2-AZONIAALLENYLIDENE COMPLEXES OF MANGANE SE - SYNTHESIS, STRUCTURE AND REACTIVITY

CP(CO)3Mn (1) reacts with [N=C(R1)R2]- and [Et3O]BF4 to give alkyliden eamino(ethoxy)carbene complexes, CP(CO)2Mn=C(OEt)N=C(R1)R2 (3) [C(R1)R 2=CPh2 (a), C(C6H4)2O (b), C(CMe3)2 (c), C(CMe3)Tol (d), Tol=C6H4Me-p] . From 1, [N=CPh2]- and MeOSO2F the complex CP(CO)2Mn=C(OMe)N=CPh2 (4a ) is obtained. The reaction of 1 with [N=C((i)Pr)Ph]- and Me3SiCl, how ever, yields an isocyanide complex, Cp(CO)2Mn-C=N-C(Ph)=CMe2 (7). Phot olysis of 3a in THF in the presence of PTol3 affords Cp(CO)(PTol3)Mn=C (OEt)N--CPh2 (6a). According to the X-ray structure analysis of 4a the C-N-C fragment is strongly bent (C-N-C angle: 130.0(2)-degrees) and b oth C-N distances are significantly different. Alkoxide abstraction fr om 3a-c 4a And 6a by BF3 gives 2-azoniaallenylidene complexes 13a-c an d 14a, [Cp(CO)(R)Mn=C=N=C(R1)R2]BF4 [R=CO(13), PTol3 (14a)], respectiv ely. The structure of 14a-BF4 has also been determined by an X-ray dif fraction analysis. The Mn-C-N-C fragment is almost linear and allows t he formation of two orthogonal pi-systems. Both C-N distances differ s ignificantly. The complexes are best described as hybrids of three res onance structures with that of the carbocationic structure beeing the main contributor. Accordingly, 13a-BF4 adds a number of nucleophiles ( OEt2, PMe3, H-, Me-, (t)BuSH, PHPh2, PH2Mes) at the terminal carbon of the Mn-C-N-C fragment to give, depending on the nucleophile, cationic or, after H+ abstraction, neutral isocyanide complexes.