Organometallics 1995, 14, 1453-1460
1453
The Use of Tetradentate (N202)Ligands To Form Monomeric, Trimetallic Aluminum Complexes David A. Atwood,” Jolin A. Jegier, Kyli J. Martin, and Drew Rutherford Department of Chemistry, North Dakota State University, Fargo, North Dakota 58105 Received November 9, 1994@ Members of the SalanH4 class of tetradentate (-N202) ligand, N,”-bis(o-hydroxybenzyl)1,2-diaminoethane (SaleanH4), N,”-bis(o-hydroxybenzyl)-1,3-diaminopropane (SalpanHa), N,iV’-bis(o-hydroxybenzyl)-1 ,a-diaminobenzene (SalophanHJ, and N,iV’-bis(o-hydroxybenzyl)1,2-diamino-4,5-dimethylbenzene (SalomphanH4), demonstrate a wide range of chemistry with AlMe3. For instance, SalpanH4 will react with 1 and 2 equiv of AlMe3 to produce the complexes SalpanHz(AlMe) (1)and [SalpanAl(AlMe2)]2 (2), respectively. When 3 equiv of AlMe3 is added to the appropriate ligand, the novel trimetallic derivatives Salean(AlMe)(AlMe2)2 (3),Salpan(AlMe)(AlMe2)2(41, Salophan(AlMe)(AlMe2)2(5), and Salomphan(A1Me)(AlMe& (6)result. A general feature of 3-6 is the presence of a rigid solution-state geometry as evidenced by the lH NMR. A crystallographic study of 3 has shown that the molecules are comprised of a central AlMe group coordinated in a planar array to the nitrogens and oxygens of the ligand. The two AlMe2 groups each bridge a n oxygen and nitrogen atom. The overall morphology of 4 and 5 is similar to that shown for 3. However, structural characterization of 4 and 5 indicates that the AlMe2 groups are inequivalent, with one bridging the two oxygens and the other bridging the two nitrogens. Crystal data for 3: C21H31A13N202, space group Pi (No. 2) with u = 7.946(3) b = 9.662(3) c = 15.804(6) a = 89.192(5)”,O, = 84.434(6)”, y = 79.926(4)”, V = 1189.0(7) A3 and 2 = 2. With 253 parameters refined on 2954 reflections having F > 4.0a(F), the final R values were R = 0.0667 and R, = 0.0651. Crystal data for 4: C44H6&N404, space group Pi (No. 2) with a = 7.821(7) b = 17.890(15) c = 18.668(16) a = 89.10(4)”,B = 89.86(4)”,y = 89.78(5)”, V = 2612(4) Hi3, and 2 = 2. With 523 parameters refined on 2068 reflections having F > 4.0a(F), the final R values were R = 0.0690 and R, = 0.0691. C stal data for 5: C39H47&N&, s ace group monoclinic P21 (No. 4) with a = 10.881(7)1, b = 17.170(10) c = 11.288(7) p = 113.275(12)”,V = 1937(2) A3 and 2 = 2. With 401 parameters refined on 4313 reflections having F > 4.0a(F), the final R values were R = 0.0619 and R, = 0.0642.
A,
A,
A,
A,
A,
A,
A,
1,
Introduction
diverse chemistry, with the capacity to form (3 bonds through the amine groups. Schiff base molecules, derived from the condensation In this paper are described a series of products of a diamine with 2 equiv of salicylaldehyde,l have been resulting from the reaction of AlMe3 with the SalanH4 used extensively as ligands in transition-metal chemligands N,”-bis(o-hydroxybenzyl)-l,2-diaminoethane With regards t o the main-group elements, the (SaleanHd, N,”-bis(o-hydroxybenzyl)-1,3-diaminopromajority of research has involved the reaction of such pane (SalpanHd, N,”-bis(o-hydroxybenzyl)-1,2-diamiSchiff base complexes as N,”-bis(o-hydroxybenzy1ene)nobenzene (Saloph-), and N,”-bis(o-hydroxybenzyl)ethyleneimine (SalenH2; Figure l a ) with aluminum3 1,2-diamino-4,5-dimethylbenzene ( S a l o m p h e ) (Figure and gallium4 alkyls and various aluminum alk~xides.~ lb-e). Specifically, complexes with l i g a n d 4 stoichiNovel complexes of the group 13 elements may also be ometries of 1:l (SalpanHAlMe (111, 1:2 ([SalpanAlexpected to result when using the reduced version of (AlMe2)12(2)), and 1:3 (Salean(AlMe)(AlMez)z(3),Salpanthis ligand (Figure lbh6 By comparison, however, this (AlMe)(AlMe2)2(41, Salophan(AlMe)(AlMe2)2(€9,Salompotentially tetracoordinate ligand, known generally as phan(AlMe)(AlMe2)2(6)) are reported. The structures SalanH4, may be anticipated t o show an even more of compounds 3-5 have been determined by singlecrystal X-ray analysis. @Abstractpublished in Advance ACS Abstracts, February 1, 1995. (1)Dubsky, J. V.; Sok61, A. Collect. Czech. Chem Commun. 1931,3, S48. (2) Holm, R. H.; Everett, G. W., Jr.; Chakravorty, A. Prog. Inorg. Chem. 1966,7,83. (3) Dzugan, S. J.; Goedken, V. L. Inorg. Chem. 1986,25,2858. (4)Chong, K. S.;Rettig, S. J.; Storr, A.; Trotter, J . Can. J. Chem. 1977,55,2540. ( 5 ) Gurian, P.L.; Cheatham, L. K.; Ziller, J . W.; Barron, A. R. J. Chem. Soc., Dalton Trans. 1991,1449. (6) The synthesis and characterization of a series of these ligands, including SaleanH4, SalpanHd, SalophanH4, and SalomphanH4, is reported in: Atwood, D. A.; Benson, J.; Jegier, J . A,; Lindholm, N. F.; Martin, K. J.; Rutherford, D. Main Group Chem., in press.
