No abstract

The Lappert stannylene SnR2, R = CH(SiMe3)2, adds water and methanol to yield the low-melting-point, crystalline hydroxy- and methoxydiorganostannanes R2SnH(OH) (1) and R2SnH(OMe) (2). The corresponding deuterated derivatives R2SnD(OD) (1-d 2) and R2SnD(OCD3) (2-d 4) have also been prepared. Compounds 1 and 2 react with D2O with retention of the Sn−H bond to give R2SnH(OD) (1-d(SnOD)). The reaction is thought to proceed by an SN2 type mechanism via a [R2SnH(OR‘)2]- (R‘ = H, D, or Me) intermediate or transition state. Consistent with this, 2-d 4 is hydrolyzed to R2SnD(OH) (1-d(SnD)). A single-crystal X-ray structure analysis of 1 reveals that individual molecules form C i -symmetrical dimers in the solid with short O−H···O* hydrogen bridges (O···O* = 2.854(2) Å). Reaction of 1 with (iPr2PC2H4PiPr2)Pd(C2H4) results in oxidative addition of the Sn−H bond to Pd0 to give the known (iPr2PC2H4PiPr2)Pd(H)−SnR2(OH) (3).

Displacement of the ethene ligand in (dippe)Pd(C2H4) (dippe = iPr2PC2H4PiPr2) by 1-alkynes RC⋮CH affords the mononuclear complexes (dippe)Pd(RC⋮CH) (R = Me (2a), Ph (3a), CO2Me (4), SiMe3 (5)). The molecular structure of 3a has been determined by X-ray crystallography. Mononuclear 2a and 3a have been reacted with stoichiometric amounts of (dippe)Pd(η1-C3H5)2 as a source for [(dippe)Pd0] to yield the dinuclear derivatives {(dippe)Pd}2(μ-RC⋮CH) (R = Me (2b), Ph (3b)). By the reaction of (dippe)Pd(C2H4) with difunctional vinylacetylene the mononuclear complex (dippe)Pd{(1,2-η2)-RC⋮CH} (R = CHCH2 (6a)) is formed, which is in equilibrium with isomeric (dippe)Pd{(3,4-η2)-H2CCHC⋮CH} (6b). Addition of [(dippe)Pd0] to 6a,b yields dinuclear {(dippe)Pd}2(μ-RC⋮CH) (R = CHCH2 (6c)). Reaction of (dippe)Pd(C2H4) with butadiyne affords (dippe)Pd(η2-HC⋮CC⋮CH) (7c). From dippe, Pt(cod)2, and C4H2 the Pt homologue has also been synthesized and thus, together with the already known Ni derivative, the series (dippe)M(η2-HC⋮CC⋮CH) (M = Ni (7a), Pd (7c), Pt (7f)) is now complete. When 7c and [(dippe)Pd0] are combined, the dinuclear complex {(dippe)Pd}2(μ-RC⋮CH) (R = C⋮CH (7e)) is formed in solution, whereas isomeric {(dippe)Pd}2{μ-(1,2-η2):(3,4-η2)-HC⋮CC⋮CH} (7d) is present in the solid state. The preparation of the Pd0−1-alkyne complexes refutes the conventional wisdom that this type of compound is inherently unstable. By reaction of (dippe)Pd(C2H4) with internal alkynes C2R2 the complexes (dippe)Pd(RC⋮CR) (R = Me (8a), Ph (9), CO2Me (10), SiMe3 (11)) have also been prepared. Combining 8a with [(dippe)Pd0] affords dinuclear {(dippe)Pd}2(μ-MeC⋮CMe) (8b). Finally, solution thermolysis of 2b and 8b gives rise to dinuclear alkyne-free Pd2(dippe)2 (12).