Coordination complexes of metal halides with substituted 4-nitrosoanilines

Polyhedron Vol. 13, No. 9, pp. 1371-1377, 1994 Copyrieht 0 1994 Elswier Science Ltd Printed in Gnat Britain. All rights nerved 0277-5387/94 s7.oo+o.rm

Pergamon

COORDINATION COMPLEXES OF METAL HALIDES SUBSTITUTED CNITROSOANILINES MAILER

CAMERON

WITH

and BRIAN G. GOWENLOCK*

Department of Chemistry, Heriot-Watt

GIUSEPPE

University, Edinburgh EH14 4AS, U.K.

VASAPOLLO

Centro M.I.S.O. de1 C.N.R., Istituto di C&mica de1 Politecnico di Bari, Via Amendola 173, 70126 Bari, Italy (Received 28 October 1993 ; accepted 25 November 1993)

Abstract-Complexes of substitutedp-nitrosoanilines with metal halides have been prepared and studied by solid state CP/MAS NMR spectroscopy. The 13C and “N NMR spectra give information concerning the structural changes that occur in the C-nitrosoligand on coordination to metals. Supplementary information is provided in some cases by ’ 19Snand ‘13Cd NMR spectra and also by Mijssbauer spectroscopy for Sn complexes. It is shown that it is not possible to distinguish between IJN and cro coordination on the basis of IR spectroscopy.

In previous papers l-3 we have commented on the ability of 4-nitrosodimethylaniline (NODMA) to undergo co coordination to d” metals and have related this o. coordination to the dipolar resonance contribution to the structure of NODMA. We have used X-ray photoelectron spectroscopy4 to provide further evidence for the coordination mode of NODMA to various metals. NODMA complexes of metal halides have been known for over fifty years and these include palladium chloride,’ platinum (II) chloride, 6 nickel chloride, 7 lanthanum and cerium chlorides,8 manganese, cobalt and copper chlorides, 9 and uranyl chloride. ’ ‘7’ ’ Other 4-nitrosoanilines have also been shown to coordinate to metals, e.g. 4-nitrosodiethylaniline (NODEA) 3*8, I0 nitrosoaniline (NOA), 3,” 3,5,N,Ntetramethyl-4-nitrosoaniline (NOTMA)3,‘3 and 3,N,N-trimethyl-4-nitrosoaniline. ’ 3 There have been many reports of infrared and electronic spec-

*Author to whom correspondence should be addressed at Department of Chemistry, University of Exeter, Exeter EX4 445, U.K.

troscopic studies of the complexes and four X-ray crystallographic measurements of bond lengths and bond angles for two co coordinated [Me,SnClz, I4 ZnCl,“] and two ON coordinated [RhCl(cod),13 CoCl, ’ “1 complexes. In these complexes, the C-C and C-N bond lengths suggest a significant participation of the quinonoid canonical structure to the nitrosoaniline ligand. We have recently shown that solid state CPMAS “N NMR spectroscopy also implies the participation of such quinonoid forms to the structures of nitrosoanilines coordinated to dimethyl tin dichloride. 3 The present study uses solid state 15N and 13C NMR spectroscopy as a structural tool in the understanding of the character of the ligand in a number of NODMA and NOTMA complexes of metal halides. In this connection it is important to draw attention to a significant feature of the orientation of the nitroso group with respect to the plane of the benzene ring in the solid complexes. In the solid NODMA itself the two carbon atoms ortho to the NO group are not equivalent’ 7 as demonstrated by 13CNMR spectroscopy. Some other functional groups also exhibit the same effect but the difference

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CAMERON et al.

between the C-2 and C-6 chemical shifts (A& for the NO group is far larger than for any other functional group. (In our treatment of the NMR spectra of nitrosoanilines we employ the convention that the ring C attached to NO is designated C-l.) The same effect is observed for low temperature solution ’3C NMR spectra of aromatic C-nitrosocompounds ‘K’~where the rotation of the NO group is “frozen out”. In those cases where the C-2 and C-6 chemical shifts of an aromatic nitrosocompound are identical, the NO group must either be freely rotating or held orthogonal to the plane of the ring. *’ The free rotation possibility does not apply in the solid state and therefore13C NMR spectroscopy enables a prediction to be made for the orthogonal orientation of the NO group in the coordination complexes of aromatic C-nitrosocompounds.

