Tetrakis(sulfurdiimido)silane, -germane and -stannane Max Herberhold*, Silke Gerstmann, Bernd Wrackmeyer* Laboratorium für Anorganische Chemie der Universität Bayreuth, D-95440 Bayreuth Z. Naturforsch. 53 b, 573-580 (1998); received March 30, 1998 Silicon, Germanium, Tin, Sulfur Diimides, Heterocycles, NMR Data Two tetrakis(sulfurdiimido)silanes [Si(NSNR )4 (R = rBu la, SiMe3 lb)], two germanes [Ge(NSNR)4 (R = rBu 2a, SiMe3 2b)] and one stannane [Sn(NSN?Bu) 4Sn 3a] were prepared and characterised by 'H, l 3C, i5N, 29Si and ll9Sn NMR spectroscopy in solution, and 3a was also studied in the solid state by 1 l9Sn CP/MAS NMR. Whereas la,b and 2a,b are monomeric in solution, the 119Sn NMR data suggest that 3a is associated both in solution and in the solid state, and that the tin atoms are hexa-coordinated. The attempted stepwise synthesis of la by using one, two, three or four equivalents of K[(NSN)rBu] led to mixtures of la with Cl3Si(NSNrBu) 4a, Cl2Si(NSN/Bu)2 5a, and ClSi(NSNfBu)3 6a. Only one sulfurdiimido ligand of the silane la reacted with hexachlorodisilane by oxidative addition and cleavage of the Si-Si bond to give the new heterobicyclic derivative 7a which is held together by two different coordinative N-Si bonds.
Introduction to improve the solubility of the potassium salts, K[(NSN)R] (R = 'Bu, SiMe_3), and thus acceler The chemistry of MX 4 compounds (M = Si, ates the reaction. The products 1 - 3 are isolated Ge, Sn) is well developed for various substitutents as yellow to orange oils (lb, 2a,b) or orange solids X such as halides, pseudohalides, chalcogenides, (la, m.p. 112°C; 3a, m.p. 253°C). They are sensi amides, or organyl groups [1, 2]. However, analo tive to moisture and readily soluble in toluene or gous derivatives of the type M(NSNR )4 have not chlorinated solvents. been reported as yet. Such compounds should be hexane/DME of interest with respect to their structural flexibil 4 K[(NSN)R] + MCI4 ------— -----* M(NSNR)4 + 4 KCI ity and their reactivity, since the M-N bonds [3] M Si Ge Sn and the NSN cumulene systems [4] invite to carry ( 1) 1a 2a 3a out further transformations. Derivatives with two or R = tBu R = SiMe3 1b 2b three sulfurdiimido ligands linked to organosilicon,
-germanium and -tin fragments have already been CI3Si(NSN‘ Bu) described [5, 6]. In the present paper, we report on 4a the synthesis of tetrakis(sulfurdiimido)silicon ( 1 ), - + germanium (2) and -tin (3) compounds and on their xK[(NSN)tBu] + SiCI 4 CI2Si(NSNtBu)2+ Si(NSNtBu )4 NMR spectroscopic characterisation. 5a 1a product distribution in (%) + 4a 5a 6a 1a CISi(NSNtBu )3 Results and Discussion x = 1 45.2 36.3 15.0 3.5 6a
x = 2 33.3 42.0 19.4 5.3 ( ) Synthesis of the M(NSNR)4 compounds 2 x = 3 28.0 46.6 25.4 The reaction of four equivalents of the potassium x = 4 100.0 salt K[(NSN)R] (R = rBu, SiMe3) with the respec Reactions of one, two or three equivalents of tive element tetrachloride leads directly to the cor K[(NSN)?Bu] with SiCU lead to mixtures con responding tetrakis(sulfurdiimido) compound [eq. taining CLSi(NSN'Bu) (4a), Cl2Si(NSNrBu)2 (5a), (1)]. Addition of 1,2-dimethoxyethane (DME) helps ClSi(NSNrBu)3 (6a) and Si(NSN'Bu)4 (la) [Eq. (2)]. This indicates that the reactivities of SiCU and of substituted silanes such as CUSKNSN'Bu) Reprint requests to Prof. Dr. M. Herberhold or Prof. Dr. B. Wrackmeyer; or Cl 2Si(NSN'Bu)2 are comparable (equation ( 2)). E-mail: [email protected].
