The allenylidene complex [Ru(eta(5)-C5H5)(C=C=CPh2) (CO)((PPr3)-Pr-i)]BF4 as a precursor of novel pyrido[1,2-a]pyrimidinyl and 1,3,-thiazinyl complexes

The allenylidene complex [Ru(eta (5)-C5H5)(C=C=CPh2)(CO)((PPr3)-Pr-i)]BF4 ( 1) reacts with 2-aminopyridine to give a mixture of the complexes [Ru(eta ( 5)-C5H5){2,2-diphenyl-2H-pyridinium-[1,2-alpha ]pyrimidin-4-yl}(CO)((PPr3)- Pr-i)]BF4 (2) and [Ru(eta (5)-C5H5){C(CH=CPh2)=NHC(CH)(4)N}-(CO)((PPr3)-Pr- i)]BF4 (3). The molar ratio of the isomers in the mixture depends on the re action temperature. At temperatures lower than -30 degreesC, isomer 2 is th e main reaction product, while at 0 degreesC an inverse relationship is obs erved. The structure of 2 has been determined by an X-ray Investigation, re vealing a Ru-C(bicycle) distance of 2.08(1) Angstrom. Treatment of 2 with s odium methoxide results in the deprotonation of the NH group of the heteroc ycle to give the pyrido[1,2-alpha ]pyrimidinyl derivative Ru(eta (5)-C5H5){ 2,2-diphenyl-2H-pyrido[1,2-alpha]- pyrimidin-4-yl}(Co)((PPr3)-Pr-i) (4), wh ich has been also characterized by an X-ray diffraction analysis. In this c ase, the study reveals a Ru-C(bicycle) distance of 2.097(5) Angstrom. The d eprotonation of 2 is reversible. Thus, the addition of HBF4. OEt2 to dichlo romethane solutions of 4 regenerates 2, Similarly, the treatment of 4 with methyl trifluoromethanesulfonate affords [Ru(eta (5)-C5H5){1-methyl-2,2-dip henyl-2H-pyridium[1,2-alpha ]pyrimidin-4-yl}(CO)- ((PPr3)-Pr-i)1CF(3)SO(3) (5). Complex 1 also reacts with thioisonicotinamide. The reaction yields [R u-(eta (5)-C5H5){4,4-diphenyl-2-(p-pyridinyl)-4H-1,3-thiazinium-6-yl}(CO)(( PPR3)-P-i)BF4 (6), which in the presence of sodium methoxide affords Ru(eta (5)-C5H5){4,4-diphenyl-2-(p-pyridinyl)-4H-1,3-thiazin-6-yl}(CO)((PPr3)-Pr- i) (7) The structure of 7 has been determined by an X-ray investigation, re vealing a Ru-C(cycle) distance of 2.067(4) Angstrom The deprotonation of 6 is also reversible. Thus, the addition of HBF4. OEt2 to dichloromethane sol utions of 7 regenerates 6. Similarly, treatment of 7 with methyl trifluorom ethanesulfonate gives [Ru(eta (5)-C5H5){3-methy1-4,4-diphenyl-2-(p-pyridiny l)-4H-1,3-thiazininium-6-yl}(CO)((PPR3)-P-i)]CF3SO3 (8). (8).