EXPERIMENTAL NODMA was commercially available. Labelling with 5% ’ 5N0 was achieved by direct nitrosation of dimethylaniline using 5% “N enriched sodium nitrite.3 NOTMA was prepared by direct nitrosation of 3,5,N,N_tetramethylaniline. 3 Preparation of coordination complexes

CUI(NODMA)~. A suspension of copper (I) iodide (0.2 g, 1.04 mmol) and NODMA (0.37 g, 2.08 mmol) in diethyl ether (10 cm3) was stirred at room temperature for 24 h. The solid was filtered off, washed with cold ether and air dried giving the complex as a green powder (0.3 g, 78%), m.p. 195196 dec. (lit 155-200 dec.‘). Hg12(NODMA)2. A suspension of mercury (II) iodide (0.2 g, 0.44 mmol) and NODMA (0.2 g, 1.1 mmol) in diethylether (10 cm3) was stirred at room temperature for 24 h. The solid was filtered off, washed with cold ether and dried giving the complex as a dark purple powder (0.2 g, 72%) m.p. 118-l 19 dec. ZnC12(NODM,4)2. Zinc chloride (0.15 g, I.1 mmol) in methanol (8 cm3) was added to a stirred solution of NODMA (0.35 g, 2.3 mmol) in methanol (8 cm’). The reaction mixture was stirred for 2 h and the precipitate was filtered off, washed with methanol and air dried. The brick-red solid (0.23 g, 48%) had m.p. 189.5-190 (ref. 15 does not cite the m.p.). Cd12(NODMA)2. Cadmium iodide (0.5 g, 1.36 mmol) in absolute alcohol (10 cm’) was stirred while a solution of NODMA (1.2 g, 8 mmol) in absolute alcohol (10 cm3) was added dropwise. The resulting

precipitate was filtered off, washed with chloroform and air-dried, giving a red powder, m.p. 154-155. Found : C, 28.6 ; H, 2.9 ; N, 8.2. Calc. for C,gH20N40212Cd: C, 28.2; H, 3.0; N, 8.4%. CdC12(NODMA). Cadmium chloride (0.5 g, 2.7 mmol) in absolute alcohol (10 cm ‘) was stirred while NODMA (2.38 g, 16 mmol) in absolute alcohol (10 cm”) was added dropwise. The resulting precipitate was filtered off, washed with chloroform and airdried giving a dark-red powder, m.p. 230 dec. Found: C, 27.9; H, 3.0; N, 7.9. Calc. for CsHloN20C12Cd: C, 28.8; H, 3.0; N, 8.4%. SnC14(NODM& Tin tetrachloride (0.2 g, 0.77 mmol) in dichloromethane (10 cm’) was stirred under nitrogen while a solution of NODMA (0.29 g, 1.9 mmol) in dichloromethane was added dropwise. The precipitate was filtered off, washed with benzene and air-dried giving an orangebrown powder (0.35 g, 81%) m.p. 187-188 dec. Found: C, 34.4; H, 3.9; N, 9.9. Calc. for C’gH20N40zC14Sn: C, 34.2; H, 3.6; N, 10.0%. SnBr4(NODMA)*. Tin tetrabromide (0.2 g, 0.45 mmol) in benzene (10 cm3) was stirred while NODMA (0.2 g, 1.3 mmol) in benzene (10 cm’) was added dropwise. The precipitate was filtered off, washed with benzene and air-dried giving an orange-brown powder, m.p. 173-173.5 dec. Found C, 26.0; H, 2.8; N, 7.3. Calc. for C16H20N402 Br,Sn: C, 26.0; H, 2.7; N, 7.5%. SnI&VODMA)2. Tin tetraiodide (0.3 g, 0.48 mmol) in benzene (10 cm’) was stirred while NODMA (0.18 g, 1.2 mmol) in benzene (10 cm’) was added dropwise. The resultant solid was filtered off, washed with benzene and air dried giving a brick-red powder (0.25 g, 56%) m.p. 107-108 dec. Found: C, 21.4; H, 2.5; N, 6.7. Calc. for Cl,H20N40214Sn requires : C, 20.7 ; H, 2.2 ; N, 6.0%. TiCl,(NODMA),. Titanium tetrachloride (0.2 g, 1.05 mmol) in dichloromethane (20 cm3) was stirred under nitrogen while NODMA (0.4 g, 2.67 mmol) in dichloromethane (30 cm ‘) was added. The resultant solid was filtered off, washed with benzene and airdried giving a yellow-orange powder (0.2 g, 39%), m.p. unobtainable due to decomposition beginning at 80. The formula is assumed, microanalysis was not attempted due to instability ; the compound is stable at - 78 under nitrogen. The other NODMA complexes, PdCl 2 (NODMA)* and RhCl(cod)NODMA [cod = cycloocta-1,5-diene] were prepared by established procedures. 4,5,’ ‘*’ ’ ZnC12(NOTMA)2. Zinc chloride (0.15 g, 1.1 mmol) in methanol (10 cm3) was added to a stirred solution of NOTMA (0.4 g, 2.2 mmol) in methanol (10 cm’). Ether (20 cm’) was added and the ensuing

