ACETONITRILE AND CYANIDE COMPOUNDS CONTAINING METAL-METAL BONDS - SYNTHESES, STRUCTURES AND APPLICATIONS TO SOLID-STATE CHEMISTRY

被引:30
作者
BARTLEY, SL
BERNSTEIN, SN
DUNBAR, KR
机构
[1] MICHIGAN STATE UNIV,DEPT CHEM,E LANSING,MI 48824
[2] MICHIGAN STATE UNIV,CTR FUNDAMENTAL MAT RES,E LANSING,MI 48824
关键词
D O I
10.1016/S0020-1693(00)83832-3
中图分类号
O61 [无机化学];
学科分类号
070301 ; 081704 ;
摘要
Compounds with acetonitrile and cyanide ligands have been prepared from mild substitution reactions of well-known metal-metal bonded precursors. Facile non-redox substitution of the carboxylate ligands in Mo-2(O2CCH3)(4) occurs in chlorinated solvents treated with excess [R(4)N][CN] (R=Et, Bu(n)) to produce the salts [R(4)N](4)[Mo-2(CN)(8)] (R=Et (3); Bu(n) (1)) in high yields. These reactions were found to be solvent dependent, with the major product isolated from reactions performed in THF being [Bu(4)(n)N](3)[Mo-2(O2CCH3)(CN)(6)] (2). The chloride ligands in multiply-bonded dirhenium compounds are readily displaced by cyanide as demonstrated by the reaction between Re2Cl4(dppm)(2) and [Bu(4)(n)N]CN to give [Bu(4)(n)N](2)[Re-2(CN)(6)(dppm)(2)] (4). Compounds 1-4 were characterized by IR and electronic spectroscopies; single crystal X-ray data were collected for 1, 2 and 4.1.8CHCl(3): orthorhombic, Pbca, a=20.526(8), b=28.122(5), c=19.855(7) Angstrom, V=11461(4) Angstrom(3), R=0.082, R(w)=0.083; 2: monoclinic, P2(1), a=12.046(3), b=16.050(10), c=16.854(3) Angstrom, beta-94.11(2)(0), V=3250(2) Angstrom(3), R=0.067, R(w)=0.067; 4.8CH(2)Cl(2): triclinic, P1, a=13.835(2), b=18.172(2), c=12.261(1) Angstrom, alpha=106.788(8), beta=107.850(9), gamma=93.894(9)(0), V=2767.5(6) Angstrom(3), R=0.041, R(w)=0.045. The molecular structure of [Bu(4)(n)N](4)[Mo-2(CN)(8)] contains dimolybdenum(II) centers ligated by eight CN- ligands in the familiar unbridged M(2)L(8) arrangement, with the two Mo(CN)(4) units being perfectly eclipsed as expected for a molecule with a 6 component to the M-M bond. The Mo-Mo distance of 2.122(2) Angstrom is the shortest reported distance for an unbridged homoleptic Mo(2)(II,II)L(8) compound. The related salt, [Bu(4)(n)N](3)[Mo-2(O2CCH3)(CN6] (2), contains an anion displaying a structure similar to 1, but with one bridging acetate ligand, the presence of which results in a slight contraction of the Mo-Mo bond to 2.114(2) Angstrom. The hexacyanodirhenium compound, 4, is reminiscent of M(III) complexes of the type M(2)X(6)(dppm)(2) with one important exception, namely it is of the type [M(2)X(6)(dppm)(2)](2-) with divalent metal centers. The equatorial plane in 4, bisected by two trans dppm ligands, consists of four unidentate terminal cyanide ligands and two cyanide groups that adopt an unusual eta(2)-(sigma,pi) bridging arrangement. The Re-Re distance of 3.0505(6) Angstrom is formally a single bond based on the conventional overlap scheme for a d(5)-d(5) M(2)L(10) compound, viz. sigma(2) pi(2)(delta(2) delta*(2))pi*(2); this assignment is supported by the diamagnetism of the compound as revealed by NMR and magnetic susceptibility studies. With the exception of the bridging cyanides in 4, the v(CN) stretches in the new compounds 1-4 occur at higher frequencies than free CN-, indicating that they are acting purely as donors. In related chemistry, the alkylcyanide CH3CN is used as the sole supporting ligand in dinuclear metal cations. The compo
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页码:213 / 231
页数:19
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