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Dieses Werk wurde im Jahr 2013 vom Verlag Zeitschrift für Naturforschung This work has been digitalized and published in 2013 by Verlag Zeitschrift in Zusammenarbeit mit der Max-Planck-Gesellschaft zur Förderung der für Naturforschung in cooperation with the Max Planck Society for the Wissenschaften e.V. digitalisiert und unter folgender Lizenz veröffentlicht: Advancement of Science under a Creative Commons Attribution Creative Commons Namensnennung 4.0 Lizenz. 4.0 International License. 574 M. Herberhold et al. ■ Tetrakis(sulfurdiimido)silane, -germane and -stannane
A prominent feature of many sulfur diimides of the sulfurdiimido groups reacts with Si 2Clö. The is their fluxionality with respect to E/Z isomeri- reaction proceeds by oxidative cleavage of the Si-Si sation. This is evident for alkyl groups as sub bond, accompanied by reduction of sulfur (IV) to stituents [7-9J and also for numerous sulfur di sulfur (II); this step of the reaction corresponds to imides bearing organometallic substituents [ 10- previous findings for various sulfur diimides [ 6a, 13]. For steric reasons, isomers with Z/Z config 14]. However, intramolecular coordination of nitro uration are unfavourable, in particular if a 'Bu gen atoms of two different sulfurdiimido ligands to or a MeiSi group is linked to one of the ni the NSiCl^ groups prevents further reaction with trogen atoms. This would leave fifteen configu Si2Cl6. The products are stable at room tempera rational isomers for M(NSNR )4 compounds, as ture for several days and can be stored at -20°C for suming rigid structures. If the E/E configuration longer periods without decomposition. is also excluded as unfavourable because of elec tron pair repulsion, five principal isomers remain, tBu NT 'N ---- SiCI3 either with four times Z/E, four times E/Z, or I RlM(NSNtBu ) 3 + CI3 Si-SiCI3 Z/E and E/Z configurations as shown in Scheme CI3 Si„ M— NL (3) M = Si, R1 = NSNtBu 1a 1. This situation corresponds closely to the find R1 M = Ge, R1 = Me tBuN' NtBu ings for bis- and tris(sulfurdiimido) compounds [ 6]. M = Si, R1 = NSNtBu 7a M = Ge, R1 = Me 8a R— N N1(i Reaction of tetrakis(N-tert-butylsulfurdiimido)- I I stannane with triethylborane R R (Z/E)2(E/Z)2 We have investigated the reactivity of tetrakis(N- R\ /R tert -butylsulfurdiimido)-stannane 3a towards tri R-N S' (Z/E)4 ethylborane in order to compare with the analo "sr N* gous reactions of trimethyltin-substituted sulfur di R imides R’(NSN)SnMe3 (R' = SnMe3, fBu, SiMe3). (Z/E)(E/Z)3 N The latter have been transformed quantitatively
R \ ,S ^ /R into trimethylstannyl-amino(diethylborylamino)- I N I R h R sulfanes [15], Although it cannot be excluded that the initial steps of the reaction of 3a with E^B (1:4 (E/Z)4 or 1:8) are similar to that of R'(NSN)SnMe 3, de (Z/E)3(E/Z) composition becomes dominant in the case of 3a. Scheme 1. The five most likely configurations of The identified decomposition products [eq. (4)] sug tetrakis(sulfurdiimido)element compounds M(NSNR )4 gest that S-alkylation, followed by elimination of (R = rBu, SiMe?; M = Si, Ge, Sn); the first letter (E or Z) ethene, is favoured over rearrangement (migration refers to the position of the substituent R. of the stannyl fragment) and N-alkylation [15].
decomposition into Reaction of tetrakis(N-tert-butylsulfurdiimido)- SntNSNtBu^xBEfa ^ «> v Et3B-NH2tBu (10), silane with hexachlorodisilane 3a x = 4, 8 anC| unidentified products Treatment of tetrakis(N-rm-butylsulfurdiimi- do)silane la with hexachlorodisilane [eq. (3)], NMR spectroscopic results either in an equimolar ratio or in excess, General gave an orange oil which was characterised by 'H, l 3C, 14N, 15N and 29Si NMR in so The NMR data of all new compounds are given lution. For comparison, the analogous reac in Tables I (1-3), II (4-6) and III (7, 8 ). It has tion was carried out with methyl-tris(N-ter/- been shown that l5N NMR data of sulfur diimides butylsulfurdiimido)germane. Apparently, only one [6,12,13] are particularly useful for the configu- M. Herberhold et al. ■ Tetrakis(sulfurdiimido)silane, -germane and -stannane 575
Table I. NMR data |al of tetrakis(sulfurdiimido) compounds M(NSNR )4 (la - 3a, lb. 2b).