Coordination complexes of metal halides with substituted 4-nitrosoanilines precipitate was filtered off, washed with ether and air dried giving a red powder (0.34 g, 60%) m.p. 203-204 dec. Found : C, 50.3 ; H, 6.3 ; N, 11.3. Calc. for C20H28N402C12Zn: C, 48.8; H, 5.7; N, 11.4%. NiCl#VOTJt4& Nickel chloride (0.2 g, 0.84 mmol) in absolute alcohol (10 cm3) was stirred while NOTMA (0.37 g, 2.1 mmol) in acetone (10 cm’) was added dropwise. The precipitate was filtered off, washed with ether and air dried giving a brown powder (0.29 g, 59%) m.p. > 350. Found : C, 44.8 ; H, 5.9; N, 10.1. Calc. for CZ,,H28N402C12Ni: C, 46.4; H, 5.5; N, 10.8%. CoCl,(NOTMA). Cobalt (II) chloride hexahydrate (0.2 g, 0.84 mmol) was stirred in 2,2-dimethoxypropane for 30 min and then added to NOTMA (0.6 g, 3.4 mmol) in acetone (10 cm’). The mixture was stirred at room temperature overnight and ether (15 cm’) was added. The precipitate was filtered off, washed with ether and air dried giving a dark green powder (0.22 g, 53%) m.p. 171-172 dec. Found: C, 39.3 ; H, 5.3 ; N, 9.0. Calc. for C,0H,4N20C12C~: C, 38.9; H, 5.3; N, 9.0%. SnI,(NOTK4)2. Tin tetraiodide (0.3 g, 0.48 mmol) in benzene (10 cm’) was stirred while NOTMA (0.21 g, 1.2 mmol) in benzene (10 cm3) was added dropwise. The precipitate was filtered off, washed with benzene and air dried giving a yellow-orange powder m.p. 143-144 dec. Found : C, 24.4; H, 3.6; N, 6.4. Calc. for C20H28N40214Sn : C, 23.7, H, 2.8; N, 5.5%. Solid state CPMAS NMR spectra ( 13C, ’ 'N, ’ 19Sn, ‘13Cd) were measured by the SERC service at the Industrial Research Laboratories, University of Durham. 13CNMR spectra of solid samples were obtained at 75.431 MHz using cross-polarization (CP), magic angle spinning (MAS), and high power decoupling. Contact times ranged from 1.0 to 5.0 ms. Relaxation delays ranged from 0.5 to 20 s. MAS rates were 415&9300 Hz. All cross-polarization spectra were obtained with the Hartman-Hahn match condition fulfilled. The carbon secondary reference standard was adamantane CH2 signal at 38:4 ppm relative to TMS. ’ 'N NMR spectra were obtained at 30.405 MHz. Contact times ranged from 1.0 to 9.0 ms. Relaxation delays ranged from 1.0 to 20.0 s. MAS rates were 3270 to 9200 Hz. The nitrate signal in a 20% enriched solid sample of ammonium nitrate was used as the primary reference (i.e. 0 ppm). The magic angle is set by minimizing the nitrate signal linewidth for the ammonium nitrate sample. ’ 19Sn NMR spectra were obtained at 111.862 MHz using CP MAS and high power decoupling. Contact times ranged from 4.0 to 5.0 ms, and relaxation delays from 2.0 to 5.0 s. MAS rates were 810& 10 300 Hz. The secondary reference standard was

