PhGeCl₃ reacts with Na{[OP(OEt)₂]₃CoCp} to give the six-coordinate complex PhCl₂Ge{[OP(OEt)₂]₃CoCp}, characterised spectroscopically and by an X-ray crystal structure determination which showed a firmly-attached tridentate ligand [Ge–O 1.973(2) Å]

Davidson, Kelly A.

Kilpin, Kelly Joan

Lloyd, Nicholas C.

Nicholson, Brian K.

English

Research Commons@Waikato

1Correspondence to: Professor B K Nicholson  Chemistry Department  University of Waikato  Private Bag 3105  Hamilton  New Zealand  Email: b.nicholson@waikato.ac.nzFax: 64 7 838 4219  COMMUNICATION:  A six-coordinate aryl-germanium complex formed by the Kläui ligand Kelly A. Davidson, Kelly J. Kilpin, Nicholas C. Lloyd and Brian K. Nicholson*  Department of Chemistry, University of Waikato, Private Bag 3105, Hamilton, New Zealand.Synopsis  The first structurally-characterised six-coordinate aryl-germanium(IV) complex is described.  CoP(OEt) 2(EtO) 2P P(OEt) 2OOOGeClClPh 2Abstract.PhGeCl3 reacts with Na{[OP(OEt)2]3CoCp} to give the six-coordinate complex PhCl2Ge{[OP(OEt)2]3CoCp}, characterised spectroscopically and by an X-ray crystal structure determination which showed a firmly-attached tridentate ligand [Ge-O 1.973(2) Å]. -------------------------------------------------------------------------------------------------------  Whilst six-coordinate organo-tin complexes are common [1], corresponding derivatives are rare in organo-germanium chemistry. There are some cyclometallated examples based on Ge-CH2-heteroatom motifs [2], but there appear to be no structurally characterised aryl-germanium six-coordinate species [3]. We have recently reported some novel six-coordinate organo-tin complexes based on the Kläui ligand 1 (LR) [4] which showed good stability even for the example incorporating the weak Lewis acid group Ph3Sn+ [5]. We now report the synthesis and structure of a related compound of germanium, PhCl2Ge{[OP(OEt)2]3CoCp} (2a). As far as we are aware, the only previous use of the Kläui ligand in germanium chemistry is the report from Filipou et al [6] of some inorganic Ge(II) and Ge(IV) compounds, of which (N3)3Ge{[OP(OEt)2]3CoCp} (2b) is the only six-coordinate example relevant to the present work.  PhGeCl3 reacts smoothly with NaLEt in CH2Cl2 to give crude 2a as an oil in essentially quantitative yield. This can be crystallised to give yellow, air-stable crystals. The structure was determined by single-crystal X-ray methods and is illustrated in Figure 1. It shows true six-coordination, with only minor deviations from ideal octahedral geometry with the angles around germanium in the range 86-95°. There are no systematic 3variations in the Ge-O distances despite the differences in the trans groups from the PhCl2Ge moiety. Table 1 compares some bond parameters with those from the corresponding (N3)3GeLEt (2b) [6] and PhCl2SnLMe [5] compounds. The Ge-O distances in 2a are 1.973(2) Å, almost exactly as predicted from the sum of the covalent radii of Ge(IV) and O (1.21 and 0.74 Å respectively [7]) but are marginally longer than those in the (N3)3GeLEt complex [1.893(5) Å]. This suggests the Kläui ligand is moderately strongly bonded to the Ge centre in both germanium examples. The Sn-O distances in the tin analogue of 2a are longer by only 0.102(4) Å, which is less than expected given that the covalent radius of Sn(IV) is ca 0.17 Å larger than that of Ge(IV), based on a comparison of the E-E and E-C bonds in Ph6E2 (E = Ge, Sn) [8], indicating even stronger attachment of the Kläui ligand for tin.  