Results and Discussion Synthesis and Characterization. Compounds 1 and 2 were prepared by the exothermic reaction of AlMe3 with SalpanH4 in a 1:l and 2:l stoichiometry (paths a and b in Scheme 1, respectively). For 1, the proton NMR data indicated four broad resonances that could be attributed to the propylamine methylene groups. The PhCH2 groups were manifested as a broad
0276-733319512314-1453$09.00/00 1995 American Chemical Society
Atwood et al.
1454 Organometallics, Vol. 14, No. 3, 1995
L
(d)
(C)
SalomphanH4 (e)
Figure 1. Example of a Schiff base ligand (a) and a display of ligands used in this study (b-e). Scheme 1. Syntheses of Compounds 1-6
112
resonance centered at 6 3.95ppm. This may be indicative of a nonplanar arrangement of the PrNzAl sixmembered ring or an indication that the complex is fluxional in solution. A similar situation was observed for the Schiff base analog SalenAlEt. Crystal structure data for SalenAlEt have demonstrated a squarepyramidal geometry for the central aluminum atom.3 A similar structure is proposed for 1. Additionally, a broad ( W I D= 6249 Hz) 27Alresonance for 1 at 6 15 ppm is also indicative of a five-coordinate geometry for the aluminum atom. The reaction of 2 equiv of AlMe3 with SalpanH4 proceeds through elimination of 4 mol of CH4 to form CSalpanAl(AlMe2)12 (2; path b in (Scheme 1). This formulation is supported by the mass spectral data and by the presence of lH NMR resonances for two AlMe2 groups and two Al resonances in the 27AlNMR at 6 75 (w1/2= 3645 Hz) and 155 ( w m = 3125 Hz)ppm. In keeping with the literature p r e ~ e d e n tthe , ~ broader of the two peaks is assigned to the central aluminum atom, (7) Delpuech, J. J. In NMR of Newly Accessible Nuclei; Laszlo, P., Ed.; Academic Press: New York, 1983; Vol. 2, p 153.
which may be in a five-coordinate geometry as a result of the dimerization. In comparison t o 1, the lH NMR data for the Salpan ligand in 2 are indicative of a more symmetrical solution-state structure. There are two resonances for the propylamine backbone at 2.14 and 2.80ppm, which are integrated in a 2:4ratio. Additionally, there is one PhCHz resonance a t 3.85 ppm. Consideringthe IH NMFt spectra of complexes 3-6 (vide infra), this may be interpreted as a tendency for the ligands in these complexes to adopt a more rigid geometry as each additional alkylaluminum moiety is added. We propose that the structure of 2 is a dimeric molecule containing bridging nitrogens (for the central Al atoms) and that the AlMez groups bridge one oxygen from each ligand (Scheme lb). With regards to the group 13 elements, it is important to note that this complex marks the first deviation of the chemistry of the SalanH4 ligands from that of the SalenH2 derivatives. For example, the composition of 2 contrasts with that found in the gallium derivative Salen(GaMed2, wherein the ligand acts as a bidentate chelate for the two GaMez group^.^
Monomeric, Trimetallic A1 Complexes
Organometallics, Vol. 14, No. 3, 1995 1455
Table 1. Selected NMR Data (ppm) for Compounds 1-6 "AI, ppm ( w z , Hz)
'H, ppm compd SalpanHzAlMe (1) [SalpanAl(AlMez)]z (2) Salean(AlMe)(AlMez)z (3) Salpan(AlMe)(AlMeZ)z(4) Salophan(AlMe)(AlMez)2 (5) Salomphan(AlMe)(AlMe2)2 (6)
PhCH2 3.95 3.85 3.27,4.37 3.13,4.42 3.89,4.70 4.00.4.53
NCHz 2.10, 2.95 2.80 2.51, 2.81 2.59, 2.94
NCH2CHz 0.90, 1.13 2.14 1.15, 2.15
AlCH3 -0.79 -0.82 -0.66 -0.41 -1.22 -1.25
to to to to
-0.28 -0.10 -0.11 -0.10
A1 (central)
AlMez
15 (6249) 75 (3645) 55 (6770) 85 (3126) 66 (3645) 60 (5208)
155 (3125) 185 (9374) 185 (9374) 182 (16143) 147 (2083)
Table 2. Crystal Data for Salean(AlMe)(AIMez)z(3), Salpan(AlMe)(AIMez)z(41, and Salophan(AlMe)(AlMe&(5) 5 C39H47A13NzOz 656.7 monoclinic p21 10.881(7) 17.170(10) 11.288(7)
1.185 0.6 x 0.6 x 0.6 Mo; 0.710 73
4 C~Hd1d404 876.9 triilinic P1 7.821(7) 17.890(15)) 18.668(16) 89.10(4) 89.86(4) 89.78(5) 2612(4) 2 1.115 0.4 x 0.2 x 0.2 Mo; 0.710 73
298 2.0-45 28-8 1-60
298 2.0-45 28-13 1-60
298 2.0-45 28-13 1-60
0.55 4464
0.55 4034
0.55 7272
3265 2068 ( F > 4.0a(F)) 25 3 0.0667 0.065 1 0.89 0.34
3864 4313 ( F > 4.0o(F)) 523 0.0690 0.0691 2.28 0.21
4913 2954 ( F > 4.0a(F)) 40 1 0.0619 0.0642 3.11 0.41
3 CziH3iA13N~Oz 424.4 triclinic pi 7.946(3) 9.662(2) 15.804(4) 89.192(5) 84.434(6) 79.926(4) 1189.0(7) L
