Nine new tripodal NS 2 ligands of the bis(mercaptoimidazolyl)(pyrazolyl)borate type with varying 3-R-mercaptoimidazolyl moieties were prepared as their potassium salts. Treatment with zinc salts yielded the complex types L·Zn−Cl, L·Zn−I, L·Zn−ONO 2 , L·Zn−OClO 3 and [L·Zn(imidazole)]ClO 4 . Attempts at the formation of L·Zn−OH or cationic L·Zn complexes resulted in dismutation and formation of ZnL 2 complexes. Hydrolytic destruction yielded one [OZn 4 (thiooimidazolate) 6 ] complex. The ZnS 2 NO coordination which is pre-

The zinc hydroxide complexes Tp*Zn-OH of highly substi-ents, could be incorporated. Thus, the arylmethoxides tuted pyrazolylborate ligands react with phenols, and alco-OCH2C6F, and OCJ-I,C6H4N0,-p, as well as the alkoxides hols, of sufficient acidity, in a condensation reaction with re-OCH2CF3 and OCH2CC13, were attached.

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The zinc hydroxide complexes Tp*Zn-OH with TpCUmjMe = tris(3-cumenyl-5-methylpyrazolyl)borate and TptBurMe = tris(3-tert-butyl-5-methylpyrazolyl)borate can be converted to the alkyl carbonate complexes Tp*Zn-OCOOR by reaction with dialkyl dicarbonates or with alcohol and COz. An alternative formation reaction is the treatment of the pyrazolyl borate with zinc perchlorate and potassium carbonate in alcohol. The interconversion between TpcUmrMeZn-OH and TpCUmrMeZn-OCOOMe in methanol-containing solution can be repeatedly performed in both directions by bubbling either C 0 2 or N2 through the solution. The alkyl carbonate complexes show a variable sensitivity towards hydrolytic destruction with reformation of the hydroxide complexes. The complexes Tp'Ru,MeZn -0COOR (R = Me, Et) release C 0 2 under high vacuum to form the alkoxide complexes TptBurMeZn-OR, which could not be obtained pure due to their extreme water sensitivity. Indirect evidence for their existence is also obtained by the reaction between TpCunl,MeZn--OCOOMe and methyl iodide, forming TpC"nl~MeZn-I and dimethyl ether. The zinc hydroxide complexes catalyse the formation of diethyl carbonate from ethanol and C 0 2 .

Dokal et a1 (1 989), and maybe also as a result of the previous splenectomy, we observed a prompt engraftment in spite of the myelofibrosis, which might have adversely affected posttransplant haematopoietic reconstitution (Rajantie et al, 1986). We agree with these authors that BMT should be considered as treatment of choice for young patients with primary myelofibrosis, especially when poor prognosis features are present.

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