The liberation, characterisation and X-ray crystal structure of 1,5,9- trip hosp ha- 1 5 9 - tris( 2-prop yl)cyclododecane Simon J. Coles, Peter G. Edwards,* James S. Fleming, Michael B. Hursthouse and Sudantha S. Liyanage zy HG Department zyxwvutsrq DCBA of Chemistry, University of Wales Cardiff, PO zyxwvu FEDCB Box 912, Cardiff, UK CFl 3TB zyxwv 1,5,9-Triphospha-1,5,9-tris(2-propyl)cyclododecane is liberated from the molybdenum template upon which it is formed by action of aqueous base and after oxidation of the metal with halogens. Complexes of triphosphorus macrocycles are rare. A series of macrocyclic ligands generated from 1,2-diphosphinobenzene and derivative complexes has been reported by Kyba et al.' Since these ligands are prepared by high-dilution methods, the syntheses are not stereospecific. Some while ago Norman and coworkers2 reported the first 1,5,9-triphosphacyclododecane complex; they also prepared the 1,6,11 -triphosphacyclopenta- decane analogue. We have extended this chemistry to tungsten and have recently reported the syntheses and characterisations of the first complexes of tritertiary derivatives of 1,5,9-triphos- phacyclododecane.3 These complexes are the only examples of symmetrical triphosphorus macrocycles (i.e. where all three backbone links are identical) and the free, uncoordinated macrocycles until now were unknown, despite attempts at their liberation from the metaltemplate upon which they were prepared. We have also recently reported oxidations of molybdenum and tungsten complexes of 1,5,9-triphosphacy- clodo- decane and its tertiary derivatives with halogens4 and chromium analogues.5 In this communication we report the high yield and stereoselective liberation of the tritertiary macrocycle 1,5,9-triphospha- 1,5,9-tris(2-propyl)cyclodo- decane, L, from its molybdenum(I1) dihalogeno complex [MoL(CO)*Br2] and the spectroscopic and crystallographic characterisation of the free macrocycle. Reaction of [ M o L ( C O ) ~ B ~ ~ ] with strong base (NaOH) in ethanol followed by digestion of inorganic by-products in water, causes a loss of colour of the mixture and the separation of a colourless oil. Extraction of this oil with light petroleum enables the isolation of colourless needles of the free macro- cycle in good yield (80% based on [MoL(C0)2Br2] zyxwvu CBA ] .t These crystals are readily characterised spectroscopically. The 31P( IH} NMR spectrum shows a singlet at 6 -19.8 consistent with an uncoordinated tertiary trialkylphosphine and shifted upfield from the parent molybdenum(I1) complex by zyxwvut CBA 29.5 ppm. The 'H NMR and l3C(IH} NMR spectral consist of 4 resonances assignable to the four different proton and carbon environments respectively and are similarto the spectra observed for the molybdenum-(0) and -(II) precursors. Since there are two possible geometric isomers of L, the spectra indicate that the liberation is stereospecific for isomer a (Fig. 1) P P zyxwvutsr u u z s a b R = Pr' Fig. 1 Possible conformations for L since isomer b would require an A2B spin pattern in the IP { I H ) NMR spectrum as well as correspondingly more complex 'H and 13C NMR spectra. The IR spectrum of L shows absorptions assignable to v(C-H), v(P-C) and the absence of bands that would arise from any metal-ligand vibrations. In the mass spectrum, the molecular ion is observed (m/z 349, 9%) along with a fragmentation pattern due to loss of CH3 and Prl groups. No heavier ions are evident. The X-ray crystal structure (Fig. 2)s confirms the charac terisation of L and that only one stereoisomer is present in the solid state with all lone pairs on the same side of the molecule, consistent with the solution NMR data. The P-C distances and angles are within expected ranges. Of intFrest are the non- bonded P.-P distances [average 5.199(4) A]. This compares with 3.660(8) 8, in the molybdenum(I1) complexcation [MoL(C0)3Br]+ and 3.487(5) 8, in the molybdenum(0) parent complex, [ M O L ( C O > ~ ] . ~ , ~ Clearly, the macrocycle opens out upon decomplexation as might be expected for such a flexible ring system. This flexibility indicates that this macrocycle may well be an effective tridentate ligand for a range of metals o different radii. We are currently studying the application of this synthe route to the liberation of 1,5,9-triphosphacyclododecane itself as well as other derivatives; preliminary results indicate that th approach is successful for a range of homologues. We are also studying the coordination chemistry of 1,5,9-triphospha- cyclododecane macrocycles with other metals. Again, prelimi- nary results indicate that a range of new complexes are readily formed. We are grateful to the EPSRC for a research grant (J. S. F.) and support for the X-ray crystallography unit and to the Association of Commonwealth Universities and the University of Sri Jaywardenepura of Sri Lanka for a Scholarship (S. s. L.). Fig. 2 X-Ray structure and atom labelling scheme for 1,5,9-triphosph 1,5,9-tris(2-propyl)cyclododecane L. Selected bond lengths (A): P( I )-C( 1 ) 1.842(5), P( 1)-C(9) 1.862(5), P(2)-C(4) 1.852(5), P(2)-C( 13) 1.844(5), P(3)-C(6) 1.835(5), P(3)-C(7) I .83 1(5), P( 1)-C( 10) 1.855(5), P(2)-C(3) 1.859(5), P(3)-C(16) 1.861(5). Selected bond angles ("): C( 1)-P( 1)-C(9) 100.9(2), C( 1)-P( 1)-C( 10) 99.9(2), C(9)-P( 1)-C( 10) 103.2(2), C(3)-P(2)- C(4) 10 1.1 (2), C(3)-P(2)-C( 13) 100.9(2), C(4)-P(2)-C( 1 3 ) 10 1.6(2), C(6)-P(3)-C(7) 102.5(2), C(6)-P(3)-C( 16) 101.6(2), C(7)-P(3)-C( 16) 99.3 (2). Chem. Commun., 1996 293 Published on 01 January 1996. Downloaded by University of Western Ontario on 26/10/2014 21:56:05. View Article Online / Journal Homepage / Table of Contents for this