U
2.51(d)
Dcalc(g/cm3) cryst size (mm) radiation, &;
1 (A) temp 6) 28 range (deg) scan type scan speed (deg/min) scan range (deg) no. of rflns collected no. of indep rflns no. of obsd rflns
no. of params
R R W
GOF largest diff peak (e/A3) U
I.l5(m)
(E)
Figure 2. Side views and selected IH NMR assignments for compounds 3 (A) and 4 (B). When 3 equiv of AlMe3 is added t o each of the SalanH4 ligands, followed by reflux in toluene, compounds 3-6 result (paths c and d in Scheme 1). Interestingly, in each case the 'H NMR data revealed a complex pattern of coupling indicative of a rigid solution-state geometry for the complexes. A hallmark of this behavior is the presence of a doublet of doublets which can be assigned to the PhCH2 groups (see Table 1). In this interpretation, each of the methylene groups are equivalent, while the protons within the methylene group are inequivalent as an AB spin system, giving rise t o two doublets. The alkyl backbones of 3 and 4 also demonstrate a complex pattern of coupling (parts A and B of Figure 2, respectively). In 3 the N-CH2 resonances result in two doublets of doublets centered at 6 2.51 and 2.81 ppm. In 4 the propyl resonances were manifested as multiplets a t Q 1.15 and 2.15 ppm for the NCH2CH2 group and as multiplets at 6 2.59 and 2.94 ppm for the NCHzCH2 groups. Although such rigid solution-state geometries as observed for 3-6 are
113.275(12) 1937(2) 2 1.126 0.4 x 0.4 x 0.8 Mo; 0.710 73
uncommon for the heavier main-group elements, a similar solution-state geometry was found for [Ph(CH20)212A1Me(AlMe2)2.8 The chief difference between compound 3 and compounds 4-6 lies in the disposition of the AlMe2 groups. In 3, these groups give rise t o two lH NMR resonances, indicating the symmetrical bridging of a nitrogen and oxygen atom by each aluminum. In 4-6, however, these groups are manifested as four distinct resonances. There are two for the AlMe2 bridging the oxygens and two for the bridging group on the nitrogens. There are also two resonances in the 27AlNMR spectrum of these compounds. One corresponds to the central fivecoordinate Al which is assigned to the resonances in the range 6 60-85 ppm, and the other t o the peripheral four-coordinateAl atoms, assigned to the resonances in the range 6 147-185 ppm. The formulations for compounds 3-6 were confirmed by X-ray crystallography. An X-ray crystallographic study of 3-5 was undertaken in order to correlate the proposed solution-state structures with the solid state. A summary of crystallographic data for these molecules is given in Table 2. Selected bond distances and angles are given in Table (8) Pasynkiewicz, S.; Ziemkowska, W. J. Organomet. Chem. 1992, 423, 1.
1456
Organometallics, Vol. 14, No. 3, 1995
Atwood et al.
Table 3. Bond Lengths (A) and Angles (deg) for ComDounds 3-5 4B 4A
3
atoms Al( 1)-A1(2) A1(2)-A1(3) Al(l)-N(l) Al( 1)-N(2) Al(2)-0( 1) Al(2)-O(2) A1(2)-N( 1) Al(2) -N( 2) Al(3)-0( 1) Al(3)-O(2) Al(1)-O(2) A1(3)-N(2)
Bond Lengths 2.870(2) 2.854(6) 2.868(2) 2.969(7) 1.960(4) 2.001(14) 2.022(12) 1.982(3) 1.942(10) 1.959(3) 1.931(8) 1.931(3) 2.005(10) 1.931(4) 2.002(15) 1.849(4) 1.903(8) 1.873(10) 1.847(3) 1.947(4)
N(l)-Al(l)-N(2) 0(1)-A1(2)-0(2) O(l)-Al(2)-N(l) 0(1)-A1(2)-N(2) 0(2)-A1(2)-N(l) 0(2)-A1(2)-N(2) N(l)-Al(2)-N(2) O( l)-A1(3)-0(2) Al(2) -0( 1)-A1(3) A1(2)-0(2)-A1(3) Al(l)-N(l)-Al(2) Al(l)-N(2)-Al(2) N(l)-Al(l)-0(2) Al( 1)-0(2)-A1(2) N(2)-A1(3)-0(1)
Bond Angles 80.1(5) 163.0(1) 76.7(4) 87.9(1) 90.8(5) 80.1(1) 142.4(6) 80.5(1) 146.0(5) 88.7(1) 90.4(5) 80.5(5) 95.7(2) 79.0(4) 96.9(2) 101.1(4) 102.6(4) 95.0(2) 90.9(5) 95.4(3) 90.3(6) 82.6(1) 97.8(2) 83.0(2)
Table 5. Atomic Coordinates ( x 105) and Equivalent Isotropic Displacement Coefficients (A2 x lo4) for 4
(not shown)
5
2.839(6) 2.963(7) 2.031(10) 2.060(13) 1.911(9) 1.946(11) 1.956(12) 2.014(16) 1.886(11) 1.902(8)
2.869(3) 2.897(3) 1.970(5) 1.994(4) 1.886(4) 1.891(3) 2.002(5) 1.983(5) 1.847(3) 1.848(5)
78.3(5) 77.3(4) 90.3(4) 141.5(5) 144.8(5) 88.4(4) 81.1(4) 78.9(4) 102.6(5) 100.7(4) 90.8(5) 88.3(5)
73.7(2) 77.3(2) 89.2(2) 135.4(2) 137.9(1) 88.9(2) 73.3(2) 79.3(2) 101.8(2) 101.6(2) 92.5(2) 92.3(2)
Table 4. Atomic Coordinates ( x 105) and Equivalent Isotropic Displacement Coefficients (A2lo4) for 3 atom
X
Y
Z
Wed
