Organometallics 1994, 13, 4143.

Table 3. Atomic Parameters x, y, z and BeqValues, Where Esd’s

Refer to the Last Digit Printed

x y z Beq Compound 1 Al 0.0926(2) 0.1008(2) 0.1135(1) 2.43(7) C(1) 0.3787(2) 0.1307(2) 0.1017(2) 6.2(1) N(1) 0.01448(2) 0.2055(4) 0.2632(3) 2.5(2) N(2) -0.0335(5) -0.1179(4) 0.0652(3) 2.8(2) C(1) -0.1763(7) 0.2018(5) 0.2843(5) 3.1(2) C(2) -0.1981(7) 0.3543(6) 0.2903(5) 4.9(3) C(3) -0.2744(7) 0.1395(6) 0.4084(5) 4.9(3) C(4) 0.1328(6) 0.3057(5) 0.3748(5) 3.3(3) C(5) 0.2829(7) 0.4372(6) 0.3304(5) 4.8(3) C(6) 0.2138(8) 0.2222(7) 0.4474(5) 5.2(3) C(7) -0.2012(8) -0.1712(6) 0.1547(5) 4.4(3) C(8) -0.3141(9) -0.3370(6) 0.1141(6) 7.2(4) C(9) 0.0898(8) -0.2092(6) 0.0586(5) 4.6(3) C(10) 0.151(1) -0.2140(7) 0.1951(6) 7.0(4) Compound 6 Al(1) 1.0000 0.0902(1) 0.4575(1) 4.87(5) N(1) 1.0000 0.1302(3) 0.3212(4) 4.9(1) N(2) 0.9693(3) 0.0000 0.5000 5.1(1) C(1) 1.0000 0.0709(5) 0.2254(5) 6.4(2) C(2) 0.9182(4) 0.0802(4) 0.1563(4) 9.9(2) C(3) 1.0000 0.2281(5) 0.2936(6) 7.2(2) C(4) 0.9183(4) 0.2774(4) 0.3359(4) 11.2(2) C(5) 0.8530(3) -0.0362(3) 0.4109(4) 7.4(2) C(6) 0.7893(3) -0.1124(4) 0.4417(4) 10.9(2) Compound 7 Al(1) 0.40561(5) 0.1164(2) 0.07064(7) 3.25(7) Al(2) 0.35275(6) 0.0849(2) 0.17133(8) 3.95(8) Al(3) 0.31763(5) -0.0287(2) 0.04034(8) 3.94(8) Al(4) 1_/ 2 0.3494(2) 1/4 3.5(1) Cl(1) 0.46783(5) 0.1950(2) 0.04125(8) 5.18(8) Cl(2) 0.34654(6) 0.1250(2) 0.27266(8) 7.1(1) Cl(3) 1_/ 2 0.1331(2) 1/4 4.3(1) Cl(4) 0.44918(5) 0.4529(1) 0.19362(7) 5.1(1) N(1) 0.3718(1) 0.2357(4) 0.1234(2) 3.1(2) N(2) 0.4100(1) 0.0137(4) 0.1493(2) 3.7(2) N(3) 0.3674(1) 0.0371(4) 0.0157(2) 3.8(2) N(4) 0.3116(1) 0.0005(4) 0.1230(2) 4.4(2) N(5) 0.5405(1) 0.3419(4) 0.0128(2) 4.4(2) N(6) 0.2697(2) 0.0463(7) -0.0068(3) 10.1(4) N(7) 0.3160(2) -0.2093(6) 0.0237(3) 10.6(4) C(1) 0.3394(2) 0.3331(5) 0.0956(2) 3.9(3) C(2) 0.0721(2) 0.4078(6) 0.1485(3) 6.8(4) C(3) 0.3622(2) 0.4258(6) 0.0489(3) 6.1(3) C(4) 0.4187(2) -0.1301(5) 0.1492(3) 4.8(3) C(5) 0.4631(2) -0.1621(6) 0.1199(3) 7.6(4) C(6) 0.4157(3) -0.1852(5) 0.2176(3) 8.5(4) C(7) 0.3756(2) 0.0205(5) -0.0563(3) 5.1(3) C(8) 0.4166(2) -0.0595(7) -0.0694(3) 7.7(4) C(9) 0.3768(3) 0.1497(7) -0.0905(3) 8.3(5) C(10) 0.2687(2) -0.0515(7) 0.1486(3) 7.6(4) C(11) 0.2396(2) 0.0552(9) 0.1747(4) 11.6(6) C(12) 0.2768(3) -0.1582(8) 0.1993(4) 12.4(6) C(13) 0.5585(2) 0.4672(6) 0.1422(3) 5.5(3) C(14) 0.5406(3) 0.4845(7) 0.0739(3) 8.8(4) C(15) 0.6081(2) 0.4675(7) 0.1455(4) 9.6(5)

