A series of chiral tungsten(IV) oxo-alkyne complexes of the type Tp′W(O)(I)(RCtCR′) (R ) R′ ) H (1); R ) H, R′ ) Me (2); R ) R′ ) Me (3); R ) Me, R′ ) Ph (4); Tp′ ) hydridotris-(3,5-dimethylpyrazolyl)borate) has been prepared. These complexes were synthesized by reaction of Tp′W(O)(CO)(I) with Me 3 NO in the presence of an excess of alkyne. Phenylpropyne complex 4 was isolated as a 2:1 mixture of alkyne rotamers. For the propyne complex, a second route involving deprotonation of acetylene complex 1 followed by addition of MeI also produced complex 2. The oxidation pathway to 2 with Me 3 NO resulted in a 1:1.5 ratio of alkyne rotamers, while the elaboration of 1 via deprotonation/methylation gave 2 in a 9:1 ratio of alkyne rotamers. Addition of n-BuLi to propyne complex 2 resulted in deprotonation of the terminal acetylene site, and electrophile addition then produced the vinylidene complexes Tp′W(dCdCMe 2 )(O)(I) (5) and Tp′W[dCdC(Me)(H)](O)(I) (6) upon addition of MeI or HCl, respectively. X-ray structure determinations for alkyne complexes 2 and 4 and for vinylidene complex 5 are reported.

The linked Cp ligand [C5H4SiMe2CH2PPh2]- has been used to synthesize several rhodium derivatives. Reaction with [RhClL2]2, where L = C2H4, C8H14, or CO, gives (η5:η1-C5H4SiMe2CH2PPh2)Rh(L) complexes, which have been characterized by single-crystal X-ray diffraction. Reaction of the ethylene complex with CO or PMe3 gives the carbonyl- and phosphine-substituted derivatives, respectively. Irradiation of the ethylene complex in the presence of hydrogen gives a new binuclear polyhydride, also structurally characterized, in which the chelating ligand spans the two metal centers. Reaction of the ethylene complex with iodine leads to the formation of the diiodide (η5:η1-C5H4SiMe2CH2PPh2)RhI2, which in turn can be converted to the dihydride (η5:η1-C5H4SiMe2CH2PPh2)RhH2 by reaction with NaAl(OCH2CH2OCH3)2H2. The reactivity of the dihydride toward C−H bond activation has been investigated. While benzene does not give a stable oxidative addition adduct, pentafluorobenzene yields (η5:η1-C5H4SiMe2CH2PPh2)Rh(C6F5)H, which was structurally characterized as its chloro derivative. Reaction of the dihydride with C6F6 gives the η2 complex (η5:η1-C5H4SiMe2CH2PPh2)Rh(η2-C6F6), also structurally characterized.

Chiral tungsten(IV) aqua-oxo-alkyne complexes, [Tp'W(O)(H2O)(RC identical to CR)][OTf] (R = H (1); R = Me (2)); (Tp' = hydridotris(3,5-dimethylpyrazolyl)borate; OTf = trifluoromethanesulfonate), have been prepared by halide abstraction from iodide precursors. These cationic complexes have been characterized with triflate as the counteranion. The tautomeric dihydroxo isomer has not been observed. The neutral triflate adduct Tp'W(O)(OTf)(HC identical to CH) (3) has also been isolated. Cationic complexes 1 and 2 undergo deprotonation and isomerization when exposed to Al2O3 to give the dioxo-vinyl compounds Tp'W(O)2(CH=CH2) (6) and Tp'W(O)2[C(Me)=C(H)(Me)] (7), reflecting the conversion of the WIV(OH)(RC identical to CR) fragment to WVI(=O)(RC=CHR). The presumed intermediates, neutral oxo-hydroxo compounds Tp'W(O)(OH)(RC identical to CR) (R = H (9); R = Me (10)), can be accessed by deprotonation of 1 or 2 with NaOH. Conversion of 9 to 6 was achieved thermally upon heating at 100 degrees C for 2 days. X-ray structural data have provided solid-state structures of both the cationic aqua complex 2 and the dioxo-vinyl complex 6.

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