1,3,2-Diazastanna-[3]ferrocenophanes bearing alkyn-1-yl groups at tin and their 1,1-organoboration with triethylborane—molecular structure of a novel spirotin compound

2,2-Dichloro-1,3-bis(trimethylsilyl)-1,3,2-diazastanna-[3]ferrocenophane (3) reacts with lithium alkynides LiCCR1 to give the corresponding di(alkyn-1-yl)tin derivatives 4a (R1=tBu) and 4b (R1=SiMe3). 1,1-Organoboration of 4 with triethylborane affords the spirotin compounds 5 which contain both a ferrocenophane and a stannacyclopentadiene ring. The crystal structure of 5b was determined by X-ray analysis. The compounds 4 and 5 were characterised in solution by multinuclear magnetic resonance (1H-, 11B-, 13C-, 15N-, 29Si-, 119Sn-NMR), using pulsed field gradients in HMBC experiments for the 1H detected 15N- and 119Sn-NMR signals. The compound 5b was also studied by solid-state 13C, 29Si and 119Sn MAS NMR in order to correlate liquid and solid-state NMR data with the structural evidence.