Figure 2. ORTEP drawing of the compound Al2(µ-NEt2)2(NiPr2)2H2

(6).

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assigned to methyl groups the and methine carbon of the

isopropyl group. The

27

_{Al NMR spectrum showed a chemical}

shift at

δ

)

89 ppm which was assigned to a four-coordinated

environment of the organoaluminum compound.

28

_Mass

spec-tral data showed the base-ion peak at m/z

)

468 which was

assigned to the molecular ion. The above spectral data are in

good agreement with the crystal structure obtained from X-ray

diffraction techniques.

After several days, the

1

_{H NMR}

spectrum of 1 gradually appeared to have the additional peaks

δ

)

0.95 (d) and 2.81 (sep), which were assigned to the methyl

protons and methine protons of the cis form of Al

2

(

µ-NEt

2

)

2

(N

i

-Pr

2

)

2

Cl

2

. In the characterization of 2, the

1

H NMR spectrum

displayed chemical shifts at

δ

)

1.25 (d) due to methyl groups

of the isopropyl and at

δ

)

3.40 (sep) which was assigned to

the methine groups. Mass spectral data contain the base-ion

peak at m/z

)

489 was assigned to the dimer ion less one

chloride group. Compound 2 was isolated by sublimation at

75

°

C after solvent removal. It is reasonable to suggest two

species, cis and trans, to exist in the solutions of compounds 1

and 2. On variation of the molar ratio of compound b to LiN

i

-Pr

2

from 1:2 to 1:4, product 3 was obtained as shown in eq 2,

while compound 1 did not react further with lithium

diisopro-pylamide.

The

1

_{H NMR spectrum of 3 displayed a chemical shift at}

_δ

)

1.27 (d) due to methyl groups of isopropyl, and the septet at

δ

)

3.41 was assigned to the methine groups of isopropyl. Mass

spectral data contained the base-ion peak at m/z

)

328 assigned

to the monomeric species plus one hydrogen group. The X-ray

diffraction data

35

_{for compound 3 showed identical parameters}

with the published report.

13

Substitution Reactions of Al

2

(NR

2

)

2n

Cl

6-2n

(R

)

Et,

i

_Pr;

n

)

1

-

3) with Excess LiNR

′

R

′′

. Some intermediates were

difficult to purify when different chemical stoichiometries

were used. For instance, we were able to isolate the compounds

2 and 3 using Al

2

(N

i

Pr

2

)

2

Cl

4

and LiN

i

Pr

2

in 1:2 and 1:4

stoichiometric ratios while we could not isolate the rest of the

intermediates when the stoichiometry was 1:1, 1:3, 1:5, etc. They

may form aluminum complexes with more amido substituents.

So we used excess lithium amide to isolate the products.

Compounds 4 and 5 were synthesized by the reactions of a, b,

1, and 2 with excess lithium amide LiNR

′

R

′′

as shown in eqs

3 and 4. However, one additional compound 6, Al

2

(NEt

2

)

2

(N

i

-Pr

2

)

2

H

2

, was isolated during the synthesis of 5. We presume

that compounds 5 and 6 were obtained through the substitution

(28) Benn, R.; Rufinsky, B.; Lehmkuhl, H.; Janssen, E.; Kruger, C. Angew.

Chem., Int. Ed. Engl. 1983, 10, 779.

Figure 3. ORTEP drawing of the compound AlCl3(iPrNH2)2{Al(NH3)(NH2)[Al(NiPrH)(NiPr)Cl2}2(7).

Figure 4. ORTEP drawing of the compound{Al(NH3)(NH2)[Al(Ni

-PrH)(Ni_Pr)Cl] 2}2(X).

