Polyhedron Vol. 12, No. 21, pp. 260~2609, 1993 0277-5387/93 $6.00+ .I0 Printed in Great Britain Q 1993 Pergamon Press Ltd zyxwvutsr MOLYBDENUM(V1) DIOXO COMPLEXES WITH MACROCYCLIC AMINE LIGANDS ABDESSADEK LACHGAR,* PAUL FARRALL and JAMES M. MAYER? Department of Chemistry BG-10, University of Washington, Seattle, WA 98195, U.S.A. zyxwvutsrqpon (Received 1 M arch 1993 ; accepted 19 M ay 1993) Abstract-Reaction of Mo02C12 with the tetradentate amine ligand 1,4,8,1 Ztetra- azacyclopentadecane ([ 1 SIaneNd) yields the molybdenum(V1) dioxo complex [MOO, ([lS]aneN,-H)]Cl (I), a rare example of a cationic complex containing the Moos’+ unit. The 0x0 ligands are cis and the macrocyclic amine coordinates in a non-planar fashion, as revealed by X-ray crystal structure and NMR data. One of the nitrogen donors cis to the 0x0 groups has been deprotonated to give an amide ligand (NR,-). In contrast, reaction of Mo02C1, with tetramethylcyclam (1,4,8,1 I-tetramethyl- 1,4,8,11-tetraazacyclotetradecane, TMC) yields the neutral adduct MoO~C~~(~~-TMC) (III), in which only two of the amine nitrogens are coordinated. An X-ray structure of III shows it to have an all-& octahedral geometry, very unusual for M002X2L2 complexes, with one 0x0 ligand tram to an amine and the other trunS to a chloride. Compounds [MoO,([lS]aneN,-H)]BPh, II and III are not very stable in solution ; II is not reduced electrochemically or by PPh,. The chemistry of molybdenum 0x0 complexes has been intensively studied, particularly as models for active sites in metalloenzymes and on hetero- geneous catalysts.’ Yet, despite the large number of molybdenum(V1) 0x0 complexes,’ to our knowl- edge there is only one well-characterized cationic derivative, [MoOaBr(tacn)]+ (tacn = triazacyclo- nonane), 3 and there are no complexes with tetra- dentate amine ligands.’ We report here two complexes formed from reaction of Mo02C12 with the macrocyclic amine ligands 1,4,8,12-tetraaza- cyclopentadecane ([15]aneN4) and 1,4,8,1 l-tetra- methyl- 1,4,8,11-tetraazacyclotetradecane (tetra- methylcyclam, TMC). [ WaneN, * Currently at : Department of Chemistry, Wake For- est University, Winston-Salem, NC 27109, U.S.A. t zyxwvutsrqponmlkjihgfedcbaZYXWVUTSRQPONMLKJIHGFEDCBA Author to whom correspondence should be addressed. EXPERIMENTAL General considerations All experiments were performed under a nitrogen atmosphere or under vacuum employing high vacu- um-line, Schlenk and standard glove-box tech- niques, unless otherwise noted. Solvents were dried according to standard procedures.4 Acetonitrile was first dried over 3 A molecular sieves and then vacuum transferred into a flask containing CaH,, from which it was vacuum transferred immediately before use. Mo02C12 (Aldrich) was sublimed at 50°C under a static vacuum. 1,4,8,12-Tetraaza- cyclopentadecane (A) and 1,4,8,1 l-tetramethyl- 1,4,&l I-tetraazacyclotetradecane (B) were sub- limed in vucuo at 73 and 4O”C, respectively, and stored under nitrogen. ‘H NMR spectra were acquired at ambient temperatures using a Varian VXR-300 Fourier-transform spectrometer (300 MHz). The ‘H NMR spectra are reported in ppm downfield of TMS or DSS and were referenced relative to the residual protons in the solvent or to DSS for spectra in D20. The 13C{ ‘H) NMR spectra were recorded at 75.43 MHz. Spectra are reported as: 6 (ppm) [multiplicity, coupling constants (in Hz), number of hydrogens]. IR spectra were re- corded on a Perkin-Elmer 1600 FT-IR spectrometer 2603