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cyclohexyl tin (signal at -97.4 ppm relative to tetramethyl tin the primary standard). ‘13Cd NMR spectra were obtained at 66.547 MHz with contact time 5.0 ms and relaxation delay 5.0 s. The MAS rates were 8350 and 8650 Hz. The secondary reference was cadmium acetate (signal at -65.3 ppm relative to a cadmium perchlorate solution). Miissbauer spectra were obtained by Dr R. V. Parish, the experimental details being as previously described. 3 RESULTS

AND DISCUSSION

The ’3C and ’ 'N NMR spectra of the NODMA complexes are given in Table 1 and of the NOTMA complexes in Table 2. The shifts of the cod carbons in the complex RhCl(cod)(NODMA) are 95.9,86.2, 81.7 and 74.5 ppm (CH) and 41.7, 36.0, 34.2 and 29.4 ppm (CH,) contrasting with the CDCl, solution spectra where the sp2 carbons occur as two doublets at 77.8 and 90.2 ppm. In the solid state therefore the members of the two groups of carbon atoms are structurally non-equivalent. The crystal structure data for the corresponding complex of 2-methyl-4-dimethylaminonitrosobenzene clearly demonstrate this feature of the cod ligand. We have attempted to obtain CPMAS ’3C NMR spectra for the complex COC~~(NODMA)~. The crystal structure of this complex is known. ’ 6Unfortunately, several different preparations did not yield any signal in the 13CNMR spectrum for this solid material in contrast to the case of the corresponding NOTMA complex which gave a straightforward spectrum. We were therefore unable to interrelate the NMR spectrum and the crystal structure. Such an interrelation is however possible for the ZnC12(NODMA), crystal structureI and complements our previous study3,14 of (CH,), SnC12(NODMA)2. The 13C NMR spectra provide information on the effect of coordination upon the structure of the ligand as judged by (1) the C(1) shift, (2) the C(4) shift, (3) the N(CH3)2 shift, and (4) the magnitude of AC2.6. We discuss each of these in turn. The C(1) shift for coordinated NODMA is always at a lower value than for the free ligand, a behaviour mirrored by the spectra of the NOTMA ligand and for four nitrosoanilines coordinated to dimethyl tin dichloride.3 The palladium and rhodium complexes are (TNcoordinated and the others are a0 coordinated by the NO group in NODMA and it is apparent therefore that it is not possible to use the C(1) shifts to give a simple discriminatory test for coordination mode. It may be noted that in the course of our studies on coordination by

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Table 1. ’3C and ’5N NMR spectra of NODMA complexes (values in ppm) Compound

C(lY

C(2)

C(3)

C(4)

C(5)

C(6)

N(CH&

Cul(NODMA) HgI ,(NODMA) 2 ZnCl,(NODMA), Cd1 ,(NODMA) 2 CdCl ,(NODMA) SnCl,(NODMA) z SnBr,(NODMA) z SnI,(NODMA), TiCl,(NODMA) 2 PdCl ,(NODMA) z RhCl(cod)(NODM A)’