The 1H and 13C NMR spectra gave the expected signals for the Ph and Cp groups, with those of the OCH2CH3 groups on the ligand appearing as single broad lines with no resolved splitting, despite their inequivalence and expected 1H and 31P coupling. Obviously at room temperature fluxional averaging is much faster for the germanium complex than for the tin one, where the 1H and 13C spectra of the analogous complex gave resolved signals from the three conformationally distinct OCH2CH3 groups, further complicated by virtual coupling [5]. The 31P spectrum of 2a gave a broad singlet at room temperature through averaging; at 220 K an overlapping doublet and triplet, strongly distorted by second-order effects, was clearly resolved for the A2B spin system with very similar  values (113.9 and 115.0 ppm) (Figure 2).   Spectroscopic evidence suggested that Ph2ClGeLEt could also be synthesised by the same route, but this product has so far only been isolated as an impure oil which we have 4been unable to crystallise. On the other hand the reaction of Ph3GeCl with NaLEt gave no indication that a stable complex forms, with Ph3GeOGePh3 the only species isolated from the reaction mixture. This suggests that Ph3Ge+ has a significantly lower tendency towards six-coordination than does Ph3Sn+ [5].  Experimental  General. The Kläui ligand was purchased from Strem Chemicals, and PhGeCl3 from Gelest. 1H, 13C and 31P NMR spectra were recorded at 303 K on a Bruker Avance DRX300 instrument (1H 300.1 MHz; 13C 75.5 MHz; 31P 121.5 MHz). Preparation of PhCl2Ge{[OP(OEt)2]3CoCp}, (PhCl2GeLEt, 2a). (a) NaLEt (0.650 g, 1.17 mmol) was dissolved in dry CH2Cl2 (10 mL). To this a solution of PhGeCl3 (0.19 mL, 3.0 g, 1.17 mmol) was added and the mixture was stirred for 30 min.  The solution was filtered and the solvent evaporated to leave a yellow oil that was crystallised from CH2Cl2/petroleum spirits at -20°C to give yellow crystals of 2a. Found: C 36.54, H 5.41 %; C23H40Cl2CoGeO9P3 requires C 36.54, H 5.33%; NMR (CDCl3): 1H:  Q 1.24 (br s, CH3), 4.15 (br s, CH2), 5.13 (s, Cp), 7.15 (m, H-3, Ph), 7.56 (m, H-4, Ph), 7.98 (m, H-2, Ph) ; 13C{1H}:  Q 16.5 (br s, CH3), 63.1 (br s, CH2), 89.6 (s, Cp), 126.4 (C-3), 126.9 (C-4), 132.2 (C-2); 31P{1H} (290 K);  112.4 br s; (220 K) 113.9 (2nd order doublet, 3JP-P 114 Hz), 115.0 (2nd order triplet, 3JP-P 114 Hz). X-ray crystal structure of PhCl2Ge{[OP(OEt)2]3CoCp}.CH2Cl2 (2a.CH2Cl2)X-ray intensity data were collected on a Siemens SMART CCD diffractometer using standard procedures and software. An empirical absorption correction was applied 5(SADABS [9]). The structure was solved by direct methods and developed and refined on F2 using the SHELX programmes [10] operating under WinGX [11]. Hydrogen atoms were included in calculated positions. Yellow needle crystals of 2a were obtained by slow diffusion of pentane into a CH2Cl2 solution of the compound. Crystal data: C23H40Cl2CoGeO9P3.CH2Cl2, M = 840.81, monoclinic, space group Pc, a = 11.821(1), b = 17.951(2), c = 9.386(1) Å,  = 112.45(5)°, U =1840.8(7) Å3, T= 93 K, Z = 2, Dcalc = 1.517 g cm-3, µ(Mo-K) = 1.731 mm-1, F(000)= 860;  35843 reflections collected with 1° <  < 33°, 13285 unique (Rint 0.0928) used after correction for absorption (Tmax, min  0.724, 0.423). Crystal dimensions 0.60 x 0.25 x 0.20 mm3.Refinement was on F2 .Towards the end of the refinement, racemic twinning was indicated and was included using the TWIN/BASF options of SHELXL-97. This converged with a 0.71/0.29 twinning ratio and final agreement indices of R1 0.0432 [I > 2 (I)] and wR2 0.1176 (all data), GoF 1.013.   