SYNTHESES AND X-RAY CRYSTAL-STRUCTURES OF DICHLOROBIS(TERT-BUTYLIMIDO) COMPLEXES OF MOLYBDENUM(VI) - POTENTIAL PRECURSORS TO MOLYBDENUM NITRIDE AND MOLYBDENUM CARBONITRIDE

The bistertbutylimido complexes [MoCl(mu L-Cl)(NBu(t))(2)(NH(2)Bu(t))] (2), 1, and MoCl2(NBu(t))(2)(py)(2), 2 (py = pyridine), were prepared by reacting MoCl2(NBu(t))(2)(dme) (dme = dimethoxyethane) with excess Bu(t)NH(2) and pyridine, respectively. Their structures were determine d by X-ray crystallography. 1 has a pseudo edge-shared bioctahedral ge ometry with two Cl ligands bridging the Mo centers unequally. Pertinen t bond distances and angles for 1, Mo = NBu(bent)(t) = 1.737(3) Angstr om, angle Mo = N-CMe(3) = 154.0(2)degrees; Mo = NBu(linear)(t) = 1.725 (3) Angstrom, angle Mo = N-CMe(3) = 172.4(2)degrees; Mo-Bu(t)NH(2) = 2 .233(2) Angstrom; Mo=Cl-bridging = 2.575(1) and 2.835(1) Angstrom, and Mo-Cl-leminal = 2.428(1) Angstrom. Crystal data for 1: triclinic, spa ce group P (1) over bar, a = 8.897(4) Angstrom, b = 10.518(3) Angstrom , c = 10.663(3) Angstrom, alpha = 107.68(2)degrees, beta = 98.03(3)Ang strom, gamma = 99.26(3)degrees, V = 919.3(5) Angstrom(3), Z = II D-c = 1.381 g/mL. 2 is mononuclear with a distorted octahedral geometry wit h two trans Cl ligands, two cis-oriented Bu(t)N = ligands, and two py ligands trans to the imido groups. Pertinent averaged bond distances a nd angles for 2, Mo = NBu(bent)(t) = 1.736(4) Angstrom, angle Mo = N-C Me, = 161.8(4)degrees; Mo = NBu(linear)(t) = 1.705(5) Angstrom, angle Mo = N-CMe(3) = 173.4(4)degrees; Mo-N(py)= 2.44(1), Mo-Cl = 2.421(3) A ngstrom Crystal data for 2: orthorhombic, space group Pna2(1) a = 16.8 60(2) Angstrom, b = 8.920(3) Angstrom, c = 15.120(3) Angstrom, V = 227 4.1(9) Angstrom(3), Z = 4, D-c = 1.362 g/mL. A potential application o f 2 as a single-source precursor to grow molybdenum nitride and molybd enum carbonitride thin films by low pressure chemical vapor deposition (LPCVD) was explored. Cubic phase thin films (a(thin film) = 4.16 - 4 .20 Angstrom) were grown at temperatures between 450 degrees C and 650 degrees C with hydrogen as carrier gas. At 450 degrees C, thin films of molybdenum nitride were obtained. With temperature of deposition in creased from 450 degrees C to 650 degrees C, the ratio C/Mo increased from 0.03 to 0.5 whereas the ratio C/Mo decreased from 0.7 to 0.3. Thu s, thin films of molybdenum carbonitride were deposited at 650 degrees C.