158.3 158.7 160.0 159.7 158.9 159.5 159.8 160.9 162.1 159.3 161.6

121.4 121.3 119.8 119.6 112.6 124.3 121.0 122.6 121.3 122.8 119.9

114.6 113.5 117.0 114.4 119.5 120.2 118.6 122.6 124.2 115.3 112.0

156.8 156.7 157.5 157.4 156.4 153.7 152.2 150.2 149.7 157.3 155.2

114.6 116.4 118.3 114.4 119.5 120.2 123.3 122.6 124.2 117.0 112.0

134.9 141.0 142.6 143.7 141.3 142.6 142.8 140.8 141.1 137.6 146.9

40.5 43.5,40.2 44.5,42.0 42.3 43.5 44.1 44.6 44.4 45.2 43.2 41.8

NODMA NODMA * HCl 3

165.0 162.8

112.0 126.0

112.0 121.8

161.4 151.5

112.0 124.4

142.5 142.8

41.3 45.7

NO

90.0 214.3 191.2 429.7 54.8

WCH3h

- 276.9 -271.8, -276.0 - 252.9 -257.7, -268.5 -245.5 - 228.6 -213.9, -228.4 - 234.9 -205.1 -254.5 -291.8 -295.3, -299.1 - 207.3

‘The carbon attached to the NO group is numbered (1) ; the carbon syn to the 0 of the NO group is numbered (2). Where the C(3) and C(5) chemical shifts are not identical it is possible that the assignments may be interchanged. *For cod chemical shifts see the main text.

substituted nitrosobenzenes we have found only one example where the C(1) shift in the ligand rises on coordination, namely (C6HSNO)PtC13- in which the coordination mode is crN.22 The C(4) shifts for the o. coordinated compounds are much lower for the complexes of the tetrahalides which are probably octahedral. If we consider the difference between the C(1) and the C(4) shifts in the go complexes we note that for the four tetrahalides this difference falls within the range 5.8-12.4 ppm, for the four dihalides 2.0-2.5 ppm and for the monohalide 1.5 ppm. It appears that there is some effect transmitted to the C(4) atom which is remote from the C(1) atom to which is attached the ligating group. In the quinonoid form23 of NODMA .HCl this C(l)/C(4) difference is 11.3 ppm. We have noted that both crystal structure evidence and ’ 'N NMR spectra have both indicated the enhanced participation of such structures on coordination by NODMA. The dimethylamino C shifts of the tetrahalide

NODMA complexes fall in the range 44.1-45.2 ppm slightly higher than those of the other o. complexes although in two of these latter (mercuric iodide and zinc chloride) the methyl groups are clearly not equivalent. The rrN complex of rhodium is interesting in that the methyl groups have chemical shifts closely akin to that of NODMA itself. With two exceptions the methyl shifts of all the complexes lie within the range 41.3 (NODMA) and 45.7 ppm (NODMA * HCl). The fourth feature of interest in the 13C NMR spectra is the difference between the C(2) and C(6) chemical shifts, A2,+ Attention has been drawn to this difference3,‘8-20 and it has been ascribed to the magnetic anisotropy of the NO group. It is of interest to see how A2,6 is altered by coordination to a metal. If the NO group were to be rotated so as to be at 90” to the plane of the benzene ring, i.e. orthogonal to the ring, then A2,6would fall to zero. It is evident that this is not taking place in the NODMA complexes. If the magnetic anisotropy of

Table 2. 13Cand “N NMR spectra of NOTMA complexes (values in ppm) Compound

C(1)

C(2)

C(3)

C(4)

C(5)

C(6)

2,6-CH3

N(CH,),

NO

ZnCl,(NOTMA), NiCl ,(NOTMA) z CoCl *(NOTMA) SnI ,(NOTMA) 2 NOTMA

158.2 159.2 160.3 160.3 162.0

136.0 142.9 143.8 144.9 138.7

113.1 120.6 121.4 119.9 112.7

155.3 153.7 155.0 154.8 153.9

116.3 120.6 121.4 119.9 111.3

136.0 22.6, 19.7 42.9 148.1 25.2, 19.6 45.5 62.5 148.3 25.0, 19.7 45.0 148.4 25.4, 19.2 48.0 58.8, 56.8 135.2 22.8, 20.9 39.2, 38.4 6.4

