The hydrolysis of (η 5 -C 5 Me 5 )WMe 4 leads to the formation of the two compounds (η 5 -C 5 -Me 5 ) 2 W 2 O 2 (µ-CH 2 ) 2 ( 6) and (η 5 -C 5 Me 5 ) 2 W 2 O 2 (µ-CH 2 )(µ-O) (9), containing both methylidene and oxo moieties in one molecule. Reaction of (η 5 -C 5 Me 5 )MoMe 4 with water leads to the trinuclear cluster (η 5 -C 5 Me 5 ) 3 Mo 3 (µ-O) 2 (µ-CH 2 )(µ 3 -CH) (10) with oxo, methylidene, and methylidyne groups. Compounds 6, 9, and 10 were characterized by single-crystal X-ray structural analysis. 6, 9, and 10 can be considered as model compounds for catalysis on metal oxide surfaces.

The reaction of (eta 5-C5Me5)TaMe4 with tert-butylphosphonic acid leads to the formation of a mixture of compounds: [[(eta 5-C5Me5)TaMe][t-BuP(O)(OH)][t-BuP(O)(OH)2]]2(t-BuPO3)2 (1) and [[(eta 5-C5Me5)Ta][t-BuP(O)(OH)2]]2(t-BuPO3)2(mu-O)2 (2). Compound 2 was also obtained by recrystallization of 1 from a THF/hexane mixture. Reaction of (eta 5-C5Me5)MCl4 (M = Mo, W) with PhP(O)(OH)2 yields the binuclear phosphonates [[(eta 5-C5Me5)M][PhP(O)(OH)2]]2(PhPO3)2(mu-O)2 (M = Mo (3); M = W (4)). Compounds 2.THF and 3(.)2.5THF were characterized by single-crystal X-ray studies. The tantalum and molybdenum phosphonates 2.THF and 3(.)2.5THF have different structures as compared to those of the previously reported titanophosphonate cages.

The tetramethyl ester of (hydroxy)(phenyl)methylenebis-(phosphonic acid) reacts with morpholinosulfur trifluoride (MOST) to provide, along with the expected product of the substitution of a hydroxy group by fluorine, the adduct of (morpholino)(phenyl)carbene with PF 5 , compound 3a. Fluorination of dimethyl α-aroylphosphonates with MOST yields adducts of (amino)(aryl)carbene with PF 5 (p-XC 6 H 4 )(Morph)-C:ǞPF 5 [3a-f, where Morph is morpholyl, X = H (a), Me (b), Results and DiscussionWe have elaborated a new approach to the synthesis of α-fluoromethylenebis(phosphonic acid)s by nucleophilic [a] Scheme 3. Fluorination of methyl esters of α-aroylphosphonic acids (yields are given for isolated products).

The reactions of alkyltantalum chlorides with trimethyltin fluoride were found to be highly dependent on the number of organic ligands on tantalum as well as on the electronic and the steric nature of the substituents. The synthesis of trialkyltantalum difluorides of general formula (RCH2)3TaF2 (R = Ph, 1; R = p-Tol, 2; R = Me3Si, 3) and the first example of the alkyltantalum tetrafluoride (Me3Si)2CHTaF4 (8) are reported. The compounds (p-MeC6H4CH2)3TaF2, (Me3SnCl·Me3SnF·TaF5) n , (Me3Si)2CHTaCl4, {(Me3Si)2CHTaCl4·[(Me3Si)2CH]2Ta2Cl6(μ2-O)}, and (Me3Si)2CHTaF4 respectively have been characterized by single-crystal X-ray structural analysis.