A series of structurally characterized new examples of pentacoordinated heteroleptic tungsten(VI)-guanidinates complexes are described. Starting out from [WCl(2)(Nt-Bu)(2)py(2)] (1) (py = pyridine) and the guanidinato transfer reagents (TMEDA)Li[(Ni-Pr)(2)CNi-Pr(2)] (2a) (TMEDA = N,N,N',N'-tetramethylethylendiamine) and [Li(NC(NMe(2))(2))](x) (2b), the title compounds [WCl(Nt-Bu)(2)[(Ni-Pr)(2)CNi-Pr(2)]] (3) and [W(Nt-Bu)(2)Cl{NC(NMe(2))(2)]](2) (6) were selectively formed by the elimination of one mole equivalent of lithium chloride. The isopropyl-substituted guanidinato ligand [(Ni-Pr)(2)CNi-Pr(2)} of monomeric 3 is N(1),N(3)-bonded to the tungsten center. The introduction of the sterically less-demanding tetramethyl guanidinato ligand [NC(NMe(2))(2)] expectedly leads to dimeric 6 exhibiting a planar W(2)N(2) ring with the guanidinato group bridging the two tungsten centers via the deprotonated imino N-atom. The remaining chloro ligand of 3 is labile and can be substituted by sterically less-crowded groups such as dimethylamido or azido that yield the presumably monomeric compounds 4 and 5, respectively. A similar treatment of 6 with sodium azide yields the dimeric azido derivative 7. Reacting [WCl(2)(Nt-Bu)(2)py(2)] directly with an excess of sodium azide leads to the dimeric bis-azide species [[W(Nt-Bu)(2)(N(3))(mu(2)-N(3))py](2)]. The new compounds were fully characterized by single-crystal X-ray diffractometry (except 2, 4, and 5), NMR, IR, and mass-spectroscopy as well as elemental analysis. Compound 5, [W(N(3))(Nt-Bu)(2)[(Ni-Pr)(2)CNi-Pr(2)]], can be sublimed at 80 degrees C, 1 Pa.

Novel mixed amido-/imido-/guanidinato-complexes of tantalum are reported. The complexes were synthesised by insertion reactions of carbodiimides of the type C(NR)2(R =iso-propyl (i-Pr)) into the M-N bonds of tantalum mixed amido/imido complexes. Three representative complexes were synthesised and fully characterised by 1H-NMR, 13C-NMR, CHN-analysis and mass spectroscopy. The crystal structure of the complex [Ta(NMe2){(i-Pr-N)2C(NMe2)}2(N-t-Bu)](1)(Me = methyl, t-Bu =tert-butyl) is presented and discussed. The complexes are solids that can be quantitatively sublimed at moderate temperatures (120-130 degrees C) without any sign of decomposition. The thermal properties of the new compounds were studied (TGA) and preliminary MOCVD-experiments were performed. TaN films were deposited and characterised by XRD and XPS.

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Two new tungsten complexes, [W(NtBu) 2 (NMe 2 ){(iPrN) 2 CNMe 2 }] (2) and [W(NtBu) 2 (H){(iPrN) 2 CNMe 2 }] (3), as precursors for metal-organic chemical vapor deposition (MOCVD) of tungsten nitride thin films were synthesized from the starting compound [W(NtBu) 2 (Cl){(iPrN) 2 CNMe 2 }] (1) by substitution of the chloro ligand by a dimethylamido and a hydrido group, respectively. Compounds 1-3 were characterized by 1 H NMR, 13 C NMR, EI-MS, IR, and elemental analysis including single-crystal X-ray diffraction studies on 1 and 3. The thermal properties of the compounds were studied by thermogravimetric and differential thermal analysis. Precursors 2 and 3 were compared for the growth of tungsten nitride thin films by MOCVD. The obtained films were characterized by X-ray diffraction and scanning electron microscopy and by depth-profiling the composition with secondary neutron mass spectroscopy. Films grown without ammonia had surprisingly low nitrogen levels, indicating that 2 and 3 are not suited as single-source precursors for pure WN x phases. When ammonia was used as a co reactant gas, the carbon content in the films decreased significantly and crystalline β-W 2 N was obtained. Interestingly, films grown in the presence of ammonia by amido compound 2 yielded lower carbon contents than films obtained from hydrido compound 3. Supporting Information Available: X-ray crystallographic data in CIF format for the structures of compounds 1 and 3 and schemetic of the MOCVD reactor and table with film composition (PDF). This material is available free of charge via the Internet at http://pubs.acs.org. CM061999D

Tungsten nitride and molybdenum nitride are electrically conducting refractory metal nitrides. Their applicability as novel gate electrode materials in CMOS technology is actually under investigation. MOCVD is one of the most prominent processes to deposit thin films of these materials. In order to improve the quality of MOCVD grown thin films it is important to optimize the chemical design of the employed precursors. Herein, we report on the synthesis of different imido-guanidinato-molybdenum complexes like [Mo(N t Bu) 2 (X){( i PrN) 2 CNMe 2 }], (X = Cl, I, or N 3 ). In particular we want to highlight that we were able to synthesize the new all nitrogen coordinated imido-amidinato-molybdenum complex [Mo(N t Bu) 2 {( i PrN) 2 CMe} 2 ]. The chemical and thermal properties of these new molybdenum compounds were investigated, to check their potential use as precursors for the MOCVD of molybdenum nitride.