Al

₂

(NR

₂

)

₂

Cl

₄

a, b

+

2LiN

i

_Pr

2

f

Al

₂

(NR

₂

)

₂

(N

i

Pr

₂

)

₂

Cl

₂

R

)

Et, 1

R

)

i

Pr, 2

+

2LiCl (1)

Al

₂

(N

i

Pr

₂

)

₂

Cl

₄

b

9

8

2 LiNiPr₂ -2LiCl

Al

₂

(N

i

Pr

₂

)

₄

Cl

₂

2

9

8

2LiNiPr₂ -2LiCl

2Al(N

i

Pr

₂

)

₃

3

(2)

Al

₂

(NR

₂

)

₂

Cl

₄

R

)

Et, a

R

)

i

_{Pr, b}

+

6 LiNR

′

R

′′

9

8

-4LiCl

{

Al(NR

′

R

′′

)

₃

}

_n

R

′

)

R

′′

)

Et, 4

R

′

)

i

_{Pr, R}

_′′

)

H, 5

+

2LiNR

₂

(3)

Al

₂

(NR

₂

)

₂

(NR*

₂

)

₂

Cl

₂

R

)

Et, R*

)

i

Pr

R

)

R*

)

i

_Pr

9

8

6LiNR′R′′ -2LiCl

{

Al(NR

′

R

′′

)

₃

}

_n

R

′

)

R

′′

)

Et, 4

R

′

)

i

_{Pr, R}

_′′

)

H, 5

+

2LiNR

₂

+

2LiNR*

₂

(4)

Downloaded by NATIONAL TAIWAN UNIV on August 14, 2009

reaction of compound 1, Al

2

(NEt

2

)

2

(N

i

Pr

2

)

2

Cl

2

, by lithium

hydride and lithium isopropylamide, respectively. The lithium

hydride may be a side product in the synthesis of lithium

isopropylamide. Compounds 3

-

5 can be synthesized by other

routes. Reaction of Al

2

Cl

6

with LiNR

′

R

′′

in 1:6 stoichiometric

ratio yields all three compounds. This result is similar to that

found by Ruff et al.

29-32

Also, compounds 4 and 5 could also

be synthesized by substitution reaction of 3 and 4 with lithium

amide LiNR

′

R

′′

, respectively (eq 5). The

1

_{H NMR spectrum}

of 4 displayed a chemical shift at

δ

)

1.24 (t) due to the methyl

groups of the ethyl, and the quartet at

δ

)

3.14 was assigned

to the methylenyl groups. Mass spectral data contained the

base-ion peak at m/z

)

487 assigned to the dimeric ion plus one

hydrogen group.

The FT-IR spectrum of the complex 5 showed a broad peak

in the 3340 cm

-1

region which was assigned to the N

-

H

stretching vibrations. The

1

_{H NMR spectrum of 5 displayed a}

chemical shift at

δ

)

0.19 (br) due to NH of isopropylamide;

the doublet peaks at

δ

)

1.23 and 1.38 were assigned to the

terminal and bridged methyl groups of isopropylamide,

respec-tively. Mass spectral data contained the base-ion peak at m/z

)

603 assigned to be a trimeric ion. Hence it is suggested that

5 exists as a trimer.

Formation of AlCl

3

(N

i

PrH

2

)

2{

[Al(NH

3

)(NH

2

)[Al(N

i

PrH)-(N

i

_PrH)(N

i

_Pr)Cl]

2}2

_{(7). Reaction of aluminum trichloride with}

lithium isopropylamide yielded a single product, Al(N

i

_PrH)

3

,

5. However, similar reactions of aluminum trichloride with

lithium isopropylamide in the presence of isopropylamine have

generated compound 7.

In an attempt to rationalize the

formation of 7, we propose the possible involvement of an

unidentified species LiNH

2

. A logical retrosynthesis scheme

is shown in eqs 6

-

9.