N(CH,), -261.1 -214.1 -214.4 -215.7 -294.5

Coordination complexes of metal halides with substituted 4-nitrosoanilines the NO group were to be considerably modified by coordination and if the NO group were to remain close to planarity with the benzene ring in the solid complex then A2,6values similar to that of the isoelectronic CHO group (- 6.7 ppm)’ ’ might well result. For our complexes the A2,6values lie within the range of - 13.5 to 28.7 ppm comparable with that for the dimethyl tin dichloride complex (- 22.2) ppm.3 Crystal structure data are available in three cases. These show that the NO group is only twisted slightly from coplanarity with the plane of the benzene ring for the cN complex (NODMA),CoCl, (5.4 and 7.2), ’ 6is “almost coplanar” for the o. complex (NODMA)2(CH3)2SnC12,‘4 and for go (NODMA)*ZnC12 the angles between the CNO plane and the corresponding ring carbons are 5.2 and 3.3, respectively. 25 The combination of the evidence from X-ray crystal structure determinations and from the solid state 13C NMR data implies that coordination of NODMA to a metal leads to only minor changes in the twisting of the NO group from coplanarity with the ring and that the coordinated NO group retains a substantial degree of the magnetic anisotropy that is present in the free ligand NO group. The ’ 'N chemical shifts for the NODMA complexes show similar features to that observed for the dimethyl tin dichloride complex.3 The dimethylamino nitrogen can provide the “N shift at natural abundance and the values obtained lie between those observed for NODMA and NODMA.HCI. Although this nitrogen is remote from the coordination site the chemical shift obtained provides useful evidence of the enhancement of the quinonoid contribution to the ligand molecule when coordination occurs. In this respect ’ 5N NMR spectroscopy complements the crystal structure determinations. ’‘N chemical shifts have been measured for NO using 5% “N enriched samples. For the two cases studied, both of which are (TNcoordinated, the changes that occur in the ’ 5N shifts are greater than those observed in the a0 coordinated dimethyl tin dichloride complex. In the case of SnCl,(NODMA), it was possible to obtain the ” 9Sn NMR spectrum and the value obtained (- 606 ppm) is comparable with the low temperature solution data for trans-L2SnC14 of -7OO(L = Bun3PO) and -622(L = Me,CO) ppm and the corresponding cis-L2SnC14 compounds where the corresponding values are -707 and - 634 ppm. 24It should be noted that the NODMA complexes of tin tetraiodide and titanium tetrachloride are relatively unstable in the presence of air. The solid state NMR spectra were determined as rapidly as possible after preparation, the compounds being stored under nitrogen at -78 and

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taken to Durham for immediate analysis on arrival. The tin tetrachloride and tetrabromide complexes were more stable than the tetraiodide. This was apparent when the Miissbauer spectrum of the tetraiodide was studied with the above precautions omitted. The isomer shift and quadrupole splitting obtained were virtually identical with that for tin dioxide. On the other hand the spectra for the other complexes SnX,(NODMA), at 70 K gave isomer shifts relative to SnO, of 0.43 (X = Cl) and 0.63 (X = Br) mm s- ’ with respective linewidths of 1.09 and 1.18 mm s- ‘, the quadrupole splitting being zero in both cases. The shifts are in accord with the expected octahedral structure of the two complexes. The ’ ’ 3Cd NMR spectra are shown in Fig. 1. The values of the resonances [174.4 ppm CdC12NODMA; 218.0 and 163.0 ppm CdI,(NODMA),] are close to those obtained for other Cd complexes ligated by oxygen26 (- 100 to + 150 ppm) although also close to the range noted for coordination to nitrogen (+200 to + 350 ppm). There is, however, much less spinning side band structure than appears in other cases of complexes of cadmium linked to nitrogen and the fine structure that has been observed*’ when indirect coupling between ’ ’ 3Cd and two equivalent 14Nnuclei takes place is not apparent in our spectra. We have previously drawn attention’ to the opinion that the NO stretching frequency in NODMA complexes can be used as a diagnostic test for the coordination mode and have shown that this has frequently been based upon a faulty assignment of this frequency in NODMA itself. We therefore draw attention to the bands in the range 1290-1410 cm-’ and to the definitive assignments by Knieriem*’ which are fully substantiated by isotopic substitutions. It appears that the NO frequency is increased slightly upon coordination to metals and that this is independent of the coordination mode (see Table 3). We finally draw attention to the NMR data for the NOTMA complexes which show some interesting variations from those of the NODMA complexes. If we turn first to the solid state “C NMR spectrum of NOTMA it is apparent that the shifts of the C(2) and (6) although different have only a very SInd AZ,6 Vale and that this is also the case for the attached methyl groups. The probable explanation is that the NO group is twisted out of the plane of the ring and that any effect of the magnetic anisotropy of the NO group is substantially reduced, and that the NO group is almost orthogonal to the plane of the ring. There are only small changes in the complexes and we therefore suggest that in these molecules there will be a similar twisting of the NO group. The increase in the difference