<5'H <$13C «$29Si <$I5N Compound lBu; SiMei 'Bu; SiMe3 (<$ll9 Sn) N'Bu / NSiMe3 NM [b]
la Si(NSN'Bu)4 [c] (Z/E)4 1.44 29.5/63.0 -74.7 -48.6 -84.8 A, B 2a Ge(NSN'Bu)4 [d] 1.31 28.6/63.4 -48.0 (Z) -71.3 (E) C 1.33 28.8/63.1 -49.6 (Z) -72.6 (E) 1.36 28.7/62.8 -51.3 (Z) -73.3 (E) 1.39 28.8/62.6 -53.6 (Z) -73.6 (E) 0.89 31.0/62.2 +32.4 (E) -150.1 (Z) 0.92 31.2/61.7 +36.9 (E) 3a Sn(NSN'Bu)4 [e] 1.54 29.9/60.6 (-624.0) n.m. n.m. 1.22 32.0/60.7 32.4/63.5 lb Si(NSNSiMe3)4 0.20 0.8 -77.1 -60.7 -62.4 A, B (6.8 ) (57.8) +4.6 2b Ge(NSNSiMe3)4 0.09 0.8 +5.2 -49.9 -72.4 A, C (6.4)
[a] Measured at +27°C, in [Dg]toluene; coupling constants in Hz: '/ ( 29 Sil3C) and 2/(29Si' H) in parentheses; n.m. = not measured; [b] l5N NMR methods : A = refocused INEPT pulse sequence with 'H decoupling; B = 'H inverse-gated decoupling; C = direct measurement, 1H coupled; D = direct measurement, 1 ^N{1H}; [c] <5I',N(-40°C) =-49.6 (N Bu), -83.5 (NSi); 15N NMR methods: A, D; [d] l:>N NMR spectrum recorded at -50°C; H and l3C NMR spectra recorded at -70°C; assignment of the proton and carbon resonances is based upon heteronuclear 2D i 3C/'H shift correlations ( 7 ( ,JC'H) = 145 Hz, /( C H) = 5 Hz); [e] Measured at -60°C; all ‘H and UC NMR signals are broad; Table II. NMR data|al of compounds 4a - 6a. tß u — N II 6] H 6,3C ^29Si N* Compound 'Bu rBu SiCl ^ * SL • N'5' ChSi(NSN?Bu) 4a 1.24 29.1/65.1 -38.7 I N* Cl,Si(NSN?Bu)2 5a 1.32 29.3/64.2 -53.3 tßu tBu ClSi(NSNrBu)3 6a 1.38 29.4/63.5 -65.2 • (Z/E)4 • tB u—N [a] Measured at +27°C, in C6Ö6. usual trend for the influence exerted by electro negative substituents. The same trend is found in the series Cl3Si(NSN/Bu) (4a, <529Si -38.7), Cl?Si(NSN'Bu)2 (5a, <$29Si -53.3), ClSi(NSN'Bu)3 (6a, <529Si -65.2) and Si(NSN'Bu )4 (la, <529Si - 74.7) (Table II, Fig. 4). Furthermore there is a systematic shift of the 29Si(SiMe3) resonances to wards lower frequencies when an increasing num ber of NSNSiMe 3 groups is attached to the central element [Me3M(NSNSiMe3): <529Si 1.6 (M = Si), 0.1 (M = Ge) [12a]; Me2M(NSNSiMe3)2: <529Si 2.8 (M = Si), 1.3 (M = Ge) [6a]; MeM(NSNSiMe3)3: 629Si 4.0 (M = Si), 2.8 (M = Ge) [ 6b]; M(NSNSiMe3)4: <529Si 4.6 (M = Si, lb), 5.2 (M = Ge, 2b)]. According to the 'H, 13C and 119Sn NMR spectra the structure of the tin derivative 3a is still fluxional at -80°C. The <5119Sn value (-624.0) of tetrakis(N- te/t-butyl-sulfurdiimido)tin 3a falls in the typical -30 -50 -70 -90 515n range for hexa-coordinated tin atoms [18]. The 119Sn resonance is broad both at room temperature Fig. 1. A: 50.6 MHz l 5N{'H inverse-gated} NMR Spec and at lower temperatures, possibly as a result of trum of Si(NSN'Bu )4 (la),measured in [Ds]toluene at dynamic processes. It seems likely that the increase 300K. Note the fairly broad resonance signals with hi /2 of the coordination number at the tin atom is caused = 15 Hz. B: 30.4 MHz l5N{'H} NMR spectrum of Si(NSN?Bu)4 (la),measured in [Ds]toluene at 233 K. by intermolecular association via the free electron pairs at the nitrogen atoms of the NSN system, <515N(NSiMe3) values of l band 2 bare typical aver analogous