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a l d e r a z z o [ * ]The synthetic potential and the mechanistic aspects of inorganic insertion reactions of carbon monoxide, especially into metal-carbon 0-bonds, are considered. Reactions of this type are encountered among most 3d, 4d, and 5d elements. In one case it has been demonstrated that the CO insertion proceeds by alkyl migration; this is likely to be a general feature of all such reactions. If an alkyl migration takes place, then insertion of CO into the M-C bond is governed kinetically by the cleavage of that bond. CO abstraction from RCO-M bonds most commonly proceeds by rate-determining vacation of a coordination position. Both CO insertion and abstraction are usually highly stereospecific.

The dibenzyl-substituted carbamic acid (PhCH 2 ) 2 NC(O)OH (1), its deprotonation product [(PhCH 2 ) 2 NH 2 ]-[(PhCH 2 ) 2 NCO 2 ] (2) and CoCl(NO) 2 [PhP(OCH 2 CH 2 ) 2 N-C(O)OH]•2MeCOMe(3•2MeCOMe) are reported, the diffractometric study showing the carbamic acids 1 and 3 to be paired through hydrogen bonds.

The molecular structure of 1,10-phenanthroline-5,6-dione has been determined by X-ray diffraction analysis. The compound reacts with the tetrachlorides of Group 4 metals affording adducts of general formula [MCl 4 (C 12 H 6 N 2 O 2 )] (M = Ti, Zr or Hf) and [(MCl 4 ) 2 (C 12 H 6 N 2 O 2 )] (M = Ti or Hf), N,NЈ-and N,NЈ,O,OЈ-co-ordinated respectively. The compound [HfCl 4 (C 12 H 6 N 2 O 2 )] is reactive towards TiCl 4 affording the bimetallic compound [Cl 4 Hf(C 12 H 6 N 2 O 2 )-TiCl 4 ]. The reaction of the dione with bis-cyclopentadienyl derivatives of titanium(), zirconium(), [MCp 2 (CO) 2 ], and vanadium(), VCp 2 , affords derivatives O,OЈ-co-ordinated to the MCp 2 moiety. By reaction of [TiCp 2 -(C 12 H 6 N 2 O 2 )] with [TiCp 2 (CO) 2 ] the bimetallic derivative [(TiCp 2 ) 2 (C 12 H 6 N 2 O 2 )] is obtained, which is suggested to contain two TiCp 2 fragments, O,OЈ-and N,NЈ-co-ordinated to 1,10-phenanthroline-5,6-dione. The [MCp 2 -(C 12 H 6 N 2 O 2 )] (M = Ti, Zr or V) derivatives react with MЈCl 4 (MЈ = Ti or Hf) to give [Cp 2 M(C 12 H 6 N 2 O 2 )MЈCl 4 ] bimetallics.

Some 1 : 2 adducts of oxygen with A"'-ethylenebis(salicylideneiminato)cobalt(il), Co salen, and its ring-substituted analogues are reported. These compounds, which were obtained from solutions of the cobalt( 11)-Schiff's base complexes, were found to be substantially diamagnetic from room temperature to 90°K. The magnetic susceptibility of the 1 :2 adduct of oxygen with Co salen obtained by the solid-state reaction has been measured from room temperature to 90°K: it is concluded that, when allowance is made for small impurities of unconverted Co salen, this product is substantially diamagnetic. Finally, conditions have been found in which Co 3-methoxysalen gives a 1 : I adduct with oxygen in pyridine as solvent. 1.r. and magnetic susceptibility data suggest that the oxygen group in this adduct of formula Co 3-methoxysalen,py,O, is symmetrically bonded to cobalt in an ethylene-like type of arrangement.THE oxygen-carrying properties of NN'-ethylenebis-(salicylideneiminato)cobalt (II), hereinafter Co salen, were 4 3Conditions under which a complex having a Cosalentype of structure forms a 1 : 1 adduct have also been identified. H2C -CH2recognised by Tsumaki.ls2 Calvin and his co-workers later studied the oxygenation of Co d e n , particularly RESULTS AND DISCUSSION 1 : 2 Adducts.-Co salen and its ring-substituted derivatives have been found to absorb oxygen in aprotic solvents giving rise to adducts in which the oxygen : cobalt ratio is 1 : 2. The compounds obtained (I-VI) are presented in Table 1, together with some of their propert ies. TABLE 1 Oxygen adducts of Co salen and its ring-substituted derivatives los x diamagnetic correction/ 106XNb mole p0it b*= Compound Colour (c.g.s.u.) (c.g.s.u.) * (B.M.)

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