The structure of 2a is illustrated in Figure 1, with selected bond parameters summarised in the caption.  5. Supplementary material. Crystallographic data for the structural analysis have been deposited with the Cambridge Crystallographic Data Centre, CCDC 627741. Copies of this information may be obtained free of charge from the Director, CCDC, 12 Union Rd., Cambridge CB2 1EZ, UK (Fax: +44-1223-336033; e-mail: deposit@ccdc.cam.ac.uk or www: http://www.ccdc.cam.ac.uk). 6Acknowledgements We thank Dr Tania Groutso, University of Auckland, for collection of X-ray intensity data. References. 1. J. A. Zubieta, J. J. Zuckerman, Progr. Inorg. Chem., 24 (1978) 251; A. G. Davies, Organotin Chemistry, VCH, Germany, 1997; C. E. Holloway, M. Melnik, Main Group Metal Chem., 23 (2000) 1  2. S.A. Artamkin, V. N. Sergeev, Y. I. Baukov, A O. Mozzhukhin, M. Y. Antipin, Y. T. Struchkov, Metalloorg. Khim., 4 (1991) 1024; Y. E. Ovchinnikov, S. A. Pogozhikh, V. N. Khrustalev, S. Y. Bylikin, V. V. Negrebetsky, A. G. Shipov,Y. I Baukov, Izv. Akad. Nauk SSSR (2000) 1799; S. Mahboob, M. Parvez, M. Mazhar, S. Ali Acta Cryst., E61 (2005) m358. 3. Cambridge Crystallographic Database, October 2006 release. 4. W. Kläui, Angew. Chem. Int. Ed. Eng., 29 (1990) 627. 5. N. C. Lloyd, B. K. Nicholson, A. L. Wilkins, J. Organometal. Chem., 691 (2006) 2757. 6. A. C. Filippou, P. Portius, G. Kocok-Köhn and V. Albrecht, J. Chem. Soc., Dalton Trans., (2000) 1759. 7.  SI Chemical Data, G. Aylward and T. Findlay, 5th Ed, Wiley, Australia, 2002. 8. R. E. Marsh, Acta Cryst, B55 (1999) 931; D. Dakternieks, F. S. Kuan, A.Duthie, E. R. T. Tiekink, Main Group Metal Chem., 24 (2001) 65. 9. R. H. Blessing, Acta Cryst., A51, (1995) 33. 710. G. M. Sheldrick, SHELX97 Programs for the solution and refinement of crystal structures, University of Göttingen, Germany, 1997. 11. L. J. Farrugia, WinGX, Version 1.70.01, University of Glasgow, UK; L. J. Farrugia, J. Appl. Cryst., 32 (1999) 837. 8CoP(OEt)2(EtO)2P P(OEt)2OOOGeR2R3R1CoP(OR)2(RO)2P P(OR)2OOO-(1)2a R1 = Ph, R2 = R3 = Cl2b R1 = R2 = R3 = N39Table 1 Selected bond lengths(Å) and angles (°) for 2a and related complexes  PhCl2GeLEt PhCl2SnLMe (N3)3GeLEt (M = Ge) (M = Sn [5]) (M = Ge[6]) M(1)-C(41)  1.994(3)  2.111(5) M(1)-Cl(av)  2.327(1)  2.385(2)  M(1)-O(11)  1.973(2)  2.075(3) 1.893(5)  O-M(1)-O(av)   87.9(1)  84.9(1) 89.9(3) Cl(1)-M(1)-Cl(2)  94.35(3)  97.40(5)  C(41)-M(1)-Cl(1)  95.37(9)  99.3(1) C(41)-M(1)-Cl(2)  94.83(9) 95.5(1)  10Caption to Figures:Figure 1. The structure of complex 2a, with the ethyl groups on the peripheral oxygen atoms omitted for clarity. Selected bond parameters include: Ge(1)-C(41) 1.994(3), Ge(1)-Cl(1) 2.3257(8), Ge(1)-Cl(2) 2.3292(8), Ge(1)-O(11) 2.010(2), Ge(1)-O(21) 1.938(2), Ge(1)-O(31) 1.970(2) Å; O-Ge(1)-O (avg)  87.9(1)°, Cl(1)-Ge(1)-Cl(2) 94.35(3)°, C(41)-Ge(1)-Cl(1) 95.37(9)°, C(41)-Ge(1)-Cl(2) 94.83(9)°.  Figure 2. The 31P{1H} NMR spectrum of 2a at 220 K. showing the distorted doublet (113.9) and triplet ( 115.0) in a 2:1 ratio, 3JP-P 114 Hz. 11Cl(2)Cl(1)C(41)C(42)O(21)Ge(1)O(31)O(11)O(12)P(1) O(32)Co(1)O(33)O(23)O(22)O(13)C(1)C(5)C(4)C(43)C(44)C(45) C(46)Figure 1 12109110111112113114115116117118119 ppmFigure 2 

A six-coordinate aryl-germanium complex formed by the Kläui ligand

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A six-coordinate aryl-germanium complex formed by the Kläui ligand

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