Zirconium complexes cyanides

Air- and moisture-sensitive complex cyanides of composition M5Zr(CN)5 (M = K or Rb) have been prepared by reaction at -50 °C in anhydrous ammonia of zirconium(III) bromide with an excess of either KCN or RbCN. In the case of the reaction involving KCN, the 1 3 distribution of zirconium between the gray, ammonia-insoluble K5Zr(CN)5 and the soluble zirconium(IV) products is in accord with the disproportionation shown in equation (1). The... 

Very little is known about cyanide complexes of zirconium(IV) or hafnium(IV). Just one compound has been reported. [Hf(CN) N(SiMe3)2 3] (m.p. 170-172 °C dec. v(CN) 2160 cm-1) has been prepared by reaction of [HfCl N(SiMe3)2 3] with Me3SiCN in toluene at reflux.33... 

The complications which result from the hydrolysis of alkali metal cyanides in aqueous media may be avoided by the use of non-aqueous solvents. The one most often employed is liquid ammonia, in which derivatives of some of the lanthanides and of titanium(III) may be obtained from the metal halides and cyanide.13 By addition of potassium as reductant, complexes of cobalt(O), nickel(O), titanium(II) and titanium(III) may be prepared and a complex of zirconium(0) has been obtained in a remarkable disproportion of zirconium(III) into zirconium(IV) and zirconium(0).14 Other solvents which have been shown to be suitable for halide-cyanide exchange reactions include ethanol, methanol, tetrahydrofuran, dimethyl sulfoxide and dimethylformamide. With their aid, species of different stoichiometry from those isolated from aqueous media can sometimes be made [Hg(CN)3], for example, is obtained as its cesium salt form CsF, KCN and Hg(CN)2 in ethanol.15... 

Reactions of monochloro complexes of zirconium and hafnium stabilized by tripodal trianionic ligands (such as MeC(CH2NR)3 , HC(SiMe2NR)3 - and MeSi(SiMe2 NR)3 ) with the late transition metal organometallic complexes K[CpM(CO)2] (M = Fe, Ru) gives heterodinuclear complexes with unbridged metal-metal bonds. These het-erobimetallic complexes react with, for example, methyliso-cyanide to yield insertion products (Scheme 6). ... 

Kobayashi has developed the zirconium-BINOL-derived complex 148 as a catalyst for enantioselective Strecker reactions with Bu3SnCN as the cyanide source [106], Subsequent investigations led to a protocol for the three-component in situ coupling of aldehydes, amines, and HCN (Equation 21) [107]. For example, aminonitrile 149 can be prepared in 99% yield and 94% ee in the presence of 5 mol% of zirconium catalyst 148. 

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