AlCl

₃

(N

i

PrH

₂

)

₂

{

Al(NH

₃

)(NH

₂

)[AlCl(N

i

PrH)(N

i

Pr)]

₂

}

₂

7

r

2

{

Al(NH

₃

)(NH

₂

)[AlCl(N

i

PrH)(N

i

Pr)]

₂

}

X

+

AlCl

₃

(N

i

PrH

₂

)

₂

Y

(6)

Al

₂

(N

i

PrH)

₄

Cl

₂

8

7

9

4 LiNi_PrH -4LiCl

Al

₂

C

₆

(7)

Al

₂

(N

i

PrH)

₂

(NH

₂

)

₄

9

7

9

2 LiNi_PrH -2LiCl

Al

₂

(NH

₂

)

₄

Cl

₂

7

9

4LiNH2 -4LiCl

Al

₂

Cl

₆

(8)

{

Al(NH

₃

)(NH

₂

)[AlCl(N

i

PrH)(N

i

Pr)]

₂

}

X

7

9

-NiPrH 2

Al

₂

(N

i

PrH)

₄

Cl

₂

8

+

1

_/

2

Al

2

(N

i

_PrH)

2

(NH

2

)

4

9

(9)

The compound 7 contains two different moieties with a

general composition of X

2

Y.

The X part possess the

π

interaction delocalized in the Al

3

N

2

planar framework, which

may be hypothetically built from Al

2

(N

i

PrH)

4

Cl

2

(8) and Al(N

i

-PrH)(NH

2

)

2

(9). Moreover, the synthesis of compounds 8 and

9 could be rationalized by the above substitution reactions. The

clarification of the mechanistic details would require extensive

work. However, it seems worthy of further investigation.

The FT-IR spectrum of the compound 7 showed three broaden

peaks in the region 3205

-

3361 cm

-1

which were attributed to

the stretching vibrations of the N

-

H groups. The

1

_{H NMR}

spectrum of 7 displayed chemical shift at

δ

)

0.89 (br) and

3.87 (br) due to NH of Al(NH

3

)(NH

2

) and N

i

PrH, respectively.

The chemical shifts of various protons of Al(NH

2

)(NH

3

) are

comparable to those of the corresponding values in the

{

t

_Bu

2

-AlNH

2

}

3

derivative.

33

The chemical shifts at

δ

)

0.95 (d), 1.23

(d), and 1.31 (br) with integral ratio 1:2:2 are due to methyl

groups of isopropyl of AlCl

3

(N

i

PrH

2

), isopropylimido, and

isopropylamido, respectively. The

13

_{C NMR spectrum showed}

chemical shifts at

δ

)

23.70, 25.66, and 25.90 assigned to the

methine carbon of isopropyl of imido, amido, and amine,

respectively. The peaks at

δ

)

65.45, 46.29, 46.01 were

assigned to methyl carbon of isopropyl of imido, amido, and

amine. The

27

_{Al NMR spectrum showed a chemical shift at}

_δ

)

112 ppm assigned to a four-coordinated environment of

organoaluminum complex.

28

_{These spectral data support the}

structure as determined by X-ray diffraction technique.

Acknowledgment. We thank the National Science Council

of the Republic of China for financial support.

Supporting Information Available: Text describing X-ray

pro-cedures and tables of crystal data, complete bond distances and bond angles, final fractional coordinates, and thermal parameters (21 pages). Ordering information is given on any current masthead page. IC950539B

(29) Ruff, J. K. J. Am. Chem. Soc. 1961, 83, 2835.

(30) Ruff, J. K.; Hawthorne, M. F. J. Am. Chem. Soc. 1960, 82, 2141. (31) Ruff, J. K.; Hawthorne, M. F. J. Am. Chem. Soc. 1961, 83, 535. (32) Ruff, J. K. Inorg. Chem. 1962, 1, 612.

(33) Interrante, L. V.; Sigel, G. A.; Garbauskas, M.; Hejna, C.; Slack, G. A. Inorg. Chem. 1989, 28, 252.

(34) Janik, J. F.; Duesler, E. N.; Paine, R. T. Inorg. Chem. 1988, 27, 4335. (35) AlN3C18H42(3): a)15.747(2) Å, b)12.648(2) Å, c)10.110(3) Å,R)102.91(2)°,β)83.54(2)°,γ)110.19(2)°, V)2251(4) cm

3_, triclinic, space group P1.

(36) Loopy, A.; Tchoubar, B. Salt Effects in Organic and Organometallic

Chemistry; VCH: Weinheim, Germany, 1992; Chapter 7, p 241.

(5)

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