Alkyl, hydrido-, and related compounds of ruthenium( II ) with trimethylphosphine. X-Ray crystal structures of hydrido(tetrahydroborato-HH′)tris(trimethylphosphine)ruthenium( II ), tri-µ-chloro-bistris(trimethylphosphine)ruthenium( II ) tetrafluoroborate, and biscis-methyltetrakis(trimethylphosphine)rutheniomercury( II )–tetrahydrofuran(1/1)