THE SYNTHESIS OF SOME ALKYLTELLURIDE-MANGANESE(I) COMPLEXES, AND AN ASSESSMENT OF THEIR SUITABILITY FOR MOCVD APPLICATIONS

Tellurium does not insert directly into the Mn-C bond of RMn(CO)5 (R = Me or PhCH2). However, reactions between RMn(CO)5 (R = Me, PhCH2) and TePR'3 (R' = Me, Et) result in Te insertion accompanied by CO substit ution to produce RTeMn(CO)3(PR'3)2 complexes. These complexes are form ed by initial substitution to give RMn(CO)3(PR'3)2 followed by Te inse rtion. The crystal structure of the complex with R = PhCH2 and R' = Et has been determined from X-ray diffraction data. Crystal data: C22H37 O3P2MnTe; M = 594.0; P1BAR, a = 9.263(2), b = 14.650(5), c = 20.265(7) angstrom, alpha = 91.27(3), beta = 90.67(2), gamma = 103.96(2)degrees, U = 2667.7(14) angstrom3; D(calc) = 1.479 (Z = 4), D(meas) = 1.480(5) mg m-3, mu = 1.687 mm-1 for Mo-K(alpha) radiation (lambda = 0.7107 an gstrom), final R = 3.11, R(w) = 5.46, from 7788 observed reflections ( 12974 collected). The geometry about manganese is slightly distorted o ctahedral with a trans-arrangement of the phosphine groups and a merid ional placement of the carbonyls. Pyrolysis of PhCH2TeMn(CO)3(PEt3)2 a t 300-degrees-C in a hydrogen stream gives a film of MnTe. Treatment o f Mn(CO)5Br with LiTeR yields the dimeric products [Mn(CO)4(mu-TeR)]2 (R = Me, Et, Pr(i), CH2SiMe3, Si(SiMe3)3, and Ph). For most of these c omplexes, two conformations have been detected by multinuclear NMR spe ctroscopy. Variable temperature H-1 NMR spectroscopy shows that the co nformers interconvert for R = Me and CH2SiMe3. The mass spectra of [Mn (CO)4(mu-TeR)]2 (R = Me, Et, Pr(i)) show gas phase fragmentation to Mn (x)Te(y) species. Pyrolysis of two of these complexes (R = Me, Et) in a hydrogen atmosphere produced a film containing MnTe. Addition of PEt 3 to a solution of [Mn(CO)4(mu-TeMe)]2 results in bridge cleavage to y ield MeTeMn(CO)3(PEt3)2, but the reaction is slow and other unidentifi ed products are formed. A similar reaction occurs when R = CH2SiMe3. T he formation of MeTeMn(CO)3 (PEt3)2 was also achieved from the reactio n between BrMn(CO)3(PEt3)2 and LiTeMe. The Hg-Mn complex MeHgMn(CO)5 w as obtained by treatment of [Mn(CO)5]- with MeHgCl. This complex readi ly disproportionates to Me2Hg and Hg[Mn(CO)5]2. Pyrolysis of MeHgMn(CO )5 at 300-degrees-C gives a film of manganese with no retention of mer cury.