C(17) C(18) C(19) C(20) C(21)
72 855(19) 45 064(16) 38 821(19) 58 451(44) 56 793(43) 31 576(37) 64 052(37) 26 389(62) 13 374(66) 7 871(87) 15 523(102) 28 477(82) 34 516(65) 48 260(65) 67 610(56) 72 064(53) 62 240(62) 71 118(52) 79 291(58) 87 073(63) 87 270(65) 79 391(61) 71 603(52) 97 443(61) 63 814(80) 26 446(63) 45 699(75) 22 740(72)
19 965(15) 32 671(13) 33 202(14) 14 165(35) 6 751(34) 24 276(31) 37 696(30) 11 262(53) 8 790(61) -4 052(81) - 14 280(77) - 11 724(57) 1068(50) 2 936(49) 11 511(44) 25 170(44) 50 686(46) 55 357(43) 66 997(47) 72 534(53) 66 466(55) 54 855(51) 49 363(44) 14 206(57) 17 776(62) 44 041(55) 20 323(52) 50 549(56)
60 833(9) 72 738(8) 90 919(9) 70 554(22) 82 303(20) 82 019(20) 65 155(17) 81 910(33) 87 836(37) 87 954(49) 82 124(54) 76 458(41) 76 OlO(35) 69 125(32) 78 393(28) 81 743(27) 82 255(28) 74 108(28) 74 516(32) 67 539(37) 59 721(37) 59 023(30) 66 094(27) 61 608(33) 50 032(32) 67 577(36) 100 034(31) 93 649(40)
682(5) 567(5) 669(5) 591(13) 547(12) 675(12) 620(11) 7 1l(20) 873(24) 1 116(34) 1 198(39) 948(27) 726(20) 753(20) 624(17) 594(16) 675( 18) 577(16) 695(18) 796(22) 816(22) 706( 19) 563(16) 846(22) 1 014(27) 894(23) 869(23) 1 048(26)
3, and positional parameters are given in Tables 4-6. Molecular structures and atom-numbering schemes are shown in Figures 3-5. In the structure of 3,the Salean ligand is coordinated in a tetradentate fashion to a central AlMe unit which is in a distorted-trigonalbipyramidal geometry. In this geometry, the oxygen atoms are located at the axial positions and the nitrogens and methyl carbon in equatorial positions. All of the bond angles are distorted from ideal. However, the most significant deviations occur for the N-AI-C
atom
X
Y
Z
Wq)
Al(1)
33 623(58) 15 758(59) 7 435(62) 3 284(111) 21 420(107) 18 911(155) 39 359(184) 53 155(186) 21 662(187) -1 399(195) 21 459(227) -13 295(202) 2 555(168) -6 697(168) -15 314(168) -23 734(186) -22 506(189) -13 778(174) -5 391(165) 32 997(187) 33 414(191) 44421(190) 5 5 516(219) 55 430(192) 44488(179) 44 595(189) 51 976(244) 44 289(199) 32 104(233) 4 116 463(60) 34 052(57) 42 660(66) 28 633(124) 46 645(113) 10 827(141) 30 937(137) -3 163(201) 27 902(210) 51 259(179) 28 638(216) 63 477(220) 5 458(197) 6 210(207) -5 126(197) -5 532(263) 5 324(229) 16 885(202) 17 124(254) 55 403(247) 63 496(262) 72 735(190) 73 820(281) 65 866(292) 56 120(209) 47 438(219) 17 576(189) 5 718(173) -2 394(197)
126 662(29) 134 496(29) 146 660(30) 143 887(51) 138 182(51) 135 828(73) 130 261(84) 127 346(96) 116 801(90) 126 515(97) 155 929(90) 144 969(107) 137 436(85) 144 590(88) 148 924(84) 155 641(94) 158 649(92) 154 496(87) 147 868(83) 134 986(92) 137 943(87) 134 818(97) 129 103(106) 126 lOl(98) 129 189(83) 125 257(90) 136438(119) 143 997(103) 142 340(109) 76 770(30) 84 512(29) 96 561(31) 88 053(55) 93 854(55) 80 646(71) 86 357(68) 77 147(90) 66 775(81) 76 397(90) 10 5641(91) 95 077(109) 75 131(85) 79 170(109) 76 186(82) 79 049(121) 84 665( 118) 88 056(91) 85 038(110) 97 602(138) 10 46 13(115) 10 8703(87) 10 5965(125) 99 248(128) 94 942(109) 87 652( 104) 92 512(97) 93 694(84) 87 032(88)
36 594(18) 25 460(17) 15 027(18) 24758(34) 15 973(34) 36018(49) 26 556(60) 43 605(66) 36 978(65) 23 696(70) 14 016(72) 9 073(68) 39 835(55) 37 453(55) 42 375(60) 40 563(69) 33 547(65) 28 484(62) 30 180(59) 10 935(57) 3 897(60) -1 304(66) 673(70) 7 793(64) 13 150(57) 20 761(57) 27519(78) 30 629(61) 37 185(62) 36 601(18) 25 443(17) 14 993(18) 16 004(41) 24 744(39) 26 597(47) 35 981(45) 43 714(62) 37 029(69) 23 463(64) 13 999(69) 9 099(70) 20 674(57) 13 003(71) 7 713(71) 652(90) -1 170(82) 3 852(63) 11 053(72) 30 014(68) 28 295(81) 33 375(81) 40 731(92) 42 381(78) 37 388(77) 39 784(60) 37 227(58) 30 530(66) 27 458(64)
585(20) 574(20) 669(21) 634(40) 600(39) 468(51) 650(62) 1078(87) 834(78) 792(78) 1 048(94) 1 197(94) 614(64) 515(60) 547(60) 762(75) 824(74) 663(67) 412(57) 735(70) 721(69) 789(77) 1075(95) 884(77) 639(65) 757(71) 1 139(113) 923(86) 690(77) 683(23) 532(21) 676(22) 530(42) 472(40) 596(54) 476(49) 925(80) 876(78) 784(78) 1137(93) 1301(106) 665(69) 525(70) 667(72) 903( 109) 740(92) 785(74) 651(83) 735(91) 685(84) 639(72) 847( 100) 827(96) 597(78) 595(72) 822(81) 472(64) 652(74)