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(a)

Fig. 1. ’ “Cd CPMAS NMR spectra of (a) CdClz *NODMA and (b) Cd1 ,(NODMA) 2.

between the 2 and 6 methyl group shifts from 1.9 ppm in NOTMA itself to 2.7-6.2 ppm in the complexes may be the result of a small increase in the twist of the NO group away from orthogonality in the complexes as compared with the free ligand.

Table 3. Infra-red

NODMA” Assignment” NODMAb NODMA’ Complexes Ptcl, PdCI2’ Me,SnCl,’ NiCl 2d GUI ZnCl, I-W, SnCl, SnBr, CdCl 2 CdI, CeCl ,d LaCl jd RhCl(cod)

absorption

Such changes require X-ray crystallographic studies for confirmation. The changes in the C( 1) and C(4) shifts are similar to those in the NODMA complexes as also are those for the dimethylamino group, both C and N resonances.

bands in the range 1290-1410 cm-’ coordination complexes

1302 VCH 1302 1305

1337 1337 1341

1366 1367

1307 1312 (1318)* 1305 1318 1293 1305 (1304)b 1304 1301 1299 1311 1302 1306 1305 1310

1337 1340 (1338)b 1337 1331 1326 1343 (1341)b 1326 1360 1358 1333 1333 1352 1352 1340

1374 1377 (1363)b 1372 1370sh 1368 1374 (1371)b 1367 1375 1372 1371 1370 1371 1371 1372

vCN

1363 vNO

for NODMA

and

1397 ? 1398 1400 Mode

“See ref. 28. *See ref. 15. ’ See ref. 1. dPrepared according to refs 7, 8. ‘See ref. 21.

1397 1403 (1408)’ 1399 1400 1393 1402 (1400)’ 1398 1405 1402 1402 1399 1397 1396

ON fJN QO QN 60 00 QO 00 00 QO QO 00 DO QN

Coordination

complexes of metal halides with substituted 4-nitrosoanilines

It is therefore apparent that solid state CPMAS NMR spectroscopic studies can give useful information for the structures of complexes of NODMA and NOTMA with metal halides, and that in particular enables us to understand how the C-nitrosoligand is changed structurally on coordination to a metal. On the other hand these studies do not enable a definitive conclusion to be drawn concerning whether the mode of coordination is aN or ao. Such information is best provided by crystal structure determination. Where this is not yet available it seems probable that our earlier proposal of aN coordination by NODMA to transition metals and a0 coordination to d” metals is the best available generalization. Acknowledgements-M.C. thanks the SERC for a research studentship. B.G.G. thanks the Leverhulme trust for the award of an Emeritus Fellowship and the SERC for the use of the solid state NMR facility in the University of Durham, and Professor R. K. Harris and Dr D. C. Apperley for the spectra obtained and discussion thereof. We thank Dr R. V. Parish for the Mossbauer spectra. We thank Dr B. E. Robertson for information on the crystal structure of the NODMA complex of zinc chloride.

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