to bis- and tris(sulfurdiimido)tin com aged values [12], indicating fast E/Z-Z/E isomeri- pounds [ 6b]. The structure of 3a in the solid state sation processes (Fig. 3). must be similar as in solution, since the solid-state 1 l9Sn CP/MAS NMR spectrum reveals an isotropic bx 19Sn value of -604.0, close to the value in solution 29Si and U9Sn NMR data (-624.0). Comparing different sulfurdiimido compounds we have observed that the 29Si nuclear shield Ntßu tßuN S ing of the central silicon atom increases with S an increasing number of sulfurdiimido groups N [Me^SKNSNSiMeO: 'SnC <529Si 1.6 [12a]; Me2Si(NSNSiMe3)2: <*>29Si - N N S S 16.2 [6a]; MeSi(NSNSiMe3)3: S29Si -44.5 [6b]; tßuN Ntßu Si(NSNSiMe3)4 (lb):<529Si -77.1], which is the M. Herberhold et al. • Tetrakis(sulfurdiimido)silane, -germane and -stannane 577 Fig 2. 30.4 MHz l5N NMR spectrum (' H coupled) of Ge(NSNfBu )4 (2a), measured in [Ds]toluene at 223 K. CI3Si(NSN'Bu) 4a Si(NSNSiMe3)4 1b B CI2Si(NSN'Bu)2 5a Si(NSN'Bu)4 1a CISi(NSN'Bu)3 6a I -54 -58 -62 -66 815N -35 -45 -55 -65 -75 529Si Fig. 3. 50.6 MHz l5N NMR spectra of Si(NSNSiMe ,)4 (lb), measured in [Dgjtoluene at 300 K. A: I 3N{'H Fig. 4. 59.6 MHz 29Si NMR spectrum ('H coupled; C 6D6 inverse-gated}. B: Recorded by using the refocused IN solution; 300K) of a mixture of CU-« Si(NSN/Bu)« (n = EPT pulse sequence with 1H decoupling (for polarisation 1 -4), obtained from the 1:1 reaction of K[(NSN/Bu] with transfer. ’■V(15N'H) was assumed to be 1 .8 Hz). The reso- SiCl4. nance of S(NSiMe 3)2 is marked by #. is therefore suggested that the silicon atoms are 15N and 2gSi NMR data of the heterocycles 7a and 8a penta-coordinated due to an additional coordina- tive N-Si bond [ 6a], The signal for the central Si Two 29Si NMR signals are observed for NSiC^ atom in 7a lies at fairly high frequency, when com groups in 7a and 8a at rather low frequencies. It pared with la. This 29Si deshielding is caused by 578 M. Herberhold et al. ■ Tetrakis(sulfurdiimido)silane, -germane and -stannane Table III. NMR data|a| of the compounds 7a and 8a. CI3Si-SiCI3 tBu\ N N---- S 1CI3 I ? t C I s S i ^ M — N ^ | R1 II tBuN'*' NtBu M = Si, R1 = NSNtBu 7a M = Ge, R1 = Me 8a Com <5I3C b29Si bl5N pound 'Bu MeGe SiCl3 Si =N'Bu =NM 7a [b ] 29.6/63.9 -42.0 -26.2 -31.8 -67.0 29.6/64.4 -45.1 -32.3 -97.0 (br) 31.0/63.4 -35.2 8a [c] 29.5/63.9 12.8 -42.6 -30.8 -96.6 29.6/64.5 -45.1 -35.3 -98.5 31.1/63.1 [a] Measured at +27°C, in [D^Jtoluene; '"’N NMR spec tra were recorded at -50°C. direct measurement, 1H cou pled; br = broad; s = singulet; [b] b1 H[corresponding b 13C value]: 1.34 (s, 18H. 'Bu) [29.6/64.4], 1.38 (s, 9H, 'Bu) [29.6/63.9]. 1.51 (s,9H,'Bu) [31.0/63.4]; <5,4N :-25.0 (br, N'Bu), -100.0 (br, NSi), region between -270.0 and -320.0 (br, NSiCh); [c] b 'H[corresponding£I3C value]: 1.18 (s, Fig. 5. 59.6 MHz 29Si NMR spectrum (' H coupled) of the 3H, MeGe) [12.8], 1.33 (s, 9H, 'Bu) [29.6/64.5], 1.36 (s, heterocycle 7a, measured in [Dsjtoluene at 300K. 9H, 'Bu) [29.5/63.9], 1.39 (s, 9H. 'Bu) [31.1/63.1 ]; [1] D. A. Armitage, R. J. 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