AU) O(1) O(2) N(1) N(2) C(1) C(2) C(3) C(4) C(5) C(6) C(7) C(8) C(9) C(10) C(11) C(12) C(13) C(14) C(15) C(16) C(17) C(18) C(19) C(20) C(21) C(22) ~ ~ Al(5) Al(6) O(3) O(4) N(3)
angles. This may be explained by the fact that the ligand is distorting toward a square-pyramidal geometry wherein the oxygen and nitrogens form the basal plane. Through one oxygen and one nitrogen atom the ligand also acts as a bidentate chelate for the two peripheral AlMe2 groups, which adopt distorted-tetrahedral geometries. The ethylene group of the ligand and the central Al-Me are oriented trans to one another to reduce steric interactions. In keeping with the electronegativity difference between oxygen and nitrogen, the Al-0 bond distances for these atoms are somewhat shorter than the Al-N distances. However, for Al(2) the opposite trend is observed. The oxygen atoms are occupying the
Monomeric, Trimetallic A1 Complexes
Organometallics, Vol. 14,No. 3, 1995 1457
Table 6. Atomic Coordinates ( x 105) and Equivalent IsotroDic Displacement Coefficients x 104) for 5
(Az
atom
X
9 979( 18) 16 345(14) 15 566(15) 25 911(30) 5 701(31) 20 437(39) -236(37) 36 470(47) 42 870(55) 53 330(72) 57 673(65) 51 083(61) 40 422(50) 34 079(48) 340(50) 11 336(54) -235(68) - 12 202(62) -12 941(56) -1 832(53) -12 01 l(51) -16 021(57) -29 305(58) -33 688(72) -25 332(83) - 12 093(62) -7 653(55) 18 158(66) 1458(74) 25 792(51) 24 502(66) 6 617(55)
Y 73 080(3635) 65 197(3635) 64 146(3635) 68 289(3635) 61 248(3635) 75 531(3635) 68 687(3635) 73 546(3635) 73 801(3635) 78 834(3635) 83 178(3635) 83 236(3635) 78 395(3635) 78 538(3635) 79 871(3635) 86 911(3635) 89 830(3635) 85 713(3635) 78 758(3635) 75 806(3635) 63 443(3635) 59 910(3635) 57 620(3635) 54 137(3635) 52 807(3635) 55 243(3635) 58 842(3635) 65 456(3635) 82 128(3635) 56 401(3635) 55 292(3635) 72 162(3635)
Z
Ueq)
29 743( 16) 10 480(13) -15 424(14) 515(30) -6 057(30) 19 411(36) 12 228(37) 3 301(49) -5 043(56) -2 797(90) 7 761(90) 15 864(68) 14 095(49) 23 891(50) 9 161(46) 3 897(52) -5 779(58) - 10 280(60) -4 764(59) 4 983(50) 8 090(52) -5 114(52) -11 575(65) -23 108(82) -29 308(71) -23 184(56) - 11 402(47) 43 393(53) 33 428(65) 20 603(52) -19 513(63) -27 710(51)
932(8) 673(6) 766(7) 71 l(14) 734(15) 674(18) 727(19) 733(24) 924(28) 1209(42) 1233(42) 1050(33) 736(23) 836(26) 655(23) 79 l(26) 9 14(30) 9 19(30) 842(29) 677(23) 856(27) 797(26) 929(3 1) 1184(41) 1171(37) 932(29) 733(25) 1301(36) 1394(44) 918(27) 1231(38) 990(29)
axial positions of the trigonal bipyramid and experience a stronger steric repulsion than the equatorially located nitrogens. In the structure of 4, there are two identical molecules in the independent unit and no solvent of crystallization. The metrical parameters for these two molecules are the same to within experimental error, and only one representative molecule is depicted in Figure 4. As demonstrated for Salean, the Salpan ligand acts in both a chelating (Al(2))and bridging (Al(1)and Al(3))capacity, giving rise to square-pyramidal and tetrahedral geometries, respectively. Additionally, the alkyl or aryl group of the ligand “backbone” is oriented trans to the central AI-Me group. A similar bonding arrangement is observed for the isostructural Salophan compound (5). Interestingly, the arrangement of the AlMe2 groups in 4 and 5 contrasts with that seen for 3 in which each AlMe2 unit bridges both an oxygen and a nitrogen atom. The reason for this difference can be understood when the structure of SaleanHzSn is considered (Figure 6L9 In this structure the Sn atom adopts a square-pyramidal geometry in which the ligand is approximately planar with both oxygen and nitrogen atoms located on the same side of the N202 plane. The distance between the nitrogens in this structure is 2.886 A. The same value for 3 is 2.863 A. By comparison, these distances in 4 and 5 are 2.588 and 2.378 A, respectively. Thus, if this type of cis structure is considered for the Salean ligand in 3,then the AlMez bridging group would have to adopt a significantly widened N-AI-N bond angle due to the wide N-N spread. To avoid this, the molecule adopts a trans orientation for the nitrogen and oxygen atoms leading t o bond angles around the bridging aluminum (9)Atwood, D. A,; Jegier, J. A,; Martin, K. J.; Rutherford, D. J . Orgunomet. Chem., submitted for publication.
