Fulminato complexes

Hg(CNO)2 is decomposed by heat (equation 8).4 It crystallizes in the orthorhombic form and contains linearly coordinated mercury.21 It reacts with alkali metal fulminate solutions to form the highly explosive compounds M2Hg(CNO)4 (M = K, Rb, Cs) with larger cations such as Ph4As+ more stable complexes are formed.219,220 Besides the homogeneous anionic mercury(II) fulminato complexes there are a few mixed species with unknown structures, e.g. Na Hg(CNO)2X (X = Cl, Br) or Na2S203-2Hg(CNO).221... 

The only directly accessible metal fulminates are those of mercury(II) and silver(I), very dangerously exposive solids obtained by the action of nitric acid and ethanol on the metals or their salts. Most modern preparations of fulminato complexes involve the conversion of a known amount of mercury fulminate into aqueous sodium fulminate by the action of sodium amalgam and ice-cold water the sodium fulminate solution is then allowed to react with the appropriate amount of a transition metal salt, and the resulting complex fulminato ion is precipitated as the salt of a large cation, most frequently Ph4As+ or R4N+ these are not explosive,4,35 Alkali and alkaline earth metal salts containing complex fulminato anions may be isolated from aqueous solutions, but they are reported to be as exposive as the binary silver and mercury fulminates, and are therefore usually avoided. 

In addition to the phosphineplatinum(II) fulminate complexes mentioned already, many other mixed complexes have been prepared and their vibrational spectra studied.4,35 Equations (2)-(6) illustrate typical preparations. In each case the fulminato complex formed closely resembles the... 

Group IV Donors. The fulminato complex trans-[Rh(CNO)(PPh3)2(CO)] has been obtained as an intermediate in the formation of the corresponding isocyanato species from frtms-[RhCl(PPh3)2(CO)] and MeN02.143 An alternative safe route to this and other Pdu and Pt11 fulminato species is via attack of (AsPh4)CNO on appropriate substrates.157... 

A safe synthesis of a number of metal fulminato-complexes, including [Pt(R3E)2-(CNO)J (E = P, As or Sb) and [PtX(CNO)(PPh3)2], (X = H, H, Me, CN or NCO) by reaction of AsPh4CNO with the appropriate Pt substrate has been reported." The thermally very stable complex [Pt(CNO)2(PPh3)2] was shown to isomerize to the isocyahato-complex under mild conditions, and to be reduced by phosphines to the cyanide [Pt(CN)2(PPh3)2].99 Other fulminato-complexes have been synthesized (equation 39) (R = Ph, Me or Et), and again i.r. evidence also shows isomerization... 

The chemistry of osmium is dominated here by the cyanide ligand there is one fulminato complex, and a number of species containing Os—Sn bonds. 

The only reported example of an osmium fulminato complex is (Ph4As)2[0s02(CN0)4], made by reaction of Os04 and potassium fulminate in a sealed tube followed by precipitation with tetraphe-nylarsonium chloride. The IR spectrum has v(C=N) at 2297 and 2181 cm-1 and vas (Os02) at 824 cm-1.44... 

The fulminate (CNO ) ion may coordinate to a metal through the carbon (M—CNO) or the oxygen (M—ONC) or both. So far, all the complexes containing the CNO group are presumed to be C-bonded. Table 111-44 lists the observed CNO frequencies of typical fulminate complexes. Thus far, not much work has been done on fulminato complexes. 

Table lH-44. Observed Frequencies of Typical Fulminato Complexes (cm" )... 

Oxidative addition steps are an important feature in the mechanisms of reactions of Pt(alkyne)(PPh3)a complexes with protonic acids (c/. Scheme 2 in Chapter 2), of reaction of Pt(PMePha)4 with chloroalkenes to give platinum(n) acetylides, and of Pt(PPhs)4 with nitromethane, in benzene-ethanol-water solvent, which provides a safe route to the fulminato-complex Pt(CNO)a(PPh3)2. ... 

---