atoms that are comparable to those seen in 4 and 5. Thus, the structure observed for 3 is dictated by the steric requirements of the ethylamine backbone. Some structures similar to those seen for 3-5 have been observed for the bidentate alkylamine complexes HA1[(EtN(CH2)2NEt)AlH2l2l0 and MeAl[(HN(CH2)2NH)AIMe212.11 It is interesting to note that in the tridentate open-chain amine complexes [(MeAl)2CsHzoNsl(A1Me2)2l2 and [ ( M ~ A ~ ) ~ C I ~ H ~ ~the N ~central I ( A Ifive-coorM~~)~~~ dinate Al atoms also adopt trigonal-bipyramidal geometries. Conclusion. We have demonstrated that there is an interesting range of complexes that are accessible in reactions involving AlMe3 and the SalanHd class of ligands. For instance, the trimetallic derivatives of general formula SalaxAlMe(AlMe2)z offer evidence for solution-state rigidity. Additionally, the solution-state geometry of these molecules was shown by X-ray crystallography to be the same as that of the solid state. Future research will focus on the use of other SalanH4 ligands in the synthesis of novel group 13 compounds.
Experimental Section General Considerations. All manipulations were conducted using Schlenk techniques in conjunction with an inertatmosphere glovebox. All solvents were rigorously dried prior to use. The Schiff bases SalenHz, SalpenHz, SalophenHz, and SalomphenHz were synthesized according to literature techniques.2 NMR data were obtained on JEOL-GSX-400 and -270 instruments at 270.17 (lH), 67.94 (13C),and 104.17 (27Al)MHz. Chemical shifts are reported relative to Si(CH3)4 (for C and H) and Al(HzO)6 (for Al)and are in ppm. All data were taken at 295 K unless otherwise noted. Elemental analyses were obtained on a Perkin-Elmer 2400 analyzer. Mass spectral data were obtained on a Hewlett-Packard 5988 spectrometer using electron impact ionization (70 eV) with a direct ionization probe (DIP). Infrared data were recorded as Kl3r pellets on a Matheson Instruments 2020 Galaxy Series spectrometer and are reported in cm-l. Synthesis of S a l p a n H m e (1). Trimethylaluminum (0.122 g, 1.70 mmol) in 20 mL of toluene was added to a rapidly stirred solution of SalpanH~(0.488 g, 1.70 mmol) in toluene (20 mL) at 25 “C. The vigorous exothermic reaction subsided after a few seconds to give a colorless solution which was stirred for 2 h. The volatiles were removed under reduced pressure to give 0.483 g (87%)of a white solid, mp 238 “C dec. ‘H NMR ( c a s ) : 6 -0.79 (3H, s, AlCH3), 0.90 (lH, m, CHzCHz), 1.13 (lH, m, CH~CHZ), 2.10 (2H, br s, NCHz), 2.95 (2H, br s, NCH2), 3.95 (4H, br s, PhCHZ), 6.60-7.35 (8H, m, Ph H).13C NMR (C6D6): 6 = -11.3 (AlCH3),25.8 (CH~CHZ), 46.0 (NCHz), 50.5 (PhCH2), 117.4, 119.9, 120.0, 123.5, 130.1, 160.1 (Ph). 27Al NMR (CsDs): 6 15 ( ~ 1 1 2= 6249 Hz). IR: 3253 m, 2920 m, 1602 s, 1573 m, 1487 s, 1298 s, 1037 m, 893 s, 757 s, 668 s, 686 s. MS: mle 326 (M+),311 (M+ - Me), 267 (M+ - Me Pr). Anal. Calcd: C, 66.26; H, 7.06. Found: C, 66.53; H, 6.67. Synthesis of [SalpanAl(AlMez)ln(2). The procedure was similar to that described for 1, except 2 equiv of trimethylaluminum (0.252 g, 3.50 mmol) was used (SalpanH1; 0.500 g, 1.75 mmol). After removal of volatiles, 0.563 g of a n off-white solid remained: yield 88%; mp 265 “C dec. ‘H NMR (THFds): 6 -0.82 (6H, s, AlCH,), 2.14 (2H, m, NCH~CHZ), 2.80 (4H, (10) Perego, G.; Del Piero, G.; Corbellini, M.; Bruzzone, M. J. Orgunomet. Chem. 1977,136, 301. (11)Zhiping, J.; Interrante, L. V.; Kwon, D.; Tham, F. S.; Kullnig, R. Inorg. Chem. 1991,30,995. (12) Robinson, G. H.; Sangokoya, S. A. J . Am. Chem. SOC.1987,109, 6852. (13)Robinson, G.H.; Moise, F.; Pennington, W. T.; Sangokoya, S. A. Polyhedron 1989,8, 1279.
Atwood et al.
1458 Organometallics, Vol. 14,No. 3, 1995
Figure 3.
Figure 4. Molecular structure and atom-numbering scheme for 4. m, NCHz), 3.85 (4H, m, PhCHz), 6.45-7.25 (8H, m, Ph H).13C NMR (THF-ds): 6 -11.0 (AlCH3),24.7(CHzCHz),47.0 (NCH21, 50.6 (PhCH2), 116.8 (Ph), 120.0 (Ph), 126.0 (Ph), 128.9 (Ph), 129.7 (Ph), 162.0 (Ph). "4 NMR (CsDs): 6 75 ( ~ 1 1 2= 3645 Hz), 155 (w1/2 = 3125 Hz). IR: 2928 m, 1602 s, 1574 w, 1488 s, 1298 s (br), 759 s, 688 m (br). MS: mle 732 (M+), 367 (monomer), 351 (monomer - Me), 309 (SalpanAl+), 307 (Salp a d l - 2H+), 190 ([PhO(AIMe)CH2N(CH2)2+1), 176 ([PhO(AIMe)CHzNCH2+1),162 ([PhO(AlMe)CH2N+I). Anal. Calcd: C, 62.29; H, 6.60. Found: C, 62.36; H, 6.67. Synthesis of Salean(AlMe)(AlMe& (3). Trimethylaluminum (0.394 g, 5.47 mmol) was added to a rapidly stirred
solution of SaleanHd (0.495 g, 1.82 mmol) in 50 mL of toluene at 25 "C. The exothermic reaction mixture was stirred until the evolution of gas ceased (15 min); then it was refluxed for 5 h. After filtration and concentration, colorless crystals were grown at -30 "C (0.679 g, 88%): mp 165 "C dec. 'H NMR (CsDs): 6 -0.66 (s,6H, AlCH31, -0.35 (s, 3H, AlCH3), -0.28 (s, 6H, AlCH3), 2.51 (d, J = 8 Hz, 2H, NCHz), 2.81 (d, J = 8 Hz, 2H, NCHz), 3.27 (d, J = 17 Hz, 2H, PhCHz), 4.37 (d, J = 17 Hz, 2H, PhCHz), 6.63 (d, J = 9 Hz, 2H, Ph H),6.66 (d, J = 9 Hz, 2H, Ph H ) , 6.76 (m, 2H, Ph H ) , 6.92 (m, 2H, Ph H ) . 13C NMR (CsDs): 6 -13.9, (AlCH3), -9.6 (AlCHa),47.6 (NCH21, 50.8 (PhCHZ), 121.1, 122.3, 123.4, 128.5, 129.7, 151.2 (Ph). 27-
Organometallics, Vol. 14, No. 3, 1995 1459
Monomeric, Trimetallic A1 Complexes
CNI
ciin
Figure 5. Molecular structure and atom-numbering scheme for 5. C181
c1131 C141
C12J
a31
Figure 6. Molecular structure and atom-numbering scheme for SaleanHzSn. Al NMR (C&5): 6 55 ( ~ 1 1 2= 6770 H d , 185 ( ~ 1 1 2= 9374 Hz). IR: 2932 s, 2888 m, 1604 m, 1581 s, 1491 vs, 1452 vs, 1268 vs, 1239 vs, 1200 vs, 1079 vs, 885 vs, 759 vs, 703 VS, 639 vs, 591 s. MS: mle 424 (M+),409 (M+ - Me), 351 (M+ - Me AlMe, - H), 293 (M+ - Me - 2AlMe2 - 2H), 176 ([(PhO)CH2N(AlMe)CHz+]),162 ([(PhO)CHzN(AlMe)+l),57 (AlMe2+). Anal. Calcd: C, 59.43; H, 7.36. Found: C, 59.26; H, 7.29. Salpan(AlMe)(AlMe2)2 (4).Trimethylaluminum (0.440 g, 6.11 mmol) was added to a rapidly stirred solution of SalpanHl (0.500 g, 1.75 mmol) in 50 mL of toluene at 25 "C. The exothermic reaction mixture was stirred until the evolution of gas ceased (15 min); then it was refluxed for 5 h. After filtration and concentration, colorless crystals were grown at -30 "C (0.637 g, 83%): mp 211-213 "c. 'H NMR (CsDs): 6 -0.41 (9, 3H, AlCH3), -0.39 (s, 3H, AlCH3), -0.31 (s, 3H, AlCH3), -0.25 (8,3H, AlCH3), -0.10 (s, 3H, AlCH3), 1.15 (m, l H , CH2CHz),2.15 (m, l H , CH~CHZ), 2.59 (m, 2H, NCH21, 2.94 (m, 2H, NCHz), 3.13 (d, J = 16 Hz, 2H, PhCHz), 4.42 (d, J = 16 Hz, 2H, PhCHz), 6.66-6.93 (m, 8H, Ph H). I3C NMR (CsD6): 6 -9.99 (McH3), -6.25 (AlCH3),24.5 (CH~CHZ), 47.5 (NCHz),52.6 (PhCHz), 118.7,122.0,124.7, 128.2,131.2,152.7 (Ph). 27AlNMR(CsD6): 6 85 ( W m = 31261, 185 (Wiiz = 9374).
I R 2942 s, 1603 m, 1580 m, 1491 s, 1200 s, 1036 s, 80 s, 754 vs, 696 vs, 644 vs. MS: mle 423 (M+ - Me), 365 ([M+- Me AlMe2 - HI), 307 ([M+ - Me - 2A1Me2 - 2H]), 190 ([PhO(AIMe)CHdWHz)2+]),176 ([P~OWM~)CHZNCHZ+I), 162 ([PhO(AlMe)CHzN+]),57 (AlMe2+). Anal. Calcd for C ~ Z H ~ ~ N Z O Z A ~ ~ : C, 60.25; H, 7.60. Found: C, 60.11; H, 7.37. Salophan(AlMe)(AlMe2)2 (5). Trimethylaluminum (0.350 g, 4.86 mmol) was added neat to a rapidly stirred solution of SalophanH4 (0.500 g, 1.56 mmol) in 50 mL of toluene at 25 "C. The exothermic reaction mixture was stirred until the evolution of gas ceased (15 min); then it was refluxed for 5 h. After filtration and concentration, colorless crystals were grown at -30 "C (0.633 g, 86%): mp 185 "C dec. 'H NMR (CsDs): 6 -1.22 (S, 3H, &cH3), -0.96 (S, 3H, McH3), -0.22 (s, 3H, A1CH3), -0.19 (s, 3H, AlCH3), -0.11 (s, 3H, AlCH3), 3.89 (d, J = 17 Hz, 2H, PhCHz), 4.70 (d, J = 17 Hz, 2H, PhCHZ), 6.35-7.12 (m, 12H, P h M . 13CNMR (CsD6): 6 -7.8, -8.9, -10.2, -13.5, -14.3 (AICH3),45.9 (PhCHz),114.0,119.0, 122.7, 122.8, 123.2, 128.1, 128.2, 128.5, 129.2, 129.7, 138.7, 151.3 (Ph). 27AlNMR (CsD6): 6 66 ( ~ 1 1 2= 3645 Hz), 182 (W112 = 16 143 Hz). IR: 2935 m, 1605 m, 1585 s, 1495 vs, 1450 vs, 1223 VS, 1113 S, 1030 9, 879 vs, 765 vs, 698 vs, 663 vs, 445 m.
Atwood et al.
1460 Organometallics, Vol. 14, No. 3, 1995 MS: mle 472 (M+),457 (M+ - Me), 400 (M+- Me - AlMez), 341 (M+ - Me - 2AlMez - 2H), 237 ([(PhO)CH&€"PAl+l), 57 ([AlMez+]). Anal. Calcd: C, 63.55; H, 6.61. Found: C, 63.68; H, 6.32. Salomphan(AlMe)(AlMe)2(6). Trimethylaluminum (0.331 g, 4.60 mmol) was added neat t o a rapidly stirred solution of SalomphanH4 (0.500 g, 1.44 mmol) in 50 mL of toluene at 25 "C. The exothermic reaction mixture was stirred until the evolution of gas ceased (15 min); then it was refluxed for 5 h. After filtration and concentration, pale green crystals were isolated after cooling t o -30 "C (0.649 g, 90%): mp 148 "C dec. IH NMR (CsDs): 6 -1.25 (s, 3H, AcH3), -0.88 (9, 3H, AlCH3), -0.22 (s,3H, AlCH3), -0.17 (s, 3H, AlCH3), -0.10 (9, 3H, AlCH3), 1.71 (s, 6H, PhCH3), 4.00 (d, J = 18 Hz, 2H, PhCHZ), 4.53 (d, J = 18 Hz,2H, PhCHz), 6.31 (s, 2H, P h H), 6.80-7.12 (m, 8H, Ph H). I3C NMR (CsDs): 6 -14.4, -13.8, -8.7, -7.5, -7.1 (AlCH31, 19.5 (PhCHd, 45.9 (PhCHd, 115.5, 119.0, 122.8, 128.5, 129.2, 129.6, 130.1, 136.2, 151.3 (Ph). 27Al NMR (CsDs): 6 60 ( ~ 1 1 2= 5208 Hz), 147 ( ~ 1 1 2= 2083 Hz). IR: 2935 m, 1605 m, 1585 s, 1495 vs, 1450 vs, 1223 vs, 1113 s, 1030 s, 879 vs, 765 vs, 698 vs, 663 vs, 445 m. MS: mle 500 (M+),485 (M+ - Me), 428 (M+ - Me - AlMeZ), 369 (M' - Me - 2AlMez - 2H), 57 (AlMeZ+). Anal. Calcd: C, 64.53; H, 7.42. Found: C, 64.65; H, 7.11. X-ray Experiment, Details of the crystal data and a summary of data collection parameters for 3-5 are given in
Table 2. Data were collected on a Siemens P4 diffractometer using graphite-monochromated Mo Ka radiation. The check reflections, measured every 100 reflections, indicated a less than 5%decrease in intensity over the course of data collection; hence, no correction was applied. All calculations were performed on a personal computer using the Siemens software package SHEIXTL-Plus. The structures were solved by direct methods and successive interpretation of difference Fourier maps, followed by least-squares refinement. All non-hydrogen atoms were refined anisotropically. The hydrogen atoms were included in the refinement in calculated positions using fixed isotropic parameters.
Acknowledgment. Gratitude is expressed to the National Science Foundation NSF-EPSCoR program (Grant RII-861075) and the NDSU Grant-in-Aid program for generous financial support. SupplementaryMaterial Available: Tables giving structure determination summaries, bond lengths and angles, positional parameters, and anisotropic thermal parameters and figures giving unit cell views for 3-5 and a figure showing the shortest intermolecular contacts for 4 (41 pages). Ordering information is given on any current masthead page. OM9408526
